JP7025997B2 - Pulsation damper - Google Patents

Description

The present invention relates to a pulsation damper capable of suppressing pressure fluctuations of low pressure fuel sucked into a fuel pump.

Conventionally, for example, as a fuel supply system for a diesel engine, a fuel pump for increasing the pressure of low-pressure fuel pumped from a fuel tank and a pressure accumulator chamber for storing high-pressure fuel discharged from the fuel pump are provided, and the high-pressure fuel in the accumulator chamber is used as fuel. A pressure-accumulation type fuel supply system that injects fuel from an injection valve into an engine cylinder is known. The fuel pump is configured to operate by the rotation of the engine, and the plunger reciprocates in synchronization with the rotation of the engine, and the fuel is pressurized in the pressurizing chamber according to the reciprocating movement. In addition, the fuel pump is provided with a metering valve that opens and closes the suction port of the pressurizing chamber, and by adjusting the closing timing of the metering valve, the fuel discharge amount from the pressurizing chamber can be set as the target fuel discharge amount. I try to control it.

In the technique described in Patent Document 1, the valve closing timing of the metering valve is learned and corrected based on the pressure in the accumulator chamber (that is, the discharge pressure of the fuel pump) during the operation of the fuel pump. Specifically, the discharge pressure is detected for each reciprocating cycle of the plunger, and the metering valve is closed in the current reciprocating cycle based on the deviation between the discharge pressure detected in the previous reciprocating cycle and the target pressure. By learning and correcting the timing, the fuel discharge amount becomes the target fuel discharge amount.

Japanese Patent Application Laid-Open No. 2003-322048

The technique described in Patent Document 1 is a technique for suppressing a fluctuation in the fuel discharge amount when the fluctuation occurs. Apart from such a technique, there is a demand for a technique for suppressing fluctuations in the fuel discharge amount. One of the causes of fluctuations in the amount of fuel discharged is fluctuations in the pressure of the low-pressure fuel supplied to the fuel pump. When the fuel is repeatedly sucked and discharged in the fuel pump, the low pressure fuel supplied to the fuel pump fluctuates in pressure, and the fuel discharge amount fluctuates based on the pressure fluctuation. Therefore, there is a demand for a technique for suppressing pressure fluctuations in the low-pressure fuel supplied to the fuel pump.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a pulsation damper capable of suppressing pressure fluctuations of a low-pressure fuel supplied to a fuel pump.

The present invention comprises a fuel pump that sucks and pumps fuel in a pressurizing chamber by reciprocating a plunger, a suction passage that supplies low-pressure fuel from a fuel tank to the fuel pump, and the suction passage at a branch point on the suction passage. A pulsation damper applied to a fuel supply system including a return passage for branching from a passage and returning fuel to the fuel tank, wherein the pressure in the suction passage is higher than the reference pressure. In this case, the valve body that moves from the closed position to the open position and causes the fuel in the suction passage to flow out to the return passage is provided integrally with the valve body and is based on the force received in the opening / closing direction of the valve body. A damper portion having a higher responsiveness to the pressure in the suction passage than the valve body is provided.

When fuel is repeatedly sucked and discharged in the fuel pump, pressure variation occurs in the suction passage. This pulsation damper responds based on the force received in the opening / closing direction of the valve body, and includes a damper portion having a higher responsiveness to the pressure in the suction passage than the valve body. Therefore, when the damper section receives a force in the opening / closing direction of the valve body due to the pressure fluctuation of the low pressure fuel in the suction passage, the response of the damper section even if the pressure of the low pressure fuel does not become higher than the reference pressure. Therefore, the pressure fluctuation of the low pressure fuel can be suitably suppressed.

Further, the damper portion is integrally provided with the valve body. If the valve body and the damper part are provided separately, when the pressure fluctuation of the low pressure fuel occurs, the valve body and the damper part respond separately, so that the pressure fluctuation of the low pressure fuel due to resonance or the like occurs. May not be able to be suppressed. In this pulsation damper, since the damper portion is integrally provided on the valve body, it is possible to suppress the occurrence of resonance and the like, and preferably suppress the pressure fluctuation of the low pressure fuel.

Further, the damper portion responds based on the force received in the opening / closing direction of the valve body. Therefore, in the valve body and the damper portion provided integrally, it is possible to smoothly switch from the response of the damper portion to the movement of the valve body in accordance with the pressure fluctuation of the low-pressure fuel.

The block diagram which shows the outline of the fuel injection system. The figure for demonstrating the structure and operation of a high pressure pump. The figure which shows the transition of the suction pressure with the reciprocating movement of a plunger. The block diagram which shows the outline of a high pressure pump and a damper. The block diagram which shows the outline of the damper which concerns on 1st Embodiment. The block diagram which shows the outline of the damper which concerns on 2nd Embodiment. The block diagram which shows the outline of the damper which concerns on 3rd Embodiment. The figure which shows the transition of the suction pressure when the fluctuation of the suction pressure occurs.

(First Embodiment)
Hereinafter, the fuel injection system 100 to which the pulsation damper (hereinafter referred to as a damper) 70 according to the first embodiment will be described with reference to the drawings. The fuel injection system 100 is a common rail fuel injection system for a vehicle diesel engine. In this embodiment, the fuel injection system 100 corresponds to the "fuel supply system".

FIG. 1 is a block diagram showing an outline of the fuel injection system 100. In FIG. 1, a multi-cylinder diesel engine (hereinafter referred to as an engine) 10 is provided with an electromagnetic injector 11 for each cylinder, and these injectors 11 are connected to a common rail (accumulation pipe) 12 common to each cylinder. A high-pressure pump 13 as a fuel pump is connected to the common rail 12. The high-pressure pump 13 sucks the low-pressure fuel pumped from the fuel tank 16 by the feed pump 15 through the low-pressure passage 36, pressurizes it, and discharges it to the common rail 12 through the high-pressure passage 41. As a result, the high-pressure fuel is stored in the common rail 12. In this embodiment, the low pressure passage 36 corresponds to the "suction passage".

Next, the structure and operation of the high-pressure pump 13 will be described with reference to FIG. The high-pressure pump 13 is provided with a cylinder 31 in the pump body, and the plunger 32 is housed in the cylinder 31 so as to be reciprocating. One end of the plunger 32 is in contact with the cam ring 33. The cam ring 33 is fixed to the cam shaft 34 connected to the crank shaft, and rotates by the rotation of the crank shaft accompanying the engine drive. The plunger 32 reciprocates with the rotation of the cam ring 33.

A pressurizing chamber 35 is provided in the cylinder 31 adjacent to the plunger 32. The low pressure passage 36 and the high pressure passage 41 are connected to the pressurizing chamber 35. The fuel in the low pressure passage 36 is sucked in accordance with the movement of the plunger 32, and the sucked fuel is pressurized and pumped from the pressurizing chamber 35.

A fuel pressure sensor 18 is provided in the low pressure passage 36, and the fuel pressure sensor 18 detects the fuel pressure (hereinafter referred to as suction pressure) PB in the low pressure passage 36. In this embodiment, the suction pressure PB corresponds to the "pressure in the suction passage".

A metering valve 38 is provided on the low pressure passage 36 side of the high pressure pump 13. The metering valve 38 is, for example, an electromagnetic flow rate control valve (PCV), and is configured as a normally open valve that opens when the power is off. Specifically, a solenoid 39 is provided around the metering valve 38, and the low-voltage passage 36 is opened and closed by the magnetic force generated by the drive current In flowing through the solenoid 39 (see FIG. 2A). The metering valve 38 is not limited to the electromagnetic flow rate control valve, but may be a piezoelectric type flow rate control valve. The solenoid 39 closes the metering valve 38 by supplying a drive current In during the pumping period Tp (see FIG. 2B). Then, after the drive current In is supplied to the solenoid 39 only for a predetermined time, the supply is cut off. Hereinafter, supplying the drive current In to the solenoid 39 is referred to as energizing the metering valve 38.

A discharge valve 42 is provided on the high pressure passage 41 side of the high pressure pump 13. The discharge valve 42 is composed of a well-known check valve, and only allows fuel to flow out from the pressurizing chamber 35 according to the fuel pressure of the pressurizing chamber 35, and fuel is supplied from the common rail 12 to the pressurizing chamber 35. Regulate the inflow.

During the suction period Tb where the volume in the pressurizing chamber 35 increases, the metering valve 38 is opened because the energization of the metering valve 38 is cut off. That is, the pressurizing chamber 35 and the low pressure passage 36 are in a communicating state. At this time, with the metering valve 38 open, the plunger 32 moves from the top dead center (TDC) to the bottom dead center (BDC), and the volume of the pressurizing chamber 35 increases (FIG. 2 (c)). reference). Then, the low-pressure fuel pumped from the feed pump 15 is sucked into the pressurizing chamber 35.

In the pressure feeding period Tp in which the volume in the pressurizing chamber 35 is reduced, when the plunger 32 moves from the bottom dead center to the top dead center, the metering valve 38 is not energized and the valve is kept open to pressurize. The fuel in the chamber 35 flows back to the low pressure passage 36 side. The period before the metering valve 38 is closed is the prestroke period Tk.

Due to this backflow, the suction pressure PB in the low pressure passage 36 before the valve closing start time Tf temporarily rises (see FIG. 2 (d)). The valve closing start time Tf is a time when the valve closing operation of the metering valve 38 is started, and specifically, it is a time when the supply of the drive current In to the solenoid 39 is started. Hereinafter, this temporarily increased suction pressure PB is referred to as a surge pressure Pc.

After that, when the metering valve 38 is closed at the valve closing time Tc, the pressure of the fuel in the pressurizing chamber 35 rises, and the high-pressure fuel increased in pressure due to the pressure rise passes through the common rail via the discharge valve 42. It is discharged to 12. The period during which the high-pressure fuel is discharged to the common rail 12 is the fuel discharge period Ts.

Therefore, the high-pressure pump 13 sucks and pumps fuel in the pressurizing chamber 35 by the reciprocating motion of the plunger 32. Then, the fuel discharge amount Q can be controlled by adjusting the valve closing timing Tc of the metering valve 38, that is, adjusting the prestroke period Tk. That is, the fuel discharge amount Q increases by advancing the valve closing timing Tc of the metering valve 38, and the fuel discharge amount Q decreases by delaying the valve closing timing Tc.

When the metering valve 38 is closed by energization and the pressure in the pressurizing chamber 35 rises, the metering valve 38 is closed due to the fuel pressure in the pressurizing chamber 35 even if the energization to the metering valve 38 is cut off. Is held in. Therefore, as shown in FIG. 2, the energization of the metering valve 38 is cut off before the plunger 32 reaches the top dead center.

Returning to the description of FIG. 1, the common rail pressure sensor 17 is provided on the common rail 12, and the fuel pressure (hereinafter referred to as discharge pressure) PS in the common rail 12 is detected by the common rail pressure sensor 17. Although not shown, the common rail 12 is provided with an electromagnetically driven (or mechanical) pressure reducing valve, and when the discharge pressure PS rises excessively, the pressure reducing valve is opened to reduce the pressure. It has become like.

The ECU 60 is an electronic control unit including a well-known microcomputer including a CPU, ROM, RAM, EEPROM (registered trademark) and the like. In addition to the detection signals of the fuel pressure sensor 18 and the common rail pressure sensor 17, the ECU 60 includes a rotation speed sensor for detecting the rotation speed of the engine 10, an accelerator opening sensor for detecting the accelerator operation amount by the driver, and the temperature of the engine cooling water. Detection signals are sequentially input from various sensors such as a water temperature sensor for detecting the above and a fuel temperature sensor for detecting the fuel temperature in the common rail 12. Then, the ECU 60 determines the optimum fuel injection amount and injection timing based on the engine operation information such as the engine rotation speed and the accelerator opening degree, and outputs the injection control signal corresponding to the optimum fuel injection amount and the injection timing to the injector 11. As a result, fuel injection from the injector 11 to the combustion chamber is controlled in each cylinder.

Further, the ECU 60 sets the target pressure PBtg (see FIG. 3) of the suction pressure PB and the target pressure PStg (see FIG. 3) of the discharge pressure PS based on the engine operation information, and the discharge pressure PS is the target pressure. The fuel discharge amount Q and the like are controlled so as to match PStg.

By the way, when the high pressure pump 13 is in a predetermined operating condition, the first state St1 in which the discharge pressure PS becomes higher than the target pressure PStg and the second state St1 in which the discharge pressure PS becomes lower than the target pressure PStg for each reciprocating cycle of the plunger 32 It was confirmed that a pressure pulsation (see graph F1 in FIG. 3 (e)) in which St2 and St2 are repeated alternately occurs. This pressure pulsation was confirmed for the first time by the experiments and analysis of the present inventors.

The cause of the pressure pulsation will be described with reference to FIG. FIG. 3 shows the transition of the suction pressure PB with the reciprocating movement of the plunger 32. Here, FIG. 3A shows the transition of the open / closed state of the metering valve 38, and FIG. 3B shows the transition of the reciprocating movement of the plunger 32. FIG. 3C shows the transition of the suction pressure PB in the normal state, and FIG. 3D shows the transition of the suction pressure PB when the supply state of the low-pressure fuel deteriorates. FIG. 3 (e) shows the transition of the discharge pressure PS, and FIG. 3 (f) shows the transition of the fuel discharge amount Q. 3 (d), (e), and (f) show a graph F1 (solid line) showing the transition of various values in the high-pressure pump 13 not provided with the damper 70, and high pressure provided with the damper 70. A graph F2 (broken line) showing the transition of various values in the pump 13 is shown.

As shown in FIG. 3, in the pumping period Tp, the metering valve 38 is kept in the open state during the prestroke period Tk, so that a surge pressure Pc in which the suction pressure PB temporarily rises from the target pressure PBtg is generated. .. As shown in FIG. 3C, the surge pressure Pc is maintained at a predetermined threshold value Pth under a normal state in which the low pressure fuel supply state is good.

However, during suction and discharge of the high-pressure pump 13, pressure pulsation occurs in the low-pressure passage 36, which reduces the control accuracy of the fuel discharge amount Q. For example, if the supply state of the low-pressure fuel deteriorates for some reason, the low-pressure fuel sucked into the pressurizing chamber 35 decreases, and the fuel discharge amount Q decreases. Further, the occurrence time of the surge pressure Pc is delayed due to the deterioration of the supply state, and the peak height of the surge pressure Pc increases above the threshold value Pth. In the next reciprocating cycle in which the fuel discharge amount Q is reduced, the suction to the pressurizing chamber 35 is reduced in the previous reciprocating cycle, so that the pressure in the low pressure passage 36 recovers quickly and is sucked into the pressurizing chamber 35. The amount of low-pressure fuel increases, and the fuel discharge amount Q increases. Further, the surge pressure Pc is generated earlier, and the peak height of the surge pressure Pc is smaller than the threshold value Pth.

After that, in the high-pressure pump 13, the increase and decrease of the fuel discharge amount Q are alternately repeated for each reciprocating cycle of the plunger 32. Along with this, the surge pressure Pc has a pressure variation in which a state where the surge pressure Pc is higher than the threshold value Pth and a state where the surge pressure Pth is lower than the threshold value Pth are alternately repeated for each reciprocating cycle of the plunger 32 (FIG. 3 (d)). reference). When the surge pressure Pc varies, pressure pulsation occurs in the discharge pressure PS (see graph F1 in FIG. 3 (e)). The mechanism by which pressure pulsation occurs due to pressure variation has not yet been completely elucidated.

Therefore, in the present embodiment, as shown in FIG. 4, a damper 70 is provided in order to suppress fluctuations in the suction pressure PB including pressure variations in the surge pressure Pc. The damper 70 has a valve body 71 that moves from the closed position to the open position and discharges the fuel in the low pressure passage 36 to the return passage 43 when the average suction pressure obtained by averaging the suction pressure PB over time is higher than the reference pressure PBk. , Which is integrally provided on the valve body 71, elastically deforms (hereinafter, simply referred to as deformation) based on the force received in the opening / closing direction of the valve body 71, and has responsiveness to the suction pressure PB (hereinafter, simply referred to as responsiveness). It is provided with a diaphragm 81 which is higher than the valve body 71 and can suppress a momentary fluctuation of the suction pressure PB within a cycle such as a surge pressure Pc. In the damper 70 of the present embodiment, the fuel does not flow out to the return passage 43 due to the momentary fluctuation of the suction pressure PB in the low pressure passage 36, and this fluctuation is absorbed by the diaphragm 81. As a result, it is possible to suppress the outflow of unnecessary fuel through the return passage 43, and it is possible to avoid insufficient intake of fuel into the low pressure passage 36, which is one of the causes of pressure pulsation. The surge pressure Pc, which is one of the generating factors, can be reduced, and these two generating factors can be eliminated at the same time.

Next, the damper 70 will be described. As shown in FIG. 5A, the damper 70 is provided in the return passage 43 that branches from the low pressure passage 36 and returns the fuel to the fuel tank 16 at the branch point B on the low pressure passage 36, and includes the casing 50 and the casing 50. A valve body 71, a spring 80, and a diaphragm 81 are provided.

The casing 50 has a substantially cylindrical shape, and an internal space 51 communicating with the low pressure passage 36 is formed inside the casing 50. The side surface 52 of the casing 50 is provided with a first communication portion 53 that communicates the internal space 51 and the return passage 43.

Further, a connecting portion 55 for connecting to the low pressure passage 36 is provided on the end surface 54 on one side of the casing 50 in the axial direction X (the lower side of the drawing, hereinafter simply referred to as one side). The connecting portion 55 has a hollow tubular shape and extends in the axial direction X from substantially the center of the end face 54. A groove 56 having an enlarged inner diameter is provided at a substantially central portion of the connecting portion 55 in the axial direction X. The groove 56 is provided with a second communication portion 57 that communicates the space in the connecting portion 55 with the return passage 43.

The valve body 71 has a substantially columnar shape along the axial direction X, and a hollow portion extending in the axial direction X of the valve body 71 and opening to the low pressure passage 36 side on one side end surface 72 of the valve body 71. It has 73. The one-sided portion 74 of the valve body 71 is housed in the connecting portion 55 of the casing 50, and the one-sided portion 74 is arranged so as to cover the groove portion 56. By arranging the one side portion 74 so as to cover the groove portion 56, the flow of fuel from the low pressure passage 36 to the return passage 43 is blocked via the second communication portion 57.

The other side (hereinafter referred to simply as the other side in the drawing) portion 75 in the axial direction X of the valve body 71 is housed in the internal space 51, and is provided with an enlarged diameter portion 76 having an enlarged outer diameter. The outer diameter of the enlarged diameter portion 76 is larger than the inner diameter of the connecting portion 55 excluding the groove portion 56. As a result, the movement of the valve body 71 to the low pressure passage 36 is suppressed.

The spring 80 is provided between the other end surface 58 of the casing 50 and the other side surface 76A of the enlarged diameter portion 76. As shown in FIG. 5A, the position where one side portion 74 of the valve body 71 covers the groove 56 is set as the reference position of the valve body 71. The spring 80 elastically compresses when the valve body 71 moves to the other side of the reference position, and the valve body 71 responds to the amount of movement of the valve body 71 from the reference position so that the valve body 71 returns to the reference position. Apply an elastic force in the direction opposite to the direction of movement (that is, one side). In the present embodiment, the reference position of the valve body 71 corresponds to the “closed position”.

As shown in FIG. 5B, the valve body 71 is movable as the suction pressure PB in the low pressure passage 36 fluctuates. When the suction pressure PB in the low pressure passage 36 rises above the predetermined reference pressure PBk (see FIG. 3 (d)), the valve body 71 has the other side shown in FIG. 5 (b) from the reference position shown in FIG. 5 (a). Move to the side position. The predetermined reference pressure PBk is determined by the elastic modulus of the spring 80, the sliding resistance between the one side portion 74 of the valve body 71 and the connecting portion 55 of the casing 50, and the pressure of the fuel in the return passage 43. .. The position on the other side means a position on the other side of the reference position, and the position on which one side portion 74 of the valve body 71 does not cover the groove portion 56. By moving the valve body 71 from the reference position to the other side position, the fuel in the low pressure passage 36 can be discharged to the return passage 43 via the second communication portion 57. In the present embodiment, in the present embodiment, the axial direction X of the valve body 71 corresponds to the "opening / closing direction", and the position on the other side of the valve body 71 corresponds to the "open position".

In the present embodiment, the valve body 71 returns the fuel to the return passage 43 due to the momentary fluctuation of the suction pressure PB within the cycle such as the surge pressure Pc due to the inertia of the valve body 71, the elastic modulus of the spring 80, and the like. It is specified that the average suction pressure is equal to or less than the reference pressure PBk without causing outflow. Therefore, the outflow of fuel due to the momentary fluctuation of the suction pressure PB is suppressed, and it becomes easy to avoid the intake shortage which is one of the causes of the pressure pulsation. On the other hand, since the effect of reducing the surge pressure Pc, which is another cause of pressure pulsation, is small, it is not possible to suppress the occurrence of pressure pulsation, and there is a concern that fluctuation ΔQ of the fuel discharge amount Q may occur.

The damper 70 of the present embodiment includes a diaphragm 81 integrally provided with the valve body 71 in order to solve the above problem. As shown in FIG. 5A, the diaphragm 81 is a thin metal plate, and the outer edge portion 82 thereof is fixed to one side end surface 72 of the valve body 71 over the entire circumference. Further, the central portion 83 of the diaphragm 81 has a convex shape protruding into the hollow portion 73. The central portion 83 of the diaphragm 81 extends in the longitudinal direction of the hollow portion 73, that is, along the axial direction X of the valve body 71. The diaphragm 81 is arranged with respect to the valve body 71 so that the width between the hollow portion 73 and the central portion 83 is equal to or larger than the reference width over the entire circumference of the central portion 83. In the present embodiment, the diaphragm 81 corresponds to the "damper portion" and the central portion 83 corresponds to the "convex portion".

Therefore, the hollow portion 73 is divided into a first region R1 on the low pressure passage 36 side and a second region R2 on the opposite side of the low pressure passage 36 by the central portion 83 of the diaphragm 81. The other side portion 75 of the valve body 71 surrounding the second region R2 is provided with a communication hole 77 for communicating the second region R2 and the internal space 51. Therefore, the second region R2 communicates with the return passage 43 through the communication hole 77. On the other hand, since the first region R1 and the second region R2 are partitioned by the diaphragm 81, the flow of fuel from the low pressure passage 36 to the return passage 43 via the communication hole 77 is blocked.

The diaphragm 81 is deformable based on the force received in the axial direction X of the valve body 71. For example, as shown in FIG. 5 (c), the suction pressure PB in the low pressure passage 36 (that is, the pressure in the first region R1) is higher than the pressure of the fuel in the return passage 43 (that is, the pressure in the second region R2). When the height is increased, the diaphragm 81 receives a force toward the other side, and the central portion 83 of the diaphragm 81 is deformed so as to be close to the valve body 71. As a result, the volume of the first region R1 is increased, and the increase in the suction pressure PB is suppressed.

The diaphragm 81 is more responsive than the valve body 71, and is deformed because the suction pressure PB in the low pressure passage 36 becomes higher than the fuel pressure in the return passage 43 even when the suction pressure PB suddenly fluctuates. do. As a result, as shown in the graph F2 of FIG. 3D, the fluctuation of the suction pressure PB is suppressed, and the peak pressure of the surge pressure Pc is suppressed to be lower than the threshold value Pth. As a result, the pressure pulsation of the discharge pressure PS is suppressed, and the fuel discharge amount Q is controlled to be the target fuel discharge amount Qtg (see graphs F2 in FIGS. 3 (e) and 3 (f)).

According to the present embodiment described above, the following effects are obtained.

When the fuel is repeatedly sucked and discharged in the high-pressure pump 13, the suction pressure PB fluctuates. The fuel injection system 100 of the present embodiment includes a damper 70, and the damper 70 is deformed based on the force received in the axial direction X of the valve body 71, and the responsiveness to the suction pressure PB is higher than that of the valve body 71. Also equipped with a high diaphragm 81. Therefore, when a force is applied in the axial direction X of the valve body 71 due to the fluctuation of the suction pressure PB, the suction pressure PB fluctuates due to the deformation of the diaphragm 81 even if the suction pressure PB does not become higher than the reference pressure PBk. Can be suitably suppressed.

In this embodiment, the diaphragm 81 is integrally provided with the valve body 71. It is preferable that the diaphragm 81 and the valve body 71 are arranged close to the high-pressure pump 13 in order to suppress the fluctuation ΔQ of the fuel discharge amount Q due to the fluctuation of the suction pressure PB. If the diaphragm 81 is provided separately from the valve body 71, it is difficult to arrange both the diaphragm 81 and the valve body 71 in close proximity to the high pressure pump 13. Further, both the diaphragm 81 and the valve body 71 need to be arranged close to the high pressure pump 13. Therefore, when the movement of the valve body 71 and the deformation of the diaphragm 81 occur at the same time due to the fluctuation of the suction pressure PB, resonance is likely to occur and the fluctuation of the suction pressure PB is increased.

In the damper 70 of the present embodiment, since the diaphragm 81 is integrally provided with the valve body 71, both the diaphragm 81 and the valve body 71 can be arranged close to the high pressure pump 13. Further, it is possible to suppress the occurrence of resonance and the like, and preferably suppress the fluctuation of the suction pressure PB.

In particular, in the present embodiment, the damper 70 is configured to be deformed based on the axial direction X of the valve body 71, that is, the force received in the moving direction of the valve body 71. Therefore, in the valve body 71 and the diaphragm 81 provided integrally, the mode of response in the damper 70 can be smoothly switched from the deformation of the diaphragm 81 to the movement of the valve body 71 as the suction pressure PB increases. can.

In the damper 70 of the present embodiment, the diaphragm 81 is provided in the hollow portion 73 extending in the axial direction X of the valve body 71 and opening on the low pressure passage 36 side. Therefore, when the diaphragm 81 and the valve body 71 are integrated to form the damper 70, the damper 70 can be miniaturized and formed.

In the damper 70 of the present embodiment, the other side portion 75 of the valve body 71 is provided with a communication hole 77 for communicating the second region R2 and the internal space 51. The volume of the hollow portion 73 provided in the valve body 71 is limited. If the valve body 71 is not provided with the communication hole 77, the pressure in the second region R2 increases when the capacity of the first region R1 increases due to the increase of the suction pressure PB, and the capacity increase of the first region R1 is suppressed. Therefore, the fluctuation of the suction pressure PB cannot be sufficiently suppressed.

In the damper 70 of the present embodiment, the valve body 71 is provided with a communication hole 77. Therefore, the pressure increase in the second region R2 when the capacity of the first region R1 is increased is suppressed, and the fluctuation of the suction pressure PB can be suitably suppressed.

In the damper 70 of the present embodiment, the central portion 83 of the diaphragm 81 extends in the longitudinal direction of the hollow portion 73, that is, along the axial direction X of the valve body 71. Therefore, the pressure receiving area of the diaphragm 81 can be increased, which can improve the responsiveness of the diaphragm 81.

(Second Embodiment)
Next, the fuel injection system 100 according to the second embodiment will be described with reference to FIG. The fuel injection system 100 according to the second embodiment has a different structure of the damper 70 than the fuel injection system 100 according to the first embodiment. Specifically, the damper 70 of the second embodiment includes a piston 90 and springs 91 and 92 in place of the diaphragm 81. Hereinafter, the structure of the valve body 71, the piston 90, and the springs 91 and 92 will be described. In this embodiment, the piston 90 and the springs 91 and 92 correspond to the "damper portion".

As shown in FIG. 6A, the valve body 71 has a substantially columnar shape, and the valve body 71 extends to one side end surface 72 of the valve body 71 in the axial direction X of the valve body 71 and opens to the low pressure passage 36 side. It has a hollow portion 73 to be formed. In the present embodiment, the hollow portion 73 is provided so as to penetrate the valve body 71 along the axial direction X of the valve body 71. A protrusion 78 having a reduced inner diameter is provided at one end of the hollow portion 73.

The piston 90 is provided in the hollow portion 73, and its side surface is arranged in a state of being in contact with the inner surface of the hollow portion 73 over the entire circumference. Since the side surface of the piston 90 is in contact with the inner surface of the hollow portion 73 over the entire circumference, the flow of fuel from the low pressure passage 36 to the return passage 43 via the hollow portion 73 is blocked. Further, the hollow portion 73 is divided into a first region R1 on the low pressure passage 36 side and a second region R2 on the opposite side of the low pressure passage 36 by the piston 90. The second region R2 communicates with the return passage 43 via the first communication portion 53. In this embodiment, the piston 90 corresponds to the "moving part".

The piston 90 is inserted into the hollow portion 73 from the other side of the hollow portion 73 in which the protrusion 78 is not provided, and then the stopper 79 is attached to the other end of the hollow portion 73. The protrusion 78 and the stopper 79 prevent the piston 90 from moving out of the hollow portion 73. In the present embodiment, the stopper 79 corresponds to the "movement control unit".

The first spring 91 is provided between the protrusion 78 of the valve body 71 and the one side surface 90A of the piston 90. The second spring 92 is provided between the stopper 79 and the other side surface 90B of the piston 90.

As shown in FIG. 6A, the position where the piston 90 is aligned with the enlarged diameter portion 76 in the axial direction X of the valve body 71 is set as the reference position of the piston 90. The first spring 91 elastically compresses when the piston 90 moves to one side from the reference position, and urges the piston 90 to the other side according to the amount of movement of the piston 90 from the reference position. Further, the second spring 92 elastically compresses when the piston 90 moves to the other side from the reference position, and urges the piston 90 to one side according to the amount of movement of the piston 90 from the reference position. As a result, the piston 90 is supported so as to be reciprocating in the longitudinal direction of the hollow portion 73, that is, in the axial direction X of the valve body 71. In this embodiment, the springs 91 and 92 correspond to the "urging portion".

As shown in FIG. 6B, the valve body 71 is movable as the suction pressure PB in the low pressure passage 36 fluctuates. When the suction pressure PB in the low pressure passage 36 rises above the reference pressure PBk, the valve body 71 moves from the reference position shown in FIG. 6A to the other side position shown in FIG. 6B. In this embodiment, the reference pressure PBk is determined by the elastic modulus of the springs 91 and 92 and the pressure of the fuel in the return passage 43. The other side position is a position where one side portion 74 of the valve body 71 does not cover the groove portion 56, and the other side portion 75 of the valve body 71 is a position where the other side portion 75 of the valve body 71 comes into contact with the other end surface 58 of the casing 50.

The piston 90 can move based on the force received in the axial direction X of the valve body 71. For example, as shown in FIG. 6 (c), the suction pressure PB in the low pressure passage 36 (that is, the pressure in the first region R1) is higher than the pressure of the fuel in the return passage 43 (that is, the pressure in the second region R2). When it becomes high, the piston 90 receives a force toward the other side and moves to the other side (see arrow Ya in FIG. 6).

The elastic modulus of the springs 91 and 92 is smaller than the elastic modulus of the spring 80. Therefore, the piston 90 has a higher responsiveness than the valve body 71, and moves in response to a sudden change in the suction pressure PB that cannot be absorbed by the valve body 71. As a result, as shown in the graph F2 of FIG. 3D, the fluctuation of the suction pressure PB is suppressed, and the peak pressure of the surge pressure Pc is suppressed to be lower than the threshold value Pth. As a result, the pressure pulsation of the discharge pressure PS is suppressed, and the fuel discharge amount Q is controlled to be the target fuel discharge amount Qtg (see graphs F2 in FIGS. 3 (e) and 3 (f)).

As described above, when the high pressure pump 13 repeatedly sucks and discharges fuel, the suction pressure PB fluctuates. The fuel injection system 100 of the present embodiment includes a damper 70, and the damper 70 moves based on the force received in the axial direction X of the valve body 71, and the responsiveness to the suction pressure PB is higher than that of the valve body 71. Also equipped with a high piston 90. Therefore, when a force is applied in the axial direction X of the valve body 71 due to the movement of the suction pressure PB, the suction pressure PB fluctuates due to the deformation of the piston 90 even if the suction pressure PB does not become higher than the reference pressure PBk. Can be suitably suppressed.

(Third Embodiment)
Next, the fuel injection system 100 according to the third embodiment will be described with reference to FIGS. 7 and 8. The fuel injection system 100 according to the third embodiment has a different structure of the piston 90 from the fuel injection system 100 according to the second embodiment. Hereinafter, the structure of the piston 90 and the fluctuation of the suction pressure PB will be described.

As shown in FIG. 7A, the piston 90 is provided with a contact portion 94 extending from the other side surface 90B of the piston 90 in the axial direction X of the valve body 71. The outer diameter of the contact portion 94 is larger than the inner diameter of the stopper 79 attached to the valve body 71. Therefore, when the piston 90 is located at the reference position, the contact portion 94 comes into contact with the stopper 79 from one side in the axial direction X, that is, from the low pressure passage 36 side. That is, in the present embodiment, the position where the abutting portion 94 and the stopper 79 abut is the reference position, and the axial direction X of the valve body 71 is such that the abutting portion 94 and the stopper 79 abut at the reference position. The length of the contact portion 94 and the elastic modulus of the springs 91 and 92 are set. As a result, the springs 91 and 92 can urge the piston 90 to the other side in the axial direction X and bring the contact portion 94 into contact with the stopper 79. In the present embodiment, the other side in the axial direction X corresponds to the "valve opening direction".

Therefore, the piston 90 does not move from the reference position to the other side, that is, the side opposite to the low pressure passage 36, but can move only to one side from the reference position, that is, the low pressure passage 36 side. That is, as shown in FIG. 7 (c), the suction pressure PB in the low pressure passage 36 (that is, the pressure in the first region R1) is higher than the pressure of the fuel in the return passage 43 (that is, the pressure in the second region R2). When it becomes smaller, the piston 90 receives a force toward one side and moves to one side (see arrow Yb in FIG. 7). In the present embodiment, the pressure of the fuel in the return passage 43 is, for example, atmospheric pressure. Therefore, in the present embodiment, when the suction pressure PB in the low pressure passage 36 becomes a negative pressure, the piston 90 moves away from the stopper 79 and moves to one side.

By moving the piston 90 to one side, fluctuations in the suction pressure PB can be suitably suppressed. Hereinafter, the reason for this will be described with reference to FIG. FIG. 8 shows the transition of the suction pressure PB when the suction pressure PB fluctuates. Here, FIG. 8 (a) shows the transition of the suction pressure PB when the damper 70 is not used, and FIG. 8 (b) shows the transition of the suction pressure PB when the damper 70 is used. c) shows the transition of the discharge pressure PS, and FIG. 8D shows the transition of the fuel discharge amount Q. 8 (c) and 8 (d) show a graph F1 (solid line) showing the transition of various values when the damper 70 is not used, and a graph F2 (solid line) showing the transition of various values when the damper 70 is used. (Dashed line) and is shown.

As shown in FIG. 8, when the suction pressure PB fluctuates and the peak pressure of the surge pressure Pc rises above the threshold value Pth, the suction pressure PB may temporarily decrease due to the reaction (FIG. 8 (a). )reference). Hereinafter, this temporarily lowered suction pressure PB is referred to as a reverse surge pressure Pb.

The reverse surge pressure Pb becomes lower as the surge pressure Pc is higher. Then, when the reverse surge pressure Pb becomes a negative pressure, in the next reciprocating cycle in which the reverse surge pressure Pb becomes a negative pressure, the surge pressure Pc is generated earlier and the surge pressure Pc peak pressure becomes lower than the threshold Pth. do. After that, in the high-pressure pump 13, the increase and decrease of the fuel discharge amount Q by the feedback control are alternately repeated for each reciprocating cycle of the plunger 32.

In the present embodiment, the piston 90 can move to one side of the valve body 71 when a reverse surge pressure Pb is generated and the reverse surge pressure Pb becomes a negative pressure. As a result, the volume of the first region R1 decreases, the suction pressure PB rises, and the suction pressure PB can be restored to a positive pressure. As a result, the pressure pulsation of the discharge pressure PS is suppressed, and the fuel discharge amount Q is controlled to be the target fuel discharge amount Qtg (see graphs F2 in FIGS. 8C and 8D).

As described above, when the suction and discharge of fuel are repeatedly performed in the high pressure pump 13, the suction pressure PB may temporarily increase and then temporarily decrease. Then, when the temporarily lowered suction pressure PB becomes a negative pressure, the suction pressure PB fluctuates. The fuel injection system 100 of the present embodiment includes a damper 70, which is located on the low pressure passage 36 side of the reference position when the suction pressure PB becomes lower than the pressure of the fuel in the return passage 43. It is equipped with a piston 90 that can be moved to a position. Therefore, even when the reverse surge pressure Pb is generated, it is possible to suppress the decrease in the suction pressure PB by moving the piston 90 to the low pressure passage 36 side, and it is preferable that the fuel discharge amount Q fluctuates. Can be suppressed.

In particular, in the present embodiment, the pressure of the fuel in the return passage 43 is maintained at atmospheric pressure. Therefore, when a reverse surge pressure Pb is generated and the reverse surge pressure Pb becomes a negative pressure, the suction pressure PB can be restored to a positive pressure by moving the piston 90 toward the low pressure passage 36 side. , It is possible to appropriately suppress the fluctuation of the fuel discharge amount Q.

In the present embodiment, the piston 90 is provided with the contact portion 94, and the piston 90 is immovably supported on the side opposite to the low pressure passage 36 at the reference position. Therefore, the volume of the second region R2 can be reduced and provided, whereby the volume of the first region R1 can be increased, and fluctuations in the suction pressure PB can be suitably suppressed.

The present invention is not limited to the description of the above embodiment, and may be implemented as follows.

In the first embodiment, the embodiment in which the communication hole 77 is provided in the other side portion 75 of the valve body 71 is exemplified, but the present invention is not limited to this, and the communication hole 77 may not be provided. When the communication hole 77 is not provided, the casing 50 may not be provided with the first communication portion 53.

Further, the valve body 71 may be provided with the communication hole 77, and the casing 50 may not be provided with the first communication portion 53. In this case, the pressure in the internal space 51 can be set to a pressure different from the pressure of the fuel in the return passage 43, which is suitable for suppressing the fluctuation of the suction pressure PB. Fluctuations in the suction pressure PB can be suitably suppressed.

In the second embodiment, the position where the piston 90 is aligned with the enlarged diameter portion 76 in the axial direction X of the valve body 71 is exemplified as the reference position of the piston 90, but the present invention is not limited to this. For example, by setting the reference position on the low pressure passage 36 side, it is possible to suitably suppress an increase in the suction pressure PB such as the surge pressure Pc. Further, by setting the reference position on the side opposite to the low pressure passage 36 side, it is possible to suitably suppress a decrease in the suction pressure PB such as the reverse surge pressure Pb.

In the third embodiment, the contact portion 94 extends from the other side surface 90B of the piston 90 in the axial direction X of the valve body 71, and the contact portion 94 and the stopper 79 interfere with each other at the reference position. However, it is not limited to this. For example, the contact portion 94 may extend from one side surface 90A of the piston 90 in the axial direction X of the valve body 71 so that the contact portion 94 and the protrusion 78 interfere with each other at the reference position.

In this case, the piston 90 can move from the reference position to the side opposite to the low pressure passage 36. Therefore, when the suction pressure PB rises, the movement of the piston 90 to the side opposite to the low pressure passage 36 can suppress the rise in the suction pressure PB, which causes a fluctuation in the fuel discharge amount Q. This can be suitably suppressed.

In the above embodiment, the embodiment in which the diaphragm 81 and the piston 90 are provided in the hollow portion 73 provided in the valve body 71 is exemplified, but the present invention is not limited to this. For example, in the case of the diaphragm 81, the diaphragm 81 may have a flat plate shape and may be fixed to one side end surface 72 of the valve body 71 provided with the hollow portion 73. Further, in the case of the piston 90, a spring extending in the axial direction X of the valve body 71 is attached to one side end surface 72 of the valve body 71 in which the hollow portion 73 is not provided, and one end portion of this spring is attached. The piston 90 may be attached to the.

13 ... high pressure pump, 16 ... fuel tank, 32 ... plunger, 35 ... pressurizing chamber, 36 ... low pressure passage, 43 ... return passage, 70 ... damper, 71 ... valve body, 81 ... diaphragm, 90 ... cylinder, 91 ... 1 spring, 92 ... 2nd spring, 100 ... fuel injection system, B ... branch point.

Claims (7)

A fuel pump (13) that sucks and pumps fuel in the pressurizing chamber (35) by reciprocating the plunger (32), and a suction passage (36) that supplies low-pressure fuel from the fuel tank (16) to the fuel pump. It is applied to a fuel supply system (100) including a return passage (43) for branching from the suction passage and returning fuel to the fuel tank at a branch point (B) on the suction passage, and is provided in the return passage. It is a fuel pump (70)
When the pressure (PB) in the suction passage is higher than the reference pressure (PBk), the valve body (71) that moves from the closed position to the open position and causes the fuel in the suction passage to flow out to the return passage.
A damper portion (81, 90,91,92) and a pulsation damper. The valve body has a hollow portion (73) extending in the opening / closing direction of the valve body and opening to the suction passage side.
The pulsation damper according to claim 1, wherein the damper portion is provided in the hollow portion (73). The damper portion is a diaphragm (81) that divides the hollow portion into a first region (R1) on the suction passage side and a second region (R2) on the opposite side of the suction passage. The pulsation damper described in 2. The pulsation damper according to claim 3, wherein in the hollow portion, the second region communicates with the return passage. The pulsation damper according to claim 3 or 4, wherein the diaphragm has a convex portion (83) extending along the longitudinal direction of the hollow portion. The damper part is
A moving portion (90) provided in the hollow portion so as to be reciprocating in a state of being in contact with the inner surface thereof,
An urging portion (91, 92) that urges the moving portion in at least one of the opening / closing directions of the valve body is provided.
The pulsation damper according to claim 2, wherein the urging portion has a higher responsiveness than the valve body. The urging portion urges the moving portion in the valve opening direction of the opening / closing direction of the valve body, and brings the moving portion into contact with the movement restricting portion (79) provided in the hollow portion. ,
When the pressure in the suction passage becomes lower than the pressure in the return passage, the moving portion can move from the position in contact with the movement restricting portion to the position closer to the suction passage than the position. The pulsation damper according to claim 6 provided in the above.

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