JP2002242794A - High pressure pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent lubrication operation without the occurrence of a trouble, such as feed of a poor fuel pressure and an increase in cost. SOLUTION: In a high pressure pump 10, a feed pump 14 is coupled to a drive shaft 13. When the feed pump 14 is driven along with the rotation of the drive shaft 13, fuel is sucked in the feed pump 14 from a fuel tank T. An oil seal 31 formed of, for example, a fluorine rubber material and a bush 32 forming a part of a bearing are situated on the outer peripheral part of the drive shaft 13. The bearing part of the drive shaft 13 is cut off from an external part by the oil seal 31. A part of the fuel flowing in the feed pump 14 flows to the oil seal 31 through the outer peripheral part of the drive shaft 13 and further flows in a cam chamber 35 after flowing through a fuel passage 34. Further, the fuel in the cam chamber 35 flows out to the fuel tank T through an outlet valve 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a high-pressure pump embodied as a variable discharge high-pressure pump in, for example, a common rail fuel injection device for a diesel engine, and particularly to a lubricating structure for the high-pressure pump.

[0002]

2. Description of the Related Art As a prior art of this kind, a high-pressure pump having a structure shown in FIG. 2 is known. In the high-pressure pump 40 of FIG. 2, a feed pump 42 for supplying low-pressure fuel is connected to the drive shaft 41, and the drive shaft 4
When the feed pump 42 is driven in accordance with the rotation of 1, the fuel is sucked into the feed pump 42 from a fuel tank (not shown) via the inlet valve 43 and the fuel passage 44. Then, the fuel pressurized by the feed pump 42 is sent to the low-pressure channel 45. For convenience, the feed pump 42 is shown in FIG.

In the high-pressure pump 40, a part of the fuel is used for lubrication and cooling. That is, an oil seal 46 made of a fluorine-based rubber material and a bush 47 forming a part of a bearing portion are provided on the outer peripheral portion of the drive shaft 41, and a part of the fuel flowing into the feed pump 42 is The oil reaches the oil seal 46 through the outer peripheral portion of the oil seal 41. In this case, the fuel that has reached the oil seal 46 flows through the fuel passage 48 into the fuel suction portion (the fuel passage 44), and then returns to the feed pump 4.
2 was to flow. Although not shown, a fuel filter (not shown) is provided upstream of the inlet valve 43, and fuel is supplied from the fuel tank to the high-pressure pump 40 via the fuel filter.

[0004]

However, in the high-pressure pump 40 shown in FIG. 2, the fuel filter is clogged at a very low temperature due to precipitation of paraffin component of the fuel (light oil), and the negative pressure increases at the inlet of the high-pressure pump. At the same time, the oil seal 46 hardens and cannot follow the rotational eccentricity of the drive shaft 41. Then, external air is sucked in from the gap between the oil seal 46 and the drive shaft 41. Further, the air is supplied to the fuel passages 48, 4
When the high pressure pump 40 flows into the feed pump 42 through the pump 4, a malfunction such as a poor pumping occurs in the high pressure pump 40.

In order to eliminate the inhalation of air from the oil seal 46, it is necessary to use an expensive rubber material which does not cure even at a low temperature and retains elasticity, in order to eliminate the inhalation of air from the oil seal 46. Become.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a high-pressure pump capable of obtaining a good lubricating action without causing problems such as fuel pumping failure and cost increase. It is to provide.

[0007]

According to the first aspect of the present invention, the feed pump is drivingly connected to the drive shaft, and rotates together with the drive shaft to draw fuel from the fuel tank. Part of the fuel that has flowed into the feed pump is circulated to the bearing portion of the drive shaft, thereby lubricating and cooling the inside of the pump. The high-pressure pump is provided with a seal member for shutting off the bearing of the drive shaft from the outside. A fuel circulation passage extending from the feed pump through the seal member provides a fuel return passage from the high-pressure pump to the fuel tank. Connected to the passage. In this case, even if negative pressure increases at the inlet of the high-pressure pump due to hardening of the seal member at extremely low temperatures or clogging of the fuel filter, no air is sucked in because the pressure near the seal member does not become negative. That is, the air is not sucked from the seal member and flows into the feed pump, so that the fuel pumping failure of the high-pressure pump does not occur. In this case, it is not necessary to use an expensive rubber material which does not cure even at an extremely low temperature as the sealing member. As a result, in the high-pressure pump of the present invention, a good lubricating action can be obtained without causing problems such as fuel pumping failure and cost increase.

In a high-pressure pump, a cam chamber is generally filled with fuel for the purpose of lubricating and cooling a cam member and the like.
The fuel is returned from the cam chamber to the fuel tank as it is.
In such a situation, according to the invention described in claim 2, the cam chamber is used as a part of the fuel return passage,
A fuel circulation passage is connected to the cam chamber. In this case, the desired effect described above is obtained using the existing configuration,
A configuration suitable for practical use can be realized.

Further, the present invention can be suitably embodied as a high-pressure pump which pressurizes fuel sucked by a feed pump in a common rail type fuel injection device and sends it to the common rail under pressure.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The present embodiment is embodied as a common rail type fuel injection device for a diesel engine, and as an overview, a variable discharge high pressure pump sucks low pressure fuel from a fuel tank and increases the pressure of the low pressure fuel. After that, it is fed to the common rail. The common rail accumulates fuel at a high predetermined pressure corresponding to the fuel injection pressure. The fuel pressure in the common rail is controlled by a well-known electronic control unit (ECU), the discharge amount of the variable discharge high-pressure pump is determined so that the common rail pressure becomes an optimum value, and the solenoid valve is driven accordingly. It is controlled.

The detailed configuration of the variable discharge high pressure pump will be described with reference to FIG. However, FIG. 1 mainly illustrates the configuration around the feed pump, which is a main part of the present invention, and omits illustration of well-known configurations such as a fuel pumping unit.

In FIG. 1, a variable discharge high pressure pump (hereinafter simply referred to as a high pressure pump) 10 includes a pump housing 1.
1, the pump housing 11 of which has a sliding bearing 12
Thereby, the drive shaft 13 is rotatably supported. The drive shaft 13 is, for example, の of the engine.
It is driven to rotate in synchronization with the rotation of. Drive shaft 1
3 is connected to a feed pump 14 for supplying low-pressure fuel. When the feed pump 14 is driven with the rotation of the drive shaft 13, the feed pump 1 is supplied from the fuel tank T via an inlet valve 15 and a fuel passage 16.
Fuel is sucked into 4. Then, after the fuel is pressurized to a predetermined low pressure level by the feed pump 14, the fuel is sent to the low pressure passage 17. For convenience, the feed pump 14 is shown in FIG. By the way, the fuel tank T
A fuel filter F is disposed between the fuel pump F and the high-pressure pump 10.

The low-pressure fuel delivered from the feed pump 14 is delivered to a fuel pumping section via a solenoid valve (flow control valve) not shown. A part of the low-pressure fuel is returned to the fuel passage 16 via the fuel passage 18, the regulating valve 19, and the fuel passage 20.

The fuel pumping section will be described briefly. An inner cam 21 is integrally provided at a tip (right end in the figure) of the drive shaft 13. This inner cam 2
According to 1, the fuel sucked into the pressurizing chamber 22 is pressurized with the rotation of the drive shaft 13, and the pressurized fuel is sent to a delivery valve (not shown) through the high-pressure passage 27, and further from the delivery valve to the common rail. Sent out. That is, when the inner cam 21 rotates, the pair of plungers 23 and 24 disposed opposite to each other reciprocate via the cam roller 25 and the shoe 26. Thereby, the pressurizing chamber 2
2 is pressurized and the fuel is sequentially pumped.

