JPH11294296A - Fuel pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent a fuel leakage by arranging a heating wire in a housing near a shaft seal or on the outer periphery of the housing near the shaft seal. SOLUTION: A heating wire 12 is wound on the outer periphery of a housing 1 near a rotary shaft seal 22 preventing a fuel leakage. The heating wire 12 can be heated by the electric power of a battery, and it is excited when an engine is started at a fixed temperature or below. The housing 1 and the gasoline in it are heated by the heat from the heating wire 12, the hardened rubber material of a seal lip recovers its elasticity, it sufficiently follows micro- irregularities on the shaft surface, and a fuel leak to the outside can be prevented. When a fixed time elapses after a start, the temperature is kept at the ordinary temperature or above by the heat transfer from the engine even in use at a cold district, and the excitation to the heating wire 12 is stopped, thereby the reliability for the prevention of a fuel leak can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel pump for a direct injection gasoline engine, and more particularly to a fuel pump mounted on an automobile used in a cold region.

[0002]

2. Description of the Related Art A high-pressure fuel pump for supplying fuel to an in-cylinder injection gasoline engine is a device for pressurizing fuel supplied from a low-pressure pump in a fuel tank to a high pressure for direct injection into an engine cylinder. Consisting of a housing, a compression mechanism housed in the housing, a drive shaft for transmitting a driving force from a camshaft or the like to the internal compression mechanism of the pump, a shaft seal for preventing the working fluid from leaking to the outside of the pump along the drive shaft. ing.

[0003] As a shaft seal, a so-called oil seal, which seals an internal fluid by bringing an elastic body such as rubber into contact with the shaft surface, is often used.

[0004]

However, automobiles are used under a wide range of temperature conditions, from a low temperature at the start in a cold region to a high temperature in traffic congestion in midsummer.

[0005] There are various types of rubber used for the lip portion of the oil seal. However, the rubber is hardened at low and high temperatures, the elasticity is reduced, and it is impossible to follow the unevenness of the shaft surface and the shaft eccentricity. It is easy to happen. In particular, the present invention relates to a fuel pump for in-cylinder injection gasoline engines. Gasoline, which is a sealed fluid, has a viscosity one hundredth lower than that of general lubricating oil, and therefore has a large potential to cause leakage. . If a large amount of fuel leaks from the pump to the outside, it will lead to a serious accident, and sufficient reliability must be ensured.

[0006] Rubbers having high temperature adaptability and low temperature adaptability have been developed, but it is difficult to satisfy both at the same time.
If one adaptive temperature range is widened, the other adaptive temperature range must be narrowed. Therefore, it can be said that there is a limit in responding to material development. Incidentally, Japanese Patent Application Laid-Open No. 9-144536 can be mentioned as this kind of technology.

[0007]

In order to solve the above-mentioned problems, the present invention has devised a fuel leakage preventing means in which a heating wire is arranged in a housing near a shaft seal.

[0008] The curing of rubber by high temperature is an irreversible reaction that does not return, but the curing of rubber by low temperature returns to its original state when heated. Therefore, even when the vehicle is used in a cryogenic region, it is not necessary to consider a period other than during driving. Only when the engine is started, electricity is supplied to the heating wire from the battery to warm the seal lip and gasoline and prevent the lip from hardening.

After the start, heat is transferred from the engine and heat generated in the sliding portion in the pump, and the temperature of the seal lip immediately returns to the normal temperature or higher, and the sealing property is ensured. Good. Only a small amount of battery power is consumed.

An object of the present invention is to eliminate the need to develop a material adapted to low-temperature conditions such as below freezing point, and to develop and adopt a material excellent in high-temperature resistance to improve reliability,
An object of the present invention is to provide a fuel pump that can reduce material costs.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view of a fuel pump according to an embodiment of the present invention.

This embodiment is a fuel pump for a direct injection gasoline engine. Unlike the conventional gasoline engine that injects gasoline into the intake port, the above-mentioned engine is of a type in which gasoline is directly injected into a high-pressure combustion cylinder, so that the fuel pump is supplied with gasoline at a high pressure of 5 MPa or more. Required to press. As long as the internal compression chamber and the drive shaft are not completely separated from each other by using a bellows or a magnetic coupling, the drive shaft needs a shaft seal for preventing fuel from leaking to the outside.

Unlike the case where high-viscosity oil is sealed, gasoline has a low viscosity. Therefore, if the elasticity of the rubber material of the seal lip is reduced, the risk of leakage is particularly increased. In order to reduce the leakage potential at low temperatures, the present embodiment was devised.

First, the mechanism of the movement will be described. The drive shaft 2 is connected to an engine camshaft via a coupling 3 and transmits driving force to a pump. The drive shaft is rotatably supported in the housing 1 by a rolling bearing 4 and a bush bearing 5. The axial movement of the drive shaft 2 includes a retaining ring 6 attached to the drive shaft and a collar 7 provided at an end of the drive shaft.
Regulated by

The oscillating plate has a plate portion 8 having a shape obtained by cutting a sphere in two parallel planes, and a shaft-shaped convex portion 9 having a central axis perpendicular to the plane and passing through the center of the sphere and protruding outside the sphere. Consists of The plate part 8 and the convex part 9 are integral.

