JP3298088B2 - Safety device for constant pressure injection valve for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety device mounted on a fuel injection valve of an internal combustion engine.

[0002]

2. Description of the Related Art A safety device disclosed in Japanese Patent Application Laid-Open No. 60-159366 discloses a valve member movably provided inside a body, a valve seat portion for closing a flow passage when the valve member is seated, The spring includes a spring that biases the valve member away from the valve seat, and a piston whose position is determined by the balance between the spring and the fluid force. The piston is provided with a throttle passage communicating between the upstream side and the downstream side.

When the fuel supplied to the internal combustion engine exceeds the allowable maximum flow rate of the injection flow rate, the flow path is closed by the valve member sitting on the valve seat. In the case where the flow rate is equal to or less than the maximum flow rate, the position of the piston is determined by the balance between the fluid force and the spring force caused by the differential pressure across the throttle passage.

[0004]

However, according to such a conventional safety device attached to a fuel injection valve of an internal combustion engine, the operating condition is determined by the flow rate detection performance of a fixed-shaped throttle passage. The nature of the
For example, there is a problem that the operating condition of the safety device is different depending on the used fuel because it is easily affected by a difference in fluid viscosity due to the used fuel. For this reason, according to the above-mentioned conventional safety device, it is necessary to change the throttle passage portion for each fuel having different properties, and the variation of the safety device is increased, which causes a problem that the production management becomes complicated.

The present invention has been made in view of the above problems, and has as its object to provide a safety device for a constant-pressure injection valve for an internal combustion engine that can operate stably when various types of fuels are used. .

[0006]

According to the present invention, there is provided a safety device for a constant-pressure injection valve for an internal combustion engine according to the present invention, comprising: a tubular body having a fuel passage formed therein; A first throttle passage that is guided movably in the axial direction by a fixed cylindrical sleeve and an inner wall of the sleeve, and communicates with the front and rear of the sleeve; A piston moving to an outlet side, a valve seat formed on an outlet side inner wall of the fuel passage,
While being guided movably in the axial direction by the inner wall of the fuel passage located between the sleeve and the valve seat portion,
A valve member that moves to the outlet side of the fuel passage via the piston and sits on the valve seat to block the fuel passage, and urges the valve member in a direction away from the valve seat. A biasing means, wherein the inner wall of the sleeve is a flow area variable means for forming an annular second throttle passage between the inner wall of the sleeve and the outer wall of the piston.
The maximum fluid when the valve member is seated on the valve seat.
As the pressure is constant regardless of the fuel property, the piston before and after the fuel differential to the fuel passage path exit side corresponding to the pressure of
Wherein the move entailment to the second throttle flow path area is to flow area varying hand stage increases the passageway is provided.

[0007]

According to the above construction of the present invention, the first throttle passage having a constant flow passage area is formed in the piston, and the flow path area is variable in the inner wall of the sleeve so that the inner diameter increases in the downstream direction of the flow passage. The formation of the means forms a second throttle passage as a variable clearance between the sleeve and the piston. Thus, the effective flow passage area of the second throttle passage increases or decreases according to the axial movement amount of the piston.

[0008] According to the above configuration, the first flow rate detection is performed.
By forming the throttle passage, the size of the safety device is avoided. Furthermore, since the flow path area varying means is formed on the inner wall of the sleeve, the effective flow path area of the second throttle passage is variable according to the axial position of the piston, so that the flow is less affected by the viscosity of the fluid. The flow rate is detected based on the road area.

[0009]

An embodiment of the present invention will be described with reference to the drawings.
1 to 3 show a first embodiment in which the present invention is applied to a fuel injection device for a multi-cylinder diesel engine. In FIG. 2, a diesel engine (hereinafter referred to as an “engine”) 1 is provided with injectors 2 corresponding to a plurality of cylinders, respectively, and fuel is injected from the injector 2 into each cylinder by an injection control solenoid valve 3. Is controlled by turning on and off the switch. The injector 2 is connected to the pressure accumulating chamber 4 of the high-pressure accumulating vessel 20 common to each cylinder, and during the period in which the injection control solenoid valve 3 is open, the pressure accumulating chamber 4
Is injected from the injector 2 into each cylinder of the engine 1. Since it is necessary to continuously accumulate a high predetermined pressure corresponding to the fuel injection pressure in the pressure accumulating chamber 4, the high pressure supply pump 7 is connected via the supply pipe 5 and the discharge valve 16. The high-pressure supply pump 7 pressurizes fuel sucked from a fuel tank 8 through a known low-pressure supply pump 9 to a high pressure, and
The fuel inside is controlled and maintained at a high pressure.

