Patent Grant
7182336
1. Field of the Invention
The present invention relates to a paper feeder which stores a stack of recording materials, and feeds the recording materials sheet by sheet from the uppermost recording material to the downstream side, a recording apparatus for recording an image on a recording material, and a method of detecting a position of the terminal edge of a recording material.
2. Description of the Related Art
A printer is known as one form of the recording apparatus. Some of the printers are each equipped with a paper feeder for feeding the recording materials as printing sheets sheet by sheet from the uppermost recording material to a downstream side. The paper feeder includes a paper feed roller rotatably driven, and a hopper. The hopper is formed with a plate member long in the width direction of the printing sheet, and includes a fulcrum which is slanted when viewed from the side a sheet transport path of the printing sheet and is located in an upper part. When turned, it angularly moves toward the paper feed roller, and is pressed against the paper feed roller, or angularly moves apart from the paper feed roller. When printing sheets stacked in the hopper are moved upward by the hopper, the printing sheets are fed sheet by sheet from the uppermost printing sheet of the stack.
The hopper is urged by an urging device to turn in such a direction in which it is pressed against the paper feed roller. As a result, the stacked printing sheet is abutted on the paper feed roller. The hopper is provided with a release device, and is turned by the hopper release device in such a direction that it moves apart from the paper feed roller and its state is retained. The hopper is angularly moved between a sheet feeding position at which the uppermost printing sheet is abutted against the paper feed roller (paper feeding state) and a stand-by position at which it is most apart from the paper feed roller (release state). The sheet feeding position varies depending on the number of printing sheets as set (stacked).
When the hopper is moved from the stand-by position to the sheet feeding position, it is energetically turned to the paper feed roller or in a pressing-contact direction by the urging force of the urging device. With the turn, the printing sheet hits the paper feed roller, and a great sound (hitting sound) is generated from component parts around the hopper and the roller.
An angle (swing angle) developed when the hopper is moved from the stand-by position to the sheet feeding position, somewhat varies depending on the stack amount of the printing sheets as mentioned above. As the stack amount of the printing sheets is larger, the swing angle is smaller, and while the stack amount is smaller, the swing angle becomes larger. Accordingly, when the stack amount of the printing sheets is small where the swing angle is large, much time is taken for the sheet feeding operation, viz., high speed repeating sheet feeding operation cannot be performed.
An ink jet printer prints an image on a printing sheet in a manner that an operation of ejecting ink to the printing sheet while the recording head is reciprocated in the main scan direction and an operation of moving the printing sheet in the sub-scan direction are alternately repeated. The ink jet printer generally uses a sheet detector for detecting the printing sheet for the purpose of detecting a leading edge and a terminal edge of the printing sheet. Various types of sheet detectors for detecting the printing sheets are present. One of those known detectors is constructed such that when the printing sheet is fed, a rotatable lever part is projected and the printing sheet presses forward and turns the lever part to thereby detect the printing sheet.
There is known a sheet detector in which a mechanism having some movable part, not the rotatable lever part, engages with the printing sheet to thereby detect the printing sheet. This type of detector may take various forms. Any of those detectors detects the leading position of the printing sheet when the movable part of the sheet detector starts to engage with the recording sheet, and detects the terminal edge of the printing sheet when its engagement with the recording sheet ends.
The sheet detector of the type which detects the printing sheet through the engagement of the mechanism having the movable part engages with the printing sheet, has the following defect. At the instant that the terminal edge of the printing sheet leaves the movable part following the ending of the engagement of the movable part with the printing sheet, the sheet detector cannot recognize the leaving of the terminal edge. Exactly, a slight time elapses from the instant that the terminal edge of the printing sheet leaves the movable part till the movable part starts to move under its weight or urging force of the urging device as it returns to a fixed position and reaches a position at which the movable part can recognize the fact that the printing sheet does not engage with the movable part. That is, a slight time lag occurs.
If the sheet detector of the non-contact type, such as an optical sensor, is used, the time lag is almost negligible. On the other hand, in the case of the sheet detector which detects the printing sheet through the engagement of the movable part with the printing sheet, when it detects the terminal edge of the printing sheet, a fixed time lag occurs. The position of the terminal edge of the printing sheet, when detected, is shifted from its correct position by a distance that the printing sheet is transported during the delay time.
However, the detection offset of the terminal edge position of the printing sheet, which is caused by the delay time, is almost negligible since the transporting speed is relatively slow. It little affects the print quality.
In recent ink jet recording apparatuses, there is a tendency that the transporting of the printing sheet is performed at high speed in order to reduce the recording execution time. Accordingly, the detection offset of the terminal edge position of the printing sheet is not negligible. As a result, the following problems will be created: the blank part at the terminal edge of the printing sheet becomes narrow or the recording operation is continued beyond the terminal edge of the sheet.
The delay time may be reduced by narrowing the movable range of the movable part. If the movable range is too narrowed, the movable part will erroneously be moved responsive to a slight variation of the state of the printing sheet engaging the movable part, vibration and the like. In this respect, there is a limit in reducing the delay time by the narrowing the movable range of the movable part.
When the movable part is urged to a fixed position by an urging device having a strong urging force in order to increase the moving speed at which the movable part returns to the fixed position from the instant that the printing sheet leaves the movable part, the urging force is too strong. As a result, in the case of the printing sheet having a high rigidity, there is a danger that the leading edge of the printing sheet cannot move the movable part. For this reason, there is a limit in increasing the moving speed at which the movable part returns to the fixed position by urging the movable part to the fixed position by a strong urging force.
A possible solution to this problem is to uniquely correct the terminal edge position of the printing sheet based on the transporting speed of the printing sheet, which is set at the time of the recording control. However, the transporting speed of the printing sheet is not always constant since the transporting speed is repeatedly accelerated and decelerated by intermittently stopping the transporting of the printing sheet. For this reason, the terminal edge position of the printing sheet, which is uniquely computed from the transporting speed of the printing sheet that is set at the time of recording control, will be poor in precision.
Accordingly, an object of the present invention is to reduce noise generated when the hopper is turned, and to realize a high speed paper feeding operation.
Another object of the invention is to provide a recording apparatus equipped with a sheet detector for detecting a printing sheet through the entangling of a movable mechanism with the printing sheet, which the recording apparatus is free from such a disadvantage that the printing sheet is transported at high speed and a printing operation is performed, and then a position of the terminal edge of the printing sheet is shifted from its correct position.
