JPH04335628A - Speed controller for copying machine optical system - Google Patents

Abstract

PURPOSE:To accurately stop an optical system at its home position regardless of the heat, generation of an electric motor which drives the optical system and to shorten the copying time. CONSTITUTION:A microcomputer 1 determines a relatively high applied voltage UA-B for reversing for current copying operation according to the movement distance XA-B between a 1st speed reduction start position RA and a position RB set in last copying operation. The last movement distance XA-B is determined according to the relatively high applied voltage UA-B for reversing and the resistance of an armature, so when the resistance of the armature decreases becomes gradually larger than before, the applied voltage UA-B for reversing is reduced by a specific value alpha for reducing the current movement distance XA-B so that the speed YLAST at a 2nd speed reduction start position RC reaches a target speed. Further, when the resistance of the armature is less than before and the current movement distance XA-B is large, the applied voltage UA-B for reversing is reduced, but when the resistance of the armature becomes gradually larger than before, the last applied voltage UA-B for reversing is set again.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for an optical system of a copying machine, and more particularly to a speed control device for returning the optical system of a copying machine to its home position.

0002

2. Description of the Related Art In general, the optical system of a copying machine moves at a constant speed depending on the copying magnification when an electric motor scans an original image, but when returning to the home position, it moves as fast and as quickly as possible. It is preferable to move in time. In this case, if the optical system returns at high speed, it becomes difficult to accurately stop it at the home position due to inertia, and mechanical shock becomes large when the optical system is decelerated or stopped by a clutch or brake, respectively.

Conventionally, this type of speed control device was disclosed in Japanese Patent Application Laid-open No. 6
As shown in Japanese Patent No. 4-3637, the optical system has a predetermined first
Optimum regulator control is performed so that the speed reaches a predetermined target speed when the braking start position is reached, and when the optical system decelerates below the predetermined target speed due to this control, the steady state quantity of this target speed is determined. Optimum regulator control is performed as a new initial value, and the optical system is configured to shift to the stop mode when it reaches a predetermined second braking start position.

0004

[Problem to be Solved by the Invention] However, when the number of continuous copies is large, the motor heats up due to long-term operation and the resistance of the armature increases, causing current flow to decrease even when the deceleration voltage is constant. As a result, the generated torque for deceleration becomes smaller. Therefore, in the above conventional speed control device for the optical system of a copying machine, since braking is started from a predetermined braking start position, the optical system does not stop at a predetermined home position even if braking is started from a predetermined braking start position. , there is a problem that in the worst case, it will collide with the housing.

The above problem can be solved by setting the braking start position farther from the home position. However, in this case, it takes a long time to return to the home position, resulting in a long copy time.

In view of the above conventional problems, the present invention can accurately stop the optical system at the home position regardless of the heat generated by the electric motor that drives the optical system, and can speed up the copying time. An object of the present invention is to provide a speed control device for an optical system of a copying machine.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the first means has the following features:
The first reversing voltage is applied to the motor while the rotation speed of the motor decreases to a predetermined speed from the first deceleration start position of the optical system, and the second reversal voltage is applied from the second deceleration start position of the optical system to the stop position. In a speed control device that applies a reversing voltage to an electric motor, when the moving distance from the first deceleration start position of the optical system during the previous copy to the time when the rotational speed of the electric motor decreases to a predetermined speed is relatively long. , comprising control means for making the first reversing voltage during the current copy equal to the previous one and making the first reversing voltage during the current copy smaller than the previous one when the moving distance is relatively short; It is characterized by

[0008] The second means is such that the control means of the first means is
The present invention is characterized in that the first reversal voltage is set to the maximum value so that the optical system stops at the home position even if the electric motor generates heat when copying the first sheet.

The third means is such that the control means of the first and second means adjusts the first deceleration start position from the home position when the first reversal voltage at the time of current copying is at the maximum value. The first deceleration start position is set at a position relatively close to the home position when the current first reversal voltage is set at a relatively distant position and the current first reversal voltage is made small.

[0010] The fourth means is such that the control means of the third means:
If the speed of the optical system at the second deceleration start position during the previous copy is higher than the predetermined speed, the first reversal voltage during the current copy is increased, and the second deceleration during the previous copy is started. The present invention is characterized in that when the speed of the optical system at the position is lower than a predetermined speed, the first reversal voltage during the current copying is reduced.

[0011] The fifth means is such that when the speed of the optical system at the second deceleration start position during the previous copy is higher than a predetermined speed, the control means of the first to fourth means controls the speed during the current copy. If the speed of the optical system at the second deceleration start position during the previous copy is lower than a predetermined speed, the second reversal voltage during the current copy is decreased. It is characterized by

0012

[Operation] In the first means, with the above-mentioned configuration, the current copying time is determined according to the moving distance during which the rotational speed of the electric motor decreases to a predetermined speed from the first deceleration start position of the optical system during the previous copying. The first reversal voltage of is optimized, and therefore the optical system can be accurately stopped at the home position regardless of the heat generated by the electric motor that drives the optical system.
Additionally, copying time can be sped up.

In the second means, when copying the first sheet, the first reversing voltage of the electric motor is set to the maximum value,
Therefore, even if the electric motor generates heat when copying the first sheet after a long period of time has elapsed since the power was turned on, the optical system can be stopped at the home position.

In the third means, when the first reversal voltage at the time of the current copy is at the maximum value, the first deceleration start position is set to a position relatively far from the home position, and the current first reversal is performed. When reducing the operating voltage, the first deceleration start position is set relatively close to the home position, so the optical system can be accurately stopped at the home position regardless of the heat generated by the motor. Time can be sped up.

In the fourth means, the first reversing voltage during the current copying is optimized based on the speed of the optical system at the second deceleration start position during the previous copying, so that the electric motor gradually generates heat. It is possible to accurately stop the optical system at the home position even when the optical system is cooled, or when it suddenly generates heat or cools down, and it is also possible to prevent the copying time from slowing down.

In the fifth means, the second reversal voltage during the current copy is optimized based on the speed of the optical system at the second deceleration start position during the previous copy, and therefore the optical system is brought to the home position. Can be stopped accurately.

[0017]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a speed control device for an optical system of a copying machine according to the present invention, FIG. 2 is a perspective view of essential parts showing an optical system controlled by the speed control device of FIG. 1, and FIG. 4 is a graph for explaining the relationship between the applied voltage of the motor and the speed of the optical system in the speed control device of FIG. 1; FIG. 4 is a flowchart for explaining the schematic operation of the speed control device of FIG. 1;
FIG. 5 is a flowchart for explaining the details of the copying operation for the first sheet in FIG. 4, and FIGS. 6 to 8 are flowcharts for explaining the details of the copying operation for the second and subsequent sheets in FIG. 4.

In FIG. 1, a microcomputer 1 includes a microprocessor (μ) 2 and a read-only memory (in which programs for the microprocessor 2 are stored in advance).
The microprocessor 2 has a random access memory (RAM) 4 having a ROM) 3 and a work area for the microprocessor 2, and the microprocessor 2 executes the processes shown in FIGS. 4 to 8 based on the programs in the ROM 3.

The microprocessor 2, ROM 3, and RAM 4 of the microcomputer 1 are connected to a command generation circuit 5 and a motor drive interface (I/F) 6 via a bus.
and the optical system detection interface 10, and the drive circuit 7 of the electric motor 8 is, for example, a power MOSFET.
It is made up of. The command generation circuit 5 includes an optical system 11
The motor drive interface 6 transmits the digital value commanded by the microprocessor 2 to the power MOSFET of the drive circuit 7.
The pulse signal is converted into a pulse signal for operating the ET, and the drive circuit 7 controls the voltage applied to the electric motor 8 according to this pulse signal.

The electric motor 8 moves the optical system 11 at a speed corresponding to the drive voltage from the drive circuit 7, and the direction and speed of movement of the optical system 11 is determined by the rotational direction and speed of the electric motor 8, which is determined by an incremental encoder 9. is detected by detecting. The optical system detection interface 10 counts the output pulses of the incremental encoder 9, identifies a detection signal from a home position sensor HPS of the optical system 11, which will be described later, and outputs it to the microcomputer 1.

Next, the detailed configuration of the optical system 11 will be explained with reference to FIG. This optical system 11 includes a light source 31a for illuminating the original, a mirror base MB1 for integrally supporting a second mirror (not shown), and a third mirror, and a mirror base MB1 for integrally supporting a second mirror (not shown), and a mirror base MB1 for reflecting light reflected from the original in the direction of the second mirror. the first mirror 31 of
mirror base MB2 for supporting the second
The reflected light from the mirror is reflected by a third mirror and guided onto a photosensitive drum (not shown).

The mirror bases MB1 and MB2 are arranged horizontally (in the feed direction A in the figure) along two rails 32 and 33.
and the return direction B) so as to be integrally movable back and forth. One end 34 of the mirror base MB1 is fixed to a wire 35, and the one end 34 is provided with a vertical piece 34a for detecting that the optical system 11 is located at the home position HP. The wire 35 is connected to a pulley 36,
37, and the pulley 37 is rotated by the electric motor 8. Therefore, when the electric motor 8 rotates forward or reverse, the wire 35 moves and the mirror bases MB1 and MB2 move accordingly.

A home position sensor HPS is arranged on the movement path of the vertical piece 34a. The home position sensor HPS is composed of, for example, a photointerrupter, and detects that the optical system 11 is located at the home position HP when the vertical piece 34a interrupts the optical path. Note that the home position HP of the optical system 11 is the vertical piece 34a.
This is the position where the rear end C has moved about several millimeters in the return direction B after crossing the optical path of the home position sensor HPS.

Next, referring to FIG. 3, the relationship between the voltage applied to the motor 8 and the speed of the optical system 11 in the speed control device of this embodiment will be explained. After the optical system 11 moves in the feed direction A, scans the original image, and reaches the final scanning position, when a relatively high constant return voltage is applied to the motor 8, the optical system 11 moves in the return direction. B starts moving to a constant high speed (between position RS and first deceleration start position RA). When the optical system 11 reaches the first deceleration start position RA, a relatively high reversal voltage UA-B is applied to the electric motor 8 (from the first deceleration start position RA to the position RB where the electric motor 8 becomes below a predetermined speed). ), the speed of the optical system 11 gradually decreases.

Next, when the motor 8 reaches a predetermined speed or less, a relatively low constant return voltage is applied to the motor 8 (between the position RB and the second deceleration start position RC), and the optical system 11 The speed becomes constant and low from a position slightly past RB. When the optical system 11 reaches the second deceleration start position RC, the relatively low reversing voltage, that is, the stopping reversing voltage U
C-D is applied to the electric motor 8 (second deceleration start position R
C and the stop position RD), the optical system 11 gradually decreases its speed again and stops at the stop position RD. Note that the first
The integral type optimal control is performed between the deceleration start position RA and between the position RB and the second deceleration start position RC.

