JP2012052464A - Constant residual pressure valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constant residual pressure valve which can improve the fuel-discharge efficiency of a high-pressure pump.SOLUTION: A constant residual pressure valve 60 is disposed in a communication passage 9 that communicates the pressurized chamber and high-pressure fuel piping of a high-pressure pump. The valve element 61 of the constant residual pressure valve 60 blocks an inner communication passage 55 of a relief valve element 51 by sitting on a valve seat 65, and opens the inner communication passage 55 by leaving the valve seat 65. A first spring 63 energizes the valve element 61 towards the side of the valve seat 65. Due to the fact that a flow control means 70, which can make a sliding contact with the inner wall of the small diameter part 57 of the communication passage 9, moves together with the valve element 61, the opening cross-section of the inner communication passage 55 becomes larger when the valve element 61 is fully opened than the opening cross-section of the inner communication passage 55 when the valve element 61 starts opening the valve. As a result, fuel returned to the pressurizing chamber from a delivery piping side during the intake stroke of the high-pressure pump can be reduced. Furthermore, the fuel pressure of the delivery piping can be promptly reduced when the engine is stopped or when the accelerator is off.

Description

  The present invention relates to a constant residual pressure valve used in a fuel supply device that supplies fuel to an engine, and is particularly suitable for a constant residual pressure valve used in a fuel supply device of a direct injection internal combustion engine for a vehicle.

  2. Description of the Related Art Conventionally, a high-pressure pump that pressurizes fuel supplied from a fuel tank is provided in a fuel supply device that supplies fuel to an engine, particularly a cylinder injection internal combustion engine for a vehicle. The high-pressure pump pressurizes the fuel sucked into the pressurizing chamber by a plunger that reciprocates as the engine rotates, and discharges the fuel to the delivery pipe. The fuel accumulated in the delivery pipe is injected from the injector into each cylinder of the engine.

In this type of fuel supply device, a constant residual pressure valve is provided in a communication path that connects a pressurizing chamber of a high-pressure pump and a delivery pipe (see Patent Document 1).
The constant residual pressure valve quickly reduces the fuel pressure in the delivery pipe and maintains it at a predetermined pressure after the engine is stopped and when the accelerator is off. Thereby, after the engine is stopped, fuel leakage from the injector into the cylinder is suppressed, and the generation of vapor is suppressed. Therefore, the deterioration of the emission at the time of restarting the engine is suppressed, and the deterioration of the restartability of the engine due to the vapor is suppressed.
Further, when the accelerator is depressed again after the accelerator is turned off, the fuel injection amount from the injector into the cylinder can be appropriately controlled. Therefore, a shock at the time of transition to acceleration is suppressed, and deterioration of fuel consumption and emission are suppressed.

JP 2009-121395 A

However, the constant residual pressure valve opens the communication path when the fuel pressure in the pressurizing chamber becomes smaller than the fuel pressure in the delivery pipe in the intake stroke in which fuel is sucked into the pressurizing chamber of the high-pressure pump during engine operation. For this reason, the fuel is sucked back from the delivery pipe to the pressurizing chamber via the communication path.
In particular, when the engine is started, since the engine speed is low, the suction stroke and the discharge stroke of the high-pressure pump become long. This increases the flow rate that is sucked back from the delivery pipe into the pressurizing chamber during the suction stroke. For this reason, the ratio of the flow rate sucked back with respect to the discharge amount of the high-pressure pump increases, and the discharge efficiency of the high-pressure pump may be deteriorated. As a result, there is a concern that the pressure of the fuel becomes insufficient and the startability of the engine deteriorates. Further, there is a concern that the fuel efficiency deteriorates when the load of the engine for reciprocating the plunger increases as the discharge efficiency of the high-pressure pump deteriorates.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a constant residual pressure valve capable of enhancing the discharge efficiency of a high-pressure pump and a fuel supply device using the same.

In order to solve the above-described problem, according to the first aspect of the present invention, the pressurizing chamber that pressurizes the fuel by the reciprocating movement of the plunger communicates with the high-pressure side passage through which the fuel pressurized in the pressurizing chamber flows. The constant residual pressure valve provided in the communication path includes a valve body, an urging unit, and a flow rate control unit.
The valve body closes the communication path by sitting on a valve seat formed on the inner wall of the communication path, and opens the communication path by separating from the valve seat. The urging means urges the valve body toward the valve seat. The flow rate control means has a sliding contact portion that can be slidably contacted with the inner wall of the communication path, and moves together with the valve body so that the valve body is fully opened from the opening cross-sectional area of the communication path when the valve body starts to open. Increase the opening cross-sectional area of the communication passage.
When the engine is in operation, if the fuel pressure in the pressurizing chamber becomes smaller than the fuel pressure in the high-pressure side passage due to the reciprocating movement of the plunger, the valve body separates from the valve seat. Immediately after the valve element is opened, the fuel flows through a minute gap between the inner wall of the communication passage and the sliding contact portion, so that the opening cross-sectional area of the communication passage is small, and the fuel sucked back from the high-pressure side passage to the pressurizing chamber The flow rate is low. For this reason, the ratio of the flow rate sucked back from the high pressure side passage to the pressurization chamber becomes smaller than the flow rate fed from the pressurization chamber to the high pressure side passage. Therefore, the discharge efficiency of the high-pressure pump that pressurizes the fuel in the pressurizing chamber can be increased.
On the other hand, when the engine is stopped and the accelerator is off, the valve body remains in the fully open position until the fuel pressure in the high pressure side passage decreases to a predetermined pressure, so that the opening cross-sectional area of the communication passage increases and the fuel pressure in the high pressure side passage quickly increases. descend. When the fuel pressure in the high-pressure side passage reaches a predetermined pressure, the constant residual pressure valve is closed, and the fuel pressure in the high-pressure side passage is maintained at the predetermined pressure. Therefore, the original function of the constant residual pressure valve is exhibited, and the deterioration of emission and restartability during engine restart are suppressed. In addition, acceleration shock when the accelerator is depressed again after the accelerator is turned off is suppressed, and deterioration of fuel consumption and emission are suppressed.

  According to the invention which concerns on Claim 2, a communicating path has a small diameter part which slidably contacts with a sliding contact part, and a large diameter part with a larger internal diameter than a small diameter part in the downstream from this small diameter part. When the valve body is in the fully closed position, the sliding contact portion is located on the inner side of the small diameter portion. When the valve body is in the fully open position, the sliding contact portion is located inside the large diameter portion. When the sliding contact portion is positioned inside the small diameter portion, a minute gap is formed between the outer wall of the sliding contact portion and the inner wall of the small diameter portion. For this reason, the opening cross-sectional area of the communicating path immediately after the valve body starts to open becomes small. When the sliding contact portion is positioned inside the large diameter portion, the opening cross-sectional area between the outer wall of the sliding contact portion and the inner wall of the large diameter portion increases.

  According to the invention which concerns on Claim 3, the sliding contact part forms the micro clearance gap which can control the distribution | circulation of a fuel between the outer wall of the radial direction, and the inner wall of a small diameter part. The flow rate at the start of valve opening can be controlled by setting the opening cross-sectional area by the minute gap. Thereby, the flow rate sucked back into the pressurizing chamber from the high-pressure side passage during the suction stroke of the high-pressure pump can be controlled, and the discharge efficiency of the high-pressure pump can be increased.

  According to the invention which concerns on Claim 4, the flow volume control means formed separately from a valve body is urged | biased to the valve body side by the 2nd urging | biasing means with smaller urging | biasing force than an urging | biasing means. Thereby, it becomes possible to make a valve body and a flow control means coaxial easily, and the inner wall of a communicating path and a flow control means can be slid smoothly. Therefore, when the engine is stopped and the accelerator is off, the fuel pressure in the high-pressure side passage can be quickly reduced.

  According to the invention which concerns on Claim 5, a valve body and a flow control means are integrally formed. Thereby, a 2nd biasing means can be abolished and manufacturing cost can be reduced.

  The invention according to claim 6 is an invention of a fuel supply device including the constant residual pressure valve according to any one of claims 1 to 5 described above. The fuel supply device includes a high-pressure pump having a plunger and a pressurizing chamber that can reciprocate in the axial direction, a delivery pipe that stores fuel pressurized in the pressurizing chamber of the high-pressure pump, and a pressure accumulated in the delivery pipe. An injector for injecting fuel into the cylinder of the engine is provided. As a result, the fuel supply device can increase the discharge efficiency of the high-pressure pump, and can quickly reduce the fuel pressure of the delivery pipe when the engine is stopped and the accelerator is off, and maintain it at a predetermined pressure.

It is sectional drawing of the constant residual pressure valve by 1st Embodiment of this invention. It is a block diagram of the fuel supply apparatus to which the constant residual pressure valve by 1st Embodiment of this invention is applied. It is an enlarged view of the III part of FIG. It is sectional drawing which shows the valve opening state of the constant residual pressure valve by 1st Embodiment of this invention. It is sectional drawing of the VV line of FIG. FIG. 6 is a characteristic diagram comparing the constant residual pressure valve according to the first embodiment of the present invention and a conventional constant residual pressure valve. FIG. 6 is a characteristic diagram comparing the constant residual pressure valve according to the first embodiment of the present invention and a conventional constant residual pressure valve. FIG. 6 is a characteristic diagram comparing the constant residual pressure valve according to the first embodiment of the present invention and a conventional constant residual pressure valve. It is principal part sectional drawing of the constant residual pressure valve by 2nd Embodiment of this invention. It is sectional drawing of the constant residual pressure valve by 3rd Embodiment of this invention. It is sectional drawing of the constant residual pressure valve by 4th Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
The constant residual pressure valve of 1st Embodiment of this invention is shown in FIGS.
As shown in FIG. 2, the constant residual pressure valve of the present embodiment is used in a fuel supply device 1 that supplies fuel to an engine, particularly a cylinder injection internal combustion engine for a vehicle. In the fuel supply device 1, the fuel in the fuel tank 2 is pumped up by the low pressure pump 3 and supplied to the high pressure pump 10. The high pressure pump 10 pressurizes the fuel sucked into the pressurizing chamber 12 by the reciprocating movement of the plunger 11.

The high-pressure pump 10 includes a plunger 11, a suction valve 20, an electromagnetic drive unit 30, a discharge valve 40, and the like.
The plunger 11 is formed in a substantially cylindrical shape and is provided so as to be capable of reciprocating in the axial direction. A pressurizing chamber 12 is formed on one side of the plunger 11. A lifter 13 is provided on the side of the plunger 11 opposite to the pressurizing chamber 12. The lifter 13 is pressed against the camshaft 15 by a coil spring 14. The plunger 11 reciprocates in the axial direction by rotating the camshaft 15 with the rotation of an engine (not shown). As the volume of the pressurizing chamber 12 changes due to the reciprocating movement of the plunger 11, the fuel is sucked into the pressurizing chamber 12 and pressurized.

The suction valve 20 provided in the supply passage 16 connecting the fuel inlet of the high-pressure pump 10 and the pressurizing chamber 12 opens and closes the supply passage 16 by the operation of the electromagnetic drive unit 30.
A spring 31 provided on the electromagnetic drive unit 30 side biases the mover 32 toward the pressurizing chamber 12 side. The load of the spring 31 on the electromagnetic drive unit 30 side is set to be larger than the load of the spring 22 that urges the valve body 21 of the suction valve 20 from the pressurizing chamber 12 side to the electromagnetic drive unit 30 side. For this reason, when the electromagnetic drive unit 30 is not energized, the mover 32 is biased toward the pressurizing chamber 12 by the spring 31 on the electromagnetic drive unit 30 side. For this reason, the valve body 21 of the suction valve 20 is urged toward the pressurizing chamber 12 via a needle (not shown) whose one end abuts on the movable element 32 and the other end abuts on the valve body 21 of the suction valve 20. . As a result, the valve body 21 of the suction valve 20 is separated from the valve seat 23 and opens the supply passage 16.
On the other hand, when the coil 33 of the electromagnetic drive unit 30 is energized, the mover 32 moves away from the pressurizing chamber 12 side by the magnetic force generated by the coil 33. For this reason, the valve element 21 of the suction valve 20 moves in a direction away from the pressurizing chamber 12 due to the elastic force of the spring 22 on the pressurizing chamber 12 side and the flow of fuel flowing from the pressurizing chamber 12 to the supply passage 16. As a result, the valve body 21 of the intake valve 20 is seated on the valve seat 23 and closes the supply passage 16.

A discharge valve 40 provided in the discharge passage 17 connecting the pressurizing chamber 12 and the fuel outlet of the high-pressure pump 10 opens and closes the discharge passage 17. In the discharge valve 40, the force that the valve body 41 of the discharge valve 40 receives from the fuel on the pressurizing chamber 12 side is the elastic force of the spring 42 that biases the valve body 41 of the discharge valve 40 toward the pressurizing chamber 12 side. When the 40 valve bodies 41 are larger than the sum of the force received from the fuel on the delivery pipe 4 side, the discharge passage 17 is opened.
Further, the discharge valve 40 has a force that the valve body 41 of the discharge valve 40 receives from the fuel on the pressurizing chamber 12 side, and the elastic force of the spring 42 that biases the valve body 41 of the discharge valve 40 toward the pressurizing chamber 12 side. When the valve body 41 of the discharge valve 40 is smaller than the sum of the force received from the fuel on the delivery pipe 4 side, the discharge passage 17 is closed.

When the discharge valve 40 is opened, the high-pressure fuel discharged from the discharge passage 17 is pumped to the delivery pipe 4 via the high-pressure fuel pipe 5. The high pressure fuel accumulated in the delivery pipe 4 is injected from the injector 6 connected to the delivery pipe 4 to each cylinder of the engine.
The fuel pressure in the delivery pipe 4 is detected by the pressure sensor 7 and transmitted to the controller 8. The controller controls each part of the engine such as the electromagnetic drive unit 30 of the high-pressure pump 10 based on outputs from the pressure sensor 7, an accelerator opening sensor (not shown), a rotation angle sensor (not shown) of the camshaft 15, and the like.

A pressure control valve including a relief valve 50 and a constant residual pressure valve 60 is provided in the communication passage 9 that connects the pressurizing chamber 12 of the high-pressure pump 10 and the high-pressure fuel pipe 5.
The communication passage 9 may communicate the discharge passage 17 of the high-pressure pump 10 and the pressurization chamber 12 of the high-pressure pump 10, or may communicate the delivery pipe 4 and the pressurization chamber 12 of the high-pressure pump 10. Also good. That is, the discharge passage 17 through which the fuel pressurized in the pressurizing chamber 12 flows, the high-pressure fuel pipe 5, the delivery pipe 4, and the like correspond to the “high-pressure side passage” recited in the claims.

As shown in FIG. 1, the relief valve 50 includes a relief valve body 51, an adjustment pipe 52, a relief spring 53, and the like. The relief valve body 51 is formed in a cylindrical shape, and is provided so as to be capable of reciprocating in the axial direction through the communication path 9. The relief valve body 51 is seated on a relief valve valve seat 54 formed on the inner wall of the communication passage 9 to close the communication passage 9 outside the diameter of the relief valve body 51, and is separated from the relief valve valve seat 54. By doing so, the communication path 9 outside the diameter of the relief valve body 51 is opened.
The adjustment pipe 52 is fixed to the inner wall of the communication path 9 on the side opposite to the relief valve valve seat 54 of the relief valve body 51. One end of the relief spring 53 is locked to the relief valve body 51, and the other end is locked to the adjustment pipe 52. The relief spring 53 urges the relief valve body 51 toward the relief valve seat 54. The load of the relief spring 53 can be set arbitrarily. In this embodiment, for example, the load of the relief spring 53 is set so that the relief valve body 51 opens at a pressure equal to or higher than the fuel pressure of the delivery pipe 4 in normal operation of the engine and below the pressure at which the electromagnetic injector 6 cannot inject fuel. The

The constant residual pressure valve 60 includes a valve body 61, a support body 62, a first spring 63 as an urging means, a spring stopper 64, a flow rate control means 70, and the like. These are accommodated in an inner communication passage 55 formed inside the relief valve body 51. The inner communication path 55 also corresponds to a “communication path” recited in the claims.
The inner communication passage 55 is formed with a concave taper portion 56 having a valve seat 65 on which the valve body 61 can be seated and separated. The concave tapered portion 56 corresponds to a “large diameter portion” described in the claims.
On the upstream side of the concave taper portion 56, a small diameter portion 57 in which the flow rate control means 70 is accommodated is formed.

The valve body 61 of the constant residual pressure valve 60 is formed in a spherical shape. The valve body 61 closes the inner communication path 55 by sitting on the valve seat 65, and opens the inner communication path 55 by separating from the valve seat 65.
A substantially cylindrical support body 62 is provided on the opposite side of the valve body 61 from the valve seat 65. The end of the support body 62 on the valve body 61 side is recessed in a substantially hemispherical shape, supports the valve body 61 and suppresses buckling of the first spring 63. A chamfer (not shown) extending in the axial direction is formed on the radially outer wall of the support 62, and fuel can flow between the chamfer and the inner wall of the inner communication passage 55.

The spring stopper 64 is press-fitted into the inner wall of the inner communication path 55. A through hole 66 communicating in the axial direction is formed at the center of the spring stopper 64 so that fuel can flow through the through hole 66.
The first spring 63 is a compression coil spring, and one end is locked to the spring stopper 64 and the other end is locked to the support body 62. The first spring 63 biases the support body 62 and the valve body 61 toward the valve seat 65.
The load of the first spring 63 can be arbitrarily set. In the present embodiment, a differential load between the first spring 63 and a second spring 67 as second urging means to be described later so that the fuel pressure in the delivery pipe 4 is equal to or higher than a predetermined pressure and the constant residual pressure valve 60 opens. Is set. The predetermined pressure at which the constant residual pressure valve 60 is opened is exemplified by a pressure that allows vapor generated in the delivery pipe 4 after the engine is stopped to be less than an allowable value and fuel leakage from the injector 6 to be less than an allowable value. Is done.

As shown in FIGS. 3 to 5, the flow rate control means 70 is provided on the upstream side of the valve body 61. The flow rate control means 70 includes a cylindrical sliding contact portion 71 and a locking portion 72 provided on the upstream side of the sliding contact portion 71. The slidable contact portion 71 has an outer diameter that is slightly smaller than the inner diameter of the small diameter portion 57 of the inner communication passage 55, and can be slidably contacted with the inner wall of the small diameter portion 57. A minute gap 58 (see FIG. 5) is formed between the radially outer wall of the sliding contact portion 71 and the inner wall of the small diameter portion 57. Note that the sliding contact portion 71 has an end on the valve body 61 side recessed in a substantially hemispherical shape, and suppresses the valve body 61 from moving in the radial direction when the valve is opened.
The locking portion 72 is formed in a substantially rectangular parallelepiped shape extending in the vertical direction on the paper surface of FIG. 3, and as shown in FIG. 5, both ends in the radial direction have an arc shape having the same radius as the radial outer wall of the sliding contact portion 71. Is formed. Therefore, the locking portion 72 can also slide in contact with the inner wall of the small diameter portion 57. The locking portion 72 locks the second spring 67 provided on the upstream side of the flow rate control means 70. The load of the second spring 67 is set to be smaller than the load of the first spring 63 and biases the flow rate control means 70 toward the valve body 61. Therefore, the valve body 61 and the flow rate control means 70 move together in the axial direction.

As shown in FIG. 3, when the valve element 61 of the constant residual pressure valve 60 is in the fully closed position, the sliding contact portion 71 is positioned on the inner side of the small diameter portion 57 and a minute gap is formed between the inner wall of the small diameter portion 57. 58 is formed. For this reason, the opening cross-sectional area of the inner communication passage 55 when the valve body 61 starts to open becomes the opening cross-sectional area of the minute gap 58, and the flow of fuel is controlled. The opening cross-sectional area of the minute gap 58 is set smaller than the opening cross-sectional area of the orifice 59 described later.
On the other hand, as shown in FIG. 4, when the valve body 61 of the constant residual pressure valve 60 is in the fully open position, the sliding contact portion 71 is located on the inner side of the concave taper portion 56. Therefore, the minute gap 58 described above is not formed, and the fuel flows promptly. At this time, the locking portion 72 is positioned on the inner side of the small diameter portion 57 and maintains the coaxiality between the flow control means 70 and the small diameter portion 57.

  On the upstream side of the second spring 67, an orifice 59 that restricts the flow of fuel is provided. The orifice 59 adjusts the time during which the delivery pipe 4 is decompressed when the engine is stopped and the accelerator is off. Further, the orifice 59 suppresses the valve element 61 from being separated from the valve seat 65 due to fuel pressure pulsation propagating from the high-pressure fuel pipe 5 to the communication passage 9.

Next, the operation of the constant residual pressure valve 60 as well as the operation of the high-pressure pump 10 will be described. During engine operation, the high-pressure pump 10 repeats the intake stroke, metering stroke, and pressurization stroke.
(1) Suction stroke When the plunger 11 descends from the top dead center toward the bottom dead center, the pressure chamber 12 is depressurized. At this time, energization to the coil 33 is stopped and the intake valve 20 is opened, so that the supply passage 16 is opened. On the other hand, the discharge valve 40 is closed and the discharge passage 17 is closed. As a result, fuel is sucked into the pressurizing chamber 12 from the supply passage 16.
At this time, the fuel pressure in the pressurizing chamber 12 is lower than the fuel pressure in the discharge passage 17. For this reason, a differential pressure is generated between the fuel pressure upstream of the valve seat 65 of the constant residual pressure valve 60 and the fuel pressure downstream of the valve seat 65. Thereby, the valve body 61 is separated from the valve seat 65 and opens the inner communication path 55. Accordingly, the fuel is sucked back from the delivery pipe 4 side to the pressurizing chamber 12 side.

(2) Metering stroke When the plunger 11 rises from the bottom dead center toward the top dead center, the energization to the coil 33 is stopped until the predetermined time, and the suction valve 20 is in the open state. Therefore, the low pressure fuel in the pressurizing chamber 12 is returned to the supply passage 16.
When energization of the coil 33 is started at a predetermined time during the metering process, the mover 32 moves in a direction away from the pressurizing chamber 12 side by the magnetic force generated by the coil 33. The valve body 21 of the suction valve 20 is seated on the valve seat 23 by the elastic force of the spring 22 on the pressurizing chamber 12 side and the dynamic pressure of the low-pressure fuel discharged from the pressurizing chamber 12 to the supply passage 16. Occlude.
Thus, the metering process for returning the low-pressure fuel from the pressurizing chamber 12 to the supply passage 16 is completed. That is, the amount of low-pressure fuel discharged from the pressurizing chamber 12 to the supply passage 16 is adjusted by adjusting the energization time of the coil 33. Thereby, the amount of fuel pressurized in the pressurizing chamber 12 is determined.

(3) Pressurization stroke When the plunger 11 further rises toward the top dead center with the intake valve 20 closed, the pressure of the fuel in the pressurization chamber 12 rises. When the pressure of the fuel in the pressurizing chamber 12 exceeds a predetermined pressure, the discharge valve 40 opens against the elastic force of the spring 42 and the force received by the valve body 41 of the discharge valve 40 from the fuel on the delivery pipe 4 side. To do. As a result, the high-pressure fuel pressurized in the pressurizing chamber 12 is discharged from the discharge passage 17 of the high-pressure pump 10 to the delivery pipe 4 through the high-pressure fuel pipe 5.
When the discharge valve 40 opens, the fuel pressure in the discharge passage 17 and the fuel pressure in the pressurizing chamber 12 are substantially the same. For this reason, the fuel pressure upstream of the valve seat 65 of the constant residual pressure valve 60 and the fuel pressure downstream are substantially the same. Therefore, the valve element 61 of the constant residual pressure valve 60 is seated on the valve seat 65 by the urging force of the first spring 63 and closes the inner communication passage 55.

When the plunger 11 rises to the top dead center, the energization to the coil 33 is stopped and the suction valve 20 is opened again. Then, the plunger 11 descends again and the suction stroke is performed.
Thus, by repeating the steps (1) to (3), the high-pressure pump 10 pressurizes and discharges the sucked fuel. At the same time, the constant residual pressure valve 60 repeats opening and closing in the suction stroke and the pressurization stroke.

Next, the difference in operation between the constant residual pressure valve 60 of the present embodiment and the conventional constant residual pressure valve not provided with the flow rate control means will be described with reference to FIG.
As shown by the solid line A, the cam lift shifts from the lowest point to the highest point between time T1 and time T2. As the cam lift operates, the plunger 11 of the high-pressure pump 10 moves from the bottom dead center to the top dead center, whereby the discharge stroke of the high-pressure pump 10 is performed.
On the other hand, the cam lift shifts from the highest point to the lowest point between time T2 and time T7. The suction stroke of the high-pressure pump 10 is performed by the plunger 11 moving from the top dead center to the bottom dead center in accordance with the operation of the cam lift.

As shown by the solid line B, when the discharge valve 40 is opened during the time T1 to the time T2, the outlet pressure of the high-pressure pump 10 increases. Thereafter, when the discharge valve 40 is closed, the outlet pressure of the high-pressure pump 10 changes at a pressure approximate to that of the delivery pipe 4.
As shown by the broken line C, the pressurizing chamber pressure increases as the plunger 11 rises between time T1 and time T2, and decreases as the discharge valve 40 opens. Further, the pressurizing chamber pressure is reduced as the plunger 11 is lowered during the time T2 to the time T7.
Thus, the outlet pressure of the high-pressure pump 10 and the pressurizing chamber pressure change in substantially the same manner from time T1 to time T2. On the other hand, the outlet pressure of the high pressure pump 10 becomes higher than the pressurizing chamber pressure during the time T2 to the time T7.

As shown by the broken line D, the conventional constant residual pressure valve starts opening at time T3 when the differential pressure between the outlet pressure of the high pressure pump 10 and the pressurizing chamber pressure becomes equal to or higher than a predetermined pressure set in the constant residual pressure valve. To do. At time T4, the lift amount of the valve body becomes maximum, and thereafter, the lift amount gradually decreases as the outlet pressure of the high-pressure pump 10 is reduced. When the high pressure pump 10 shifts to the suction stroke at time T7 and the differential pressure between the outlet pressure of the high pressure pump 10 and the pressurizing chamber pressure becomes smaller than a predetermined pressure, the constant residual pressure valve is closed.
As shown by the broken line E, the amount of fuel sucked back in the conventional constant residual pressure valve increases in a short time from time T3 to time T4, and then gradually decreases with the lift amount of the valve body from time T4 to time T7. However, it becomes 0 when the constant residual pressure valve is closed.

  On the other hand, the constant residual pressure valve 60 of the present embodiment starts to open at time T3 of the suction stroke of the high-pressure pump 10 as indicated by the solid line F. Between time T3 and time T5, the valve opening speed is slow due to the frictional force between the outer wall of the sliding contact portion 71 or the locking portion 72 and the inner wall of the small diameter portion 57 or the like. When the sliding contact portion 71 moves from the small diameter portion 57 toward the concave taper portion 56 at time T5, the valve opening speed is increased, and the lift amount of the valve element 61 is maximized at time T6. Thereafter, as the outlet pressure of the high-pressure pump 10 is reduced, the lift amount gradually decreases. At time T7, the high-pressure pump 10 moves to the suction stroke, and the differential pressure between the outlet pressure of the high-pressure pump 10 and the pressurizing chamber pressure is smaller than a predetermined pressure. Then, the constant residual pressure valve 60 is closed.

The amount of fuel sucked back in the constant residual pressure valve 60 of the present embodiment is formed between the outer wall of the sliding contact portion 71 and the inner wall of the small diameter portion 57 from time T3 to time T5, as shown by the solid line G. The fuel flow is controlled by the minute gap 58. Thereafter, when the sliding contact portion 71 moves from the small diameter portion 57 toward the concave tapered portion 56 at time T5, the opening cross-sectional area of the inner communication passage 55 increases, and the amount of fuel sucked back increases in a short time from time T5 to time T6. To do. Thereafter, it gradually decreases with the lift amount of the valve body 61 between time T6 and time T7, and becomes 0 when the constant residual pressure valve 60 is closed.
Therefore, the constant residual pressure valve 60 of the present embodiment does not immediately start depressurization of the delivery pipe 4, but substantially starts depressurization of the delivery pipe 4 from time T5. Therefore, the constant residual pressure valve 60 of the present embodiment has a small amount of sucking back immediately after the valve opening from time T3 to time T5, so that the amount of fuel sucking back during the intake stroke is reduced compared to the conventional constant residual pressure valve. Can do.

Next, the relationship between the suction process time of the high-pressure pump 10 and the suck back amount will be described with reference to FIG.
The solid line H shows the amount of fuel sucked back by the constant residual pressure valve 60 of the present embodiment, and the broken line I shows the amount of fuel sucked back by the conventional constant residual pressure valve not provided with the flow rate control means 70.
The constant residual pressure valve 60 of the present embodiment reduces the amount of fuel sucked back when the suction stroke time of the high-pressure pump 10 is the same as that of the conventional constant residual pressure valve. The difference between the suction back amount by the constant residual pressure valve 60 of this embodiment and the suction back amount by the conventional constant residual pressure valve increases as the suction stroke time increases.

In FIG. 8, the solid line J shows the discharge efficiency of the high-pressure pump 10 in the fuel supply apparatus 1 having the constant residual pressure valve 60 of the present embodiment, and the discharge efficiency of the high-pressure pump in the fuel supply apparatus not having the constant residual pressure valve is one point. The broken line L shows the discharge efficiency of the high-pressure pump in the fuel supply device provided with the conventional constant residual pressure valve.
A high-pressure pump in a fuel supply apparatus that does not include a constant residual pressure valve has the highest discharge efficiency because there is no fuel suck back.
The discharge efficiency of the high-pressure pump in the conventional fuel supply apparatus including the constant residual pressure valve is lower than that of the high-pressure pump not including the constant residual pressure valve.
The high-pressure pump 10 in the fuel supply apparatus 1 including the constant residual pressure valve 60 of the present embodiment is more particularly suitable for discharge in a low engine speed range where the intake stroke takes longer time than that of a conventional constant residual pressure valve. Reduction in efficiency is suppressed.

The constant residual pressure valve 60 of this embodiment has the following effects.
(1) During the operation of the engine, the amount of fuel sucked back can be reduced in the intake stroke of the high-pressure pump 10. For this reason, the discharge efficiency of the high-pressure pump 10 can be increased. In particular, the constant residual pressure valve 60 of the present embodiment can greatly increase the discharge efficiency of the high-pressure pump 10 at the start of the engine with a low engine speed. Therefore, the startability of the engine can be improved.
Moreover, since the engine load is reduced by increasing the discharge efficiency of the high-pressure pump 10, fuel efficiency can be improved.
(2) On the other hand, when the engine is stopped and the accelerator is off, the constant residual pressure valve 60 is fully opened and remains in the fully open position until the fuel pressure of the delivery pipe 4 drops to a predetermined pressure, so the fuel pressure of the delivery pipe 4 is quickly reduced. And can be maintained at a predetermined pressure. Therefore, it is possible to suppress the deterioration of emissions and the restartability when the engine is restarted, which is the original function of the constant residual pressure valve 60. In addition, it is possible to suppress acceleration shock when the accelerator is depressed again after the accelerator is turned off, and to suppress deterioration in fuel consumption and emission.
(3) Since the flow rate control means 70 and the valve body 61 are formed separately, the valve body 61 and the flow rate control means 70 can be easily made coaxial, and the small diameter portion 57 of the inner communication passage 55 can be obtained. The inner wall and the flow rate control means 70 can be smoothly slid. Therefore, the fuel pressure of the delivery pipe 4 can be quickly reduced when the engine is stopped and the accelerator is off.

(Second Embodiment)
A constant residual pressure valve according to a second embodiment of the present invention is shown in FIG. Hereinafter, in a plurality of embodiments, the same numerals are given to the composition substantially the same as a 1st embodiment mentioned above, and explanation is omitted. In the constant residual pressure valve of the present embodiment, the valve body 61 and the flow rate control means 70 are integrally formed by welding or adhesion. For this reason, the 2nd spring 67 is abolished.
In the present embodiment, the production cost of the constant residual pressure valve can be reduced by eliminating the second spring 67.

(Third embodiment)
A constant residual pressure valve according to a third embodiment of the present invention is shown in FIG. In the constant residual pressure valve of the present embodiment, a needle valve 68 is employed as the valve body. On the upstream side of the needle valve 68, a flow rate control means 73 is integrally formed. The flow rate control means 73 includes a cylindrical sliding contact portion 74 and a conical portion 75 provided on the upstream side of the sliding contact portion 74. A minute gap is formed between the outer wall in the radial direction of the sliding contact portion 74 and the inner wall of the small-diameter portion 57 of the inner communication passage 55, and the fuel flow can be controlled.
When the needle valve 68 is in the fully closed position, the sliding contact portion 74 is located inside the small diameter portion 57 of the inner communication passage 55 and forms a minute gap with the inner wall of the small diameter portion 57. For this reason, the opening cross-sectional area of the inner communication passage 55 when the needle valve 68 starts to open becomes the opening cross-sectional area of the minute gap, and the flow of fuel is controlled.
On the other hand, when the needle valve 68 is in the fully open position, the slidable contact portion 74 is located inside the concave tapered portion 56. Therefore, the above-mentioned minute gap is not formed, and the fuel flows promptly.
Also in this embodiment, the same operational effects as those of the first and second embodiments described above can be achieved.

