JPH0546926B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Object> The present invention relates to a motor control device capable of switching between step drive and brushless drive. The present invention relates to a motor control device that can switch between step drive and brushless drive in a motor that is installed in a motor that combines a step motor and a brushless motor.

<Description of Prior Art> In recent years, so-called automatic focusing devices have been incorporated in camera and lens photographing systems to automatically control the movement of the focusing lens in the lens barrel to the in-focus position without the manual intervention of the photographer. camera automation is being promoted.

The above-mentioned automatic focusing device controls the movement of the focus lens to the in-focus position using the rotational force of the motor, but the structure of this motor has been improved by making the rotor hollow. For example, a hollow motor that uses the hollow shape of the rotor as a photographing optical path or a housing for various optical systems is disclosed in Japanese Patent Application Laid-Open No.
186738, proposed as Utility Model No. 57-28424.

The motor type of the hollow motor may be a linear motor, a step motor, a coreless motor, or a brushless motor. Among the various types of motors mentioned above, the step motor accurately determines the output value (output amount) of the rotation angle for one input signal, and if the focus lens is driven and controlled by the step motor, the control performance for the amount of movement of the focus lens can be improved. can. However, the step motor is characterized in that it performs a stepwise rotational movement using pulse signals, and it takes a long time to drive the focus lens from its initial position to its final in-focus position. (If the driving frequency is increased, the motor will step out.) Furthermore, in the case of a step motor, the starting torque is weaker than that of other motors, such as brushless motors, and the driving force of the focus lens is small. If you try to secure enough size to move the motor, the shape of the motor will become large, and if you are planning to incorporate the lens barrel into a portable lens barrel, there will be disadvantages in terms of power supply energy, shape, etc.

In addition, when the movement of the focus lens is controlled by a brushless motor through a conversion means that converts the rotational movement of the focus lens into a direct movement, when the focus lens moves from the start position to the in-focus position, it must stop correctly at the in-focus position. In order to achieve this, it is necessary to control the stop of the rotor with high precision, and this requires control of the inertia of the rotor and brake control of the rotor, resulting in problems such as a complicated control system.

<Problem of the Invention> The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a motor control device that is preferably built into a lens barrel or the like and is also preferable for controlling the movement of a focus lens.

For the above purpose, the present invention eliminates the disadvantages of the step motor and adopts the advantages thereof, and also eliminates the disadvantages of the brushless motor and utilizes only the advantages thereof. The present invention provides a motor control device that adopts a motor that combines a step motor and a brushless motor by integrally providing a rotor magnet for driving, and switches the motor between step drive and brushless drive.

Therefore, in the present invention, a rotor magnet for step drive and a rotor magnet for brushless drive are integrally provided, and a first coil for step drive and a second coil for brushless drive are attached to these rotor magnets. A switching means for selectively operating the first step drive coil and the second brushless drive coil in a motor control device in which a step motor and a brushless motor are arranged in correspondence with each other. , further comprising a determining means for determining the drive amount according to the rotation of the rotor magnet, and a detecting means for detecting a pulse generated according to the rotation of the rotor magnet, and the switching means is configured to detect a drive amount according to the rotation of the rotor magnet. and a counter for counting the output pulses of the motor, and the switching means switches from brushless drive to step drive when the count value reaches a predetermined value according to the determination by the discrimination means. .

Furthermore, in the present invention, the switching means switches to step driving from the beginning when the determining means determines that the amount of drive is small.

<Description of Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, the driving method of the motor of the present invention will be explained. The distance to the subject is measured by the distance measuring means, and this distance measurement signal is converted into a rotor rotation angle θ ₁ that drives the focus lens to the in-focus position. If the rotor is driven in steps, the driving time of the focus lens, that is, the moving time _t2 of the focus lens from the initial starting position to the in-focus position becomes very long. In comparison, the focus lens is moved from the starting position to θ _s in front of the in-focus position by brushless driving, and from the θ _s position to the in-focus position θ ₁
By driving up to step motor-like, the time t ₁ for moving the focus lens can be shortened compared to the time t ₂ required by only step driving described above. In FIG. 1, the vertical axis represents the rotation angle of the motor, and the horizontal axis represents time. The characteristic graph is an example in which brushless driving is performed before the focal point position of the lens, that is, up to the set value θ _s , and then stepwise driving is performed from θ _s to the focal point position θ ₁ .

