JP2009036238A - Speed reducing mechanism, and lubrication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep a good lubrication state by returning lubricant dropped from a tooth flank to the tooth flank with a simple structure. <P>SOLUTION: In a speed reducing mechanism 2 having a sector-shaped worm wheel 17 having a less rotation range than one rotation, grease dropped from the tooth flank is collected in a round hole 21. A cam 17a formed on the worm wheel 17 moves a piston 20 forward to push out the grease collected in the round hole 21 is extruded to a circulating passage 23, thereby returning the grease to the tooth flank of the worm shaft 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a speed reduction mechanism and a lubrication method.

There has been one that decelerates the rotation of the electric motor with a worm gear, converts the rotational motion into a linear motion of a tie rod, and steers the rear wheels (see Patent Document 1).
Japanese Utility Model Publication No. 5-65748

However, in the conventional example described in Patent Document 1, since the worm wheel is disposed below the worm having a horizontal rotation shaft, the grease of the worm gear hangs downward. Moreover, since the worm hole is formed in a substantially fan shape and does not rotate once, the grease that hangs downward does not return to the worm gear again. Therefore, if grease is not replenished frequently, problems such as abnormal noise, wear, and reduced efficiency may be caused.
An object of the present invention is to return a lubricant dripping from a tooth surface to the tooth surface with a simple structure and maintain a good lubricating state.

In order to solve the above-described problem, a speed reduction mechanism according to the present invention includes at least one of a pair of meshing gears having a rotation range of less than one rotation, and a lubricant supplied to at least one tooth surface. A storage cylinder for storing the lubricant dripping from the tooth surface, a circulation path having one end communicating with the storage cylinder and the other end disposed above the tooth surface, and a lubricant for the storage cylinder by rotation of the gear. And a pressure source for transferring the gas to the other end side of the circulation path.
That is, a circulation path capable of transferring the lubricant dripping from the tooth surface to the tooth surface is formed, and in this circulation path, the dripping lubricant is transferred to the tooth surface by rotation of a gear. .

  According to the speed reduction mechanism according to the present invention, the lubricant dripping from the tooth surface can be returned to the tooth surface again with a simple structure including a pressure source driven by the rotation of the gear without providing a pump. A good lubrication state can be maintained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<< One Embodiment >>
"Constitution"
FIG. 1 is a schematic configuration of a 4WS rear wheel steering actuator. The rotation of the electric motor 1 is decelerated by the speed reduction mechanism 2 and then converted into a linear motion by the rack and pinion 3, and the suspension link pivot 4 is pushed or pulled by this linear motion, thereby moving the suspension link 5 in the vehicle width direction. The rear wheel 5 can be steered. In addition, although the rotational motion is converted into the linear motion by the rack and pinion 3, it is not limited to this, For example, you may employ | adopt combining an offset shaft and a spherical bearing.

  FIG. 2 is a schematic configuration of the speed reduction mechanism 2. The electric motor 1 is fixed to a gear box 10, and a motor rotating shaft 1 a is connected to a worm shaft 12 by a spline 11 inside the gear box 10. The worm shaft 12 is pivotally supported by a pair of bearings 13 and 14 fitted in the gear box, and one bearing 14 is fixed by a retaining plug 15 whose outer peripheral surface is screwed with the inner wall surface of the gear box 10. Is done. The worm shaft 12 is restrained from moving in the axial direction with respect to the bearing 14 by the large-diameter portion 12 a on the shaft and the snap ring 16.

  The worm shaft 12 meshes with the worm wheel 17 on the lower side, and the rotating shaft 18 of the worm wheel 17 is connected to the pinion shaft of the rack and pinion 3. The number of teeth of the worm wheel 17 is determined according to the steering angle range (lock-to-lock) of the rear wheel, and if it is a general passenger car, it is not necessary to steer the rear wheel greatly. It has a substantially fan shape formed by the number. That is, the worm wheel 17 does not rotate once. A sufficient amount of grease as a lubricant is supplied to the tooth surfaces of the worm shaft 12 and the worm wheel 17 (particularly at the meshing portion).

  The worm wheel 17 is formed with a cam 17 a around the rotation shaft 18, and the cam 17 a is in sliding contact with a piston 20 that can advance and retreat in the vertical direction according to the rotation of the worm wheel 17. As shown in FIG. 3, when the rotation angle of the worm wheel 17 is in the neutral position of the rear wheel rudder angle and the reference circle of the cam 17a is at the position where the piston 20 abuts, the worm wheel 17 is moved from this state. The contour of the cam 17a is formed so that the distance from the center becomes longer than the reference circle as it rotates, that is, as the rear wheel steering angle increases. The piston 20 is slidably fitted into a round hole 21 formed in the bottom of the gear box, and is urged upward by a spring 22.

The gear box 10 is formed with a circulation path 23 capable of transferring the dropped grease to the tooth surface. One end thereof communicates with the side surface of the round hole 21, and the other end is opened above the worm shaft 12, and a check valve that allows only flow from one end side to the other end side at a position close to the round hole 21. 24.
On the floor surface in the gear box, a downward inclined surface 25 is formed toward the round hole 21. Further, as shown in FIG. 4A, a plurality of notches 20a along the axial direction are formed on the cylindrical surface of the piston 20 in the circumferential direction at the lower end side. Assuming that the rear wheel rudder angle is in the neutral position, the piston 20 is pushed up to the top dead center contacting the reference circle by the elastic force of the spring 22 while being guided by the round hole 21. In this state, the notch 20a is rounded. It arrange | positions so that it may extend above the edge of the hole 21. FIG.

<Action>
A sufficient amount of grease as a lubricant is supplied to the tooth surfaces of the worm shaft 12 and the worm wheel 17 (particularly at the meshing portion), but the grease gradually drops due to gravity.
As shown in FIG. 5A, if the rear wheel rudder angle is in the neutral position, the piston 20 is pushed up to the top dead center contacting the reference circle by the elastic force of the spring 22 while being guided by the round hole 21. ing. Accordingly, the dripping grease flows along the downward inclined surface 25, flows into the round hole 21 from the notch 20a formed in the piston 20, and is stored therein. In general, the rear wheel steering actuator is often laid out near the exhaust pipe, and since the ambient temperature becomes high (may exceed 120 degrees), the viscosity of the grease also decreases, and the round hole 21 is smooth. Flow into.

As shown in FIG. 5 (b), when the rear wheel steering angle increases, the piston 20 is pushed down by the cam 17 a against the elastic force of the spring 22. However, until the notch 20a is completely immersed in the round hole 21, the notch 20a becomes an escape path, and no pressure is generated in the round hole 21.
As shown in FIG. 5C, when the rear wheel steering angle is further increased and the notch 20a is completely immersed in the round hole 21, pressure is generated in the round hole 21 from that point in time according to the advancement amount of the piston 20. . Accordingly, the grease is discharged through the circulation path 23 above the worm shaft 12 and is supplied again to the tooth surfaces of the worm shaft 12 and the worm wheel 17.

  By the cycles of FIGS. 5A to 5C, the grease that has dropped from the tooth surface can be returned to the tooth surface again, and a good lubricating state can be maintained. Conventionally, a gear that does not rotate once does not return to the gear again, so if the grease is not replenished frequently, problems such as abnormal noise, wear, and reduced efficiency may occur. However, if a good lubrication state can be maintained as in the present embodiment, maintenance is facilitated.

When the rear wheel rudder angle decreases, the piston 20 moves backward (pushes up), but since the check valve 24 is provided in the circulation path 23, the check valve 24 is already included in the grease remaining in the circulation path 23. The portion pushed through the valve 24 is stocked in the circulation path 23 until the next time the rear wheel steering angle increases without flowing backward.
The cam 17a is contoured so that as the rear wheel rudder angle increases, the amount of advancement of the piston 20 increases. To send it back to. That is, during turning, the external force acting on the speed reduction mechanism 2 is greater than when traveling straight, and the contact pressure on the tooth surface is increased, so that more grease can be supplied and a good lubricating coating can be formed. Because it is desired.

The amount of grease taken into the round hole 21 is determined by the width, depth, and number of the notches 20a, and the rear wheel steering angle at which the grease starts to be pushed out to the circulation path 23 is determined by the length. First, the width, depth, and number are set to such an extent that the piston 20 can maintain the required rigidity. The length is set so that the grease starts to be pushed out after the rear wheel steering angle reaches a minute steering angle (for example, about 0.2 to 0.3 deg). This is because the grease is not pushed out during the substantially straight traveling in which the contact pressure of the tooth surface is lower than that during the turning traveling, thereby reducing the burden on the electric motor 1 and suppressing the power consumption.
The push-out amount of grease is determined by the diameter and stroke amount of the piston 20. When it is desired to increase the amount of extrusion, if the piston diameter is increased, a larger thrust is required and the power consumption of the electric motor 1 increases. Therefore, it is desirable to reduce the piston diameter as much as possible and increase the stroke amount. Stroke amount is adjusted by cam shape.

《Application example》
In the above embodiment, the columnar piston 20 is employed. However, if the necessary rigidity can be maintained, as shown in FIG. 4B, the substantially cylindrical piston 20 with the end side in the forward direction closed is used. It may be adopted.
The other end of the circulation path 23 is disposed above the worm shaft 12, but the other end of the circulation path 23 is disposed in the vicinity of the meshing portion of the worm shaft 12 and the worm wheel 17 as shown in FIG. May be. In short, the outlet of the circulation path 23 may be arranged anywhere as long as the lubricant can be sprayed or poured out on at least one tooth surface of the worm shaft 12 and the worm wheel 17.
Moreover, although the deceleration mechanism which employ | adopted the worm gear was demonstrated, it is not limited to this. In other words, if the speed reduction mechanism is such that at least one of the meshing gears has a rotation range of less than one rotation, the lubricant dripping from the tooth surface will not return to the tooth surface again, so any other gear Even so, the present invention can be applied.

