JP2011106680A - Electric linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric linear actuator which precisely moves a moving member to a target position while saving energy. <P>SOLUTION: Since a ball screw mechanism has generally high efficiency, when power transmission is carried out by moving a nut 21 according to the rotations of a screw shaft 20a which is a rotation shaft of an electric motor 20, in case of the power supply to the electric motor 20 is stopped and receiving force in a moving direction of the nut 21, it is accepted that power is transmitted in an opposite direction to rotate the rotation shaft 20a of the electric motor. By using this, in a case where a roller 32a is not engaged with any one of a plurality of recessed portions 31b of a detent lever 31, while the power supply to the electric motor 20 is interrupted, if the roller 32a is energized toward any one of the recessed 31b, a range switching valve 10 is driven to any position to be held and held there by using the energizing force. During that, the power is not supplied to the electric motor 20, so that energy can be saved. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric linear actuator, and more particularly to an electric linear actuator suitable for use in switching a shift range of an automatic transmission of a vehicle.

  The range switching device for switching the shift range of the conventional automatic transmission includes a manual valve in the transmission and a shift lever connected to the manual valve by a shift cable. The driver operates the shift lever. The manual valve is switched via a shift cable. Therefore, the shift lever needs to be provided at a position where the shift cable can be operated without difficulty by the driver's force. On the other hand, recently, it is necessary to install a shift lever at an arbitrary location in response to a request for increasing the degree of freedom in vehicle interior design and a request for increasing the number of derived models from the same platform.

  Japanese Patent Application Laid-Open No. H10-228473 discloses a range switching device that meets such a request. This range switching device performs range switching using a motor, detects that the manual valve has reached the target position, and stops driving the motor.

JP-A-7-190180 JP 2001-182828 A

  By the way, since the motor and the drive system have inertia, the manual valve may be driven past the target position even if power supply to the motor is interrupted when the target position is reached. Therefore, in the above-mentioned Patent Document 1, the proximity of the target position is detected by a sensor, and then the motor is reverse braked at a predetermined timing so that the manual valve accurately reaches the target position.

  However, supplying reverse electric power for braking to the motor in this way is disadvantageous in terms of energy saving. In Patent Document 1, a worm mechanism is provided to transmit power from the motor to the detent mechanism. However, since the worm mechanism is generally inefficient, there is a problem that it is further contrary to energy saving.

  On the other hand, in Patent Document 2, in order to accurately move the manual valve to the target position, an electromagnetic clutch that is operated when approaching the target position is operated so that the roller can be engaged with the recess of the detent mechanism. A shift switching mechanism is disclosed in which the valve reaches a target position. However, the provision of an electromagnetic clutch that operates with power supply is disadvantageous in terms of energy saving and increased cost.

  The present invention has been made in view of the problems of the prior art, and an object thereof is to provide an electric linear actuator that can accurately move a moving member to a target position while saving energy.

The electric linear actuator of the present invention is
A moving member;
A drive mechanism for driving the moving member to any one of a plurality of positions to be held;
An electric motor;
A power transmission mechanism that transmits power from the electric motor to the drive mechanism;
The drive mechanism includes a plurality of recesses provided corresponding to a plurality of positions to be held in the moving member, and an engagement member that can be selectively engaged with the recesses,
The power transmission mechanism includes a ball screw mechanism including a screw shaft, a nut, and a plurality of balls disposed between the screw shaft and the nut;
When the engagement member is not engaged with a predetermined position of any of the plurality of recesses in a state where power supply to the electric motor is substantially interrupted, the engagement member is The ball is urged toward any predetermined position, and using the urging force, the moving member is driven to one of the positions to be held and held there, and the ball The screw mechanism is characterized in that a part of the urging force can be transmitted to the electric motor.

