JPH11343945A - Fuel pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a start failure due to an insufficient force feed quantity at an engine start and the cavitation erosion of a plunger due to an insufficient supply of fuel to a pump chamber in a high speed rotation area. SOLUTION: An overflow valve 70 is attached to a cylinder 14 so that a passage 72 provided in a valve body 71 faces gallery 41. This overflow valve 70 is formed in such a manner that first and second valve springs disposed in a valve body 71 so as to urge a ball 74 to close the passage 72 successively operate with the rise of the pressure of fuel in a fuel sump 19 so that the passage 72 is opened and closed by the ball 74 and the quantity of fuel exhausted from an exhaust hole 73 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel pump for boosting and discharging fuel in a pump chamber, and more particularly to a fuel pump structure capable of changing the pressure of fuel flowing into a pump chamber. This fuel pump can be applied, for example, as a variable discharge high pressure pump for pumping high pressure fuel into a common rail of a common rail type fuel injection device in which high pressure fuel stored in a common rail is injected into each cylinder of a diesel engine by an injector. .

[0002]

2. Description of the Related Art FIG. 10 is a sectional view showing the structure of a conventional high-pressure pump with a variable discharge amount. In FIG. 10, a cam chamber 11 is formed at a lower end of the pump housing 10. A cam shaft 12 that is driven to rotate by an internal combustion engine is inserted into the cam chamber 11.
Are formed. The cam 13 performs an ascending step twice per rotation of the camshaft 12. A cylinder 14 is mounted in the pump housing 10, and a plunger 15 is reciprocally and slidably fitted in the cylinder 14. A pump chamber 16 is formed by the upper end surface of the plunger 15 and the inner peripheral surface of the cylinder 14, and a fuel reservoir 19 is provided between the cylinder 14 and the pump housing 10.
Are formed. A fuel reservoir 19 is provided in the cylinder 14.
And a discharge hole 18 communicating with the pump chamber 16 at a position above the spill groove 17 in FIG.
Are formed. Further, the introduction pipe 28 is attached to the pump housing 10 so as to communicate with the spill groove 17. A discharge valve 20 is attached to the cylinder 14, and the discharge valve 20 is connected to the pump chamber 1 through a discharge hole 18.
It communicates with 6. The lower end of the plunger 15 is connected to a valve seat 24.
Is pressed against the slider 26. Slider 26
Has a cam roller 27, and the cam roller 27
3 is in sliding contact. Note that the reciprocating stroke of the plunger 15 is determined by the process difference of the cam 13.

[0003] A solenoid valve 3 as a low-pressure passage closing means is provided in the cylinder 14 at a position facing the upper end surface of the plunger 15.
0 is screwed and fixed. The solenoid valve 30 has a valve body 38 driven by a solenoid (not shown) and a spring (not shown). One end of the valve body 38 opens to the pump chamber 16 and the other end of the solenoid valve 30 moves to the low pressure side. The communicating low pressure passage 31 is communicated / blocked. The solenoid valve 30 is a pre-stroke type solenoid valve that sets the pressure start timing of the plunger 15 by energizing the solenoid at a predetermined timing. The solenoid valve 30 discharges by controlling the energization timing of the solenoid valve 30. The amount can be varied. The low-pressure passage 31 communicates with the fuel reservoir 19 via a gallery 41 and a passage 42. Also, the fuel pool 19,
The low-pressure passage 31, the gallery 41, and the passage 42 constitute a low-pressure fuel passage. Further, an overflow valve 60 is screwed and fixed to the cylinder 14 so as to face the gallery 41. This overflow valve 60 is
As shown in FIG. 11, a flow path 62 communicating with the gallery 41 is provided.
And a valve body 61 provided with a discharge hole 63 communicating with the flow path 62, and housed in the valve body 61,
A ball 64 for communicating and blocking the flow path 62;
1 and a valve spring 65 for urging the ball 64 in a direction of blocking the flow path 62. In addition, the discharge hole 63 is connected to a pump drain via a pipe when mounted on an actual machine.

In the variable discharge high-pressure pump 7 as a fuel pump configured as described above, low-pressure fuel is supplied to the fuel reservoir 19 through the introduction pipe 28 and the spill groove 17 by a feed pump (not shown). And the camshaft 12
The rotation of the cam 13 causes the plunger 15 to reciprocate through the cam roller 27 and the valve seat 24. Therefore, the low pressure fuel supplied to the fuel pool 19 is
When the low pressure passage 31 is communicated by the solenoid valve 30,
The gas is supplied to the pump chamber 16 through the passage 42, the gallery 41 and the low-pressure passage 31. Then, when the low pressure passage 31 is shut off by the solenoid valve 30, the plunger 15 moves up, and the fuel in the pump chamber 16 is pressurized. The fuel pressurized in the pump chamber 16 pushes the valve body 21 of the discharge valve 20 open against the urging force of the return spring 22, and the pressurized high-pressure fuel is discharged through the discharge port body 23. Is done. The discharge amount of the high-pressure fuel is adjusted by controlling the communication / shutoff timing of the low-pressure passage 31 by the solenoid valve 30.
When the pressure of the fuel supplied to the fuel pool 19 overcomes the urging force of the valve spring 65, the fuel pushes the ball 64 open against the urging force of the valve spring 65,
It is discharged from the discharge hole 63 via the flow path 62. Thus, the pressure of the fuel in the fuel reservoir 19, that is, the pressure of the fuel supplied to the pump chamber 16 is controlled.

Next, a fuel injection device employing the conventional variable discharge high pressure pump 7 configured as described above will be described with reference to FIG. In this fuel injection device, 3
The two variable discharge high pressure pumps 7 are arranged so that the phase of each of the cams 13 with respect to the cam lift angle is different from each other by 120 degrees of the pump rotation angle. The camshaft 12, which is the drive shaft of the three variable discharge high pressure pumps 7, rotates at half the speed of the engine. The fuel 8 sucked up by the feed pump 9 is supplied to the fuel reservoir 19 in the spill groove 17 of each variable discharge high pressure pump 7. When the pressure of the fuel supplied to the fuel reservoir 19 gradually increases and overcomes the urging force of the spring 65 of the overflow valve 60, the fuel 64 is pushed open, and is discharged from the flow passage 62 and the discharge hole 63 to the pump drain. .
That is, the pressure of the fuel in the fuel pool 19 increases linearly with the increase in the engine speed until the pressure of the fuel in the fuel pool 19 matches the urging force of the spring 65.
After that, the gradient becomes gentle and increases linearly with an increase in the engine speed. The fuel in the fuel reservoir 19 is supplied to the pump chamber 16 through the passage 42, the gallery 41, and the low-pressure passage 31. Thus, the pressure of the fuel in the pump chamber 16 is determined by the pressure of the fuel in the fuel reservoir 19, as shown in FIG. In FIG. 13 showing the relationship between the fuel pressure in the pump chamber 16 and the engine speed, the gradient of the straight line is determined by the spring force of the spring 65, and the inflection point indicates the operation start point of the overflow valve 60. The outlet 23 of each variable discharge high pressure pump 7 is connected to the common rail 4.

