Patent Publication Number: US-7591518-B2

Title: Image forming apparatus

Description:
TECHNICAL FIELD 
   The present invention relates to an image forming apparatus such as a printer, a facsimile apparatus, a copying machine, or a multifunction machine having all functions of the above apparatuses. More particularly, the present invention relates to an image forming apparatus which can adjust a gap between a face of a recording head and a sheet according to a thickness of the sheet, and can mount a recording head unit on a carriage with ease and accuracy. The present invention also relates to a computer program for controlling a print operation of the image forming apparatus. 
   BACKGROUND ART 
   Up to now, in some of image forming apparatuses such as a facsimile apparatus and a copying machine, a dot-like image is formed on a sheet by placing an ink ribbon on a surface of the sheet and striking the ink ribbon with dot pins of a recording head, or an image is formed on a sheet by discharging ink drops to the sheet from a nozzle of an ink jet head as in an ink jet type image forming apparatus. In these image forming apparatuses, since a gap between a face of a recording head and a sheet significantly affects print quality, there have been devised various image forming apparatuses each of which is provided with a mechanism capable of adjusting the gap between the face of the recording head and the sheet according to a thickness of the sheet. 
   For example, in JP 5-104817A, an image forming apparatus is disclosed in which: a carriage mounted with a dot pin type recording head is attached on a guide shaft positioned in parallel with a platen and laterally slidably; and an eccentric shaft decentered with respect to an axis of this guide shaft is pivoted by a contact and separation mechanism, thereby making it possible to adjust a distance (gap) between a head face of the recording head and a sheet. 
   In addition, in JP 11-348373A, an image forming apparatus is disclosed in which a gap adjustment member is positioned displaceably in a position opposed to an ink jet type recording head across a sheet conveying path. 
   With these image forming apparatuses, for example, an operator executes gap adjustment by selecting and inputting a sheet type to be used with an input unit of a computer or the like according to a thickness of a sheet on which an image is to be printed and actuating a drive motor of the contact and separation mechanism (gap adjustment member) in response to an input signal from the input unit, or the operator executes manual adjustment by actuating the contact and separation mechanism (gap adjustment member) with a manual lever. In the above-related arts, the carriage or the gap adjustment member is actuated such that the face of the recording head moves away from or close to the surface of the sheet in a parallel manner. 
   On the other hand, in image forming apparatuses disclosed in JP 8-300768A and JP 10-250184A, one end of a carriage mounted with a recording head is slidably and pivotably attached to a guide shaft with a round shaft shape, a lever provided on the other end side of the carriage is attached to a guide plate, which guides the other end side of the carriage, pivotably around a spindle, an eccentric cam is provided around the spindle, and a projection is provided in a hold portion of the lever. Further, the guide plate is nipped by the eccentric cam and the projection vertically. According to selection of a pivotal position of the lever, in a state in which the guide plate is nipped by a major diameter portion of the eccentric cam and the projection, a gap between a face of the recording head and a sheet is set to be large as the carriage pivots around the spindle. On the contrary, in a state in which the guide plate is nipped by a minor diameter of the eccentric cam and the projection, the gap is set to be small. The lever is manually operated by an operator. 
   However, in order to select and input a sheet type to be used with the input unit of the computer or the like to adjust a gap to a predetermined amount as described above, a complicated electric mechanism member is required. In addition, in the image forming apparatus in which the lever is operated manually, unless a user knows that the lever is manually operated, the user cannot perform gap adjustment and an image is formed with an inappropriate gap with respect to a thickness of a sheet, which provides inconveniences such as a waste of sheets and a waste of time. 
   In addition, in the case of the ink jet type image forming apparatus, there are provided a chip type in which a recording head is directly attached to a carriage which is reciprocatingly movable in a direction crossing a conveying direction of a recording medium, and another type in which a recording head unit is detachably mounted on a carriage and an ink cartridge (ink tank) is further detachably mounted thereon. In both the types, positioning of the recording head (recording head unit) to the carriage significantly affects print quality. 
   For example, in JP 2001-18416A, a carriage is provided with a receiving portion including four side plates and a bottom plate to provide upper open end, and a covering portion is provided on one side of the open end. While one end of the recording head unit is inserted below the covering portion, the other end thereof is pivoted downward to be dropped into the receiving portion, and the other end side of the recording head unit is pressed by a pressing lever provided in the other side plate of the carriage for positioning the recording head. 
   However, in the related art described in JP 2001-18416A, a nozzle portion in the recording head unit is faced with a nozzle placing portion which is constituted by the side plate having a cut away portion and vertically provided in a direction perpendicular to the pair of parallel side plates. Therefore, there is a problem in that a pressing force of the pressing lever does not act on the positioning of the nozzle portion at all and the recording head unit tends to be unsteady with respect to the receiving portion of the carriage and also tends to positionally deviate. 
   Besides, since the recording head unit is inserted obliquely downward with respect to the receiving portion as described above, there is also a problem in that mounting work thereof is not easy. 
   Moreover, as a flow of a basic operation of an ink jet printer of this type, first, after moving the carriage to a retract position at the time of sheet feeding, a sheet is fed so as to reach a position directly below a position to which the recording head is moved. Thereafter, movement of the carriage and conveyance of sheets are alternately performed according to a print command or a paper feed command. Thereafter, when the ink jet printer receives a paper supply command following the paper feed command without receiving the print command, after the carriage is moved to the retract position at the time of sheet feeding, feeding of a sheet is performed according to the paper feed command, and sheet discharge is performed such that the sheet is guided to a sheet discharge portion through the position directly below the position of the movement of the recording head. In addition, after printing of one page is finished, in order to detect ink empty, it is necessary to move the carriage to a position where an ink empty detection sensor is positioned. Alternatively, after printing of all pages is finished, it is necessary to move the carriage to a head protection position. 
   Consequently, in the above-mentioned image forming apparatus, many positioning operations are performed for moving and stopping the carriage, supplying and discharging sheets, and the like. Thus, there is a waste of movements in operations related to printing which are performed from supply to discharge of sheets, and speeding-up of printing cannot be realized easily. 
   For example, a reference for determination on stop of the carriage for reversing the carriage from deceleration to acceleration during printing is substantially fixed without any change from a reference for moving the carriage to a retract position at the time of sheet feeding and discharge, a head protection position, a flushing position, or the like to determine that the carriage stops. Thus, a time required for an entire reciprocal movement of the carriage is never shortened. 
   In addition, prior to discharge of a sheet according to a sheet discharge command, it is necessary to move the carriage to the retract position for sheet feeding or discharge. Thus, time is wasted by an amount of time required for moving the carriage from a print end position to the retract position at the time of sheet feeding and discharge, and sheet discharge cannot be performed promptly. 
   The present invention has been established in order to solve these problems, and it is an object of the present invention to provide an image forming apparatus which makes it possible to adjust a size of a gap between a recording head and a recording medium by a simple operation of only moving a carriage in a reciprocating scanning direction. 
   Another object of the present invention is to provide an image forming apparatus which can, with a simple structure, realize accurate positioning of a recording head unit to a carriage and make the recording head unit detachably attachable. 
   Still another object of the present invention is to provide an image forming apparatus which can perform high speed printing, and to provide a computer program for realizing operations of such an apparatus. 
   DISCLOSURE OF THE INVENTION 
   In order to attain the above-mentioned objects, the present invention provides an image forming apparatus which includes: a frame extending in a direction crossing a conveying direction of a recording medium; a guide shaft positioned in parallel with the frame; a carriage provided to reciprocate along the guide shaft and is mounted with a recording head; and a gap adjustment mechanism which adjusts a gap between the recording head and the recording medium. The gap adjustment mechanism is provided with abutment portions which come into slide contact with the frame and move in parallel with the frame together with the carriage. The abutment portions have different heights. The heights of the abutment portions are switched during the movement of the carriage to a predetermined position in one direction parallel with the frame and movement of the carriage to a predetermined position in the other direction. Accordingly, the gap between the recording head and the recording medium can be adjusted. 
   According to such a structure, since the abutment portion having a desired height is selected by moving the carriage to the predetermined positions laterally along the frame. Therefore, the abutment portion comes into slide contact with a slide contact portion of the frame, so that the gap between the recording head and the recording medium can be automatically changed. And a trouble can be eliminated for an operator to manually change the gap between the recording head and the recording medium every time an image is formed. 
   Here, in the gap adjustment mechanism, a switching portion for selecting and switching any one of the abutment portions, and pushing means for pushing and actuating the switching portion are further provided independently from the carriage. The pushing means pushes the switching portion during the movement of the carriage in one direction parallel with the frame and during the movement of the carriage in the other direction, so that any one of the abutment portions is selected and the gap between the recording head and the recording medium is adjusted. 
   According to such a structure, since the pushing means provided separately from the switching portion pushes the switching portion during the movement of the carriage, switching of the abutment portions is performed reliably, and timing for switching can be easily taken. 
   In addition, the pushing means include first pushing means for pushing the switching portion in one direction, and second pushing means for pushing the switching portion in the other direction. The first pushing means pushes the switching portion in one direction during the movement of the carriage in the direction parallel with the frame. The second pushing means pushes the switching portion in the other direction during the movement of the carriage in the other direction, so that any one of the abutment portions is selected, and the gap between the recording head and the recording medium can be adjusted. 
   Since the pushing means are provided in several forms including the first pushing means and the second pushing means in accordance with the lateral movements of the carriage, precise control becomes possible. 
   In addition, the pushing means are provided in the frame, the heights of the abutment portions are switched by the pushing means between the movement of the carriage in one direction and the movement thereof in the other direction. And the abutment portions with the different heights come into slide contact with the frame selectively, so that the gap between the recording head and the recording medium can be adjusted. Further, the pushing means are positioned at substantial terminal ends of the movement paths of the carriage in one direction and the other direction, respectively. 
   By providing the pushing means in the frame, the abutment portions provided in the carriage which comes into slide contact with the frame and laterally moves can be switched reliably. Accordingly, the structure can be simplified without providing a complicated pushing mechanism anew. 
   The present invention further provides an image forming apparatus which includes: a frame extending in a direction crossing a conveying direction of a recording medium, the frame being provided with a horizontal portion having a sliding surface; a guide shaft positioned in parallel with the horizontal portion of the frame; a carriage provided to reciprocate along the guide shaft and mounted with a recording head; and a switching block member provided in the carriage. The switching block member can be changed in posture between the movement of the carriage in one direction parallel with the horizontal portion of the frame and the movement of the carriage in the other direction. The switching block member is provided with several abutment portions with different heights which come into slide contact with the sliding surface of the frame according to the posture change. Pushing means is provided in the frame to switch the posture of the switching block member during the movement of the switching block member. The abutment portions with different heights selectively come into slide contact with the frame to adjust a gap between the recording head and the recording medium. 
   The switching block member provided with the plural abutment portions to come into slide contact with the frame is utilized as a switching mechanism of the abutment portion. Accordingly, it becomes possible to switch the abutment portions by simply pushing the switching block member with the pushing means. And the switching mechanism with a reduced space and a simple structure can be realized. 
   Here, it is preferable that the carriage is constituted pivotably about an axis of the guide shaft, and a portion where the abutment portions of the switching block member abut against a slide contact portion of the frame is positioned on the opposite side of the recording head across the guide shaft. 
   The slide contact portion of the switching block member with respect to the frame is positioned on the opposite side of the recording head across the guide shaft, so that it becomes possible to adjust the gap between the recording head and the recording medium simply through adjustment of the carriage to pivot around the guide shaft. The adjustment accuracy is improved. 
   In addition, it is preferable that the recording head is mounted on the carriage such that a print side thereof faces downward. A portion close to one side of a lower end of the carriage is slidably supported by the guide shaft. The frame has a vertical portion which extends in a vertical direction along a back of the carriage and is in a position higher than the guide shaft. The switching block member is positioned so as to face the sliding surface on the opposite side of the side, where the carriage is located, of the vertical portion of the frame, and is made pivotal with respect to the carriage via a horizontal axis perpendicular to a moving direction of the carriage and to the vertical portion of the frame. 
   The slide contact portion of the switching block member with respect to the frame is placed in an upper portion of an opposite surface of a surface, where the carriage is located, of the vertical portion of the frame on the back of the carriage. Accordingly, the existing frame can be utilized, and inspection and maintenance such as attachment. And replacement work of the switching block member can be performed easily. 
   In addition, biasing means for holding the posture changed at the time when the switching block member crosses a dead center of pivoting is connected to the switching block member. 
   When the biasing means crosses the dead center, since the switching block member can hold a posture, the switched abutment portion is never switched unnecessarily and is held reliably. 
   In addition, the pushing means are provided in positions where the pushing means can abut against the block member during the movement of the carriage in one direction and during the movement of the carriage in the other direction. Further, the pushing means includes first pushing means positioned on one end side of a moving range of the carriage for switching the plural abutment portions with different heights at the time of movement of the carriage to the one side. The pushing means has second pushing means positioned on the other end side of the moving range of the carriage for switching the plural abutment portions with different heights during the movement of the carriage to the other end side. 
   Since the switching block can engage with the frame to change its posture during the movement of the carriage, switching failure is less likely to occur. 
   The present invention further provides an image forming apparatus which includes: a frame extending in a direction crossing a conveying direction of a recording medium; a guide shaft positioned in parallel with the frame; a carriage provided to be reciprocatingly movable to the guide shaft and is mounted with a recording head; and a gap adjustment mechanism adjusting a gap between the recording head and the recording medium adjustable. The gap adjustment mechanism includes a first abutment portion adhered to the carriage, a second abutment portion which projects to or retracts in the carriage during the movement in one direction parallel with the frame and during the movement in the other direction. The second abutment portion has a height different from that of the first abutment portion. And pushing means performs switching between the projection and the retraction of the second abutment portion during the movement of the carriage in one direction and during the movement of the carriage in the other direction. During the movement of the carriage, the first or second abutment portion comes into slide contact with the frame selectively, so that the gap between the recording head and the recording medium can be adjusted. 
   According to such a structure, the first abutment portion is fixed to the carriage, the second abutment portion having a height different from that of the first abutment portion is caused to retract or project by the pushing means. And the first abutment portion or the second abutment portion selectively comes into slide contact with the frame. Therefore, the structure is simple, and it becomes possible to realize remarkable improvement of accuracy with which at least the first abutment portion comes into slide contact with the frame. 
   Here, the pushing means are preferably constituted by left and right side plates of the frame. 
   The left and right side plates of the image forming apparatus are utilized as the pushing means, so that new components and mechanisms are not required. Thus, it becomes possible to improve dimensional accuracy of the pushing means as well. 
   In addition, the carriage is provided pivotably around an axis of the guide shaft, and a portion where the first and second abutment portions with different heights selectively come into slide contact with the frame is positioned on the recording head side across the guide shaft. 
   The slide contact portion of these first and second abutment portions with respect to the frame is positioned on the recording head side across the guide shaft, so that it becomes possible to adjust the gap between the recording head and the recording medium simply through adjustment of the carriage to pivot about the guide shaft. And adjustment accuracy is improved. 
   In addition, the recording head is mounted on the carriage such that a print side thereof faces downward. A portion close to one side of a lower end of the carriage is slidably supported by the guide shaft. The frame has a vertical portion which extends in a vertical direction to above the carriage along a back of the carriage at a position higher than the guide shaft. An upper part of the vertical portion is bent vertically downward and a lower end of a bent portion is positioned to be adjacent to an upper surface of the carriage. The first and second abutment portions are positioned so as to slide facing a vertical surface of the bent portion of the frame, which is a surface on the opposite side of the side where the carriage is located. 
   Simply by bending the upper part of the frame on the back of the carriage and bringing an edge portion of the vertical surface of the frame close to the upper surface of the carriage from above the carriage, the existing frame can be utilized as a slide contact portion. The solid frame is utilized as the slide contact portion, so that adjustment accuracy can be improved. 
   In addition, the second abutment portion comes into slide contact with the frame when it projects. The first abutment portion comes into slide contact with the frame when the second abutment portion retracts. 
   The present invention further provides an image forming apparatus which includes: a frame extending in a direction crossing a conveying direction of a recording medium; a guide shaft positioned in parallel with the frame; a carriage provided to reciprocate along the guide shaft and mounted with a recording head; a switching portion provided in the carriage; and pushing means which are in an abutment relationship with the switching portion in relation to movement of the carriage. The switching portion including a first abutment portion which is adhered to the carriage and selectively comes into slide contact with the frame, and a movable second abutment portion which projects higher than the first abutment portion and is received lower than the first abutment portion. The pushing means including first pushing means which is positioned at substantial one terminal end of a moving range of the carriage in one direction, and causes the second abutment portion to retract by pushing the switching portion in one direction. The pushing means further includes second pushing means which is positioned at the substantial other terminal end of the moving range of the carriage in the other direction and causes the second abutment portion to project by pushing the switching portion in the other direction. The first abutment portion comes into slide contact with the frame in parallel thereto by moving the carriage to the substantial one terminal end to receive the second abutment portion. The second abutment portion comes into slide contact with the frame in parallel thereto by moving the carriage to the substantial other terminal end to cause the second abutment portion to project. Thus, a gap between the recording head and the recording medium can be adjusted. 
   In the above-mentioned structure, the pushing means are preferably positioned within the moving range of the carriage and outside a printable range. 
   In addition, it is preferable that the first pushing means changes the abutment portions with different heights so as to reduce the gap between the recording head and the recording medium. The second pushing means changes the abutment portions with different heights so as to increase the gap between the recording head and the recording medium. 
   The pushing means for switching projection and retraction of the second abutment portion are provided in the substantial terminal ends of the moving ranges in one direction and in the other direction of the carriage. The pushing means are positioned outside the print range, so that printing can be executed without the pushing means affecting a print operation. 
   In addition, it is preferable that the recording head is an ink jet head for discharging ink to perform recording. The recording head is provided with a cap mechanism for performing capping with respect to the recording head at substantially the same position as or on an outer side of a position where the second pushing means completes an operation at the time of movement of the carriage. 
   According to such a structure, the second abutment portion is retracted by the first pushing means of the pushing means. The first abutment portion comes into slide contact with the frame to reduce the gap between the recording head and the recording medium. The second abutment portion is projected by the second pushing means, and the second abutment portion comes into slide contact with the frame to adjust the gap between the recording head and the recording medium to be large. In this structure, a capping position is positioned at the same position as or on an outer side of the position where the second pushing means completes an operation. That is, the recording head is capped reliably in a state in which the gap between the recording head and the recording medium is large. Accordingly, it is unlikely that ink drops leaked from a nozzle portion of the recording head to the outside at the time of replacement of an ink cartridge are rubbed against a wall of the capping mechanism to soil the capping mechanism. 
   In addition, the first pushing means is positioned on an outer side of a printable range in reducing the gap between the recording head and the recording medium to perform a print operation. Alternatively, the first pushing means is positioned on an outer side of a printable range in reducing the gap between the recording head and the recording medium to perform a print operation and in an outside position at least of a portion which is required for accelerating or decelerating the carriage. 
   The first pushing means is positioned on an outer side of the print range in reducing the gap between the recording head and the recording medium to perform a print operation. Alternatively, the first pushing means is positioned more outside than a position made by adding the acceleration and deceleration portion of the carriage to the print range. Therefore, when the gap is reduced to perform a print operation, it becomes possible to perform a continuous print operation with high accuracy at a constant carriage speed while keeping a predetermined gap. 
   In addition, the recording head is an ink jet head for discharging ink to perform recording. A flushing mechanism for performing preliminary discharge at substantially the same position as or on an inner side of a position where the first pushing means completes an operation. 
   The second abutment portion is retracted by the first pushing means of the pushing means. The first abutment portion comes into slide contact with the frame to narrow the gap between the recording head and the recording medium. The second abutment portion is projected by the second pushing means. The second abutment portion comes into slide contact with the frame to widen the gap between the recording head and the recording medium. In this structure, since the flushing position is positioned at the same position as or on an inner side of the position where the first pushing means complete an operation, during printing in a state in which the gap is small, it becomes possible to perform flushing in the state of the gap. 
   In addition, the second pushing means is positioned on an outer side of a print range in increasing the gap between the recording head and the recording medium to perform a print operation. Alternatively, the second pushing means is positioned on an outer side of a print range in increasing the gap between the recording head and the recording medium to perform a print operation and in an outside position at least of a portion which is required for accelerating or decelerating the carriage. 
   The second pushing means is positioned on an outer side of the print range in increasing the gap between the recording head and the recording medium to perform a print operation. Alternatively, the second pushing means is positioned on an outer side of a position made by adding the acceleration and deceleration portion of the carriage to the print range. Therefore, when the gap is increased to perform a print operation, it becomes possible to perform a continuous print operation with high accuracy at a constant carriage speed while keeping a predetermined gap. 
   In addition, switching of the abutment portions with different heights by the pushing means is executed before a print operation on the recording medium is started based upon an instruction from a host computer connected to the image forming apparatus. 
   At this point, a changing operation of the abutment portions with different heights by the pushing means is executed so as to increase the gap based upon an instruction from the host computer indicating that an envelope has been selected as the recording medium. Alternatively, a changing operation of the abutment portions with different heights by the pushing means is executed so as to reduce the gap based upon an instruction from the host computer indicating that a plain paper has been selected as the recording medium. 
   When the host computer is used, since the switching of the abutment portions (gap between the recording head and the recording medium) by the pushing means is performed before a print operation is started according to an instruction of sheet type selection, it becomes possible to perform printing with a gap suitable for a sheet. 
   The present invention further provides an image forming apparatus which includes: a carriage reciprocates in a direction crossing a feeding direction of a recording medium; and a recording head unit which is detachably mounted to the carriage. In the carriage, portions being pressed are provided to project on both left and right sides of the recording head unit. An upward opening head receiving portion, which receives the recording head unit and has left and right side plates engaging with the portions to be pressed, is formed in the carriage. The left and right side plates are provided with elastic pressing members for pressing the portions to be pressed and locking portions for locking the elastic pressing members. 
   According to such a structure, the recording head unit can be easily attached to and detached from the upward opening head receiving portion. And the recording head unit can be pressed uniformly on the portions to be pressed on both the left and right sides thereof with the pair of left and right elastic pressing members from the carriage side. 
   Here, it is preferable that the head receiving portion of the carriage is provided with a bottom supporting portion and a back supporting portion, both of which respectively support a bottom and a back other than a nozzle portion of the recording head unit. The recording head unit is biased against the bottom supporting portion and the back supporting portion by the elastic pressing members. 
   According to such a structure, an upper space on the opposite side of the back can be secured wide, so that it becomes easy to insert/take out the recording head unit with respect to the head receiving portion. In addition, the recording head unit can be efficiently pressed only to the respective supporting portions of the bottom and the back of the carriage by the respective elastic pressing members. And positioning of the recording head unit with respect to the receiving portion of the carriage can be performed accurately. 
   In addition, it is preferable that the portions being pressed are pressed obliquely downward by the elastic pressing members, such that a pressing force of the elastic pressing members to the back supporting portion becomes larger than a pressing force thereof to the bottom supporting portion. 
   According to such a structure, it is unnecessary to increase strength (rigidity) of the bottom supporting portion compared with strength (rigidity) of the back supporting portion in the carriage, and the carriage never becomes bulky. 
   In addition, it is preferable that the elastic pressing members are constituted by wire springs. Ends of the wire springs are pivotably mounted on external surfaces of the left and right side plates of the carriage. And the locking portions include first locking portions provided on the external surfaces of the left and right side plates of the carriage for pressing and locking longitudinal middle portions of the wire springs obliquely downward, and second locking portions for locking free ends of the wire springs not to allow the free ends to be unlocked in an external direction of the side plates. 
   According to such a structure, since attaching and detaching operations of the wire springs can be performed outside the carriage, the operations can be performed easily. Further, a method of applying a load of a pressing force through the wire springs to the portions being pressed of the recording head unit is set in the first locking portions. Posture holding of the wire springs can be executed in the second locking portions. Accordingly, handling work of the wire springs becomes easy. 
   In addition, it is preferable that the recording head unit has an upward opening ink cartridge receiving portion for detachably receiving an ink cartridge. And the carriage is provided with a pressing lever for pressing the ink cartridge against the recording head unit. 
   According to such a structure, since the ink cartridge is pressed against the recording head unit through the pressing lever under a state in which the recording head unit is fixed to the carriage and does not deviate positionally, mounting work of respective components of the recording head unit and the ink cartridge can be performed reliably and easily. 
   In addition, it is preferable that a pressing force of the pressing lever is set such that the ink cartridge is directed toward a bottom of the recording head unit. 
   Consequently, adhesion of the recording head unit and the ink cartridge is improved, and leakage of ink from a connecting portion between both the members can be avoided. 
   The present invention further provides an image forming apparatus which includes: a carriage reciprocating substantially perpendicular to a feeding direction of a sheet; a recording head mounted on the carriage for performing printing on the sheet; reciprocating movement means which moves the carriage repeatedly and reciprocatingly by accelerating the carriage in one direction into a constant speed state, decelerating the carriage after the constant speed state of a short time, and decelerating the carriage after accelerating it in the opposite direction into the constant speed state again. First determining means determines that the carriage is stopped when decelerated to a speed equal to or lower than a first speed if the carriage moved by the reciprocating movement means stops at a predetermined position. Second determining means determines that the carriage is stopped when decelerated to a speed equal to or lower than a second speed higher than the first speed if the carriage moved by the reciprocating movement means performs printing. 
   According to such an image forming apparatus, criteria for determination on stop of the carriage reciprocatingly moving at the print time can be varied according to an operation state. When printing is performed, time required for the entire reciprocating movement is reduced by partially making the determination on stop earlier. And high-speed printing can be performed easily. 
   Here, it is preferable that an encoder for detecting a moving speed of the carriage is provided. And as to the carriage under deceleration, when a detection signal is not obtained from the encoder for a first time, the first determining means determines that the carriage has stopped at that point. When a detection signal is not obtained from the encoder for a second time shorter than the first time, the second determining means determines that the carriage has stopped at that point. 
   According to such an image forming apparatus, a stop determination point for determining that the carriage has stopped can be varied in terms of timing according to a detection signal from the encoder. 
   In addition, it is preferable that the recording head is an ink jet head according to an ink jet system. And the first determining means determines stop of the carriage according to the first speed at the time of movement to a head protection position, a retract position, or a flushing position. 
   According to such an image forming apparatus, unlike the case in which the carriage is moved to the head protection position, the retract position, and the flushing position, determination on stop of the carriage can be made earlier when the carriage is reciprocatingly moved for printing. 
   The present invention further provides an image forming apparatus which includes: a carriage reciprocating substantially perpendicular to a feeding direction of a sheet; a recording head mounted on the carriage for performing printing on the sheet; reciprocating movement means which reciprocates the carriage substantially perpendicular to the feeding direction of a sheet to apply printing to the sheet with the recording head, and on the other hand. When the carriage reverses for reciprocating movement, the apparatus performs feeding of the sheet in association therewith. And carriage movement control means controls movement of the carriage, in which the reciprocating movement means accelerates the carriage in one direction into a constant speed state, decelerates the carriage after it undergoes the constant speed state of a short time, and decelerates the carriage after it is accelerated in the opposite direction into the constant speed state again, thereby repeatedly reversing the carriage to move it reciprocatingly. When discharge of a sheet is performed, the apparatus retracts the carriage to the outside of a reciprocating movement portion of the carriage. The carriage movement control means brings the carriage into the constant speed state with the reciprocating movement means according to the print command, when it receives a sheet discharge command indicating that discharge of a sheet is to be performed together with a paper feed command indicating that feeding of a sheet is to be performed without any other print command following a print command indicating that printing is to be performed by the recording head. The carriage movement control means retracts the carriage to the outside of the reciprocating movement portion continuously with the reciprocating movement means according to the sheet discharge command immediately after the printing ends. 
   According to such an image forming apparatus, feeding of a sheet is never performed even if a paper feed command is received immediately before a sheet discharge command prior to discharge of the sheet according to the sheet discharge command, and the carriage is retracted to the outside of the reciprocating movement portion immediately after last printing. Therefore, sheet discharge can be performed promptly following a print operation according to a last print command. And high-speed printing can be performed easily. 
