JPH0953699A - Thrust actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify electronic wiring and reduce a cost, while realizing minia turizing of a device and lightening of its weight, by forming a structure which prevents a load from being applied to a power transmitting system after carry ing of a current to a motor is stopped. SOLUTION: In a power transmission mechanism transmitting rotational torque of a motor 2 to a rod 3, a torque limiter fixing transmitting torque is provided. In this torque limiter, a viscous material is sealed between an input side gear 8 and an intermediate rotary unit, and when generated relative rotation therebetween, transmitting torque is generated by viscous shearing resistance of the viscous material sealed between both the input side gear 8 and the intermediate rotary unit. This torque limiter has a transmitting torque characteristic in which a torque change relating to a rotational speed change of the input side gear 8 is decreased in the vicinity of prescribed torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thrust actuator for converting a rotational force of a motor into thrust in an axial direction to drive a rod, and more particularly to a switching device for switching between two-wheel drive and four-wheel drive in a four-wheel drive vehicle, Alternatively, it is suitable for use as a device for switching between a locked state and an unlocked state of a differential fixing device (commonly called differential lock).

[0002]

2. Description of the Related Art For example, as a switching device for switching between two-wheel drive and four-wheel drive in a four-wheel drive vehicle, Japanese Examined Patent Publication No. 5-55331.
The one disclosed in Japanese Patent Application Laid-Open Publication No. H10-260, 1993 is known. In this switching device, a slider is operated by a shift fork fixed to a fork shaft, and a spline provided on a front wheel side drive shaft and a spline provided on a rear wheel side drive shaft are connected via the slider. By doing so, it becomes four-wheel drive, and when separated, it becomes two-wheel drive. A thrust actuator is used as a means for reciprocating the fork shaft in the axial direction.

In a thrust actuator, the rotational force of a motor is increased by a combination of gears and is transmitted to a pinion gear, which is then transmitted from a pinion gear to a rack gear arranged coaxially with a rod and converted into thrust (power in the axial direction). . A torsion spring for storing a reaction force (elasticity) when the rod is locked is arranged between the motor and the rod.

The operation of this thrust actuator will be briefly described with reference to the time chart shown in FIG. When the start switch is turned on and the motor rotates, the rod is actuated by the thrust to drive the fork shaft connected to the rod. Here, even when the rod is locked (that is, when the movement of the fork shaft is stopped because the slider does not mesh with the spline / time point X in FIG. 7),
When the torsion spring receives the rotational force of the motor and is twisted, the motor continues to rotate without being locked, and after a predetermined amount of rotation, the energization is stopped (time Y in FIG. 7). In this state, waiting for the slider and the spline to mesh with each other, and when the slider and the spline mesh with each other (time Z in FIG. 7), the rod is operated by the elastic force stored in the torsion spring.

[0005]

However, the conventional thrust actuator has the following problems. B) A system in which the power supply to the motor is stopped after the motor has rotated a predetermined amount. Therefore, in order to know the timing of stopping the power supply to the motor, the amount of rotation (rotation angle) of the motor
Is required, and a signal line for sending a signal from this detection device to a control unit (ECU) for controlling the energization of the motor is required, which results in a high system cost.

(B) The torsion spring is arranged on the side closer to the motor (the amount of deceleration can be reduced) for the purpose of reducing the torsion torque. Therefore, the torsion amount (rotation amount) of the torsion spring is often set to a large value, and since the angle is usually large at 180 degrees,
It requires a spring with an extremely small spring constant. In order to realize this, the number of turns of the spring must be extremely increased, the torsion spring itself becomes large, and the size of the entire apparatus is increased. If a spring with a large spring constant is used, the degree of increase in the output load of the rod increases according to the amount of twisting of the motor, resulting in an overload, which is difficult to apply. On the other hand, when the torsion spring is provided on the rod side, the angle of twist becomes smaller, but the twist torque needs to be increased, and the torsion spring itself also becomes large.

C) When the rod is locked in the above explanation of the operation, that is, in the so-called "waiting state" until the slider engages with the spline, the reaction force accumulated in the torsion spring prevents the motor from rotating in the reverse direction. In addition, it is necessary to provide a worm gear with a small lead angle. However, even after the slider is engaged with the spline and the operation of the rod is completed, the set load of the torsion spring (torsion torque due to the residual torsion) is applied to the rod.
Therefore, if the motor cannot rotate in the reverse direction due to the worm gear having a small lead angle, a load is constantly applied to each gear and shaft for transmitting power between the motor and the rod, the housing supporting the shaft, and the like. For this reason, it is necessary to use a gear, a shaft, and a housing having high proof stress and high creep strength, which leads to an increase in size of the device and an increase in cost.

The present invention has been made in view of the above circumstances, and realizes downsizing and weight reduction of a device as a structure in which a load is not applied to a power transmission system after power supply to a motor is stopped and electric wiring is simplified. The purpose of the present invention is to provide a thrust actuator in which the cost is reduced.

[0009]

[Means for Solving the Problems]

(Structure of Claim 1) A motor that generates a rotational torque by being energized for a predetermined time, a rod that is reciprocally movable in the axial direction, and a rod that is provided between the output shaft of the motor and the rod, And a power transmission mechanism for converting the rotational torque of the motor into thrust in the axial direction and transmitting the thrust to the rod. The power transmission mechanism includes an input side rotation member and an output side rotation member that are provided so as to be relatively rotatable. A viscous body is sealed in between, and when a relative rotation occurs between the input side rotation member and the output side rotation member, a viscous body has a torque limiter that generates a transmission torque by viscous shear resistance. Characterize.

(Operation of Claim 1) Rotational torque generated by the motor is converted into axial thrust by the power transmission mechanism having a torque limiter and transmitted to the rod. Here, the torque limiter generates a transmission torque by viscous shear resistance of the viscous body enclosed between the input side rotating member and the output side rotating member when relative rotation occurs. However, the viscous shear resistance value of the viscous body increases as the rotation speed increases while the rotation speed of the input side rotation member is low (the relative rotation speed between the two is small). When it becomes larger than a certain fixed value (the relative rotational speed of both is large), it reaches the ceiling and the generated transmission torque becomes constant. Therefore, even when the load applied to the power transmission system from the motor to the rod suddenly increases (for example, when the rod locks during operation), the torque limiter absorbs the impact force due to the rotational inertia of the power transmission system. Do not overload the power transmission system.

According to the present invention, since the torque limiter is provided in the power transmission mechanism, if the motor is stopped after the operation is completed, the input side rotating member and the output side rotating member of the torque limiter can be separated. Since the relative rotation speed becomes 0 and no transmission torque is generated, no load remains in the power transmission system. Therefore, it is possible to reduce the size and weight (resin) of each component of the power transmission mechanism (eg, gear, shaft, bearing, etc.). Further, since the transmission torque (that is, the thrust) can be kept constant by the torque limiter, it is not necessary to use the torsion spring of the conventional device, and the size of the entire device can be reduced. Further, according to the configuration of the present invention, it is not necessary to detect the rotation amount of the motor in order to know the power supply stop timing to the motor as in the conventional device. Therefore, the electric wiring can be simplified and the cost can be reduced accordingly. Can be planned.

(Structure of Claim 2) In the thrust actuator according to Claim 1, the torque limiter is adapted to the rotation speed change of the input side rotation member within the fluctuation range of the rotation torque characteristic of the motor. It is characterized by having a transmission torque characteristic in which the viscous shear resistance value of the viscous body is substantially constant. (Operation and Effect of Claim 2) Within the fluctuation range of the rotation torque characteristic of the motor, a substantially constant transmission torque can be generated even if the rotation speed of the input side rotation member of the torque limiter changes, so that it is transmitted to the rod. Thrust can be made almost constant.

