JPS592027A - Variable magnification image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

The present invention relates to a variable magnification image forming apparatus. In a variable magnification image forming device, such as a variable magnification electrophotographic copying machine,
It is common to change the imaging magnification of an original image by changing the position of optical members such as lenses and/or mirrors that constitute an optical system that projects and forms an original image on a photosensitive surface. One conceivable method is to control the amount of movement of the optical member as described above by counting the pulses generated by the pulse train generating means when changing the magnification, but even if the driving means is stopped after counting a predetermined number of pulses, , if the optical member deviates from its normal position corresponding to the selected magnification due to the inertial force of the optical member and stops, or if there is a difference between the number of pulses and the amount of rotation of the driving means due to uneven rotation of the driving means, etc. A deviation from a predetermined relationship may occur, causing the optical member to deviate from the normal position and stop. As a result, while the magnification changing operation is repeated many times, the deviation of the image may accumulate, making it impossible to form an original image of the required magnification on the photosensitive surface, or causing the image to be out of focus. Ru. SUMMARY OF THE INVENTION An object of the present invention is to provide a variable magnification image forming apparatus that solves the above-mentioned disadvantages. The present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory diagram of a variable magnification electrophotographic copying machine to which the present invention can be applied. In the figure, a photosensitive drum having an electrophotographic photosensitive member on its circumferential surface rotates in the direction of the arrow. This drum 1
As the original 0 rotates, it is first uniformly charged by a corona discharger 2, and then charged through a slit 3 by an optical system to be described later.
The optical image at the selected magnification is slit exposed. As a result, the electrostatic latent image formed on the drum 1 is developed by the developing device 4, and a toner image is obtained. This toner image is then transferred under the action of a transfer corona discharger 5 to a transfer paper P that is conveyed in the direction of the arrow. This transfer paper P is then sent to the fixing device 6, and the transferred toner image is transferred to the paper P.
K-fixing is carried out - After the transfer, the drum 1 is cleaned by a cleaning device 7 and used again for the image forming process. The document 0 is placed on the identified transparent document table 8. This original () is illuminated by the rung 9, and the light reflected from the original is sequentially reflected from the mirrors 1 (1, 11, 12) and enters the zoom lens 13. The image light beam is reflected by the mirror 14 and is incident on the photosensitive drum IK as described above, forming an optical image of the document 0 at the selected magnification. Lens 13 is at solid line position 1 in the figure.
3, an m8 times image of the document is formed on the drum 1, and the lens 13 is at 13. When moved to the position, the m2 magnification is
When moved to position 133, an r, im, magnified image is formed. Here, nll )mt )m. For convenience, the description will be made assuming that tj:mt=1 in the embodiment, but the present invention can also be applied to an apparatus that can copy an enlarged image of a document. Note that 134 is the reference position of the lens 13. When the position of the zoom lens 13 is changed as described later,
In conjunction with this, zooming/mirror is performed, and the lens focal length is changed to a value corresponding to the new lens position, or, if converted, to a value corresponding to the selected copying magnification. Here, the sum ft of the optical path lengths t and h between the original and the lens, the optical path length t between the lens and the photoreceptor (t is assumed to be constant), and the original f1.
The imaging magnification of one image (that is, the selected image magnification) is Tν],
If the lens focal length is f, then t, =------, --
-- fη + 1 The position and focal length of the lens may be changed in accordance with the selected magnification m. The apparatus shown in FIG. 1 is of an original scanning type. In order to scan the original, a mirror 10 is integrated with a lamp 9, and the reciprocal of the copying magnification selected for the circumferential speed of the drum 1 is 1/rn in order to set the copying magnification in the direction of rotation of the drum to m in the J direction. The mirror 11.12I/'i moves in the direction of the arrow at half the speed of the mirror 10 in order to keep the optical path length between the original and the lens constant. In this way, the original O is passed through and its image is exposed to the drum IK slit. When scanning of the original is completed, the members 9 to 12 move backward and return to their forward movement starting positions. FIG. 2 shows the movement and zooming mechanism of the lens 13. In the figure, the lens barrel has 15 built-in zoom lenses 13. This iron part 15 is fixed to a lens stand 16. Slide bearings 17 and 18 are fixed to the lens stand 16, and these bearings 17 and 18 are slidably fitted into a linear guide rail 19 fixed to the substrate 20. Therefore, the lens stand 16 on which the lens 13 is mounted can reciprocate under the guidance of the guide rail 19 in a direction parallel to the guide rail (in direction, B direction). Therefore, the direction of the rail 19 is inclined with respect to the moving direction t of the lens 13 and the optical axis X of the lens 13, but this is because the side edge of the original is the reference point of the side edge of the original platen 8 when copying at any magnification. Placement according to the position [7] This is to focus the image of this document side edge on the reference position of the photoreceptor side edge. Therefore, in a copying machine in which the center of the document is placed at the center of the document table when copying at any magnification, and the image of the center of the document is formed at the center of the photoreceptor, the rail 19 is placed parallel to the optical axis X. It's okay. Both ends 21' and 21'' of the wire 21 are attached to the lens stand 16.