(Fourth embodiment)
A constant residual pressure valve according to a fourth embodiment of the present invention is shown in FIG. In the constant residual pressure valve of this embodiment, a cylindrical flow rate control means 76 is provided inside the through hole 66 of the spring stopper 64. Between the radially outer wall of the flow rate control means and the inner wall of the through hole 66, a minute gap capable of controlling the fuel flow is formed. The flow control means 76 and the needle valve 68 are connected by a connecting rod 77. Thereby, the flow control means 76 can move together with the needle valve 68.
In the present embodiment, the through hole 66 of the spring stopper 64 corresponds to a “small diameter portion” recited in the claims. Further, the communication passage 9 on the downstream side of the through hole 66 of the spring stopper 64 corresponds to a “large diameter portion” recited in the claims.
When the needle valve 68 is in the fully closed position, the flow rate control means 76 is located inside the through hole 66 of the spring stopper 64 and a minute gap is formed between the inner wall of the through hole 66. For this reason, the opening cross-sectional area of the inner communication passage 55 when the valve body starts to open becomes the opening cross-sectional area of the minute gap, and the fuel flow is controlled.
On the other hand, when the needle valve 68 is in the fully open position, the flow rate control means 76 is located in the communication passage 9 on the downstream side of the spring stopper 64. Therefore, the above-mentioned minute gap is not formed, and the fuel flows promptly.
Also in this embodiment, the same operational effects as those of the first to third embodiments described above can be achieved.

(Other embodiments)
In the embodiment described above, the constant residual pressure valve 60 is provided in the inner communication passage 55 formed inside the relief valve body 51. On the other hand, in the present invention, the constant residual pressure valve and the relief valve may be provided separately. Moreover, the valve body of the discharge valve of a high pressure pump may be formed in a cylinder shape, and a constant residual pressure valve may be provided in the communication path formed inside thereof. Further, a communication passage may be formed in the pump body of the high-pressure pump, and a constant residual pressure valve may be provided in the communication passage.
In the embodiment described above, the sliding contact portions 71, 74 of the flow rate control means 70, 73, 76 are formed in a columnar shape. On the other hand, in the present invention, the sliding contact portion of the flow rate control means may be formed in a taper shape having an upstream outer diameter smaller than the downstream outer diameter.
Thus, the present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 1 ... Fuel supply apparatus 5 ... High pressure fuel piping (high pressure side passage)
9 ... Communication passage 10 ... High pressure pump 11 ... Plunger 12 ... Pressure chamber 55 ... Inner communication passage (communication passage)
56 ... Concave taper part (large diameter part)
57 ... Small diameter part 58 ... Minute gap 60 ... Constant residual pressure valve 61 ... Valve body 63 ... First spring (biasing means)
65 ... Valve seats 70, 73, 76 ... Flow rate control means 71, 74 ... Sliding part 72 ... Locking part

Claims (6)

A constant residual pressure valve provided in a communication passage that connects a pressurizing chamber that pressurizes fuel by reciprocating movement of a plunger and a high-pressure side passage through which fuel pressurized in the pressurizing chamber flows;
A valve body that closes the communication path by sitting on a valve seat formed on an inner wall of the communication path and opens the communication path by separating from the valve seat;
Biasing means for biasing the valve body toward the valve seat;
The valve body has a slidable contact portion that can be slidably contacted with the inner wall of the communication path, and moves together with the valve body so that the valve body is fully opened from an opening cross-sectional area of the communication path when the valve body starts to open. And a flow rate control means for increasing an opening cross-sectional area of the communication passage when the constant residual pressure valve is provided. The communication path includes a small-diameter portion that is in sliding contact with the sliding contact portion, and a large-diameter portion that has a larger inner diameter than the small-diameter portion downstream from the small-diameter portion,
When the valve body is in the fully closed position, the sliding contact portion is located on the inner diameter side of the small diameter portion,
2. The constant residual pressure valve according to claim 1, wherein when the valve body is in a fully open position, the sliding contact portion is located inside the diameter portion of the large diameter portion.   The constant residual pressure valve according to claim 2, wherein the sliding contact portion forms a minute gap capable of controlling the flow of fuel between an outer wall in a radial direction and an inner wall of the small diameter portion. The valve body and the flow rate control means are formed separately.
The constant flow rate according to any one of claims 1 to 3, wherein the flow rate control means is biased toward the valve body by a second biasing means having a biasing force smaller than that of the biasing means. Pressure valve.   The constant residual pressure valve according to any one of claims 1 to 3, wherein the valve body and the flow rate control means are integrally formed. A plunger capable of reciprocating in the axial direction and a high-pressure pump having a pressurizing chamber for pressurizing fuel by reciprocating movement of the plunger;
A delivery pipe for storing fuel pressurized in the pressurizing chamber of the high-pressure pump;
An injector for injecting fuel accumulated in the delivery pipe into a cylinder of the engine;
The constant residual pressure valve according to any one of claims 1 to 5, provided in a communication passage that connects the pressurization chamber and a high-pressure side passage through which fuel pressurized in the pressurization chamber flows. A fuel supply device.

Images