JP5829736B2 - Electric actuator - Google Patents

Description

  The present invention relates to an electric actuator provided with a ball screw mechanism used in a drive unit of a general industrial electric motor, an automobile, a ship, etc., and more specifically, a position detection function and a rotation input from an electric motor. It is related with the electric actuator which converts into linear motion of a drive shaft via.

  In electric actuators used in various drive units, a gear mechanism such as a trapezoidal screw or a rack and pinion is generally used as a mechanism for converting the rotational motion of the electric motor into a linear motion in the axial direction. Since these conversion mechanisms involve a sliding contact portion, the power loss is large, and it is necessary to increase the size of the electric motor and increase the power consumption. Therefore, a ball screw mechanism has been adopted as a more efficient actuator.

  For example, in a relatively small ship that drives a screw with an internal combustion engine, the wire connected to a lever operated by an operator can be switched between the rotation of the screw in the forward direction and the rotation of the screw in the reverse direction. And the dog clutch is switched via this wire and engaged with the forward gear or the reverse gear. However, in recent years, electric actuators that switch dog clutches electrically have been developed to save labor.

  Here, it is necessary to consider that the electric actuator for ships is used on the open sea, and it is desired to develop it with a concept different from that of a general actuator. For example, since a general linear actuator is often controlled by detecting displacement in the axial direction, a limit switch is provided at a portion that is displaced in the axial direction. In many cases, the electric motor serving as the drive source of the actuator is assembled in a state of being exposed on the outer wall of the housing.

  However, if the stroke position of the linear actuator is detected with the limit switch, the forward position and the reverse position of the dog clutch are detected at two positions. In this case, since the position in the middle cannot be detected, there is a problem that when the dog clutch stops between two positions for some reason, the drive circuit cannot determine in which direction the dog clutch should be moved.

  As an electric actuator that solves such a problem, one shown in FIG. 4 is known. The electric actuator 100 includes a cylindrical housing 101, an electric motor 102 attached to the housing 101, a first power transmission mechanism including a plurality of gears for transmitting the rotational force of the electric motor 102, and a measurement shaft 113a. And a second power transmission mechanism that includes a plurality of gears and that transmits the rotational force of the electric motor 102 to the measurement shaft 113a of the potentiometer 113.

  The housing 101 includes a housing main body 101A, a cover member 101B assembled to an end surface thereof, and a motor bracket 101C. The housing body 101A has a motor chamber 101a and a screw shaft chamber 101b, and a motor 102 is disposed in the motor chamber 101a. The electric motor 102 is fixed to a plate-like motor bracket 101C. The motor bracket 101C is attached so that the outer ring of the ball bearing 114 is sandwiched between the housing main body 101A and the motor chamber 101a and the screw shaft chamber 101b of the housing main body 101A are closed.

  A rotating shaft 102a of the electric motor 102 protrudes from the motor bracket 101C, and a first gear 103 is attached to the end of the rotating shaft 102a so as not to be relatively rotatable by press-fitting. A second gear 105 is rotatably disposed around the long shaft 104 whose one end is press-fitted into the bag hole of the motor bracket 101C, and meshes with the large gear portion 106a of the first gear 103 and the third gear 106. Yes.

  The third gear 106 has a large gear portion 106a and a small gear portion 106b formed coaxially, and is attached to the end portion of the screw shaft 107 so as not to be relatively rotatable by serration coupling. A support member 108 is attached to the motor bracket 101C so as to cover a part of the third gear 106. Here, the first gear 103, the second gear 105, and the third gear 106 constitute a first power transmission mechanism.

  A fourth gear 109 disposed adjacent to the second gear 105 is rotatably supported around the long shaft 104. In the fourth gear 109, a large gear portion 109a and a small gear portion 109b that are meshed with the small gear portion 106b of the third gear 106 are formed coaxially.

  The small gear portion 109 b of the fourth gear 109 meshes with the large gear portion 111 a of the fifth gear 111 that is rotatably supported with respect to the short shaft 110 implanted in the support member 108 in parallel with the long shaft 104. ing. The fifth gear 111 has a large gear portion 111a and a small gear portion 111b formed coaxially. The small gear portion 111 b meshes with a sixth gear 112 that is disposed adjacent to the fifth gear 111 and rotatably supported around the long shaft 104.

  A potentiometer 113 as a sensor is fitted and disposed in the hole of the cover member 101B. The measuring shaft 113a of the potentiometer 113 is connected to the sixth gear 112 so as to rotate integrally. The tip end of the long shaft 104 extending in a cantilever manner is supported by the potentiometer 113 via the sixth gear 112 and the measurement shaft 113a. Here, the first gear 103, the second gear 105, the third gear 106, the fourth gear 109, the fifth gear 111, and the sixth gear 112 constitute a second power transmission mechanism.

  The right end side of the screw shaft 107 is rotatably supported by a ball bearing 114 with respect to the housing main body 101A. The screw shaft 107 penetrates the cylindrical nut 115 and forms a male screw groove 107a on the left end side. A female screw groove 115a is formed on the inner peripheral surface of the nut 115 so as to face the male screw groove 107a, and a large number of balls 116 are arranged to roll in a spiral space formed by both the screw grooves 107a and 115a. Has been. The nut 115 is provided with a detent with respect to the housing main body 101A, and is relatively movable in the axial direction within the screw shaft chamber 101b, and is not relatively rotatable. A nut 115 as an axial movement element, a screw shaft 107 as a rotation element, and a ball 116 as a rolling element constitute a ball screw mechanism, and the ball screw mechanism and the drive shaft 117 constitute a drive mechanism. To do.

  The left end of the screw shaft 107 penetrates into a bag hole 117a formed in the round shaft-shaped drive shaft 117. The right end of the drive shaft 117 is coaxially fitted to the nut 115 and is connected by a pin so as to move integrally. The drive shaft 117 is supported by the bush 118 so as to be movable in the axial direction with respect to the housing main body 101A. A hole 117b for connecting to a link member (not shown) is formed at the end of the drive shaft 117 protruding from the housing main body 101A.

  The rotational force of the rotating shaft 102a is transmitted to the measuring shaft 113a of the potentiometer 113 via the first gear 103, the second gear 105, the third gear 106, the fourth gear 109, the fifth gear 111, and the sixth gear 112. . A signal corresponding to the rotation of the measuring shaft 113a is input from the potentiometer 113 to a drive circuit (not shown). If it is determined that the screw shaft 107 has rotated by a predetermined rotation amount based on this signal, the drive circuit stops the power supply to the electric motor 102. On the other hand, when the operator operates a lever (not shown) in the reverse direction, electric power having a reverse polarity is supplied to the electric motor 102 and the rotating shaft 102a rotates in the reverse direction. Then, the drive shaft 117 of the electric actuator 100 moves in the retracting direction.

  As described above, the centers of the second gear 105, the fourth gear 109, and the sixth gear 112 coincide with each other and are rotatably disposed around the same long shaft 104, so that a reduction ratio with a high gear ratio can be obtained. A compact configuration can be achieved while using a five-stage gear train. In this way, in the electric actuator 100 in which a plurality of gears are built in, the three gears have the same rotation center axis. This means that the number of center axes is reduced, and the support holes for housings that support the center axes. There are many advantages such as being reduced.

  Moreover, since the rotational displacement of the screw shaft 107 is detected by the potentiometer 113 instead of detecting the displacement position by a limit switch or the like, arbitrary position control is possible. When the rotation of the screw shaft 107 is directly detected, the screw shaft 107 is multi-rotation, and thus the rotational displacement decelerated through the gear train of the second power transmission mechanism is detected by the potentiometer 113. On the other hand, the rotational motion output from the electric motor 102 is decelerated through the gear train and transmitted to the screw shaft 107. By providing a common rotation center shaft in a part of the two gear trains, a compact layout is possible, and there is a great contribution in terms of cost (for example, see Patent Document 1).

JP 2008-228557 A

  In such a conventional electric actuator 100, the potentiometer 113 can generally set an effective detection angle in the range of 80 ° to 170 °, and although it is a highly accurate sensor, the potentiometer 113 has a relationship between the screw shaft 107 and the potentiometer 113. In order for the electric actuator 100 having multiple gears (spur gears) to obtain a large reduction, it is necessary to increase the difference in the number of teeth between the small gear and the large gear. This not only increases the number of parts and the number of parts, but also increases the size of the electric actuator 100 that accommodates each gear.

  Further, although the mechanism detects the position of the linear movement of the drive shaft 117, the drive shaft 117 and the potentiometer 113 are indirectly connected to convert the rotation amount of the screw shaft 107 into the detection angle of the potentiometer 113 through the reduction of the spur gear. As the number of parts interposed between the screw shaft 107 and the potentiometer 113 increases, the position detection accuracy decreases.

  The present invention has been made in view of the problems of the prior art, can directly detect the position, and even when a potentiometer is used, the position detection accuracy is improved without using a multistage gear, It is an object to provide an electric actuator with improved reliability.