"effect"
From the above, the worm shaft 12 and the worm wheel 17 correspond to “a pair of gears”, the round hole 21 corresponds to a “storage cylinder”, the circulation path 23 corresponds to a “circulation path”, the cam 17a, the piston 20 And the spring 22 correspond to a “pressure source”.
(1) Of a pair of gears engaged with each other, at least one rotation range is less than one rotation, and the lubricant dripping from the tooth surface is stored in the reduction mechanism in which the lubricant is supplied to at least one tooth surface. A storage cylinder, a circulation path having one end communicating with the storage cylinder and the other end disposed above the tooth surface, and a pressure source for transferring the lubricant in the storage cylinder to the other end side of the circulation path by rotation of a gear. .
This makes it possible to return the lubricant dripping from the tooth surface to the tooth surface with a simple structure with a pressure source driven by the rotation of the gear without providing a pump, maintaining a good lubrication state. can do.

(2) The pressure source includes a cam that rotates together with the gear, and is fitted to the storage cylinder in a state that can advance and retreat according to the rotation of the cam. And a piston that pushes out to the side.
Thereby, it is possible to return the circulating agent dripping from the tooth surface to the tooth surface again with a simple structure including a cam and a piston driven by the rotation of the gear without providing a pump.
(3) In the speed reduction mechanism mounted on the steering device that steers the wheel, the cam is contoured so that the advance amount of the piston increases as the steering angle of the wheel increases.
As a result, it is possible to supply a larger amount of lubricant and to form a good lubricating coating film during turning traveling in which the contact pressure of the tooth surface becomes higher than during straight traveling.

(4) The notch along the axial direction is formed at the tip of the piston in the forward direction.
As a result, the timing at which the lubricant starts to be pushed out into the circulation path can be delayed with respect to the stroke of the piston. Therefore, the lubricant is not pushed out during the substantially straight traveling in which the contact pressure of the tooth surface is lower than that during the turning traveling, so that the rotation load of the gear can be reduced and the driving loss can be suppressed.

(5) The circulation path includes a check valve that allows only the flow from one end side to the other end side.
As a result, of the lubricant remaining in the circulation path, the part already pushed through the check valve can be stocked in the circulation path until the next time it is pushed out without backflow. .
(6) A downwardly inclined surface toward the storage cylinder is provided in a region where the lubricant hangs down from the tooth surface.
Thereby, the dripped lubricant can be smoothly introduced into the storage cylinder.

This is a rear wheel steering actuator. It is a deceleration mechanism. It is a worm wheel. It is a piston. Indicates grease circulation. It is another Example of a rear-wheel steering actuator.

Explanation of symbols

12 Worm shaft 17 Worm wheel 17a Cam 20 Piston 21 Round hole 22 Spring 23 Circulation path 24 Check valve 25 Inclined surface

Claims (7)

In a speed reduction mechanism in which at least one rotation range is less than one rotation among a pair of meshing gears, and a lubricant is supplied to at least one tooth surface,
A storage cylinder for storing the lubricant dripping from the tooth surface; a circulation path having one end communicating with the storage cylinder and the other end disposed above the tooth surface; and rotation of the gear to rotate the storage cylinder. And a pressure source for transferring the lubricant to the other end side of the circulation path.   The pressure source includes a cam that rotates together with the gear, and is fitted to the storage cylinder in a state that can advance and retreat in accordance with the rotation of the cam. The speed reduction mechanism according to claim 1, further comprising: a piston that pushes out to the other end side. In the speed reduction mechanism mounted on the steering device that steers the wheels,
The speed reduction mechanism according to claim 2, wherein the cam is contoured so that the advance amount of the piston increases as the steering angle of the wheel increases.   The speed reduction mechanism according to claim 2 or 3, wherein the piston is formed with a notch along the axial direction at a front end in the forward direction.   The speed reduction mechanism according to any one of claims 1 to 4, wherein the circulation path includes a check valve that allows only the flow from one end side to the other end side.   The speed reduction mechanism according to any one of claims 1 to 5, further comprising a downwardly inclined surface facing the storage cylinder in a region where the lubricant hangs down from the tooth surface. A rotation mechanism in which at least one rotation range of the pair of meshing gears is less than one rotation, and a lubricant is supplied to at least one tooth surface;
A circulation path capable of transferring the lubricant dripping from the tooth surface to the tooth surface is formed, and in the circulation path, the lubricant dripping from the tooth surface is transferred to the tooth surface by rotation of the gear. And a lubrication method.

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