JP2000130281A - Distributor-type fuel injection pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distributor-type fuel injection pump capable of reducing the number of parts and capable of being obtained at low cost. SOLUTION: A multi-functional valve 55 provided with a valve body 71, a piston 72, a plug 73 and a spring 74 and having a regulator function and an overflow function is attached to a pump housing 52. The body 71 is provided with a regulating fuel hole 79 communicated with a fuel return passage 80 in the housing 52 and an overflow hole 81 communicating with an overflow pipe 83 outside the housing 52. The piston 72 housed in the body 71 is provided with a first valve part 91 for opening and closing the fuel hole 79, a second valve part 92 for opening and closing the hole 81, a fuel reservoir 93 extending to the second valve part 92, and a fuel passage 94 for making a pressure receiving surface 91a of the first valve part 91 on which feed fuel acts communicate with the fuel reservoir 93. The spring 74 for always energizing the piston 72 in the valve closing direction is provided between the plug 73 and the piston 72 housed in the body 71.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distribution type fuel injection pump provided in an internal combustion engine, for example, a diesel engine, for distributing and supplying fuel to each cylinder of the engine.

[0002]

2. Description of the Related Art In a conventional distribution type fuel injection pump, a part of fuel pressurized by a feed pump is returned to a suction side of the pump as exemplified in Japanese Utility Model Laid-Open No. 57-63931, and a pump is provided. A regulating valve for maintaining the pressure of the pumped fuel to be pumped into the chamber at a set value, and opening part of the fuel in the pump chamber at a pressure lower than the valve opening pressure set for the regulating valve. An overflow valve for releasing to the fuel tank side is provided.

FIG. 4 shows an actual distribution type fuel injection pump having such a structure. In FIG. 4, 1 is a pump housing, 2 is a feed pump, 3 is a pump chamber,
Is a face cam, 5 is an automatic timer, 6 is a pump cylinder, 7 is a pump plunger, 8 is a delivery valve, 9 is a regulating valve, and 10 is an overflow valve.

[0004] As shown in FIG. 4 (B), a valve body 12 having a fuel hole 11 of a regulating valve 9 in a peripheral portion.
Is disposed between a passage 13 communicating with the discharge port of the feed pump 2 and a passage 14 communicating with the pump chamber 3. Inside the body 12, a piston 15 for opening and closing the fuel hole 11 is slidably accommodated, and a coil spring 16 for urging the piston 15 and a hermetically sealed spring receiver 17 for supporting the spring 16 are provided. And are housed respectively. The regulating valve 9 has a coil spring 16
The pressure of the fuel sucked up from the fuel tank by the feed pump 2 and supplied to the pump chamber 3 is maintained at the set value by the spring force of.

An overflow valve 10 provided separately from the valve 9 is mounted facing the pump chamber 3 as shown in FIG. This valve 10
Is a valve base 21 connected to the pump housing 1.
A valve body 22 is screwed through the valve body 22. A peripheral portion of the body 22 has an outlet communicating with the fuel tank, and a stopper 23 is screwed into the valve body 22. And the valve body 22
Inside, a valve body 24 made of a ball, and a coil spring 2 for pressing the valve body 24 against a valve seat provided inside the valve body 22.
5 are accommodated. An end of the coil spring 25 opposite to the valve body 24 is supported by a stopper 23. When the fuel pressure in the pump chamber 3 becomes higher than the overflow pressure set by the coil spring 25, the valve body 24 is pushed and moved by the fuel pressure to open the valve. A part of the fuel.

[0006]

As described above, the conventional distribution-type fuel injection pump controls the pressure characteristic of the pump chamber 3 by opening and closing the regulating valve 9 and at the same time, the valve opening pressure of the valve 9 or less. Since the pressure characteristic of the pump chamber 3 is controlled by opening and closing the overflow valve 10 in the low speed range, two types of independent valves 9 and 10 are required, and the number of parts and the number of assembling steps are large and the cost is high.
Further, since the overflow valve 9 having the above configuration does not have a function of adjusting the valve opening pressure, the pressure characteristics of the pump chamber 3 in the low-speed range greatly vary. This is one of the causes of the poor startability of the diesel engine.

Therefore, a first object of the present invention is to provide a distribution type fuel injection pump which can reduce the number of parts and can be obtained at low cost. A second object of the present invention is to provide a distribution type fuel injection pump capable of reducing variations in pump chamber pressure characteristics in a low-speed range in solving the first problem.

[0008]

According to a first aspect of the present invention, there is provided a fuel supply system comprising: a regulator function for adjusting a pressure of fuel fed into a pump chamber of a pump housing to a first valve opening pressure; A multi-function valve having an overflow function of opening the valve at a second valve opening pressure lower than the first valve opening pressure and allowing a part of the fuel in the pump chamber to escape is attached to the pump housing. It is.

According to the first aspect of the present invention, by providing a multi-function valve, the multi-function valve is provided by integrating these two valves without using two types of valves, a regulation valve and an overflow valve, which are independent of each other. The pressure characteristics of the pump chamber can be controlled by the regulator function and the overflow function of the valve.

In practicing the first aspect of the present invention, as in the second aspect of the present invention, the multifunctional valve includes a regulating fuel hole communicating with a fuel return passage in the pump housing; A valve body having an overflow hole communicating with an overflow pipe outside the pump housing, a first valve portion for opening and closing the fuel hole, a second valve portion for opening and closing the overflow hole, and a fuel connected to the second valve portion A piston, which has a fuel passage communicating the pressure receiving surface of the first valve portion on which the pumped fuel acts and the fuel reservoir together with the reservoir, and is accommodated in the valve body so as to reciprocate in its axial direction; A plug housed in the valve body away from the piston, and constantly biasing the piston in a valve closing direction to sandwich the plug between the plug and the piston. It is preferable to a structure provided with the spring for setting the first valve opening pressure.

According to the second aspect of the present invention, the pump chamber pressure increases as the rotation speed of the feed pump increases,
Accordingly, the piston is gradually moved toward the spring side against the biasing force of the spring. When the pump chamber reaches the second valve opening pressure, the overflow hole is opened by the second valve portion of the piston and communicates with the fuel reservoir at that point, so that the pump guided through the fuel passage and the fuel reservoir of the piston is provided. Part of the fuel in the chamber flows out of the overflow hole into the overflow pipe, and pressure control of the pump chamber in the low-speed range is performed (overflow function). When the pressure in the pump chamber further increases from this point and reaches the first valve opening pressure, at that point the fuel hole is opened by the first valve portion of the piston, and the feed pump is sucked through the fuel return passage. Since a part of the fuel is returned to the side, the pressure of the pump chamber is controlled by the first valve opening pressure (regulator function). As described above, the multi-function valve opens and closes the overflow hole and the regulating fuel hole according to the respective fuel pressure by moving one piston biased by one spring, thereby performing the overflow function and the regulator function. Can demonstrate.

[0012] In order to solve the second problem, a third aspect of the invention according to the second aspect is characterized in that the plug is provided so as to be movable and adjustable in the axial direction. .

The third aspect of the present invention is dependent on the second aspect of the invention, and has the following operation in addition to the operation of the second aspect of the invention. That is, since the overflow hole and the regulating fuel hole are opened and closed by the same piston as described above, a constant pressure difference (valve opening pressure difference) is always maintained between opening and closing these holes. Under such conditions, the plug that supports the spring that sets the first valve opening pressure can move its position in the axial direction. Therefore, the movement of the plug urges the piston, that is, the first valve opening pressure. The variation can be reduced by making a change, and at this time, the valve opening pressure difference is maintained, so that the variation in the pump chamber pressure characteristic in the low speed range can be reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. Reference numeral 51 in FIG. 1 showing the entire structure of the electronic distribution type fuel injection pump is a drive shaft driven by a diesel engine, and is a rotary feed pump 5 provided in a pump housing 52.
3 is connected. The feed pump 53 sucks fuel from a fuel tank (not shown) outside the pump housing 52 through a fuel filter, and supplies the fuel to a fuel chamber (pump chamber) 54 in the pump housing 52. A multifunctional valve 55 described below is attached to the pump housing 52 so as to be located in a fuel path that is pressure-fed from the feed pump 53 to the fuel chamber 54.

A plunger 57 is connected to the drive shaft 51 via a coupling 56. The plunger 57 is
A face cam 58 formed with a cam profile having a number of cam ridges along the circumferential direction corresponding to the number of cylinders of the engine.
Is provided integrally. When a cam roller (not shown) comes into contact with the cam profile, the face cam 58 and the plunger 57 reciprocate according to the number of cylinders of the engine during one rotation.

When the plunger 57 is in the suction stroke, when one of the suction grooves 59 formed in the peripheral surface of the distal end portion of the plunger 57 communicates with the suction port 60, the fuel in the fuel chamber 54 is introduced into the pressure feed chamber 61 through these. Is done. When the plunger 57 is in the compression stroke, the fuel in the pressure feed chamber 61 is pressurized by the plunger 57, and this fuel is pushed out to a discharge passage 62 formed in the plunger 57.
At this time, since the plunger 57 is rotating, when the port 63 opened on the peripheral surface communicates with one of the plurality of discharge ports 64, the fuel outflow passage communicated with this port 64 From 65, the fuel is supplied to a fuel injection valve (not shown) installed in the cylinder through a delivery valve 66.

The multifunctional valve 55 has a regulator function for adjusting the pressure of the fuel fed into the fuel chamber 54 to a first valve opening pressure P2 (see FIG. 3), and a second function lower than the first valve opening pressure P2.
This is a single valve having an overflow function of opening the valve at the valve opening pressure P1 (see FIG. 3) and releasing a part of the fuel in the fuel chamber 54 to the fuel tank side. This valve 55 is installed at the place where the regulation valve was conventionally attached.

Next, a specific configuration of the multi-function valve 55 will be described with reference to FIG. The valve 55 includes a valve body 71, a piston 72, a plug 73, and a spring 74.

A cylindrical valve body 71 whose upper and lower ends are respectively opened is connected by screwing a lower portion thereof into a valve mounting hole 52a of the pump housing 52, and a portion above the screwing portion between the valve mounting hole 52a and the valve body 71. A pair of upper and lower liquid-tight packings 75 and 76 each composed of an O-ring or the like are disposed below and below, respectively. A bush 77 is fitted and attached to the lower end of the valve body 71, and the lower end of the bush 77 is connected to the fuel pump 54 from the feed pump 53 to the fuel chamber 54 through a passage 78 provided in the pump housing 52. Some are to be guided. A plurality of regulating fuel holes 79 are formed in the peripheral wall of the valve body 71 between the pair of upper and lower packings 75 and 76.
Are opened, and these fuel holes 79 communicate with a fuel return passage 80 that communicates with the discharge port of the feed pump 53 provided in the pump housing 52.

The pump housing 52 of the valve body 71
An overflow hole 81 made of an orifice is formed in the upper peripheral wall that protrudes more outward. An overflow chamber 82 is fitted and attached to the upper outer periphery of the valve body 71 with an overflow hole 81 located inside. An overflow pipe 83 communicating with the overflow hole 81 is connected to the chamber 82. A detachable cap nut 84 is screwed into the upper end of the valve body 71. By tightening the nut 84, the chamber 82 is fixed in a state where a liquid-tight packing 85 such as a gasket disposed above and below the chamber 82 is compressed. In FIG. 2, reference numeral 86 denotes a through hole provided in an upper portion of the body 71 for communicating the inside of the chamber 82 with the inside of the valve body 71.

The piston 72 is accommodated in the valve body 71 so as to be able to reciprocate in the axial direction. The lower end of the piston 72 is used as a first valve portion 91 for opening and closing the fuel hole 79, and the front end surface (lower end surface) is used as a pressure receiving surface 91 a on which the pumped fuel exerted via the passage 78 acts. . The upper end of the piston 72 is used as a second valve portion 92 for opening and closing the overflow hole 81. At an upper portion of the piston 72, a fuel reservoir 93 which is continuous with a lower end of the second valve portion 92 is provided. This fuel pool 9
Numeral 3 is formed by a groove continuous in the circumferential direction of the piston 72. The piston 72 is provided with a fuel passage 94 composed of a vertical hole and a horizontal hole communicating the pressure receiving surface 91 a and the fuel reservoir 93.

The plug 73 is housed in the upper end portion of the valve body 71 with a slight press fit. The plug 73 is provided so as to be movable in the axial direction of the valve body 71 even in the press-fit state, and is provided with a screw hole 73a opened on the upper surface to enable the movement. The plug 73 can be moved in the axial direction by operating the tool with the screwed portion of a tool (not shown) screwed into the screw hole 73a. The plug 73
Of course, due to the pressure contact with the valve body 71, regardless of the urging force of the spring 74 and the pressure of the fuel that overflows, it is of course mounted and held in a stationary state.

As the spring 74, a coil spring is used. The spring 74 is for setting the first valve opening pressure P2, and is sandwiched between the plug 73 and the piston 72 in a compressed state. The urging force of the spring 74 constantly urges the piston 72 downward (in other words, in the valve closing direction), so that when the pump pressure of the feed pump 53 is zero, the pressure receiving surface 91a of the piston 72 is 77 and is maintained in a closed state. In this valve closed state, the fuel hole 79 is, of course,
Of the piston 72, and the overflow hole 81 is also closed by the second valve portion 92 of the piston 72.

The control of the pressure characteristic of the fuel chamber 54 in the distribution type fuel injection pump having the above configuration will be described below in accordance with the operation of the multifunctional valve 55. The fuel sucked up by the operation of the feed pump 53 fills the fuel chamber 54 and the passage 7 communicated with the discharge port of the feed pump 53.
8, the fuel pressure in the passage 78 increases together with the fuel chamber 54 as the rotation speed of the feed pump 53 increases, and the fuel pressure in the passage 78
Acts on 1a. This fuel pressure causes the piston 72 to move upward in FIG. 2 against the urging force of the spring 74.

Therefore, the fuel pressure in the passage 78 becomes P
When the second valve opening pressure indicated by 1 is reached, the second
The valve portion 92 is moved above the overflow hole 81 of the valve body 71, and this hole 81 is opened, and the overflow hole 81 communicates with the fuel reservoir 93 of the piston 72. Therefore, part of the fuel in the fuel chamber 54 is
8, the fuel is guided to the fuel passage 94 and the fuel reservoir 93 of the piston 72, passes through the overflow hole 81, and returns from the overflow chamber 82 to the fuel tank via the overflow pipe 83. Then, the fuel chamber 5 in the low speed range below the second valve opening pressure P1 by such an overflow function.
4 is controlled.

FIG. 2 shows the state at the time of the start of the overflow operation. At this time, the first valve portion 91 of the piston 72 still maintains the state in which the fuel hole 79 of the valve body 71 is closed. Also, the piston 7 as described above
Along with the rise in 2, a part of the fuel filled in the spring chamber between the piston 72 and the plug 73 is pushed out to the overflow chamber 82 through the through hole 86, and flows out therefrom to the overflow pipe 83. Therefore, the fuel in the spring chamber does not prevent the piston 72 from rising.

Then, the piston 72 further rises by the fuel pressure which increases as the rotation speed of the feed pump 53 further rises, and the urging force of the spring 74, that is, the first force shown in FIG.
When the valve opening pressure P2 is reached, the first valve portion 91 of the piston 72 opens the fuel hole 79 of the valve body 71 at that point. Therefore, part of the fuel pumped from the feed pump 53 into the fuel chamber 54 is returned from the passage 78 to the inlet side of the feed pump 53 through the fuel return passage 80 through the fuel hole 79 of the multi-function valve 55. The pressure characteristic of the fuel chamber 54 is controlled by such a regulator function.

As described above, when the pressure in the fuel chamber 54 reaches the second valve opening pressure P1 as the rotation speed of the feed pump 53 increases, a part of the fuel in the fuel chamber 54 is The pressure of the fuel chamber 54 in the low-speed range is controlled by the overflow function of flowing out to the fuel chamber 54. From this point on, the pressure of the fuel chamber 54 further increases, and
When the valve opening pressure P2 is reached, the pressure of the fuel chamber 54 can be controlled by a regulator function that returns a part of the fuel to the fuel return passage 80 through the fuel hole 79.

That is, the multifunctional valve 55 is configured such that the movement of one piston 72 urged by a single spring 74 causes the overflow hole 81 and the regulating fuel hole 79 to move.
Are opened and closed in accordance with the respective fuel pressures P1 and P2 to exhibit an overflow function and a regulator function. Therefore, in controlling the pressure of the fuel chamber 54, two types of regulator valves and overflow valves independent of each other are used. It is not necessary to use a valve. Therefore, by employing the multifunctional valve 55, the number of parts of the whole fuel injection pump can be reduced and the number of assembling steps can be reduced, so that the cost can be reduced and the cost can be reduced.

In the multi-function valve 55 provided in the fuel injection pump having the above-described structure, the same piston 72 is provided as described above.
The opening and closing of the overflow hole 81 and the regulating fuel hole 79 can be always performed to maintain a constant pressure difference (valve opening pressure difference) for opening and closing these. Under such conditions, the axial position of the plug 73 supporting the spring 74 for setting the first valve opening pressure P2 can be adjusted as necessary. That is,
To adjust the position of the plug 73, a tool (not shown) is screwed into the screw hole 73a of the plug 73 from the outside of the valve body 71 with the cap nut 56 removed, and connected.
In this state, the plug 73 is operated by operating the tool in the valve body 7.
It can be easily implemented by moving in one axial direction.

The variation of the force of the spring 74 for urging the piston 72 by the movement of the plug 73, that is, the first valve opening pressure P2 can be reduced. And, despite the adjustment of the first valve opening pressure P2, the valve opening pressure difference between the overflow hole 81 and the regulating fuel hole 79 is kept constant, so that the pressure characteristic of the fuel chamber 54 in the low speed range is reduced. Variations can be reduced and the startability of the diesel engine can be improved accordingly.

[0032]

The present invention is embodied in the form described above and has the following effects. According to the invention described in claim 1 and dependent claim 2,
Since it has a multi-function valve that can control the pump chamber pressure characteristics by the regulator function and the overflow function,
It is not necessary to use two types of valves, a regulating valve and an overflow valve, which are independent from each other. Accordingly, the number of parts can be reduced and the number of assembling steps can be reduced.

According to the third aspect of the invention, which is dependent on the second aspect, in addition to the effect of the second aspect, the first valve opening pressure by the spring for biasing the piston is set in the axial direction of the plug. Since it can be changed by the movement, it is possible to reduce the variation in the pressure characteristics of the pump chamber in the low speed range while keeping the valve opening pressure difference between the overflow hole and the regulating fuel hole constant.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the overall configuration of an electronically controlled distribution type fuel injection pump according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the configuration of the multifunctional valve along the line ZZ in FIG. 1;

FIG. 3 is a graph showing a relationship between a fuel chamber pressure of the fuel injection pump shown in FIG. 1 and a feed pump rotation speed.

FIG. 4A is a cross-sectional view illustrating the configuration of an entire distribution type fuel injection pump according to a conventional example. FIG. 5B is an enlarged cross-sectional view showing the configuration of the regulation valve along the line YY in FIG. 4.

[Explanation of symbols]

 52: pump housing, 54: fuel chamber (pump chamber), 55: multifunctional valve, 71: valve body, 72: piston, 73: plug, 74: spring, 78: passage, 79: fuel hole for regulation, 80 ... fuel return passage, 81 ... overflow hole, 83 ... overflow pipe, 91 ... first valve part, 91a ... pressure receiving surface, 92 ... second valve part, 93 ... fuel pool, 94 ... fuel passage.

Claims (3)

[Claims] And a regulator for adjusting the pressure of the fuel to be pumped into the pump chamber of the pump housing to a first valve opening pressure, and opening the valve with a second valve opening pressure lower than the first valve opening pressure. A multi-function valve having an overflow function for allowing a part of fuel to escape is attached to the pump housing. A valve body having a regulating fuel hole communicating with a fuel return passage in the pump housing and an overflow hole communicating with an overflow pipe outside the pump housing; A first valve portion that opens and closes, a second valve portion that opens and closes the overflow hole, and a fuel reservoir connected to the second valve portion, a pressure receiving surface of the first valve portion on which the pumped fuel acts, and a fuel reservoir. A piston accommodated in the valve body so as to reciprocate in its axial direction, a plug accommodated in the valve body apart from the piston, and a valve always closing the piston in the valve closing direction A spring interposed between said plug and said piston to set said first valve opening pressure. 2. The distribution type fuel injection pump according to 1. 3. The distribution type fuel injection pump according to claim 2, wherein said plug is provided so as to be movable in said axial direction.