JP2003184704A - Fuel injection pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable fuel injection pump which prevents an oil seal from being damaged. <P>SOLUTION: Fuel for lubricating sliding parts is supplied from a feed pump 60 to a storage chamber 40 inside a housing 10 which houses a driving shaft 15, a cam 22, and a plunger 20. Excess fuel in the chamber 40 is recirculated to a fuel tank 6 through a fuel delivery passage 57 and a recirculation passage 58. If the fuel delivery passage 57 or the recirculation passage 58 is clogged for some reason and the pressure of fuel inside the chamber 40 rises, a check valve 82 opens, and the fuel in the chamber 40 recirculates through a communication passage 81 to the inlet side of the feed pump 60. Thereby, a pressure rise in the chamber 40 is avoided, preventing any damages to the oil seal 17, to which the fuel from the chamber 40 is supplied. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an internal combustion engine (hereinafter,
An internal combustion engine is called an "engine." ) Fuel injection pump.

[0002]

2. Description of the Related Art Conventionally, a common rail type fuel injection system applied to, for example, a diesel engine includes a fuel injection pump that pressurizes fuel and supplies it to the common rail. The fuel injection pump is driven by a drive shaft connected to the crankshaft of the engine. The plunger as a movable member is reciprocally driven inside the cylinder as the drive shaft rotates. When the plunger is reciprocally driven, fuel is sucked into the pressurizing chamber and pressurized. A feed pump that supplies fuel to the pressurizing chamber is integrally formed with the fuel injection pump. Like the plunger, this feed pump is also driven by the rotation of the drive shaft, sucks fuel from the fuel tank and supplies it to the pressurizing chamber.

In the above fuel injection pump, a plurality of sliding portions are formed inside the housing, such as between the cam and the plunger for transmitting the driving force from the drive shaft to the plunger, or between the plunger and the housing. ing. Therefore, the fuel discharged from the feed pump is not only supplied to the pressurizing chamber but also to the accommodating chamber inside the housing in which the drive means is accommodated. The sliding portion is lubricated by the fuel supplied to the storage chamber.

The temperature of the fuel supplied to the inside of the storage chamber rises due to the heat generated inside the housing including the sliding portion. Therefore, the fuel injection pump is provided with a return passage that communicates between the accommodation chamber and the inlet side of the feed pump, and the fuel discharged from the feed pump is recirculated to the inlet side of the feed pump through the accommodation chamber and the return passage. ing. As a result, the sliding portion formed in each portion inside the housing is lubricated, and at the same time, the inside of the housing is cooled.

[0005]

The drive shaft for driving the fuel injection pump is rotatably supported by the housing. A part of the fuel pressurized by the feed pump as described above is supplied to the accommodation chamber inside the housing. Therefore, the fuel in the pressurized storage chamber may leak to the outside of the fuel injection pump from the boundary between the housing and the drive shaft along the outer wall of the drive shaft. Therefore, an oil seal is installed between the housing and the drive shaft, and the oil seal prevents the fuel from leaking out. The oil seal communicates with the accommodation chamber, and uses the pressure of the fuel supplied from the accommodation chamber to seal between the drive shaft and the housing.

However, if the return passage communicating between the storage chamber and the inlet side of the feed pump is blocked for some reason, the fuel is not discharged from the storage chamber and the pressure of the fuel rises inside the storage chamber. As a result, the pressure of the fuel rises even in the oil seal that communicates with the storage chamber, and the oil seal may be damaged.

Therefore, an object of the present invention is to provide a highly reliable fuel injection pump which prevents breakage of the oil seal.

[0008]

According to the fuel injection pump of the first aspect of the present invention, the recirculation means has a check valve in the communication passage that connects the accommodation chamber and the inlet side of the feed pump. The check valve opens when the fuel pressure in the storage chamber becomes higher than a predetermined pressure, and allows the fuel to flow from the storage chamber to the inlet side of the feed pump. Therefore, for example, when the return path for discharging the fuel in the storage chamber is blocked due to clogging, etc., and the pressure of the fuel in the storage chamber rises, the check valve opens, and the fuel in the storage chamber opens at the inlet side of the feed pump. Is returned to. Therefore, the rise of the fuel pressure in the storage chamber is suppressed, and the oil seal is prevented from being damaged,
The reliability can be increased. According to the fuel injection pump of the second aspect of the present invention, the temperature sensor for detecting the temperature of the fuel in the storage chamber is installed in the storage chamber. Therefore, when the temperature of the fuel in the storage chamber rises, for example, the operation of the fuel injection pump can be stopped.

According to the fuel injection pump of the third aspect of the present invention, the operation is stopped when the temperature of the fuel in the accommodation chamber detected by the temperature sensor becomes higher than a predetermined value. For example, when the return passage for discharging the fuel in the storage chamber is closed, the fuel in the storage chamber is recirculated to the inlet side of the feed pump via the recirculation means. As a result, the fuel circulates through the feed pump, the accommodating chamber, and the recirculation means, and the temperature of the fuel rises due to the heat generation of the driving part. That is, when the temperature of the fuel in the storage chamber becomes higher than the predetermined value, the fuel supply by the fuel injection pump is stopped and the operation of the engine is stopped. According to the fuel injection pump of the fourth aspect of the present invention, the recirculation means is provided in the housing. Therefore, the flow path through which the fuel flows is not exposed outside the housing. Therefore, breakage or blockage of the flow path can be prevented.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment showing an embodiment of the present invention will be described below with reference to the drawings. A fuel injection pump according to an embodiment of the present invention is shown in FIGS. The fuel injection pump is applied to the common rail fuel injection system 1 shown in FIG. As shown in FIG. 2, the housing 10 of the fuel injection pump 2 has a housing body 11 and a cylinder head 12. In the case shown in FIG. 1, the portion surrounded by the two-dot chain line corresponds to the fuel injection pump 2, and the portion surrounded by the broken line corresponds to the housing 10.

The housing body 11 is made of aluminum. The cylinder heads 12 and 13 are made of iron, and the plungers 20 as movable members are reciprocally supported by the cylinders 12a and 13a formed inside. A pressurizing chamber 30 is formed by the inner peripheral surfaces of the cylinder heads 12 and 13, the end surface of the check valve 14, and the end surface of the plunger 20. In this embodiment, the cylinder head 12 and the cylinder head 13 are formed in substantially the same shape, but the forming positions of screw holes, fuel passages, etc. are different. On the other hand, it is also possible to form the screw holes and the fuel passages at the same position and to make the cylinder head 12 and the cylinder head 13 have the same shape.

The drive shaft 15 is rotatably supported by the housing 10 via a journal 16. Housing 1
An oil seal 17 seals between 0 and the drive shaft 15. As shown in FIG. 3, the cam 2 has a circular cross section.
Reference numeral 1 is eccentric to the drive shaft 15 and is integrally formed. As shown in FIG. 2, a plunger 20 is arranged on the opposite side of 180 ° across the drive shaft 15. As shown in FIG. 3, the cam ring 22 has a rectangular outer shape, and the cam ring 22 is provided between the cam ring 22 and the cam 21.
A slidable bush 23 is interposed between the cam 21 and the cam 21. The outer peripheral surface of the cam ring 22 facing the plunger 20 and the end surface of the plunger 20 are formed in a flat shape and are in contact with each other.

The spring 24 urges the plunger 20 toward the cam ring 22. As the cam 21 rotates, the cam ring 22 slides on the cam 21 and revolves without rotating. As a result, the cam ring 22 and the plunger 20 that form the sliding portion slide while reciprocating in the left-right direction in FIG. The plunger 20 is driven by the drive shaft 15, the cam 21, the cam ring 22, and the spring 24.
Drive means for driving the. Plunger 20
Is reciprocally driven by the cam 21 via the cam ring 22 as the drive shaft 15 rotates, and pressurizes the fuel sucked into the pressurizing chamber 30 from the fuel inflow passage 31 through the check valve 14. The check valve 14 prevents the fuel from flowing backward from the pressurizing chamber 30 to the fuel inflow passage 31.

The plunger 20, the drive shaft 15, the cam 21 and the cam ring 22 which constitute the drive means are housed in a housing chamber 40 formed by the housing body 11, the cylinder head 12 and the cylinder head 13. The storage chamber 40 is filled with light oil which is a fuel. As shown in FIG. 1, a temperature sensor 41 that detects the temperature of the fuel in the storage chamber 40 is installed in the storage chamber 40. The temperature sensor 41 is connected to the ECU 3, and the temperature sensor 41 uses the detected temperature as an electric signal corresponding to E.
Output to CU3. Not only the temperature sensor 41 but also various information such as engine speed, accelerator opening, and cooling water temperature are input to the ECU 3 from various parts of the engine. E
The CU 3 determines the operating state of the engine from various input information. Then, based on the determined operating state of the engine, the ECU 3 controls the fuel injection pump 2 and the entire fuel injection system.

