JPH053739Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a fuel injection valve, and more particularly to a fuel injection valve equipped with a pressure wave damping valve.

[Prior Art] In internal combustion engines, particularly diesel engines, high-pressure fuel is injected by opening and closing fuel injection valves. With these fuel injection valves, in order to perform more suitable fuel injection, if the fuel injection valve is opened and closed rapidly,
Pressure waves were sometimes generated at the needle tip when the valve was closed. If this pressure wave occurs after the end of the pilot injection, it will be difficult to accurately control the fuel injection amount in the main injection after the end of the pilot injection, or if the pressure wave occurs after the end of the main injection, unintended fuel injection will occur after the end of the main injection. There was a problem that caused the next injection.

Therefore, various proposals have been made to prevent the adverse effects of these pressure waves. For example, a fuel injection valve that is equipped with a check valve that allows fuel to flow in the direction of the nozzle (utility open 1984-84357)
This includes proposals for a fuel injection device (Japanese Patent Application Laid-Open No. 115461/1983) in which an absorption chamber for absorbing pressure waves is provided at the outlet of a fuel pump.

[Problems to be solved by the invention] However, such conventional fuel injection valves have the following problems. That is, (1) in a fuel injection valve equipped with a check valve that allows fuel to flow in the nozzle direction, the pipeline through which the pressure waves reciprocate is shortened from the nozzle to the check valve, and the period of pressure fluctuation is shortened.
Therefore, although the cycle is shortened, there is a problem that the pressure amplitude may not become sufficiently small, which may lead to secondary injection.

(2) Furthermore, fuel injection devices equipped with an absorption chamber that absorbs pressure waves have a complex and large structure, resulting in large pressure loss, and there are problems in integrating the structure with the fuel injection valve.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems and to provide a fuel injection valve that can effectively attenuate pressure waves with a simple configuration.

Structure of the invention [Means for solving the problems] In order to achieve the above object, the present invention has the following structure as a means for solving the problems. That is, a needle pressurizing chamber is provided which faces a pressure-receiving surface formed on a needle spring-biased in the valve-closing direction and presses the needle in the valve-opening direction by means of fuel pressure, and when the needle moves in the valve-opening direction, , a fuel injection valve that injects fuel from a nozzle, comprising: a control rod slidably disposed in series with the needle; and a control rod that faces the rear end of the control rod and presses the needle in the valve closing direction with fuel pressure. a fuel chamber; a control rod pressurizing chamber that faces a pressure receiving surface formed in the control rod and presses the control rod in the valve opening direction of the needle by means of fuel pressure; a piezoelectric actuator that pressurizes and depressurizes by expanding and contracting; a fuel passage that communicates the needle pressurizing chamber and the fuel chamber with a pressure accumulating chamber that stores pressurized fuel; and the needle pressurizing chamber and the fuel chamber. and a first valve element biased by a spring in the fuel passage between the fuel passage and the pressure accumulation chamber, a first check valve through which fuel can pass in the direction of the nozzle, and a first check valve slidably inserted into the first valve body. This is a configuration of a fuel injection valve characterized by comprising: a second check valve whose second valve body is biased by a spring to allow fuel to pass in a direction opposite to the nozzle.

[Function] In the fuel injection valve of the present invention having the above configuration, when the valve is opened, the piezoelectric actuator pressurizes the fuel pressure in the control rod pressurizing chamber and causes the control rod to slide in the needle valve opening direction. Due to the rapid sliding of the control rod, the pressure waves generated in the fuel chamber are damped by the second valve body of the second check valve, which is biased by a spring.

Further, the first valve body of the first check valve is moved against the biasing force of the spring, and pressurized fuel is supplied from the pressure accumulation chamber to the needle pressurization chamber via the fuel passage. Then, the pressure receiving surface receives the fuel pressure supplied to the needle pressurizing chamber, the needle slides in the valve opening direction, and fuel is injected from the nozzle.

Also, when the valve is closed, the piezoelectric actuator reduces the fuel pressure in the control rod pressurizing chamber, and the fuel pressure in the fuel chamber causes the control rod to press the needle in the valve closing direction, and the needle is pressed by the spring biasing force in the valve closing direction. This moves the valve in the valve closing direction. The pressure wave generated by the valve closing is applied to the second check valve, which is biased by a spring.
Attenuated by the valve body.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a sectional view showing a fuel injection valve as an embodiment of the present invention together with a fuel supply system. This fuel supply system includes a fuel supply pump P connected to the fuel tank T whose discharge pressure can be controlled, a pressure accumulation chamber R that temporarily stores fuel pressurized to a predetermined pressure by the fuel supply pump P,
A fuel supply pipe K and the like for supplying the fuel stored in the pressure accumulation chamber R to the fuel injection valve 1 are provided.

This fuel injection valve 1 includes a fuel injection valve body 2, a nozzle 6 in which a nozzle hole 4 is formed, a spacer 8, a nozzle holder 10 for fixing the nozzle 6 and the spacer 8 to the fuel injection valve body, and a side surface of the fuel injection valve body 2. A piezoelectric actuator 12 is attached to the fuel injection valve body 2, and a damping valve 14 is attached to the upper end of the fuel injection valve body 2.

A control rod 16 is provided inside the fuel injection valve main body 2 so as to be slidable in the axial direction, and a pressure pin 18 and a pressure pin 18 are also provided inside the nozzle 6 and the spacer 8 so as to be slidable in the axial direction. Needles 20 are each arranged in series. Further, a fuel chamber 22 is formed in the fuel injection valve body 2 at the rear end of the control rod 16 and communicates with the damping valve 14.
is supplied with pressurized fuel, which will be described later. Therefore, the fuel pressure in the fuel chamber 22 acts on the rear end of the control rod 16.

Further, the control rod 16 has a conical pressure receiving surface 16a at its intermediate portion, and a control rod pressurizing chamber 2 is provided in the fuel injection valve body 2 around the pressure receiving surface 16a.
4 is formed. This control rod pressurizing chamber 24
are the piezoelectric actuator 12 and the fuel injection valve body 2
It communicates with a pressure chamber 26 formed by.

On the other hand, a spring 28 is inserted into the fuel injection valve body 2 to urge the pressure pin 18 downward in the figure, and the needle 20 is pressed downward by the spring 28 via the pressure pin 18. This needle 20 has a conical pressure receiving surface 20a formed in its middle portion, and a needle pressurizing chamber 30 is provided in the nozzle 6 around this pressure receiving surface 20a. The needle pressurizing chamber 30 includes fuel passages 32, 34, which are formed in the fuel injection valve body 2, the spacer 8, and the nozzle 6, respectively.
an annular fuel passage 38 formed around the needle 20 and in communication with the fuel chamber 22 by 36;
The nozzle hole 4 is connected to the nozzle hole 4 through the nozzle hole 4.

The piezoelectric actuator 12 includes a piston 42 inserted into a sliding hole 40 formed in the fuel injection valve body 2, a disc spring 44 inserted between the piston 42 and the fuel injection valve body 2, and a disc spring 44 inserted into the fuel injection valve body 2. 2, and a piezoelectric element 48 inserted between the piston 42 and the casing 46. This piezoelectric element 48 has a laminated structure in which a large number of thin plate-shaped piezoelectric elements are laminated, and when a voltage is applied to this piezoelectric element 48, it expands in the axial direction due to an electrostrictive effect. Although the amount of elongation is small, around 50 μm, the response is extremely good, and the response time from application of voltage to elongation is about 80 μsec. When the voltage is removed, piezoelectric element 48 immediately contracts.

Further, the damping valve 14 has a fuel supply pipe K at one end.
A damping valve body 50 is connected to the valve body 50 and the other end is screwed into the fuel injection valve body 2, a valve body 52 is inserted into the damping valve body 50, and a valve body 52 is slidably supported by the valve body 52 and is attached to the lower end of the valve body 52. A valve body 54 that engages with the formed valve seat 52a, a spring 55 inserted between the valve body 54 and the valve body 52, and a second valve body that engages with the valve seat 54a formed within the valve body 54. A plug 58 is screwed into one end of the valve body 54, and a spring 60 is inserted between the plug 58 and the ball 56.

Further, a fuel passage 62 is formed on the fuel supply pipe K side of the damping valve body 50, and a fuel passage 64 is formed on the fuel injection valve body 2 side. Furthermore, the plug 58
A fuel passage 66 is formed in the valve body 54, a large diameter fuel passage 68 is formed in the valve body 54, and a small diameter fuel passage 70 is formed in connection with the fuel passage 68. Furthermore, an annular chamber 72 is formed on the outer periphery of the valve body 54, and a fuel passage 74 that communicates the annular chamber 72 with the fuel passage 68 is also formed (see FIG. 2).

Next, the operation of the fuel injection valve 1 of this embodiment described above will be explained in detail.

First, the fuel supply pump P is driven, the fuel in the fuel tank T is pressurized to a predetermined pressure, and the fuel is supplied to the fuel injection valve 1 via the pressure accumulation chamber R. The supplied fuel flows into the fuel passage 68 via the fuel passages 62 and 66. The pressure of the fuel that has flowed into the fuel passage 68 causes a downward force to act on the valve body 54, and when this force overcomes the upward force in the figure due to the urging force of the spring 55 on the valve body 54, the valve body
4 moves downward in the figure. This movement causes the valve body 54 to separate from the valve seat 52a of the valve body 52, thereby communicating the fuel passage 68 and the fuel passage 64 via the fuel passage 74 and the annular chamber 72. This communication supplies pressurized fuel to the fuel chamber 22 via the fuel passage 64.

When fuel at a predetermined pressure is supplied to the fuel chamber 22, the fuel pressure in the fuel chamber 22 presses the control rod 16 downward in the figure, and together with the spring force of the spring 28, the pressure pin 1
A downward acting force that presses the needle 20 downward in the figure acts through the needle 8 . On the other hand, the fuel supplied to the fuel chamber 22 is also supplied to the needle pressurizing chamber 30 via the fuel passages 32, 34, and 36. When fuel is supplied to the needle pressurizing chamber 30, the needle pressurizing chamber 30
An acting force acts on the pressure receiving surface 20a of the needle 20 due to the fuel pressure. Further, the upper end area of the control rod 16 is formed to be slightly larger than the pressure receiving surface 20a of the needle 20. Therefore, the force acting downward in the figure overcomes the force acting upward in the figure and presses the needle 20 downward in the figure. As a result, the fuel passage 38 and the nozzle hole 4
(state shown in Figure 1). Therefore,
No fuel is injected from the nozzle hole 4.

Next, from this state, the piezoelectric actuator 12
A positive voltage is applied to the piezoelectric element 48 of the piston 4.
2 is moved quickly, the pressure in the pressure chamber 26 rises rapidly. Along with this, the control rod pressurizing chamber 24
The pressure suddenly increases and pushes the control rod 16 upward in the figure.

When the control rod 16 rises rapidly, the fuel chamber 2
Pressure waves may occur within 2. When the generated pressure wave reaches the fuel passage 70 via the fuel passage 64, the pressure within the fuel passage 70 increases, and this increased pressure acts on the ball 56 in an upward direction in the figure. When this upward acting force exceeds the downward biasing force exerted on the ball 56 by the spring 60, the ball 56 is pushed up (the state shown in FIG. 3).
Due to the pressure caused by this pressure increase, the spring 60
The ball 56 is made to work to push up the ball 56 by overcoming the urging force of the ball 56. At this time, pressure energy is consumed,
Attenuates pressure waves.

On the other hand, the fuel chamber 22 and the fuel passages 32, 34, 36
Since the fuel pressure from the fuel pump P is constantly applied to the needle pressurizing chamber 30 which is communicated through the needle pressurizing chamber 30, this pressure rapidly pushes the needle 20 upward in the figure against the spring force of the spring 28. Therefore, the fuel passage 38 and the nozzle hole 4 are communicated with each other, and fuel is quickly injected from the nozzle hole 4.

Furthermore, when the voltage applied to the piezoelectric element 48 is removed, the piston 42 rapidly moves to the right in the figure, and due to the fuel pressure in the fuel chamber 22 and the spring force of the spring 28, the piston 42 moves through the control rod 16 and the pressure pin 18. needle 2
0 rapidly downwards in the figure. Therefore, communication between the fuel passage 38 and the nozzle hole 4 is rapidly cut off.
Immediately stop fuel injection.

This rapid blocking of the nozzle hole 4 by the needle 20 may generate pressure waves. The generated pressure wave flows from the tip of the needle 20 to the fuel passage 3.
8, needle pressurization chamber 30, fuel passages 36, 34,
32 and the fuel chamber 22 to reach the fuel passage 64. When the pressure wave reaches the fuel passage 64,
The pressure in fuel passage 64 increases and becomes higher than the pressure in fuel passage 62. Therefore, an upward acting force acts on the valve body 54 due to the biasing force of the spring 55 and the pressure due to the pressure increase, and the valve body 54 acts on the valve body 52.
is seated on the valve seat 52a. This seating blocks communication between the fuel passage 64 and the annular chamber 72 (second
condition). Next, when the pressure wave reaches the fuel passage 70, the pressure within the fuel passage 70 increases, and this increased pressure acts on the ball 56 in an upward direction in the figure. When this upward acting force exceeds the downward biasing force acting on the ball 56 by the spring 60,
Push up the ball 56 (state shown in Figure 3). The pressure resulting from this pressure increase overcomes the biasing force of the spring 60 and works to push the ball 56 up.

As described above, according to the fuel injection valve 1 of this embodiment,
Fuel is supplied to the needle pressurizing chamber 30 through the annular chamber 72 of the valve body 54, which has moved downward in the drawing due to the fuel pressure, the fuel passages 64, 32, etc., and the control rod 16 is moved upward in the drawing by the expansion of the piezoelectric element 1. At the same time, the needle 2 is heated by the fuel pressure in the needle pressurizing chamber 30.
0 upward in the figure, and fuel injection is performed from the nozzle hole 4.

In addition, the piezoelectric element 1 is contracted, the control rod 16 is moved downward in the figure by the fuel pressure, and the nozzle hole 4 is rapidly blocked by the needle 20. When a pressure wave is generated due to this blockage, the pressure wave is transmitted to the fuel passage 3.
8, 32, 64, etc., and when the pressure wave reaches the fuel passage 70, the pressure within the fuel passage 70 increases, pushing the ball 56 upward against the biasing force of the spring 60. At this time, pressure energy is consumed to attenuate the pressure wave.

In the present embodiment described above, when pilot fuel injection and main fuel injection are performed using the piezoelectric actuator 12, the pressure change at the tip of the needle 20, the lift amount of the needle 20, and the injection amount per unit time are each changed over time. FIG. 4 also shows this. As shown in the figure, according to the fuel injection valve 1, the pressure change due to the generation of pressure waves during rapid valve closing after the pilot injection a is the same as that without the damping valve 14 (dashed line).
(solid line). Therefore, the effect on the injection amount due to the pressure change during the main injection b is significantly smaller (solid line) than in the case without the damping valve 14 (broken line).

On the other hand, when a positive pressure wave (wave with increased pressure) acts on the needle pressurizing chamber 30, the moving speed of the needle 60 slows down, the valve closing time is delayed, and conversely, an expansion wave (wave with increased pressure) acts on the needle pressurizing chamber 30. When the wave (reduced wave) acts, the moving speed of the needle 60 becomes faster and the valve closing time becomes faster. In this way, if there is a difference in the pressure acting on the needle pressurizing chamber 30 due to pressure waves, a difference occurs in the valve opening time. Therefore, the fuel injection amount characteristics are affected and controllability is deteriorated. Therefore, controllability can be improved by damping the pressure waves using the damping valve 14.

In addition, since the pressure waves are sufficiently attenuated, the problem that secondary injection due to the pressure waves occurs at the end of the expansion stroke of the internal combustion engine, resulting in an increase in smoke in diesel engines, for example, is satisfactorily solved. Furthermore,
Secondary injection occurs in the intake stroke of a high-speed rotating internal combustion engine, and problems such as difficulty in controlling output by fuel injection amount, increase in noise due to increase in cylinder internal pressure, and even damage to the engine are all solved.

On the other hand, the pressure in the fuel passage 70 can be maintained higher than the pressure in the fuel passage 62 due to the biasing force of the spring 60 of the damping valve 14, so even if the pressure in the pressure accumulation chamber R decreases, the pressure in the fuel passage 70 can be maintained by the spring. 6
It can be maintained high by the pressure difference due to the biasing force of 0. Therefore, the downward force acting on the needle 60 when the valve is closed can be maintained in a large state, and even if the pressure in the pressure accumulation chamber R decreases, fuel leakage from the nozzle hole 4 and combustion gas intrusion from the nozzle hole 4 can be prevented. It can be prevented.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way, and it goes without saying that it can be implemented in various forms without departing from the gist of the present invention. .

Effects of the Invention As explained above, according to the fuel injection valve of the present invention, when the valve is opened, the pressure wave generated in the fuel chamber by the rapid movement of the control rod is transferred to the second valve body of the second check valve which is biased by the spring. The first
Fuel is supplied to the nozzle through the check valve, and when the valve is closed, the pressure wave generated by the valve closing is attenuated by the second valve body of the second check valve, which is an excellent effect. Therefore, secondary injection due to the generation of pressure waves can be prevented. In addition, by biasing the second valve body with a spring, the residual pressure inside the fuel injection valve can be maintained high, and in valves that close due to the action of fuel pressure, the valve can be closed more reliably. It also has this effect.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a fuel injection valve as an embodiment of the present invention together with a fuel supply system, FIG. 2 is an enlarged sectional view of the vicinity of the valve body, and FIG. 3 is an enlarged sectional view illustrating the operation of the valve body. FIG. 4 is a graph showing the pressure change, needle lift amount, and injection amount of the fuel injection valve of this embodiment over time. 20... Needle, 54... Valve body, 55, 60
... Spring, 56 ... Ball, 62, 64,
66, 68, 70, 74...Fuel passage.

Claims (1)

[Claims for Utility Model Registration] A needle pressurizing chamber is provided which faces a pressure receiving surface formed on a needle spring-biased in the valve closing direction and presses the needle in the valve opening direction by means of fuel pressure; In a fuel injection valve that injects fuel from a nozzle by movement in the valve opening direction, a control rod is slidably disposed in series with the needle, and a control rod facing the rear end of the control rod injects the needle with fuel pressure. a fuel chamber that presses in the valve closing direction; a control rod pressurizing chamber that faces a pressure receiving surface formed on the control rod and presses the control rod in the valve opening direction of the needle with fuel pressure; a piezoelectric actuator that increases or decreases the fuel pressure in the pressure chamber by expansion and contraction; and a fuel passage that communicates the needle pressurization chamber and the fuel chamber with a pressure accumulation chamber that stores pressurized fuel; a pressure chamber and a first valve element biased by a spring in a fuel passage between the fuel chamber and the pressure accumulation chamber; a first check valve through which fuel can pass in the nozzle direction; and a first check valve inside the first valve body. A fuel injection valve comprising: a second check valve whose second valve element slidably inserted is biased by a spring to allow fuel to pass in a direction opposite to the nozzle.