JP2952963B2 - Variable discharge high pressure pump - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable discharge high-pressure pump that changes a fuel discharge amount according to an energization timing of a solenoid valve.

[Prior Art] As an example of a conventional technique, a technique disclosed in Japanese Patent Application Laid-Open No. 64-73166 is known.

In this technique, as shown in FIG. 3, a fuel intake means 101 for supplying fuel into a variable discharge high pressure pump 100 is a tappet.
It was attached to a housing 103 that held 102. For this reason, the fuel supplied from the fuel intake means 101 passes through a low-pressure chamber 106 between the cylinder 105 holding the plunger 104 and the housing 103, and passes through the fuel supply passage of the cylinder 105.
It was supplied to 107 and supplied to the pump chamber 108.

[Problem to be Solved by the Invention] Since the conventional variable discharge amount high pressure pump 100 includes the low pressure chamber 106 at the joint portion between the housing 103 and the cylinder 105, the variable discharge amount high pressure pump 100 moves in the axial direction of the plunger 104. It was long formed.

Further, the conventional variable discharge amount high pressure pump 100 is
The housing 103 and the cylinder 105 on the cam 109 side
It was necessary to provide a seal member 110 at the junction with the seal member 110 in order to maintain liquid tightness. For this reason, the conventional variable discharge amount high pressure pump 100 is formed long in the axial direction of the plunger 104.

That is, since the conventional variable discharge amount high pressure pump 100 is formed to be long in the axial direction of the plunger 104, there is a problem that the variable discharge amount high pressure pump 100 is large and heavy.

Further, in the conventional variable discharge high pressure pump 100, since the fuel intake means 101 is attached to the housing 103 below the pump chamber 108, when the fuel is supplied from the fuel intake means 101 and air is released, the low pressure Only the chamber 106 could be filled with fuel, and the pump chamber 108 could not be evacuated.

An object of the present invention is to provide a small and lightweight variable discharge high-pressure pump and a variable discharge high-pressure pump capable of evacuating a pump chamber.

[Means for Solving the Problems] A variable discharge high pressure pump according to the present invention includes: (a) a camshaft that is driven to rotate and has a cam surface around the periphery thereof; and (b) pressed against the cam surface. A tappet displaced along the cam surface; (c) a housing for holding the tappet in a reciprocating manner; and (d) a plunger mounted on the upper side of the tappet and reciprocating with the reciprocating movement of the tappet. (E) a cylinder attached to the housing and holding the plunger in a reciprocating manner; and (f) a pump chamber attached to the cylinder and formed by an inner peripheral surface of the cylinder and an upper end surface of the plunger. A fuel intake means for guiding fuel through a fuel supply passage; and (g) a fuel intake means mounted on the cylinder above the pump chamber, and An electromagnetic valve for opening and closing a supply passage, (h) a fuel discharge means attached to the cylinder and discharging fuel compressed in the pump chamber, and (i) a fuel discharge passage provided in communication with the fuel supply passage, A relief joint for opening the solenoid valve to return the fuel pushed back to the fuel supply passage to the fuel tank; and (j) being provided above a valve seat of the solenoid valve and providing the relief from the fuel supply passage. A relief check valve provided in a passage leading to a joint, for preventing backflow of fuel from the relief joint side to the fuel supply passage side.

[Operation] The fuel supplied by the fuel intake means is guided to the pump chamber without passing through the joint between the housing and the cylinder. That is, the conventional low-pressure chamber does not exist at the joint between the housing and the cylinder. Further, since there is no low-pressure chamber at the joint between the housing and the cylinder, the conventional seal member for keeping the joint between the housing and the cylinder liquid-tight can be eliminated.

[Effects of the Invention] As described in the above operation, the present invention can eliminate the low-pressure chamber at the joint between the housing and the cylinder, and the seal member that prevents fuel in the low-pressure chamber from leaking to the housing side. In addition, the axial length of the plunger of the variable discharge high pressure pump can be reduced.

By reducing the axial length of the plunger of the variable discharge high-pressure pump, the size and weight of the variable discharge high-pressure pump can be reduced as compared with the related art.