is locked. The wire 21 is fixed to the substrate 2° and is rotatably supported by shafts 22' and 23'.
．． 23, and is wound around the drive pulley 24 several times between the hook IJs 22 and 23. This drive pulley 24 is a torque limiter 2, an example of which is shown in FIG.
5 to the shaft 26. This shaft 26K
A Vi worm wheel 27 is fixed, and is meshed with a worm gear 28 identified on the output shaft 30 of the motor 29. Then motor 2
When 9 rotates forward, worm gear 28 and worm wheel 2
7 rotates the shaft 26 clockwise, and the torque limiter
When the shaft 26 and the pulley 24 are fixedly connected to each other, the pulley 24 rotates clockwise, so the lens stand 16 on which the lens 13 is mounted is pulled by the wire 2 and moves in the direction of arrow A. Similarly, when the engine 29 is reversed, the pulley 24
is rotated counterclockwise, and the lens stand 16 is pulled by the wire 21 and moves in the direction of arrow B. A disk 31 as shown in FIG. 3 is fixed to the output shaft 30 of the motor 29. 8 Therefore, this disk 31. t, 1
Rotates in synchronization with 1126, thus torque limiter-2
As is clear from the above, when the shaft 26 and the pulley 24 are fixedly connected by the shaft 26 and the pulley 24, the disc 31 rotates in synchronization with the movement of the lens stand 16 on which the lens 13 is mounted. The disc 31 is an opaque disc 31 as shown in FIG.
A large number of light transmitting slits 31'' of the same width are provided at equal intervals in . .
2" is an IH arranged with the slit forming area of the disc 31 in between. Therefore, as the disc 310 rotates due to the operation of the motor 29, the emitted light from the light emitting element section 32' passes through the slit 31". Since the light is transmitted periodically, the light receiving element section 32
5 periodically generates electric pulses, and the rotation angle of the shaft 26 that rotates during one pulse period of this pulse train is the same at any time. The amount of movement of the lens stand 16 is the same at any time.When changing the magnification, when the motor 29 is driven, the lens 13 starts moving completely (as described above).
7. In synchronization with this, the above pulse train starts to be generated, but the number of these pulses is counted as described later, and when the number of pulses corresponding to the selected magnification is counted, the motor 29 is de-energized. , which stops the lens movement. Therefore, the lens 11 moves by a distance corresponding to the selected magnification. Like the hb He, the lens 13 is a zoom lens, and in the embodiment shown in FIG. 2, the -C lens is zoomed in conjunction with the lens movement. That is, lens barrel 1
5 is provided with a cam hole 15', and this cam hole 15
', a pin 33 fixed to a focal length changing lens holding cylinder movable in the optical axis direction within the lens barrel 15 is projected and engaged. 34 is lens m2 @ tube 1
5 to 1. This is a zoom ring that does not move relative to the optical axis, but is rotatably mounted around the optical axis. The zoom ring 34 is provided with a long hole 34'.
' is engaged with the bin 33. Therefore, when this zoom ring 34 is rotated, the bin 33 is moved to the cam hole 15'.
The lens 13
The focal length of the image also changes. The mechanism for rotating the zoom ring 34 is as follows. That is, the wire 35 is wound around the zoom ring 34 once to several times. 36 is a wire support member slidably attached to the lens stand 16, and one end 3 of the wire 35
5' is locked to one end of the support member 36, and the wire 3
The other end 35't of the support member 36 is connected to the other end of the support member 36 through a tension spring 37 for preventing loosening. shape guide j
, ff rod 38 is fixed, and this rod 38i,
It is slidably inserted into slide bearings 39 and 40 fixed to the T lens stand 16. Therefore, the wire support member 36
moves relative to the lens stand 16 in a direction perpendicular to the optical axis X, and this movement drives the wire 35, causing the zoom ring 34 to rotate. Here, a cam follower 41 is fixed to the wire support member 36, and this follower 41
is provided on the cam plate 43 fixed to the substrate 20, and is tilted by degrees Celsius with respect to the direction of lens movement.

[Cam groove 42 long in the - direction
is engaged in. Therefore, if the lens stand 16 on which the lens 13 is mounted is moved as described above, the wire support member 36r/i will move relative to the lens stand 16 under the control of the cam 42 as described above, and the zoom ring 34 will thereby move. While rotating, the focal length of the lens 13 is changed. As can be seen from the upper ML, the amount of lens movement and the amount of lens zooming correspond. Zoshide cam 15'. The shape and installation direction of 42 are set so that the three equations described above hold between the position of the lens and the focal length. Now, 44 is a stopper fixed to the substrate 20. In FIG. 2, the stopper 44 is provided at one end of the lens moving path. Then, when the lens stand 16 moves in the direction of arrow A and reaches the end position of its movement, the side surface 18' of the bearing 18 mentioned above comes into contact with the side surface 44' of the stopper 44, and the lens stand 16 moves in the direction of arrow A. Further movement of is prevented. The lens stand 1 stopped with the bearing 18 of the lens stand 1G in contact with the stopper 44 as described above.
The position 6 is the reference position of this lens stand 16. In other words, the position of the lens 13 in this state (13. W in FIG. 1) is the reference position of the lens 13. The stopper 44. A microswitch 45 is fixed to the actuator of this microswitch 45, and when the bearing 18 comes into contact with the stopper 44, the bearing 1
When the side surfaces 18' of the lens 8 come into contact with each other, that is, when the lens stand 16 comes to the reference position, the lens 13 moves back to the reference position 13.
．． , the -F microswitch 45 outputs a signal. As mentioned above, rotate the motor 29 in the forward direction to move the lens in the direction of arrow A.
If the movement continues in this direction, the microswitch 45 will issue a signal after a certain amount of time has elapsed. This signal is a signal indicating that the lens 13 has reached the reference position as described above, but at the same time as this signal is generated, the motor 29 is deenergized and the driving of the lens stand 16 is stopped.
In this case, the lens 13 may stop at a position deviated from its reference position 134. This may be due to an error in the installation position of switch 45, or if switch 45 is installed incorrectly.
This is because there may be an error in the operation timing of the stopper 5, or the stand 16 may be displaced in the direction B due to the reaction of the collision between the bearing 18 and the stopper 44. In any case, if the lens 13 stops at a position deviated from the reference position 134, when the lens 13 is moved from this position a distance corresponding to the number of pulses corresponding to the selected magnification, the new lens position will be Position 13 corresponding to the selected magnification.
or 132 or 13. I've become something out of place,
This makes it difficult to obtain copies with the required magnification. Therefore,
A torque limiter is installed in the drive force transmission path to the lens stand 16.
25 is provided to continue operating the motor 29 at a moment slightly after the moment when the microswitch 45 forms the signal, thereby ensuring that the bearing 18 is pushed against the stop 44.
After attaching the lens (in other words, move the lens 13 to the reference position 1)
34) After the motor 29 is securely stopped and held
It seems to be de-energizing. In addition to the switch 45 shown in the illustrated example, as a means for detecting the position of the lens, it is also possible to use a device in which a magnet is attached to one of the lens stand 16 and the stopper 44, and a pole element is attached to the other. The signal emitted by the Hall element at the time can be used in the same way as the signal from the microswitch 45. Fig. 4 shows an example of a torque limiter. Figure 4
The shaft 26 is rotatably supported on a bearing 46, 47 fixed to the base plate 20, and a flange 26' is integrally provided on this shaft 26. There is. Also, a perforated disc 48 is loosely fitted to the shaft 26. Spacers 49, 50, 51 are provided between the base of the pulley 24 and the shaft 26.
is interposed. A compression spring 53 is interposed between the disc 48 and another perforated disc 520 which is loosely fitted onto the shaft 26. A compression spring 53 is inserted between the disc 48 and another perforated disc 520 which is loosely fitted onto the shaft 26. The spring 53 is connected to the disk 4 by tightening the nut 54 with 6 knots AL'' with a nut screwed into the provided screw.