When performing continuous copying, in this embodiment, the first deceleration start position RA at the time of the current copy is such that the motor 8 has reached a predetermined speed from the first deceleration start position RA at the time of the previous copy. Travel distance XA-B to position RB that is less than or equal to
Determined by In addition, the relatively high applied voltage UA-B for reversing during the current copy is the same as the second voltage applied during the previous copy.
Determined by the speed YLAST of the deceleration start position RC,
Similarly, the relatively low applied voltage UC-D for reverse rotation is equal to the speed YLAST at the second deceleration start position RC during the previous copy.
Determined by

[0027] After the power of the copying machine is turned on, 1
When making the first copy, the first deceleration start position RA
In order to ensure that the optical system 11 accurately stops at the home position HP even when the electric motor 8 generates heat, the initial value of is selected to be a position relatively farther from the home position than when the electric motor 8 does not generate heat; A value smaller than that in the case where the electric motor 8 does not generate heat is selected as the applied voltage UA-B for reverse rotation, which has a high target value. Therefore, even if the electric motor 8 generates heat when the power is turned on and the resistance of the armature becomes high when copying the first sheet, the optical system 11 is moved to the home position HP.
can be stopped accurately.

Furthermore, when the resistance of the armature increases, even if the relatively high applied voltage UA-B for reverse rotation is large, the speed from the first deceleration start position RA to the position RB where the motor 8 becomes lower than the predetermined rotational speed is reduced. The moving distance XA-B increases. Therefore, when copying the second and subsequent copies, if the previous movement distance When B is the maximum value, the deceleration start position RA is set to a position relatively far from the home position HP. On the other hand, if the resistance of the armature does not increase, the previous moving distance XA-B is smaller than the predetermined value, so the previous relatively high applied voltage UA-B for reversing is reduced to move to the first deceleration start position RA. is set relatively close to the home position HP.

Furthermore, in this embodiment, the applied voltage U for reversal
A-B is determined by the speed YLAST at the previous second reverse rotation start position RC. Previous speed YLAST
is larger than a predetermined value, that is, when the resistance of the armature increases and the deceleration between the positions RA and RB is small, the current applied voltage UA-B for reversal is set to be large. In addition, even if the previous speed YLAST is greater than a predetermined value, the resistance of the armature will decrease if copying is not performed for a long time, so the current applied voltage UA for reversal is -Set B small.

[0030] Also, the applied voltage for reversal, UC-, is relatively small.
D is similarly determined by the speed YLAST at the previous second reverse rotation start position RC. Previous speed YLAS
If T is larger than a predetermined value, the current applied voltage for reversal UC-D is set to a large value so that the optical system 11 does not collide with the housing, and if the previous speed YLAST is smaller than a predetermined value, , the current applied voltage UC-D for reversal is set small so that the optical system 11 stops accurately at the home position HP.

Next, the general operation of the speed control device shown in FIG. 1 will be explained with reference to FIG. 4. First, in step S1,
When the power is turned on, an initial setting routine is executed to initialize the RAM 3 and peripheral circuits, and then, when the first copy is to be made, the process proceeds from step S2 to step S3, and a routine as shown in detail in FIG. 5 is executed. . Further, when copying the second and subsequent sheets, the process advances from step S2 to step S4, and a routine shown in detail in FIGS. 6 to 8 is executed.

Next, the details of the first copy operation will be explained with reference to FIG. 5, the optical system 11 moves in the feed direction and then starts moving in the return direction, and FIG.
The program after the position RS shown in is shown. Step P1
1, a relatively high constant return voltage is applied to the electric motor 8 through optimal control in order to perform high-speed copying. Therefore, with this optimal control, the optical system 11 can be controlled at the target speed even if the frictional force of the optical system 11 fluctuates or the resistance of the armature of the electric motor 8 changes.

In the following step P12, it is determined whether the optical system 11 has reached the first deceleration start position RA, and if it has reached the first deceleration start position RA, the process advances to step P13. In step P13,
The relatively high applied voltage UA-B for reversing is set to the maximum value UMAX that allows the optical system 11 to accurately stop at the home position HP even if copying is not performed for a long time even after the power is turned on and the motor 8 generates heat. Set. Next step P1
In step 4, it is determined whether the optical system 11 has reached the position RB, and if the optical system 11 has reached the position RB, the process proceeds to step P15. Here, the position RB is a value higher than the target speed between the position RB and the second deceleration start position RC, taking into account the target speed of the integral optimal control and the delay in sampling time.

