JPH04312370A - Vibration motor control circuit - Google Patents

Abstract

PURPOSE:To shift to the highest speed smoothly by changing the frequency speed before and after the start of a motor is confirmed, and increasing the scan speed before the start than the scan speed after the start, and dropping the scan speed after the start is confirmed. CONSTITUTION:While the frequency scan at the start of a motor 9 is being performed, a detection circuit 16 detects whether the motor 9 is started or not at all times. Hereupon, the speed of frequency before it detects the motor 9 having started actually after the frequency scan is made high. Next, the speed of frequency after the start of the motor 9 being detected is made lower than the scan speed before the start being confirmed. Hereby, the motor 9 can be started smoothly in a short time, and can be shifted into the condition of high-speed in a short time.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention generates progressive vibration waves on the surface of a vibrating body by applying a frequency voltage to an electro-mechanical energy conversion element such as an electrostrictive element or a piezoelectric element, and moves by the vibration waves. This invention relates to a control circuit for a vibration motor that drives the body.

0002

2. Description of the Related Art Conventionally, a method is known in which the frequency of the above-mentioned frequency voltage is varied in adjusting the speed of this type of motor.

When setting the motor to a desired speed using this method, it is sufficient to select a frequency corresponding to the desired speed and apply it to the electro-mechanical energy conversion element. It will start rotating.

[0004] Therefore, in order to rotate the motor smoothly, a method is used in which when starting the motor, the drive frequency is gradually lowered from a high frequency and shifted to a frequency corresponding to a desired speed.

In this case, the high frequency at startup is set to the frequency at which the motor actually starts rotating, and if the frequency is gradually lowered from this set frequency, the motor can be smoothly driven to the desired speed in a short time. Although it is possible to
The characteristics of the motor mentioned above are not constant and are affected by environmental changes such as temperature, so if the frequency at the start of startup is fixed, it will not be able to cope with changes in temperature etc., and the time until the start of startup will be longer, or There is a risk that the engine will suddenly start rotating, and in the worst case, it will not be able to start.

[0006] As a method for solving the above problem, for example,
Japanese Patent Laid-Open No. 63-209481 proposes the following method. That is, the method is to memorize the frequency at which the movement started when it was driven last time, and scan from the memorized frequency to a lower frequency the next time it is moved.

[0007]

[Problem to be Solved by the Invention] However, in the conventional example described above, if the motor is left without being driven for a long time since the last time it was driven, and a change in temperature etc. occurs during that time, the characteristics of the motor will change. This will result in the scan start frequency setting being inappropriate. As a result, the time required to start the motor may become longer, or the motor may suddenly start rotating, or even start may not be possible.

[0008] Furthermore, when driving the lens with the motor, there are cases where the lens hits the close end or the infinity end while the lens is being driven, or when the movable part of the focus lens is configured to be exposed to the outside. If the lens is stopped by hand while it is being driven, the next scan start frequency is set to the highest frequency within the settable range and then started. Again, there was an inconvenience that it took a long time to start up.

[0009]

[Means for Solving the Problems] The present invention constantly detects whether the motor has started while performing a frequency scan when starting the motor, and detects whether the motor has actually started after starting the frequency scan. By setting the frequency scan speed high until the motor is detected, and making the frequency scan speed after motor startup is slower than the scan speed until motor startup is confirmed, sudden changes in the environment such as temperature can be avoided. Even if the motor is unable to drive due to a collision or is stopped by hand, the motor can be started smoothly and in a short time, and the motor can be driven at high speed in a short time. This allows for migration.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing an embodiment of a driving circuit for a vibration type motor according to the present invention, and FIG. 1 shows an example in which a lens is driven by the motor. In the same figure,
1 is a microcomputer (hereinafter referred to as microcomputer);
A D/A converter 2 has the function of converting the digital output signal (D/Aout) of the microcomputer 1 into a voltage. A voltage controlled oscillator (VCO) 3 outputs a signal (voltage) at a frequency corresponding to the output voltage of the D/A converter 2. 4 is a frequency divider/phase shifter that divides the frequency signal from VCO3, and divides the frequency signal from π/
Outputs a rectangular wave with two phase differences. 5 and 6 are power amplifiers,
4 is amplified to a voltage and current value that can drive the vibration motor 9. 7 and 8 are matching coils, 9 is a vibration type motor, 9a is data, 9b is a stator, 10 is a pulse plate, which has a plurality of slits in the radial direction as shown in the figure, and together with the gear 11, the vibration type motor It is coaxial with the axis of 9, and rotates together with the data 9a of the vibration wave motor. A gear 12 is fitted into an outer gear portion of the lens barrel 13. 14 is a lens, 15 is a photo interrupter,
The rotation of the pulse plate 10 is detected.

