JPH0436073A - Variable displacement high pressure pump - Google Patents

Abstract

PURPOSE:To miniaturize a variable displacement high pressure pump and reduce the weight and manufacturing cost of the pump by forming a pump using the inner peripheral face of a cylinder and the end face of a plunger, and providing a fuel inlet means, a solenoid valve for opening and closing a fuel supply passage, and a fuel discharging means for discharging compressed fuel. CONSTITUTION:A pump room 22 is formed in a portion enclosed by the upper end face of a plunger 21 and the inner peripheral face of the hole 20 of a cylinder 19. When the plunger 21 is lowered by rotation of a cam shaft 11, electricity transmission to a solenoid valve 26 is stopped by a controller and fuel is supplied to the pump room 22 via a fuel supply passage 24. If electricity transmission to the solenoid valve 26 is being stopped during the rise of a plunger 26, the fuel overflows from the relief joint 25 of a fuel inlet means 23 through the fuel supply passage 24. When electricity is transmitted to the solenoid valve 26, the fuel supply passage 24 is closed and fuel retained in the pump room 22 and compressed by means of the rise of the plunger 21 pushes a check valve 29 open and the fuel is discharged to a common rail by a fuel discharging means 27. The number of revolution of a crank shaft and the number of threads of a cam are decided according to the type of the engine applied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a variable discharge amount high-pressure pump that varies the amount of fuel discharged by changing the timing of energization of a solenoid valve.

[Prior Art] As an example of the prior art, the technology disclosed in Japanese Patent Application Laid-open No. 73166/1983 is known.

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

L Problems to be Solved by the Invention] The conventional variable discharge amount high pressure pump 100 has a housing 10
Since the low pressure chamber 106 was provided at the joint between the plunger 3 and the cylinder 105, the variable discharge amount high pressure pump 100 was formed to be long in the axial direction of the plunger 104.

Further, the conventional variable discharge amount high pressure pump 100 has a low pressure chamber 1
At the joint between the housing 103 and the cylinder 105 on the cam 109 side from 06, it was necessary to provide a sealing portion or material 110 to maintain liquid tightness. For this reason, the conventional variable discharge amount high pressure pump 100 has a plunger 104.
It was formed long in the axial direction.

That is, in the conventional variable discharge amount high pressure pump 100, the plunger 104 was formed to be long in the axial direction, so the variable discharge amount high pressure pump 100 had the problem of being large and heavy.

An object of the present invention is to provide a variable discharge amount high pressure pump that is small and lightweight.

[Means for Solving the Problems] In order to achieve the above object, the variable discharge amount high pressure pump of the present invention has a camshaft that is rotationally driven and has a cam surface around the camshaft, and a camshaft that is pressed toward the cam surface. a tappet that is displaceable along the cam surface; a housing that holds the tappet so that it can reciprocate; a plunger that is attached to the tappet and that moves reciprocally in conjunction with the reciprocating movement of the tappet; and a plunger that is attached to the housing. , a cylinder that holds the plunger in a reciprocating manner, and a fuel attachment that is attached to the cylinder and that guides fuel through a fuel supply passage into a pump chamber formed by an inner circumferential surface of the cylinder and an end surface of the plunger. an electromagnetic valve that is attached to the cylinder and performs rM closing of the fuel supply passage depending on the energization state; and a fuel discharge means that is attached to the cylinder and discharges the fuel compressed in the pump chamber. Adopt technical means to prepare for

1 Effect] 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. In other words, at the joint between the housing and the cylinder,
There is no conventional low pressure chamber.

Furthermore, since there is no low pressure chamber at the joint between the housing and the cylinder, it is possible to eliminate the conventional sealing member that keeps the joint between the housing and the cylinder liquid-tight.

[Effects of the Invention] As explained above, the present invention can eliminate the low pressure chamber at the joint between the housing and the cylinder and the sealing member that prevents the fuel in the low pressure chamber from leaking to the housing side. , the axial length of the plunger of the variable discharge amount high pressure pump can be shortened.

By shortening the length in the axial direction of the plunger of the variable discharge amount high pressure pump, the variable discharge amount high pressure pump can be made smaller and lighter than the conventional variable discharge amount high pressure pump.

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

(Configuration of Embodiment) Figures 1 and 2 show an embodiment of the present invention. Figure 1 is a cross-sectional view of a variable discharge amount high-pressure pump, and Figure 2 is a schematic block diagram of a common rail type fuel injection device. It is a diagram.

b) First, the fuel injection device l will be explained.

The engine 2 of this embodiment is a 4-cylinder 4-cycle engine, and each cylinder has an injector 3 that injects fuel into a combustion chamber.
Equipped with The fuel injection timing and injection period by the injectors 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 fuel accumulator, and while the injection control solenoid valve 4 is open, the high-pressure fuel stored in the common rail 5 is transferred to the injector 3.
The fuel is injected into the fuel chamber of the engine 2.

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

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

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

The variable discharge amount high pressure pump 6 includes a camshaft 11 that is rotationally driven by the crankshaft of the engine 2. The camshaft 11 is provided so as to rotate 172 times when the crankshaft rotates once. A cam surface 12 is formed around this camshaft 11 . The cam surface 12 moves up and down four times when the camshaft 11 rotates once. In other words, it forms a four-way cam.

The camshaft 11 is disposed in a cam chamber 14 in the lower part of the housing 13 (lower side in FIG. 1 when mounted on a vehicle). A cylindrical chamber 15 is provided inside the housing 13, and a tappet 16 is provided inside the chamber 15.
is supported so as to be able to reciprocate in the direction. This tappet 16 is pressed against the cam surface 12 by a spring 11. The tappet 16 includes a cam roller 18 on the cam surface 12 side, and as a result, when the camshaft 11 rotates, the cam roller 18 rotates along the cam surface 12, and the tappet 16 is displaced in accordance with changes in the cam surface 12. In addition,
When the camshaft 11 rotates once, the tappet 16 reciprocates four times within the cylinder 19.The center part of the upper part of the housing 13 (the upper side in FIG. 1 when mounted on a vehicle) enters the inside of the chamber 15. In this state, the cylinder 19 is fixed. A rod-shaped hole 20 with a circular cross section passes through the center of the cylinder 19 . Inside this hole 20, a plunger 21 is supported so as to be able to reciprocate in the axial direction of the hole 20. The plunger 21 has a rod shape with a circular cross section, and is attached to the tappet 16 at its lower end. Therefore, when the tappet 16 reciprocates, the plunger 21 reciprocates within the hole 20 in response to the movement of the tappet 16.

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. Then, fuel is supplied to the cylinder 19 in a pump chamber 22.
A fuel intake means 23 is attached thereto for guiding the fuel to the pump chamber 22, and a fuel supply passage 24 is provided for guiding the fuel supplied by the fuel intake means 23 to the pump chamber 22. The fuel intake means 23 is a fuel pipe 7 that supplies fuel pumped up by the low pressure pump 9.
It is a joint that connects. The fuel intake means 23 of this embodiment is also integrally provided with a relief joint 25 for returning fuel that has not been discharged from the lower fuel discharge means to the fuel tank 8.

The fuel intake means 23 is installed above the pump chamber 22 when mounted on the vehicle.

A solenoid valve 26 whose energization is controlled by the control device 10 is attached to the upper side of the cylinder 19 . This solenoid valve 26 has a well-known structure for opening and closing the fuel supply passage 24. For example, when the solenoid valve 26 is energized, the fuel supply passage 24 is opened, and when the energization is stopped, the fuel f:4 is supplied. This closes the passage 24.

A fuel discharge means 27 for guiding the fuel compressed in the pump chamber 22 to the outside of the variable discharge amount high pressure pump 6 is attached to the cylinder 19. Fuel for guiding the fuel compressed in the pump chamber 22 to the fuel discharge means 27 A discharge passage 28 is provided. The fuel discharge means 27 is a joint to which the fuel pipe 7 is connected, and the fuel pipe 7 connected to the fuel discharge means 27 is connected to the common rail 5.

Note that a check valve 29 is provided in the passage through which the fuel of the fuel discharge means 27 flows, and prevents the fuel stored in the common rail 5 from flowing back to the variable discharge amount high pressure pump 6.

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

When the engine 2 is running, the crankshaft is rotating, and the plunger 21 is descending, the control device 10 controls the energization of the solenoid valve 26.
, and fuel is supplied to the pump chamber 22 via the fuel supply passage 24.

