JP4632985B2 - Linear actuator - Google Patents

Description

  The present invention relates to a linear motion actuator suitable for a vehicle height adjustment device for a vehicle, and more particularly to a technique for realizing a reduction in size, weight, smooth operation, and the like.

  As a vehicle height adjusting device provided in the suspension of an automobile, a hydraulic type or a hydropneumatic type is generally used, but the control accuracy is high and the system configuration is simplified (a hydraulic unit, an accumulator, etc. are not required). Therefore, an electric type equipped with a worm reduction mechanism, a ball screw type feeding mechanism, and the like has been developed (see Patent Document 1). However, since the vehicle height adjusting device of Patent Document 1 uses a worm speed reduction mechanism having a low mechanical efficiency and an expensive ball screw type feed mechanism, not only an increase in torque loss and power consumption is inevitable, but the device However, it is difficult to reduce the size and the cost.

Therefore, the present inventors have housed two driven gears (fixed side driven gear and moving side driven gear) having different numbers of teeth and a single drive gear for driving these driven gears, and between the two driven gears. The application of a linear motion actuator (see Patent Document 2) provided with a feed screw mechanism to a vehicle height adjusting device was examined. In the linear actuator of Patent Document 2, the feed screw mechanism is operated by the rotational difference between the two driven gears driven by the drive gear, so that a large reduction ratio can be realized with a compact configuration and the torque cross during operation is relatively small. Therefore, when applied to a vehicle height adjusting device, the electric motor can be reduced in size and power consumption can be reduced, and can be installed on a suspension for an automobile with limited space.
JP-A-11-108100 Japanese Patent Publication No.8-19971

  However, the linear motion actuator of Patent Document 2 has the following problems due to the radial load acting on the moving driven gear. In such a linear motion actuator, the fixed driven gear can be supported by the housing via the bearing, but the moving driven gear cannot be supported by the bearing because it moves straight by the feed screw mechanism. As a result, a radial load generated by meshing with the drive gear is applied as a side pressure to the screwing surface of the feed screw mechanism, making it difficult to perform a smooth feeding operation, and also causing wear of the screwing surface due to long-term use. There was a problem. In addition, since it is necessary to set a large amount of movement of the moving driven gear in the vehicle height adjusting device, there is a possibility that the feed screw mechanism may be locked (locked) when the fixed driven gear and the moving driven gear are separated from each other. there were.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a linear motion actuator that achieves a reduction in size and weight, smooth operation, and the like.

  A linear motion actuator according to a first aspect of the present invention includes a housing that constitutes an outer shell of the apparatus, a first rotor that is rotatably supported by the housing and has a first driven gear formed on the outer periphery thereof, and a linear motion that is linear. A first rotor coupled to the first rotor through a feed means for converting into motion and having a second driven gear formed on the outer periphery thereof, and a first drive rotatably supported by the housing and meshing with the first driven gear A drive shaft having a gear, a second drive gear meshing with the second driven gear, and a rotational drive means for rotationally driving the drive shaft; a tooth between the first driven gear and the first drive gear In a linear motion actuator in which the number ratio of teeth between the second driven gear and the second drive gear is different with respect to the number ratio, A radial support means connected to the housing and supporting the second rotor in a radial direction at a position where the angular phase differs by about 180 ° with respect to the meshing portion of the second drive gear and the second driven gear. Features.

  A linear motion actuator according to a second aspect of the present invention is the linear motion actuator according to the first aspect, wherein the drive shaft has a hollow cylindrical shape, and the first drive gear circumscribes the first driven gear. The second drive gear is an internal gear that circumscribes the second driven gear, and the radial support means is interposed between the drive shaft and the second rotor, Along with this, a support piece that moves linearly is provided.

Further, linear actuator according to the invention of claim 3 is the linear actuator according to claim 2, wherein said supporting piece having a supporting portion made of sliding contact oleoresin to the second rotor .

