JP4075993B2 - Fuel injection device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection device for an internal combustion engine.
[0002]
[Prior art]
As a fuel injection device for an internal combustion engine, a fuel pressure control system that opens a valve body by using fuel pressure is generally used (for example, see Patent Document 1). In this fuel pressure control system, the valve body for opening and closing the nozzle hole is normally urged in the valve closing direction by a spring. In addition, the fuel pressure in the control chamber is applied in the valve closing direction on the base end side of the valve body. By filling the control chamber with high-pressure fuel, the valve body is closed on the base end side with high-pressure fuel. The valve body is closed by the biasing force of the spring in order to cancel the valve opening force due to the high pressure fuel acting on the distal end side of the valve body.
[0003]
On the other hand, when the fuel pressure in the control chamber is reduced, the valve closing force due to the fuel pressure acting on the base end side of the valve body is reduced, and the opening due to the high pressure fuel acting on the tip end side of the valve body against the urging force of the spring is reduced. The valve element is opened by the valve force. In this method, it takes time to change the fuel pressure in the control chamber to open and close the valve body, and the responsiveness of the valve body cannot be increased. In general, a throttle part for supplying high-pressure fuel to the control chamber and a throttle part for discharging the high-pressure fuel from the control chamber are provided, and these throttle parts affect the opening and closing speed of the valve body. The injection performance is greatly changed. Accordingly, the processing of these two drawn portions requires very high accuracy and is expensive.
[0004]
In order to increase the responsiveness of the valve body, the valve body that is normally urged in the valve closing direction by a spring or the like is opened using the magnetic attractive force of the solenoid instead of the control chamber that controls the fuel pressure. An electromagnetic fuel injection device has been proposed (see, for example, Patent Document 2).
[0005]
In this electromagnetic system, since the high pressure fuel is acting on the tip side of the valve body that is being opened, a valve closing force that is greater than the valve opening force of the high pressure fuel is always applied to the valve body. I'm closing my body. The magnetic attraction force of the solenoid is made larger than the valve closing force acting on the valve body as a resultant force with the valve opening force by the high-pressure fuel acting on the distal end side of the valve body, thereby opening the valve body.
[0006]
Generally, when the valve body is closed, high-pressure fuel does not act on the tip side from the seal portion, that is, the pressure receiving pressure on the tip side of the valve body being closed compared to the valve body being opened. The area decreases. As described above, the valve closing force that always acts on the valve body that is necessary for closing the valve body that is being opened must be greater than the valve opening force that is generated with the entire front end side of the valve body as the pressure receiving area. On the other hand, the valve opening force required to open the valve body that is being closed must be larger than this valve closing force. This valve opening force is the resultant force of the valve opening force due to the high pressure fuel acting on the tip side of the valve body and the magnetic attraction force of the solenoid, but the valve opening force due to the high pressure fuel decreases as the pressure receiving area decreases. In addition, the magnetic attraction force of the solenoid must be set high for that amount, and the size of the solenoid increases, so that the vehicle mountability of the fuel injection device is greatly deteriorated.
[0007]
In order to solve this problem, the pressure receiving area on the front end side does not change between the valve body that is open and the valve body that is closed. A moving part is provided, and the diameter of the projecting sliding part is made equal to the diameter of the seal part of the valve body, and the tip of the projecting sliding part has a high-pressure fuel regardless of whether the valve body is opened or closed. It has been proposed to prevent this from acting (see, for example, Patent Document 3).
[0008]
As a result, the pressure receiving area does not decrease in the valve body that is closed, so there is no need to set a high magnetic attraction force for the solenoid to open the valve body. Is done. Furthermore, the valve opening force due to the fuel pressure is always acting on the tip side of the valve body, but this valve opening force changes not only by the pressure receiving area but also by the fuel pressure. The magnetic attractive force must be set higher in consideration of the decrease in fuel pressure. In order to prevent this, it has been proposed that a part of the valve closing force always acting on the valve body is caused by the fuel pressure so that the pressure receiving area in the valve opening direction is equal to the pressure receiving area in the valve closing direction ( For example, see Patent Document 3). As a result, the opening force due to the fuel pressure acting on the valve body and the closing force are always equal regardless of the fuel pressure, and the valve body is closed by providing a relatively weak spring for closing the valve body. Thus, the magnetic attraction force of the solenoid for opening the valve body should be able to overcome the valve closing force by this spring without considering the fuel pressure.
