Image recording apparatus with improved conveying system for recording medium

Abstract: An image recording apparatus for controlling an image recording operation on the basis of a detected width of a recording medium by a paper width detecting means after the recording medium is fed to a predetermined position on a platen. Whether the recording medium is desirably conveyed or not is determined on the basis of a signal obtained by said paper width detecting means.

Description: The present invention relates to an image recording apparatus for recording an image on a recording medium. In a conventional recording apparatus such as an ink jet recording apparatus, a paper feeding means comprising a pair of rollers etc. is disposed upstream of a platen with respect to a conveying direction in which a recording medium such as a recording paper or a clear sheet for OHP is supplied along the platen, while downstream of the platen a paper discharge means comprising a pair of rollers etc. is disposed. Further, a paper feeding sensor and a paper discharge sensor respectively for detecting the presence of the recording medium are provided in vicinity of the paper feeding means and the paper discharge means. A recording head is mounted on a carriage reciprocably movable between the paper feeding means and the paper discharging means in a direction perpendicular to the conveying direction (hereinafter referred to as "paper width direction"), the recording head being opposed to the recording medium on the platen with a predetermined space therebetween. A paper width sensor is provided near a recording head of the carriage to detect the difference between the amount of light reflected from the platen and that reflected from the recording medium so as to detect the width of the recording medium (hereinafter referred as "paper width") and the kind of the recording medium (hereinafter referred to as "paper kind"). A method for controlling such an ink jet recording apparatus will now be described. (1) Normal Mode In this mode, firstly, the recording medium is fed by the paper feeding means along the platen by a paper feeding amount required to make the rear end of the recording medium reach the paper discharging means from a position detected by the paper feeding sensor disposed upstream of the platen. At this time, the presence of the recording medium is detected by the paper discharging means disposed downstream of the platen. If the detection result shows an absence of any recording medium, an indication is given that jamming has occurred by judging that the recording medium has not reached the paper discharging means. If the paper discharging sensor detects that a recording medium is present, it is considered that the recording medium has reached the paper discharge means and then the carriage is moved to detect the paper width and the paper kind. Thereafter, the recording operation starts. In this normal mode, a large blank area where nothing is recorded is generated due to the distance between the rear end of the recording medium and the position where the recording head records. Therefore, a leading and rear end mode has been proposed in which the recording operation is started from a position immediately near the rear end of the recording medium, without producing any large blank. (2) Leading and Rear Ends Mode In this mode, firstly the recording medium is fed toward the platen by the paper feeding means, and the paper feeding sensor judges whether the rear end of the recording medium has reached the paper feeding sensor. If no recording medium is detected, the paper feeding operation continues. If, however, a recording medium is detected, the rear end of of the recording medium is fed in the conveying direction along the platen by the paper feeding means by a predetermined paper feeding amount A required to make the rear end of the recording medium pass over the recording position of the recording head. Next, the carriage is moved in the paper width direction to detect the paper width and the paper kind using paper width sensor, and the resulting signal pattern therefrom is be used to judge the paper kind. If the paper width sensor output is judged as being abnormal, this is indicated. Otherwise, a signal indicating that the paper is a predetermined recording paper or a clear sheet for OHP is output to judge the paper width, and thereafter the recording operation starts. In the method for controlling the ink jet recording apparatus described above, in the normal mode it is possible to judge using the paper discharging sensor whether the recording medium is correctly supplied to the paper discharging means. But in the leading and rear ends mode, even if the recording paper is correctly fed by a predetermined paper feeding amount, the rear end of the recording medium does not reach the paper discharging means, leading sometimes to a case in which it is not possible to judge by using a sheet exhaust sensor or a paper discharging sensor whether the recording medium has been correctly fed. Further, in either mode, for performing a successive recording operation, it is necessary to delicately adjust the rotation angle of the driving motor and the ink outlet opening at the time of stepping feeding in which the sheet member passes out from the conveying upper and lower roller for increasing the interfacing accuracy particularly after completing the recording operation for one sheet for shifting to for the next sheet. For this purpose, it is necessary to accurately detect the remaining amount of the rear end of the sheet member from the conveying upper and lower rollers Therefore, the number of step feeding of the sheet member by the conveying roller from the start of the recording operation is counted, and the size of the sheet member is detected as one of a number of fixed sizes on the basis of the number of step feedings until the rear end of the sheet member passes through the paper sensor, thereby judging the remaining amount of the rear end of the sheet member. This method, however, has the disadvantage that, there arise cases where any optimum controlling operation in accordance with the remaining amount at the respective rear end of each sheet member becomes impossible. Such cases include ones in which an indefinite sheet member passes through the paper sensor by accidentally the same number of step feedings as that for a definite size sheet member, and another case in which the paper sensor undesirably detects the rear end from the same number of times for the step feedings when the difference in length of sheet members is less than the feeding amount for one step, for example, between a sheet of A5 size (148 x 210 mm) and one of 5.5 x 8.5 inches (139.7 x 215.9 mm), a difference of 5.9 mm. As a result, it becomes impossible to perform an optimum controlling operation corresponding to the remaining amount of the rear end of the respective sheet member. JP-A-60-257279 describes a paper