Further, linear actuator according to the invention of claim 4 is the linear actuator according to claim 2, characterized in that the support piece holding the rolling contact rolling element to the second rotor.

  According to the linear motion actuator of the present invention, even if a radial load is applied due to meshing with the drive gear, the movement-side driven gear is supported by the radial support means, so that the displacement in the radial direction is suppressed, and the feed means It is difficult for the operation to be hindered due to the side pressure being applied to the screwing surface, and the screwing surface to be worn or bitten.

  Hereinafter, an embodiment in which the present invention is applied to a rear suspension of a four-wheel vehicle and a partial modification thereof will be described in detail with reference to the drawings.

[Embodiment]
1 is a perspective view showing a rear suspension according to the embodiment, FIG. 2 is an enlarged vertical sectional view of a portion II in FIG. 1, and FIG. 3 is a plan view showing a meshed state of a drive shaft, an idler gear, and a drive pinion. It is. 4 is a perspective view showing a combination state of each gear and the radial support mechanism, FIG. 5 is an exploded perspective view showing a configuration of the radial support mechanism, and FIG. 6 is a perspective view showing a back surface of the slider. FIG. 7 is a cross-sectional view showing the operation of the radial support mechanism.

<< Configuration of Embodiment >>
<Suspension configuration>
As shown in FIG. 1, the rear suspension 1 of the embodiment is a so-called multilink suspension, and includes a knuckle 2 that rotatably supports a wheel W via a hub bearing (not shown), and an upper end of the knuckle 2. An upper arm 3 connected to the vehicle body side, a lower arm 4 connecting the lower end of the knuckle 2 to the vehicle body side, a trailing arm 5 connecting the front end of the knuckle 2 to the vehicle body side, a lower arm 4 and a suspension member (vehicle body side member) 6 Between the spring 7 and the suspension member 6, between the spring 7 and the suspension member 6, between the spring 7 and the suspension member 6. The installed vehicle height adjusting device (linear motion actuator) 9 is a main component. 1 is an ECU (Electronic Control Unit) that drives and controls the vehicle height adjusting device 9, and is mounted in a vehicle compartment or a trunk room.

<Vehicle height adjustment device>
As shown in FIG. 2, the vehicle height adjusting device 9 includes a housing 21 having an upper half 21 a and a lower half 21 b, which is divided into upper and lower parts, and a cylindrical holding cylinder portion 21 c projecting downward from the center. A first rotor 24 rotatably supported by an upper half 21a via an angular bearing 22, a cylindrical second rotor 25 coupled to the first rotor 24 so as to be relatively rotatable, and a holding cylinder portion 21c of the housing 21 are surrounded. A sheet holder 27 having a cylindrical portion 27a and connected to the lower end of the second rotor 25 via an angular bearing 26, and an upper spring seat 28 fixed to the lower surface of the upper end of the sheet holder 27 and supporting the upper end of the spring 7. , A pair of upper and lower needle bearings that surround the first and second rotors 24, 25 and are housed in the housing 21. , A drive shaft 31 supported rotatably via 29, an idler gear 33 rotatably supported via a needle bearing 32 to the housing 21, and rotatably supported via a pair of upper and lower ball bearings 34 to the housing 21. The drive pinion 35, the electric motor 36 that is fastened to the housing 21 and drives the drive shaft 31, the rotary encoder 37 that detects the rotation amount of the drive shaft 31 and outputs it to the ECU 10, and the housing 21 holds the second rotor 25. A radial support mechanism 38 for supporting in the radial direction is a main component.

  In the case of this embodiment, the cylindrical part 27a of the sheet holder 27 is in sliding contact with the outer peripheral surface of the holding cylindrical part 21c of the housing 21 via a cylindrical bearing 51 fixed to the upper part thereof. The holding cylinder portion 21 c of the housing 21 is in sliding contact with the outer peripheral surface of the second rotor 25 through a cylindrical bearing 52 fixed to the lower end thereof. In the case of this embodiment, the cylindrical bearings 51 and 52 are made of oil-containing resin such as polyacetal.

