JPH10153155A - Accumulator type fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure accumulator type fuel injection device with an easy processing which can obtain a desired injection characteristic, even if the lift amount of the movable member of a solenoid valve is minified. SOLUTION: A cylindrical fuel space 68 with a larger diameter than a second throttle hole 67, in short a smaller passage resistance than the second throttle hole 67 is formed so as to communicate with the second throttle hole 67 in the fuel flow out side of the second throttle hole 67. At the open time of a solenoid valve 30, the passage resistance of a ring shape fuel passage formed between the plane part 43a of a spherical member 43 and a plane valve seat 53 becomes smaller in comparison with the case when the second throttle hole 67 is directly opened/closed by the plane part 43a without providing the fuel space 68. Therefore, even if the lift amount of a movable member 40 is minified, a desired injection characteristic decided by the flow rate characteristic of first/second throttle holes 66, 67 can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetically controlled pressure-accumulating fuel injection device which accumulates high-pressure fuel in a common rail, which is a kind of surge tank, and injects the accumulated high-pressure fuel into an internal combustion engine. Things.

[0002]

2. Description of the Related Art Conventionally, a high-pressure supply pump pumps high-pressure fuel to a common rail under pressure and accumulates the pressure, and injects the high-pressure fuel accumulated on the common rail into an internal combustion engine (hereinafter referred to as an "internal combustion engine"). JP-A-5-133296 discloses a control type accumulator type fuel injection device.
The one shown in U.S. Pat. No. 5,464,156 is known. In these fuel injection devices, a pressure control chamber communicating with the high pressure fuel passage is provided on the side opposite to the injection hole of the valve member that opens and closes the injection hole, and the pressure control chamber and the low pressure side space are connected and disconnected by an electromagnetic two-way valve. Controlling fuel injection. The first throttle hole regulates the flow rate of the fuel flowing from the high-pressure fuel passage into the pressure control chamber, and the second throttle hole controls the fuel flow rate flowing out of the pressure control chamber to the low-pressure side space when the electromagnetic two-way valve is opened. Regulated by

Accordingly, the fuel injection amount and the fuel injection rate are controlled by the flow rate of the fuel flowing from the high pressure fuel passage into the pressure control chamber and the flow rate of the fuel flowing from the pressure control chamber to the low pressure side space when the electromagnetic two-way valve is opened. Will be done. Also,
The injection start time, the injection end time, and the injection amount at the beginning of the injection flow out from the high-pressure fuel passage into the pressure control chamber when the electromagnetic two-way valve is opened, and flow out from the pressure control chamber to the low-pressure side space. It is determined by the difference from the fuel flow rate, and the injection amount in the latter half of the injection is determined by the fuel flow rate flowing into the pressure control chamber from the high-pressure fuel passage when the electromagnetic two-way valve is closed. That is, the pressure accumulating fuel injection device having the above-described configuration has a structure in which the injection timing, the injection amount, and the fuel injection rate are almost uniquely determined by the flow rate characteristics of the first throttle hole and the second throttle hole. ing. In order for the injection characteristic to be uniquely determined by the flow characteristics of the first throttle hole and the second throttle hole in this manner, the movable member of the electromagnetic two-way valve and the valve seat when the electromagnetic two-way valve is opened. Must be smaller than the passage resistance of the second throttle hole.

In general, the smaller the lift amount of the movable member of the electromagnetic two-way valve is set, the higher the response, the lower the operating noise,
Although effective for improving wear resistance and reducing bounce of the on-off valve, when the lift amount of the movable member of the electromagnetic two-way valve is set small, the pressure loss between the movable member and the valve seat is smaller than the pressure loss of the second throttle hole. Since the pressure loss of the fuel passing through the fuel passage becomes larger, the injection amount characteristic to be determined by the flow rate characteristics of the first throttle hole and the second throttle hole may greatly change.

[0005] The accumulator type fuel injection device disclosed in Japanese Patent Application Laid-Open No. 5-133296 has a structure in which the movable member and the valve seat abut against each other in a plane to directly close the second throttle hole. If the lift amount is set small, the second
Since the passage resistance of the fuel passage formed between the valve seat at the periphery of the opening of the throttle hole and the flat portion of the movable member is larger than the passage resistance of the second throttle hole, desired injection characteristics can be obtained. Can not. Therefore, the passage resistance of the fuel passage formed between the valve seat at the periphery of the opening of the second throttle hole and the flat portion of the movable member when the solenoid valve is opened is smaller than the passage resistance of the second throttle hole. It is necessary to increase the lift amount of the movable member to some extent so that there is a certain limit value for problems such as improvement of responsiveness, reduction of operation noise, improvement of wear resistance, and reduction of bounce of the on-off valve. Further, if the lift amount is reduced more than necessary, the dispersion of the lift amount causes the dispersion of the fuel flow rate passing through the fuel passage formed between the valve seat around the opening of the second throttle hole and the flat portion of the movable member. As a result, there is a problem that the injection characteristics between the individual injectors vary.

[0006]

SUMMARY OF THE INVENTION United States Patent No. 546
In the accumulator type fuel injection device described in the specification of Japanese Patent No. 4156,
There is shown a configuration in which a tapered valve seat having an enlarged diameter is provided on the fuel outflow side of the second throttle hole, and the second throttle hole is opened and closed by separating or abutting the valve seat and the ball valve of the electromagnetic two-way valve. Have been. The opening diameter of the tapered valve seat is larger than the diameter of the second throttle hole, and when the ball valve is separated from the valve seat, the passage resistance of the fuel passage formed between the ball valve and the valve seat is reduced. It becomes smaller than the passage resistance of the second throttle hole. Therefore, even if the lift amount of the ball valve as the movable member is small, the passage resistance of the fuel passage formed between the ball valve and the valve seat can be made smaller than that of the second throttle hole, so that the responsiveness is improved and the operation noise is improved. It can meet the demands for reduction, improvement of wear resistance, bounce of on-off valve, etc.

However, in a configuration in which a tapered valve seat is provided on the fuel outlet side of the second throttle hole and the movable member of the electromagnetic two-way valve abuts on the valve seat, the contact area between the movable member and the valve seat is reduced. Since both are small, in order to seal the high-pressure fuel in the pressure control chamber satisfactorily, both need to be processed with high precision, and there is a problem that the number of processing steps increases. An object of the present invention is to provide a pressure-accumulation type fuel injection device which can obtain desired injection characteristics even when the lift amount of a movable member of an electromagnetic valve is reduced and which is easy to process.

Another object of the present invention is to provide an accumulator type fuel injection device which can be reduced in size.

[0009]

According to the pressure accumulating fuel injection device of the present invention, the movable member of the solenoid valve and the flat valve seat can contact each other in a plane, and the second throttle hole is provided. And a fuel space having an opening diameter larger than the diameter of the second throttle hole and having an opening area smaller than the area of the flat portion of the movable member. When the two-way valve is opened, the passage resistance of the fuel passage formed between the plane portion of the movable member and the plane valve seat can be made smaller than the passage resistance of the second throttle hole. Therefore, even if the lift amount of the movable member is small, the injection characteristics are uniquely determined by the flow characteristics of the first throttle hole and the second throttle hole.

Further, since the lift amount of the movable member can be reduced, there are effects such as improvement of responsiveness, reduction of operation noise, improvement of wear resistance, and reduction of bounce of the on-off valve. Further, since the flat portion of the movable member and the flat valve seat abut on each other, the fuel can be sealed well without processing the abutting surfaces with high precision, so that the working becomes easy and the number of working steps is reduced. Decrease.

According to the pressure accumulating fuel injection device of the second aspect of the present invention, a fuel release passage communicating with the low pressure side space is formed in one of the contact surfaces of the flat portion and the flat valve seat. When the solenoid valve is closed, the pressure receiving area in which the movable member receives a force in the lift direction from the high-pressure fuel that enters between the flat contact portion between the flat portion and the flat valve seat is reduced. Therefore, a reliable sealing property can be ensured without increasing the seat surface pressure, so that the force of the urging means for urging the movable member toward the flat valve seat can be reduced, and the electromagnetic valve that lifts the movable member in the lift direction can be attracted. Power can be reduced. Therefore, the size of the solenoid valve can be reduced, and the fuel injection device can be reduced in size.

According to the pressure accumulating fuel injection device according to the third aspect of the present invention, the pressure distribution of the fuel acting in the lift direction of the movable member is point-symmetric with respect to the center of the plane portion as the center of symmetry.
The inclination and eccentricity of the movable member are suppressed. Therefore, stable opening / closing control of the electromagnetic valve is possible, and a uniform fuel amount can be injected from the injection nozzle. In particular, it is possible to control the minute amount injection with high accuracy.

According to the pressure accumulating type fuel injection device according to the fourth aspect of the present invention, after the fuel space is formed on the flat valve seat side, the second fuel injection device can be used.
Since the second throttle hole having a smaller diameter than the fuel space can be formed using the fuel space as a guide and the processing length of the second throttle hole can be shortened, the second throttle hole having a smaller diameter can be formed. Processing becomes easy. The second throttle hole only needs to be able to communicate between the pressure control chamber and the fuel space when the solenoid valve is closed. Therefore, even if an axis misalignment between the second throttle hole and the solenoid valve occurs, no problem occurs in performance. Absent.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention; (First Embodiment) FIGS. 1 to 4 show an accumulator type fuel injection device according to a first embodiment of the present invention. Injector 1 shown in FIG.
Is an electromagnetically controlled accumulator type fuel injection device for intermittently injecting fuel into a combustion chamber of a diesel engine (not shown). A fuel pipe (not shown) is connected to an inlet 60 from a common rail (not shown) for accumulating high-pressure fuel. And high-pressure fuel is supplied from the common rail. A wire harness for transmitting a control signal from an engine control device (not shown) (hereinafter, referred to as an “ECU”) to the injector 1 is connected to the connector 70, and the control signal transmitted from the ECU controls the injector 1. Fuel injection is controlled.