In step P15, the moving distance XA-B between the first deceleration start position RA and the position RB is set in the RAM 4 and used for control of the second and subsequent frames as described later. Next, in step P16, from position RB to second deceleration start position RC, a relatively low constant applied return voltage is applied to the motor 8 by optimal control, and the second
When the deceleration start position RC is reached, the process advances from step P17 to step P18. Note that the second deceleration start position RC is a position that is approximately several mm ahead of the home position HP.

In step P18, the stop reversing voltage UC-D is determined based on the speed YLAST of the optical system 11 at the second deceleration start position RC. That is, the speed YLA
If ST is smaller than the target speed, the stop reversing voltage UC
-D is set smaller than the reference value (step P19),
If the speed YLAST is equal to the target speed, set the stop reversing voltage UC-D to the reference value (step P20),
If the speed YLAST is higher than the target speed, the stop reversing voltage UC-D is set higher than the reference value (step P21). In addition, this reversal voltage for stopping UC-D is
Instead of the above three methods, control may be performed in more detailed manner.

Next, in step P22, the electric motor 8
If the reverse rotation of the motor 8 is detected, the process proceeds to step P23, where the voltage application to the motor 8 is stopped and the first copy control is ended.

Next, details of the copying operation for the second and subsequent sheets will be explained with reference to FIGS. 6 to 8. First, step P3
1, 2 Determine the relatively high applied voltage UA-B for reversal after the first sheet. This previous movement distance XA-B is determined by the relatively high reverse rotation applied voltage UA-B and the resistance of the armature, so
If the resistance of the armature gradually decreases from the previous time, the applied voltage UA-B for reverse rotation this time is changed to the current moving distance XA-B so that the speed YLAST at the second deceleration start position RC becomes the target speed. is reduced by a predetermined value α (step P32), and the process proceeds to step P36.

Further, if the resistance of the armature is smaller than the previous one and the previous moving distance XA-B is large, the applied voltage UA-B for reversal is reduced (step P33), and the process proceeds to step P36. If the resistance of the armature gradually increases from the previous time, the previous applied voltage UA-B for reverse rotation is set again (step P34), and the process proceeds to step P35. In step P35, this applied voltage UA-B for reversal is compared with the maximum value UMAX, and if they are not equal, the process proceeds to step P36, and if they are equal, the process proceeds to step P37.

In step P36, the applied voltage UA for reverse rotation is
-B is smaller than the maximum value UMAX, the first deceleration start position RA is set to a position relatively closer than the home position HP, and in step P37, the reverse rotation applied voltage UA
Since -B is the maximum value UMAX, the first deceleration start position RA is set to a position relatively far from the home position HP.

In the following step P38, integral optimal control is performed to move the optical system 11 in the feed (forward) direction. Note that this speed control is performed at a target speed according to the magnification ratio. Next, steps P39 and P40
In step P11 and P12 described above, optimal control is performed in the return direction from the position RS to the first deceleration start position RA, and when the optical system 11 reaches the first deceleration start position RA, step P41 is performed. Proceed to.

In step P41, the current applied voltage UA-B for reverse rotation is determined based on the speed YLAST at the previous second deceleration start position RB. That is, if the previous speed YLAST is less than the predetermined speed, the previous applied voltage for reverse rotation UA-B is set as is (step P4).
2) Proceed to step P46. Also, the previous speed YLAS
If T is slightly larger than the predetermined speed, the current applied voltage UA for reversing is determined by adding a value β that takes into account the increase in armature resistance and the number of copies to the previous applied voltage UA-B for reversing.
-B is set (step P43), and step P44
Proceed to. In addition, if the previous speed YLAST is considerably larger than the predetermined speed, the current applied voltage UA for reversal is applied so that the optical system 11 reliably stops at the home position HP.
-B is determined to be the maximum value UMAX (step P45)
, proceed to step P46.