FIGS. 2A, B ₁ and B ₂ show the rotor and stator of a hybrid motor combining a brushless motor and a step motor according to the present invention. In the figure, 1 is a hollow cylindrical permanent magnet, and this permanent magnet 1 has a bearing 9a in a fixed barrel 9 of a lens barrel.
It is fixed on the outer periphery of the rotary cylinder 9A which is pivotally supported by the rotary cylinder 9a. 9B is a lens holder holding the lens _L1 , and is helicoidally coupled to the rotary tube 9A. 9
C is a key member for moving the lens holder straight. As shown in FIG. _2B1 , multiple poles are attached to one end 1A of the lens in the direction along the optical axis so that the S and N poles function as a step motor. The other end 1 of the permanent magnet 1 is magnetized with two or four S and N poles. The 1A side of the permanent magnet acts as a step drive permanent magnet, and the 1B side acts as a rotor as a brushless drive permanent magnet. 2 and 4
shows a coil for a step motor and a coil for a brushless motor, where the coil 2 is arranged outside the step drive permanent magnet section 1A of the permanent magnet 1 and fixed inside the fixed cylinder via a coil bobbin, which will be described later. 4 is arranged outside the brushless drive permanent magnet section 1B and fixed to the fixed cylinder. The coil 2 is a coil bobbin having mutually meshing pole teeth 6A, 8A as shown in FIG. 2C. The step drive coil 2 is formed in a ring shape in the coil bobbin 3 in order to generate magnetic poles in the comb teeth, and the brushless drive coil 4 is formed in an arc shape as shown in FIG. 2D.

FIG. 3 shows a control circuit block diagram for brushless drive and step drive.

FIG. 4 shows a timing diagram of each part of the control circuit block diagram of FIG. 3.

12 is a circuit that detects the rotation angle of the rotor required to move the imaging lens to the in-focus position based on the signal from the distance measuring device 10. The output signal of this rotation angle detection circuit 12 is assumed to be θ ₁ . 14
is a discrimination circuit. Reference numeral 16 denotes a circuit that generates a comparison reference signal θ _s and inputs it to the discrimination circuit 14 . The comparison reference signal θ _s represents a level signal supplied to the brushless coil. The discrimination circuit 14 receives the output θ ₁ of the detection circuit.
Compare the magnitude relationship between the comparison reference signal θ _s and θ ₁
-θ _s difference signal θ _A indicates whether θ _A >0 or θ _A <0 as a logic signal high (H) or low (L) and outputs it. Now, when θ _A E > 0, it is set to H, and when θ _A ≦0, it is set to L. Reference numeral 15 denotes a circuit for determining the rotor rotation direction of the motor, which outputs a logic "H" or "L" by determining CW (clockwise) or CCW (counterclockwise). 18 is a brushless motor drive circuit, 20 is a step motor distribution circuit, and 22 is a step motor drive circuit. 2
4 is a circuit that detects the back electromotive force generated in coils _L3 and _L4 of the step motor. Reference numeral 26 denotes a subtraction counter which starts counting in synchronization with the operation of the brushless motor, and outputs a carry signal C _A after counting a predetermined count number, that is, the count number at which driving by the brushless motor is stopped. Further, 27 is a clock generation circuit.

1N-1, 1N-2, 1N-3 indicate inverters, D ₁ -D ₂ are OR gates consisting of diodes,
OR1 indicates an or gate, respectively.

Next, the operation of the above configuration will be explained.

First, the object distance is measured by a distance measurement operation, and then a rotation angle θ ₁ detection operation is performed to move the imaging lens to the in-focus position by rotating the rotor using a distance measurement signal based on the distance measurement operation. The detection circuit 1
It will be held in 2. The signal from the detection circuit 12 is input to the discrimination circuit 14, which calculates θ ₁ - θ _s = θ _A and determines whether θ _A >0 or θ _A ≦0, and the result of the determination is converted into a logic signal. Output as “H” and “L”.

When the object distance is far, if θ ₁ is sufficiently larger than θ _s (θ _A >0), the discrimination circuit 14 outputs an "H" signal. Further, the rotation direction determining circuit 15 selects the coil to be driven. The signal _e1 from the rotational direction determination circuit 15 is input to the transistor Q1 of the brushless motor drive circuit ₁₈ or to the base terminal of the transistor via the inverter 1N-1, and
Coil the brushless motor through Q ₁ or Q ₂
Electrify either L ₁ or L ₂ . As a result, the hollow cylindrical permanent magnet rotates around the optical axis, and this rotation is caused by a helicoid mechanism (shown in figure 2-A) between the permanent magnet and the lens holding frame of the imaging lens to move the imaging lens along the optical axis. Moving.

As the permanent magnet rotates, waveforms _e2 and _e3 representing back electromotive force are output to the step motor coils _L3 and _L4 . This back electromotive force signal is determined by the step angle of the permanent magnet for the step motor, and while the permanent magnet rotates 180° or 90° by brushless drive, it generates a waveform corresponding to the step angle of the permanent magnet of the step motor. This waveform is counted by a counter 26. Signals corresponding to the comparison reference signals θ _s and θ ₁ are set in the counter 26, and the back electromotive force output pulse and the comparison reference signal θ _s are sequentially compared, and when the counts match, a carry signal C _A is output. This carry signal is applied to the base terminals of the transistors Q ₃ and Q ₄ of the brushless drive circuit through the diode D ₁ or D ₂ to disable the brushless drive circuit. That is, the state in which the carry C _A outputs an output means that the lens L has left the brushless drive range.

