JP3505926B2 - Linear motor control circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear motor control circuit, and more particularly to a linear motor control circuit used for moving a movable lens of a video camera, for example.

[0002]

2. Description of the Related Art Generally, a lens barrel of a video camera or the like is provided with a driving means for moving a movable lens in the optical axis direction in order to exert an autofocus function and an electric zoom function. As this type of drive means, a linear motor is used to linearly move the movable lens. This linear motor is an electromagnetic drive type actuator having a drive coil and a drive magnet. The movable lens moves in order to form a subject image on an image pickup surface of a solid-state image pickup device such as a CCD provided behind the lens barrel.

A linear motor used for autofocusing a movable lens has a structure as shown in FIG. A frame body 200 in FIG. 10 includes a magnet 201 of a driving linear motor 220, and a movable lens 202 is fixed to a movable frame body 203. The movable lens 202 is arranged corresponding to the solid-state image sensor CCD. The movable frame 203 includes a driving coil 204, and by energizing the coil 204, the movable frame 203 and the movable lens 202 can be moved and positioned in the arrow X direction. A position detection sensor 205 is provided near the movable frame 203. This position detection sensor 20
5 includes a magnet 206 and a magnetoresistive element sensor (MR sensor) 207, and the magnet 206 is a movable frame 203.
It is fixed to.

FIG. 11 shows the position detecting sensor 205 in more detail, and the magnet 206 has a magnetizing portion 208. The magnetized portion 208 is magnetized such that N poles and S poles are alternately magnetized. The magnetoresistive element sensor 207 includes a magnetic sensing section 209, and the magnet 206 moves in the X direction together with the movable frame 203, so that the magnetic sensing section 2 is detected.
09 detects the magnetic fluxes of the N and S poles of the magnetizing unit 208 and sends a detection signal 210 to the counter 211. The counter 211 can detect the position of the movable lens 202 in the X direction by counting the detection signal 210.

The driving coil 204 and the driving magnet 201 shown in FIG. 10 constitute a linear motor 220. The linear motor 220 is a position servo loop 23.
Movable lens 202 with zero magnetoresistive element sensor 207
Position is detected and the speed servo loop 240
Thus, the speed of the movable lens 202 in the X direction is obtained. The position servo loop 230 including the magnetoresistive element sensor 207 has a function of applying a servo to the linear motor 220 when the movable lens 202 focuses on the solid-state image sensor CCD.

[0006]

On the other hand, the speed servo loop 240 looks at the speed of the movable lens 202, and the processing speed of the microcomputer 241 must be increased in order to detect this speed. Instead, a dedicated high speed microcomputer is required. Further, as shown in FIGS. 10 to 12, the position detection sensor 205 is necessary in order to detect the position of the movable lens 202 and try to align the position of the movable lens 202 with the target position.
Increasing costs is inevitable. That is, it is necessary to set, wire, and inspect the magnetoresistive element sensor 207 and the magnet 206, so that the cost increases.

Since it is necessary to dispose the position detection sensor 205 near the frame body 200 or inside the frame body 200,
There is a problem that it is difficult to downsize the video camera. The magnetic sensing section 20 of the magnetoresistive element sensor 207 of FIG.
If 9 is not positioned very close to the magnet 206, the output failure of the detection signal 210 is likely to occur. Therefore, the magnetic sensing section 209 needs to be arranged close to the magnet 206. However, the magnetic sensing unit 209 and the magnet 20
Even if 6 are arranged close to each other, the magnet 20
If the shape accuracy of 6 and the feeding accuracy of the movable frame 203 in the X direction are not high, there is a problem that the magnet 206 and the magnetic sensing section 209 come into contact with each other. Therefore, an object of the present invention is to solve the above problems and to provide a linear motor control circuit capable of controlling a linear motor without using a position detection sensor.

