JP2009108783A - High pressure fuel pump - Google Patents

Abstract

【Task】
The purpose is to obtain a mechanism that controls the discharge capacity with one electromagnetic drive mechanism and a mechanism that functions as a safety valve when the fuel pressure in the pressure accumulator (common rail) is abnormally high.
[Solution]
In order to achieve the above object, the present invention is provided with an electromagnetic solenoid mechanism for controlling the movement of the valve body of the discharge valve based on a signal from the control device, and when the solenoid is de-energized, the valve of the discharge valve The body is in a valve open position by a spring, and the discharge passage is opened. In the present invention configured as described above, in normal times, the valve closing timing of the electromagnetically driven discharge valve is controlled by a signal to control the discharge capacity, and when the fuel pressure in the pressure accumulator (common rail) is abnormally high, By keeping the valve open, it can function as a safety valve, and the discharge capacity control and the safety valve function can be achieved with one electromagnetic drive mechanism.
[Selection] Figure 2

Description

  The present invention relates to a high-pressure fuel pump that pumps high-pressure fuel to a fuel injection valve of an internal combustion engine, and more particularly to a discharge valve that is driven by an electromagnetic drive mechanism.

  Japanese Patent Laid-Open No. 10-318060 discloses a safety valve in which a valve provided in a discharge passage is a two-way valve, and this valve is opened when the fuel pressure in the pressure accumulator (common rail) is abnormally high so that the high pressure fuel flows back to the pump. A functioning high pressure fuel pump is described.

Japanese Patent Laid-Open No. 10-318060

  However, in the above-described conventional example, another electromagnetically driven valve mechanism is required to control the discharge capacity. For this reason, when an automobile is mounted as an actual product, the cause is that power consumption is large and fuel consumption is deteriorated. become.

  In order to solve this problem, an object of the present invention is to make it possible to use an electromagnetically driven discharge valve mechanism for controlling discharge capacity.

  In order to achieve the above object, the present invention provides an electromagnetic solenoid mechanism that controls the movement of the valve body of the discharge valve based on a signal from the control device. The body is in a valve open position by a spring, and the discharge passage is opened.

  In the present invention configured as described above, in normal times, the valve closing timing of the electromagnetically driven discharge valve is controlled by a signal to control the discharge capacity, and when the fuel pressure in the pressure accumulator (common rail) is abnormally high, By keeping the valve open, it can function as a safety valve, and the discharge capacity control and the safety valve function can be achieved with one electromagnetic drive mechanism.

  Examples of the present invention will be described below.

  FIG. 1 shows a first cross-sectional view of a high-pressure fuel pump in which the present invention is implemented.

  FIG. 2 shows a second cross-sectional view of a high-pressure fuel pump in which the present invention is implemented.

  FIG. 3 shows an alternative plan for the discharge joint position of the high-pressure fuel pump in which the present invention is implemented.

  FIG. 4 shows a fuel system diagram in which the present invention is implemented.

  FIG. 5 shows a fuel pressure behavior explanatory diagram of a conventional system.

  FIG. 6 shows a fuel pressure behavior explanatory diagram of a high-pressure fuel pump in which the present invention is implemented.

  FIG. 7 is a flow characteristic explanatory diagram showing effects when the present invention is implemented.

  First, the basic operation of the high-pressure fuel pump will be described with reference to FIGS.

  The low-pressure fuel pumped from the fuel tank by the low-pressure fuel pump is regulated by the regulator and introduced into the suction joint 2. The suction joint 2 that press-fits the filter 2b in the internal passage 2a is fixed to the pump body 1, and the internal passage 2a communicates with the suction passage 1a provided in the pump body 1. A damper chamber 1aa is formed in the suction passage 1a, and a damper 3 that absorbs pressure pulsation of low-pressure fuel is stored therein. The low-pressure fuel that has passed through the damper chamber 1aa is introduced into the intake valve 4. The intake valve 4 functions as a check valve that restricts the flow direction of the fuel by the valve body 4a being pressed against the seat 4c by the spring 4b. Further, a cylinder 6 is fixed to the pump body 1 for anchoring a plunger 5 reciprocally moved by a cam for driving a high-pressure fuel pump formed on a camshaft of the engine so as to be reciprocally movable with a circumferential clearance. A pressurizing chamber 1c whose volume is changed by the reciprocating motion is formed. The low pressure fuel introduced into the pressurizing chamber 1c through the suction valve 4 is increased in pressure when the plunger 5 moves in the direction of the top dead center. The high-pressure fuel whose pressure has been increased in the pressurizing chamber 1 c is pumped to the discharge joint 8 via the discharge valve 7. The discharge joint 8 is coupled to the pump body 1 and forms a threaded portion 8a, thereby enabling coupling with a high-pressure pipe. The high-pressure fuel discharged from the discharge joint 8 to the high-pressure pipe F is directly injected from the fuel injection valve H into the combustion chamber of the engine via the common rail. The discharge valve 7 can control the valve closing timing by a solenoid 7d, and the valve closing timing is controlled by a signal from the ECU.

  Next, the structure and basic operation of the discharge valve 7 will be described in detail. The discharge valve 7 includes a valve body 7a, a seat 7b on which the valve body 7a is seated, and a return spring 7c configured so that a spring force acts in a direction away from the seat 7b (the valve opening direction). . A solenoid 7d for operating the valve body 7a by magnetic force is provided on the outer periphery of the valve body 7a. When the solenoid 7d is not energized, the valve body 7a is separated from the seat 7b by the return spring 7c, and the discharge valve 7 is kept open. Normally, while the plunger 5 moves from the bottom dead center to the top dead center, the solenoid 7d is not energized, and most of the process volume of the plunger 5 is made via the discharge valve 7 that maintains the valve open state. It is discharged from the discharge valve 7 to the high-pressure pipe through the discharge passage 8a2 in the discharge joint 8a. In the state where there is no injection by the injector, the downstream side of the discharge valve 7 (hereinafter referred to as the high-pressure pipe side) is a closed space, so the fuel pressure rises by the discharged volume. On the other hand, even when the plunger 5 moves from the top dead center to the bottom dead center, when the solenoid 7d is not energized, the high pressure fuel flows backward from the high pressure pipe side to the pressurizing chamber 1c. During this time, the high-pressure piping side pressure is reduced by the fuel volume that has flowed back to the pressurizing chamber 1c. When the solenoid 5d is energized while the plunger 5 is moving from the top dead center to the bottom dead center, the valve body 7a moves in the direction of the seat 7b by the electromagnetic force and the fluid force of the high-pressure fuel that flows backward. When the valve body 7a contacts the seat 7b, the valve body 7a is pressed against the seat 7b by the generated differential pressure, and the backflow of the high-pressure fuel is completed. When the plunger 5 further moves in the direction of the bottom dead center, the pressure in the pressurizing chamber 1c decreases and the suction valve 4 opens. A new low-pressure fuel flows from the intake valve 4 into the pressurizing chamber 1c for the process volume during which the plunger 5 moves to the bottom dead center after the intake valve 4 is opened. Therefore, the discharge capacity can be changed by changing the energization timing to the solenoid 7d as required. The high-pressure fuel once discharged from the pressurizing chamber 1c to the high-pressure pipe side again flows into the pressurizing chamber 1c and acts to push down the plunger 5, so that the discharge valve 7 is closed from the top dead center. In the meantime, a part of the work required in the raising process of the plunger 5, that is, the pressurizing process can be recovered. Furthermore, according to this capacity control system, even when the fuel cut control is performed at a high rotation speed, that is, when the injection of the fuel injection valve is stopped when the high-pressure fuel pump is fully discharging, the solenoid 7d is energized. Thus, the discharge valve 7 can be held open for a necessary period. During this time, even if the plunger 5 reciprocates, the high-pressure fuel simply moves back and forth between the pressurizing chamber 1c and the high-pressure pipe side via the discharge valve 7, and the pressure on the high-pressure pipe side does not increase. In addition, since the pressurizing chamber 1c and the suction passage 1a are always in communication with each other by the circumferential gap e formed by the outer diameter of the plunger 5 and the inner diameter of the cylinder 6, the high-pressure pipe side fuel moves to the suction passage 1a. The piping side pressure gradually decreases. Further, since the discharge valve 7 can be held open for a certain period of time after the engine is stopped, the pressure on the high-pressure piping side can be reduced in a short time. Therefore, in this embodiment, it is possible to reduce the pressure on the high-pressure piping side when necessary, that is, pressure reduction control. That is, it can contribute to low emission.

  A discharge passage 8a2 is formed inside the discharge joint 8a, and a plunger rod 7a1 is held therein so as to be capable of reciprocating in the axial direction. A discharge valve 7a is integrally formed at the tip of the plunger rod 7a1. The rear end of the plunger rod 7a1 is supported by a bearing 8a5. The bearing 8a5 is press-fitted and fixed to the inner periphery of the discharge joint 8a. The bearing 8a5 has an insertion hole for the plunger rod 7a1 at the center, and a plurality of fuel passages are perforated therearound. A magnetic material core 8a3 is fixed at an intermediate position of the plunger rod 7a1. Discharge joint 8a-core 8a3-plunger rod 7a1-regulator member 8a4 (described later) -When magnetic flux is generated through a magnetic path formed by the discharge valve housing, the core 8a3 resists the force of the return spring 7c. It moves to the right side of the drawing to the position 8a4. At this time, the discharge valve 7a contacts the sheet 7b and closes the discharge port. The restricting member 8a4 and the core 8a3 are actually designed so as not to collide with each other, and do not prevent the discharge valve 7a from being blocked. The regulating member 8a4 functions as a magnetic path forming member and also functions as an intermediate bearing for the plunger rod 7a1. The discharge valve housing and the pump body 1 are welded and joined to each other at the joining portion 81 to seal between the atmosphere. Thus, the plunger rod 7a1 is supported at the center of the discharge joint 8a, and the solenoid is fixed to the outer periphery of the discharge joint 8a.

Next, the fuel pressure behavior when this embodiment is applied will be described. In the conventional system in which the volume control is performed by controlling the timing of opening and closing of the suction valve to cause part of the low-pressure fuel flowing into the pressurizing chamber to flow backward (spill) to the suction passage side, the pressure pulsation (ΔPs on the suction passage side) is controlled. ) Is the sum (ΔPs = ΔP1 + ΔP2) of the pressure drop (ΔP1) generated in the suction process and the pressure increase (ΔP2) generated in the reverse flow, that is, the spill process. On the other hand, in the case of the high-pressure fuel pump of the present embodiment, there is no spill process for backflowing the intake valve 4, and only the required amount of fuel (the fuel flow rate required by the engine + the fuel flow rate required to maintain the pressure on the high-pressure piping side). Since the pressure chamber 1c only needs to be sucked, the pressure pulsation on the suction passage side is only the pressure drop (ΔP1 ′) generated in the suction process (ΔPs = ΔP1 ′). In the above conventional method, a volume change (= process volume Vth) corresponding to the full stroke when the plunger moves from the top dead center to the bottom dead center occurs in the suction passage in the suction process. Only a small amount needs to be inhaled, and the volume change occurring in the suction passage 1a can be minimized. Therefore, even in a high-pressure fuel pump having the same theoretical discharge amount (= process volume Vth), the pressure pulsation generated on the suction passage side is smaller in the present embodiment than in the conventional method (ΔP1 ′ ≦ ΔP1). That is, in the case of the present embodiment, the pressure increase caused by the spill process can be eliminated, only the required amount of fuel during the suction process can be sucked, and the pressure generated in the suction passage 1a than the conventional method by the above two points. The pulsation can be reduced. Further, in the embodiment, as shown in FIG. 3, the plunger 5 has a stepped shape and is provided with a balance chamber 1d that generates a volume change when the plunger 5 reciprocates. When moving to the bottom dead center or from the bottom dead center to the top dead center, the volume of the balance chamber 1d changes depending on the difference between φD of the plunger 5 and the small diameter φd. That is, if the stroke from the top dead center to the bottom dead center of the plunger 5 is L, the volume change amount Vb at this time is Vb = π × L × (D ² −d ² ) / 4. Since the volume change Vb induces a volume change in the suction passage 1a communicating with the balance chamber 1d, the process volume Vth when the plunger 5 moves from the top dead center to the bottom dead center in the suction process. Is partially compensated by the volume change Vb of the balance chamber 1d. Therefore, the volume change Vs generated in the suction passage 1a is substantially Vs = Vth−Vb, and part of the pulsation generated in the suction passage 1a can be reduced. However, when the plunger 5 moves from the bottom dead center to the top dead center, that is, in the pressurizing process, there is no spill process as in the conventional method, and the volume change Vb of the balance chamber remains as it is as the volume change of the suction passage 1a. It appears. Therefore, when setting the volume change Vb of the balance chamber 1d, the intake amount in the rotation speed region where the pulsation damping characteristic of the damper 3 is inferior or the fuel injection region with the highest use frequency is set to the volume change Vb of the balance chamber 1d. It is effective to set to.

  Next, the pressure pulsation generated on the high-pressure pipe side when the present embodiment is applied will be described. By controlling the timing of opening and closing the intake valve, the conventional system in which a part of the low-pressure fuel that has flowed into the pressurizing chamber flows backward (spills) to the suction passage side and performs capacity control. ΔPd) is a pressure increase (ΔPd1) generated in the pressurizing step. That is, since the pressure drop (ΔPinj) when the fuel injection valve injects is increased, ΔPd = ΔPd1 = ΔPinj. However, in the pressure pulsation (ΔPd), when the discharge amount per cam peak of the high-pressure fuel pump and the injection amount of the fuel injection valve are the same, the discharge timing of the high-pressure fuel pump and the injection amount timing of the fuel injection valve are synchronized. This is the case. When the timing is not synchronized, the fuel pressure on the high-pressure pipe side increases by ΔPd1. In the case of the high-pressure fuel pump of this embodiment, the plunger 5 moves from the bottom dead center to the top dead center (process volume Vth), whereby the pressure in the high-pressure pipe rises by ΔPd1, but is once discharged into the high-pressure pipe. Unnecessary fuel flows back to the pressurizing chamber 1c through the discharge valve 7 held open by the return spring 7c when the plunger 5 moves from the top dead center to the bottom dead center. . Therefore, when the reverse flow is performed, the pressure in the high pressure pipe drops (ΔPdr) by the reverse flow volume (Vr). That is, the pressure pulsation (ΔPd) on the high-pressure pipe side in this embodiment is the pressure rise (ΔPd1) generated in the pressurization step, the pressure drop (ΔPr) when the high-pressure fuel flows back to the pressurization chamber 1c, and the fuel From the pressure drop (ΔPinj) when the injection valve injects, ΔPd = ΔPd1 = ΔPr + ΔPinj. Therefore, the pressure pulsation on the high-pressure piping side in this embodiment has a potential that is larger than that of the conventional system by ΔPr, and therefore the engine cylinder that matches the discharge timing of the high-pressure fuel pump and the injection timing of the fuel injection valve. It is desirable to combine pulsation reduction measures such as combining the number with the number of cams that drive the high-pressure fuel pump. That is, ideally, the relationship between the fuel volume (Vd) discharged in the pressurizing step, the backflow volume (Vr) to the pressurizing chamber 1c, and the injection amount (Vi) of the fuel injection valve is Vd = Vr + Vi. Is effective for suppressing pressure pulsation on the high-pressure piping side.

  Next, a manufacturing advantage when this embodiment is applied will be described. According to the present embodiment, the suction valve 4 does not need to be an electromagnetic valve and can be configured by simply pressing the valve element 4a against the seat 4c by the spring 4b. Therefore, the mounting hole 1g of the suction valve 4 may be formed on the same axis of the discharge valve 7 mounting hole 1e formed in the pump body 1 or the cylinder 6 mounting hole (coaxial on the plunger 5) 1f. It becomes possible. In particular, by forming the mounting hole 1g of the suction valve 4 at a position where the damper chamber 1aa and the pressurizing chamber 1c communicate with each other, it is possible not only to reduce the processing time but also to contribute to miniaturization. . At this time, when the suction valve 4 is arranged on the same axis of the cylinder 6 mounting hole (on the same axis of the plunger 5) 1f, the suction joint 2 can be directly attached to a member forming the damper chamber 1aa. This is advantageous in reducing the processing time of the pump body 1. In the case of the present embodiment, the discharge joint is established even if it is not arranged coaxially with the discharge valve 7 as shown in FIG. Furthermore, the present invention can also be applied to a fuel system in which a relief valve is set for the purpose of preventing abnormal pressure increase on the high-pressure piping side as in the conventional method. At the same time, a high-pressure fuel pump that controls the flow rate by changing the opening / closing timing of the intake valve is also established. According to the present embodiment, the flow rate on the high rotation side is not lowered, that is, there is no leakage from the relief valve, and the discharge can be performed with high efficiency, compared to the conventional relief valve disposed inside the high-pressure pump or common rail. It becomes.

  According to the present embodiment, the following technical problems can be solved.

  In a system in which a safety valve is incorporated in a multi-cylinder high pressure fuel pump having a plurality of plungers and an outlet of the safety valve is connected to a suction flow path as disclosed in Japanese Patent Application Laid-Open No. 10-339231, an alternative fuel in which a plurality of plungers are substituted , The pressure pulsation generated in the discharge flow path in the high-pressure fuel pump is relatively small. Therefore, as long as the internal combustion engine is operating normally, the pressure pulsation in the discharge flow path will not cause the pressure difference between the inlet and outlet of the safety valve to rise above the valve opening pressure, and the safety valve will not open. .

  However, the multi-cylinder high-pressure fuel pump has a large number of parts such as a plunger and a complicated structure, and is further disadvantageous in terms of cost in terms of assembly. Therefore, as in JP 2003-343395 A, a single-cylinder high-pressure fuel pump that performs high-pressure discharge with only one plunger is incorporated with a safety valve as in the case of a multi-cylinder high-pressure fuel pump, and the outlet side of the safety valve Was connected to the suction channel. However, the single cylinder type high-pressure fuel pump is higher than the multi-cylinder type high-pressure fuel pump as compared with the multi-cylinder type high-pressure fuel pump. Pressure pulsation generated in the inner discharge flow path becomes very large. As a result, the pressure difference between the inlet and outlet of the safety valve becomes equal to or higher than the valve opening pressure due to the pressure increase in the discharge flow path, and the safety valve opens in a region that should not be opened. This malfunction of the safety valve has a problem in that the discharge amount and the energy efficiency of the high-pressure fuel pump are reduced.

  In addition, even in a structure in which a safety valve is provided in a single-cylinder high-pressure fuel pump, a system in which the opening and closing timing of the intake valve is controlled by a solenoid and the intake valve is closed by a spring when the solenoid is de-energized. When the solenoid stops operating due to disconnection or the like, the full discharge state is always obtained, and the discharge side pressure rises without being controlled. In order to suppress the pressure increase at this time within the specified value, it is necessary to suppress the pressure increase associated with the increase in the flow rate of the safety valve. It is inevitable that the differential pressure before and after the body increases, and it is difficult to avoid the above pressure increase.

  Furthermore, in the conventional fuel system, the upper limit of the discharge side pressure can be limited by the safety valve. However, when it is desired to reduce the pressure in the pressure region below the opening pressure of the safety valve (from the injection valve to the combustion chamber) For example, when it is desired to suppress fuel leakage, it is necessary to provide an electronically controlled safety valve that can be intentionally opened and closed, which increases the system cost.

  In this embodiment, a solenoid is provided in the discharge valve section, the valve body behavior of the discharge valve is controlled by a control signal sent to the solenoid, and when the solenoid is de-energized, the discharge valve is opened by a spring force or the like. The structure is a valve. Therefore, when abnormal pressure increase on the downstream side of the discharge valve is prevented, or when pressure reduction on the downstream side of the discharge valve is required, the solenoid current is cut off or partially cut off and the discharge valve is maintained in the open state. .

  According to the embodiment configured as described above, the discharge valve remains open even when an abnormally high pressure occurs due to a failure of the fuel injection valve, or when the solenoid becomes uncontrollable due to disconnection or the like. Therefore, the fuel discharged (pressurized) to the high-pressure pipe side through the discharge valve in the ascending process of the plunger flows back to the pressurizing chamber in the descending process of the plunger. That is, no fuel is newly introduced from the suction valve into the pressurization chamber until the differential pressure between the pressure in the pressurization chamber and the pressure upstream of the suction valve exceeds the valve opening pressure of the suction valve. Even if it continues to operate, the pressure on the high-pressure piping side does not rise. Therefore, it is possible to prevent abnormal pressure increase on the high-pressure piping side. In addition, by intentionally shutting off the energization of the solenoid or shortening the energization time, the fuel that has flowed back to the pressurizing chamber is released to the low pressure side (upstream side of the intake valve) through the gap between the plunger and the cylinder. That is, by maintaining the open state of the discharge valve, it is possible to control the pressure of the high-pressure pipe side communicating with the pressurizing chamber via the discharge valve. According to the present invention, since the discharge valve can be provided with a safety valve function, the structure is simplified, the pump is reduced in size and cost, and the discharge side pressure reduction control is possible. A high pressure fuel pump suitable for the above can be obtained.

1 shows a first cross-sectional view of a high-pressure fuel pump in which the present invention is implemented. 2 shows a second cross-sectional view of a high-pressure fuel pump in which the present invention is implemented. The alternative plan of the discharge joint position of the high-pressure fuel pump in which the present invention is implemented is shown. 1 shows a fuel system diagram in which the present invention is implemented. An explanatory view of fuel pressure behavior of a conventional method is shown. The fuel pressure behavior explanatory view of the high-pressure fuel pump with which the present invention is carried out is shown. The flow characteristic explanatory view which shows the effect when the present invention is carried out is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pump body 1c Pressurizing chamber 2 Suction joint 3 Damper 4 Suction valve 5 Plunger 6 Cylinder 7 Discharge valve 7a Valve body 7a1 Plunger rod 7b Seat 7c Return spring 7d Solenoid 8 Discharge joint 8a1, 81 Seal part 8a2 Discharge passage 8a3 Electromagnetic movable Core 8a4 stopper

Claims (8)

Reciprocating plunger,
A cylinder for slidingly holding the plunger in a reciprocating manner;
A pressure chamber whose volume changes as the plunger reciprocates;
A suction channel for sucking fuel into the pressurizing chamber;
A discharge passage for discharging the fuel from the pressurizing chamber;
A suction valve provided in the suction flow path;
A discharge valve provided in the discharge flow path;
In what has an electromagnetic solenoid mechanism for controlling the movement of the valve body of the discharge valve based on a signal from the control device,
A high-pressure fuel pump in which when the solenoid is de-energized, the valve body of the discharge valve is in an open position by a spring and the discharge passage is opened. The high-pressure fuel pump according to claim 1, wherein the flow rate is controlled by controlling the valve closing timing of the discharge valve by the solenoid. The high-pressure fuel pump according to claim 1 or 2,
When the solenoid is de-energized, the valve body of the discharge valve is opened by a spring, and the high-pressure fuel pump permits the back flow of fluid. The high-pressure fuel pump according to claim 1 or 2,
A high-pressure fuel pump configured to determine a position of the valve body by a differential pressure and a fluid force before and after the valve body of the discharge valve when the solenoid is de-energized. The high-pressure fuel pump according to claim 1 or 2,
Forming the discharge flow path, and having a discharge joint for connecting a high-pressure pipe;
A high pressure fuel pump in which a coil of the solenoid is disposed on a coaxial circumference of the discharge joint, and a high pressure fuel passage is formed inside the coil. The high-pressure fuel pump according to claim 1 or 2,
A high-pressure fuel pump, wherein the suction valve and the discharge valve are arranged coaxially. The high-pressure fuel pump according to claim 1 or 2,
A high-pressure fuel pump, wherein the intake valve and the plunger are arranged coaxially. The high-pressure fuel pump according to claim 5,
A high pressure fuel pump in which a plunger rod operated by the solenoid is disposed on a central axis of the coil, and the discharge valve is provided at a tip thereof.

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