JP2003206825A - High pressure pump for alternate fuel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high pressure pump 1 for alternate fuel for improving an output for a fuel consumption of an internal combustion engine by keeping a suitable force feed amount of DME fuel, by reducing and retrieving the DME fuel leaking from a clearance between a plunger 9 and a cylinder 7. <P>SOLUTION: The DME fuel leaking from a pump chamber 22 between the cylinder 7 and the plunger 9 is decreased in pressure in two high and low stages by a retrieving groove 28 and a seal chamber 32, and is sealed doubly by a high-pressure X-shaped seal 43 and an oil seal 31. Much of the DME fuel passing through the high-pressure X-shaped seal 43 is retrieved from a leak passage to a purge tank in a liquified state. A slight amount of DME fuel leaking from the oil seal 31 to a cam chamber 2a is sealed by a seal 37 for lubricating oil and a seal 38 for fuel, retrieved by the purge tank or the like via a through hole 42 for retrieval, thereby largely reducing external leakage of the DME fuel. <P>COPYRIGHT: (C)2003,JPO

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 in a fuel injection system for an internal combustion engine, which uses a fuel such as dimethyl ether which has a low viscosity and is relatively easily vaporized.

[0002]

2. Description of the Related Art As an alternative fuel for diesel engines, which replaces light oil, etc., physical properties tend to have low viscosity and high vapor pressure in consideration of environmental measures. Dimethyl ether as a representative of this alternative fuel has substantially the same cetane number as light oil, and the concentration of NOx and HC contained in the exhaust gas after combustion is low. Therefore, when dimethyl ether is applied to a diesel engine, it is expected that dimethyl ether will be a clean alternative fuel with less black smoke in the entire output range. High-pressure pumps that use dimethyl ether as the main fuel in diesel engines are described in JP-A-10-281029 and JP-A-10-281030.

In both of Japanese Patent Application Laid-Open No. 10-281029 and Japanese Patent Application Laid-Open No. 10-281030, the gap between the plunger and the plunger barrel (less than 3 μm) is set to be small to reduce fuel leakage, and the fuel leaks from this gap. Fuel is supplied from the leak gas introduction pipe to the intake pipe of the diesel engine for reuse.

[0004]

However, the gap between the plunger and the plunger barrel (cylinder) is 3 μm.
In the vicinity of, it becomes a general value in the known pump,
The design will not be particularly narrow. Further, since the fuel under high pressure is collected by a single path, the fuel is likely to leak from the gap between the plunger and the plunger barrel due to the rapid pressure increase in the plunger chamber, and the leak tends to be large.

Particularly, at high temperature, the viscosity of the fuel decreases and the amount of fuel leakage increases rapidly. Therefore, the total injection amount of the leaked fuel introduced into the intake pipe and the fuel from the injection nozzle exceeds a proper value and becomes excessive, which may make it difficult to appropriately control the diesel engine.

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

[0007]

Fuel is pumped by a feed pump through a fuel gallery into a pump chamber. The cam shaft has a cam portion that is rotationally driven while being lubricated by the lubricating oil of the internal combustion engine. The plunger reciprocates in the cylinder by the cam portion to press the fuel in the pump chamber and inject it into the internal combustion engine via the discharge valve and the injector. As the plunger reciprocates, the high-pressure leak recovery passage recovers fuel that leaks from the pump chamber through the gap between the cylinder and the plunger.
First sealing means and second sealing means are provided for sealing fuel leakage from the high-pressure leak recovery passage.
The low-pressure leak recovery passage collects fuel that has leaked through the first sealing means. The leak fuel recovery passage recovers fuel that has passed through the second sealing means and leaks to the cam chamber. Leak Fuel recovery passage for sealing fuel leakage from fuel recovery passage
And a fourth sealing means.

When the leaked fuel is collected, the leaked fuel recovery passage is divided into two systems, that is, the high pressure and low pressure leak recovery passages. The leaked fuel is not depressurized rapidly, but is depressurized in two steps, high and low. As a result, most of the leaked fuel is recovered in a liquefied state, so that the recovery rate is high and the amount of fuel leakage can be reduced. That is, the fuel leaking from the high-pressure leak recovery passage is sealed by the first sealing means, but the fuel leaking through the first sealing means is still recovered via the low-pressure leak recovery passage. Further, the fuel leaking into the cam chamber after passing through the second sealing means is sealed by the third sealing means in the cam chamber, but the leaking fuel passing through the third sealing means is still leaked into the cam chamber. The external leak is sealed by the sealing means 4 and is collected through the leak fuel collecting passage.

As described above, the fuel leaked into the high pressure leak recovery passageway is subjected to the depressurization while undergoing the first sealing means and the second sealing means.
The sealing means is redundantly sealed, the amount of leakage is reduced, and most of it is recovered in a liquefied state. Further, the fuel leaking into the cam chamber is redundantly sealed by the third sealing means and the fourth sealing means, and is collected while reducing the leakage amount. Therefore, the amount of leaked fuel can be effectively reduced and high-rate recovery can be achieved, and the amount of leaked fuel to the outside can be significantly reduced. As a result, an appropriate amount of fuel to be pumped can be maintained, the high-pressure pump can be made highly efficient, and the output of the internal combustion engine with respect to fuel consumption can be significantly improved. That is, it is possible to correct the change in the physical properties of the fuel that is easily vaporized according to the operating state of the internal combustion engine, and to supply the required amount of fuel having the appropriate physical property value to the internal combustion engine during injection.