   The present invention further provides an image forming apparatus which includes: a carriage reciprocating substantially perpendicular to a feeding direction of a sheet; a recording head mounted on the carriage for performing printing on the sheet; a gap adjustment mechanism which automatically switches a gap between the sheet and the recording head at a gap switching position located outside a reciprocating movement portion of the carriage. Reciprocating movement means accelerates the carriage in one direction into a constant speed state, decelerates the carriage after the constant speed state of a short time, and decelerates the carriage after it is accelerated in the opposite direction into the constant speed state again, thereby repeatedly reversing the carriage to move it reciprocatingly. The reciprocating movement means moves the carriage to the gap switching position. Carriage movement control means moves the carriage to the gap switching position with the reciprocating movement means during feeding of a sheet. 
   According to such an image forming apparatus, in automatically switching a gap, since the carriage is moved to the gap switching position at the time of feeding a sheet, the sheet feeding is not delayed due to the gap switching. And high-speed printing can be performed easily. 
   The present invention further provides a computer program for controlling an image forming apparatus which reciprocatingly moves a carriage substantially perpendicular to a feeding direction of a sheet and performs printing to the sheet with a recording head mounted on the carriage. The computer program including: a reciprocating movement program for accelerating the carriage in one direction into a constant speed state, decelerating the carriage after the constant speed state of a short time, and decelerating the carriage after accelerating it in the opposite direction into the constant speed state again, so that the carriage can repeatedly reciprocates. A first determination program determines that the carriage is stopped when decelerated to a speed equal to or lower than a first speed, if the carriage moved based upon the reciprocating movement program is stopped at a predetermined position. A second determination program determines that the carriage is stopped when decelerated to a speed equal to or lower than a second speed higher than the first speed if the carriage is reciprocatingly moved based upon the reciprocating movement program to perform printing. 
   According to such a computer program, by operating a CPU based on the computer program, criteria for determination on stop of the carriage reciprocatingly moving at the print time can be varied according to an operation state. When printing is performed, time required for the entire reciprocating movement is reduced by partially making the determination on stop of the carriage earlier. And high-speed printing can be performed easily. 
   The present invention further provides a computer program for controlling an image forming apparatus which reciprocatingly moves a carriage substantially perpendicular to a feeding direction of a sheet to perform printing to the sheet with a recording head mounted on the carriage. When the carriage is reversed for reciprocating movement, the apparatus performs feeding of the sheet. The computer program including: a reciprocating movement program for accelerating the carriage in one direction into a constant speed state, decelerating the carriage after the constant speed state of a short time, and decelerating the carriage after accelerating it in the opposite direction into the constant speed state again, thereby repeatedly reciprocating the carriage. When discharge of a sheet is performed, the apparatus retracts the carriage to the outside of a reciprocating movement portion of the carriage. And a carriage movement control program brings the carriage into the constant speed state based upon the reciprocating movement program according to the print command, when a sheet discharge command indicating that discharge of a sheet is to be performed is received together with a paper feed command indicating that feeding of a sheet is to be performed without any other print command following a print command indicating that printing is to be performed by the recording head mounted on the carriage. The apparatus retracts the carriage to the outside of the reciprocating movement portion continuously based upon the reciprocating movement program according to the sheet discharge command immediately after the printing ends. 
   According to such a computer program, by operating the CPU based upon the computer program, feeding of a sheet is never performed even if a paper feed command is received immediately before a sheet discharge command prior to discharge of the sheet according to the sheet discharge command. The carriage is retracted to the outside of the reciprocating movement portion immediately after last printing. Therefore, sheet discharge can be performed promptly following a print operation according to a last print command. And high-speed printing can be performed easily. 
   The present invention further provides a computer program for controlling an image forming apparatus which reciprocatingly moves a carriage substantially perpendicular to a feeding direction of a sheet to perform printing to the sheet with a recording head mounted on the carriage. The apparatus is provided with a gap adjustment mechanism for automatically switching a gap between the sheet and the recording head. The computer program includes a reciprocating movement program for accelerating the carriage in one direction into a constant speed state, decelerating the carriage after the constant speed state of a short time, and decelerating the carriage after accelerating it in the opposite direction into the constant speed state again, thereby repeatedly reversing and reciprocating the carriage. The program moves the carriage to a switching position of the gap located outside a reciprocating movement portion of the carriage. A carriage movement control program moves the carriage to the switching position of the gap based upon the reciprocating movement program during feeding of a sheet. 
   According to such a computer program, by operating the CPU based upon the computer program, the carriage is moved to the switching position of the gap at the time of feeding of a sheet in order to automatically switch the gap. Therefore, sheet feeding is not delayed due to the switching of the gap. And high-speed printing can be performed easily. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an external perspective view showing a multifunction facsimile/printer apparatus according to a first embodiment of the present invention. 
       FIG. 2  is a schematic side sectional view showing an inside of the printer apparatus. 
       FIG. 3A  is a schematic plan view showing a lateral movement area of a carriage with respect to a frame in the first embodiment. 
       FIG. 3B  is a schematic front view showing the lateral movement area of the carriage with respect to the frame in the first embodiment. 
       FIG. 4A  is a schematic plan view showing various stop points and the lateral movement area of the carriage in the first embodiment. 
       FIG. 4B  is a schematic front view showing the various stop points and the lateral movement area of the carriage in the first embodiment. 
       FIG. 5  is a side sectional view of a recording portion showing a posture of the recording portion in a state in which a gap between a tip end surface of the recording portion and a platen is small in the first embodiment. 
       FIG. 6  is a side sectional view of a recording portion showing a posture of the recording portion in a state in which the gap between the tip end surface of the recording portion and the platen is large in the first embodiment. 
       FIG. 7  is a side sectional view of the carriage mounted with a recording head in the first embodiment and shows a state before mounting an ink cartridge. 
       FIG. 8  is a perspective view of a recording head unit in the first embodiment. 
       FIG. 9  is a cross-sectional view taken along the line IX-IX of  FIG. 12 . 
       FIG. 10  is a bottom view showing a recording head in a lower part of the carriage in the first embodiment. 
       FIG. 11  is an explanatory view concerning an arrangement form of a nozzle array in the recording portion of the first embodiment. 
       FIG. 12  is a front view of the carriage mounted with the recording head unit in the first embodiment. 
       FIG. 13  is a right side view of the carriage mounted with the recording head unit in the first embodiment. 
       FIG. 14  is a side sectional view of the carriage showing a state before fixing the ink cartridge in the first embodiment. 
       FIG. 15A  is a side view showing a state in which a pressing lever of the carriage is wide open in the first embodiment. 
       FIG. 15B  is a view in an arrow XVb-XVb direction of  FIG. 15A . 
       FIG. 16A  is a side view showing a state in which the pressing lever is closed in the first embodiment. 
       FIG. 16B  is a partially cutout view in an arrow XVIb-XVIb direction of  FIG. 16A . 
       FIG. 17A  is a rear view of a switching block member according to the first embodiment. 
       FIG. 17B  is a front view of the switching block member. 
       FIG. 17C  is a left side view of the switching block member. 
       FIG. 17D  is an enlarged sectional view in an arrow XVIId-XVIId direction of  FIG. 17B  of the switching block member and shows a height of an abutment portion. 
       FIG. 18A  is a front view showing a change in a posture of the switching block member on the left side of the frame before the switching abutment portion abuts against a first pushing piece in the first embodiment. 
       FIG. 18B  is a view in an arrow XVIIIb-XVIIIb direction of  FIG. 18A . 
       FIG. 19A  is a front view showing a state in which the switching block member crosses a dead center. 
       FIG. 19B  is a left side view showing a state in which the switching block member crosses the dead center. 
       FIG. 20A  is a front view at the time when the switching abutment portion has abutted against the first pushing piece and the posture of the switching block member has been completely switched. 
       FIG. 20B  is a left side view at the time when the switching abutment portion has abutted against the first pushing piece and the posture of the switching block member has been completely switched. 
       FIG. 21A  is a front view immediately before the switching abutment portion abuts against a second pushing piece in the first embodiment. 
       FIG. 21B  is a left side view immediately before the switching abutment portion abuts against a second pushing piece in the first embodiment. 
       FIG. 22A  is a front view showing a state in which the switching abutment portion passes over the second pushing piece. 
       FIG. 22B  is a left side view showing the state in which the switching abutment portion passes over the second pushing piece. 
       FIG. 23A  is a front view at the time when the switching abutment portion has passed the part of the second pushing piece and the posture of the switching block member has been completely switched. 
       FIG. 23B  is a left side view at the time when the switching abutment portion has passed the part of the second pushing piece and the posture of the switching block member has been completely switched. 
       FIG. 24  is a block diagram showing a circuit structure of the multifunction facsimile/printer apparatus in the first embodiment. 
       FIG. 25  is a time chart showing timing of an operation of the carriage and movement of a sheet in the first embodiment. 
       FIG. 26  is a flowchart showing a flow of entire print processing in the first embodiment. 
       FIG. 27A  is a front view of a switching block member in a second embodiment which has an abutment portion with heights different in three stages. 
       FIG. 27B  is an enlarged sectional view in an arrow XXVIIb-XXVIIb direction of  FIG. 27A . 
       FIG. 28  is an upper perspective view of a carriage in accordance with a third embodiment. 
       FIG. 29A  is a rear view of an actuator portion  102  showing a state in which second abutment portions  109  and  111  are received in the third embodiment. 
       FIG. 29B  is a plan sectional view of  FIG. 29A . 
       FIG. 29C  is a front view of  FIG. 29A . 
       FIG. 30A  is a rear view of the actuator portion  102  showing a state in which the second abutment portions  109  and  111  are projected in the third embodiment. 
       FIG. 30B  is a plan sectional view of  FIG. 30A . 
       FIG. 30C  is a front view of  FIG. 30A . 
       FIG. 31  is a side sectional view of a recording portion in a state in which a gap G 1  is small in the third embodiment. 
       FIG. 32  is a side sectional view of a recording portion in a state in which the gap G 1  is large in the third embodiment. 
       FIG. 33A  is a schematic plan view showing a state of lateral movements of a carriage with respect to a frame in the third embodiment. 
       FIG. 33B  is a schematic front view showing a positional relationship of a gap adjustment mechanism with respect to the frame in the third embodiment. 
       FIG. 34A  is a view showing a gap adjustment mechanism according to a fourth embodiment and showing a structure capable of switching a gap between a recording head and a recording medium into three stages, i.e., large, medium, and small, and showing a state where the gap is switched between medium gap and small gap. 
       FIG. 34B  is a view showing an operation and a state in which the gap having switched to medium is switched to large. 
   

   BEST MODE FOR CARRYING OUT THE INVENTION 
   Next, an image forming apparatus according to a first embodiment of the present invention will be described based upon  FIGS. 1 to 26 . This image forming apparatus is a multifunction facsimile/printer apparatus. 
   Outline of the Multifunction Facsimile/Printer Apparatus 
   As shown in  FIG. 1 , in the multifunction facsimile/printer apparatus, a main body case  1  is constituted by a main lower case  1   a  made of synthetic resin and an upper case  1   b  made of synthetic resin covering an upper side of the main lower case  1   a . The main lower case  1   a  receives an ink jet recording portion  2  ( FIG. 2 ) and is provided with a sheet supply tray  3  ( FIG. 2 ) for supplying a sheet P on which an image is formed. The tray  3  is inclined and positioned at a rear upper side of the main lower case  1   a . An original mounting portion  4  is positioned in a part close to the rear of the upper case  1   b . In that part, a pair of left and right original guide plates  8  are mounted which laterally slides in accordance with a width of an original to guide both the left and right side edges of the original to be conveyed. In addition, an operation panel portion  6  is provided on a front side of the original mounting portion  4  in the upper case  1   b . The operation panel portion  6  is provided with an operation key portion  6   a  including various function keys, ten keys, and the like, and a display portion  6   b  such as a liquid crystal panel on which a value inputted by the operation key portion  6   a  and various characters and numbers for operations can be displayed. A sheet discharge tray  26  for receiving a printed sheet is provided on a front side of the main body case  1 . 
   In  FIG. 2 , an original reading unit (reading portion)  5  serving as an original reading portion is mounted below the operation panel portion  6 . A bottom surface of the main lower case  1   a  is blocked by a bottom cover plate  7  made of a metal plate or the like. In an internal space of the main lower case  1   a , there is positioned a control portion  9  ( FIG. 24 ) for a control substrate, a power supply substrate, and a Network Control Unit (NCU) substrate for allowing conversation or transmission and reception of facsimile data with other telephone sets or facsimile apparatuses via a telephone line, which are not illustrated. 
   Moreover, although not illustrated, a transmitter/receiver (handset) for performing conversation with other telephone sets is mounted on a cradle protrudingly provided outward so as to protrude from a side of the main lower case  1   a . In addition, speakers for call-out and monitor are fixed to a rear side or the like of a right side in the main lower case  1   a.    
   An ink jet printer is roughly divided into a mechanism for conveying a sheet (not shown) and a mechanism for performing printing on the sheet. The sheet conveying mechanism is constituted by the sheet supply tray  3  serving as a sheet set portion, a sheet supply roller  21 , a sheet separation piece  120 , a sheet sensor  80 , a registration roller  22 , conveying rollers  23  and  24 , and a sheet discharge tray  26  which are positioned along a sheet conveying path, as well as a not-shown feed motor for driving the respective rollers  21 ,  22 , and  23 . The printing mechanism is constituted by a carriage  10  reciprocatingly moving substantially perpendicular to a feeding direction of a sheet, a recording head  15  provided below the carriage  10 , a platen  25  positioned to be opposed to the recording head  15 , a guide shaft  11  and a frame  12  which support the carriage  10 , a linear encoder  82  and an encoder slit  83  for detecting a moving position of the carriage, as well as a DC motor for reciprocatingly moving the carriage  10 , an ink tank mounted on the carriage  10 , and the like, which are not illustrated. 
   On the sheet supply tray  3 , a large number of sheets are stacked and are brought into a standby state for being fed in a posture in which a leading edge of each sheet abuts against the sheet separation piece  120 . When the sheet supply roller  21  rotates in the clockwise direction, one sheet contacting the sheet supply roller  21  is separated from the sheet separation piece  120  and fed into the printer and a leading edge of the sheet abuts against the sheet sensor  80  before long, whereby a position of the sheet is detected. Then, when the sheet is fed by a predetermined amount, a leading edge of the sheet reaches the registration roller  22  and a direction of the sheet is adjusted. When the sheet further moves, it is brought into a state in which it is nipped between the registration roller  22  and the conveying roller  23 , whereby the sheet supplying operation ends. 
   Thereafter, printing is performed on the sheet nipped by the registration roller  22  and the conveying roller  23  via the recording head  15 . At the time of the print operation, the sheet is fed by a fixed width via the registration roller  22  and the conveying roller  23  every time printing of the fixed width is finished. When a trailing edge of the sheet reaches a predetermined position, a sheet discharge operation is started and the entire sheet finally reaches the sheet discharge tray  26  via the conveying roller  23 , whereby the sheet discharge operation ends. 
   A lower rear end of the carriage  10  in the recording portion  2  is slidably and pivotably mounted on the guide shaft  11  of a round shaft shape on a surface (front) side of a lower part of the horizontally oblong frame  12  ( FIG. 3B ). Further, the carriage  10  reciprocatingly moves along a direction penetrating a sheet surface of  FIG. 2 . As shown in  FIG. 6 , a timing belt  18  extending in parallel with the guide shaft  11  is wound around a driven pulley (not shown) positioned close to one side of the frame  12  and a driving pulley  20  fixed to an output shaft of a drive motor  19  such as a reversible stepping motor, and a portion of the timing belt  18  is coupled to the carriage  10 , whereby the carriage  10  is provided reciprocatingly movable in parallel with the guide shaft  11 . While the carriage  10  is reciprocatingly moving once, ink is injected from the recording head  15  and a print operation is performed. However, there are also a two-way printing for performing printing twice in forward and backward movements while a carriage is reciprocatingly moving once, and a one-way printing for performing printing only in one direction of forward movement or backward movement. In any case, the print operation is performed while the carriage  10  is moving at a constant speed in a state in which a sheet is temporarily stopped without being fed. Therefore, feeding of a sheet is basically performed when the carriage  10  turns around (reverses) in the middle of the reciprocating movement. A position of the carriage  10  reciprocatingly moving in this way is detected as the linear encoder  82  integrally formed with the carriage  10  optically reads the encoder slit  83  fixed along a reciprocating movement path. 
   The Carriage and the Recording Head 
   In the carriage  10 , left and right side plates  32  ( FIG. 3B ) are projected forward from both left and right sides of a rear plate  31  ( FIG. 5 ). In lower ends of the respective side plates  32 , supporting portions  33  for supporting left and right sides of a bottom plate of the recording head  15  are provided so as to protrude inward. A nozzle portion  15   a  of the recording head  15  is positioned so as to be exposed downward between both the supporting portions  33 . Engaging pins  34  (see  FIGS. 7 and 8 ) projected outward from both the left and right side of the recording head  15 , which is positioned between the left and right side plates  32 , are positioned in recessed portions  35  ( FIG. 6 ) recessed in the left and right side plates  32 . The parts of the respective engaging pins  34  are pressed obliquely downward in a halfway part in a longitudinal direction of wire springs  36  (only one of them is shown in  FIG. 6 ) made of a metal or the like having elasticity, which are pivotably attached to attaching holes  38  ( FIG. 6 ) on upper end sides outside the left and right side plates  32 . On the other hand, lower end sides (free end sides) of the respective wire springs  36  are locked so as to not to move upward by first locking portions  37  which are formed outside the side plates  32  so as to protrude therefrom. Moreover, the free end sides of the respective wire springs  36  are prevented from coming off to the outside of the side plates  32  by second locking portion  39  of a hook shape formed obliquely downward. In this way, the recording head  15  is mounted firmly to the carriage  10  so as not to wobble. 
   On the other hand, the recording head unit  15  is a color ink jet recording head of a cartridge type and is detachably mounted downward to the carriage  10 . The recording head  15  for executing color recording has four nozzle portions  15   a  for discharging inks of colors of cyan, yellow, magenta, and black on its lower surface side. Ink cartridges  16  for the respective colors in which inks to be supplied to the recording head  15  can be detachably mounted on an upper surface side of the recording head  15  as shown in  FIG. 3B . The respective ink cartridges  16  can be pressed and fixed downward to the recording head  15  by pressing levers  17  which are vertically pivotable forward on the upper end side of the carriage  10 . 
   As shown in  FIGS. 8 and 9 , the nozzle portions  15   a  are provided on a lower surface side of a bottom plate  15   b , and the inside surrounded by the bottom plate  15   b , left and right side plates  15   c  and  15   c , a rear plate  15   d , and a front plate  15   e  constitutes an upward opening ink cartridge receiving portion D 2  for receiving the ink cartridges  16 . Further, in this ink cartridge receiving portion D 2 , four manifold ports  62  which fit in ink discharge ports  16   a  (see  FIGS. 7 and 14 ) on the lower surfaces of the ink cartridges  16  of four colors are opened upward on the upper surface of the bottom plate  15   b . In addition, partition plates  15   f  are vertically provided such that the ink cartridges  16  of respective colors can be partitioned from each other. 
   On external surfaces of the left and right side plates  15   c  and  15   c  of the recording head unit  15 , the engaging pins  34  and  34  (see  FIG. 8 ) as an example of portions to be pressed are projected sideways in portions close to the top of the recording head unit  15 . In addition, an abutment block  45  protrudes from an external surface close to the lower part of the right side plate  15   c . The abutment block  45  is adapted to abut against a cam  44   a  (see  FIG. 13 ) in an inclination adjustment mechanism  44  provided on the carriage side  10  for adjusting left and right inclinations of the recording head unit  15 . 
   Moreover, abutment projections  46  and  46  projecting backward are formed in portions close to the upper end on both the left and right sides of the rear plate  15   d  (see  FIGS. 7 ,  9 , and  13 ). Further, on both the left and right sides of the bottom plate  15   b  of the recording head unit  15 , bottom abutment portions  47  projecting downward are provided integrally, and a positioning projected portion  47   a  projecting downward is provided in one (left) bottom abutment portion  47 . 
   In order to accurately perform positioning and firmly fix the recording head unit  15  positioned in an upward opening head receiving portion D 1  in the carriage  10 , first, as shown in  FIGS. 7 and 12 , the engaging pins  34  and  34  as an example of a portion to be pressed, which is projected outward from both the left and right sides of the recording head unit  15 , are positioned in the recessed portions  35  which are recessed and formed in the left and right side plates  32  and  32  in the carriage  10 . Then, the bottom abutment portions  47  are placed and mounted on the bottom supporting portions  33  and  33  on the bottom portions on both the left and right sides of the carriage  10  and, at the same time, the positioning projected portion  47   a  is fit in a receiving groove  48  (see  FIG. 7 ), which is recessed and formed in one (left) bottom supporting portion  33 , and supported. In this state, the respective engaging pin  34  are pressed obliquely downward by the halfway part in the longitudinal direction of the wire springs  36  (the left side wire spring shown in  FIG. 5  and the right side wire spring shown in  FIG. 13 ) pivotably attached to the attachment holes  38  on the upper end side on the outer side of the left and right side plates  32  and  32 . 
   On the other hand, the lower ends sides (free end sides) of the respective wire springs  36  are locked so as not to move upward by the first locking portions  37  which protrude outwardly from the side plates  32 . Moreover, the free end sides of the respective wire springs  36  are prevented from coming off to the outside of the side plates  32  by second locking portion  39  of a hook shape formed obliquely downward. 
   If the wire springs  36  are locked in this way, as shown in  FIGS. 5 and 13 , the engaging pins  34  of the recording head unit  15  are pressed in an oblique direction toward the rear side of the carriage  10  at the middle of the respective wire springs  36  extending obliquely downward, whereby the abutment projections  46  and  46  are pressed substantially in the horizontal direction to abut against projection shaped supporting portions (abutment surfaces)  49  and  49  in the rear plate  31  of the carriage  10  by an X component of force (in X direction (horizontal direction of  FIG. 7 )) of the pressing force (see  FIGS. 9 and 13 ) and, at the same time, the abutment block  45  presses the cam  44   a  (see  FIG. 13 ). On the other hand, a downward force from the bottom abutment portions  47  can be supported on the bottom supporting portions  33  and  33  on both the left and right sides of the carriage  10  by a Y component of force in a Y direction (vertical direction in  FIG. 7 ). Then, the X component of force can be designed to be larger than the Y component of force by setting an inclination angle θ of the wire springs  36  with respect to a vertical line to 45 degrees or more. 
   Consequently, a pressing force of the recording head unit  15  against the rear supporting portions  49  of the carriage  10  is made larger than its pressing force in the direction toward the bottom supporting portions  33  to ensure close attachment of the recording head unit  15  to the rear plate  31  with high rigidity in the carriage, and it is unnecessary to make the rigidity of the bottom supporting portions  33  large. Moreover, the recording head unit  15  can be mounted on the carriage  10  firmly so as not to wobble, and posturing and positioning of the recording head unit  15  become easy. Furthermore, since the head receiving portion D 1  is opened largely with respect to the front side of the carriage  10  (and consequently the front side of the printer apparatus  1 ), attachment and detachment work of the recording head unit  15  from the front side of the printer apparatus  1  becomes extremely easy. 
   Next, a structure for attachment and detachment of the ink cartridges  16  will be described. As shown in  FIGS. 5  to  7 ,  12 ,  15 A,  15 B,  16 A, and  16 B, on the upper end side of the left and right side plates  32  and  32  in the carriage  10 , a pivotably supporting shaft  63  is laid and suspended, and base end of the pressing lever  17  for pressing the upper surface of each ink cartridge  16  individually is pivotably supported by the pivotably supporting shaft  63  via mounting holes  64  of a downward potbelly shape. A diameter of a lower side of the mounting holes  64  is set to be substantially equal to a diameter of the pivotably supporting shaft  63 , and a diameter of an upper side of the mounting holes  64  is set to be approximately 1.5 times as large as the diameter of the pivotably supporting shaft  63 . Further, one end  65   a  of a torsion spring  65  loosely fitted to the pivotally supporting shaft  63  is locked by an upper locking portion  31   a  of the rear plate  31  in the carriage  10  and is always biased in an upward pivotal direction (see  FIGS. 5 ,  15 A, and  16 A)). 
   A pressing block  66  for pressing the upper surface in each ink cartridge  16  downward is mounted on a portion close to a free end on a lower surface of each pressing lever  17 . The lower surface of the pressing lever  17  is formed with a downward C-shape recess in its cross-section, and the pressing block  66  is movable vertically and is unable to drop. Further, the pressing block  66  is biased downward via a biasing spring  67  positioned between a top board of the pressing lever  17  and the pressing block  66 . Further, a pressing point of the ink cartridge  16  pressed by this pressing block  66 , i.e., a position of the pressing force in the Y direction, is set to be in the vicinity of a manifold port  62  in the recording head unit  15 . Consequently, in a fixed state in which the recording head unit  15  is pressed in the XY direction of the carriage  10  by the wire spring  36 , since the recording head unit  15  does not shift in the XY direction any more, the ink cartridge  16  can be mounted firmly without applying a large load of external force to the bottom supporting portions  33  and  33  of the carriage  10  by pressing the recording head unit  15  downward in the Y direction with the pressing levers  17  via the ink cartridge  16 . 
   Note that, since the pressing lever  17  is loosely fit with respect to the pivotably supporting shaft  63  via the mounting holes  64  which has a vertically oblong shape, when the upper portion on the opening end side of the pressing lever  17  is pushed downward, in a state in which the ink cartridge  16  is pressed by the pressing block  66  on the front side of the pressing lever  17 , the base end side of the pressing lever  17  moves upward around the pressing point of the pressing block  66  with respect to the ink cartridge  16 , and a vertical locking surface  68  of the pressing lever  17  locks a front end surface  69   a  in a top cover plate  69  of the carriage  10  and the posture of the pressing lever  17  is held (see  FIGS. 5 and 16A ). When an operating portion  70  close to the base end on the upper surface of the pressing lever  17  is pressed downward in order to release pressing with respect to the ink cartridge  16 , the base end side in the pressing lever  17  moves downward via the mounting holes  64 . When the locking surface  68  unlocks from the front end surface  69   a , since the front side (free end side) of the pressing lever  17  can pivot largely upward because of the biasing force of the torsion spring  65 , a large space is formed on the upper front side of the carriage  10 , and attachment and detachment work of the ink cartridge  16  can be performed easily (see  FIGS. 8 and 14 ). In that case, the operating portion  70  abuts against the front-end surface  69   a  and can hold the upward pivotal posture of the pressing lever  17  (see  FIG. 15A ). 
   Note that, as shown in  FIG. 16B , since a regulating piece  71  is provided so as to protrude downward from each lower surface in the middle in the front and back direction of each pressing lever  17 , the regulating piece  71  comes into slide contact with inner surfaces of upward side plates  72  and  72  on both the left and right sides on the upper surface of the ink cartridge  16  in a state in which the ink cartridge  16  is pressed by the pressing lever  17 , whereby the ink cartridge  16  can be regulated so as to avoid its inclination in its lateral direction. 
   As shown in  FIG. 13 , an adjustment lever  86  is provided on a left surface side of the carriage  10 . The adjustment lever  86  is adapted for manually positioning the recording head  15  provided in the lower part of the carriage  10  in a lateral direction (direction penetrating the paper surface of  FIG. 13 ) and, as an example, adjustment positions of five stages are provided. In addition, as shown in  FIG. 10 , two row nozzle arrays  15 A and  15 B for injecting ink from an ink tank to a sheet side by an operation of a piezoelectric element or the like are provided in the recording head  15  in the lower part of the carriage  10 . The ink tank is independent for each of four colors of black, cyan, yellow, and magenta, of which black and cyan are injected through one nozzle array  15 A and yellow and magenta are injected through the other nozzle array  15 B. That is, in the nozzle array  15 A, nozzles Bk for black and nozzles C for cyan are positioned in zigzag in two rows as a pair along a conveying direction of a sheet and, in the nozzle array  15 B, nozzles Y for yellow and nozzles M for magenta are positioned in zigzag in two rows as a pair along the conveying direction of a sheet in the same manner. 
     FIG. 11  is an explanatory view for explaining an arrangement form of the nozzle arrays. As shown in  FIGS. 10 and 11 , for example, a pitch T of the nozzles Bk for black is approximately 1/75 inches, and an interval t along a vertical direction between the nozzles Bk for black and the nozzles C for cyan adjacent to each other is set to 1/150 inches. That is, the nozzles Bk for black and the nozzles C for cyan adjacent to each other are shifted by a half of the nozzle pitch T in a row direction, thereby being positioned in zigzag. The same is true on other nozzles. In addition, a total number of nozzles Bk, C, Y, and M is set to, for example, seventy-five. Consequently, a large printing width in one movement of the carriage  10  is secured, which contributes to speeding-up of printing significantly. 
   Reciprocating Movement of the Carriage 
     FIGS. 3A ,  3 B, and  4  are explanatory views for explaining movement of the carriage  10 . In  FIGS. 4A and 4B , the carriage  10  moves in a reciprocating movement portion following a print operation. This reciprocating movement portion is divided into a printing area in which the printing operation is performed by the recording head  15  while the carriage  10  is moving at a constant speed (constant speed portion L; L 1  and L 3  in  FIG. 3 ) and acceleration and deceleration portions ΔL on both sides of the printing area in which the carriage  10  decelerates from a constant speed state and starts to accelerating in the opposite direction in order to reverse. In addition, in feeding and discharging sheets, sheets P are continuously conveyed. And, at this time, print surfaces of the sheets P are soiled if the sheets P are brought into contact with the nozzle portion of the recording head  15 . Therefore, a position to which the carriage  10  is retracted at the time of sheet feed and sheet discharge (retract position at the time of sheet feed and sheet discharge) is set outside the reciprocating movement portion. In addition, outside the reciprocating movement portion, there are also set an ink empty sensor position for detecting a remaining amount of ink with a not-shown sensor, a flushing position for removing stains on the head with a flushing portion  29  to be described later, a head protection position (home position) for putting a rubber cap  28  on the head to protect it at non-operation time with a purge device  28  to be described later and where a purge operation can be performed, a small gap switching position for switching to a gap with a shorter distance between a sheet and the surface of the recording head  15 , a large gap switching position for switching to a gap with a longer distance between a sheet and the surface of the recording head  15 . Note that boundaries among the positions or the portions are determined with a nozzle position as a reference. 
   In  FIGS. 3A and 3B , a maintenance portion  27  is provided in the vicinity of a movement end of the carriage  10  outside the recording area, for example, on the right side of the platen  25 . In this maintenance portion  27 , there are positioned a nozzle wiping device (wiper device) for wiping ink drops adhered to a surface (face) of the nozzle portion  15   a  of the recording head  15  and a purge device (nozzle suction device)  28  for restoring stop of discharge or discharge failure of ink in the recording head  15 . In this purge device  28 , the nozzle portion in the recording head  15  is covered by a suction cap  28   a , and recording failure is removed by sucking inferior ink in the recording head  15  with a negative pressure generated by a not-shown pump. Note that the purge device  28  in the maintenance portion  27  also serves as a cap mechanism (protection device) which is in a home position at the movement end of the carriage  10  and covers all the nozzles  15   a  of the recording head  15  of the carriage  10  to prevent drying of ink. The suction cap  28   a  made from rubber also carries out a function of a protection cap. In addition, on the left end of the platen  25 , there is provided the flushing portion  29  for experimentally discharging ink from the respective nozzle portions  15   a  of the recording head  15  to eliminate ink clogging. 
   L 1  represents a recordable (printable) range of a plain paper, on which characters or the like can be printed on plain paper. Note that a range of L 2  including the recordable (printable) range L 1  therein is a range of carriage return in the case of printing on plain paper and is located on the left side of the large gap switching position. In other words, the large gap switching position is in a position on the right side of the right end position of L 2 , And, the home position (capping position) is in a position on the further right side of the large gap switching position. On the other hand, the flushing position is at least in a position on the left side of the left end position of the recordable range L 1 , and the small gap switching position is in a position on the left side of the flushing position and on the left side of the left end position of L 2 . In addition, L 3  represents a recordable range where printing is performed on a thick medium such as an envelope, which is narrower than the recordable range L 1  for plain paper and is set on the inner side of L 1 . For printing, the carriage  10  is constituted to be reciprocatingly movable in a range of L 4  made by adding the acceleration and deceleration portions (ΔL) to both left and right sides of L 3 , respectively. 
   Gap Adjustment Mechanism 
   An adjustment mechanism  30  of a gap between the face of the recording head  15  and the sheet P will be described based on  FIGS. 3 to 23B . A gap switching mechanism  14  for automatically switching the gap between the nozzle portion of the recording head  15  and the sheet P is provided in the carriage  10 . In addition, projected portions (pushing pieces)  57  and  56  for abutting against the gap switching mechanism  14  due to the movement of the carriage  10  and causing this gap switching mechanism  14  to operate automatically are provided in a guide frame  12 . For example, when the gap switching mechanism  14  abuts against one projected portion  57  to operate, the carriage  10  is brought into a posture slightly risen around a guide shaft  11 , and the gap between the recording head  15  and the sheet P increases. On the other hand, when the gap switching mechanism  14  abuts against another projected portion  56  to operate, the nozzle surface of the recording head  15  is kept substantially horizontally, and the gap between the recording head  15  and the sheet P decreases. Such switching of a gap is performed for securing a gap between an object of printing and the recording head  15  to some extent while reducing it as much as possible according to the case in which printing is performed on an envelope or the like which is relatively thick, or the case in which printing is performed on plain paper which is thin. Therefore, the above-mentioned gap switching position for causing the gap switching mechanism  14  to abut against the projected portion  57  and  56  to switch a gap is set on the outer side of the retract position at the sheet feeding/sheet discharging time outside the reciprocating movement portion. 
   A bracket portion  40  facing rearward and downward is integrally formed on the upper end side of the rear plate  31  in the carriage  10  via a pair of left and right bracket coupling portions  40   a . A switching block member  13  made of synthetic resin to be pivotably mounted on the bracket portion  40  is formed in a fan shape viewed from the front (viewed from the back) as shown in  FIG. 17A  which is a back view and  FIG. 17B  which is a front view. A backward pivotal shaft  50  on the upper end is pivotably fitted in a support hole  41  ( FIG. 5 ) drilled in the bracket portion  40 . A spring lower attachment portion  51  provided backward so as to protrude in the central part at the lower end of the switching block member  13  and a spring upper attachment portion  42  provided backward so as to protrude at the upper end of the bracket portion  40  are coupled by a switching coil spring  43  serving as biasing means for switching the switching block member  13  into a lateral pivot posture and keeping the posture (see  FIGS. 5 ,  6 ,  18 A to  20 B,  21 A to  23 B). Note that when the switching block member  13  takes a posture pivoted left or right largely, a fan-shaped end face of the switching block member  13  abuts against a lower surface of one of the left and right bracket coupling portions  40   a  ( 40   a ) so that the switching block body  13  is regulated so as not to pivot exceeding an angle defined above. 
   On the front surface side of the switching block member  13 , as shown in  FIGS. 17B to 17D , a first abutment portion  52  and a second abutment portion  53 , which selectively abut against a slide contact portion  12   a  on the upper end side on the back of the frame  12  at different heights, are continuously provided via an inclined guide surface  54 . The first abutment portion  52 , the second abutment portion  53 , and the inclined guide surface  54  are set so as to have substantially equal radial diameter from a central axis of the pivotal shaft  50 . A height H 1  from the surface of the switching block member  13  is set larger for the first abutment portion  52 , and a height H 2  of the second abutment portion  53  is set to be smaller. In addition, on the surface of the switching block member  13 , a switching abutment portion  55  is integrally provided facing forward so as to protrude toward a position having a radial distance from the central axis of the pivotal shaft  50  which is shorter than those of the respective abutment portions  52  and  53 . 
   On the other hand, the frame  12  has a horizontal rail portion  12   b  which is bent forward at a position higher than the slide contact portion  12   a . A first pushing piece  56 , which is cut and raised in a substantially vertical direction and serves as first pushing means for switching and guiding the lateral pivot posture of the switching block member  13 , is provided in the vicinity of a left end of the horizontal rail portion  12   b  (left side of the flushing portion  29 ). A second pushing piece  57  having a chevron shape (reverse V shape) viewed from the front is provided as second pushing means in the vicinity of a right end of the horizontal rail portion  12   b  (in substantially a center in the lateral direction of the maintenance portion  27 ) (see  FIGS. 3 ,  18 A to  20 B, and  21 A to  23 B). 
   Next, the case in which printing is performed on plain paper by the printer apparatus  1  will be described. The carriage  10  located in the home position (cap position)  28  of  FIG. 3A  moves in a direction of arrow A of  FIG. 5B  when a print instruction is issued. A test of ink discharge in the nozzle portions  15   a  is executed in the flushing portion  29  (this flushing may be performed after a pushing operation to be discussed later as long as it is performed at least before starting printing). After that, when the carriage  10  (switching block member  13 ) further moves in a left direction (direction of arrow A) in  FIG. 3B . A side of the switching abutment portion  55  collides with a right surface of the first pushing piece  56  which extends a substantially vertically. And then, the switching block member  13  pivots in a counterclockwise direction viewed from the front as shown in  FIGS. 18A and 19A . 
   In this case, in  FIG. 18A , a central axial line of the switching coil spring  43  is located on a left side of the center of the pivotal shaft  50  which is the pivotal center of the switching block member  13 . The posture of the switching block member  13  is held such that its left side faces upward, and the first abutment portion  52  having a larger height is in slide contact with the slide contact portion  12   a . In a state of  FIG. 19A , a central axial line  43 A of the switching coil spring  43  (line connecting the spring upper attachment portion  42  and the spring lower attachment portion  51 ) is brought close to the center of the pivotal shaft  50 , which is the pivotal center of the switching block member  13 , form its left side. And the inclined guide surface  54  pivots while being in slide contact with the slide contact portion  12   a . When the inclined guide surface  54  further moves to the right, it crosses a so-called dead center, whereby the switching block member  13  pivots in the counterclockwise direction to a state of  FIG. 20A  such that its right side faces upward. Consequently, the switching block member  13  is changed to a posture in which the first abutment portion  52  shifts in the upward direction from the slide contact portion  12   a  and, on the other hand, the second abutment portion  53  with a smaller height is in slide contact with the slide contact portion  12   a . In this state, as shown in  FIG. 5 , since the guide shaft  11  of a round shaft shape is offset to the left side of a center of gravity position of the carriage  10 , and the carriage  10  is pivotable in the clockwise direction around the guide shaft  11  due to its own weight. Thus, the carriage  10  pivots such that the second abutment portion  53  with a smaller height on the front surface of the switching block member  13  on the upper side of the carriage  10  is brought close to the back of the frame  12  extending vertically. Therefore, the face, which is the lower surface of the nozzle portions  15   a  of the recording head  15  in the carriage  10 , is brought close to the upper surface of the platen  25 , and its posture is changed to a state in which a gap G 1  becomes small. Note that the switching block member  13 , in which the side of the switching abutment portion  55  has collided with the right surface of the first pushing piece  56  extending substantially vertically, as well as the carriage  10 , become unable to further move in the left direction. 
   Subsequently, the carriage  10  is moved in a right direction (direction of arrow B) of  FIG. 3A , and characters can be printed on plain paper within the recordable (printable) range of L 1 . Note that, the range of L 2  including the recordable (printable) range L 1  corresponds to a range of carriage return in the case of performing printing on plain paper, which is on a left side of a position for switching to a larger gap to be described later. 
   That is, in the case of performing printing on plain paper, it is necessary to move the carriage  10  in the range of L 2  made by adding the acceleration and deceleration portions (ΔL) to both left and right sides of the recordable range L 1  for plain paper, respectively. However, even when the carriage  10  moves to a right end position of L 2 , a gap is still kept small (the switching abutment portion  55  does not abut against the second pushing piece  57  of a chevron shape). 
   Therefore, a pushing operation by the second pushing piece  57  for increasing the gap is performed in a position on the further right side of the right end position of L 2 . Furthermore, the home position (capping position)  28  is in a position on the right side of the position where the pushing operation is performed. On the other hand, a flushing position is at least on the left side of the left end position of the recordable range L 1 . The pushing operation by the first pushing piece  56  for reducing the gap is set to be performed in a position on the further left side of the flushing position and on the left side of the left end position of L 2 . Thus, at least while the carriage  10  reciprocatingly moves within the range of L 2 , printing on plain paper is performed with the gap kept small. In addition, during the printing, for example, even when flushing is performed for every fixed time, the flushing operation is performed with the gap kept small. 
   In the case of performing printing on a thick envelope, unless the gap is increased, the envelope moving in a sheet conveying path is brought into contact with the nozzle portions  15   a  to soil a surface of the envelope with ink. Thus, the gap is adjusted to be wider (see  FIGS. 19A to 23B ). In this case, for example, when the previous print operation is the printing on plain paper, the carriage  10  is first moved in the right direction (direction of arrow B) of  FIG. 3A  in an attempt to retract the carriage  10  toward the home position (cap position)  28  after the printing ends. The switching block member  13  held with the gap for plain paper is held in a posture with its right side facing upward as in  FIG. 20A  by a biasing force of the switching coil spring  43  until the switching abutment portion  55  passes over the second pushing piece  57  of a chevron shape ( FIG. 21A ). As shown in  FIG. 22A , as the switching abutment portion  55  passes over the upper end of the second pushing piece  57  at the time of movement of the carriage  10  to the right, the switching block member  13  pivots in the clockwise direction, and the first abutment portion  52  with a larger height is moved to be in slide contact with the slide portion  12   a  of the frame  12  via the inclined guide surface  54 . At this point, when the central line of the switching coil sprint  43  connecting the spring upper attachment portion  42  and the spring lower attachment portion  51  shifts to the left side of the central line  43 A of the pivotal shaft  50  to cross the dead center, the switching block member  13  promptly changes its posture such that its left side comes to an upper position, and the posture thereof is kept by a biasing force of the switching coil spring  43  (see  FIG. 23A ). 
   Therefore, since the first abutment portion  52  with a larger height on the front surface of the switching block member  13  on the upper side of the carriage  10  slides to the slide portion  12   a  on the back of the frame  12  extending vertically, the lower surface side of the carriage  10  is raised and caused to pivot upward about the guiding axis  11  (counterclockwise direction in  FIG. 6 ) and the carriage  10  pivots so as to increase the gap dimension G 1  (see  FIG. 6 ). Therefore, the surface of the envelope does not rub against the nozzle portions  15   a , whereby stains due to adhesion of unnecessary ink can be prevented. 