In order to control the solenoid valves 30a, 30b, 30c, a number corresponding to the number of engine cylinders (6 in this example)
A rotating disk 51 having a projection of (d) is mounted coaxially with the camshaft 12, and a cam angle sensor 50 is arranged to face the projection. Each time the projection passes near the cam angle sensor 50, a signal is electronically controlled. It is sent to the unit (ECU) 40. Here, the mounting phase of the rotating disk 51 is determined so as to approach the sensor 50 at a rotating phase near each bottom dead center of the cam 13. Further, the camshaft 12 has a pair of disks 61.
And a cylinder discriminating sensor 62 are also coaxially mounted. Only one protrusion is formed on the disk 61, so that the ECU 40 receives one signal per one rotation of the pump from the sensor 62. From the signals of the cylinder discriminating sensor 62 and the cam angle sensor 50, the ECU 40 can accurately discriminate and obtain the bottom dead center signal of the pump specific cylinder.

Therefore, the camshaft 12 is rotated by the internal combustion engine at half the rotation speed of the internal combustion engine. And
The plunger 15 is reciprocated by the cam 13 which rotates with the rotation of the cam shaft 12. When the plunger 15 moves down, the fuel fed from the feed pump 9 is supplied into the pump chamber 16. When the plunger 15 moves up, the solenoid valve 30 is not energized, so the valve body 38 of the solenoid valve 30 is open. Therefore, the fuel in the pump chamber 16 is supplied to the low-pressure passage 31, the gallery 41, and the passage 42.
Spills over sequentially and is not pressurized. This pump chamber 16
When a control pulse is sent to the solenoid valve 30 during the overflow of the fuel inside the valve, the valve body 38 closes the low pressure passage 31 and the plunger 1
5 starts pressurizing the fuel in the pump chamber 16. When the fuel pressure in the pump chamber 16 overcomes the urging force of the spring 22 of the discharge valve 20, the fuel pumped through the discharge hole 18 pushes the discharge valve 20 open and enters the common rail 4 through the discharge port 23. Discharged.

The ECU 40 can detect the specific cam phase of the specific cylinder of the pump from the signal of the cylinder discriminating sensor 62 and the signal of the cam angle sensor 50. In a three-cylinder × two-mount cam configuration, six pressure feeds corresponding to the number of engine cylinders are performed during one rotation of the camshaft 12. And E
The CU 40 sends a control signal to each of the solenoid valves 30a, 30b, 30c at a predetermined timing from the cam angle signal, and this control signal is interrupted by the next cam angle signal. Therefore, while the control signal is being sent to the solenoid valve 30, the solenoid valve 30 is closed.
The fuel in the pump chamber 16 pressurized by the discharge valve 2
It flows into the common rail 4 through 0 and is accumulated in the common rail 4. And the solenoid valves 30a, 30b, 30c
By controlling the timing of power supply to the motor according to the engine load (detected by a load sensor not shown), the engine speed (detected by a speed sensor not shown), or the common rail pressure (detected by the pressure sensor 37), It is possible to control the amount of fuel required to generate and maintain a target common rail pressure, and to achieve a desired common rail pressure. That is, if the energization timing is lengthened, the communication time between the pump chamber 16 and the low-pressure passage 31 is lengthened, so-called pre-stroke time is lengthened, and the fuel discharge amount is reduced. Conversely, if the energization timing is shortened, the pump chamber 16
The communication time between the pressure and the low-pressure passage 31 is shortened, so-called pre-stroke time is shortened, and the fuel discharge amount is increased.

Next, the relationship between the discharge amount of the feed pump 9 and the variable discharge amount high-pressure pump 7 and the set pressure of the valve spring 65 of the overflow valve 60 will be described with reference to FIG. In the figure, the discharge amount of the variable discharge amount high pressure pump 7 represents the case of the maximum discharge amount (the solenoid valve 30 is closed at the lowest position of the plunger 15). A _{0 of} FIG.
A ₃ is shows the relationship between the set pressure of the spring 65 of the discharge amount and the overflow valve 60 of the feed pump 9, A ₀ is the theoretical discharge amount of the feed pump 9, A ₁ ~
A ₃ is weakly a set pressure of the valve spring 65, respectively,
Medium and strong cases are shown. In addition, B _{0 to} B _{3 in} FIG.
Shows a relation between the discharge amount and the set pressure of the valve spring 65 of the overflow valve 60 of the variable discharge high pressure pump 7, B ₀ is the theoretical discharge amount of the variable discharge high pressure pump 7, B ₁ .about.B ₃ Indicates a case where the set pressure of the valve spring 65 is weak, medium and strong.

From A _{0 to} A _{3 in} FIG. 14, it can be seen that the pump rotation speed of the feed pump 9 increases as the rotation speed of the engine increases, and the discharge rate also increases. The discharge amount of the feed pump 9 decreases as the set pressure of the valve spring 65 increases. This is because the leak amount in the feed pump 9 increases as the set pressure of the valve spring 65 increases. Discharge amount of the variable discharge high pressure pump 7, as shown in B ₀ in FIG. 14, theoretically, increases with increase in the rotational speed of the engine. However, the discharge amount of the variable discharge amount high pressure pump 7 is actually B
₁ As shown in .about.B _3, in the region of the pump speed is low rotational speed, much higher set pressure of the valve spring 65 is weak,
As the pump rotation speed shifts to the higher rotation speed side, the greater the set pressure of the valve spring 65, the greater the increase. This is because in a region where the pump rotation speed is low, the plunger 15 moves up and down and the solenoid valve 30 opens longer, so that the pump chamber of the fuel supplied from the feed pump 9 to the fuel reservoir 19 is long. 16 is sufficiently long. Therefore, the amount of fuel flowing into the pump chamber 16 increases as the set pressure of the valve spring 65 decreases, as the amount of leakage decreases and the amount of fuel supplied from the feed pump 9 to the fuel pool 19 increases. On the other hand, in a region where the pump rotation speed is high, the rising and lowering time of the plunger 15 is short and the opening time of the solenoid valve 30 is short, so that the pump chamber 16 of the fuel supplied from the feed pump 9 to the fuel pool 19 is The inflow time into the tank becomes shorter. Therefore, the higher the pressure of the fuel in the fuel reservoir 19, that is, the higher the set pressure of the valve spring 65, the greater the amount of fuel flowing into the pump chamber 16.

As described above, when the set pressure of the valve spring 65 of the overflow valve 60 is increased, the feed pump 9 has a small pumping amount at a low rotation speed and low fuel temperature, and cannot pump the amount filling the pump chamber 16. . As a result, the variable discharge amount high pressure pump 7 cannot pump the fuel injected from the injector at the time of engine start to the common rail 4, resulting in poor starting. On the other hand, if the set pressure of the valve spring 65 of the overflow valve 60 is reduced, the valve opening time of the solenoid valve 30 is short in the high engine speed region, and the amount that fills the pump chamber 16 cannot be supplied. As a result, sufficient fuel is not supplied to the pump chamber 16 and the hatched area shown in FIG.
6 and the actual variable discharge high pressure pump 9
(Difference from the discharge amount) becomes bubbles (cavitation) and mixes with fuel in the pump chamber 16, and the destruction of the bubbles causes the plunger 15 to undergo cavitation erosion.

[0012]

As described above, the conventional variable discharge amount high pressure pump uses the overflow valve 60 having one valve spring 65, so that the set pressure of the overflow valve 60 becomes one type, and the engine pressure is reduced. From the low rotation speed range to the high rotation speed range, the fuel injected from the injector at the time of engine startup cannot be pumped to the common rail 4, causing start failure, or cavitation erosion of the plunger 15 in the engine high rotation speed range. There was a problem of generating a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. The present invention has been made to make it possible to change the set pressure of an overflow valve in accordance with the number of rotations of a pump, and to provide a starting failure due to an insufficient amount of pumping when starting the engine. It is another object of the present invention to provide a fuel pump capable of preventing cavitation erosion of a plunger due to a shortage of fuel supply to a pump chamber in a high rotation range.

[0014]

A fuel pump according to the present invention is provided with a cylinder, a plunger reciprocally and slidably fitted in the cylinder, and an inner periphery of the cylinder provided in the cylinder. A low-pressure fuel passage serving as a passage for low-pressure fuel flowing into a pump chamber formed of a surface and an upper surface of the plunger; a cam fixed to a cam shaft rotatably driven by an engine, for driving the plunger up and down; A low-pressure fuel passage closing unit that closes the low-pressure fuel passage and controls a period in which the fuel in the pump chamber is boosted by the plunger ascending step, and a discharge passage that communicates with the flow passage, A valve body attached to the cylinder such that the flow path faces the low-pressure fuel path, a valve body housed in the valve body so as to open and close the flow path, and The valve body is disposed in the valve body so as to urge the valve body in a direction to close the passage, and sequentially operates as the fuel pressure in the low-pressure fuel passage increases to open and close the flow passage by the valve body. A plurality of valve springs for controlling the amount of fuel discharged from the discharge hole, and the low-pressure fuel passage supplied from a feed pump whose discharge amount increases in conjunction with an increase in the engine speed. An overflow valve for adjusting the fuel pressure in accordance with the engine speed.

Further, the fuel pump according to the present invention includes a cylinder, a plunger reciprocally and slidably fitted in the cylinder, and a plunger provided in the cylinder. A low-pressure fuel passage that serves as a passage for low-pressure fuel flowing into the pump chamber formed by the upper surface of the pump chamber and a cam shaft that is rotationally driven by the engine;
A cam for driving the plunger to move up and down, a low-pressure fuel passage closing means attached to the cylinder, and closing the low-pressure fuel passage to control a period for raising the pressure of the fuel in the pump chamber by the ascending step of the plunger; A valve body having a discharge hole communicating with the flow passage, the valve body attached to the cylinder such that the flow passage faces the low-pressure fuel passage, a valve body housed in the valve body so as to open and close the flow passage, A valve spring disposed in the valve body, for urging the valve body in a direction to close the flow path, and adjusting a spring force of the valve spring in accordance with the engine speed by the valve body. The feed passage is constituted by a spring force adjusting means for opening and closing the flow passage and controlling the amount of fuel discharged from the discharge hole. The pressure of fuel in the in the low-pressure fuel passage are those with a overflow valve to adjust according to the rotation speed of the engine.

The spring force adjusting means includes a rod provided on the valve body so as to reciprocate in the direction of expansion and contraction of the valve spring, and a stepping motor for reciprocating the rod in the direction of expansion and contraction of the valve spring. It is configured.

Further, the low-pressure fuel passage closing means is constituted by an electromagnetic valve.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a cross-sectional view showing a configuration of a variable discharge high-pressure pump according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view showing a configuration of an overflow valve used in the variable discharge high-pressure pump.

Referring to FIG. 1, in a variable discharge high pressure pump 100 as a fuel pump, an overflow valve 70 is provided.
Are screwed and fixed to the cylinder 14 so as to face the gallery 41. As shown in FIG. 2, the overflow valve 70 has a valve body 71 provided with a flow path 72 communicating with the gallery 41 and a discharge hole 73 communicating with the flow path 72, and is housed in the valve body 71. A ball 74 as a valve body for communicating and blocking the flow path 72, a first valve spring 75 contracted in the valve body 71 and biasing the ball 74 in a direction for blocking the flow path 72, An annular stopper 76 is disposed in the discharge hole 73 side of the ball 74, contacts the ball 74 and cooperates with the ball 74 to communicate and shut off the flow path 72. The second for urging the stopper 76 toward the ball 74
And a valve spring 77. Here, the urging force of the first valve spring 75 is set weaker than the urging force of the second valve spring 77. Note that the variable discharge amount high-pressure pump 10 according to the first embodiment
Numeral 0 is the same as the conventional variable discharge amount high pressure pump 7 except that an overflow valve 70 is used instead of the overflow valve 60.