[0008]

SUMMARY OF THE INVENTION In the present invention, the above object is to provide an induction circuit for detecting an induced voltage generated in a drive coil when a movable part of the linear motor moves in a control circuit of the linear motor. The drive coil has a voltage detection means and an integrator for integrating the detected induced voltage to obtain the position of the movable part, and compares the position of the movable part from the integrator with a preset target position to drive the drive coil. The position servo loop that applies voltage to the motor, the speed servo loop that subtracts the induced voltage from the voltage applied to the drive coil from the position servo loop , and the movable part is pressed against the origin of the mechanism when the power is turned on.
Then, so that the induced voltage detected at this time becomes zero,
Offset the induced voltage detection means and reset the integrator.
And a control circuit for the linear motor , which includes:

In the present invention, the induced voltage detecting means detects the induced voltage generated in the drive coil when the movable portion of the linear motor moves. The position servo loop integrates the detected induced voltage with an integrator to obtain the position of the movable part. Then, the position servo loop compares the position of the movable part from the integrator with a preset target position and applies a voltage to the drive coil. The velocity servo loop subtracts the induced voltage generated by the drive coil from the voltage applied to the drive coil from the position servo loop. Adjustment means when power is turned on
Is detected when the movable part is pressed against the origin of the mechanical part.
Offset the induced voltage detection means so that the induced voltage becomes zero.
Adjust and reset the integrator. By doing this, it is possible to stably detect the position of the moving part of the linear motor without using the position detection sensor, and to detect the induced voltage in the zero speed state.
Offset adjustment and positioning control of the stage can be performed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The embodiment described below is a preferred specific example of the present invention,
Although various technically preferable limitations are given, the scope of the present invention is not limited to these forms unless otherwise specified in the description below.

Embodiment 1 FIG. 1 shows a lens barrel of a video camera to which a linear motor control circuit of the present invention is applied and its internal structure. FIG. 1 is an exploded perspective view showing the internal structure of the lens barrel of this video camera, FIG. 2 is a front view showing the inside of the lens barrel of FIG. 1, and FIG. 3 is taken along the line CC of FIG. FIG. The linear motor control circuit 100 of the present invention is
As shown in FIG. 3, the linear motor M used for autofocusing the movable lens 12 is controlled. 1 to 3
The outer casing 1 has a fixed member 2, two shafts 4a, 4 inside thereof.
b, the movable part 3, etc. are accommodated. The shafts 4a and 4b are fixed in parallel to the outer casing 1 as shown in FIGS.

The fixing member 2 includes a yoke frame 5 made of metal and 4
One magnet 6 is provided, and each magnet 6 is fixed to the yoke frame 5. The yoke frame 5 has a connecting plate 8
An outer frame yoke 9 and an inner frame yoke 10 are provided. The outer frame yoke 9 and the inner frame yoke 10 are arranged so as to face each other, and the outer frame yoke 9 and the inner frame yoke 10 are each formed with a notch 11. The connecting plate 8 has a hole 7. Each magnet 6 is fixed to the outer surface of the inner frame yoke 10 with an adhesive or the like, and is magnetized so that the magnetic poles are different along the direction from the inner frame yoke 10 to the outer frame yoke 9. That is, FIGS. 4 and 5 show the outer casing 1 and the magnet 6 and the like,
For example, the inside is magnetized as N pole and the outside is magnetized as S pole.

Next, the movable portion 3 is provided with a lens holder 13 and a bobbin 14 as shown in FIG. 1, FIG. 6 and FIG. The lens holder 13 includes a movable lens (also referred to as a focus lens) 12. The lens holder 13 is made of metal or synthetic resin, and has bearing portions 18a and 18b and reinforcing portions 19 and 19. Shafts 4a and 4b of the outer casing 1
Passes through the holes 17a, 17b of the bearings 18a, 18b. The bobbin 14 is made of, for example, a synthetic resin and has a rectangular tube shape, around which a driving coil Rd is wound. The driving coil Rd, the four magnets 6, the inner frame yoke 10, the outer frame yoke 9 and the like constitute a linear motor M.

