JP2006118448A - Fuel injection pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress occurrence of abnormal wear of a seal lip part of an oil seal 9 without executing expansion of volume of a storage chamber 30 in a pump housing 7, elimination of abolition of a fuel passage 32 or the like. <P>SOLUTION: An orifice 34 is provided in a middle of the fuel passage 32 making communication between the oil seal 9 and the storage chamber 30 in the pump housing 7. Consequently, rising speed of fuel pressure transmitted to the lip seal part of the oil seal 9 from the storage chamber 30 can be dulled even if a pump drive shaft 2 rotates at high speed and fuel pressure in a variable volume space 31 of the storage chamber 30 rises. Consequently, sudden rise of pressure on acting surface of the seal lip part of the oil seal 9 can be prevented and occurrence of abnormal wear of a lip tip part of the seal lip part can be suppressed. Consequently, leak of fuel to outside of a supply pump can be surely prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection pump used in a fuel injection device for an internal combustion engine, and more particularly to a supply pump used in a common rail fuel injection system.

[Conventional technology]
Conventionally, a common rail type fuel injection system (accumulation type fuel injection device) is known as a fuel injection system for diesel engines. This is provided with a fuel injection pump that pressurizes and sucks fuel sucked into the pressurizing chamber and supplies it to the common rail (see, for example, Patent Document 1). The fuel injection pump includes a cam integrated with a pump drive shaft that is driven to rotate by a crankshaft of an engine, and a cam ring whose outer shape revolves along a predetermined circular path when the cam rotates. And a plunger drivingly connected to the cam ring. When the cam integrated with the camshaft rotates, the cam ring revolves along a predetermined circular path. Along with this, the plunger reciprocates in a cylindrical cylinder fixed to the pump housing to pressurize the fuel in the pressurizing chamber to increase the pressure.

  The fuel injection pump has a built-in feed pump that supplies fuel into the pressurizing chamber. In the fuel injection pump, as shown in FIGS. 8 and 9, the housing between the cam 101 and the cam ring 102, between the cam ring 102 and the plunger 103, between the pump housing 104 and the pump drive shaft 105, etc. A plurality of sliding portions are formed inside. For this reason, the fuel discharged from the feed pump is not only supplied to the pressurizing chamber, but also supplied to the accommodating chamber 106 inside the pump housing 104 in which the cam 101, the cam ring 102 and the plunger 103 are accommodated. . The sliding portions inside the housing are lubricated by the fuel supplied to the storage chamber 106.

Here, as described above, part of the fuel pressurized by the feed pump is supplied to the accommodation chamber inside the pump housing 104 of the fuel injection pump. Therefore, the pressurized fuel in the storage chamber 106 may leak out from between the pump housing 104 and the pump drive shaft 105 along the pump drive shaft 105 to the outside of the fuel injection pump.
Therefore, the fuel injection pump is provided with an oil seal 107 between the pump housing 104 and the pump drive shaft 105, and the oil seal 107 prevents the fuel from leaking out of the fuel injection pump. ing. An annular space 111 communicating with the storage chamber 106 through the fuel passage 110 is formed on the storage chamber 106 side of the oil seal 107.

[Conventional technical problems]
However, in the conventional fuel injection pump, as shown in FIG. 8, when the pump drive shaft 105 rotates at a high speed, the fuel in the storage chamber 106, particularly the fuel between the cam ring 102 and the wall surface of the pump housing 104, Therefore, the fuel pressure in the storage chamber 106 increases. As a result, the increased pressure in the storage chamber 106 is transmitted to the annular space 111 through the fuel passage 110, so that a high pressure acts on the lip portion of the oil seal 107. Further, as shown in FIG. 9, when the volume between the cam ring 102 and the wall surface of the pump housing 104 increases and the fuel pressure in the storage chamber 106 decreases, the fuel in the annular space 111 passes through the fuel passage 110. As a result, the pressure in the annular space 111 decreases, and a low pressure acts on the lip portion of the oil seal 107.

  As described above, in the fuel injection pump, the pressure fluctuation in the accommodation chamber 106 propagates to the annular space 111 via the fuel passage 110, and at the sliding contact portion between the pump drive shaft 105 and the lip portion of the oil seal 107. The working surface pressure repeats the amplitude of the high surface pressure and the low surface pressure. Therefore, particularly when a high pressure is applied to the lip portion of the oil seal 107, the working surface pressure at the sliding contact portion between the pump drive shaft 105 and the lip portion of the oil seal 107 is high surface pressure (the seal width is wide). Therefore, abnormal wear may occur in the lip portion of the oil seal 107. When abnormal wear occurs in the lip portion of the oil seal 107 as described above, the tightness of the lip portion of the oil seal 107 is reduced, so that the sealing performance between the pump housing 104 and the pump drive shaft 105 is lowered. Thus, there is a possibility that the fuel leaks to the outside of the fuel injection pump.

In addition, it is possible to reduce the wear amount of the lip portion of the oil seal 107 by suppressing the working surface pressure at the sliding contact portion between the pump drive shaft 105 and the lip portion of the oil seal 107. As a method of reducing the wear amount of the lip portion of the oil seal 107, it is conceivable to suppress the pressure increase by expanding the volume of the storage chamber 106 and to eliminate the fuel passage 110, but the physique of the fuel injection pump is limited. There are demerits such as an increase in the size and a decrease in the lubricity of the oil seal 107, which is difficult to implement.
JP 2000-240531 A (page 1-10, FIG. 1 to FIG. 18)

  The present invention is configured so that each sliding portion inside the housing is lubricated by using the fuel supplied to the storage chamber, and an oil seal is installed between the housing and the drive shaft. In a fuel injection pump configured to prevent leakage of fuel to the outside of the fuel injection pump by the seal, the storage chamber is changed to an oil seal without enlarging the volume of the storage chamber or abolishing the fuel passage. An object of the present invention is to prevent the occurrence of abnormal wear of the oil seal due to the propagating pressure fluctuation, thereby reliably preventing fuel leakage to the outside of the fuel injection pump.

  According to the first aspect of the present invention, the fuel passage that communicates the storage chamber and the oil seal is provided in the housing of the fuel injection pump, and the fixed throttle that restricts the cross-sectional area of the passage is provided in the middle of the fuel passage. As a result, even if the drive shaft rotates at a high speed and the pressure in the storage chamber increases, the rate of increase in pressure propagating from the storage chamber to the oil seal can be achieved. This prevents fluctuations in the operating surface pressure (the operating surface pressure of the lip portion of the oil seal) at the sliding contact portion between the drive shaft and the oil seal without enlarging the volume of the storage chamber or eliminating the fuel passage. Therefore, the occurrence of abnormal wear of the oil seal can be suppressed. Therefore, it is possible to reliably prevent the fuel in the housing chamber from leaking from between the drive shaft and the housing along the drive shaft to the outside of the fuel injection pump, so that a highly reliable fuel injection pump can be obtained. it can.

  According to the second aspect of the present invention, the volume of the storage chamber inside the housing of the fuel injection pump varies with the rotation of the drive shaft, and the phases of the high pressure operation step and the low pressure operation step are opposite to each other. Two first and second variable volume spaces are provided. In addition, by providing a first fuel passage that communicates the first variable volume space and the oil seal and a second fuel passage that communicates the second variable volume space and the oil seal inside the housing of the fuel injection pump, If the drive shaft rotates at high speed, the fuel pressure in the first variable volume space (or second variable volume space) rises, and the increased fuel pressure in the first variable volume space (or second variable volume space) Even if it propagates through the first fuel passage (or the second fuel passage) to the oil seal, the fuel pressure propagated to the oil seal passes through the second fuel passage (or the first fuel passage) to the second variable volume space. (Or the first variable volume space). This prevents fluctuations in the operating surface pressure (the operating surface pressure of the lip portion of the oil seal) at the sliding contact portion between the drive shaft and the oil seal without enlarging the volume of the storage chamber or eliminating the fuel passage. Therefore, the occurrence of abnormal wear of the oil seal can be suppressed. Therefore, it is possible to reliably prevent the fuel in the housing chamber from leaking from between the drive shaft and the housing along the drive shaft to the outside of the fuel injection pump, so that a highly reliable fuel injection pump can be obtained. it can.

  According to the third aspect of the present invention, a fuel passage is provided in the housing of the fuel injection pump to connect the storage chamber and the oil seal, and an air reservoir for storing air is provided in the vicinity of the oil seal. Yes. By connecting the fuel passage and the air reservoir, even if the drive shaft rotates at a high speed and the pressure in the storage chamber rises, the increase in pressure propagated from the storage chamber to the oil seal is reduced in the air reservoir. It can suppress by the damper effect by air. This prevents fluctuations in the operating surface pressure (the operating surface pressure of the lip portion of the oil seal) at the sliding contact portion between the drive shaft and the oil seal without enlarging the volume of the storage chamber or eliminating the fuel passage. Therefore, the occurrence of abnormal wear of the oil seal can be suppressed. Therefore, it is possible to reliably prevent the fuel in the housing chamber from leaking from between the drive shaft and the housing along the drive shaft to the outside of the fuel injection pump, so that a highly reliable fuel injection pump can be obtained. it can.

  According to the invention described in claim 4, a rubber-based annular elastic body having excellent oil resistance may be used as the oil seal. Further, by providing an annular lip portion on the annular elastic body, the lip portion of the oil seal is brought into close contact with the drive shaft by the pressure of the fuel supplied from the storage chamber, so that the gap between the drive shaft and the housing is surely secured. Can be sealed. Therefore, it is possible to reliably prevent the fuel in the accommodation chamber from leaking along the drive shaft from between the drive shaft and the housing to the outside of the fuel injection pump.

  According to the fifth aspect of the present invention, by providing the oil seal with an annular spring, it is possible to properly maintain the surface pressure at the sliding contact portion between the drive shaft and the lip portion of the oil seal. Thus, the lip portion of the oil seal is brought into close contact with the drive shaft by the biasing force of the spring, so that the gap between the drive shaft and the housing can be reliably sealed. Therefore, it is possible to reliably prevent the fuel in the accommodation chamber from leaking along the drive shaft from between the drive shaft and the housing to the outside of the fuel injection pump.

  According to the sixth aspect of the present invention, the fuel is not only supplied to the pressurizing chamber, but also a cam that rotates eccentrically with respect to the rotational axis of the drive shaft, and a predetermined circular path when the cam rotates. A cam ring that revolves along the shaft is also supplied to a cam chamber inside a housing in which the cam ring is rotatably accommodated. The fuel injection pump is configured so that the sliding parts inside the housing are lubricated by the fuel supplied to the cam chamber. The fuel injection pump includes an oil seal that seals between the drive shaft and the housing using the pressure of the fuel supplied from the cam chamber inside the housing.

  According to the seventh aspect of the present invention, the sliding portion between the drive shaft and the housing is provided closer to the storage chamber than the oil seal. The fuel injection pump is configured so that the sliding portion is lubricated by using the fuel supplied to the storage chamber. The annular space formed between the oil seal and the sliding portion can block and temporarily store the fuel supplied from the storage chamber. As a result, the oil seal (the lip portion) seals between the drive shaft and the housing by utilizing the pressure of the fuel stored in the annular space. According to the eighth aspect of the present invention, the bearing for rotatably supporting the drive shaft is installed at the sliding portion between the drive shaft and the housing, so that the fuel can be slid by the fuel supplied to the storage chamber. The moving part is lubricated.

  The best mode for carrying out the present invention is to suppress the occurrence of abnormal wear of an oil seal that prevents leakage of fuel to the outside of the fuel injection pump, and to prevent a decrease in lubricity of the oil seal. This was realized by providing a fixed throttle in the middle of the fuel passage that connects the containment chamber and the oil seal to reduce the propagation speed of the fuel pressure propagating from the containment chamber to the oil seal. In addition, the first and second fuel passages that communicate between the storage chamber and the oil seal are provided to suppress an increase in fuel pressure that propagates from the storage chamber to the oil seal. In addition, an air reservoir is provided in the vicinity of the oil seal to suppress an increase in fuel pressure propagating from the storage chamber to the oil seal.

[Configuration of Example 1]
FIGS. 1 to 5 show a first embodiment of the present invention. FIGS. 1 (a) and 1 (b) show the main configuration of the fuel injection pump. FIGS. 2 and 3 show the fuel injection pump. It is the figure which showed the whole structure.

  The fuel injection device for an internal combustion engine of the present embodiment is a common rail fuel injection system (accumulation fuel injection device) known as a fuel injection system for an internal combustion engine (hereinafter referred to as an engine) such as a multi-cylinder diesel engine. The high-pressure fuel stored in the cylinder is injected and supplied into the combustion chamber of each cylinder of the engine via an injector mounted corresponding to each cylinder of the engine. This common rail fuel injection system includes a common rail for accumulating high pressure fuel corresponding to the fuel injection pressure, and a plurality of injectors (electromagnetic fuel injection) that inject high pressure fuel into the combustion chamber of each cylinder of the engine at a predetermined timing. Valve), a fuel injection pump (supply pump) 1 that supplies high pressure fuel that has been pressurized by increasing the pressure of the sucked fuel to the common rail, an electromagnetic valve of a plurality of injectors, and a suction metering valve 4 of the supply pump 1 It includes an engine control unit (hereinafter referred to as ECU) that performs electronic control.

  The supply pump 1 of this embodiment is driven by a pump drive shaft (drive shaft or camshaft) 2 that rotates in synchronization with the crankshaft of the engine, and passes through the intake metering valve 4 to provide two first and second two pumps. There are two pumping systems (pump elements) that pressurize the fuel sucked into the pressurizing chamber 5 and pump it into the common rail, and one suction metering valve 4 allows the fuel pumping amount or fuel discharging amount of all pumping systems. Is a high-pressure supply pump of a type (inhalation metering type) that controls by metering the amount of intake fuel. This supply pump 1 adds fuel sucked into two first and second pressurizing chambers 5 via a feed pump (low pressure supply pump) 3 driven by a pump drive shaft 2 and a suction metering valve 4. There are provided two first and second plungers 6 that are pressurized to increase pressure, and plunger drive means for transmitting a driving force from the pump drive shaft 2 to the two first and second plungers 6.

  The housing of the supply pump 1 includes a pump housing 7 having a cylindrical shaft bearing portion that rotatably supports the pump drive shaft 2, and two first and second cylinder heads fixed to the pump housing 7. 8. In this embodiment, the two first and second plungers 6 and the two first and second cylinder heads 8 constitute a pump element (high pressure supply pump) of the supply pump 1. An oil seal 9 seals between the outer periphery of the pump drive shaft 2 and the inner periphery of the shaft bearing portion of the pump housing 7.

  The pump drive shaft 2 is made of, for example, an iron-based metal material, and is rotatably supported in a through hole 11 of a shaft bearing portion of the pump housing 7 via a journal bearing (metal bush) 10. A drive pulley (not shown) is connected to the outer periphery of the tip end portion (the left end portion shown in FIG. 2) of the pump drive shaft 2 so as to be driven and connected via a crank pulley of the engine crankshaft and a belt. . An inner rotor 12 of the feed pump 3 is assembled to the rear end portion (the right end portion shown in FIG. 2) of the pump drive shaft 2.

  The feed pump 3 is a trochoid pump that pumps fuel from a fuel tank (not shown) as the pump drive shaft 2 rotates. The feed pump 3 includes an inner rotor 12 and an outer rotor 13 accommodated between an outer wall surface of the pump housing 7 and a pump cover 14 fixed to the outer wall surface of the pump housing 7. And the feed pump 3 pressurizes the normal pressure fuel stored in the fuel tank by relatively rotating the inner rotor 12 and the outer rotor 13 with the rotation of the pump drive shaft 2, so that the two first, Supply to the second pressurizing chamber 5. Here, the fuel discharged from the feed pump 3 toward the two first and second pressurizing chambers 5 is an intake metering valve 4, a fuel inflow passage 15, and two first and second intake valves 16. Then, the two first and second pressurizing chambers 5 are distributed and supplied.

  The intake metering valve 4 has a valve body (spool valve) that changes the opening area of a fuel flow path such as an inlet port (or outlet port) formed in the sleeve housing, and a spool driven by a pump drive current applied from the ECU. It has a valve body biasing means such as an electromagnetic actuator that drives the valve in the valve opening direction (or valve closing direction) and a spring that biases the spool valve in the valve closing direction (or valve opening direction). The intake amount of fuel supplied from the pump 3 to the two first and second pressurizing chambers 5 is adjusted. The supply pump 1 according to the present embodiment corresponds to the operating state of the engine with the intake amount of fuel supplied from the feed pump 3 to the two first and second pressurizing chambers 5 by the intake metering valve 4. Thus, the amount of fuel discharged from the two first and second pressurizing chambers 5 through the fuel discharge passage 17 and the two first and second discharge valves 19 is adjusted. As a result, the fuel pressure in the common rail is controlled to an optimum value.

  Here, the plunger drive means (power transmission mechanism) of the present embodiment is constituted by a cam 20, a cam ring 21, a bush 22 and the like. A cam 20 is integrally formed on the outer periphery of the intermediate portion of the pump drive shaft 2, and is in a symmetrical position in the vertical direction in the figure across the cam 20, and the phases of the suction process and the pumping process are opposite to each other. The two first and second plungers 6 are arranged so as to be in phase. The cam 20 is provided eccentrically with respect to the axis of the pump drive shaft 2 and has a circular cross section. On the outer periphery of the cam 20, a cam ring 21 having a substantially rectangular outer shape is slidably held via an annular bush 22. A hollow portion having a circular cross section is formed inside the cam ring 21, and the cam 20 and the bush 22 are accommodated therein.

  Further, the two first and second plungers 6 are pressed against the upper and lower end surfaces of the cam ring 21 by the urging force of the coil springs 23 disposed on the outer peripheral sides of the two first and second plungers 6. . With this configuration, when the cam 20 integrated with the pump drive shaft 2 rotates, the cam ring 21 revolves along a predetermined circular path. The two first and second plungers 6 are reciprocated by the cam 20 via the cam ring 21 as the pump drive shaft 2 rotates, and pass through the two first and second intake valves 16 from the fuel inflow passage 15. The fuel sucked into the two first and second pressurizing chambers 5 is pressurized to increase the pressure.

  The two first and second intake valves 16 include a valve body that closes when the fuel pressure in the two first and second pressurizing chambers 5 rises above a predetermined value, and the valve bodies in the valve closing direction. This is a check valve having valve body urging means such as an urging spring for preventing the fuel from flowing backward from the two first and second pressurizing chambers 5 to the fuel inflow passage 15. The fuel discharge passage 17 is formed linearly in each of the two first and second cylinder heads 8 and directly communicates with the two first and second pressurizing chambers 5. A long-hole fuel passage 24 having a passage cross-sectional area larger than that of the fuel discharge passage 17 is formed on the downstream side of the fuel discharge passage 17 formed in each of the two first and second cylinder heads 8. First and second discharge valves 19 are accommodated in the passage 24.

  The two first and second discharge valves 19 are opened when the fuel pressure in the two first and second pressurizing chambers 5 rises above a predetermined value, and the valve bodies are closed in the valve closing direction. This is a check valve that has valve body urging means such as an urging spring and prevents the fuel from flowing backward from the fuel passage 24 to the fuel discharge passage 17 and the two first and second pressurizing chambers 5. . Further, an outlet pipe 26 having a fuel passage 25 therein is fastened and fixed to the downstream side of the fuel passage 24. The outlet pipe 26 is connected to the common rail via a fuel supply pipe (not shown).

  In the supply pump 1 of this embodiment, for example, two first and second cylinder heads 8 made of, for example, an iron-based metal material are fixed to the upper and lower ends of the pump housing 7 made of a metal material such as aluminum. is doing. Two first and second plungers 6 are accommodated in the sliding holes of the two first and second cylinder heads 8 so as to be slidable in both directions. An interior formed by the sliding holes of the two first and second cylinder heads 8, the end faces of the two first and second intake valves 16, and the end faces of the two first and second plungers 6. The space is made up of two first and second pressurizing chambers 5. That is, the two first and second pressurizing chambers 5 are configured so that low-pressure fuel flows from the outlet portion of the intake metering valve 4 through the fuel inflow passage 15 and the two first and second intake valves 16. It is configured.

  The pump drive shaft 2, the two first and second plungers 6, the cam 20, and the cam ring 21 are accommodated in the pump housing 7 and the accommodating chamber 30 formed inside the two first and second cylinder heads 8. Has been. In the storage chamber 30, there are supply pumps such as between the cam 20 and the cam ring 21, between the cam ring 21 and the two first and second plungers 6, and between the pump drive shaft 2 and the pump housing 7. Fuel for lubricating each sliding portion inside the housing 1 is supplied from the feed pump 3 via a fuel passage (not shown).

  As described above, the fuel discharged from the feed pump 3 is not only supplied to the two first and second pressurizing chambers 5 but also the pump drive shaft 2 and the two first and second plungers 6. The cam 20 and the cam ring 21 are also supplied to the storage chamber 30 inside the pump housing 7. In the supply pump 1 of this embodiment, the sliding parts inside the housing of the supply pump 1 are lubricated by the fuel supplied from the feed pump 3 to the storage chamber 30. The storage chamber 30 functions as a cam chamber that rotatably stores the cam 20 and the cam ring 21. The accommodating chamber 30 has a variable volume space (shaded area in FIG. 1) 31 formed between the end surface of the cam ring 21 (the right end surface shown in FIG. 1) and the wall surface of the pump housing 7 as the cam ring 21 revolves. The volume of is increased and decreased.

  Further, as shown in FIGS. 1 and 2, a fuel passage 32 that functions as a breathing hole is formed inside the pump housing 7. The fuel passage 32 communicates the variable volume space 31 of the storage chamber 30 with the annular space 33 closer to the storage chamber 30 than the oil seal 9. The fuel passage 32 is formed so as to penetrate the inside of the pump housing 7, and supplies part of the fuel stored in the storage chamber 30 to the oil seal 9. Here, in the middle of the fuel passage 32 of the present embodiment, as shown in FIG. 1, the passage cross-sectional area is made smaller than the fuel passage 32 to adjust the flow rate of the fuel flowing in the fuel passage 32. A fixed orifice (orifice) 34 is provided.

  As shown in FIGS. 1, 2 and 4, the oil seal 9 is a rubber-based annular elastic body (for example, nitrile rubber: NBR, acrylic rubber: ACM, silicone rubber: VMQ, fluoro rubber: An annular seal lip portion 41 that is in close contact with the outer peripheral surface of the pump drive shaft 2 by the pressure of the fuel supplied from the storage chamber 30 and prevents leakage of the fuel to the outside of the supply pump 1. An annular spring 42 for properly maintaining the surface pressure at the sliding contact portion between the pump drive shaft 2 and the seal lip 41; an annular dust strip 43 for preventing dust from entering the supply pump 1; And the fitting part 44 which closely_contact | adheres to the internal peripheral surface of the through-hole 11 of the pump housing 7 is provided.

  The seal lip portion 41 keeps the contact of the lip tip portion 45 with the outer peripheral surface of the pump drive shaft 2 in a stable state, and the fitting portion 44 connects the oil seal 9 to the inner periphery of the through hole 11 of the pump housing 7. In addition to being fixed to the surface, fuel leakage from the contact surface between the outer peripheral surface of the oil seal 9 and the inner peripheral surface of the pump housing 7 or dust intrusion is prevented. Further, a metal ring may be attached to the fitting portion 44 for the purpose of fixing the oil seal 9 to the pump housing 7 and improving the fitting force. Further, as the spring 42, an annular spring having an annular shape by connecting both ends of the coil spring may be used. Further, the dust lip 43 may not be provided.

[Operation of Example 1]
Next, the operation of the supply pump 1 used in the common rail fuel injection system of this embodiment will be briefly described with reference to FIGS.

  When the pump drive shaft 2 of the supply pump 1 is driven by the belt driven by the engine crankshaft and rotated, the cam 20 rotates with the rotation of the pump drive shaft 2, and the cam ring 21 rotates with the rotation of the cam 20. And revolves along a predetermined circular path. As the cam ring 21 revolves, the cam ring 21 and the two first and second plungers 6 slide, and the two first and second plungers 6 move into the two first and second cylinder heads 8. Are slid back and forth in the vertical direction in the figure. As the cam ring 21 revolves, the two first and second plungers 6 are alternately lifted. In the state shown in FIG. 2, the first plunger 6 is at the top dead center and the second plunger 6 is at the bottom dead center. is doing.

  When the first plunger 6 located at the top dead center is lowered in the figure as the cam ring 21 revolves, the fuel pressure in the first pressurizing chamber 5 is reduced, and the valve body of the first intake valve 16 is reduced by this fuel pressure. And the fuel metered by the suction metering valve 4 is sucked into the first pressurizing chamber 5 from the fuel inflow passage 15 via the first suction valve 16. Then, when the first plunger 6 reaches the bottom dead center and starts to rise again toward the top dead center, the fuel pressure in the first pressurizing chamber 5 rises, and the first suction valve 16 is increased by this fuel pressure. The valve body closes. When the fuel pressure in the first pressurizing chamber 5 further increases, the valve body of the first discharge valve 19 is opened, and the high-pressure fuel pressurized and pressurized in the first pressurizing chamber 5 is fueled. The fuel is discharged to the fuel passages 24 and 25 via the discharge passage 17. The high-pressure fuel discharged to the fuel passages 24 and 25 is pressure-fed and supplied into the common rail via the high-pressure fuel pipe.

  On the other hand, the second plunger 6 is reciprocally slid between the top dead center and the bottom dead center in the same manner as the first plunger 6 to pressurize and increase the pressure in the second pressurizing chamber 5. Is fed into the common rail through the fuel discharge passage 17, the fuel passages 24 and 25, and the high-pressure fuel pipe. Thus, the supply pump 1 is configured such that the suction stroke and the pressure feed stroke are performed for two cycles per rotation of the pump drive shaft 2. The high-pressure fuel accumulated in the common rail is injected and supplied into the combustion chamber of each cylinder of the engine at a predetermined timing by driving the electromagnetic valve of the injector at an arbitrary injection timing.

  Here, a feed pump 3 for supplying fuel into the two first and second pressurizing chambers 5 is integrally assembled with the supply pump 1 of the present embodiment. In the supply pump 1, between the cam 20 and the cam ring 21, between the two first and second plungers 6 and the cam ring 21, two first and second plungers 6 and the two first, A plurality of sliding portions are formed inside the housing of the supply pump 1 such as between the sliding surface in the second cylinder head 8 and between the pump drive shaft 2 and the through hole 11 of the pump housing 7. For this reason, the fuel discharged from the feed pump 3 is not only supplied to the two first and second pressurizing chambers 5 but also the cam 20, the two first and second plungers 6, and the cam ring 21. Is also supplied to the storage chamber 30 inside the pump housing 7. Further, since the sliding parts inside the housing of the supply pump 1 are lubricated by the fuel supplied to the storage chamber 30, seizure of each sliding part inside the housing is prevented.

  Here, the pump drive shaft 2 of the supply pump 1 of the present embodiment is rotatably supported in the through hole 11 of the pump housing 7 via the journal bearing 10 and protrudes from the outer wall surface of the pump housing 7. A drive pulley that is drivingly connected to a crank pulley of a crankshaft of an engine via a belt is attached to the tip of the drive shaft 2. Further, as described above, a part of the fuel pressurized by the feed pump 3 is supplied to the storage chamber 30 inside the pump housing 7. Accordingly, the fuel in the storage chamber 30 pressurized by the feed pump 3 leaks out of the supply pump 1 from between the through hole 11 of the pump housing 7 and the pump drive shaft 2 along the pump drive shaft 2. there is a possibility. For this reason, the supply pump 1 is provided with an oil seal 9 between the pump drive shaft 2 and the through hole 11 of the pump housing 7, and the oil seal 9 prevents fuel from leaking outside the supply pump 1. It is out.

[Features of Example 1]
As described above, in the supply pump 1 configured to lubricate each sliding portion inside the housing using the fuel supplied from the feed pump 3 to the storage chamber 30, the pump drive shaft 2 is provided. By installing the oil seal 9 between the pump housing 7 and the through hole 11 of the pump housing 7, the fuel in the storage chamber 30 pressurized by the feed pump 3 penetrates the pump housing 7 along the pump drive shaft 2. Leakage from between the hole 11 and the pump drive shaft 2 to the outside of the supply pump 1 is prevented. An annular space 33 is formed closer to the accommodation chamber 30 than the oil seal 9, and the annular space 33 communicates with the accommodation chamber 30 via the fuel passage 32. As a result, the oil seal 9 seals between the outer periphery of the pump drive shaft 2 and the inner periphery of the through hole 11 of the pump housing 7 using the pressure of the fuel supplied from the storage chamber 30 via the fuel passage 32. It becomes possible to do.

  However, in the supply pump 1, when the pump drive shaft 2 is rotated at a high speed by the crankshaft of the engine, the volume of the variable volume space 31 of the storage chamber 30 is rapidly expanded and contracted. In particular, when the volume of the variable volume space 31 of the storage chamber 30 is most reduced (when the cam angle is 90 ° in FIG. 5), the variable volume space 31 of the storage chamber 30 is shown in FIG. The fuel inside is compressed between the right end surface in the figure of the cam ring 21 and the wall surface of the pump housing 7, and the pressure rises. Since the fuel passage 32 communicating with the storage chamber 30 and the annular space 33 is opened in the variable volume space 31 of the storage chamber 30, the increased pressure is transmitted through the fuel passage 32 and the seal lip portion of the oil seal 9. Propagate to 41.

  Then, as shown in FIG. 4B, the working surface pressure at the sliding contact portion between the pump drive shaft 2 and the seal lip portion 41 of the oil seal 9 (the working surface pressure of the seal lip portion 41 of the oil seal 9) is increased. The lip tip 45 of the seal lip 41 is pressed against the outer peripheral surface of the pump drive shaft 2. Thus, when a high pressure is applied to the seal lip 41 of the oil seal 9, the seal width of the sliding contact portion (lip tip 45) between the pump drive shaft 2 and the seal lip 41 of the oil seal 9 is widened.

  Further, when the volume of the variable volume space 31 of the storage chamber 30 is expanded most (when the cam angle is 270 ° in FIG. 5), the volume between the right end surface of the cam ring 21 and the wall surface of the pump housing 7 increases. The fuel pressure in the variable volume space 31 of the storage chamber 30 decreases. As a result, the fuel in the annular space 33 is sucked into the accommodation chamber 30 via the fuel passage 32, and the pressure in the annular space 33 is reduced.

  Then, as shown in FIG. 4A, the working surface pressure at the sliding contact portion between the pump drive shaft 2 and the seal lip portion 41 of the oil seal 9 (the working surface pressure of the seal lip portion 41 of the oil seal 9) is increased. The lip tip 45 of the seal lip 41 is pressed against the outer peripheral surface of the pump drive shaft 2 only by the urging force of the spring 42. Thus, when a low pressure acts on the seal lip 41 of the oil seal 9, the seal width of the sliding contact portion (lip tip 45) between the pump drive shaft 2 and the seal lip 41 of the oil seal 9 becomes narrow.

  As described above, in the supply pump 1 configured to lubricate each sliding portion inside the housing using the fuel supplied from the feed pump 3 to the accommodation chamber 30, the accommodation chamber 30 is variable. The pressure fluctuation in the volume space 31 propagates to the annular space 33 via the fuel passage 32, and the working surface pressure at the sliding contact portion between the pump drive shaft 2 and the seal lip portion 41 of the oil seal 9 is high and low. The amplitude with pressure will be repeated. For this reason, particularly when a high pressure is applied to the seal lip 41 of the oil seal 9, abnormal wear may occur at the lip tip 45 of the seal lip 41 of the oil seal 9.

  When abnormal wear occurs in the seal lip portion 41 of the oil seal 9 as described above, the tightening margin of the lip tip portion 45 of the seal lip portion 41 of the oil seal 9 decreases, so that the outer periphery of the pump drive shaft 2 and The sealing performance between the inner periphery of the through hole 11 of the pump housing 7 is lowered, and the fuel in the storage chamber 30 pressurized by the feed pump 3 penetrates the pump housing 7 along the pump drive shaft 2. There is a possibility of leakage from between the hole 11 and the pump drive shaft 2 to the outside of the supply pump 1.

  Therefore, in the supply pump 1 of the present embodiment, as shown in FIG. 1, an orifice 34 is provided in the middle of the fuel passage 32 that connects the storage chamber 30 inside the pump housing 7 and the oil seal 9. Thereby, even when the pump drive shaft 2 rotates at a high speed and the fuel pressure in the variable volume space 31 of the storage chamber 30 increases, the rate of increase in pressure transmitted from the storage chamber 30 to the seal lip 41 of the oil seal 9 Is possible. As a result, it is possible to suppress a sudden rise in the working surface pressure at the sliding contact portion between the pump drive shaft 2 and the seal lip portion 41 of the oil seal 9, so that the seal lip portion between the pump drive shaft 2 and the oil seal 9 rotating at high speed. The sliding contact width (seal width) with the lip tip 45 of 41 is reduced.

  In particular, sudden fluctuations in pressure acting on the seal lip portion 41 of the oil seal 9 can be suppressed, and the working surface pressure (seal lip portion of the oil seal 9) at the sliding contact portion between the pump drive shaft 2 and the seal lip portion 41 of the oil seal 9 can be suppressed. 41), the occurrence of abnormal wear of the lip tip 45 of the seal lip 41 of the oil seal 9 can be suppressed. Therefore, the fuel in the storage chamber 30 pressurized by the feed pump 3 leaks along the pump drive shaft 2 from between the through hole 11 of the pump housing 7 and the pump drive shaft 2 to the outside of the supply pump 1. Therefore, it is possible to provide the supply pump 1 with high reliability.

  Further, by suppressing the fluctuation of the pressure acting on the seal lip 41 of the oil seal 9 without increasing the volume of the storage chamber 30 or eliminating the fuel passage 32, the seal lip 41 of the oil seal 9 is suppressed. Since the abnormal wear of the lip tip 45 of the lip can be suppressed, it is possible to prevent an increase in the size of the supply pump 1 or a decrease in the lubricity of the oil seal 9.

  FIG. 6 shows a second embodiment of the present invention, and FIGS. 6A and 6B show the main configuration of the supply pump.

  The oil seal 9 of the supply pump 1 according to the present embodiment uses the pressure of the fuel supplied from the storage chamber 30 via the two first and second fuel passages 32a and 32b formed inside the pump housing 7. The gap between the outer periphery of the pump drive shaft 2 and the inner periphery of the through hole 11 of the pump housing 7 is sealed. In the storage chamber 30 of this embodiment, the cam 20 rotates along with the rotation of the pump drive shaft 2, and the cam ring 21 does not rotate along with the rotation of the cam 20, but revolves along a predetermined circular path. In doing so, there are two first and second variable volume spaces 31a, 31b in which the volume between the wall surface of the pump housing 7 and the both end faces of the cam ring 21 is variable.

  These first and second variable volume spaces 31a and 31b are high-pressure operation steps in which the volume between the wall surface of the pump housing 7 and both end surfaces of the cam ring 21 is reduced (in the case of the first variable volume space 31a, for example, FIG. 5 (a cam angle range of 0 ° to 180 °), a low-pressure operation step in which the volume between the wall surface of the pump housing 7 and both end surfaces of the cam ring 21 is expanded (in the case of the first variable volume space 31a, for example, FIG. The phases of the cam angles (180 to 360 °) are opposite to each other. Inside the pump housing 7 of the supply pump 1, the first fuel passage 32 a that communicates the first variable volume space 31 a of the storage chamber 30 and the annular space 33 and the second variable volume space 31 b of the storage chamber 30 are annular. A second fuel passage 32 b that communicates with the space 33 is formed.

  As a result, the pump drive shaft 2 rotates at a high speed to increase the fuel pressure in the first variable volume space 31a of the storage chamber 30, and the increased fuel pressure in the first variable volume space 31a passes through the first fuel passage 32a. Even if the fuel pressure propagates to the seal lip portion 41 of the oil seal 9 and propagates to the seal lip portion 41 of the oil seal 9, the fuel pressure propagated to the seal lip portion 41 of the oil seal 9 enters the second variable volume space 31b of the storage chamber 30 via the second fuel passage 32b. Sucked out. That is, the working surface pressure at the sliding contact portion between the pump drive shaft 2 and the seal lip portion 41 of the oil seal 9 (the working surface pressure of the seal lip portion 41 of the oil seal 9) does not vary and is maintained at a substantially constant value. . As a result, the same effects as those of the first embodiment can be obtained, so that it is possible to provide the supply pump 1 with high reliability.

  FIG. 7 shows a third embodiment of the present invention, and FIGS. 7A and 7B show the main configuration of the supply pump.

  The oil seal 9 of the supply pump 1 according to this embodiment is configured such that the outer periphery of the pump drive shaft 2 and the pump housing are utilized by using the pressure of the fuel supplied from the storage chamber 30 through the fuel passage 32 formed inside the pump housing 7. 7 is sealed between the inner periphery of the through hole 11. In the vicinity of the oil seal 9, an air reservoir 35 for storing air is provided inside, and the fuel passage 32 and the air reservoir 35 communicate with each other.

  Thus, even when the pump drive shaft 2 rotates at a high speed and the fuel pressure in the variable volume space 31 of the storage chamber 30 rises, the oil seal 9 passes from the variable volume space 31 of the storage chamber 30 via the fuel passage 32. The increase in the fuel pressure propagating to the seal lip portion 41 can be suppressed by the damper effect by the air in the air reservoir portion 35. As a result, the same effects as those of the first embodiment can be obtained, so that it is possible to provide the supply pump 1 with high reliability. Here, if the air reservoir 31 is installed in the top direction of the supply pump 1, air will not escape even when fuel is supplied into the supply pump 1. Even if the air is forcibly released, a small amount of air is sucked by the pump action of the oil seal 9 and supplied to the air reservoir 35 so that the air is accumulated.

[Modification]
In the present embodiment, the example in which the present invention is applied to the supply pump 1 used in the common rail fuel injection system has been described. However, the present invention is not limited to the distribution type fuel injection pump used in the fuel injection device for the internal combustion engine. You may apply to a row type fuel injection pump. Note that the number of pump elements, that is, the number of plungers may be one or three or more. Further, the oil seal 9 may be divided into two parts, a seal lip portion 41 and a dust lip portion 43.

  In the present embodiment, as a fuel injection pump used in a fuel injection device for an internal combustion engine, the fuel pumping amount or the fuel discharge amount of all pumping systems (pump elements) is set to the amount of fuel sucked by one suction metering valve 4. Although the supply pump 1 of the type controlled by metering is used, the fuel pumping amount or fuel discharge of a plurality of pumping systems (pump elements) is used as the fuel injection pump used in the fuel injection device for the internal combustion engine. A supply pump of a type in which the amount is controlled by metering the amount of fuel sucked by a plurality of suction metering valves may be used.

