JP2001295726A - High-pressure fuel supply device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-pressure fuel supply device for internal combustion engines capable of restraining pulsation of fuel pressure in a low-pressure fuel system although using a return-less structure, while maintaining the accuracy of regulating the amount of fuel forcibly fed through the control opening and closing of a spill valve. SOLUTION: A device for diving a high-pressure fuel pump 20 is equipped with a camshaft 35, a pump cam 36 serving as a three-dimensional cam, and a hydraulic actuator or the like. The maximum lift of a plunger 22 is variable by moving the pump cam 36 in the direction of the axis of the cam. The maximum lift is set so that fuel is sucked into a pressurization chamber 23 in an amount slightly greater than the required amount of fuel to be forcibly fed into a high-pressure fuel passage 53. Therefore, when the control to opening and closing of the spill valve 25 is performed during the process of forcible feeding by the high-pressure fuel pump 20, the amount of fuel returned from the pressurization chamber 23 to the low-pressure fuel passage 50 is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-pressure fuel supply system for an internal combustion engine, in which fuel stored in a fuel tank is supplied to a high-pressure fuel injection system of the internal combustion engine under pressure, and the amount of the pressure is regulated by a spill valve. .

[0002]

2. Description of the Related Art Conventionally, as a high-pressure fuel supply device of this type, for example, a device described in Japanese Patent Application Laid-Open No. Hei 10-176618 or Japanese Patent Application Laid-Open No. Hei 10-176609 has been known.

[0003] As is clear from the descriptions in these publications,
This type of high-pressure fuel supply device usually includes a high-pressure fuel pump, and a plunger in the cylinder is reciprocated by a cam driven by an internal combustion engine. Then, in the suction stroke in which the volume of the pressurized chamber defined by the cylinder and the plunger of the pump is increased, fuel is sucked from the fuel tank into the pressurized chamber via the low-pressure fuel system. On the other hand, in the pumping stroke in which the volume of the pressurizing chamber is reduced, the sucked fuel is pumped to the high-pressure fuel system.
However, in this pumping stroke, the closing period of the spill valve (electromagnetic spill valve) is controlled, and the actual fuel pumping amount in the stroke is determined according to the controlled closing period of the spill valve. That is, although the spill valve is in the open state, the fuel pressurized in the pressurizing chamber overflows into the fuel tank via the return pipe even though the spill valve is in the pressure-feeding stroke. Only when the spill valve is closed at an appropriate timing during the period, fuel pressure feeding to the high-pressure fuel system is started. Then, at the timing when the spill valve is opened again, the fuel being pumped is spilled to the return pipe, and the pumping of the fuel is interrupted. In the high-pressure fuel supply device, the use of the spill valve makes it possible to accurately control the fuel pumping amount.

[0004] In such a high-pressure fuel supply device, since the fuel which has been drawn into the pressurizing chamber and has a high temperature is returned to the fuel tank via the return pipe, the fuel evaporating in the fuel tank is performed. The amount will increase. Therefore, the return pipe is abolished, and excess fuel that does not need to be pumped from the pressurized chamber to the high-pressure fuel system is returned to the low-pressure fuel system that is maintained at a constant fuel pressure by a pressure regulator or the like. A so-called returnless high-pressure fuel supply device has also been considered.

[0005]

According to such a returnless high-pressure fuel supply system, the excess fuel sucked into the pressurizing chamber is supplied to the low-pressure fuel system by utilizing the opening period of the spill valve. Even if the fuel is returned, the low-pressure fuel system is filled with the fuel maintained at a substantially constant pressure by the pressure regulator or the like, so that the returned fuel does not directly return to the fuel tank. For this reason, fuel evaporation in the fuel tank is certainly suppressed. However, in the case of this device, when the amount of fuel required to be pumped into the high-pressure fuel passage is small, such as when the engine is under a low load, the amount of fuel returned from the pressurizing chamber to the low-pressure fuel system increases. Fuel pressure pulsation increases. In this case, the generation of noise due to the fuel pressure pulsation and the decrease in the reliability of the components in the low-pressure fuel system cannot be ignored.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a returnless structure and to maintain a low pressure while maintaining the accuracy of fuel pumping through opening and closing control of a spill valve. An object of the present invention is to provide a high-pressure fuel supply device for an internal combustion engine that can suppress fuel pressure pulsation in a fuel system.

[0007]

The means for achieving the above object and the effects thereof will be described below. According to the first aspect of the present invention, fuel from a low-pressure fuel system is sucked into a pressurized chamber defined by a cylinder and a plunger reciprocating in the cylinder, and fuel in the pressurized chamber is sent to a high-pressure fuel system. In the high-pressure fuel supply device of the internal combustion engine, which controls the fuel pumping amount through the opening / closing control of the spill valve and returns excess fuel to the low-pressure fuel system, the fuel pumping amount to the high-pressure fuel system And a variable means for varying the maximum lift amount of the plunger according to the required value.

According to the above construction, the maximum lift amount of the plunger is made variable so that the reciprocating width of the plunger is changed, and the amount of fuel sucked from the low-pressure fuel system into the pressurizing chamber during the suction stroke is changed. Is done. That is, the amount of fuel sucked into the pressurizing chamber is reduced by reducing the maximum lift amount and decreasing the reciprocating width of the plunger, and conversely, increasing the maximum lift amount and increasing the reciprocating width of the plunger. More. Of the fuel thus sucked into the pressurizing chamber, the amount of fuel pumped to the high-pressure fuel system is precisely adjusted to a required value through opening / closing control of the spill valve during the pumping process. Excess fuel not pumped into the system is returned to the low pressure fuel system. Therefore, the maximum lift amount of the plunger is made variable in accordance with the required value of the amount of fuel pressure supplied to the high-pressure fuel system, and the fuel corresponding to the required value is sucked from the low-pressure fuel system into the pressurized chamber during the suction stroke. Thus, the surplus fuel returned from the pressurizing chamber to the low-pressure fuel system during the pumping stroke can be reduced. Then, by reducing the amount of the surplus fuel, the fuel pressure pulsation generated in the low-pressure fuel system due to the return of the surplus fuel can be suppressed.

According to a second aspect of the present invention, in the high-pressure fuel supply system for an internal combustion engine according to the first aspect, the variable means reduces the maximum lift amount of the plunger as the required value of the fuel pumping amount decreases. The gist is that

According to the above configuration, the smaller the required value of the fuel pumping amount is, the smaller the amount of fuel sucked into the pressurizing chamber during the suction stroke is. Excess fuel returned to the low-pressure fuel system without being pumped to the low-pressure fuel system is accurately reduced.

According to a third aspect of the present invention, in the high-pressure fuel supply system for an internal combustion engine according to the first or second aspect, the variable means includes a fuel supply amount slightly larger than a required value of the fuel pumping amount. The gist is that the maximum lift amount is set so as to be sucked into the pressurizing chamber.

According to the above construction, the amount of fuel sucked into the pressurizing chamber during the suction stroke is slightly larger than the required value of the amount of fuel pumped to the high-pressure fuel system. And the excess fuel returned to the low-pressure fuel system can be reduced as much as possible.

According to a fourth aspect of the present invention, in the high-pressure fuel supply device for an internal combustion engine according to any one of the first to third aspects, the variable means is provided on a camshaft driven to rotate by the engine. A cam for reciprocating the plunger and having a cam profile continuously changing in the axial direction thereof; and an actuator for displacing the three-dimensional cam in the axial direction. Make a summary.

According to the above configuration, when the three-dimensional cam is gradually displaced in the direction of the cam shaft, the amount of fuel sucked into the pressurizing chamber gradually changes accordingly. Therefore, by adjusting the position of the three-dimensional cam in the cam shaft direction, the amount of fuel sucked into the pressurizing chamber can be accurately controlled to an appropriate value.

According to a fifth aspect of the present invention, in the high-pressure fuel supply system for an internal combustion engine according to any one of the first to fourth aspects, the spill valve includes a required value of the fuel pumping amount and the variable means. The opening and closing period of the plunger is controlled in accordance with the maximum lift amount of the plunger which is made variable.

The amount of fuel sucked into the pressurized chamber from the low-pressure fuel system during the suction stroke is changed by making the maximum lift of the plunger variable. By controlling the closing period of the spill valve during the pumping stroke, the amount of fuel pumped from the pressurizing chamber to the high-pressure fuel system is adjusted to a required value, and the fuel is fed back from the pressurizing chamber to the low-pressure fuel system. The amount of surplus fuel that is changed. According to the above configuration, since the closing period of the spill valve is controlled according to the required value of the fuel pumping amount and the maximum lift amount of the plunger, the fuel pumping amount to the high-pressure fuel system can be accurately adjusted to the required value. The surplus fuel returned to the low-pressure fuel system can be accurately reduced while metering.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying a high-pressure fuel supply device for an internal combustion engine according to the present invention will be described below in detail.

FIG. 1 shows a schematic configuration of a high-pressure fuel supply device for an internal combustion engine according to the present embodiment. This high-pressure fuel supply device is a device for directly injecting and supplying high-pressure fuel to the combustion chamber of each cylinder of the engine 11, and includes a high-pressure fuel pump 20, a pressure accumulation pipe (delivery pipe, common rail, etc.).
14, an injector 15 and the like.