The electronic control unit ECU 40 for controlling this system is supplied with information on the number of revolutions and the load from the engine revolution number sensor 12 and the load sensor 13, for example, and according to the engine operating state determined from these signals. The ECU 40 outputs a control signal to each of the injection control solenoid valves 3 so that the determined optimum injection timing and injection amount (injection period) are obtained. At the same time, the ECU 40 outputs a control signal to the high-pressure supply pump 7 so that the injection pressure becomes an optimum value according to the rotation speed, the load, and the like. The pressure accumulating chamber 4 is provided with a pressure sensor 14 for detecting a common rail pressure. The discharge amount of the high-pressure supply pump 7 is adjusted so that the signal of the pressure sensor 14 becomes an optimum value set in advance according to the rotation speed and the load. Control. The safety device 10 is attached to the pressure accumulator 20.

As shown in FIG. 1, the safety device 10 includes a compression coil spring 34, a slider 32, a ball 30, a sleeve 28, a piston 26,
The plate 24 and the connector 22 are accommodated. The compression coil spring 34 is housed in a spring chamber 67,
One end 341 contacts the shoulder 61 of the body 6, and the other end 342 contacts the shoulder 321 of the slider 32.
The urging force of the compression coil spring 34 is extremely small, and serves to return the piston 26 to the lower end position where it comes into contact with the plate 24 when there is no flow rate.

As shown in FIGS. 1 and 4, the slider 32 has a cylindrical projection 3 for guiding a compression coil spring 34.
22 and a sliding portion 324 that slides on the inner wall 62 of the body 6. The sliding portion 324 has chamfered portions 325 and 326 at an axial end thereof for improving sliding with the inner wall 62. A ball 3 is provided on the lower end surface of the sliding portion 324.
Conical guide recess 327 to prevent zero displacement
Are formed.

The ball 30 functions as a valve member, contacts the guide recess 327 of the slider 32, and
6 also contacts the upper end surface 262. When the ball 30 is at the uppermost position, the ball 30 abuts on the seat portion 69 as a valve seat portion, thereby completely closing the flow path formed by the inner wall 62. The piston 26 is shown in FIGS.
As shown in FIG.
61 is formed, and a communication passage 263 corresponding to a first throttle passage connecting the concave portion 261 and the upper end surface 262 is formed. The outer peripheral wall 264 of the piston 26 is formed in a cylindrical shape having the same diameter in the axial direction. And this piston 2
6 is accommodated in a cylindrical sleeve 28 so as to be movable in the axial direction.

The sleeve 28 is provided on the cylindrical inner wall 6 of the body 6.
It is fixed to 3. The inner wall of the sleeve 28 has an inner diameter larger than the outer diameter of the piston 26, and is formed with a tapered inner wall 282 so that the inner wall is gradually narrowed downward from the upper end in the axial direction. Thereby, an annular variable clearance 284 is formed between the outer wall 264 of the piston 26 and the inner wall 282 of the sleeve 28 as shown in FIG. Since this variable clearance 284 is formed between the outer wall 264 of the piston 26 and the inner wall 282 of the sleeve 28, the piston 2
The effective area of the annular flow passage cross section formed by the variable clearance 284 is variable according to the axial relative position of No. 6. That is, the variable clearance 284 functions as a second throttle passage in which the effective area of the flow passage cross section increases as the piston 26 moves toward the upper end in the axial direction with respect to the sleeve 28.

The plate 24 is fixed to the inner wall 63 of the body 6. The plate 24 has a disk shape and has communication paths 241 and 242 penetrating in the thickness direction of the plate.
Are formed. This plate 24 has a piston 26
Functions as a stopper at the lowest position of. Connector 22
Has a fuel inlet 221 for introducing fuel from the pressure accumulating chamber 4 into the body 6, and has a convex portion 22 formed on the outer wall thereof.
2 abuts against the tapered slope 64 and is caulked and fixed by the body tip 65.

In the configuration of the safety device 10, the communication passage 263 corresponding to the first throttle passage has a constant flow passage area.
The variable clearance 284 corresponding to the second throttle passage is
It changes according to the relative axial position of the piston 26 with respect to the sleeve 28. Next, the operation of the safety device 10 will be described. When high-pressure fluid is introduced into the fuel inlet 221 from the accumulator chamber 4 of the accumulator 20 shown in FIG.
3. From the fuel outlet 68 through the gap between the inner wall 62 and the end surface 328 and the spring chamber 67, the injector 2
Supplied to

According to the present embodiment, when the flow rate is zero, the initial position shown in FIG. 1 is attained, and the piston 26 is in contact with the plate 24 by the urging force of the compression coil spring 34. When the flow rate increases from this state, the piston 2
A differential pressure of the fluid before and after the sixth communication passage 263 is generated. When the fluid force due to the pressure difference is smaller than the spring force of the compression coil spring 34, the positions of the piston 26, the ball 30, and the slider 32 are held at the lowest position as shown in FIG.