In step P44, the reverse applied voltage UA-B and the maximum value U set in step P43 are
MAX, and the applied voltage UA-B is the maximum value UMAX.
In the above case, the process branches to step P45 and the current applied voltage UA-B for reverse rotation is set to the maximum value UMAX. If the applied voltage UA-B is less than the maximum value UMAX, the process advances to step P46, and in steps P46 to P55, the control from position RB to stop position RD is performed as in steps P14 to P23 shown in FIG. I do.

That is, in step P46, the optical system 1
1 has reached position RB, and if so, the process advances to step P47. Here, position RB is position R
This is the value when the target speed is higher than the target speed between B and the second deceleration start position RC, taking into consideration the target speed of the integral type optimal control and the sampling time delay.

In step P47, the moving distance XA-B between the current first deceleration start position RA and position RB is calculated as RA.
Set it to M4 and use it for control during the next copy. Next, in step P48, a relatively low constant applied return voltage is applied to the electric motor 8 by optimal control from the position RB to the second deceleration start position RC, and when the motor 8 reaches the second deceleration start position RC. The process advances from step P49 to step P50.

In step P50, the stop reversing voltage UC-D is determined based on the speed YLAST of the optical system 11 at the previous second deceleration start position RC. That is, if the previous speed YLAST is smaller than the target speed, the stopping reversing voltage UC-D is set smaller than the reference value (step P51), and if the previous speed YLAST and the target speed are equal, the stopping reversing voltage UC-D is set to be lower than the reference value. -D is set as the reference value (
In step P52), if the previous speed YLAST is higher than the target speed, the stop reversing voltage UC-D is set to be larger than the reference value (step P53). Note that this stopping reversing voltage UC-D may be controlled in more subdivided manners, rather than in the above three ways.

Next, in step P54, the electric motor 8
If the reverse rotation of the motor 8 is detected, the process proceeds to step P55, where the voltage application to the motor 8 is stopped and the current copy control is ended.

[0047]

As explained above, the invention as claimed in claim 1 provides a method for reducing the speed from the first deceleration start position of the optical system when the copying machine optical system is returned from the scanning end position to the home position by the electric motor for each copy. Speed control in which a first reversing voltage is applied to the motor while the rotational speed of the motor decreases to a predetermined speed, and a second reversing voltage is applied to the motor from a second deceleration start position to a stop position of the optical system. In the apparatus, when the moving distance from the first deceleration start position of the optical system during the previous copy to the time when the rotation speed of the electric motor is reduced to a predetermined speed is relatively long, the first reversal during the current copy The present invention is equipped with a control means that makes the first reversing voltage the same as the previous one and makes the first reversing voltage smaller than the previous one when the moving distance is relatively short. Regardless of the situation, the optical system can be accurately stopped at the home position, and the copying time can be sped up.

According to the second aspect of the invention, when the control means according to the first aspect copies the first sheet, the optical system is stopped at the home position even if the electric motor is generating heat.
Since the first reversing voltage is set to the maximum value, it is possible to stop the optical system at the home position even if the electric motor is generating heat, for example when making the first copy after a long period of time has passed after the power was turned on. can.

[0049] In the invention as set forth in claim 3, the control means of claims 1 and 2 compares the first deceleration start position from the home position when the first reversing voltage during the current copying is at the maximum value. If the first reversing voltage is set at a position far from the target and the current first reversal voltage is made small, the first deceleration start position is set at a position relatively close to the home position, so the optical system can be operated regardless of the heat generated by the motor. It can be stopped accurately at the home position, and the copying time can be sped up.

