JP3220931B2 - Ultrasonic motor controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor for controlling the rotational speed in accordance with the frequency of a power supply pressure, and more specifically, to reliably start this type of ultrasonic motor. The present invention relates to a control device capable of performing the following.

[0002]

2. Description of the Related Art Ultrasonic motors have been widely used in focusing devices for AF (autofocus) cameras. In such a focus adjusting device, an ultrasonic motor is mounted in a lens barrel mounted on a camera body, and a lens unit for focus adjustment that is rotationally driven by a helicoid screw is rotationally driven by the ultrasonic motor. It has become.

On the other hand, the ultrasonic motor decelerates as the frequency of the power supply pressure increases, and accelerates as the frequency decreases. However, in this motor, when the frequency is lowered too much and the resonance point is passed, the rotation speed decreases rapidly. When the frequency is increased, the rotation speed gradually decreases and the rotation stops. Since it has a characteristic of increasing in speed after passing the point, it is difficult to control the frequency near the resonance point.

[0004] Further, if this type of ultrasonic motor is started directly at an arbitrary low frequency, it may not start. For this reason, starting means for scanning the frequency from the high frequency side to the low frequency side at the time of starting has been proposed.
This is because a high frequency is easier to start than a low frequency.

[0005]

As described above, since the ultrasonic motor may not be activated, some measures must be taken to reliably activate the ultrasonic motor. However, the ultrasonic motor is activated as in the prior art. If the drive frequency is scanned every time, it takes a long time to start up, and the responsiveness of the start-up deteriorates.

Accordingly, an object of the present invention is to propose a control apparatus for an ultrasonic motor in which a frequency is scanned only when the apparatus is not started, and the apparatus is started reliably without impairing the responsiveness of the start. And

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a control apparatus for an ultrasonic motor which controls the speed in accordance with the frequency of the power supply pressure.

In the present invention, the presence or absence of activation of the motor is detected at the time of activation, and a motor activation signal is output if the motor is activated, and a motor deactivation signal is output if the motor is not activated. It has a detecting means.

Further, the frequency is set to a predetermined frequency according to a motor starting signal of the detecting means, and the frequency is changed continuously from a high frequency side to a low frequency side according to a motor non-starting signal. Control means.

[0010] The present invention having the above-described structure is an ultrasonic motor.
When a motor is started when a power supply pressure of a predetermined frequency is applied to the motor, the detecting means outputs a motor start signal, and the frequency control means responds to the motor start signal by the power supply pressure. Is set to a predetermined frequency. Thus, the motor rotates at a rotational speed according to this frequency.

If the motor does not start when the power supply pressure is applied, the detecting means outputs a motor non-start signal, and the frequency control means responds to the motor non-start signal. Change the frequency.

At this time, the frequency is continuously changed from the high frequency side to the low frequency side, and if the motor is started by this frequency change, the frequency control means according to the motor start signal from the detection means changes the frequency. Set to a predetermined frequency. Thus, the motor rotates at a rotational speed according to the frequency.

Such a change in frequency can be configured to be repeated several times from the high frequency side to the low frequency side until the motor starts. If the motor does not start even after being repeated several times, the power supply to the ultrasonic motor may be stopped as a failure of the motor or the circuit.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment in which the present invention is applied to a focus adjusting device of an AF camera will be described with reference to the drawings. FIG. 1 shows a schematic diagram of an AF camera. As shown in the figure, this camera has a camera body composed of an outer body 11 and an inner body 12, and the inner body 12 is guided by a guide shaft 13 fixed below the outer body 11, and the light of the photographing lens 14 is It is provided in the outer body 11 so as to advance and retreat in the direction of the shaft 15.

The inner body 12 has a mirror box 16, a finder unit 18 to which photographing light is guided by a quick return mirror 17, and a total reflection mirror 1.
9 is provided with a distance measuring unit 20 for guiding photographing light. Further, the inner main body 12 has a film feeding / rewinding mechanism, a film feeding unit including a guide roller, a pressure plate, etc., and a focal plane shutter. And so on.

The external body 11 includes a mount for mounting the photographing lens 14, a battery compartment, a rear lid, a release button and other operation buttons, and a focus adjustment unit described below.

The focus adjustment unit includes a CPU (microprocessor) 21 forming signal processing means, and a driver-2.
2. The main components are a drive mechanism including the ultrasonic motor 23 and a monitor for detecting the actual speed of the ultrasonic motor 23.

The CPU 21 has a preset ultrasonic mode.
And outputs a D / A signal corresponding to the target speed of the motor 23. The driver 22 receives the D / A signal, performs voltage-frequency conversion (V / f conversion) in accordance with the target speed, and converts the two AC voltages Va and Vb (power supply pressure) of the frequency into nine.
The output is provided with a phase difference of 0 °, and the ultrasonic motor 23 is supplied with the AC voltage.

The ultrasonic motor 23 has a two-system AC voltage V
a, Vb, for example, power is supplied to the A phase and the B phase,
The motor is driven to rotate at a rotation speed according to the frequency of the power supply pressure.
The first output gear 24 of the ultrasonic motor 23 is a reduction gear 25
, And this reduction gear 25 moves and drives a rack gear 26 provided on the inner main body 12. That is, when the rack gear 26 is driven by the reduction gear 25, the inner body 1
2 is guided by the guide shaft 13 and advances toward the optical axis 15;
Also retreat.

The ultrasonic motor 23 is provided with a second output gear 27 for monitoring the number of revolutions. An interlocking gear 28 meshes with the output gear 27, and the impeller 29 rotates by the rotation of the interlocking gear 28, and the photointerrupter 30 controls the rotation speed (or rotation speed) of the ultrasonic motor 23. The corresponding pulse signal S1 is supplied to the CPU 2
Sent to 1.

The CPU 21 processes the pulse signal S1 sent from the photo interrupter 30 and the distance measurement signal S2 of the object sent from the distance measurement unit 20, and focuses the image on the film surface according to the processed value. The moving amount of the inner main body 12 is determined. That is, the AC voltages Va and Vb are output from the driver 22 by the signal processing, and the internal body 12 is moved to the in-focus position by the rotation of the ultrasonic motor 23.

In this AF camera, a first end position detection switch (for example, an infinity end switch) 31 is provided on the front side of the external body 11, and a second end position detection switch (for example, the closest end switch) is provided on the rear side. Switch 32) and the inner body 1
2 is in contact with the first end position detection switch 31,
The PU 21 resets the count of the pulse signal S 1, adds and counts the pulses by the backward movement of the internal main body 12, and stops the pulse counting when the internal main body 12 comes into contact with the second end position detection switch 32. When the internal main body 12 moves in the opposite direction, the CPU 21 counts down. Note that the camera's main switch is OF
When F is pressed, the pulse count value of the CPU 21 is stored in the nonvolatile memory.

FIG. 2 shows a specific circuit example of the driver-22. As shown in the figure, a required rotation speed (target speed) of the ultrasonic motor 23 is set in the CPU 21, and a voltage signal according to the set value is transmitted from the CPU 21 to the V / f conversion / sawtooth wave generation circuit 33. / A signal. That is, by changing the D / A setting input, the CPU 21 outputs a D / A signal (voltage signal) whose level changes stepwise from a D / A signal generator (for example, a register).

The V / f conversion / sawtooth wave generating circuit 33 performs a voltage-frequency conversion of the input voltage signal, generates a sawtooth signal having a frequency fn, and inputs the signal to the distributor 34. The distributor 34 shapes the fn sawtooth signal into a rectangular wave while delaying the phase by 90 ° by the 4fn clock, and distributes the signal into four. That is, a rectangular wave signal is output from φ3 by delaying the phase of 90 ° from φ1 and 90 ° from φ3 and 90 ° from φ2 and φ4, respectively.

The rectangular wave signal divided into four is supplied to an AND circuit 3
5a to 35d. AND circuits 35a to 35
The ON signal of the ultrasonic motor 23 is input to the third input terminal d, and the PWM signal described later is input to the second input terminal, and each of the AND circuits 35a to 35d has a gate open. Is input to the bases of the transistors 36a to 36d for amplifying.