  The electric linear actuator of the present invention includes a moving member, a driving mechanism that drives the moving member to any one of a plurality of positions to be held, an electric motor, and power from the electric motor to the driving mechanism. A power transmission mechanism that selectively engages the recesses with a plurality of recesses provided corresponding to a plurality of positions to be held in the moving member, respectively. And the power transmission mechanism includes a ball screw mechanism including a screw shaft, a nut, and a plurality of balls disposed between the screw shaft and the nut. Since the screw mechanism is generally high in efficiency, for example, when the screw shaft is connected to the rotating shaft of the electric motor and the nut is moved in accordance with the rotation to transmit power, the electric motor is used. If stopping the power supply to the motor, when subjected to a force in the direction in which the nut is moved, it allows the rotation shaft of the electric motor is transmitted power in the opposite direction so as to rotate. Using this, when the engagement member is not engaged with any predetermined position of the plurality of recesses in a state where the supply of electric power to the electric motor is substantially interrupted, the engagement is performed. If the combined member is urged toward one of the predetermined positions of the recess, the moving member is driven to one of the positions to be held using the urging force, It will be retained. During this time, since no electric power is supplied to the electric motor, energy saving can be achieved. The “state in which the supply of electric power to the electric motor is substantially interrupted” means that the output torque is weak even if the electric motor is supplied in addition to the state in which the supply of electric power is completely interrupted. For this reason, a state in which the engagement member cannot be prevented from being biased toward any predetermined position of the concave portion is included.

  Furthermore, it is preferable that the moving member is driven and held at the plurality of positions corresponding to a shift position of the transmission.

  The driving mechanism includes a plurality of recesses and is rotatable, and includes a detent lever connected to the moving member, and the moving member is held by the rotation of the detent lever. It is preferable to be driven to a plurality of positions.

  Further, it is preferable that a sensor for detecting a rotation angle of the detent lever is provided, and the electric motor is configured such that power supply is controlled based on an output of the sensor.

  Further, it is preferable that the electric motor is configured such that power supply is controlled in accordance with the rotation angle of the rotation shaft.

  Furthermore, it is preferable that the supply of electric power to the electric motor is interrupted before the moving member reaches any of the plurality of positions to be held.

  The power transmission mechanism preferably includes a speed reduction mechanism using a plastic gear.

  Furthermore, it is preferable to have a regenerative braking circuit that electromagnetically brakes the electric motor and to connect the regenerative braking circuit to the electric motor after the supply of electric power is interrupted.

  Further, it is preferable that the electric motor is decelerated before the moving member reaches any of the plurality of positions to be held.

It is a perspective view of the shift switching mechanism containing the electric linear actuator which is this Embodiment. It is a flowchart which shows control of a shift switching mechanism. It is a figure which shows the modification of this Embodiment. It is a control circuit diagram of the motor concerning this modification. It is sectional drawing which shows the modification which attaches a plastic gear with respect to a screw shaft. It is sectional drawing which shows the modification which attaches a plastic gear with respect to a screw shaft. It is sectional drawing which shows the modification which attaches a plastic gear with respect to a screw shaft. It is sectional drawing which shows the modification which attaches a plastic gear with respect to a screw shaft. It is sectional drawing which shows the modification which attaches a plastic gear with respect to a screw shaft. It is sectional drawing which shows the modification which attaches a plastic gear with respect to a screw shaft. It is sectional drawing which shows the modification which performs the motive power transmission between an electric motor and a screw shaft by belt drive.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a shift switching mechanism including an electric linear actuator according to the present embodiment. In FIG. 1, a range switching valve 10 as a moving member is of a spool valve type, and a line hydraulic pressure serving as a basic hydraulic pressure for controlling an automatic transmission (not shown) is supplied to the range switching valve 10. Has been. The range switching valve 10 controls the engagement and disengagement of a friction engagement device (not shown) for switching the port and setting each shift range by operating the spool 10a in the axial direction.

  The range switching valve 10 is driven by a DC motor (electric motor) 20. The drive system will be described more specifically. The rotating shaft of the electric motor 20 fixed to the vehicle body (not shown) is a screw shaft 20a having a male screw groove formed on the outer periphery. A nut 21 is disposed around the screw shaft 20a. A female screw groove is formed on the inner periphery of the nut 21, and a large number of balls (not shown) are rotatably disposed between the male screw groove of the screw shaft 20 and the female screw groove of the nut 21. . Therefore, the rotation of the screw shaft 20a is converted into the axial movement of the nut 21. The screw shaft 20a, the nut 21, and a ball (not shown) constitute a ball screw mechanism, that is, a power transmission mechanism.