The pressing force applied to 8 can be adjusted. In any case, spring 53
Due to the elastic pressing force of the disc 48 and the spacer 5L,
1-51 and the base of the shea 924, the base of the pulley 24 and the spacer 5(), and the spacer 50 and the flange 26' are brought into pressure contact. Therefore, unless a load exceeding a predetermined value is applied to the wire 21, the shaft 26 and the pulley 24 are fixedly connected, and when the wheel 27 is driven to rotate, the pulley 24 also rotates integrally with the shaft 26, and the lens 24 is rotated as shown in the front 14t. move in direction B and direction B. However, 1, as mentioned above, the bearing 1 of the lens stand 16
If the motor 29 is rotated in the forward direction while the lens holder 8 is in contact with the stopper 44, and the lens stand 16 is further moved in the direction of the arrow, the load applied to the wire 21 will exceed the predetermined value. Space+J49,5+1.
51, and the shaft 26, flange 26', and disc 48 that are in contact with each other, slipping occurred, and the pulley 24 stopped rotating f! In this state, the worm wheel 27 simply rotates integrally with the shaft 26. The motor 29 idles. In this way, accurate positioning of the lens 13 at the reference position 13a is guaranteed. Next, the operation of the above mechanism will be explained. A microcomputer is used for operation control. That is, as shown in FIG. 5, the 1-chip microcomputer computer MC#Ctl has a copy key S W C that instructs the copying machine to perform a copy operation, an m0x key S W 1 that specifies the copy magnification m1, and a copy magnification m! Specify m7x key SW2. , ffl magnification m,
The signals from the m3x key 8W3, the pulse train generator 32, and the lens position detector 45 specifying the i is marked +n and motor 29 is rotated forward. <Drive circuit 1) Signal ('eh) that energizes A, drive circuit D that reverses the motor 29
J (to the signal that energizes), outputs various signals (C1) that cause the complex J4 + 7P operation.When the signal F3 (I) is at the 1■ level, the circuit DA is energized, and the lens 13 i, l: Move in the direction of arrow A in Fig. 2. When the signal (1)) is at the 1r level, circuit 1) B is energized, and the lens 13 moves in the direction of arrow B in Fig. 2. Signal (
When n) and (b) are at level 17, circuits 1)A and I)B are not energized and the lens 13 is stopped. , sunda signal (c
), the driving means for the photosensitive drum 1, the charger 2.
5 driving means, developing device 4 driving means, fixing device 6 driving means, lamp 9 driving means, mirror in, 11.12 driving means, paper P conveying section + 1ijI means
The driving means (hereinafter collectively referred to as CI) are energized according to a predetermined sequence, and the copying process described in FIG. 1 is performed to form a copy image from original 0 onto paper P. Since the sequence of multiple culms operated by each of the driving means (1) is known in the art, the description thereof will be omitted in this specification to avoid complexity. Mata microcomputer Me is a pulse train generator 320
Counter (TNI) that counts the number of generated pulses
The pulse train generator 32UP generates pulses at position 13. P7 pulses are generated to move from position 132 when copying m7 times, and position 13. From m, 1t# at double belly shot, 13. Assume that P pulses are generated to move up to P. Now, FIGS. 6(A), 6(B), and 6(0) are flowcharts of the control software by the microcomputer MC. In FIG. 6(A), when the power source is connected to the copying machine (power ON), the micro switch 45
Step S+
), in the case of Ye8, the process jumps to step S4, but in the case of No, the signal G) is set to the ti level and the lens 13 is moved in the direction of the arrow A (step s,), so that the lens 13 moves to the reference position 13. ．． It is determined by the signal from the microswitch 45 that this has been reached (step SN).
, clear the counter TN2 in step S, ),
Next, the number of count pulses P4 is set in the counter rN1 (step S). This is done by continuing to drive the motor 29 in the normal rotation until a time point corresponding to 24 pulses after the bearing 18 acts on the microswitch 45.
This is to keep the motor 29 rotating in the normal direction until after fc when the reference voltage of lens 3 is stopped, and to accurately hold the lens 13 at the reference position of 13 degrees as described above. (Therefore, P4 (d) does not need to be a very large value, and is selected to be as small as possible within the range that allows the lens 13 to be accurately positioned at the position 134.)
For this reason, after step S, it is determined whether or not the pulse input from the pulse train generator 32 is input to the counter TNI (step S), and each time the counter 'I' N 11'c enters the pulse signal, the counter TNI is The value is decremented (step S7). Thus 'I' N 1 = 0
In other words, it is determined whether the time corresponding to P3 pulses has elapsed since the microswitch 45 issued the signal (step Ss), and if Yes, the signal 6 is detected.
) is set to L level to stop driving the motor 29 (step s,). Next, the counter TN2 is set to 1 (step S+o). This counter TN2 indicates how many times the lens 13 is at position 13. or 13. or 13. (In other words, each position when the copying process is performed) K movement positioning is counted. (selected according to the positioning error, etc.), the lens 13 is temporarily returned to the reference position 134, and from that position the lens 13 is moved to 6 positions corresponding to the selected magnification □3. Or □3.
Eh, □3. K $ fl) This is for clarification. Therefore, in the embodiment, t, [this counter']"Nli
, the lens 13 is placed in the above position 131 or 13. Mata iJ 13
．． Before moving up, count the movement up as one time. In any case - Step 8. . Next,
Set the number of counting pulses (+1 to P. 4■) necessary to move the lens 13 from the reference position #134 to the position 131 for forming the same-magnification image (step So), then set the signal (h) is set to H level and the lens 13 starts moving in the direction of arrow B from position 134 (step S7.
). Then, it is determined whether or not the lens is in position 1y134 (Step Sl)).Next, it is determined whether or not there is an input from the pulse generator 32 to the collar 71TN1. , (step 514), if there is this input, the counter TNI
K Decrement, step Sl! l', and then it is determined whether the counter TN1 has counted all of the set 1, 'lc hash number (p, + 1) +1], ) (step S, , ), this sf rough S
When it is determined that TN1=0 in , , the lens has reached the 137th position, so next, the signal (b) is set to the L level, the motor 29 is stopped, and the lens movement is stopped (step SI7). . Ka<'if,? When the power is turned on to the J camera, the lens 13 is first positioned at the reference position 134,
From that position to position 13 when copying at the same size. Therefore, when the copy key SWC is turned on next time, an accurate same-size image of the original can be copied. (The highest copying frequency is the same-size copy.) Now, the operator presses the keys SWI, SW2, SW.
3. Turn on the desired magnification designation key. Therefore, the microcomputer MC first determines whether or not there is a magnification specifying key manually in the step Si image, and if NO, the process goes to step Sue, which will be described later, but if YES, in step S+e, the lens It is determined whether the current position of is the position corresponding to the selected magnification specifying key, in other words, whether it is necessary to move the lens to the position corresponding to the selected magnification, and if No, the process proceeds to step SSS. return. The presence or absence of the manual input of the magnification specifying key is determined again in Step 7' S I@, but at this time, this input information has already been determined and deleted, so the determination is No, and step S ve Ic
Line<. In step St., it is determined whether or not the copy key SWC has been turned on. If Yes, the copying step Sk+ described in iiJ is carried out by the signal (2), but if No, the process returns to Step So. Therefore, S+s until the next time you turn on the copy key SWC or turn on the magnification specification key.
The steps of St. are continued repeatedly. On the other hand, if it is determined in step S+e that it is necessary to move the lens I3, the counter TN2 is incremented in step sty, and then this counter T
It is determined whether the count number of N2 has reached (α+1) (step S!s). If here TN2=(α+1)
If it is determined that
Since the movement to the 3+, 13g, or 13g position is being performed, the lens 13 is moved to the 90 system shown in FIG. However, if No in step S!s, move to step S in Figure 6(B), where the lens is moved from position 13+ to 1.
