JPH0759366A - Driving circuit for ultrasonic motor - Google Patents

Abstract

PURPOSE:To provide a driving circuit for an ultrasonic motor where proper frequency setting range can be obtained without comprising a monitor phase detection circuit at all times. CONSTITUTION:The drive circuit of an ultrasonic motor, which drives a driven body by generating oscillatory waves by applying AC driving voltage, possesses an oscillating circuit 1, which sets the frequency of DC driving voltage, a memory 7, which stores the lower limit frequency of AC drive voltage, an oscillation state detecting electrode, which generates the voltage geared to the state of oscillatory waves, being provided in the ultrasonic motor 4, and a monitor terminal, which leads out the output of the oscillation state detecting electrode to outside. And the value stored in the memory 7 is stored by an adjusting circuit 22, connected to a monitor terminal, reading the output of the oscillation state detecting electrode through the monitor terminal and deciding the lower limit value of AC driving voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor drive circuit, and more particularly to an ultrasonic motor drive circuit for setting an optimum drive frequency of the ultrasonic motor.

[0002]

2. Description of the Related Art Conventionally, various technical means have been proposed for speed control of ultrasonic motors. For example, in Japanese Unexamined Patent Publication No. 63-204482, a monitor electrode is provided in an ultrasonic motor, and the resonance point of the ultrasonic motor is constantly detected by the phase of an output signal from the monitor electrode. A technical means for performing speed control by frequency in a higher frequency region is disclosed.

In Japanese Patent Laid-Open No. 59-178981, the rotational speed of the ultrasonic motor is measured by changing the driving frequency, and the resonance point of the ultrasonic motor is detected from the rotational speed of the ultrasonic motor. A technical means for storing and controlling speed is disclosed.

[0004]

However, the technical means disclosed in the above Japanese Patent Laid-Open No. 63-204482 requires a monitor phase detecting circuit for detecting the phase of the output signal from the monitor electrode, and Software for processing is required, which is a factor of increasing the size of the device and increasing the cost.

On the other hand, when the drive frequency range is determined by the rotational speed of the ultrasonic motor as in the technical means disclosed in Japanese Patent Laid-Open No. 59-178981, variations in the output value or load of the ultrasonic motor will occur. For example, when the rotation characteristic shows a flat characteristic at the peak portion (see FIG. 3), there is a problem that an accurate resonance frequency cannot be detected.

The present invention has been made in view of the above problems, and does not always include a monitor phase detection circuit.
An object of the present invention is to provide a driving circuit for an ultrasonic motor that can obtain an appropriate frequency setting range.

[0007]

In order to achieve the above object, a drive circuit for an ultrasonic motor according to the present invention generates an oscillating wave by applying an AC drive voltage to an ultrasonic wave for driving a driven body. In the motor drive circuit, an oscillating means for setting the frequency of the AC drive voltage, a storage means for storing the lower limit frequency of the AC drive voltage, and a voltage provided in the ultrasonic motor according to the state of the vibration wave. And a monitor terminal for drawing out the output of the vibration state detection electrode to the outside. The stored value of the storage means is connected to the monitor terminal by an external device, and the external device is connected to the monitor device. Is read by reading the output of the vibration state detection electrode via the monitor terminal and determined by determining the lower limit value of the AC drive voltage.

[0008]

In the ultrasonic motor drive circuit according to the present invention, the frequency of the AC drive voltage is set by the oscillation means, and the lower limit frequency of the AC drive voltage is stored by the storage means. Then, the vibration state detection electrode generates a voltage according to the state of the vibration wave,
The output of the vibration state detection electrode is pulled out from the monitor terminal. Further, the stored value of the storage means is an external device connected to the monitor terminal, the external device reads the output of the vibration state detection electrode via the monitor terminal, and determines the lower limit value of the AC drive voltage. It is stored by

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual diagram showing a drive circuit for an ultrasonic motor according to a first embodiment of the present invention.

As shown in the figure, the drive circuit for the ultrasonic motor of the first embodiment comprises a drive circuit section indicated by reference numeral 21,
It is composed of an adjusting circuit section indicated by reference numeral 22. These circuit portions 21 and 22 are detachable from each other by contact pins, and after the drive circuit portion 21 is assembled, the adjustment circuit portion 22 is assembled to the drive circuit portion 21 by the contact pins. After the adjustment circuit section 22 is adjusted as will be described later, the adjustment circuit section 22 is removed from the drive circuit section 21, and the drive circuit section 21 alone drives the ultrasonic motor.

The drive circuit section 21 divides the original clock by a counter to output a pulse signal φ0 having a frequency about four times the drive frequency, and the pulse signal φ0 to pulse signals φ1 to φ4. A pulse conversion circuit 2 for dividing the frequency into
A power amplifier circuit 3 for driving a transformer with four-phase pulses of the pulse signals φ1 to φ4 to generate two-phase AC voltages φA and φB, and as disclosed in JP-A-63-234881 by the present applicant. A traveling waveform ultrasonic motor 4 with electrodes for vibration detection, an encoder 5 for detecting the number of rotations of a driven body driven by the ultrasonic motor 4, a rotation speed from the output of the encoder 5, and a memory 7 The oscillation control circuit 6 controls the oscillation frequency of the oscillation circuit 1 within a range that does not fall below the lower limit frequency stored in the above.

FIG. 2 is a diagram showing the waveforms of the pulse signals φ0, φ1 to φ4, the AC voltages φA and φB, and the output VM from the vibration detecting electrodes in the first embodiment.

The adjustment circuit section 22 includes the phase comparison circuit 11
In the phase comparison circuit 11, the pulse signal φ1 and the output VM from the vibration detection electrode are input from the pulse conversion circuit 2 through the contact pin, and the phase difference QM (monitor position) Phase difference) adjustment control circuit 1
It outputs to 2. The adjustment control circuit 12 can communicate with the oscillation control circuit 6 by Sig1 and can write a numerical value in the memory 7 by Sig2.

Next, an adjusting method by the adjusting circuit section 22 will be described.

As described above, in the present embodiment, the adjustment circuit section 22 is temporarily connected to the drive circuit section 21 of the ultrasonic motor for adjustment. That is, the adjustment circuit unit 22 is not disposed in the drive circuit unit 21 or the apparatus main body in which the ultrasonic motor is installed, and is connected to the drive circuit unit 21 only when adjusting the drive circuit unit 21. It is supposed to be done.

FIG. 3 is a diagram showing changes in the monitor phase difference QM and the rotation speed N of the ultrasonic motor with respect to the drive frequency. In the figure, the symbol fL is the lower limit frequency of the ultrasonic motor, and the symbols QML and NL are the phase difference and the rotational speed at the lower limit frequency, respectively. As can be seen from this figure, the phase difference QM is more sensitive to the drive frequency f than the rotation speed N, and the direction is known. The frequency corresponding to the code QML is the optimum lower limit value.

FIG. 4 is a flow chart showing an adjusting method by the adjusting circuit section 22.

When the adjustment is started (step S10)
1) First, the data of the initial drive frequency f (lower limit frequency f
(An arbitrary frequency near L) and a drive start instruction command are transmitted from the adjustment control circuit 12 to the oscillation control circuit 6 to start the motor (step S102). next,
The monitor phase difference QM is detected by the phase comparison circuit 11 (step S103), it is checked whether the value is a predetermined value (VML) (step S104), and if it is a predetermined value, the drive frequency f instructed at that time is set to the lower limit. The frequency fL is written in the memory 7 (step S108). Then, the driving is stopped (step S109) and the adjustment is finished (step S1).
10).

On the other hand, when the monitor phase difference QM is not the predetermined value in step S104, the magnitude of the predetermined value is checked (step S105). When it is larger than the predetermined value, the drive frequency f is decreased by a certain amount. And transmits the frequency to the oscillation control circuit 6 (step S10).
6). On the other hand, if it is smaller than the predetermined value, the drive frequency f is increased by a fixed amount and the frequency is transmitted to the oscillation control circuit 6 (step S107). Then, the process returns to step S103.

Next, the drive control method of the ultrasonic motor will be described.

FIG. 5 is a flowchart showing the drive control method.

When the adjustment by the adjusting circuit section 22 is completed, the adjusting circuit section 22 is removed from the drive circuit section 21, and the ultrasonic motor is driven and controlled by the drive circuit section 21.

When the oscillation control circuit 6 first enters the drive mode (step S201), the adjustment circuit section 22 is moved from the memory 7 to the adjustment circuit section 22.
The lower limit frequency fL written by is read (step S202). Then, a driving frequency f higher than the lower limit frequency fL is set (step S203), and driving is started (step S204).

Next, the rotation speed N is detected from the output of the encoder 5 (step S205), it is judged whether it is higher or lower than the target speed (step S206), and if it is higher, the drive frequency f is increased by a certain amount (step S206). Step S209) and the process returns to step S205. On the other hand, when the rotation speed N is smaller than the target speed, first, the current drive frequency f is set to the lower limit frequency fL.
Is checked (step S207). If they are equal, the current drive frequency is the lower limit value, so the process does not go down further and the process returns to step S205. If the lower limit frequency fL is not reached, the drive frequency f is kept constant. The amount is reduced (step S208), and the process returns to step S205. In this way, the ultrasonic motor can be driven in a frequency region that is higher than the lower limit frequency fL and can be stably driven.

As described above, in the first embodiment,
Based on the output of the vibration detection electrode of the ultrasonic motor, the adjustment circuit part of the ultrasonic motor adjusts the drive circuit part of the ultrasonic motor, so it is necessary to dispose the processing circuit and software of the vibration detection electrode in the drive circuit body. There is no. Therefore, the drive circuit unit itself or the device to which the ultrasonic motor is applied can be downsized, and the cost can be reduced. Also, because the adjustment is performed by the monitor phase difference,
Can be adjusted accurately and quickly.

Next, the drive circuit for the ultrasonic motor of the second embodiment of the present invention will be explained.

The drive circuit of the ultrasonic motor of the second embodiment is applied to a replaceable camera lens.

FIGS. 6 and 7 are block diagrams showing the configuration when the second embodiment is applied to an interchangeable camera lens. FIG. 6 shows a normal use and FIG. 7 shows an adjustment. The respective connection states are shown. In the figure, reference symbol L denotes a camera lens, reference symbol B denotes a camera body, and reference symbol AD.
Each J indicates a regulator.

As shown in FIG. 6, the camera lens L has an EEP corresponding to the memory 7 in the first embodiment.
ROM 51 and drive circuit main part 5 corresponding to the oscillation circuit 1, the pulse conversion circuit 2, the power amplification circuit 3, and the encoder 5.
2 and an LCPU which is a control unit including the oscillation control circuit 6
53 and the ultrasonic motor 4 described above. Also,
As shown in FIG. 9, the camera lens L has terminals P1 to P8 connectable to the camera body B and the adjuster ADJ.
And terminals P9 and P10 which are connected only to the adjuster ADJ.

The terminals P1 and P2 are a power supply terminal and an IC power supply terminal, respectively, and the terminals P3, P4, P5,
P6 is a terminal for a lens communication request signal, a body communication request signal, a lens clock, and a data signal, respectively. The terminals P7 and P8 are an IC system ground and a power system ground, respectively. Further, a signal corresponding to the pulse signal φ1 is output to the terminal P9, and the above V signal is output to the terminal P10.
M is output.

On the other hand, the camera body B has a BCPU 61 which is a control unit on the camera body side and a D which generates an IC power source.
It has a C / DC converter 62 and a DC power supply 63. Further, as shown in FIG. 8, the mount portion of the camera body B has a terminal P1 of the camera lens L.
To P8 are provided. The camera lens L and the camera body B are connected to the terminal P during normal use.
It is electrically connected by 1 to P8.

Further, as shown in FIG. 7, the adjuster ADJ includes the adjustment control circuit 12 in the first embodiment A.
The JCPU 71, the DC / DC converter 72, the DC power supply 73, and the phase difference counter 74 corresponding to the phase comparison circuit 11 constitute a main part. Further, as shown in FIG. 10, the adjuster ADJ is also provided with terminals connectable to the terminals P1 to P10 arranged on the camera lens L.

In the second embodiment, the adjusting device ADJ is connected to the camera lens L only at the time of adjustment, the same adjustment as that in the first embodiment is performed, and then the adjusting device ADJ is removed to remove the camera lens L. Is connected to the camera body B. However, the AJCPU and the LCPU are designed to transmit and receive data and commands by serial communication.

FIGS. 8, 9, and 10 are front views showing the camera body B, the camera lens L, and the adjuster ADJ, respectively. Each of them is provided with a contact as shown in the figure and a bayonet claw 31 for coupling, which are detachable. The terminals P9 and P10 are arranged at the ends so that when the camera lens L is connected to the camera body B, the terminals will not come into contact with the camera body B and other parts. There is.