A disk-shaped gear portion 53 is formed on the outer periphery of the upper portion of the drive shaft 31. As shown in FIG. 3, this gear portion 53 is connected to a drive pinion 35 via an idler gear 33, thereby providing a primary reduction mechanism. It is composed. In the case of this embodiment, since the gear portion 53 has 72 teeth and the drive pinion 35 has 11 teeth, the reduction ratio RP of the primary reduction mechanism is
RP = 72/11 = 6.545
It becomes.

  As shown in FIG. 2, the first rotor 24 includes a cylindrical shaft portion 24a and a gear portion 24b having a larger diameter than the shaft portion 24a formed at the upper end of the shaft portion 24a. The second rotor 25 includes a cylindrical portion 25a that is fitted on the shaft portion 24a of the first rotor 24, and a gear portion 25b that is formed on the upper portion of the cylindrical portion 25a. A male screw portion 24 c is formed on the outer periphery of the shaft portion 24 a of the first rotor 24, while a female screw portion 25 c that engages with the male screw portion 24 c of the first rotor 24 is formed on the inner periphery of the cylindrical portion 25 a of the second rotor 25. The feed screw mechanism (feed mechanism) 39 is formed by the male screw portion 24c and the female screw portion 25c. 2 is a stopper fastened to the lower end in the cylindrical portion 25a of the second rotor 25, and a metal touch with the second rotor 25 when the shaft portion 24a of the first rotor 24 is lowered. To prevent.

  A first driven gear 41 having the number of teeth Za (35 in this embodiment) is formed on the outer periphery of the gear portion 24b of the first rotor 24, and the number of teeth Zb (present) is formed on the outer periphery of the gear portion 25b of the second rotor 25. In the case of the embodiment, the second driven gear 42 of 36) is formed. On the other hand, on the inner periphery of the drive shaft 31, the first drive gear 43 having the number of teeth Zc meshed with the first driven gear 41 (40 in this embodiment) and the number of teeth Zd meshed with the second driven gear 42 (this embodiment). In this case, two internal gears with the second drive gear 44 of 40) are formed. The first drive gear 43 and the first driven gear 41 have substantially the same axial length, but the second drive gear 44 has a length so that the meshing is maintained even if the second driven gear 42 moves up and down. The axial length is set sufficiently larger than the axial length of the second driven gear 42. Hereinafter, the first drive gear 43 and the first driven gear 41 will be described as a first gear set, and the second drive gear 44 and the second driven gear 42 will be described as a second gear set.

  The rotary encoder 37 is composed of an encoder disk 37 a fixed to the upper portion of the drive shaft 31 and a sensor 37 b attached to the upper half 21 a of the housing 21. During driving of the vehicle, a detection signal is constantly output from the sensor 37b of the rotary encoder 37 to the ECU 10, and the ECU 10 feedback-controls the vehicle height adjusting device 9 based on this detection signal.

<Radial support mechanism>
As shown in FIGS. 4 and 5, the radial support mechanism 38 includes a guide plate 61 whose upper and lower ends are held by the housing 21, a slider 62 that slides up and down while being guided by the inner surface of the guide plate 61, and a slider 62. The upper and lower washers 63 are fixed to each other, and the upper and lower adjustment blocks 64 and 65 are interposed between the guide plate 61 and the housing 21. The radial support mechanism 38 has an angular phase of about 180 ° with respect to the meshing portion of the second driven gear 42 and the second drive gear 44 so as to bias the second rotor 25 toward the axial center (left side in FIG. 2). The slider 62 is installed at a different position, and the slider 62 moves up and down as the second rotor 25 moves up and down.

  As shown in FIG. 5, the guide plate 61 is a relatively long steel plate press-formed product having an arcuate cross section, and includes a guide hole 61 a drilled in the longitudinal direction, an upper half 21 a and a lower half 21 b of the housing 21. And a pair of upper and lower insertion portions 61b and 61c that are respectively inserted into the two. The slider 62 is an oil-impregnated resin injection-molded product having an arcuate cross section. As shown in FIGS. 5 and 6, the slider 62 is provided in a recess 62a in which the gear portion 25b of the second rotor 25 is loosely fitted, and in the upper and lower portions of the gear portion 25b. A pair of sliding contact portions 62 b and 62 c that are in sliding contact with each other, and an engaging convex portion 62 d that fits into the guide hole 61 a of the guide plate 61 are provided. The washer 63 is an arc-shaped steel plate stamped product, and is fixed to the upper and lower ends of the recess 62 a of the slider 62 to prevent contact between the gear portion 25 b of the second rotor 25 and the slider 62. The adjustment blocks 64 and 65 are manufactured by resin injection molding or the like, and various thicknesses are prepared so that the contact pressure between the second rotor 25 and the slider 62 can be adjusted.

<< Operation of Embodiment >>
When the vehicle starts driving and there is an operation of the vehicle height adjustment switch by the driver or a change in the vehicle driving condition (change from normal driving to rough road driving or high speed driving, etc.), the ECU 10 After setting the ground clearance, a drive current is output to the electric motor 36 of each vehicle height adjusting device 9.

When the electric motor 36 is activated, the drive pinion 55 fixed to the output shaft 36 a rotates in either the forward or reverse direction, and the drive shaft 31 is rotationally driven via the idler gear 33. Then, the first driven gear 41 (namely, the first rotor 24) meshed with the first drive gear 43 of the drive shaft 31 and the second driven gear 42 (namely, the second rotor 25) meshed with the second drive gear 44 are obtained. It is rotationally driven in the same direction. At this time, the reduction ratio R1 of the first gear set and the reduction ratio R2 of the second gear set are respectively
R1 = Za / Zb = 36/40 = 0.900
R2 = Zc / Zd = 35/40 = 0.875
It becomes.

In the case of the present embodiment, the reduction ratio R1 of the first gear set and the reduction ratio R2 of the second gear set are very slightly different. Therefore, when the drive shaft 31 rotates, the first rotor 24 and the second rotor 25 are slightly different. The second rotor 25 moves up and down relative to the first rotor 24 by differential rotation and the action of the feed screw mechanism 39. As a result, the upper spring seat 28 pressed against the lower surface of the second rotor 25 via the angular bearing 26 and the seat holder 27 also moves up and down, and the suspension member 6 that is the vehicle body side member and the lower arm 4 that is the wheel side member The distance between them (ie, the vehicle height) changes. At this time, if the ratio of the rotational speed of the drive shaft 31 and the rotational speed of the feed screw mechanism 39 is the total reduction ratio RT, the total reduction ratio RT has the reduction ratio RP of the primary reduction mechanism described above.
RD = RP.R1.R2 / (R1-R2)
= 6.545.0.900.0.875 / (0.900-0.875) = 206.2
As a result, the electric motor 36 can be downsized and power consumption can be reduced.

  On the other hand, when the vehicle height adjusting device 9 is operated, a radial load acts on the second driven gear 42 (that is, the second rotor 25) by meshing with the second drive gear 44 as shown by an arrow in FIG. To do. However, in the case of the present embodiment, the second rotor 25 is supported by the slider 62 of the radial support mechanism 38 at a position where the angular phase differs by approximately 180 ° with respect to the meshing portion, and therefore is almost displaced in the radial direction. No. As a result, the side pressure is not applied to the feed screw mechanism 39, a smooth feed operation is realized, and there is no possibility that the threaded surface wears or the feed screw mechanism is bitten by long-term use. The radial load acting on the slider 62 is transmitted to the housing 21 via the guide plate 61 and the adjustment blocks 64 and 65. Further, since the first rotor 24 is rotatably supported by the upper half 21 a of the housing 21 via the angular bearing 22, even if a radial load due to meshing between the first driven gear 41 and the first drive gear 43 is applied. Almost no displacement in the radial direction.

