WO2005111406A1

WO2005111406A1 - High-pressure fuel pump

Info

Publication number: WO2005111406A1
Application number: PCT/JP2004/006790
Authority: WO
Inventors: Kenichiro Tokuo; Hideaki Yamauchi; Minoru Hashida; Toru Onose
Original assignee: Hitachi, Ltd.
Priority date: 2004-05-13
Filing date: 2004-05-13
Publication date: 2005-11-24
Also published as: JPWO2005111406A1

Abstract

A high-pressure fuel pump allowing the prevention of the jumping of a cam and a tappet and a reduction in pumping loss, comprising a plunger, a cam mechanism providing a reciprocating driving force to the plunger, and a cam follow-up mechanism operating the plunger to follow up the cam mechanism. The cam follow-up mechanism comprises a spring having non-linear spring characteristic with respect to load-deflection wherein the ratio of the variation amount of an energizing force to the displacement of the plunger is larger in the top dead center state of the plunger than in the bottom dead center state, and the maximum outside diameter of the spring is formed smaller than the outside diameter of the tappet which stores the spring.

Description

Description High-pressure fuel pump Technical field

The present invention relates to a high-pressure fuel pump used in a fuel supply system that supplies fuel to a fuel injection valve of an internal combustion engine. Background art

Japanese Patent Application Laid-Open No. 2000-08997 has a suction flow path for sucking fuel into a pump chamber, and a discharge flow path for discharging the fuel from the pump chamber. In a variable flow high-pressure fuel pump that performs suction and discharge of fuel by a reciprocating plunger and supplies it during injection, a suction check valve is provided in the suction flow passage, and a discharge check valve is provided in the discharge flow passage. An electromagnetic valve for controlling the suction flow path or the discharge-flow fuel flow rate, wherein the electromagnetic valve opens and closes the electromagnetic valve to open the suction flow path and the pump chamber or the discharge flow path. By switching between communication and non-communication with the pump chamber, the fuel flow rate is controlled, and when the solenoid valve is not energized and does not open and close, the suction check valve is The plunger A constant flow rate of fuel is sucked into the pump chamber from the suction flow path according to the return movement, and the discharge check valve is configured to discharge a constant flow rate of fuel from the pump chamber according to the reciprocating movement of the plunger. A variable flow high pressure fuel pump discharging to a pump is described.

Japanese Patent Application Laid-Open Publication No. 2000-4-1128 discloses that a cam driven by an internal combustion engine reciprocates a plunger in a cylinder, and a pressurized section defined by the cylinder and the plunger. Fuel is sucked from the fuel tank into the pressurizing chamber in a suction stroke in which the volume of the chamber is expanded, and is adjusted based on control of a closing period of a spill valve in a discharge stroke in which the volume of the pressurizing chamber is reduced. In a high-pressure fuel pump in which fuel is discharged from the pressurizing chamber to a discharge passage by an amount to be measured, the volume change rate of the pressurizing chamber in the discharge stroke is controlled by A speed varying means for decreasing the volume change speed of the pressurizing chamber; the speed varying means is the cam; and the cam has an asymmetrical cam profile between the discharge stroke and the suction stroke. A high-pressure fuel pump is described in which a force angle in a discharge stroke is set to be larger than a cam angle in a suction stroke.

Also, Japanese Patent Application Laid-Open No. 2000-145573 discloses a fuel injection pump in which a plunger is piled on a return spring by a cam provided on a camshaft to push up and feed fuel. In the above, there is described a fuel injection pump in which the projection is formed in the force so that the plunger is pushed by the return spring to cancel the positive torque applied to the force shaft.

Japanese Unexamined Patent Publication No. 5-227424 describes that the characteristic of a spring for biasing a flow control valve is made non-linear. Brief Description of Drawings

FIG. 1 is a diagram showing a configuration of a fuel injection system.

FIG. 2 is a vertical sectional view of one embodiment.

FIG. 3 is a partially enlarged sectional view of FIG.

FIG. 4 shows the spring load characteristics of one embodiment.

FIG. 5 is an explanatory diagram of one embodiment.

FIG. 6 is a partially enlarged sectional view of one embodiment.

FIG. 7 is a partially enlarged cross-sectional view of one embodiment.

FIG. 8 shows a pressure change characteristic of one embodiment.