According to the fourth aspect of the invention, when the speed of the optical system at the second deceleration start position during the previous copy is higher than a predetermined speed, the control means according to the third embodiment controls the speed of the optical system at the second deceleration start position during the previous copy. If the speed of the optical system at the second deceleration start position during the previous copy is smaller than the predetermined speed, the first reversal voltage during the current copy is reduced. The optical system can be accurately stopped at the home position even when the electric motor gradually heats up and cools down, and when it suddenly heats up and cools down, and it is also possible to prevent the copying time from slowing down.

[0051] The invention described in claim 5 is based on claims 1 to 4.
When the speed of the optical system at the second deceleration start position during the previous copy is greater than a predetermined speed,
Increase the second reversal voltage during the current copy, and if the speed of the optical system at the second deceleration start position during the previous copy is smaller than the predetermined speed, the second reversal voltage during the current copy Since the voltage is reduced, the optical system can be accurately stopped at the home position.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a speed control device for a copying machine optical system according to the present invention.

FIG. 2 is a perspective view of a main part showing an optical system controlled by the speed control device of FIG. 1;

FIG. 3 is a graph for explaining the relationship between the voltage applied to the motor and the speed of the optical system in the speed control device of FIG. 1;

FIG. 4 is a flowchart for explaining the general operation of the speed control device in FIG. 1;

FIG. 5 is a flowchart for explaining details of the first copy operation in FIG. 4;

FIG. 6 is a flowchart for explaining details of the copying operation for the second and subsequent sheets in FIG. 4, and together with FIGS. 7 and 8, shows one process.

FIG. 7 is a flowchart for explaining details of the copying operation for the second and subsequent sheets in FIG. 4, and shows one process together with FIGS. 6 and 8;

FIG. 8 is a flowchart for explaining details of the copying operation for the second and subsequent sheets in FIG. 4, and shows one process together with FIGS. 6 and 7;

[Explanation of symbols]

1 Microcomputer 8 Electric motor 9 Encoder 11 Optical system

Claims (5)

[Claims] [Claim 1] When the copying machine optical system is returned by an electric motor from the scanning end position to the home position for each copy,
While the rotational speed of the electric motor decreases from the first deceleration start position of the optical system to a predetermined speed, the first reversal voltage is applied to the electric motor, and the rotational speed of the electric motor decreases from the second deceleration start position of the optical system to the stop position. In a speed control device for a copying machine optical system that controls speed by applying a reversing voltage to an electric motor, the rotation speed of the electric motor decreases to a predetermined speed from a first deceleration start position of the optical system during the previous copy. If the moving distance during the current copy is relatively long, the first reversing voltage during the current copy is set equal to the previous one, and when the moving distance is relatively short, the first reversing voltage during the current copy is set equal to the previous one. A speed control device for an optical system of a copying machine, which is equipped with a control means for making the speed smaller than the previous time. 2. The control means is configured to set the first reversal voltage to a maximum value so that the optical system stops at the home position even if the electric motor generates heat when copying the first sheet. 2. The speed control device for an optical system of a copying machine according to claim 1, wherein the speed control device is set to . 3. The control means is configured to move the current first deceleration start position to a position relatively far from the home position when the first reversal voltage at the time of the current copy is at a maximum value. 3. The copying machine according to claim 1, wherein the first deceleration start position is set to be relatively close to a home position when the reversing voltage is reduced. Optical system speed control device. 4. The control means increases the first reversal voltage during the current copy when the speed of the optical system at the second deceleration start position during the previous copy is higher than a predetermined speed; If the speed of the optical system at the second deceleration start position during the previous copy is lower than a predetermined speed, the first reversing voltage during the current copy is set to be reduced. 4. A speed control device for an optical system of a copying machine according to claim 3. 5. The control means increases the second reversal voltage during the current copy if the speed of the optical system at the second deceleration start position during the previous copy is higher than a predetermined speed; If the speed of the optical system at the second deceleration start position during the previous copy is smaller than a predetermined speed, the second reversal voltage during the current copy is set to be reduced. A speed control device for an optical system of a copying machine according to any one of claims 1 to 4.