Reference numeral 16 denotes a signal detection circuit for the photointerrupter 15, which amplifies the minute signal from the photointerrupter 15 and converts it into a pulse signal.

An up/down counter 17 counts pulse signals from the signal detection circuit 16 generated by the rotation of the pulse plate 10.

Next, each terminal of the microcomputer 1 will be explained.

DIR1 is an output terminal that instructs the counting direction of the up/down counter 17, and for convenience of explanation, it is referred to as "
"H" means up, "L" means down.

PULSE IN is an input terminal for the count value of the up/down counter 17.

MON is an input terminal for directly monitoring the output of the detection circuit 16.

RESET is the Reset output terminal of the up/down counter 17 and is set to "H" for Reset.

CNT EN/DIS is an output terminal for instructing the counter 17 to enable/disable counting, and "H" enables counting and "L" disables counting.

D/Aout is an output terminal to the D/A converter 2.

DIR2 is a frequency signal A, B applied to the vibration type motor 9 in order to switch the rotation direction of the vibration type motor 9.
This is an output terminal for giving an instruction to the frequency divider/phase shifter 4 to change the phase shifter to 90° or 270°. USM
EN/DIS is a terminal for turning on/off the output of the frequency divider/phase shifter 4, and is turned on at "H" and turned off at "L".

Next, the vibration type motor 9 will be explained using FIG. 2.

FIG. 2 is an explanatory diagram showing the arrangement of piezoelectric elements arranged on the back surface of the stator 9b. A1 and B1 in FIG. 2 are first and second piezoelectric element groups arranged on the stator 9b in the illustrated phase and polarization relationships, respectively. Also S
Reference numeral 1 denotes a sensor piezoelectric element arranged at a position 45° out of phase with the first piezoelectric element group B1. Each of these piezoelectric elements may be attached to the vibrating body individually, or may be formed integrally by polarization treatment. Returning to FIG. 1, A, B, and S represent drive electrodes and sensor electrodes for the first and second piezoelectric element groups A1, B1, and sensor piezoelectric element S1, respectively, and A progressive vibration wave is formed on the back surface of the stator 9b by applying the frequency signal (voltage) to the electrode B and applying the frequency signal (voltage) via the amplifier 6 to the electrode B. Moreover, when the above-mentioned vibration waves are formed in the vibrating body,
The sensor piezoelectric element S outputs an output (frequency voltage) according to the state of this vibration wave, and this is detected by the sensor electrode S. In addition, in a resonant state, the vibration wave motor has a characteristic that the phase relationship between the drive voltage to the A electrode and the output voltage from the sensor electrode is a specific relationship, and a frequency signal is applied at the electrode A. It is determined by the positional relationship between the first piezoelectric element group A1 and the sensor piezoelectric element S1, and in the case of this embodiment, the phase of the signal waveform with the electrodes A and S is 13 in the normal rotation state.
It shows a resonance state when it is shifted by 5 degrees, and when it is reversed, it shows a resonance state of 45 degrees.
It is assumed that a resonance state is indicated when the phase shift is deviated by .degree., and that the phase difference relationship shifts as the phase difference deviates from resonance.

FIG. 3 shows the RO built in the microcomputer 1 in FIG.
1 is a program diagram showing a program flow programmed in M, and the microcomputer 1 executes control operations according to the program flow.

Next, the operation of the embodiment according to the above configuration will be explained.

When entering the vibration type motor drive control routine,
First, step 1 is executed. The operation of each step will be explained below. It is assumed that this routine is executed upon detection of turning on of a start switch (not shown) or the like.

Step 1: Input the initial value of the up/down counter 17 from PULSE IN and set it as variable FPCOL.
Store in D.

Step 2: Set the value of variable FMAX to variable FR.
Transfer to EQ. Note that FMAX is the initial frequency determined based on the drive frequency the last time it was driven, and if it stopped normally last time, it is the frequency when it is confirmed that it has started moving, and if it stops in a drive-unable state, it is 0. Assume that it is stored. Also these variables FMAX and FREQ
It is assumed that the value actually output to D/Aout is stored as is, and the smaller the value, the higher the driving frequency.

Step 3: FR set in step 2
Outputs the EQ value to D/Aout. This allows D/A
Converter 2 converts the digital value output from D/Aout into an analog voltage and outputs it to VCO 3. VCO
3 is a frequency divider/phase shifter 4 that converts the voltage output from the D/A converter 2 into a frequency signal having a frequency corresponding to the voltage.
Output to.

