JPH1193796A - Variable discharge high-pressure pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure valve opening operation of a check valve and preventing high pressure from acting on an electromagnetic valve for improving reliability. SOLUTION: Plungers 21 are arranged in a plurality of sliding holes 2 to apply pressure to fuel in a pressure chamber 23 to be forcibly fed with the reciprocation of the plungers 21. To the pressure chamber 23, low-pressure fuel is supplied through a flow control electromagnetic valve 6 and a check valve 4. A flow passage 43a between the check valve 4 and the electromagnetic valve 6 is communicated with a space in a pump via a throttle flow passage 53. As the space in the pump is almost at an atmospheric pressure, fuel is momentarily escaped from the throttle flow passage 53 with a difference in pressure when pressure begins to be applied to fluid during starting forcible feed, to generate a flow from the pressure chamber 23 to the check valve, so that oil impact is operated on the valve disc of the check valve 4 in the opening direction to quickly close the valve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable discharge high pressure pump used for pumping a high pressure fluid into a common rail in a common rail injection system of a diesel engine, for example.

[0002]

2. Description of the Related Art A common rail injection system is known as one of the systems for injecting fuel into a diesel engine. In the common rail injection system, a common pressure accumulation pipe (common rail) communicating with each cylinder is provided, and a variable discharge high pressure pump is used to supply high-pressure fuel at a required flow rate to thereby keep the fuel pressure in the pressure accumulation pipe constant. keeping. The high-pressure fuel in the accumulator pipe is injected into each cylinder by an injector at a predetermined timing (for example,
JP-A-64-73166, etc.).

FIG. 15 shows an example of a variable discharge high pressure pump used for such an application.
Inside the plunger 9 driven by a cam (not shown)
2 is reciprocally fitted, and a pressure chamber 93 is formed by the inner wall surface of the cylinder 91 and the upper end surface of the plunger 92.
An electromagnetic valve 94 is mounted above the pressure chamber 93. The electromagnetic valve 94 is provided with a low-pressure flow path 95 formed therein.
And a valve body 96 for opening and closing between the pressure chamber 93 and the pressure chamber 93.

The valve body 96 is in the valve-opening position in the state shown in the drawing, in which the coil 97 is not energized. When the plunger 92 is lowered, the fuel is supplied from the low-pressure supply pump (not shown) to the low-pressure flow path 95 and the gap around the valve body 96. Through the pressure chamber 93. When the coil 97 is energized, the valve body 96 is attracted upward, and its substantially conical tip sits on the seat portion 98 to close the valve. At the same time, the fuel in the pressure chamber 93 is pressurized by the rise of the plunger 92, and is sent to the pressure accumulating pipe from the flow path 99 provided on the side wall of the pressure chamber 93.

When the plunger 92 is raised, a force in the valve closing direction acts on the valve body 96 due to the fuel pressure in the pressure chamber 93. Therefore, once the valve body 96 is closed, energization of the coil 97 is stopped. Even if it does not open. For this reason, in the variable discharge high-pressure pump having the above-described configuration, the flow rate sent to the pressure accumulation pipe is controlled by so-called pre-stroke control that controls the valve closing timing. That is, after the plunger 92 moves to the rising stroke, the valve is not closed immediately, the valve is kept open until the fuel in the pressure chamber 93 reaches a predetermined amount, and excess fuel is released to the low-pressure flow path 95 side, Thereafter, by closing the valve and starting pressurization, a required amount of pressurized fluid is pumped to the accumulator pipe.

However, when the oil feed rate of the pump increases with an increase in the engine speed, there arises a problem that the valve 96 closes (self-closes) regardless of the valve closing signal. This is because when the plunger 92 is raised, the valve body 96 directly receives the dynamic pressure of the fuel in the pressure chamber 93 on the lower end surface.
This is due to a force in the valve closing direction due to the throttle effect of the fuel flowing toward the low pressure flow path 95 from the gap between the valve and the seat portion 98, and the flow rate control may not be performed properly.

As a countermeasure, it is conceivable to increase the operating stroke of the valve body 96 or to increase the return spring force of the valve body 96, but in any case, the valve closing response is reduced. In order to maintain the valve-closing response, it is necessary to increase the amount of power supplied to the coil or increase the size of the coil to increase the attraction force of the solenoid valve, which increases the power cost and manufacturing cost of the solenoid valve. There was a problem.

In the variable discharge high-pressure pump having the above-described structure, the flow passage to the pressure chamber 93 is opened and closed by the solenoid valve 94, and the valve body 96 is seated in response to a valve closing signal to close the flow passage. Since a certain period of time is required until this time, usually, the operation response time is calculated in advance to control the valve closing timing.
However, when the rotation speed of the engine increases and the oil supply rate of the pump increases, the opening / closing operation cannot be performed in time, and there is a possibility that sufficient control cannot be performed.

Accordingly, the present inventors have made it possible to easily and reliably control the flow rate of pressure-feeding to the pressure accumulating pipe even when the engine speed is increased and the oil supply rate of the pump is high. In order to avoid the increase in pressure and to eliminate problems such as response delay due to the use of an electromagnetic valve for opening and closing the flow path, a variable discharge amount high pressure pump of the following suction amount adjustment type was proposed. (Japanese Patent Application No. 8-195653
issue).

As shown in FIG. 16, the variable discharge high-pressure pump has a check valve 112 which is opened only when the low-pressure fuel is sucked into the pressure chamber 110, and is provided upstream of the pressure chamber 110. , A solenoid valve 111 for controlling the flow rate of the low-pressure fuel sucked into the pressure chamber 110 is provided. The solenoid valve 111 operates while the valve body 111a is open.
The low-pressure fuel flows toward the pressure chamber 110, and the pressure of the fuel causes the ball-shaped valve body 112a of the check valve 112 to move downward. The pressure chamber 110 is formed by the inner wall surface of the cylinder 110a and the upper end surface of the plunger 110b.
The rotation of c causes the plunger 110b to move up and down. In this way, by separately providing a valve body that opens and closes between the low-pressure flow path and the pressure chamber and a valve body that controls the flow rate of the low-pressure fuel sucked into the pressure chamber from the low-pressure flow path, self-control in the pre-stroke control is performed. The problem of closing is eliminated.

FIG. 17 shows an application of this method.
10 are formed between the end faces of four plungers 109 radially arranged. In the figure, a drive shaft 101 is inserted and held in a pump housing 100, and a low-pressure fuel is supplied to low-pressure channels 103 and 104 by a feed pump 102 that rotates integrally with the drive shaft 101.
Thus, the fuel flows into the fuel pool 105.
At the right end of the drive shaft 101, an inner cam 106 is integrally formed.
In 06, the left end of the head 107 is inserted.

In the left end portion of the head 107, four cylinder sliding holes 108 are formed radially (only two of them are shown in the figure), and the plunger 109 reciprocates in each sliding hole 108. It is movably supported. The pressure chamber 110 is formed by the inner end surface of the plunger 109 and the inner wall of the slide hole 108, and pressurizes the introduced fuel by reciprocating the plunger 109.
In the flow path from the fuel reservoir 105 to the pressure chamber 110, a flow control electromagnetic valve 111 and a check valve 112 are arranged from the upstream side. The check valve 112 is a solenoid valve 11
While the valve 1 is open, the valve is opened by the pressure of the inflowing fuel, the solenoid valve 111 closes, and closes when pressurization is started.

When the required flow rate is supplied into the pressure chamber 110 in advance by the solenoid valve 111, the check valve 112 controls the pressure chamber 11 from the start of pressurization of the low-pressure fuel to the end of pumping.
The flow path to zero is closed. At this time, only the feed pressure (approximately 15 atm) acts on the solenoid valve 111 even at the maximum pressure. Therefore, it is not necessary to increase the size of the solenoid valve 111, and the size and cost can be reduced.

[0014]

However, FIG.
In the variable discharge amount high-pressure pumps having the configurations 6 and 17, when the suction of the fuel into the pressure chamber 110 is completed and the pumping is started, the check valve 112 may not be quickly closed. Occurred. This is because the check valve 112 is configured to be closed by the pressure of the pressurized fuel. Therefore, even when the solenoid valve 111 is closed and the suction is completed, the check valve 112 is not closed. The flow path from the solenoid valve 111 to the pressure chamber 110 is in communication. Then, even when the plunger 109 is raised and pressurization is started, since the solenoid valve 111 is closed, no flow from the pressure chamber 110 toward the check valve 112 occurs, and the check valve 112 is closed. Oil hammer in the valve direction is less likely to act. For this reason, not only may there be a possibility that the pressurized pressure feeding is not performed because the valve closing operation of the check valve is not reliably performed, but also the electromagnetic valve 111 which should not be applied with a pressure higher than the feed pressure (about 15 atm). There is a possibility that high pressure may be applied, and the durability may be reduced.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to reliably perform a valve closing operation of a check valve, prevent a high pressure from being applied to an electromagnetic valve, and improve reliability.

[0016]

According to the first aspect of the present invention, the variable discharge high pressure pump comprises a plunger which is reciprocally fitted in a cylinder, an inner wall surface of the cylinder and an end face of the plunger. Having a pressure chamber formed, a low-pressure fluid introduced from the low-pressure channel into the pressure chamber,
The reciprocating motion of the plunger pressurizes and sends it to the high-pressure channel. Also, an electromagnetic valve that controls the flow rate of the low-pressure fluid supplied from the low-pressure channel to the pressure chamber, and a solenoid valve that is provided between the electromagnetic valve and the pressure chamber and has a low pressure only in the direction from the low-pressure channel to the pressure chamber. A check valve through which fluid flows. The flow path upstream of the valve seat portion of the check valve communicates with the pump internal space having the same pressure as the back pressure of the plunger or a return flow path leading to a low-pressure fluid storage tank by a throttle flow path.

Since the internal space of the pump is almost at atmospheric pressure,
When the fluid starts to be pressurized at the start of the pressure feed, the fluid momentarily flows out of the throttle channel due to the pressure difference. Using this,
A flow can be generated from the pressure chamber in the direction of the check valve, and the valve body of the check valve exerts an oil hammer force in the valve closing direction,
The valve closing operation can be performed promptly and reliably. Further, even if a check failure or the like occurs in the check valve, the fuel escapes from the throttle passage, so that a high pressure can be prevented from being directly applied to the solenoid valve, and the reliability can be improved. Instead of connecting the throttle channel to the pump internal space, the throttle channel may be connected to a return channel leading to a low-pressure fluid storage tank, and the same effect can be obtained.

In the structure of the second aspect, instead of providing the throttle flow path, the check valve is provided with a flow path leading to the pressure chamber,
A valve body for opening and closing the flow path and a return spring for urging the valve body in a valve closing direction are provided. At this time, when the suction is completed, the check valve immediately starts the closing operation due to the spring force of the spring. Therefore, the valve can be quickly and reliably closed without applying the oil hammer, and the same effect can be obtained.

According to a third aspect of the present invention, in addition to the check valve structure of the second aspect, the throttle flow path of the first aspect is provided. With these combinations, the closing operation of the check valve can be made more reliable, and even if the return spring is damaged, the check valve can be closed by the action of the throttle flow path. Can be. In addition, it is possible to prevent a high pressure from being applied to the solenoid valve when a check failure of the check valve or the like occurs.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment in which a variable discharge high pressure pump according to the present invention is applied to a common rail injection system of a diesel engine will be described with reference to the drawings. FIG. 2 is a system diagram. The engine E is provided with a plurality of injectors I corresponding to the combustion chambers of the respective cylinders, and these injectors I are connected to a common high-pressure accumulator pipe, a so-called common rail R, for each cylinder. Injection of fuel from the injector I into each combustion chamber of the engine E is controlled by ON / OFF of the injection control solenoid valve B1, and while the solenoid valve B1 is open, fuel in the common rail R is injected by the injector I. It is injected into the engine E. Therefore, it is necessary to continuously accumulate the fuel at a high predetermined pressure corresponding to the fuel injection pressure in the common rail R.
Via the discharge valve B2, the variable discharge amount high pressure pump P of the present invention is connected.

The variable discharge high-pressure pump P has a structure in which a feed pump P1 is built in, and the feed pump P1 pressurizes fuel sucked from a fuel tank T, which is a storage tank, to a high pressure. The fuel is controlled to a high pressure. In common rail R,
A pressure sensor S1 for detecting a common rail pressure is provided, and an electronic control unit ECU serving as control means for controlling the system is configured to determine whether a signal from the pressure sensor S1 is an optimum value set in advance according to a load or a rotation speed. Thus, the discharge amount of the variable discharge amount high-pressure pump P is determined, and a control signal is output to the discharge control device P2. The electronic control unit ECU further includes an engine speed sensor S2 (detects a missing tooth signal (NE pulse) as shown in FIG. 11 described later from a coupling K connected to a cam shaft), TDC (top dead center). ) Sensor S3, throttle sensor S4, temperature sensor S
5, the information of the rotation speed, the position of the TDC, the accelerator opening, and the temperature is input, and the electronic control unit ECU determines the optimal injection timing and injection amount (injection period) according to the engine state determined by these signals. Is determined, and a control signal is output to the injection control solenoid valve B1.

Next, the details of the variable discharge amount high pressure pump P will be described with reference to FIGS. In FIG. 1, a drive shaft D is rotatably supported in a pump housing 1 via a bearing D2 and a bush D1, and a fuel tank T (FIG.
) Through an inlet valve B3, and is connected to a vane type feed pump P1 which sucks fuel and feeds it under pressure to a feed passage 11 serving as a low pressure passage. At the right end of the drive shaft D, an inner cam 13 is integrally formed, and the inner cam 13 rotates together with the drive shaft D at half the speed of the engine. When the inner cam 13 rotates, the rotor P12 of the feed pump P1 rotates via the half-moon plate P11, and the rotation causes the fuel in the fuel tank T to pass through the inlet valve B3 through a flow path (not shown). The space inside the feed pump P1 (the rotor P12, the casing P13, the cover P14,
5). The introduced fuel is pressure-fed to the feed passage 11 by a vane P16 disposed on the rotor P12 as the rotor P12 rotates.

The fuel in the feed passage 11 is used not only for pressure feeding to the common rail R as described below, but also flows into the pump from the squeezing s and is used for lubrication inside the pump. The lubricated fuel comes out of the valve V and is returned to the fuel tank T. Further, the pressure inside the pump is adjusted by the valve V so as to be almost the atmospheric pressure.

A head H is fitted into the right end opening of the pump housing 1, and the head H is inserted into the inner cam 13 with its left end center protruding. As shown in FIG. 3, a plurality of sliding holes 2 serving as cylinders are provided in the center of the left end of the head H. A plunger 21 is reciprocally movable and slidable in each of the plurality of sliding holes 2. It is freely supported. A shoe 21a is provided at an outer end of each plunger 21, and a cam roller 22 is rotatably held by each shoe 21a.

The inner cam 13 is disposed so as to be in sliding contact with the outer periphery of the cam roller 22. On the inner peripheral surface of the inner cam 13, a cam surface 13a having a plurality of equally arranged cam ridges is provided. Is formed. The space formed between the inner end surface of each plunger 21 and the inner wall surface of each slide hole 2 is a pressure chamber 23. Then
When the cam 13 integrated with the drive shaft D rotates, the plunger 21 reciprocates in the slide hole 2 and the pressure chamber 2
The fuel in 3 is pressurized. Here, four plungers 21
, Four cam ridges are formed, and four pressure feeds are performed per cam rotation. FIG. 3 shows a state in which the plunger 21 is at the highest position (innermost position).

In the conventional variable discharge high pressure pump,
In many cases, a spring that constantly presses the plunger 21 against the inner cam 13 is provided. However, the variable discharge high-pressure pump of the present invention employs a suction amount control method, and when the suction amount is small, the plunger 21 descends to the lowest point. , Pressure chamber 2
Cavitation may occur due to the reduced pressure of 3. For this reason, in the present invention, no spring is provided,
The reciprocating motion of the plunger 21 is performed by a cam lift by rotation of the drive shaft D at the time of pressure feeding, and by the pressure (feed pressure) of the low-pressure fuel at the time of suction. Therefore, when the suction amount is small, the plunger 21 moves in the direction of the cam 13 only by the supply of the low-pressure fuel, and the cam roller 22 and the inner cam 13 are separated.

As shown in FIG. 4A, a lock adapter 5 is attached to the right end of the head H via a stopper 41 and a check valve 4. A fuel reservoir 12 is formed between the lock adapter 5 and the pump housing 1, and a solenoid valve 6 for controlling the amount of fuel supplied to the pressure chamber 23 is provided at the right end of the lock adapter 5. ing. The lock adapter 5 is formed with a flow path 51 that communicates with the fuel reservoir 12.
Is communicated with a fuel reservoir 52 formed on the outer periphery of the left end of the fuel cell. At this time, the feed flow path 11, the fuel reservoir 12, the flow path 5 from the feed pump P1 provided in the pump.
1. The flow path leading to the fuel pool 52 constitutes a low-pressure flow path.
The check valve 4 and the solenoid valve 6 constitute the discharge control device P2 in FIG.

The check valve 4 has a flow path 43 penetrating the body 42 in the left-right direction, and a valve body 44 for opening and closing the flow path 43. The flow path 43 expands in the direction of the pressure chamber 23 (leftward in the drawing) on the way to form a conical seat surface 45 serving as a valve seat portion. The right half of the valve body 44 has a plurality of grooves on the outer periphery as shown in FIG. 4B, and fuel flows along the grooves. Thus, when the solenoid valve 6 is opened and fuel flows into the flow passage 43, the valve body 44 is opened by the pressure of the fuel.

The stopper 41 has communication holes 41a and 41b at a plurality of positions on the plate surface. These communication holes 41
The fuel can flow between the flow path 43 and the pressure chamber 23 through the pressure chambers 23a and 41b. When the pumping starts, the valve body 44 is moved from the pressure chamber 23 by the communication hole 41b at the center of the stopper 41. It is made easy to receive the dynamic pressure of the fuel flowing backward. The stopper 41 and the check valve 4 are sandwiched between the head H and the lock adapter 5 by screwing a lock adapter 5 having a threaded portion on the outer periphery from the right side of the check valve 4.

FIGS. 5A and 5B show details of the solenoid valve 6. The solenoid valve 6 includes a housing 61 containing a coil 62 and a valve body 7 fitted and fixed to the left end thereof.
1 and a flange 63 provided on the outer periphery of the housing 61
Is bolted to the upper surface of the lock adapter 5 (see FIGS. 1 and 4). At this time, the valve body 71 passes through the center of the lock adapter 5 and faces the check valve 4. The check valve 4 is provided between the valve body 71 and the check valve 4.
A channel 43a communicating with the channel 43 is formed.

In FIG. 5A, the valve body 71
Holds a needle valve 73 slidably in the left-right direction in a cylinder 72 formed at a central portion in the axial direction. An annular flow path 74a is formed around the left end of the needle valve 73, and a flow path 74b communicating with the fuel reservoir 52 (FIG. 4) opens on the side of the flow path 74a. A channel 74c communicating with the channel 43a is open (see FIG. 4). A substantially conical seat surface 75 serving as a valve seat portion is formed at the open end of the flow passage 74c.
The substantially conical tip 3 is seated on the seat surface 75 to close the passages 74a and 74c.

Here, the needle valve 73 is provided with a sliding portion 73a.
The diameter (φd ₁ ) is made equal to the diameter (φd ₂ ) of the seat edge portion 73b (the contact edge with the seat surface 75 when the valve is closed). At this time, no hydraulic action force is generated in the needle valve 73 by the feed fuel supplied into the flow path 74a around the needle valve 73. A filter 76 is usually provided in the flow path 74b, and a needle valve 73 is provided.
This prevents foreign substances from entering between the seat surface 75 and the normally open valve. The filter 76 may be made of, for example, a metal mesh and its opening may be smaller than the flow path area at the time of the maximum lift when the needle valve 73 is opened. The filter 76 is not limited to the inside of the flow path 74b, and may be installed anywhere in the low-pressure flow path from the fuel tank T to the solenoid valve 6.

An armature 64 is press-fitted and fixed to the right end of the needle valve 73, and the armature 64 faces the stator 65 at a fixed interval (l ₂ ). The coil 62 is arranged on the outer periphery of the stator 65.
A spring 67 is disposed in a spring chamber 66 provided inside the chamber, and urges the armature 64 to the left in the drawing.

FIG. 5 shows that the coil 62 is not energized.
In the state (a), the needle valve 73 integrated with the armature 64 is urged leftward by the force of the spring 67,
The distal end thereof is seated (closed) on the seat surface 75 of the volve body 71, and closes the flow path 74c serving as a communication path to the pressure chamber 23 (FIG. 1). As described above, the electromagnetic valve 6 is configured to be closed in a non-energized state, so that there is an effect of preventing the fuel from being pumped when the coil is damaged.

The armature 64 is energized by energizing the coil 62.
Is sucked and moves rightward against the spring force of the spring 67, the tip of the needle valve 73 integrated therewith separates from the seat surface 75 (valve open), and the low pressure flow path and the pressure chamber 2
3 is opened (FIG. 5B). The lift amount (l ₁ ) at this time is determined by the distance between the right end face 73c of the needle valve 73 and the shim 68 provided opposite thereto (FIG. 5A). The armature 64 and the stator 65
Distance (l _2), the time of closing the l ₁ +0.05, when the valve opens becomes 0.05.

In FIG. 5B, the needle valve 7
The angle .theta.1 formed by the distal end of the valve body 3 is about 1 DEG greater than the angle .theta.2 formed by the seat surface 75 of the valve body 71.
Thereby, the adhesion of the seat edge portion at the time of closing the valve is improved, and wear can be prevented.

When the valve is opened, the armature 64 moves rightward, and the volume of the spring chamber 66 is reduced by that amount. Therefore, the spring chamber 66 communicates with other parts so that the fuel in the spring chamber 66 can move. Need to be done. In the present embodiment, flow paths 77 and 78 are provided inside the needle valve 73 so as to penetrate the needle valve 73 in the left-right direction.
And the flow path 74c on the left side of the needle valve 73. This allows the fuel in the spring chamber 66 to move, and at the same time, the spring chamber 66 and the flow path 74c have the same pressure even if the pressure in the flow path 74c increases when the valve is opened. No operation is performed, and malfunction of the needle valve 73 can be prevented.

The feature of the present invention is that, as shown in FIG. 4, the body 42 of the check valve 4 and the valve body 7 of the solenoid valve 6
1 is communicated with the space inside the pump via the annular groove M1 and the flow path M2 provided in the head H by the throttle flow path 53 provided in the lock adapter 5. is there. The throttle channel 53 has an end connected to the upper end surface of the channel 43a as a small-diameter throttle portion 53a. At the start of pressurized fuel pressurization, a small amount of fuel flows from the throttle portion 53a. Throttle channel 53, annular groove M1, channel M
By passing through 2 to the space inside the pump,
The flow of the check valve 4 in the valve closing direction is formed.

When the feed fuel is sucked into the pressure chamber 23, the feed fuel not only flows from the flow path 74c of the solenoid valve 6 to the pressure chamber 23 via the flow path 43a and the flow path 43 of the check valve. The flow from the flow passage 43a to the inside of the pump via the throttle flow passage 53 is also reduced. The throttle flow passage 53 has a flow area required for the pressure chamber 23 by sufficiently reducing the flow passage area of the throttle portion 53a. Can be secured. Specifically, the flow path area of the throttle portion 53a is set to the value of the valve element 4 of the check valve 4.
It is preferable that the opening area of the valve seat 4 is not more than one-tenth of the opening area of the valve seat when the valve 4 is opened.

When the solenoid valve 6 is opened, fuel flows into the flow passage 43 from the fuel reservoir 52, and when the valve body 44 is opened by the pressure of the fuel, the seat surface 45 of the check valve 4 and the stopper 41 are opened. Flows into the pressure chamber 23 via the flow path 41c in the inside and the flow path 23a in the head H. The pressurized fuel is supplied from the sliding hole 2 to the flow path 23a in the head H, and from the discharge hole 24 to the head H.
Through the discharge valve 3 fixed to the wall, the pressure is fed to the common rail R (FIG. 2) which is a pressure accumulation pipe. The discharge valve 3 is a valve element 31
And a return spring 32 that urges the return spring 32 in a valve closing direction. When the pressurized fuel exceeds a predetermined pressure, the return spring 32 opens against the spring force of the return spring 32 to open a discharge passage that is a high-pressure passage. 33.

Next, the operation of the variable discharge high-pressure pump P of this embodiment will be described with reference to FIG. FIG. 6 is an exploded view showing the lift of the inner cam 13 and the plunger 21. The sliding hole 2 serving as a cylinder of the plunger 21 is shown in FIG.
Movement of the plunger 21 in the radial direction corresponds to movement of the plunger 21 in the radial direction, and movement of the plunger 21 in the radial direction corresponds to movement of the plunger 21 downward in the development view. 6 (b) to 6 (c) show a fuel suction stroke. After the fuel pumping is completed, that is, the plunger 21 moves in the sliding hole 2 in the radial center direction by the rotation of the inner cam 13. The flow control solenoid valve 6 is started by energizing the solenoid valve 6 so that the solenoid valve 6 opens after reaching the highest point of the cam lift (FIG. 6B). When the needle valve 73 is opened by energization, the low-pressure fuel supplied from the feed pump P1 (FIG. 2) is supplied to the feed passage 11, the fuel reservoir 12, the passage 51, and the fuel reservoir 5.
2. The fluid sequentially passes through the flow paths 74b, 74a, 74c, and 43a and flows into the flow path 43 in the check valve 4. The check valve 4 is opened as shown in the drawing at the time of suction, and fuel is introduced into the pressure chamber 23 through the communication hole 41 a of the stopper 41 from the gap between the valve body 44 and the seat surface 45. At this time, the plunger 21 is pushed down (radially) by the introduced fuel. This process is called a suction process. In this process, the cam roller 22 and the inner cam 13 are in sliding contact with each other.

When the energization of the flow control solenoid valve 6 is stopped by a control signal from the electronic control unit ECU of FIG.
The needle valve 73 closes to close the flow path to the pressure chamber 23, and the suction ends (FIG. 6C). When the inhalation is completed, the plunger 21 is not further pushed down, so that the cam roller 22 and the inner cam 13 are separated (FIG. 6).
(D)). At this time, the valve body 44 of the check valve 4 is in an open state as shown in FIG.

FIGS. 6 (e) to 6 (f) show the fuel feeding process. After the end of the suction, when the plunger 21 starts to move up (moves radially outward) again with the rotation of the inner cam 13, at the same time, the pressurized fuel flows instantaneously into the flow path 41a of the stopper and the flow in the check valve 4. Channel 43 via channel 43
a, through the throttle channel 53, the annular groove M1, and the channel M2. Therefore, the valve body 44 of the check valve 4 moves rightward by receiving the force in the valve closing direction due to the fuel flowing backward from the communication holes 41a and 41b of the stopper 41, and seats on the seat surface 45 to close the valve. . Therefore, the fuel in the pressure chamber 23 is compressed as the plunger 21 moves up to a high pressure, and when the pressure exceeds a predetermined pressure, the valve body 31 of the discharge valve 3 is moved to the return spring 3.
Push open against the urging force of 2. As a result, all the pressurized fuel is sent from the discharge valve 3 to the common rail R via the discharge flow path 33 under pressure. The space inside the pump communicating with the flow path 43a via the throttle flow path 53 has the same pressure as the plunger back pressure, so that fuel does not flow from the throttle flow path 53.

When all of the pressurized fuel in the pressure chamber 23 is discharged from the discharge valve, the pressure feeding is completed, and the discharge valve 3 is closed by the return force of the return spring 32 (FIG. 6 (f)). During this pumping stroke, the pressure in the pressure chamber 23 always acts in a direction to close the valve body 44 of the check valve 4, so that the check valve 4 does not open.

As described above, in the above configuration, the amount of fuel sucked into the pressure chamber 23 is controlled by the flow control solenoid valve 6, and the check valve 4 is provided in the middle of the flow path to the pressure chamber 23, A suction amount control method is used in which all the sucked fuel is pressurized and sent to the common rail R, and the flow rate of the sucked fuel to the high-pressure flow path can be easily and reliably controlled with a simple configuration. In particular, the throttle channel 5
3 to provide a flow path 43a between the check valve 4 and the solenoid valve 6.
And the pump internal space are communicated with each other.
4, a flow in the valve closing direction (oil hammering force) acts, and the valve closing operation is quickly and reliably performed. In the event that the check valve fails to seal, the pressurized fuel escapes from the throttle passage 53, which also has the effect of preventing high pressure from being applied to the solenoid valve 6. Therefore, a desired effect can be obtained with a simple configuration without increasing the number of parts, and the reliability is excellent.

Here, an optimal control method for the variable discharge amount high pressure pump P having the above configuration will be described with reference to FIG. The engine speed sensor S2 in FIG. 2 can detect a missing tooth signal (NE pulse) as shown in FIG. 6 from the coupling K connected to the cam shaft of the pump P. The position of the top of the cam lift is at a predetermined angle. The electronic control unit ECU determines the angle (or time) from the missing tooth signal based on the missing tooth signal.
Is calculated to control the timing at which the solenoid valve 6 is energized.

FIG. 6 shows the operation of the solenoid valve 6 and the check valve 4 and the lift of the plunger 21 and the inner cam 13 when the optimal control is performed. Normally, a certain time t1, from the time when the solenoid valve 6 is energized to the time when the needle valve 73 starts to open and until the opening of the needle valve 73 ends,
It requires t2. Know this time in advance (or
A lift sensor or the like may always be used to detect this, and the valve opening start timing is just at the top of the cam lift (FIG. 6).
The energization timing is adjusted according to the number of revolutions so that (a)).

In this way, the suction is started simultaneously with the start of the suction stroke, and the plunger 21 starts to lower the cam lift from the start of energization during the energizing period of the solenoid valve 6 (FIG. 6B).
(The position in (radial direction)) by the angle (or time) θ obtained by subtracting the time (t3) up to the position (in the radial direction). And
The fuel supplied to the pressure chamber 23 is pressurized with the rise of the plunger 21 (movement toward the center of the radius) and sent to the common rail R in the pressure feed stroke of the next cycle. In this pumping step, the check valve 4 is pressurized so that the valve body 44 does not open. Therefore, the suction amount is the pressure feeding amount, and the control of the common rail pressure can be easily performed.

The amount of suction is controlled by the duration of energization of the solenoid valve 6. The longer the duration of energization, the greater the intake, and the shorter the duration, the smaller the intake. The drawing shows the respective cases where the inhalation amount is small, medium, and large. When the inhaled volume is the maximum,
The plunger 21 descends to the lowest descending point to suck and pump the maximum amount of fuel. If the suction volume is small, use plunger 2
No. 1 moves down only to a position corresponding to the suction amount, and the amount of pressure feeding becomes small. When the amount of suction is small, the plunger 21
When the solenoid valve 6 is closed, the cam roller 22 and the inner cam 13 are in sliding contact with each other.
Is stopped, the cam roller 22 and the inner cam 13 are separated from each other.

FIG. 7 shows the pressure feed amount characteristics when such control is performed. Here, from the power supply period of a certain pump rotation speed, the time (t) from the start of power supply to the start of lowering of the cam lift
The angle obtained by subtracting 3) is defined as θ. As the angle θ increases, the pumping amount monotonously increases, and it can be seen that the pumping amount (suction amount) can be controlled based on this.

Therefore, as shown in FIG. 6, the needle valve 73 is opened at the time when the cam lift starts to descend, so that the inner cam 13 and the cam roller 22 descend while sliding while sucking. By controlling the energization timing,
It is possible to improve the controllability of the suction amount, that is, the pumping amount.

