JPH10288151A - Accumulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce pressure pulsation in an extensive range in simple constitution. SOLUTION: This accumulator 39 is capable of reducing pressure pulsation in an extensive range received by a first chamber in simple constitution as it is constituted so that it is divided into the first chamber 46, a second chamber 51 and a third chamber 41 by first and second diaphragms 47, 49 arranged in a housing 43, the first chamber 46 is communicated to a fuel discharge passage as a pressure chamber, the second chamber 51 is communicated to a fuel supply passage through a restriction 55 as a fuel pressure chamber and the third chamber 41 is filled with gas. Additionally, as the restriction 55 is interposed between the fuel supply passage and the second chamber 51, the second chamber 51 is never influenced by pulsation of the fuel discharge passage and the first diaphragm 47 which is the pressure receiving surface never synchronously promotes pulsation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an accumulator for reducing pulsation in a fuel passage of a fuel injection device, and more particularly to an accumulator for reducing pulsation of a high-pressure fluid in a direct injection type fuel injection device or the like.

[0002]

2. Description of the Related Art Generally, a single-cylinder pump used in a direct injection type fuel injection device (GDI) has a large pressure pulsation, and therefore has an accumulator to reduce such pressure pulsation.

[0003] In this type of accumulator, generally, one diaphragm is arranged in a housing, and the housing is defined as a back pressure chamber and a pressure receiving chamber. 2. Description of the Related Art There is known a configuration in which a pressure receiving chamber communicates with a fuel supply passage (fuel passage) to reduce pulsation generated in the fuel supply passage.

[0004] However, the range of fluid pressure to which such an accumulator can be applied depends on the fixed gas pressure in the back pressure chamber, so that the range of application is narrow. Therefore, when an accumulator is arranged in the fuel discharge passage between the fuel discharge pump (single-cylinder pump) and the pressure regulator (P / R), there is a problem that it cannot sufficiently cope with various set pressures of the pressure regulator.

On the other hand, JP-A-8-200178 discloses a communication passage connecting the back pressure chamber to a fuel supply passage on the high pressure side. There is disclosed a configuration in which the piston is moved in accordance with a change in pressure in the fuel supply passage so as to change the volume on the back pressure chamber side.

[0006]

However, according to the technique disclosed in the above-mentioned publication, the back pressure chamber receives the pressure of the fuel supply passage, and therefore, the pressure depends on the set pressure of the fuel supply passage (the set pressure of the pressure regulator). Since the pressure in the back pressure chamber changes, the application range of the accumulator is widened, but if pulsation occurs in the fuel supply path, the back pressure chamber is directly affected by the piston as it is, and the pulsation in the fuel supply path is reduced. There is a problem that it cannot be suppressed effectively.

Further, in the case of the technique disclosed in the above-mentioned publication, when the back pressure chamber receives a pulsation, the pulsation may be synchronized with the pulsation received on the pressure receiving side when the back pressure chamber receives the pulsation. In addition, it is necessary to dispose the piston in the communication passage, and it is necessary to securely seal the back pressure chamber and the fuel supply passage side by the piston, which is disadvantageous in that the configuration becomes complicated.

An object of the present invention is to provide an accumulator that can reduce pressure pulsation over a wide range with a simple configuration.

[0009]

According to one aspect of the present invention, there is provided an accumulator for reducing pressure pulsation in a fuel passage of a fuel injection device. A first chamber defined by the first diaphragm and the housing, a second chamber defined by the second diaphragm and the housing, and a first and a second chamber defined in the housing. The first and second chambers are partitioned by a second diaphragm and a third chamber. The first chamber is communicated with the fuel passage, the second chamber is communicated with the fuel passage via a throttle, and the third chamber is filled with gas. It is characterized by having.

According to the first aspect of the invention, when the accumulator is deformed by the fuel pressure in the fuel passage in the three chambers defined by the two diaphragms, the second diaphragm defining the second chamber is deformed by the fuel pressure. The pressure in the gas chamber of the third chamber changes due to the corresponding volume change. Since the third chamber is a back pressure chamber of the first diaphragm, which is a pressure receiving surface, the back pressure changes according to the pressure in the fuel passage. When the pressure in the fuel passage increases, the back pressure also increases. It changes according to the internal pressure. Therefore, the range of pulsation that can be reduced by the first diaphragm can be changed according to the pressure in the fuel passage, and the range of application of pulsation reduction can be widened with one accumulator.

The fuel passage and the second chamber communicate with each other via a throttle to prevent the second chamber from being directly affected by the pulsation generated in the fuel passage. The pulsation is not affected, and the pulsation is not increased in synchronization with the first diaphragm which is the pressure receiving surface.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG.
An embodiment of the present invention will be described in detail with reference to FIG.
FIG. 1 is a cross-sectional view of a fuel supply pump equipped with an accumulator according to an embodiment of the present invention cut from the front side, and FIGS. 2 to 4 are cross-sectional views illustrating a schematic configuration and operation of the accumulator. FIG. 5 is a conceptual diagram showing an arrangement state of the accumulator.

[0013] The fuel supply pump 3 according to the present embodiment.
Injects gasoline directly into the combustion chamber of a gasoline engine, and is used in a fuel supply system referred to as a so-called direct injection gasoline engine to pump high-pressure gasoline. That is, as shown in FIG. 5, the fuel supply pump 3 pumps high-pressure fuel through a high-pressure fuel passage (fuel passage) 40 to a common rail 2 on which a plurality of injection valves for injecting fuel are arranged. In the passage 40, the pressure in the high-pressure fuel passage 40 is set by a pressure control valve (pressure regulation valve) 6.

As shown in FIG. 1, the fuel supply pump 3 includes a pump housing 7 in which a plunger 5 is housed,
A lower body (not shown) that houses a cam 9 for driving the plunger 5. The cam 9 is connected to a shaft driven by an engine (not shown). The cam 9 rotates by driving of the engine, and the cam 9 comes into circumferential contact with a cam contact shoe 11 disposed at a lower end of the plunger 5. It is configured to be driven up and down.

The pump housing 7 is provided with a suction port 13 for supplying low-pressure fuel and a discharge port 17 for discharging fuel pressurized by the plunger 5. The suction port 13 is connected to a pump chamber (fuel compression chamber) via a low-pressure fuel suction passage 19 formed in the pump housing 7.
The discharge port 17 communicates with the pump chamber 21 via a fuel discharge passage 23, and discharges the fuel compressed in the pump chamber 21 from the discharge port 17 by opening and closing a valve.

A fixed member 29 is screwed into a large-diameter hole formed in the pump housing 7, and a plunger barrel 33 for guiding the sliding of the plunger 5 is fixed inside the fixed member 29. ing. A bellows 27 is disposed below the fixed member 29 so that its axis is substantially coincident with the axis of the plunger 5. The upper end of the bellows 27 is fixed to a fixed member 29 assembled to the pump housing 7, and the lower end of the bellows 27 is fixed to a support member 31 that contacts the lower end of the plunger 5. The bellows 27 expands and contracts in conjunction with the vertical movement of the plunger 5, and receives fuel leaked from a sliding clearance between the plunger 5 and the plunger barrel 33, and a bellows chamber formed inside the bellows 27. The leak fuel is received in the inside 27a and is sealed to the cam chamber, and is formed in a bellows shape made of metal.

On the other hand, a push rod 24 is interposed between the plunger 5 and the above-mentioned cam contact shoe 11, and the plunger 5 is pressed through the push rod 24 to slide in the plunger barrel 33. Let me. In the present embodiment, the push rod 24 is provided separately from the plunger 5, but contacts the lower end of the plunger 5 and reciprocates integrally with the plunger 5. It may be one. The plunger 5 slides up and down along the plunger barrel 33. In plunger 5,
The lower end of the spring 35 is in contact. The spring 35 constantly urges the plunger 5 downward. As shown in FIG. 1, the upper end of the spring 35 is supported on the lower surface of the fixed member 37. The pump chamber 21 for pressurizing the fuel is formed between the lower surface of the fixing member 37 and the plunger 5.

The plunger barrel 33 has a plunger 5
At the lower end (opposite the pump chamber) of the plunger 5
Pulsation reducing space 26 defined by the push rod 24
Are formed. The pulsation reducing space 26 communicates with the fuel suction port 13 through a low-pressure passage 28 to reduce pulsation on the low-pressure side generated by the reciprocating operation of the pump chamber 21. That is, the pulsation reduction space 26 is
When the plunger 5 descends, the fuel in the pulsation reduction space 26 is returned to the low-pressure fuel suction passage 19 through the low-pressure passage 28, and when the plunger 5 rises, the fuel supply port 13 is formed. The fuel is sucked into the pulsation reduction space 26 from the side through the low-pressure fuel suction passage 19. In the present embodiment, the volume ratio between the pulsation reducing space 26 and the pump chamber 21 is, for example, 1: 2, and the suction amount at the fuel supply port 13 is sucked into the pump chamber 21 when the plunger 5 descends. The return amount from the pulsation reducing space 26 is 1 with respect to the fuel volume ratio 2, and when the plunger 5 is raised, fuel is supplied only from the low-pressure fuel suction passage 19 to the pulsation reducing space 26.
The amount returned to 3 becomes -1. Therefore, the fuel supply port 1
When the plunger 5 descends and ascends, the volume ratio of the fuel sucked from the plunger 3 is generally 1 in each case.
become.

On the other hand, the high-pressure fuel discharge passage 23 is connected to the high-pressure accumulator 3 provided in the upper part of the pump housing 7.
The pressure receiving chamber 46 communicates with the pressure receiving chamber 46 through the passages 23a and 23b. That is, the high-pressure accumulator 39 suppresses high-pressure pulsation caused by reciprocation of the plunger 5.

Here, the high-pressure accumulator 39 according to the present invention will be described. The high-pressure accumulator 39
As shown in FIG. 1 and FIG.
And first and second diaphragms 47 and 49 disposed in the housing 43. In the housing 43, a pressure receiving chamber 46 (first chamber) is defined by the first diaphragm 47 and the housing 43.
Is connected to the pump chamber 21 through the passages 23a and 23b as described above. A fuel pressure chamber (second chamber) 51 is defined by the housing 46 and the second diaphragm 49. The fuel pressure chamber 51 is provided with a fuel discharge port 17.
And receives the pressure of the discharged fuel via the communication passage 53. A narrowing (orifice) 55 having a narrow passage is formed in the communication passage 53 so as not to directly receive the pulsation generated in the high-pressure fuel passage 40 (see FIG. 5) on the discharge port 17 side.

A back pressure chamber (third chamber) 41 defined between the first diaphragm 47 and the second diaphragm 49 is partitioned. A gas of a predetermined pressure is sealed in the back pressure chamber 41, and the back surface of the first diaphragm 47 is deformably supported. The pulsation received in the pressure receiving chamber 46 is reduced through the first diaphragm 47. .

The first and second diaphragms 47, 49
Are hermetically fixed to the casing 43 by intermediate members 57 via O-rings 57 (see FIG. 1).

Next, the operation of the present embodiment will be described. When the cam 9 rotates, the plunger 5 moves up and down via the cam contact shoe 11, whereby fuel is supplied to the pump chamber 21 through the low-pressure fuel suction passage 19 and the fuel in the pump chamber 21 is Is pressurized and discharged to the fuel discharge passage 23.

The pulsation in the pump chamber 21 on the side of the low-pressure low-pressure fuel suction passage 19 is reduced by the pulsation reduction space 26. That is, when the plunger 5 rises, fuel is sucked into the pulsation reduction space 26 from the low-pressure fuel supply port 13 side. When the plunger 5 descends, the low-pressure fuel
Is supplied to the pump chamber 21 from the pump chamber 21. Since the fuel in the pulsation reduction space 26 is also supplied to the pump chamber 21 via the low-pressure passage 28, the fuel supply amount from the low-pressure fuel suction passage 19 is
When the plunger 5 descends and ascends, the plunger 5 becomes the same, and the amount of fuel sucked from the suction port 13 becomes
Equalization or leveling reduces suction pulsation.

The fuel discharged from the pump chamber 21 is supplied to the pressure receiving chamber 4 of the accumulator 39 through the passages 23a and 23b.
The accumulator 39 reduces high-pressure pulsation caused by pumping. That is, in the pressure receiving chamber 46, when the pulsation is received, the first diaphragm 47 receives the pulsation and deforms against the gas pressure in the back pressure chamber 41 to reduce the pulsation.

On the other hand, in the back pressure chamber 41, when the second diaphragm 49 is deformed by receiving the fuel pressure in the high pressure fuel passage 40 through the communication passage 53, the volume of the back pressure chamber 41 changes accordingly. In other words, the pressure in the high-pressure fuel passage 40 is set by setting the pressure control valve 6. However, as shown in FIG. 2, when the fuel pressure in the high-pressure fuel passage 40 is set to the reference value, the second diaphragm 49 is set. Is not greatly deformed, and the pressure of the back pressure chamber 41 is the initially set pressure,
When the pressure in the high-pressure fuel passage 40 is set low, as shown in FIG. 3, the second diaphragm 49
It is largely recessed on one side, and the volume of the back pressure chamber 41 is increased. As a result, the pressure in the back pressure chamber 41 decreases,
The diaphragm 47 can be easily deformed even with relatively low-pressure pulsation, and can effectively reduce pulsation even when the set pressure of the high-pressure fuel passage 40 is relatively low.

On the other hand, when the set pressure of the high-pressure fuel passage 40 is high, as shown in FIG.
Is largely recessed toward the back pressure chamber 41, and the volume of the back pressure chamber 41 is reduced. As a result, the pressure in the back pressure chamber 41 increases, so that the first diaphragm 47 does not deform too much even with relatively high-pressure pulsation, and does not break even if it deforms with respect to pulsation. . Therefore, even when the pressure in the high-pressure fuel passage 40 is relatively high, pulsation can be effectively reduced, and damage to the diaphragm is prevented.

Further, since the throttle 55 is interposed in the communication passage 53 that communicates the fuel pressure chamber 51 with the high-pressure fuel passage 40, instantaneous pressure pulsations generated in the high-pressure fuel passage 40 are transmitted to the fuel pressure chamber 51. Has no effect.

That is, according to the accumulator 39 according to the present embodiment, a single high-pressure accumulator 39 can cope with a wide range of set pressure in the high-pressure fuel passage 40, and pressure pulsation can be reduced.

The present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention. For example, the accumulator 39 according to the present invention is not limited to the one provided in the high-pressure fuel passage 40, and the same effect can be obtained even if it is provided in the low-pressure passage.

The same effect can be obtained not only in the gasoline fuel injection pump or circuit but also in a light oil fuel injection pump used in a diesel engine.

[0032]

According to the first aspect of the present invention, the accumulator is divided into three chambers by the first and second diaphragms arranged in the housing, and the first chamber is communicated with the fuel passage. Since the second chamber is connected to the fuel passage via a throttle and the third chamber is filled with gas,
The pulsation received by the first chamber can be reduced with a simple configuration and in a wide pressure setting range. Moreover, the fuel passage and the second
The second chamber is not directly affected by the pulsation generated in the fuel passage because it communicates with the chamber through a throttle, and therefore the second chamber is affected by the pulsation of the fuel passage, One of the first diaphragms does not synchronously increase the pulsation.

[0033]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fuel supply pump equipped with an accumulator according to an embodiment of the present invention, cut from the front side.

FIG. 2 is a schematic sectional view illustrating the operation of the accumulator shown in FIG.

FIG. 3 is a schematic cross-sectional view illustrating an operation of the accumulator when a set pressure of a fuel passage is low.

FIG. 4 is a schematic sectional view for explaining the operation of the accumulator when the set pressure of the fuel passage is high.

FIG. 5 is a conceptual diagram showing an arrangement state of accumulators.

[Explanation of symbols]

 39 high-pressure accumulator (accumulator) 40 high-pressure fuel passage (fuel passage) 41 back pressure chamber (third chamber) 43 housing 46 pressure receiving chamber (first chamber) 47 first diaphragm 49 second diaphragm 51 fuel pressure chamber (second chamber) 55 aperture

Claims (1)

[Claims] 1. An accumulator for reducing pressure pulsation in a fuel passage of a fuel injection device, comprising: a housing; first and second diaphragms disposed in the housing; and inside the housing, the first diaphragm and the housing. , A second chamber defined by the second diaphragm and the housing, and a third chamber defined by the first and second diaphragms. An accumulator, wherein the accumulator communicates with the passage, the second chamber communicates with the fuel passage via a throttle, and the third chamber is filled with gas.