To achieve the above objects, the invention provides a first paper feeder comprising:
a paper feed roller for feeding a recording material to a downstream side of transportation by the paper feed roller;
a hopper formed with a plate member long in a width direction of the recording material, the hopper being angularly moved around a fulcrum thereof so as to be apart from and to be abutted against the paper feed roller;
an urging device located opposite to the paper feed roller with respect to the hopper for urging the hopper toward the paper feed roller from a backside of the hopper; and
a hopper release device for moving the hopper apart from the paper feed roller while resisting the urging device;
wherein a plurality of the recording materials are stacked in the hopper and are pushed upward so as to be successively fed to the downstream side of transportation from an uppermost recording material of the stacked recording materials; and
the hopper release device has a non-release mode where the uppermost recording material is abutted against the paper feed roller by an urging force of the urging device,
a small release mode where the hopper is turned and held so that the uppermost recording material is slightly separated from the paper feed roller, and
a large release mode where the hopper is turned and held so that the hopper is at the most apart from the paper feed roller.
In the first paper feeder, a stand-by position (release state) of the hopper is controlled to be an appropriate position in accordance with an amount of stacked recording materials. As a result, the swing angle of the hopper is minimized, noise generated when the hopper is swung is reduced, and high speed paper feeding operation is ensured.
The hopper release device for separating the hopper from the paper feed roller has three modes: a non-release mode, a large release mode, and a small release mode, which is at a medium level between the former modes.
In the non-release mode, the hopper release device does not impart any external force to the hopper, and the recording material is abutted against the paper feed roller by only the urging force of the urging device. In this mode, the hopper is at a sheet feeding position (sheet feeding state).
In the large release mode, the hopper is turned so that the hopper is most apart from the paper feed roller, and retains its state. In his mode, the hopper is at a perfect sand-by position (release state), and in this state, the user may set recording materials on the hopper.
The first paper feeder has the small release mode, which is at a medium level between the non-release mode and the large release mode. In the small release mode, the hopper is turned so that the uppermost recording material is slightly separated from the paper feed roller, and its state is retained. Accordingly, when the hopper is turned from this state to feed a second or next recording material, an angle (swing angle) of the hopper developed when the recording material is abutted against the paper feed roller is minimized. For example, when the next paper feeding job arrives, the small release mode is executed. If so done, the noise generated when the recording material is abutted against the paper feed roller is reduced, and high speed paper feeding (repetitive paper feeding) is possible.
A second paper feeder of the invention, which depends from the first paper feeder, is provided. In the second paper feeder, the hopper release device is brought in the small release mode during a period between an end of feeding the uppermost recording material and a start of feeding the successive recording material.
In the second paper feeder, during a period of time from the end of feeding the uppermost recording material till the feeding of a second recording material starts, the hopper release device retains a state that the second recording material is slightly separated from the paper feed roller, by the small release mode. Therefore, the swing angle is minimized as described above, and the noise generated when the hopper is swung is reduce, and high speed paper feeding operation is ensured.
A third paper feeder, which depends from the first or second paper feeder, is provided. In the third paper feeder, the hopper release device is brought in the large release mode after an end of feeding a final recording material.
In this paper feeder, after execution of a series of paper feeding jobs ends, the hopper release device retains a state that the hopper is most apart from the paper feed roller, by the large release mode. Even when the user sets additional recording materials on the hopper after execution of a series of paper feeding jobs ends, there is no need of user's operation to manually press down the hopper. In this respect, the recording material setting work is easy.
A fourth paper feeder, which depends from any of the first to third paper feeders, is provided. In the fourth paper feeder, the hopper release device including
a rotary cam,
a cam lever engaging with the rotary cam and displacing in a radial direction of the rotary cam when the rotary cam rotates, and
a cam lever holder axially supporting the cam lever so as to be swingable in an axial direction of the rotary cam, and having a hopper acting part through which a rotational force for the hopper is imparted, whereby the cam lever holder swings around a rotation shaft parallel to the axial direction of the rotary cam to thereby angularly move the hopper when the cam lever displaces in the radial direction of the rotary cam,
the rotary cam being provided with
a stepped cam part provided with a plurality of fan-shaped cams which are disposed in a stepped manner from an outer periphery of the rotary cam to a center of rotation thereof, an outer peripheral surface of each of the fan-shaped cams forming a cam face and being engageable with the cam lever,
a non-cam part for displacing the cam lever to an inner periphery side of the rotary cam till the uppermost recording material is abutted against the paper feed roller, and
a cam lever guide for guiding the cam lever to one of the cam faces of the fan-shaped cams which is located on an outer periphery side of the rotary cam and is the closest to a position of the cam lever in which the uppermost recording material is in pressing contact with the paper feed roller,
wherein the hopper release device is brought into the large release mode when the cam lever is engaged with the cam face of the outermost fan-shaped cam,
the hopper release device is brought into the non-release mode when the cam lever is engaged with the non-cam part or the cam lever guide part, and
the hopper release device is brought into the small release mode when the cam lever is guided to one of the cam faces of the fan-shaped cams by the cam lever guide.
In the fourth paper feeder, any of the three modes, non-release mode, large release mode and small release mode, may be selected by rotating the rotary cam without using a complicated drive force mechanism.
A fifth paper feeder, which depends from the fourth paper feeder, is provided in which the rotary cam is integrally formed with a resin.
In the case that the rotary cam is integrally formed with a resin, cost to manufacture the rotary cam is reduced.
A sixth paper feeder, which depends from the fourth paper feeder, is provided in which the rotary cam engages with a rotation shaft of the paper feed roller by a gear device, and rotates in accordance with a rotation of the paper feed roller.
In this paper feeder, the rotary cam engages with a rotation shaft of the paper feed roller by a gear device, and rotates in accordance with rotation of the paper feed roller. Accordingly, there is no need of using a drive source provided exclusively for the rotary cam, leading to cost reduction.
A seventh paper feeder, which depends from any of first to sixth paper feeders, is provided in which an action point at which the urging device imparts a force to the hopper and an action point at which the hopper release device imparts a force to the hopper are located at substantially the same position as viewed from the front of the hopper.
In the seventh paper feeder, little bending moment is generated in the hopper. Deformation of the hopper is prevented, and hence, a normal sheet feeding operation is maintained. The hopper consists of a plate member long in the width direction of the recording material. Its lower part is turned around a fulcrum provided at its upper part. Accordingly, it is easy to bend when it receives an external force. The paper feeder includes an urging device for turning the hopper in such a direction as to be pressed against the paper feed roller, and a release device for turning the hopper apart from the paper feed roller. In the seventh paper feeder, an action point at which the urging device imparts a force to the hopper and an action point at which the hopper release device imparts a force to the hopper are located at substantially the same position as viewed from the front of the hopper. With this feature, little bending moment is generated in the hopper. The bending of the hopper is prevented, and hence, a normal sheet feeding operation is maintained.