detector for a printer which detects the presence or absence of paper, and the width and the inclination of the paper when present. According to the present invention, there is provided an image recording apparatus for recording with a recording head on a recording medium conveyed by conveying means to a platen located opposite to said recording head, said apparatus comprising: paper width detecting means for detecting a width of the recording medium after the conveying means has conveyed the recording medium to a predetermined position on the platen and for outputting a signal representative of the width; and determining means for determining any positional deviation of the recording medium, the recording medium having been conveyed on the platen by the conveying means, on the basis of the signal from said paper width detecting means characterised by: selecting means for selecting execution or inhibition of recording in accordance with the amount of deviation determined by said determining means. An image recording apparatus embodying the invention has a structure capable of accurately judging the state of feeding a recording medium without needing any complicated composition and is reliable. An image recording apparatus embodying the invention is capable of performing a high-quality image recording operation by securely feeding the recording medium. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: FIG. 1 is a cross-sectional view of an ink jet recording apparatus according to the present invention included for illustrative purposes only. FIG. 2 is a plan view showing a platen part of the apparatus shown in Figure 1. FIG. 3 is a perspective view of a carriage of the apparatus shown in Figure 1. FIGS. 4A to 4D are diagrams showing signal patterns obtained from a paper width sensor of the apparatus shown in Figure 1. FIGS. 5A to 5B are diagrams showing a potential recording area in the normal mode and in the leading and rear ends mode, in which FIG. 5A is in the normal mode while FIG. 5B is in the leading and rear ends mode. FIG. 6 is a diagram showing an operation panel of the apparatus shown in Figure 1. FIG. 7 is a block diagram showing a control system of apparatus shown in in Figure 1 FIG. 8 is a flow diagram showing a controlling method of the ink jet recording apparatus shown in Figure 1. FIG. 9 is a perspective view showing a carriage in another example of an ink jet recording apparatus included for illustrative purposes only. FIG. 10 is a plan view showing platen parts corresponding to the carriage shown in Figure 9. FIG. 11 is the third flow diagram showing a method for controlling an ink jet recording apparatus according to a first embodiment of the present invention. FIG. 12 is a flow diagram showing a flow of the positional judging process of a recording medium according to the first embodiment of the present invention. FIGS. 13A to 13C are diagrams showing an output pattern of a paper width sensor. FIGS. 14A to 14C are diagrams showing a relationship between a paper feeding state and an image area of the recording medium. FIG. 15 is a plan view showing platen parts of the ink jet recording apparatus according to a second embodiment of the present invention. FIG. 16 is a flow diagram showing a flow of the positional judging process according to the second embodiment of the present invention. FIGS. 17A to 17C are diagrams showing a state of the recording medium fed over the platen. FIGS. 18A and 18B are diagrams showing a state of the recording medium supplied diagonally. FIG. 19 is a diagram for the explanation of a reflective photosensor . FIG. 20 is a diagram showing a sensor circuit . FIG. 21 is a diagram for the explanation of an irregular reflective medium . FIG. 22 is a diagram showing an aspect where the sensor is diagonally mounted . FIG. 23 is a diagram showing a relationship between the kind of the recording medium and the detected output. FIG. 24 is a diagram showing a detected output property when a mirror is used as a recording medium. FIG. 25 is a diagram showing a detected output property when an OHP sheet is used as a recording medium. FIG. 26 is a diagram showing a detected output property when a coat paper is used as a recording medium. FIG. 27 is a diagram showing a measuring jig for varying the relative positional relationship between the sensor and the recording medium. FIG. 28 is a diagram for the explanation of the direction property of the sensor. FIG. 29 is a comparative diagram for the detected output properties with respect to the recording mediums . FIG. 1 is a cross-sectional view of an example of an ink jet recording apparatus included for illustrative purposes only, FIG. 2 is a plan view of platen parts of the same apparatus, and FIG. 3 is a perspective view of a carriage of the same apparatus. As shown in FIG. 1, at the bottom of the body 1, a cassette 2 incorporating a recording medium such as a coated paper (a paper with a coating on its surface for promoting the absorption of ink) cut out in a predetermined magnitude or a clear sheet for OHP is removably mounted thereon. Above an end of the recording medium 3, a pick-up roller 4 is disposed with two guide plates 5a, 5b in vicinity thereof. At the left-hand side of the guide plates 5a, 5b in the drawing, a pair of paper feeding rollers 6a, 6b as paper feeding means, a platen 7 and a pair of paper discharging rollers 8a, 8b as paper discharging means are sequentially disposed as a row. A conveying means is composed of this paper feeding means and the paper discharging means. At the left-hand side of the pair of paper discharging rollers 8a, 8b in the drawing, a paper discharging tray 9 is removably mounted on the body 1 as projecting externally. In the guide plate 5a, a paper feeding sensor 10 is disposed closely to the paper feeding roller 6a, while a paper discharging sensor 11 is disposed at a position close to the right-hand side of the paper discharging roller 8a in the drawing (see FIG. 2). Each of the paper feeding sensor 10 and the paper discharging sensor 11 is composed as a type for reading out reflected light from the recording medium by a reflective photosensor disposed to face the recording medium 3, or a type for detecting a shift of a lever movable in contact with the recording medium by a photosensor or a microswitch. Although not shown, a movable lever of the paper discharging sensor 1 is disposed in vicinity of the paper discharging tray 9 side of the paper discharging roller 8a for detecting the rear and of the recording medium having been manually inserted through the paper discharging tray 9 in case of manually inserting recording case as mentioned later. The carriage 12 is slidably coupled to a guide shaft 13 mounted on the body 1 in parallel to the paper feeding roller 6a, and reciprocally moved in the paper width direction (arrow B direction and its reverse direction) perpendicular to the conveying direction (arrow A direction) being the direction for feeding