Head maintenance mechanism for ink jet printer and ink jet printer incorporating the same

A head cap is reciprocally movable between a capping position for covering nozzles of a print head and a retracted position separated from the nozzle surface. A pump is connected to the head cap. A pump gear is rotated by a drive source to drive the pump. A cylindrical cam is reciprocally rotatable between a first position and a second position to reciprocally move the head cap. A frictional clutch rotates the cylindrical cam together with the pump gear, but rotates only the pump gear when the cylindrical cam reaches each one of the first position and the second position.

BACKGROUND OF THE INVENTION

The present invention relates to a head maintenance mechanism for a serial type ink jet printer in which a carriage mounting thereon a print head is reciprocated in a widthwise direction of printing. More specifically, the invention relates to a head maintenance mechanism in which a single rotary drive source is used to drive a head cap, wiper and an ink suction pump.

With a serial type ink jet printer, a head maintenance mechanism is arranged in a position outside a region of printing performed by a print head, and wiping of dirt on a nozzle surface of the print head, capping intended for prevention of plugging of a nozzle orifice, and an operation of sucking ink in an increased viscosity from the nozzle orifice are performed by the head maintenance mechanism. To meet the needs of making a head maintenance mechanism for an ink jet printer small-sized, compact and inexpensive, related art head maintenance mechanisms are constituted by a configuration in which a single rotary drive source, such as stepping motors or the like, is used to cause movement of a wiper for wiping a nozzle surface, a capping action of a head cap for capping the nozzle surface, and an operation of sucking ink from a nozzle orifice as capped.

For example, Japanese Patent Publication No. 2000-141673A discloses a head maintenance mechanism of such configuration. With the head maintenance mechanism disclosed in this publication, rotation of a single motor in one direction causes a head cap and a wiper to be driven through a slide type rack and a cam mechanism, and reverse rotation of the motor causes a diaphragm suction pump to be driven through a cylindrical cam.

However, a head maintenance mechanism of a type in which rotation of a single motor in one direction causes a head cap and a wiper to be driven, and reverse rotation of the motor causes a suction pump to be driven, involves the following problems.

First, a cylindrical cam is generally used to convert rotary movements of a motor into reciprocal movements. Since such a cylindrical cam is continuously rotationally driven in one direction, there is a need of providing a position detector for detecting a reference or initial position of the cylindrical cam in order to control respective motions of the cylindrical cam.

Also, there is a need of separately providing a power transmitting mechanism for driving of a head cap and a wiper and a power transmitting mechanism for driving of an ink suction pump, which is disadvantageous in making a head maintenance mechanism small-sized and compact.

Further, a pump, for example, a tube pump needed to rotate forward and rearward cannot be adopted as an ink suction pump. More specifically, in the case where a tube pump is used, a roller rotates flattening an ink tube to perform an ink sucking action when a pump gear being a drive force input element of the pump is rotated forward, and the roller is put in a release state, in which the ink tube is not flattened, when the pump gear is rotated rearward. Since the release state is necessary after the ink sucking action, a tube pump cannot be used in the case of rotary driving in one direction.

Also, a head maintenance mechanism for an ink jet printer involves as an ink sucking configuration from a head cap with an ink sucking action, the case where ink is sucked from a nozzle orifice and the case where ink accumulated in the head cap is sucked (idle suction) in a state in which the head cap made in capping is put in an atmospheric opening state. In order to realize both of these ink sucking configurations, it is necessary to provide a mechanism for opening and closing a vent valve mounted on a head cap after there is established a state in which the head cap caps the nozzle surface. When such mechanism can be made compact, it is advantageous in making a head maintenance mechanism small-sized, compact or thin.

SUMMARY OF THE INVENTION

An object of the invention is to propose a head maintenance mechanism for an ink jet printer which is capable of controlling motions of a head cap, wiper and an ink suction pump without the use of any position detector.

Also, an object of the invention is to propose a head maintenance mechanism for an ink jet printer which is capable of driving an ink suction pump forward and rearward.

Further, an object of the invention is to propose a head maintenance mechanism for an ink jet printer in which a power transmitting mechanism for driving a head cap, wiper and an ink suction pump can be made compact.

Further still, an object of the invention is to propose a head maintenance mechanism for an ink jet printer in which a mechanism for switching an interior of a head cap capping a nozzle surface between opening to the atmosphere and not opening is made compact.

In order to achieve the above objects, according to the present invention, there is provided a maintenance mechanism for a print head having a nozzle surface in which are formed a plurality of nozzles, comprising:

a head cap, reciprocally movable between a capping position for covering the nozzles and a retracted position separated from the nozzle surface;

a pump, connected to the head cap;

a drive source;

a pump gear, rotated by the drive source to drive the pump;

a cylindrical cam, reciprocally rotatable between a first position and a second position to reciprocally move the head cap; and

a frictional clutch, which rotates the cylindrical cam together with the pump gear, but rotates only the pump gear when the cylindrical cam reaches each one of the first position and the second position.

Preferably, a cam groove is formed on an outer peripheral surface of the cylindrical cam in a predetermined circumferential angular range. The maintenance mechanism further comprises a cap driving pin slidably movable along the cam groove to reciprocally move the head cap.

Here, it is preferable that the maintenance mechanism further comprises an urging member which urges the cap driving pin toward a bottom surface of the cam groove.

Preferably, a first engagement member and a second engagement member are provided with the cylindrical cam, and a third engagement member is disposed at a predetermined position. A rotation of the cylindrical cam in a first direction is stopped when the first engagement member engages with the third engagement member, and a rotation of the cylindrical cam in a second direction is stopped when the second engagement member engages with the third engagement member.

Alternatively, it is preferable that a rotation of the cylindrical cam in a first direction is stopped when the cap driving pin reaches at a first dead end of the cam groove, and a rotation of the cylindrical cam in a second direction is stopped when the cap driving pin reaches at a second dead end of the cam groove.

Here, it is preferable that the pump gear and the cylindrical cam are coaxially arranged, so that they can be arranged in a compact manner.

Still here, it is preferable that the frictional clutch includes an urging member which presses one circular end surface of the pump gear and one circular end surface of the cylindrical cam together.

Further, it is preferable that the pump is a tube pump which performs a sucking operation only when the cylindrical cam is rotated in either one of the first direction and the second direction.

Here, it is preferable that the pump is arranged coaxially with the cylindrical cam.

Preferably, the head cap includes:

a cap body having an opening which faces the nozzle surface;

a cap holder, which holds the cap body;

an urging member, disposed in the cap holder to urge the cap body in a direction that the cap body is projected from the cap holder; and

a vent valve, closed when the cap body of the head cap placed at the capping position is pushed toward the cap holder by a predetermined amount against an urging force of the urging member, so that an interior space of the head cap is isolated from atmosphere.

Here, it is preferable that the cam groove includes:

a first portion which moves the cap driving pin so as to place the cap holder at a first capping position where the cap body covers the nozzles and the vent valve is closed; and

a second portion which moves the cap driving pin so as to place the cap holder at a second capping position where the cap body covers the nozzles and the vent valve is opened.

Still here, it is preferable that the cam groove includes a guide portion which guides the cap driving pin situated in the first portion to the second portion. The cap driving pin situated in the vicinity of one end of the first portion is guided to the second portion via the guide portion, when the cap driving pin is moved away from the one end of the first portion.

Still here, it is preferable that: the first portion includes a depth-decreasing portion in which a depth thereof gradually decreases toward the one end thereof; and the guide portion connects a part in the first portion in the vicinity of the depth-decreasing portion and the second portion.

Preferably, the cam groove is one continuous groove, and the predetermined circumferential angular range is 360 degrees or less.

Preferably, the maintenance mechanism further comprises an intermittent gear arranged coaxially with the cylindrical cam, so as to rotate integrally with the cylindrical cam. A driving force of the driving source is transmitted to the intermittent gear only in a predetermined circumferential angular range of the cylindrical cam between the first position and the second position.

Preferably, the maintenance mechanism further comprises:

a wiper, reciprocally movable between a wiping position for wiping the nozzle surface and a standby position; and

a wiper driving pin, slidably moving along the cam groove to reciprocally move the wiper.

The cam groove includes:

a first dead end portion, at which the wiper driving pin is placed when a rotation of the cylindrical cam in a first direction is stopped;

a wiper driving portion, continued from the first dead end portion, which moves the wiper driving pin to reciprocally move the wiper;

a second dead end portion, at which the cap driving pin is placed when a rotation of the cylindrical cam in a second direction is stopped; and

a cap driving portion, continued from the second dead end portion, which moves the cap driving pin to reciprocally move the head cap.

Here, it is preferable that the maintenance mechanism further comprises an intermittent gear arranged coaxially with the cylindrical cam, so as to rotate integrally with the cylindrical cam. A driving force of the drive source is transmitted to the intermittent gear only in a predetermined circumferential angular range of the cylindrical cam between the first dead end portion and the second dead end portion of the cam groove.

Here, it is preferable that the pump is a tube pump which performs a sucking operation only when the cylindrical cam is rotated in the second direction.