Next, when the fluid force due to the differential pressure of the fluid before and after the communication passage 263 corresponding to the first throttle passage overcomes the spring force of the compression coil spring 34, the piston 2
6. The ball 30 and the slider 32 move upward in the axial direction from the lowermost position. In this state, the piston 26 is located at a position where the fluid force due to the pressure difference between the fluid before and after the communication passage 263 and the variable clearance 284 and the spring force of the compression coil spring 34 are balanced.

Then, when the fluid force due to the pressure difference between the fluid before and after the communication passage 263 and the variable clearance 284 further increases, the ball 30 eventually comes into contact with the seat portion 69.
At the position where the ball 30 abuts on the seat portion 69, the fluid force due to the differential pressure of the fluid before and after the communication passage 263 and the variable clearance 284, the urging force of the compression coil spring 34, and the reaction force acting on the seat portion 69. To balance. At this position, the high pressure fluid no longer flows. This regulates excessive flow due to excessive fluid pressure,
Acts as a safety valve. The maximum fluid pressure at this time is substantially constant irrespective of the viscosity difference of the fluid.

In general, for a fuel having a high fluid viscosity, it is difficult for the fuel to flow relatively through the first throttle passage and the second throttle passage, and the pressure difference between the upstream side and the downstream side of the first throttle passage is relatively small. Although the pressure difference is large, the variable clearance 284 is increased with an increase in the movement of the piston 26 in the downstream direction of the flow path due to the differential pressure, the flow path area is increased, and the fuel flow rate is increased to a predetermined fuel flow rate. Is done.

In the case of a fuel having a low fluid viscosity, the fuel flows relatively easily through the first throttle and the second throttle, and the differential pressure between the upstream side and the downstream side of the first throttle passage is relatively small. The lower the differential pressure, the lower the fuel flow rate, and the lower the differential pressure becomes. To compensate for this, a variable clearance 28 is set according to the amount of movement of the piston 26 in the downstream direction of the flow path due to the differential pressure.
4 changes, the flow path area increases, and the fuel flow rate increases to a predetermined fuel flow rate, and the differential pressure is adjusted.

According to this embodiment, most of the fuel flows through the communication passage 263 corresponding to the first throttle passage, and the minute adjustment of the fuel is adjusted by the variable clearance 284 as the second throttle passage. Since the size of the clearance 284 can be set within a narrow range, the overall configuration of the safety device can be reduced in size. Further, according to the present embodiment, by setting the influence of the communication passage 263 corresponding to the first throttle passage of the piston 26 to be small, it is possible to reduce the difference value of the maximum flow rate due to the difference in the type of fuel used. it can.

Next, FIG. 6 shows a comparative example having no tapered inner wall 282 which is a characteristic part of the present embodiment, and the operation of this comparative example will be described. In this comparative example, first, when a differential pressure of the fluid before and after the communication path 81 of the piston 72 is generated, the fluid force due to the differential pressure is generated by the compression coil spring 8.
When the spring force is smaller than 0, the positions of the piston 72, the ball 73 and the slider 74 are held at the lowermost position.

Next, when the fluid force due to the differential pressure of the fluid before and after the communication passage 81 corresponding to the throttle passage overcomes the spring force, the piston 72, the ball 73 and the slider 74 move upward from the lower end position. And the communication passage 81
When the flow rate flowing through the communication passage 81 further increases in a state where the fluid force due to the pressure difference between the fluids before and after the force overcomes the spring force, the fluid force increases as the pressure difference increases.

Further, when the flow rate flowing through the communication passage 81 further increases, the ball 73 comes into contact with the seat portion 79. Then, the fluid force and the urging force of the compression coil spring 80 and the seat portion 7
The reaction force acting on 9 balances. At this position, the high pressure fluid no longer flows. As a result, an excessive flow rate due to an excessive fluid pressure is regulated and acts as a safety valve.