(Structure of Claim 3) In the thrust actuator according to claim 1 or 2, the torque limiter has a characteristic that the transmission torque decreases as the ambient temperature increases, and the ambient temperature is 100 ° C. It is characterized in that the degree of decrease in the transmission torque is greater when the temperature is 100 ° C. or higher than when the temperature is less than 100 ° C. According to the present invention, since the transmission torque of the torque limiter has a characteristic that it decreases with an increase in the ambient temperature (in particular, the degree of decrease is large at 100 ° C. or higher), the power transmission mechanism It is possible to reduce the weight and the cost by making the constituent parts made of resin. That is, when resin components are used, the ambient temperature is 100 ° C.
At the above high temperatures, there is a risk of damage due to strength reduction, but damage at high temperatures can be avoided if the torque limiter's transmission torque is greatly reduced at 100 ° C or higher.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the thrust actuator of the present invention is applied to a switching device for switching between two-wheel drive and four-wheel drive of a four-wheel drive vehicle will be described with reference to the drawings. (First Embodiment) FIG. 1 is a plan view showing the internal structure of a thrust actuator (with the upper case removed), and FIG. 2 is a side sectional view showing the internal structure of the thrust actuator. First, the structure of the switching device 100 that switches between two-wheel drive and four-wheel drive will be described with reference to FIG. Switching device 10
0 is a spline 111 provided on the outer periphery of the front wheel drive shaft 110, and a spline 12 provided on the rear wheel drive shaft 120.
1, a slider 130 provided so as to be engageable with the splines 111 and 121 of the both, a fork shaft 150 to which a shift fork 140 for operating the slider 130 is fixed, and the like.

Driving force is transmitted from the engine to the front wheel drive shaft 110 via a transmission (not shown), and the front wheel drive shaft 110 constantly rotates during operation of the engine (rear wheel drive shaft 1).
20 may be a structure in which the driving force of the engine is transmitted).
The rear wheel drive shaft 120 is arranged to face the front wheel drive shaft 110 in the axial direction, and the bearing 1 is attached to an end portion of the front wheel drive shaft 110.
It is rotatably supported via 60. Slider 13
0 is the spline 1 of the front wheel drive shaft 110 when driving two wheels
11 is engaged with the rear wheel drive shaft 12 when moving from 2 wheel drive to 4 wheel drive.
It also meshes with the 0 spline 121 (a state in which it meshes with both splines 111 and 121). That is, the slider 130 is operated by the shift fork 140 fixed to the fork shaft 150, and the spline 111 of the front wheel drive shaft 110 and the rear wheel drive shaft 1 are operated via the slider 130.
The 20 splines 121 are connected to form four-wheel drive, and the splines 121 are separated to form two-wheel drive.

The thrust actuator 1 drives and operates the fork shaft 150. As shown in FIGS. 1 and 2, the thrust actuator 1 receives a current and generates a rotational torque.
A power transmission mechanism (which will be described later) that transmits the rotational torque of the motor 2, a rod 3 that reciprocates in the axial direction by receiving the power (thrust) transmitted by the power transmission mechanism, and a case 4 that houses each component. Etc. The motor 2 is energized and rotated by an electronic control unit (ECU) (not shown) for a predetermined time (for example, 1 second).

The power transmission mechanism is attached to the output shaft 2a of the motor 2, and is a worm gear 5 that rotates integrally with the output shaft 2a, and a worm wheel 6 that meshes with the worm gear 5.
Small diameter gear 7 provided coaxially with worm wheel 6, input side gear 8 meshing with small diameter gear 7, output side gear 9 coaxially arranged with input side gear 8, plate gear 10 meshing with output side gear 9, plate gear The pinion gear 11 rotates integrally with the gear 10, the rack gear 12 meshes with the pinion gear 11, and the like. Worm gear 5
Uses a motor having a large lead angle (pitch) so that the motor 2 can rotate in the reverse direction when the power supply to the motor 2 is stopped. The worm wheel 6 and the small-diameter gear 7 are integrally provided with a support shaft 13 rotatably supported by the case 4 via a bearing (not shown), and rotate in synchronization with the support shaft 13.