FIG. 8 is a flowchart showing an example of control by the electronic control unit ECU. As shown in the system diagram of FIG. 2, various information is constantly input from the sensors to the electronic control unit ECU, and the electronic control unit ECU receives the engine signal from the NE signal detected by the engine speed sensor S2. The pump) rotation speed is calculated based on an accelerator opening detected by the throttle sensor S5 and a target common rail pressure (CPTRG) and an injection amount (a pumping amount) based on a previously input control map (steps 1 and 2).
Step 2). Subsequently, the power supply start timing and power supply period (angle or time or both) of the solenoid valve 6 according to the pump rotation speed and the pumping amount are calculated (step 3), and the power is supplied to the solenoid valve 6.

The electronic control unit ECU always detects the common rail R pressure (CPTRT) by the pressure sensor S1, and detects the detected common rail R pressure (CPTRT) and the target common rail pressure (CPTRT).
TRG) (step 4), and if different, correct. As the correction method, (CPTRT-CPT
RG) is calculated to calculate the necessary increase in the pumping amount (step 5), and the current supply period (valve opening angle) corresponding to this increase is changed (step 6). Then, again, (CP
It is determined whether or not (TRT = CPTRG) (step 7). If not (CPTRT = CPTRG), the process returns to step 5 to repeatedly perform feedback control until (CPTRT = CPTRG).

FIG. 9 shows a second embodiment of the present invention.
In the first embodiment, the throttle valve 53 is provided to quickly close the check valve 4. However, in the present embodiment, the check valve is replaced with the check valve 53. 4 is provided with a return spring 47 for closing the valve. The return spring 47 is held in a spring chamber provided at the center of the stopper 41, and urges the valve body 44 in the valve closing direction (rightward in the figure). In this configuration,
At the start of the pressure feeding, the valve is forcibly closed by the spring force of the return spring 47 instead of applying an oil hammer to the valve body 44 of the check valve. FIG. 10 shows the operation of the solenoid valve 6 and the check valve 4 and the state of the plunger lift and the cam lift in this case. As shown in the figure, when the suction step is completed (FIG. 10C), the valve closing operation is promptly started by the spring force, the valve is securely closed, and the pumping is completed (FIG. 10).
(F)).

FIG. 11 shows a third embodiment of the present invention. In the present embodiment, in addition to the configuration having the throttle channel 53 shown in the first embodiment, the second embodiment further includes
In this embodiment, the return spring 47 shown in the embodiment is provided. At this time, the valve closing operation of the check valve 4
This is performed by the spring force of the return spring 47 as in the case of the first embodiment. In addition, in the event that the return spring 47 is broken, the valve body 44 of the check valve 4 can be reliably closed by the action of the throttle channel 53. Further, it is possible to prevent high pressure from being applied to the solenoid valve 6 when the check valve 4 becomes defective in sealing.

FIG. 12 shows a fourth embodiment of the present invention, in which the throttle passage 53 shown in the first embodiment is applied to a variable discharge high pressure pump having a different basic configuration. . In each of the above embodiments, the four plungers 21 arranged in the four sliding holes 2 communicating with each other pressurize and pressure-feed one pressure chamber 23. However, in this embodiment, Pressure chambers 23 are independently provided in four cylinder sliding holes 2 (only two of them are shown in the figure), and four plungers 21 are disposed in each pressure chamber 23.
(Only two of them are shown in the figure), but the fuel is pressurized independently. Here, of the four pressure chambers 23, a pair of opposed pressure chambers 23 shown
And another pair of opposing pressure chambers 23 (not shown) are alternately pumped. The pair of pressure chambers 23
Are connected to one discharge valve 3 by discharge holes 24, respectively. In the fourth embodiment, although not shown, another discharge valve 3 is provided, and the other pair of pressure chambers 23 is similarly connected to the other discharge valve 3 by the discharge holes 24. It is connected.

On the left side of the pressure chamber 23, there are provided four check valves 4 corresponding to the pressure chambers 23, respectively, and a flow passage 43 (FIG. 13) in the check valve 4 and the electromagnetic valve 6 are provided. Channel 23a to reach
The connection and the cutoff are switched by the distribution rotor 70. The distribution rotor 70 has a T-shaped flow path 70a inside.
The flow path 23a communicates with the flow path 43 of the check valve 4 via the flow path 70a. In the illustrated state, the two upper and lower check valves 4 of the distribution rotor 70 communicate with the flow path 23a. When the distribution rotor 70 rotates 90 ° together with the drive shaft D, two check valves (not shown) The valve 4 communicates with the flow path 23a. Here, the inner cam 13 has a shape having two cam ridges at opposing positions. At this time, two opposing plungers 21 alternately perform pressure feeding as the inner cam 13 rotates. With this configuration, the peak value of the driving torque can be reduced.

As shown in FIG. 13, the check valve 4 has a flow path 43 formed in a body 42 and a ball-shaped valve element 44 for opening and closing the flow path 43. The rightward movement of the valve body 44 is restricted by the stopper 41. The fuel flows into the flow path 43 from the flow path 70a of the distribution rotor 70 via an annular flow path 43b provided on the outer periphery of the left end, and the valve body 44 is opened by the pressure of the fuel. It is. Here, the left end of the flow path 43 communicates with the inside of the pump via a throttle flow path 48 formed on the left side thereof and a space in the body 42.

The throttle channel 48 has the same function as the throttle channel 53 in the first embodiment. At the start of the pressure feed, the flow path to the solenoid valve 6 is blocked by the distribution rotor 70, so that a throttle flow path 48 communicating with the inside of the pump is provided between the distribution rotor 70 and the valve seat of the check valve 4. By utilizing the fact that the fuel flows out of the throttle passage 48 for a moment, the valve closing operation of the check valve 4 can be reliably performed. Further, as shown in FIG. 14, if a configuration is provided in which a litter spring 47 for urging the valve body 44 in the valve closing direction (rightward in the figure) is added, the valve closing operation can be performed more reliably.

As described above, the structure of the present invention can be applied to various configurations of the variable discharge high-pressure pump in addition to the basic structure shown in the first embodiment. Not only the inner cam type pump shown in
The present invention can be applied to any pump using a suction metering system, such as a row type pump and an outer cam type pump.

In each of the above embodiments, the structure in which the throttle passage is communicated with the inside of the pump is shown. However, the throttle passage is communicated with the outside of the pump, for example, a return passage leading to the fuel tank, instead of the inside of the pump. It is also possible.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a variable discharge high pressure pump showing a first embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a fuel injection system including a variable discharge high pressure pump according to the first embodiment.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

4A is a partially enlarged sectional view of FIG. 1, and FIG. 4B is a sectional view taken along line BB of FIG.

FIGS. 5A and 5B are overall sectional views of a flow control solenoid valve used in the first embodiment, wherein FIG. 5A shows a state when the valve is closed, and FIG. 5B shows a state when the valve is opened.

FIG. 6 is a view for explaining the operation of the variable discharge high pressure pump according to the first embodiment.

FIG. 7 is a diagram showing a pumping amount characteristic of the variable discharge amount high-pressure pump according to the first embodiment.

FIG. 8 is a flowchart illustrating a control method of the variable discharge high pressure pump according to the first embodiment.

FIG. 9 is a partially enlarged cross-sectional view of a variable discharge amount high-pressure pump according to a second embodiment of the present invention.

FIG. 10 is a diagram for explaining the operation of the variable discharge high pressure pump according to the second embodiment.

FIG. 11 is a partially enlarged cross-sectional view of a variable discharge high pressure pump according to a third embodiment of the present invention.

FIG. 12 is an overall sectional view of a variable discharge high pressure pump according to a fourth embodiment of the present invention.

FIG. 13 is an overall sectional view of a check valve used in a fourth embodiment.

FIG. 14 is an overall sectional view showing another example of the check valve configuration.

FIG. 15 is an overall sectional view of a conventional variable discharge high pressure pump.

FIG. 16 is an overall sectional view of a conventional variable discharge high pressure pump.

FIG. 17 is an overall sectional view of a conventional variable discharge high pressure pump.

[Explanation of symbols]

 P Variable discharge amount high pressure pump 1 Pump housing 11 Feed passage (low pressure passage) 12 Fuel reservoir (low pressure passage) 13 Inner cam (cam) 2 Sliding hole (cylinder) 21 Plunger 22 Cam roller 23 Pressure chamber 24 Discharge hole 3 Discharge valve 31 Valve element 32 Return spring 33 Discharge flow path (high-pressure flow path) 4 Check valve 41 Stopper 41a, 41b Communication hole 42 Body 43 Flow path 43a Flow path 44 Valve element 45 Seat surface 47 Return spring 48 Throttle flow path Reference Signs List 5 lock adapter 51 flow path (low pressure flow path) 52 fuel pool (low pressure flow path) 53 throttle flow path 53a throttle section 6 flow control electromagnetic valve 73 needle valve

Continuation of the front page (72) Inventor Yasuhiro Horiuchi 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside DENSO Corporation

Claims (3)

[Claims] A plunger fitted reciprocally in a cylinder, and a pressure chamber formed by an inner wall surface of the cylinder and an end face of the plunger, and are introduced into the pressure chamber from a low-pressure channel. A variable discharge high-pressure pump that pressurizes the low-pressure fluid by reciprocating motion of the plunger and pressure-feeds the high-pressure fluid to the high-pressure channel, and an electromagnetic valve that controls a flow rate of the low-pressure fluid supplied from the low-pressure channel to the pressure chamber. A check valve that is provided between the solenoid valve and the pressure chamber and that allows a low-pressure fluid to flow only in the direction of the pressure chamber from the low-pressure flow path;
In addition, a throttle flow path is provided for communicating the flow path upstream of the valve seat portion of the check valve with a pump internal space having the same pressure as the back pressure of the plunger or a return flow path leading to a low-pressure fluid storage tank. The variable discharge high pressure pump characterized by the above. A pressure chamber formed by an inner wall surface of the cylinder and an end face of the plunger, the pressure chamber being introduced into the pressure chamber from a low-pressure flow path. A variable discharge high-pressure pump that pressurizes the low-pressure fluid by reciprocating motion of the plunger and pressure-feeds the high-pressure fluid to the high-pressure channel, and an electromagnetic valve that controls a flow rate of the low-pressure fluid supplied from the low-pressure channel to the pressure chamber. A check valve that is provided between the solenoid valve and the pressure chamber and that allows a low-pressure fluid to flow only in the direction of the pressure chamber from the low-pressure flow path;
The check valve has a flow path leading to the pressure chamber, a valve element for opening and closing the flow path, and a return spring for urging the valve element in a valve closing direction. Variable discharge high pressure pump. 3. A throttle flow path for communicating a flow path upstream of a valve seat portion of the check valve with a pump internal space having the same pressure as the back pressure of the plunger or a return flow path leading to a low-pressure fluid storage tank. The variable discharge high pressure pump according to claim 2, further comprising: