JP2002364491A - High pressure pump for alternative fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high pressure pump 1 for alternative fuel, in which an amount of DME fuel leaking from a clearance between a plunger 9 and a cylinder 7 is reduced and the DME fuel is collected, a proper pressure feed amount of the DME fuel is kept to increase output with respect to fuel economy of an internal combustion engine, and quiet operation is implemented. SOLUTION: The DME fuel from a feed pump is fed to a pump chamber 22 by a feed pressure. The DME fuel is pressed by the reciprocating movement of the plunger 9 and is injected to the internal combustion engine through an injector. At this time, the DME fuel from the pump chamber 22 leaks from the clearance between the cylinder 7 and the plunger 9. While pressure of the leaking DME fuel is gradually reduced in a collection groove 28 of a high pressure leak collection passage, the leaking DME fuel is collected through a seal chamber 32 of a low pressure leak collection passage. Therefore, large part of the leaking DME fuel is collected in a liquefied state, and thereby the leaking amount is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-pressure pump for an alternative fuel, which uses a fuel having a low viscosity and easy to vaporize, such as dimethyl ether, in a fuel injection device for an internal combustion engine.

[0002]

2. Description of the Related Art Alternative fuels to diesel fuels such as light oil have been moving toward physical properties with low viscosity and high vapor pressure. Dimethyl ether as a representative of this alternative fuel has substantially the same cetane number as light oil, and has low concentrations of NOx and HC in exhaust gas after combustion. For this reason, when dimethyl ether is applied to a diesel engine, dimethyl ether is expected to be a clean alternative fuel with less black smoke over the entire output range. A high pressure pump using dimethyl ether as a main fuel in a diesel engine is disclosed in Japanese Patent Application Laid-open No.
There is one described in Japanese Patent Publication No. 0-281030.

[0003] In both Japanese Patent Application Laid-Open Nos. 10-281029 and 10-281030, the gap between the plunger and the plunger barrel (less than 3 µm) is set to be narrow to reduce fuel leakage. Further, the fuel leaked from the gap between the plunger and the plunger barrel is returned to the intake pipe of the engine via the leak gas introducing pipe, and is reused as fuel.

[0004]

However, the gap between the plunger and the plunger barrel (cylinder) is 3 μm.
, It becomes a general value for known pumps,
In particular, the setting is not narrow. Furthermore, since the fuel under high pressure is recovered in a single path, the amount of fuel leakage from the gap between the plunger and the plunger barrel tends to be large.

[0005] In particular, at high temperatures, the viscosity of the fuel decreases and the amount of fuel leakage increases rapidly. For this reason, the total injection amount of the leaked fuel introduced into the intake pipe and the fuel from the injection nozzle exceeds an appropriate value and becomes excessive, which may make it difficult to control the diesel engine.

The present invention has been made in view of the above circumstances, and has as its object to reduce and recover fuel leaking from a gap between a plunger and a cylinder, and to prevent an external leak to maintain an appropriate amount of fuel to be pumped for internal combustion. An object of the present invention is to provide a high-pressure pump for an alternative fuel which improves the output with respect to the fuel efficiency of the engine and leads to quiet operation.

[0007]

According to a first aspect of the present invention, in a high-pressure pump for an alternative fuel, easily vaporized fuel is sent from a feed pump to a pump chamber through a fuel gallery by a feed pressure. The fuel in the pump chamber is pressed by the reciprocating movement of the plunger, and is injected into the internal combustion engine via the discharge valve and the injector. In this case, as the plunger reciprocates in the cylinder, fuel from the pump chamber leaks out through a gap between the cylinder and the plunger. The leaked fuel is recovered through two passages, a high-pressure leak recovery passage and a low-pressure leak recovery passage.

[0008] When recovering the leaked fuel, the leaked fuel recovery passage is divided into two systems, a high and low pressure leak recovery passage, and most of the leaked fuel passing through the high pressure leak recovery passage is recovered in a liquefied state. For this reason, the amount of fuel leakage can be reduced as compared with the related art in which the leaked fuel is recovered under a high pressure through a single system passage. By reducing the leakage amount, it is possible to maintain an appropriate amount of fuel to be pumped, make the high-pressure pump highly efficient, and improve the output with respect to fuel efficiency of the internal combustion engine.
That is, it is possible to correct a change in the physical properties of the fuel that is easily vaporized in accordance with the operation state of the internal combustion engine, and to supply a required amount of fuel having appropriate physical property values to the internal combustion engine at the time of injection.

The high pressure leak recovery passage is maintained at a high pressure through a feed circuit communicating with the fuel gallery. In addition, the low pressure leak recovery passage faces a seal chamber provided below the plunger, and thus has a low pressure. In this way, the leakage fuel recovery passage is divided into two systems, a high and low pressure leak recovery passage.

[0010] The fuel flowing through the low pressure leak recovery passage is recovered to a purge tank or the like via a recovery means and reused as fuel.

Since the collecting means is formed in the side wall of the cylinder as a leak passage, it is not necessary to separately provide a separate member, and the structure is advantageous in cost and simple.

(Claim 5) A valve body of a control solenoid valve is mounted on the upper end of the cylinder in a liquid-tight manner. Further, an opening / closing valve portion is provided between the pump chamber and the fuel gallery, and the amount of fuel discharged from the discharge valve is adjusted by opening / closing the valve portion. In this case, a plurality of cores arranged substantially concentrically with a non-magnetic material interposed therebetween are rigidly connected in a liquid-tight manner by welding inside the control solenoid valve. Due to the rigid connection of the core by welding, the constituent electrical components of the control solenoid valve, the pump chamber and the fuel gallery can withstand the feed pressure of the high-pressure fuel. In addition, due to the liquid-tight structure of the core by welding, it is possible to prevent fuel from leaking to the outside, as well as to block the passage of fuel into the core, and to allow fuel to enter components such as coils of the solenoid valve for control. There is no.

Since the discharge valve is set to open at a pressure lower than the feed pressure of the fuel, a smooth valve opening operation can be obtained and the backflow of the fuel can be suppressed. Can be.

The fuel gallery is provided with a pressure regulating valve urged in a closing direction by a spring. When the pressure regulating valve is opened against the spring to release the overflowing fuel, the vapor pressure generated from the fuel due to the temperature rise is added as back pressure in the direction of closing the pressure regulating valve. Therefore, a load is added to the pressure regulating valve as the sum of the urging force of the spring and the steam pressure. Thus, it is possible to prevent the fuel in the fuel gallery from being vaporized due to the additional closing force of the pressure regulating valve.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments in which the present invention is applied to a diesel engine as an internal combustion engine will be described with reference to the drawings. FIG. 1 shows a high-pressure pump 1 according to a first embodiment of the present invention. The high-pressure pump 1 supplies a high-pressure fuel containing dimethyl ether (DME) as a main component as an alternative fuel in a fuel supply device of a diesel engine.
This alternative fuel may be pure or only a dimethyl ether component adjusted to various purities, or may be dimethyl ether as a main component and may contain other diesel fuels. Shall be. Since this alternative fuel has a low viscosity and is easily vaporized, the terms “liquid-tight” or “oil-tight” used in the present invention include:
The meaning of "airtight" is assumed.

The high-pressure pump 1 is driven by a diesel engine and sends an alternative fuel (hereinafter referred to as "DME fuel") to an injector (neither is shown) via a high-pressure pipe and a common rail as a high-pressure fuel accumulator. On this occasion,
The pressure of the DME fuel depends on the speed and load of the diesel engine,
The control is performed based on the temperature and input pressure of fuel, intake air, and cooling water.

The high-pressure pump 1 has a camshaft 3 rotatably mounted at a lower portion inside a housing 2 and driven to rotate by a diesel engine. The camshaft 3 has a cam 4 having cam portions 4a and 4b opposed in a radial direction. In this case, only one of the cam portions 4a and 4b may be provided, or the cam portions 4a and 4b are not limited to two and may be provided in plural at predetermined angular intervals.

The cam 4 comes into contact with a roller 6 slidably provided on the tappet 5 and moves the tappet 5 in the vertical direction via the roller 6 as the cam shaft 3 rotates. A cylinder 7 is provided with a tappet 5 in the upper end opening of the housing 2.
While maintaining a predetermined stroke interval, and is fixed in a liquid-tight manner by screws (not shown). Tappet 5
The plunger 9 urged downward by the compression coil spring 8 reciprocates up and down along the inner wall 7a of the cylinder 7.

Between the housing 2 and the cylinder 7, there is formed an annular fuel gallery 10 which is filled with DME fuel supplied by a feed pump (not shown) and forms a feed circuit. The housing 2 is provided with an inlet hollow screw 11 and an outlet hollow screw 12 for introducing the DME fuel in a liquid-tight manner.
The inlet hollow screw 11 communicates with the fuel gallery 10 via the fuel passage 13.

The hollow screw 12 for the outlet is connected to the fuel passage 1.
6, a pressure regulating valve 14 for regulating the maximum pressure in the fuel gallery 10 and a coil spring 15 for setting the valve opening pressure of the pressure regulating valve 14 are incorporated. The outlet hollow screw 12 is connected to the fuel tank by a pipe so as to return the DME fuel released by the pressure regulating operation when the valve is opened to a fuel tank (not shown).

With the opening of the pressure regulating valve 14, the DME fuel passes so as to overflow from the fuel passage 16. At this time, DM
A part of the DME fuel is vaporized due to the temperature rise of the E fuel.
The pressure of the vapor component generated by the vaporization of the DME fuel is regulated by the pressure regulating valve 1.
4 in the direction to close the valve. Therefore, as the temperature of the DME fuel changes, the valve opening pressure of the pressure regulating valve 14 set by the coil spring 15 changes in magnitude according to the amount of vaporization of the DME fuel. That is, as the temperature of the DME fuel rises, the valve opening pressure of the pressure regulating valve 14 automatically increases, and the internal pressure of the fuel gallery 10 is increased to prevent the DME fuel in the fuel gallery 10 from evaporating.

A housing 18 of a control solenoid valve 17 as a solenoid is screwed into the upper end opening of the cylinder 7 in a liquid-tight manner by a fastening structure 19 between a male screw and a female screw. An annular upper fuel gallery 21 is formed between the valve body 20 of the control solenoid valve 17 and the cylinder 7. The space surrounded by the valve body 20 of the control solenoid valve 17, the cylinder 7, and the plunger 9 is defined as a pump chamber 2.
It is 2.

The DME fuel from the fuel gallery 10 is
The upper fuel gallery 21 is filled through the introduction passage 53 formed in the side wall of the cylinder 7. The DME fuel in the upper fuel gallery 21 fills the pump chamber 22 through a communication passage 23 formed in the valve body 20 as described later.

Further, the cylinder 7 has a hollow discharge valve holder 24 mounted thereon. The discharge valve holder 24 incorporates therein a discharge valve 25 and a compression coil spring 26 for setting a valve opening pressure of the discharge valve 25. The discharge valve 25 is
The pump chamber 22 communicates with the pump chamber 22 through the fuel passage 27, and sends out high-pressure DME fuel from the pump chamber 22 to the common rail.
Then, as the pressure in the pump chamber 22 decreases, the discharge valve 25 closes liquid-tight (oil-tight) to maintain the common rail pressure at a predetermined value.

On the inner wall 7a of the cylinder 7, which is the sliding surface of the plunger 9, an annular collecting groove 28 forming a high-pressure leak collecting passage is formed in the circumferential direction. The recovery groove 28 communicates with a recovery path 29 formed on the side wall of the cylinder 7.
The high-pressure DME fuel leaking from the pump chamber 22 along the space between the cylinder 7 and the plunger 9 is recovered through a recovery path 29.

The cylinder 7 is connected to the hollow screw 30 for purging, and is formed with an elongated leak passage 33 which forms a low pressure leak recovery passage in a substantially vertical direction. The purge hollow screw 30 communicates via a leak passage 33 with a seal chamber 32 (low-pressure leak recovery passage) in a cup-shaped oil seal 31 fitted in a liquid-tight manner at the lower end of the cylinder 7 as described later. ing.

Therefore, the low-pressure DME fuel leaking from the recovery groove 28 between the cylinder 7 and the plunger 9 reaches the seal chamber 32. The DME fuel in the seal chamber 32 is
It is connected to a pipe collected in a purge tank (not shown) via a leak passage 33 and a guide passage 34 in the purge hollow screw 30 in order.

FIG. 2 is an enlarged vertical sectional view showing the oil seal 31 in detail. This oil seal 31 is
Has a cylindrical metal portion 31a press-fitted to the outer peripheral portion of the lower end of the cylindrical portion.
The inner peripheral edge of the lower end of the metal portion 31a is press-fitted into a rubber bottom portion 31b having an insertion hole 31c for receiving the plunger 9. An upper lip 35 for a fuel seal and a lower lip 36 for a lubricating oil seal are formed on the inner peripheral edge of the insertion hole 31c so as to be in elastic contact with the outer peripheral surface of the plunger 9, respectively.

DME fuel and lubricating oil adhering to the plunger 9 as the plunger 9 moves up and down are removed from the upper lip 35.
Most of the plunger 9 is removed by the lower lip portion 36 and the upper lip portion 35 and the lower lip portion 36 while the remaining DME fuel and lubricating oil are attached.

The DME fuel removed by the upper lip portion 35 and the lower lip portion 36 is accommodated in the seal chamber 32, and is provided with a leak passage 33 and a hollow screw 30 for purging.
Is collected in the purge tank via the guide path 34 in the order. Similarly, the removed lubricating oil is returned to the cam chamber 2a in the housing 2 along the space between the tappet 5 and the inner wall of the housing 2.

FIG. 3 is an enlarged longitudinal sectional view showing the control solenoid valve 17 in detail. The control electromagnetic valve 17 mainly includes a solenoid part 37 and a valve part 38. Solenoid part 37
Has a coil 44 and cores 39 and 41 arranged substantially concentrically with each other, and a non-magnetic material 42 is sandwiched between the core 39 and the core 41. The cores 39 and 41 are mounted in a solenoid case 40 made of a non-magnetic material. The cores 39 and 41 are welded to the non-magnetic material 42 in a liquid-tight manner by welding, and a welding portion 43 formed of an annular bead.
(43b, 43c). The core 41 is welded to the solenoid case 40 to form a welded portion 43a. These welds 43a, 43 realize a liquid-tight and rigid connection and prevent external leakage of fuel along the coil 44. Of course, high-pressure DME fuel is supplied to the coil 44 existing between the core 39 and the core 41. We do not invade.

The valve portion 38 has a valve body 45 fitted in a liquid-tight manner at an inner peripheral portion of the lower end of the housing 18 and a needle 47 inserted vertically movably through a vertical shaft hole 46 formed in the valve body 45. It has. An armature 48 is fitted to the upper end of the needle 47, and a needle valve 50 is attached to the lower end thereof via a small diameter portion 49.

The valve body 45 has a pressure relief hole H communicating the upper fuel gallery 21 and the armature chamber 45a. The lower end face of the valve body 45 has a DM
In order to restrict the lower limit position of the needle valve 50 while allowing the E fuel to pass, a stop plate K having an outflow / inflow hole is attached.

When the control solenoid valve 17 is energized, the armature 48 and the solenoid 37 form a magnetic circuit and generate an attractive force. Due to the suction force, the needle 47 is suction-moved upward from the valve-open position against the urging force of the compression coil spring 51. For this reason, the needle valve 50 is closed in close contact with the seat portion 52, and the communication between the upper fuel gallery 21 and the pump chamber 22 via the communication passage 23 is cut off.

In the above configuration, when the roller 6 driven by the cam 4 of the cam shaft 3 is located on the base circle of the cam 4, the plunger 9 is located at the bottom dead center and the control solenoid valve 17 Is in a non-energized state. For this reason,
The needle 47 is displaced to the valve-opening position in FIG. 3 by the urging force of the compression coil spring 51, and the needle valve 50 is in the valve-open state separated from the seat portion 52. Thereby, the upper fuel gallery 21 and the pump chamber 22 are communicated via the communication passage 23.

In this state, the DME fuel pressurized by the feed pump is charged into the fuel gallery 10 via the inlet hollow screw 11 and the fuel passage 13, and the introduction passage formed in the side wall of the cylinder 7. 5
The fuel is filled into the upper fuel gallery 21 through the third fuel gallery 3. The DME fuel in the upper fuel gallery 21 is charged into the pump chamber 22 through the communication passage 23, the small diameter portion 49 in the shaft hole 46, the seat portion 52, and the stop plate K in this order.

At this time, if the common rail pressure is lower than the feed pressure of the DME fuel (for example, when the diesel engine is started), the feed pressure overcomes the sum of the set load of the compression coil spring 26 of the discharge valve 25 and the common rail pressure.
With this feed pressure, the discharge valve 25 is opened against the urging force of the compression coil spring 26, and the D
ME fuel is charged into the common rail via the fuel passage 27.

On the other hand, the DME filled in the pump chamber 22
As for the fuel, the cam portion 4 a pushes up the tappet 5 via the roller 6 as the cam shaft 3 rotates. As a result, the plunger 9 is displaced upward against the urging force of the compression coil spring 8, and is driven in a direction to reduce the volume of the pump chamber 22.

For this reason, the DME fuel in the pump chamber 22 is discharged to the upper fuel gallery 21 via the seat portion 52 of the needle 47, the small diameter portion 49, and the communication passage 23 in the control solenoid valve 17.

During the lift of the cam 4, the control solenoid valve 17 is energized in accordance with the rotational speed of the diesel engine or the feed pump and the accelerator opening. Then, a magnetic flux is generated as a magnetic attractive force in a magnetic circuit formed by the solenoid 37 and the armature 48. Therefore, the needle 47 is sucked upward from the valve opening position against the urging force of the compression coil spring 51, and the needle valve 50 is brought into close contact with the seat portion 52 and closed. Thereby, the communication between the upper fuel gallery 21 and the pump chamber 22 via the communication passage 23 is cut off.

Further, as the cam shaft 3 rotates, the cam portion 4
When a is lifted, the volume of the pump chamber 22 is further reduced by raising the plunger 9. Then, the pressure in the pump chamber 22 increases based on the reduced volume of the pump chamber 22 and the bulk modulus of the DME fuel. In this process, the pump chamber 22
The internal pressure is the common rail pressure and compression coil spring 2
When the sum exceeds the set valve opening pressure, which is the urging force of No. 6, the discharge valve 25 opens against the compression coil spring 26, and DM
Pump E fuel to the common rail.

When the seat portion 52 is closed by the needle valve 50 and the pressure in the pump chamber 22 rises above a predetermined value, the energization of the coil 44 of the control solenoid valve 17 is cut off. At this time, since the fuel pressure in the pump chamber 22 is greater than the opening force of the needle valve 50 by the compression coil spring 51, the needle valve 50 is pushed up and kept in the closed state.

When the cam portion 4a reaches the top dead center, the pressurization of the pump chamber 22 of the plunger 9 stops, and the fuel pressure starts to decrease. When the cam portion 4a starts to descend by reducing the lift amount, the pressure in the pump chamber 22 further decreases. The discharge valve 25 is closed by the common rail pressure and the urging force of the compression coil spring 26, the common rail is closed, and the common rail pressure is maintained at a predetermined value.

The pump chamber 2 is moved with the downward movement of the cam portion 4a.
The pressure of 2 continues to drop. When the pressure in the pump chamber 22 becomes lower than the urging force of the compression coil spring 51 in the control solenoid valve 17, the needle valve 50 is displaced downward by the urging force of the compression coil spring 51, and opens apart from the seat portion 52. . As a result, the upper fuel gallery 2
The DME fuel from 1 is connected to the communication passage 23,
The pump chamber 22 is filled again via the seat 6 and the seat portion 52 in this order. When the cam portion 4a moves down to the bottom dead center with the rotation of the camshaft 3, the reciprocating movement of the plunger 9 up and down is completed and one cycle is completed.

On the other hand, as the plunger 9 is driven up and down by the cam 4, the oil seal 31 functions to prevent the DME fuel and the lubricating oil adhering to the outer surface of the plunger 9 from passing downward by a predetermined amount or more. I do. That is, when the plunger 9 rises and passes through the insertion hole 31c, the lower lip portion 36 shown in FIG. 2 leaves lubricating oil of a predetermined thickness on the outer surface of the plunger 9. For this reason, the lubricating oil having a predetermined thickness or more attached to the plunger 9 is scooped by the lower lip portion 36 and returned to the cam chamber 2a in the housing 2.

Further, the plunger 9 is lowered to insert the insertion hole 3c.
2, the upper lip 35 shown in FIG. 2 leaves the DME fuel of a predetermined thickness on the outer surface of the plunger 9. For this reason, the DME fuel having a predetermined thickness or more attached to the plunger 9 is scooped up by the upper lip 35 and stored in the seal chamber 32.

The amount of lubricating oil and DME fuel having a predetermined thickness remaining on the outer surface of the plunger 9 is only an amount necessary for lubrication between the plunger 9 and the upper and lower lip portions 35 and 36. The upper and lower lip portions 35 and 36 are in elastic contact with the plunger 9 at a predetermined pressure so that most of the lubricating oil and the DME fuel do not pass through the upper and lower lip portions 35 and 36. The DME fuel collected in the seal chamber 32 is collected in the purge tank via the leak passage 33 and the guide passage 34 of the hollow screw 30 for purging.

As described above, the high pressure DM in the pump chamber 22 is
The E fuel does not leak directly into the seal chamber 32, but is once collected in the collecting groove 28, and is reduced to the feed pressure by the collecting passage 29 communicating with the fuel gallery 10. Next, the DME fuel in the recovery groove 28 is supplied to the plunger 9 and the cylinder 7.
The pressure is reduced in two stages from a high pressure to a low pressure, such as leaking down to the seal chamber 32 and flowing down, and is collected.

Therefore, unlike the configuration in which the high-pressure DME fuel leaks directly into the low-pressure seal chamber, the amount of vaporization of the DME fuel can be reduced in a stepwise decompression process. This makes it possible to reduce the amount of DME fuel leakage as compared with the conventional method in which DME leakage fuel is recovered under a high pressure through a single system passage. By reducing the leakage amount, it is possible to maintain an appropriate amount of DME fuel to be pumped, make the high-pressure pump highly efficient, and improve the output with respect to fuel efficiency of the diesel engine.

FIG. 4 shows a second embodiment of the present invention. In this embodiment, the same members as those in FIG. 2 of the first embodiment are denoted by the same reference numerals, and only different portions will be described. The second embodiment differs from the first embodiment in that the metal part 31a of the oil seal 31 is directly pressed into the lower end of the cylinder 7 in the first embodiment, whereas the metal part of the oil seal 31 is pressed in the second embodiment. Part 31a
Is that a retaining structure has been added.

That is, an annular concave portion 54 is formed on the outer peripheral surface of the lower end portion of the cylinder 7, and an annular projecting portion 55 is formed on the inner peripheral surface of the metal portion 31a. When fitting the metal portion 31a to the lower end of the cylinder 7, the protrusion 55
To prevent the metal part 31a from accidentally falling off.

An O is provided between the cylinder 7 and the metal part 31a.
A ring 56 is provided to seal the metal part 31a and the seal chamber 32 in a liquid-tight manner. According to this configuration, the metal part 31
A slight deformation of the plunger 9 due to the press-fitting of a can be prevented, and a dimensional change does not occur in the gap between the plunger 9 and the cylinder 7, thereby improving reliability.

FIG. 5 shows a third embodiment of the present invention. In this embodiment, the same members as those in FIG. 2 of the first embodiment are denoted by the same reference numerals, and only different portions will be described. The difference between the third embodiment and the first embodiment is that the third embodiment has a second collecting groove 57 provided below the collecting groove 28 and an oil seal 31.
The upper lip 35 is omitted.

That is, the second recovery groove 57 is formed on the inner wall 7 a of the cylinder 7 so as to be located below the recovery groove 28. The collecting groove 57 communicates with the leak passage 33 of the first embodiment. In the oil seal 31, the upper lip 35 of the rubber bottom 31b is omitted, and only the lower lip 36 is left.

According to this configuration, since the low-pressure DME fuel is recovered from the second recovery groove 57, the upper lip 35 becomes unnecessary. By omitting the upper lip 35, only the lower lip 36 slides on the plunger 9, and the sliding length on the plunger 9 can be reduced.

FIG. 6 shows a fourth embodiment of the present invention. In this embodiment, the same members as those in FIG. 2 of the first embodiment are denoted by the same reference numerals, and only different portions will be described. In the fourth embodiment, in addition to the oil seal 31 of the first embodiment, the second
Oil seal 100 is provided. For this reason, an annular groove 110 is provided near the lower end of the cylinder 7 so that the seal chamber 1
The second oil seal 100 is arranged in this seal chamber 111 so as to be in elastic contact with the plunger 9.

The second oil seal 100 has a shape having a pressure resistance against the feed pressure of the fuel gallery 10, for example, an X-shaped section (FIG. 6), a star, an upward C-shaped section, or an E-shaped section. Various things can be applied. Due to the second oil seal 100, the fuel leaking from the fuel gallery 10 along the space between the plunger 9 and the cylinder 7 hardly leaks into the seal chamber 32 against the gallery pressure. As a result, the leak passage 3
3 can further reduce the amount of fuel leaked.

(Modification) In the above embodiment, the collecting groove 28 and the second collecting groove 57 are formed in an annular shape. However, these collecting grooves may be formed in several spirals. Further, the lower end of the leak passage 33 in the third embodiment may be bifurcated, one of which may be connected to the second collecting groove 57 and the other facing the seal chamber 32. In addition, in specific implementation, various changes can be made without departing from the gist of the present invention.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a high-pressure pump according to a first embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional view showing an oil seal in detail.

FIG. 3 is an enlarged vertical sectional view showing a control solenoid valve in detail.

FIG. 4 is an enlarged vertical sectional view of an oil seal according to a second embodiment of the present invention.

FIG. 5 is an enlarged vertical sectional view of an oil seal according to a third embodiment of the present invention.

FIG. 6 is an enlarged vertical sectional view of an oil seal according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High-pressure pump 7 Cylinder 7a Inner wall 8 Compression coil spring 9 Plunger 10 Fuel gallery (feed circuit) 11 Inlet hollow screw 12 Outlet hollow screw 13, 16 Fuel passage 14 Pressure regulator 15 Coil spring 17 Control solenoid valve 18 Housing 21 Upper part Fuel gallery 22 Pump chamber 25 Discharge valve 28 Recovery groove (high-pressure leak recovery passage) 29 Recovery passage 31 Oil seal 32 Seal chamber 33 Leak passage (recovery means) 35 Upper lip portion 36 Lower lip portion 37 Solenoid portion 38 Valve portion 39, 41 Core 40 Solenoid case 42 Non-magnetic material 43 Welded part 45 Valve body 50 Needle valve (valve part) 51 Compression coil spring (spring) 53 Introductory passage 57 Second recovery groove (High pressure leak recovery passage) 100 Second oil seal

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) F02M 59/46 F02M 59/46 Y (72) Inventor Yoshihisa Yamamoto 1-1-1 Showa-cho, Kariya-shi, Aichi Stock Shares F term in company DENSO (reference) 3G066 AA07 AB04 AC09 AD12 BA16 BA22 BA34 BA37 CA01S CA05 CA05T CA08 CA09 CD10 CD12 CD14 CD17 CE02 CE22

Claims (7)

[Claims] 1. A pump chamber for receiving easily vaporized fuel from a feed pump through a fuel gallery by a feed pressure, and a fuel in the pump chamber is pressed by reciprocating in a cylinder, and internal combustion is performed through a discharge valve and an injector. A plunger for injecting into the engine, and a high-pressure leak recovery passage and a low-pressure leak recovery passage provided for recovering fuel leaking from the pump chamber through a gap between the cylinder and the plunger with the reciprocating movement of the plunger. A high-pressure pump for alternative fuel, comprising: 2. The high pressure leak recovery passage is provided via a feed circuit communicating with the fuel gallery, and the low pressure leak recovery passage faces a seal chamber provided below the plunger. 2. A high-pressure pump for an alternative fuel according to claim 1. 3. The alternative fuel according to claim 1, wherein the fuel flowing through the low-pressure leak recovery passage is recovered via recovery means along the cylinder. High pressure pump. 4. The apparatus according to claim 3, wherein the collecting means is a leak passage formed in a side wall of the cylinder.
2. A high-pressure pump for an alternative fuel according to claim 1. 5. An opening / closing valve portion is provided at an upper end portion of the cylinder and communicates with the pump chamber, and is provided between the pump chamber and the fuel gallery. A valve body of a control solenoid valve mounted in a liquid-tight manner so as to adjust the amount of fuel discharged from the valve is provided. The control solenoid valve is disposed substantially concentrically with a non-magnetic material interposed therebetween. The high-pressure pump for an alternative fuel according to any one of claims 1 to 4, wherein the plurality of cores are rigidly connected in a liquid-tight manner by welding. 6. The high-pressure pump for an alternative fuel according to claim 1, wherein the discharge valve is set to open at a pressure lower than the feed pressure. 7. The fuel gallery is provided with a pressure regulating valve which is biased in a closing direction by a spring, and opens the pressure regulating valve against the spring to release fuel that overflows. The high-pressure pump for an alternative fuel according to any one of claims 1 to 6, wherein a back pressure due to a steam pressure is applied to the pressure regulating valve in a valve closing direction.