  The nut 21 is connected to one end of the control shaft 22 via a pair of levers 23. Therefore, when the nut 21 is moved, the control shaft 22 is rotated by an amount corresponding thereto. A detent lever 31 is attached to the other end of the control shaft 22 so as to rotate integrally. The pin 31a implanted in the detent lever 31 is engaged with a recess at the tip of the range switching valve 10, and the range switching valve 10 moves in the axial direction in accordance with the rotation of the detent lever 31. ing. A rotation sensor 25 that measures the rotational force is provided at the end of the control shaft 22.

  An output signal from the rotation sensor 25 is input to the CPU 54 via the A / D converter 51. On the other hand, a signal from the range detector 52 that detects the shift position of the shift lever SL disposed in the passenger compartment is also input to the CPU 54. Based on these signals, the CPU 54 supplies power to the electric motor 20 via the amplifier 53 in the control mode shown in FIG.

  Next, the detent mechanism 30 will be described. The detent lever 31 has a substantially fan shape, and a plurality of recesses 31b are formed on the outer periphery thereof. A roller (engaging member) 32a provided at an end of a detent spring 32 having one end fixed to a vehicle body (not shown) can be engaged with one of the recesses 31b. With this engagement, the rotational position of the control shaft 22, that is, a plurality of range positions (P-R-N-D-L) of the range switching valve 10 are determined. The recess 31b has a smoothly deep shape, and the detent spring 32 made of a spring material exerts an urging force downward in FIG. 1 when attached, so that the control shaft 22 can rotate freely. In this case, the roller 32a is stably held on any bottom of the recess 31b. The detent lever 31 and the detent spring 32 constitute a detent mechanism 30, that is, a drive mechanism.

  The range switching valve 10 is switched through the detent lever 31 by the rotation of the control shaft 22. At this time, at each range position of the range switching valve 10, the roller 32a engages with the adjacent recess 31b while overcoming the projection separating the recess 31b of the detent lever 31 against the biasing force of the detent spring 32. Repeat the operation.

  Next, basic control of the shift switching mechanism of the present embodiment will be described with reference to FIG. In step S101, the CPU 54 detects the current position of the shift lever SL from the signal from the range detector 52, and in step S102, compares it with the stored position to determine whether or not the shift lever SL has moved. to decide. If it is determined that the shift lever SL has moved, it is determined that the driver desires a shift, and power supply to the electric motor 20 is started in step S103.

  Further, the CPU 54 obtains the shift position of the shift lever SL in step S104, compares it with the rotational position of the control shaft 22 based on the signal from the rotation sensor 25, and obtains the deviation in step S105. The CPU 54 continues to supply power to the electric motor 20 based on the deviation, but the control shaft 22 rotates through the screw shaft 20a and the nut 21. The detent lever 31 is rotated while the roller 32a is moved to the concave portion 31b, and the range switching valve 10 is moved.

  The CPU 54 compares the deviation obtained in step S105 with a set value, and if it is equal to or greater than the set value, continues to supply power to the electric motor 20 and repeatedly obtains the deviation. On the other hand, when the deviation obtained in step S105 is less than the set value, the CPU 54 stops power supply to the electric motor 20 in step S107. At this time, if the roller 32a is not positioned at the bottom (predetermined position) of the recess 31b of the detent lever 31, the range switching valve 10 may be in an inappropriate position, and thus needs to be moved to an appropriate position. There is.