Determine whether or not to move to the 3rd generation, and if no, further step S
At tS, it is determined whether or not to move the lens from position 13t to 13g, and if the answer is No, the lens is moved to position 13! 13m from
It is determined in step st. whether or not to move to. Step 814. S□ and Sl• are both determinations as to whether or not to move the lens in the A direction. Then step se
If Yes in a, the divisor bus number Ps is set at step Se.
If Yes at @, count pulse number (p, +p,); if Yes at Stella jss, count pulse number (Pass number Pa,
Set each to the counter TNI (Step S! 79 boxes, Se@). Se (step S gentleman), step S@HSt s・
. S, similar steps Sat I Sst, Sss
Execute HSsa and set the lens 13 to the counter TN.
Move the distance corresponding to the number of pulses set in l. The lens 13 is moved and stopped at a position corresponding to the magnification designated by the magnification designation key. When this force is completed, it jumps to the point (■) in Fig. 6 (A). On the other hand, if the answer is NO in step Su, the remaining case is to move the lens 13 in the direction B. Then, in step 8ss, the lens 13 Step 5ss to determine whether to move the lens from position 13° to position 13+; if no, step SsJ to determine whether to move the lens from position 113m to position 13+; if no, move the lens to position 13s , to 13! Since it is requested to move to the counter TNI, the number of counted pulses P! Seratos (step Ss'). On the other hand, step Sm @ is Yes
In the case of , the number of counted pulses PI is
In the case of s, the number of counted pulses (pt+ps) is set to each counter TNIK (steps Sst, So
) 6 Next, in step 8ao, the signal (2) is set to the H level, and the lens 13 starts moving in the direction of arrow B from the position where it is actually inserted. And step tsu. Move the distance corresponding to the number of pulses set. The lens 13 is moved and stopped at a position corresponding to the magnification designated by the magnification designation key. When this is completed, the program jumps to the point ◯ in FIG. 6(A). Next, if the answer is Yes in step 5ffil in FIG. 6(A), move to step S in FIG.
8m, Si, 8B, Ss, Sv, Ss,
A step similar to Ss, S+o? Sts HSis
, S4t, S4s, Sas, Sgo,
S.B.I. , S'; 3 Ss, repeatedly positions the lens at the reference position 134 and initializes the counter TN2. Set the exemption value l. Next, in step 8, it is determined whether or not to move the lens to 133rd position false', and if no, in step S-14-, the °C lens is moved to 13z position 1! If the answer is No, the objective is to move the lens to 13+]It, so in step S#, the counter T is
Set the number of pulses (PL + Ps + Ps) to NI. On the other hand, if Step S bee is YesO field, Shiai, and Step S is Yes, then Stenwa et al.
s7 F5tt-, counter 'l'Nlf/(1
Set the number of pulses + (F'I and P2) respectively. Then, in step Sse, set the signal ■ to H level and start moving the lens 13 from the reference position 134 in the direction B. Set the above counter TNI. 7 corresponding to the number of pulses... The separation reference position 134 is also moved.In other words, the lens 13 is moved to the position specified by the magnification designation key, and the reference position 1 is moved.
Move and stop from i134. Once this is completed, the 6th
Janobu to ■ in the figure (Δ). Steps S+s and Sso are repeated unless the magnification designation key is turned on during the rare 11th work of lens transfer 11 written in fsiJ. Then, when the copy key SWC is turned on, a copying process Sn is performed to form a copy image at the selected magnification. Move your eyes! During the 8II operation, if the magnification designation key is turned on elsewhere and returns to 1, the process moves to steps S, . . . via steps S+s and S+e, and the target is controlled. In the example above, the lens is returned to the standard position after changing the magnification multiple times, but if you don't mind that it takes time each time to change the magnification, you can change the magnification by changing the magnification. , each time, return the lens to its reference position and position it accurately, then move it to the position corresponding to the selected magnification.