FIG. 9 is a partially enlarged sectional view of one embodiment. Disclosure of the invention

The inventors have found that the high-pressure fuel pump has the following problems. This is due to the large inertial force of the reciprocating plunger, sunset, etc. in engines with high rotational speeds, especially in the case of an evening car, and a large spring force is required to urge it. . The same problem occurs when a large evening pet such as a roller overnight pet is applied. However, to increase the spring force, general In order to maintain the durability of the spring, it is necessary to increase the outer diameter of the spring. If the outer diameter of the spring is large, the pets receiving the spring will also be large, and the mass of the reciprocating part will be further increased, causing a vicious cycle. Also, if the spring force is large, the frictional force between the cam and the sunset increases, and there is also a problem that the bombing loss increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-pressure fuel pump which prevents the cam and the evening pet from jumping and has a small bomping loss.

The present invention provides a high-pressure fuel pump comprising: a plunger; a cam mechanism that applies reciprocating driving force to the plunger; and a cam follow-up mechanism that operates the plunger to follow the cam mechanism. The spring characteristic with respect to one deflection shows a non-linear characteristic in which the ratio of the change amount of the biasing force to the displacement of the plunger is larger in the top dead center state of the plunger than in the bottom dead center state. Shown, for example, a conical coil spring, bamboo coil spring, tall coil spring, or a concentric combination of two cylindrical springs with large and small outside diameters. The cam end of the inner spring is Provided is a high-pressure fuel pump in which a spring having a shape disposed inward in a longitudinal direction from a cam-side end of an outer spring is used.

The present invention relates to a high-pressure fuel pump comprising: a plunger; a cam mechanism that applies reciprocating driving force to the plunger; and a force follow-up mechanism that operates the plunger by following the force mechanism. Comprises a spring having a non-linear characteristic in a spring characteristic with respect to a deflection of a load, a spring reciprocatingly urged by the cam mechanism, wherein the sunset is connected to one end of the spring. Provided is a high-pressure fuel pump in which the outer diameter of the evening pet is smaller than the maximum outer diameter of the spring at a portion where the spring is placed.

The present invention provides a plunger, a cam mechanism having a cam for applying reciprocating driving force to the plunger, a force follower mechanism for operating the plunger to follow the cam mechanism, and a reciprocating mechanism urged by the cam mechanism. In a high-pressure fuel pump having a moving sunset, the cam follow-up mechanism applies an urging force for bringing the evening into contact with the cam mechanism. A high-pressure fuel having a biasing force increasing means for following the displacement of the lift curve of the cam except near the top dead center of the plunger and providing a biasing force added to the displacement near the top dead center of the plunger. Provide a pump

The present invention provides a plunger, a cam mechanism having a cam for applying reciprocating driving force to the plunger, a force follower mechanism for operating the plunger to follow the cam mechanism, and a reciprocating mechanism urged by the cam mechanism. In the high-pressure fuel pump having a moving sunset, the cam follow-up mechanism includes a spring that applies an urging force for bringing the evening pet into contact with the cam mechanism. A high-pressure fuel pump that has a non-linear characteristic that follows the amount of displacement of the cam lift curve except near the top dead center and provides a biasing force added to the displacement near the top dead center of the plunger provide. BEST MODE FOR CARRYING OUT THE INVENTION

The high-pressure fuel pump is a high-pressure fuel pump that includes a plunger, a cam mechanism that applies reciprocating driving force to the plunger, and a force-following mechanism that urges the plunger to the cam mechanism to operate the plunger following the cam mechanism. Therefore, in the force follow-up mechanism, the ratio of the change in the biasing force to the displacement of the plunger is larger in the state at the top dead center of the high-pressure fuel pump than in the state at the bottom dead center of the high-pressure fuel pump. It is composed.

Further, the high-pressure fuel pump includes: an evening pet that reciprocates by a rotating cam; a force transmitting member that transmits the translational motion of the evening pet; and fuel injection by the force transmitted by the force transmitting member. A piston-type high-pressure fuel pump for pressurizing and supplying a valve, comprising: a return mechanism for applying a biasing force so that the reciprocating sunset always returns to a position where it comes into contact with the cam. It is configured such that the rate of increase of the urging force with respect to the displacement of the plunger increases as the urging force increases.

The high-pressure fuel pump includes a high-pressure fuel pump that pressurizes and supplies fuel to a fuel injection valve by reciprocating a plunger, a retainer that engages with the plunger, a housing of the high-pressure fuel pump, and the retainer. Engaged with one A return spring for urging the plunger in the extension direction; a force transmitting member for transmitting the urging force of the plunger; a evening pet urged by the urging force transmitted by the force transmitting member; A high-pressure fuel pump comprising: a cam for applying a driving force; and the return spring is a non-cylindrical spring, and an outer diameter of one end of the non-cylindrical spring is smaller than an outer diameter of the tuft. The maximum outer diameter of the non-cylindrical spring is configured to be larger than the outer diameter of the evening.

An evening pet that reciprocates with a rotating force, a force transmitting member that transmits the translational motion of the evening pet, and a piston-type high pressure that pressurizes and supplies fuel to the fuel injection valve with the force transmitted by the force transmitting member. The high-pressure fuel pump includes a return mechanism that applies a biasing force so that the reciprocating sunset always returns to a position where it comes into contact with the cam, and the return mechanism is a rate of increase of the biasing force with respect to the plunger displacement. Is increased with an increase in the biasing force. As a result, similarly to the above, the biasing force generated by the force follow-up mechanism near the top dead center where jumping occurs most can be increased, and jumping can be effectively suppressed. In addition, since the biasing force is small except near the top dead center, the bombing loss does not increase.

A plunger that pressurizes and supplies fuel to the fuel injection valve by reciprocating; a retainer that engages the plunger; and a housing and retainer of the high-pressure fuel pump that extend the plunger in the extending direction. A spring that transmits the urging force of the plunger to form a cam follow-up mechanism; a sunset that is urged by the urging force transmitted by the force transmitting member; A high-pressure fuel pump comprising: a cam for providing a translational driving force to the non-cylindrical spring; the return spring is a non-cylindrical spring; the outer diameter of one end of the non-cylindrical spring is smaller than the outer diameter of the evening pet; The maximum outer diameter of the spring is larger than the outer diameter of the sunset. As a result, the non-cylindrical spring has a non-linear load characteristic in the same manner as described above, and furthermore, by reducing the outer diameter of the end on the evening pet side, the evening and the reciprocating motion accompanying the evening are reduced. The mass of the moving parts (retainers, force transmitting members, etc.) can be reduced, and jumping can be prevented. Also, since the mass of the reciprocating part can be designed to be small, the biasing force of the spring for preventing jumping can be designed to be small. Bing loss can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a fuel injection system, FIG. 2 shows a high-pressure fuel pump 100 according to an embodiment of the present invention used in the fuel injection system, and FIG. 3 is a part of FIG. FIG.

In FIG. 1, fuel is guided from a tank 50 by a low pressure pump through a fuel inlet of a high pressure fuel pump 1. The introduced fuel is pressurized by the high-pressure fuel pump 1 and sent to the common rail 53 from the fuel discharge port.

The common rail 53 is equipped with an injector 54, a relief valve 55, and a pressure sensor 56.

The injector 54 is mounted in accordance with the number of cylinders of the internal combustion engine, is controlled by an engine control unit (ECU) 40, and performs injection by a signal from the ECU 40. The ECU 40 also controls the low-pressure pump 51 and controls the pressure of the fuel guided to the fuel inlet. The relief valve 55 opens when the pressure in the common rail 53 exceeds a predetermined value to prevent damage to the piping system.

The plunger 2 is slidably held by a cylinder 20 and is reciprocated as indicated by an arrow by a cam follower including a cam, which will be described later, which is rotated by an engine power shaft (not shown). The volume in the pressurizing chamber 12 in the cylinder 20 is changed to discharge fuel.

The high-pressure fuel pump 1 includes a fuel intake passage 10, a discharge passage 11, and a caropressure chamber 12. A discharge valve 6 is provided in the discharge passage 11. The suction valve 5 and the discharge valve 6 are held in one direction by springs 5a and 6a, respectively, and serve as check valves for restricting the fuel flow direction.

The pressurizing chamber 12 is formed by communicating a suction hole and a discharge hole with a pump chamber 300 in which a plunger 2 as a pressurizing member slides.

The high-pressure fuel pump 1 holds a solenoid 200, and an engagement member 201 and a spring 202 are arranged in the solenoid 200. When the solenoid 20 ° is OFF, the engaging member 201 opens the suction valve 5 by the spring 202. The urging force is applied in the direction. Since the urging force of the spring 200 is larger than the urging force of the suction valve spring 5a, when the solenoid 200 is OFF, the suction valve 5 is in the open state. As shown in the figure, a current i is applied to the solenoid 200 at a time t in a state of a solenoid drive current waveform.

In FIG. 2, the pump main body 90 of the high-pressure fuel pump 1 is provided with a fuel intake passage 1 ◦, a discharge passage 11, and a pressurization chamber 12 as described above. The suction passage 10 and the discharge passage 11 are provided with a suction valve 5 and a discharge valve 6, which are held in one direction by springs 5a and 6a, respectively.

A hole 19 is formed in the pump body 90, a cylinder 20 is arranged in the hole 19, and the plunger 2 slides in the cylinder 20. The cylinder 20 is held by a cylinder holding member 21. The cylinder holding member 21 is held by the pump body 90.

A plunger seal 30 is provided on the cylinder holding member 21 below the cylinder 20 and toward the surface of the plunger 2 to prevent fuel from flowing out to the cam 100 side. The pressurizing chamber 12 is provided with a suction hole 5 b communicating with the suction valve 5 and a discharge hole 6 b communicating with the discharge valve 6.

As described above, the high-pressure fuel pump 1 holds the solenoid 200 for controlling the flow rate, and the solenoid 200 is provided with the engaging member 201 and the spring 202.

A suction chamber 10 a is formed in the suction passage 10.

In the upper part of the high-pressure fuel pump 1, a fuel chamber 10b communicating with the suction chamber 10a is provided with two metal diaphragms 80 and 84, and a fisher 86 is provided therebetween. . 10 c is a pressure sensor, and 10 d is a damper case.

The horseshoe-shaped retainer 31 is engaged with the side of the lower end of the plunger 2, the shim 32 is engaged with the lower end, and the retainer 31 and the shim 3 2 are engaged by the evening pet 3. Will be retained. A roller 33 is provided on one side of the sunset 3, and the mouth roller 33 reciprocates up and down along the cam shape by the cam 100. Therefore, the evening 3 is urged by the cam mechanism including the cam 100 to reciprocate. It will be.

A recess (spring accommodation portion) is formed on the other side of the sunset 3, and the retainer 31 and the shim 32 described above are disposed in the recess. In this case, a gap is provided between the side wall of the recess and the retainer 31, and a lower end 4b of a conical coil spring 4 (plunger spring) forming a cam follow-up mechanism is disposed in the gap. Is done. The upper end 4a of the conical coil spring is arranged in a recess formed in the lower end 91 of the pump and held by a part of the cylinder holding member 21. That is, the conical coil spring 4 has one end held by the pump body 90 and the other end 4 b held by the evening pet 3. In this case, as described above, the conical coil spring 4 functions as a cam following mechanism.

In FIG. 3, the outer diameter d of the cylindrical pet 3 is smaller than the maximum outer diameter D of the conical coil spring 4. The outer diameter d indicates a portion where the conical coil spring 4 is housed and placed inside the evening pet 3. In the example shown in Fig. 3, the maximum outer diameter is near the top end of the conical coil spring. As described later, depending on the structure, the maximum outer diameter may be provided in the middle of the spring. It is desirable to be provided near the uppermost end in design. In this way, the configuration of evening 3 can be reduced.

As described above, the retainer 31 is engaged with the lower end of the plunger 2, and the urging force of the spring 4 is transmitted to the sunset 3 via the shim 32 which is a force transmission mechanism. Energize 3 to cam 100. As the spring 4, a spring whose one end has a smaller diameter than the other end, for example, a conical coil spring is used. The operation of the above configuration will be described.

When the suction valve 5 is closed during the compression stroke of the plunger 2, the pressure in the pressurizing chamber 12 is increased, whereby the discharge valve 6 is automatically opened and fuel is pumped to the common rail 53.

The suction valve 5 automatically opens when the pressure of the pressurizing chamber 12 becomes lower than the fuel inlet, but the closing of the valve is determined by the operation of the solenoid 200. When the solenoid 200 is kept in the ON (energized) state, an electromagnetic force greater than the biasing force of the spring 202 is generated, and the engaging member 201 is drawn to the solenoid 200 side. For this purpose, the engagement member 201 and the suction valve 5 are separated. In this state, the suction valve 5 is an automatic valve that opens and closes in synchronization with the reciprocation of the plunger 2. Therefore, during the compression stroke, the suction valve 5 is closed, and the fuel corresponding to the reduced volume of the pressurizing chamber 12 pushes the discharge valve 6 and is fed to the common rail 53.

On the other hand, when the solenoid 200 is kept OFF (non-energized), the engaging member 201 is engaged with the suction valve 5 by the biasing force of the spring 202, and the suction valve 5 is opened. Keep in state. Therefore, even during the compression stroke, the pressure in the pressurizing chamber 12 is maintained at a low pressure almost equal to that of the fuel introduction port, so that the discharge valve 6 cannot be opened, and the volume of the pressurizing chamber 12 is reduced. The reduced fuel is returned to the fuel inlet side through the suction valve 5.

Also, if the solenoid 200 is set to the 〇N state during the compression stroke, the fuel is fed to the common rail 53 from this time. In addition, once the pressure feeding starts, the pressure in the pressurizing chamber 12 increases, so that even if the solenoid 200 is turned off, the suction valve 5 remains closed, and the suction stroke starts. Automatically opens in synchronization.

The conical coil spring shown in Fig. 1, that is, the non-cylindrical spring has a non-linear load deflection characteristic as shown in Fig. 4. Also, such non-cylindrical springs usually have non-linear load deflection characteristics. The reason for this is that, for example, a portion with a large diameter is likely to bend, so when a compressive load is applied to a spring, bonding starts from a portion with a large diameter, indicating directness in a load-deflection relationship, followed by a deflection with a small diameter. The curve shows the load-deflection relationship, that is, the ability to bear a large load with a small deflection.

By utilizing this characteristic, it is possible to improve the volumetric efficiency of the pump. The method and the reason are described below.

Fig. 5 shows one cycle of the evening 3 under a certain operating condition, that is, the lift curve L of the plunger 2, the biasing force F spr of the cam follow-up mechanism 4, and the reciprocating part when a normal spring is used. The time change of the inertia force F i of the plunger 2 is shown. If a spring having a normal linear load deflection characteristic is used, the increase or decrease of the urging force F spr is proportional to the displacement of the lift curve L. That is, follow. As a result, as shown in the figure, when the inertia force F i increases near the top dead center (TDC) of the pump, the urging force F spr becomes insufficient, and the state in which the sunset 3 does not follow the cam 100 may occur. Occurs. Conventionally, in order to avoid such a state, there has been known a measure for devising a force shape so as to reduce the acceleration near the top dead center (see Patent Document 3). An example of the inertial force in such a case is shown by Fi 2 in FIG. However, it is known that when such a cam shape is used, the volume efficiency of the pump is reduced as a rebound (see Patent Document 2). Although details are omitted, the speed and acceleration near the bottom dead center increase as a rebound that reduces the acceleration near the top dead center, which leads to a decrease in efficiency. However, if a spring having a non-linear spring load characteristic as shown in Fig. 4 is provided in the cam follow-up mechanism, the force that urges the sunset by the cam follow-up mechanism near the top dead center of the pump becomes particularly strong. . An example is shown in Fspr 2 in FIG. By doing so, it is not necessary to suppress the inertial force near the top dead center, and a cam profile having a large acceleration near the top dead center (cam profile that generates the inertia force of Fi shown in Fig. 5) Apply and can achieve high volumetric efficiency.

With the configuration described above, the force is transmitted by the force transmitting member, such as the sunset 3 that performs reciprocating motion by the rotating cam 100, the plunger 2 that transmits the translational motion force of the evening 3, and the force transmitting member. A piston type high pressure fuel pump that pressurizes and supplies fuel to the fuel injection valve with a certain force, and applies an urging force so that the reciprocating evening 3 always returns to the position where it comes into contact with the cam 100. A high-pressure fuel pump can be configured such that a return mechanism is provided, and the return mechanism increases the rate of increase of the urging force with respect to the displacement of the plunger as the urging force increases.

The return mechanism is composed of a return spring, and the return spring is a non-cylindrical spring. The outer diameter of one end of the non-cylindrical spring is substantially smaller than the outer diameter of the sunset 3, and the maximum outer diameter of the non-cylindrical spring is It can be larger than the outer diameter of the pet 3.