(Claim 2) The high-pressure leak recovery passageway is maintained at a high pressure because it passes through the feed circuit communicating with the fuel gallery. Also, the low-pressure leak recovery passage faces the seal chamber provided below the plunger, and thus has a low pressure. For this reason, the leak fuel recovery passage can be divided into two systems, the high-pressure and low-pressure leak recovery passages. As a result, unlike the case where the leaked fuel is collected under a high pressure through a single system passage, most of the leaked fuel can be collected in a liquefied state by the high and low two-step depressurization, and the amount of leaked fuel can be reduced. Further, since the leak fuel recovery passage forms the inside of the seal holder that surrounds the cam shaft, the fuel leaking from the second sealing means to the cam chamber reaches the inside of the seal holder along the cam shaft and leaks the fuel recovery passage. Good recovery via.

(Claim 3) The fuel leaking through the high pressure leak recovery passage, the first sealing means, the low pressure leak recovery passage, the second sealing means and the leak fuel recovery passage is recovered through the recovery means. It For this reason, since the leaked fuel is returned and used again, the leaked fuel does not wastefully disappear as an external leak.

(Claim 4) Fuel is pumped from the feed pump through the fuel gallery into the pump chamber.
The cam shaft has a cam portion that is driven to rotate while being lubricated by the fuel of the internal combustion engine in the fuel gallery. The plunger is provided in the fuel gallery and reciprocates in the cylinder by a cam portion to press the fuel in the pump chamber and inject it into the internal combustion engine via the discharge valve and the injector. As the plunger reciprocates, the leak fuel recovery passage collects fuel that leaks from the fuel chamber along the cam shaft through the gap between the cylinder and the plunger. First sealing means and second sealing means are provided for sealing fuel leakage from the leak fuel recovery passage.

In this case, the cam portion is lubricated by the fuel of the internal combustion engine and is in contact with the fuel in the fuel gallery. Therefore, the fuel leaking from the fuel gallery along the cam shaft is sealed by the first sealing means, but the leaking fuel passing through the first sealing means is still leaked to the outside by the second sealing means. It is recovered in the sealed state through the leak fuel recovery passage. The amount of leaked fuel can be significantly reduced by reducing and collecting the leaked fuel.

(Claim 5) The fuel leaking from the pump chamber to the cam chamber through the gap between the cylinder and the plunger is recovered by the recovery means formed in the seal holder surrounding the cam shaft. For this reason, as in the third aspect, the leaked fuel is returned and used for reuse, so that the leaked fuel does not wastefully disappear as an external leak.

(Claim 6) Fuel is pumped from the feed pump through the fuel gallery into the pump chamber.
The plunger reciprocates in the cylinder by the cam portion provided on the crankshaft of the internal combustion engine in the cam chamber, presses the fuel in the pump chamber and injects it into the internal combustion engine via the discharge valve and the injector. As the plunger reciprocates, the high-pressure leak recovery passage recovers fuel that leaks from the pump chamber through the gap between the cylinder and the plunger. First sealing means and second sealing means are provided to seal fuel leakage from the high pressure leak recovery passage into the cam chamber.
A low-pressure leak recovery passage is provided for recovering fuel that has leaked through the first sealing device while being prevented by the second sealing device.

In this case, since the cam portion is provided on the crankshaft of the internal combustion engine, it is necessary to strictly prevent fuel leakage into the cam chamber. Therefore, the first sealing means and the second sealing means
The sealing means seals fuel leakage from the high pressure leak recovery passage into the cam chamber. As a result, the low-pressure leak recovery passage can recover the fuel leaking through the first sealing device while preventing the fuel leakage to the cam chamber by the second sealing device, so that the amount of leaked fuel can be greatly increased. It can be reduced.

(Claim 7) The high-pressure leak recovery passageway is maintained at a high pressure because the feed circuit communicates with the fuel gallery. Also, the low-pressure leak recovery passage faces the seal chamber provided below the plunger, and thus has a low pressure. For this reason, the leak fuel recovery passage can be divided into two systems, the high-pressure and low-pressure leak recovery passages. As a result, unlike the case where the leaked fuel is collected under a high pressure through a single system passage, most of the leaked fuel can be collected in a liquefied state by the high and low two-step depressurization, and the amount of leaked fuel can be reduced.

(Claims 8 and 10) The fuel leaking from the low-pressure leak recovery passage and the leak fuel recovery passage is introduced into the intake pipe of the internal combustion engine as a premixed fuel and reused, so that it is wasted to the outside. It never disappears.