An eighth paper feeder, which depends from the seventh paper feeder, is provided in which the hopper release device includes
a release bar having a first shaft part extending in the longitudinal direction of the hopper above the urging device, a second shaft part which extends vertically from one end of the first shaft part to the urging device and engages with an engaging part provided on the backside of the hopper, and a third shaft part extending from another end of the first shaft part substantially parallel to the second shaft part, and
a bearing part for axially supporting the first shaft part,
wherein the release lever is turned around the first shaft part to separate the hopper from the paper feed roller.
In this paper feeder, the hopper release device includes a release bar, shaped like U in plan view, which engages with the backside of the hopper. By turning the release bar, the hopper is turned in such a direction as to be apart from the paper feed roller. Accordingly, a space on the backside of the hopper is minimized.
A recording apparatus for recording an image on a recording material is provided with any of the first to eighth paper feeders.
Since the recording apparatus for recording an image on a recording material is provided with any of the first to eighth paper feeders, the recording apparatus has operation and effects similar to those of any of the first to eighth paper feeders.
According to another aspect of the invention, there is provided a first terminal edge position detecting method for detecting a terminal edge position of a recording sheet in a recording apparatus for recording an image on a recording sheet while the recording sheet is transported in a fixed direction at a predetermined transportation quantity, comprising the steps of:
detecting a passage of the terminal edge of the recording sheet and obtaining a detected position of the terminal edge of the recording sheet by a sheet detector which detects the recording sheet by contacting therewith;
acquiring a transporting speed of the recording sheet at a time point of the passage of the terminal edge of the recording sheet;
computing a detect delay error transportation quantity of the recording sheet which is performed in the fixed direction during a detect delay time defined between an instant that the terminal edge of the recording sheet leaves the sheet detector and an instant that the sheet detector detects the passage of the terminal edge of the recording sheet; and
computing the terminal edge position of the recording sheet by correcting the detected position of the terminal edge the detected by the sheet detector with the detect delay error transportation quantity.
Thus, in the sheet detector for detecting the recording sheet in a state that the sheet detector is in contact with the recording sheet, a detect delay error transportation quantity of transportation of the recording sheet which is performed during a detect delay time of detecting the terminal edge of the recording sheet is computed from a transporting speed of the recording sheet at a time point that the sheet detector detects passage of the terminal edge of the recording sheet, and a position of the terminal edge of the detected by the sheet detector is corrected using the detect delay error transportation quantity computed. Accordingly, a detect offset of the terminal edge position of the recording material by the detect delay time is greatly reduced.
As described above, the transporting speed of the printing sheet is not always constant since the transporting speed is repeatedly and intermittently transported and stopped. Therefore, to make an exact correction of the terminal edge position of the recording material, the detect delay error transportation quantity of transportation of the recording sheet must be computed from a transporting speed of the recording sheet at a time point that the sheet detector detects passage of the terminal edge of the recording sheet. By so doing, an exact correction of the terminal edge position of the recording material is secured.
Accordingly, according to the first terminal edge position detecting method, in the sheet detector which detects the recording material through the entangling of a movable mechanism with the printing sheet, there is successfully eliminated such a disadvantage that the printing sheet is transported at high speed and a printing operation is performed, and then a position of the terminal edge of the printing sheet is shifted from its correct position, and as a result, the print quality is deteriorated.
In a second terminal edge position detecting method, which depends from the first terminal edge position detecting method, the detect delay error transportation quantity is given by the following equation
y=kx
where x: transporting speed of the recording sheet at a time point that the sheet detector detects the passage of the terminal edge of the recording sheet,
y: detect delay error transportation quantity
k: delay coefficient.
The detect delay error transportation quantity is a quantity of transportation of the recording material which is performed during the delay time, as described above. Therefore, it is larger as the transporting speed of the recording material at a time point that the sheet detector detects passage of the terminal edge of the recording sheet is higher. It increases proportional to the transporting speed of the recording material. Accordingly, the detect delay error transportation quantity can be obtained by multiplying the transporting speed by a fixed delay coefficient. The delay coefficient “k” varies depending on a detecting characteristic of the sheet detector and a relation between the position at which the sheet detector is disposed and the sheet transport path. The delay coefficient is a known value determined every specification of the recording apparatus.
Thus, the second terminal edge position detecting method has the effects similar to those of the first terminal edge position detecting method. Further, a transporting speed at a time point that the sheet detector detects passage of the terminal edge of the recording material is multiplied by the fixed delay coefficient “k”, whereby the detect delay error transportation quantity is automatically computed.
A third terminal edge position detecting method, which depends from the first or second terminal edge position detecting method, is provided in which the transporting speed of the recording sheet at the time of the passage of the terminal edge is computed from an encoder signal output from an encoder device which detects a rotational displacement quantity of a transport drive roller for transporting the recording sheet.
Thus, a transporting speed of the recording sheet is computed from an encoder signal output from an encoder device. Therefore, a transporting speed of the recording sheet is exactly computed from an encoder signal output from a high performance encoder device.
The third terminal edge position detecting method has the effects similar to those of the first and second terminal edge position detecting methods. Further, since a transporting speed of the recording sheet is exactly computed from an encoder signal output from a encoder device, the terminal edge position of the terminal edge of the recording material is accurately corrected which is based on the detect delay error transportation quantity computed from the transporting speed of the recording material.
According to yet another aspect, there is provided a first recording apparatus comprising:
a record executing device for recording an image on a recording sheet while transporting the recording sheet in a fixed direction at a predetermined transportation quantity;
a sheet detector for detecting the recording sheet by contacting therewith so as to obtain a detected position of the terminal edge of the recording sheet; and
a control part for controlling the record executing device;
wherein the control part computes a detect delay error transportation quantity of the recording sheet which is performed during a detect delay time from an instant that the terminal edge of the recording sheet leaves the sheet detector and to an instant that the sheet detector detects a passage of the terminal edge of the recording sheet, with a transporting speed of the recording sheet at the passage of the terminal edge of the recording sheet detected by the sheet detector, and
the control part computes the terminal edge position of the recording sheet by correcting the detected position of the terminal edge of the recording sheet with the detect delay error transportation quantity.
The recording apparatus has the effects similar to those of the first terminal edge position detecting method.
A second recording apparatus depends from the first recording apparatus. In the second recording apparatus, the detect delay error transportation quantity is given by the following equation
y=kx
where x: transporting speed of the recording sheet at a time point that the sheet detector detects the passage of the terminal edge of the recording sheet,
y: detect delay error transportation quantity
k: delay coefficient.
The second recording apparatus has the effects similar to those of the second terminal edge position detecting method.
