JP2000297724A - Fuel supply pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce impacts generated in pressure-fed fuel and to improve resolution of pressure-feeding amount of fuel by giving a profile to a pump drive cam so as to moderate a plunger lift speed before a press-feeding top death center. SOLUTION: A pump drive cam 77 for lifting a plunger 83 of a fuel supply pump 80 has a cam profile 78 in which a rotation angle range θe corresponding to a pressure-feed stroke of the plunger 83 is wider than a rotation angle range θi corresponding to a suction stroke of the plunger 83 and a lift speed of the plunger 83 per rotation angle of a pump drive shaft 77a is slower than a drop speed of that. Impacts given to fuel during fuel pressure-feed period is reduced to suppress vibration and noise of the fuel supply pump 80. Resolution of fuel pressure-feed amount during the pressure-feed stroke is thereby improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a fuel supply pump, and more particularly to a fuel supply pump for pumping fuel to a common rail in a common rail type fuel injection system.

[0002]

2. Description of the Related Art Conventionally, for example, regarding a fuel injection control of an engine, a method of increasing an injection pressure and optimally controlling injection conditions such as a fuel injection timing and an injection amount in accordance with an operation state of the engine is known. A common rail fuel injection system is known. The common rail type fuel injection system stores a working fluid for fuel injection control pressurized to a predetermined pressure by a pump in a common rail in a pressurized state, and uses an operating fluid pressure to dispose an injector arranged in each cylinder. It is a system that operates to inject fuel from the injector into the corresponding combustion chamber. A controller controls the operation of a control valve provided in each injector so that fuel is injected in each injector under optimal injection conditions for the operating state of the engine.

[0003] In the fuel flow path from the common rail to the injection hole formed at the tip of each injector through the fuel supply pipe, a fuel pressure equivalent to the injection pressure always acts, and each injector supplies the fuel through the fuel supply pipe. An on-off valve for performing control to pass or shut off the fuel to be supplied and an electromagnetic actuator for opening and closing the on-off valve. The controller controls the pressure of the common rail and the operation of the electromagnetic actuator of each injector so that the pressurized fuel is injected in each injector under optimal injection conditions for the operating state of the engine. In addition, common rail fuel injection of a type in which engine oil is stored in a common rail as a working fluid and fuel supplied to a pressure increasing chamber in the injector is increased to a predetermined pressure by oil pressure supplied from the common rail to a pressure chamber of the injector. A system has also been proposed.

A conventional common rail fuel injection system will be described with reference to FIG. The fuel sucked from the fuel tank 7 by the feed pump 6 is sent to the fuel supply pump 1. The fuel supply pump 1 is, for example, a plunger-type variable displacement high-pressure pump driven by an engine, and pumps fuel to a common rail 2. The supplied fuel is stored in the common rail 2 in a pressure accumulated state, and is supplied to the injector 3 from the common rail 2. In general, a plurality of injectors 3 are provided corresponding to the respective cylinders in accordance with the type of the engine, and inject fuel supplied from the common rail 2 into each corresponding combustion chamber.

The fuel supply pump 1 includes a pump driving cam 10 driven by the output of the engine, and a plunger 11 which reciprocates in contact with the pump driving cam 10. The top surface of the plunger 11 is a pump chamber. Twelve wall surfaces are formed. The fuel delivered by the feed pump 6 flows into the pump chamber 12 through the fuel passage 13.
An inlet valve 15 is provided in the fuel passage 13 and controls an amount of fuel flowing into the pump chamber 12 through the fuel passage 13. A fuel discharge passage 14 connecting the discharge side of the pump chamber 12, that is, the pump chamber 12 and the common rail 2.
Is provided with a check valve 17.

The common rail 2 is provided with a normally closed relief valve 20 to prevent the common rail pressure from abnormally increasing due to a system abnormality or the like. The normally closed relief valve 20 opens when the common rail pressure becomes higher than a predetermined set pressure, releases the fuel in the common rail 2 to the fuel tank 7 through the discharge path 21, and reduces the fuel pressure in the common rail 2. Lower. The fuel stored in the common rail 2 is supplied to the injector 3 through the fuel supply pipe 23. The common rail pressure Pr detected by the pressure sensor 22 provided on the common rail 2 is input to a controller 8 which is an electronic control module (ECM) of the engine.