(Claims 9 and 11) Fuel leaking from the low-pressure leak recovery passage and the leak fuel recovery passage is supplied to a catalyst for purifying exhaust gas provided in an exhaust pipe of an internal combustion engine as a reducing agent or a heating source. To be done. Therefore, it can contribute to the reduction of NOx contained in the exhaust gas from the exhaust pipe.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION 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. 1 to 4 show 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 (not shown) of a diesel engine. This alternative fuel may be pure or various dimethyl ether components adjusted to various purities, may contain other diesel fuels containing dimethyl ether as a main component, and generally has a low viscosity and is relatively easily vaporized. Shall have. Since this alternative fuel has a low viscosity and is relatively easily vaporized, the term "liquid tight" or "oil tight" used in the present invention means "air tight".
The meaning of is included.

The high-pressure pump 1 is driven by a diesel engine and pressure-feeds an alternative fuel (hereinafter referred to as DME fuel) to an injector (neither is shown) through a high-pressure pipe and a common rail as a high-pressure fuel accumulator. At this time, the pressure of the DME fuel is controlled based on the rotation speed and load of the diesel engine, and the temperature and input pressure of the fuel, intake air, cooling water.

As shown in FIGS. 1 and 2, the high-pressure pump 1 includes a cam shaft 3 which is rotatably attached to a lower portion of a housing 2 and is rotationally driven by a diesel engine. This camshaft 3 is a base circle (base circle) 3C.
4 having cam portions 4a and 4b facing each other in the radial direction
have. Only one of the cam portions 4a and 4b may be provided, or a plurality of cam portions such as three and four may be provided at a predetermined angular interval without being limited to two.

The cam portions 4a, 4b contact a roller 6 slidably provided on the tappet 5, and move the tappet 5 in the vertical direction via the roller 6 as the cam shaft 3 rotates. A cylinder 7 is fitted into the upper end opening of the housing 2 while keeping a predetermined stroke interval with the tappet 5, and is liquid-tightly fixed by a screw (not shown). The tappet 5 slides a plunger 9 biased downward by a compression coil spring 8 up and down along an inner wall 7 a of a cylinder 7.

An annular fuel gallery 10 is formed between the housing 2 and the cylinder 7 and filled with DME fuel supplied by a feed pump (not shown) to form a feed circuit. An inlet hollow screw 11 and an outlet hollow screw 12 for introducing DME fuel are liquid-tightly attached to the housing 2.
The hollow inlet screw 11 communicates with the fuel gallery 10 via the fuel passage 13.

The hollow outlet screw 12 is used for the fuel passage 1
A pressure regulating valve 14 that communicates with the fuel gallery 10 via 6 and that regulates the maximum pressure in the fuel gallery 10 and a coil spring 15 that sets the valve opening pressure of the pressure regulating valve 14 are incorporated. The outlet hollow screw 12 is connected by a pipe so as to return the DME fuel released by the pressure regulating action to the fuel tank (not shown) when the valve is opened.

When the pressure regulating valve 14 is opened, the DME fuel is supplied to the fuel tank through the pressure regulating valve 14 so as to overflow from the fuel passage 16. At this time, part of the DME fuel is vaporized due to the temperature rise of the DME fuel. The pressure regulator valve 1 uses the vapor component pressure generated by the vaporization of DME fuel as a load.
4 is added in the direction of closing 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 depending on the vaporization amount of the DME fuel. That is, the valve opening pressure of the pressure regulating valve 14 automatically increases as the temperature of the DME fuel rises, and the internal pressure of the fuel gallery 10 is increased to prevent the DME fuel in the fuel gallery 10 from vaporizing.

The housing 18 of the control solenoid valve 17 is screwed into the upper end opening of the cylinder 7 in a liquid-tight manner by a fastening structure 19 of 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. A space surrounded by the valve body 20 of the control solenoid valve 17, the cylinder 7 and the plunger 9 is a pump chamber 22.

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

Further, the cylinder 7 is attached with a hollow discharge valve holder 24. The discharge valve holder 24 incorporates a discharge valve 25 and a compression coil spring 26 that sets the valve opening pressure of the discharge valve 25 inside. The discharge valve 25 is
It communicates with the pump chamber 22 through the fuel passage 27, and sends high-pressure DME fuel from the pump chamber 22 to the common rail.
As the pressure in the pump chamber 22 decreases, the discharge valve 25 closes its valve opening 25a liquid-tightly (oil-tightly) to maintain the common rail pressure at a predetermined level.

On the inner wall 7a of the cylinder 7 which is the sliding surface of the plunger 9, an annular recovery groove 28 forming a high pressure leak recovery passage is formed in the circumferential direction. The recovery groove 28 communicates with the fuel gallery 10 via a recovery passage 29 formed in the side wall of the cylinder 7, and the high-pressure DME leaking from the pump chamber 22 along the space between the cylinder 7 and the plunger 9.
A high-pressure leak recovery passage that forms fuel at the feed pressure is formed. Further, as shown in FIG. 4, an annular space 7b located below the recovery groove 28 is formed on the inner peripheral surface of the lower end of the cylinder 7. A high-pressure X-shaped seal (first sealing means) 43 having a substantially X-shaped cross section is fitted into the plunger 9 in a liquid-tight manner in the annular space 7b, whereby a cup-shaped oil seal (second sealing means) described later is formed. ) 31 and a double seal structure is realized.

Further, the cylinder 7 is connected to the purging hollow screw 30, and is formed with an elongated leak passage 33 which is a low pressure leak recovery passage in a substantially vertical direction. This purging hollow screw 30 is used for the cylinder 7
Through a leak passage 33 to a seal chamber 32 (low-pressure leak recovery passage) formed by a cup-shaped oil seal 31 that is liquid-tightly fitted to the lower end surface of the.

From the recovery groove 28 to the cylinder 7 and the plunger 9.
The low-pressure DME fuel that leaks through the high-pressure X-shaped seal 43 along the space reaches the seal chamber 32 forming the low-pressure leak recovery passage. The DME fuel in the seal chamber 32 is recovered in a purge tank (not shown) via the leak passage 33 and the guide passage 34 in the hollow hollow screw 30 in order.

The oil seal 31 shown in FIG. 4 has a cylindrical metal portion 31a which is press-fitted into the outer periphery of the lower end of the cylinder 7. 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. At the inner peripheral edge of the insertion hole 31c, an upper lip portion 35 for fuel sealing and a lower lip portion 3 for lubricating oil sealing are provided.
6 and 6 are formed so as to make elastic contact with the outer peripheral surface of the plunger 9, respectively.

The DME fuel and the lubricating oil that adhere to the plunger 9 as the plunger 9 moves up and down are absorbed by the upper lip portion 35.
And the lower lip 36 largely eliminates it. Therefore, the plunger 9 has the upper lip portion 35 and the lower lip portion 36 with a predetermined amount of DME fuel and lubricating oil attached.
Slide back and forth.

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

Lubricating oil and DM leaking along the camshaft 3
E To effectively seal the fuel, the small diameter portion 3a of the camshaft 3
Is a double seal by inserting a lubricating oil seal (third sealing means) 37 and a fuel seal (fourth sealing means) 38 covered with a seal holder 39 as shown in FIGS. The structure is realized. The lubricating oil seal 37 is formed in a substantially U-shaped cross section and is attached to the small diameter portion 3a by a clip 40, prohibits the lubricating oil from passing through the cam chamber 2a, and allows the vaporized DME fuel to pass therethrough. The fuel seal 38 is formed as a high-pressure X-seal with a substantially X-shaped cross section, and its tip end is in close contact with the outer peripheral portion of the small diameter portion 3a and the inner peripheral portion of the seal holder 39 in a close contact state.

Therefore, the DME fuel that has passed through the lubricating oil seal 37 in a vaporized state is sealed by the fuel seal 38 and prevented from leaking to the outside along the small diameter portion 3a of the cam shaft 3. A space 41 formed in the seal holder 39 between the lubricating oil seal 37 and the fuel seal 38 communicates with the purge tank through a recovery through hole (recovery means) 42 formed in the seal holder 39. There is.

With the operation of the diesel engine, the roller 6 driven by the cam 4 of the cam shaft 3 moves the base circle 3C of the cam 4.
When sliding up, the plunger 9 is located at the bottom dead center and the control solenoid valve 17 is in the non-energized state. Therefore, the communication passage 23 of the control solenoid valve 17 communicates the upper fuel gallery 21 and the pump chamber 22 via the communication hole of the stopper plate K shown in FIG.

In this state, the DME fuel pressurized by the feed pump is filled in the fuel gallery 10 through the inlet hollow screw 11 and the fuel passage 13, and the introduction passage 53 formed in the side wall of the cylinder 7 is filled. The upper fuel gallery 21 is filled therewith. The DME fuel in the upper fuel gallery 21 is connected to the communication passage 2 of the control solenoid valve 17.
The pump chamber 22 is filled through the communication holes 3 and the stop plate K in 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 is larger than the total amount of the set load of the compression coil spring 26 of the discharge valve 25 and the common rail pressure. Become. Due to this feed pressure, the compression coil spring 2
6, the discharge valve 25 is opened against the biasing force of the pump chamber 22,
The DME fuel inside is filled into the common rail through the fuel passage 27.

With the rotational drive of the cam shaft 3, the cam portion 4a
Pushes up the tappet 5 with the roller 6, the plunger 9 is displaced upward against the biasing force of the compression coil spring 8 and is driven in a direction to reduce the volume of the pump chamber 22. Therefore, the DME fuel in the pump chamber 22 passes through the communication passage 23 of the control solenoid valve 17 and the upper fuel gallery 2
It is discharged to 1.

When the control solenoid valve 17 is energized according to the number of revolutions of the diesel engine or the feed pump and the accelerator opening in the process of lifting the cam 4, the upper fuel gallery 21 and the pump chamber via the communication passage 23 are connected. The communication with 22 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 due to the rise of the plunger 9. Then, the pressure in the pump chamber 22 rises based on the reduced volume of the pump chamber 22 and the bulk elastic coefficient of the DME fuel. In this process, the pump chamber 22
The internal pressure is common rail pressure and compression coil spring 2
When it becomes larger than the total amount of the urging force of 6 and the set valve opening pressure, the discharge valve 25 opens against the urging force of the compression coil spring 26 and pumps the DME fuel to the common rail. The energization of the control solenoid valve 17 stops when the fuel pressure in the pump chamber 22 rises, but when the fuel pressure in the pump chamber 22 is high, the control solenoid valve 17 maintains the closed state.

When the cam portion 4a reaches the top dead center, the pressurization of the plunger 9 to the pump chamber 22 is stopped and the fuel pressure starts to decrease. When the cam portion 4a reduces the lift amount and starts descending, 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, and the common rail is maintained at a predetermined pressure.

The pump chamber 2 is moved along with the downward movement of the cam portion 4a.
The pressure of 2 continues to drop, the control solenoid valve 17 opens, and the DME fuel is refilled into the pump chamber 22 from the upper fuel gallery 21. When the cam portion 4a descends to reach the bottom dead center with the rotation of the cam shaft 3, the vertical reciprocating movement of the plunger 9 is completed, and one cycle is completed.

During operation of the high-pressure pump 1, the DME leaks through the gap between the plunger 9 and the inner wall 7a of the cylinder 7.
The fuel reaches the recovery groove 28 together with the high pressure DME fuel from the pump chamber 22. In the recovery groove 28, the fuel gallery 10
Since the feed pressure is applied to the fuel, it easily reaches a few MPa in the case of a fuel that is easily vaporized such as DME fuel. Therefore, the relatively high pressure DME fuel leaks from the recovery groove 28 along the gap between the plunger 9 and the inner wall 7 a of the cylinder 7. The leakage of the DME fuel cannot withstand a high feed pressure with a normal oil seal structure having a pressure resistance of several atmospheres, and almost all of the leaked fuel passes through.

On the other hand, the high-pressure X-shaped seal 43 shown in FIG. 4 has a special shape having a substantially X-shaped cross section, and therefore the tip end portion thereof is in close contact with the plunger 9 and the inner wall 7a of the cylinder 7. Realizes a high withstand voltage structure that makes a strong elastic contact with the state. Therefore, the high-pressure X-shaped seal 43 leaks through the gap between the plunger 9 and the inner wall 7a of the cylinder 7 into the DME.
The passage of fuel can be sealed almost completely. Even if the DME fuel slightly leaks from the high pressure X-shaped seal 43, the leaked DME fuel can be dealt with by the low pressure oil seal 31.

That is, as the plunger 9 is driven in the vertical direction by the cam 4, the oil seal 31 prevents the DME fuel and the lubricating oil attached to the outer surface of the plunger 9 from passing downward by a predetermined amount or more. Function. The plunger 9 rises and the insertion hole 31c of the oil seal 31
4 passes, the lower lip portion 36 shown in FIG. 4 leaves a predetermined thickness of lubricating oil on the outer surface of the plunger 9. Therefore, 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 descends to move into the insertion hole 3c.
When passing through, the upper lip portion 35 leaves the DME fuel having a predetermined thickness on the outer surface of the plunger 9. Therefore, the DME fuel having a predetermined thickness or more attached to the plunger 9 is scooped by the upper lip portion 35 and is housed 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 the amount necessary for lubricating 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 with a predetermined pressure so that most of the lubricating oil and DME fuel do not pass through the upper and lower lip portions 35 and 36. The DME fuel that has passed through the high-pressure X-shaped seal 43 is the upper lip portion 3 of the oil seal 31.
Most are recovered by 5. If the DME fuel slightly passes from the upper lip portion 35, the passed DME fuel leaks to the cam chamber 2a and is processed as described later. The lubricating oil that has passed through the lower lip portion 36 of the oil seal 31 is
The high pressure X-shaped seal 43 is reached, and a part thereof passes through the high pressure X-shaped seal 43 and is used for lubricating the plunger 9.

The DME fuel accumulated in the seal chamber 32 is
It is collected in the purge tank via the leak passage 33 and the guide passage 34 of the hollow hollow screw 30 for purging. In this case, the high-pressure DME fuel in the pump chamber 22 is not leaked directly to the seal chamber 32, but is collected in the collection groove 28 and becomes feed pressure by the collection passage 29 communicating with the fuel gallery 10. Further, the plunger 9 and the inner wall 7 of the cylinder 7
DME fuel leaking along with a
3, but the DME fuel that still slightly passes through the high pressure X-shaped seal 43 is sealed by the oil seal 31.

When the DME fuel slightly passes through the oil seal 31 and leaks to the cam chamber 2a, the leaked DME fuel passes through the lubricating oil seal 37 along the cam shaft 3 in a vaporized state. It is sealed by the fuel seal 38. As a result, the DME fuel leaking into the cam chamber 2a is prevented from leaking to the small diameter portion 3a.
To prevent leakage along the outside. The DME fuel that has passed through the lubricating oil seal 37 is collected in the purge tank from the space 41 through the collecting through hole 42 of the seal holder 39.

Thus, the high pressure DM in the pump chamber 22
The E fuel is not directly leaked into the seal chamber 32, but is temporarily collected in the collection groove 28, and becomes the feed pressure of the high pressure leak collection passage by the collection passage 29 communicating with the fuel gallery 10. Then, the DME fuel in the recovery groove 28 is depressurized in two steps from high pressure to low pressure, for example, leaking from the gap between the plunger 9 and the cylinder 7 to the seal chamber 32 of the low pressure leak recovery passage. Are recovered in a liquefied state.