Next, the operation of the thus-configured variable discharge high pressure pump 100 will be described. The low-pressure fuel is supplied to the fuel reservoir 19 through the introduction pipe 28 and the spill groove 17 by a feed pump (not shown). When the cam 13 rotates due to the rotation of the cam shaft 12, the plunger 15 reciprocates through the cam roller 27 and the valve seat 24. Therefore, the low-pressure fuel supplied to the fuel pool 19 is supplied to the passage 42, the gallery 41 and the low-pressure passage 3 when the low-pressure passage 31 is communicated with the solenoid valve 30.
1 is supplied to the pump chamber 16. Then, when the low pressure passage 31 is shut off by the solenoid valve 30, the plunger 15 moves up, and the fuel in the pump chamber 16 is pressurized. The fuel pressurized in the pump chamber 16 is supplied to the discharge valve 2
0 valve element 21 is pushed open against the urging force of the return spring 22, and the high-pressure fuel pressurized by this is discharged to the discharge port element 2.
3 is discharged. The discharge amount of the high-pressure fuel is adjusted by controlling the communication / shutoff timing of the low-pressure passage 31 by the solenoid valve 30. When the pressure of the fuel supplied to the fuel reservoir 19 overcomes the urging force of the first valve spring 75, the fuel pushes the ball 74 open against the urging force of the first valve spring 75, and the flow path 72 Through the discharge hole 7
It is discharged from 3. When the pressure of the fuel in the fuel pool 19 further increases, the ball 74 moves while contracting the first valve spring 75, and finally contacts the stopper 76 to shut off the flow path 72. When the pressure of the fuel in the fuel pool 19 overcomes the urging force of the second valve spring 77, the fuel pushes and opens the ball 74 and the stopper 76 against the urging force of the second valve spring 77,
It is discharged from the discharge hole 73 through the flow path 72. Thus, the pressure of the fuel in the fuel reservoir 19, that is, the pressure of the fuel supplied to the pump chamber 16 is controlled.

Next, a fuel injection system employing the variable discharge high pressure pump 100 configured as described above will be described with reference to FIG.
This will be described with reference to FIG. In this fuel injection device, three variable discharge amount high-pressure pumps 100 are arranged such that the phases of the cams 13 with respect to the cam lift angle are different from each other by a 120-degree pump rotation angle. The camshaft 12, which is the drive shaft of the three variable discharge high-pressure pumps 100, rotates at half the speed of the engine. The fuel 8 sucked up by the feed pump 9 is supplied to the fuel reservoir 19 in the spill groove 17 of each variable discharge amount high pressure pump 100. Then, they are introduced into each pump chamber 16 when the solenoid valves 30a, 30b, 30c are opened. The fuel introduced into each pump chamber 16 is pressurized by the upward movement of the plunger 15, and is fed to the common rail 4 through the discharge port 23.

The pressure of the fuel supplied to the fuel reservoir 19 gradually increases with an increase in the engine speed.
First valve spring 7 of overflow valve 70
5 and pushes the ball 74 open, and the flow path 7
2 and is discharged from the discharge hole 73 to the pump drain. Then, the engine speed further increases, and the fuel pool 19
The pressure of the fuel supplied to the nozzle 74 rises, and the ball 74 comes into contact with the stopper 76. In addition, the engine speed increased,
When the pressure of the fuel supplied to the fuel reservoir 19 overcomes the urging force of the first and second valve springs 75 and 77, the ball 74 and the stopper 76 are pushed open, and the fuel is discharged from the flow path 72 and the discharge hole 73 to the pump drain. You. That is, the pressure of the fuel in the fuel reservoir 19 increases linearly with the engine speed until it matches the urging force of the first valve spring 75.
After that, the gradient becomes gentler and then rises linearly as the engine speed increases until the ball 74 comes into contact with the stopper 76.
After the ball 74 contacts the stopper 76, the gradient of the fuel becomes steep and rises linearly with an increase in the engine speed, and the pressure of the fuel rises in the first and second valve springs. After matching with the urging forces of 75 and 77, the gradient becomes gentle and increases linearly with an increase in the engine speed. Since the fuel in the fuel reservoir 19 is supplied to the pump chamber 16 through the passage 42, the gallery 41 and the low-pressure passage 31, the pressure of the fuel in the pump chamber 16 is determined by the pressure of the fuel in the fuel reservoir 19, As shown in FIG. In FIG. 4, the point P
Reference numeral ₁ denotes an operation start point of the first valve spring 75 and a point P
₂ is a point P when the ball 74 contacts the stopper 76.
Reference numeral ₃ denotes an operation start point of the second valve stopper 77, and the first valve spring 75 has an operating pressure of 0.3MPa.
The spring force of the second valve spring 77 is set such that the operating pressure becomes 0.8 MPa. In FIG. 4, for comparison,
The dashed line indicates the fuel pressure in the pump chamber 16 of the conventional variable discharge high pressure pump 7.

In order to control the solenoid valves 30a, 30b and 30c, the number corresponding to the number of engine cylinders (6 in this example)
A rotating disk 51 having a projection of (d) is mounted coaxially with the camshaft 12, and a cam angle sensor 50 is arranged to face the projection. Each time the projection passes near the cam angle sensor 50, a signal is electronically controlled. It is sent to the unit (ECU) 40. Here, the mounting phase of the rotating disk 51 is determined so as to approach the sensor 50 at a rotating phase near each bottom dead center of the cam 13. Further, the camshaft 12 has a pair of disks 61.
And a cylinder discriminating sensor 62 are also coaxially mounted. Only one protrusion is formed on the disk 61, so that the ECU 40 receives one signal per one rotation of the pump from the sensor 62. From the signals of the cylinder discriminating sensor 62 and the cam angle sensor 50, the ECU 40 can accurately discriminate and obtain the bottom dead center signal of the pump specific cylinder.

Then, the camshaft 12 is rotated by the internal combustion engine at half the rotation speed of the internal combustion engine. And
The plunger 15 is reciprocated by the cam 13 which rotates with the rotation of the cam shaft 12. When the plunger 15 moves down, the fuel fed from the feed pump 9 is supplied into the pump chamber 16. When the plunger 15 moves up, the solenoid valve 30 is not energized, so the valve body 38 of the solenoid valve 30 is open. Therefore, the fuel in the pump chamber 16 is supplied to the low-pressure passage 31, the gallery 41, and the passage 42.
Spills over sequentially and is not pressurized. This pump chamber 16
When a control pulse is sent to the solenoid valve 30 during the overflow of the fuel inside the valve, the valve body 38 closes the low pressure passage 31 and the plunger 1
5 starts pressurizing the fuel in the pump chamber 16. When the fuel pressure in the pump chamber 16 overcomes the urging force of the spring 22 of the discharge valve 20, the fuel pumped through the discharge hole 18 pushes the discharge valve 20 open and enters the common rail 4 through the discharge port 23. Discharged.

The ECU 40 can detect the specific cam phase of the specific pump cylinder from the signal of the cylinder discriminating sensor 62 and the signal of the cam angle sensor 50. In a three-cylinder × two-mount cam configuration, six pressure feeds corresponding to the number of engine cylinders are performed during one rotation of the camshaft 12. And E
The CU 40 sends a control signal to each of the solenoid valves 30a, 30b, 30c at a predetermined timing from the cam angle signal, and this control signal is interrupted by the next cam angle signal. Therefore, while the control signal is being sent to the solenoid valve 30, the solenoid valve 30 is closed.
The fuel in the pump chamber 16 pressurized by the discharge valve 2
It flows into the common rail 4 through 0 and is accumulated in the common rail 4. And the solenoid valves 30a, 30b, 30c
By controlling the timing of power supply to the motor according to the engine load (detected by a load sensor not shown), the engine speed (detected by a speed sensor not shown), or the common rail pressure (detected by the pressure sensor 37), It is possible to control the amount of fuel required to generate and maintain a target common rail pressure, and to achieve a desired common rail pressure.

Next, the relationship between the discharge amount of the feed pump 9 and the variable discharge amount high-pressure pump 100 and the pump speed will be described with reference to FIG. In the figure, the discharge amount of the variable discharge amount high pressure pump 100 represents the case of the maximum discharge amount (the solenoid valve 30 is closed at the lowest position of the plunger 15). In FIG. 5, A ₄ is set pressure first weak of the valve spring 75 and the set pressure is a second intensity of the valve spring 77
The figure shows the discharge amount of the feed pump 9 when the overflow valve 70 having
₀ the theoretical discharge amount of the feed pump 9, A ₁ is the discharge amount of the feed pump 9 when the set pressure using a conventional overflow valve 60 with a valve spring 65 weak, A ₃ is the strength set pressure 5 shows the discharge amount of the feed pump 9 when the conventional overflow valve 60 having the valve spring 65 is used. Further, B ₄ is variable discharge high pressure pump in the case of using an overflow valve 70 which set pressure and a second valve spring 77 is strong first valve spring 75 and the set pressure of the weak 1
Shows the discharge amount of 00, If B0 for comparison theoretical discharge amount of the variable discharge high pressure pump 100, B ₁ is using a conventional overflow valve 60 which set pressure is provided with a valve spring 65 weak Variable discharge high pressure pump 7
Valve spring 6 of the discharge rate, B ₃ is of strong set pressure
5 shows the discharge amount of the variable discharge amount high-pressure pump 7 when the conventional overflow valve 60 provided with the pump 5 is used. Further, C represents the minimum discharge required for the variable discharge high-pressure pump 100 to supply fuel to the engine.

[0027] From A ₄ in FIG. 5, the discharge amount of the feed pump 9 is in a low speed region of the pump speed is defined by a first valve spring 75 weak set pressure, high rotational speed of the pump speed It can be seen that the region is defined by the second valve spring 77 having a high set pressure. That is, the discharge amount of the feed pump 9 in the first embodiment linearly increases (coincides with the straight line A1) with an increase in the pump rotation speed, and when the operation amount exceeds the operation start point P1 of the first valve spring 75, the gradient thereof increases. Gradually rises as the pump speed increases, and the second valve spring 7
5 exceeds operation start point P ₃ of the linearly increases with increasing pump speed is the slope steep to (matches the straight line A _3). From _{B 4} of FIG. 5, the variable discharge high pressure pump 1
The discharge amount of 00 is defined by the first valve spring 75 having a low set pressure in a region where the pump rotational speed is low, and the second valve spring 77 having a strong set pressure in a region where the pump rotational speed is high. It can be seen that this is defined by That is, the discharge amount of the variable discharge high pressure pump 100 in the first embodiment, increases linearly with increasing pump speed to (matches a straight line B _1), operation start point of the first valve spring 75 P ₁ the exceeding the increases with increasing pump speed is the gradient gentle, it exceeds the operating start point P ₃ of the second valve spring 75 increases with the slope increase in the pump speed becomes steeper (linear B ₃ to match) to.

Therefore, the variable discharge amount high pressure pump 100
In the region where the pump rotation speed is low, the first valve spring 75 having a low set pressure regulates the leakage from the feed pump 9 and the fuel pool 19.
Is sufficiently introduced into the pump chamber 16 during the long valve opening time of the solenoid valve 30, while the second valve spring 77 having a high set pressure is used in a region where the pump rotational speed is high. As specified, feed pump 9
The high-pressure fuel supplied to the fuel reservoir 19 from the
During a short valve opening time of 0, the gas flows sufficiently into the pump chamber 16, and a discharge amount that ensures the minimum discharge amount C is obtained in the entire range of the pump rotation speed.

From B ₁ , B ₃ , and C in FIG. 5, in the conventional variable discharge amount high pressure pump 7, when the set pressure of the valve spring 65 is reduced, the minimum discharge amount in the high rotation speed region of the pump rotation speed is reduced. C could not be secured and the valve spring 65
It can be seen that if the set pressure is increased, the minimum discharge amount C cannot be secured in the low rotation speed region of the pump rotation speed.

According to the first embodiment, the fuel flowing into the pump chamber 16 using the overflow valve 70 including the first valve spring 75 having a weak set pressure and the second valve spring 77 having a strong set pressure. The pressure is controlled. Therefore, the variable discharge amount high pressure pump 10
As for the discharge amount of 0, the minimum discharge amount C can be ensured in the entire range of the pump rotation speed. Further, since the discharge amount is defined by the first valve spring 75 having a low set pressure in a region where the pump rotational speed is low, the fuel can be sufficiently supplied to the pump chamber 16 even at low rotational speed and low fuel temperature. In addition, the variable discharge high pressure pump 100 can pump the fuel injected from the injector at the time of starting the engine to the common rail 4 to prevent the occurrence of poor starting. On the other hand, in the region where the pump rotation speed is high, the fuel pressure becomes high because it is regulated by the second valve spring 77 having a strong set pressure.
The fuel can be sufficiently supplied to the pump chamber 16 during the short valve opening time of the solenoid valve 30, the mixture of fuel bubbles in the pump chamber 16 can be suppressed, and cavitation erosion of the plunger 15 can be prevented.

In the first embodiment, the overflow valve 70 having the first and second valve springs 75 and 77 is used. However, the number of valve springs is not limited to two, but may be three. More than one valve spring may be used. In this case, the discharge amount of the feed pump or the variable discharge amount high-pressure pump can be more optimally controlled according to the engine speed.

Embodiment 2 FIG. FIG. 6 is a sectional view showing a configuration of a variable discharge amount high pressure pump according to Embodiment 2 of the present invention.
FIG. 7 is a configuration diagram showing a fuel injection device employing a variable discharge high pressure pump according to Embodiment 2 of the present invention. In the second embodiment, the overflow valve 80 is screwed and fixed to the cylinder 14 so as to face the gallery 41. The overflow valve 80 includes a valve body 81 having a flow path 82 communicating with the gallery 41 and a discharge hole 83 communicating with the flow path 82.
1 and a ball 84 serving as a valve body for communicating / blocking the flow path 82, and a spring force adjusting means provided on the valve body 81 so as to be able to reciprocate in a direction of coming and going with respect to the ball 84. Rod 85 and ball 8 in valve body 81
4 and the rod 85, and the ball 84
A valve spring 86 for biasing the valve spring 2 in a direction to shut off the valve spring 2;
The rod 85 is driven to drive the ball 8 of the valve spring 85.
And a stepping motor 87 as a spring force adjusting means for adjusting the urging force of the stepping motor 4. This stepping motor 87 includes an annular rotor 88 and a rotor 8.
And a coil 89 that is provided on the outer periphery of the motor 8 and drives the rotor 88 to rotate. Means for converting the rotational torque of the rotor 88 into a linear movement force and transmitting the linear torque to the rod 85 is not shown, but, for example, a pin is erected on the rod 85, and a spiral groove is provided on the inner peripheral surface of the rotor 88. The rod 85 may be configured to be linearly reciprocated by the rotation of the rotor 88 by fitting the pin and the spiral groove. The variable discharge amount high pressure pump 101 according to the second embodiment is
The configuration is the same as that of the first embodiment except that an overflow valve 80 is used instead of the overflow valve 70.

In the second embodiment, the rotor 88 is rotated by energizing the coil 89.
The rod 85 is moved left and right in FIG. 6 by the rotation of
The movement of the rod 85 causes the valve spring 86 to expand and contract. By controlling the amount of current supplied to the coil 89, the urging force of the valve spring 85 is adjusted. Further, the moving direction of the rod 85 is determined by the rotating direction of the rotor 88. Then, the fuel supplied to the fuel reservoir 19 by the feed pump 9 gradually increases in pressure as the engine speed increases, and when the pressure of the fuel overcomes the urging force of the valve spring 86 of the overflow valve 80, the ball 84 is pushed open. The liquid is discharged to the pump drain from the flow path 82 and the discharge hole 83. At this time, the ECU 40 controls the amount of current supplied to the coil 89 so that the fuel pressure in the pump chamber 16 becomes optimal based on the engine speed and the fuel temperature.
That is, the spring set load of the valve spring 85 is increased in a high engine speed range, and the spring set load of the valve spring 85 is reduced in a low engine speed range.

Here, the ECU 40 determines that the operating pressures of the valve spring 86 are 0.3 MPa and 0.5 MPa, respectively, in the low rotation speed range, the middle rotation speed range, and the high rotation speed range of the engine.
a, the spring force of the valve spring 86 is adjusted by controlling the amount of current supplied to the coil 89 so as to be 0.8 MPa. Then, when the engine speed increases and the pressure of the fuel supplied to the fuel reservoir 19 reaches 0.3 MPa, the ball 84 is pushed open, and the fuel is discharged to the pump drain via the flow path 82 and the discharge hole 83. . Further, when the engine speed rises and enters the middle rotation range, the operating pressure of the valve spring 86 is set to 0.5 MPa, and the ball 8
4 is pushed back and the flow path 82 is shut off. Then, when the engine speed increases and the pressure of the fuel supplied to the fuel reservoir 19 becomes 0.5 MPa, the ball 84 is pushed open again, and the fuel is discharged to the pump drain via the flow path 82 and the discharge hole 83. You. Furthermore, when the engine speed increases and enters the high speed region, the operating pressure of the valve spring 86 is set to 0.8 MPa, the ball 84 is pushed back, and the flow path 82 is shut off. Then, the engine speed increases and the pressure of the fuel supplied to the fuel pool 19 becomes 0.8 M
When the pressure reaches Pa, the ball 84 is pushed open again, and the fuel is discharged to the pump drain via the flow path 82 and the discharge hole 83. Thus, the pressure of the fuel in the pump chamber 16 fluctuates as the engine speed increases, as shown in FIG. In FIG. 8, the point _{Q 1} is the operation starting point of the valve spring 86 which spring force is set to 0.3 MPa, the point _{Q 2}
Is the operation start point of the valve spring 86 which spring force is set to 0.5 MPa, the point Q ₃ are shows the operation starting point of the valve spring 86 which spring force is set to 0.8 MPa.

Next, the relationship between the discharge amount of the feed pump 9 and the variable discharge amount high-pressure pump 101 and the pump speed will be described with reference to FIG. In the figure, the discharge amount of the variable discharge amount high pressure pump 101 represents the case of the maximum discharge amount (the solenoid valve 30 is closed at the lowest position of the plunger 15). Valve In Figure 9, A ₅ is shows the discharge amount of the feed pump 9 according to the second embodiment, the A ₀ is the theoretical discharge amount of the feed pump 9 for comparison, A ₁ and a minimum engine speed The spring force of the spring 86 is 0.3M
Medium If set to Pa the discharge amount of the feed pump 9 (set pressure weak), A ₂ when the spring force of the valve spring 86 is set to 0.5MPa in the entire region of engine speed (set pressure the discharge amount of the feed pump 9), a ₃ is shows a discharge amount of the feed pump 9 when the spring force of the valve spring 86 in the entire engine speed is set to 0.8 MPa (set pressure strength) I have. Also, B ₅ is shows the discharge amount of the variable discharge high pressure pump 101 according to the second embodiment, B for comparison
₀ is the theoretical discharge amount of the variable discharge amount high pressure pump 101, and B ₁
Are valve springs 86 over the entire engine speed range.
If the spring force of which is set to 0.3MPa the discharge amount of the variable discharge high pressure pump 101 (the set pressure weak), _{B 2} is the spring force of the valve spring 86 in the entire engine speed 0.5MPa the discharge amount of the variable discharge high pressure pump 101 when it is set (middle set pressure), B ₃ when the spring force of the valve spring 86 is set to 0.8MPa in the entire region of engine speed (set pressure The variable discharge amount of the high pressure pump 101 is shown as the discharge amount. Further, C represents the minimum discharge amount required for the variable discharge amount high pressure pump 101 to supply fuel to the engine.

[0036] From A ₅ in FIG. 9, the discharge amount of the feed pump 9, the spring force is at a low rotational speed region of the pump speed is zero.
The spring force is set by the valve spring 86 set to 3 MPa, the spring force is set by the valve spring 86 set to 0.5 MPa in the region of medium rotation speed, and the spring force is set to 0.8 MPa in the region of high rotation speed. It can be seen that it is defined by the valve spring 86. FIG. 9B
_{From 5} , the discharge amount of the variable discharge amount high-pressure pump 101 is defined by the discharge amount of the feed pump 9 when the spring force of the valve spring 86 is set to 0.3 MPa in the low rotational speed region of the pump rotational speed. In the region of medium rotation speed, the spring force of the valve spring 86 is defined by the discharge amount of the feed pump 9 when the spring force is set to 0.5 MPa.
It can be seen that it is defined by the discharge amount of the feed pump 9 when it is set to MPa.

Therefore, the variable discharge amount high pressure pump 101
In the region where the pump rotation speed is low, the fuel pressure is low, but the leakage of the feed pump 9 is small and the fuel pool 1
9 is supplied to the solenoid valve 30 because the amount of fuel supplied to the solenoid valve 9 increases.
During the long valve opening time of the pump. Further, in the region of the medium rotation speed, the leakage of the feed pump 9 increases, but the pressure of the fuel is correspondingly increased.
The fuel sufficiently flows into the pump chamber 16 during the opening time of the solenoid valve 30. Further, in the high rotation speed region, the leakage of the feed pump 9 is further increased, but the pressure of the fuel is further increased, so that the fuel is sufficiently retained in the pump chamber 16 even during the short valve opening time of the solenoid valve 30. Is flowed in. Therefore,
A discharge amount that ensures the minimum discharge amount C is obtained in the entire range of the pump rotation speed.

As described above, also in the second embodiment, the same effects as in the first embodiment can be obtained. Also,
According to the second embodiment, since the spring force of the valve spring 86 can be adjusted according to the engine speed by using the stepping motor 87, the discharge amount of the feed pump 9 and the variable discharge amount high-pressure pump 101 is optimally controlled. be able to. When the engine is started, the valve spring 86
If the spring force is set to be even weaker, leakage at the feed pump 9 is significantly reduced, the amount of pressure feed is increased, and a smooth engine start can be realized. In the second embodiment,
When the set value of the valve spring 86 is set to three levels and the engine speed reaches an arbitrary speed, the set value of the valve spring 86 changes, so that the pump chamber pressure rapidly changes. Therefore, by gradually increasing the set pressure of the valve spring 86 as the engine speed increases, the pump chamber pressure can be smoothly increased without a sudden increase in the pump chamber pressure.

In each of the above embodiments, the solenoid valve 30 is used as the low-pressure fuel passage closing means. However, the low-pressure fuel passage closing means is not limited to the solenoid valve 30, and may be, for example, a check valve. May be used. Further, in each of the above embodiments, the opening / closing timing of the solenoid valve 30 is not described in detail, but the solenoid valve 30 may be closed during the upward inclination of the cam 13 or between the cam bottom and the cam top. Open / close control. The discharge amount can be adjusted by adjusting the closing timing of the solenoid valve 30.

[0040]

Since the present invention is configured as described above, it has the following effects.

According to the present invention, the cylinder, the plunger reciprocally and slidably fitted in the cylinder, and the inner peripheral surface of the cylinder and the upper surface of the plunger provided in the cylinder. A low-pressure fuel passage serving as a passage for low-pressure fuel flowing into the pump chamber, a cam that is fixed to a cam shaft that is rotationally driven by the engine, and that drives the plunger up and down, and is attached to the cylinder;
A low-pressure fuel passage closing unit that closes the low-pressure fuel passage and controls a period during which the fuel in the pump chamber is boosted by the plunger ascending step; and a flow passage and a discharge hole that communicates with the flow passage. A valve body attached to the cylinder so as to face the low-pressure fuel passage, a valve body housed in the valve body so as to open and close the flow path, and biasing the valve body in a direction to close the flow path Disposed in the valve body so as to sequentially operate as the pressure of the fuel in the low-pressure fuel passage rises to open and close the flow passage by the valve body, thereby reducing the amount of fuel discharged from the discharge hole. The pressure of the fuel in the low-pressure fuel passage supplied from the feed pump, which is constituted by a plurality of valve springs to be controlled and is increased in accordance with an increase in the rotation speed of the engine, is increased according to the rotation speed of the engine. Adjust over Since a flow valve,
It is possible to obtain a fuel pump capable of preventing cavitation erosion of a plunger due to insufficient starting due to insufficient pumping amount at the time of engine start and insufficient supply of fuel to a pump chamber in a high rotational speed region.

The fuel pump according to the present invention also includes a cylinder, a plunger reciprocally and slidably fitted in the cylinder, and a plunger provided in the cylinder, the inner peripheral surface of the cylinder and the plunger. A low-pressure fuel passage that serves as a passage for low-pressure fuel flowing into the pump chamber formed by the upper surface of the pump chamber and a cam shaft that is rotationally driven by the engine;
A cam for driving the plunger to move up and down, a low-pressure fuel passage closing means attached to the cylinder, and closing the low-pressure fuel passage to control a period for raising the pressure of the fuel in the pump chamber by the ascending step of the plunger; A valve body having a discharge hole communicating with the flow passage, the valve body attached to the cylinder such that the flow passage faces the low-pressure fuel passage, a valve body housed in the valve body so as to open and close the flow passage, A valve spring disposed in the valve body, for urging the valve body in a direction to close the flow path, and adjusting a spring force of the valve spring in accordance with the engine speed by the valve body. The feed passage is constituted by a spring force adjusting means for opening and closing the flow passage and controlling the amount of fuel discharged from the discharge hole. And an overflow valve that adjusts the pressure of the fuel in the low-pressure fuel passage according to the engine speed, so that the pump discharge amount can be optimally controlled according to the engine speed. A fuel pump is provided which can prevent cavitation erosion of the plunger due to insufficient starting due to insufficient pumping amount and insufficient supply of fuel to the pump chamber in a high rotation range.

The spring force adjusting means includes a rod provided on the valve body so as to reciprocate in the direction of expansion and contraction of the valve spring, and a stepping motor for reciprocating the rod in the direction of expansion and contraction of the valve spring. With this configuration, the pump discharge amount can be optimally controlled according to the engine speed.

Further, since the low-pressure fuel passage closing means is constituted by an electromagnetic valve, the discharge amount of the pump can be easily controlled with high precision.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a variable discharge amount high pressure pump according to Embodiment 1 of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of an overflow valve used in the variable discharge high-pressure pump according to Embodiment 1 of the present invention.

FIG. 3 is a configuration diagram showing a fuel injection device that employs the variable discharge amount high-pressure pump according to Embodiment 1 of the present invention.

FIG. 4 is a diagram showing a relationship between an engine speed and a pump chamber pressure in the variable discharge high-pressure pump according to Embodiment 1 of the present invention.

FIG. 5 is a diagram showing a relationship between a discharge amount of the variable discharge amount high-pressure pump and an engine speed according to the first embodiment of the present invention.

FIG. 6 is a sectional view showing a configuration of a variable discharge amount high pressure pump according to Embodiment 2 of the present invention.

FIG. 7 is a configuration diagram showing a fuel injection device employing a variable discharge high pressure pump according to Embodiment 2 of the present invention.

FIG. 8 is a diagram showing a relationship between an engine speed and a pump chamber pressure in a variable discharge high-pressure pump according to Embodiment 2 of the present invention.

FIG. 9 is a diagram showing a relationship between a discharge amount of a variable discharge amount high pressure pump and an engine speed according to a second embodiment of the present invention.

FIG. 10 is a cross-sectional view illustrating a configuration of a conventional variable discharge high pressure pump.

FIG. 11 is a cross-sectional view showing a configuration of an overflow valve used in a conventional variable discharge high pressure pump.

FIG. 12 is a configuration diagram showing a fuel injection device employing a conventional variable discharge high pressure pump.

FIG. 13 is a diagram showing a relationship between an engine speed and a pump chamber pressure in a conventional variable discharge high pressure pump.

FIG. 14 is a diagram showing a relationship between a discharge amount of a conventional variable discharge amount high pressure pump and an engine speed.

FIG. 15 is a view for explaining cavitation erosion of a plunger in a conventional variable discharge amount high pressure pump.

[Explanation of symbols]

9 feed pump, 12 camshaft, 13 cam, 14
Cylinder, 15 plunger, 16 pump room, 19
Fuel pool (low-pressure fuel passage), 30 solenoid valve (low-pressure fuel passage closing means), 31 low-pressure passage (low-pressure fuel passage),
41 gallery (low-pressure fuel passage), 42 passage (low-pressure fuel passage), 70, 80 overflow valve, 71,
81 valve body, 72, 82 flow path, 73, 83 discharge hole, 74, 84 ball (valve element), 75 first valve spring, 77 second valve spring, 85
Rod (spring force adjusting means), 86 valve spring,
87 Stepping motor (spring force adjusting means), 10
0, 101 Variable discharge high pressure pump (fuel pump).

Claims (4)

[Claims] 1. A pump comprising: a cylinder; a plunger reciprocally and slidably fitted in the cylinder; and a pump provided in the cylinder, the inner peripheral surface of the cylinder and an upper surface of the plunger. A low-pressure fuel passage serving as a passage for the low-pressure fuel flowing into the chamber; a cam fixed to a cam shaft rotatably driven by an engine, for driving the plunger up and down; and being attached to the cylinder and closing the low-pressure fuel passage. A low-pressure fuel passage closing means for controlling a period during which the fuel in the pump chamber is pressurized by the plunger ascending step; and a flow passage and a discharge hole communicating with the flow passage, such that the flow passage faces the low-pressure fuel passage. A valve body attached to the cylinder, a valve body housed in the valve body so that the flow path can be opened and closed, and a valve body urged in a direction to close the flow path. A plurality of valves disposed in the valve body and sequentially operated in accordance with an increase in the pressure of fuel in the low-pressure fuel passage to open and close the flow path by the valve body and control the amount of fuel discharged from the discharge hole; An overflow for adjusting the pressure of the fuel in the low-pressure fuel passage supplied from the feed pump in accordance with the engine rotation speed, the discharge amount increasing in accordance with the increase in the rotation speed of the engine. A fuel pump comprising a valve. 2. A pump comprising: a cylinder; a plunger reciprocally and slidably fitted in the cylinder; and a pump provided in the cylinder, the inner peripheral surface of the cylinder and an upper surface of the plunger. A low-pressure fuel passage serving as a passage for the low-pressure fuel flowing into the chamber; a cam fixed to a cam shaft rotatably driven by an engine, for driving the plunger up and down; and being attached to the cylinder and closing the low-pressure fuel passage. A low-pressure fuel passage closing means for controlling a period during which the fuel in the pump chamber is pressurized by the plunger ascending step; and a flow passage and a discharge hole communicating with the flow passage, such that the flow passage faces the low-pressure fuel passage. A valve body attached to the cylinder, a valve body housed in the valve body so that the flow path can be opened and closed, and a valve body disposed in the valve body to close the flow path with the valve body A valve spring that urges in the direction, and adjusts the spring force of the valve spring in accordance with the rotation speed of the engine to open and close the flow path by the valve body, thereby controlling the amount of fuel discharged from the discharge hole. The pressure of the fuel in the low-pressure fuel passage supplied from the feed pump, which increases the discharge amount in conjunction with the increase in the engine speed, is adjusted in accordance with the engine speed. A fuel pump, comprising: 3. The spring force adjusting means includes a rod provided on the valve body so as to be reciprocally movable in the direction of expansion and contraction of the valve spring, and a stepping motor for reciprocating the rod in the direction of expansion and contraction of the valve spring. The fuel pump according to claim 2, wherein the fuel pump is configured. 4. The apparatus according to claim 1, wherein said low-pressure fuel passage closing means comprises an electromagnetic valve.
The fuel pump according to any one of the above.