In the above configurations, the torque of a single drive source is transmitted to the cylindrical cam through the frictional clutch from the pump gear, and a finite rotation of the cylindrical cam causes at least one of the head cap and the wiper to move. Accordingly, it is possible to place the cylindrical cam of the finite rotation type in an initial or reference position without the use of a position detector for detecting the rotation angle of the cylindrical cam. Therefore, an inexpensive head maintenance mechanism easy to control can be realized.

Since there is no need of separately arranging the power transmitting mechanisms for the suction pump, the head cap and the wiper, it is possible to realize a small-sized and compact head maintenance mechanism.

Since forward and rearward rotations from the drive source can be transmitted to the suction pump, it is possible to switchingly control a state of a pump, such as a tube pump, by switching of a direction of rotation of the drive source.

Since the cam groove is formed so as to establish a state in which the head cap seals the nozzle surface, and a state in which the head cap seals the nozzle surface but the interior space of the head cap is communicated to atmosphere, there is no need of separately providing a drive mechanism for driving a valve mechanism for opening of the head cap to the atmosphere and it is possible to realize a small-sized and compact head maintenance mechanism.

Since the cylindrical cam, the pump gear and the suction pump are arranged in a coaxial manner, a predetermined space in a direction perpendicular to the coaxes can be saved so that a small-sized and compact head maintenance mechanism can be realized.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of a head maintenance mechanism of an ink jet printer according to the invention will be described below with reference to the accompanying drawings. Since the ink jet printer in which the head maintenance mechanism of the invention is incorporated is provided with a well-known structure, there will be omitted specific explanation and illustrations for the same.

As shown inFIGS. 1 and 2, a head maintenance mechanism1comprises: a head cap2for capping a nozzle surface of a print head; a wiper3for wiping the nozzle surface; and a tube pump4as an ink suction pump for sucking ink from the head cap2. Also, the head maintenance mechanism1further comprises a stepping motor5as a common drive source for driving the head cap2, wiper3, and the tube pump4. Further, the head maintenance mechanism1comprises a power transmitting mechanism6for transmitting torque of the stepping motor5to the head cap2, wiper3, and the tube pump4. These respective parts are mounted to a housing7.

As shown inFIG. 2, the power transmitting mechanism6comprises a cylindrical cam11, on an outer peripheral surface of which is formed a cam groove12having a predetermined depth in a circumferential direction. A cap driving pin13for movement of the head cap is inserted into the cam groove12in a state of being slidable along the cam groove12as the cylindrical cam11rotates. Also, a wiper driving pin14for movement of the wiper is inserted in a position offset clockwise substantially 90 degrees into the cam groove12in a state of being slidable along the cam groove12as the cylindrical cam11rotates. Further, a pump gear16being a drive power input element of the tube pump4is coaxially opposed to and disposed immediately below a circular bottom surface11a of the cylindrical cam11.

Disposed immediately below the pump gear16is the tube pump4, of which a central shaft17extends centrally through the pump gear16and the cylindrical cam11to project upward. The central shaft17has its lower end17arotatably supported on the housing7and its upper end17brotatably inserted into a shaft hole8aformed in an upper wall8fixed to an upper surface of the housing by a pair of screws.

The cylindrical cam11and the pump gear16are held in frictional engagement by a frictional clutch mechanism18. The frictional clutch mechanism18in the embodiment comprises the circular bottom surface11a, an upper end surface16aof the pump gear16, and a coil spring20mounted in a central hole11bof the cylindrical cam11. The coil spring20is mounted in a compressed state between the cylindrical cam11and the upper wall8to constantly push the cylindrical cam11with a predetermined bias. Accordingly, the circular bottom surface11aof the cylindrical cam11and the upper end surface16aof the pump gear16are pushed together with a predetermined bias to be made rotatable together by frictional forces generated thereby. When load exceeding the frictional forces acts, sliding is established between both elements.

The pump gear16is connected to the stepping motor5through a reduction gear mechanism19. The reduction gear mechanism19comprises a composite reduction gear22meshing with a motor gear21mounted on a motor shaft, and a reduction gear (drive gear)23meshing with a small-diameter gear22aof the composite reduction gear22, the reduction gear23meshing with the pump gear16.

Here, the cylindrical cam11is formed at an outer peripheral surface of a lower end thereof with an intermittent gear25, which is formed over an angular range of substantially 200 degrees with teeth24. The teeth24can also mesh with the reduction gear23.

Also, the cylindrical cam11in the embodiment is of finite rotation type, and there are provided rotation limiters for defining a clockwise dead end and a counterclockwise dead end. The rotation limiters in the embodiment comprise stopper walls11d,11efor defining both ends of an arcuate groove11cformed over a predetermined angular range along an inner peripheral edge of an annular upper surface of the cylindrical cam11, and a projection8bprojected into the arcuate groove11cfrom the back of the upper wall8. When the cylindrical cam11rotates clockwise, the stopper wall11dstrikes against (contacts) the projection8bto inhibit rotation of the cylindrical cam11. Also, when the cylindrical cam11rotates counterclockwise, the other stopper wall11estrikes against (contacts) the projection8bto inhibit rotation of the cylindrical cam11.