Further, in the high-pressure pump 10, a part of the fuel is used for lubrication and cooling, and the configuration will be described below. On the outer periphery of the drive shaft 13,
For example, an oil seal 31 made of a fluorine rubber material and a bush 32 forming a part of a bearing portion are provided, and the bearing portion of the drive shaft 13 is shut off from the outside by the oil seal 31. Part of the fuel that has flowed into the feed pump 14 is the outer peripheral portion (bearing portion) of the drive shaft 13.
Through the oil seal 31. Further, part of the low-pressure fuel flowing out of the feed pump 14 into the low-pressure passage 17 also flows through the passage 33 to the oil seal 31. Due to such circulation of the fuel, lubrication and cooling of the drive shaft bearing are achieved.

The fuel flows into the cam chamber 35 accommodating the inner cam 21 from the low-pressure passage 17 through an orifice (not shown), and the fuel flowing around the oil seal 31 also flows through the fuel passage 34, and the inner cam 21 Each member such as 21 is lubricated and cooled. Also,
The fuel in the cam chamber 35 flows out to the fuel tank T via the outlet valve 36. In the present embodiment, a portion from the feed pump 14 to the fuel passage 34 via the outer periphery of the drive shaft and the seal member corresponds to a “fuel circulation passage” described in the claims, and the cam chamber 35 is connected to the fuel passage 34 via an outlet valve 36. Up to the fuel tank T corresponds to the “fuel return passage”.

According to the embodiment described above, the hardening of the oil seal 31 at extremely low temperatures and the fuel filter F
Even if the negative pressure in the pump inlet channel increases due to clogging,
As a result, no air is sucked from the oil seal 31. That is, air is not sucked from the oil seal 31 and flows into the feed pump 14,
Fuel pumping failure of the high-pressure pump 10 does not occur. In this case, it is not necessary to use an expensive rubber material that does not cure even at extremely low temperatures as the oil seal 31. As a result, in the high-pressure pump 10 according to the present embodiment, a favorable lubricating action can be obtained without causing problems such as fuel pumping failure and cost increase.

Further, with the above configuration, in the common rail type fuel injection device, the amount of fuel pumped by the high pressure pump 10 can be properly controlled, and the controllability of the common rail pressure (fuel pressure) is improved.

The present invention can be embodied in the following modes other than the above. In the above embodiment, the fuel passage 34 (fuel circulation passage) is connected to the cam chamber 35, but this configuration may be changed. For example, it may be connected directly to the fuel tank. The point is that the fuel circulation passage may be connected to the fuel return passage leading to the fuel tank.

In the above-described embodiment, the present invention is embodied as a variable discharge high pressure pump of a common rail type fuel injection device, but may be embodied as a distribution type fuel injection pump for a diesel engine, for example. The fuel injection pump may be either an inner cam type or a face cam type.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a high-pressure pump according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a high-pressure pump according to the related art.

[Explanation of symbols]

10 high pressure pump, 13 drive shaft, 14 feed pump, 21 inner cam, 23, 24 plunger, 31 oil seal, 32 bush, 34 fuel passage, 35 cam chamber, 36 outlet valve.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) F02M 41/14 360 F02M 41/14 360Z F-term (reference) 3G066 AA07 AC03 AC09 AD02 BA29 BA36 BA61 CA09 CA19 CA35 CA36 CD02 CD07 CD09 CD10 CD23

Claims (3)

[Claims] 1. A high-pressure pump, which is provided with a feed pump that is drivingly connected to a drive shaft and sucks fuel from a fuel tank, and circulates a part of the fuel flowing into the feed pump to a bearing portion of the drive shaft. A seal member for blocking the bearing of the drive shaft from the outside is provided, and a fuel circulation passage extending from the feed pump is connected to a fuel return passage extending from the high-pressure pump to the fuel tank via the seal member. High pressure pump characterized. 2. A high-pressure pump for rotating a cam member with the rotation of the drive shaft and thereby reciprocating a plunger to increase the fuel pressure, wherein the fuel circulation passage is connected to a cam chamber accommodating the cam member. The high-pressure pump according to claim 1. 3. A common rail fuel injection system for injecting high pressure fuel accumulated in a common rail into each cylinder of a diesel engine, wherein the pressure of the fuel sucked by the feed pump is increased and the fuel is pumped to the common rail. Or the high-pressure pump according to 2.