In order to achieve such an object, the invention according to claim 1 of the present invention includes a housing, an electric motor attached to the housing, and a speed reduction mechanism that transmits the rotational force of the electric motor via a motor shaft. A ball screw mechanism that converts the rotational motion of the electric motor into a linear motion in the axial direction of the drive shaft through the speed reduction mechanism, a screw shaft that is configured integrally with the drive shaft, The screw shaft is extrapolated via a large number of balls, and the rotational movement of the electric motor is transmitted via the speed reduction mechanism , and can be rotated via a rolling bearing mounted on the housing and cannot be moved in the axial direction. is composed of a supported nut, the electric actuator comprising a potentiometer for detecting the position of said drive shaft, said housing includes a first housing, its A second housing assembled to the end face, a disk-shaped motor bracket is disposed inside the first housing, the electric motor is fixed via the motor bracket, and the rolling bearing The outer ring is sandwiched between the motor bracket and the second housing, and the motor bracket is attached so as to close the first housing and the second housing, and the tip of the joint portion of the potentiometer One end of the swing link is connected to the shaft, and the other end of the swing link engages with a pin protruding from the drive shaft. The pin and the swing link rotate the drive shaft. It is configured so as to prevent and prevent movement of the drive shaft in the axial direction, and is arranged so as to be capable of pendulum movement in conjunction with linear movement of the drive shaft. Nshometa detects the swing angle of the swing link, and to detect the axial position of the drive shaft.

Thus, a reduction mechanism that transmits the rotational force of the electric motor via the motor shaft, a ball screw mechanism that converts the rotational movement of the electric motor to a linear movement in the axial direction of the drive shaft via this reduction mechanism, The ball screw mechanism is inserted into the drive shaft integrally with the drive shaft, and the screw shaft is extrapolated via a large number of balls, and the rotational motion of the electric motor is transmitted via the speed reduction mechanism and mounted on the housing. An electric actuator including a potentiometer configured to detect a position of a drive shaft, the nut being supported by a nut that is rotatable and non-movable in an axial direction through a rolling bearing . A second housing assembled to the end face, and a disk-shaped motor bracket is disposed inside the first housing. Thus, the electric motor is fixed, the outer ring of the rolling bearing is sandwiched between the motor bracket and the second housing, and the motor bracket is attached so as to close the first housing and the second housing. One end of the swing link is connected to the tip of the joint portion of the potentiometer, and the other end of the swing link is engaged with a pin protruding from the drive shaft. It is configured to prevent rotation of the drive shaft and to prevent movement of the drive shaft in the axial direction, and is arranged to allow pendulum movement in conjunction with linear movement of the drive shaft, and the potentiometer swings the swing link. Since the angle is detected and the axial position of the drive shaft is detected, it is possible to accurately detect the position of the drive shaft accurately, and an electric actuator with improved reliability can be obtained. It can be provided.

  Preferably, as in the invention described in claim 2, the swing link is formed in a bifurcated shape so that the pin is engaged, and the pin is larger than a bifurcated groove width of the swing link. If it has a large collar and the swing link is slidably engaged with the pin, the rotation of the drive shaft is prevented, and the drive shaft can be directly moved without disturbing the axial movement of the drive shaft. Position detection can be performed with high accuracy.

  Further, as in the third aspect of the invention, if the swing link is set to be the midpoint of the axial stroke of the drive shaft when it reaches the lowest point, the electric actuator can be made compact. Can be further promoted.

An electric actuator according to the present invention includes a housing, an electric motor attached to the housing, a reduction mechanism that transmits the rotational force of the electric motor via a motor shaft, and rotation of the electric motor via the reduction mechanism. A ball screw mechanism that converts the motion into a linear motion in the axial direction of the drive shaft, the ball screw mechanism is integrated with the drive shaft, and the screw shaft is extrapolated via a large number of balls And a rotation nut that is transmitted through the speed reduction mechanism and supported via a rolling bearing mounted on the housing, and is supported so as not to move in the axial direction. the electric actuator and a potentiometer for detecting the position of the axis, the said housing has a first housing, attached to the end face The disk-shaped motor bracket is disposed inside the first housing, the electric motor is fixed via the motor bracket, and the outer ring of the rolling bearing is connected to the motor bracket. The motor bracket is sandwiched between the second housing and attached so as to close the first housing and the second housing, and one end of the swing link is attached to the tip of the joint portion of the potentiometer. And the other end of the swing link engages with a pin protruding from the drive shaft, the pin and the swing link prevent rotation of the drive shaft, and the drive shaft The axial movement of the drive shaft is not hindered, and the pendulum can be moved in conjunction with the linear movement of the drive shaft. Since the swing angle of the link is detected and the axial position of the drive shaft is detected, direct position detection of the drive shaft can be accurately performed, and an electric actuator with improved reliability can be obtained. Can be provided.