When the solenoid valve is open, it communicates with the fuel intake means → the fuel supply passage → the pump chamber and communicates with the fuel supply passage → the relief joint. Since the relief check valve is located above the valve seat of the solenoid valve, when fuel is supplied from the fuel intake means with the solenoid valve opened to release air, the air in the pump is released. The fuel is discharged from the relief joint through the check valve and can be filled up to the level of the relief check valve. Since the pump chamber and the like are below the solenoid valve, the pump chamber can be filled with fuel by bleeding air.

Embodiment Next, a variable discharge amount high pressure pump according to the present invention will be described based on an embodiment shown in the drawings.

(Structure of Embodiment) FIGS. 1 and 2 show an embodiment of the present invention.
FIG. 1 is a sectional view of a variable discharge high pressure pump, and FIG. 2 is a schematic block diagram of a common rail type fuel injection device.

B) First, the fuel injection device 1 will be described.

The engine 2 of this embodiment is a four-cylinder four-cycle engine, and each cylinder includes an injector 3 for injecting fuel into a fuel chamber. The fuel injection timing and the injection period by the injector 3 are controlled by the ON / OFF state of the injection control solenoid valve 4 provided in each injector 3.

On the other hand, each injector 3 is connected to a common rail 5 common to each cylinder. The common rail 5 is a high-pressure accumulator for fuel. The high-pressure fuel stored in the common rail 5 is injected from the injector 3 into the fuel chamber of the engine 2 while the injection control solenoid valve 4 is open.

The common rail 5 is connected via a fuel pipe 7 to a variable discharge high pressure pump 6 to which the present invention is applied, which replenishes consumed fuel and keeps a high fuel pressure at all times. The variable discharge high pressure pump 6 pressurizes the fuel sucked from the fuel tank 8 via the well-known low pressure pump 9 to a high pressure as necessary, and supplies the fuel to the common rail 5.

The control device 10 that controls the fuel injection device 1 includes, for example, a sensor for detecting a crank angle, a rotation speed sensor for the engine 2,
Input the information of the engine state such as load sensor. Then, the control device 10 turns ON the injection control solenoid valve 4 so that the optimum injection timing and injection period determined from each information are obtained.
Outputs the OFF control signal. At the same time, the control device 10 also outputs a control signal to the variable discharge amount high pressure pump 6 such that the amount of fuel supplied to the common rail 5 is optimized.

B) Next, the variable discharge amount high pressure pump 6 will be described.

The variable discharge high pressure pump 6 includes a camshaft 11 that is driven to rotate by a crankshaft of the engine 2. The camshaft 11 makes 1 /
It is provided to rotate twice. This camshaft 11
A cam surface 12 is formed at the periphery of the cam surface. The cam surface 12
One rotation of the camshaft 11 performs four ascending and descending steps. That is, it takes the form of a quadruple cam.

The camshaft 11 is disposed in a cam chamber 14 at a lower portion of the housing 13 (in a state where the vehicle is mounted, and a lower side in FIG. 1). Inside the housing 13, there is a cylindrical room
A tappet 16 is supported inside the room 15 so as to be able to reciprocate in the cylinder direction. The tappet 16 is pressed against the cam surface 12 by a spring 17. The tappet 16 has a cam roller 18 on the cam surface 12 side. As a result, when the cam shaft 11 rotates, the cam roller 18
, The tappet 16 is displaced in accordance with a change in the cam surface 12. When the camshaft 11 makes one rotation, the tappet 16 reciprocates four times in the cylinder 19.

Upper part of the housing 13 (when the vehicle is mounted,
On the upper side (in the figure), a cylinder 19 is fixed in a state where the central part has entered the interior of the room 15. This cylinder
A rod-shaped hole 20 having a circular cross section penetrates a central portion of 19. A plunger 21 is supported inside the hole 20 so as to be able to reciprocate in the axial direction of the hole 20. This plunger 21
Has a rod shape with a circular cross section, and is attached to the tappet 16 at the lower end. For this reason, when the tappet 16 makes a reciprocating motion, the plunger 21
Perform reciprocating motion at 20.

A pump chamber 22 is formed in a portion surrounded by the upper end surface of the plunger 21 and the inner peripheral surface of the hole 20 of the cylinder 19.
A fuel intake means 23 for guiding fuel to the pump chamber 22 is attached to the cylinder 19, and a fuel supply passage 24 for guiding the fuel supplied by the fuel intake means 23 to the pump chamber 22.
Is provided. The fuel intake means 23 is a joint for connecting the fuel pipe 7 for supplying the fuel pumped by the low-pressure pump 9. The fuel intake means 23 of this embodiment is also provided with a relief joint 25 for returning the fuel not discharged from the fuel discharge means described below to the fuel tank 8.

The fuel supply passage 24 is provided above the pump chamber 22 (the upper and lower sides in this embodiment indicate the upper and lower sides when the vehicle is mounted), and the fuel intake means 23 and the relief joint 25 communicate with the fuel supply passage 24. It is provided. Also,
A relief check valve 25a for preventing a backflow of fuel from the relief joint 25 to the fuel supply passage 24 is provided in a passage leading from the fuel supply passage 24 to the relief joint 25. The relief check valve 25a is provided above the valve seat 26a of the solenoid valve 26, and is used when the air is released.
It is provided so that air can be vented to the height of 5a.

Above the cylinder 19, an electromagnetic valve 26 that is controlled to be energized by the control device 10 is attached. This solenoid valve 26
Has a well-known structure that opens and closes the fuel supply passage 24,
For example, the fuel supply passage 24 is opened when the solenoid valve 26 is energized, and the fuel supply passage 24 is closed when the energization is stopped.

The cylinder 19 has a fuel discharge means 27 for guiding the fuel compressed in the pump chamber 22 to the outside of the variable discharge high pressure pump 6.
And a fuel discharge passage 28 for guiding the fuel compressed by the pump chamber 22 to the fuel discharge means 27. Fuel discharge means
Reference numeral 27 denotes a joint to which the fuel pipe 7 is connected. The fuel pipe 7 connected to the fuel discharging means 27 is connected to the common rail 5. A check valve 29 is provided in the passage of the fuel of the fuel discharging means 27 to prevent the fuel stored in the common rail 5 from flowing back to the variable discharge high pressure pump 6.

(Operation of Embodiment) Next, the operation of the above embodiment will be briefly described.

When the engine 2 operates, the crankshaft rotates, and the plunger 21 descends, the energization of the solenoid valve 26 is stopped by the control device 10 and the pump chamber 22 is moved through the fuel supply passage 24.
Is supplied with fuel.

When the plunger 21 moves up, there are times when the solenoid valve 26 is energized and times when the energization is stopped. Solenoid valve 26
When the energization of is stopped by the control device 10, the fuel in the pump chamber 22 is compressed in accordance with the rise of the plunger 21, but the fuel supply passage 24 is open. For this reason, the pressure in the pump chamber 22 does not reach the pressure at which the check valve 29 is opened, and as a result, overflows from the relief joint 25 of the fuel intake means 23 through the fuel supply passage 24.

When the solenoid valve 26 is energized by the operation of the control device 10 while the plunger 21 is being raised, the fuel in the pump chamber 22 that has been compressed due to the rise of the plunger 21 does not escape from the fuel supply passage 24, and Pressurized to high pressure. And the pump room
When the pressure in 22 reaches a pressure that overcomes check valve 29, the check valve
29 is pushed open, and the pressurized fuel is discharged from the fuel discharging means 27 into the common rail 5.

Next, the reason why the low-pressure chamber used in the prior art is no longer needed will be described.

Since the engine 2 of this embodiment is a four-cylinder four-cycle engine, each injector 3 injects fuel four times in total during two rotations of the crankshaft. That is, while the crankshaft rotates twice, the pressure of the common rail 5 decreases four times in total.

On the other hand, the variable discharge high-pressure pump 6 operates while the camshaft 11 makes one rotation (during which the crankshaft makes two rotations).
The plunger 21 reciprocates four times. That is, the plunger 21 reciprocates four times while the camshaft 11 makes one rotation, and discharges fuel four times. Therefore, for a four-cylinder four-cycle engine, the variable discharge high-pressure pump 6 may be one cylinder.