When the bobbin 14 is housed in the outer casing 1 as shown in FIGS. 2 and 3, the coil R for driving the bobbin 14 is used.
d is located between the structure of the inner frame yoke 10 and the magnet 6 and the outer frame yoke 9. The closed magnetic path through which the magnetic flux emitted from the driving magnet passes is, for example, the path of the magnet 6, the inner frame yoke 10, the connecting plate 8, the outer frame yoke 9, and the magnet 6. The coil Rd for driving the bobbin 14 is arranged in such a closed magnetic circuit. When a drive current is supplied to the drive coil Rd from the control circuit 100 of the linear motor, a magnetic flux is generated in the direction of the drive current, so that the drive coil Rd moves in the X direction (forward direction) in FIG. Alternatively, a moving force is applied to the rear), and the moving force allows the movable lens 12 to move along the axes 4a and 4b.

Next, the control circuit 100 of the linear motor shown in FIG. 3 will be described with reference to FIG. The linear motor control circuit 100 includes an induced voltage detecting means 110,
A position servo loop 130, a speed servo loop 160, and a microcomputer 180 as an adjusting means are provided.

First, the induced voltage detecting means 110 will be described. The induced voltage detecting means 110 is provided for the driving coil Rd described in FIGS. 1 and 7, and the linear motor M is moved based on the induced voltage Vv generated by the driving coil Rd. This is a part that outputs an output voltage VS proportional to the speed of the movable part 3 of FIG. The induced voltage detecting means 110 is the Wheatstone bridge 1
12, the differential amplifier 114, and the reference voltage unit 116 (Vre
f). Wheatstone Bridge 112
A bridge structure is formed by three resistors R2, R3, R4 and a coil Rd for driving the linear motor M.

Specifically, one end of the resistor R2 is connected to one end of the driving coil Rd, and the other end of the resistor R2 is connected to one end of the resistor R4. The other end of the resistor R4 is connected to one end of the resistor R3, and the other end of the resistor R3 is connected to the other end of the driving coil Rd. The + terminal of the differential amplifier 114 is
It is connected to the connection point P1 between the driving coil Rd and the resistor R2, and the-terminal of the differential amplifier 114 is connected to the connection point P2 between the resistors R3 and R4. Therefore, the differential amplifier 114
Takes the differential voltage VR of the voltage V1 at the connection point P1 and the voltage V2 at the connection point P2,
The output voltage VS proportional to the speed of the movable part 3 is output.

In this way, the induced voltage detecting means 110 is
The output voltage VS proportional to the speed of the movable portion 3 can be output based on the change in the induced voltage Vv generated in the driving coil Rd. The Wheatstone bridge 112
Then, the relationship between the driving coil Rd and the resistors R2, R3 and R4 is Rd × R4 = R2 × R3.

Next, the speed servo loop 160 will be described. The speed servo loop 160 includes the differential amplifier 114.
The output voltage VS proportional to the output speed is output from the operator 122 by a predetermined process by the filter and the amplifier 120. That is, the speed servo loop 160 creates the processing voltage VSP by processing the output voltage VS proportional to the speed with the filter or the amplifier 120,
This processing voltage VSP plays a role of minus (subtracting) the position servo voltage VP in the operator 122.
By doing so, damping is given to the movement of the linear motor M, and stability of the control system of the control circuit 100 of the linear motor is provided.

Next, the position servo loop 130 will be described. The position servo loop 130 includes a differential amplifier 114.
The integrator 135 and the comparator 137 are provided to perform necessary processing on the output voltage VS (which is a speed signal) proportional to the speed output from the. The integrator 135 integrates the output voltage VS proportional to the speed from the differential amplifier 114, and supplies it as a position signal VPP to the comparator 137. That is, the output voltage VS proportional to the speed is integrated by the integrator 135 to be converted into the position signal VPP representing the position of the movable portion 3 in FIG.