Moreover, the DM leaks when the feed pressure drops.
The E fuel is sealed by the high pressure X-shaped seal 43,
The DME fuel slightly passing through the shape seal 43 is sealed by the oil seal 31 and is collected in the purge tank via the leak passage 33. In addition, the DME fuel that has passed through the oil seal 31 and leaked to the cam chamber 2a is protected by the lubrication seal 3
7 and the fuel seal 38, and is collected in the purge tank through the collecting through hole 42. This allows
It is possible to effectively reduce the leakage amount of DME fuel and to recover it at a high rate.
It is possible to maintain an appropriate amount of E fuel pumped, to make the high-pressure pump highly efficient, and to significantly improve the output of the internal combustion engine with respect to fuel consumption.

It should be noted that, with the amount of DME fuel leakage reduced to a value equal to or less than the idle required injection amount, the DME fuel leaking through the leak passage 33 and the recovery through hole 42 is used as the intake pipe of the diesel engine instead of the purge tank. It may be supplied as premixed intake air. Further, the leaked DME fuel may be supplied to the exhaust pipe of the diesel engine or the catalyst for exhaust gas treatment and used as a reducing agent or catalyst heating fuel to reduce the NOx emission amount from the diesel engine.

Further, in the first embodiment, the high pressure X-shaped seal 4
Although 3 and the oil seal 31 are doubly provided as the first sealing means and the second sealing means, another sealing means may be added to form a double or triple sealing structure. Similarly, the lubricating oil seal 37 and the fuel seal 38 can have overlapping seal structures.

5 and 6 show a second embodiment of the present invention. In the second embodiment, a composite seal structure (first sealing means) 4 is used instead of the high pressure X-shaped seal 43 of the first embodiment.
5A is provided. This composite seal structure 45A includes a seal ring 44 made of Teflon (registered trademark) and an O installed on a support ring 46 penetrating the plunger 9 in the seal chamber 32.
Consisting of a ring 45

The seal ring 44 is slidably fitted in the plunger 9 in a close contact state, and the O-ring 45 is fitted in the outer peripheral portion of the seal ring 44 in an elastic contact state. Composite seal structure 45 consisting of seal ring 44 and O-ring 45
By A, it is possible to effectively seal the DME fuel leaking from the gap between the plunger 9 and the cylinder 7 as in the case of the high pressure X-shaped seal 43. In this case, the seal ring 44 is excellent in sliding on the plunger 9, and O-
Since the ring 45 is excellent in sealing between the seal ring 44 and the inner wall of the annular space 7b, a good sealing effect can be obtained by combining the two.

7 and 8 show a third embodiment of the present invention. In the third embodiment, instead of the composite seal structure 45A and the support ring 46 of the second embodiment, a U-shaped seal (first
Sealing means) 47 is provided. The U-shaped seal 47 having a substantially U-shaped cross section is fitted in the annular groove 9 a formed in the outer surface portion of the plunger 9. In the U-shaped seal 47, when the DME fuel pressure is applied to the upper surface depression 47a, the tip portions 47b and 47c are moved to the inner wall 7a of the cylinder 7.
And the inner wall of the annular groove 9a are elastically brought into close contact with each other to firmly seal between the cylinder 7 and the plunger 9. Nevertheless, when the DME fuel slightly leaks from between the cylinder 7 and the U-shaped seal 47, the leaked DME fuel is received in the seal chamber 32 and is recovered from the leak passage 33 to the purge tank as in the first embodiment. It

FIG. 9 shows a fourth embodiment of the present invention. In this embodiment, the same members as those in the first embodiment are designated by the same reference numerals and only different parts will be described. In the fourth embodiment, the cam 4 and the tappet 5 are applied to the fuel lubrication pump 1A in which the DME fuel is lubricated. In this case, Fuel Gallery 10
Includes the cam 4, the tappet 5, the cylinder 7 and the plunger 9, and introduces the DME fuel leaking from the gap between the cylinder 7 and the plunger 9 into the fuel gallery 10, so that the high pressure X-shape of the first embodiment is used. The members corresponding to the seal 43 and the oil seal 31 are unnecessary and are not provided.

The camshaft 3 is attached to the small diameter portion 2A of the housing 2.
A seal holder 48 through which the input side of is inserted is connected. In order to seal between the small diameter portion 2A and the cam shaft 3,
A plate washer 50 and a first high-pressure X-shaped seal (first sealing means) 49 are fitted on the camshaft 3. In order to seal between the seal holder 48 and the cam shaft 3, a second high-pressure X-shaped seal (second sealing means) 51 is fitted on the cam shaft 3. The plate washer 50 has a first high pressure X
It functions as a presser for elastically contacting the shaped seal 49, and an oil-tight state is maintained between the small diameter portion 2A of the housing 2 and the seal holder 48.

In the fourth embodiment, the fuel gallery 10
The leakage of the relatively high pressure DME fuel inside along the camshaft 3 is sealed by the first high pressure X-shaped seal 49. First
When a small amount of low-pressure DME fuel leaks from the high-pressure X-shaped seal 49 of No. 2, the leak is sealed by the second high-pressure X-shaped seal 51. The low pressure DME fuel leaking from the first high pressure X-shaped seal 49 is recovered from the space 41 through the recovery through hole 42 into the purge tank.

10 to 12 show a fifth embodiment of the present invention. In this embodiment, the same members as those in the first embodiment are designated by the same reference numerals and only different parts will be described. The fifth embodiment is different from the first embodiment in that it is applied to a crank-coupled high-pressure pump 1B including a cam portion 4a provided on a crankshaft H of a diesel engine.

In this crank-coupled high-pressure pump 1B,
Since it is necessary to strictly prevent the DME fuel from leaking to the cam chamber 2a, the entire amount of the DME fuel leaking from the gap between the cylinder 7 and the plunger 9 is collected.
Therefore, two high pressure X-shaped seals (first sealing means) 52 are used instead of the single high pressure X-shaped seal 43 of the first embodiment.
a and 52b are provided.

These high pressure X-shaped seals 52a and 52b are
As shown in FIGS. 10 and 11, in the annular space 7b of the cylinder 7 and in the seal chamber 32, the plunger 9 is fitted in two steps, that is, between the plunger 9 and the inner wall of the annular space 7b. 32 is kept airtight. A plate washer 54 fitted into the plunger 9 through a fitting hole 54a is arranged between the high-pressure X-shaped seals 52a and 52b to hold the high-pressure X-shaped seal 52a. As shown in FIG. 12, the plate washer 54 is formed so as to make a plurality of (for example, four) radial feed grooves 54b from the fitting hole 54a in the front-back direction.

The high-pressure DME fuel leaking from the gap between the cylinder 7 and the plunger 9 is sealed by the high-pressure X-type seal 52a, but the DME fuel is still high-pressure X-type seal 5.
When passing slightly through 2a, the passing slight amount of DME fuel is completely sealed by the high pressure X-shaped seal 52b and the oil seal 31. The DME fuel sealed by the high pressure X-shaped seal 52b and the oil seal 31 is guided to the feed groove 54b of the plate washer 54, and the feed groove 54b.
Is collected in the purge tank through the leak passage 33 as in the first embodiment.

In the fifth embodiment, the oil seal 31
The upper lip portion 35 is omitted and only the lower lip portion 36 is provided. By omitting the upper lip portion 35, only the lower lip portion 36 slides on the plunger 9, and the sliding length on the plunger 9 can be shortened. In the present invention, the terms such as “leak”, “pass”, “leak”, or “pass and leak” are used for the DME fuel, but these terms have the same meaning as “fuel leak”. There is. Further, the "leakage fuel amount" and the "fuel leakage amount" have the same meaning.

In the above embodiment, the recovery groove 28 is formed in an annular shape, but it may be formed in several spiral shapes. Further, the lower end of the leak passage 33 may be bifurcated to face the seal chamber 32. In addition, various modifications can be made without departing from the gist of the invention in implementing the invention.

[Brief description of drawings]

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

FIG. 2 is a vertical sectional view taken along the line AA of FIG.

FIG. 3 is an enlarged vertical sectional view showing a seal for lubricating oil and a seal for fuel.

FIG. 4 is an enlarged vertical sectional view showing a seal structure.

FIG. 5 is an enlarged vertical sectional view showing a seal structure (second embodiment).

FIG. 6 is an enlarged exploded perspective view showing a seal structure.

FIG. 7 is an enlarged vertical sectional view showing a seal structure (third embodiment).

FIG. 8 is an enlarged perspective view of a U-shaped seal.

FIG. 9 is a vertical cross-sectional view showing a fuel lubrication high-pressure pump (fourth embodiment).

FIG. 10 is a vertical sectional view showing a crank-coupled high-pressure pump (fifth embodiment).

FIG. 11 is an enlarged vertical sectional view showing a seal structure.

FIG. 12 is an enlarged perspective view showing a plate washer.

[Explanation of symbols]

1 high pressure pump 3 cam shaft 4 cams 7 cylinders 9 Plunger 10 Fuel gallery (feed circuit) 11 Hollow screw for inlet 12 Hollow screw for outlet 13, 16 Fuel passage 14 Regulator 17 Control solenoid valve 18 housing 21 Upper Fuel Gallery 22 Pump room 25 discharge valve 28 Recovery groove (high pressure leak recovery passage) 29 Recovery route 31 Oil seal (second sealing means) 32 Seal chamber (low pressure leak recovery passage) 33 Leak passage (low-pressure leak recovery passage) 35 Upper lip 36 Lower lip 37 Lubricating oil seal (third sealing means) 38 Fuel seal (fourth sealing means) 39, 48 Seal holder 41 space (leak fuel recovery passage) 42 Collection through hole (collection means) 43 High-pressure X-shaped seal (first sealing means) 47 U-shaped seal (first sealing means) 49 First high-pressure X-shaped seal (first sealing means) 51 Second high-pressure X-shaped seal (second sealing means) 52a, 52b High-pressure X-shaped seal (first sealing means) 1A fuel lubrication high pressure pump 1B crank linked high pressure pump 2a Cam room 4a, 4b cam part 7a inner wall 45A composite seal structure (first sealing means) H crank shaft

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hisaharu Takeuchi             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Shigeki Enomoto             14 Iwatani Shimohakaku-cho, Nishio-shi, Aichi Stock Association             Company Japan Auto Parts Research Institute (72) Inventor Moriyasu Goto             14 Iwatani Shimohakaku-cho, Nishio-shi, Aichi Stock Association             Company Japan Auto Parts Research Institute F term (reference) 3G066 AA07 AB04 AC01 AD02 BA36                       CD10 CD17 CE02

Claims (11)

[Claims] 1. A pump chamber that receives fuel from a feed pump through a fuel gallery, a cam shaft that has a cam portion that is driven to rotate while being lubricated by lubricating oil of an internal combustion engine in the cam chamber, and a cylinder that includes the cam portion. A plunger that reciprocates inside to press the fuel in the pump chamber and inject it into the internal combustion engine via a discharge valve and an injector; and as the plunger reciprocates, the plunger and the cylinder from the pump chamber A high-pressure leak recovery passage provided to recover fuel leaking through a gap between the high-pressure leak recovery passage and a first sealing means and a second sealing means provided to seal fuel leakage from the high-pressure leak recovery passage. , A low-pressure leak recovery passage provided to recover fuel leaking through the first sealing means, and a second low-pressure leak passage A leak fuel recovery passage provided to recover fuel leaking to the cam chamber, and third sealing means and fourth seal provided to seal fuel leakage from the leak fuel recovery passage to the outside. A high-pressure pump for an alternative fuel, characterized by comprising: 2. The high-pressure leak recovery passage communicates with the fuel gallery via a feed circuit, and the low-pressure leak recovery passage has a seal chamber provided on a side of the cylinder opposite to the pump chamber. The high-pressure pump for alternative fuel according to claim 1, characterized in that the leak fuel recovery passage, which is exposed through a means, forms the inside of a seal holder surrounding the cam shaft. 3. The fuel leaking through the high pressure leak recovery passageway, the first sealing means, the low pressure leak recovery passageway, the second sealing means and the leak fuel recovery passageway is recovered by the recovery means. The high-pressure pump for alternative fuel according to claim 1 or 2, characterized in that. 4. A pump chamber that receives fuel from a feed pump through a fuel gallery, a cam shaft having a cam portion that is driven to rotate while being lubricated by the fuel of the internal combustion engine in the fuel gallery, and in the fuel gallery. A plunger that is reciprocally moved in the cylinder by the cam portion, presses the fuel in the pump chamber and injects the fuel into the internal combustion engine through a discharge valve and an injector, and as the plunger reciprocates, A leak fuel recovery passage for recovering fuel leaking from the fuel gallery along the cam shaft through a gap between the pump chamber and the cylinder and the plunger, and for sealing fuel leakage from the leak fuel recovery passage. A high-pressure pump for alternative fuel, characterized in that it comprises a first sealing means and a second sealing means provided. . 5. The fuel leaking through the first seal means of the leak fuel recovery passage is recovered via a recovery means formed in a seal holder surrounding the cam shaft. Item 5. A high-pressure pump for an alternative fuel according to Item 4. 6. A pump chamber for receiving fuel from a feed pump through a fuel gallery, and a cam portion provided on a crankshaft of an internal combustion engine in the cam chamber to reciprocate in the cylinder to press the fuel in the pump chamber. A plunger for injecting into the internal combustion engine via a discharge valve and an injector, and provided for collecting fuel leaking from the pump chamber through a gap between the cylinder and the plunger as the plunger reciprocates. A high-pressure leak recovery passage, first sealing means and second sealing means provided to seal fuel leakage from the high-pressure leak recovery passage into the cam chamber, and a passage through the first sealing means. The leaking fuel is the second
And a low-pressure leak recovery passage provided for recovering in a state of being prevented by the sealing means of 1. 7. The high-pressure leak recovery passage communicates with the fuel gallery via a feed circuit, and the low-pressure leak recovery passage has a seal chamber provided on a side of the cylinder opposite to the pump chamber. A high-pressure pump for alternative fuel according to claim 6, characterized in that it is exposed via means. 8. The fuel leaking through the sealing of the leaked fuel recovery passage is introduced as a premixed fuel into an intake pipe of an internal combustion engine, according to any one of claims 1 to 5. High-pressure pump for the alternative fuel described. 9. The fuel leaking through the sealing of the leaked fuel recovery passage is supplied to a catalyst for purifying exhaust gas provided in an exhaust pipe of an internal combustion engine as a reducing agent or a heating source. The high pressure pump for the alternative fuel according to any one of claims 1 to 5. 10. The fuel leaking into the low-pressure leak recovery passage after passing through the first sealing means is introduced into an intake pipe of an internal combustion engine as a premixed fuel. A high-pressure pump for an alternative fuel according to claim 3, claim 6, or claim 7. 11. The fuel that passes through the first sealing means and leaks into the low-pressure leak recovery passage is supplied as a reducing agent or a heating source to an exhaust gas purifying catalyst provided in an exhaust pipe of an internal combustion engine. The high pressure pump for the alternative fuel according to any one of claims 1, 2, 3, 6 and 7.