The shaft-shaped convex portion 9 of the rocking plate is fitted through a ball joint 10 into a spherical concave portion 11 eccentrically spaced from an end face of the drive shaft 2 from the center axis, and freely rotates and tilts freely. doing. The rotation of the drive shaft causes the recess 11
Swings around the central axis, and the swinging plate convex portion 9 also revolves. One rocking plate portion 8 is pressed against a spherical bearing 13 press-fitted into the housing 1 and is fixed in position, and can only rotate or tilt. In this way, the rotational motion of the drive shaft 2 is converted into the rocking motion of the rocking plate 8.

The cylinder block 14 is provided with a plurality of cylinders arranged at equal circumferential intervals, and a compression chamber is formed by the plunger 15 reciprocating in the cylinder and the cylinder. The plunger 15 is pressed against the flat portion of the rocking plate 8 by the spring force of the spring 17 via the slipper 16. The slipper 16 has a flat bottom surface and a spherical bottom surface, and slides on the flat portion of the swing plate 8 and the spherical portion of the plunger 15, respectively, so that the swing motion of the swing plate is reciprocated by the plunger. Convert to movement.

Next, the fuel path will be described. The fuel is introduced into the slipper side space 19 of the rocking plate from the suction port 18, and passes through a groove provided on the plane side of the rocking plate 8 and a passage inside the slipper 16, and a ball and a spring provided in the plunger 15. And enters the compression chamber 20 through a check valve. The fuel pressurized by the plunger in the compression chamber is discharged from another check valve to the discharge port 21. The inside of the housing 1 is basically at a feed pressure or higher, and a lip made of a rubber material is provided inside the rolling bearing 4 in order to prevent fuel from leaking outside along the outer periphery of the drive shaft 2. A rotary shaft seal 22 is provided.

The heating wire 12 is wound around the outer periphery of the housing near the rotary shaft seal 22. The heating wire 12 can generate heat by the power of the battery, and is controlled so as to be energized when the engine is started when the temperature is lower than a certain temperature.

The heat generated from the heating wire 12 heats the housing 1 and gasoline therein, and the rubber material of the hardened seal lip recovers its elasticity, sufficiently follows the micro unevenness on the shaft surface, and the outside of the fuel. Is prevented from leaking.

After a certain period of time has elapsed from the start, the temperature is maintained at a normal temperature or higher irrespective of use in a cold region due to heat transfer from the engine and heat generated from the sliding portion such as the bearing bush 5. Accordingly, energization of the heating wire 12 is stopped.

The present invention eliminates the need for the lip material of the rotary shaft seal 22 to accommodate low temperature conditions, such as below freezing. If it is not necessary to omit the low-temperature resistance, a material having excellent high-temperature resistance can be used, thereby improving the reliability at high temperatures.

FIG. 2 is a conceptual diagram of the fuel pump of the embodiment shown in FIG. 1 of the present invention. A compression mechanism 23 is provided inside the pump housing 1, and mechanically pressurizes gasoline sucked from a low-pressure feed pump or a low-pressure regulator in a fuel tank and sends the gasoline to an engine or a high-pressure regulator. Although the illustrated compression mechanism is a conceptual diagram of a rotary swash plate type axial pump, the same effect can be obtained by using another compression mechanism such as a gear pump or a rotary pump without being limited to the illustrated example.

FIG. 3 is a system diagram of the fuel pump of the embodiment shown in FIG. A single line indicates connection of the electric system, a double line indicates connection of the fuel system, and a thick line indicates connection of the drive system.

An automobile is already equipped with a computer for controlling an engine fuel injection valve, an antilock brake system, and the like. Incorporating a heating wire control program into the computer, and using information from a temperature sensor installed around the high-pressure pump, if the temperature is low, such as below freezing,
Apply current to the heating wire. The energization time may be determined using feedback information from the temperature sensor, or may be given in advance as a function of the initial temperature. In the latter case, a new temperature sensor is not required,
There is also a method of using equipment installed in current automobiles.

In this embodiment, the pump is driven by using the rotational force of the camshaft of the engine. However, the present invention has the same effect even when a drive system using an electric motor is used.

The same effect can be obtained even if the heating wire is not wound around the housing, but a hole or groove is provided in the housing and the heating wire is embedded.

[0029]

As described above, according to the present invention, without developing a rubber material having both low temperature resistance and high temperature resistance,
It is possible to provide a high-pressure fuel pump for a direct injection gasoline engine, which sufficiently ensures reliability against fuel leakage.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fuel pump according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram of a fuel pump according to the embodiment of FIG. 1;

FIG. 3 is a system diagram of a fuel pump according to the embodiment of FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pump housing, 2 ... Drive shaft, 12 ... Heating wire, 2
2 ... rotating shaft seal, 23 ... compression mechanism.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F04B 53/00 F04B 21/00 R

Claims (1)

[Claims] 1. A housing comprising: a housing; a drive shaft that penetrates through the housing to transmit a driving force from the outside; and a rubber lip-type rotary shaft seal between the housing and the drive shaft that prevents fuel from leaking to the outside of the pump. In a fuel pump, a heating wire is arranged in a housing near the shaft seal or on an outer periphery of the housing near the shaft seal.