The high-pressure fuel pump 20 pressurizes the fuel to a high pressure and sends it to the pressure accumulating pipe 14. The high-pressure fuel pump 20 includes a pump cylinder 21, a plunger 22 reciprocating in the pump cylinder 21, and Pump cylinder 21
And a spill valve (electromagnetic spill valve) 25 provided in the pressurizing chamber 23. The pressurizing chamber 23 is defined by the inner peripheral wall surface and the upper end surface of the plunger 22.

The high-pressure fuel pump 20 constructed as described above
2, the pump lifter 26 attached to the lower end of the plunger 22 is pressed against the pump cam 36 provided on the camshaft 35 by the urging force of the spring 27. The camshaft 35 is driven to rotate by the engine 11, and the pump cam 36 rotates with the rotation of the camshaft 35, whereby the plunger 22 reciprocates in the pump cylinder 21 and the volume of the pressurizing chamber 23 changes.

The pressurizing chamber 23 of the high-pressure fuel pump 20 is connected to the fuel tank 12 via a spill valve 25 and a low-pressure fuel passage 50. In the fuel tank 12, a low-pressure feed pump 13, a fuel filter 51, and a pressure regulator 52 are provided. The low-pressure feed pump 13 is electrically driven when the engine 11 is started,
The fuel in the fuel tank 12 is transferred to the high-pressure fuel pump 20 via the low-pressure fuel passage 50. When the fuel passes through the low-pressure fuel passage 50, impurities mixed in the fuel are removed by the fuel filter 51. Further, the fuel pressure (fuel pressure) in the low-pressure fuel passage 50 is maintained at a predetermined constant value by the pressure regulator 52. That is, when the fuel pressure in the low-pressure fuel passage 50 becomes equal to or higher than the predetermined value, the fuel is returned from the low-pressure fuel passage 50 into the fuel tank 12 through the pressure regulator 52.

The fuel that has passed through the low-pressure fuel passage 50 is passed through the spill valve 25 to the pressurizing chamber 2 of the high-pressure fuel pump 20.
3 is introduced. The spill valve 25 is a normally-open solenoid valve, and is controlled to a closed state or an open state based on whether or not the solenoid coil 28 is energized.
That is, when the solenoid coil 28 is not energized, the valve 30 is kept open from the seat 31 of the pressurizing chamber 23 by the urging force of the spring 29. On the other hand, when the solenoid coil 28 is energized, the valve body 30 is seated on the seat portion 31 against the urging force of the spring 29, and the valve is closed.

The pressure accumulating pipe 14 is connected to the pressurizing chamber 23 via a check valve 54 and a high-pressure fuel passage 53. And, from the pressurizing chamber 23 to the pressure accumulating pipe 14,
High-pressure fuel is supplied. The pressure accumulating pipe 14 is for maintaining the fuel at a high pressure and distributing the fuel to the injectors 15 provided in each cylinder of the engine 11. A predetermined amount of fuel is injected from each of the injectors 15 into a combustion chamber of each cylinder of the engine 11. A check valve 54 provided in the high-pressure fuel passage 53 is connected to the pressure accumulating pipe 14 from the pressurizing chamber 23.
The valve permits only the flow of fuel toward the
This restricts the backflow of fuel from the pressure accumulation pipe 14 to the pressurizing chamber 23.

During the suction stroke of the high-pressure fuel pump 20 in which the plunger 22 moves downward with the rotation of the camshaft 35, the fuel in the low-pressure fuel passage 50 is sucked into the pressurizing chamber 23. On the other hand, during the high-pressure fuel pump 20 in which the plunger 22 rises with the rotation of the camshaft 35, the fuel in the pressurizing chamber 23 is pressure-fed to the high-pressure fuel passage 53 and the pressure accumulation pipe 14. However, the fuel is pressure-fed to the high-pressure fuel passage 53 and the pressure accumulation pipe 14 only during a period in which the spill valve 25 is closed during the pressure-feeding process, and the spill valve 25 is opened during the pressure-feeding process. During this period, the fuel in the pressurizing chamber 23 is returned to the low-pressure fuel passage 50. Therefore, by controlling the closing period of the spill valve during the pumping stroke, the fuel pumped to the high-pressure fuel passage 53 can be metered.

The opening / closing control of the spill valve 25 for adjusting the amount of fuel supplied to the high-pressure fuel passage 53 is performed by an electronic control unit (hereinafter referred to as “EC
U ") 60. The ECU 60 controls the closing period of the spill valve 25 during the pumping process by controlling the power supply start time to the solenoid coil 28 (the valve closing start time of the spill valve 25) during the pumping process,
The fuel pumping amount to the high-pressure fuel passage 53 is adjusted to a required value with high accuracy.

Here, in response to a change in the valve closing start timing (valve closing period) of the spill valve 25, the amount of fuel pressure fed to the high-pressure fuel passage 53 and the amount of fuel returned from the pressurizing chamber 23 to the low-pressure fuel passage 50. Will be described with reference to FIG. 4A illustrates the concept of the change in the lift amount of the plunger 22 according to the rotation of the pump cam 36 (change in the cam angle), and FIG. 4B illustrates the spill valve 25 according to the rotation of the pump cam 36. FIG.

The required value of the amount of fuel pressure fed to the high-pressure fuel passage 53 changes according to the amount of fuel injected from the injector 15. That is, when the amount of fuel injection from the injector 15 is large, such as when the engine is heavily loaded, the required fuel pumping amount is large, and when the amount of fuel injection from the injector 15 is small, such as when the engine is low load, the required fuel pumping amount is small. Become. When the required fuel pumping amount is large, for example, at a high engine load when the fuel injection amount from the injector 15 is large,
As shown in FIG. 4B, the closing start timing of the spill valve 25 is advanced to, for example, the initial stage of the pumping stroke and changes to the left in the drawing, and the closing period of the spill valve 25 during the pumping stroke is lengthened. You. Then, during the closing period of the spill valve 25, the fuel is fed from the pressurizing chamber 23 to the high-pressure fuel passage 53, so that the amount of fuel corresponding to the portion indicated by G in FIG. The fuel is fed to the fuel passage 53 and the required amount of fuel is fed. Also, during the opening of the spill valve 25 before the spill valve 25 starts to close during the pumping process, fuel (excess fuel) not pumped to the high-pressure fuel passage 53 is supplied to the pressurizing chamber 2
3 is returned to the low-pressure fuel passage 50. Low pressure fuel passage 50
The amount of surplus fuel returned to is a value corresponding to the area of the portion indicated by F in FIG.

On the other hand, when the required fuel pumping amount is small, such as at a low engine load when the fuel injection amount from the injector 15 is small, the closing start timing of the spill valve 25 during the pumping stroke is, for example, until the end of the pumping stroke. It is delayed and changes to the right in the figure, and the closing start timing of the spill valve 25 during the pressure feeding stroke is shortened. During the closing period of the spill valve 25, the fuel is fed from the pressurizing chamber 23 to the high-pressure fuel passage 53, so that the amount of fuel corresponding to the portion indicated by I in FIG. The fuel is fed to the passage 53, and the required fuel feed amount can be obtained. In this case, as the closing period of the spill valve 25 is shortened during the pumping process, the valve opening period of the spill valve 25 before the start of closing is longer. As a result, the amount of surplus fuel returned from the pressurizing chamber 23 to the low-pressure fuel passage 50 has a value corresponding to the area of the portion indicated by H in FIG. 4A, and the required fuel pumping amount is large. It becomes larger than the value at the time (corresponding to the portion indicated by F in the figure).

As described above, when the required fuel pumping amount is small, such as when the engine is under a low load, the amount of fuel returned from the pressurizing chamber 23 to the low-pressure fuel passage 50 increases. When the amount of fuel returned to the low-pressure fuel passage 50 increases, the fuel pressure pulsation in the low-pressure fuel system increases, and the generation of noise due to the fuel pressure pulsation and the decrease in the reliability of components in the low-pressure fuel system are ignored. It will not be possible.

Therefore, in the present embodiment, a maximum lift variable device for varying the maximum lift of the plunger 22 is provided, and the smaller the required value of the amount of fuel pumped to the high-pressure fuel passage 53, the smaller the maximum lift of the plunger 22 becomes. Activate the variable device to reduce the value. In this case, as the maximum lift of the plunger 22 is reduced by the variable device, the reciprocating width of the plunger 22 is reduced, and the amount of fuel sucked from the low-pressure fuel passage 50 into the pressurizing chamber 23 during the suction stroke. Is reduced. Therefore, by making the maximum lift amount of the plunger 22 variable according to the required value of the amount of fuel pressure supplied to the high-pressure fuel passage 53, fuel corresponding to the required value is transferred from the low-pressure fuel passage 50 to the pressurizing chamber 23. Can be inhaled.
Accordingly, when the amount of fuel pumped to the high-pressure fuel passage 53 is accurately adjusted to a required value through the opening / closing control of the spill valve 25 during the pressure-feeding process, the surplus returned from the pressurizing chamber 23 to the high-pressure fuel passage 53 is adjusted. The amount of fuel is reduced, and fuel pressure pulsation in the low-pressure fuel passage 50 is suppressed.

Next, the maximum lift variable device will be described in detail with reference to FIG. This variable device includes a pump cam 36 which is a three-dimensional cam attached to a cam shaft 35, and a hydraulic actuator 4 for displacing the pump cam 36 in the axial direction of the cam shaft 35 (cam axis direction).
And an oil control valve (OCV) 70 for controlling the operation of the hydraulic actuator 40.

The pump cam 36 has a camshaft 35
Have two cam ridges 36a projecting in opposite directions with respect to each other. The height (projection amount) of the cam peak 36a gradually increases in the direction indicated by the arrow A1 in FIG. Therefore, as the pump cam 36 is displaced in the direction opposite to the arrow A1, the maximum lift of the pump lifter 26 (plunger 22) gradually increases. In the present embodiment, when the left end of the pump cam 36 in the figure comes into contact with the pump lifter 26, the maximum lift amount of the plunger 22 becomes “0”, and when the right end in the figure of the pump cam 36 comes into contact with the pump lifter 26, Then, the maximum lift amount of the plunger 22 becomes the largest.

A cam shaft 35 to which the pump cam 36 is attached is rotatably mounted on a cylinder head (not shown) of the engine 11 so as to be movable in the axial direction. The hydraulic actuator 40 is disposed at one end (right end in the drawing) of the camshaft 35.

The actuator 40 has a piston 43 disposed in a case 41 so as to be displaceable in the direction of the cam shaft. One end of a rod 42 extending on the same axis as the camshaft 35 is connected to the piston 43, and the camshaft 35 is connected to the other end of the rod 42 via a bearing 44 or the like. And Case 4
1 is provided with a hydraulic chamber 45a and a hydraulic chamber 45 by a piston 43.
b.

The hydraulic oil discharged from the oil pump 71 is selectively supplied to the hydraulic chambers 45a and 45b via the OCV 70 and the oil passages 46a and 46b. The OCV 70 switches the connection state between the hydraulic chambers 45 a and 45 b and the oil pump 71, and is driven and controlled by the ECU 60. ECU60
By controlling the drive of the OCV 70, the hydraulic chamber 45
a, control the supply of the hydraulic oil to 45b. When hydraulic oil is supplied into the hydraulic chamber 45a, the piston 43 (pump cam 36) moves in the direction of arrow A1, and the plunger 22 moves.
Is reduced, and the amount of fuel sucked into the pressurizing chamber 23 from the low-pressure fuel passage 50 during the suction stroke decreases.
When hydraulic oil is supplied to the inside of 45b, the piston 43
The (pump cam 36) moves in the direction opposite to the arrow A1, the maximum lift of the plunger 22 increases, and more fuel is sucked into the pressurizing chamber 23 from the low-pressure fuel passage 50 during the suction stroke.

The ECU 60 adjusts the position of the pump cam 36 in the axial direction of the camshaft 35 by controlling the drive of the OCV 70 in accordance with the required value of the amount of fuel pressure supplied to the high-pressure fuel passage 53. A slightly larger amount of fuel is supplied from the low-pressure fuel passage 50 to the pressurizing chamber 2 during the suction stroke.
3 to be inhaled. That is, the ECU 60 controls the drive of the OCV 70 so that the pump cam 36 is gradually displaced in the direction of the arrow A1 in the figure as the required value that changes according to the operating state of the engine 11 becomes smaller, and the plunger 22
So that the maximum lift amount gradually decreases. Then, by making the maximum lift amount of the plunger 22 variable as described above, the amount of fuel sucked into the pressurizing chamber 23 is adjusted to a value slightly larger than the required value. In other words, E
The CU 60 sets the variable amount of the maximum lift amount so that the amount of fuel sucked into the pressurizing chamber 23 is slightly larger than the required value, and changes the maximum lift amount based on such a setting.

Next, as described above, when the maximum lift of the plunger 22 is made variable in accordance with the required amount of fuel pressure supplied to the high-pressure fuel passage 53, the closing start timing of the spill valve 25 during the suction stroke FIGS. 3 and 3 show how the amount of fuel pumped to the high-pressure fuel passage 53 and the amount of fuel returned from the pressurizing chamber 23 to the low-pressure fuel passage 50 change in comparison with the related art. This will be described with reference to FIG. Note that FIG.
4A shows the concept of the change in the lift amount of the plunger 22 due to the rotation of the pump cam 36 (change in the cam angle), which corresponds to FIG. 4A, and FIG. Indicates the open / closed state of the spill valve 25, and corresponds to FIG. 4B.

As shown in FIG. 3 (a), when the required value of the amount of fuel supplied to the high-pressure fuel passage 53 is large, such as when the load is high, the maximum lift of the plunger 22 is made large. In this state, during the suction stroke, the low-pressure fuel passage 50
The amount of fuel sucked into the pressurizing chamber 23 becomes a value slightly larger than the required value. Then, the ECU 60 determines that the spill valve 25 is to be closed during the pumping process (valve closing period).
To control the amount of fuel pressure fed to the high-pressure fuel passage 53 to a value required with high accuracy. During the pressure feeding process, the amount of pressure fed from the pressurizing chamber 23 to the high-pressure fuel passage 53 based on the closing of the spill valve 25 has a value corresponding to the area of the portion indicated by C in the figure. Also, during the opening of the spill valve 25 during the pumping stroke, the fuel in the pressurizing chamber 23 is supplied as excess fuel that is not pumped to the high-pressure fuel passage 53 as the low-pressure fuel passage 50.
Is returned to. The amount of surplus fuel returned to the low-pressure fuel passage 50 is small because the amount of fuel sucked into the pressurizing chamber 23 is slightly larger than the required value of the fuel pumping amount. The value corresponds to the area of the portion indicated by B.

On the other hand, when the required value of the fuel supply amount to the high-pressure fuel passage 53 is small, such as at a low load, the maximum lift of the plunger 22 is smaller than that at the high load as shown in FIG. Becomes Even in this state, the amount of fuel sucked into the pressurizing chamber from the low-pressure fuel passage 50 during the suction stroke becomes a value slightly larger than the required value. And ECU6
0 controls the valve closing start timing (valve closing period) of the spill valve 25 during the pressure feeding stroke, and adjusts the amount of fuel pressure fed to the high-pressure fuel passage 53 to a value required with high accuracy.

During such a pumping stroke, the spill valve 25
Is controlled in consideration of the maximum lift amount of the plunger 22, which is made variable according to the required fuel pumping amount. That is, since the maximum lift amount of the plunger 22 is variable so that the amount of fuel sucked into the pressurizing chamber 23 is slightly larger than the required value of the above-mentioned fuel pumping amount, the spill valve 25 Is controlled such that the valve closing start timing is earlier than in the past. This is because the maximum lift amount of the plunger 22 is conventionally set to a constant value so that the required fuel pumping amount can be obtained even under a high load.
As described above, in the present embodiment, the closing start timing of the spill valve 25 is controlled according to the maximum lift amount of the plunger 22.

During the pumping stroke, the spill valve 2
The fuel in the pressurizing chamber 23 is returned to the low-pressure fuel passage 50 during the opening of the valve 5 before the start of the valve closing. However, in the suction stroke, the pressure chamber 2
Since the amount of fuel sucked into the fuel tank 3 is slightly larger than the required value, the closing timing of the spill valve 25 is controlled to control the fuel pumping amount to the required value with high accuracy. , Fuel returned to the low-pressure fuel passage 50 (excess fuel)
Is reduced as indicated by D in FIG. The area of the portion indicated by D in FIG. 3A corresponds to the amount of the surplus fuel, and is a value corresponding to the conventional amount of the surplus fuel in FIG. It is smaller than the area of the portion shown. In the suction stroke, the pressure chamber 2
By setting the amount of fuel sucked into the fuel tank 3 to be slightly larger than the required value, there is no shortage of the amount of fuel pumped to the high-pressure fuel passage 53.

When the maximum lift amount of the plunger 22 is changed in accordance with the required change in the fuel pumping amount, the maximum lift amount is changed due to the flow resistance of hydraulic oil for moving the hydraulic actuator 40 and the like. A response delay occurs due to the change in However, even during such a response delay period, control of the closing start timing (valve closing period) of the spill valve 25 is performed through the ECU 60 to adjust the fuel pumping amount to the required value. Therefore, even if a response delay occurs in the change in the maximum lift amount, it is possible to suppress a decrease in the adjustment accuracy of the fuel pumping amount due to the response delay.

As described in detail above, according to the high-pressure fuel supply device for an internal combustion engine according to this embodiment, the following excellent effects can be obtained. (1) By making the maximum lift amount of the plunger 22 variable, the reciprocating width of the plunger 22 is changed, and the amount of fuel sucked into the pressurizing chamber 23 during the suction stroke of the high-pressure fuel pump 20 changes. Of the fuel sucked into the pressurizing chamber 23 during the suction stroke, the fuel pumped into the high-pressure fuel passage 53 has its pumping amount accurately adjusted to a value required by opening and closing the spill valve 25 during the pumping stroke. Metered. On the other hand, fuel that is not pumped from the pressurizing chamber 23 to the high-pressure fuel passage 53 during the pumping stroke is returned from the pressurizing chamber 23 to the low-pressure fuel passage 50 during opening of the spill valve 25 in the pumping stroke. Becomes Therefore, in accordance with the required value of the amount of fuel pressure supplied to the high-pressure fuel passage 53, the smaller the required value, the more the plunger 2
2 by reducing the maximum lift amount, and sucking the fuel corresponding to the required value into the pressurizing chamber 23 during the suction stroke, so that the fuel returned from the pressurizing chamber 23 to the low-pressure fuel passage 50 during the pumping stroke. Is reduced. In this way, the amount of fuel returned from the pressurizing chamber 23 to the low-pressure fuel passage 50 is accurately reduced while maintaining the accuracy of adjusting the amount of fuel pressure fed to the high-pressure fuel passage 53 through the opening / closing control of the spill valve 25. The fuel pressure pulsation in the inside can be suppressed.

(2) The maximum lift amount is set through the ECU 60 so that the amount of fuel sucked into the pressurizing chamber 23 during the suction stroke is slightly larger than the required value of the amount of fuel pumped into the high-pressure fuel passage 53. The maximum lift amount of the plunger 22 is changed based on the setting of the variable amount. By making the fuel sucked into the pressurizing chamber 23 slightly larger than the required value in this way, the amount of fuel pumped into the high-pressure fuel passage 53 is not insufficient and the low-pressure fuel passage 50
The amount of fuel returned to the fuel cell can be minimized.

(3) Changing the maximum lift of the plunger 22 is performed by moving the pump cam 36, which is a three-dimensional cam, in the axial direction of the camshaft 35 (camshaft direction) by the hydraulic actuator 40. When the pump cam 36 is gradually moved in the cam shaft direction, the maximum lift amount of the plunger 22 also changes gradually, and the amount of fuel sucked into the pressurizing chamber 23 during the suction stroke also changes gradually. I do. Therefore, by adjusting the position of the pump cam 36 in the cam shaft direction, the pressure chamber 23
The amount of fuel sucked into the vehicle can be accurately controlled to an appropriate value.

(4) By controlling the valve closing start timing (valve closing period) of the spill valve 25 during the pressure feeding stroke, the amount of fuel pressure fed from the pressurizing chamber 23 to the high pressure fuel passage 53 can be accurately adjusted to a required value. While being metered, the amount of surplus fuel returned from the pressurizing chamber 23 to the high-pressure fuel passage 53 changes. Accordingly, the closing start timing of the spill valve 25 (valve closing period) according to the required value of the fuel pumping amount and the maximum lift amount of the plunger 22.
, The amount of surplus fuel returned from the pressurizing chamber 23 to the low-pressure fuel passage 50 can be accurately reduced while accurately adjusting the amount of fuel pressure fed to the high-pressure fuel passage 53 to a required value. it can.

(5) When the required value of the amount of fuel pumped to the high-pressure fuel passage 53 changes, a response delay occurs when the maximum lift amount of the plunger 22 is changed in accordance with the change. Through the opening and closing control of the spill valve 25, the fuel pumping amount is precisely adjusted to a required value.
Therefore, even if a response delay occurs in the change of the maximum lift amount as described above, it is possible to suppress a decrease in the accuracy of adjusting the fuel pumping amount due to the response delay.

(6) When the fuel pressure pulsation in the low-pressure fuel passage 50 becomes excessively large, parts such as joints in the low-pressure fuel passage 50 are usually made to be highly reliable to withstand the fuel pressure pulsation. Although a sound insulating material must be provided to shield the pulsation noise caused by the fuel pressure pulsation, it is not necessary to take measures against the problem caused by such excessive fuel pressure pulsation.

The configuration of the above embodiment can be appropriately changed as follows, for example. In order to further suppress the fuel pressure pulsation generated in the low-pressure fuel passage 50, a pulsation damper or the like may be provided in the middle of the low-pressure fuel passage 50.

In the pump cam 36, the cam peak 3
The number of 6a may be changed to three or the like, or the inclination angle of the cam ridge 36a in the cam axis direction may be changed as appropriate. In the above embodiment, the spill valve 2 during the pumping stroke
By controlling the valve closing period by controlling the valve closing period of No. 5, the amount of fuel pumped to the high-pressure fuel passage 53 was adjusted.
The present invention is not limited to this. For example, by fixing the valve closing start timing of the spill valve 25 at the beginning of the pumping stroke and adjusting the valve closing period by controlling the valve closing end timing of the spill valve 25, the amount of fuel pumped to the high-pressure fuel passage 53 can be reduced. It may be metered. In this case, by controlling the opening and closing of the spill valve 25 so as to open the spill valve 25 when the fuel pumping amount reaches the required value during the pumping stroke, it is possible to obtain the required fuel pumping amount more accurately. Can be.

In the above-described embodiment, the amount of fuel sucked into the pressurizing chamber 23 in the suction stroke does not necessarily need to be slightly larger than the required value of the amount of fuel pumped into the high-pressure fuel passage 53. .

In the above embodiment, the pump cam 36 is displaced in the cam axis direction by the hydraulic actuator 40. However, as the hydraulic actuator for displacing the pump cam 36 in the cam axis direction, another actuator such as an electric motor is employed. Is also good.

In the above embodiment, the plunger 2 is moved by moving the pump cam 36, which is a three-dimensional cam, in the cam shaft direction.
2, but the present invention is not limited to this. For example, a plurality of cams having different heights of the cam peaks are provided, and one of the cams is provided with the plunger 2.
A cam switching mechanism for switching the cam may be provided so as to be used as a cam for reciprocating 2 and the maximum lift amount may be changed by switching the cam by the cam switching mechanism. Further, as a mechanism for changing the maximum lift amount, a mechanism may be employed in which a protruding piece is provided on the pump cam so as to be able to protrude and retract so that the height of the cam peak is variable. In this mechanism,
By making the protruding piece protrude from the pump cam, the cam ridge becomes high and the maximum lift amount is made large. By making the protruding piece immersed in the pump cam, the cam ridge becomes low and the maximum lift quantity is made small.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of an embodiment of a high-pressure fuel supply device according to the present invention.

FIG. 2 is a schematic diagram showing a schematic configuration of a maximum lift amount variable device for making a maximum lift amount of a plunger variable.

FIG. 3 is a timing chart showing a concept of a change in a lift amount of a plunger caused by rotation of a pump cam and an opening / closing mode of a spill valve.

FIG. 4 is a timing chart showing a concept of a change in the lift amount of a plunger accompanying rotation of a pump cam and a conventional example of an opening / closing valve mode of a spill valve.

[Explanation of symbols]

Reference numeral 11 denotes an engine, 12 denotes a fuel tank, 13 denotes a low pressure feed pump, 14 denotes a pressure accumulating pipe, 15 denotes an injector, 20
... high-pressure fuel pump, 21 ... pump cylinder, 22 ... plunger, 23 ... pressurizing chamber, 25 ... spill valve (electromagnetic spill valve), 26 ... pump lifter, 30 ... valve element, 35 ... camshaft, 36 ... pump cam, 36a ... Cam ridge, 40 ... Hydraulic actuator, 45a, 45b ... Hydraulic chamber, 46a,
46b: oil passage, 50: low pressure fuel passage, 51: fuel filter, 52: pressure regulator, 53: high pressure fuel passage, 54: check valve, 60: electronic control unit (ECU),
70: oil control valve (OCV), 71: oil pump.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G060 AC08 BA23 CA00 DA06 DA12 FA07 3G066 AB02 AC09 AD12 BA12 BA22 BA46 CA01S CA01T CA08 CA09 CA20U CB17 CE04 CE12 DA00 3G301 JA37 LB13 LB16 LC01 LC08 MA28 ND03

Claims (5)

[Claims] When a fuel is sucked from a low-pressure fuel system into a pressurized chamber defined by a cylinder and a plunger reciprocating in the cylinder, the fuel in the pressurized chamber is pressure-fed to a high-pressure fuel system. In a high-pressure fuel supply device for an internal combustion engine that controls the fuel pumping amount through opening / closing control of a spill valve and returns excess fuel to the low-pressure fuel system, the required value of the fuel pumping amount to the high-pressure fuel system A high-pressure fuel supply device for an internal combustion engine, comprising: a variable means for varying a maximum lift amount of the plunger in response to the change. 2. A high-pressure fuel supply system for an internal combustion engine according to claim 1, wherein said variable means reduces the maximum lift amount of said plunger as the required value of said fuel pressure delivery amount decreases. 3. A maximum lift amount of said variable means is set such that a slightly larger amount of fuel than a required value of said fuel pumping amount is sucked into said pressurizing chamber.
3. A high-pressure fuel supply device for an internal combustion engine according to claim 2. 4. A three-dimensional cam provided on a camshaft rotatably driven by the engine to reciprocate the plunger, wherein the cam profile continuously changes in the axial direction thereof. The high-pressure fuel supply device for an internal combustion engine according to any one of claims 1 to 3, further comprising an actuator for displacing the three-dimensional cam in an axial direction thereof. 5. The high-pressure fuel supply device for an internal combustion engine according to claim 1, wherein said spill valve is a maximum value of said plunger which is made variable by said required value of said fuel pumping amount and said variable means. A high-pressure fuel supply device for an internal combustion engine, wherein an open / close period is controlled according to a lift amount.