JPS6020851Y2 - Internal gear holding mechanism of reduction gear for starting motor - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an internal gear holding mechanism for a speed reduction device for a starter motor.

Conventionally, in a starter motor equipped with a speed reduction device using a planetary gear, an internal gear 1' is fixed with a knock pin 6 to prevent it from idling under normal loads as shown in Fig. 1, and an internal gear 1' is fixed with a knock pin 6 as shown in Fig. 2. There are known devices in which the outer periphery of the gear is press-fitted into the gear housing 5, or in which it is held from the side by a pressing mechanism such as a spring 4 as shown in FIG.

However, in these holding mechanisms, concentrated stress is applied to the dowel pin part, which tends to cause local damage, the press-fitting mechanism has difficulty controlling the press-fitting margin, and the pressing mechanism applies large side pressure, resulting in an increase in spring capacity. There were drawbacks such as the need to consider strengthening the tightening machine.

In addition, when starting an engine, if excessive torque is transmitted due to the impact when the engine ring gear meshes with the starter motor's pinion or the engine reversal (kickback) phenomenon at the start of startup, damage to bearings and internal gears may occur. There was a risk of damage.

The object of the invention is to eliminate the above-mentioned drawbacks and to provide a suitable gear holding machine.

As a means for achieving the above object, the present invention has a configuration that combines the following elements.

(1) A wedge-shaped or trapezoidal shape is formed on the protruding side surface of the internal gear, and the wedge-shaped or trapezoidal shape is opposed to the holder that fits therein. (2) The internal gear is held by pressing both together with a disc spring. In the invention, by providing a holder with a wedge-shaped or trapezoidal protrusion and a groove that fits into the protrusion, a wide friction surface can be obtained and, as will be described later, a high pressure contact load can be obtained. The amount of movement of the holder, that is, the amount of deformation of the pressing spring, increases significantly.

By the way, when multiple coil springs are used as pressure springs, the load tends to be uneven, and the characteristic of coil springs is that the relationship between the load and the amount of deformation is linear, and as the amount of deformation increases, the load changes. It has the disadvantage of being large and difficult to deal with wear and tear.

On the other hand, disc springs have curvilinear characteristics and can be designed so that the change in load is small relative to the amount of deformation, and have the ability to cope with wear accordingly.

An example of implementing the present invention will be described below with reference to FIGS. 4 and 5.

As shown in FIG. 4, in the starter motor of the present invention, a motor (not shown) is disposed within a housing 8, and a gear at the tip of the motor shaft meshes with a planetary gear 7.

The planetary gear 7 is rotatably supported by a gear shaft 10 that is press-fitted into a drive shaft 11, and the internal gear 1
It is housed in a meshing gear housing 5.

One side of the internal gear 1 is in contact with a flaket 9, and the other side is formed with a concentric annular protrusion 2 having a wedge-shaped or trapezoidal cross section, and an annular groove 3a that fits into the protrusion 2. A retainer 3 provided therein is fitted.

The holder 3 is formed with a rotation stopper 3b that engages with the groove 5a of the gear housing 5, and is housed in the gear housing 5' in a non-rotatable manner.
is under pressure.

The pressing force of the disc spring 4 generates a frictional force on the sliding surface 2a where the annular R3a of the holder 3 and the protrusion 2 of the internal gear 1 come into contact.

Since the present invention is constructed as described above, when the electric motor rotates, the planetary gear 7 that meshes with the gear at the tip of the electric motor shaft rotates in the opposite direction to the electric motor, and since the planetary gear 7 constitutes a planetary gear, The drive shaft 11 rotates in the same direction as the electric motor.

Here, the pinion attached to the drive shaft 11 engages with the engine ring gear, but the impact at this time,
A sudden torque in the opposite direction acts on the drive shaft 11 due to a reverse rotation (kickback) phenomenon of the engine after engagement.

This torque is about to be transmitted to the internal gear 1 and the motor shaft via the planetary gear 7.

However, the internal gear 1 slips on the sliding surface 2a with the holder 3, and idles in the direction in which the torque is applied.

The idling torque is determined by the frictional force of the sliding surface 2a, and the frictional force depends on the pressing force of the disc spring 4 and the angle of the sliding surface 2a.

Figures 5A and 5B show the relationship between the pressing force P and the frictional force F in the lateral pressure spring mechanism.If the friction coefficient is μ, then A
In the case shown in the figure, the relationship FA=μP stands out.

In the case of diagram B, the frictional force F8 generated because the friction surface is tapered and has an angle θ is Fn=p/sinθ/2+μ
cO3θ/2) relationship stands out.

In this case, FB>FA, and the latter can obtain a larger frictional force than the former with the same pressing force.

As described above, the present invention provides a holder having a wedge-shaped or trapezoidal protrusion and a groove that fits into the protrusion, so that a wide friction surface and therefore a high pressure welding effect can be obtained, and the disc spring 4 is used as a pressing spring. This makes it possible to cope with the large amount of deformation of the pressing spring, which is a disadvantage of the wedge-shaped protrusion, etc., and to provide a small and durable internal gear holding mechanism.

[Brief explanation of drawings]

Figures 1 to 3 are cross-sectional side views of essential parts showing a conventional example, Figure 4 is a cross-sectional side view of essential parts of an example of the implementation of the present invention, and Figure 5 is the relationship between the pressing force and frictional force of the lateral pressure spring mechanism. FIG. The symbols in the figure indicate the following, respectively. 1, 1': Internal gear, 2: Protrusion, 2a: Sliding surface,
3: Holder, 3a: Groove, 3b: Rotation stopper, 4: Spring, 5
: gear housing, 6: knock pin, 7: planetary gear, 8: housing, 9 nib bracket, 10: gear shaft, 11 nib drive shaft, P: pressing force, F: friction force.

Claims (1)

[Scope of utility model registration request] In a starter motor equipped with a planetary gear reduction device, an annular protrusion 2 concentric with the internal gear 1 built in the gear housing 5 is integrally provided on the side surface thereof, and the protrusion 2
A ring having tapered surfaces on both the inner and outer sides thereof to have a wedge-shaped or trapezoidal cross section, and having a rotation stopper 3b that is disposed opposite to the internal gear 1 on the side surface and engages with the groove 5a of the gear housing 5. In addition to providing a holder 3 having a shape,
The opposing surface of the holder 3 has a groove 3a that fits into the protrusion 2.
and the inner surface of the gear housing 5 and the holder 3
A disc spring 4 is inserted between the rear surface of the internal gear 1 and the internal gear 1 held in the gear housing 5 by the frictional force between the fitting projection 2 and the tapered surface of the groove 3a. Internal gear holding mechanism for electric motor reduction gear.