[0009]
[Patent Document 1]
Patent No. 2601977 [Patent Document 2]
JP 2000-257534 A
[Patent Document 3]
JP 2000-161174 A
[0010]
[Problems to be solved by the invention]
In the above-described prior art, a protruding sliding portion having the same diameter as the protruding sliding portion on the distal end side is also provided on the proximal end side of the valve body, and fuel is also provided on the proximal end of the protruding sliding portion on the proximal end side. The pressure is prevented from acting so that the pressure receiving area in the valve opening direction and the pressure receiving area in the valve closing direction of the valve body are equalized.
[0011]
In the fuel injection device main body that houses the valve body, respective support portions for supporting the projecting sliding portion on the distal end side and the projecting sliding portion on the proximal end side of the valve body are required. Since the cross-sectional area of the valve body between the two projecting and sliding parts is larger than the cross-sectional area of the two projecting and sliding parts, at least one support part must be a separate member from the fuel injection device main body. The valve body cannot be assembled into the fuel injection device main body. However, in such a configuration, after the fuel injection device is assembled, when the valve body is removed due to a sealing failure or the like, the support portion as a separate member must be removed, which requires a lot of time.
[0012]
Accordingly, an object of the present invention is to provide a fuel injection device that opens a valve body for opening and closing an injection hole by means of a magnetic attraction force by a solenoid. The pressure receiving areas in the valve closing direction and the valve closing direction are made equal, and the valve body can be easily removed when necessary.
[0013]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a fuel injection device for an internal combustion engine, which is disposed in a fuel chamber, has a distal end side seal portion and opens and closes an injection hole, and uses fuel pressure in the fuel chamber. And a solenoid for generating a magnetic attractive force for opening the valve body against the urging force in the valve closing direction by the urging means. The valve body includes a first sliding portion projecting from the distal end side to the outside of the fuel chamber from the seal portion, and a second sliding portion on the proximal end side projecting to the outside of the fuel chamber, The diameter of the sliding portion is equal to the diameter of the seal portion, and any diameter on the tip side from the second sliding portion of the valve body is equal to or less than the diameter of the second sliding portion, The second sliding portion or the base end side of the second sliding portion communicates with the fuel chamber via a communication path. Is Linda chamber formed above the cylinder chamber fixed piston is arranged, the cross-sectional area of the cylinder chamber is equal to the valve opening direction pressure receiving area of the valve body, the fuel passage is formed in the fixed piston, wherein the fuel passage, and said cylinder chamber, said communication passage and fuel into the fuel chamber through, characterized in that the supplied.
[0014]
In this fuel injection device, regardless of when the valve body is closed or opened, the pressure receiving area in the valve opening direction of the valve body is outside the seal portion due to the presence of the first sliding portion. On the other hand, the pressure receiving area in the valve closing direction of the valve body is the cross-sectional area of the second sliding portion or the cylinder chamber formed on the proximal side from the second sliding portion, and this cross-sectional area is the valve opening direction of the valve body. It is made equal to the pressure receiving area. Thereby, the valve closing force and the valve opening force acting on the valve body by the fuel pressure in the fuel chamber are always equal. In this way, the solenoid only needs to generate a magnetic attractive force that can overcome the valve closing force by the biasing means. Further, in the valve body, since any diameter on the tip side from the second sliding portion is equal to or less than the diameter of the second sliding portion, the tip side from the second sliding portion of the valve body is the second sliding portion. It can pass through the support part of the moving part. In this fuel injection device, the inner diameter of the cylinder chamber increases due to the expansion of the cylinder chamber due to the fuel pressure, but the outer diameter of the fixed piston also increases due to the expansion due to the fuel pressure of the fuel passage. Increase in the gap between the two can be suppressed.
[0015]
According to a second aspect of the present invention, there is provided a fuel injection device for an internal combustion engine according to the first aspect, wherein the communication passage is provided with a throttle portion. .
[0016]
In this fuel injection device, when the valve body is opened, the fuel must flow out from the cylinder chamber to the fuel chamber via the communication path. When the valve body is closed, the communication path The fuel must flow from the fuel chamber to the cylinder chamber via By restricting the outflow and inflow of the fuel by the throttle portion provided in the communication passage, the valve opening and closing speed of the valve body can be appropriately reduced.
[0017]
According to a third aspect of the present invention, there is provided a fuel injection device for an internal combustion engine according to the first aspect, wherein the end surface of the fixed piston on which the fuel pressure in the cylinder chamber acts is provided on the end surface of the fixed piston. A concave hole is formed.
[0018]
In this fuel injection device, the inner diameter of the cylinder chamber increases due to the expansion of the cylinder chamber due to the fuel pressure, but the outer diameter of the fixed piston also increases due to the expansion due to the fuel pressure of the concave hole portion. An increase in the gap between them can be suppressed.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a sectional view showing a first embodiment of a fuel injection device for an internal combustion engine according to the present invention. This fuel injection device, for example, injects high-pressure fuel pressurized in a pressure accumulating chamber in order to inject fuel directly into a cylinder of an internal combustion engine. Reference numeral 1 denotes a fuel injection device body formed by a plurality of members. A fuel chamber 2 is formed in the fuel injection valve main body 1, and an injection hole 3 communicates with the tip of the fuel chamber 2. The high pressure fuel pressurized in the pressure accumulating chamber is supplied into the fuel chamber 2 through the fuel passage 4, and this high pressure fuel is injected through the injection hole 3.
[0022]
A valve body 5 for opening and closing the injection hole is disposed in the fuel chamber 2. The valve body 5 protrudes from the fuel chamber 2 via the first sliding portion 5a on the distal end side, and protrudes from the fuel chamber 2 via the second sliding portion 5b on the proximal end side. The proximal end side of the second sliding portion 5b of the valve body 5 is connected to a movable member 6 made of a magnetic material. The movable member 6 is opposed to the fixed member 7 made of a magnetic material in the axial direction. In the fixed member 7, a spring 8 is arranged as a biasing unit that biases the movable member 6 so as to be separated from the fixed member 7. Solenoids 9 are disposed so as to surround the opposing end portions of the movable member 6 and the fixed member 7, and together with the magnetic material around the solenoid 9, the opposing end portions of the movable member 6 and the fixed member 7 are magnetic. Form a circuit.
[0023]
In this way, a magnetic flux is generated in the magnetic circuit by energizing the solenoid 9, and the magnetic circuit is arranged between the movable member 6 and the fixed member 7 constituting a part of the magnetic circuit in order to minimize the magnetic resistance. Generate magnetic attraction. As a result, the valve body 5 connected to the movable member 6 is closed by the spring 8 and opened by the magnetic attractive force of the solenoid 9. In the present fuel injection device, the fuel leaked from around the second sliding portion 5b is collected into the fuel tank via the passage 12.
[0024]
FIG. 2 is an enlarged cross-sectional view of the tip portion of the fuel injection device. As shown in the figure, the tip of the valve body 5 is tapered, and the position where the tip of the valve-shaped body 5 abuts on the seat 1a formed on the fuel injection valve body 1 is the seal part 5c of the valve body. Become. The first sliding portion 5a of the valve body 5 protrudes from the valve body 5 via the small diameter portion 5d on the distal end side from the seal portion 5c of the valve body, and with respect to the first support portion 1b of the fuel injection valve main body 1. Slide. Thus, when the valve body 5 is closed, the fuel chamber 2 is sealed by the valve body seal portion 5c. On the other hand, when the valve body 5 is opened, the fuel chamber 2 passes through the narrow diameter portion 5d of the valve body 5. Thus, the fuel in the fuel chamber 2 is injected through the nozzle hole 3 so as to communicate with the nozzle hole 3 formed on the front end side of the seat portion 1 a of the fuel injection valve body 1.
[0025]
Regardless of when the valve body 5 is opened or closed, the fuel pressure in the fuel chamber 2 does not act on the distal end side of the first sliding portion 5a of the valve body 5. The diameter of the first sliding portion 5a is equal to the diameter of the seal portion 5c of the valve body 5. Thereby, the pressure receiving area in the valve opening direction between the seat portion 5c and the small diameter portion 5d of the valve body 5 and the pressure receiving area in the valve closing direction between the first sliding portion 5a and the small diameter portion 5d are: Regardless of whether the valve body 5 is opened or closed, the pressure receiving area in the valve opening direction of the valve body 5 is equal to the sectional area outside the seal portion 5c (the second sliding portion 5b and the seat portion 5c). No change in cross-sectional area). That is, the valve opening force of the valve body 5 due to the fuel pressure in the fuel chamber 2 does not change regardless of whether the valve body 5 is opened or closed.
[0026]
If such a first sliding portion is not provided, the pressure receiving area when the valve body is closed is smaller than that when the valve is opened, and therefore the valve body is against the valve closing force. When opening the valve, the valve opening force due to the fuel pressure is reduced. Therefore, a large magnetic attraction force must be generated by the solenoid, and the solenoid becomes larger and the vehicle mounting property of the fuel injection device deteriorates. Will be. In the present fuel injection device, the valve body 5 is provided with the first sliding portion 5a to prevent the solenoid 9 from being enlarged.
[0027]
Further, if the pressure receiving area in the valve closing direction of the valve body 5 is made equal to the pressure receiving area in the valve opening direction, the valve closing force due to the fuel pressure in the fuel chamber 2 is applied to the valve body 5. Even if the internal fuel pressure decreases, the magnetic attraction force of the solenoid 9 necessary for opening the valve body 5 may not be increased. This is because when the fuel pressure in the fuel chamber 2 decreases, the valve opening force of the valve body 5 due to the fuel pressure also decreases, but similarly, the valve closing force of the valve body due to the fuel pressure also decreases.
[0028]
In the fuel injection device of the present embodiment, the proximal end side of the second sliding portion 5b of the valve body 5 is connected to the above-described movable member 6 via the enlarged diameter portion 5e, and the enlarged diameter portion 5e A cylinder chamber 5f is formed. A fixed piston 10 is disposed in the cylinder chamber 5f. The fixed piston 10 is supported on the base end side of the fuel injection valve main body 1 by a support shaft 11 so as not to move with respect to the fuel injection main body 1. The leaked fuel around the fixed piston 10 is also collected into the fuel tank via the passage 12 described above. The movable member 6 and the movable member 7 described above are hollow so that the support shaft 11 penetrates.
[0029]
The cylinder chamber 5f communicates with the fuel chamber 2 through a communication passage 5g that opens to the fuel chamber 2 on the tip side from the second sliding portion 5b of the valve body 5 and penetrates through the second sliding portion 5b. Thus, since the inside of the cylinder chamber 5f is filled with fuel having the same pressure as the inside of the fuel chamber 2, the cross-sectional area of the cylinder chamber 5 becomes a pressure receiving area in the valve closing direction of the valve body 5. Thereby, if the cross-sectional area of the cylinder chamber 5 is made equal to the cross-sectional area outside the seal portion 5c of the valve body, the pressure receiving areas in the valve opening direction and the valve closing direction of the valve body 5 can be made equal. Even if the fuel pressure in the fuel chamber 2 fluctuates, the valve closing force and the valve opening force due to the fuel pressure applied by the valve body 5 are always canceled. Thus, the magnetic attraction force generated by the solenoid 9 may be set so as to overcome only the valve closing force by the spring 8 regardless of the fuel pressure in the fuel chamber 2.
[0030]
In the present embodiment, in the valve body 5, since any diameter on the tip side from the second sliding portion 5b is set to be equal to or smaller than the diameter of the second sliding portion 5b, the second sliding portion 5b of the valve body 5 is used. The more distal end side can pass through the second support portion 1 c of the second sliding portion 5 b of the fuel injection valve main body 1. Thereby, after assembly, even if it is necessary to replace the valve body 5 due to factors such as a failure of the seal portion 5c, the valve body 5 can be removed from the fuel injection valve body 1 without disassembling the fuel injection valve body 1. It can be easily pulled out from the base end side.