   That is, in the case of performing printing on an envelope, the recordable range L 3  for the envelope is narrower than the recordable range L 1  for plain paper and is set on the inner side of L 1 . Thus, when the carriage  10  is moved in the range of L 4  made by adding the acceleration and deceleration portions (ΔL) to both left and right sides of L 3 , respectively, even when the carriage  10  has moved to the left end position of L 4 , and, moreover, when the carriage  10  has moved to the flushing position, the gap is still kept large (the switching abutment portion  55  does not collide with the first pushing piece  56  standing substantially vertically). 
   Therefore, printing on the envelope is performed with the gap kept large at least while the carriage  10  reciprocatingly moves within the range of L 4 . In addition, during the printing, for example, even when flushing is performed for every fixed time, the flushing operation is performed with the gap kept large. Consequently, when the flushing is performed, it is unnecessary to idly move the carriage  10  to a position, where the switching abutment portion  55  abuts against the second pushing piece  57  of a chevron shape, each time the flushing is performed. Thus, a printing operation on the envelope can be carried out promptly. 
   Note that, when the carriage  10  moves to the home position  28 , for example, even in a state in which the gap is switched to be small, since the gap dimension G 1  is switched to be large in a position before the home position, the respective caps  28   a  are reliably capped keeping a predetermined correspondence relationship with respect to the nozzle portions  15   a  at the time of movement of the carriage  10  to the home position  28 . In addition, a replacement position of the ink cartridge is set to a right side of a pushing position where the gap is switched to be small (position where the switching abutment portion  55  collides with the first pushing piece  56  extending substantially vertically), whereby an interference state can be prevented in which ink drops leaked to the outside from the nozzle portions  15   a  at the time of replacing the ink cartridge are rubbed against a wall of the maintenance portion  27 . 
   Note that, as shown in  FIG. 17A , a horn-like elastic projection  58  for buffering is provided on one end face (right end face) of the fan-shaped portion of the switching block member  13 . Consequently, when the switching abutment portion  55  passes over the upper end of the second pushing piece  57  at the time of movement of the carriage  10  to the right, the gap dimension G 1  as defined cannot be set if pivotal displacement of the switching block member  13  in the clockwise direction is insufficient. Therefore, the elastic projection  58  is abutted against a regulating piece (not shown) provided in the frame  12  when the carriage  10  is moved to the home position  28 , whereby a pivotal posture of the switching block member  13  is ensured. 
   Moreover, in a state in which the carriage  10  is retracted to the home position  28 , when the carriage  10  is subjected to an impulsive load causing the carriage  10  to move further in the right direction, for example, when the product is dropped by mistake when it is transported, intense collision of the carriage  10  against the regulating piece provided in the frame  12  can be eased by the projection  58 , and damages to the switching block member  13  can be prevented. 
   Circuit Configuration and a Series of Operations 
   The printer apparatus  1  as described above is provided with a usual function for, according to various instructions from an operation to be inputted in response to various key operations in the operation panel portion  6 , executing setting of various processing operations, reading of an original image with the original reading unit  5 , conversion of the original image into transmission data, conversion of the transmission data into a code, transmission and reception of facsimile data to be transmitted to another facsimile apparatus via communication network such as telephone lines, decoding of received data, and recording of the decoded facsimile data on a sheet P with a recording unit. In addition to this function, the printer apparatus  1  is also provided with a copy processing function for reading an original with a contact image sensor (CIS) of the original recording unit  5  and forming a color image on the sheet P with each unit of the recording portion, a printer processing function for receiving print data transmitted via a printer cable or wireless means such as infrared rays from an external apparatus such as a not-shown personal computer (host computer) and forming a color image on the sheet P according to the data, and a scanner processing function for transmitting image data read with the original reading unit  5  to the external apparatus. 
     FIG. 24  is a block diagram showing a circuit structure of a facsimile apparatus A. As shown in this figure, the multifunction facsimile/printer apparatus is generally provided with a CPU  230 , an NCU  231 , a RAM  23 , a modem  233 , a ROM  234 , an NVRAM (Non-Volatile RAM)  235 , a gate array  236 , a codec  237 , and a DMAC  238  other than the above-described original reading unit  5 , the recording portion  2 , the operation portion  6   a , and the display portion  6   b . The CPU  230 , the NCU  231 , the RAM  232 , the modem  233 , the ROM  234 , the NVRAM  235 , the gate array  236 , the codec  237 , and the DMAC  238  are connected with each other by a bus line  247 . An address bus, a data bus, and a control signal line are included in the bus line  247 . The reading portion  5 , the recording portion  2 , the operation portion  6   a , and the display portion  6   b  are connected to the gate array  236 . A public telephone line  248  is connected to the NCU  231 . 
   The CPU  230  controls whole operations of the printer apparatus. The NCU  231  is connected to the public telephone lines to perform network control. The RAM  232  provides a work area for the CPU  230  and a development area of print data. The modem  233  performs modulation and demodulation of facsimile data. The ROM  234  has stored therein a program which the CPU  230  should execute. The NVRAM  235  stores data and various kinds of information. The gate array  236  functions as an interface between the CPU  230  and the recording portion  2 , the reading portion  5 , the operation portion  6   a , and the display portion  6   b . The codec  237  performs coding and decoding of data. The DMAC  238  mainly writes data in and reads it out from the RAM  232 . The reading portion  5  reads an image from an original or the like according to control of the CPU  230 . The recording portion  2  performs aforementioned various operations according to control of the CPU  230 . In addition, according to an operation of the operation portion  6   a , an input signal from a user is transmitted to the CPU  230  and different kinds of information is displayed on the display portion  6   b.    
   The CPU  230  realizes: reciprocating movement means which makes the carriage  10  repeatedly and reciprocatingly movable by accelerating the carriage  10  in one direction to bring it into a constant speed state, decelerating the carriage after making it undergo the constant speed state for a short time, and decelerating the carriage after accelerating it in the opposite direction to bring it into the constant speed state again; first determining means which, in stopping in a predetermined position the carriage  10  reciprocatingly moved by the reciprocating movement means, determines that the carriage is stopped when it is decelerated to a speed equal to or lower than a first speed; and second determining means which, when the carriage  10  is reciprocatingly moved by the reciprocating movement means to perform printing, determines that the carriage is stopped when decelerated to a speed equal to or lower than a second speed higher than the first speed. 
   The CPU  230  further realizes: reciprocating movement means which, when discharge of a sheet is performed, retracts the carriage  10  to the outside of a reciprocating movement portion of the carriage  10 ; and carriage movement control means which brings the carriage  10  into the constant speed state with the reciprocating movement means according to the print command when it receives a sheet discharge command indicating that discharge of a sheet is to be performed together with a paper feed command indicating that feeding of a sheet is to be performed without any other print command following a print command indicating that printing is to be performed by the recording head mounted on the carriage  10 . The carriage movement control means retracts the carriage  10  to the outside of the reciprocating movement portion continuously with the reciprocating movement means according to the sheet discharge command immediately after the printing ends. 
   The CPU  230  further realizes: reciprocating movement means which moves the carriage  10  to a gap switching position located outside a reciprocating movement portion of the carriage  10 ; and carriage movement control means which moves the carriage  10  to the gap switching position during feeding of a sheet P. 
   On the other hand, there is a computer program, which is stored in the ROM  234 , for executing control for reciprocatingly moving a carriage  10  substantially perpendicular to a feeding direction of a sheet to apply printing to the sheet with a recording head  15  mounted on the carriage  10 . The computer program includes: a reciprocating movement program for accelerating the carriage  10  in one direction to bring it into a constant speed state, decelerating the carriage after making it undergo the constant speed state for a short time, and decelerating the carriage after accelerating it in the opposite direction to bring it into the constant speed state again, thereby making the carriage repeatedly and reciprocatingly movable; a first determination program for, in stopping the carriage reciprocatingly moved based upon the reciprocating movement program, determining that the carriage is stopped when decelerated to a speed equal to or lower than a first speed; and a second determination program for, when the carriage is reciprocatingly moved based upon the reciprocating movement program to perform printing, determining that the carriage is stopped when decelerated to a speed equal to or lower than a second speed higher than the first speed. 
   Further, there is a computer program, which is stored in the ROM  234 , for controlling, when the carriage  10  reverses for reciprocating movement, feeding of a sheet P in association therewith. The computer program includes: a reciprocating movement program for accelerating the carriage  10  in one direction to bring it into a constant speed state, decelerating the carriage  10  after making it undergo the constant speed state for a short time, and decelerating the carriage  10  after accelerating it in the opposite direction to bring it into the constant speed state again, thereby repeatedly reversing the carriage  10  to move it reciprocatingly, and on the other hand, when discharge of a sheet P is performed, retracting the carriage  10  to the outside of a reciprocating movement portion of the carriage  10 ; and a carriage movement control program for, when a sheet discharge command to the effect that discharge of the sheet P is to be performed is received together with a paper feed command to the effect that feeding of the sheet P is to be performed without any other print command following a print command to the effect that printing is to be performed by the recording head  21  mounted on the carriage  10 , bringing the carriage  10  into the constant speed state based upon the reciprocating movement program according the print command, and on the other hand, immediately after the printing ends, retracting the carriage  10  to the outside of the reciprocating movement portion continuously based upon the reciprocating movement program according to the sheet discharge command. 
   Further, there is a computer program, which is stored in the ROM  234 , for executing control for automatically switching a gap between the sheet P and the recording head  15 . The computer program includes: a reciprocating movement program for accelerating the carriage  10  in one direction to bring it into a constant speed state, decelerating the carriage  10  after making it undergo the constant speed state for a short time, and decelerating the carriage  10  after accelerating it in the opposite direction to bring it into the constant speed state again, thereby repeatedly reversing the carriage  10  to move it reciprocatingly, and on the other hand, moving the carriage  10  to a switching position of the gap located outside a reciprocating movement portion of the carriage  10 ; and a carriage movement control program for moving the carriage  10  to the switching position of the gap based upon the reciprocating movement program during feeding of the sheet P. 
   Next, operations will be described based upon  FIGS. 25 and 26 . Note that, In  FIG. 26 , processing concerning operations of the carriage  10  is indicated by solid lines and processing concerning movements of the sheet P is indicated by broken lines. 
   In starting print processing, first, the CPU  230  causes the carriage  10  to move from the head protection position to the retract position at sheet feeding time (S 1 ). 
   In addition, during the movement of the carriage  10 , the CPU  230  starts sheet feed (S 2 ). Consequently, the sheet P is fed into the inside via the sheet supply roller  21 . 
   Simultaneously with feeding the sheet P in this way, the CPU  230  monitors the movement of the carriage  10  according to whether or not an output interval of encoder signals from the linear encoder  82  has exceeded, for example, 100 ms (S 3 ). 
   When it is determined that the output interval of encoder signals has exceeded 100 ms and the carriage  10  has stopped (S 3 : YES), the CPU  230  causes the carriage  10  to move to the flushing position in order to perform flushing of ink (S 4 ). Then, when it is determined that the output interval of encoder signals has exceeded 100 ms and the carriage  10  has stopped (S 5 : YES), the CPU  230  issues an instruction for performing a flushing operation (S 6 ). Thereafter, if the apparatus is not set in a print mode for thick paper for printing on an envelope or the like (S 7 : NO), the CPU  230  causes the carriage  10  to move to the gap switching position (S 8 ). Note that, such a switching operation of a gap is performed by the time when the sheet P being conveyed reaches the registration roller  22  such that the recording head  15  of the moving carriage  10  is not brought into contact with the sheet P. Note that, although the operation of S 8  is effective when printing is performed on plain paper with the printer apparatus set in the thick paper mode at first, the carriage  10  is kept in a state in which it is stopped in the retract position at sheet feeding time when it is unnecessary to switch a gap. 
   Thereafter, when the CPU  230  determines that the output interval of encoder signals has exceeded 100 ms and the carriage  10  has stopped (S 9 : YES), and detects a leading edge position of the sheet P by the sheet sensor  80 , and the leading edge of the sheet P is then sent out from the registration roller  22  by a predetermined amount, and the CPU  230  ends the sheet feed accordingly (S 10 ). 
   Then, after controlling the DC motor to accelerate the carriage  10  to a certain speed, the CPU  230  causes the carriage  10  to move at a constant speed along one direction (forward path). The CPU  230  controls the recording head  15  while the carriage  10  is moving at the constant speed, so that printing is performed (S 11 ). That is, while the carriage  10  is moving on the sheet P at the constant speed, ink is injected from the nozzle arrays  15 A and  15 B of the recording head  15  and deposits on the sheet P with a fixed width, so that printing is performed. 
   When the printing in one direction is finished, the CPU  230  controls the DC motor to decelerate the carriage  10  (S 13 ) while performing feeding of the sheet P (S 12 ). 
   Moreover, during the deceleration of the carriage  10 , the CPU  230  monitors whether or not the output interval of encoder signals from the linear encoder  82  has exceeded, for example, 5 ms (S 14 ). 
   When the output interval of encoder signals has exceeded 5 ms (S 14 : YES), the CPU  230  determines that the carriage  10  has stopped and executes printing of the next line when the feeding of the sheet P ends. Note that, considering the determination time in the order of 5 ms, the carriage  10  cannot be in a completely stopped state but may be slightly moving. In addition, when the feeding of the sheet P ends during the deceleration of the carriage  10 , since the printing of the next line is started immediately, a slight load is applied to the DC motor when the carriage  10  is accelerated in the opposite direction in such a state. However, since the carriage  10  starts to accelerate in the opposite direction in the middle of the predetermined acceleration and deceleration portion, a reverse operation of the carriage  10  is performed promptly. 
   The CPU  230 , which controls two-way printing as described above, is constituted so as to perform the two-way printing for each print command while sequentially receiving print commands and storing them. Such a CPU  230  determines whether or not a sheet discharge command has been received together with a last print command (S 20 ). Note that, after the last print command, the sheet discharge command may be issued for processing subsequent to a paper feed command. 
   When the sheet discharge command has been received together with the last print command (S 20 : YES), after accelerating the carriage  10  to a certain speed according to the last print command, the CPU  230  performs printing of a last line by controlling the recording head  15  while the carriage  10  is moving at the constant speed (S 21 ). 
   Thereafter, upon finishing the printing of the last line, the CPU  230  causes the carriage  10  to move to the retract position at sheet discharge time without stopping the carriage  10  once in the acceleration and deceleration portion according to the sheet discharge command (S 23 ). That is, when the paper feed command is caused to wait for processing before the sheet discharge command, the CPU  230  neglects this paper feed command to cause the carriage  10  to move to the retract position at sheet discharge time immediately after the printing of the last line. When the CPU  230  determines that the output interval of encoder signals has exceeded 100 ms and the carriage  10  has stopped (S 24 : YES), the sheet P is thus discharged promptly without a wasteful feeding operation of the sheet P (S 25 ). 
   Thereafter, the CPU  230  causes the carriage  10  to move to the initial head protection position (S 26 ). When the CPU  230  determines that the output interval of encoder signals has exceeded 100 ms and the carriage  10  has stopped (S 27 : YES), the CPU  230  ends this print processing. 
   When it is determined in S 27  that the output interval of encoder signals has not exceeded 100 ms and the carriage  10  is moving (S 27 : NO), the CPU  230  stands by for the next processing until it determines that the carriage  10  comes into a stopped state. 
   When it is determined in S 24  that the output interval of encoder signals has not exceeded 100 ms and the carriage  10  is moving (S 24 : NO), the CPU  230  stands by for the next processing until it determines that the carriage  10  comes into a stopped state. 
   When the last print command and the sheet discharge command have not been received in S 20  (S 20 : NO), the CPU  230  returns to S 11  to continue the two-way printing. 
   In S 14 , when the carriage  10  is moving in deceleration even in the time interval set to 5 ms during the two-way printing (S 14 : NO), the CPU  230  stands by for execution of the next operation until the carriage  10  comes into the stopped state. 
   When it is determined in S 9  that the output interval of encoder signals has not exceeded 100 ms and the carriage  10  is moving (S 9 : NO), the CPU  30  stands by for the next processing until it determines that the carriage  10  comes into a stopped state. 
   In S 7 , when the printer apparatus is set in the thick paper mode from the beginning and it is unnecessary to switch the mode in S 7  (S 7 : NO), the CPU  230  proceeds to S 10 . 
   When it is determined in S 5  that the output interval of encoder signals has not exceeded 100 ms and the carriage  10  is moving (S 5 : NO), the CPU  230  stands by for the next processing until it determines that the carriage  10  comes into a stopped state. 
   When it is determined in S 3  that the output interval of encoder signals has not exceeded 100 ms and the carriage  10  is moving (S 3 : NO), the CPU  230  stands by for the next processing until it determines that the carriage  10  comes into a stopped state. 
   Therefore, according to the multifunction facsimile and printer apparatus which is provided with the above-mentioned ink jet printer, a reference for determination for stopping the carriage  10  in the head protection position, the retract position, or the gap switching position (in the above-mentioned example, the time interval of 100 ms during which the movement of the carriage  10  is detected based upon the encoder signals) and a reference for determining that the carriage  10  is in the stopped state when the carriage  10  in the middle of printing is reversed (in the above-mentioned example, the time interval of 5 ms during which the movement of the carriage  10  is detected based upon the encoder signals) are different therebetween. That is, when printing is performed, determination on stop as timing for reversing the carriage  10  is set earlier than timing in causing the carriage  10  to move to each predetermined position to stop there. Consequently, time required for the entire reciprocating movement of the carriage  10  at the printing time is reduced and speeding-up can be realized easily. 
   In addition, prior to the discharge of the sheet P according to the sheet discharge command, feeding of the sheet P is never performed even if there is the paper feed command received immediately before receiving the sheet discharge command, and the carriage  10  moves to the retract position at sheet discharge time immediately after the last printing. Thus, the sheet discharge can be performed promptly following the print operation according to the last print command and speeding-up can be realized easily. 
   Moreover, simultaneously with the feeding of the sheet P, the carriage  10  moves to the gap switching position, whereby the gap is automatically switched. Thus, sheet feed is not delayed due to switching of the gap, and speeding-up can be realized easily. 
   Second Embodiment Concerning the Gap Adjustment Mechanism 
   The gap dimension G 1  is switched to two types, a small one and a large one in the above-mentioned first embodiment, switching to three types if gaps can be executed in a gap adjustment mechanism  30   a  according to this embodiment. As shown in  FIGS. 27A and 27B , three states with different heights of abutment portions  59   a ,  59   b , and  59   c  provided on the surface of the switching block member  13  laterally pivotable are set. Next, the lowest first abutment portion  59   a  and the second highest second abutment portion  59   b  are connected by a first inclined guide surface  60   a . The highest third abutment portion  59   c  is set so as to have a second inclined guide surface  60   b  which is in a position parallel with the second highest abutment portion  59   b . Two pushing pieces  61   a  and  61   b  of a chevron shape with different heights are provided to be apart from each other appropriately in a moving direction of a carriage on an upper surface of the horizontal rail portion  12   b  of the frame  12 . The higher pushing piece  61   b  is positioned on a side closer to a movement terminal of the carriage  10 . 
   In that case, only the second highest abutment portion  59   b  abuts against the slide contact portion  12   a  of the frame  12  when the switching abutment portion  55  is selected to be in a state in which it has passed over the lower pushing piece  61   a  but has not passed over the higher pushing piece  61   b . Only the highest third abutment portion  59   c  abuts against the slide contact portion  12   a  of the frame  12  when the switching abutment portion  55  passes over the higher pushing piece  61   b . Accordingly, the carriage  10  pivots around the guide shaft  11  and the cap dimension G 1  can be switched to one of three types of small, medium, and large. 
   Third Embodiment Concerning the Gap Adjustment Mechanism 
   In the gap adjustment mechanisms  30  and  30   a  according to the first and second embodiments, the abutment portions with different heights of the switching block member  13  are switched to perform size adjustment of the gap by utilizing the first pushing piece  56  and the second pushing piece  57  provided in the frame  12 , respectively, according to the reciprocating lateral movement of the carriage  10 . The third embodiment relates to a gap adjustment mechanism which is capable of increasing accuracy of gap formation while further miniaturizing and simplifying a structure for adjustment of the gap. 
   An upper perspective view of a carriage  10   b  in accordance with this embodiment is shown in  FIG. 28 . Since a structure of the carriage  10   b  is substantially the same as that of the carriage  10  of the first embodiment except the gap adjustment mechanism  30  of the first embodiment, detailed descriptions of the structure will be omitted. A gap adjustment mechanism  30   b  provided at a rear end on an upper surface of the carriage  10   b  of this embodiment will be mainly described with reference to  FIGS. 28 to 33 . 
   As shown in  FIG. 28 , a first abutment portion  101 , which has a first abutment surface  100  ( FIG. 29B ) to be in slide contact with the a vertical rail portion  12   c  of the frame  12 , is adhered to substantially a central part of the rear end on the upper surface of the carriage  10   b . Moreover, a pressing plate  121  ( FIG. 29A ) of an actuator portion  102  is screwed to the rear end on the upper surface of the carriage  10   b  so as to cover the first abutment portion  101  from above. The actuator portion  102  is provided with a switching lever  103  in which a first projected portion  104  and a second projected portion  105  (not shown) are formed at respective ends in a longitudinal direction, a metal pressing plate  121  carrying out a function as a frame of the actuator portion  102 , and two second abutment portions  109  and  111  which project and retract in connection with a longitudinal movement of the switching lever  103  about shafts fixed to the pressing plate  121  as pivotally supporting shafts  107  and  108  ( FIG. 29A ). 
   Next, details of the actuator portion  102  will be described based upon  FIGS. 29A to 29C  and  FIGS. 30A to 30C .  FIG. 29A  is a rear view of the actuator portion  102  showing a state in which the second abutment portions  109  and  111  are received.  FIG. 29B  is a plan sectional view of the actuator portion  102 .  FIG. 29C  is a front view of the actuator portion  102 . The second abutment portions  109  and  111  are fittingly inserted pivotably in the actuator portion  102  with the first pin  107  and the second pin  108  vertically provided on the pressing plate  121  as pivotally supporting shafts, respectively. The second abutment portions  109  and  111  are coupled to one ends of coupling arms  112  and  114 , respectively. The other ends of the coupling arms  112  and  114  are respectively inserted in a third pin  110   a  and a fourth pin  110   b , which are formed on upper and lower end faces of the switching lever  103 . A first projected portion  104  and a second projected portion  105  which, when the switching lever  103  is pushed by pushing means to be described later, abuts against the pushing means are formed at both ends in the longitudinal direction of the switching lever  103 . In addition, the pressing plate  121  has a spring retainer  119  which is bent vertically downward in a central part of a back of the pressing plate  121 . The pressing plate  121  presses a leaf spring  118  inserted in a recessed portion  120  on an upper part of a back of the switching lever  103 . Thus, the switching lever  103  becomes reciprocatingly movable in the lateral longitudinal direction, so that a first stopping projected portion  115  or a second stopping projected portion  116  formed on the lower end face of the switching lever  103  collides with a stopper  117  formed on the upper surface of the carriage. Therefore, the movement of the switching lever  103  is reliably stopped and a posture of the switching lever  103  is held by a force of the leaf spring  118 . 
   When the pushing means pushing down the second projected portion  105  moves the switching lever  103  in a C direction shown in the figure ( FIG. 29B ), the other ends of the coupling arms  112  and  114  are pulled in the C direction in association with the switching lever  103 . At the same time, the second abutment portions  109  and  111  coupled to one ends of the coupling arms  112  and  114 , respectively, rotate counterclockwise (see  FIG. 29B ) about the first pin  107  and the second pin  108  as pivotally supporting shafts for the respective abutment portions. When the pushing means pushes the switching lever  103  to a certain predetermined position, a force rotating the second abutment portions  109  and  111  in the same rotating direction is generated by a force of the leaf spring  118  pushing the spring retainer  119 . Thus, even if the switching lever  103  is not pushed by the pushing means, the second abutment portions  109  and  111  rotate to a position where the second stopping projected portion  116  abuts against the stopper  117 . Furthermore, the posture of the switching lever  103  is held by the force of the spring retainer  119  pushing the leaf spring  118 , so that postures of the second abutment portions  109  and  111  are also held in a position shown in  FIG. 30B . 
   On the other hand, when the pushing means pushing down the first projected portion  104  moves the switching lever  103  in a D direction shown in  FIG. 30A , the other ends of the coupling arms  112  and  114  are pulled in the D direction in association with the switching lever  103 . At the same time, the second abutment portions  109  and  111  coupled to one ends of the coupling arms  112  and  114 , respectively, rotate clockwise (see  FIG. 30B ) about the first pin  107  and the second pin  108  as pivotally supporting shafts for the respective abutment portions. When the pushing means pushes the switching lever  103  to a certain predetermined position, a force rotating the second abutment portions  109  and  111  in the same rotating direction is generated by a force of the leaf spring  118  pushing the spring retainer  119 . Thus, even if the switching lever  103  is not pushed by the pushing means any more, the second abutment portions  109  and  111  rotate to a position where the first stopping projected portion  115  abuts against the stopper  117 . Thereafter, the posture of the switching lever  103  is held by the force of the spring retainer  119  pushing the leaf spring  118 , so that postures of the second abutment portions  109  and  111  are also held in a position shown in  FIG. 29B . 
   In addition, the first abutment portion  101  having the first abutment surface  100  shown in  FIGS. 29B and 30B  is adhered and fixed to the upper surface of the carriage. A height from an axial line of the first pin  107  or the second pin  108  which is parallel with a moving direction of the switching lever  103  to the first abutment surface  100  is set to T 2 . In this case, a relationship of T 2  with respective heights T 1  and T 3  at the time when the second abutment portions  109  and  111  retract or project is T 1 &lt;T 2 &lt;T 3 . That is, the height T 3  is projected most in a front direction in the figure, next T 2 , and then T 1 . 
   Subsequently, an action of gap adjustment according to cooperation of the gap adjustment mechanism  30   b , which is composed of the first abutment portion  101  and the actuator portion  102 , and the frame  12  will be described.  FIG. 31  is a side sectional view of a recording portion in a state in which the gap G 1  is small. An upper part of the frame  12  provided vertically on the back (left side in the figure) of the carriage  10   b  is bent in two portions. A vertical surface of a tip end portion thereof forms a vertical rail portion  12   c , which is opposed to the first abutment portion  101  and the second abutment portions  109  and  111 . In addition, the vertical rail portion  12   c  abuts against the first abutment portion  101  or the second abutment portions  109  and  111 , thereby sliding to guide them with a surface on the opposite side of the ink cartridge  16  as a frame sliding surface  12   d .  FIG. 31  shows a state in which the second abutment portions  109  and  111  of the actuator portion  102  are retracted, having the height of T 1 , that is, the state shown in  FIGS. 29A to 29C . In  FIGS. 29A to 29C , the guide shaft  11  of a round shaft shape offsets to the left side from the position of the center of gravity of the carriage  10   b . The carriage  10   b  is made pivotable in the clockwise direction around the guide shaft  11  due to its own weight. Thus, the first abutment portion  101 , which is adhered and fixed to the carriage upper surface and has the surface at the height T 2  larger than T 1 , abuts against the frame sliding surface  12   d . As a result, the carriage  10   b  is brought into a state in which it pivots at a maximum angle in the clockwise direction about the guide shaft  11 . The face, which is the lower surface of the nozzle portions  15   a  of the recording head  15  in the carriage  10   b , is brought close to the upper surface of the platen  25  so that its posture is held in the state in which the gap dimension G 1  is small. 
     FIG. 32  is a side sectional view of the recording portion in a state in which the gap G 1  is large. In  FIG. 32 , the second abutment portions  109  and  111  of the actuator portion  102  are projecting, and the second abutment portions  109  and  111  having the height T 3  larger than T 2  abut against the frame sliding surface  12   d.    
   That is, since the above state is the same as the state shown in  FIGS. 30A to 30C , the carriage  10   b  pivots in the counterclockwise direction about the guide shaft  11 , and the posture of the face which is the lower surface of the nozzle portions  15   a  of the recording head  15  in the carriage  10   b  is changed to the state in which the gap dimension G 1  is large so as to separate from the upper surface of the platen  25  more than that in  FIG. 31 . 
   Note that, when the guide shaft  11  to be a pivotal center of the carriage  10   b  displaces to the front side (right side in the figure) of the position of the center of gravity of the carriage  10   b  depending upon a structure of the carriage  10   b , it is possible to obtain the same effect even if the first abutment portion  101  and the second abutment portions  109  and  111  are constituted so as to abut against the front surface (right side in the figure) or the upper surface of the frame  12 . Various layouts are possible for positions of the abutment portions and the abutment surface (horizontal rail portion) taking into account a piercing position of the guide shaft with respect to the carriage and the center of gravity of the carriage. 
   As to the printer apparatus according to the above-mentioned structure, an operation for adjusting a gap between the recording head  1  and the upper surface of the platen  25  (which is a surface and a passing route of the sheet P as a recording medium) will be described. For example, when the above-mentioned printer processing function is executed, printer driver software installed in an external apparatus such as a personal computer is started up. Then, a type of a recording medium on which printing (recording) is to be performed (sheet P) is selected. At this time, it is assumed that the gap can be set small if plain paper (e.g., a letter sheet and an A4 sheet) is selected and the gap can be set large if an envelope is selected. 
   First, the case in which printing is performed on plain paper will be described.  FIG. 33A  is a schematic front view showing a state of lateral movements of a carriage with respect to the frame  12 .  FIG. 33B  is a schematic top view showing a positional relationship of a gap adjustment mechanism with respect to the frame  12 . When a print instruction is issued, the carriage  10   b  located in the home position (cap position)  28  of  FIG. 33A  moves in a direction of arrow A and executes a test of ink injection in the nozzle portions  15   a  in the flushing portion  29  (this flushing may be performed before switching of the gap to be described later as long as it is performed at least before start of printing). When the carriage  10   b  further continues movement, a left side plate  12   e  (side frame) of the printer apparatus  1  is located in a substantial terminal end portion of its movement. The left side plate  12   e  pushes the first projected portion  104 , which is formed in the left end in the longitudinal direction of the switching lever  103  of the actuator portion  102  in  FIG. 33B , as first pushing means. Thus, the actuator portion  102  is brought into the state which is described based upon  FIGS. 29A to 29C  and  FIG. 31 , that is, a state in which the second abutment portions  109  and  111  are retracted, and the first abutment portion  101  abuts the frame sliding surface  12   d  to change the gap to be small. 
   Subsequently, the carriage  10   b  is moved in a direction of arrow B, and characters can be printed on plain paper within the recordable (printable) range of L 1 . Note that the range of L 2  including the recordable (printable) range L 1  is a range of carriage return in the case of printing on plain paper and is located on the left side of a position for performing switching to increase a gap to be described later. 
   That is, when printing is performed on plain paper, it is necessary to move the carriage  10   b  in the range of L 2  made by adding the acceleration and deceleration portions (ΔL) to both left and right sides of the recordable range L 1  for plain paper, respectively. However, even when the carriage  10  moves to a right end position of L 2 , a gap is still kept small (the second projected portion  105  of the switching lever  103  does not abut against a right side plate  12   f ). 
   Therefore, a pushing operation by the right side plate  12   f  (side frame) serving as second pushing means for increasing a gap is performed in a position on a right side of the right end position of L 2 . A home position (capping position)  28  is located in substantially the same position as the position where pushing operation is performed. On the other hand, the flushing position is located at least on the left side of the left end position of the recordable range L 1 , and the pushing operation by the first pushing means for decreasing a gap is set to be performed in a position on the left side of the flushing position and on the left side of the left end position of L 2 . Thus, at least while the carriage  10   b  is reciprocatingly moving within the range of L 2 , printing on plain paper is performed with the gap kept small. In addition, during the printing, for example, when flushing is performed for every fixed time, a flushing operation is performed with the gap kept small as described above. 
   When printing is performed on a thick envelope, unless a gap is increased, the envelope moving on a sheet conveying path is brought into contact with the nozzle portions  15   a  to soil a surface of the envelope. Thus, as described above, the gap is changed and adjusted to be large. In this case, for example, if the previous print operation is printing on plain paper, when the carriage  10   b  is moved in the direction of arrow B in an attempt to retract the carriage  10  toward the home position (cap position)  28  after the printing ends, the second projected portion  105  formed at the right end of the switching lever  103  of the actuator portion  102  is pushed to the left direction in the figure by the right side plate  12   f  serving as the second pushing means. 
   Therefore, the actuator portion  102  changes to the state described based on  FIGS. 30A to 30C  and  32 , that is, the state in which the second abutment portions  109  and  111  are projected. The second abutment portions  109  and  111  abut against the frame sliding surface  12   d  to be changed to the state in which a gap is large (state of printing on an envelope). Accordingly, the surface of the envelope does not rub against the nozzle portions  15   a  in printing, so that stains due to adhesion of unnecessary ink can be prevented. 
   That is, in the case of performing printing on an envelope, the recordable range L 3  for the envelope is narrower than the recordable range L 1  for plain paper and is set to be on the inner side of L 1 . When the carriage  10   b  is moved in the range of L 4  made by adding the acceleration and deceleration portions (ΔL) to both left and right sides of L 3 , respectively, and the carriage  10   b  has moved to the left end position of L 4 , and, moreover, even when the carriage  10   b  has moved to the flushing position, the gap is still kept large (the first projected portion  104  of the switching lever  103  does not abut against the left side plate  12   e ). 
   Therefore, printing on the envelope is performed with the gap kept large at least while the carriage  10   b  reciprocatingly moves within the range of L 4 . In addition, during the printing, for example, even when flushing is performed for every fixed time, the flushing operation is performed with the gap kept large. Consequently, when the flushing is performed, it is unnecessary to idly move the carriage  10   b  to a position, where the first projected portion  104  of the actuator portion  102  abuts against the left side plate  12   e  to be switched, each time the flushing is performed, so that a printing operation on the envelope can be carried out promptly. 
   Note that, when the carriage  10  moves to the home position  28 , for example, even in a state in which the gap is switched to be small, the switching lever  103  is pushed by the right side plate  12   f  serving as the second pushing means from a position before the home position. The gap dimension G 1  is switched to be large at substantially the same position as the home position. 
   Fourth Embodiment Concerning the Gap Adjustment Mechanism 
   Next, a structure by which the gap dimension G 1  of the third embodiment is switched to, for example, three types will be described. As shown in  FIGS. 34A and 34B , the switching becomes possible by forming the above-mentioned actuator portion  102  in a vertically stacked structure viewed from its front.  FIG. 34A  is a view showing an operation and a state for, in a structure in which a gap between a recording head and a recording medium can be switched to large, medium, and small, switching the gap in two stages of medium and small.  FIG. 34B  is a view showing an operation and a state for switching the gap having switched to medium to large. In this structure, a first abutment portion ( FIGS. 29B and 30B ) having the height of T 2 , which is not shown, is adhered and fixed to the upper surface of the not-shown carriage  10   b . A lower actuator portion  142   a  and an upper actuator portion  142   b  are stacked and fixed by being screwed to the upper surface of the not-shown carriage  10   b . Since respective structures and components of the lower actuator portion  142   a  and the upper actuator portion  142   b  are the same as those of the actuator portion  102  ( FIGS. 29C and 30C ) of the above-mentioned second embodiment except parts to be described later, detailed descriptions of them will be omitted. 
   In addition, as illustrated, a pushing portion of the right side plate  12   f  for pushing the switching lever  143  of the lower actuator portion  142   a  is constituted by a pushing plate  130 , a slide pin  132 , and a compression coil sprint  131 . The pushing plate  130  is made laterally movable on the figure with the slide pin  132  fixed to the right side plate  12   f  as a reciprocating slide shaft. Thus, when a force for pushing the pushing plate  130  from the left of the figure does not work, the compression coil spring  131  is in a state in which it is extended by an elastic force of the compression coil sprint  131  as shown in  FIG. 34A . Moreover, a repulsive force of this compression coil spring  131  is set such that the compression coil spring  131  is hardly compressed and is capable of switching the switching lever  143  of the lower actuator portion  142   a  to a direction of C. In addition, a switching abutment portion  133  against which the second projected portion  145   b  of the upper actuator portion  142   b  abuts is provided on the right side plate  12   f.    
   Now, a state is assumed in which the gap between the recording head and the recording medium is adjusted to small. That is, it is assumed that first abutment portions  149  and  151  of the lower actuator portion  142   a  are retracted, third abutment portions  149   b  and  151   b  of the upper actuator portion  142   b  are retracted, and the first abutment portion  101  (see  FIG. 29B ) is in contact with the frame sliding surface  12   d . In this case, the switching levers  143  and  143   b  are in a state in which they have moved to the right side and have been switched, respectively, viewed from the front. In this state, it is assumed that a direction in which the not-shown carriage  10   b  moves toward the side plate  12   f  is B and the opposite direction is A. When the carriage  10   b  moves in the B direction, first, a second projected portion  145  of the lower actuator portion  142   a  abuts against the pushing plate  130 . When the carriage  10   b  continues to further move in the B direction, the movement of the switching lever  143  is restricted by the elastic force of the compression spring  131 , and the switching lever  143  is switched to a left direction (C direction in the figure) with respect to the carriage  10   b . Then, the second abutment portions  149  and  151  having the height of T 3  project, and the gap between the recording head and the recording medium is switched to medium. At this point, the second projected portion  145   b  of the upper actuator portion  142   b  is just before abutting the switching abutment portion  133 . A state at this point is shown in  FIG. 34A . In this state, when the movement of the carriage  10   b  is switched to the A direction to perform a print operation, printing becomes possible in a state in which the gap is switched to medium. 
   When the not-shown carriage  10   b  continues to move in the B direction from the above-mentioned state of  FIG. 34A , the switching lever  143  of the lower actuator portion  142   a  is locked by a stopper  157  formed on the upper surface of the carriage through a second stop projected portion  156 . Therefore, the carriage  10   b  does not move any farther in the C direction shown in the figure. Thus, the pushing plate is pushed to the right by the second projected portion  145  and the carriage  10   b  continues to move in the B direction. On the other hand, the second projected portion  145   b  of the upper actuator portion  142   b  abuts against the switching projected portion  133  of the right side plate  12   f . At the same time, the switching lever  143   b  moves in a direction of D to be switched as the carriage  10   b  moves in the B direction. Simultaneously, Since the third abutment portions  149   b  and  151   b  of the upper actuator portion  142   b , which has a height of T 4  thicker than the thickness of T 3 , project and abut against the frame sliding surface  12   d  (see  FIGS. 32 and 33B ) at the upper end of the frame  12 , the gap between the recording head and the recording medium is switched to large.  FIG. 34B  is a view showing the state at this time. In this way, the switching of the gap becomes possible in the three stages of large, medium, and small. 
   The multifunction facsimile and printer apparatus according to the present is not limited to the above-mentioned embodiments, and various modifications and improvements are possible within a scope defined in claims. For example, in the above-mentioned embodiments, when printing is performed on plain paper, the carriages  10  and  10   b  are moved in the range of L 2  found by adding the acceleration and deceleration portions (ΔL) to both left and right sides of the recordable range L 1  for plain paper, respectively. In addition, when printing is performed on an envelope, the carriage  10  is moved in the range of L 4  made by adding the acceleration and deceleration portions (ΔL) to both left and right sides of the recordable range L 3  for an envelope, respectively. Thus, there is an advantage that a speed of the carriage  10  in performing an ink discharge operation becomes substantially constant and timing control of ink discharge becomes easy. 
   However, the present invention is not limited to the above embodiments. For example, when discharge timing of ink is controlled so as to discharge ink even during the acceleration of a carriage, the second pushing piece  57  can be positioned at least on the outer side (right side in  FIG. 3A ) of the recordable range L 1  for plain paper in the first embodiment. In addition, the first pushing piece  56  can be positioned at least on the outer side (left side in  FIG. 3A ) of the recordable range L 3  for an envelope when it has a structure which allows the carriage  10  to move to the outer side even after completion of a pushing operation, and a structure to perform flushing in an arbitrary place on a platen in the same manner as the second pushing piece  57 . 
   Likewise, when discharge timing of ink is controlled such that ink discharge is possible even during the acceleration of a carriage, a point where the switching lever  102  is switched to make a gap large can be positioned at least on the outer side (right side in  FIG. 33B ) of the recordable range L 1  for plain paper in the third embodiment. In addition, a point where the switching lever  102  makes the gap small can be positioned at least on the outer side (left side in  FIG. 33B ) of the recordable range L 3  for an envelope when the switching lever  102  has a structure which allows the carriage  10   b  to move to the outer side even after completion of a switching operation and a structure to perform flushing even in an arbitrary place on a platen. 
   In addition, in the gap adjustment mechanisms in the first and second embodiments, instead of arranging the frame  12  uprightly, the frame  12  may be extended substantially linearly to the opposite side of the nozzle portions  15   a  across the guide shaft  11 . The switching bock member  13  may be provided pivotably on the lower surface side of the carriage  10  such that one of several abutment portions with different heights is selected and come into slide contact (abutment) with the slide contact portion  12   a  at an end of the frame  12 . The present invention can be applied not only to the above-mentioned printer apparatus but also a copying machine and an image scanner of a carriage mount type. 
   In the third embodiment, the left side plate  12   e  and the right side plate  12   f  are utilized as the first and second pushing means, respectively. Depending upon a structure of the printer apparatus  1 , it is also possible to provide an extension portion extending to a front side from both side edges of a vertical portion of the frame  12  or provide an extension portion extending downward from both side of a horizontal portion located above the frame  12 , thereby using this extension portion as the first and second pushing means. 
   Further, in the series of procedures in the above-mentioned embodiments, timing at which the carriage  10  makes a complete change from deceleration to acceleration is set to be different at the left and right ends of the reciprocating movement portion in the case of the two-way printing. Such timing may be set to be different in the case of a one-way printing. In addition, the stop determination of 100 ms is also applied to the movement to the flushing position for preventing ink clogging periodically during page printing. 
   INDUSTRIAL APPLICABILITY 
   The present invention can be applied not only to the above-mentioned multifunction facsimile/printer apparatus but also to a copying machine, an image scanner of a carriage mounted type, an ink jet printer as a unit, and a serial printer of a dot impact system. The present invention is technically useful.