The input side gear 8 and the output side gear 9 are, as shown in FIG. 3, a torque limiter TL together with the intermediate rotor 14.
(Described later). The plate gear 10 is provided in a fan shape as shown in FIG.
It is rotatably supported by the support shaft 15 at a (see FIG. 1). The pinion gear 11 is the boss portion 1 of the plate gear 10.
0a is extended in the axial direction and is integrally provided on the outer periphery of the extended portion. The rack gear 12 is integrally provided at the end of the rod 3 and converts the rotational force of the pinion gear 11 into thrust (power in the axial direction).

The rod 3 includes a case 4 (upper case 4
b) is supported by the seal member 16 so as to be able to reciprocate, and the tip portion projects to the outside of the case 4 (left side in FIG. 2),
It is connected to the fork shaft 150 of the switching device 100 via a connecting pin 3a (see FIG. 4) provided at the tip thereof. The rod 3 receives the thrust converted by the rack gear 12 and operates integrally with the rack gear 12 (moves in the axial direction), whereby the fork shaft 1
50 is driven.

The case 4 is composed of a lower case 4a for accommodating the respective components, and an upper case 4b which is airtightly fitted over the opening of the lower case 4a via a seal member 17, both of which are fastened and fixed by screws 18. There is.
The lower case 4a is integrally provided with a waterproof connector 20 from which the energizing terminal 19 of the motor 2 is taken out.

In the torque limiter TL, the intermediate rotating body 14 is rotatably fitted to the inner periphery of the input side gear 8 so that the inner peripheral surface of the input side gear 8 and the outer peripheral surface of the intermediate rotating body 14 are connected to each other. The viscous body S (for example, silicon oil) is enclosed in the annular volume chamber 21 formed between them. Also, the output side gear 9
Is fitted to the outer circumference of a rotary shaft 23 rotatably supported by the case 4 via a bearing 22 (see FIG. 1), and is fixed to the intermediate rotating body 14 by a snap fit 9a provided on itself. It rotates integrally with the intermediate rotating body 14. The volume chamber 21 in which the viscous body S is enclosed is hermetically sealed by the sealing materials 24 and 25 mounted on the fitting surfaces of the input gear 8 and the intermediate rotating body 14.

This torque limiter TL has an input side gear 8
When relative rotation occurs between the intermediate rotating body 14 (output side gear 9) and the intermediate rotating body 14 (output side gear 9), a predetermined transmission torque is generated by viscous shear resistance of the viscous body S enclosed between the two. That is, when the input side gear 8 rotates by receiving the rotation torque of the motor 2,
Since relative rotation occurs between the input-side gear 8 and the intermediate rotating body 14, the rotation of the input-side gear 8 is transmitted to the intermediate rotating body 14 by viscous shear resistance of the viscous body S enclosed between them. However, the viscous shear resistance of the viscous body S is
The rotational speed of the input gear 8 increases as the rotational speed of the input gear 8 increases, but the rate of change decreases as the rotational speed of the input gear 8 increases, and becomes a substantially constant value at a certain rotational speed or higher. Therefore, the transmission torque of the torque limiter TL also changes according to the viscous shear resistance value of the viscous body S, and the transmission torque becomes substantially constant even if the input gear 8 reaches a certain rotation speed or more.

Therefore, as shown in FIG. 5, if the transmission torque characteristic of the torque limiter TL is set so that the torque change with respect to the change in the rotation speed of the input side gear 8 is small near a predetermined torque, the torque characteristic of the motor 2 becomes the battery voltage. Even if it fluctuates due to fluctuations in the temperature of the motor 2 or heat generated by the motor 2 itself, the fluctuation of the torque transmitted to the output side gear 9 can be reduced within the fluctuation range (range of T1 to T2). In FIG. 5, a graph a is a transmission torque characteristic of the torque limiter TL (relationship between rotation speed and torque), and a graph b is a rotation of the input side gear 8 that rotates by receiving the rotation torque of the motor 2 (in the case of maximum value) Number-torque characteristics Graph c; Rotational speed-torque characteristics of the input side gear 8 that rotates by receiving the rotation torque (in the case of the minimum value) of the motor 2 T1; Minimum transmission torque value of the output side gear 9 T2; Output side gear 9 Transmission torque maximum value T3; residual torque remaining in the output gear 9 when the input gear 8 is stopped (= motor 2 is stopped).