A third recording apparatus is provided which depends from the first or second recording apparatus, and in this device, the record executing device includes a transport drive roller for transporting the recording sheet in the fixed direction by a rotational drive force, and an encoder device for detecting a rotational displacement position of the transport drive roller, and
the control part computes a transporting speed of the recording sheet at a time point where the sheet detector detects the passage of the terminal edge of the recording sheet from an encoder signal output from the encoder device.
The third recording apparatus has the effects similar to those of the third terminal edge position detecting method.
A fourth recording apparatus depends from any of the first to third recording apparatuses, and in this recording apparatus, the sheet detector includes a lever which is granted with self-resetting habit for standing attitude, and pivotally supported to be rotatable in a state that the lever is protruded into a sheet transport path of the recording sheet, and
the recording sheet is detected by a turning of the lever when a tip of the lever is pushed with the recording sheet.
The fourth recording apparatus, which is quipped with the sheet detector in which such a lever is pivotally supported to be rotatable in a state that the lever is protruded into a sheet transport path of the recording sheet, and when the lever is pushed with the recording sheet, the lever is turned and the recording sheet is detected, has also the effects similar to those of the first to fourth recording apparatuses.
As described above, the recording apparatus has three modes: a large release mode in which the hopper is most apart from the paper feed roller, and retains its state, a non-release mode in which the recording material is abutted against the paper feed roller, and a small release mode which is at a medium level between those two modes, and in which the recording material is slightly separated from the paper feed roller. The swing angle of the hopper may be minimized when an amount of stacked recording materials is small in a manner that the recording material is retracted from the paper feed roller by the small release mode, the large release mode, during a time period from the en of the paper feeding operation till the feeding of a second recording material starts. In other words, the retracting position of the hopper may be controlled to a position dependent on the amount of stacked recording materials. As a result, the swing angle of the hopper is minimized, noise generated when the hopper is swung is reduced, and high speed paper feeding operation is realized.
The present invention succeeds in providing a recording apparatus equipped with a sheet detector for detecting a printing sheet through the entangling of a movable mechanism with the printing sheet, which the recording apparatus is free from such a disadvantage that the printing sheet is transported at high speed and a printing operation is performed, and then a position of the terminal edge of the printing sheet is shifted from its correct position.
The above and other objects, features and advantages of the present invention will become apparent from the following description of the presently preferred exemplary embodiments of the invention taken in conjunction with the accompanying drawings, in which:
<First Embodiment>
A first embodiment of the present invention will be described with reference to the accompanying drawings. The description will be given in the order of “overall construction of the ink jet printer”, “overall construction of the paper feeder” and “construction of hopper release device”
<Overall Construction of Ink Jet Printer>
An overall construction of an ink jet printer according to a first embodiment of the present invention will be described with reference to
Referring to
A sheet transporting path in the printer 100 will be described with reference to
A length of an arcuate part of the paper feed roller 3 is longer than such a length as to allow the tip of a printing sheet P fed from the hopper 6 to reach the nip point between a transport drive roller 162 and a transport follower roller 163, viz., a length of the sheet transport path ranging from an abutment point between the paper feed roller 3 and the printing sheet P to reach the nip point between a transport drive roller 162 and a transport follower roller 163. Accordingly, for example, when a number of printing sheets P are stacked on the hopper 6 in
A sheet guide 167 as a plate member is substantially horizontally provided under a downstream part of the paper feed roller 3. The tip of a printing sheet P fed by the paper feed roller 3 comes in contact with the sheet guide 167 in an oblique direction, and smoothly guided to the downstream side. The transport drive roller 162 and the transport follower roller 163, which is brought into contact with ht transport drive roller 162, are provided downstream of the sheet guide 167. The printing sheet P is nipped between transport drive roller 162 and the transport follower roller 163, and transported downstream at a fixed pitch.
The transport follower roller 163 is supported by a shaft at a position downstream of a transport follower roller 164. The transport follower roller 163 is rotatable around a rotation shaft 164a clockwise or counterclockwise in
Subsequently, a platen 166 and the ink jet recording head 124 are vertically and oppositely disposed downstream of the transport drive roller 162. The platen 166 is long in the main scan direction (see
A part downstream of the ink jet recording head 124 forms a sheet discharge part of the printer 100, and contains a sheet-discharge drive roller 165, a sheet-discharge follower roller 131, and an auxiliary sheet-discharge roller 132. A plurality of sheet-discharge drive rollers 165 are provided while being arranged in the axial direction of a sheet-discharge drive roller shaft 165a, which is rotatably driven (see
The hopper 6, movable guide 4, fixed guide 5 and paper feed roller 3 are contained in the paper feed unit 1 shown in
The sheet guide 167, transport drive roller 162, transport follower roller 164 and sheet-discharge drive roller shaft 165a are contained in the transport unit 160, as shown in
The ink system unit 180 as maintenance device of the ink jet recording head 124 is coupled to the right side part of the transport unit 160. The ink system unit 180, as shown in
The carriage guide 125 and the sheet detector 136 are provided in the carriage unit 120. A base of the carriage unit 120, as shown in
As shown in
In
The main body of the printer 100 is thus constructed, and The four units are composed and coupled together, and the printer 100 is operable.
<Detailed Configuration of Paper Feed Unit>>
A detailed construction (overall construction) of the paper feed unit 1 will be described with reference to
Firstly, a base of the paper feed unit 1, as described above, is constructed with the sheet feeding unit frame 2. The paper feed unit includes a transmission gear device on the left side surface (left side in
The paper feed roller shaft 3a is provided between them.
The transmission gear device 17 comes in mesh with a transmission gear (not shown) of the transport unit 160 in a state that the paper feed unit 1 is coupled to the carriage unit 120 (see
The paper feed roller 3 that is driven and rotated by the paper feed roller shaft 3a, as shown in
The hopper 6 as a plate member long in the width direction of the printing sheet P as described above is provided while being slanted as shown in
A separation pad holder 9 and a guide member 13 are provided under the hopper 6. The separation pad holder 9, as shown in
The separation pad 8 that is provided on a separation pad holder 9 cooperates with the paper feed roller 3 to nip the uppermost printing sheet P comes in contact with the separation pad 8 at a contact (paper plug-in) angle α, to thereby prevent the double feeding of a second printing sheet P and the subsequent ones. More exactly, materials of the rubber member 3b and the paper feed roller 3 are selected so as to satisfy a relation μ1>μ2>μ3 where μ1 is a friction coefficient between the paper feed roller 3 and the printing sheet P, μ2 is a friction coefficient between the printing sheets P, and μ3 is a friction coefficient between the printing sheet P and the separation pad. By selecting the friction coefficients so, the uppermost printing sheet P to be fed is reliably fed downstream with rotation of the paper feed roller 3, while a second printing sheet P and the subsequent ones stays at the separation pad 8. As a result, the double feeding of a second printing sheet P and the subsequent ones is prevented. In a lower part of the hopper 6, a holding pad 6b is provided at a position opposed to the paper feed roller 3 and a holding pad 6b. The holding pad 6b prevents a stack of printing sheets P on the hopper 6 from moving downstream when the uppermost printing sheet P is fed.