A needle valve 20 for opening and closing the injection hole 11a is accommodated in the nozzle body 11 of the injection nozzle 10 provided on the injection hole side of the injector 1 in a reciprocating manner.
The nozzle body 11 and the injector body 13 are connected by a retaining nut 14 with the packing tip 12 interposed therebetween. A pressure pin 21 is disposed on the side opposite to the injection hole of the needle valve 20, and a control piston 22 that is in contact with or is connected to the pressure pin 21 is disposed on the side opposite to the injection hole of the pressure pin 21. The needle valve 20, the pressure pin 21, and the control piston 22 constitute a "valve member" described in the claims. The pressure pin 21 is inserted through a spring 23, and the spring 23 urges the pressure pin 21 downward in FIG. 2, that is, in the injection hole closing direction. Reference numerals 25 and 26 denote spacers for adjusting the set load of the spring 23 for urging the needle valve 20 in the valve closing direction. A pressure control chamber 62 is provided on the side opposite to the injection hole of the control piston 22.

The high-pressure fuel introduced from the fuel filter 61 housed in the inlet 60 branches into a high-pressure fuel passage 63 and a high-pressure fuel passage 64. The high-pressure fuel branched to the high-pressure fuel passage 63 is supplied to a fuel reservoir 24 formed in an annular shape around the needle valve 20, and the high-pressure fuel branched to the high-pressure fuel passage 64 is supplied to a pressure control chamber 62. The pressure of the high-pressure fuel in the fuel reservoir 24 urges the needle valve 20 in the upward direction of FIG. 2, that is, in the lift direction in which the fuel reservoir 24 and the injection hole 11a communicate with each other, and the pressure of the high-pressure fuel in the pressure control chamber 62 becomes The lower part of FIG.
The control piston 22 is urged in a direction to close a.

The low-pressure fuel passage 65 shown in FIG. 1 is a fuel passage for recovering leaked fuel from the sliding clearance between the control piston 22 and the needle valve 20, and the spring chamber 27 shown in FIG. Is in communication with As shown in FIG. 1, the low-pressure fuel passage 65 communicates with a low-pressure fuel chamber 45a as a low-pressure space via fuel passages 51a and 52a formed in a first throttle plate 51 and a second throttle plate 52, respectively, which will be described later. doing. Low pressure fuel chamber 45a
Is supplied to the low-pressure fuel passage 45b provided in the valve cylinder 45 and the low-pressure fuel passage 41 provided in the valve shaft 41.
a, a low-pressure fuel passage 42a provided in the pressing member 42, a through-hole 34a penetrating the armature 34, a low-pressure fuel passage 31a communicating the center of the core 31, and a low-pressure fuel passage 69 provided in the housing 50. 2 flows out to the low-pressure fuel passage 73a in the union 73 for collecting leaked fuel. Therefore, surplus fuel in the injector is finally discharged to the outside of the injector 1 through the low-pressure fuel passage 69 and the low-pressure fuel passage 73a.

As shown in FIG. 1, the first throttle plate 51 and the second throttle plate 52 are sandwiched between the injector body 13 and the valve cylinder 45 so as to overlap. The first throttle hole 66 is formed in the first throttle plate 51, and regulates the flow rate of fuel flowing from the high-pressure fuel passage 64 into the pressure control chamber 62. The second throttle hole 67 is formed in the second throttle plate 52 and regulates the flow rate of fuel flowing from the pressure control chamber 62 to the low-pressure fuel chamber 45a.

As shown in FIG. 3A, the second diaphragm plate 52 is formed in a disk shape, and has two through holes 52b at positions offset by the same distance from the center axis. The first diaphragm plate 51 is also formed in a disk shape similarly to the second diaphragm plate 52, is offset from the center axis by the same interval, and corresponds to the through hole 52b formed in the second diaphragm plate 52. Are formed with two through holes (not shown). Each through hole is a hole through which a positioning knock pin is inserted. Injector body 1 with two knock pins
The injector body 13 and the valve cylinder 45 are screwed together with each throttle plate positioned with respect to 3.

As shown in FIGS. 3 and 4, a cylinder having a larger diameter than the second throttle hole 67, that is, a passage resistance smaller than that of the second throttle hole 67, is provided on the fuel outflow side of the second throttle hole 67. A fuel space 68 is formed so as to communicate with the second throttle hole 67. The opening area of the fuel space 68 is smaller than the area of the flat portion 43 a formed on the spherical member 43 of the solenoid valve 30. Since the fuel space 68 communicates with the low-pressure fuel chamber 45a when the solenoid valve 30 is opened, the high-pressure fuel in the pressure control chamber 62 flows out to the low-pressure fuel chamber 45a via the fuel space 68.

The flat valve seat 53 comprises an annular valve seat 53a and a fan-shaped valve seat 53b, and is formed so as to be in contact with the flat portion 43a of the spherical member 43 in a plane. Annular valve seat 53a
Is formed in an annular shape around the opening of the fuel space 68,
Four fan-shaped valve seats 53b are formed on the outer peripheral side of the annular valve seat 53a. The annular valve seat 53a and the fan-shaped valve seat 53b are formed in the same plane, and the flat portion 43a can contact the entire surface of the annular valve seat 53a and the inner peripheral side of the fan-shaped valve seat 53b.

