JPH02146255A - Fuel injection device - Google Patents

Abstract

PURPOSE:To prevent the breakage of a plate valve in a device provided with the plate valve, having an orifice corresponding to an oil passage, in a pressure control chamber for free separation from a seat part in a pressure control chamber by constructing the device in such a way as to guide the motion of the plate valve along the inner wall of the pressure control chamber. CONSTITUTION:In a fuel injection device, a nozzle needle 9 is slidably fitted into a valve body sliding hole 6 formed in a valve casing 4. A piston 16 connected integrally with the needle 9 is also fitted into a cylinder 18 formed in a body lower 2, and a pressure control part 19 is partitioned at the upper edge part of the piston 16 in the cylinder 18. A plate valve 35 provided with an orifice 36 corresponding to the oil passage 30 is fitted into the pressure control part 19, but in this case, the plate valve 35 is slided along the inner wall 19a of the pressure control chamber 19 as well as a cutout part 38 closed when it is in contact with a seat part 37 and released when it is separated from the seat part 37 is formed at the plate valve 35.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a fuel injection device used for injecting and supplying fuel to, for example, a diesel engine. [Prior art 1] Conventionally, as a fuel injection device for a diesel engine, for example,
As disclosed in Japanese Unexamined Patent Publication No. 59-165858, fuel pressurized to a constant high pressure by a pressure accumulator is guided into a fuel reservoir chamber provided so as to surround the outer periphery of the intermediate portion in the longitudinal direction of the needle. The hydraulic pressure is applied to the needle as a force in the valve opening direction, while a piston that moves integrally with the needle is provided at the other end of the needle opposite to the valve body, and the valve is closed against the end face of the piston. This pressure side forms a pressure control chamber filled with fuel through an oil passage to apply a force in the direction? 7 [There is a structure in which the force of the piston in the valve closing direction is controlled by the inflow and outflow of fuel in one chamber, the initial injection rate is suppressed, and the fuel is sharply cut at the end of injection. Figure 8.9 shows the configuration of the pressure control chamber and plate valve in the above fuel injection device, and shows the configuration of the pressure control chamber and plate valve in the above fuel injection device.
0 and the lower casing 51 form a pressure control chamber 52. An oil passage 53 through which fuel flows in and out is formed in the upper casing 50 and opens into a seat portion 54 on the lower surface of the casing 50. A cylinder 55 formed in the lower casing 51 has a piston 56 that moves integrally with a needle (not shown) whose end is connected to the pressure control chamber 52.
It is slidably fitted in the state facing the front side. A plate valve 57 having an orifice 58 corresponding to the oil passage 53 is housed in the pressure control chamber 52 so as to be able to move toward and away from the seat portion 54 . Further, a return spring 6° is provided between the lower surface of the plate valve 57 and the bottom of the recess 59 formed on the end surface of the piston 56 to urge the plate valve 57 toward the seat portion 54. Due to this return spring 60, the seat is always seated on the seat portion 54, and only when high-pressure fuel flows from the oil passage 53, the seat portion 54 is seated.
It is designed to be separated from the As shown in FIG. 9, the diameter of the plate valve 57 is set smaller than the inner diameter of the pressure control chamber 52, and the valve opens 57.
A predetermined gap is formed between the outer periphery and the inner wall 52a of the pressure control chamber 52, so that the pressure control chamber 52 at the end of injection
The aim is to achieve a sharp cut in fuel without obstructing the flow of fuel into the engine. [Problems to be Solved by the Invention] However, the outer periphery of the plate valve 57 and the pressure control chamber 52
Since a predetermined gap is provided between the plate valve 57 and the inner wall 52a of the plate valve 57, the plate valve 57 is not guided. When approaching and separating, the plate valve 57 may fall, as shown by the two-dot chain line in FIG.
Movement in the radial direction is likely to occur (there is a problem that this causes an uneven load to act on the return spring 60, reducing durability. Also, if an uneven load acts on the return spring 60, the plate valve 57 There is a problem that the return spring 60 may be broken due to slipping between the lower surface and the recess 59 and being pinched between the plate valve 57 and the piston 56.
4, if the plate valve 57 is tilted down as shown in FIG. 8, the outer peripheral edge is likely to abut against the edge of the seat portion 54 and be worn out, resulting in a problem of poor sealing. This invention was made to solve the above-mentioned problems, and its purpose is to eliminate the tilting and play of the plate valve by guiding the movement of the plate valve by the inner wall of the pressure control chamber, and to prevent the plate valve from returning. To provide a fuel injection device that can prevent a spring from folding and R, and can also prevent damage to the seat portion of a plate valve, prevent wear on the outer peripheral edge, and maintain good sealing performance. It's about doing. [Means for Solving the Problems] In order to achieve the above object, the present invention has a valve body sliding hole, a fuel reservoir chamber for receiving high pressure fuel from a pressure accumulator, and a nozzle hole at the tip. The casing member is slidably fitted into the valve body sliding hole of the casing member,
By moving in the axial direction, the valve body at the tip opens and closes the nozzle hole.
The nozzle needle, which receives the hydraulic pressure in the fuel reservoir chamber as a force in the valve opening direction, is slidably fitted into a sill formed in the casing member, and the nozzle needle is fitted on the proximal end side of the nozzle needle. A piston that moves integrally with the nozzle needle and fuel that applies a force in the valve closing direction to one end surface of the piston are filled through an oil passage, and the plate valve is provided with an orifice corresponding to the oil passage. The plate valve is housed so as to be able to come into contact with and be separated from the seat portion where the oil passage opens, and further includes a return spring that urges the plate valve toward the seat portion. A pressure control chamber that controls the force in the valve closing direction, a high-pressure side passage that supplies high-pressure fuel from the pressure accumulator to the oil passage, and a low-pressure side passage that releases fuel in the pressure control chamber to the low-pressure side are selectively connected. In the fuel injection device, the plate valve is slidably fitted to the inner wall of the pressure control chamber, and the plate valve has a control valve that is closed when in contact with the seat part and that is closed from the seat part. The gist of the fuel injection device is a fuel injection device that has a notch that opens when the fuel injection device is separated from the fuel injection device. Further, a locking recess for housing and locking a part of the return spring may be provided on the lower surface of the plate valve.