Step 4: Determine the drive rotation direction, and if the rotation is forward, proceed to step 5; if the rotation is reverse, proceed to step 6. The direction of rotation is determined by the switch (not shown) on the microcomputer 1.
shall be instructed in advance.

Step 5: Since the drive rotation direction is normal rotation, "H" is output to DIR1 and the counting direction of the up/down counter 17 is set in the up direction. Also DI
"H" is output to R2 to set the phase difference between the signals A and B output from the frequency divider/phase shifter 4 to 90 degrees, and the process proceeds to step 7.

Step 6: Since the drive rotation direction is reverse, "L" is output to DIR1 and the counting direction of the up/down counter 17 is set to the down direction. Also, D
"L" is output to IR2 to set the phase difference between signals A and B output from frequency divider/phase shifter 4 to 270 degrees, and the process proceeds to step 7.

Step 7: “CNT EN/DIS”
H" is output, and the up/down counter 17 is placed in a count enable state.

Step 8: “
H" and enables the outputs A and B of the frequency divider/phase shifter 4. As a result, the frequency divider/phase shifter 4 changes the phase of the frequency signal from the VCO 3 according to the level output from the DIR2. Frequency signals having a phase difference are output from A and B by differential phase shifting.The output frequency signals A and B are amplified by power amplifiers 5 and 6, and applied to a vibration type motor 9 via matching coils 7 and 8. As a result, the vibration type motor 9 attempts to start rotating.

Step 9: Store 0 in the variable TIMER. Incidentally, TIMER is a timer for measuring a certain period of time when the frequency is lowered every time a certain period of time elapses when no rotational movement of the motor is detected.

Step 10: Add a predetermined value (1) to FREQ and store it in FREQ.

Step 11: If FREQ is greater than the lowest frequency MIN FREQ within the settable range, proceed to step 12; otherwise, proceed to step 13
Proceed to.

Step 12: MIN in step 11
Since no pulse input was recognized even after scanning up to FREQ, it is determined that the drive is not possible, 0 is stored in the next scan start frequency FMAX, and the process proceeds to step 24.

Step 13: FRE to D/Aout terminal
Output the value of Q.

Step 14: Up/down counter 17
Input the counter value and store it in the variable FPC.

Step 15: Variables FPC and FPCOLD
are compared, and if they are equal, proceed to step 16; if not equal, proceed to step 18. That is, the detection circuit 16
When detects the rotating operation of the pulse plate 10 and the up/down counter 17 performs a counting operation, FPC≠F
Since the status is PCOLD, the process advances to step 18. Furthermore, if the rotational movement of the pulse plate 10 is not detected, FPC=F
Since the status is PCOLD, the process advances to step 16.

Step 16: Since the rotational movement of the pulse plate 10 is not detected, TIMER is incremented.

Step 17: TIMER is a predetermined time TI
It is determined whether or not they are equal to ME-LMT, and if they are equal, the process proceeds to step 9. Also, if they are not equal, step 13
Proceed to.

Step 18: In step 15, pulse plate 1
Since a rotational movement of 0 was detected, the frequency FR at that time
Store EQ in FMAX.

Step 19: Compare the actual speed of the motor with a target speed previously stored in the ROM based on information such as remaining drive amount, and if the actual speed is faster than the target speed, step 20 If it is slow, proceed to step 21. It is assumed that the speed of the motor is determined by the microcomputer 1 from the interval of pulses from the detection circuit 16 input to the input terminal MON of the microcomputer 1.

Step 20: Since the speed is fast, FR
A value obtained by subtracting a predetermined value (3) from EQ is stored in FREQ, and after the frequency is scanned toward higher frequencies, the process proceeds to step 22.

Step 21: Since the speed is slow, FR
A value obtained by adding a predetermined value (2) to EQ is stored in FREQ, and the frequency is scanned toward lower frequencies. Note that the predetermined value (2) has a value smaller than the predetermined value (1).

Step 22: Set the value of FREQ to D/Aou
Output to t.

Step 23: Determine how much drive remains, and if it is greater than 0, proceed to step 19. If it is less than 0, proceed to step 24. It is assumed that the remaining drive amount is determined by counting the pulses input to the input terminal MON in the microcomputer and subtracting this counted value from the target drive amount previously set in the microcomputer.

Step 24: Since the remaining drive amount ≦0, that is, the driving amount has been completed or overrun has occurred, “L” is output to USM EN/DIS, and the output of the frequency divider/phase shifter 4 is A and B are disabled. This causes the vibration wave motor 9 to stop.