The comparator 137 has a position signal VPP indicating the current position of the movable part 3 and a predetermined target position signal VM.
Compare with P. The target position signal VMP is given from the microcomputer 180 to the comparator 137. The comparator 137 compares the position signal VPP with the target position signal VMP, and outputs the difference signal VD to the filter or the amplifier 143 to generate the position servo voltage VP. This position servo voltage VP is added to the operator 122. That is, the position servo voltage VP is subtracted by the processing voltage VSP from the speed servo loop 160,
It is given to the drive amplifier 145. This drive amplifier 145
Is applied to the coupling point P4 of the Wheatstone bridge 112 of the induced voltage detecting means 110.

Next, the microcomputer 180 will be described. This microcomputer 180 gives the offset adjustment signal SF to the differential amplifier 114 of the induced voltage detecting means 110, gives the integration reset signal SR to the integrator 135, and as described above to the comparator 137. Target position signal VMP.

Moreover, the microcomputer 180 includes
Output voltage V proportional to the speed output by the differential amplifier 114
S is digitally input via the A / D converter 155, and the position signal VPP is also input. Thus, the output voltage VS proportional to the speed is A
The input is made via the / D converter 155 in order to see whether or not the speed of the movable part 3 in FIG. 1 is zero. End part EN) to see if the speed of the movable part 3 is zero, that is, the driving coil Rd.
It is checked whether the induced voltage Vv generated by is zero.

The microcomputer 180 may have all the functions of the integrator 135, the comparator 137, the filter amplifier 143, and the speed servo loop 160. In this case, that is, the input to the microcomputer 180 is the A / D converter 155 having the output voltage VS, and the output is VP.
Become R. This is the original aim.

Next, an operation example of the above-mentioned linear motor control circuit will be described. Movable part 3 in FIGS.
However, when the movable part 3 of the linear motor M moves in order to move in the X direction with respect to the fixed member 2 and the outer casing 1, the driving coil Rd of the control circuit 100 of the linear motor of FIG. An induced voltage Vv is generated between the connecting points P1 and P4. As a result, the differential amplifier 114 of the induced voltage detecting means 110 outputs the output voltage VS proportional to the speed of the movable portion 3 of the linear motor M of FIG. This output voltage VS
However, the speed servo loop 160 and the position servo loop 130
Output supplied to.

When the power is turned on, the movable part 3 of FIGS. 1 and 3 is brought into contact with the mechanical end (mechanical end) EN of FIG. 3 to make the speed of the movable part 3 zero. At this time, the microcomputer 180 of FIG. 8 gives the offset adjustment signal SF to the differential amplifier 114 so that the output voltage VS proportional to the speed becomes zero. The microcomputer 180 also resets the integration reset signal SR for the integrator (integration circuit) 135 to set the position signal VPP to zero and set the initial position of the movable portion 3. The output voltage VS proportional to the speed output by the differential amplifier 114 is sent to the integrator 135 of the position servo loop 130 to be integrated, and the position signal VPP with respect to the mechanical end EN of the movable portion 3 is obtained. Output to the comparator 137. The microcomputer 180 uses the target position signal V
The MP is given to the comparator 137. This target position signal V
MP is a signal corresponding to a target position to be set for autofocusing the movable lens 12 shown in FIGS.

The comparator 137 takes the difference between the position signal VPP and the target position signal VMP to produce a difference signal VD. The difference signal VD is filtered by the filter or the amplifier 143 to the position servo voltage VD.
P. This position servo voltage VP is applied to the operator 122. At this time, the output voltage VS proportional to the speed is subjected to predetermined processing by the filter of the speed servo loop 160 and the amplifier 120 to generate the processing voltage VSP.
This processing voltage VSP minuses the position servo voltage VP based on the induced voltage Vv, and the minus position servo voltage VPR is sent to the drive amplifier 145. By thus subtracting the processing voltage VSP from the position servo voltage VP, damping of the movement of the linear motor M can be provided, and the stability of the control system of the control circuit 100 of the linear motor can be brought about.

The drive amplifier 145 uses the position servo voltage VPR.
By supplying a voltage signal to the driving coil Rd and the resistor R3 on the basis of, the linear motor M moves and positions the movable lens 12 in the X direction to the target position given by the target position signal VMP. . In this way, the control circuit 100 of the linear motor can apply the position servo of the movable part 3 based on the output voltage VS proportional to the speed, without using the position detection sensor used conventionally.