In addition, the carry signal C _A is the OR gate OR1
The set terminal 27a of the clock generation circuit 27
is input to the clock pulse generation circuit 27.
starts and generates clock pulse C _P. The clock pulse C _P is input to a pulse distribution circuit 20, which outputs timing pulses φ1 to φ4 for driving the step motor coil. The timing pulses φ1 to φ4 are input to the step motor drive circuit 22 and energize the step motor coils _L3 and _L4 to step drive the motor. Furthermore, the clock pulse C _P is also input to the counter circuit 26 through the inverter 1N-33. The counter circuit 26 counts the rotation angle until it matches the in-focus position _θ1 .
When θ ₁ is reached, a second carry signal C _B is generated. The carry signal C _B is input to the reset terminal 27b of the clock pulse generation circuit 27, resets the operation of the clock pulse generation circuit 27, and stops the generation of the clock pulse C _P.
Deactivates the step motor drive circuit.

If the result of comparison between the output signal θ ₁ of the detection circuit 12 and the reference signal θ _s is θ _A <0, the output of the discrimination circuit 14 becomes L.

This L signal is inverted by inverter 1N-2,
Clock generation circuit 27 through OR gate OR1
is input to generate a clock pulse CP, and thereafter the permanent magnet 1 is driven in steps.

The above explanation will be explained again based on the timing chart shown in FIG. 4. In FIG. 4, θ indicates the rotation angle, and it is assumed that the in-focus position is when θ=θ ₁ . As shown in FIG. 4, when θ<θ _s, the brushless coil is driven by e ₁ and counter electromotive forces e ₂ and e ₃ are generated in the step motor coil. When θ=θ _s , the first and carry signal
C _A is generated, and at the same time the brushless coil is no longer energized, a clock pulse C _P is generated.
The step coil becomes φ1 due to the clock pulse C _P.
It is energized according to the timing of ~φ4 and performs a step operation. When θ=θ ₁ , a second carry signal C _B is generated to stop the generation of the clock pulse C _P and stop the step operation.

As described above, the present invention employs a motor that combines a step motor and a brushless motor by integrally providing a rotor magnet for step drive and a rotor magnet for brushless drive. Since the motor drive is controlled by switching between brushless drives, the motor can be efficiently driven to the target position. When the rotational angle of the drive is large, the initial drive is accelerated by the brushless motor, and when the end of the drive approaches, the drive is switched to the step motor drive, allowing control to a predetermined position without vibration. In other words, it is possible to perform efficient and highly accurate control in which the brushless motor accelerates without step-out and the step drive motor performs positioning.

[Brief explanation of the drawing]

Fig. 1 is a motor drive characteristic diagram for explaining the drive method of the present invention, Fig. 2A is a sectional view of a lens drive device that employs a motor that combines a step motor and a brushless motor, and Fig. _2B1 is a 2 A diagram showing the stator and rotor of the motor shown in Figure A,
Figure 2 B ₂ is a diagram showing the stator and rotor for the brushless motor shown in Figure 2 B ₁ , and Figure 2 C is a diagram showing the stator and rotor for the brushless motor shown in Figure 2 B 1.
_B1 is a detailed view of the coil bobbin for a step motor shown in FIG. 2D, _FIG . 2D is a detailed view of the coil bobbin for a brushless motor shown in FIG. FIG. 4 is a timing chart of each part of the control circuit shown in FIG. 1... Permanent magnet, 2... Coil for step motor, 4... Coil for brushless motor, 10
... Distance measuring device, 12 ... Rotation angle detection circuit, 14
... Discrimination circuit, 18 ... Brushless motor drive circuit, 20 ... Back electromotive force detection circuit, 22 ... Step motor drive circuit, 26 ... Counter, 27
...Clock generation circuit.

Claims (1)

[Claims] 1. A rotor magnet for step drive and a rotor magnet for brushless drive are integrally provided, and these rotor magnets are provided with a first coil for step drive and a second coil for brushless drive. In a motor control device that combines a step motor and a brushless motor by arranging coils in correspondence with each other, the first coil for driving the step and the second coil for brushless driving are switched for selectively operating the first coil for driving the step and the second coil for brushless driving. The switching means is provided with a determining means for determining the amount of drive according to the rotation of the rotor magnet, and a detecting means for detecting a pulse generated according to the rotation of the rotor magnet, and the switching means is connected to the detecting means. It has a counter for counting output pulses from the motor, and the counter switches the switching means from brushless drive to step drive when the count value reaches a predetermined value according to the determination by the determination means. Motor control device that can switch between step drive and brushless drive. 2. Claim 1, wherein the switching means switches to step drive from the beginning when the determining means determines that the drive amount is small.
A motor control device that can switch between step drive and brushless drive as described in .