JPH04152312A - Displacement transmission mechanism - Google Patents

Abstract

PURPOSE:To exactly position a body to be moved by driving a motor by exceeding a backlash amount in the direction reverse to the direction which is set with regard to a backlash, thereafter, driving it in the forward direction, in the case of displacing the body. CONSTITUTION:By measuring the distance to the body by a distance measuring sensor 1, the driving position D of a motor is calculated. Subsequently, by reading out the present position C of the motor from the memory area of a micro- computer 2 and calculating the difference of positions D and C, a driving quantity X is derived. When the driving quantity X is larger than three steps obtained by adding the variance of a camera to the backlash quantity, the motor is driven by X staps and stopped. On the other hand, when the driving quantity X is smaller than three steps, the motor driven by (X-3) steps and a backlash operation for executing an overrun and returning it is executed. Subsequently, the present position is stored in the memory area of the microcomputer 2. In such a manner, the misalignment caused by the vibration shock can also be cancelled and the body can be positioned exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a displacement transmission mechanism, and more particularly to a displacement transmission mechanism that transmits driving force from a motor to a driven object via a drive system having backlash.

[Prior Art] Displacement transmission mechanisms that transmit the driving force of a motor to a driven object via a drive system such as a deceleration mechanism have been widely used in electronic devices in various fields. It is often used in automatic focus adjustment devices that control the focusing lens to be driven to the focal position. The block configuration of this type of automatic focus adjustment device will be explained with reference to FIG.
The microcomputer 2 calculates the driving amount of the lens, determines the driving direction, etc. The lens drive signal output from the microcomputer 2 is supplied to the stepping motor 4 via the motor drive circuit 3, and when the motor 4 rotates, the lens drive signal is sent to the focusing lens 6 via the drive system 5 consisting of a deceleration mechanism, etc.
moves in the optical axis direction. When driving and controlling the focusing lens 6 by the motor 4, so-called oven loop control, in which the final lens position is not fed back, is customary from the viewpoint of cost and volume.

By the way, unless a driven object such as a focusing lens is directly connected to the rotating shaft of the motor and driven, the drive system 5 such as a speed reduction mechanism is inserted between the motor and the driven object as described above. Therefore, a difference in reciprocation due to play in the drive system 5, that is, backlash is unavoidable. Therefore, when it is desired to precisely position the driven object by driving it under open-loop control, backlash cancellation driving is performed.

This backlash canceling drive attempts to accurately stop the driven object at a target position with the inevitable backlash in the drive system shifted to one predetermined side. In other words, the motor moves the driven object in a predetermined direction (
When driving in the A direction (hereinafter referred to as the A direction), the motor is stopped as it is when it reaches the target position, but when driving in the B direction, which is opposite to the input direction, the motor is overrun from the target position. After that, it is driven in the incoming direction and stopped at the target position.

FIGS. 4(A) to 4(D) are diagrams of the focusing lens extending and retracting operation in an automatic focusing device for explaining the conventional backlash cancellation drive.
The numbers 0 to 30 in the upper row indicate the number of driving stages of the focusing lens, from the reference position 0 to 30, which corresponds to the close end, when the focusing lens is retracted and focused on the subject (3). This is what is shown. The thick solid line N,,N1□”31 connecting the black circle and the arrow is the rotation range of the motor, and the black circle LL'L11' L2□
, L3□ indicates the motor position before driving, and the tip of the arrow P
1°P1□ and P3□ indicate the target drive positions, respectively. On the other hand, the H-shaped thin solid line ai"ii'a
21”3□ indicates the lens position at the start of driving, as shown by the dashed dotted line b1
, is the lens position at the start of reversal, and the two-dot chain line Ct,
C1l and C3□ each simulate the lens position when driving is completed, and the backlash width is 2.5.
I'm assuming the steps.

In FIG. 4(A), the drive amount X is 6 stages, that is, the current position L1 of the motor indicated by a black circle is 4 stages, and the target displacement position P1 is 10
This is the case for Dan. In this case, before driving, the motor is in four driving stages, and the lens is stopped with its right side in contact with the motor. When the motor is driven by six driving stages from this current position L toward the target displacement position Pl, the lens is driven with its right side in contact with the motor and stops at the position indicated by the two-dot chain line C1. In other words, in this drive, the target stop position is the position where the lens stops with its right side in contact with the motor.