[0007] The injector 3 is hermetically attached to a hole provided in a base such as a cylinder head (not shown) by a seal member. The injector 3 includes a needle valve 31 that can reciprocate in the injector body, and an injection hole 32 that opens when the needle valve 31 is lifted and injects fuel into a combustion chamber (not shown). Top surface 33 of needle valve 31
Forms a part of the wall surface of the balance chamber 30 to which the fuel pressure from the fuel supply pipe 23 is supplied. A fuel passage 34 connected to the fuel supply pipe 23 communicates with a fuel reservoir 35 formed around the needle valve 31. Fuel pool 35
And a second tapered surface 37 formed at the tip of the needle valve 31 and seated on the tapered valve seat of the injector body to open and close the injection hole 32. Acts to give a lift force to the needle valve 31. On the other hand, a pressing force based on the fuel pressure in the balance chamber 30 and a returning force of a return spring (not shown) act on the needle valve 31. The lift of the needle valve 31 is controlled by the balance between the lift force, the pushing force, and the return force.

The high-pressure fuel in the common rail 2 is supplied to the balance chamber 30 through a fuel supply pipe 23 constituting a part of a fuel flow path and a supply path 38 branched from the fuel supply pipe 23. An orifice 39 is provided in the supply path 38. In order to control the fuel pressure in the balance chamber 30, the balance chamber 30 is provided with a discharge path 40. The discharge passage 40 is also provided with an orifice 41, and the effective passage cross-sectional area of the orifice 41 is equal to orifice 39.
Is set so as to be larger than the effective passage cross-sectional area. Further, the discharge path 40 is connected to the fuel return pipe 4 by the discharge path 40.
An on-off valve 44 for opening the valve 6 is provided.

When the on-off valve 44 provided in the discharge passage 40 is opened under the control of the controller 8, the orifice 39 restricts the flow of fuel more strongly than the orifice 41, so that the fuel pressure in the balance chamber 30 is reduced. descend. When the lifting force for lifting the needle valve 31 exceeds the combined force of the pressing force based on the fuel pressure in the balance chamber 30 and the spring force of the return spring, the needle valve 31 is lifted. When the needle valve 31 is lifted, the injection hole 32 is opened.
The fuel guided from the common rail 2 to the injector 3 through the fuel supply pipe 23 and the fuel passage 34 passes through a passage around the needle valve 31 from an injection hole 32 formed at the tip of the nozzle into a combustion chamber (not shown). It is injected. The fuel flowing out of the balance chamber 30 through the discharge passage 40 and not consumed for injection into the combustion chamber is collected in the fuel tank 7 through the fuel return pipe 46.

The controller 8 includes an engine speed Ne.
Detection signals are input from various sensors 9 such as an engine speed sensor for detecting the acceleration and an accelerator pedal depression amount sensor for detecting the accelerator pedal depression amount Ac. The common rail pressure Pr detected by the common rail pressure sensor 22 is input to the controller 8. Other input signals to the controller 8 include a cooling water temperature sensor, an engine cylinder discrimination sensor, a top dead center detection sensor, an atmospheric temperature sensor,
There are signals from various sensors for detecting the operating state of the engine, such as an atmospheric pressure sensor and an intake pipe pressure sensor.

The controller 8 controls the opening and closing of the on-off valve 44 and the lift control of the needle valve 31 in accordance with a target injection characteristic set based on the detection signal from each of the sensors 9 and a previously determined injection characteristic map. I do. The target injection characteristics determine the fuel injection conditions by the injector 3, that is, the fuel injection timing and the injection amount, so that the engine output becomes an optimum output according to the operating state of the engine. The opening / closing control of the opening / closing valve 44 is performed by the electromagnetic solenoid 4.
5, the timing and amount of fuel injection are determined by the injection pressure (substantially equal to the common rail pressure) and the lift of the needle valve 31 (lift amount, lift period). The drive current determined based on the command pulse output from the controller 8 is sent to the electromagnetic solenoid 45, and the needle valve 3
One lift is controlled.

For example, the relationship between the fuel injection amount of the injector 1 and the pulse width of the command pulse output by the controller 8 is determined by a map using the common rail pressure Pr (fuel pressure in the common rail 2) as a parameter. Since fuel injection is started or stopped with a certain time delay from the falling time and rising time of the command pulse, it is possible to control the injection timing by controlling when the command pulse is turned on or off. It is. A constant relationship between the basic injection amount and the engine speed is previously given as a basic injection amount characteristic map using the accelerator pedal depression amount Ac as a parameter, and the fuel injection amount for each combustion cycle depends on the operating state of the engine. Is calculated from the basic injection amount characteristic map in accordance with. In the illustrated example, only one injector 3 is shown, but the engine is a multi-cylinder engine such as a four-cylinder or six-cylinder engine, and a controller 8 is provided for each injector 3 arranged corresponding to each cylinder. Perform fuel injection control.

[0013] In a fuel supply pump used in a common rail type fuel injection system, a sudden pumping of fuel causes vibration and noise of an engine. In particular, in an engine in which the fuel supply pump mounted on the cylinder head and the common rail, and the common rail and the injector are each directly connected,
There is a problem that the vibration generated in the fuel supply pump is transmitted to the common rail and the injector to increase engine noise.

In a conventional fuel supply pump in which a plunger is reciprocated by a pump driving cam, the pump driving cam has a symmetrical cam profile with respect to a radial reference line connecting the apex of the cam peak and the rotation center. Alternatively, it has a profile in which the fuel is slowly sucked into the pump chamber and the fuel is rapidly pumped from the pump chamber. Such a cam profile ensures that in line pumps the required fuel pumping rate during short pumping periods is
This is due to the fact that it is designed in response to the requirement of increasing the fuel discharge pressure.

Since the injection pressure of the fuel injected from the injector 3 is substantially equal to the pressure of the fuel stored in the common rail 2, the injection pressure can be controlled by controlling the common rail pressure. Although the common rail pressure Pr decreases due to the fuel being injected by the injector 3 and the fuel in the common rail 2 being consumed, the controller 8 controls the pressure of the common rail 2 by controlling the pumping amount of the fuel supply pump 1. I do. That is, the common rail pressure Pr
In accordance with the pumping amount of the fuel supply pump 1, if the operating state of the engine is constant, a constant pressure corresponding to the state is maintained, or if the operating state of the engine is changed, The pressure is controlled to increase or decrease in pressure so as to be optimal for the operating state of the engine.

The control of the pressure of the common rail 2 is performed in such a manner that a target common rail pressure is determined in accordance with the operation state of the engine, and a deviation between the target common rail pressure and the actual pressure of the common rail 2 detected by the pressure sensor 22 is eliminated. This is performed by feedback-controlling the pumping amount of the fuel supply pump 1, that is, the pumping amount associated with one plunger lift.

In the common rail type fuel injection system shown in FIG. 3, the amount of pressure supplied by the fuel supply pump 1 is controlled by an inlet valve 15. Inlet valve 15
Controls the pumping amount of the fuel pump 1 by exciting the electromagnetic solenoid 16 with a control current from the controller 8. That is, at any time during the ascent stroke of the plunger 11, the electromagnetic solenoid 16 is energized and the inlet valve 1
When the valve 5 is opened, the plunger 11 is operated during its operation.
Is returned to the fuel passage 13 through the inlet valve 15 and is not pumped to the fuel discharge passage 14. The period from when the inlet valve 15 is closed to when the plunger 11 reaches the top dead center is the fuel pumping period. By controlling the pumping period, that is, the closing period of the inlet valve 15, the pumping amount of the fuel supply pump 1 can be controlled, and the common rail pressure, that is, the injection pressure is controlled by the pumping amount of the fuel supply pump 1. can do. Since the upper limit of the fuel pressure (feed pressure) in the fuel passage 13 is limited by the relief valve 18, excess fuel sent by the feed pump 6 is returned to the fuel tank 7 through the relief valve 18 and the return pipe 19. .

As one method of controlling the pumping amount of the fuel supply pump, if the inlet valve is closed while the plunger is in the pumping stroke, the fuel sucked into the pump chamber is pumped to the discharge side. There is known a pre-stroke control in which the fuel in the pump chamber returns through the inflow passage when the inlet valve is opened to control the valve operation timing of the on-off valve in the inflow passage.

[0019]

When a pump drive cam for driving a plunger of a fuel supply pump has a cam profile for rapidly pumping fuel from a pump chamber, the fuel supply is caused by an oil hammer generated in the fuel. The pump generates vibration and noise. When a common rail fuel injection system is applied, this oil hammer also spreads to the common rail, which prevents accurate detection of the common rail pressure by the pressure sensor. Therefore, in the fuel supply pump, there is a problem to be solved in that attention is paid to the cam profile of the pump driving cam so as to prevent instantaneous sudden increase in pressure of the fuel to be pumped.

Further, in order to accurately control the fuel injection, it is necessary to accurately control the common rail pressure to the target pressure. Accurate control of the common rail pressure requires accurate control of the pumping amount of the fuel supply pump. For a fuel supply pump of the type that controls the pumping amount by pre-stroke control, the on-off valve of the inflow passage is closed. It is necessary to control the timing accurately. The rotation speed of the pump drive shaft provided with the pump drive cam is generally considered to be constant during one rotation, and the amount of fuel pumped is determined by the amount of lift of the plunger. It is important how to accurately control the closing timing of the on-off valve of the inflow passage and the lift position of the plunger.
That is, it is difficult to remove variations and errors in the closing timing of the on-off valve of the inflow passage. Therefore, if the lift speed of the plunger is high, the lift position of the plunger at the time when the on-off valve closes greatly fluctuates. . Therefore, when the plunger is in the pumping stroke, even if there is variation or error in the closing timing of the on-off valve of the inflow passage, the change in the lift position of the plunger when the on-off valve closes is reduced, and the fuel pumping amount is reduced. There is a problem that needs to be solved in terms of increasing the decomposition ability.

[0021]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel supply pump for pumping fuel in a pump chamber by a plunger reciprocated by driving a pump driving cam. When the plunger is in the pumping stroke, the on-off valve arranged in the inflow passage to the pump chamber closes even if there is variation or error in the closing timing of the on-off valve in the inflow passage. The change in the lift position of the plunger during the period is reduced to improve the decomposition capacity of the fuel pumping amount, and as a result, it is possible to accurately control the common rail pressure and accurately perform the fuel injection such as the fuel injection amount. It is to provide a fuel supply pump. Another object of the present invention is to provide a fuel supply pump in which, when applied to a common rail fuel injection system, the pressure of fuel stored under pressure in the common rail is not disturbed by oil hammer.

According to the present invention, there is provided a pump cylinder formed in a pump body, a plunger reciprocating in the pump cylinder, and formed by the pump cylinder and the plunger provided on a pump drive shaft and pressing the plunger. A pump driving cam for pumping the fuel in the pump chamber, wherein the pump driving cam adjusts the rotation angle range of the pump drive shaft corresponding to the pressure feeding stroke of the plunger to the pump stroke corresponding to the suction stroke of the plunger. The present invention relates to a fuel supply pump having a cam profile which is wider than a rotation angle range of a shaft, and has a cam profile in which a lift amount of the plunger per rotation angle of the pump drive shaft in a pumping stroke of the plunger is moderately increased.

According to the fuel supply pump of the present invention, the pump driving cam changes the rotation angle range of the pump driving shaft corresponding to the pressure feeding stroke of the plunger to the rotation angle of the pump driving shaft corresponding to the suction stroke of the plunger. Since the cam profile has a width larger than the range and the amount of lift of the plunger per rotation angle of the pump drive shaft during the pumping stroke of the plunger is moderated, the rotation of the pump drive shaft during one rotation is achieved. When the speed is considered to be uniform, the pump drive cam is driven before the pumping top dead center by the amount of increase in the amount of lift of the plunger per rotation angle of the pump drive shaft, i.e., per hour. It becomes smaller than the magnitude of the decrease in the lift amount of the plunger later. Since the plunger lift per rotation angle of the pump drive shaft is defined by the cam profile of the pump drive cam, the plunger reciprocally driven by the pump drive cam rises gently before the top dead center of the pumping stroke and reaches the end of the pumping stroke. The pumping of the fuel in the stages is moderated, and the pumped fuel does not suffer a great oil hammer.

In this fuel supply pump,
The pump body has a fuel passage connected to the pump chamber for supplying fuel to the pump chamber, and an inlet valve for opening and closing the fuel passage. The inlet valve is provided with the plunger. The valve is closed at a predetermined timing during the pressure feeding stroke, whereby pre-stroke control for adjusting the amount of fuel sucked into the pump chamber to the fuel passage is performed. In the pre-stroke control, the inlet valve is closed at a predetermined timing when the plunger is in the pressure-feeding stroke, and during the period until the valve is closed, the fuel sucked into the pump chamber is returned to the suction side, and after the valve is closed. The fuel is pumped to the discharge side in the stroke before the top dead center. The lift speed of the plunger is suppressed as compared with the case of the symmetrically formed cam profile, and the lift position of the plunger at which fuel pumping starts when the on-off valve is closed depends on the closing time of the on-off valve. Even if there are variations or errors in the data, the fluctuation range is reduced. Therefore, even if there is a variation or error in the closing timing of the on-off valve when the plunger is in the pumping stroke, the ability to resolve the fuel pumping amount is improved.

Further, the fuel supply pump is provided corresponding to each cylinder of the engine and a common rail for storing the fuel pumped from the fuel supply pump in a pressurized state, and supplies the fuel supplied from the common rail to each of the cylinders. An injector for injecting the fuel into the combustion chamber of the cylinder, a detecting means for detecting an operating state of the engine, and an injection condition of fuel to be injected from the injector based on a detection signal from the detecting means; The present invention is applied to a common rail type fuel injection system including a controller for controlling the fuel pressure of the injector and the fuel injection from the injector.

When applied to a common rail type fuel injection system, the fuel supply pump, the common rail and the injector are mounted on a cylinder head of the engine, and the fuel supply pump and the common rail are directly connected to each other. The common rail and the injector are directly connected to each other. If the fuel supply pump is directly connected to the common rail,
The oil hammer generated by the fuel supply pump is immediately transmitted to the common rail, which not only prevents accurate detection of the common rail pressure, but also causes the fuel supply pump to resonate with the common rail, causing vibration and noise. Since the occurrence of oil hammer in the fuel supply pump is suppressed, vibration and noise caused by such oil hammer can also be suppressed.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fuel supply pump according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a fuel supply pump according to the present invention, and FIG. 2 is an exploded perspective view showing an upper structure of a cylinder head to which the fuel supply pump is applied. The common rail type fuel injection system itself to which the fuel supply pump is applied can employ the system shown in FIG. 3 except for the specific configuration of the fuel supply pump.
Therefore, a repeated description of the common rail fuel injection system to which the fuel supply pump according to the present invention is applied will be omitted. The same applies to the injector applied to the common rail type fuel injection system.

Referring to FIGS. 1 and 2, the fuel supply pump 80 of the present invention is mounted on a cylinder head together with the common rail 50 and the injector 60. Further, a common rail 50 is directly connected to the fuel supply pump 80, and an injector 60 is further directly connected to the common rail 50 via an injector arm 61. The injector 60 includes an electromagnetic actuator 62 of a piezoelectric element type stacked to release the fuel pressure in the balance chamber 30.

Referring to FIG. 2, the cylinder head 70
(Or its upper structure) includes a plurality of valve driving cams 73,
The cam shafts 71 and 72 integrally formed with the respective cams 74 are rotatably held by brackets 75. The valve drive cams 73 and 74 drive intake and exhaust valves for opening and closing an intake port and an exhaust port that open to the combustion chamber of the engine. Each injector 60 has four valve drive cams 7.
It is inserted from above into the space surrounded by 3, 74, and mounted in a sealed state via a seal member in a hole (not shown) provided in the cylinder head 70, so that it is assembled to the engine. The fuel supply pump 80 is fixed to the bracket 76 of the cylinder head 80 at a fixing portion 81a (see FIG. 1) protruding from the pump body 81.

The torque from the output shaft of the engine is input to the camshaft 71 from the input end 77a, and rotates the pump drive cam 77 provided integrally with the camshaft 71. The plunger 83 of the fuel supply pump 80 reciprocates in the pump cylinder 82 formed in the pump body 81 by the cam action of the rotating pump drive cam 77. A spring 85 is provided between the plunger 83 and the pump body 81, and the plunger 83 always moves following the cam surface of the pump driving cam 77 by the action of the spring 85. Between the pump cylinder 82 and the plunger 83, a pump chamber 84 for sucking and pumping fuel is formed. The plunger 83 has a bottom dead center A most protruding from the pump cylinder 82 shown by a solid line and a pump cylinder 82 shown by an imaginary line.
Reciprocate with the top dead center B that has entered most. When the plunger 83 occupies the bottom dead center A, the volume of the pump chamber 84 becomes maximum, and when the plunger 83 occupies the top dead center B, the volume of the pump chamber 84 becomes minimum.

The fuel supplied from the feed pump 6 (see FIG. 3) to the fuel supply pump 80 through the fuel passage 13 passes through the passage 13a in the pump body 81, and flows into the inflow chamber 86 formed in the upper part of the pump body 81. Leads to. An inflow passage 87 constituting a part of the fuel passage is formed between the pump chamber 84 and the inflow chamber 86, and the inflow chamber 86 and the pump chamber 84 are connected by an inlet valve 88 so as to be able to communicate and shut off. ing. The inlet valve 88 includes a valve stem 89 extending with a gap in the inflow passage 87, a valve head 90 disposed on the pump chamber 84 side of the valve stem 89,
And a spring 91 for urging the valve stem 89 and the valve head 90 in the valve opening direction. A check valve 13b for returning fuel from the low-pressure chamber 103 to the fuel passage 13 is provided between the fuel passage 13 and the low-pressure chamber 103 in which fuel leaking around the plunger 83 is stored.

The head 92 of the valve stem 89 is connected to the pump body 8.
The pressure control chamber 94 is formed by fitting into a hole formed in the adapter 93 mounted on the top surface of the first adapter 1. A part of the fuel is introduced into the pressure control chamber 94 from the passage 13 a through passages 100 and 95 formed in the adapter 93. When the passage 95 is closed by the on-off valve 96 during the pumping stroke of the plunger 83, the fuel in the pressure control chamber 94 does not escape through the passage 95 when the inlet valve 88 attempts to lift by the pressure of the pump chamber 84. The valve 88 is prevented from lifting, but when the on-off valve 96 is opened and the passage 95 is opened, the fuel pressure in the pressure control chamber 94 is released and decreases, and the inlet valve 88 is lifted by the pressure in the pump chamber 84. It becomes possible. Therefore, the fuel pressure in the pressure control chamber 94 is maintained or released in accordance with whether the on-off valve 96 is opened or closed in the pressure feeding stroke of the plunger 83,
It is possible to control the opening and closing of the inlet valve 88, that is, the communication between the pump chamber 84 and the inflow chamber 86 through the inflow passage 87 or the cutoff thereof. The on-off valve 96 includes a valve body 97 that can open and close the outlet of the inflow passage 87, a solenoid 98 that drives the valve body 97 in the valve closing direction, and a spring 99 that urges the valve body 97 in the valve opening direction. ing.

When the plunger 83 is in the suction stroke with the on-off valve 96 opened, the pump chamber 84 is under negative pressure, the inlet valve 88 is opened, and the inflow chamber 8 is opened.
The fuel flows into the pump chamber 84 from the inlet 6 through the inflow passage 87. When the plunger 83 is in the pumping stroke, the fuel in the pump chamber 84 is pressurized, so that the valve head 90 of the inlet valve 88 is seated on the valve seat formed at the inlet of the inflow passage 87 and the inlet valve 88 is closed. . The fuel pressurized in the pump chamber 84 is sent to the common rail 50 (see FIG. 2) through the discharge passage 102 by opening the check valve 101 provided on the discharge side. The fuel supply pump 80 and the common rail 50 are not connected by a fuel pipe, and the high-pressure fuel pumped from the fuel supply pump 80 is directly supplied to the common rail 50.

In the fuel supply pump 80, the opening and closing valve 96 is closed at an early stage of the pressure feeding stroke of the plunger 83 to open the inlet valve 88. As the volume in the pump chamber 84 decreases, the inside of the pump chamber 84 decreases. The fuel is returned to the inflow side through the inflow passage 87, and thereafter, the on-off valve 96 is opened to close the inlet valve 88, and the fuel is pumped as the volume of the pump chamber 84 decreases with the lift of the plunger 83. Is performed, that is, the pre-stroke control of the fuel pumping amount becomes possible.

The pump drive cam 77 has a cam profile in which the rotation angle range θe of the pump drive shaft 77a corresponding to the pressure feeding stroke of the plunger 83 is wider than the rotation angle range θi of the pump drive shaft 77a corresponding to the suction stroke of the plunger 83. have. The cam profile 78 in a relatively wide rotation angle range θe corresponding to the pumping stroke has a smooth curved surface such that the lift amount of the plunger 83 per rotation angle of the pump drive shaft 77a gradually increases before the pumping top dead center. is there. In a relatively narrow rotation angle range θi corresponding to the suction stroke, the plunger 83 descends rapidly. That is, the rotation center axis O of the pump drive shaft 77a is
If the radius of the base circle from R is R and the direction of rotation of the pump drive shaft 77a is the direction indicated by C, the cam profile 78 for lifting the plunger 83 has a rotation angle range θe
, The radius r of the cam gradually increases toward the maximum radial position 78a corresponding to the top dead center of the lift. The cam profile 79 on the side for lowering the plunger 83 beyond the apex of the cam has a rotation angle range θ.
The shape is such that the radius r of the cam rapidly decreases from the maximum radius position 78a corresponding to the lift top dead center over i.

When the pump drive shaft 77a rotates at a uniform rotational speed, the fuel in the pump chamber 84 is gently pumped before the top dead center B of the plunger 83, and the oil hammer generated in the fuel is reduced. . Therefore, vibration and noise generated in the fuel supply pump 80 and the common rail 50 directly connected to the fuel supply pump 80 can be suppressed, and the fuel pressure in the common rail 50 greatly fluctuates due to the above-mentioned oil hammer. Can be suppressed,
It is possible to detect the common rail pressure Pr that is less affected by oil hammer. After the fuel pumping, the plunger 83 descends rapidly, sucks the fuel into the pump chamber 84 rapidly, and prepares for the next fuel pumping.

In the case of performing the pre-stroke control, the inlet valve 88 is closed at a predetermined timing when the plunger 83 is in the pressure-feeding stroke, and the fuel sucked into the pump chamber 84 flows until the valve closes. The fuel is returned to the suction side through the passage 87, and the fuel is pressure-fed to the discharge side in a stroke before the top dead center of the pressure feeding after the valve is closed. Even when the rotation speed of the pump drive shaft 77a is high, the lift speed of the plunger 83 can be suppressed as compared with the case of a cam profile formed symmetrically. Therefore, even if there is a variation or an error in the closing timing of the inlet valve 88 provided in the inflow passage 87, the fluctuation of the lift position at which the fuel pumping of the plunger 83 is started is reduced, and the plunger during the pumping stroke is reduced. The decomposition ability of the fuel pumping amount is improved.

[0038]

According to the fuel supply pump of the present invention, the plunger lift amount per rotation angle of the pump drive shaft is defined by the cam profile of the pump drive cam. The fuel gradually rises before the top dead center, and the fuel pumping at the final stage of the pumping stroke can be moderated, so that a large oil hammer does not occur in the fuel being pumped. Therefore, in the fuel supply pump, it is possible to suppress the generation of noise and vibration caused by the fuel pumping of the plunger. In addition, when the fuel supply pump is applied to a common rail type fuel injection system arranged on a cylinder head in a state where the fuel supply pump and the common rail are directly connected, oil hammer transmitted to the common rail is also suppressed, The generation of vibration and noise due to resonance between the fuel supply pump and the common rail can be reduced.

When the fuel supply pump is applied to a common rail fuel injection system, the fuel pumped from the fuel supply pump is stored in the common rail in a state of accumulated pressure, and the controller detects the operating state of the engine including the common rail pressure. The control of the injector for injecting the fuel supplied from the common rail into the combustion chamber is performed based on the target fuel injection condition obtained in accordance with the detection signal from the detecting means. In this case, the pressure sensor provided on the common rail can detect the common rail pressure that is less affected by the oil hammer from the fuel supply pump, and is expected to operate the common rail fuel supply pump injection system more accurately. it can.

Further, the closing timing of the on-off valve of the inflow passage and the lift position of the plunger can be accurately controlled. In a fuel supply pump of the type in which the amount of pressure feed is controlled by pre-stroke control, the inflow passage is opened and closed. By precisely controlling the closing timing of the valve, it is possible to improve the decomposition ability of the fuel pumping amount determined by the lift amount of the plunger. Therefore, the pumping amount of the fuel supply pump is accurately controlled, the pressure of the common rail is accurately controlled to the target pressure based on the operation state of the engine, and the fuel injection is accurately performed so as to satisfy the injection condition according to the operation state of the engine. Can be controlled.

[Brief description of the drawings]

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

FIG. 2 is an exploded perspective view of a common rail type fuel injection system to which the fuel supply pump according to the present invention is applied.

FIG. 3 is a schematic diagram showing a conventional common rail fuel injection system.

[Explanation of symbols]

 8 Controller 22 Pressure Sensor 50 Common Rail 60 Injector 70 Cylinder Head 77a Pump Drive Shaft 77 Pump Drive Cam 78, 79 Cam Profile 80 Fuel Supply Pump 81 Pump Body 82 Pump Cylinder 83 Plunger 84 Pump Chamber 87 Inflow Passage (Fuel Passage) 88 Inlet Valve

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 47/00 F02M 47/00 E 55/02 330 55/02 330A 350 350E 59/36 59/36 59 / 46 59/46 Y 61/14 320 61/14 320A F term (reference) 3G024 AA04 AA18 BA29 DA18 FA02 FA05 3G066 AA07 AB02 AC01 AC09 AD02 AD05 AD12 BA12 BA22 BA65 CA01S CA03 CA04T CA04U CA08 CA09 CA22T CA34 CB01 CB04 CC05 CB05 CC12 CC CC14 CC26 CC64U CC66 CC67 CC68T CC70 CD04 CD25 CD26 CE04 CE27 DC18 3G301 HA02 JA37 LB13 MA11 ND01 PB08A PB08Z

Claims (4)

[Claims] 1. A pump cylinder formed in a pump body, a plunger reciprocating in the pump cylinder, and a pump drive shaft formed by the pump cylinder and the plunger by pressing the plunger. A pump drive cam for pumping fuel in the pump chamber;
The pump drive cam is configured to increase a rotation angle range of the pump drive shaft corresponding to a pressure stroke of the plunger than a rotation angle range of the pump drive shaft corresponding to a suction stroke of the plunger. A fuel supply pump having a cam profile in which an increase in the lift amount of the plunger per rotation angle of the pump drive shaft is moderated. 2. The pump body has a fuel passage connected to the pump chamber for supplying fuel into the pump chamber, and an inlet valve for opening and closing the fuel passage. Since the inlet valve is closed at a predetermined timing when the plunger is in the pressure feeding stroke, the pre-stroke control for adjusting the amount of fuel sucked into the pump chamber to the fuel passage is performed. The fuel supply pump according to claim 1, comprising: 3. The fuel supply pump according to claim 1, wherein the fuel supply pump is provided corresponding to each cylinder of an engine and stores a fuel supplied from the fuel supply pump in a pressure-accumulated state. An injector for injecting the fuel into the combustion chamber of the cylinder, a detecting means for detecting an operating state of the engine, and an injection condition of fuel to be injected from the injector based on a detection signal from the detecting means; The fuel supply pump according to claim 1, wherein the fuel supply pump is applied to a common rail fuel injection system including a controller that controls a fuel pressure of the fuel and a fuel injection from the injector. 4. The fuel supply pump, the common rail, and the injector are attached to a cylinder head of the engine, the fuel supply pump and the common rail are directly connected to each other, and the common rail and the injector are directly connected to each other. 4. The fuel supply pump according to claim 3, comprising: