JPH0444842Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention particularly relates to a fuel injection valve provided in a fuel supply system of a diesel engine.

[Conventional technology and problems]

This type of fuel injection valve is electrically controlled to open and close using a piezoelectric element as an actuator in order to inject a predetermined amount of high-pressure fuel at a predetermined time. The valve is configured to directly close the valve by applying a voltage to the valve, and open the valve by releasing the voltage. However, when the fuel pressure is high, the piezoelectric element must exert a large biasing force to overcome the fuel pressure and close the needle valve, which forces the structure to be larger. Furthermore, if an abnormality occurs in the drive circuit of the piezoelectric element and voltage application becomes impossible, the needle valve opens and enters a fuel injection state, which is not a failsafe for the engine.

An object of the present invention is to obtain a fuel injection valve that has a compact structure and that does not inject fuel by mistake even when voltage cannot be applied to the piezoelectric element.

In addition, as an injection valve using a piezoelectric element,
Japanese Patent No. 47-35245 discloses a configuration in which a needle valve is closed by a spring when not in operation, and opened by high-pressure fuel when fuel is injected.

[Means for solving problems]

The fuel injection valve according to the present invention receives high-pressure fuel from the reservoir by constantly communicating with an actuator having a piezoelectric element that expands and contracts in response to applied voltage and a reservoir that holds high-pressure fuel at a predetermined pressure. a fuel reservoir that is connected to the fuel reservoir; a nozzle that can communicate with the fuel reservoir; Therefore, the needle valve is biased in the valve opening direction, and on the contrary, the spring biases the needle piece in the valve closing direction in order to close the jet port, and the needle valve cooperates with the spring to bias the needle valve in the valve closing direction. a pressurized chamber on which pressure is applied to bias the actuator in the valve-closing direction; and a switching valve that is displaced in response to expansion and contraction of the actuator to selectively communicate the low-pressure fuel storage section and the reservoir with the pressurized chamber. The switching valve is slidably arranged in a bore that passes through the housing in the axial direction, and the pressure of the pump chamber of the actuator is guided to the upper end surface of the switching valve, and the pressure of the pump chamber of the actuator is guided to the lower end surface of the switching valve. is provided with a return spring, and when no voltage is applied to the actuator, it is displaced toward the actuator by the pressing force of the return spring, communicating the reservoir and the pressurizing chamber, and causing the pressurizing chamber to communicate with the reservoir. The needle valve is closed by increasing the pressure in the pressure chamber, and when voltage is applied to the actuator, the actuator is closed against the pressing force of the return spring due to the increase in pressure in the pump chamber. The needle valve is configured to be displaced to the opposite side of the pressurizing chamber and communicating with the low-pressure fuel storage section, and to open the needle valve by lowering the pressure in the pressurizing chamber. do.

〔Example〕

The present invention will be explained below with reference to the illustrated embodiments.

FIG. 1 shows an embodiment of the present invention. The fuel stored in the fuel tank 10 is fed under pressure to the fuel injection valve via a low pressure pump 11 for fuel feed, a high pressure pump 12, and a reservoir 13 that suppresses pressure fluctuations in the fuel, and the needle valve as described in detail later. 21
is pushed up and ejected from the nozzle 22. The needle valve 21 is controlled by an actuator 23 to be forcibly closed or opened. The actuator 23 has a drive circuit 14 connected to the electrode plug 1.
5 by applying or releasing a voltage. An electronic control unit (ECU) 16 including a microcomputer controls the drive circuit 14 based on various data obtained from the engine 17. Note that the high-pressure pump 12 is driven by an engine 17.

The actuator 23 is formed by laminating and polymerizing a large number of piezoelectric elements, and extends in the axial direction when a voltage is applied, and contracts when the voltage is released. Actuator 23 is housed within upper body 24 . The upper end of the actuator is the body 24
The piston 25 is fixed to the upper inner wall of the
is attached, and a disc spring 26 is inserted between the piston 25 and the inner wall stepped portion 27 of the body 24. A pump chamber 28 is formed between the lower surface of the piston 25 and the lower inner wall of the body 24. Thus, when voltage is applied to the actuator 23, the piston 25 is lowered against the disk spring 26, compressing the pump chamber 28 and pressurizing the chamber. Conversely, when the voltage is released, the actuator 23 contracts, so the piston 25 is moved by the disc spring 26.
The pump chamber 28 expands and is depressurized. Note that fuel is introduced into the upper body 24 via the low-pressure pump 11 to cool the actuator 23.

A housing 32 and a disk member 33 are contained in the lower body 31 fixed to the lower end of the upper body 24.
A cylinder member 35, a distance piece 36, and a nozzle body 37, which are housed therein and are integrally connected to each other via a pin 34, are connected to the disk member 3.
It is placed below 3. These housings 3
2. The disk member 33, cylinder member 35, distance piece 36 and nozzle body 37 are as follows:
They are mutually fixed by a retaining nut 38 screwed onto the lower body 31. Lower body 31
has an inlet port 41 for guiding high-pressure fuel into the body 31 and an outlet port 42 for discharging excess fuel to the outside of the body 31, the inlet port 41 is connected to the reservoir 13, and the outlet port 41 is connected to the reservoir 13. 4
2 communicates with the fuel tank 10.

The housing 32 is provided in close contact with the lower surface of the upper body 24, and a switching valve 44 is slidably accommodated in a bore 43 formed through the axial center of the housing 32. The return spring 45 is provided between the switching valve 44 and the disk member 33, and always urges the switching valve 44 upward. Bore 43 has the first
and second annular grooves 46 and 47 are formed, the first annular groove 46 communicating with the inlet port 41 and the second annular groove 47 exiting through a passage 48 bored in the switching valve 44 and the bore 43. It communicates with port 42.
The switching valve 44 has a small diameter portion 44a formed in the center of the outer peripheral surface, and this small diameter portion 44a communicates with the first annular groove 46 when the switching valve 44 is in the upper position.
communicates with the second annular groove 47 when in the lower position.

Hole 51 formed in the lower end wall of the upper body 24
A displacement width increasing piston 52 is slidably supported on the. This displacement-enhancing piston 52 has a smaller cross-sectional area than the pump chamber 28 and therefore
The displacement is larger than that of 5. The lower end of the displacement width increasing piston 52 is always in contact with the upper end surface of the switching valve 44. The piston 25 descends via the actuator 23 and the pump chamber 28
When pressurized, the displacement width increasing piston 52 descends and pushes down the switching valve 44 against the return spring 45, and conversely, the actuator 23 contracts, the piston 25 rises, and the pump chamber 28 is depressurized. and,
The switching valve 44 is biased by the return spring 45 and pushes up the displacement amplifying piston 52 to rise.

A pressurizing piston 61 is slidably accommodated in a hole formed in the center of the disk member 33, and a pressurizing chamber 62 formed by this hole and the upper surface of the pressurizing piston 61 is bored in the housing 32. passage 6
3 into the bore 43. This passage 63
opens into the bore 43 between the first and second annular grooves 46,47. Thus, the passage 63 communicates with the first annular groove 46 via the small diameter portion 44a of the switching valve 44 when the switching valve 44 is in the upper position, and communicates with the first annular groove 46 via the small diameter portion 44a when the switching valve 44 is in the lower position. It communicates with the second annular groove 47 .

A chamber 64 bored in the axial center of the cylinder member 35
A push rod 65 is accommodated therein, and this push rod 65 is constantly urged downward by a spring 66. The upper end of the push rod 65 is
It fits into the hole of the disk member 33 and comes into contact with the pressurizing piston 61, while the lower end is urged by the spring 66 and comes into contact with the upper end of the needle valve 21.
The needle valve 21 is slidably supported within the hole 67 of the nozzle body 37 , and its upper end passes through the central hole 68 of the distance piece 36 and fits into the chamber 64 of the cylinder member 35 . Therefore, the needle valve 21 is always urged downward by the elastic force of the spring 66 and the pressure in the pressurizing chamber 62, and is at the lower end position to close the nozzle 22 when not in operation.

A fuel reservoir 71 is formed in the center of the hole 67 of the nozzle needle 21, and a portion of the needle valve 21 below the fuel reservoir 71 is formed to have a small diameter, and a space 72 is formed between the fuel reservoir 71 and the hole 67. The fuel passage 73 is formed through the housing 32, the disk member 33, the cylinder member 35, the distance piece 36, and the nozzle body 37, communicates the inlet port 41 with the fuel reservoir 71, and constantly supplies high-pressure fuel to the fuel reservoir 71. lead.

The apparatus of this embodiment operates as follows to perform fuel injection.

When a voltage is applied by the drive circuit 14, the actuator 23 expands and pushes down the piston 25, increasing the volume of the pump chamber 28 by S ₁ ×X ₁ (S ₁ is the cross-sectional area of the piston 25, and X ₁ is the cross-sectional area of the piston 25. displacement). Fuel oil is held in the pump chamber 28 , and the oil corresponding to the decrease in the volume of the pump chamber 28 flows into the hole 51 and pushes down the displacement increasing piston 52 . At this time, the displacement width increasing piston 52 is displaced by S ₁ /S ₂ ×X ₁ , assuming that its cross-sectional area is S ₂ .

That is, the switching valve 44 compresses the spring 45 and is displaced downward by S ₁ /S ₂ ×X ₁ , and as a result, as shown in FIG. 2, the switching valve 44 closes the first annular groove 46 and The two annular grooves 47 are communicated with the passage 63. Thus, the pressurizing chamber 62 communicates with the fuel tank 10 via the passage 63, the second annular groove 47, and the outlet port 42, and the pressure within the pressurizing chamber 62 decreases. The high-pressure fuel supplied by the pumps 11 and 12 is led from the inlet port 41 through the fuel passage 73 to the fuel reservoir 71, and urges the needle valve 21 upward. As the pressure decreases, the needle valve is raised against this pressure and the elastic force of the spring 66. That is, the nozzle 22 is opened and high pressure fuel is discharged from the nozzle 22.

In the above fuel injection operation, the force with which the displacement amplifying piston 52 presses down the switching valve 44 is equal to the force with which the actuator 23 displaces the piston 25 downward.
S ₂ /S becomes ₁ times, and decreases by the ratio of the cross-sectional area of the displacement amplifying piston 52 to the cross-sectional area of the pump chamber 28. However, in this embodiment, the actuator 23 does not directly close the needle valve 21, but merely displaces the switching valve 44 against the return spring 45 via the displacement-increasing piston 52. There is no need to forcefully press down the width piston 52.

Contrary to the above, when the voltage application to the actuator 23 is cut off, the actuator 23 contracts and returns to its original length, and the piston 25 is pushed up by the disc spring 27 to increase the volume of the pump chamber 28. Therefore, the displacement amplifying piston 52 and the switching valve 44
is raised and returned to its original position by the negative pressure generated in the pump chamber 28 and the elastic force of the return spring 45. As a result, as shown in FIG. 1, the switching valve 44 closes the second annular groove 47 and the first
The annular groove 46 and the passage 63 are communicated with each other. High pressure fuel supplied to the inlet port 41 is guided into the pressurizing chamber 62 through the first annular groove 46 and the passage 63, and the pressurizing piston 61 is urged downward. This biasing force is transmitted to the needle valve 21 via the push rod 65, and the needle valve 21 applies the biasing force from the pressurizing piston 61 to the nozzle port 21 by the elastic force of the spring 66.
2 to end fuel injection.

The switching valve 44 selectively connects the inlet port 41 and the outlet port 42 to a passage 63, i.e., a pressure chamber 6
Any other structure may be used as long as it leads to the valve 2. Also, the displacement amplifier piston 52 may be omitted and the switching valve 44 may be directly driven by the actuator 23.

[Effect of idea]

In the present invention, an actuator having a piezoelectric element does not directly drive the needle valve, but a highly responsive piezoelectric element controls the high pressure of fuel supplied from a high-pressure pump to open and open the valve. Since the piezoelectric element can be used to drive the needle valve in both cases of closing and closing, the actuator is small and has a small output, compared to the conventional example in which a piezoelectric element is directly used to drive the needle valve. In addition, compared to the conventional example in which either the valve opening or closing is performed by the force of a spring, the responsiveness to control is improved for both valve opening and closing. Therefore, it becomes possible to accurately control the injection timing and injection amount of the fuel injection valve. Furthermore, when no voltage is applied to the actuator, a fail-safe function is provided in which the needle valve is reliably closed and fuel is never released.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing one embodiment of the present invention;
The figure shows the operating state of the embodiment and is a cross-sectional view showing the structure in a simplified manner. 10...Fuel tank (low pressure fuel storage section), 12
... High pressure pump (pressure source), 21 ... Needle valve,
22... spout, 23... actuator, 44...
...Switching valve, 62...pressurization chamber.

Claims (1)

[Scope of utility model registration request] an actuator having a piezoelectric element that expands and contracts in response to applied voltage; a fuel reservoir that receives high-pressure fuel from the reservoir by being in constant communication with a reservoir that holds high-pressure fuel at a predetermined pressure; and the fuel a nozzle that can communicate with a reservoir, and a valve that is biased in the valve opening direction by the pressure of fuel that is constantly supplied to the fuel reservoir in order to open and close the nozzle and inject the fuel in the fuel reservoir from the nozzle. conversely, a spring that biases the needle piece in a valve-closing direction to close the nozzle port, and a spring that works together with the spring to bias the needle valve in the valve-closing direction. It is equipped with a pressurization chamber to which pressure acts, and a switching valve that is displaced in response to expansion and contraction of the actuator to selectively communicate the low-pressure fuel storage section and the reservoir with the pressurization chamber, and the switching valve is configured to is slidably disposed in a bore that passes through the housing in its axial direction, the pressure of the pump chamber of the actuator is guided to its upper end surface, and a return spring is disposed on its lower end surface. When the actuator is not energized and no voltage is applied to it, the actuator is displaced toward the actuator side by the pressing force of the return spring to communicate the reservoir and the pressurizing chamber, thereby increasing the pressure in the pressurizing chamber. When the needle valve is closed and a voltage is applied to the actuator, the actuator is displaced to the opposite side of the actuator against the pressing force of the return spring due to the increase in pressure in the pump chamber. A fuel injection valve characterized in that the pressurization chamber and the low-pressure fuel storage section are communicated with each other, and the needle valve is opened by lowering the pressure in the pressurization chamber.