the recording medium 3 on the platen 7 by a driving means such as a timing belt, a pulley and a motor which are not shown. The carriage 12 is provided with a removable recording head 14 for ejecting an ink through an ejection opening (not shown) to perform the recording. An ejecting opening surface 14a at which the ejecting opening of the recording head 14 is opened is opposed to the platen 7 with a predetermined gap (e.g.: 0.75 mm) therebetween. Immediately near the ejecting opening surface 14a, a paper width sensor 15 is provided on the carriage 12, composed of a reflective photosensor for radiating light and reading the amount of the reflected light. At a part of the radiated light path of the paper width sensor 15 on the platen 7, a silver plate 16 (see FIG. 2 being nickel-plated for increasing the light amount of the reflected light is disposed. Further, the paper width sensor 15 and the ejecting opening of the recording head 14 are separated by a distance between the rear end of the recording medium 3 and the rear end of the recording potential region 3b in case of a leading/rear ends mode (see FIG. 5) mentioned later. The operation of the apparatus shown in Figure 1 when the recording medium 3 is conveyed will now be described. The top recording medium 3 is fed between the two guide plates 5a, 5b by a pick-up roller 4, and the rear end thereof will reach the nip portion of the pair of paper feeding roller 6a, 6b. Thereafter, the recording medium 3 is fed in the conveying direction (arrow A) along the platen 7 by being held between the pair of paper feeding rollers 6a, 6b which are rotating in the direction of the shown arrow (FIG. 1). The recording medium having passed through the platen 7 will be discharged to the paper discharging tray 9 after feeding being held between the pair of paper discharging rollers 8a, 8b which are rotating in the shown arrow (FIG. 1) direction synchronously with the pair of paper feeding rollers 6a, 6b. The recording head 14, being moved by the carriage 12, ejects the ink against the recording medium 3 on the platen 7 to carry out the recording operation. Further, in the case of manual paper insertion recording operation, the recording medium 3 is inserted along the paper discharging tray 9 to reach the nip portions of the pair of the paper discharging rollers 8a, 8b, which is then sensed by a movable lever not shown of the paper discharging sensor 11. The pair of the paper discharging rollers 8a, 8b are rotated in the reverse direction of the shown arrow direction (FIG. 1) to feed the recording medium 3 along the platen 7 in the reverse direction of the arrow A direction by a predetermined paper feeding amount. At this time, the pair of paper feeding rollers 6a, 6b also rotate in the reverse direction of the shown arrow direction (FIG. 1) in synchronism with the pair of the paper discharging rollers 8a, 8b. After the recording medium 3 is fed to a predetermined position, the recording medium 3 is conveyed in the arrow A direction as the recording head 14 performs the recording operation to be discharged on the paper discharging tray 9. Next, the operation to detect the paper width and the paper kind will now be described. The carriage 12 moves from a position shown in FIG. 2 to a reverse side of the platen 7 in the arrow B direction. Namely, the paper width sensor 15 moves in the arrow B direction to pass an area where the rear end of the recording medium is to be present in the case of the leading/rear ends mode. During this movement, the paper width sensor 15 radiates light toward the platen 7 side to read the reflected light amount. FIGS. 4A - 4B show signal patterns obtained from the paper width sensor 15, in which the lateral axis corresponds to the moving path of the radiated light on the platen 7, while the transverse axis represents the light amount of the reflected light. When the recording medium 3 is in the position shown by the solid line in FIG. 2, namely when it does not reach yet the moving path of the radiated light, the signal pattern obtained by the paper width sensor 15 will be as a signal pattern 1 as shown in FIG. 4A. The convex portion with a small signal pattern 1 stands for the reflected light amount from the silver plate 16 of the platen 7. In case that the recording medium 3 is at the position shown by an alternate long and short dash line in FIG. 2, i.e. when the rear end of the recording medium 3 covers the silver plate 16 reaching a predetermined position in the leading/rear ends mode, while the recording medium 3 consists of a coat paper (white), the signal pattern obtained from the paper width sensor 15 will be as a signal pattern 2 shown in FIG. 4B. The convex portion of the signal pattern 2 represents the reflected light amount from the coat paper. When the recording medium 3 is a clear sheet (transparent) for OHP, the signal pattern obtained from the paper width pattern will be as a signal pattern 3 shown in FIG. 4C. The wide convex portion in the signal pattern 3 stands for the reflected light amount, while the small convex portion stands for the reflected light amount of the silver plate 16 having passed the clear sheet. The case where no signal pattern is obtained as shown in FIG. 4D would suggest an occurrence of fails in the paper width sensor 15 and the platen 7. FIG. 5A shows a possible recording area in case of normal mode of the ink jet recording apparatus shown in Figure 1, while FIG. 5B shows a possible recording area in case of the leading/rear ends mode. The rear end of the possible recording area 3a (shadowed area in FIG. 5B)) in the conveying direction (arrow A) is at a position internal by 16 mm from the rear end of the recording medium, while the rear end of the possible recording area 3a is at a position internal by 18mm from the rear end of the recording medium 3. The rear end and the leading end of the possible recording area 3b in the case of leading/rear ends mode will be at a position internal by 5 mm respectively from the leading and rear ends of the recording medium 3. The selection of the normal mode or the leading/rear ends mode is carried out through a normal mode key 17b or a leading/rear ends mode key 17c on the console (operation) panel 17 mounted on the body 1 (see FIG. 6). The start key 17a is to start recording. FIG. 7 is a block diagram showing a controlling system of the ink jet recording apparatus shown in Figure 1. The controlling section 18 comprises a CPU 18a for controlling the ink jet recording apparatus mentioned later, a ROM 18b for storing fixed data such as programs in accordance with the aforementioned process, and a RAM 18c for operation. FIG. 8 is a flow diagram showing a controlling method of the ink jet recording apparatus shown in Figure 1. In response to a recording start order, the recording medium 3 is supplied from the cassette 2 by the pick-up roller 4 (step S1). In the step S2, the presence of the recording medium 3 is judged by the paper feeding