Thus, in the second embodiment, the bayonet claw 31 and the mount pins P1 to P10 enable quick and reliable mechanical / electrical coupling. Also, the adjustment terminal P
Even if 9 and P10 are attached to the camera body B, they will not come into contact with other contacts, preventing the circuit from being damaged by a short circuit or the like.

Next, the drive circuit of the ultrasonic motor of the third embodiment of the present invention will be explained.

FIG. 11 is a perspective view showing a camera lens to which the third embodiment is applied.

As shown in the drawing, the third embodiment has substantially the same structure as the second embodiment, but the adjusting terminals P9 and P10 are arranged on the peripheral surface of the lens barrel. And is covered with a cover. Other configurations and operations are the same as those of the second embodiment, and therefore the description thereof is omitted here.

As described above, in the third embodiment, when the camera lens B is still attached to the camera body B at the time of failure,
It can be monitored from terminals P9 and P10 and can be used for failure analysis.

As described above, the ultrasonic motor drive circuit of each of the above-described embodiments does not require a circuit for processing the vibration detection electrodes and does not require software, so the entire circuit can be downsized and the cost can be reduced. Moreover, since the output of the vibration detection electrode is used during the adjustment, it is possible to accurately detect the lower limit value of the frequency.

In the above-mentioned first to third embodiments, the ultrasonic motor may have other than the traveling waveform as long as it is provided with the vibration detecting electrode, and its usage is not limited to the phase difference with the input voltage, but for example, the amplitude. It is possible to use the value.

Needless to say, the means for generating the AC voltage applied to the ultrasonic motor is not limited to the above-mentioned means, and other technical means can be used.

Furthermore, when the ultrasonic motor is actually driven, it can be used not only for speed control but also for position control or variable speed control.

[0045]

As described above, according to the present invention, it is possible to provide a drive circuit for an ultrasonic motor capable of obtaining an appropriate frequency setting range without always having a monitor phase detection circuit.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a drive circuit for an ultrasonic motor according to a first embodiment of the present invention.

FIG. 2 shows pulse signals φ0, φ1 to φ4, AC voltage φA, in the drive circuit of the ultrasonic motor of the first embodiment.
It is a diagram showing a waveform of an output VM from φB and a vibration detection electrode.

FIG. 3 is a diagram showing changes in the monitor phase difference QM and the rotational speed N of the ultrasonic motor with respect to the driving frequency in the ultrasonic motor driving circuit of the first embodiment.

FIG. 4 is a flowchart showing an adjusting method by an adjusting circuit unit in the drive circuit of the ultrasonic motor of the first embodiment.

FIG. 5 is a flowchart showing a drive control method in the drive circuit for the ultrasonic motor of the first embodiment.

FIG. 6 is a block diagram showing a connection state during normal use when the drive circuit of the ultrasonic motor according to the second embodiment of the present invention is applied to a replaceable camera lens.

FIG. 7 is a block diagram showing a connection state at the time of adjustment when the drive circuit of the ultrasonic motor of the second embodiment is applied to a replaceable camera lens.

FIG. 8 is a front view showing a camera body to which the drive circuit for the ultrasonic motor of the second embodiment is applied.

FIG. 9 is a front view showing a camera lens to which the drive circuit for the ultrasonic motor of the second embodiment is applied.

FIG. 10 is a front view showing an adjuster to which the drive circuit for the ultrasonic motor of the second embodiment is applied.

FIG. 11 is a perspective view showing a camera lens to which a driving circuit for an ultrasonic motor according to a third embodiment of the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Oscillation circuit 2 ... Pulse conversion circuit 3 ... Power amplification circuit 4 ... Ultrasonic motor 5 ... Encoder 6 ... Oscillation control circuit 7 ... Memory 11 ... Phase comparison circuit 12 ... Adjustment control circuit 21 ... Drive circuit section 22 ... Adjustment circuit section

Claims (1)

[Claims] 1. An ultrasonic motor driving circuit for driving a driven body by generating an oscillating wave by applying an AC driving voltage, and an oscillating means for setting a frequency of the AC driving voltage, and the AC driving voltage. Storage means for storing the lower limit frequency of the, a vibration state detection electrode that is provided in the ultrasonic motor and that generates a voltage according to the state of the vibration wave, and a monitor terminal that draws out the output of the vibration state detection electrode to the outside. An external device is connected to the monitor terminal, the external device reads the output of the vibration state detection electrode through the monitor terminal, and stores the value of the AC drive voltage. A driving circuit for an ultrasonic motor, which is stored by determining a lower limit value.