With the power transmitting mechanism6in the embodiment constructed in this manner, rotation of the stepping motor5is transmitted to the pump gear16through the reduction gear mechanism19, and rotation of the pump gear16is transmitted to the cylindrical cam11through the frictional clutch mechanism18. Also, rotation of the stepping motor5is transmitted directly to the cylindrical cam11in a state, in which the intermittent gear25of the cylindrical cam11meshes with the reduction gear23.

When the cylindrical cam11rotates, the cap driving pin13and the wiper driving pin14, which are inserted into the cam groove12of the cam in predetermined positions, are moved in a direction (up and down direction inFIGS. 2 to 6) along an axis of rotation of the cylindrical cam11to afford a capping state by the head cap2and a wiping state by the wiper3. Also, the tube pump4sucks ink from the head cap2put in the capping state.

Next, the construction of the head cap2in the embodiment will be described with reference toFIGS. 6 to 9. The head cap2comprises a box-shaped cap body31facing a nozzle surface101of a print head100and opened upward, and a cap holder32holding the cap body31in a state to receive the same from the upper opening. A horizontal arm32ais projected from a side of the cap holder32, and the cap driving pin13is inserted into a pin hole32bformed on a tip end of the arm32a.In the embodiment, a coil spring32cinserted into the pin hole32bconstantly biases the cap driving pin13in a projecting direction from the pin hole32b.Accordingly, a tip end of the cap driving pin13is constantly pushed against a bottom surface of the cam groove12of the cylindrical cam11.

An ink absorbing member33is housed in the cap body31, and ink recovered by the ink absorbing member33is discharged from an ink discharging port34formed in a bottom plate portion of the cap body31.

Also, configured between the bottom plate portion of the cap body31and the cap holder32is a vent valve mechanism35for opening an interior of the cap body to the atmosphere. More specifically, a vent port36is extended downward from the bottom plate portion of the cap body31, and a valve seat37is formed on the cap holder32to be opposed to a lower end of the vent port36. The cap body31is mounted in a state to be vertically movable a predetermined amount with regard to the cap holder32. Normally, the cap body31is biased upward by a coil spring38, and therefore the vent port36is spaced away from the valve seat37to be held in an atmospheric opening state. When the cap body31is pressed a predetermined amount from above, a lower end of the vent port36abuts against the valve seat37to be closed thereby, and so the vent valve mechanism35is put in a closed state.

InFIG. 7, the head cap2is in a state to be disposed in a retracted position2A. In contrast,FIGS. 8 and 9show a state in which the head cap2caps the nozzle surface101. In a state shown inFIG. 8, the head cap2is disposed in an ink sucking position2B in which capping is effected when the vent valve mechanism35is put in a closed state. In this position, the cap holder32rises a distance L1from the retracted position2A shown inFIG. 7while the cap body31abuts against the nozzle surface101of the print head100disposed right above to be relatively pushed downward to have the vent port36seated on the valve seat37. In this state, when the tube pump4performs an ink sucking action, ink is sucked from the nozzle orifice on the print head100to be discharged outside.

In contrast,FIG. 9shows an idle sucking position2C, in which the cap holder32rises a smaller distance L2than the distance L1from the retracted position2A and the cap body31caps the nozzle surface101, but the vent valve mechanism35is remained in a opened state since the lift L2is small. In this state, when the tube pump4performs an ink sucking action, ink is not sucked from the nozzle orifice on the print head100and ink recovered by the ink absorbing member33is sucked and discharged outside.

As shown inFIGS. 2 and 3, the wiper3comprises a rectangular wiper blade3a,and a blade holder3bholding the blade, and the blade holder3bis mounted on the housing7in a manner to be able to reciprocate between a retracted position and a wiping position in which the nozzle surface101of the print head100can be wiped. A horizontal arm3cis extended from a side of the blade holder3b,and the wiper driving pin14is mounted to a tip end of the horizontal arm3c.

Next, the construction of the tube pump4will be described mainly with reference toFIGS. 2,10, and11. The tube pump4comprises a rotor42rotatably inserted into a circular recess41formed in the housing7, the rotor42comprising the central shaft17, a lower end plate43formed at a lower end of the shaft17, and a roller driving disk44formed midway up the central shaft17. A pair of rollers45,46are rotatably mounted between the lower end plate43and the roller driving disk44. An ink tube47is laid between the rollers45,46and an inner peripheral surface41aof the circular recess41on the housing7. One end of the ink tube47is communicated to the ink discharging port34of the head cap2, and the other end thereof is communicated to an ink recovery section (not shown).

An upper end surface of the roller driving disk44is opposed to a lower end surface of the pump gear16. Formed at one position in a circumferential direction on both surfaces are engagement projections (not shown), and when the roller driving disk44rotates approximately 360 degrees, both projections engage with each other to cause the pump gear16and the tube pump4to rotate together.

Arcuate grooves44a,44bare formed on the roller driving disk44as shown inFIGS. 10 and 11to guide central shafts45a,46aof the rollers45,46. When the tube pump4rotates in a direction indicated by an arrow inFIG. 10, the pair of rollers45,46move radially outward along the arcuate grooves44a,44bto revolve while flattening the ink tube47. Thereby, an ink sucking action (pumping action) is made. Meanwhile, when the tube pump4rotates in a reverse direction shown inFIG. 11, a release state, in which the ink tube47is not flattened, is created since the pair of rollers45,46retract radially inward along the arcuate grooves44a,44b.

Next, a detailed explanation will be given to the cam groove12formed on the cylindrical cam11in the embodiment.FIG. 12Ashows a development of the cam groove12of the cylindrical cam11in plan,FIG. 12Bis a view showing groove depths of respective portions, andFIG. 12Cis a view showing positions of the intermittent gear25and the reduction gear23.

The cam groove12in the embodiment comprises a first dead end51, against which the wiper driving pin14abuts, or close to which the wiper driving pin is disposed when the cylindrical cam11rotates counterclockwise, a wiper driving region52, which is contiguous to the first dead end51and in which the wiper driving pin14is moved, a cap driving region53, in which the cap driving pin13is moved, and a second dead end54formed at an end of the cap driving region53. When the cylindrical cam11rotates clockwise, the cap driving pin13abuts against or is disposed close to the second dead end54. In the embodiment, the cam groove12is formed over an angular range of approximately 350 degrees, and a connecting region55connects between the wiper driving region52and the cap driving region53. Of course, wiper driving region52and cap driving region53may include discontinuous cam grooves.

Here, as described above, the dead ends of the cylindrical cam11in clockwise and counterclockwise rotation are defined by the stopper walls11d,11eof the cylindrical cam11and the projection8bformed on the upper wall8. In the embodiment, the cylindrical cam11rotates clockwise and the stopper wall11dstrikes against the projection8b,whereby clockwise rotation of the cylindrical cam is stopped. In this state, the cap driving pin13abuts against the second dead end54or comes to a position immediate before it abuts against the second dead end54. Conversely, the cylindrical cam rotates counterclockwise and the stopper wall11estrikes against the projection8b, whereby counterclockwise rotation of the cylindrical cam is stopped. In this state, the wiper driving pin14abuts against the first dead end51or comes to a position immediate before it abuts against the first dead end51.

The wiper driving region52comprises a trapezoidal portion extending over an angular range of approximately 90 degrees, and the wiper driving pin14disposed at the first dead end51slides relative to and along the wiper driving region52to move up and down when the cylindrical cam11rotates clockwise. When the cylindrical cam11rotates approximately 45 degrees, the wiper3comes to the wiping position enabling wiping the nozzle surface101from the retracted position, and when the cylindrical cam11further rotates approximately 45 degrees, it returns to the retracted position again. In a state in which the wiper driving pin14is disposed in the connecting region55of the cam groove12as shown inFIG. 12A, the wiper3rises to the wiping position and then returns to the retracted position when the cylindrical cam rotates counterclockwise.

The cap driving region53comprises a slope portion61contiguous to the horizontally extending connecting region55and slanted upward at a predetermined angle, an upper horizontal portion62contiguous to an upper end of the slope portion61and extending horizontally, and a lower horizontal portion63formed in parallel to and below the upper horizontal portion62. Also, the cap driving region53further comprises a guide portion64for guiding the cap driving pin13, which is disposed at adjacent the second dead end54of the upper horizontal portion62, to the lower horizontal portion63when the cylindrical cam11rotates counterclockwise.

In a state in which the cap driving pin13is disposed in the connecting region55shown inFIG. 12A, the head cap2is disposed in the retracted position2A (seeFIG. 7). In this state, when the cylindrical cam11rotates clockwise, the cap driving pin13rises along the slope portion61to reach the upper horizontal portion62. This state corresponds to an ink sucking position2B in which the head cap2caps the nozzle surface101in a state, in which the vent valve mechanism35is closed, as shown inFIG. 8. In contrast, a state, in which the cap driving pin13is disposed in the lower horizontal portion63, corresponds to an idle sucking position2C, in which the head cap2caps the nozzle surface101in a state, in which the vent valve mechanism35is opened, as shown inFIG. 9.

