JPH0447414Y2 - - Google Patents

Description

[Detailed description of the invention] Purpose of the invention [Industrial application field] The present invention is a fuel injection pump that is provided in communication with a pressurizing chamber of a fuel injection pump and that performs pilot injection before main fuel injection. This invention relates to a pilot injection device.

[Conventional technology] Conventionally, when a diesel engine is idling, etc.
In order to reduce fuel noise in low-speed, low-load operating ranges and improve fuel ignitability, pilot injection is performed before the main fuel injection of the fuel injection pump.
There is a pilot injector for a fuel injection pump that is configured to perform main fuel injection when pilot-injected fuel ignites in the combustion chamber of a diesel engine.

This type of pilot injection device is, for example,
As described in Japanese Patent No. 59-51660, an attached cylinder communicating with a pressurizing chamber of a fuel injection pump, an accumulation piston that is pressed and moved within the cylinder by the fuel pressure of the pressurizing chamber, and this accumulation piston. It includes a spring that presses the rate piston toward the pressurizing chamber and a stopper that limits the amount of movement of the accumulation rate piston toward the side opposite to the pressurizing chamber. When the fuel pressure in the chamber increases, the accumulation piston moves, temporarily stores fuel in the cylinder, and temporarily stops fuel injection, thereby executing pilot injection.

[Problems to be solved by the invention] However, in the conventional pilot injection device described above, when the accumulation piston moves toward the side opposite to the pressurization chamber when the pressure rises on the pressurization chamber side, the accumulation piston moves away from the pressurization chamber. There was a problem in that the end part was hit violently against the stopper and stopped, which caused a loud banging sound and an unpleasant noise when idling. Further, since the accumulation piston and the stopper collide violently, there is a problem in that these parts are worn out and the durability is reduced.

SUMMARY OF THE INVENTION The object of the present invention is therefore to provide a pilot injection device for a fuel injection pump that can reduce the speed at which the accumulation piston moves and hits the stopper during pilot injection, thereby reducing the hitting noise. It has the following structure. Structure of the invention [Means for solving the problems] That is, the structure of the invention as a means for solving the above problems is as follows: A cylinder connected to a pressurizing chamber of a fuel injection pump through a communication hole. , an accumulation piston that is fitted into the cylinder and is movable under pressure by the fuel pressure in the pressurizing chamber, and moves at high speed by the fuel pressure at the start of the pressing movement to depressurize the pressurizing chamber; a spring that presses and biases the accumulation piston toward the pressurizing chamber; and a movement restriction that restricts movement of the accumulation piston by coming into contact with the accumulation piston that moves due to an increase in fuel pressure in the pressurizing chamber. and a pilot injection device for performing pilot injection before the main fuel injection of the fuel injection pump, wherein the spring has a spring constant that is small when the accumulation piston starts moving; The gist of the present invention is a pilot injection device for a fuel injection pump, which is characterized in that the rate piston is large when it comes into contact with the movement restricting portion.

[Function] In the pilot injection device for the fuel injection pump of the present invention configured as described above, first, when the fuel pressure in the pressurizing chamber of the fuel injection pump increases, the fuel pressure moves the accumulation piston toward the opposite side of the pressurizing chamber. to press. On the other hand, the spring presses the accumulation piston toward the pressurizing chamber by its elastic force. When the fuel pressure rises and exceeds the pressing force of the spring, the accumulation piston starts moving toward the movement restriction section provided on the side opposite to the pressurizing chamber. At the start of movement, the movement speed is high.

The spring constant of the spring is small when the accumulation piston starts moving, but is large when the accumulation piston comes into contact with the movement restricting part. Therefore, the moving speed of the accumulation piston decreases as it moves, and when it hits the movement restricting part, it is almost zero or at a low speed, so the hitting sound at that time becomes small.

[Examples] Examples of the present invention will be described below with reference to the drawings.
Figure 1 shows a pilot injection device according to an embodiment of the present invention.
FIG. 2 is a cutaway explanatory view showing a fuel injection pump of a diesel engine to which this pilot injection device is attached.

First, the configuration of the fuel injection pump to which the pilot injection device of this embodiment is attached will be explained using FIG.

As shown in the figure, the fuel injection pump 1 is of a distribution type, and inside the pump housing 11 is a cam plate 13 connected to a drive shaft 12 via a coupling, and a pump plunger that rotates and reciprocates integrally with the cam plate 13. 14 are arranged. This pump plunger 14 has a suction port 15 that sucks fuel inside the pump housing 11.
The pump cylinder 16 is fitted into the pump cylinder 16 and pressurizes the sucked fuel in the pressurizing chamber 17. The pump plunger 14 has a distribution port 14a for distributing the pressurized fuel to each distribution passage 18 at a predetermined timing and forcefully delivering the fuel to each cylinder of the diesel engine via a delivery valve 19, A spill port 14b is provided for overflowing fuel. A pilot injection device 20 is provided in communication with the pressurizing chamber 17 of the pump cylinder 16. The configuration of the pilot injection device 20 will be explained in detail later.

Also, a spill ring 3 is slidably fitted onto the pump plunger 14 near the spill port 14b.
1 adjusts the end timing of fuel pressurization by the pump plunger 14 and controls the fuel injection amount. This spill ring 31 is connected by a supporting lever 32 to a governor sleeve 34 which responds to the movement of the flyweight 33, and a control lever 37 which is linked to the accelerator pedal by a tension lever 35 and a governor spring 36.
and is moved according to the vehicle speed and the depression of the accelerator pedal. In addition, the pump housing 11
A timer device 39 is provided at the bottom of the pump housing 11 and is operated according to the fuel pressure within the pump housing 11 to control the fuel injection timing.

The pilot injection device 20 attached to the fuel injection pump 1 configured as described above operates when the fuel pressure in the pressurizing chamber 17 is increased by the movement of the pump plunger 14 and fuel injection is started. The system is configured as shown in FIG. 1 to perform pilot injection by once lowering the fuel pressure in the pressurizing chamber and temporarily stopping fuel injection.

That is, as shown in FIG. 1, the pilot injection device 20 includes a cylinder 44 in which an accumulation piston 43 is fitted inside a housing 42 in which a threaded portion 41 is formed, which is attached to the fuel injection pump 1. It is provided with a stopper 45 for restricting the movement of the rate piston 43, a spring 46 and a pressure pin 47 for urging the accumulation rate piston 43 toward the pressurizing chamber. The stopper 45 corresponds to a movement regulating section. The spring 46 is wound so that the coil diameter increases with each turn, and is installed so that the end portion with the smaller coil diameter is on the pressure pin 47 side.

Further, at the end of the housing 42 on the side opposite to the pressurizing chamber, oil leaked from the pressurizing chamber 17 side of the fuel injection pump 1 through the fitting surface of the accumulation piston 43 and the cylinder 44 is stored in a fuel tank. A cap 49 having a return passage 48 for returning the spring 46 to the lock nut 5 is fitted into the cap 49 for fixing the spring 46.
It is tightened and fixed by 0. Furthermore, spring 4
A shim 51 is fitted between the spring 6 and the cap 49 to adjust the biasing force of the spring 46.

Here, the cylinder 44 into which the accumulation piston 43 is fitted is communicated with the pressurizing chamber 17 via the communication hole 52. Further, the inner wall surface 44a of the end portion on the side of the communication hole 51 is formed into a funnel shape from the communication hole 52, and the peripheral edge 44b thereof is connected to the accumulation piston 4.
The diameter is larger than 3.

On the other hand, the head 43 of the accumulation rate piston 43
a is tapered at an angle smaller than the inner wall surface 44a of the funnel-shaped end of the cylinder 44, and the end surface thereof is connected to the communication hole 5 of the cylinder 44.
It is formed larger than 2 diameters.

Therefore, the inner wall surface 44a of the funnel-shaped end of the cylinder 44 becomes a seat against which the end edge of the accumulation piston head 43a comes into contact when the fuel pressure inside the pressurizing chamber 17 decreases.

Furthermore, as shown in the figure, a gasket 53 is provided for connecting the pilot injection device 20 into the pressurizing chamber 17 in an oil-tight manner, and a gasket 5 is provided for attaching the cap 49 to the housing 42 in an oil-tight manner.
4 is provided.

Next, the operation of the pilot injection device 20 will be explained.

When the pump plunger 14 of the fuel injection pump 1 is moved by the cam plate 13 to the right in FIG. The fuel enters the fuel tank and is force-fed through the delivery valve 19 to the fuel injection nozzle of the diesel engine. In this way, at the initial stage when pressure feeding of fuel is started, fuel injection (pilot injection) is performed from the fuel injection nozzle.
When the biasing force 6 is exceeded, the accumulation piston 43 moves rightward in FIG. 1, and its head 43a separates from the end inner wall surface 44a of the cylinder 44. Then, the pressure receiving area of the accumulation piston 43 increases from the end surface of the head 43a to the entire tapered surface, so the accumulation piston 43 rapidly moves to the right.

At this time, the spring 46 begins to contract as the accumulation piston 43 moves, starting with the coil on the cap 49 side, which has a smaller spring constant, and gradually contracts the coil on the pressure pin 47 side, which has a larger spring constant.
Therefore, the spring constant of the spring 46 increases as the amount of compression of the spring 46 increases, as shown in the graph of FIG. As a result, as shown in the graph of Fig. 4, the accumulation rate piston 4
The moving speed of the accumulating piston 43 is gradually reduced, and the speed of the accumulation piston 43 reaches almost zero or low speed, and then it hits the stopper 45 and stops. Therefore, the hitting sound when the accumulation piston 43 hits the stopper 45 is reduced, and the noise caused by this pilot injection device is improved.

On the other hand, when the accumulation piston 43 moves, the fuel pressure in the pump pressurizing chamber 17 once decreases, and the pressure feeding of fuel is temporarily stopped. After the accumulation piston 43 hits the stopper 45 and stops, the fuel is pumped again by the movement of the pump plunger 14 of the injection pump 1, and main fuel injection is executed.

When the fuel injection stroke of the fuel injection pump 1 is completed, the pressurizing chamber 17 is opened to the low pressure chamber of the fuel and the pressure decreases. It is returned to the position where it touches. At this time, since the angle of the funnel-shaped seat portion 44a is larger than the tapered surface of the accumulation piston head 43a, and the periphery of the seat portion is larger than the diameter of the accumulation piston 43, this portion becomes an oil sump. As a result, the moving speed of the accumulation piston 43 is reduced, and the seating noise is reduced.

In addition, in the above embodiment, although the above noise prevention effect was obtained, the accumulation rate piston 43
This does not cause large variations in the initial setting of the valve opening pressure. This is because if the spring constant is simply increased uniformly in order to prevent the hammering noise between the accumulation rate piston 43 and the stopper 45, the valve opening pressure of the accumulation rate piston 43 will fluctuate with respect to the set length of the spring. There is a problem in that the initial setting of the valve opening pressure is too large, and large variations occur in the initial setting of the valve opening pressure.In the case of the spring 46 of this embodiment, the valve opening pressure is Variations in initial settings can be suppressed.

Next, other shapes of the spring 46 will be explained with reference to the drawings.

The spring 46 in this embodiment is configured so that the coil diameter increases with each turn.
As the amount of compression of the spring 46 increases, the spring constant gradually increases.
For example, by configuring the coil to have two types of diameters as shown in FIG. 5, the spring constant may be increased in steps, and the same effect as in the above embodiment can be obtained with a simpler configuration. be able to.

Furthermore, instead of changing the coil diameter as described above, it is also possible to change the spring constant by changing the winding pitch, and as shown in Figure 6, the winding pitch can be configured to increase with each winding. Good too,
Further, as shown in FIG. 7, it may be configured to have two types of winding pitches.

Furthermore, it is also possible to change the spring constant by changing the thickness of the wire of the spring, and as shown in FIG. 8, the thickness of the wire may be increased with each turn. It is also possible to change the spring constant by changing two or more of the above-mentioned coil diameter, winding pitch, and wire diameter in combination. For example, as shown in Figure 9, the coil diameter It is also possible to configure the wire rod to have a smaller thickness and a larger wire thickness.

Further, although each of the examples described above uses one spring, two springs having different coil diameters, winding pitches, wire thicknesses, etc. may be used. For example, as shown in FIG.
The spring 61 may be fixed to a second spring 62 having a different wire thickness through a member 63.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiments, and may be modified in various ways without departing from the gist of the present invention.

Effects of the Invention As detailed above, in the pilot injection device of the fuel injection pump of the present invention, the spring that presses the accumulation piston toward the pressurizing chamber side of the fuel injection pump is activated when the accumulation piston starts moving. It has a small spring constant, and is configured to have a large spring constant when the accumulation piston comes into contact with the movement restricting part. As a result, when the accumulation rate piston hits the movement restriction part,
Since the moving speed of the accumulation piston is almost zero or low, the hitting sound when it hits is reduced, and noise can be prevented.

Further, wear of the accumulation piston and the movement regulating portion is also reduced, and durability can be improved.

Furthermore, when the accumulation piston starts moving, a spring with a small spring constant is used as the spring so that the accumulation piston starts moving with a small fuel pressure, so the valve opening pressure of the accumulation piston is reduced. Variations in initial settings can be suppressed.

[Brief explanation of the drawing]

Fig. 1 to Fig. 4 show an embodiment of the present invention, Fig. 1 is a cutaway explanatory diagram showing the configuration of the pilot injection device of this embodiment, Fig. 2 is a cutaway explanatory diagram showing the configuration of a fuel injection pump in which this pilot injection device is used, Fig. 3 is a graph showing the relationship between the elastic deformation amount of the spring and the spring constant, Fig. 4 is a graph showing the relationship between the spring constant and the moving speed of the accumulated piston, Fig. 5 to Fig. 10 are cross-sectional views showing various shapes of the spring of this invention. 1 ... fuel injection pump, 17 ... pressurizing chamber, 20
......pilot injector, 43...accumulated piston, 44...cylinder, 45...stopper, 46...spring.

Claims (1)

[Scope of Claim for Utility Model Registration] A cylinder connected to a pressurizing chamber of a fuel injection pump through a communication hole; a cylinder that is fitted into the cylinder and is movable by pressure in the pressurizing chamber; an accumulation piston that moves at high speed by the fuel pressure to depressurize the pressurizing chamber at the start of the pressing movement; a spring that presses and biases the accumulation piston toward the pressurizing chamber; and fuel in the pressurizing chamber. a movement regulating section that comes into contact with the accumulation piston that moves due to a pressure increase and limits the movement of the accumulation piston, and a pilot injection that executes a pilot injection before the main fuel injection of the fuel injection pump. In the pilot injection device for a fuel injection pump, the spring has a small spring constant when the accumulation piston starts moving, and a spring constant when the accumulation piston comes into contact with the movement restriction part. Device.