  When the range switching valve 10 is not in an appropriate position, the roller 32a is positioned on the slope of the recess 31b. Therefore, the roller 32a is biased toward the bottom of the recess 31b by the biasing force of the detent spring 32. Thereby, the detent lever 31 tries to move to the rotational position where the range switching valve 10 is set to an appropriate shift position. Here, in this embodiment, since the control shaft 22 and the electric motor 20 are connected by a low friction ball screw mechanism, if the power supply to the electric motor 20 is stopped, the control shaft 22 has a resistance. As a result, the rotational force (that is, a part of the urging force of the detent spring 32) is transmitted to the electric motor 20. That is, the range switching valve 10 moves to an appropriate position without supplying power or performing complicated position control. Therefore, the “set value” here means the shift position and the rotational position of the control shaft 22 that allow the roller 32a to be positioned on either of the slopes of the specific recess 31b with the target position of the roller 32a as the bottom. This is the deviation between them. Note that the “bottom part” that is the predetermined position does not need to be the deepest part of the recess 31b. For example, the “bottom part” is in a certain range across the deepest part, and an appropriate shift position is set by the range switching valve 10 positioned thereby. Any position that can be secured is sufficient.

  Further, in step S108, the CPU 54 stores the finally settled position of the roller 32a as an optimum angle of the control shaft 22, and uses it for the subsequent control.

  FIG. 3 is a diagram showing a modification of the present embodiment. FIG. 4 is a control circuit diagram of a motor according to this modification. In this modification, as shown in FIG. 3, the rotating shaft 20b of the electric motor 20 and the screw shaft 20a are separated, and further, a plastic gear 20c having a small number of teeth coupled to the rotating shaft 20b, and a screw By meshing with a plastic gear 20d having a large number of teeth coupled to the shaft 20a, the rotational force of the rotating shaft 20b can be decelerated and transmitted to the screw shaft 20a. The plastic gears 20c and 20d constitute a speed reduction mechanism.

  When the rated torque of the electric motor 20 is small, it is necessary to increase the torque by providing a speed reduction mechanism. However, if a metal gear pair is provided in the speed reduction mechanism, in addition to the weight increase, there is a problem of increased inertial force. Arise. In such a case, when the CPU 54 interrupts the power supply to the electric motor 20, the nut 21 may not stop immediately due to inertia and may greatly deviate from the target stop position. On the other hand, according to the present embodiment, by using the plastic gears 20c and 20d for the speed reduction mechanism, it is possible to achieve speed reduction while keeping the inertial force low, thereby facilitating braking control. it can.

  5-10 is a figure which shows the modification which attaches a plastic gear with respect to a screw shaft. In the modified example shown in FIG. 5, a male spline 120m is formed at the end of the screw shaft 120a, a female spline 120f is formed on the inner periphery of the plastic gear 120c, and these splines are engaged with each other, whereby the screw shaft The plastic gear 120c can be attached to the 120a in a relatively non-rotatable manner.

  In the modification shown in FIG. 6, the plastic gear 220c can be attached to the screw shaft 220a so as not to rotate relative to the screw shaft 220a by molding the plastic gear 220c at the end of the screw shaft 220a.

  In the modification shown in FIG. 7, a plastic gear 320c is molded on the outer periphery of a cylindrical base metal 320g, and a male spline 320m is formed on the end of the screw shaft 320a. By forming the female spline 320f and engaging the splines with each other, the plastic gear 320c can be attached to the screw shaft 320a so as not to be relatively rotatable.

  In the modification shown in FIG. 8, a key groove 420m is formed at the end of the screw shaft 420a, a key groove 420f is formed on the inner periphery of the plastic gear 420c, and a key 420g is inserted between these grooves, thereby The plastic gear 420c can be attached to the shaft 420a so as not to rotate relative to the shaft 420a.

  In the modification shown in FIG. 9, a plastic gear 520c is molded on the outer periphery of a cylindrical base metal 520g, and the base metal 520g is fitted and press-fitted into the end of the screw shaft 520a, whereby the screw shaft 520a. On the other hand, the plastic gear 520c can be attached in a relatively non-rotatable manner.

  In the modification shown in FIG. 10, a plastic gear 620c is molded on the outer periphery of a cylindrical base metal 620g, and after inserting the base metal 620g into the end of the screw shaft 620a, the pin 620h is inserted. By allowing the base metal 620g to penetrate the screw shaft 620a in the radial direction, the plastic gear 620c can be attached to the screw shaft 620a so as not to be relatively rotatable.

  In addition, as a raw material of a plastic gear, what mixed the glass fiber in the polyacetal is preferable. Alternatively, a plastic gear may be formed using a material impregnated with a lubricant.

  In FIG. 4, both terminals of the DC electric motor 20 are selectively connected to a power source E or a resistor R constituting a regenerative braking circuit. Such selection is made by operating the switch S, and the switch S is performed by the CPU 54. According to the present embodiment, after interrupting the power supply to the electric motor 20 by the operation of the switch S, the CPU 54 connects both terminals of the electric motor 20 to the resistor R immediately. At this time, although electric power is generated at both terminals of the electric motor 20, by consuming it with the resistance R, the rotating shaft 20b of the electric motor performs work, that is, is provided with regenerative braking. By utilizing such regenerative braking, the movement of the nut 21 can be stopped immediately against the inertia after the power supply to the electric motor 20 is interrupted. Instead of the resistor R, an energy recovery device such as a capacitor or a battery may be used.

  The CPU 54 detects the rotational speed of the rotating shaft 20b of the electric motor 20 and decelerates when it approaches the target position so that the convex portion 32a stays in the concave portion 31b of the detent lever 31 without decelerating and overrunning. It is also possible to control.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. For example, instead of providing the rotation sensor 25 for detecting the rotation position of the control shaft 22, a sensor 22 'for detecting the rotation axis of the electric motor 20, that is, the rotation position of the screw shaft 20a may be provided (see FIG. 1).

  The power transmission between the electric motor and the screw shaft is not limited to gears. For example, as shown in FIG. 11, a pulley 720B may be attached to the rotating shaft 720A of the electric motor 720, while a pulley 720D may be attached to the end of the screw shaft 720C, and the belt may be driven between both pulleys by a belt 720E. Of course.

10 range switching valve 20 electric motor 20a screw shaft 21 nut 22 control shaft 31 detent lever 31b recess 32 detent spring 32a roller

Claims (9)

A moving member;
A drive mechanism for driving the moving member to any one of a plurality of positions to be held;
An electric motor;
A power transmission mechanism that transmits power from the electric motor to the drive mechanism;
The drive mechanism includes a plurality of recesses provided corresponding to a plurality of positions to be held in the moving member, and an engagement member that can be selectively engaged with the recesses,
The power transmission mechanism includes a ball screw mechanism including a screw shaft, a nut, and a plurality of balls disposed between the screw shaft and the nut;
When the engagement member is not engaged with a predetermined position of any of the plurality of recesses in a state where power supply to the electric motor is substantially interrupted, the engagement member is The ball is urged toward any predetermined position, and using the urging force, the moving member is driven to one of the positions to be held and held there, and the ball The screw mechanism is capable of transmitting a part of the urging force to the electric motor.   The electric linear actuator according to claim 1, wherein the moving member is driven and held at the plurality of positions corresponding to a shift position of a transmission.   The driving mechanism includes a plurality of recesses and is rotatable, and includes a detent lever connected to the moving member, and the moving member is to be held in accordance with the rotation of the detent lever. The electric linear actuator according to claim 1, wherein the electric linear actuator is driven to a position of A sensor for detecting a rotation angle of the detent lever;
The electric linear actuator according to claim 3, wherein the electric motor is configured such that power supply is controlled based on an output of a sensor.   The electric linear actuator according to any one of claims 1 to 3, wherein the electric motor is configured such that power supply is controlled according to a rotation angle of a rotation shaft thereof.   6. The supply of electric power to the electric motor is interrupted before the moving member reaches any of the plurality of positions to be held. Electric linear actuator.   The electric linear actuator according to claim 1, wherein the power transmission mechanism includes a speed reduction mechanism using a plastic gear.   8. A regenerative braking circuit that electromagnetically brakes the electric motor, and after the supply of power is interrupted, the regenerative braking circuit is connected to the electric motor. An electric linear actuator according to any one of the above.   The electric linear actuator according to any one of claims 1 to 8, wherein the electric motor is decelerated before the moving member reaches any of the plurality of positions to be held.

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