JP2005176526A - Electric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric actuator capable of keeping an actuator movable portion action on a side which can always secure safety by detecting malfunction of the actuator movable portion. <P>SOLUTION: This electric actuator includes a case 1, an electric motor 2, and a ball screw mechanism 3 having a ball nut 5 screwed with a ball screw 4. Besides, an output shaft 7 of which one end facing the inside of the case 1 is jointed with the ball nut 5 is provided. A displacement detector 11 for detecting the malfunction of the actuator movable portion is provided. The displacement detector 11 is provided with a displacement sensor 12 and a computer 13, and the displacement sensor 12 is constituted out of a pair of Hall elements 14a, 14b attached so as to face a guide groove 10 of the case 1, and a permanent magnet 15 attached at a lock member 9. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electric actuator that, when an actuator moving part tries to move beyond a stop position due to a malfunction, detects the operation so that the actuator operation is always kept on a safe side.

  A manual transmission that uses the latest technology to achieve sequential operation for shifting is drawing attention. This manual transmission is equipped with an actuator for smooth gear shifting. A typical means of this actuator is a hydraulic actuator. The hydraulic actuator operates a manual transmission gearshift mechanism in conjunction with a hydraulic power unit that operates under computer control, enabling sequential operation for shifting.

  It has been proposed to replace this actuator with an electric actuator that is lighter and easier to maintain. When an electric actuator is adopted, a hydraulic power unit, an electromagnetic switching valve, piping, and the like, which are indispensable for a hydraulic actuator, are unnecessary, and it is possible to greatly contribute to a reduction in vehicle weight by avoiding the mounting of these devices. In an electric actuator, generally, a ball screw mechanism or a gear device is used because a speed reducer is required to convert a rotational motion into a linear motion. In the case of an electric actuator for gear shift, a ball screw mechanism that can sufficiently satisfy the requirements in positioning accuracy is used.

  Incidentally, a shift operation for shifting is performed by a switching operation shaft 33 provided upright through a sleeve 32 on the mission case 31 as shown in FIG. That is, in the shift operation, the electric motor 35 of the gear shift electric actuator 34 is rotated, and the arm member 36 connected to the ball screw mechanism (not shown) inside the electric actuator 34 is displaced in the axial direction (perpendicular to the paper surface in the figure). To be done. When the arm member 36 is displaced, the cylindrical member 37 integrated therewith is rotated, the switching operation shaft 33 coupled with the splines is rotated, and a shift operation for changing the gear engagement can be performed. This gear shift electric actuator is described in Patent Document 1.

  By the way, the electric motor incorporated in the electric actuator is preferably a direct current motor (hereinafter referred to as a DC motor) whose rotation direction can be easily changed and battery driving is easy. The DC motor can perform highly accurate control by linking rotation angle control and speed control. That is, by adding speed control as a minor loop to the rotation angle control of the main loop, the rotation angle control can be performed while performing the speed control, and it can be said that the positioning accuracy is almost ideal.

In both controls, a speed sensor that detects the speed of the DC motor and a position sensor that detects the rotation angle are used, and the current rotation angle detected by the position sensor is sent as a feedback signal to the first deviation detector, Compared with the command, the deviation at that time is calculated. Next, the position deviation is converted into a speed signal of the DC motor by the first arithmetic processing unit, and further compared with the current motor speed detected by the speed sensor by the second deviation detection unit to obtain the speed deviation. The speed deviation is converted and amplified into a voltage signal for driving the motor by the second arithmetic processing unit and the amplifier, and the DC motor is rotated until the speed deviation becomes zero. As a result, the ball nut of the ball screw is positioned and the state is maintained.
JP 2003-227657 A, (3rd page, FIG. 17)

  However, in this positioning, if the rotation angle control is unsatisfactory for some reason, the ball screw malfunctions against the high accuracy in the normal state even if the speed control itself is normal. In this case, since the movement amount of the actuator movable portion such as the ball nut and the output member changes, the safety of the actuator is greatly impaired.

  For example, when the rotation angle control position sensor malfunctions due to a failure, an error is mixed in the feedback signal given from the position sensor, and the rotation angle control is in trouble due to an erroneously calculated position deviation. If such an error becomes excessive, the ball nut may move beyond the stop position due to the rotation exceeding the degree of the ball screw, and there is a possibility that a part of the device may be damaged due to overrun of the actuator movable part.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electric actuator in which an actuator operation is always kept on the side where safety can be ensured by detecting a malfunction of an actuator movable portion.

  The present invention relates to a cylindrical case, an electric motor connected to the case, a ball screw mechanism connected to the electric motor and having a ball screw and a ball nut screwed to the ball screw via a plurality of balls, and the case One end facing the inside is coupled to the ball nut, and the output shaft is provided so as to be slidable in the axial direction with respect to the case. The ball nut is rotated while the ball screw is rotating. In the electric actuator provided with a detent member engaged with the guide groove of the case, a displacement detector for detecting a malfunction of the actuator movable portion is provided.