Here, as seen fromFIG. 12B, a groove depth H1is deepest in the connecting region55, the slope portion61, and the upper horizontal portion62, while a groove depth of the upper horizontal portion62gradually decreases from a portion on a side of the second dead end54and is made constant over a portion up to the second dead end54. Also, a groove side of a lower portion of the upper horizontal portion62is cut out in a stepwise manner to form a lower horizontal portion63having a small groove depth H2. The lower horizontal portion63extends between the second dead end54and the slope portion61.

The guide portion64is formed by cutting out a bottom surface of the lower horizontal portion63while leaving a lower portion63a,and comprises a portion64ahaving a groove depth H3between groove depths of the portions62,63, and a portion64b,of which groove depth gradually decreases from the portion64ato the slope portion61. An end of the portion64ais situated near the portion at which the groove depth of the upper horizontal portion62starts decreasing, or the portion at which the groove depth of the upper horizontal portion62is decreasing. An end of the portion64bis continuous to the lower horizontal portion63

FIG. 13is a view showing a movement of the cap driving pin13, which moves along the cap driving region53provided with these portions61to64. Explained with reference to the figure, when the cylindrical cam11rotates in a clockwise direction A, the cap driving pin13moves along the slope portion61from a position13(1) in the connecting region55as shown by an arrow “a” to be guided into the upper horizontal portion62to reach the second dead end54.

When the cylindrical cam11rotates in a counterclockwise direction B in a state in which the cap driving pin13is disposed in the position13(2), the cap driving pin13moves in an opposite direction along the upper horizontal portion62as shown by an arrow “b” and when reaching the guide portion64, the cap driving pin falls onto the guide portion64from the upper horizontal portion62to descend along the portion to reach the lower horizontal portion63.

When the cylindrical cam11rotates in the clockwise direction A again in a state in which the cap driving pin13is disposed in the position13(3), the cap driving pin13moves in the lower horizontal portion63along the narrow groove bottom63ato reach a position13(4) on the second dead end54.

Here, the teeth24of the intermittent gear25formed on the cylindrical cam11are formed over an angular range from an angular position near the second dead end54in the cam groove12to an angular position near the slope portion61(seeFIG. 12C). In other words, in the case where the cylindrical cam11rotates clockwise, in a rotating angle position immediate before the cap driving pin13moving relative to and along the cam groove12abuts against the second dead end54of the cam groove12, one end24aof the teeth24of the intermittent gear25passes the reduction gear23to be released of meshing with the reduction gear23. Also, in the case where the cylindrical cam11rotates counterclockwise, in a rotating angle position immediate before the wiper driving pin14moving relative to and along the cam groove12abuts against the first dead end51of the cam groove12, the other end24bof the teeth24of the intermittent gear25passes the reduction gear23to be released of meshing with the reduction gear23.

Next, operation of the head maintenance mechanism1according to the embodiment will be described mainly with reference toFIGS. 14 to 16. First, an explanation will be given to the operation when the head cap2is moved to the ink sucking position2B from the retracted position2A. The cap driving pin13and the wiper driving pin14are disposed in initial positions shown inFIG. 12, andFIG. 16Ashows the positional relationship of respective parts in the initial positions. One end24bof the teeth24of the intermittent gear25is in a position slightly offset counterclockwise relative to the reduction gear23.

When the stepping motor5is reversely rotated in this state (point of time t0, the reduction gear23rotates counterclockwise. The pump gear16meshing with the reduction gear23rotates clockwise A, and the cylindrical cam11connected to the pump gear16via the frictional clutch mechanism18also rotates clockwise A. When the cylindrical cam11rotates clockwise A, the teeth24of the intermittent gear25shift to a state of meshing with the reduction gear23in the meantime (point of time t1, and thereafter torque of the stepping motor5is transmitted to the cylindrical cam11not through the frictional clutch mechanism18. Therefore, the cylindrical cam11can be surely rotated even when load on the cylindrical cam11increases.

Owing to clockwise rotation of the cylindrical cam11, the wiper driving pin14sliding relative to the cam groove12slides along the wiper driving region52of the cam groove12to lift the wiper3to the wiping position from the retracted position (from point of time t2to point of time t4. At this point of time t3, the print head100is moved via the position of the wiper3to thereby permit the wiper blade3ato wipe the nozzle surface101.