Next, the operation of this embodiment will be described. However,
The following description is the operation when switching from two-wheel drive to four-wheel drive. When the motor 2 is rotated by being energized by the ECU, the rotational torque of the motor 2 is transmitted by each component of the power transmission mechanism and converted into an axial thrust between the pinion gear 11 and the rack gear 12. The thrust converted by the rack gear 12 operates the rod 3 (moves to the right in FIG. 2) to drive the fork shaft 150. As a result, the slider 130 moves (moves to the right in FIG. 4) via the shift fork 140 fixed to the fork shaft 150, and the rear wheel drive shaft remains engaged with the spline 111 provided on the front wheel drive shaft 110. 1
The front wheel drive shaft 110 and the rear wheel drive shaft 120 are connected to each other by meshing with a spline 121 provided on the wheel 20, and the two-wheel drive is switched to the four-wheel drive.

Here, when the slider 130 moving via the shift fork 140 meshes with the spline 121 of the rear wheel drive shaft 120, it may come into contact with the end face of the spline 121 and smooth meshing may not be performed.
In this case, as the front wheel drive shaft 110 rotates, the slider 1
The movement of the slider 130 is stopped until the tooth traces of the 30 and the spline 121 match each other. As a result, the load applied to each gear of the power transmission mechanism increases rapidly because the rod 3 locks (stops operation) when the slider 130 stops moving, but the torque limiter TL absorbs the impact force associated with the rapid increase in load. , No excessive load is applied to the power transmission mechanism. After that, as the front wheel drive shaft 110 rotates, the tooth traces of the slider 130 and the spline 121 of the rear wheel drive shaft 120 coincide with each other and start to mesh with each other.
The rod 3 moves again to move the slider 130 and the spline 1
Complete engagement with 21.

After the meshing, the fork shaft 150 further moves in a state where the slider 130 and the spline 121 mesh with each other, and the shift fork 140 comes into contact with the stopper 170 to stop. When the shift fork 140 comes into contact with the stopper 170 and stops, the load applied to each gear of the power transmission mechanism increases again. However, since the torque limiter TL absorbs the impact force as described above, the power transmission mechanism receives the impact force. No excessive load is applied. Then, after a lapse of a predetermined time (1 second) from the start of energization of the motor 2, the energization is stopped, and the switching operation from the two-wheel drive to the four-wheel drive ends.

(Effect of the first embodiment) In this embodiment, the torque limiter TL is provided in the power transmission mechanism, so that if the motor 2 is stopped after the operation is completed, the input side gear 8 and the output side gear of the torque limiter TL will be described. 9 (intermediate rotator 14) has a relative rotational speed of 0 and no transmission torque is generated, so that no load remains in the power transmission system. Therefore, each component of the power transmission mechanism (for example, each gear, shaft, bearing, etc.) can be miniaturized and can be made lightweight by using resin, and the cost can be reduced accordingly. Further, even if the rod 3 locks and the load applied to each gear of the power transmission mechanism increases rapidly, the torque limiter TL can absorb the impact force due to the sudden increase of the load, so that the power transmission system (motor 2, power transmission mechanism, rod 3) and the life of the member on the load side can be extended.
Further, since the transmission torque (that is, the thrust) can be kept constant by the torque limiter TL, it is not necessary to use the torsion spring of the conventional device, and the size of the entire device can be reduced.

Further, according to the configuration of this embodiment, the motor 2
The energization time is set in advance, and energization is stopped after a predetermined time has elapsed from the start of energization. Therefore, since it is not necessary to detect the rotation amount of the motor 2 in order to know the power supply stop timing to the motor 2 as in the conventional device, the electric wiring is simplified (system simplification) and the cost is reduced accordingly. Can be achieved. It should be noted that the above-described operation is performed from 2 wheel drive to 4
Although the case of switching to the four-wheel drive has been described, it goes without saying that the same operation and effect can be obtained in the case of switching from the four-wheel drive to the two-wheel drive.