It is a longitudinal section showing one embodiment of an electric actuator concerning the present invention. It is sectional drawing which shows the ball screw mechanism of FIG. It is explanatory drawing which shows the operation | movement in the state which the connection link engaged with the drive shaft. It is a longitudinal cross-sectional view which shows the conventional electric actuator.

A cylindrical housing, an electric motor attached to the housing, a reduction mechanism that transmits the rotational force of the electric motor via a motor shaft, and a rotational movement of the electric motor via the reduction mechanism. A ball screw mechanism that converts the linear motion into an axial direction, a screw shaft that is integrally formed with the drive shaft, and an externally inserted screw through the ball shaft, and the electric motor And a nut supported so as to be rotatable through a rolling bearing mounted on the housing and not movable in the axial direction, and to detect the position of the drive shaft. the electric actuator comprising a potentiometer, the housing consists of a first housing, a second housing that is assembled to an end face, A disk-shaped motor bracket is disposed inside the first housing, the electric motor is fixed via the motor bracket, and the outer ring of the rolling bearing is connected to the motor bracket and the second housing. And the motor bracket is attached so as to close the first housing and the second housing, and one end of the swing link is connected to the tip of the joint of the potentiometer. The other end of the swing link is formed in a bifurcated shape and is engaged with a pin protruding from the drive shaft, and this pin has a flange that is larger than the bifurcated groove width of the swing link. The swing link is slidably engaged with the pin, and the potentiometer detects the swing angle of the swing link to detect the axial position of the drive shaft. It was way.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 is a longitudinal sectional view showing an embodiment of an electric actuator according to the present invention, FIG. 2 is a sectional view showing a ball screw mechanism of FIG. 1, and FIG. 3 is a state in which a swing link is engaged with a drive shaft. It is explanatory drawing which shows the operation | movement in.

  The electric actuator 1 includes a cylindrical housing 2, an electric motor 3 attached to the housing 2, and a pair of spur gears 4 and 5 for transmitting the rotational force of the electric motor 3 through a motor shaft 3a. A speed reduction mechanism 6, a ball screw mechanism 8 that converts the rotational motion of the electric motor 3 into a linear motion in the axial direction of the drive shaft 7 via the speed reduction mechanism 6, and a potentiometer that detects the position (rotation angle) of the drive shaft 7. 9 and.

  The housing 2 includes a first housing 2a and a second housing 2b assembled to the end surface. An electric motor 3 is disposed inside the first housing 2a. The electric motor 3 is fixed to a disk-shaped motor bracket 10. The motor bracket 10 is attached so that the outer ring of the ball bearing 18 is sandwiched between the first housing 2a and the first housing 2a and the second housing 2b are closed.

  A motor shaft 3a of the electric motor 3 protrudes from the motor bracket 10, and a small spur gear 4 is attached to the end of the motor shaft 3a so as not to be relatively rotatable by press fitting. The large spur gear 5 is press-fitted into a nut 16 constituting a ball screw mechanism 8 described later, and meshes with the small spur gear 4.

  The potentiometer 9 as a sensor is formed of a Hall IC, and a non-contact type that detects a rotation angle is used. The potentiometer 9 is positioned and fixed on the back surface of the second housing 2b above the drive shaft 7. The joint 11 of the potentiometer 9 has a tip projecting into the second housing 2b and connected to one end of the swing link 12. The other end of the oscillating link 12 is engaged with a pin 13 projecting from the drive shaft 7, and is disposed so as to be capable of pendulum movement in conjunction with the linear motion of the drive shaft 7. The swing link 12 is formed in a bifurcated shape so as to prevent the drive shaft 7 from rotating and to prevent the drive shaft 7 from moving in the axial direction, and is slidable with respect to the pin 13 in accordance with the swing angle. Is engaged. The drive shaft 7 is configured integrally with a screw shaft 15 constituting the ball screw mechanism 8 and is supported via a support bearing 14 so as not to rotate but to move in the axial direction with respect to the second housing 2b. A hole 7a for connecting to a link member (not shown) is formed at the end of the drive shaft 7.

  As shown in an enlarged view in FIG. 2, the ball screw mechanism 8 has a screw shaft 15 having a spiral thread groove 15a formed on the outer periphery thereof, and is opposed to the screw groove 15a of the screw shaft 15, and has a spiral shape on the inner periphery thereof. The nut 16 is formed with a thread groove 16a, and a large number of balls 17 are rotatably accommodated in a spiral space formed by the thread grooves 15a and 16a. The above-described large spur gear 5 is press-fitted and fixed to the outer periphery of the nut 16, and the ball bearing 18 fitted to the first housing 2 a and the motor bracket 10 is positioned and fixed via a retaining ring 19, and is relatively relative to the axial direction. It cannot move and can rotate relatively.