  In the present invention, since a displacement detector for detecting a malfunction is provided, it is possible to detect a malfunction directly from the operation of the actuator moving part, and it is possible to keep it on the side where safety can be ensured by taking a retracting action immediately. Become. Thereby, it can prevent that the safety | security of an electric actuator is impaired.

  An embodiment of an electric actuator according to the present invention will be described with reference to the drawings. In FIG. 1A, the electric actuator of the present invention has a cylindrical case 1 and a DC motor 2 connected to one end of the case 1 to simultaneously perform rotation angle control and speed control. The case 1 accommodates a ball screw mechanism 3 that converts rotational motion into linear motion. The ball screw mechanism 3 includes a ball screw 4 that is directly connected to the DC motor 2 and a ball nut 5 that is screwed to the ball screw 4 via a plurality of balls (not shown). The ball incorporated in the ball screw mechanism 3 rotates and moves from one end to the other along the side surface of the screw thread in the same manner as the ball bearing sphere. The ball is collected at the other end, returned through the passage to one end of the starting point, enters the ball nut 5 again, and continues to circulate. One end of this ball screw mechanism 3 is supported by a bearing 6.

  Further, an output shaft 7 having one end facing the case 1 is provided. The output shaft 7 is connected to the ball nut 5 and can slide in the axial direction with respect to the case 1. The other end of the output shaft 7 protrudes from the case 1 and can be connected to an arm member (not shown) that operates the driven body. The output shaft 7 is supported by a plain bearing 8.

  On the other hand, an anti-rotation member 9 is provided above the ball nut 5 of the ball screw mechanism 3. The anti-rotation member 9 extends over a guide groove 10 formed on the upper surface of the case 1, and keeps the engagement with the case 1 and stops the rotation of the ball nut 5 while the ball screw 4 is rotating. Further, during rotation of the ball screw 4, the anti-rotation member 9 slides in the axial direction along the guide groove 10 to guide the output shaft 7 integrated with the ball nut 5.

  This electric actuator is provided with a displacement detector 11 for detecting a malfunction of the actuator movable portion. The displacement detector 11 includes a displacement sensor 12 that detects the axial displacement of the actuator movable portion, and a calculator 13 that outputs an actuator operation signal when a malfunction is detected.

  As shown in FIG. 1B, the displacement sensor 12 is positioned on a straight line connecting the pair of hall elements 14a and 14b and the hall elements 14a and 14b, which are attached to each other in the guide groove 10 of the case 1. And a permanent magnet 15 attached to the anti-rotation member 9. The Hall elements 14a and 14b utilize the Hall effect that generates an electromotive force by the magnetic field of the permanent magnet 15 during energization of the Hall element made of a semiconductor.

  On the other hand, returning to FIG. 1A again, the calculator 13 calculates based on the displacement signals given from the Hall elements 14a and 14b, and outputs an actuator operation signal when a displacement signal exceeding the reference value is input. . In addition, an amplifier 16 is provided that amplifies the output signal of the arithmetic unit 13 and outputs the amplified signal as a switching signal. The output signal of the amplifier 16 is input to the DC motor control controller 17.

  During the operation of the electric actuator, for example, the rotation angle control is malfunctioned due to a malfunction of the position sensor, and the ball screw 4 is rotated by a signal with an error, so that the actuator movable portion tries to move beyond the stop position. When the actuator moving part goes straight, the permanent magnet 15 approaches, for example, the Hall element 14a, and an electromotive force is generated in the Hall element 14a. At this time, the displacement sensor 12 outputs a displacement signal in accordance with the potential generated in the Hall element 14a.

  The displacement signal is sent to the calculator 13 where it is compared with a reference value. When the displacement signal exceeds the reference value, an actuator operation signal is output from the calculator 13. This operation signal is amplified by the amplifier 16 to become a switching signal. The switching signal is given to the forward / reverse switching circuit of the motor drive circuit of the controller 17. As a result, the DC motor 2 is switched from forward rotation to reverse rotation, and the ball nut 5 is retracted by the reverse rotation of the ball screw 4 according to the DC motor 2, thereby changing the moving direction in the reverse direction immediately before the actuator movable part overruns. To do.

  As described above, since the displacement detector 11 for detecting a malfunction is provided in the present embodiment, the malfunction can be directly detected from the operation of the actuator movable portion during the operation of the electric actuator, and the ball screw 4 is reversed. Therefore, it is possible to keep the safety on the side where safety can be ensured, thereby preventing the safety of the electric actuator from being impaired.

  Different embodiments of the present invention will be described. As shown in FIG. 2A, the main configuration of the electric actuator is the same as that of the above embodiment. This electric actuator is provided with a displacement detector 18 for detecting a malfunction of the actuator movable portion. The displacement detector 18 includes a displacement sensor 19 that detects an axial displacement of the actuator movable portion, and a calculator 20 that outputs an actuator operation signal when a malfunction is detected.