In FIG. 4(B), the drive amount
This is the case where □ has 10 stages. Note that the incoming direction drive of the motor is defined as 10, and the B direction drive is defined as -. This figure 4 (B)
In this case, when driving in the B direction, a backlash canceling operation is performed in which the lens is overrun and returned. However, at the starting position of the motor "N", assume that the lens is at the lens position a11 with its right side in contact with the motor. This state The motor drives in direction B, but the number of lens drive stages is 13.
The lens position is a11 until it passes more than half the step in the B direction.
Since the backlash is within the range of , the lens is still stopped and does not move in either direction.

When the motor is driven in direction B from between the 12th and 13th stages, the left side of the lens touches the motor, so the lens moves in direction B.
Start moving in the direction. When the motor reaches the 7th stage, which is three stages overrunning the target stop position of the 10th stage, the lens reaches the position indicated by the dashed line b1. In other words, the lens moves with its left side in contact with the motor. In this way, when the motor is overrun by 3 steps exceeding the 25 steps of lens backlash, the right end of the lens position is in the B direction by 0.5 steps from the target drive position of 10 steps.

From this state, when the motor is driven 3 steps in the A direction, the right end of the lens will come into contact with the motor between the 9th and 10th steps, so the lens will move in the direction of 0 and 5 steps A, and the two-dot chain line C1
Reach position 1. This operation of overrunning 3 stages and returning 3 stages is a backlash canceling operation, but if you drive from 15 stages to 10 stages in direction B and then stop without overrunning, as shown by the broken line a′
The lens ends up stopping at position 11.

Figure 4 (C) shows a case where the drive JiX is 0, that is, the stop position in the previous positioning operation was 10 steps, and the next target displacement position is also 10 steps, so the lens can be left in the same position. It is. Therefore, conventionally, no motor drive was performed.

In FIG. 4(D), the drive amount
This is the case of 0 stage. In this case, before the motor starts driving, the lens is at the lens position a where its right side is in contact with the motor.
31, if the motor is driven two steps in the input direction, the motor will reach the target displacement position P3□, that is, the 10th step,
The lens also reaches the position indicated by the two-dot chain line c3□.

[Problems to be Solved by the Invention] The problem here is that if the lens position at the end of the previous positioning is subjected to vibrations, shocks, etc. before the start of the next positioning, backlash of the lens will occur. This means that it will fluctuate within the range of . Generally, the motor itself has a detent torque even when it is not energized, so its stopping position is considerably regulated. If a larger stopping torque is required, the rotational position of the rotor will be completely regulated by the holding torque as long as the motor continues to be energized. However, within the backlash range of the drive system inserted between the motor and focusing lens, the torque is very small, so even if the motor is fixed, the lens can easily move due to vibrations and shocks. .

To explain this in the case of FIG. 4(C) above where the drive amount
There is no problem if it continues to be held in the position indicated by 1, but
In the worst case, there is a possibility that the lens will move to the position a'21 shown by the broken line, that is, the left end of the lens will be in contact with the motor.

Therefore, the lens is originally a21=' 2 shown by the solid line.
The position that should be at position 1 has been moved to a'2□-c 21 shown by the broken line. The above is a case where the drive amount X is zero, but the case where the drive amount X is smaller than the backlash amount of 2.5 stages will be explained with reference to FIG. 4(D).

FIG. 4(D) shows a case where the drive amount X is 2, and conventionally, two stages of feed were carried out in the incoming direction, but the same problem as in FIG. 4(C) occurs in this case as well. That is, if there is no vibration or impact, as described above, when the motor is driven in two steps in the input direction, the lens is thereby driven to the position shown by the two-dot chain line '31. However, when there is a vibration shock, the lens position before driving changes to the broken line a'3, as shown in Fig. 4 (C) above.
, it is possible to deviate up to . Therefore, even if the motor is driven in two steps in the A direction with the lens positioned at this broken line a'3□, the motor will only move within the backlash range and the lens will not move, so 0.5 The lens remains positioned at the dashed line position "31" which has been shifted by steps.

In this way, in the conventional backlash cancellation drive,
If the amount of drive is zero or smaller than the amount of backlash, there is a possibility that the lens will shift due to vibrations, shocks, etc.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a displacement transmission mechanism that eliminates the above-mentioned problems and cancels not only positional deviations due to backlash but also positional deviations due to vibration and impact, thereby making it possible to perform accurate positioning. It is in.

[Means and effects for solving the problem] The displacement transmission mechanism of the present invention is a displacement transmission mechanism that transmits the driving force of a motor to a driven body via a drive system having backlash, and which a subject position recognition means for recognizing the current position of the subject including an error within the range;
Required displacement recognition means that recognizes a required displacement amount as a difference between the current position of the driven object by the driven object position recognition means and a target displacement position regarding the driven object, and the required displacement determined by the required displacement recognition means is set with respect to the backlash. When the direction is opposite to the direction in which the backlash is generated, or when the backlash amount is within the range of zero to the above-mentioned backlash amount even if it is in the forward direction, the motor is driven in the above-mentioned reverse direction so as to exceed the backlash amount, and then the above-mentioned A displacement transmission mechanism for transmitting the driving force of the motor to a driven body via a drive system having backlash, the displacement transmission mechanism comprising a motor drive control means for driving the driven body in a forward direction. A motor drive control means is provided for driving the motor in the -displacement direction so as to exceed the amount of backlash with respect to the direction set for the backlash at the time of initial movement when the body is displaced, and then driving the motor in the forward direction. It is characterized by:

[Embodiment] The present invention will be specifically described below with reference to the drawings. In the following embodiments, an example in which the displacement transmission mechanism according to the present invention is applied to an automatic focus adjustment device of a camera will be described.

FIGS. 1(A) to 1(D) are diagrams illustrating backlash cancellation drive during the focusing lens extension and retracting operations in an automatic focusing device to which the displacement transmission mechanism according to the present invention is applied. In FIGS. 4(A) to 4(D) showing the conventional example, it is determined whether or not to perform the backlash canceling operation to overrun and return the drive direction, depending only on whether the driving direction is the six directions or the B direction. On the other hand, in the embodiment shown in FIGS. 1(A) to (D), even if the driving direction is six, if the driving amount is less than the backlash amount or is zero, the backlash canceling operation is performed. ing.

In Fig. 1, the case (A) where the drive amount X is 6 and the case (B) where the drive amount Therefore, the same motor position, lens position, etc. are given the same reference numerals and their explanations will be omitted.

Fig. 1 (C) shows the case where the drive amount move. Therefore, even if the lens is located at the thin solid line a21 at the motor's previous positioning operation position "21", or even if it has moved to the position indicated by the broken line a'21 due to vibration, impact, etc., the motor is moved in the direction B. By driving in three steps, the focusing lens moves to the position indicated by the dashed-dotted line b2□.Then, while moving the motor again in the direction A by three steps, the lens moves to the position indicated by the dashed-dotted line c21, with its right end touching the motor. In other words, even if the lens moves to the position indicated by the broken line a'2 due to vibration, impact, etc. when the previous positioning was completed, according to this embodiment, the lens is moved to the position indicated by the two-dot chain line c21. It can be returned.

Next, the operation of this embodiment in the case of X-2, where the drive amount is smaller than the backlash M2.5 stages even if the drive amount is in the A direction, will be explained with reference to FIG. 1(D). In this case, the motor starts moving from the black circle 3□ with 8 lens drive stages.At this time, the lens should originally be located at the thin solid line "31," but due to vibrations, shocks, etc. '3
There is a possibility that it is located at 1. in this way,
Even if the lens is located at the dashed line a'3, the motor is moved by the black circle 3 and 1 in the direction B as shown by the thick solid line g.
Since the step is shifted, the lens moves to the dashed line b3. Next, at a target displacement position P31 where the motor is moved three steps, that is, driven two steps in the A direction from the position "31" at the end of the previous positioning, the lens is located at the two-dot chain line c31.

Figure 2 is a flowchart from distance measurement with the automatic focus adjustment device to lens drive. To explain the above operation using Figure 2, the distance measurement sensor 1 (see Figure 3 above) measures the object distance. (Step Sl). Based on the measured object distance information, the driving position of the motor is calculated (step S2). By the way, all positions in FIG. 2 are motor positions, and since the lens driven by this motor via a drive system with backlash is under open-loop control, the positions cannot be determined in a strict sense.

In step S3, the current position C of the motor is determined by the microcomputer 2 (
(see Figure 3).

This current position C is a value stored in a memory area within the microcomputer as the current position as a result of the motor positioning operation during the previous AF (autofocus). Then, the difference between the drive position and the current position C is calculated to obtain the drive amount X (step S4).

Check whether the above drive amount Then, the motor is stopped (step S6). Note that this case corresponds to the case shown in FIG. 1(A) above. On the other hand, returning to step S5 above, the driving amount
If is smaller than 3 stages, it is driven by (X-3) stages (step S7), that is, by driving 3 stages more in the B direction than the X stage, and then by driving 3 stages in the A direction (step S8
), performs a backlash cancellation operation that overruns and returns. Finally, the current position is stored in the memory area C of the microcomputer (step S9), and this flow ends.