[Effect]

High-pressure fuel from the pressure accumulator is supplied to a fuel reservoir provided within the casing member, and a force in the valve-opening direction always acts on the nozzle needle. When the control valve is switched so that the oil passage is connected to the low-pressure side passage that releases fuel in the pressure control chamber to the low-pressure side, the plate valve is seated on the seat of the pressure control chamber by the biasing force of the return spring. The fuel in the pressure control chamber flows out through the opening orifice, the nozzle needle moves together with the piston, and the fuel in the fuel reservoir chamber is injected from the nozzle hole. Then, when the control valve is switched to connect the high pressure side passage to the oil passage, the plate valve separates from the seat portion while being guided by the inner wall of the pressure control chamber against the biasing force of the return spring. As the plate valve is spaced apart, the notch is opened, high pressure fuel flows into the pressure control chamber, the pressure rises rapidly, the nozzle hole is closed by the nozzle needle, and the injection is sharply cut. In addition, by providing a locking recess on the lower surface of the plate valve that accommodates and locks a portion of the return spring, the return spring is securely locked in a predetermined position of the plate valve and does not slip. It is not pinched between the pistons, thus preventing the return spring from breaking. [Embodiment] An embodiment in which the present invention is embodied in a fuel injection device for a diesel engine will be described below with reference to FIGS. 1 to 5. FIG. 5 is a sectional view of the fuel injection device for a diesel engine according to this embodiment. The lower casing member 1 is the body lower 2
It consists of a connecting portion 3 and a valve casing 4, and each member 2.degree. 3.4 is integrated by a retaining ring 5. A valve body sliding hole 6 and a fuel reservoir chamber 7 are formed in the valve casing 4, and a nozzle hole 8 communicating with the fuel reservoir chamber 7 is formed at the tip. A large diameter portion 10 of a nozzle needle 9 is slidably fitted into the valve body sliding hole 6. A connecting portion 11 is formed on the large diameter portion 10 of the nozzle needle 9, and a small diameter portion 12 and a valve body portion 13 are integrally formed on the lower tip portion. And this valve body part 1
3, the seat portion X is opened and closed, and the injection from the nozzle hole 8 is turned on and off. A flange 14, a piston pin 15, and a piston 16 are integrally connected to the base end of the connecting portion 11 of the nozzle needle 9. Further, the nozzle needle 9 is urged in the closing direction by a spring 17. The piston 16 is slidably fitted into a cylinder 18 formed in the lower body 2, and a pressure control chamber 19 is formed within the cylinder 18 from which the end of the piston 16 is exposed. An upper casing member 20 having a three-way control valve 21 (electromagnetic valve) is closely connected to the body lower 2 . That is, the cylindrical body upper 22 is screwed onto the body lower 2, the three-way valve body 23 is placed in the internal hole of the body upper 22, and the retaining nut 24 is attached to the body upper 2.
It is screwed into the internal hole of 2. An outer valve 25 is slidably fitted into the three-way valve body 23, and an inner valve 26 is disposed in the inner hole of the outer pulp 25. When the coil 27 is demagnetized, the outer valve 25 is in the lower position due to the biasing force of the spring 28, and the high pressure side passage 29 and the pressure control chamber 19 are communicated via the oil passage 30. Also, coil 2
7 is excited, the outer valve 25 moves upward, and the pressure control chamber 19 and the drain passage (low pressure side passage) 31 are communicated via the oil passage 30. A fuel supply passage 32 is formed in the lower casing member l, one end of which is connected to the casing member (body lower 2).
The other end is exposed to the surface of the fuel reservoir chamber 7 and is connected to the high pressure side passage 2 of the upper casing member 20.
It is connected to 9. Furthermore, the lower casing member (body lower 2) 1
An inlet 33 is screwed into the surface of the fuel supply passage 32 and communicates with the fuel supply passage 32 . The common pressure accumulating device (common rail) 34 accumulates pressure of fuel supplied from the fuel pump, and supplies it to each fuel injection valve. The high-pressure fuel in the common pressure accumulator 34 is supplied to the fuel reservoir chamber 7 via the inlet 33 and the fuel supply passage 32, and is also supplied to the three-way control valve 21. Further, the fuel in the drain passage 31 can be drained into a drain tank. As shown in FIGS. 1 and 2, an orifice 36 corresponding to the oil passage 30 is provided in the pressure control chamber 19. A plate valve 35 equipped with a plate valve 35 is slidably fitted along the inner wall 1.93 and can be moved toward and away from a seat portion 37 in which the oil passage 30 opens. A plurality of (four in this embodiment) arc-shaped notches 38 are formed at predetermined intervals in the corner.Each of the notches 38 is cut out by the seat part 37 when the valve opening 35 is in contact with the seat part 37. Closed and seat part 37