(Second Embodiment) This embodiment shows an example in which the transmission torque characteristic of the torque limiter TL changes depending on the ambient temperature. The transmission torque characteristic of the torque limiter TL can be adjusted depending on the grade of the viscous body S to be enclosed, but generally, the transmission torque characteristic is such that the transmission torque decreases as the ambient temperature rises. Therefore, as shown in FIG. 6, if the transmission torque is greatly reduced at an ambient temperature of 100 ° C. or higher, a resin whose strength is reduced at a high temperature of 100 ° C. or higher (for example, a polyacetal resin is 10
Even if it is used), the damage at high temperature can be avoided. In the case of the present embodiment, it can be widely used by changing the characteristics of the torque limiter TL according to the temperature-strength characteristics of the resin used.

[Modification] In the present embodiment, the worm gear 5 having a large advance angle is used so that the motor 2 can rotate in the reverse direction when the motor is stopped. However, by using the torque limiter TL, the residual load when the motor is stopped is used. Since it can be eliminated, the worm gear 5 having a small advance angle (= large reduction ratio) may be used. Further, a spur gear having a small diameter may be used instead of the worm gear 5. In this embodiment, a switching device 100 for switching the thrust actuator 1 between two-wheel drive and four-wheel drive.
However, it can also be applied to a switching device for switching between the locked state and the unlocked state of the differential fixing device.

[Brief description of drawings]

FIG. 1 is a plan view showing an internal structure of a thrust actuator.

FIG. 2 is a side sectional view showing an internal structure of a thrust actuator.

FIG. 3 is a sectional view of a torque limiter.

FIG. 4 is an overall sectional view of a switching device including a thrust actuator.

FIG. 5 is a graph showing a transmission torque characteristic of a torque limiter.

FIG. 6 is a graph showing a transmission torque characteristic of a torque limiter with respect to an ambient temperature (second embodiment).

FIG. 7 is a time chart relating to the operation of the conventional device.

[Explanation of symbols]

 1 Thrust Actuator 2 Motor 2a Output Shaft 3 Rod 5 Worm Gear (Power Transmission Mechanism) 6 Worm Wheel (Power Transmission Mechanism) 7 Small Diameter Gear (Power Transmission Mechanism) 8 Input Gear (Input Side Rotating Member) 9 Output Gear (Output Side) Rotating member 10 Plate gear (power transmission mechanism) 11 Pinion gear (power transmission mechanism) 12 Rack gear (power transmission mechanism) 14 Intermediate rotating body (output side rotating member) S Viscous body TL Torque limiter

Claims (3)

[Claims] 1. A motor that generates a rotational torque by being energized for a predetermined time, a rod that is reciprocally movable in an axial direction, and a rod that is provided between an output shaft of the motor and the rod,
And a power transmission mechanism that converts the rotational torque of the motor into thrust in the axial direction and transmits the thrust to the rod. The power transmission mechanism includes an input side rotation member and an output side rotation member that are provided so as to be relatively rotatable. When a viscous body is enclosed between the input side rotation member and the output side rotation member, relative rotation occurs,
A thrust actuator having a torque limiter for generating a transmission torque by viscous shear resistance of the viscous body. 2. The torque limiter is a transmission torque characteristic in which a viscous shear resistance value of the viscous body is substantially constant with respect to a change in the rotation speed of the input side rotation member within a variation range of the rotation torque characteristic of the motor. The thrust actuator according to claim 1, further comprising: 3. The torque limiter has a characteristic that the transmission torque decreases as the ambient temperature rises, and is 100% lower than when the ambient temperature is lower than 100 ° C.
The thrust actuator according to claim 1 or 2, wherein the degree of decrease in the transmission torque is greater when the temperature is equal to or higher than ° C.