When the cylindrical cam11rotates further, the wiper3descends and returns to the retracted position (point of time t5), the cap driving pin13begins ascending along the slope portion61of the cam groove12. Thereby, the head cap2begins ascending from the retracted position2A. Before a point of time t6which is immediate before a point of time t7when the cap driving pin13reaches the upper horizontal portion62of the cam groove12, the cap body31of the head cap2is put in a state to cap the nozzle surface101of the print head100having stood by immediately above, and thereafter only the cap holder32ascends and the cap body31is relatively depressed downward. As a result, the vent valve mechanism35of the head cap2shifts to a closed state at a point of time t6and thereafter the head cap2reaches the ink sucking position2B. This state is shown inFIGS. 8 and 16B.

Subsequently, when the cylindrical cam11rotates further clockwise, one end24aof the teeth24of the intermittent gear25of the cylindrical cam11passes the reduction gear23, so that meshing of the intermittent gear25and the reduction gear23is released (point of time t8). Thereafter, the cylindrical cam11rotates together with the pump gear16via the frictional clutch mechanism18, and the cap driving pin13is disposed at the second dead end54of the cam groove12at a point of time t9.

In this state, the stopper wall11dof the cylindrical cam11strikes against the projection8bof the upper wall8to inhibit rotation of the cylindrical cam11. Accordingly, slip is then generated in the frictional clutch mechanism18, so that the cylindrical cam11makes no rotation and is held in a stop state and only the pump gear16continues to rotate.FIG. 16Cshows this state. When the pump gear16makes substantially one revolution from the initial position, the pump gear16engages with the roller driving disk44of the tube pump4(a point of time t10), and the tube pump4is then drivingly rotated clockwise. As a result, the pair of rollers45,46revolve while flattening the ink tube47as shown inFIG. 10, and ink suction is performed in the head cap2capped in a state in which the vent valve mechanism35is closed. As a result, ink is sucked from the nozzle orifice on the print head100to be discharged outside.

When the stepping motor5is rotated forward after the ink sucking action is terminated, a reverse operation to the above is effected and the respective parts are returned to an initial state. More specifically, the cylindrical cam11rotates counterclockwise to a position where the wiper driving pin14is disposed at the first dead end51of the cam groove12(state at a point of time t0). In a state in which the wiper driving pin14is disposed at the first dead end51of the cam groove12, the stopper wall11eof the cylindrical cam11strikes against the projection8bof the upper wall8to inhibit rotation of the cylindrical cam11. Accordingly, slip is then generated in the frictional clutch mechanism18so that the cylindrical cam11is held in that position. Meanwhile, the pump gear16continues to rotate counterclockwise to rotate the tube pump4counterclockwise, and the pair of rollers45,46retract radially inward to establish a pump release state in which flattening of the ink tube47is released. This state is shown inFIG. 16D, the relative positions of the respective parts being the same as those in the initial state shown inFIG. 16A.

Next, an explanation will be given to the operation when the head cap2is moved to the idle sucking position2C with reference toFIG. 15. In this case, the operation until the point of time t9inFIG. 15is also the same as described above. At the point of time t9, the head cap2reaches the ink sucking position2B and the cap driving pin13is disposed at the second dead end54of the cam groove12.

Thereafter, at the point of time t11, the rotation of the stepping motor5is reversed in a forward direction (clockwise direction) for a predetermined period of time (from the point of time t11to a point of time t13). As a result, the cylindrical cam11rotates counterclockwise such that the cap driving pin13moves within the cam groove12along a path indicated by an arrow b inFIG. 13, and reach the lower horizontal portion63at the point of time t13. Here, since the cap holder32of the head cap2descends, the cap body31pressed against the nozzle surface101is relatively pushed upward while being kept in the capping state, and the vent valve mechanism35having been in a closed state returns to an open state at the point of time t12immediate before the point of time t13.

When the stepping motor5is reversely driven in the counterclockwise direction at the point of time t13, the cylindrical cam11rotates clockwise to cause the cap driving pin13to slide along the lower horizontal portion63of the cam groove12to be disposed at the second dead end54(at a point of time t14). After this time of point, only the pump gear16rotates while the cylindrical cam11stops. After a point of time t15, the pump gear16engages with the roller driving disk44of the tube pump4to drive the tube pump4, thus starting the ink suction. In this state, since the vent valve mechanism35of the head cap2is opened, ink is not sucked from the nozzle orifice but ink contained in the ink absorbing member33is sucked and discharged outside (that is, idle suction is performed).

After the idle suction is performed, rotating the stepping motor5forwardly, the cylindrical cam11rotates counterclockwise, so that the cap driving pin13situated in the second dead end54is moved along the lower horizontal portion63to the initial position via the slope portion61.

As described above, with the head maintenance mechanism1of the ink jet printer in the embodiment, rotation of the stepping motor5is transmitted to the cylindrical cam11through the reduction gear mechanism19, the pump gear16, and the frictional clutch mechanism18. Also, in an operating state, in which there is no need of causing the cylindrical cam11to move the head cap2and the wiper3, the stopper walls11d,11eof the cylindrical cam11are made to strike against the projection8bof the upper wall8to inhibit rotation of the cylindrical cam11to generate slip in the frictional clutch mechanism18, thereby enabling rotation of only the pump gear16for driving of the tube pump.

Accordingly, the cylindrical cam11rotates clockwise or counterclockwise only in a range of rotating angle prescribed by the stopper walls11d,11e,and so can be constantly returned to the initial or reference position. Therefore, unlike the case where a cylindrical cam continuously rotated in the same direction by one direction of a motor is used to drive a head cap, wiper or an ink suction pump, there is no need of providing a detector for detecting the position of a cylindrical cam and the respective parts can be operatively controlled on the basis of the number of steps in the stepping motor5. As a result, it is possible to realize inexpensive drive control of good controllability.

Also, it is possible to use the tube pump4to control an amount of ink as sucked on the basis of the number of steps in the stepping motor5.

Further, since the pump gear16is rotated clockwise and counterclockwise, the tube pump4can be switched between a pumping state, in which the rollers45,46revolve while flattening the ink tube47, and a pump release state, in which the rollers45,46retract from the ink tube47. Therefore, unlike a head maintenance mechanism, in which an ink suction pump is driven only in rotation in one direction, a state of a pump can be switchingly controlled by forward and rearward rotation of a motor.

Besides, since play of about 360 degrees is present between the pump gear16and the tube pump4, the tube pump4does not operate when only the capping action and the wiping action from the pump release state are made. Therefore, an unnecessary action of the tube pump4, that is, the flattening action of the ink tube47can be avoided, so that it is possible to maintain durability of the ink tube47. Also, since the ink tube47is not flattened in the capping state, there is obtained an effect that there is no deformation of the ink tube47.

Also, the upper horizontal portion62and the lower horizontal portion63are formed in the cam groove12of the cylindrical cam11so that when the cylindrical cam11is rotated counterclockwise, the cap driving pin13disposed at the upper horizontal portion62is guided to the lower horizontal portion63through the guide portion64. Accordingly, a state, in which capping of the head cap2is made in a closed state to permit ink to be sucked from the nozzle orifice, and a state, in which capping of the head cap2is made in an atmospheric opening state to permit ink to be sucked from the ink absorbing member33but not to permit ink to be sucked from the nozzle orifice can be realized without separate provision of a drive mechanism for driving of the vent valve mechanism35.

Besides, with the embodiment, the pump gear16and the tube pump4are provided below the cylindrical cam11in a coaxial manner, so that an installation space therefor, in particular, an installation area in a lateral direction can be considerably reduced so that a very compact head maintenance mechanism can be realized.

Further, with the embodiment, the rotation stop position of the cylindrical cam11is prescribed by engagement between the stopper walls11d,11eof the cylindrical cam11and the projection8bof the upper wall8. Rotation of the cylindrical cam can be restricted by engagement of the cap driving pin13and the second dead end54and engagement of the wiper driving pin14and the first dead end51. In this case, clutch forces are applied on the respective pins13,14to cause movements of the head cap2and the wiper3, so that failure of positioning relative to the print head100or the like is liable to occur, and fixing portions (mount portions) of the respective pins13,14are also liable to cause a problem in durability. In the embodiment, the projection8bformed on the upper wall8fixed to the housing7receives forces for stopping the rotation of the cylindrical cam, so that failure of positioning of the head cap2and the wiper3can be avoided and mount portions of the respective pins13,14cause no problem in durability.

While a tube pump is used as an ink suction pump in the above embodiment, other ink suction pumps can be also used.

Also, while a stepping motor drives the head cap, wiper and the tube pump in the above embodiment, the invention can be likewise applied to, for example, the head maintenance mechanism configured to drive only the head cap and the ink suction pump.

Further, while the cam groove is a single cam groove extending substantially continuously over an angular range of at most 360 degrees, it can be formed as a cam groove comprising a portion for driving of a wiper and a portion for driving of a head cap, which portions are discontinuous or separate. Also, the angular range of the cam groove can be 360 degrees or more.

Also, while the intermittent gear can be used in the above embodiment to smoothly and surely rotate the cylindrical cam even when a large load is applied on the cylindrical cam, it is possible to omit the intermittent gear in the case where load applied on the cylindrical cam is small.

In addition, in the case where a force for preventing rotation of the cylindrical cam11is small, it is also possible in the above embodiment to omit the stopper walls11d,11eand the projection8bof the upper wall8for restricting the cylindrical cam11and then to restrict the rotation of the cylindrical cam11by engagement of the respective pins13,14and the respective dead ends54,51.