[0031]
In the present embodiment, the cylinder chamber 5f is formed in the enlarged diameter portion 5e on the proximal end side with respect to the second sliding portion 5b of the valve body 5. However, the diameter of the second sliding portion 5b is increased to increase the second sliding portion. The cylinder chamber 5f may be formed in the moving part 5b.
[0032]
By the way, when the valve body 5 is opened and closed, the wall portion of the enlarged diameter portion 5e forming the cylinder chamber 5f slides relative to the stationary fixed piston 10, and the volume of the cylinder chamber 5f changes. Specifically, when the valve body 5 is closed, the volume of the cylinder chamber 5f increases, and the fuel in the fuel chamber 2 flows into the cylinder chamber 5f through the communication passage 5g. Further, when the valve body 5 is opened, the volume of the cylinder chamber 5f decreases, and the fuel flows out from the cylinder chamber 5f to the fuel chamber 2 through the communication passage 5g.
[0033]
FIG. 3 is an enlarged cross-sectional view of the vicinity of the communication path showing the second embodiment of the fuel injection device. In the present embodiment, as shown in FIG. 3, a throttle portion 5h is provided in the communication passage 5g that connects the cylinder chamber 5f and the fuel chamber 2, and the inflow of fuel into the cylinder chamber 5f and the flow of fuel from the cylinder chamber 5f are provided. The outflow is controlled. Thereby, when the valve closing speed of the valve body 5 by the spring 8 and the valve opening speed of the valve body 5 by the solenoid 9 are too high, the valve closing speed and the valve opening speed can be appropriately reduced. Thus, the collision energy of the valve body 5 is too large when the valve is closed, and the valve body 5 rebounds from the seat portion 1a of the fuel injection device main body 1 or the collision energy of the movable member 6 connected to the valve body 5 when the valve is opened. It is possible to prevent the movable member 6 and the fixed member 7 from bouncing off together with the valve body 5 due to being too large.
[0034]
FIG. 4 is an enlarged cross-sectional view of the vicinity of a cylinder chamber showing a third embodiment of the fuel injection device. In the present embodiment, as shown in FIG. 4, a concave hole 10a ′ is formed on the end surface of the fixed piston 10 ′ where the fuel pressure acts. In the enlarged diameter portion 5e of the valve body 5, the wall thickness forming the cylinder chamber 5f cannot be increased so much in order to reduce the weight of the entire valve body. Thereby, the cylinder chamber 5f is expanded by the fuel pressure, and the inner diameter of the cylinder chamber 5f is increased. As a result, the gap between the cylinder chamber 5f and the fixed piston 10 ′ increases, and the amount of fuel leaked from the cylinder chamber 5f passing through the gap increases.
[0035]
In the present embodiment, the concave hole 10a ′ formed in the fixed piston 10 ′ expands due to the fuel pressure in the cylinder chamber 5f, and the outer diameter of the fixed piston 10 ′ increases accordingly. It is possible to suppress an increase in the gap between the fixed piston 10 ′ and suppress an increase in leaked fuel. The diameter of the concave hole 10a ′ is preferably selected so that the increase in the outer diameter of the fixed piston 10 ′ due to the fuel pressure is equal to the increase in the inner diameter of the cylinder chamber 5f due to the fuel pressure. By doing so, it is possible to prevent an increase in the gap between the cylinder chamber 5f and the fixed piston 10 ′.
[0036]
FIG. 5 is a cross-sectional view showing a fourth embodiment of the fuel injection device. The same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. The difference between the present embodiment and the first embodiment is that a fuel passage 40 for supplying fuel from the pressure accumulation chamber to the fuel chamber 2 is formed on the base end side of the fuel injection device main body 1. Specifically, the fuel passage 40 is formed through the fixed piston 100. Thereby, the fuel from the pressure accumulating chamber is supplied to the fuel chamber 2 through the fuel passage 40, the cylinder chamber 5f, and the communication passage 5g.