The fuel release passage 54 includes an annular passage 54a and a communication passage 54b, and communicates with the low-pressure fuel chamber 45a even when the flat portion 43a is in contact with the flat valve seat 53 when the solenoid valve 30 is closed. I have. The annular passage 54a is formed substantially concentrically with the fuel space 68 on the outer peripheral side of the annular valve seat 53a and on the inner peripheral side of the fan-shaped valve seat 53b. Communication passage 54b
Are connected to the annular passage 54a, and extend radially from the annular passage 54a at intervals of 90 ° between the fan-shaped valve seats 53b. In the state shown in FIG. 1 in which the flat portion 43a is seated on the flat valve seat 53, the communication passage 54b communicates with the low-pressure fuel chamber 45a. Therefore, the annular passage 54a is also connected to the low-pressure fuel chamber 4
5a.

The annular space 55 is formed on the outer periphery of the communication passage 54b and communicates with the communication passage 54b. Annular space 55
Is for supplementing the volume of the low-pressure fuel chamber 45a,
When the solenoid valve 30 is opened, the high-pressure fuel can easily flow out to the low-pressure side. The solenoid valve 30 shown in FIG.
2 is an electromagnetic two-way valve for intermittently connecting the low pressure fuel chamber 45a to the
It is arranged between the retaining nut 59 and the injector body 13. The pin 56 is for positioning the core 31 and the housing 50 in the rotational direction, and is a power supply terminal (not shown) for rotating the core 31 and the housing 50 relative to each other when the retaining nut 59 is tightened to supply power to the coil 32. This is to prevent the load from being applied to the vehicle.

The coil 32 is wound around the core 31, and the terminal 7 embedded in the connector 70 shown in FIG.
1 supplies power. The core 31 is formed by stacking silicon steel plates having a thickness of about 0.2 mm in a spiral shape, and the silicon steel plates are welded to a cylindrical member 33 disposed on the inner periphery and shown in FIG. Pressing member 4 of movable member 40 described later
2 is inserted through the inside of the cylindrical member 33.

The movable member 40 includes a valve shaft 41, a pressing member 4
2. It comprises a spherical member 43 and a support member 44. Valve shaft 4
1 and the pressing member 42 are pressed against each other by the force received from the fuel pressure in the pressure control chamber 62 and the urging force of the spring 47, and reciprocate without being separated from each other although they are formed separately. The pressing member 42 is made of non-magnetic stainless steel or the like in order to avoid affecting the magnetic circuit. Valve shaft 41
Is reciprocally supported by a valve cylinder 45 disposed on the injection hole side of the core 31, and is formed of a material having excellent wear resistance. Since the valve shaft 41 is outside the magnetic circuit, it may be formed of a magnetic material. An armature 34 accurately positioned in the radial and axial directions is fixed to the core side of the valve shaft 41 by one or more of press-fitting, caulking, and welding, and the valve shaft 41 reciprocates together with the armature 34. . The armature 34 is required to have a characteristic as a part of the magnetic circuit rather than the wear resistance, and is made of, for example, silicon steel. A plurality of through holes 34a are formed in the armature 34 in order to reduce the movement resistance in the fuel.

The lift amount of the movable member 40 can be adjusted by changing the axial length of the spacer 57. The maximum lift position of the movable member 40 is defined by locking the valve shaft 41 to the cylindrical member 33. At this time, since an air gap is secured between the armature 34 and the core 31, the movable member 40 quickly moves downward in FIG. 1 when the power supply to the coil 32 is turned off from on.

As shown in FIG. 4A, a cylindrical support member 44 is fixed to the distal end of the valve shaft 41 by press-fitting or welding. Support member 44 and spherical member 43
The spherical member 43 is rotatably assembled with a conical concave surface formed at the tip of the valve shaft 41 and the inner wall of the support member 44. By caulking the tip of the support member 44, the spherical member 43 is prevented from dropping from the support member 44.
The spherical member 43 has a structure in which a flat portion 43a is machined on a part of a ceramic or cemented carbide sphere. Valve shaft 4
Since the lift amount of 1 is about 100 μm, the flat portion 43 a is locked to the second throttle plate 52 even if the spherical member 43 attempts to rotate by a predetermined angle or more regardless of the lift position of the valve shaft 41. Therefore, the flat portion 43a always faces the second diaphragm plate 52. Since the flat portion 43a closes the fuel space 68 by abutment of the flat surfaces with the flat valve seat 53 formed on the second throttle plate 52, the sealing area between the spherical member 43 and the second throttle plate 52 is large. The fuel leak from the pressure control chamber 62 can be reduced. Further, even when the position and the relative angle between the spherical member 43 and the fuel space 68 are shifted, the spherical member 43 can reliably close the fuel space 68.

The pressing member 42 forms a clearance larger than the sliding clearance with the cylindrical member 33, and is inserted through the cylindrical member 33 so as to be reciprocally movable. Spring 47
Urges the pressing member 42 in the direction in which the spherical member 43 closes the fuel space 68. The biasing force of the spring 47 can be adjusted by changing the thickness of the shim 46. Next, the dimensions of each part in the first embodiment will be described.

The diameter a of the first throttle hole 66 is 0.19 m.
m, diameter b of second throttle hole 67 = 0.29 mm, diameter c of fuel space 68 (inner diameter of annular valve seat 53a) = 0.4 m
m, inner diameter d of annular passage 53a (outer diameter of annular valve seat 53a)
= Φ0.7mm, outer diameter e of the annular passage 53a = φ1.2mm,
Depth of annular passage 53a = 0.1 mm, width of communication passage 53b =
0.4 mm, depth of communication passage 53b = 0.1 mm, spherical member 4
3, the ball diameter f = φ2.0 mm, the diameter g of the plane portion 43a = φ
1.63 mm, diameter h of control piston 22 = 5.0 mm, lift amount of movable member 40 = 0.1 mm, diameter of needle valve 20 = 4.0 mm, seat diameter of needle valve 20 = 2.2
5mm, load of spring 47 = 50N, spring 23
Is 40N.

Next, the operation of the injector 1 will be described. (1) When the power to the coil 32 is turned off, the urging force of the spring 47 pushes the pressing member 42 downward in FIG. The flat portion 43a of the spherical member 43 is seated on the flat valve seat 53 of the second throttle plate 52, and the communication between the pressure control chamber 62 and the low-pressure fuel chamber 45a is cut off.

When the solenoid valve 30 is closed and high-pressure fuel is sealed, or when the movable member 40 immediately before closing is in a low lift state, the high-pressure fuel seals between the flat portion 43 a and the flat valve seat 53. Attempts to penetrate between the contact surfaces.
However, the outer peripheral side of the annular valve seat 53a and the fan-shaped valve seat 5
3b, an annular passage 54a is formed on the inner peripheral side, and the annular passage 54a communicates with the low-pressure fuel chamber 45a.
4b, the pressure in the fuel release passage 54 can be completely reduced to a low pressure (drain pressure).

The pressure distribution between the flat contact portion between the flat portion 43a and the annular valve seat 53a depends on the pressure in the pressure control chamber 62 (the pressure at the opening of the fuel space 68) at the inner peripheral edge of the annular valve seat 53a. The LOG function distribution has a point symmetrical shape such that the pressure decreases to the drain pressure (the pressure in the communication passage 54b) at the outer peripheral edge of the annular valve seat 53a. On the other hand, in the case of the conventional solenoid valve in which the fuel release passage is not formed, the pressure distribution of the LOG function up to the outer diameter (> the inner diameter of the annular passage 53a) on the smaller diameter side of either the flat portion of the movable member or the flat valve seat. Is generated, so that the integrated value of the pressure is larger than that in the case where the fuel release passage is provided. Therefore, if the fuel release passage is formed, the hydraulic load acting in the valve opening direction when the solenoid valve is closed can be reduced.

In the first embodiment, the inner diameter c of the annular valve seat 53a
= Φ0.4 mm, and the outer diameter d of the annular valve seat 53a is set to 0.7 mm. In addition to the force received from the fuel space 68, the point object between the close contact surfaces of the flat portion 43a and the annular valve seat 53a is set. Considering the LOG function distribution of the pressure of the shape, even when the fuel pressure (≒ pressure control chamber pressure) introduced from the common rail is 150 MPa, the hydraulic load for operating the solenoid valve 30 in the valve opening direction is 35N. Also, the solenoid valve 30
The set load of the spring 47 for urging the movable member 40 in the valve closing direction may be set based on the above-described hydraulic load. If the hydraulic load is reduced, the set load of the spring 47 can be reduced. In the first embodiment, the value is set to 50 N, and the movable member 40 does not lift as long as the power supply to the coil 32 is turned off.

The diameter of the control piston 22 = φ5.0
mm, diameter of needle valve 20 = φ4.0 mm, needle valve 2
Since the sheet diameter of 0 is φ2.25 mm, the pressure receiving area of the control piston 22 is larger than the pressure receiving area of the needle valve 20, and the difference is set to about 11 mm ² . Further, since the urging force of the spring 23 acts in the injection hole closing direction, the force received by the control piston 22 in the injection hole closing direction from the fuel pressure in the pressure control chamber 62 and the spring force as long as the power to the coil 32 is turned off. The sum of the urging force of the needle valve 23 and the urging force of the needle valve 20 is greater than the force received by the needle valve 20 in the lift direction from the fuel pressure of the fuel reservoir 24. Therefore, the needle valve 2
With 0, the injection hole 11a is closed and fuel injection is not performed.

(2) Since the electromagnetic force generated by turning on the power supply to the coil 32 is set to about 60 N, the electromagnetic force for attracting the armature 34 generated in the coil 32 and the fuel pressure of the pressure control chamber 62 are Since the sum of the force received by the movable member 40 in the valve opening direction is larger than the urging force of the spring 47, the movable member 40 is lifted, and the spherical member 43 is moved to the second position.
From the diaphragm plate 52. When the spherical member 43 is separated from the second throttle plate 52, the fuel space 68 and the low-pressure fuel chamber 45
a and the fuel in the pressure control chamber 62 flows through the second throttle hole 6.
7, the fuel flows out of the fuel space 68 into the low-pressure fuel chamber 45a.

At this time, since the diameter of the fuel space 68 is set to be larger than the diameter of the second throttle hole 67, the annular valve seat 5
The flow path area at the innermost periphery of the annular fuel passage formed between 3a and the plane portion 43a is smaller than that in the case where the second throttle hole 67 is directly opened and closed by the plane portion 43a without providing the fuel space 68. It becomes bigger. Therefore, in the first embodiment in which the fuel space 68 is provided, the second throttle hole 67 is provided without the fuel space 68.
The annular valve seat 53a and the flat portion 43 are
a becomes smaller. Therefore, even if the lift amount of the movable member 40 is reduced, the passage resistance of the fuel passage can be set to be smaller than the passage resistance of the second throttle hole 67, so that the annular valve seat 53a.
The flow rate of fuel passing through the fuel passage formed between the second throttle hole 67 and the flat portion 43a does not decrease less than the flow rate of fuel passing through the second throttle hole 67. Since the passage resistance of the second throttle hole 67 is smaller than the passage resistance of the first throttle hole 66, the spherical member 43 is separated from the second throttle plate 52, and the pressure control chamber 62 communicates with the low-pressure fuel chamber 45a. Then, the fuel pressure in the pressure control chamber 62 decreases. The fuel pressure in the pressure control chamber 62 decreases, and the sum of the force received by the control piston 22 in the injection hole closing direction and the urging force of the spring 23 from the fuel pressure in the pressure control chamber 62 is:
When the force received by the needle valve 20 in the lift direction becomes smaller from the fuel pressure in the fuel pool 24, the needle valve 20 is lifted, and fuel is injected from the injection hole 11a.

Since the fuel space 68 having a diameter larger than that of the second throttle hole 67 is provided on the fuel outlet side of the second throttle hole 67, the fuel flow rate flowing out to the low-pressure fuel chamber 45a when the solenoid valve 30 is opened. Is determined by the flow characteristic of the second throttle hole 67. Therefore, the injection characteristics of the injector 1 are determined by the fuel flow rate flowing into the pressure control chamber 62 from the first throttle hole 66 and the fuel flow rate flowing from the pressure control chamber 62 to the low-pressure fuel chamber 68 through the second throttle hole 66. And is generally determined by Among the injection characteristics, the injection start timing and the degree of increase of the initial injection rate are determined by the flow rate of the fuel flowing into the pressure control chamber 62 after the solenoid valve 30 is opened and the low pressure fuel chamber 68 from the pressure control chamber 62.
Is determined by the difference from the flow rate of the fuel flowing out of the tank. That is, if the flow characteristics of the first throttle hole 66 and the second throttle hole 67 change, the rate of pressure drop in the pressure control chamber 62 immediately after the solenoid valve 30 is opened changes, and the injection start timing changes.

When the pressure in the pressure control chamber 22 drops and reaches the valve-opening pressure of the control piston 22 and the control piston 22 enters the valve-opening stroke, the forces in the valve-opening and valve-closing directions acting on the control piston 22 are static. The state is balanced. However, in the first embodiment, the flow rate of the fuel flowing out of the pressure control chamber 62 is reduced by making the passage resistance of the second throttle hole 67 smaller than the passage resistance of the first throttle hole 66 so that the fuel flowing into the pressure control chamber 62 flows. Since it is set to be larger than the flow rate,
At the next moment, the pressure in the pressure control chamber 62 decreases. For this reason, since the static force balance is lost and the force in the valve opening direction becomes larger than the force in the valve closing direction, the control piston 22 is lifted to a position where the force is balanced in the opening and closing valve direction. By this repetition, the control piston 22 finally reaches the set predetermined lift position. The pressure in the pressure control chamber 62 during the valve opening stroke of the control piston 22 is substantially constant. Further, the valve opening pressure, which is the pressure of the pressure control chamber 62 at which the control piston 22 starts to move, depends on the flow characteristics of the first throttle hole 66 and the second throttle hole 67, and the injection hole opening direction and the injection hole closing direction. Valve 20 and control piston 2 acting on
2 and the urging force of the spring 23 for urging the needle valve 20 in the nozzle hole closing direction. Since the time during which the constant pressure continues is the time until the control piston 22 reaches the full lift point, the first
The structure changes when the flow characteristics of the throttle hole 66 and the second throttle hole 67 change.

When the control piston 22 reaches the full lift point, the pressure in the pressure control chamber 62 falls below the valve opening pressure of the needle valve 20, and the first throttle hole 66 and the second throttle hole 6
The pressure drops to a pressure determined only by the difference in the flow characteristics of No. 7, and the pressure value is maintained. This is a region where the fuel injection rate is substantially constant, and the magnitude does not change if the pressure at the tip of the needle valve 20 is constant.

When the above state continues and a predetermined injection end time comes, the power supply to the coil 32 is cut off. At this time, the electromagnetic force 60N for sucking the armature 34 becomes 0,
The solenoid valve 30 is closed by the urging force of the spring 47 that urges the movable member 40 in the valve closing direction. Then, from the high-pressure fuel passage 64 through the first throttle hole 66, the pressure control chamber 62
The pressure in the pressure control chamber 62 rises due to the high-pressure fuel flowing into the tank.

The needle valve 20 and the control piston 2 which act in the opening direction of the injection hole and the closing direction of the injection hole, respectively, in the same manner as when the valve is opened.
When the pressure in the pressure control chamber 62 increases until the valve closing pressure reaches a valve closing pressure that is uniquely determined from the difference between the pressure receiving area of the pressure control chamber 2 and the urging force of the spring 23 that urges the needle valve 20 in the nozzle hole closing direction, Since the sum of the force that the control piston 22 receives in the injection hole closing direction from the fuel pressure of 62 and the urging force of the spring 23 becomes larger than the force that the needle valve 20 receives in the lift direction from the fuel pressure of the fuel reservoir 24, the control is performed. The piston 22 moves to the injection hole closing side. Strictly speaking, coil 3
2 is turned off, and the amount of fuel flowing out of the fuel space 68 decreases as the movable member 40 moves in the closing direction of the fuel space 68 due to the urging force of the spring 47, so that control is performed before the solenoid valve 30 is closed. The piston 22 moves to the injection hole closing side.

Although the valve closing pressure of the control piston 22 is the same as the valve opening pressure regardless of the flow characteristics of the first throttle hole 66 and the second throttle hole 67, the solenoid valve 30 is closed. From the start to the closing pressure of the control piston 22 until the pressure control chamber 62
The time required for the pressure to rise increases when the flow characteristics of the first throttle hole 66 and the second throttle hole 67 change and there is a difference in the pressure in the pressure control chamber 62 when the solenoid valve 30 is opened. Change. Further, in the valve closing process of the control piston 22, the first throttle hole 66 and the second
The time required for closing the injection hole changes according to the difference in the fuel flow rate of the throttle hole 67.

As described above, the injection start timing, the injection end timing, and the initial rise rate of the combustion injection rate are determined by the flow characteristics of the first throttle hole 66 and the second throttle hole 67. The rate of decrease of the rate is determined by the flow characteristics of the first throttle hole 66. In the first embodiment of the present invention described above, the second throttle hole 67 communicates with the second throttle hole 67 on the fuel outflow side, and has a larger diameter than the second throttle hole 67, that is, the second throttle hole. By providing the fuel space 68 having a smaller passage resistance than the hole 67, the passage resistance of the fuel passage formed between the flat portion 43a and the annular valve seat 53a can be reduced even if the lift amount of the movable member 40 is set small. Second throttle hole 6
7 can be made smaller than the passage resistance. Therefore, even if the lift amount of the movable member 40 is reduced, the solenoid valve 30
When the valve is opened, the fuel at the flow rate determined by the passage resistance of the second throttle hole 67 can flow out to the low-pressure fuel chamber 45a.

The flow to be discharged when the solenoid valve 30 is opened should be the flow that originally passes through the second throttle hole 67, so that the fuel passage having a smaller passage resistance than the second throttle hole 67. By opening and closing 68, the lift amount of the movable member 40 can be reduced. By reducing the lift amount of the movable member 40, it is possible to improve the responsiveness, reduce the operation noise, improve the wear resistance, and reduce the bounce of the on-off valve. There is no variation in the flow rate of the fuel flowing into the low-pressure fuel chamber 45a when the valve is opened.

Further, the annular passage 54a and the communication passage 5
By forming the fuel release passage 54 composed of 4b in the flat valve seat 53, the hydraulic load acting in the valve opening direction when the solenoid valve 30 is closed can be reduced. Therefore, the urging force of the spring 47 for urging the movable member 40 toward the flat valve seat 53 when the power supply to the coil 32 is turned off can be reduced,
Further, the electromagnetic force for attracting the movable member 40 in the valve opening direction when the power is turned on can be reduced. Thus, the size of the solenoid valve 30 can be reduced, and the size of the entire injector 1 can be reduced.

The annular passage 5 is formed concentrically with the fuel space 68.
4a, the distribution of the hydraulic load acting in the valve opening direction is symmetrical, so that the distribution of the load applied to the spherical member 43 is not biased. Therefore, since the inclination and eccentricity of the spherical member 43 are suppressed, stable opening / closing control of the electromagnetic valve 30 is possible, and a uniform fuel amount can be injected from the injection nozzle. In particular, it is possible to control the minute amount injection with high accuracy.

After drilling the fuel space 68, the second throttle hole 67 can be drilled by being guided by the drill mark at the processing tip of the fuel space 68. Is shortened. Therefore, the fuel space 6
The processing of the second drawing hole 67 having a smaller diameter than that of No. 8 is facilitated, and the number of processing steps is reduced. Further, since the second throttle hole 67 only has to communicate the pressure control chamber 62 and the fuel space 68,
Even if an axis misalignment between the second throttle hole 67 and the solenoid valve 30 occurs, no problem occurs in performance.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
Shown in Components substantially the same as those in the first embodiment are denoted by the same reference numerals. In the second embodiment, a cylindrical concave space 43b as a fuel space is formed not on the second throttle plate 52 but on the plane portion 43a side. The opening diameter k of the concave space 43b is larger than the diameter b of the second throttle hole 67, k = φ0.4 mm,
The diameter b is 0.29 mm. A, b, d, shown in FIG.
The dimensions of e, g and h are the same as in the first embodiment. The opening area of the concave space 43b is smaller than the area of the plane portion 43a.