It may be moved by t. For this, for example I
Step 84 of the program flowchart in J11 SIT+HS! 1) S21 is omitted, so if the microcomputer CPI-] is used to remove eggs from the cow's 1゛N2 (spawning is removed), if Yes in step Su, slfj4c4!6 Step (C) in Figure 6 84
All you have to do is make it go directly to 1. In the first row of ``1'', the reference position of the lens is taken as the end of the lens movement path B, but it is also possible to use the position C as the reference position between both ends of the lens movement path. This lifting platform L
1. The stopper is moved in and out of the lens table movement path using a solenoid, etc., and when positioning the lens at the reference position, the above-mentioned
- Return the buckwheat noodles to the above path 17 and place the lens stand there. Furthermore, in the above example, the reference position of the lens is copying page - [1
Although the lens position used in the copying process is set to a position other than the reference position, the lens position used in the copying process may be returned to the reference position. For example, if the lens is placed at the 134th position, it may be possible to print multiple images of jilt times.Also, in the embodiment described in II, it is possible to change the magnification by 3 to 4 steps. Furthermore, the present invention can be applied to a copying machine capable of copying at a magnification corresponding to the number of songs, or to a device that can change the magnification in a very large number of steps, that is, a device that can change the magnification virtually steplessly. The invention is applicable. Although the above embodiment uses a means for generating a pulse train by means of a slit disk rotated by a motor, other clock pulse excavators etc. can also be used. In this case, the above clock pulse oscillator may be used as the motor 29. Furthermore, in the embodiment described above, movement and stopping of the lens was controlled by energizing and deenergizing the motor 29, but a clutch may be used between the motor 29 and the worm gear 28, etc. may be provided, and the movement and stopping of the lens may be controlled by energizing and deenergizing this clutch.Also, although a zoom lens is used as the lens in the above example, a device using a fixed focus lens may also be used. In this case, when changing the magnification, it is necessary to change the total optical path length between the original and the photosensitive surface.
It is only necessary to change the position of , corresponding to the selected magnification. Therefore, the present invention can be applied to the above-mentioned mirror position change.Furthermore, the present invention can be applied to a type in which the document is scanned by moving the document table or by moving the document using a document transport roller, a belt, etc. The present invention can also be applied to an apparatus in which an image of the entire surface of a document is formed and exposed on a photosensitive surface at one time. The present invention can also be used in digital copying machines, fax/mi-journals, etc., which form an original image on a CCD or the like to once form an electrical signal corresponding to the original image, and then use that electrical signal to form a desired image. It is possible. In any case, according to the present invention, in a device that controls the amount of movement of an optical member by counting pulses when changing magnification, the optical member is After returning to the reference position and accurately positioning it at that reference position, the optical member is moved a distance corresponding to the required number of pulses.
The number of pulses counted [f] and corresponding to the number of pulses ('
6ii! The + optical member position is accurately associated with the selected magnification, and a document image with accurate magnification and focus can be formed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of a variable magnification electrophotographic copying machine to which the present invention is applied, FIG. 2 is an explanatory diagram of an example of the lens moving mechanism of the apparatus shown in FIG. 1, and FIG. 3 is an explanatory diagram of an example of a slit disk. 4 is an explanatory diagram of an example of a torque limiter, FIG. 5 is a block diagram of a control system according to an embodiment of the present invention, and FIG. 6 (A) J (B)
1(C) is a flowchart for explaining the software of the control system in FIG. 5, and FIG. 7 is a diagram for explaining the number of pulses for lens movement. 0 is the original 】 is the photosensitive Drano/13id zoom lens 15i: The lens barrel 16 is the lens stand 19 is the guide rail 21 is the drive wire
24 is drive pulley 2] d, torque limiter 2
6, drive shaft 27, worm wheel 28, worm gear 29, morph 31, slit disk 32, photocoupler 34, zoom ring 4
Number 4 is the 45th micro switch. Applicant Canon Co., Ltd.

Claims (1)

[Claims] A variable magnification image forming apparatus that changes the imaging magnification of the original image by changing the position of an optical member for forming an image of the original on a photosensitive surface, the apparatus comprising a pulse train generating means, In a variable magnification image forming apparatus in which the amount of movement of the upper HL optical member is controlled by counting pulses generated by the pulse train generating means, when the optical member reaches a predetermined reference position, the optical member a stopper means provided so that the support means abuts; a torque limiter means disposed in a driving force transmission path between the drive means and the optical member support means; means for temporarily moving the optical member to the reference position before bringing it to a position corresponding to the magnification, and continuing to operate the driving means for a predetermined time even after the optical member supporting means contacts the stopper means;
A variable magnification image forming apparatus comprising means for moving an optical member to a desired position by counting the number of pulses from the reference position.