When the plunger 21 rises, there are times when the electromagnetic valve 26 is energized and times when the energization is stopped. When the electromagnetic valve 26 is de-energized by the control device 10, the fuel in the pump chamber 22 is attempted to be compressed as the plunger 21 rises, but the fuel supply passage 24 is open. Therefore, the pressure in the pump chamber 22 does not reach the pressure that opens the check valve 29, and as a result, the fuel overflows through the fuel supply passage 24 and from the relief joint 25 of the fuel intake means 23.

Further, when the electromagnetic valve 26 is energized by the control device 10 during the upward movement of the plunger 21, the fuel in the pump chamber 22 that is compressed due to the upward movement of the first plunger 21 is discharged from the fuel supply passage 24. It no longer escapes and becomes pressurized to high pressure. When the pressure within the pump chamber 22 reaches a pressure that overcomes the check valve 29, the check valve 29 is pushed open and the pressurized fuel is discharged into the common rail 5 from the fuel discharge means 27.

Next, the reason why the low pressure chamber used in the prior art is no longer necessary will be explained.

Since the engine 2 of this embodiment is a four-cylinder, four-cycle engine, fuel is injected from each injector 3 a total of four times during two revolutions of the crankshaft. In other words, while the crankshaft rotates twice, the pressure on the common rail 5 increases by a total of 4
times decrease.

On the other hand, while the camshaft 11 rotates once (during which the crankshaft rotates twice), the variable discharge amount high pressure pump 6
The plunger 21 reciprocates four times.

That is, during one rotation of the camshaft 11, the plunger 21 reciprocates four times, and fuel is discharged four times.

Therefore, for a four-cylinder four-cycle engine, only one cylinder of the variable discharge high-pressure pump 6 is required.

Conventionally, when an engine has three or more cylinders, a variable displacement high pressure pump has been used for multiple cylinders. 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 other variable discharge amount high pressure pumps via this low pressure chamber.

However, in this embodiment, the variable discharge amount high pressure pump 6 is
Because it only requires a cylinder, the conventional low-pressure chamber can be eliminated.

Moreover, by eliminating the low pressure chamber, it was also possible to eliminate the conventional sealing member that keeps the joint between the housing and the cylinder liquid-tight.

(Effects of Example) In this example, the low pressure chamber at the joint between the housing 13 and the cylinder 19 and the sealing member that prevents the fuel in the low pressure chamber from leaking into the chamber 15 can be eliminated, so the variable discharge amount can be eliminated. The height dimension of the plunger 21 of the high-pressure pump 6 can be made smaller compared to 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.

In addition, by abolishing the sealing member, the variable discharge amount high pressure pump 6
The number of parts is reduced, and the manufacturing cost of the variable discharge amount high pressure pump 6 can be kept low.

Furthermore, in conventional variable displacement high-pressure pumps equipped with a low-pressure chamber, the fuel intake means was attached to the housing, so when the air in the pump was vented by the fuel intake means, fuel could only reach the low-pressure chamber. I couldn't meet it. However, since the fuel intake means 23 is attached to the cylinder 19 according to the present invention, when the air inside the pump is vented by the fuel intake means 23, it becomes possible to fill the inside of the pump chamber 22 with fuel.

(Modification) In the above embodiment, a 4-cylinder 4-stroke engine was used as an example, so the camshaft was rotated 17 times per revolution of the crankshaft.
Although the number of rotations is two and the number of cam ridges is four, the number of revolutions of the camshaft and the number of cam ridges may be changed depending on the type of engine to be applied (eg, number of cylinders, number of cycles, etc.).

[Brief explanation of drawings]

1 and 2 show embodiments of the present invention,
FIG. 1 is a sectional view of a variable discharge amount 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 amount high pressure pump.

Claims (1)

[Claims] 1) (a) a camshaft that is rotationally driven and has a cam surface around its periphery; (b) a tappet that is pressed toward the cam surface and is displaced along the cam surface; c) a housing that holds the tappet in a reciprocating manner; (d) a plunger that is attached to the tappet and that moves reciprocally in accordance with the reciprocating movement of the tappet; (e) a plunger that is attached to the housing and that causes the plunger to reciprocate. a cylinder held movably; (f) fuel intake means attached to the cylinder and guiding fuel through a fuel supply passage into a pump chamber formed by the inner peripheral surface of the cylinder and the end surface of the plunger; (g) a solenoid valve that is attached to the cylinder and opens and closes the fuel supply passage depending on the energization state; (h) a fuel discharge that is attached to the cylinder and discharges the fuel compressed in the pump chamber; Variable displacement high pressure pump with means.