In the second embodiment, since the second throttle hole 67 opens directly into the flat valve seat 53, the inner diameter of the annular valve seat 53c is equal to the diameter b of the second throttle hole 67. The width of the annular valve seat 53c is larger than that of the annular valve seat 53a of the first embodiment. In the second embodiment, since the opening diameter of the concave space 43b is set to be larger than the diameter of the second throttle hole 67, when the solenoid valve 30 is opened, the annular valve seat 53c and the flat portion 4c are opened.
The flow path area at the innermost periphery of the annular fuel passage formed between the annular valve seat 53c and the flat portion 43a when the concave space 43b is not provided. It becomes larger than the flow path area on the inner circumference. Therefore, the annular valve seat 53 is provided more than the one without the concave space 43b.
The passage resistance of the fuel passage formed between c and the plane portion 43a is reduced. In the second embodiment, the passage resistance of the fuel passage is set to be smaller than the passage resistance of the second throttle hole 67. Therefore, the flow rate of the fuel passing through the fuel passage formed between the annular valve seat 53c and the plane portion 43a does not decrease less than the flow rate of the fuel passing through the second throttle hole 67. Therefore, as in the first embodiment, the lift amount of the movable member 40 can be reduced, so that it is possible to realize improved responsiveness, reduced operation noise, improved wear resistance, and reduced bounce of the on-off valve.

Since the fuel release passage 54 is provided in the flat valve seat 53 as in the first embodiment, the valve opening pressure of the solenoid valve 30 is reduced, and the solenoid valve 30 can be downsized. In a plurality of examples showing the embodiment of the present invention described above, the fuel space is formed in a cylindrical shape, but the opening diameter of the fuel space is larger than the diameter of the second throttle hole, and the opening area of the movable member is Since it is sufficient that the fuel space is smaller than the plane portion, the fuel space can be formed in a tapered shape whose diameter increases toward the opening side. Further, a fuel space may be provided in both the flat portion and the flat valve seat.

In each of the above embodiments, the fuel escape passage is provided on the flat valve seat side. However, if the fuel escape passage is located within the contact surface between the flat portion and the flat valve seat, the fuel escape passage is provided on the flat portion side of the movable member. It is also possible to provide an escape passage. Further, a fuel release passage may be provided in both the flat portion and the flat valve seat.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of an injector according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing the injector according to the first embodiment.

FIG. 3A is a plan view showing a second diaphragm plate of the first embodiment, and FIG. 3B is a sectional view taken along line BB of FIG. 3A.

FIG. 4 is a perspective view showing a seat portion of the solenoid valve in the first embodiment.

FIG. 5 is a perspective view showing a seat portion of a solenoid valve according to a second embodiment.

[Explanation of symbols]

 Reference Signs List 1 injector (accumulation type fuel injection device) 10 injection nozzle 11a injection hole 20 needle valve (valve member) 21 pressure pin (valve member) 22 control piston (valve member) 30 solenoid valve 40 movable member 41 valve shaft (movable member) 42 Pressing member (movable member) 43 Spherical member (movable member) 43a Low-pressure fuel chamber 43b Concave space (fuel space) 44 Support member (movable member) 51 First throttle plate 52 Second throttle plate 53 Planar valve seat 53a, 53c Annular valve seat (flat valve seat) 53b Fan-shaped valve seat (flat valve seat) 54 Fuel release passage 54a Annular passage (fuel release passage) 54b Communication passage (fuel release passage) 63, 64 High pressure fuel passage 65 Low pressure fuel passage 66 First Throttle hole 67 second throttle hole 68 fuel space

Claims (4)

[Claims] 1. An accumulator type fuel injection device for injecting high pressure fuel accumulated in a common rail into an internal combustion engine, wherein a high pressure fuel passage capable of supplying accumulated high pressure fuel to an injection hole is intermittently connected to the injection hole. A valve member, a movable member and a flat valve seat that can contact the plane portion of the movable member in a plane-by-plane manner, and provided on a side opposite to the injection hole of the valve member by a fuel pressure supplied from the high-pressure fuel passage. An electromagnetic valve that shuts off communication between a pressure control chamber that urges the valve member in the injection hole shutoff direction and the low-pressure side space by contact between the flat portion and the flat valve seat; A first throttle hole that restricts a flow rate of fuel flowing into the pressure control chamber from the pressure control chamber; and a passage resistance smaller than the first throttle hole and formed between the pressure control chamber and the flat valve seat. When the valve is opened, the low pressure is released from the pressure control chamber. A second throttle hole for restricting a flow rate of fuel flowing into the compression side space, and a fuel space formed in at least one of the flat portion and the flat valve seat, wherein the second throttle hole is provided when the electromagnetic valve is closed. The opening of the flat portion is larger than the diameter of the second throttle hole, and is opened and closed by separation and contact between the flat portion and the flat valve seat. A fuel space having a smaller opening area than the second throttle hole and having a smaller passage resistance than the second throttle hole when formed in the flat valve seat. 2. A pressure-accumulating fuel injection system according to claim 1, wherein a fuel release passage communicating with the low-pressure side space is formed in one of the contact surfaces of the flat portion and the flat valve seat. apparatus. 3. An annular passage formed in a substantially concentric circle with respect to an opening of the fuel space without communicating with the fuel space when the flat portion and the flat valve seat are in contact with each other. 3. The accumulator-type fuel injection device according to claim 2, comprising: 4. The accumulator according to claim 1, wherein the fuel space is formed on the flat valve seat side, and the second throttle hole is formed after the fuel space is formed. Fuel injection device.