  In this embodiment, the fuel is supplied to the two first and second pressurizing chambers 5 and the storage chamber 30 by being driven by the pump drive shaft 2 in the pump housing (housing) 7 of the fuel injection pump (supply pump) of the present invention. However, a feed pump that supplies fuel to the pressurizing chamber and the storage chamber may be installed outside the pump housing 7.

(A) is the schematic which showed the main structures of the supply pump, (b) is AA sectional drawing of (a) (Example 1). It is sectional drawing which showed the whole structure of the supply pump (Example 1). (Example 1) which is BB sectional drawing of FIG. (A), (b) is the schematic which showed the oil seal of the supply pump (Example 1). It is the graph which showed the change of the working surface pressure of the seal lip part of an oil seal with respect to a cam angle. (A) is the schematic which showed the main structures of the supply pump, (b) is CC sectional drawing of (a) (Example 2). (A) is the schematic which showed the main structures of the supply pump, (b) is DD sectional drawing of (a) (Example 3). (A) is the schematic which showed the main structures of the fuel injection pump, (b) is EE sectional drawing of (a) (conventional technique). (A) is the schematic which showed the main structures of the fuel injection pump, (b) is FF sectional drawing of (a) (conventional technique).

Explanation of symbols

1 Supply pump (fuel injection pump)
2 Pump drive shaft (drive shaft)
3 Feed pump 4 Suction metering valve 5 Two first and second pressurizing chambers (pump elements)
6 Two first and second plungers (pump elements)
7 Pump housing (housing)
8 Two first and second cylinder heads (cylinder, housing, pump element) 9 Oil seal 10 Journal bearing (bearing)
20 cam (plunger drive means)
21 Cam ring (plunger drive means)
22 Bush (plunger drive means)
30 containment room (cam room)
31 Variable volume space 32 Fuel passage 33 Annular space 34 Orifice (fixed restriction)
35 Air reservoir 41 Oil seal seal lip (lip)
42 Oil Seal Spring 43 Oil Seal Dustrip 44 Oil Seal Fit 45 Oil Seal Lip Tip 31a First Variable Volume Space 31b Second Variable Volume Space 32a First Fuel Passage 32b Second Fuel Passage

Claims (8)

(A) a drive shaft rotated by an internal combustion engine;
(B) a plunger for pressurizing the fuel sucked into the pressurizing chamber;
(C) plunger driving means for transmitting a driving force from the driving shaft to the plunger;
(D) a housing that rotatably supports the drive shaft and has a storage chamber for storing the plunger and the plunger drive means;
(E) an oil seal that seals between the drive shaft and the housing using the pressure of the fuel supplied from the storage chamber;
A fuel passage is provided in the housing for communicating the storage chamber and the oil seal, and a fixed restrictor for reducing a cross-sectional area of the passage is provided in the middle of the fuel passage. Fuel injection pump. (A) a drive shaft rotated by an internal combustion engine;
(B) a plunger for pressurizing the fuel sucked into the pressurizing chamber;
(C) plunger driving means for transmitting a driving force from the driving shaft to the plunger;
(D) a housing that rotatably supports the drive shaft and has a storage chamber for storing the plunger and the plunger drive means;
(E) an oil seal that seals between the drive shaft and the housing using the pressure of the fuel supplied from the storage chamber;
The storage chamber has two first and second variable volume spaces in which the volume varies with the rotation of the drive shaft, and the phases of the high pressure operation step and the low pressure operation step are opposite to each other.
A first fuel passage that communicates the first variable volume space and the oil seal and a second fuel passage that communicates the second variable volume space and the oil seal are provided inside the housing. A fuel injection pump characterized by that. (A) a drive shaft rotated by an internal combustion engine;
(B) a plunger for pressurizing the fuel sucked into the pressurizing chamber;
(C) plunger driving means for transmitting a driving force from the driving shaft to the plunger;
(D) a housing that rotatably supports the drive shaft and has a storage chamber for storing the plunger and the plunger drive means;
(E) an oil seal that seals between the drive shaft and the housing using the pressure of the fuel supplied from the storage chamber;
Inside the housing is provided a fuel passage that communicates the storage chamber and the oil seal,
In the vicinity of the oil seal, an air reservoir for storing air is provided,
The fuel injection pump, wherein the fuel passage communicates with the air reservoir. The fuel injection pump according to any one of claims 1 to 3,
The oil seal is a rubber-based annular elastic body excellent in oil resistance,
A fuel injection pump comprising an annular lip portion that is in close contact with the drive shaft by the pressure of fuel supplied from the storage chamber and prevents leakage of fuel to the outside. The fuel injection pump according to claim 4.
The fuel injection pump according to claim 1, wherein the oil seal has an annular spring for properly maintaining a surface pressure at a sliding contact portion between the drive shaft and the lip portion. The fuel injection pump according to any one of claims 1 to 5,
The plunger driving means includes a cam that rotates eccentrically with respect to a rotation axis of the drive shaft, and a cam ring that performs a revolving motion along a predetermined circular path when the cam rotates.
The fuel storage pump according to claim 1, wherein the storage chamber has a cam chamber that rotatably stores the cam and the cam ring. The fuel injection pump according to any one of claims 1 to 6,
A sliding portion between the drive shaft and the housing is provided closer to the storage chamber than the oil seal,
The sliding portion is configured to be lubricated using fuel supplied to the storage chamber,
A fuel injection pump characterized in that an annular space is formed between the oil seal and the sliding portion for blocking and temporarily accumulating fuel supplied from the storage chamber. The fuel injection pump according to claim 7,
The fuel injection pump according to claim 1, wherein a bearing for rotatably supporting the drive shaft is installed on the sliding portion.

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