  As shown in FIG. 2B, the displacement sensor 19 includes a pair of light emitting diodes (hereinafter referred to as LEDs) 21 a and 21 b disposed coaxially on the upper portion of the case 1, and a guide groove 10. It consists of a pair of photo detectors 22a and 22b attached in opposition to each other, and an optical mirror 23 attached to the anti-rotation member 9 located on a straight line connecting the photo detectors 22a and 22b. The photodetectors 22a and 22b are made of, for example, a compound semiconductor such as GaAs. The photodetectors 22a and 22b utilize a photoelectric effect that generates an electromotive force when exposed to light.

  Further, with respect to the optical mirror 23, when the optical mirror approaches the photo detector 22a and the photo detector 22b, the reflection angle is such that the light from the LED 21a and the LED 21b is reflected by the optical mirror 23 and the reflected light can be sensed by the photo detector 22a and the photo detector 22b. Is set.

  On the other hand, returning to FIG. 2A again, the computing unit 20 performs computation based on the displacement signals provided from the photodetectors 22a and 22b, and outputs an actuator operation signal when a displacement signal exceeding the reference value is input. In addition, an amplifier 16 that amplifies the output signal of the arithmetic unit 20 and outputs the amplified signal as a switching signal is provided. The output signal of the amplifier 16 is input to the DC motor control controller 17.

  During the operation of the electric actuator, for example, the rotation angle control is malfunctioned due to the malfunction of the position sensor, and the ball screw 4 is rotated by a signal accompanied by an error, so that the actuator movable portion tries to move beyond the stop position. When the actuator movable part goes straight, the optical mirror 23 approaches, for example, the photodetector 22a, the light from the LED 21a is reflected by the optical mirror 23, the reflected light enters the photodetector 22a, and the light strikes the photodetector 22a. An electromotive force is generated. At this time, the displacement sensor 19 outputs a displacement signal in accordance with the potential generated in the photodetector 22a.

  The displacement signal is sent to the calculator 20 where it is compared with a reference value. When the displacement signal exceeds the reference value, an actuator operation signal is output from the calculator 20. This operation signal is amplified by the amplifier 16 to become a switching signal. The switching signal is given to the forward / reverse switching circuit of the motor drive circuit of the controller 17. As a result, the DC motor 2 is switched from forward rotation to reverse rotation, and the ball nut 5 is retracted by the reverse rotation of the ball screw 4 according to the DC motor 2, thereby moving the actuator moving portion in the reverse direction immediately before overrun. To do.

  As described above, since the displacement detector 18 for detecting a malfunction is provided in the present embodiment, the malfunction can be directly detected from the operation of the actuator movable portion during the operation of the electric actuator, and the ball screw 4 is reversed. Therefore, it is possible to keep the safety on the side where safety can be ensured, thereby preventing the safety of the electric actuator from being impaired.

1 shows an embodiment of an electric actuator according to the present invention. FIG. 1A is a configuration diagram of the electric actuator, and FIG. 1B is a plan view showing a main part of the electric actuator. FIGS. 2A and 2B show another embodiment of the electric actuator according to the present invention, and FIG. 2B is a plan view showing a main part of the electric actuator. It is sectional drawing which shows an example of the gear shift mechanism provided with the electric actuator for gear shifts by a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Case 2 ... DC motor 4 ... Ball screw 5 ... Ball nut 7 ... Output shaft 9 ... Anti-rotation member 11, 18 ... Displacement detector 14a, 14b ... Hall element 15 ... Permanent magnet 21a, 21b ... LED
22a, 22b ... Photo detector 23 ... Optical mirror

Claims (4)

  A cylindrical case, an electric motor connected to the case, a ball screw mechanism connected to the electric motor and having a ball screw and a ball nut screwed to the ball screw via a plurality of balls; One end facing the case is coupled to the ball nut, and an output shaft provided to be slidable in the axial direction with respect to the case, and fixed on the ball nut, while the ball screw is rotating. In the electric actuator comprising a detent member engaged with the guide groove of the case so as to stop the rotation of the ball nut, a displacement detector for detecting a malfunction of the actuator movable portion is provided. Electric actuator.   2. The displacement detector includes a displacement sensor that detects an axial displacement of the actuator movable portion, and a calculator that calculates based on the detected displacement signal and outputs an actuator operation signal. Electric actuator.   The electric actuator according to claim 2, wherein the displacement sensor includes a pair of Hall elements provided to face the stationary part and a permanent magnet provided to the actuator movable part. The electric actuator according to claim 2, wherein the displacement sensor includes a pair of a light source and a photodetector provided facing the stationary part, and an optical mirror provided on the actuator movable part.

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