However, according to this comparative example, the piston 7
Since the throttle formed around 2 is only the communication path 81, the pressure difference due to the fluid before and after the communication path 81 differs depending on the property of the fuel, for example, the difference in the fluid viscosity due to the difference in the fuel used. Therefore, if the flow rate of the fuel flowing through the communication passage 81 is the same, the pressure difference between the fluid before and after the communication passage 81 is lower in the fuel having the lower fluid viscosity than in the fuel having the higher fluid viscosity. Due to the difference in the fluid viscosity of the fuel, the ball 73 is
Since the pressure difference required for contacting the fuel cell 9 differs, there is a problem that the specification must be changed for each different fuel.

Next, another embodiment of the present invention will be described. In the first embodiment of the present invention, the tapered inner wall 282 of the sleeve 28 has a shape whose inner diameter linearly increases toward the downstream of the flow path. However, in the present invention, if the inner diameter increases toward the downstream of the flow path, it is not necessary to increase the inner diameter linearly. FIGS. 5A, 5B, and 5C show first, second, and third modified examples of the inner wall of the sleeve of the first embodiment.
Example 3 will be described. The piston movably housed in the sleeve is the same as the piston 26 of the first embodiment.

The sleeve 9 of the second embodiment shown in FIG.
1 has a step-like inner wall 91a, and the inner diameter increases stepwise toward the downstream of the flow path. The sleeve 92 of the third embodiment shown in FIG. 5B has a concave inner wall 92a, and the inner diameter increases in a curve toward the downstream of the flow path. The sleeve 93 of the fourth embodiment shown in FIG. 5C has a convex inner wall 93a, and the inner diameter increases in a curved line toward the downstream of the flow path.

In the second, third and fourth embodiments, the inner diameter increases in a non-linear manner toward the downstream of the flow path. Second between the sleeve and the piston depending on the directional position
Since the effective area of the flow passage cross section of the throttle passage becomes variable, the safety valve operates stably at a constant pressure which is not easily affected by the properties of the fluid.

[0030]

As described above, according to the safety device for a constant-pressure injection valve for an internal combustion engine according to the present invention, the flow path area of the fluid changes according to the amount of movement of the piston housed inside the sleeve. This makes it possible to detect a flow rate that is hardly affected by a difference in the viscosity of the fluid, so that there is an effect that a constant flow rate can be detected even when the fuel used is different. In addition, since a single safety device can cope with each used fuel even if the used fuels are different, there is an effect that defects in production management can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a safety device for a constant pressure injection valve according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a fuel injection device for an internal combustion engine to which a safety device according to an embodiment of the present invention is applied.

FIG. 3 is a cross-sectional view illustrating a sleeve and a piston according to an embodiment of the present invention.

FIG. 4 is a plan view of a slider according to the embodiment of the present invention.

FIG. 5 is a sectional view showing a modified example of the sleeve according to the embodiment of the present invention.

FIG. 6 is a sectional view of a safety device of a comparative example.

[Explanation of symbols]

 6 Body 10 Safety device 24 Plate (stopper) 26 Piston 28 Sleeve 30 Ball (valve member) 32 Slider 34 Compression coil spring (biasing means) 67 Spring chamber (fuel passage) 68 Fuel outlet (fuel passage) 69 Seat ( Valve seat) 221 Fuel inlet (fuel passage) 263 Communication passage (first throttle passage) 282 Tapered inner wall (flow passage area variable means) 284 Variable clearance (second throttle passage)

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02M 63/00 F02M 61/16 F02M 55/00 F02M 55/02 310 F02M 55/02 350

Claims (1)

(57) [Claims] A cylindrical body having a fuel passage formed therein; a cylindrical sleeve fixed to an inner wall on an inlet side of the fuel passage; an inner wall of the sleeve guided to be movable in an axial direction; A piston which has a first throttle passage communicating between front and rear of the fuel passage, and which is urged by inflowing fuel and moves to an outlet side of the fuel passage; a valve seat formed on an outlet side inner wall of the fuel passage; While being guided movably in the axial direction by the inner wall of the fuel passage located between the sleeve and the valve seat portion,
A valve member that moves to the outlet side of the fuel passage via the piston and sits on the valve seat to shut off the fuel passage; and urges the valve member away from the valve seat. A flow path forming an annular second throttle passage between the inner wall of the sleeve and the outer wall of the piston on the inner wall of the sleeve.
Area variable means, wherein the valve member is seated on the valve seat portion.
Maximum fluid pressure is constant regardless of fuel properties
As such, the transfer entailment said second throttle flow area to increase the flow area of the passage to the movement back and forth of the fuel difference before according to the pressure <br/> Symbol fuel through passage exit side of the piston safety device for an internal combustion engine for a constant pressure injection valve with a variable hand stage is provided.