  Here, in the present embodiment, as shown in FIG. 3, when the swing link 12 swings due to the axial movement of the drive shaft 7 and reaches the left and right ends (stroke end position) of the linear movement range, The angle formed by the rotation center of the potentiometer 9 and the swing link 12 is the detection angle of the potentiometer 9. With this configuration, the position of the drive shaft 7 can be directly detected, and even when the potentiometer 9 is used, the number of parts can be reduced without using multistage gears, and the size of the electric actuator 1 that accommodates each gear can be reduced. In addition, the number of parts interposed between the screw shaft 15 and the potentiometer 9 can be reduced to improve the position detection accuracy, and the electric actuator 1 with improved reliability can be provided.

  As shown in the figure, if the swing link 12 is set to the lowest point, that is, the intermediate point of the axial stroke of the drive shaft 7 when it is at a position orthogonal to the drive shaft 7, The actuator 1 can be further downsized.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

  The electric actuator according to the present invention is used in a drive unit of a general industrial electric motor, automobile, ship, etc., and has a position detection function, and a rotation input from the electric motor is converted into a linear motion of the drive shaft through a ball screw mechanism. It can be applied to an electric actuator provided with a ball screw mechanism for conversion.

DESCRIPTION OF SYMBOLS 1 Electric actuator 2 Housing 2a 1st housing 2b 2nd housing 3 Electric motor 3a Motor shaft 4 Small spur gear 5 Large spur gear 6 Reduction mechanism 7 Drive shaft 7a Hole 8 Ball screw mechanism 9 Potentiometer 10 Motor bracket 11 Joint part 12 Swing Link 13 Pin 14 Support bearing 15 Screw shaft 15a, 16a Screw groove 17 Ball 18 Ball bearing 19 Retaining ring 100 Electric actuator 101 Housing 101A Housing body 101B Cover member 101C Electric motor bracket 101a Motor chamber 101b Screw shaft chamber 102 Electric motor 102a Rotating shaft 103 First gear 104 Long shaft 105 Second gear 106 Third gear 106a Large gear portion 106b Small gear portion 107 Screw shaft 107a Male screw groove 108 Support member 109 Fourth gear 109a Large gear portion 109b Small gear portion 110 Short shaft 111 Fifth gear 111a Large gear portion 111b Small gear portion 112 Sixth gear 113 Potentiometer 113a Measuring shaft 114 Ball bearing 115 Nut 115a Female thread groove 116 Ball 117 Drive shaft 117a Bag hole 117b Hole 118 Bush

Claims (3)

A housing;
An electric motor attached to the housing;
A speed reduction mechanism for transmitting the rotational force of the electric motor via the motor shaft;
A ball screw mechanism that converts the rotational motion of the electric motor into linear motion in the axial direction of the drive shaft via the speed reduction mechanism;
This ball screw mechanism is a screw shaft integrally formed with the drive shaft;
The screw shaft is extrapolated via a large number of balls, and the rotational movement of the electric motor is transmitted via the speed reduction mechanism so that it can rotate via a rolling bearing mounted on the housing and move in the axial direction. Composed of unsupported nuts,
In the electric actuator provided with a potentiometer for detecting the position of the drive shaft,
The housing includes a first housing and a second housing assembled to an end surface thereof, and a disk-shaped motor bracket is disposed inside the first housing, and the motor bracket is interposed through the motor bracket. An electric motor is fixed, and an outer ring of the rolling bearing is sandwiched between the motor bracket and the second housing, and the motor bracket is attached so as to close the first housing and the second housing. And
One end of a swing link is connected to the tip of the joint portion of the potentiometer, and the other end of the swing link is engaged with a pin protruding from the drive shaft. And configured to prevent rotation of the drive shaft and to prevent movement of the drive shaft in the axial direction, and arranged to be capable of pendulum movement in conjunction with linear motion of the drive shaft,
The electric actuator characterized in that the potentiometer detects a swing angle of the swing link and detects an axial position of the drive shaft.   The swing link is formed in a bifurcated shape so that the pin engages, the pin has a flange that is larger than the bifurcated groove width of the swing link, and the swing link is the pin The electric actuator according to claim 1, which is slidably engaged with the actuator.   3. The electric actuator according to claim 1, wherein the electric actuator is set to be an intermediate point of an axial stroke of the drive shaft when the swing link comes to a lowest point.

Images