The collectors of the transistors 36a and 36b are connected to both ends of the primary coil of the step-up transformer 37a, respectively.
The collectors of the transistors 36c and 36d are respectively connected to both ends of the primary coil of the step-up transformer 37b.
The output terminals of the secondary coils of the step-up transformers 37a and 37b are connected to the ultrasonic motor 23.

The comparator 38 is an AND circuit 35.
PWM signals are inputted to the AND circuits 35a to 35d from a comparator 38 for inputting a D / A signal in accordance with a set value of the CPU 21 for changing the pulse width of the pulse frequency signal outputted from the signals a to 35d. . The D / A signal also changes stepwise according to the setting input. The monitor 39 is a detector for detecting the number of rotations of the motor, which includes the impeller 29 and the photo interrupter 30 as described above.

The driver 22 configured as described above is adapted to output the AC voltage Va output from the step-up transformers 37a and 37b,
The frequency of Vb is determined according to the target speed set by the CPU 21, and the ultrasonic motor 23 is driven to rotate at a rotation speed according to the frequency. That is, if the set value (D / A setting input value) of the target speed is changed by the CPU 21, the frequency of the AC voltages Va and Vb changes according to the set value of the target speed.
3 can be changed according to the set value.

However, actually, the ultrasonic motor 23
It is difficult to rotate the wheel precisely to the target speed.
As described above, the actual rotation of the ultrasonic motor 23 with respect to the set target speed is affected by variations in characteristics due to individual differences of the ultrasonic motor 23, load conditions, ambient temperature, and the like. The speed shifts. For this reason, it is not possible to control the actual rotation speed to match the target speed.

The power supply pressure of the ultrasonic motor 23 (AC voltage V
It has already been proposed to control the speed by changing the frequency of a, Vb) to a small width, but even if the frequency is controlled to a small width, the deviation of the actual speed cannot be corrected.

Therefore, in the present invention, the actual speed of the ultrasonic motor 23 is detected by the monitor means, the difference between the actual speed and the set target speed is obtained, and the ratio of this difference to the target speed is calculated. It is configured to calculate and determine the correction amount of the frequency of the power supply pressure based on the calculation result.

In other words, as long as the actual speed deviates from the target speed, the frequency correction amount is determined based on the actual speed deviation amount at that time, and the ultrasonic motor 23 changes to the corrected frequency. Therefore, it rotates at the target speed.

The actual speed of the ultrasonic motor 23 is determined by the pulse signal S1 inputted from the photo interrupter 30 by the CPU 21.
The target speed is determined from the set value of the CPU 21. Then, the CPU 21 calculates a difference signal between the actual speed signal and the target speed signal, and calculates a ratio between the difference signal and the target speed.

More specifically, the CPU 21 calculates {(target speed−actual speed) / target speed} × 100 (%).

The deviation of the rotational speed is calculated as C
The PU 21 determines a frequency correction amount from the target speed and the deviation amount, and outputs a D / A signal by changing a set value according to the correction amount. In other words, the correction amount is calculated by multiplying the calculated deviation amount by a predetermined coefficient, and the D / A setting input is adjusted so that the correction amount is added to the preset target speed. / A signal is output. As a result, the D / A signal level increases and decreases. In this manner, the correction amount of the frequency determined based on the deviation amount of the actual speed from the target speed is set, and the D / A signal according to the correction amount is sent to the V / f conversion / sawtooth wave generation circuit 33. .

As a result, the frequencies of the AC voltages Va and Vb change in accordance with the deviation amount of the actual speed, and the ultrasonic motor 23
Accelerates from the actual speed before frequency correction toward the target speed, and then decelerates.

FIG. 3 is a characteristic curve showing the relationship between the rotational speed of the ultrasonic motor 23 and the frequency. This drawing shows that when the target speed is set to r1, the frequency of the power supply pressure becomes f1, and at this time, the ultrasonic motor 23 is rotating at the actual speed of r2.

In this case, the CPU 21 calculates (r1-r2)
= Δr, (Δr / r1) × 100 (%), and calculates a deviation amount between the target speed r1 and the actual speed r2. Then, a correction amount is calculated based on the deviation amount, and a D / A setting input is adjusted according to the correction amount, and a D / A signal is output. In this case, the D / A signal level is increased according to the shift amount. As a result, the frequency of the power supply pressure is corrected by Δf. Therefore, if the target speed is set to the target speed r1, the ultrasonic motor 23 sets the target speed r1 (the frequency f1).
Rotate at the actual speed that matches the rotation.

The correction of the frequency may be performed at once based on the calculated shift amount. However, when the shift amount is large, the correction amount is limited, and the D / A signal is output according to the largest correction amount. If there is a deviation in the actual speed, the deviation amount is calculated again as described above to correct the frequency. As a result, overcorrection and overspeeding of the actual speed can be performed.
Can be prevented.

Further, the focus adjusting device of this camera, when the ultrasonic motor 23 is supplied with the AC voltages Va and Vb,
If the motor is not started, the motor is started by changing the frequency. During this operation, monitor 3
9 operates as detection means for detecting the presence or absence of activation.

That is, if the ultrasonic motor 23 is started when the AC voltages Va and Vb are applied, the pulse signal S1 is immediately input from the photo interrupter 30 to the CPU 21, so that the CPU 21 modulates the pulse signal S1. Judge as a starter signal.

In this case, the CPU 21 calculates a correction amount from the deviation amount of the actual speed in accordance with the above description, and applies the AC voltages Va and Vb of the frequency corrected by the correction amount to the ultrasonic motor 23, and Rotate motor at speed.

If the ultrasonic motor 23 does not start when the AC voltages Va and Vb are applied, the photo interrupter 30 does not generate the pulse signal S1.
Does not receive the pulse signal S1. From this, CPU2
1 judges that the non-input of the pulse signal S1 is a motor non-start signal.

In this case, the CPU 21 changes the D / A signal in accordance with a predetermined program, and
It operates to change the frequencies of a and Vb. In addition,
In this case, the CPU 21 operates to increase or decrease the D / A setting input to change the frequency.
a and 37b and AND circuits 35a-35
The PWM signal input to d is kept constant. Regarding this frequency change, as shown by way of example in FIG.
The PU 21 operates so as to continuously change the frequency from the anti-resonance frequency f2 (high-frequency side) to the resonance frequency f1 (low-frequency side). In FIG. 4, a solid line fd indicates a frequency curve, and a dotted line ωt indicates a phase curve.

If the motor does not start during the frequency change, the change is repeated from f2 to f1 again. If the ultrasonic motor 23 starts during the frequency change, Thereafter, the CPU 21 operates to correct the frequency based on the correction amount described above and to rotate the motor at the target speed.

For example, if the target speed is set to r in FIG. 4, the motor rotates according to the frequency f0. This frequency f0 is the frequency of the corrected AC voltages Va and Vb.

FIG. 5 is a flowchart showing the operation of the CPU 21 operating as described above. As shown, C
The PU 21 determines whether or not the pulse signal S1 has been input from the photo interrupter 30, and if there is no input of the pulse signal S1, the D / A signal is changed because the ultrasonic motor 23 has not been started. To start the frequency scan. (Steps 101 and 106)

If the motor is not activated by one scan activation, the scan activation is repeated several times. If the motor activation is not repeated even after the scan activation operation is repeated several times, the ultrasonic motor 23 is activated. Stop each time you start. Ultrasonic motor 23
Is activated and the pulse signal S1 is input to the CPU 21,
As described above, the CPU 21 corrects the frequency based on the correction amount and controls the speed of the motor. (Step 10
1, 102)

After the ultrasonic motor 23 is started, the CPU
21 counts the pulse signal S1, calculates the number of pulses required to move the inner body 12 to the in-focus position by signal processing with the ranging signal S2, and when the remaining pulses become "0", the ultrasonic motor -Stop the heater 23. That is, the OFF signal is input to the third input terminals of the AND circuits 35a to 35d. (Steps 103 and 105)

Such a focus position control is performed in a range where the inner main body 12 does not come into contact with the end position detection switches 31 and 32.
2, the ultrasonic motor 23 is stopped by the input of the operation signals of these switches. (Steps 104, 10
5)

FIG. 6 shows a time chart when the motor is started by changing the frequency as described above. As shown in FIGS. 9A and 9C, an A / D signal is supplied to the driver 22 and an ON signal (AND circuits 35a to 35d) is supplied.
Of the ultrasonic motor 23 to supply the AC voltage V to the ultrasonic motor 23.
If the motor 23 does not start when a and Vb are applied, the pulse signal S1 is not output from the photo interrupter 30 as shown in FIG.
21 judges that the motor is not activated, and as shown in FIG.
Change the D / A signal.

The frequency changes from f2 to f1 in FIG. 4 by the change of the D / A signal. Note that the frequency change range does not necessarily need to be f2 to f1, but may be changed within a predetermined range within f2 to f1.

The time chart of FIG. 6 shows a case where the motor is started when the frequency is repeatedly changed twice. When the motor is started during the second frequency change process, the pulse signal S1 of the interrupter 30 is input to the CPU 21 from this point. Therefore, the CPU 21
The ultrasonic motor 23 is driven at a rotation speed that matches the set target speed as described above.

FIG. 7 is a time chart similar to FIG. 6 showing an example of a configuration in which the frequency change time is lengthened each time scanning is performed when the frequency is changed. This time chart shows a case where the motor is started when the frequency is repeatedly changed three times, but the D / A signal for scanning the frequency is scanned as shown in FIG. T1 <t2 <t3... So as to be longer every time
・ ・ It is configured to be as follows. With this configuration, the motor can be more reliably started.

In the above embodiment, the focus adjusting device of the camera has been described. However, the present invention can be similarly applied to an ultrasonic motor of another device. In this case, it is not necessary to calculate the correction amount for an ultrasonic motor in which the difference between the target speed and the actual speed does not matter.

[0056]

As described above, the control device according to the present invention has a configuration in which the motor is started by changing the frequency only when the motor is not started at the time of starting, so that the response at the time of starting is impaired. Thus, the control device for the ultrasonic motor can be started without fail.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an AF camera showing an embodiment of the present invention.

FIG. 2 is a diagram showing a circuit example of a driver of an ultrasonic motor.

FIG. 3 is a diagram for explaining speed control of an ultrasonic motor.

FIG. 4 is a diagram for explaining activation of an ultrasonic motor.

FIG. 5 is a flowchart showing an operation of a CPU for controlling an ultrasonic motor.

FIG. 6 is a time chart showing a state in which a frequency is scanned and a motor is started.

FIG. 7 is a time chart similar to FIG. 6 in which the frequency scan configuration is changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 External main body 12 Internal main body 14 Photographing lens 20 Distance measuring unit 21 CPU 22 Driver 23 Ultrasonic motor 25 Reduction gear 26 Rack gear 30 Photo interrupter 39 Monitor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI G03B 13/32 (72) Inventor Tsuyoshi Okutani 2-14-9 Tamagawadai, Setagaya-ku, Tokyo Kyocera Corporation Tokyo Yoga Office (56 References JP-A-4-42783 (JP, A) JP-A-2-294281 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02N 2/00 G02B 7/04 G02B 7/08 G02B 7/09 G03B 3/04 G03B 13/32

Claims (1)

(57) [Claims] An ultrasonic motor control device for controlling the speed in accordance with the frequency of the power supply pressure detects whether or not the motor is activated at the time of activation, and outputs a motor activation signal when the motor is activated. Detecting means for outputting a motor deactivation signal if the motor is not started; and setting the frequency to a predetermined frequency in accordance with the motor starting signal of the detecting means, and setting the frequency in accordance with the motor deactivating signal. A control device for an ultrasonic motor, comprising: frequency control means for continuously changing a frequency from a high frequency side to a low frequency side.