The cam follow-up mechanism provides an urging force for bringing the sunset 3 into contact with the cam mechanism, and the increase or decrease in the urging force is caused by the displacement of the lift curve L of the cam except in the vicinity of the top dead center of the plunger 2. A high-pressure fuel pump having an urging force increasing means for applying an urging force that is added to the displacement amount near the top dead center of the plunger 2 following the amount Can be achieved.

Further, specifically, the cam follow-up mechanism includes a spring that applies an urging force for bringing the evening pet 3 into contact with the cam mechanism, and the urging force of the spring increases or decreases except for the vicinity of the top dead center of the plunger 2. A high-pressure fuel pump that follows the displacement of the lift curve L and has a non-linear characteristic that provides an urging force added to the displacement near the top dead center of the plunger 2 can be configured.

[Example 2]

FIG. 6 shows a second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and similar components are denoted by the same reference numerals with alphanumeric characters, and the description may be omitted. The same applies to the following embodiments. In the example shown in FIG. 6, a bamboo shoot spring 4 B is used in place of the conical coil spring 4.

Flat evening is used for evening 3b of the cam following mechanism. The evening part 3b in this case has a bowl-like or cup-like shape, and the inside is a concave part, in which the retainer 31b and the shim 32b are arranged.

One end 4Ba of the bamboo shoot spring is supported by the pump body 1, and the other end 4Bb is supported by the retainer 31b.

The tip of evening pet 3b directly contacts cam 100b. In this configuration, the cam follower mechanism uses a bamboo child spring 4B whose load-deflection spring characteristic shows nonlinear characteristics, and the maximum outer diameter of the bamboo child spring 4b accommodates the bamboo child spring 4B. The outer diameter is smaller than 3b.

Incidentally, a single straight plunger can be used as the plunger 2b.

[Example 3]

FIG. 7 shows a third embodiment of the present invention.

In the example shown in FIG. 7, an annular coil spring 4C is used in place of the conical coil spring 4 or the bamboo shoot spring 4B.

In this example, an annular skirt portion 302a is provided to prevent the lateral movement of the sunset 3c, and the annular skirt portion 302a is provided on the pump body 90 side. But on the cam 100c side.

One end 4Ca of the barrel type coil spring 4C is supported by the pump body 1, and the other end 4Cb is supported by the retainer 31c. In this configuration, the cam follower mechanism uses a tall-shaped coil spring 4C whose spring characteristic with respect to load deflection exhibits a non-linear characteristic, and the maximum outer diameter of the tall-shaped coil spring 4C is The spring 4C is smaller than the outer diameter of the sunset 3c that houses the spring 4C.

The shape of the roller 33c of the plunger 2c is the same as that of the first embodiment.

[Example 4]

FIG. 8 shows a fourth embodiment of the present invention.

In the example shown in FIG. 8, a drum-shaped spring 4 D is used instead of the conical coil spring 4.

In this example, a constriction at the tip of the plunger 2d is arranged in a hole provided at the center of the retainer 3Id.

One end 4Da of the drum-shaped spring 4D is supported by the pump body 1, and the other end 4Db is supported by the retainer 31d. In this configuration, the cam follow-up mechanism uses a drum-shaped coil spring 4D whose load-deflection spring characteristic shows nonlinear characteristics, and accommodates the maximum outer diameter of the drum-shaped coil spring 4d.ヅ The diameter is smaller than the outer diameter of 3d.

[Example 5]

FIG. 9 shows a fifth embodiment of the present invention. In the example shown in FIG. 9, combined coil springs 4E and 4F are used instead of the conical coil spring 4 or the hourglass coil spring 4D. FIG. 9 has two return springs (4E, 4F) as a cam follow-up mechanism. In this example, the outer return spring 4E is made thick and the inner return spring 4F is made of a thin wire. In such a configuration, since the outer spring 4F is received by the retainer, only the retainer can be lightened, and the mass of the reciprocating portion can be reduced. In addition, by giving one of the springs non-linear characteristics, the same non-linear characteristics as in the above embodiment can be obtained as the resultant force of the springs. The effect of reduction and improvement of volumetric efficiency can be obtained. Alternatively, if one of the two springs is lifted at the position of the bottom dead center of the pump (the installation length is longer than the natural length of the spring), one of the springs is located near the bottom dead center of the pump. It is urged by a spring and is urged by two springs near the top dead center, so that a non-linear spring characteristic as shown in FIG. 7 can be obtained.

In this configuration, it consists of a concentric combination of two cylindrical springs with large and small outside diameters, with the cam side end of the inner spring being more inward in the longitudinal direction than the cam side end of the outer spring. A combination of springs 4E, 4F that are arranged and used is used.

The negative ends 4∑ &, 4Fa of the combined coil springs 4E, 4 are supported by the pump body 90, and the other ends 4Eb, 4Fb are supported by the retainers 31e. In either case, the end with the larger spring diameter should be placed on the lower end 91 side of the pump body, and the end with the smaller spring diameter should be placed on the evening pet side. At this time, the spring diameter on the evening pet side has a common feature that it is smaller than the evening diameter. In general, when designing a spring having a large spring constant, it is necessary to design a spring with a large outer diameter. Therefore, the retainer 31 that engages with the spring and the evening pet 3 that covers the spring also need to be designed large, and the weight increases. However, by applying the present invention, both a strong spring constant and a small sunset mounting diameter can be achieved. According to the present invention, it is possible to provide a high-pressure fuel pump that is small, has a high effect of preventing jumping, has a high volumetric efficiency, and has a small bombing loss. Further, according to the present invention, the diameter of the cam side end of the spring used as the cam follow-up mechanism is reduced, so that a small-sized evening pet can be used, and a small high-pressure fuel pump can be provided. it can.

Claims

The scope of the claims

1. A high-pressure fuel pump comprising a plunger, a cam mechanism for applying reciprocating driving force to the plunger, and a cam follow-up mechanism for operating the plunger to follow the cam mechanism.

The cam follow-up mechanism may be configured such that the spring characteristic with respect to load-deflection is such that, when the amount of change in the biasing force with respect to the displacement of the plunger is harmful [], the plunger is in the top dead center state than in the bottom dead center state. A spring exhibiting increased nonlinear characteristics

A high pressure fuel pump characterized by the following.

2. A high-pressure fuel pump including a plunger, a cam mechanism for applying reciprocating driving force to the plunger, and a force following mechanism for operating the plunger to follow the force mechanism.

The cam follow-up mechanism includes a spring whose load-deflection spring characteristic has a non-linear characteristic, and includes a reciprocating member that is urged by the cam mechanism to reciprocate. A high-pressure fuel pump, wherein one end of the spring is housed and an outer diameter of the sunset is smaller than a maximum outer diameter of the spring at a portion where the spring is mounted.

3. The high-pressure fuel pump according to claim 1, wherein the spring is a conical coil spring.

4. The high-pressure fuel pump according to claim 1 or 2, wherein the spring is a bamboo shoot spring.

5. The high-pressure fuel pump according to claim 1, wherein the spring is a tall coil spring.

6. In claim 1 or claim 2, the spring is formed by concentrically combining two cylindrical springs having large and small outer diameters, and a cam-side end of the inner spring is provided. A high-pressure fuel pump characterized in that it has a shape disposed inward in the longitudinal direction from the cam-side end of the outer spring.

7. A plunger, a force mechanism having a cam that applies reciprocating driving force to the plunger, and a force follower that operates the plunger following the force mechanism. A high-pressure fuel pump having a sunset reciprocatingly urged by the cam mechanism,

The cam follower mechanism provides an urging force for bringing the sunset into contact with the cam mechanism, and the increase or decrease in the urging force depends on the displacement of the lift curve of the cam except near the top dead center of the plunger. A high-pressure fuel pump comprising an urging force increasing means for following the amount and providing an urging force near the top dead center of the plunger to be added to the displacement amount.

8. A plunger, a force mechanism having a cam for providing a reciprocating motion driving force to the plunger, a cam follower mechanism for operating the plunger to follow the cam mechanism, and a reciprocating motion urged by the cam mechanism. High-pressure fuel pump with a

The cam follow-up mechanism includes a spring that applies an urging force for bringing the evening into contact with the cam mechanism, and the urging force of the spring increases or decreases according to a lift curve of the cam except near the top dead center of the plunger. A high-pressure fuel pump characterized by a non-linear characteristic that follows the amount of displacement of the plunger and provides a biasing force added to the amount of displacement near the top dead center of the plunger.