Patent Publication Number: US-8109585-B2

Title: Recording apparatus

Description:
This is a division of U.S. patent application Ser. No. 11/742,901, filed May 1, 2007, which has been allowed. 
    
    
     FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to a recording apparatus for recording an image on a recording material with a recording head mounted to a carriage movable along the recording material, particularly a recording apparatus capable of switching a gap between the recording head and the recording material. 
     Generally, a recording apparatus having the functions of a printer, a copying machine, a facsimile apparatus, or the like is constituted so that an image (including characters, symbols, etc.) is formed on a recording material such as paper, a cloth, a plastic sheet, an OHP sheet, or an envelope by a recording head on the basis of image information. A scanning method in the recording apparatus includes those of a serial-type and a line-type. The serial-type scanning method is a method in which an image is recorded by alternately repeating main scanning for moving the recording head along the recording material and subscanning for feeding the recording material at a predetermined pitch. The line-type scanning method is a method in which an image is recorded only by the feeding of the recording material (subscanning) while an image portion corresponding to one line is recorded collectively. Further, the recording apparatus is classified into those of an ink jet type, a thermal transfer type, a laser beam type, a thermal (heat-sensitive) type, a wire dot type, etc. In the case of the serial-type recording apparatus, generally, the recording head is mounted on a carriage moved in a main scanning direction and an image is recorded by driving the recording head in synchronism with the movement of the carriage. By alternately repeating recording of an image portion corresponding to one line and feeding of the recording material in a predetermined amount, recording on the entire recording material is effected. 
     In the above described recording apparatuses, there is such a recording apparatus that recording is effected on a thick recording material such as an envelope or thick paper. In the case of effecting recording on the thick paper, a distance (or a gap) between the recording head and the recording material is excessively small, so that the recording head rubs the recording material in some cases. However, in order to obviate this phenomenon, it is very difficult to decrease the gap to such a degree that the gap is smaller than a certain value. Further, in recent years, a high image quality is increasingly achieved and specialty paper such as glossy paper requires recording thereon with a further decreased gap between the recording head and the recording material. In order to compatibly meet such mutually contradictory requirements, e.g., Japanese Laid-Open Patent Application (JP-A) Hei 7-276736 and U.S. Pat. No. 6,899,474 have disclosed the following constitutions. 
     JP-A Hei 7-276736 has disclosed a constitution in which a sliding member slidably and rotatably supported by a chassis of an apparatus main assembly is mounted at an upper portion of a carriage unit. The sliding member is provided with a plurality of surfaces different in distance from the center of rotation. By switching a sliding surface of the sliding member with the chassis by rotating the sliding member, the carriage is rotated about a guide shaft to switch a gap between a recording material and a recording head. As a result, the gap between the recording material and the recording head can be increased when recording on a thick recording material such as an envelope is effected and can be decreased when recording on specialty paper such as glossy paper is effected. 
     U.S. Pat. No. 6,899,474 has disclosed a constitution in which a guide shaft is provided with cams at both ends and a chassis of an apparatus main assembly is provided with a cam abutment surface and in such a state that the guide shaft is positioned with respect to the chassis in a subscanning direction, the guide shaft is displaceable in a vertical direction. In this constitution, the cams are rotationally driven, whereby it is possible to change a height position (level) of the carriage without changing a position of the guide shaft in the subscanning direction. 
     However, the above described conventional constitutions have encountered the following problems. 
     In the constitution disclosed in JP-A Hei 7-276736, the gap between the recording head and the recording material by rotating the sliding member mounted at the upper portion of the carriage unit to rotate the carriage about the guide shaft. For this reason, at at least one of the switched positions, the carriage is inclined with respect to the recording material, so that it is difficult to effect high-quality image recording at a level exceeding a certain level. Further, the sliding member for switching the gap is required to be constituted separately from the carriage. For this reason, between the chassis and sliding member of the carriage, a parts tolerance for one part is required. As a result, particularly when recording is effected on specialty paper such as glossy paper requiring recording quality, the gap between the recording head and the recording material is less controllable with sufficient accuracy. 
     In the constitution disclosed in U.S. Pat. No. 6,899,474, the guide shaft is required to be a cylindrical shaft and a spring for downwardly urging the guide shaft and the cams provided at both ends of the guide shaft. Further, a driving source for rotating the cams is also required. As a result, the constitution is complicated, thus increasing costs. 
     SUMMARY OF THE INVENTION 
     A principal object of the present invention is to provide a recording apparatus capable of readily switching a gap between a recording head and a recording material by a simple and inexpensive constitution without inclining a carriage with respect to the recording material. 
     Another object of the present invention is to provide a recording apparatus capable of effecting high-quality image recording regardless of a type of the recording material. 
     According to an aspect of the present invention, there is provided a recording apparatus for effecting recording on a recording material with a recording head mounted on a carriage movable along the recording material, the recording apparatus comprising: 
     a guide member for guiding the carriage; 
     a platen for guiding the recording material at a position opposite to the recording head; 
     a bearing member, mounted to the carriage, movable relative to the carriage in a vertical direction; and 
     a slidable member mounted slidably in a carriage movement direction between the carriage and the bearing member, 
     wherein the slidable member is slid in the carriage movement direction to move the bearing member relative to the carriage thereby to change a distance between the recording head and the platen. 
     These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view showing an embodiment of the recording apparatus according to the present invention. 
         FIG. 2  is a schematic longitudinal sectional view showing an embodiment of the recording apparatus of the present invention. 
         FIG. 3  is a schematic side view of a carriage unit shown in  FIG. 2 . 
         FIG. 4  is a schematic rear view of the carriage unit shown in  FIG. 3 . 
         FIG. 5  is a schematic perspective view of a carriage and a bearing member which are shown in  FIG. 3 . 
         FIG. 6  is a schematic perspective view of the carriage, the bearing member, and a slidable member which are shown in  FIG. 3 . 
         FIG. 7  is a schematic rear view when a gap of a switching mechanism for switching a gap between a recording head and a recording material which are shown in  FIG. 2  is increased. 
         FIG. 8  is a schematic rear view when the gap of the switching mechanism shown in  FIG. 7  is decreased. 
         FIG. 9  is a schematic side view when the gap of the switching mechanism shown in  FIG. 7  is increased. 
         FIG. 10  is a schematic side view when the gap of the switching mechanism shown in  FIG. 9  is decreased. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinbelow, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same reference numerals or symbols represent the same or corresponding members or portions. 
       FIG. 1  is a perspective view showing an embodiment of the recording apparatus according to the present invention, and  FIG. 2  is a longitudinal sectional view showing an embodiment of the recording apparatus of the present invention.  FIGS. 1 and 2  illustrate an ink jet recording apparatus as the recording apparatus of the present invention. 
     Referring to  FIGS. 1 and 2 , a recording apparatus  1  of this embodiment includes a sheet pickup portion  2 , a sheet feed portion  3 , a sheet discharge portion  4 , a recording portion  5 , and a refreshing process portion  6 . The recording portion constitutes a recording means. The recording apparatus  1  is of a serial-type in which an image is formed while a surface of a recording material is scanned with a recording head  7  mounted to a reciprocable carriage  50 . Further, to a main assembly of the recording apparatus  1 , en electric portion  9  including an electric substrate or the like on which a control circuit is mounted is attached. 
     First, the sheet pickup portion  2  will be described. The sheet pickup portion  2  is constituted by attaching a pressure plate  21  for stacking thereon the recording material such as recording sheets or the like, a sheet pickup roller  28  for picking up the recording material, a separation roller  241  for separating the recording material into a single sheet, a return lever for returning the recording material to a mounting position, and the like to a sheet pickup base  20 . To the sheet pickup base  20  or an apparatus outer casing (not shown), a sheet supply tray (not shown) for mounting and holding thereon the recording material is also attached. The sheet pickup roller  28  has a circular cross section and is disposed at a position close to a reference surface for regulating a position of the recording material in a width direction. A driving force for the sheet pickup roller  28  is transmitted via a gear train from an LF motor (not shown), as a driving source for the sheet feed portion  3  (described later), provided to the sheet pickup portion  2 . 
     To the pressure plate  21 , a movable side guide  23  for regulating the mounting position of the recording material is provided movably. The pressure plate  21  is rotatable about a rotation shaft (rotational axis) provided to the sheet pickup base  20  and is urged toward the sheet pickup roller  28  by a pressure plate spring  212 . At a portion of the pressure plate  21  opposite to the sheet pickup roller  28 , a separation sheet  213  formed of a large friction coefficient material for preventing double pickup of the recording material is provided. The pressure plate  21  is driven so as to be pressed against and moved apart from the sheet pickup roller  28  by a pressure plate cam (not shown). By the sheet pickup base  20 , a separation roller holder  24  to which the separation roller  241  is attached is rotatably supported. Further, the separation roller  241  is urged against the sheet pickup roller  28  by a separation roller spring (not shown). 
     The separation roller  241  includes a clutch spring (not shown) as a torque limiter and rotates when a load torque is not less than a predetermined value. Further, the separation roller  241  is supported by a separation roller release shaft (not shown) and a control cam (not shown) that it can be pressed against and moved apart from the sheet pickup roller  28 . At a position close to the sheet pickup roller  28  on the sheet pickup base  20 , the return lever  22  for returning sheets of the recording material other than an uppermost sheet to the mounting position is rotatably attached to the sheet pickup base  20 . The return lever  22  is urged toward a release direction by a return lever spring (not shown) and can return the recording material by being rotated by the control cam (not shown). In an ordinary standby state, the pressure plate  22  is released by a pressure roller cam and the separation roller  241  is released by the control cam (not shown). The return lever  22  is provided at a position for blocking a mounting opening so as not to further push the mounted recording material toward the sheet feed portion  3 . 
     When a sheet pickup operation is started from the standby state, first, the separation roller  241  is caused to press-contact the sheet pickup roller  28  by the drive of the motor. Then, the return lever  22  is released to press the pressure plate  21  against the sheet pickup roller  28 . In this state, pickup of the recording material is started. The recording material is limited in movement by a preliminary separation portion provided to the separation roller holder  24 , so that only a predetermined number of sheets of the recording material are sent to a nip (portion) between the sheet pickup roller and the separation roller  241 . The sent recording material is separated in the nip and only an uppermost sheet of the recording material is separated in the nip and only an uppermost sheet of the recording material is picked up and sent toward a feed roller  26  of the sheet feed portion  3 . When the recording material reaches a nip between the feed roller  36  and pinch rollers  37 , the pressure plate  21  is released by the pressure plate cam (not shown) and the separation roller  241  is released by the control cam (not shown). Further, the return lever  22  is returned to the mounting position by the control cam (not shown). At this time, the recording material which has reached the nip between the sheet pickup roller  28  and the separation roller  241  can be returned to the mounting position by the movement of the return lever  22 . 
     Next, the sheet feed portion  3  will be described. The sheet feed portion  3  includes the feed roller  36  for feeding the recording material, a paper end (PE) detection sensor (not shown), etc. The feed roller  36  has a structure in which a metal shaft is surface-coated with ceramic fine particles and is rotatably supported by bearings  38  on the chassis  11  side at both end metal portions. Between the bearing  38  and the feed roller  36 , a roller tension spring (not shown) for applying a predetermined load torque to the feed roller  36  is mounted. As a result, rotation of the feed roller  36  can be stabilized to ensure stable feeding. 
     To the feed roller  36 , a plurality of pinch rollers  37  are pressed against so as to be rotatable by the rotation of the feed roller  36 . Each of the pinch rollers is held by a pinch roller holder  30  and pressed toward the feed roller  36  by a pinch roller spring (not shown), so that a feeding force for the recording material is generated. In this case, a rotation shaft of the pinch roller holder  30  is rotatably attached to the bearings of the chassis  11 . The pinch roller holder  30  is provided with a sensor lever  31  for transmitting detection of a leading end and trailing end of the recording material to the PE sensor. On a downstream side of the feed roller  36  in a sheet feed direction, a platen  34  for guiding and supporting the recording material during recording is disposed. The platen  34  is attached to the chassis  11 . 
     The recording material picked up by the sheet pickup portion  2  is sent into the nip between the feed roller  36  and the pinch rollers  37  while being guided by the pinch roller holder  30 . At this time, the feed roller  36  is yet stopped, and initial feeding (end alignment) of the recording material is performed by feeding the recording material by a predetermined amount in a state in which the leading end of the recording material reaches the nip. Further, at this time, the sensor lever  31  detects the leading end of the recording material and determines a recording start position of the recording material. Further, the feed roller  36  is rotated by the LF motor to feed the recording material to the recording start position on the platen  34 . On the platen  34 , a rib constituting a reference feed surface is formed. By this arrangement constitution of the rib, the gap (distance) between the recording material and the recording head  7  is controlled and waving of the recording material is regulated in cooperation with the sheet discharge portion  4  described later. 
     The feed roller  36  is driven by transmitting a rotational force of a DC motor as the LF motor (Not shown) to a pulley  361  provided to the roller shaft of the feed roller  36  via a timing belt (not shown). Further, the roller shaft of the feed roller  36  is provided with a code wheel  362  for detecting a feed amount. At an outer peripheral portion of the cord wheel  362 , marking is provided at a pitch of 150-300 lines per one inch of circular arc length. An encoder sensor (not shown) for reading this marking is attached to the chassis  11  at a position adjacent to the code wheel  362 . 
     Next, the recording portion  5  will be described. At a position which is downstream from the feed roller  36  in the sheet feed direction and opposite to the platen  34 , the recording head  7  for forming (recording) an image is provided. The recording head  7  is mounted to the carriage  50  reciprocable in the width direction of the recording material. That is, the recording apparatus of this embodiment employs the serial-type recording method. The recording portion  5  is constituted by a carriage unit  50   a , including the carriage  50  and the recording head  7  and the like mounted on the carriage  50 , and a driving mechanism for the carriage unit  50   a . Further, the recording portion  5  includes the platen  34  for guiding and supporting the recording material at a position opposite to the recording head  7 . In this embodiment, as the recording head  7 , an ink jet recording head capable of color recording is used. For this reason, the recording head  7  is constituted by a plurality of recording heads corresponding to colors of inks used. To each of the recording heads, a separate ink container (tank)  71  is replaceably mounted. 
     The recording head  7  is the ink jet recording head for recording an image by ejecting ink from an ejection outlet to the recording material on the basis of image information. It is necessary to provide a predetermined distance (gap) (of, e.g., about 0.5-3.0 mm) for jetting ink droplets between an ink ejecting portion (an ink ejection surface at which a plurality of ejection outlets are arranged) of the recording head and a recording surface of the recording material. Further, as the recording material, it is possible to use various materials such as paper, a cloth, a plastic sheet, an OHP sheet, and an envelope so long as the material can form thereon an image with the ejected ink droplets. Further, as an ink ejecting method for the recording head  7 , it is possible to employ any method selected from various methods using an electrothermal transducer, an electromechanical transducer, and the like as an ejection energy generation means. For example, as the recording head  7  in this embodiment, a recording head which ejects ink by heating the ink in the ejection outlet by a heater or the like as the electrothermal transducer and by utilizing film boiling of the ink due to this heat is used. More specifically, the recording head  7  records an image on the recording material by selectively ejecting ink from the respective ejection outlets of the recording head  7  to the recording material by a change in pressure caused by growth or contraction of bubbles generated in ink by heating. 
     As described above, the carriage unit  50   a  is constituted by mounting the recording head  7  and the like to the carriage  50 . The recording head  7  is located and held at a predetermined position on the carriage  50  by a head setting lever  51 . The carriage unit  5   a  is guided and supported reciprocably in a main scanning direction perpendicular to the sheet feed direction (subscanning direction) of the recording material by a guide member (guide rail)  52  provided to the apparatus main assembly and a sliding portion  111  of the chassis  11  of the apparatus main assembly. In this case, the carriage unit  5   a  is guided and supported in a state in which an abutment (contact) surface provided at an upper portion of the carriage  50  contacts the sliding portion  111  of the chassis  11 . 
       FIG. 3  is a side view of the carriage unit  51   a  shown in  FIG. 2 .  FIG. 4  is a rear view of the carriage unit  51   a  shown in  FIG. 3 . 
     In  FIGS. 1-4 , the guide rail  52  has a substantially L-shaped cross section. To the carriage  50   m  a bearing member  58  slidable relative to the guide rail  52  is attached. The bearing member  58  is attached to the carriage  50  so as to be displaceable relative to the carriage  50  in a vertical direction. Further, the bearing member  58  is a member for stabilizing its attitude with respect to the guide rail in the subscanning direction of the carriage  50 . For this reason, a spring  581  for urging the bearing member  58  toward a downstream side in the recording material feed direction. More specifically, the guide rail  52  provided to the apparatus main assembly is interposed between the carriage  50  and the bearing member  58  by an urging force of the spring  581 , so that the attitude of the carriage  50  in the subscanning direction is stabilized. 
     At a lower portion of the carriage  50 , a sliding surface (in a height (vertical) direction  50   b  contactable with a horizontal portion of the guide rail  52  is formed. Further, at a lower portion of the bearing member  58 , a sliding surface (in a height (vertical) direction)  58   b  contactable with the horizontal portion of the guide rail  52 . These vertical sliding surfaces  50   b  and  58   b  can regulate a vertical position of the carriage  50  by contact with the guide rail  52  by weights of the carriage  50  and parts mounted thereon. Further, the attitude of the carriage  50  in a rotational direction is stabilized by causing the abutment surface  50   e  provided at the upper portion of the carriage  50  to the sliding portion  111  of the chassis  11 . Incidentally, positional adjustment of the carriage  50  is effected by adjusting a mounting position of the guide rail  52  with respect to the chassis  11  in a factory. 
     To the carriage  50 , a carriage cover  53  is attached. The carriage cover  53  functions as a guide member when a user mounts the recording head  7  to the carriage  50 . The carriage cover  53  also functions as a member for holding the ink container  71 . The carriage  50  is driven by a carriage motor  54  attached to the chassis  11  via a timing belt  55 . The timing belt  55  is stretched around an idle pulley  56  provided opposite from the carriage motor  54  under a certain tension, and is connected to the carriage  50 . A code strip  57  for detecting the position of the carriage  50  is extended in parallel to the timing belt  50 . The code strip  57  has making at a pitch of, e.g., 150-300 lines per inch. On the carriage  50 , an encoder sensor (not shown) for reading the marking of the code strip  57  is mounted. 
     The bearing member  58  switches a height position (level) of the carriage  50  with respect to the guide rail  52  by being vertically displaced relative to the carriage  50  as described later. By the switching of the height position of the carriage  50 , it is possible to switch a gap which is a distance between the recording head  7  and the recording material. A constitution and operation of the gap switching by the bearing member  58  will be described later. 
     When the image is formed on the recording material by the above described constitution, the recording material is fed to the recording start position (in the sheet feed direction) by the pair of feed rollers  36  and  37 . At the same time, the carriage  50  is moved to the recording start position (in a direction perpendicular to the sheet feed direction) by the carriage motor  54 . As a result, the recording head  7  is set at the recording start position. Then, by signals from the electric portion  9 , while controlling drive of the recording head  7 , synchronizing drive of the carriage  50 , drive of the feed roller  36 , and the like on the basis of image information, an image is recorded by ejecting ink from the recording head  7  to the recording material. 
     Next, the sheet discharge portion  4  will be described. The sheet discharge portion  4  includes a sheet discharge roller  40  disposed downstream from the recording head  7  in the sheet feed direction, spurs  42  rotatable in contact with the sheet discharge roller  40  at a predetermined pressure by the rotation of the sheet discharge roller  40 , a gear train for transmitting a driving force from the feed roller  36  to the sheet discharge roller  40 , and the like. In this embodiment, the sheet discharge roller  40  is attached to the platen  34 . The sheet discharge roller  40  has a structure in which a plurality of roller rubber portions are provided to a metal shaft. The sheet discharge roller  40  is driven in synchronism with the feed roller  36  by transmitting a driving force of the feed roller  36  thereto via an idler gear. The plurality of spurs  42  are provided in correspondence with the plurality of roller rubber portions of the sheet discharge roller  40 . Each of the spurs  42  has a structure in which a thin plate of SUS stainless steel provided with a plurality of projections at its peripheral portion is integrally formed with a resin material portion. These spurs  42  are attached to a spur holder  43  by a spur spring (not shown) consisting of a bar-like coil spring. Further, by the spur spring, the spurs  42  are caused to pressure-contact the sheet discharge roller  40 . 
     The plurality of spurs  42  are classified into two types in terms of function. One type thereof principally generates a feeding force for the recording material by being pressed against the respective roller rubber portions. The other type thereof principally suppresses rising of the recording material during the recording by being disposed between the respective roller rubber portions. Further, in order to suppress deformations of the spur holder  43  and the chassis  11 , a spur stay  44  formed of a plate-like metal member is attached to the spurs  42 . By the above described constitutions, the recording material on which the image has been formed at the recording portion  5  is nipped and conveyed between the sheet discharge roller  40  and the spurs  42  to be discharged to a sheet discharge tray (not shown) outside the apparatus main assembly. 
     Next, the refreshing process portion  6  will be described. In the ink jet recording apparatus, the refreshing process portion  6  for keeping and refreshing an ink ejection performance while preventing clogging of the ejection outlets of the recording head  7  is provided. The refreshing process portion  6  includes a suction pump  60 , a cap  61 , and a wiper  62 . The cap  61  decreases a degree of drying of ink of the recording head  7  by hermetically contacting the ejection surface of the recording head  7  to cover the ejection outlets. The suction pump  60  is actuated in a hermetically covered state of the ejection outlets with the cap  61  to suck the ink from the ejection outlets, thus refreshing the ink in the ejection outlets. The wiper  62  wipes the ink off the surface of the ejection outlets of the recording head  7  to clean the ejection outlets. As the suction pump  60 , it is possible to use not only a piston type pump and a cylinder type pump but also, e.g., such a tube pump that a negative pressure generated in a tube is caused to act on the ejection outlets by drawing the tube connected to the cap  61 . 
       FIG. 5  is a perspective view of the carriage  50  and the bearing member  58  shown in  FIG. 3 .  FIG. 6  is a perspective view of the carriage  50 , the bearing member  58 , and the slidable member  52  shown in  FIG. 3 .  FIG. 7  is a rear view when a gap of the switching mechanism for switching the gap between the recording head and the recording material shown in  FIG. 2  is decreased.  FIG. 8  is a rear view when the gap of the switching mechanism shown in  FIG. 7  is increased.  FIG. 9  is a side view when the gap of the switching mechanism shown in  FIG. 7  is decreased.  FIG. 10  is a side view when the gap of the switching mechanism shown in  FIG. 9  is increased. 
     Next, with reference to  FIGS. 1-8 , the constitution and operation of the bearing member  58  for switching the distance (gap) between the recording head  7  and the recording material will be described. In  FIGS. 3-8 , the carriage  50  is guided and supported by the guide rail  52  and the sliding portion  111  which are provided to the chassis  11  so that it is reciprocable in a stable attitude. 
     To an upstream rear surface of the carriage  50  in the sheet feed direction, as shown in  FIG. 3 , the bearing member  58  having the L-shaped cross section is attached so that it is displaceable relative to the carriage  50  in the vertical direction with the longside perpendicular surface of the L-shaped cross section toward the upstream side in the sheet feed direction. Between the carriage  50  and the bearing member  58 , a spring  581  for urging the bearing member  58  toward the downstream side in the feed direction (in a left-hand direction in  FIG. 3 ) with respect to the carriage  50  is attached. By the urging force of the spring  581 , the guide rail  52  provided to the chassis  11  is sandwiched and nipped between the feed direction sliding surface  50   a  of the carriage  50  and the feed direction sliding surface  58   a  of the bearing member  58 . As a result, the position of the lower portion of the carriage  50  in the feed direction is regulated, so that the carriage attitude is stabilized. 
     Further, the height position (level) of the carriage  50  with respect to the guide rail  52  in the vertical direction is switchably set by the contact of the lower portion of the carriage  50  or the lower portion of the bearing member  58  with the guide rail  52  by the carriage  50  under its own weight. In other words, in the case where the gap between the recording head  7  and the recording material is set to an ordinary small value, as shown in  FIG. 3 , a height direction sliding surface  50   b  of the carriage  50  is caused to contact the horizontal portion of the guide rail  52 . In this state, while moving the carriage unit  5   a  along the guide rail  52  and the sliding portion  111  (main scanning), an image is formed by ejecting ink from the recording head  7  to the recording material by the signal from the electric portion  9 . This state represents the case where the recording material is relatively thin, thus being used in the case of requiring a high image quality. The position of the carriage  50  in this state is referred to as an “ordinary position”, and the gap in this state is referred to as an “ordinary gap”. 
     The state of the bearing member  58  in this ordinary position will be described below. 
     In the ordinary position state, the bearing member  58  is urged toward the sheet feed direction by the bearing member spring  581  and slidably contacts the guide rail  52  at the sliding surface  58   a  in the feed direction. On the other hand, in the height direction, the sliding surface  58   b  of the bearing member  58  is higher in position (level) than the sliding surface  50   a  of the carriage  50 , so that the bearing member  58  does not contact the guide rail  52 . Further, between the bearing member  58  and the carriage  50 , as shown in  FIG. 4 , a slidable member  583  slidable in the carriage movement direction is mounted. As shown in  FIGS. 3-5 , in the ordinary position state, the bearing member  58  is held at a rise position by upward urging springs  582  mounted between the bearing member  58  and the carriage  50 . For this reason, in this state, the bearing member  58  does not contact the guide rail  52 . Further, bearing member  58  is also urged downwardly by the urging springs  582  attached at both end portions of the bearing member  58 , so that the bearing member  58  is also positioned in a downward direction with respect to the height direction. Further, the bearing member  58  is positioned in the main scanning direction with respect to the carriage  50  at points of the urging springs  582  at both end portions thereof. 
     In the neighborhood of the rear surface (on the feed direction upstream side) of the carriage  50 , the slidable member  583  slidable between the carriage  50  and the bearing member  58  in the carriage movement direction is mounted. The slidable member  583  is an elongated member in a direction (main scanning direction) perpendicular to the sheet feed direction and is slidable in its lengthwise direction. Further, the slidable member  583  can be regulated in its position in the sliding direction by abutment at both end portions  583   a  and  583   b  thereof against a part of the apparatus main assembly (a side surface of the chassis  11  as shown in  FIGS. 7 and 8 ) by moving the carriage  50 . The slidable member  583  is positioned in the feed direction by being interposed between the carriage  50  and the bearing member  58  as shown in  FIG. 6 . Further, the position of the slidable member  583  in the height direction is determined in the upward direction by contact with the carriage  50  and determined in the downward direction by contact with the bearing member  58 . These positionings are stabilized by the urging force of the springs acting between the carriage  50  and the bearing member  58 . 
     Next, the switching operation of the gap between the recording head  7  and the recording material by the above constituted bearing member  58  and slidable member  583  will be specifically described with reference to  FIGS. 7-10 .  FIGS. 7 and 9  show the state of the carriage unit  5   a  located at the ordinary position. When the recording on the recording material at the recording portion  5  is effected by the recording head  7 , it is necessary to determine the position of the carriage unit  5   a  in the main scanning direction. For this purpose, first, the carriage  50  is moved in the left-hand direction in  FIG. 7  to abut the left-hand end portion  583   a  of the slidable member  583  against the side surface of the chassis  11 . By this abutment operation, an initial position of the carriage  50  is determined. In this state, the slidable member  583  is regulated in position by the abutment against the part of the chassis  50  in the sliding direction (main scanning direction), so that the slidable member  583  is not further slid (displaced) in a direction indicated by a solid black arrow shown in  FIG. 7 . 
     In this embodiment, as described above, the initial position determination of the carriage  50  is performed by the abutment of the end portion  583   a  of the slidable member  583 . Instead of this, it is also possible to employ a constitution in which an end portion of the carriage  50  is abutted against the chassis  11 , when the slidable member  583  is slid to some extent, to perform the initial position determination. According to this constitution, it is possible to realize a move accurate position determination by decreasing the number of parts interposed during the initial position determination. In such an ordinary position state, an ordinary recording operation with respect to an ordinary recording material having a thickness of not more than a certain value is performed. 
     On the other hand, in the case where the recording material is an envelope or thick paper having a thickness of more than the certain value or its formed of a material more liable to curl, it is necessary to increase the gap between the recording head  7  and the recording material. For this purpose, the position of the carriage  50  is required to be switched to a position higher than the ordinary position (ordinary gap position) at which the carriage  50  contacts the guide member  52 . The higher position in this case is referred to as a “thick paper P”. At the ordinary position shown in  FIGS. 7 and 9 , the carriage unit  5   a  contacts the guide rail  52  at the height direction sliding surface under its own weight. At this time, as described above, the bearing member  58  is located at the rise position by being urged upwardly by the springs  582 . For this reason, the height direction sliding surface  58   b  of the bearing member  58  is located above the guide rail  52 , so that it does not contact the guide rail  52 . 
     The slidable member  583  changes a vertical position of the bearing member  58  relative to the carriage  50  by being regulated in its sliding position. An upward (carriage supporting) surface  583   f  formed at a part of the slidable member  583  always contacts a downward (receiving) surface  50   f  formed at a part of the carriage  50 . In other words, the carriage  50  is supported by the slidable member  583  through the receiving surface  50   f  formed on the carriage  50  and the carriage supporting surface  583   f  formed on the slidable member  583 . Accordingly, the relative position between the slidable member  583  and the carriage  50  in the vertical direction is not changed. On the other hand, at a downward surface of the slidable member  583 , a cam surface  583   e  is formed and at an upward surface of the bearing member  58 , a projection contact portion  58   e  contactable with the cam surface  583   e  is formed. By changing a sliding position of the slidable member  583  to change a contact position of the contact portion  58   e  with respect to the cam surface  583   e , it is possible to change the vertical relative position of the bearing member  58  with respect to the carriage  50 . Even in the case where the relative position is changed as described above, positional regulation is ensured in a stable state by the urging force of the springs exerted between the carriage  50  and the bearing member  58 . 
     In the above described constitution, when the recording is effected at the thick paper position, the carriage unit  5   a  is moved toward the right-hand direction in  FIGS. 7 and 8 . By the movement, the right-hand end portion  583   b  of the slidable member  583  is caused to abut against the other (right-hand) side surface of the chassis  11  which is a part of the apparatus main assembly. By this abutment, the slidable member  583  starts sliding in a direction indicated by a solid black arrow in  FIG. 8 . As a result, the bearing member  58  is moved in a direction indicated by a hatched arrow shown in  FIGS. 8 and 10  by the cam surface  583   e  provided to the slidable member  583 . That is, the bearing member  58  is displaced downwardly relative to the carriage  50 . As a result, the sliding surface  58   b  of the bearing member  58  is located at a lower position than the sliding surface  50   b  of the carriage  50 . For this reason, the bearing member  58  contacts the guide rail  52  at its sliding surface  58   b , so that the carriage  50  is displaced to a position upwardly apart from the guide rail  52 . 
     More specifically, by the abutment of the sliding surface  58   e  of the bearing member  58  against the guide rail  52 , a reaction force is transmitted to the slidable member  583  through the cam surface  583   e  and further transmitted through the slidable member  583  to the carriage  50  which regulates the rise position. As a result, the carriage unit  5   a  (the carriage  50 ) is displaced in an upward direction indicated by an arrow with transverse lines shown in  FIGS. 8 and 10 . When the end portion  583   b  of the slidable member  583  is forcedly moved to this state by the side surface of the chassis  11  in the slid black arrow direction, the slidable member  583  abuts against a part of the carriage  50  at a part thereof, so that the slidable member  583  does not further slide. That is, the slidable member does not further move in the solid black arrow direction shown in  FIG. 8 . This state is the thick paper position at which the gap between the recording head  7  and the recording material is increased. 
     At this thick paper position, since the carriage  50  is moved from the ordinary position to the upper position, the height direction sliding surface  50   b  of the carriage  50  is spaced apart from the guide rail  52 . Accordingly, the position of the carriage unit  5   a  at the thick paper position in the height direction is regulated by the height direction sliding surface  58   b  of the bearing member  58 . In this state, while performing scanning with the carriage unit  5   a  in the main scanning direction, by ejecting ink from the recording head  7  on the basis of a signal from the electric portion  9 , an image is formed with the ink ejected to a thick recording material such as an envelope or the like. The gap switching of the carriage unit  5   a , i.e., the switching of the distance between the recording head  7  and the recording material in this embodiment is realized by the above described constitution and operation. 
     In this embodiment, the height position (level) of the bearing member  58  is switched by sliding the slidable member  583  in the carriage movement direction. This may also be realized by omitting the slidable member  583  and moving the carriage unit  5   a  by a manual operation by a user to switch the position of the carriage unit  5   a  from the ordinary position to the thick paper position. Further, when the carriage unit  5   a  is moved from the thick paper position to the ordinary paper position, similarly as described above, it is possible to easily realize the movement by abutting the carriage  50  against the part of the main assembly of the recording apparatus in the initial position determination of the carriage  50 . Further, the switching between the ordinary position and the thick paper position may also be realized by moving the bearing member  58  by a manual operation by a user, so that the gap switching similar to that described above can be effected. As a result, it is possible to reduce the number of parts and improve an accuracy between the parts by the omission of the slidable member  583 . Further, a similar gap switching can also be realized by manually moving the carriage  50  by a user, so that it is possible to simplify the driving mechanism. 
     According to this embodiment described above, such a constitution that the carriage  50  or the slidable member  583  on the carriage  50  is caused to abut against one of the side surfaces of the chassis  11  used for the initial position determination of the carriage  50  is employed. As a result, it is possible to set the carriage unit  5   a  to the ordinary position. Further, by causing the carriage  50  against the other side surface of the chassis  11 , it is possible to set the carriage unit  5   a  to the thick paper position. That is, by utilizing the initial position determination performed at the time of the start of the recording, it is possible to always set the carriage unit  5   a  to the ordinary position. For this reason, without adding a sensor or a driving mechanism, it is possible to ensure gap setting of the carriage unit  5   a  with an inexpensive constitution. 
     By the above described constitution, various operations important in ensuring the height position of the carriage unit  5   a  can be stably performed. More specifically, not only an operation for keeping a quality of a recording image by proper gap setting of the recording head  7  but also a capping operation of the cap  61  at the refreshing process portion  6  shown in  FIG. 1  and a refreshing operation such as wiping cleaning with the wiper  62  can also be stably performed. Further, it is possible to prevent a lowering in image quality by recording the image on the recording material, at the thick paper position, such as glossy paper to be subjected to recording at the ordinary position. Further, in this embodiment, the carriage unit  5   a  slides along the guide rail  52  at the height direction sliding surface  50   b  of the carriage  50  when it is located at the ordinary position and slides along the guide rail  52  at the height direction sliding surface  583   b  of the bearing member  58  when it is located at the thick paper position. According to such a constitution, at the ordinary position at which a recording quality is required, the carriage unit  5   a  can slide directly by the carriage  50 , so that it is possible to obviate a lowering in accuracy due to an increase in the number of interposed parts. 
     Further, according to this embodiment, it is possible to switch the gap depending on a type or a size of the recording material selected on a driver. As a result, it is possible to automatically switch the gap only when the gap switching is required. Further, in this embodiment, the displacement of the carriage unit  5   a  in the height direction is performed only by parallel movement, so that the gap between the recording head  7  and the recording material, i.e., the height position (level) of the carriage  50  can be switched, without causing inclination of the attitude of the carriage  50  (or the recording head  7 ) with respect to the recording surface of the recording material, while ensuring a parallel state between the recording head  7  and the recording material. As a result, it is possible to reliably prevent the lowering in recording image quality during the gap switching, so that higher quality image recording can be effected. 
     In the above described embodiments, the ink jet recording apparatus for recording an image by ejecting ink from the recording head is described as an example. However, the present invention is not limited thereto but may also be similarly applicable to recording apparatuses using other recording methods so long as the recording apparatus requires setting of the gap between the recording head and the recording material. Further, the present invention is also similarly applicable irrespective of the number of recording heads and their arrangements and constitutions. In the case of the ink jet recording apparatus, it is further applicable similarly regardless of a type and property of ink used. Further, the present invention is not restricted to a single apparatus such as a printer, a copying machine, a facsimile apparatus, an image pickup and forming apparatus, or the like. In other words, the present invention is widely applicable to recording apparatuses such as multi-function apparatuses having functions of the above described apparatuses, and a multi-function apparatus for a computer system. With respect to the recording material, the present invention is applicable to any material, irrespective of types or forms of the material so long as the material is capable of recording thereon an image, in addition to the above described materials (paper, cloth, plastic sheet, OHP sheet, envelope, etc.). 
     As described hereinabove, according to the present invention, it is possible to provide a recording apparatus capable of easily switching the gap between the recording head and the recording material, without causing inclination of the carriage with respect to the recording material, with a simple and inexpensive constitution and capable of high-quality image recording regardless of a type of the recording material. 
     While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purpose of the improvements or the scope of the following claims. 
     This application claims priority from Japanese Patent Application No. 132415/2006 filed May 11, 2006, which is hereby incorporated by reference.