JPH0735738U - Fuel injection pump timer device - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To improve the operability at low temperature in the timer device of the fuel injection pump. [Structure] Cylindrical casing 1 that rotates in conjunction with a fuel injection pump, flyweight 3 housed in casing 1, springs 4 and 5 that bias flyweight 3 in a radial direction, and flyweight 3 Is provided with two sets of eccentric cams 6 as a timer mechanism for changing the fuel injection timing according to the position, and a recess 14 is formed on at least one of both end surfaces of the casing 1 so as to leave a contact surface necessary for guiding the flyweight 3. Form.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a timer device for a fuel injection pump.

[0002]

[Prior art]

 In the conventional centrifugal timer device, if the viscosity of the lubricating oil increases at low temperature, the effect is that accurate advance characteristics cannot be obtained, and the response characteristics of the flyweight deteriorate. Therefore, there is an example in which a thermo-bellows (temperature-sensitive expansion / contraction member) is provided to reduce the set load of the spring for urging the flyweights in the radial direction at low temperature (Japanese Utility Model Publication No. 55-121934).

[0003]

[Problems to be solved by the device]

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

The present invention has been made in view of these problems, and an object thereof is to ensure good operability at low temperatures with a simple configuration.

[0005]

[Means for Solving the Problems]

 Therefore, the cylindrical casing that rotates in conjunction with the fuel injection pump, the flyweights housed in the casing, the springs that urge the flyweights in the radial direction, and the fuel injection depending on the position of the flyweights. A timer mechanism for changing the timing is provided, and a recess is formed on at least one side of both end surfaces of the casing so as to leave a contact surface required for guiding the flyweight.

[0006]

[Action]

 The recess on the end surface of the casing greatly reduces the sliding contact area with the flyweight, and reduces the sliding resistance of the flyweight. As a result, the smooth operability of the flyweight is ensured even at low temperatures where the lubricating oil viscosity is high, and the fuel injection timing can be advanced accurately.

[0007]

【Example】

 In FIG. 1, reference numeral 1 denotes a cylindrical casing key-connected to the outer circumference of a camshaft (not shown) of the fuel injection pump, and a pair of flyweights 3 are provided between the casing 1 and a plate 2 forming one end face thereof. Be housed. The fly weight 3 is formed in a semi-annular shape surrounding the cam shaft, and is supported in the casing 1 so as to be displaceable to the outside of the radius of rotation of the cam shaft.

The springs 4 and 5 urge the flyweights 3 inward in the radial direction, and the flyweights 3 are centrifugal forces acting according to the rotational speed of the pump. As shown by an arrow F in FIG. It is designed to lift to a position that balances with the spring force of 5.

Two sets of eccentric cams 6 are provided as a timer mechanism for advancing the fuel injection timing according to the lift of the flyweight 3. The eccentric cam 6 is composed of a large-diameter cam 8 which is rotatably supported in a circular hole 7 of the casing 1, and a small-diameter cam 9 which is rotatably accommodated in the circular hole 10, and the large-diameter cam 8 and the flyweight 3 are arranged. The small-diameter cam 9 is supported by a connecting pin (not shown) on a pin 13 of a coupling 12 which is 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 according to the lift of the flyweight 3, but the small diameter cam 9 is a pin. Since it rotates about 13, the cam shaft rotates via the casing 1 as the cams 8 and 9 move. That is, the fuel injection timing is advanced by the lift amount of the flyweight 3.

The plate 2 of the casing 1 is provided with a recess 14 that forms a predetermined gap with the flyweight 3 such that a sliding contact surface required for guiding the flyweight 3 remains. The recess 14 is formed so as to surround the cam shaft in an annular shape with the inner peripheral portion and the outer peripheral portion of the plate 2 as sliding contact surfaces with the flyweight 3.

Therefore, the flyweight 3 is in sliding contact with the end surface of the casing 1 and the plate 2, but the annular recess 14 significantly reduces the sliding contact area with the plate 2 and reduces the sliding resistance of the flyweight 3. Good operability of the fly weight 3 is ensured even at low temperatures where the lubricating oil viscosity is high, and the fuel injection timing can be advanced accurately.

The lift amount of the flyweight 3 is represented by ST = (F−S ₁ · μ) / K. Where F is the centrifugal force acting on the fly weight, S _{1 is the} sliding contact area of the fly weight with respect to the casing, μ is the frictional force acting on the sliding contact surface of the fly weight, and K is the spring constant of the spring. When the plate 2 of the casing 1 is flat as shown in the conventional example of FIG. 4, since the sliding contact area S ₁ of the flyweight 3 is large, there is no problem at a high temperature where the lubricating oil viscosity is low, but the lubricating oil viscosity is low. When the temperature is high, the frictional force μ increases and the lift of the flyweight 3 is greatly affected.

When the recesses 14 of the plate 2 are formed so that the sliding contact surface with the flyweight 3 is left radially in the radial direction as shown in FIG. 3, not only can the flyweight 3 be stably guided, but also the flyweight. It is possible to further reduce the sliding contact area with 3. Further, not only the plate 2 side but also the end surface of the casing 1 may be formed with a recess.

[0015]

[Effect of device]

 In short, according to the present invention, the cylindrical casing that rotates in conjunction with the fuel injection pump, the flyweights housed in the casing, the springs that bias the flyweights in the radial direction, and the flyweights. A timer mechanism that changes the fuel injection timing depending on the position is provided, and a recess is formed on at least one side of both ends of the casing to leave a contact surface required for the guide of the flyweight. Since the area is greatly reduced due to the depression, good operability is ensured even at low temperatures where the viscosity of the lubricating oil is high, and it is possible to advance the fuel injection timing appropriately.

[Brief description of 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 which similarly illustrates the structure of a main part.

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

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

[Explanation of symbols]

 1 Casing 2 Plate 3 Flyweight 4, 5 Spring 6 Eccentric cam 11 Drive gear 12 Coupling 14 Plate depression

Claims (1)

[Scope of utility model registration request] 1. A cylindrical casing that rotates in conjunction with a fuel injection pump, a flyweight housed in the casing, a spring that biases the flyweight in a radial direction, and a fuel depending on the position of the flyweight. A timer device for a fuel injection pump, comprising a timer mechanism for changing the injection timing, wherein a recess is formed on at least one side of both end surfaces of the casing so as to leave a contact surface required for a guide of the flyweight.