The fuel discharge passage 32 is provided in the cylinder head 12
The cylinder head 13 and the cylinder head 13 are linearly formed and communicate with the pressurizing chamber 30. Cylinder head 1
On the downstream side of the fuel discharge passage 32 formed in No. 2, an elongated hole-shaped fuel chamber 33 having a passage area larger than that of the fuel discharge passage 32 is formed, and a check valve 34 is accommodated in the fuel chamber 33. An accommodation hole 35 having a larger passage area than the fuel chamber 33 is formed on the fuel downstream side of the fuel chamber 33. The accommodation hole 35 is opened in the outer peripheral wall of the cylinder head 12 and forms a fuel outlet. The connecting member 36 for connecting the fuel pipe 51 shown in FIG. 1 is housed in the housing hole 35 by screwing or the like. A fuel passage 37 is formed inside the connection member 36, and the fuel passage 37 communicates with the fuel discharge passage 32 via the fuel chamber 33.

The check valve 34 disposed on the fuel downstream side of the fuel discharge passage 32 of the cylinder head 12 is a check valve 34.
The fuel is prevented from flowing backward from the fuel chamber 33 and the fuel passage 37, which are on the downstream side of the fuel, to the pressurizing chamber 30 via the fuel discharge passage 32. The connecting member 36 is connected to the common rail 4 by the fuel pipe 51 shown in FIG. 1, and the fuel pressurized by the fuel injection pump 2 passes through the fuel passage 37 and the fuel pipe 51 formed in the connecting member 36. Is supplied to the common rail 4. In the common rail 4, the fuel discharged from the fuel injection pump 2 is stored in a pressure-accumulated state. An injector 5 installed in each cylinder of an engine (not shown) is connected to the common rail 4, and high-pressure fuel stored in the common rail 4 is supplied to the injector 5. The injector 5 injects the fuel supplied from the common rail 4 into each cylinder of the engine at a predetermined time and for a predetermined period according to a command from the ECU 3.
The cylinder head 13 is disposed below the housing body 11 in FIG. Similar to the cylinder head 12, the cylinder head 13 is also formed with a fuel discharge passage 32, a housing hole 35, and the like, and houses a check valve 34, a connecting member 36, and the like.

The fuel injection pump 2 has a feed pump 60 at the end of the drive shaft 15 as shown in FIG. The feed pump 60 is a trochoid pump driven by the drive shaft 15. The feed pump 60 is integrally installed in the housing 10 of the fuel injection pump 2. The feed pump 60 has an inner rotor 61 and an outer rotor 62, and the inner rotor 61 is attached to the drive shaft 15. With the rotation of the drive shaft 15,
As the inner rotor 61 and the outer rotor 62 rotate relative to each other, the feed pump 60 pressurizes the normal-pressure fuel stored in the fuel tank 6 and supplies it to the pressurizing chamber 30.

As shown in FIG. 1, the fuel discharged from the feed pump 60 passes through the fuel supply passage 52 and the metering valve 7
Supplied to zero. The metering valve 70 has, for example, a spool valve in which the opening area of the fuel passage is changed by the electric power supplied from the ECU 3.
Adjust the flow rate of fuel delivered to zero. By adjusting the flow rate of the fuel supplied to the pressurizing chamber 30 by the metering valve 70, the flow rate of the fuel discharged from the fuel injection pump 2 to the common rail 4 is adjusted, and the pressure of the fuel in the common rail 4 becomes constant. Retained.

The fuel outlet side of the feed pump 60 is branched into two parts, one communicating with the fuel supply passage 52 and the other communicating with the fuel passage 53. A return passage 54 is further branched from the fuel passage 53. Return channel 5
4 is provided with a check valve 55, and when the pressure of the fuel in the fuel supply passage 52 becomes higher than a predetermined pressure, the check valve 5
5 opens, and excess fuel is returned to the inlet side of the feed pump 60.

The fuel passage 53 connects the fuel outlet side of the feed pump 60 and the storage chamber 40. As a result, the fuel discharged from the feed pump 60 is supplied not only to the pressurizing chamber 30 but also to the accommodation chamber 40 via the fuel passage 53. An orifice 56 is installed in the middle of the fuel passage 54, and the orifice 56 limits the flow rate of the fuel flowing from the feed pump 60 to the storage chamber 40. The fuel supply passage 52, the fuel passage 53, and the return passage 54 are formed so as to penetrate the inside of the housing 10.

As shown in FIG. 2, a fuel passage 18 is formed in the housing 10. The fuel passage 18 is the accommodation chamber 4
0 and the oil seal 17 communicate with each other. Fuel passage 18
Is formed so as to penetrate through the inside of the housing 10, and the housing chamber 40
A part of the fuel stored in is supplied to the oil seal 17. The oil seal 17 is in contact with the drive shaft 15 due to the pressure of the fuel supplied from the storage chamber 40, and seals the fuel flowing along the outer wall of the drive shaft 15 to the outside of the fuel injection pump 2.

As shown in FIG. 1, a fuel discharge passage 57 communicates with the storage chamber 40. The fuel discharge path 57 is provided in the storage chamber
The surplus fuel is discharged at 0. An end portion of the fuel discharge passage 57 on the side opposite to the storage chamber communicates with the return passage 58. Not only the fuel discharge passage 57 but also the common rail 4 and the injector 5 communicate with the return passage 58, and excess fuel in each portion of the fuel injection system 1 is discharged to the return passage 58. The return path 58 communicates with the fuel tank 6 via the outside of the housing 10, and excess fuel in each part of the fuel injection system 1 is returned to the fuel tank 6. Therefore, the surplus fuel of the fuel pressurized in the feed pump 60 of the fuel injection pump 2 and the pressurizing chamber 30 is
The fuel is discharged from the return path 58 to the fuel tank 6 and is opened to the atmospheric pressure.

Next, the reflux means will be described. As shown in FIG. 1, the return means is provided in the housing 10. The recirculation means has a communication passage 81 that communicates the storage chamber 40 with the inlet side of the feed pump 60, and a check valve 82 installed in the middle of the communication passage 81. The communication passage 81 is
It is formed so as to penetrate the housing 10.

The check valve 82 allows only the flow of fuel from the accommodation chamber 40 to the inlet side of the feed pump 60. The check valve 82 is normally closed, and opens when the pressure inside the storage chamber 40 exceeds a predetermined pressure. By opening the check valve 82, the fuel in the storage chamber 40 is returned to the inlet side of the feed pump 60.

For example, the fuel discharge path 57 or the return path 5
8 bends, fuel discharge path 57 or return path 58
When foreign matter stays in the fuel, the fuel discharge passage 57 or the return passage 58 may be clogged and blocked. When the fuel discharge passage 57 or the return passage 58 is closed, the fuel supplied from the feed pump 60 to the storage chamber 40 is not discharged from the storage chamber 40. On the other hand, since the feed pump 60 supplies the pressurized fuel to the accommodation chamber 40,
The pressure of the fuel inside rises. Therefore, the fuel in the storage chamber 40 whose pressure has risen is supplied to the oil seal 17 communicating with the storage chamber 40 via the fuel passage 18, and the pressure of the fuel in the oil seal 17 rises. As a result, when the fuel pressure exceeds the pressure resistance of the oil seal 17, the oil seal 17 may be damaged.

Therefore, when the check valve 82 sets the valve opening pressure to be smaller than the pressure resistance of the oil seal 17, the check valve 82 is supplied before the pressure of the fuel supplied to the oil seal 17 exceeds the pressure resistance of the oil seal 17. 82 opens. Check valve 82
When the valve is opened, the fuel in the storage chamber 40 is supplied with the communication passage 81.
It is recirculated to the inlet side of the feed pump 60 via.
Therefore, the pressure increase of the fuel in the storage chamber 40 and the damage of the oil seal 17 are prevented.

On the other hand, when the check valve 82 is opened, a part of the fuel discharged from the feed pump 60 is fed to the fuel passage 53,
It is returned to the inlet side of the feed pump 60 via the accommodation chamber 40 and the communication passage 81. Therefore, when the period in which the check valve 82 is opened continues, a part of the fuel circulates between the feed pump 60 and the storage chamber 40. As described above, the housing 10 such as between the plunger 20 and the cam ring 22.
A plurality of sliding portions formed inside the fuel cell generate heat as the fuel injection pump 2 operates. Therefore, as the fuel circulates between the feed pump 60 and the storage chamber 40, the temperature of the fuel rises, which may cause seizure of the sliding portion.

Therefore, when the temperature of the fuel in the storage chamber 40 detected by the temperature sensor 41 becomes higher than a predetermined value, the ECU 3
Stops the operation of the fuel injection pump 2. For example, the metering valve 70 is closed and the supply of fuel from the feed pump 60 to the pressurizing chamber 30 is stopped. As a result, the supply of fuel to the common rail 4 and the injection of fuel into the combustion chamber of the engine are stopped, so the operation of the engine is stopped.

Next, the operation of the fuel injection pump 2 according to one embodiment of the present invention will be described. The cam 21 rotates with the rotation of the drive shaft 15, and the cam ring 22 revolves without rotating with the rotation of the cam 21. As the cam ring 22 revolves, the cam ring 22 and the plunger 20 slide and the plunger 20 moves.
It is reciprocally driven in a and 13a.

As the cam ring 22 revolves, the plunger 20 at the top dead center descends in the direction of the drive shaft 15,
The fuel discharged from the feed pump 60 and having its flow rate adjusted by the metering valve 70 flows from the fuel inflow passage 31 to the check valve 14
Is sucked into the pressurizing chamber 30 via. When the plunger 20 that has reached the bottom dead center rises toward the top dead center again, the check valve 14 is closed and the fuel pressure in the pressurizing chamber 30 rises. When the fuel pressure in the pressurizing chamber 30 becomes higher than the fuel pressure in the fuel passage 37, the check valve 34 opens and the fuel pressurized in the pressurizing chamber 30 is discharged to the fuel passage 37.

The fuel discharged from the pressurizing chamber 30 is delivered to the fuel passage 37 through the fuel discharge passage 32, the check valve 34 and the fuel chamber 33. The fuel delivered to the fuel passage 37 is supplied to the common rail 4 via the fuel pipe 51. In the common rail 4, the fuel with pressure fluctuation discharged from the fuel injection pump 2 is accumulated and held at a constant pressure.
The fuel stored in the common rail 4 is supplied to the injector 5. The injector 5 is opened and closed according to an instruction from the ECU 3, and injects fuel into the combustion chamber of the engine.

As described above, according to the fuel injection pump 2 of the embodiment of the present invention, when the pressure of the fuel in the storage chamber 40 rises, the check valve 82 opens and the storage chamber 40 is opened.
The fuel inside is recirculated to the inlet side of the feed pump 60.
Therefore, it is possible to prevent the fuel pressure in the housing chamber 40 from rising and the oil seal 17 from being damaged due to the pressure increase. Therefore, leakage of fuel from the fuel injection pump 2 is prevented, and reliability can be improved.

When the temperature of the fuel in the storage chamber 40 rises due to the fuel circulating between the feed pump 60 and the storage chamber 40, the operation of the fuel injection pump 2 is stopped. Therefore, the operation of the engine is stopped, and the seizure of each sliding part due to the temperature rise of the fuel in the storage chamber 40 and the fuel injection pump 2 accompanying the seizure of the sliding part 2
It is possible to prevent damage to the product.

In the above-described embodiment of the present invention, an example in which the communication passage of the circulation means and the check valve are provided in the housing has been described, but they may be provided outside the housing.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a common rail fuel injection system to which a fuel injection pump according to an embodiment of the present invention is applied.

FIG. 2 is a schematic cross-sectional view showing a fuel injection pump according to an embodiment of the present invention.

FIG. 3 is a view taken along line III-III in FIG. 2, showing the periphery of a plunger and a drive shaft.

[Explanation of symbols]

2 Fuel injection pump 10 housing 11 Housing body (housing) 12, 13 Cylinder head (housing) 12a, 13a cylinder 15 Drive shaft (drive means) 20 Plunger (movable member) 21 cam (driving means) 22 Cam ring (driving means) 24 Spring (drive means) 30 pressure chamber 40 accommodation room 41 Temperature sensor 60 feed pump 81 communication passage (reflux means) 82 Check valve (reflux means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02M 59/44 F02M 59/44 U V

Claims (4)

[Claims] 1. A movable member for pressurizing the fuel sucked into the pressurizing chamber, a drive unit having a drive shaft for driving the movable member, and the movable member forming the pressurizing chamber together with the movable member. And a housing for accommodating the movable member and the drive means, and a housing that is driven by the drive shaft and supplies fuel to the pressurization chamber and the storage chamber. A pump, a communication passage that communicates the storage chamber with an inlet side of the feed pump, and a check valve that allows a fuel flow from the storage chamber to the inlet side of the feed pump in the communication passage, The check valve is opened when the pressure of the fuel in the storage chamber becomes higher than a predetermined pressure, and a recirculation unit that recirculates the fuel in the storage chamber to the inlet side of the feed pump is provided. Fuel injection pump according to claim. 2. The fuel injection pump according to claim 1, wherein a temperature sensor for detecting the temperature of the fuel in the storage chamber is installed in the storage chamber. 3. The fuel injection pump according to claim 2, wherein when the temperature of the fuel in the storage chamber detected by the temperature sensor becomes higher than a predetermined value, the operation is stopped. 4. The fuel injection pump according to claim 1, 2 or 3, wherein the return means is provided in the housing.