[0037]
With such a configuration, the fuel passage 40 functions in the same manner as the concave hole portion of the third embodiment, and the outer diameter of the fixed piston 100 is increased by the expansion of the fuel passage 40 due to the fuel pressure. Thereby, an increase in the gap between the cylinder chamber 5f that expands due to the fuel pressure and the fixed piston 100 is suppressed, and an increase in leaked fuel can be suppressed.
[0038]
【The invention's effect】
According to the fuel injection device for an internal combustion engine according to claim 1 of the present invention, the pressure receiving area in the valve opening direction of the valve body is determined by the presence of the first sliding portion regardless of whether the valve body is closed or opened. It does not change. In addition, the pressure receiving area in the valve closing direction of the valve body is the cross-sectional area of the second sliding portion or the cylinder chamber formed on the base end side from the second sliding portion, and this cross-sectional area is the valve opening direction of the valve body. It is made equal to the pressure receiving area. Accordingly, the solenoid only needs to generate a magnetic attractive force that can overcome the valve closing force by the urging means, and can be downsized to prevent deterioration of the vehicle mountability of the fuel injection device. it can. Further, in the valve body, since any diameter on the tip side from the second sliding portion is equal to or less than the diameter of the second sliding portion, the tip side from the second sliding portion of the valve body is the second sliding portion. It can pass through the support part of the moving part. Thereby, the valve body can be easily removed when necessary. Further, according to the present fuel injection device, the solenoid can be reduced in size regardless of the injected fuel pressure, and the fuel injection device as in Patent Document 2 that requires a larger solenoid as the injected fuel pressure is higher. Compared to the above, it becomes possible to significantly increase the pressure of the injected fuel.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a first embodiment of a fuel injection device for an internal combustion engine according to the present invention.
FIG. 2 is an enlarged cross-sectional view showing a tip portion of the fuel injection device of FIG. 1;
FIG. 3 is an enlarged cross-sectional view in the vicinity of a communication path showing a second embodiment of a fuel injection device for an internal combustion engine according to the present invention.
FIG. 4 is an enlarged sectional view in the vicinity of a cylinder chamber showing a third embodiment of a fuel injection device for an internal combustion engine according to the present invention.
FIG. 5 is a cross-sectional view showing a fourth embodiment of a fuel injection device for an internal combustion engine according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Fuel injection apparatus main body 2 ... Fuel chamber 3 ... Injection hole 4,40 ... Fuel passage 5 ... Valve body 5a ... First sliding part 5b ... Second sliding part 5c ... Sealing part 5f ... Cylinder chamber 5g ... Communication path 5h: Restriction portion 6 provided in the communication path ... Movable member 7 ... Fixed member 8 ... Spring 9 ... Solenoid 10, 10 ', 100 ... Fixed piston 10a' ... Concave hole

Claims (3)

A valve body that is disposed in the fuel chamber and has a seal portion on the front end side to open and close the nozzle hole; and an urging means for closing the valve body without using fuel pressure in the fuel chamber; A solenoid that generates a magnetic attractive force for opening the valve body against the urging force in the valve closing direction by the urging means, and the valve body is located outside the fuel chamber from the tip side of the seal portion. A first sliding portion protruding to the outside of the fuel chamber and a proximal second sliding portion protruding to the outside of the fuel chamber, the diameter of the first sliding portion being equal to the diameter of the seal portion, Any diameter on the distal end side from the second sliding portion of the body is equal to or smaller than the diameter of the second sliding portion, and is closer to the proximal end side than the second sliding portion or the second sliding portion of the valve body. Is formed with a cylinder chamber communicating with the fuel chamber via a communication passage, and a fixed piston is formed in the cylinder chamber. Is arranged, the cross-sectional area of the cylinder chamber is equal to the valve opening direction pressure receiving area of the valve body, said the stationary piston fuel passage is formed, and the fuel passage, and said cylinder chamber, said communication passage the fuel injection system for an internal combustion engine, wherein a fuel is supplied to the fuel chamber via.   The fuel injection device for an internal combustion engine according to claim 1, wherein a throttle portion is provided in the communication path.   2. The fuel injection device for an internal combustion engine according to claim 1, wherein a concave hole is formed in an end face of the fixed piston on which the fuel pressure in the cylinder chamber acts.

Images