Next, the correspondence between the flowchart in FIG. 2 and the diagram in FIG. 1 will be explained. If the case of drive amount X-0 in FIG. 1(C) is made to correspond to this FIG. 2, since the determination result in step S5 is No, step S7. Proceeding to S8, 13-stage drive is performed, resulting in 3-stage drive. Furthermore, when the case of drive amount X-2 in FIG. 1(D) is made to correspond to this diagram j1!2, the determination result in step S5 is still No, so step S7. Proceed to S8,
-1 stage drive, 3 stage drive. Therefore, by driving in this manner, it is possible to cancel the displacement of the lens position due to vibrations, shocks, etc.

The above embodiment has been explained using open-loop drive using a stepping motor, but not only this open-loop drive but also drive using a DC motor and a position detector may be used in which the position detector is attached to the shaft of the motor in addition to the driven object. Even in the so-called semi-closed loop drive, the final position of the driven object cannot be detected.
The invention is equally applicable.

In addition, although the above embodiment is explained using external distance measurement, TT
Of course, it can also be applied to L distance measurement, etc.

By the way, in the above embodiment, the amount of drive is detected, and it is determined whether or not to cause the motor to overrun according to the amount of drive. However, the above '1s1 diagram (A), (B
), (C), and (D), the motor may be driven in the opposite direction by an amount of overrun corresponding to the amount of backlash before driving, and then driven to the target position. Such means are described herein as further embodiments of the invention. In this case, for example in the case of FIG. 1(A), there will be some waste in driving time, but
In terms of the overall driving time, this is insignificant.

In each of the above embodiments, the displacement transmission mechanism according to the present invention is applied to an automatic focus adjustment device of a camera, but the present invention is not limited to this, and the present invention is not limited to this. Needless to say, the present invention can be widely applied to a displacement transmission mechanism that transmits the driving force of a motor in a portable electronic device with a backlash to a driven body via a drive system having backlash.

[Effects of the Invention] As described above, in the present invention, when the required displacement by the required displacement recognition means is in the opposite direction to the direction set with respect to the backlash, and even in the forward direction, the When the rush amount is within the range,
After driving the motor in the reverse direction so as to exceed the pack rush amount, the motor is driven in the forward direction. Or, when displacing the driven object, at the time of its initial movement, - in the direction set for the backlash above.
After driving the motor so as to exceed the amount of backlash in the shifting direction, the motor is driven in the forward direction. Regardless of which of these means is adopted, it is possible to cancel not only positional deviations due to backlash (but also positional deviations due to vibrations and shocks), and the remarkable effect of being able to accurately position the driven object is demonstrated. .

[Brief explanation of the drawing]

FIG. 1 is a diagram of backlash cancellation drive during the focusing lens extension and retracting operations in an automatic focus adjustment device of a camera to which the displacement transmission mechanism according to the present invention is applied. Flowchart for measuring distance and driving the lens. Figure 3 is a block diagram of the automatic focus adjustment device. Figure 4 is a conventional backlash cancellation driving line during the focusing lens extension and retraction operations in the automatic focus adjustment device. It is a diagram. 2...Microcomputer (driven object position recognition means. Required displacement recognition means) 3...Motor drive circuit (motor drive control means) 4...・・Stepping motor (motor) 5・・・・・・・Drive system

Claims (2)

[Claims] (1) A displacement transmission mechanism that transmits the driving force of a motor to a driven object via a drive system that has backlash, and that is capable of recognizing the current position of the driven object including an error within the range of the backlash. a driven object position recognition means; a required displacement recognition means for recognizing a required displacement amount as a difference between the current position of the driven object by the driven object position recognition means and a target displacement position regarding the driven object; When the displacement is in the opposite direction to the direction set for the backlash, and when the displacement is within the range of zero to the above backlash amount even in the forward direction, the motor is moved in the above reverse direction so as to exceed the backlash amount. A displacement transmission mechanism comprising: a motor drive control means for driving the motor in the forward direction after driving the motor in the forward direction; (2) A displacement transmission mechanism that transmits the driving force of a motor to a driven object via a drive system that has backlash, and when displacing the driven object, the direction set for the backlash is once reversed when the driven object is initially moved. After driving the motor to exceed the amount of backlash in the direction,
A displacement transmission mechanism comprising a motor drive control means for driving a motor in a forward direction.