During this control operation, the output voltage VS proportional to the speed is offset due to the fluctuation of the bridge balance of the Wheatstone bridge 112 or the offset of the circuit, or the position signal VPP (integral value) output from the integrator 135 is generated. Drifts (that is, the drift of the current position detected by the movable portion 3), and as described above, the movable portion 3 has the mechanical end (mechanical end) in FIG. 3 within the movable range when the power is turned on. The microcomputer 180 applies the offset adjustment signal SF to the differential amplifier 114 so that the output voltage VS proportional to the speed is zero when the speed of the movable portion 3 is zeroed by being pressed against the EN. I try to send it. Then, as described above, the integrator 135 and the microcomputer 180 are reset by the integration reset signal SR, and the position signal VPP becomes zero.

Second Embodiment Next, another second embodiment of the linear motor control circuit 100 of the present invention will be described with reference to FIG. The linear motor control circuit 100 of FIG. 9 includes an induced voltage detection unit 310, a microcomputer 300, and a drive amplifier 345. The induced voltage detecting means 310 includes a driving coil Rd.
The voltage signal Vv of the voltage (induced voltage) at is converted by the A / D converter 325, and the microcomputer 30
The processing unit 330 of 0 is sent. When the moving speed of the movable portion 3 in FIG. 1 increases, the induced voltage Vv of the driving coil Rd increases and the current signal i decreases. The current signal i is converted from analog to digital by the A / D converter 337 from the connection point of the driving coil Rd and the current detection resistor 365a and sent to the processing unit 330.

The processing section 330 sets the induced voltage to v × K as shown in FIG. 9 and sets the speed of the movable section 3 of the linear motor M to v.
And the constant determined by the linear motor is K, the processing unit 330 obtains the current signal i = (Vv−v × K) / Rd. When this equation is modified, the speed v is obtained from the voltage signal Vv, the current signal i, the resistance value Rd of the driving coil Rd, and the constant K. Output voltage VS generated by the processing unit 330
Is a value proportional to the speed V of the movable part 3.

The microcomputer 300 includes the processing section 330, the speed servo loop 260, and the position servo loop 230 described above. The speed servo loop 260 is
A filter or amplifier 320 connected to the processing unit 330 is provided, and the output voltage VS from the processing unit 330 is subjected to predetermined processing by the filter or amplifier 320 to become the processing voltage VSP, which is subtracted from the operator 122. Given.
The position servo loop 230 includes an integrator 335, a comparator 337, a resetting unit 358, a target position signal generating unit 365, etc. which are connected to the processing unit 330.

The integrator 335 integrates the output voltage VS from the processing unit 330 and outputs the position signal VPP to the comparator 337. The reset means 358 is used when resetting the position signal VPP of the integrator 335. The target position signal generation unit 365 gives the target position signal VMP corresponding to the target position to the comparator 337. The comparator 337 calculates the difference signal V by calculating the difference between the position signal VPP and the target position signal VMP.
D is generated, and the difference signal VD is subjected to predetermined processing by a filter or amplifier 343, and the position servo voltage VP is sent to the operator 122 and added. Therefore, the processing voltage VSP is minus the position servo voltage VP. And operator 122
The position servo voltage VPR is applied to the drive amplifier 345 from. The drive amplifier 345 gives a servo-controlled voltage signal to the drive coil Rd.

In this way, the linear motor control circuit 100 shown in FIG. 9 has the processing unit 330 and the speed servo loop 26.
0 and the position servo loop 230 are connected to the microcomputer 3
It is composed of 00. This microcomputer 300
Can also be used as a microcomputer for autofocus control used when autofocusing the movable lens 12.

As described above, in the embodiment of the present invention, when performing position servo of the movable lens, the position detecting sensor conventionally used is not necessary. That is, the magnetoresistive element sensor and the magnet used as the position detecting sensor are not required, and the connection of these magnetoresistive element sensors, the assembly, the check of the electrical connection, etc. are not required. Therefore, it is possible to significantly reduce costs, and
The size of the video camera can be reduced. Since it is not necessary to use the position detection sensor, problems such as contact between the magnetoresistive element sensor and the magnet in the position detection sensor do not occur, so that reliability can be improved.

The present invention is not limited to the above embodiment. In the above-described embodiment, the control circuit of the linear motor is used to control the movement of the movable lens of the video camera. However, the present invention is not limited to this, and it is possible to control the linear motor when moving the movable portion in other types of models. Of course, it can be applied. Further, for example, in the linear motor control circuit 100 of FIG. 8, when the position signal VPP of the integrator 135 is reset, the integration reset signal SR is input to the integrator 1
I am giving to 35. As a case of resetting the integrator 135 in this way, it is needless to say that the integrator 135 is reset to a predetermined value instead of zero when the movable lens is focused, for example, in combination with a system for image recognition of a subject. I do not care.

[0037]

As described above, according to the present invention,
The linear motor can be controlled without using the position detection sensor.

[Brief description of drawings]

FIG. 1 is a perspective view showing an outer casing of a video camera including a linear motor control circuit according to the present invention and its internal structure.

FIG. 2 is a front view showing the structure of FIG.

3 is a cross-sectional view taken along the line CC of FIG.

FIG. 4 is a front view showing an outer casing and a fixing member.

5 is a cross-sectional view taken along the line AA of FIG.

FIG. 6 is a front view showing a movable part.

7 is a sectional view taken along line BB in FIG.

FIG. 8 is a diagram showing a preferred embodiment of a linear motor control circuit according to the present invention.

FIG. 9 is a diagram showing another embodiment of the control circuit of the linear motor.

FIG. 10 is a diagram showing a linear motor or the like used to move a movable lens of a conventional video camera.

FIG. 11 is a diagram showing an example of a position detection sensor for a movable lens that is conventionally used.

FIG. 12 is a diagram showing a control system of a conventional linear motor.

[Explanation of symbols]

Vv ... induced voltage, Rd ... coil for driving, VS
... Output signal proportional to speed, VP ... Position servo voltage, VSP ... Processing voltage, 3 ... Moving part, 100
... Linear motor control circuit, 110 ... Induced voltage detection means (voltage detection means), 112 ... Wheatstone bridge, 114 ... Differential amplifier, 130 ... Position servo loop, 135 ... Integrator, 137 ... Comparator, 160 ... Velocity servo loop, 180 ... Microcomputer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI G03B 13/34 G02B 7/11 P G05D 3/00 G03B 3/10 H04N 5/232 (58) Fields investigated (Int.Cl. ⁷ , DB name) H02P 5/00 101 H02P 7/00 101 G02B 7/04 G02B 7/08 G02B 7/09 G03B 3/10 G03B 13/34 G05D 3/00 H04N 5/232

Claims (3)

(57) [Claims] 1. In a control circuit of a linear motor, an induced voltage detection means for detecting an induced voltage generated in a drive coil when a movable part of the linear motor moves, and an induced voltage detected are integrated to move. It has an integrator to obtain the position of the part, compares the position of the movable part from the integrator with a preset target position, and gives a voltage to the drive coil. When the power is turned on, the moving part is pressed against the origin of the mechanical part when the power is turned on and the speed servo loop which is minus the voltage applied to the drive coil from the loop.
So that the induced voltage detected at
Offset the pressure detection means and reset the integrator
A control circuit for a linear motor, comprising: an adjusting unit . 2. The induced voltage detecting means comprises a Wheatstone bridge having a drive coil as an element, and a differential amplifier for obtaining a voltage signal proportional to the speed of a movable portion obtained from the Wheatstone bridge. The control circuit of the described linear motor. 3. An autofocus for a movable lens of a video camera.
A linear motor is used for the circus device, and the adjustment means is
The moving lens resets the integrator when it determines that the light receiving means is in focus.
The control circuit for the linear motor according to claim 1.