sensor 10, and if the judge result is negative i.e. no recording medium 3 is present it is informed that no recording medium 3 is in the cassette 2 (step S3), while if the judged result is affirmative i.e. a recording medium 3 is in the cassette 2 the process is advanced to the step S4. In step S4, whether the leading/rear ends mode is selected is judged, and if it is in the leading/rear ends mode, the operation advances to the step S5 in which the recording medium 3 is fed by the pair of paper feeding rollers 6a, 6b by a paper feeding amount C necessary to make the rear end of the recording medium 3 reach a predetermined position (shown by the alternate long and short dash line in FIG. 2), and shifting then to the step S9. In the normal mode, it is advanced to the step S6 in which the recording medium 3 is fed by the pair of paper feeding rollers 6a, 6b by a paper feeding amount D required to hold the rear end of the recording medium 3 by the pair of paper discharging rollers 8a, 8b. Subsequently, in step S7, the paper discharging sensor 11 judges the presence or absence of the recording medium 3, and if it is judged to be absent, the process advances to the step S8 to inform the state of jamming in which the distal end of the recording medium does not reach the paper discharging rollers 8a, 8b. If it is judged to be present, the process advances to step S9. In step S9, the carriage 12 is moved to the paper width direction (arrow B direction) to detect the paper width and the paper kind, and in step S10 the paper kind is judged on the basis of the signal pattern obtained by the paper width sensor 15. If the signal pattern is as a signal pattern 1 shown in FIG. 4A, it is judged that the recording medium 3 does not reach a predetermined position on the platen 7, and advances to step S101 to inform of the occurrence of jamming state. If the signal pattern is as signal pattern 2 shown in FIG. 4B, the recording medium 3 is judged to be a coat paper and the process advances to step S102. If the signal pattern is as the signal pattern 3 shown in FIG. 4C, the recording medium 3 is judged to be a clear sheet and the process advances to step S103. If the signal pattern is as a signal pattern 4 shown in FIG. 4D, it is judged that any fail has occurred in the paper width sensor 15, the platen 7 and the carriage 12 and the like and the process advances to step S104 to inform of the fail. After passing through the step S102 or the step S103, the process advances to step S11 to judge the paper width on the bases of the signal pattern 2 or 3. Thereafter, the recording operation starts. In case of manual feeding, the recording operation in leading/rear ends mode will now be described. After approximately one second has passed from the detection of the recording medium 3 inserted through the paper discharging tray 9 by the movable lever not shown of the paper discharging sensor 11, the recording medium 3 is fed in the reverse direction of the arrow A direction by the conveying means. The recording medium 3 is continued to be fed even after the paper feeding sensor 10 detected the presence of the medium, and when the paper discharging sensor 11 detects the absence of the paper the recording medium 3 is fed in the reverse direction of the arrow A direction by a paper feeding amount required to move the rear end of the recording medium 3 from that position to a predetermined position for the leading/rear ends mode. The subsequent steps are identical to those after the step S9 (including step S9) shown in FIG. 8. According to this method for controlling an ink jet recording apparatus, since the signal pattern 1 obtained by the paper width sensor 15 is used also to judge the presence or absence of the rear end of the recording medium at a predetermined position on the platen 7, the jamming state can be securely detected even in case of leading/rear ends mode in which the paper discharging sensor 11 in unavailable. As a result, the undesirable ink-jetting action against directly the platen is prevented so as to keep the surface at the side of the platen 7 of the apparatus and the recording medium 3. FIG. 9 is a perspective view showing a carriage of another example of an ink jet recording apparatus, included for illustrative purposes only, and FIG. 10 is a plan view showing the platen section of the same apparatus. The carriage 32 has two paper width sensors disposed laterally near the ejecting opening surface (not shown) of the recording head 14, a first paper width sensor 35a at the upstream side of the conveying direction and a second paper width sensor 35b at the downstream side. The first and second paper width sensors 35a and 35b are disposed along the conveying direction with a proper gap (e.g. 5mm) therebetween. Also the first paper width sensor 35a and the ejection opening (not shown) of the recording head 14 are separated from each other in the conveying direction by a distance between the rear end of the recording medium and the rear end of the possible recording area in case of leading/rear ends mode. A first silver plate 36a and a second silver plate 36b are disposed at positions on the platen 27 corresponding to the first paper width sensor 35a and the second paper width sensor 35b respectively. Other structures are the same as those of apparatus shown in Figure 1 and already described above. According to the paper width and kind detecting operation of this apparatus, the carriage 32 is moved from a position shown in FIG. 10 in paper width direction (arrow B direction) perpendicular to the conveying direction (arrow A direction). The first paper width sensor 35a is moved in the paper width direction such that the rear end of the recording medium in the leading/rear ends mode passes across a certain area (shown by alternate long and short dot line in FIG. 10), while the second paper width sensor 35b moves in the paper width direction at the downstream side of the conveying direction of the area. Next, a method for controlling the ink jet recording apparatus shown in Figure 9 will be described . In a step for judging the paper kind when the leading/rear ends mode is selected, if both signal patterns obtained by the first paper width sensor 35a and the second paper width sensor 35b are as the signal pattern 1 shown in FIG. 4A, the rear end of the recording medium 3 is judged not to have reached a predetermined position, thereby informing of the occurrence of jamming state. If the signal pattern of the first paper width sensor 35a is as the signal pattern 2 shown in FIG. 4B and the signal pattern of the second paper width sensor 35b is as the signal pattern 1 shown in FIG. 4A, it is judged that the rear end of the recording medium 3 has reached a predetermined position and that the recording medium 3 is a coat paper, and thereafter the process advances to the paper width judging step. If the signal pattern of the first paper width sensor 35a is as the signal pattern 3 shown in FIG. 4C and the signal pattern of the second paper width sensor 35b is as the signal pattern 1 shown in FIG. 4A, it is judged that the rear end of the recording medium 3 has reached a predetermined position and that the recording medium is a clear sheet for OHP, and thereafter the process advaces to the paper width judging step. If both signal patterns of the first and the second paper width sensors 35a and 35b are as the signal pattern 2 shown in FIG. 4B or as the signal pattern 3 shown in FIG. 4C, it is judged that the rear end of the recording medium 3 has passed over a predetermined position, such that the rear end of the recording medium is moved in the reverse direction of the arrow A direction by the conveying means until the rear end of the recording medium 3 comes back to the predetermined position. If at least either one of the first paper width sensor 35a and the second paper width sensor 35b is as the signal pattern 4 shown in FIG. 4D, it is judged that any fail has occurred and is informed. The other aspects than those above-described are the same as explained with reference to the apparatus shown in Figure 1. In this apparatus, in addition to the advantages obtained in the method for controlling the ink jet recording apparatus shown in Figure 1, there is an advantage that the following matters can be detected separately; the rear end of the recording medium does not reach the predetermined position on the platen; the rear end of the recording medium reaches the predetermined position on the platen 7; and the rear end of the recording medium has passed over the predetermined position on the platen 7. Next, a first embodiment of the present invention will be described. In the apparatus shown in Figure 1, in the leading/rear ends mode, whether the rear end of the recording medium has reached the predetermined position on the platen was checked on the basis of the output from the paper width sensor. Meanwnile, according to this first embodiment of the present invention, in addition thereto, the lateral (in the direction perpendicular to the conveying direction) positional deviation of the recording medium is checked on the basis of the output from the paper width sensor. FIG. 11 is a flow diagram showing a controlling sequence of this embodiment, in which the judging of the paper width is made in step S11, and thereafter the positional judgment of the recording medium is made in step S12. The processes in other steps are identical to those in FIG. 8 so as to be omitted. FIG. 12 shows a sequence of the positional judgment process for the recording medium. The recording medium is checked for any lateral (left and right) deviation on the basis of the output data from the paper width sensor 15. In this embodiment, the position of the signal pattern being the checked output from the sensor is checked for any deviation from the reference position, and if such a deviation is present the deviated amount is examined. Firstly in step S121, the output pattern of the paper width sensor 15 is checked. If it is as shown in FIG. 13A, it is judged that the recording medium has been correctly fed, and the process advances to the recording operation. If it is as a pattern as shown in FIGS.13B and 13C, the recording medium is judged as being deviated laterally in the left or right direction respectively. In step S122, the deviated amount is detected, and it is judged as jamming state if it is equal to or above 3.5 mm. If it is less than 3.5 mm, the recording position of the deviated amount is corrected in step S124. The threshold value 3.5 mm of this deviated amount judgement is based on the lateral blank amount, 5 mm respectively at the left and right end, of the recording medium of this embodiment. The recording positional correction in step S124 is to change the setting of the parameter of the recording operation as to change the recording position (x direction). FIG. 14 shows a deviation of the recording image position when the recording medium is conveyed with a lateral deviation. When the recording medium is laterally deviated in the left or right direction as shown in FIGS. 14B and 14C, the image area is subject to the corresponding deviation in the left or right direction in accordance therewith. To overcome this, such parameters as recording timing. etc. are reset so that the image can be recorded at the center of the recording medium as shown in FIG. 14A. In the case of FIG. 14, since both FIGS. 14B and 14C present 3 mm of deviation in the left and right directions respectively, a correction by 3mm is performed. Next, a second embodiment of the present invention will now be described. In the apparatus shown in Figures 9 and 10, there are provided two paper width sensors to detect the reaching or passing over of the rear end of the recording medium the predetermined position of the platen. Meanwhile, in this embodiment, a diagonal passing of the recording medium is further detected to control the operation of the apparatus. FIG. 15 is a plan view showing a platen section of the ink jet recording apparatus according to the present embodiment. In FIG. 15, the same numerals refer the same components in FIG. 10. The first paper width sensor 35a and the second paper width sensor 35b are disposed along the conveying direction with a proper gap (e.g. 10 mm approximately) therebetween. For detecting the paper width and the paper kind, the carriage 32 is moved in the paper width direction (arrow B direction) perpendicularly to the conveying direction (arrow A direction) from the position shown in FIG. 15. This is the same manner as in the apparatus shown in Figures 9 and 10. The first paper width sensor 35a moves in the paper width direction as passing through the rear portion of the recording medium in case of the leading/rear ends mode, while the second paper width sensor 35b moves in the paper width direction at the downstream side in the conveying direction of the area. The present embodiment features to detect more in detail the position of the recording medium using these two paper width sensors 35a, 35b, and to carry out controlling operation suitable for the respective case. As the total controlling sequence of this embodiment is substantially the same as that in FIG. 11, the explanation will be omitted. FIG. 16 shows a determination control flow diagram for the recording medium position. In step S121, the pattern of the first paper sensor 35a is checked. Next in steps S122 - S124, the pattern of the second paper width sensor 35b is checked. If the pattern of the paper width sensor 35a is judged in step S121 as FIG. 13A the process advances to the step S122. Likewise, if it is as FIG. 13B then to step S123, and if as FIG. 13C to step S124. In the pattern of FIG. 13A, the recording medium is judged as having been at the correct position at the time of passing through the first paper width sensor 35a, while in FIG. 13B and 13C it is deviated to the left and right side respectively. Subsequently in step S122, the output pattern of the second paper width sensor 35b is checked. If it is as shown in FIG. 13A, the process advances to the recording operation without recording positional correction in step S125, since the first and the second paper width sensors have the pattern as FIG. 13A i.e. the recording medium has been conveyed to the correct position as shown in FIG. 17A. If the output pattern of the first and the second paper width sensors are as shown in FIG. 13B and 13C, the process advances to the jamming processing routine of step S130. This is because the recording medium is considered to have been fed diagonally as shown in FIG. 18A and 18B, due to the output pattern of the first paper width sensor 35a as shown in FIG. 13A. The same is true in steps S123 and S124. Namely, if the output pattern data of the first paper width sensor 35a is as shown in FIG. 13B, when the output pattern data of the second paper width sensor 35b is as shown in FIG. 13A or 13C, they would be in jamming state respectively in step S130. Further, if the output pattern data of the first paper width sensor 35a is as shown in FIG. 13C, when the output pattern data of the second paper width sensor 35b are as shown in FIG. 13A or 13B, they would be in jamming state in step S130. Also, when both the output patterns of the first paper width sensor 35a and the second paper width sensor 35b are as shown in FIG. 13B, namely when the fed recording medium is as shown in FIG. 18A, if the deviated amount of the output patterns from the first and the second paper width sensors 35a, 35b in step S126 are less than 3.5 mm respectively with no difference therebetween (a state as shown in FIG. 17B), the recording position is corrected in step S127 to advance to the recording operation. Further, when the output patterns of the first paper width sensor 35a and the second paper width sensor 35b are both as shown in FIG. 13C, namely when the fed recording medium is as shown in FIG. 18B, likewise the process advance to the step S128 to perform the examination. If the deviated amount is equal to or less than 3.5 mm with no difference therebetween (a state as shown in FIG. 17C), the recording position is corrected in step S129 to advance to the recording operation. Thus, using the signal pattern obtained from the paper width sensor for judging the fed state of the recording medium, the undesirable direct printing on the platen can be securely prevented, thereby keeping the platen side surface of the recording medium clean. Further, when the recording medium is fed with a deviation in the X direction as shown in FIGS. 17B and 17C, the right and left blanks can be adjusted by deviating the recording start position to obtain a desired image recording. According to the present invention as composed above, it is possible to detect that the recording medium does not reach a predetermined position on the platen or that there is a positional deviation by using the signal obtained from the paper width detecting means to judge the conveyed state of the recording medium without requiring any particular sensor separately. As a result, the direct printing on the platen can be certainly prevented so as to keep the platen side surface of the apparatus and the recording medium clean. The above-described sensor can be composed to have higher sensing accuracy by using a sensor unit of the following structure. This sensor unit is composed of a reflective-type photosensor 48 shown in FIG. 19 and a circuit shown in FIG. 20. A terminal Vo in FIG. 20 is input to an A/D converter of the control section as a detected output to be processed. The reflective-type sensor unit 48 in FIG. 19 includes a light-emitting element 48A and a light-receiving element 48B. Slits 49A and 49B are formed to emit light from the vertical plane against a recording medium 47 with an angle of  (hereinafter referred to as "light emitting angle") and to receive light with an angle of  (hereinafter referred to as "light receiving angle) respectively to provide the light emitting and receiving angles with a directivity. For example, the light emitting element is a LED while the light receiving element 48B is a phototransistor. The light emitted from the light emitting element 48A impinges on the recording medium with a light emitting angle. The light reflected therefrom is received by the light receiving element 48B, and a current corresponding to the light energy received there flows as a base current for the transistor Q1. As a result, the detected output Vo is output in accordance with the energy received at the light receiving element. The VR1 is a variable resistor for adjusting the gain of the circuit. When such a sensor unit as described above is used for a recording medium, if the recording medium is substantially a regular reflector, a regular reflective light 50 having the same reflective angle as an incident angle would be the main component with thereby a small random reflection component 51. However, as to the surface of the recording medium, since it has convexes and concaves in microview due to its textile, the random reflection component 51 would be large. FIG. 23 is a graphic diagram showing a measured result of the detected output Vo by the sensor unit 48 with the kind of the recording medium and the sensor mounting angle being varied. In FIG. 23, a coat paper (a paper having a coating-processed surface to be properly ink-stained) is compared with an OHP sheet. The output Vo in case of the coat paper is adjusted by the VR1 to be 3V, in which state the output in case of OHP sheet is measured. As clearly seen from the FIG. 23, it is understood that the output level in the case of OHP sheet when measured on various sensor mounting angle would range from 1.8 V to 4.2 V. The reason can be explained on the basis of FIGS. 24 to 26, which show reflective properties of the sensor unit 3 for three kinds of mirror OHP sheet coat paper as recording medium. The measurement system is shown in FIG. 27. But as to the mirror shown in FIG. 24, the reason is because the gain of the circuit is reduced by the variable resistor VR1 in comparison with the OHP sheet or the coat paper. This is due to the fact that, since the mirror has a high light reflective rate, the detected output Vo would be minimum at a region where the rotating angle in FIG. 24 is a negative value, but even so it would reach a saturated voltage of the circuit. In the drawing, the code 1 is designated as a distance between the medium and a distance from a medium to the sensor. The lateral axis a is an angle rotated with a point located at a distance from the center of the recording. The clockwise rotation would be referred as plus direction while the counterclockwise as minus direction. But the gain, the value of VR1 in FIG. 20 is set to be different from that in the case of mirror and those of the other two cases. Further, for the sensor used in this case, the light emitting angle is formed to be smaller than the light receiving angle. From FIGS. 24 to 26, the following matters can be understood: (1) The OHP sheet is of substantially the same property as that in the case of mirror; (2) In the case of coat paper the output Vo is hardly related to the rotating angle, that is the random reflection is principal. As shown in FIGS. 24 and 25, the used sensor has a peak of the output level near 6 degrees of the angle. This will now be described with reference to FIG. 28. FIG. 28 shows a light path passing from the light emitting section 48A to the light receiving section 48B. If Tr = LED , the light emitted from the light emitting section 48A passes through the path shown by dotted line and then reflected at the point d to reach the light receiving section 48B. However, due to the relationship Tr > LED, the light emitted from the light emitting section 48A will pass through a line 121 to enter the point P on the recording medium. The line 120 designate the light when the gradient angle of the recording medium is zero, in which the reflected light is reflected along the line 121 not to reach the light receiving section 48B. But it is possible to obtain the maximum output level since the reflected light passes through the line 124 to enter the light receiving element 48B by inclining the medium surface by an angle in the same manner as in the medium 123 shown. Due to these reasons, in a regular reflection medium such as a mirror or an OHP sheet, the Vo becomes maximum when the rotating angle of the medium is set to an certain angle in the plus direction. From the results noted above, it would be clear that detecting the presence, the kind and the effective width of the recording medium by a single reflective sensor on the basis of only the absolute value of the output Vo level by a single reflective sensor 48 will have difficulty because of such reasons as the difference of the sensor mounting accuracy (distance, horizontal degree etc.) and the difference of the characteristics inherent in the sensor (directivity etc.). Therefore, a window is formed on a part of a black painting metal plate provided on a conveying path, making its part as a silver-plated pseudo-mirror surface. With such a structure, the reflective rate at the mirror surface will increase to show gradually an eminent output property as shown in FIG. 24. Further, it is also effective to approximate the light emitting - receiving relationship to a regular reflection by inclining the pseudo-mirror surface from the horizontal plane by an angle on the sensor mounting angle mentioned later. In addition, as a second feature described with reference to FIGS. 24 and 26, the directivity of the sensor 48 is previously set such that a point deviated by a predetermined angle (6 degrees in this embodiment). Namely, the sensor 48 is designed to have its best sensitivity on rotating in the "+" direction in FIG. 27. Furthermore, the relationship between the sensor and the recording medium as shown in FIG. 22 with a predetermined angle  in the direction opposite to the best sensitivity direction. In FIG. 24, this corresponds to the area of rotating angle "α < 0". As a result, the magnitude relationship of the absolute output level of the OHP paper and the coat paper can be set as "OHP paper < coat paper" from FIGS. 25 and 26. From the three features aforementioned, the detection output level with respect to each recording medium will be as shown in FIG. 29. The dotted line shows the case of coat paper, in which the output level is set to be 3.0 V by adjusting the volume VR1. At this time, if the surface of the black painted metal plate directly without placing any recording medium, the output is approximately 0.3 V. In the case of the coat paper, since the light cannot pass through the coat paper, the output level of the window portion will be 3.0 V all over the effective width of the recording. On the other hand, in the case of OHP sheet, as shown by solid lines in FIG. 29, the window portion passes approximately 70 % of the light from the sensor 48 therethrough. The passed light will then reflect on the Ni-plated pseudo-mirror surface and the majority of the reflected light passes again the OHP paper, and thereafter entering the light receiving element of the sensor 48. As previously described with reference to FIG. 24, this pseudo-mirror surface has a quite high reflection rate, which would make the detected output saturated. According to the circuit shown in FIG. 20, the upper limit of the output level is 4.2 V, above which voltage any output level would be saturated at. Therefore, in the case of the OHP sheet, the output level at the window portion is saturated as shown in FIG. 29. Further, the other portions than the window portion of the OHP sheet are equivalent to a point of α = -6 degrees in FIG. 25 because of being inclined by  = 6 degrees as shown in FIG. 22, thereby leading to 1 V approximately. However, this value of 1V contains, as previously mentioned, dispersive factors due the directive dispersion inherent in the sensor or the sensor mounting inaccuracy. Therefore, when the level difference ΔVo between the output level at the window part and that at the other parts is larger than a predetermined value C, as shown in FIG. 29, the paper kind is judged as OHP. As mentioned above, if the pseudo-mirror surface is also inclined by an angle  such that the relationship between the pseudo-mirror surface and the light-emitting/receiving approximates to a regular reflection, the detected output level at the window portion will be more highly assured. If there is no paper due to exhaustion etc., the output would be as indicated by an alternate long and short dash line in FIG. 29, the output at the window portion is saturated by the upper limit while the other parts would have an output level of the black-coated portion. As could be understood from the aforementioned explanation, according to an embodiment of the present invention, it is possible to distinguish the kind of the recording medium and to detect the effective recording width of the recording medium. Therefore, disadvantages such that erroneous recording is made on a black coated metal plate without no paper set thereon to make the inside of the apparatus dirty can be securely avoided. Further according an embodiment of the present invention, it is also possible to determine whether the front end of the recording medium has been fed to a predetermined position, and whether the rear end of the recording medium has passed the predetermined position. Thus, according an embodiment of the present invention, only a single sensor can perform such various operations as the judgment of the presence of the recording medium to be used in the recording apparatus, judgment of the king of the recording medium, detection of the effective recording width, thereby enabling to simplify, minimize in size and lower the cost of the apparatus so as to improve the cost performance.

Claims: An image recording apparatus for recording with a recording head (14) on a recording medium (3) conveyed by conveying means (6a, 6b) to a platen (7) located opposite to said recording head (14), said apparatus comprising: paper width detecting means (15) for detecting a width of the recording medium (3) after the conveying means (6a, 6b) has conveyed the recording medium to a predetermined position on the platen and for outputting a signal representative of the width; and determining means (18) for determining any positional deviation of the recording medium, the recording medium having been conveyed on the platen by the conveying means, on the basis of the signal from said paper width detecting means (15) characterised by: selecting means (18) for selecting execution or inhibition of recording in accordance with the amount of deviation determined by said determining means (18). An image recording apparatus according to claim 1, wherein said paper width detecting means comprises a first paper width sensor (35a) and a second paper width sensor (35b) for detecting the presence or absence of the recording medium at respective different positions with respect to the conveying direction of the recording medium (3), and said apparatus further comprises controlling means (18) for controlling a recording operation, said controlling means being arranged to determine a conveyance state of the recording medium (3) in accordance with any positional deviation of the recording medium determined by said determining means (18) on the basis of output signals from said first paper width sensor (35a) and said second paper width sensor (35b). An image recording apparatus according to claim 2, wherein said controlling means (18) comprises prohibiting means for prohibiting a recording operation on the recording medium (3) when positional deviation amounts determined on the basis of output signals from said first paper width sensor and said second paper width sensor are different. An image recording apparatus according to claim 2 or 3, wherein said controlling means (18) comprises means for controlling a recording position on the recording medium (3) on the basis of any positional deviation so as to record an image at a proper position on the recording medium (3), when positional deviation amounts determined on the basis of output signals from said first paper width sensor and said second paper width sensor are the same. An image recording apparatus according to claim 1, further comprising controlling means for controlling a recording position on the recording medium, wherein, when the positional deviation is less than a predetermined amount, said controlling means is arranged to control the recording position on the recording medium (3) on the basis of the positional deviation amount so as to record an image at a proper position on the recording medium (3). An image recording apparatus according to claim 1 or 5, further comprising prohibiting means for prohibiting a recording operation on the recording medium, said prohibiting means prohibiting the recording operation on the recording medium when the positional deviation amount exceeds a predetermined amount. An image recording apparatus according to claim 1, 5 or 6, wherein said paper width detecting means comprises a first paper width sensor and a second paper width sensor, each for detecting a presence or absence of the recording medium at different respective positions with respect to the conveyance direction of the recording medium and wherein said determining means is arranged to determine the conveyance state of the recording medium on the basis of output signals from said first paper width sensor and said second paper width sensor. An image recording apparatus according to any one of the preceding claims, wherein said paper width detecting means (15) comprises means for detecting a presence or absence of the recording medium (3) within a recordable area of a recording head (14). An image recording apparatus according to any one of claims 1 to 7, wherein said paper width detecting means comprises means for detecting a presence or absence of the recording medium by moving in a direction perpendicular to the conveying direction of the recording medium. An image recording apparatus according to any one of the preceding claims, further comprising an ink jet recording head (14). An image recording apparatus according to any one of claims 1 to 9, further comprising a carriage (12) for moving said recording head (14) in a direction across the conveyance direction of the recording medium (3), the paper width detecting means (15) being provided on said carriage (32) so as, in use, to be spaced apart from a recording portion of said recording head by a distance corresponding to the width of the recording medium at a non-recording area adjacent the recording area and located at a front or rear end of the recording medium along a direction across the conveyance direction of the recording medium. An apparatus according to claim 11, further comprising an ink jet recording head for discharging ink from an ink discharge port. An apparatus according to claim 12, wherein said recording portion is the ink discharge port. An apparatus according to claim 10, 12 or 13, wherein said recording head (14) is an ink jet recording head arranged to use thermal energy to discharge ink.

Inventors: NUMATA YASUHIRO, OHTANI TSUYOSHI, TAKADA HIDEAKI, TAKAYANAGI YOSHIAKI, TAKEDA AKIO, NUMATA, YASUHIRO, OHTANI, TSUYOSHI, TAKADA, HIDEAKI, TAKAYANAGI, YOSHIAKI, TAKEDA, AKIO, NUMATA, YASUHIRO, C/O CANON KABUSHIKI KAISHA, Ohtani, Tsuyoshi, c/o Canon Kabushiki Kaisha, Takada, Hideaki, c/o Canon Kabushiki Kaisha, Takayanagi, Yoshiaki, c/o Canon Kabushiki Kaisha, TAKEDA, AKIO, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1993
Main classification: B41J13
IPC codes: B41J11