When it is separated from the oil passage 30, it is opened and communicated with the oil passage 30. When each notch 38 is opened, it facilitates the inflow of high-pressure fuel into the pressure control chamber 19, accelerates the rise in fuel pressure within the same chamber 19, and moves the nozzle needle 9 instantaneously (less than 0.2 ms). Nozzle hole 8
closes to cut the jet sharply. In order to keep the injection cut time T e n d to 0°2 ms or less, it is desirable that the area of all the notches 38 be 3fi2 or more, as shown in FIG. 4, and in this embodiment, it is 4.5 ua. A locking recess 39 is formed in the center of the lower surface of the plate valve 35, and the plate valve 35 is seated between this recess 39 and a locking recess 40 formed on the end surface of the piston 16. Part 3
A spring 41 for returning 1 is interposed to urge the 7 side. Due to the return spring 41, the plate valve 35 is always seated on the seat portion 37 as shown by the solid line in FIG. and is spaced apart from the seat portion 37. Therefore, due to the action of the three-way control valve 21, the drain passage 31
When the fuel in the pressure control chamber 19 is in communication with the oil passage 30, the fuel in the pressure control chamber 19 flows out to the low pressure side through the orifice 36, the oil pressure in the pressure control chamber 19 slowly decreases, and the nozzle needle 9 moves as shown in FIG. As shown by 8, the fuel is injected by slowly moving (lifting) in the valve opening direction. Further, when the high pressure side passage 29 and the oil passage 30 communicate with each other due to the action of the three-way control valve 21, the plate valve 35 is separated from the seat portion 37 against the biasing force of the return spring 41, and each notch portion 38 is opened. When the pressure control chamber 19 is opened, high pressure fuel flows into the pressure control chamber 19 and the pressure rises rapidly.
The force applied in the valve closing direction from 6 to the nozzle needle 9 exceeds the force applied in the valve opening direction due to the pressure in the fuel reservoir chamber 7, and the nozzle needle 9 is instantly moved as shown by B in FIG. 8 is closed and the jet is sharply cut. At this time, in this embodiment, the plate valve 35 is configured to be slidably fitted along the inner wall 19a of the pressure control chamber 19, so when the plate valve 35 approaches and separates from the seat portion 37, the conventional The return spring 41 prevents the plate valve 57 (see Fig. 8) from falling or moving in the radial direction.
without applying an unbalanced load to the return spring 4.
The durability of No. 1 can be improved. Also, plate valve 3
When the plate valve 5 is seated on the seat part 37, the edge contact with the seat part 37 can be eliminated to prevent wear of the outer peripheral edge of the plate valve 35, and good sealing performance can be maintained. Furthermore, in this embodiment, a locking recess 39 for housing and locking the return spring 41 is provided on the lower surface of the plate valve 35.
The return spring 41 can be securely locked in a predetermined position of the plate valve 35 to prevent it from slipping, thereby preventing breakage of the return spring 41 due to the spring 41 being sandwiched between the plate valve 35 and the piston 16. It can be prevented. In the embodiment described above, the notch 38 formed in the plate valve 35 is arcuate, but as shown in FIG. 6, the notch 42 may be linear in order to facilitate machining. Further, in the above embodiment, a notch 38 is provided on the outer periphery of the plate valve 35.
However, as shown in FIG. 7, slot-shaped notches 43 that do not communicate with the oil passage 30 when the valve opening 35 is seated on the seat portion 37 may be formed at a predetermined corner. Moreover, if the dimension of the plate valve 35 in the axial direction is increased,
Stability can be further improved. [Effects of the Invention] As described in detail above, according to the present invention, by guiding the movement of the plate valve by the inner wall of the pressure control chamber, the plate valve is prevented from collapsing or playing, and the breakage of the spring is prevented. In addition, it has the excellent effect of eliminating edge contact with the seat portion of the plate valve, preventing wear of the outer peripheral edge portion, and maintaining good sealing performance. In addition, by providing a locking recess on the lower surface of the plate valve that accommodates and locks a portion of the return spring, the return spring is locked in a predetermined position of the plate valve to reliably prevent slippage, and the return spring breakage can be reliably prevented.

[Brief explanation of the drawing]

1-5 show an embodiment of a fuel injection device for a diesel engine embodying the present invention, FIG. 1 is a longitudinal sectional view showing a plate valve, and FIG. 2 is the same (a plan sectional view, and FIG. is a diagram for explaining the operation of the nozzle needle, FIG. 4 is a graph showing the relationship between the injection cut time and the total area of the notch, FIG. 5 is a vertical cross-sectional view showing the entire fuel injection device, and FIG. FIG. 7 is a plan sectional view showing another plate valve; FIG. 8 is a longitudinal sectional view showing a conventional plate valve;
FIG. 9 is a plan sectional view showing the same conventional plate valve. In the figure, l is the casing member, 6 is the valve body sliding hole, 7 is the fuel reservoir chamber, 8 is the nozzle hole, 9 is the nozzle needle, 13 is the valve body, 16 is the piston, 18 is the cylinder, and 19 is the pressure Control room, 19a is an inner wall, 21 is a three-way control valve, 29 is a high pressure side passage, 3o is an oil passage, 31 is a low pressure side passage, 34 is a common pressure accumulator, 35 is a plate valve, 36 is an orifice, 37 is a seat part, 38, 42, 43 are notches, 39 are locking recesses,
41 is a return spring. Patent Applicant Nippondenso Co., Ltd. Agent Patent Attorney On 1) Hirosenmi Figure 2 Figure 4 Texture curved axis (mm2) @ Figure 8 Figure 9vIJ

Claims (1)

[Scope of Claims] 1. A casing member having a valve body sliding hole, a fuel reservoir chamber for receiving high-pressure fuel from a pressure accumulator, and a nozzle hole at its tip; and a valve body of this casing member. a nozzle needle that is slidably fitted into the sliding hole, opens and closes the nozzle hole with a valve body at its tip by moving in the axial direction, and receives the liquid pressure in the fuel reservoir chamber as a force in the valve opening direction; a piston that is slidably fitted into a cylinder formed in a casing member and moves integrally with the nozzle needle on the base end side of the nozzle needle; and a valve closing direction with respect to one end surface of the piston. Fuel that applies force is filled through the oil passage, and a plate valve having an orifice corresponding to the oil passage is housed in a seat portion where the oil passage opens so as to be able to come into contact with and separate from the plate valve. It has a return spring that biases the part side.
a pressure control chamber that controls the force of the piston in the valve closing direction by the inflow and outflow of fuel by the action of the plate valve;
In the fuel injection device, the fuel injection device includes a control valve that switches and connects a high-pressure side passage that supplies high-pressure fuel from the pressure accumulator to the oil passage and a low-pressure side passage that releases fuel from the pressure control chamber to the low-pressure side. The plate valve is slidably fitted to the inner wall of the pressure control chamber, and the plate valve has a notch that is closed when it is in contact with the seat part and opened when it is separated from the seat part. A fuel injection device characterized by: 2. The fuel injection device according to claim 1, wherein a locking recess is provided on the lower surface of the plate valve to accommodate and lock a part of the return spring.