[Partial modification]
FIG. 8 is a perspective view of a slider according to a partial modification.
As shown in the figure, in the slider 62 of this modification, an arc-shaped rolling bearing 66 holding a rolling element (needle roller) 66a is fixed to the sliding contact portions 62b and 62c. The actions and effects of some modified examples are substantially the same as those of the above-described embodiment. I was able to plan.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, in the above embodiment, the present invention is applied to a vehicle height adjusting device provided in a rear suspension of a four-wheeled vehicle. However, a vehicle height adjustment provided in a suspension of a front suspension, a two-wheeled vehicle, or a six-wheeled vehicle or more. The present invention can be applied to a device, and can also be applied to a direct acting actuator other than a vehicle height adjusting device. In the above embodiment, the feed screw mechanism is used as the feed mechanism. However, a ball screw type feed mechanism, a cylindrical cam mechanism, or the like may be adopted. In the above embodiment, the drive gear is an internal gear, but the driven gear may be an internal gear that is inscribed by the drive gear, or the drive gear may be an external gear that is circumscribed by the driven gear. In addition, the specific configurations of the vehicle height adjusting device and the radial support mechanism can be changed as appropriate without departing from the spirit of the present invention.

It is a perspective view which shows the rear suspension which concerns on embodiment. It is the II section enlarged vertical sectional view in FIG. It is a perspective view which shows the meshing state of the drive shaft which concerns on embodiment, and a 1st, 2nd rotor. It is a perspective view which shows the combined state of each gear and radial support mechanism which concern on embodiment. It is a disassembled perspective view which shows the structure of the radial support mechanism which concerns on embodiment. It is a perspective view which shows the back surface of the slider which concerns on embodiment. It is a cross-sectional view which shows the effect | action of the radial support mechanism which concerns on embodiment. It is a perspective view of the slider which concerns on a partial modification.

Explanation of symbols

9 Vehicle height adjustment device (linear actuator)
21 Housing 24 First rotor 25 Second rotor 31 Drive shaft 36 Electric motor (rotation drive means)
38 Radial support mechanism 39 Feed screw mechanism (feed means)
41 1st driven gear 42 2nd driven gear 43 1st drive gear 44 2nd drive gear 61 Guide plate 62 Slider (support piece)
62b Sliding part (support part)
66 Bearing 66a Rolling element

Claims (4)

A housing constituting the outer shell of the device;
A first rotor supported rotatably on the housing and having a first driven gear formed on an outer periphery thereof;
A second rotor coupled to the first rotor via a feed means for converting a rotational motion into a linear motion and having a second driven gear formed on the outer periphery thereof;
A first drive gear that is rotatably supported by the housing and meshes with the first driven gear;
A drive shaft having a second drive gear meshing with the second driven gear;
Rotational drive means for rotationally driving the drive shaft,
In a linear motion actuator in which the gear ratio between the second driven gear and the second drive gear is different from the gear ratio between the first driven gear and the first drive gear,
A radial support means is provided that supports the second rotor in a radial direction at a position that is connected to the housing and has an angular phase that is approximately 180 ° different from a meshing portion of the second drive gear and the second driven gear. Features a linear actuator. The drive shaft has a hollow cylindrical shape, the first drive gear is an internal gear that circumscribes the first driven gear, and the second drive gear is an internal gear that circumscribes the second driven gear;
2. The linear support device according to claim 1, wherein the radial support means includes a support piece that is interposed between the drive shaft and the second rotor and moves straight along with the second rotor. Moving actuator. The linear motion actuator according to claim 2 , wherein the support piece has a support portion made of oil-impregnated resin that is in sliding contact with the second rotor. The linear motion actuator according to claim 2 , wherein the support piece holds a rolling element that is in rolling contact with the second rotor.

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