JPH11311165A - Variable displacement pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable displacement pump which can enhance the pump efficiency. SOLUTION: A variable displacement pump 2 is provided with a pump part 33, in which a plunger 23 reciprocates within a barrel 29 to transfer the fuel pressurized in a pump room 31 to a common rail, and a pressure sensor 15 for detecting the fuel pressure of the common rail. The pump part 33 is provided with a spiral groove 65 formed on the peripheral surface of the plunger 23 and communication with the pump room 31, a rotating means 53 for rotating the plunger 23, an actuator for driving the rotating means 53, a spill port 61 provided on the barrel 29 for spilling a part of the fuel in meeting the spiral grooves 65, a fuel intake valve 55 installed in the pump 31, and a delivery valve 57.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement pump for changing a discharge amount in response to a fuel pressure in a common rail, and more particularly to a variable displacement pump for pumping fuel pressurized in a pump chamber to a common rail by reciprocating plungers. Related to pumps.

[0002]

2. Description of the Related Art In general, a direct injection type internal combustion engine for directly injecting gasoline fuel into a combustion chamber of a gasoline engine is known. In a fuel supply device used for this type of internal combustion engine,
Fuel is pumped from a high-pressure pump to a common rail, and after accumulating pressure in the common rail, fuel is injected from an injector to an internal combustion engine.

[0003] In response to the fuel pressure of the common rail, the amount of discharge from the high-pressure pump is varied.
Japanese Patent Application Laid-Open No. 3-182664 discloses a technique for controlling the opening and closing of a suction valve (electromagnetic valve) in the middle of a discharge stroke to feed fuel under pressure. According to the technology of this publication, the fuel is pumped at a high position of the cam lift, so it is necessary to take a large cam nose, which exerts a high surface pressure during the fuel pumping,
The high-pressure pump has a problem that it is difficult to adapt. In addition, the valve lift must be increased in order to reduce the loss of the suction throttle, and there is a disadvantage that the responsiveness of the electromagnetic valve is reduced.

On the other hand, Japanese Patent Publication No. 6-10460 discloses a communication position between a spiral passage (lead) formed on a peripheral surface of a plunger and a fuel suction port by rotating a plunger by a rack. Is disclosed, the fuel is discharged from the suction port at the time of discharge to vary the discharge amount.

In the technique disclosed in this publication, since the spill port also serves as a fuel suction port, the plunger is lifted from the bottom position and the plunger head closes the suction port, then pressure feeding is started, and further lifted and the lead is performed. When the pressure coincides with the suction port, the pumping of the fuel is completed, and the plunger lifts and reaches the top, starts lowering, closes the suction port, and continues lowering while generating a significant negative pressure in the pump chamber. When the fuel reaches the suction port, the fuel is sucked from the suction port.

[0006] In the technique of this publication, no fuel is fed at a high position of the cam lift, so that the cam nose surface pressure can be reduced and it can be applied to a high-pressure pump.

[0007]

However, in the above-mentioned prior art, when the plunger descends to the suction port, fuel is sucked, so that a significant negative pressure is generated in the pump chamber before the start of fuel suction. Therefore, there is a problem that the pump efficiency is reduced.

Accordingly, an object of the present invention is to provide a variable displacement pump capable of improving pump efficiency.

[0009]

In order to achieve the above object, according to the present invention, a plunger reciprocates in a barrel and pumps a fuel pressurized in a pump chamber to a common rail. A pressure sensor that detects a fuel pressure of a common rail, and a variable displacement pump that changes a discharge amount from a pump unit in response to an output from the pressure sensor, wherein the pump unit is formed on a peripheral surface of a plunger. A spiral groove communicating with the pump chamber, a rotating means for engaging the plunger to rotate the plunger, an actuator for driving the rotating means in response to an output of a pressure sensor, and the spiral groove provided in the barrel. And a spill port for releasing a part of the fuel when the fuel cell is encountered, a fuel intake valve provided in the pump chamber, and a discharge valve.

According to the first aspect of the present invention, the position where the spiral groove meets the spill port is adjusted by driving the actuator and rotating the plunger in accordance with the detection pressure of the pressure sensor. The fuel supply is variable.

On the other hand, in the discharge stroke, when the plunger is lifted from the bottom position with the spill port closed and the discharge valve is opened to start pumping fuel, and further lifted, the spiral groove meets the suction port. Since a part of the fuel is spilled, the pumping of the fuel is terminated at this position. Furthermore, when the plunger rises while spilling fuel and the plunger reaches the top (dead center), the spiral groove and the suction port are in a state of being in contact with each other.

Next, while the plunger starts descending from the top position and the spiral groove meets the spill port,
Since the pump chamber is supplied with fuel from the spill port, the pump chamber is prevented from being under negative pressure. When the plunger further descends to a position where the spill port and the spiral groove do not meet, the suction valve is opened and the fuel is supplied into the pump chamber.

As described above, when the plunger is lowered, fuel is supplied from the spill port to reduce the negative pressure in the pump chamber until the suction valve is opened, so that the pump efficiency can be improved. Furthermore, when the plunger is raised, fuel can be discharged at a position where the cam lift is low, so that power consumption can be reduced and pump efficiency can be improved.

According to a second aspect of the present invention, in the first aspect of the invention, the actuator is a linear solenoid, and the rotating means engages with a control sleeve engaged with a plunger and a projection on the control sleeve. And a linear solenoid drives the control rod.

According to the second aspect of the present invention, the plunger is rotated by controlling the power supplied to the linear solenoid according to the response from the pressure sensor.
Since the configuration is simple and the rotation of the plunger is performed by driving the control rod that engages with the projection of the control sleeve, the sliding resistance is small, and the capacity of the linear solenoid that drives the control rod can be relatively small.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a circuit diagram of a fuel injection device 1 equipped with a high-pressure pump 2 according to the present invention. The fuel injection device 1 directly injects gasoline into a combustion chamber (cylinder) of a gasoline engine, and is used for a so-called direct injection gasoline engine. This fuel injection device 1 generally includes a fuel tank 3,
A low-pressure pump 5 for pumping fuel from the fuel tank 3, a high-pressure pump 2 to which fuel is supplied from the low-pressure pump 5, and a common rail 11 as a pressure accumulator for accumulating the fuel pumped from the high-pressure pump 2 are connected.

The low-pressure pump 5 is provided with a relief valve 7. When the fuel supply pressure becomes higher than a predetermined pressure, the valve is opened to return a part of the fuel to be pumped to the fuel tank 3 and supply the fuel to the fuel tank 3. Has been established. A plurality of injectors 13 are connected to the common rail 11, and fuel stored at a high pressure by the common rail 11 is injected from each injector 13 into a cylinder of an engine.

A pressure sensor 15 is provided on the common rail 11, and a detection signal (output signal) from the pressure sensor 15 is sent to a control unit 17. The control unit 17 is further supplied with a signal indicating the number of revolutions of the engine, and controls the discharge amount of the high-pressure pump 2 based on the common rail pressure and the number of revolutions of the engine.

Next, the structure of the high-pressure pump 2 is shown in FIGS.
2 is a longitudinal sectional view showing a schematic configuration, and FIG. 3 is a sectional view in a direction intersecting FIG.
This is an illustration of an actuator portion extracted. In the high-pressure pump 2, a plunger 23 is housed in a pump housing 25, and the plunger 23 reciprocates in a plunger barrel 29 by rotation of a cam 27.

The pump housing 25 is fitted with a delivery holder 32 that defines a pump chamber 31 together with a plunger barrel 29. The delivery holder 32 is provided with a pump section 33. In this pump section 33,
A suction passage 35 to which low-pressure fuel is supplied;
A discharge passage 37 for discharging the fuel pressurized by the suction passage 35 is provided. The suction passage 35 and the discharge passage 37 communicate with the pump chamber 31.

On the other hand, a push rod 39 is provided below the plunger 23, and a lower end of the push rod 39 has a support member 4 for supporting a lower end of a spring 47.
The support member 41 and a receiving member 43 provided outside the pointing member 41 form a spring 4.
7 is held at the lower end. The spring 47 always urges the plunger 23 downward.
The upper end of 7 is supported on the lower surface of the fixing member 49.

In the middle of the push rod 39, the engaging portion 4
The engaging portion 45 is engaged with the control sleeve 53 in a state where the engaging portion 45 cannot rotate relatively. The control sleeve 53 is driven by a control rod 51 described later.

The delivery holder 32 has a fuel intake valve 5.
5 and a discharge valve 57, and the suction valve 55 is seated on the suction port 34 of the suction passage 35 communicating with the pump chamber 31, and is urged by a spring 58 in the seating direction. On the other hand, the discharge valve 57 is seated on the discharge port 38 communicating with the discharge passage 37 and is urged by a spring 59 in the seating direction.

The plunger barrel 29 includes a plunger 2
A spill port 61 is provided in the sliding surface of the spill port 3. The spill port 61 communicates with the suction passage 35 through a communication passage 63. In the present embodiment, since the spill port 61 and the suction valve 55 are provided in the delivery holder 60, these pipes can be reduced and the configuration is simple.

On the other hand, a spiral groove 65 is formed on the peripheral surface of the plunger 23, and the spiral groove 65 communicates with the pump chamber 31 through a passage 67 formed in the plunger 23. The spiral groove 65 changes the timing at which it encounters the spill port 61 by rotating the plunger 23 by a predetermined angle.

The control sleeve 53 for rotating the plunger 23 has a projection 46. The projection 46 is engaged with the control rod 51, and the control rod 53 is driven to drive the control sleeve 53. As shown in FIG. 3, the control rod 51 is driven by a linear solenoid 69. The linear solenoid 69 includes a fixed permanent magnet 71
And an electromagnet 73 provided on the control rod 51 and excited by the supply of electric power.
The control sleeve 53 is moved by a predetermined amount by the excitation. The other end of the control rod 51 is
It is urged by the return spring 75.

The linear solenoid 69 controls the supply power in accordance with the drive signal from the control unit 17 to control the amount of movement of the control rod 51.
The linear solenoid 69 has good responsiveness, and the control sleeve 53 does not need to move for a constant load, so that the power consumption is small.

Next, the operation of the fuel injection device 1 will be described.
During operation of the fuel injection device 1, the fuel in the fuel tank 3 is
The fuel is supplied from the low-pressure pump 5 to the high-pressure pump 2. In the high-pressure pump 2, the fuel in the pump chamber 31 is pressurized by the reciprocating motion of the plunger 23 to supply the common rail 11 with fuel, and the fuel is ejected from each injector 13 of the common rail 11. .

In the high-pressure pump 2, the amount of pressure feed is changed in response to the amount of pressure detected by the pressure sensor 15 for detecting the pressure of the common rail 11, which will be described later.
With reference to FIG. 4 and FIG. 5, the pumping and suction of fuel will be described. FIG. 4 is a graph showing the relationship between fuel pumping, suction and spill, with the vertical axis representing the cam lift and the horizontal axis representing the cam rotation angle. FIG. 5 shows the spiral groove 65 and the spill port 61 of the plunger 23 at each position shown in FIG.
And the state of the suction valve 55.

At the time of pumping the fuel, the plunger 23 is moved as shown in FIG.
(A), and pressurizes the fuel in the pump chamber 31. In the position shown in (a), the suction valve 55 is closed, and the spiral groove 65 and the spill port 61 are not at the meeting position. Plunger 2 from (a) to (b)
When 3 rises, the fuel in the pump chamber 31 is pressurized,
The discharge valve 57 is opened to pump fuel. That is, from (a) to (b) is a fuel pumping period.
As shown in FIG. 4, oil is fed at a place where the cam lift is low, so that power consumption can be reduced.

Further, when the plunger 23 rises beyond the position shown in FIG. 5B, the spiral groove 65 and the spill port 61 meet. As a result, the spill port 61 and the pump chamber 31 communicate with each other, so that the fuel in the pump chamber 31 escapes from the spill port 61 and the fuel is not pumped even when the plunger 23 moves up. Further, the fuel is not pumped to the position (c) where the plunger 23 rises to reach the top dead center.
At the position (c), the helical groove 65 and the spill port 61 coincide with each other, and the spill port 61 and the pump chamber 31 communicate with each other.

The cam lift is at a high position between (b) and (c). At this high position of the cam lift, there is no pumping of fuel, so that the surface pressure applied to the cam 27 can be reduced. The quantity can be set easily. That is, the high-pressure pump 2 according to the present embodiment has a high degree of freedom corresponding to a high pressure and a high oil supply amount.

When the plunger 23 is lowered from the top dead center of FIG. 4C to the state shown in FIG. 4D, the spiral groove 65 and the spill port 61 meet, and the spill port 61 is formed.
Supplies fuel to the pump chamber 31. Therefore, (c)
When the plunger 23 descends from (d) to (d), the pump chamber 31 is prevented from becoming negative pressure.

In FIG. 5D, as shown in FIG.
Reference numeral 5 denotes a position where it does not meet the spill port 61. While the plunger 23 further moves down from this position to the position (a), the suction valve 55 is opened, and fuel is supplied to the pump chamber 31.

As described above, in this embodiment, the above-described steps (a) to (d) are repeated.
The pump chamber 31 is prevented from becoming negative pressure during the downward stroke of the plunger 23 in (d) and (a), and the pump efficiency can be improved by reducing the load.

Next, a description will be given of a control for changing the pumping amount in the high-pressure pump 2. When the pressure sensor 15 detects the pressure of the common rail 11, a detection signal is sent to the control unit 17. Control unit 1
In Fig. 7, from the relationship between this pressure signal and the engine speed,
By rotating the plunger 23 by a predetermined amount, the timing at which the spiral groove 65 meets the spill port 61 is controlled.

In this case, when the electromagnet 73 is excited by a predetermined amount in response to a control signal from the control unit 17, the control rod 51 moves on a straight line by a predetermined amount. In conjunction with this, the plunger 23 rotates together with the control sleeve 53. Since the control sleeve 53 is rotated by the engagement between the control rod 51 and the projection 46, the sliding resistance is small and the response is good. For example, in the present embodiment, the sliding resistance is 100 g or less, and the capacity of the linear solenoid 69 can be reduced.

As described above, by rotating the plunger 23 to shift the timing of the encounter between the spill port 61 and the spiral groove 65, the pumping time of the fuel from the pump chamber 31 changes, and the discharge amount to the common rail 11 becomes variable. Become.

The present invention is not limited to the above embodiment,
Various modifications can be made without departing from the spirit of the present invention.
For example, the drive of the control sleeve 53 for rotating the plunger 23 is not limited to the linear solenoid 69, but may be a combination of a hydraulic cylinder and an electromagnetic valve or a drive driven by a link using a rotary motor actuator as a drive source. .

[0040]

According to the first aspect of the present invention, when the plunger is lowered, the fuel is supplied from the spill port until the suction valve is opened to reduce the negative pressure in the pump chamber, thereby improving the pump efficiency. Can be achieved.

Further, when the plunger is raised, fuel can be discharged at a position where the cam lift is low, so that power consumption can be reduced and pump efficiency can be improved.

According to the second aspect of the present invention, since the linear solenoid is used as the actuator for rotating the plunger, the configuration is simple and the power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a fuel injection device according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a schematic configuration of a high-pressure pump.

FIG. 3 is a diagram extracting and showing a schematic configuration of an actuator.

FIG. 4 is a graph showing a pressure feeding and suction stroke of the high-pressure pump shown in FIG. 2;

5 is a view showing a relationship between a plunger, a suction valve, and a spill port at a rotation position of a cam shown in FIG. 4;

[Explanation of symbols]

 2 High pressure pump (variable displacement pump) 11 Common rail 15 Pressure sensor 23 Plunger 29 Plunger barrel (barrel) 33 Pump unit 53 Control sleeve 55 Suction valve 57 Discharge valve 61 Spill port 65 Spiral groove 69 Linear solenoid (actuator)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F04B 1/04 F04B 1/04 1/047 1/053

Claims (2)

[Claims] A plunger has a pump section for reciprocating in a barrel to pump fuel pressurized in a pump chamber to a common rail, and a pressure sensor for detecting a fuel pressure of the common rail, and responds to an output from the pressure sensor. A variable displacement pump that changes a discharge amount from the pump unit, wherein the pump unit is formed on a peripheral surface of the plunger, and engages with the spiral groove communicated with the pump chamber and the plunger to rotate the plunger. A rotating means, an actuator for driving the rotating means in response to the output of the pressure sensor, a spill port provided in the barrel, which escapes a part of fuel when the spiral groove is encountered, and a pump chamber. A variable displacement pump comprising a fuel intake valve and a discharge valve. 2. The method according to claim 1, wherein the actuator is a linear solenoid, and the rotating means includes a control sleeve engaged with a plunger, and a control rod engaged with a projection of the control sleeve, and the linear solenoid drives the control rod. The variable displacement pump according to claim 1, wherein: