JPH07284242A - Electrically-driven actuator - Google Patents

Abstract

PURPOSE:To provide an electrically-driven actuator which facilitates the reduction of the length in the longitudinal direction of a frame for the size reduction and the manufacture at a low cost without reducing the displacement of a table mechanism. CONSTITUTION:As a ball screw 62 which transmits the rotary motion of a motor unit 108 to a table mechanism is formed integrally with a motor shaft, a space in which coupling members, etc., are provided can be saved. Therefore, the length in the axial direction of an electrically-driven actuator 50 can be reduced without reducing the displacement of the table mechanism.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric actuator which uses an electric motor as a drive source and is provided with a detector for detecting the number of rotations, the rotation angle and the like of the electric motor.

[0002]

2. Description of the Related Art FIG. 10 shows a schematic sectional view of an electric actuator according to the prior art.

A table mechanism (not shown) is attached to the electric actuator 2, and a nut member 6 that is displaced along the axial direction under the rotating action of the ball screw 4 and a support portion that supports one end of the ball screw 4 are provided. 8, a drive unit 14 including a motor 10 and an encoder 12 that rotate and drive the ball screw 4, and a connecting unit 18 that connects the motor shaft 16 and the other end of the ball screw 4 coaxially. The supporting portion 8, the driving portion 14, and the connecting portion 18 are linearly arranged and fixed on the frame 20. In FIG. 10, the motor 10 is described as a synchronous AC servomotor, and the encoder 12 is described as an optical encoder.

One end of the ball screw 4 is rotatably supported by a bearing 24 provided on the support block 22, and the other end of the ball screw 4 is a bearing 26.
And is coaxially connected to the motor shaft 16 of the drive unit 14 via a coupling member 30 provided in the block 28.

The drive unit 14 includes casings 32 and 33,
The motor shaft 16 adjacent to the coupling member 30 includes a motor 10 supported by a bearing 34, and an encoder 12 for detecting the rotation speed, rotation angle, etc. of the motor 10. The motor 10 includes a stator 36 fixed to the casing 32 side, a coil 38 laminated and wound around the stator 36, and a magnet 40 fixed to the motor shaft side. On the other hand, the encoder 12
Light emitted from the light emitting element 46a is emitted through a rotary disc 44 connected to an end of the motor shaft 16 supported by a pair of bearings 42 and a slit (not shown) defined in the rotary disc 44. Light receiving element 46 for receiving light
b.

[0006]

However, in the electric actuator 2 according to the above-mentioned conventional technique, the ball screw 4 and the motor shaft 16 are connected via the connecting portion 18 provided with the coupling member 30. In addition, even if the displacement amount of the table mechanism is the same, there is a disadvantage that the entire length of the electric actuator 2 is increased by the space of the connecting portion 18.

Further, when the ball screw 4 and the motor shaft 16 are coaxially connected to each other, the coupling member 30 is required, and in order to support the ball screw 4 and the motor shaft 16 coaxially. Connection part 18 and drive part 14
In addition, a plurality of bearings 24, 26, 34, 42 are required, which disadvantageously increases the production cost.

The present invention has been made in order to overcome the above-mentioned inconvenience, and shortens the length of the frame in the longitudinal direction to reduce the size without reducing the displacement of the table mechanism. An object of the present invention is to provide an electric actuator that can be manufactured.

[0009]

In order to achieve the above object, the present invention provides a frame extending linearly, a motor arranged in the frame, and a rotation speed or a rotation angle of the motor. A drive mechanism including a detector for detecting; a table mechanism disposed on the frame, which is displaced along the axial direction of the frame under the drive action of the motor; and a rotary shaft of the motor integrated with the table mechanism, A driving force transmitting means for transmitting the rotational movement of the motor to the table mechanism.

[0010]

In the above electric actuator according to the present invention,
Since the driving force transmitting means for transmitting the rotational movement of the motor to the table mechanism is integrated with the rotating shaft of the motor, the space for arranging the coupling member and the like is reduced. Therefore, the length of the electric actuator in the axial direction is reduced without reducing the displacement amount of the table mechanism.

[0011]

Preferred embodiments of the electric actuator according to the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing an electric actuator according to a first embodiment of the present invention, and FIG. 2 is a line II-II in FIG.
FIG. 3 is a longitudinal sectional view taken along the line, and FIG.

The electric actuator 50 includes a base frame 52 and a pair of side covers 54a and 54b mounted on both side surfaces of the frame 52 in the lateral direction.
A pair of end covers 56 and 57 mounted on both ends of the frame 52 in the longitudinal direction, and the side cover 5
4a and 54b, and a top cover 58 that engages with the upper surfaces of the portions 4a and 54b.

Further, on the frame 52, a drive mechanism 60 fixed to one end side of the frame 52 and a drive mechanism 60 fixed to the other end side of the frame 52, and an end portion of a ball screw 62 rotatably attached. A bearing block 64 that supports the table mechanism 6 that linearly displaces between the drive mechanism 60 and the bearing block 64 under the rotating action of the ball screw 62.
And 6 are provided. A set of guide members 68a, 68b for linearly guiding the table mechanism 66 displaced by the ball screw 62 are fixed to the upper surface of the frame 52.

On the lower surface of the frame 52, two groove portions 70a, 70b having substantially the same shape and a substantially T-shaped cross section are defined so as to be substantially parallel to the longitudinal direction. Side covers 54a and 54b are provided on both side surfaces of the frame 52, which are orthogonal to the lower surface of the frame 52.
Engagement grooves 72a and 72b for attaching are respectively defined along the longitudinal direction. Further, in the frame 52, the passages 74a and 7 used as a passage for wiring and a passage for fluid.
4b, 76a, and 76b are defined along the longitudinal direction, respectively. Frame 5 close to the passages 76a, 76b
Mounting grooves 77a and 77b for mounting a detector such as an auto switch are defined along the longitudinal direction on the bottom surface of 2, and the mounting grooves 77a and 77b are leads connected to the detector. It also functions as a wiring groove for accommodating wires.

On the side surfaces of the side covers 68a, 68b, substantially L-shaped projections 78a, 78b for engaging with the engaging grooves 72a, 72b of the frame 52 are provided. By pressing the side covers 68a and 68b from the inclined position, the protrusions 78a and 78b can be fitted along the engagement grooves 72a and 72b. Incidentally, the side covers 68a, 68
When removing b from the frame 52, it is only necessary to pull the side covers 68a and 68b toward the upper side, and the side covers 68a and 68b can be easily attached and detached.

Next, as shown in FIG. 2, the table mechanism 66 holds a ball screw bush 80 for converting the rotational movement of the ball screw 62 into a linear movement and both side surface portions of the ball screw bush 80 so as to face each other. Pair of table blocks 82a, 82b and the table block 82
a, 82b and holding members 84a, 84b having a U-shaped cross section, which are interposed between the guide members 68a, 68b.
On the upper surfaces of the table blocks 82a and 82b, a connecting hole portion 86 for mounting and connecting other members and a positioning recess portion 88 for positioning a work with high accuracy are provided.
Are defined (see FIG. 1).

By forming both or one of the ball screw 62 and the ball screw bush 80 with a material of ultra-high molecular weight polyethylene, wear resistance and slidability can be improved.

Here, the guide member 68a (68b)
4A and 4B show modifications of the above. The guide member 90 has a protrusion 9 that protrudes at an acute angle along the axial direction of a guide shaft 92 fixed to the upper surface of the frame 52.
4 is provided, and by further interposing roller bearings 96a to 96c between the guide member 90 and the U-shaped holding member 97, the frictional resistance of the sliding surface of the guide member 90 is reduced and sliding is performed. It is possible to improve the sex. In this case, the adjusting screw 99 is provided on each side surface of the holding member 97 along the longitudinal direction.
a to 99c (however, 99a is not shown) are provided,
Guide member 90 through the adjusting screws 99a to 99c
By changing the pressing force of the roller bearings 96a to 96c against the guide member 90 and the bearings 96a to 96c.
The sliding contact condition with 6c can be adjusted. Therefore, the sliding contact can be made uniform along the axial direction of the guide member 90. The guide member 90 and the frame 5
2 may be integrally molded.

The roller bearings 96a to 96c made of ultra-high molecular weight polyethylene or oil-impregnated polyacetal are substantially perpendicular to the axial direction of the bearing plates 98a to 98c and the bearing plates 98a to 98c. , A cylindrical roller 102 that is rotatably mounted in the hole 100 and defines a hole 100 that linearly opens at a predetermined interval.
Composed of and. Friction resistance is reduced by the cylindrical rollers 102 of the roller bearings 96a to 96c slidingly contacting the flat surface of the guide member 90 and rolling. The bearing plates 98a to 98c have cylindrical holes 10 in the holes 100.
A flat plate bearing may be used without providing 2 or the like.

The drive mechanism 60, as shown in FIG.
The housing 106 includes a bearing 104 that supports the ball screw 62, a motor unit 108, and an encoder unit 112 closed by a cover member 110. In this case, the housing 106, which is a fixing means of the ball screw 62, also functions as a motor body.

The motor unit 108 is a housing 106.
And a stator 11 to which a plurality of divided stator cores 114 (described later) having substantially the same shape are connected
6, a coil 118 wound around each of the divided stator cores 114, and a ring-shaped permanent magnet 122 (rotor) fixed to the reduced diameter portion 62a of the ball screw via a tubular member 120. To be done.

In this case, as shown in FIG. 5, the stator core 114 is formed in a substantially T-shaped cross section, and a projection portion 124 protruding in the circumferential direction is formed on the head thereof, and the shape of the projection portion 124. Corresponding to the above, and by engaging the recess 126 of the one stator core 114 and the protrusion 124 of the other stator core 114 that are adjacent to each other, it is possible to couple the plurality of stator cores 114 in a substantially circumferential shape. it can. As a result, as compared with the conventional case where the coil is wound around the outer peripheral surface of the stator core which is not divided, the coil 118 is attached to the divided stator core 114.
By winding, it is possible to increase the winding rate and increase the electromagnetic force.

The encoder section 112 has a rotary disk 128 fixed to a cylindrical member 120 which rotates integrally with the reduced diameter portion 62a of the ball screw, and a light emitting section and a light receiving section (not shown) with the rotary disk 128 interposed therebetween. Are provided so as to face each other, and a floating joint 132 that supports the encoder detection unit 130 and is fixed to the stator 116 by screwing. In this embodiment, the floating joint 13
Although 2 is formed of a thin plate-like elastic body (see FIG. 3), it may be an elastic body such as rubber. A bearing 134 held by a ring member is provided between the rotary disk 128 and the permanent magnet 122, and the terminal end of the ball screw 62 is supported by the bearing 134.

Motor section 108 and encoder section 112
Lead wires 136 are respectively connected to the lead wires 136.
Is connected to a servo amplifier (not shown).

The electric actuator 50 according to the first embodiment of the present invention is basically constructed as described above. Next, its operation and effect will be explained.

The electric actuator 50 has a top cover 58, side covers 54a and 54b, and end covers 56, which are selected by an operator according to the installation environment.
It is possible to use the table mechanism 66, the bearing block 64, the drive mechanism 60 and the like fixed on the frame 52 without mounting the 57. In this case, a groove portion 70 having a substantially T-shaped cross section defined on the lower surface of the frame 52.
The frame 52 is fixed on a member (not shown) via a and 70b, and table blocks 82a and 82b are also provided.
By connecting a member (not shown) through the connecting hole portion 86 defined in FIG. 1, it is possible to carry a work, for example.

On the other hand, the worker uses the electric actuator 50.
Select the desired cover according to the installation environment of the frame 5
Attach to 2. That is, the pair of side covers 54a,
One side cover 54a (54b) may be selected from 54b and mounted on only one side surface of the frame 52, or may be mounted on both side surfaces. Further, not only the side covers 54a and 54b but also one end cover 56 (57) can be selectively attached to both ends of the frame 52. In this case, the end covers 56, 5
It is also possible to attach the top cover 58 by engaging with 7. The operator uses the electric actuator 5
A desired cover can be attached to the frame 52 according to the installation environment of 0 or the like.

After the operator selects a desired combination to form the electric actuator 50 in this way, the servo amplifier (not shown) is driven to lead the wire 136.
An electric current is supplied to the coil 118 wound around the stator 116 via the electric current, and the magnetic flux generated by the permanent magnet 122 is orthogonal to the electric current, whereby the ball screw 62 integrated with the motor shaft rotates. The torque of the motor unit 108 is controlled by a servo amplifier. The ball screw 62 functioning as a motor shaft is rotated by the rotation of the motor unit 108, and the ball screw bushing 80 is displaced along the axial direction under the screwing action of the ball screw 62.
Therefore, the work can be conveyed via the table blocks 82a and 82b fixed to the ball screw bush 80.

In the electric actuator 50 according to the present embodiment, by using a part of the ball screw 62 as a motor shaft without using the coupling member 30,
The length of the ball screw 62 in the longitudinal direction, that is, the length of the frame 52 in the longitudinal direction is significantly shortened as compared with the conventional technique without reducing the displacement amount of the table mechanism 66 in the axial direction. As a result, the size of the electric actuator 50 as a whole can be reduced.

Further, by winding each stator core 114 separated in the circumferential direction to increase the winding rate (see FIG. 5), the shape of the motor is reduced in the axial direction of the motor shaft, and It is possible to form a large-diameter motor that expands outward in the radial direction of the shaft. Therefore, by making the diameter of the motor unit 108 large, it is possible to secure a mounting space for the encoder unit 112 and to integrate the winding portion of the motor and the encoder unit 112.

Further, the stator 116 is usually formed by laminating silicon steel plates in consideration of relative magnetic permeability, iron loss, copper loss, hysteresis loss, generation of heat in eddy current, etc. The silicon steel plate can be reduced by reducing the shape of the motor in the direction of the motor shaft and increasing the diameter of the flat motor as in the embodiment.
Therefore, the stator 116 can be formed of an inexpensive magnetic material, and the manufacturing cost of the electric actuator 50 can be reduced. In the case of the flat motor,
Since the motor shaft portion of the ball screw 62 can be shortened, vibration of the motor shaft can be suppressed, and at the same time, there is an advantage of increasing the critical speed that matches the natural frequency of bending of the motor shaft.

Furthermore, by using the windings in the stator 116 as print coils, it is possible to form a flat motor that is further reduced in the axial direction.

As described above, in the electric actuator 50 according to the present embodiment, it is not necessary to use the coupling member 30, the connecting portion 18, etc. used in the prior art, so that the manufacturing cost can be reduced. .

Next, FIG. 6 shows an electric actuator 140 according to the second embodiment of the present invention. The first shown in FIG.
The same components as those in the embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

In this electric actuator 140, an encoder section 142 is provided at one end of the ball screw 62 and a motor section 144 is provided at the other end, and the encoder section 142 and the motor section 144 are separated by a predetermined distance. There is a feature in that

The motor section 144 is provided with a deep groove ball bearing 146 for supporting the ball screw 62, and a motor housing 152 composed of first and second block bodies 148 and 150.
And a stator 154 disposed between the first and second block bodies 148 and 150 and having a plurality of divided stator cores 114 of substantially the same shape connected to each other, and wound around each of the divided stator cores 114. Turned coil 15
6 and a permanent magnet 160 fixed to the ball screw 62 via a tubular member 158. The stator core 114 is formed similarly to the first embodiment. The deep groove ball bearing 146 is for preventing the ball screw 62 from bending in the axial direction, and the ring-shaped spring washer 162 provided in the vicinity of the deep groove ball bearing 146 is a thermal spring for the ball screw 62. Performs the function of absorbing displacement. Instead of the deep groove ball bearing 146, a tapered roller bearing, a cylindrical roller bearing or the like may be used.

The encoder section 142 includes an encoder housing 166 provided with an angular ball bearing 164 (back surface adjustment), a cover member 168 mounted on the encoder housing 166, and a connecting member tightened at the end of the ball screw 62. Rotating disk 17 held by 170
2 and an encoder detection unit 176 including a light receiving element 174b that receives the light emitted from the light emitting element 174a through a slit (not shown) defined in the rotary disk 172. The angular ball bearing 164 has a function of preventing the ball screw 62 from bending in the axial direction and ensuring a clearance between the light emitting element 174a and the light receiving element 174b and the rotating disk 172 at a predetermined interval.

Electric actuator 14 according to the second embodiment
In 0, the motor section 144 and the encoder section 142 are configured separately, so that the circumferential runout tolerance at the connecting portion of the motor section 144, the encoder section 142, and the ball screw 62 can be relaxed. In addition, the motor unit 1
44 and the encoder unit 142 are integrally connected,
Although the entire parts including the motor unit 144 and the encoder unit 142 must be replaced due to the failure of either one, in the present embodiment, the motor unit 144 and the encoder unit 1 are replaced.
Since 42 and 42 are formed separately and independently, only one of the parts in which a failure or the like has occurred needs to be replaced. Since the operation of the electric actuator 140 is the same as that of the first embodiment, its detailed description will be omitted.

Next, a control method when a synchronous AC servomotor is used as a drive mechanism for the electric actuators 50 and 140 will be described.

Normally, the synchronous AC servomotor is U,
Three sets of coils of V and W are arranged, and the rotors (permanent magnets) are rotated by sequentially exciting the coils of each set with good timing.

An encoder is connected to the AC servomotor, and the encoder has an A phase difference of 90 °.
Phase and B-phase two-phase signals, Z-phase signals for deriving only one pulse for each rotation, and U for detecting the magnetic pole position of each coil
And a magnetic pole position detection signal including a V phase, a V phase, and a W phase. In this way, when performing position control and rotation control of the synchronous AC servo motor, A, B, Z phases and U,
Six V and W phase signal lines are required.

By the way, in the induction type AC servo motor, a rotating magnetic field is generated by the current supplied to the coil, and since the rotating magnetic fields are always in phase with each other, it is not necessary to detect the position of the magnetic field. , The encoder is
It outputs a three-phase signal consisting of A, B, and Z phases.

Therefore, the encoder used for the synchronous AC servo motor is different from the ordinary encoder, and the encoder dedicated to the synchronous AC servo motor is used.

Therefore, even if a synchronous AC servomotor is used as the drive mechanism of the electric actuator according to the present embodiment, the AC is generated by three signals of A, B, and Z phases, like other electric motors. A method of controlling the servo motor will be described. In the following description, the encoder is used as including any of an optical encoder, a magnetic encoder, and a laser encoder.

First, as shown in FIG. 7A, both the A-phase signal and the B-phase signal output from the encoder sections 112 and 142 are combined to form a combined signal, and the combined signal is generated based on the Z-phase signal. The number of pulses per rotation of the combined signal is counted, and a signal of 1000 pulses is obtained, for example. Based on the counting result, the controller (not shown) outputs the commutation signals (UE, WE, VE signals) stored in advance based on the excitation timing of each set of U, V, W (see FIG. 7B). For example, the controller stores in advance predetermined UE, WE, and VE signals, the α-th pulse signal corresponds to the UE signal, the β-th pulse signal corresponds to the WE signal, and the pulse signal corresponds to the WE signal. The UE signal, WE signal, V
Derive the E signal.

Therefore, both the position / speed control of the motor and the magnetic field position detection can be controlled only by the three-phase signals of A, B, Z output from the encoder sections 112, 142. As a result, a normal commercially available encoder can be made compatible with all electric motors including a synchronous AC servomotor as a drive mechanism of the electric actuator, and the versatility of the electric actuator can be improved. it can. Also, when assembling the synchronous AC servo motor and encoder to the electric actuator,
Since U, V, W phase signals are not required, the U, V,
There is an advantage that the phase of the W-phase signal and the waveform of the encoder need not be matched. Further, the encoder unit 11
It is also possible to provide storage means for storing the three-phase signals of A, B, and Z output from Nos. 2 and 142, and serially transmit them to other devices. By accommodating the lead wires from which the three-phase signals A, B, and Z are derived in the housing of the encoder, the wiring space can be reduced.

Next, electric actuators 180, 180a according to a third embodiment of the present invention are shown in FIGS. 8A and 8B.

In the electric actuator 180, when the magnetic encoder 184 is used for the drive mechanism 182, the end portion of the ball screw 186 which functions as a driving force transmitting means has a cylindrical magnetic field which rotates integrally with the ball screw 186. The feature is that the drum 188 is provided.

That is, the drive mechanism 182 includes a permanent magnet 190 fitted to the ball screw 186 and a stator 192 around which a coil is wound. On the other hand, the magnetic encoder 184 is a disc-shaped magnetic drum 188 that is fitted to the ball screw 186 and integrally connected to the casing 194.
And a magnetic detection element 196 including a magnetic resistance element or a Hall element. On the outer peripheral surface of the cylindrical magnetic drum 188, a magnetic pole sensor track 198 in which a plurality of S poles and N poles are sequentially arranged is provided, and by a magnetic detection element 196 which is separated from the outer peripheral surface by a predetermined distance. The magnetic pole is detected.

In this case, in this embodiment, the cylindrical magnetic drum 188 is provided integrally with the casing 194 at the end of the ball screw 186 functioning as the motor shaft, so that the length of the drive mechanism 182 in the axial direction can be reduced. Shrink,
As a result, the entire length of the electric actuator 180 can be shortened. Further, when manufacturing the electric actuator 180, the magnetic encoder 184 can be easily attached to the ball screw 1.
Can be incorporated into 86.

As shown in FIG. 8B, the magnetic encoder 184 and the magnetic detection element 196 are arranged in a space defined between the protrusions 197 of the coil wound around the stator 192. May be.

Here, a modified example of this embodiment is shown in FIGS. 9A and 9B. FIG. 9A shows a magnetic absolute encoder, which is characterized in that a cylindrical magnetic drum 199 is formed by connecting three layers, and three detection elements 200 are connected according to the number of connections. Further, FIG. 9B shows that, for example, when the diameter of the ball screw 202 is 50 mm or more, a hollow hole portion 204 is defined along the axial direction at the end portion of the ball screw 202 and is fitted into the hole portion 204. The cylindrical cylindrical magnetic drum 206 is attached to the magnetic detection element 2
It is characterized in that it is detected in 08.

Since the operation of this modification is the same as that of the third embodiment, its detailed description will be omitted.

[0055]

According to the electric actuator of the present invention, the following effects can be obtained.

That is, as compared with the electric actuator according to the prior art, the space for disposing the coupling member is reduced, and the electric actuator can be downsized. Also, by reducing the number of parts, it is possible to manufacture at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view of an electric actuator according to a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view taken along the line II-II shown in FIG.

FIG. 3 is a lateral cross-sectional view of a main part of the electric actuator shown in FIG.

FIG. 4A and FIG. 4B are perspective views showing modifications of the guide member.

FIG. 5 is a cross-sectional view showing a state where the divided stator cores are circumferentially combined.

FIG. 6 is a perspective view of an electric actuator according to a second embodiment of the present invention.

7A and 7B are explanatory views of a control method of an encoder, respectively.

8A and 8B are cross-sectional views of an electric actuator according to a third embodiment of the present invention.

9A and 9B are diagrams showing modifications of the magnetic encoder shown in FIG. 8, respectively.

FIG. 10 is a lateral cross-sectional view of a main part of an electric actuator according to a conventional technique.

[Explanation of symbols]

50, 140, 180 ... Electric actuator 52 ... Frame 60 ... Drive mechanism 62 ... Ball screw 64 ... Bearing block 66 ... Table mechanism 68a, 68b,
90 ... Guide member 80 ... Ball screw bush 108 ... Motor part 112 ... Encoder part 116 ... Stator 118 ... Coil 122 ... Permanent magnet 128 ... Rotating disk 130 ... Encoder detection part

Claims (3)

[Claims] 1. A drive mechanism including a linearly extending frame, a motor arranged in the frame, and a detector for detecting a rotation speed or a rotation angle of the motor, and a driving mechanism arranged in the frame. A table mechanism that is displaced along the axial direction of the frame under the driving action of the motor; and a driving force transmission unit that is integrated with the rotation shaft of the motor and that transmits the rotational movement of the motor to the table mechanism. An electric actuator, comprising: 2. The actuator according to claim 1, wherein
An electric actuator, wherein the motor and the detector are separated from each other by a predetermined distance. 3. The actuator according to claim 1, wherein
The motor is a synchronous AC servo motor, and the A-phase, B-phase and Z-phase signals derived from the detector are used for the A
An electric actuator characterized by performing position control, speed control, and acceleration control of a C servomotor.