Conventionally, when the engine has three or more cylinders, a plurality of variable discharge high pressure pumps have been used. For this reason, as shown in the prior art, a low pressure chamber is provided at the joint between the housing and the cylinder, and fuel is supplied to another variable discharge high pressure pump via the low pressure chamber.

However, in this embodiment, since the variable discharge amount high-pressure pump 6 requires only one cylinder, the conventionally used low-pressure chamber can be eliminated.

In addition, by eliminating the low-pressure chamber, the conventional seal member that keeps the joint between the housing and the cylinder liquid-tight at the joint between the housing and the cylinder can be eliminated.

(Effects of the Embodiment) In this embodiment, since the low-pressure chamber at the joint between the housing 13 and the cylinder 19 and the seal member for preventing the fuel in the low-pressure chamber from leaking into the chamber 15 can be eliminated, the variable discharge amount can be reduced. The height of the plunger 21 of the high-pressure pump 6 can be reduced as compared with the conventional one.

As a result, the mountability of the variable discharge amount high pressure pump 6 is improved, and the weight of the variable discharge amount high pressure pump 6 can be reduced.

Further, by eliminating the seal member, the number of components of the variable discharge amount high pressure pump 6 is reduced, and the manufacturing cost of the variable discharge amount high pressure pump 6 can be reduced.

Further, a relief check valve 25a provided in a passage leading from the fuel supply passage 24 to the relief joint 25 includes an electromagnetic valve 2
6 is provided above the valve seat 26a, and when fuel is supplied from the fuel intake means 23 with the solenoid valve 16 opened to release air, the relief joint 25 is provided via the relief check valve 25a. The internal air is exhausted from the, and the fuel can be filled up to the height of the relief check valve 25a. Since the pump chamber 22 is located below the solenoid valve 26, the pump chamber 22 can be filled with fuel by bleeding air.

(Modification) In the above embodiment, a four-cylinder four-cycle engine is shown as an example.
Although the number of cam lobes is set to four while the number of cam lobes is two, the number of cam lobes and the number of cam lobes may be changed depending on the type of engine (for example, the number of cylinders and the number of cycles) to be applied.

[Brief description of the drawings]

FIG. 1 and FIG. 2 show an embodiment of the present invention.
FIG. 1 is a sectional view of a variable discharge high pressure pump, and FIG. 2 is a schematic block diagram of a common rail type fuel injection device. FIG. 3 is a sectional view of a conventional variable discharge high pressure pump. In the figure, 6: variable discharge high pressure pump, 11: cam shaft, 12: cam surface, 13: housing, 16: tappet, 19: cylinder, 21: plunger, 22: pump chamber, 23 …… Fuel intake means, 24 …… Fuel supply passage, 26 ……
Solenoid valve, 27 ... Fuel discharging means

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F04B 9/00-15/08 F02M 39/00-71/004

Claims (1)

(57) [Claims] (A) a camshaft which is driven to rotate and has a cam surface around the periphery; (b) a tappet which is pressed against the cam surface and is displaced along the cam surface; A housing for holding the tappet in a reciprocating manner; (d) a plunger mounted on the upper side of the tappet and reciprocating with the reciprocating movement of the tappet; and (e) a reciprocating movement of the plunger mounted on the housing. (F) a fuel intake means mounted on the cylinder and guiding the fuel through a fuel supply passage to a pump chamber formed by an inner peripheral surface of the cylinder and an upper end surface of the plunger. (G) a solenoid valve attached to the cylinder above the pump chamber to open and close the fuel supply passage in accordance with an energized state; and (h) the cylinder. And (i) provided in communication with the fuel supply passage, wherein the solenoid valve is opened and pushed back into the fuel supply passage. A relief joint for returning fuel to a fuel tank; and (j) a relief joint provided above a valve seat of the solenoid valve, provided in a passage leading from the fuel supply passage to the relief joint, and provided with a fuel from the relief joint side. And a relief check valve for preventing backflow of fuel to the supply passage side.