A variation range of a contact angle α in the embodiment, viz., a disposing position of the rotation shaft 6a which determines a swing angle of the hopper 6 and a dimension of the hopper 6 in the feeding direction (a longitudinal size of the printing sheet P) are selected as below. An angle developed when the hopper 6 swings from a state that it is most apart from the paper feed roller 3 to a state that the uppermost printing sheet P is abutted on the paper feed roller 3, varies depending on an amount of the printing sheets P stacked on the hopper 6. As a result, a contact angle α at which the tip of the printing sheet P comes in contact with the separation pad 8, also varies.
When in
The guide members 13 will now be described. As shown in
If a friction coefficient between the contact surface 13b and the tip of the printing sheet P is large, some time is consumed to complete an abutting operation to turn the hopper 6 and to abut the uppermost printing sheet P against the paper feed roller 3. This adversely affects the paper feeding operation, frequently. In this respect, it is desirable that the friction coefficient is as small as possible (for example, μ<0.3). In the instant embodiment, the guide member 13 is formed by using POM (polyoxymethylene) or AES (acrylonitrile ethylene styrene). The contact surface 13b is coated with lubricant to reduce its friction coefficient. The separation pad holder 9 includes a similar contact surface 9b.
As shown in
The paper feed auxiliary roller 15 thus constructed has the following two functions in the paper feed unit 1 of the embodiment.
A first function of the paper feed auxiliary roller is to control an attitude of the printing sheet P when it is fed. The paper feed roller 3 and the separation pad 8 are provided in pair. In the light of cost reduction demand, it is desirable to provide only one pair of paper feed roller 3 and separation pad 8 as in the instance embodiment. However, to deal with printing sheets P of various sizes, in particular the printing sheet P of small size, the paper feed roller 3 and the separation pad 8 are located deviated to the 0 digit side (the right side in
As shown in
The paper feed auxiliary roller 15 is shaped like D when viewed from side, like the paper feed roller 3. A diameter of the paper feed auxiliary roller is equal to that of the paper feed roller 3. In the paper feed auxiliary roller, a flat part of the D shape is more cut than that in the paper-feed roller 3. This is best illustrated in
The reason for this will be described below. When the printing sheet P is transported (in a print mode), the flat part of the paper feed roller 3 (and paper feed auxiliary roller 15) is opposed to the printing sheet P as shown in
In
A second function of the paper feed auxiliary roller 15 is a function as a “twist restricting member” for restricting a twist of the paper feed roller shaft 3a. The paper feed roller shaft 3a serves as a drive force transmission shaft which receives a rotational force from the transmission gear device 17 provided on the left side of the printer (the left side in
With provision of the paper feed auxiliary roller 15 on the paper feed roller shaft 3a, a twist is reduced at a part at which the paper feed auxiliary roller 15 is provided. The result is to alleviate the phase shift problem caused by the twist. If such a twist restricting part may be provided at another appropriate position, the phase shift problem is further alleviated. In this case, it is not essential that its configuration is the same as of the paper feed roller 3. It may take any configuration if its radial size is larger than that of the paper feed roller shaft 3a. In addition, in the instant embodiment, the paper feed roller shaft 3a, paper feed roller 3 (roller body 3c), and paper feed auxiliary roller 15 (roller body 15c) are integrally formed by using ABS resin. By so doing, the cost of manufacture those components is reduced. The integrated construction further restricts the twist. Even in a case where the paper feed auxiliary roller 15 and the paper feed roller shaft 3a are separately provided, and the former is mounted on the latter by adhesive, for example, the adhering by the adhesive will produce a given the twist restricting effect.
The rubber member 15b is wound around the outer peripheral part of the paper feed auxiliary roller 15. In the instant embodiment, the rubber member 15b is made of EPDM (ethylene polypropylene rubber), like the rubber member 3b wound on the outer periphery part of the paper feed roller 3. In the embodiment, an additive is further added to the EPDM of the rubber member 3b. As a result, the rubber member is improved in tension strength. The reason why the tension strength of the rubber member 15b wound on the paper feed auxiliary roller 15 is selected to be higher than that of the rubber member 3b wound on the paper feed roller 3, will be described hereunder.
To protect the printing surface of the printing sheet P, a elastic member is preferably wound on the outer peripheral part of the paper feed auxiliary roller 15 as in the previous case. In the light of cost reduction, it is not desirable to use the elastic member having the width equal to that of the paper feed roller 3. If the elastic member having the width shorter than that of the paper feed roller 3 is used, its strength is reduced as a whole, and the following problem arises. The guide member 13 for smoothly guiding the printing sheet. P downstream, as shown in
In the paper feed unit 1 which is constructed such that when paper jamming, for example, occurs, the paper feed roller 3 is stopped, the following problem occurs when the jamming occurs. When the roller is stopped, the drive motor 169 (see
By improving the tension strength of the rubber member 15b wound on the paper feed auxiliary roller 15, there is no fear that the rubber member 15b wound on the paper feed auxiliary roller 15 is broken even in such a situation that the jamming occurs between the paper feed auxiliary roller 15 and the two guide surfaces 13a, and the sheet bundle jammed is forcibly pulled out. Further, the width size of the rubber member may be reduced, leading to cost reduction.
In the present embodiment, as shown in
Next, a sheet holder member 14 is provided at a position facing the hopper 6 in
The description thus far made is the elaboration of the paper feed unit 1.
<Hopper Release Device Construction>
A mechanical arrangement of the hopper release device which turns the hopper 6 in a direction in which it move apart the paper feed roller 3, will be described with reference to
As described above, the hopper release device is installed on the right side surface (this side in
A cam lever 30 and a cam lever holder 35, which are swung with rotation of the rotary cam 20, are provided under the rotary cam 20. The hopper release device to be described in detail hereunder successively engages with the rotary cam 20, cam lever 30 and cam lever holder 35 in this order. By the swing operation of the cam lever holder 35, a release bar 16 (see
The description to follow is the construction, operation and effects of the release bar 16 provided on the backside of the hopper 6. As shown in
For the release bar 16, the first shaft part 16b is axially supported by a bearing part 18 located above a sub-frame 19 shaped like V. With this structure, the second shaft part 16a and the third shaft part 16c are rotatable around the first shaft part 16b clockwise and counterclockwise in
An engaging part 6c (see
An engaging part where the release bar 16 engages with the hopper 6, viz., a position where the third shaft part 16c is located, is substantially coincident with a position of the compression coiled spring 7, as shown in
More exactly, as shown in
As described above, in the paper feed unit 1, an action point where the release bar 16 imparts a force on the hopper 6 is substantially coincident in position with an action point where the compression coiled spring 7 imparts a force to the hopper 6 in the plane of the hopper 6 as shown in
Next, the rotary cam 20 as the release bar rotating device for turning the release bar 16, cam lever 30 and cam lever holder 35 will be described.
Firstly, as shown in
The guide face 23a and the fan-shaped guide faces 23b to 23e are located shifted, one by one, to the inner side of the rotary cam 20, from the outer peripheral surface of the fan-shaped cams 22a to 22e. With such an arrangement, when the rotary cam 20 is turned (counterclockwise in
The guide slopes 24a to 24c function to guide the cam lever 30 located at a non-cam part 26 (to be described later) to the guide face 23a and the fan-shaped guide faces 23b to 23e. The guide slope 24a, as shown in
The non-cam part 26 formed with a flat disc surface (within a region (3) in
Referring to
In
The cam lever 30 includes a rotation shaft 32. The rotation shaft 32 is supported by a bearing part 41 formed on the cam lever holder 35. As indicated by phantom lines in
Engaging operations of the rotary cam 20, cam lever 30 and cam lever holder 35 thus constructed will be described in brief. In
When the cam lever 30 is put on the fan-shaped cam 22a, as seen from
When an amount of printing sheets P stacked on the hopper 6 is large, the swing angle of the hopper 6 is small. Accordingly, even if the cam lever 30 is out of the fan-shaped cam 22a, it is displaced to the rotation center of the rotary cam 20, by a small quantity. Conversely, when an amount of printing sheets P stacked on the hopper 6 is small, the swing angle of the hopper 6 is large. Accordingly, in this case, the cam lever 30 is moved greatly out of the fan-shaped cam 22a, it is displaced to the rotation center of the rotary cam 20, by a large quantity.
When the rotary cam 20 is further turned counterclockwise in
As described above, a position as viewed in the radial direction of the rotary cam 20 at which the cam lever 30 is present varies depending on the amount of printing sheets P stacked on the hopper 6. The place where the cam lever 30 is to be guided, i.e., one of the fan-shaped guide face 23e, guide slope 24b (then, to the fan-shaped guide faces 23b to 23d), and guide slope 24c (then, to the guide face 23a), depends on the amount of stacked printing sheets P. Accordingly, when the amount of the stacked printing sheets P is small, the cam lever 30 is guided to the fan-shaped guide face 23e. When the amount of the stacked printing sheets P is large, the cam lever 30 is guided to the guide slope 24c (then, to the guide face 23a).
When the rotary cam 20 is further turned, the cam lever 30 moves from one of the guided guide face 23a and the fan-shaped guide face 23b, viz., the current position as viewed in the radial direction on the rotary cam 20, and climbs on the outer periphery of the fan-shaped cam (fan-shaped cams 22a to 22e) which is closest to the outer periphery. In other words, the cam lever 30 is slightly displaced in the radial direction of the rotary cam 20 (from the center of rotation of the rotary cam 20 to the outer periphery), and the cam lever holder 35 is slightly turned clockwise in
The outline of the engaging operation of the rotary cam 20, cam lever 30 and cam lever holder 35 is as described above. Thus, the hopper release device has three modes. A first mode is a “large release mode” in which the hopper 6 is turned to be farthest from the paper feed roller 3 (a state that the cam lever 30 is abutted on the outer periphery surface of the fan-shaped cam 22a located at the outermost periphery). A second mode is a “non-release mode” in which the hopper 6 is brought into pressing contact with the paper feed roller 3 (a state that the cam lever 30 is in the non-cam part 26 (region (3) or the cam lever guide part (region (2)). A third mode is a “small release mode” in which the hopper 6 is turned so that the uppermost printing sheet P is slightly separated from the paper feed roller 3, and its state is retained (a state that the cam lever 30 has been transferred from the region (2) to the region (1)). Any of those modes may be executed as desired by controlling the turning of the rotary cam 20 (paper feed roller shaft 3a).
In the instant embodiment, the number of steps of the stepped cam part (fan-shaped cams 22a to 22e) formed on the rotary cam 20 is five (5). As seen from the description, as the number of steps of the stepped cam part is larger, the hopper 6 is controlled in accordance with the amount of stacked printing sheets P more finely, as a matter of course.
Description will now be given about an actual paper feed control in the paper feed unit 1 and the operation and effects of the hopper release device. In the description, reference is made to
The areas (1) to (3) shown in
To being with, at the start of paper feeding, the cam lever 30 is put on the fan-shaped cam 22a. The hopper 6 is at the largest distance from the paper feed roller 3 (
When the paper feed roller 3 is normally rotated, the cam lever 30 starts to engage with the guide slope 24a (cam lever guide part: region (2)), and is guided to one of the guide face 23a and the fan-shaped guide faces 23b to 23d depending on the amount of printing sheets P stacked on the hopper 6 (
When the paper feed roller 3 is normally rotated, the cam lever 30 climbs from the guide face 23c onto the outer periphery of the fan-shaped cam 22c (
And, the paper feed roller 3 rotates one turn (360°), and stops its rotation when the flat part of the paper feed roller, which is shaped like D when viewed from side, is opposed to the separation pad 8, to set up a state that no transport load is imparted to the printing sheet P which is under printing (transported). And, it waits till the feeding of the next printing sheet P starts (
When the printing operation completely ends, and a paper feeding job for the subsequent printing sheets P is not present, the hopper release device executes the large release mode and enters a rest mode. More exactly, after the segment “e” in
In this instance, by normally rotating the paper feed roller 3, the cam lever 30 is moved out of the fan-shaped cam 22c and guided to the non-cam part 26. However, the cam lever may be guided to the non-cam part 26 by reversely rotating the paper feed roller 3 (the rotary cam 20 is turned clockwise in the figure). In this case, by rotating the paper feed roller 3 in the reverse direction from a state that the cam lever 30 is put on the fan-shaped cam 22c, the large release mode may be executed.
As described above, the hopper release device executes the small release mode when a paper feeding job for feeding the next printing sheet P and the subsequent ones is left after the feeding of the uppermost printing sheet P ends. Therefore, a swing range (swing angle) of the hopper 6 when the next or second printing sheet P is fed is minimized. As a result, noise generated when the hopper 6 is swung is reduced, and the high speed paper feeding operation (repetitive paper feeding operation) can be performed.
The hopper 6 is turned in such a direction as to be pressed against the paper feed roller 3 by the compression coiled spring 7. The turning of the hopper is performed through the release bar 16 being restrained by the cam lever holder 35. Accordingly, there is no chance that the printing sheets P stacked on the hopper 6 energetically hit the paper feed roller 3 by the urging force of the compression coiled spring 7. As a result, problems including unevenness and wrinkles of the printing sheet P are not created.
Returning to
In
However, if the swing operation of the hopper 6 is not smoothly performed and a timing at which the uppermost printing sheet P is pressed against the paper feed roller 3, retards, there is a possibility that the points I and II shift to points I′ and II′, respectively, as shown in
When the hopper 6 executes the small release mode, the cam lever 30 climbs from a small diameter cam part 23 to a large diameter cam part 22 as described above. Accordingly, a rotation load is imparted to the paper feed roller shaft 3a as a rotation shaft of the rotary cam 20. As a result, a twist is generated in the paper feed roller shaft 3a. When the paper feed roller shaft 3a is twisted, the quantity of feeding of the printing sheet P reduces correspondingly.
In a case where as described above, the initial setting quantity of the printing sheet P measured from the nip point between the transport drive roller 162 and the transport follower roller 163 is controlled using a timing at which a detect signal indicative of passage of the leading edge of the printing sheet P is received from the sheet detector 136, when a timing at which the uppermost printing sheet P is abutted on the paper feed roller 3 retards, and the quantity of feeding of the printing sheet P is reduced by the twist of the paper feed roller shaft 3a between the points I′ and II′ as described above, a timing at which the leading edge of the printing sheet P reaches the nip point between the transport drive roller 162 and the transport follower roller 163 retards, and as a result, an intended initial setting quantity is not obtained sometimes. This is particularly problematic because the hopper 6 is in a large release state (the paper feed unit 1 is in a rest state), and by executing the non-release mode from the large release state, the uppermost printing sheet P is abutted on the paper feed roller, and at the first printing sheet P when a series of rest jobs are executed, the swing angle of the hopper 6 is maximized.
The insufficient initial setting problem may be solved in a manner that at the start of executing a series of paper feeding jobs, only the first printing sheet is subjected to the skew removal of, for example, the called biting/releasing type (in which the leading edge of the printing sheet P is bit between the transport drive roller 162 and the transport follower roller 163, and then is released and discharged upstream). The problem may also be solved in a manner that the urging force of the urging device of the hopper 6 (compression coiled spring 7 in the embodiment) is increased to be large to ensure a reliable rotation of the hopper 6 in such a direction as to be abutted against the paper feed roller 3.
<Second Embodiment>
A paper feed tray 58 is constructed so as to feed printing sheets P. An auto paper feeder (ASF) for automatically feeding printing sheets P stacked in the paper feed tray 58 sheet by sheet is provided. The ASF is a paper feeder mechanism including a paper feed roller 57 provided on the paper feed tray 58 and a separation pad (not shown). The paper feed roller 57 is controlled by a rotational drive force output from a stepping motor or the like, and is shaped like D in cross section. The paper feed roller 57 is disposed closer to one side of the paper feed tray 58. A printing sheet guide is provided on the paper feed tray 58. The printing sheet guide has the width corresponding to the width of the printing sheet P and is slidable in an arrow direction A.
A rotational drive force of the paper feed roller 57 and frictional resistance of the separation pad cooperate to enable a plurality of printing sheets P stacked on the paper feed tray 58 to be fed exactly sheet by sheet, without simultaneous feeding of a plurality of printing sheets P. The printing sheet P as fed is intermittently transported by a given paper feed quantity toward a downstream side as a recording-execution region in the sub-scan direction Y, by means of a printing sheet transporting device disposed downstream of the paper feed roller in the sub-scan direction.
A transport drive roller 53 and a transport follower roller 54 are provided for printing sheet transport device for intermittently transporting the printing sheet P in the sub-scan direction Y. The transport drive roller 53 is rotated by a rotational-drive force of a stepping motor or the like, and a rotational force of the transport drive roller 53 transports the printing sheet P in the sub-scan direction Y. A plurality of transport follower rollers 54 are provided and are driven by the transport drive roller 53. When the printing sheet P is transported with the rotation of the transport drive roller 53, the transport follower rollers come in contact with the printing sheet P, and are rotated following the transporting of the printing sheet P.
An encoder device 71 for detecting a rotational displacement quantity of the transport drive roller 53 is disposed near one end of the transport drive roller 53. The transport drive roller 53 is controlled to rotate by a predetermined amount of rotation in accordance with a rotational displacement quantity of the transport drive roller 53 detected by the encoder device 71, whereby the printing sheet P is transported by a predetermined transport amount.
A sheet detector 63 is disposed between the paper feed roller 57 and the transport drive roller 53. The sheet detector 63 includes a rotatable lever part. When the lever part is pushed by the printing sheet P, the lever part is turned, and the printing sheet P is detected in a state that it is abutted on the printing sheet P.
A sheet-discharge drive roller 55 and a sheet-discharge follower roller 56 are provided for a device for discharging a recorded printing sheet P. The sheet-discharge drive roller 55 is rotated by a rotational drive force of a stepping motor or the like, and with rotation of the sheet-discharge drive roller 55, the printing sheet P is discharged in the sub-scan direction Y. A plurality of sheet-discharge follower rollers 56 are provided. Each sheet-discharge follower roller 56 has teeth formed around the periphery. The tip of each tooth is acute in shape so that it comes in point contact with the recording surface. Thus, each sheet-discharge follower roller 56 is a roller equipped with teeth. Those transport follower rollers are driven by a driving force, which is weaker than a drive force of the transport follower roller 54 by the sheet-discharge drive roller 55. When the printing sheet P is discharged with rotation of the sheet-discharge drive roller 55, those follower rollers come in contact with the printing sheet P and are rotated following the rotation of the printing sheet P.
Further, the ink jet printer 50 includes a recording control unit 101. The recording control unit 101 includes a CPU (central processing unit), and periphery units such as ROM and RAM. It executes a control program for the ink jet printer 50, such as a recording execution control, and controls the ink jet printer 50.
In the encoder device 71, a rotary member 72 is fastened to a gear 73a. A plurality of slits 721 are formed in the rotary member 72 and are equiangularly disposed. The slits 721 are simply illustrated in the form of an area of slanted lines. The gear 73a is rotatably supported on the main body of the ink jet printer 50. A gear 73b is mounted on the transport drive roller 53 (
In the embodiment, a gear 77a is also coupled with the printing sheet transport gear 74 by way of the endless belt 76 in a drive force transmission manner. The gear 77a is rotatably supported on the main body of the ink jet printer 50. A gear 77b is coupled to the sheet-discharge drive roller 55 (
A detector 78 for detecting the slits 721 formed in the rotary member 72 is disposed in the rotation area of the rotary member 72, as shown. The detector 78 discriminates between an intercepting part and a light transmission part, which are defined by the slits 721, detects the slits 721, and detects a rotational displacement quantity of the gear 73a coupled to the rotation shaft of the transport drive roller 53. The recording control unit 101 (
The sheet detector 63 includes a lever 631 which is granted with self-resetting habit for standing attitude, and pivotally supported to be rotatable around a fulcrum of a support part 63a only in the sub-scan direction Y in a state that it is protruded into a sheet transport path of the printing sheet P. When the tip of the carriage 61 is pushed with the printing sheet P, the lever 631 is turned around the support part 63a and the printing sheet P is detected. With rotation of the lever 631, an electrical contact (not shown) of the sheet detector 63 is turned on and off, and the on/off information is input to the recording control unit 101. Upon receipt of the on/off information derived from the electrical contact of the sheet detector 63, the recording control unit 101 detects the leading position and the terminal position of the printing sheet P.
When the printing sheet P is not transported along a sheet transport path 64, the lever 631 is at a rotational position, in a normal state indicated by reference numeral 631a. At this rotational position, an electric contact of the sheet detector 63 is in an off state. During the transportation of the printing sheet P along the sheet transport path 64, the lever 631 of the sheet detector 63 is pushed with the printing sheet P to be turned to a position of a contour line indicated by a chain line 631b. Accordingly, at the rotational position of the lever 631, the electrical contact is in an on state. A rotational position of the lever 631 indicated by a contour line of a chain line 631c, which is a mid position between a rotational position, designated by 631a, of the lever 631 and a rotational position, designated by 631b, of the lever 631, is a rotational position of the lever 631 at which the electrical contact changes its state from an on state to an off state and vice versa.
At the instant that the terminal edge of the printing sheet P having turned the lever 631 to the rotational position indicated by numeral 631b, leaves the lever 631, the electrical contact of the sheet detector 63 is still in an on state. When the lever 631 starts to turn by its self-resetting habit for standing attitude and reaches a rotational position indicated by numeral 631c, the electrical contact changes its state from the on state to the off state. At this time point, it is detected that the terminal edge of the printing sheet P passes the sheet detector 63.
A time taken from an instant that the terminal edge of the printing sheet P leaves the lever 631 till it is turned from the rotational position 631b to the rotational position 631c, is a detect delay time when the terminal edge of the printing sheet P is detected. A quantity of the transportation of the printing sheet P which is performed during the detect delay time is a detect delay error transportation quantity.
The detect delay error transportation quantity is given by the following equation (1)
Y=kx (1)
where x: transporting speed of the printing sheet P at a time point that it is detected that the terminal edge of the printing sheet P passes the sheet detector 63,
y: detect delay error transportation quantity
k: delay coefficient
The delay coefficient “k” varies depending on a detecting characteristic of the sheet detector 63 and a relation between the position at which the sheet detector 63 is disposed and the sheet transport path 64. The delay coefficient “k” is a known value determined every specification of the ink jet printer 50.
Thus, the detect delay error transportation quantity “y” increases proportional to the transporting speed “x” of the printing sheet P. Accordingly, the detect delay error transportation quantity “y” can be obtained by multiplying the transporting speed “x” by a fixed delay coefficient “k”.
Since the detect delay error transportation quantity “y” is proportional to the transporting speed “x”, its variation may be depicted as a line linearly varying upward as shown. The detect delay coefficient “k” indicates a gradation of the linear line in the graph. In the embodiment, the detect delay coefficient “k” is 0.2451.
As seen also from the graph, the transporting speed “x” is 12 ips, the detect delay error transportation quantity “y” caused at considerably high speed is about 3 mm, and a detect offset of the terminal edge of the printing sheet P is about 3 mm. Therefore, the terminal edge position of the printing sheet P can exactly be detected if the terminal edge position of the printing sheet P as detected by the sheet detector 63 is corrected by a quantity corresponding to the detect delay error transportation quantity “y”.
In the figure, an encoder period (μs) is computed using an encoder signal output from the sheet detector 63, and a transporting speed (ips) is computed using the computed encoder period. The computed transporting speed is rounded off in the unit of 1.5 ips. A detect delay error transportation quantity caused when the terminal edge of the printing sheet P passes the sheet detector 63 at the transporting speed in the unit of 1.5 ips, is expressed by a correction quantity (mm) corresponding to a detect offset of the terminal edge of the printing sheet P and a number of pulses (1/1440 dpi) of an encoder signal corresponding to the correction quantity of distance.
From the encoder period (μs) at a time point at which the sheet detector 63 detects passage of the terminal edge of the printing sheet P, the transporting speed (ips) of the printing sheet P at that time is calculated. A correction quantity for the transporting speed is computed by using the equation (1). The number of pulses of the encoder signal corresponding to the computed correction quantity (mm) are added to a transportation quantity of the printing sheet P stored in the recording control unit 101. In this way, the offset of the terminal edge of the printing sheet P as detected by the sheet detector 63 can be corrected exactly. The recording control unit 101 stores the table shown in
In the ink jet printer 50 which is presented as the embodiment of the invention of the present patent application, a correction quantity is computed from a transporting speed of the printing sheet P at a time point that the sheet detector 63 detects passage of the terminal edge of the printing sheet P, and the terminal edge position of the printing sheet P is corrected based on the computed one. Therefore, even when the printing sheet P is transported at high speed and its recording operation is performed, there is less chance that the terminal edge position of the printing sheet P is greatly shifted, and the recording quality is deteriorated.
Although the invention has been described in its preferred form with a certain degree of particularity, obviously many changes and variations are possible therein. It is therefore to be understood that the present invention may be practiced than as specifically described herein without departing from the scope and the spirit thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2001-257406 | Aug 2001 | JP | national |
| P2001-261998 | Aug 2001 | JP | national |
This is a divisional of application Ser. No. 10/228,258 filed Aug. 27, 2002, now U.S. Pat. No. 6,880,822 which is hereby incorporated by reference, and which claims benefit of Japanese Application 2001-257406 filed Aug. 28, 2001; and Japanese Application 2001-261998 filed Aug. 30, 2001.
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| Number | Date | Country | |
|---|---|---|---|
| 20050062215 A1 | Mar 2005 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10228258 | Aug 2002 | US |
| Child | 10980245 | US |