Step 25: Output "L" to CNT EN/DIS, prohibit the counting operation of the up/down counter 17, and end the vibration type motor drive control routine.

[0051] In the above operation, steps 1 to 8 are initial settings for starting the motor, including checking the initial state of the up/down counter 17, outputting the scan start frequency, determining and setting the rotation direction, and starting the motor. Start.

[0052] In steps 9 to 18, a check is made as to whether or not it has been activated, and a frequency scan is performed. That is,
It takes a predetermined time TIME-LM from when the application of the frequency signal is started to the motor 9 in step 8 until the rotation of the pulse plate 10, that is, the drive of the motor is detected in step 15.
Each time T elapses, step 10 is executed to lower the frequency by a predetermined amount. That is, if the predetermined time has not elapsed until the start of the motor is confirmed, steps 9→10→1
1→13→14→15→16→17→13→... is repeated, and when a predetermined time has elapsed, the process returns from step 17 to step 9, and in step 10, the frequency is lowered by a predetermined value (1).

[0053] During the execution of each of the above steps, if startup of the motor is confirmed in step 15, then in step 18,
Memorize the frequency at that time. And step 19-2
3, the rotational speed of the motor is servo-controlled to the target speed. That is, if the target speed is faster than the target speed, the frequency is increased by a predetermined value (3), and if it is slower than the target speed, the frequency is decreased by a predetermined value (2). Due to the characteristics of the vibration motor 9, if the frequency is lowered further than near the maximum speed, the speed will drop sharply, so it is better not to change the frequency too drastically near the maximum speed. Therefore, the predetermined value (2) is set small. On the other hand, the change in frequency at startup does not require as much sensitivity as at maximum speed, so it is possible to increase the frequency scan speed until the motor starts and start the motor as soon as possible. becomes. Therefore, the predetermined value (1) is set larger than the predetermined value (2). As described above, by changing the frequency scan speed before and after startup is confirmed, the startup speed can be increased during startup, and fine-grained control can be performed during high-speed drive.
In addition to shortening the overall driving time, it is possible to avoid unstable conditions such as stopping halfway.

FIG. 4 shows a flowchart showing another embodiment of the present invention, in which the same step numbers are described in the same parts as in the flow shown in FIG. This flow is configured by deleting steps 9, 16, and 17 in FIG.

With this configuration, the frequency can be updated even faster until the motor is driven.

[0056]

Effects of the Invention As explained above, by changing the frequency scan speed before and after confirming that the motor has started, and by making the scan speed before starting faster than the scan speed after starting, the motor can be started. It is possible to quickly determine whether or not the scan speed is active, and after activation is confirmed, the scan speed can be reduced and smoothly transitioned to maximum speed.

Therefore, unlike the conventional method, even when the motor cannot be started, the frequency is slowly lowered and it takes a long time to determine that the motor is not in a state where it can be started, that is, it is in an undriveable state. When the drive is disabled, it is possible to quickly shift to other operations. In addition, since frequency control can be finely controlled during high-speed driving, stable driving can be performed. As a result, the total driving time of the motor can be shortened and the motor can be driven smoothly, leading to faster autofocus operation and better feel.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a vibration type motor control device according to the present invention.

2 is an explanatory diagram illustrating the arrangement of piezoelectric elements arranged on the back surface of the stator 9b shown in FIG. 1. FIG.

FIG. 3 is an explanatory diagram showing a program flow of the embodiment shown in FIG. 1;

FIG. 4 is an explanatory diagram showing another program flow of the embodiment shown in FIG. 1;

[Explanation of symbols]

1. Microcomputer 9 Vibration type motor 10 Pulse plate 16 Detection circuit 17 Up-down counter

Claims (2)

[Claims] Claim 1: Applying a frequency signal to an electro-mechanical energy conversion element arranged on a vibrating body to vibrate the vibrating body,
In a control circuit for a vibration type motor that uses the vibration of the vibrating body as a driving force, a frequency changing circuit that gradually changes the frequency of the frequency signal from an initial frequency is provided, and the frequency changing state by the frequency changing circuit is adjusted to a value near the initial frequency. 1. A control circuit for a vibration type motor, characterized in that a set circuit is provided for setting a change speed in a frequency range to be faster than a change speed in a frequency range distant from an initial frequency. 2. The change circuit changes the frequency at a change speed based on change value information set by a set circuit, and also includes a detection circuit that detects the driving state of the motor, and a detection circuit that detects the driving state of the motor. 2. A control circuit for a vibration type motor according to claim 1, further comprising a switching circuit for switching said change value information to a value instructing a change at a low speed when said change value information is detected to be in a driving state.