JP2600912Y2 - Timer device for fuel injection pump - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a timer device for a fuel injection pump.

[0002]

2. Description of the Related Art In a conventional centrifugal timer device, when the viscosity of lubricating oil increases at a low temperature, there is a problem that an accurate advance angle characteristic cannot be obtained due to the influence, and the response characteristic of a flyweight also deteriorates. For this reason, there is an example in which a thermo bellows (temperature-sensitive elastic member) for reducing the set load of a spring for urging the fly weight in the radial direction at a low temperature is provided (Japanese Utility Model Laid-Open No. 55-121934).

[0003]

However, in this conventional example, it is difficult to properly set the expansion and contraction characteristics of the thermo bellows, and there is a problem that the cost of forming the thermo bellows is increased.

The present invention has been made in view of such a problem, and has as its object to secure good operability at a low temperature with a simple configuration.

[0005]

Therefore, a cylindrical casing that rotates in conjunction with a fuel injection pump, a flyweight accommodated in the casing, a spring that biases the flyweight in a radial direction, and a flyweight Equipped with a timer mechanism that changes the fuel injection timing according to the position of
Release the contact surfaces necessary for fly weight guide on at least one of the two end faces of the casing that touch the fly weight.
A depression is formed so as to leave a projection .

[0006]

The recess on the end face of the casing greatly reduces the sliding contact area with the fly weight, thereby reducing the sliding resistance of the fly weight. As a result, even at a low temperature where the viscosity of the lubricating oil is high, smooth operability of the flyweight is ensured, and the fuel injection timing can be properly advanced. This place
In such cases, keep the contact surface with the fly weight
As a result, the sliding area with the fly weight can be efficiently reduced.
And the fly weight is stable and smooth
Can guide.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 denotes a cylindrical casing which is keyed to an outer periphery of a camshaft (not shown) of a fuel injection pump, and a pair of flywheels is provided between the casing 1 and a plate 2 forming one end surface thereof. The weight 3 is accommodated. The flyweight 3 is formed in a semi-annular shape surrounding the camshaft, and is supported in the casing 1 so as to be displaceable outside the rotation radius of the camshaft.

The springs 4 and 5 urge the fly weight 3 inward in the radial direction. The fly weight 3 is a centrifugal force acting according to the pump rotation speed. 5 is lifted to a position that balances the spring force.

Two sets of eccentric cams 6 serve as a timer mechanism for advancing the fuel injection timing according to the lift of the flyweight 3.
Is provided. The eccentric cam 6 is composed of a large-diameter cam 8 rotatably supported by a circular hole 7 of the casing 1 and a small-diameter cam 9 rotatably accommodated in the circular hole 10. The small-diameter cam 9 is supported by a connecting pin (not shown) and a pin 13 of a coupling 12 connected to a drive gear 11 of the fuel injection pump.

Since the coupling 12 is fixed to the drive gear 11 of the fuel injection pump, the large-diameter cam 8 tries to rotate the small-diameter cam 9 in accordance with the lift of the flyweight 3, but the small-diameter cam 9 is To rotate around
The camshaft rotates via the casing 1 with the movement of the cams 8 and 9. That is, the fuel injection timing is advanced by the lift of the fly weight 3.

[0011] condition, such as the plate 2 of the casing 1 leaving sliding surface necessary for guide flyweight 3, FIG.
As shown in FIG. 3, a depression 14 that forms a predetermined gap between the flyweight 3 and the flyweight 3 is provided. Multiple recesses 14 which to leave the sliding surface between the flyweight 3 radially splicing the inner peripheral portion and the outer peripheral portion of the plate 2 to surround the cam shaft around
Is formed in a fan shape .

Therefore, the fly weight 3 is in sliding contact with the end surface of the casing 1 and the plate 2, but the annular recess 14 greatly reduces the sliding contact area with the plate 2, and the sliding resistance of the fly weight 3 is reduced. Even when the lubricating oil has a high viscosity at a low temperature, good operability of the fly weight 3 is ensured, and the fuel injection timing can be advanced properly.

The lift amount of the fly weight 3 is ST
= Represented by _{(F-S 1 · μ)} / K. Here, F is the centrifugal force acting on the fly weight, S _{1 is the} sliding contact area of the fly weight with the casing, μ is the friction force acting on the sliding contact surface of the fly weight, and K is the spring constant of the spring. FIG.
Conventional case plate 2 of the casing 1, as shown in the example is flat, for sliding area S ₁ of the flyweight 3 is large, although the lubricating oil viscosity is no problem low at high temperature, the friction at the time the lubricating oil viscosity is high low temperature The force μ increases and has a great effect on the lift of the flyweight 3.

[0014] This this case, recesses 14 of the plate 2 is formed so as to leave a radial sliding contact surface with the flyweight 3
And by not only the flyweight 3 can stably guide to the sliding direction, it is possible to reduce the sliding contact area between the flyweight 3 efficiently greatly. Further, not only the plate 2 side but also the recess may be formed on the end face of the casing 1.

[0015]

In summary, according to the present invention, according to the present invention, a cylindrical casing that rotates in conjunction with a fuel injection pump, a flyweight accommodated in the casing, and a spring that biases the flyweight in a radial direction are provided. A timer mechanism that changes the fuel injection timing according to the position of the fly weight is provided, and a recess is formed on at least one of both end surfaces of the casing that slides on the fly weight so as to radially leave a contact surface required for guiding the fly weight. So fly
Efficient and significant reduction of sliding area with Eight
And guide the fly weight smoothly and stably
be able to. As a result, good operability is ensured even at a low temperature where the lubricating oil viscosity is high, and the effect of appropriately advancing the fuel injection timing is obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an apparatus showing an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a configuration of a main part in the same manner.

FIG. 3 is a front view of a plate and a sectional view taken along line AA of the plate for explaining another embodiment.

FIG. 4 is an explanatory diagram of a conventional example.

[Description of Signs] 1 casing 2 plate 3 fly weight 4,5 spring 6 eccentric cam 11 drive gear 12 coupling 14 plate recess

Claims (1)

(57) [Scope of request for utility model registration] 1. A cylindrical casing which rotates in conjunction with a fuel injection pump, a fly weight accommodated in the casing, a spring for urging the fly weight in a radial direction, and a fuel according to a position of the fly weight. A timer mechanism for changing the injection timing is provided, and a recess is formed on at least one of both end surfaces of the casing in sliding contact with the fly weight so as to radially leave a contact surface necessary for guiding the fly weight. Timer device of the fuel injection pump.