JPH09170512A - Pressure control device in accumulator fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solves problems of generation of an accelerating shock at the time of reaccelerating an engine, deterioration of emission increase of noise, etc., by improving decompression responsibility of an accumulator container in case of using a hydraulic control valve of a two-way valve type for an accumulator fuel injection device. SOLUTION: A pressure control device 11 furnished with a valve body 43 to be operated to open and close by a solenoid coil 49 is installed on a common rail 5 which is an accumulator container to store fuel pressurized in high pressure. The valve body 43 is energized in the valve closing position by a comparatively weak valve spring 44. A balance rod 54 is provided in the valve body 43, a balance pressure chamber 55 communicated to a control port 52 by a communicating passage 56, and a drain port 47 is provided. A diameter of the balance rod 54 is set smaller than a valve seat part 46 of the control port 52, a valve opening tendency is given concerning hydraulic working force, and a fail-safe function to release excessive pressure is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-accumulation type fuel injection device used in an internal combustion engine, and more particularly, to rapidly changing the pressure of fuel in a pressure accumulation container (common rail, pressure accumulation pipe, etc.) used therefor according to operating conditions. The present invention relates to a pressure control device for reducing pressure.

[0002]

2. Description of the Related Art FIG. 3 shows a schematic structure of a fuel injection device using a three-way valve type directional control valve (hydraulic control valve) as an example of a pressure-accumulation type fuel injection device which has been widely used. In this device, when the pressure of the fuel in the pressure accumulation pipe M1 is higher than the control target pressure, the directional control valve M2, which is a three-way valve, is switched by the directional control valve drive means M5, so that the pressure accumulation pipe M1 and the fuel The low voltage side (drain) in the system is communicated with the low pressure side (drain) for a short time via the flow path M4. Thereby, a part of the high-pressure fuel stored in the pressure accumulation pipe M1 is discharged to the low pressure side of the fuel system, and the pressure accumulation pipe M1 is discharged.
The pressure inside can be dropped rapidly. as a result,
Even when the fuel injection valve M3 is not injecting fuel as in fuel cut, the pressure of fuel in the pressure accumulating pipe M1 can be made to quickly follow the control target pressure.

In this prior art, when the fuel pressure in the pressure accumulating pipe M1 is higher than the control target pressure, the fuel injection valve is switched for a short period of time, that is, the directional control valve M2 is switched. By repeating and switching the directional control valve M2 with a time width shorter than the delay time until M3 starts fuel injection, and intermittently connecting the high pressure side to the low pressure side for a short period of time, a minute communication time It is also possible to reduce the fuel pressure in the pressure accumulating pipe M1 by an amount corresponding to the accumulated value (duty control). Such control of the directional control valve M2 is called "switching leak" which can be applied only to the three-way valve, and is an effective method for reducing the fuel pressure on the high pressure side.

[0004]

In recent years, there has been an increasing demand for downsizing of fuel injection pumps for small diesel engines, and as a means for reducing the discharge amount of the pumps, there are three methods for accumulating fuel injection devices. There has been an increasing demand for replacing a directional control valve (hydraulic control valve) consisting of a valve with a two-way valve. However, when a hydraulic control valve consisting of a two-way valve is used, a switching operation that connects the high-pressure side and the low-pressure side at the time of switching is performed, as in the case of using a three-way valve.
Since it will not be possible to cause a leak, when fuel is not being injected, such as during fuel cut, even if the pumping of fuel from the fuel injection pump is stopped, a pressure accumulator with a comparatively large capacity such as a common rail. It is not possible to quickly reduce the pressure, and it is necessary to wait until the high pressure fuel gradually leaks to the low pressure side from the sliding parts of the pump and the valve, etc., so that the pressure is gradually reduced.

Therefore, when the two-way valve type hydraulic control valve is used, the pressure reduction response is generally deteriorated, and as a result, an acceleration shock occurs when the engine is re-accelerated,
Problems such as deterioration of emission and increase of noise occur. The present invention addresses such problems in the prior art,
The aim is to solve these problems by new means.

[0006]

According to the invention described in claim 1, the solenoid valve is energized, the valve body is attracted by the electromagnetic force, and the valve body is separated from the valve seat. Since it directly communicates with the low pressure side of the fuel system via, the high pressure fuel in the pressure accumulator is immediately discharged to the low pressure side, and the fuel pressure in the accumulator decreases rapidly. In this case, the balance rod is provided in the valve body to form the balance pressure chamber, and the pressure in the control port is constantly introduced into the balance pressure chamber by the communication passage. As a result of the hydraulic force being partially offset, the urging force of the valve spring for urging the valve body toward the closed position can be reduced. As a result, since the attraction force of the solenoid coil can be reduced, the pressure control device can be downsized as a whole.

Particularly, in the case of the present invention, the diameter of the cylinder formed inside the valve body and the diameter of the balance rod inserted therein are smaller than the valve seat of the control port, so that the hydraulic pressure for pushing down the valve body. The hydraulic acting force for pushing up the valve body becomes larger than the acting force, and the pressure control device is given a tendency to open the valve as a whole, so that the fail-safe function can be easily obtained. In this case, the urging force of the valve spring that urges the valve body toward the valve closing position may be small enough to push down the valve body against the difference in the hydraulic action force in the vertical direction.

According to a second aspect of the present invention, in the first aspect of the invention, the set load of the valve spring is exceeded by the hydraulic force acting on the valve element at the maximum pressure of the pressure accumulator container, overcoming the urging force of the valve spring. It is set to a value that can move the body to the valve open position, so when the fuel pressure in the pressure accumulator exceeds the maximum pressure, the hydraulic force that pushes down the valve body and the value that is larger than that. The force that pushes up the valve disc due to the difference between the hydraulic force that pushes up the valve disc from below will overcome the biasing force of the valve spring, so the pressure control device will automatically open the valve at the maximum pressure. Thus, an efficient fail-safe function of decompressing the pressure accumulator can be obtained. Therefore, claims 1 and 2
According to each of the inventions, it is possible to prevent the fuel pressure in the accumulator from becoming excessively high and reaching a dangerous value.

According to the third aspect of the invention, the attraction force of the solenoid coil is the sum of the hydraulic force acting on the valve element at the lowest common rail pressure (lower limit value) in the normal range and the urging force of the valve spring. Since they are set to be equal, when the common rail pressure is within the normal range, the solenoid coil can overcome the biasing force of the valve spring to open the valve element reliably, but when the common rail pressure falls below the normal range, Since the difference in the vertical hydraulic force applied to the body is reduced, the suction force of the solenoid coil alone cannot support the valve body in the valve open position against the biasing force of the valve spring. Even when electricity is supplied, the pressure control device automatically closes, and troubles due to excessive pressure reduction of the pressure accumulator can be prevented.

According to the invention of claim 4, in the invention of claim 1, since the throttle is provided between the pressure accumulating container and the valve seat of the control port, when the valve body moves to the valve opening position, the control port is provided. Has a lower fuel pressure than the high pressure in the accumulator. Therefore, the urging force of the valve spring that urges the valve element toward the closed position may be relatively small, and the attraction force of the solenoid coil may be small, so that the solenoid coil and the like can be downsized. It will be possible.

[0011]

FIG. 2 shows the overall structure of a pressure-accumulation fuel injection system 1 equipped with a pressure control device, which is a feature of the present invention. The fuel in the fuel tank 2 is pressurized by the low-pressure pump 3 to a predetermined low pressure, and then further pressurized by the high-pressure pump 4 to a high pressure exceeding the injection pressure, so that all the cylinders of the main body 6 of the multi-cylinder engine or a part thereof. Is temporarily stored in a pressure accumulating container (common rail) 5 common to a plurality of cylinders. High pressure fuel is introduced from a common rail 5 through a high pressure pipe 8 into a two-way valve injector 7 provided for each cylinder of the engine body 6.

A pressure sensor 9 is provided on the common rail 5, and a detection signal of the pressure sensor 9 indicates the common rail pressure. An electronic control unit (EC) incorporating a computer is provided.
U) 10 is input. Signals such as engine speed and accelerator opening indicating the operating state of the engine body 6 are input to the ECU 10 from other sensors, and the pressure of the common rail 5 is optimally controlled for the operating state of the engine body 6 at that time. The ECU 10 controls the high pressure pump 4 so that the target pressure is reached.

A pressure control device 11, which is a feature of the present invention, is attached to the common rail 5. Although the detailed structure will be described later, the pressure control device 11 receives a control signal as a result calculated by the ECU 10 based on the common rail pressure from the pressure sensor 9 and signals such as the engine speed and the accelerator opening. Sent. Then, for example, the common rail pressure actually detected by the pressure sensor 9 is
When it is higher than the control target pressure calculated from the operating state of the engine body 6 such as the engine speed and the accelerator opening degree,
The pressure control device 11 is controlled by a control signal from the ECU 10.
Operates to reduce common rail pressure.

Next, as an example of a pressure accumulation type fuel injection device to which the pressure control device 11 of the present invention is attached and used, a two-way valve having a simple structure and a small size but having the above-mentioned problems. The structure and operation of the pressure-accumulation type fuel injection device 1 including the type injector 7 will be described with reference to FIG. 4 in which the sectional structure is partially enlarged and simplified. Needless to say, the two-way valve injector 7 shown in FIG. 4 is representative of one provided for each cylinder, and the common rail 5, the fuel tank 2, the high pressure pump 4, etc. are all cylinders of the multi-cylinder engine 6. , Or one of them is provided as a common one for a cylinder group composed of a plurality of cylinders. It should be noted that what is shown as the fuel tank 2 in the drawing is not necessarily a fuel tank under atmospheric pressure because it may generally be a low-pressure side portion of the fuel system such as the drain passage.

The fuel pressurized to a high pressure by the high pressure pump 4 is stored in the common rail 5 which is a pressure accumulator while maintaining the high pressure, and is also supplied to the two-way valve injector 7 through the inlet 12. A part of the high-pressure fuel is guided from the inlet 12 through the passage 13 to the oil sump chamber 15 formed corresponding to the stepped portion of the valve needle 14 to generate a hydraulic force for pushing up the valve needle 14. As will be described later, when the valve needle 14 moves to the valve opening position, the fuel is injected from the fuel injection port.

The other part of the high-pressure fuel in the common rail 5 is guided to the back pressure chamber 17 through the first orifice 16 so as to apply a hydraulic force to the upper surface of the valve needle 14 in the direction of pushing it down. This back pressure chamber 17 is provided with a passage 18 to control port 20 of hydraulic control valve 19 which is a two-way valve.
Is always in communication with Although not shown, a spring that pushes down the valve needle 14 and biases the fuel injection port 39 in the direction of closing the fuel injection port 39 is irrespective of the hydraulic force acting on the oil sump chamber 15 and the back pressure chamber 17. It is provided by engaging with 14. In addition, instead of directly providing the back pressure chamber 17 on the upper surface of the valve needle 14, a command piston that is mechanically interlocked is provided on the upper portion of the valve needle 14, and the back pressure chamber 17 is formed on the upper surface of the command piston. There is also.

The hydraulic control valve 19 has a valve body 21.
A valve body 23 slidably inserted in a vertical direction is provided in a valve cylinder 22 formed in the valve body 22. The valve body 23 is urged downward by a valve spring 24.
The conical valve portion 25 formed near the tip of 3 is seated on the valve seat portion 26 at the upper edge of the control port 20 so that the control port 20 and thus the back pressure chamber 17 and the valve body 21 are provided. The communication with the drain port 27 can be cut off. The drain port 27 communicates with a low pressure side portion of the fuel system such as the fuel tank 2.

A solenoid coil 29 wound around a magnetic core 28 is attached to an upper portion of a valve body 21 of the hydraulic control valve 19 and is energized by a drive circuit (not shown) which operates in response to a command from the ECU 10. It is like this. An armature 30 made of a magnetic material is formed integrally with the valve body 23. The armature 30 has a magnetic material core 2 when the solenoid coil 29 is energized.
It is designed to be attracted upward by the magnetic force of 8.
Therefore, when the armature 30 and the valve body 23 rise upward against the bias of the valve spring 24 due to the suction of the solenoid coil 29, the conical portion 25 of the valve body 23 separates from the valve seat portion 26 and the control port 20 Is the drain port 27
Communicate with Further, in this example, the thin cylindrical pin portion 31 is formed at the tip of the valve body 23, and the inner wall surface of the control port 20 is formed into a small-diameter cylindrical shape at least at a portion corresponding thereto. , Hydraulic control valve 1
When the valve body 23 of No. 9 moves to the valve opening position and is within a specific moving range, a relatively narrow second orifice 32 as a fuel passage is provided between the pin portion 31 and the inner wall surface of the control port 20. Is formed.

In the example shown in FIG. 4, a vertical small cylinder 33 is formed inside the valve body 23 of the hydraulic control valve 19, and a slidable piston-shaped balance rod 34 is inserted therein. The balance pressure chamber 35 is formed in the lower part thereof. Then, the balance pressure chamber 35 has the valve body 23.
A communication passage 36 formed through the center of the control port 20 always communicates with the back pressure chamber 17 below the control port 20. The upper end of the balance rod 34 is brought into contact with and supported by a fixed portion such as the magnetic core 28 so that the balance rod 34 is prevented from moving in the backward direction.

Next, the operation of the two-way valve type injector 7 shown in FIG. 4 will be described. In FIG. 4, the solenoid coil 29 is not energized from the drive circuit yet, and the hydraulic control valve 1
Since the valve body 23 of No. 9 is seated on the valve seat portion 26 of the control port 20 and closes it, the high pressure of the common rail 5 acts on the back pressure chamber 17, and its hydraulic acting force is not shown in the spring. The valve needle 14 is pushed down together with the urging force of No. 3, thereby closing the fuel injection port 39 at the tip of the nozzle 37 and stopping the fuel injection. The high-pressure fuel in the common rail 5 is supplied to the inlet 12, the passage 13, and the oil reservoir 1 formed in the nozzle 37 at the tip of the injector 7.
5, it is supplied to the vicinity of the fuel injection port 39 through a passage 38 formed around the valve needle 14 passing through the center of the nozzle 37. In the state shown in FIG. 4 in which the valve body 23 is in the valve closed position, the hydraulic force acting to push up the valve needle 14 in the oil sump chamber 15 is equal to the hydraulic force force in the back pressure chamber 17,
Since it is smaller than the total force of the urging force of the spring (not shown) that pushes down the valve needle 14, the tip of the valve needle 14 stops at the position where the fuel injection port 39 is closed.

When attempting to start fuel injection, the ECU
When the solenoid coil 29 of the hydraulic control valve 19 is energized by the command from the armature 3, the armature 3
0 is attracted to the magnetic core 28 and moves upward together with the valve body 23 against the valve spring 24.
The conical portion 25 is separated from the valve seat portion 26 of the valve body 21, the control port 20 communicates with the drain port 27, and the pressure in the back pressure chamber 17 of the valve needle 14 decreases. Therefore, the pressure of the valve needle 1 in the oil reservoir chamber 15 is greater than the resultant force of the hydraulic force pushing down the valve needle 14 in the back pressure chamber 17 and the spring (not shown).
The pressure of the fuel acting on the step portion of No. 4 causes the valve needle 14
Since the force for pushing up the fuel injection force becomes larger, the valve needle 14 that closed the fuel injection port 39 at the tip moves upward, and the fuel injection port 39 is opened to pass from the oil sump chamber 15 through the passage 38. The high-pressure fuel that has reached the tip of the nozzle 37 is ejected from the fuel injection port 39 and fuel injection is started.

When the fuel injection is stopped, when the energization of the solenoid coil 29 is stopped, the electromagnetic force that has been attracting the armature 30 until then disappears, and the valve element 23 is pushed downward by the valve spring 24. And conical portion 25 seats on valve seat 26 of control port 20. As a result, the control port 20 is closed and the back pressure chamber 17 is closed.
The communication between the drain port 27 and the drain port 27 is cut off, and the high-pressure fuel from the common rail 5 flows in through the first orifice 16 so that the pressure in the back pressure chamber 17 rises to the same pressure as the common rail 5. , Its hydraulic force pushes down the valve needle 14 together with a spring (not shown). Then, when this pushing-down force becomes larger than the pushing-up force due to the pressure of the high-pressure fuel acting on the oil sump chamber 15, the valve needle 14 descends to close the fuel injection port 39, and the fuel injection is stopped.

In the example of FIG. 4, the valve element 23 is driven by the pressure of the high-pressure fuel on the side of the back pressure chamber 17 acting on the control port 20.
Force for pushing up the valve body 23 through the communication passage 36 into the balance pressure chamber 35 to push down the valve body 23 is offset at least partially by the force in the opposite direction due to the pressure of the high pressure fuel. It becomes possible not only to make the valve spring 24 that urges the valve body 23 to the closed position relatively weak, but also to resist the force and to make the valve body 23
It is also possible to reduce the electromagnetic force of the solenoid coil 29 that lifts. Therefore, it is possible to reduce the size and cost of the entire device and reduce the cost.

The two-way valve injector 7 having such a configuration
In the above, when the valve body 23 is lifted and the hydraulic control valve 19 takes the open position, the high pressure fuel flowing from the inlet 12 has a relatively small diameter (for example, a diameter of 0.2 to 0.3 mm). Through the orifice 16 and the second orifice 32, and flows out to the drain port 27. The two-way valve injector 7 has a so-called "switching leak" in which the high pressure side communicates directly with the low pressure side by switching the hydraulic control valve M2 which is a three-way valve like the three-way valve injector shown in FIG. Since there is no state, as described above, in the injection stopped state in which the hydraulic control valve 19 is closed, even if the high pressure fuel is not discharged by the high pressure pump 4, the common rail 5
Since the high-pressure fuel inside is only reduced in pressure by leaking to the low-pressure side from a slight clearance such as some sliding part, it takes a relatively long time to reduce the pressure,
Reduced pressure response to control is reduced.

Therefore, the pressure control device 1 which is a feature of the present invention and is provided as a rapid pressure reducing means for the common rail 5.
A configuration example of No. 1 will be described with reference to FIG. Since the pressure control device 11 in this example has a similar structure in many parts to the hydraulic control valve 19 used in the above-described two-way valve injector 7, common parts can be used. It is advantageous in terms. The pressure control device 11 is liquid-tightly mounted on the common rail 5 with a threaded portion 40 formed on the lower portion of the valve body 41 sandwiching a seal (not shown). A pressure sensor 9 is also attached to the common rail 5, and its signal is input to the ECU 10 by a lead wire.

The pressure control device 11 has a valve body 43 which is slidably inserted in a valve cylinder 42 formed in the valve body 41, and the valve body 43 is moved downward by a valve spring 44. Energized, the valve body 43
The conical valve portion 45 formed at the tip of the seat is seated on the valve seat portion 46 at the upper edge of the control port 52, which is in constant communication with the inside of the common rail 5 through the passage 51.
The communication between the control port 52, that is, the inside of the common rail 5 and the drain port 47 provided in the valve body 41 can be blocked. In this example, by making the passage 51 smaller than the control port 52, the passage 51
Is configured as one diaphragm. On the other hand, the drain port 47 always communicates directly with the low pressure side of the fuel system such as the fuel tank 2.

A solenoid coil 49 wound around a magnetic core 48 is provided above the valve body 41 of the pressure control device 11.
Is installed, and the EC
It is designed to be energized by a drive circuit (not shown) which operates in response to a command from U10. The valve body 43 is integrally formed with an armature 50 made of a magnetic material, and when the solenoid coil 49 is energized, the magnetic material core 48 is formed.
It is designed to be attracted by the electromagnetic force of. When the armature 50 and the valve body 43 are lifted by the suction against the bias of the valve spring 44, the conical portion 45 of the valve body 43 is separated from the valve seat portion 46, and the inside of the common rail 5 is controlled by the control port 52. And the drain port 47 via the passage 51.

A vertical small-diameter cylinder 53 is formed inside the valve body 43 of the pressure control device 11. A slidable piston-like balance rod 54 is inserted in the cylinder 53, and a balance is provided below the cylinder 53. The pressure chamber 55 is formed. The balance pressure chamber 55 is always communicated with the inside of the common rail 5 through the control port 52 and the passage 51 by the communication passage 56 that is formed by penetrating the center of the valve body 43.
The upper end of the balance rod 54 is supported by coming into contact with a fixed portion such as the magnetic core 48, and is prevented from moving in the backward direction.

Next, the operation of the pressure control device 11 shown in FIG. 1 will be described. The basic action and effect of providing the balance rod 54 are the same as the action and effect of providing the balance rod 34 in the hydraulic control valve 19 in the two-way valve injector 7 shown in FIG. The basic description will be omitted. In FIG. 1, since the solenoid coil 49 is not yet energized from the drive circuit, the valve body 43 of the pressure control device 11 is seated on the valve seat portion 46 of the control port 52 to close it. The state where high voltage is held in the common rail 5 is shown.

Considering the balance between the vertical hydraulic force acting on the valve element 43 and the urging force of the valve spring 44, the upward acting force F _U is the diameter of the valve seat portion 46 d _S. And the pressure of the common rail 5 is P, F _U = πd _S ² P / 4 The downward acting force F _D is the balance rod 54 diameter d _R and the valve spring 44 force is F _S. Then, F _D = F _S + πd _R ² P / 4.

Therefore, for example, the diameter d _S of the valve seat portion 46 is 3
mm, the diameter d _R of the balance rod 54 is 2.95 mm.
If it is, the unit of pressure P of the common rail 5 is kgf / c
If m ² is used, F _U = 7.07 × 10 ⁻² × P kgf (1) F _D = 6.83 × 10 ⁻² × P + F _S kgf (2) The force F ₁ acting downward as the resultant force with the urging force of the valve spring 44 is F ₁ = F _D −F _U = F _S −0.24 × 10 ⁻² × P kgf (3). Therefore, in this example, if the solenoid coil 49 that generates a suction force larger than this force F ₁ is used,
The valve body 43 can be driven to open by energizing the drive circuit operated by the ECU 10.

In this case, in addition to the urging force of the valve spring 44 and the electromagnetic force of the solenoid coil 49, the balance rod 54 is adjusted so that the resultant force of the vertical hydraulic acting force applied to the valve body 43 acts slightly upward. It is one of the features of the pressure control device 11 in the present invention that the diameter d _R of the pressure control device 11 (thus, the diameter of the cylinder 53) is set smaller than the diameter d _S of the valve seat portion 46.

With this setting, the pressure control of the common rail 5 becomes impossible due to some abnormality such as a failure of the pressure sensor 9, and the fail safe function works even if the pressure in the common rail 5 rises abnormally. . That is, when the maximum pressure P _max is, for example, 1400 kgf / cm ² , the value of P _max is given as the pressure P of the common rail 5 in the above equation (3), and the value of the force F ₁ acting downward as the resultant force. The force F _S of the valve spring 44 may be set so that In this example, F ₁ = F _S -0.24 from relation × 10 ^-2 × 1400 = 0, the force F _S of the valve spring 44 is 3.
It becomes 36 kgf.

Thus, the force F _S of the valve spring 44 is
By setting, even if the fuel pressure in the common rail 5 excessively rises due to some abnormal cause, the maximum pressure P _max (1400 kgf / cm ^{2 in} this example)
Since the upward hydraulic acting force applied to the valve body 43 of the pressure control device 11 becomes larger than the force of the valve spring 44 that tries to seat the valve body 43,
The valve body 43 automatically rises to the open valve position, the inside of the common rail 5 and the drain port 47 communicate with each other, and the fuel pressure of the common rail 5 immediately decreases. Therefore, damage to the common rail 5 and the like can be avoided in advance. it can.

FIG. 5 is a diagram showing the relationship between the acting force on the valve element 43 and the fuel pressure of the common rail 5 as described above. The force F _S of the valve spring 44 acting on the valve body 43 is downward, and the total hydraulic force and the required suction force by the solenoid coil 49 act upward. Therefore, from the balance of the forces in the vertical direction, the required suction force = The relationship between the force F _S of the valve spring 44 and the hydraulic force is established. Therefore, the maximum pressure P _max is 1400
In the case of kgf / cm ² , the required suction force = 3.36-3.36 = 0.

Further, when the common rail pressure is the upper limit pressure of 1200 kgf / cm ^{2 in} the normal range, the required suction force = 3.36-2.88 = 0.48 kgf, and when the minimum pressure of the normal range is 200 kgf / cm ^2. Since the required suction force = 3.36-0.48 = 2.88 kgf, the suction force of the solenoid coil 49 is 2.88.
It is recommended to use kgf. By doing so, 2
When the pressure is 00 kgf / cm ² or more, the valve body 43 can be reliably driven.

[0037] On the contrary, in the lower limit pressure 200 kgf / cm ² or less in the region of the common rail pressure is normal use range, for example when the 100 kgf / cm ² is required suction force = 3.36-0.24 = 3.12 Since it becomes kgf and the upward hydraulic force decreases,
The required suction force is greater than when 0 kgf / cm ² . Therefore, even if the solenoid coil 49 continues to be energized, the valve element 4 is not operated at a common rail pressure below the normal range.
Since 3 automatically takes the valve closing position, it is possible to prevent the engine from being damaged due to an abnormal decrease in the common rail pressure.

In the example shown in FIG. 1, the common rail 5
By setting the diameter of the passage 51 formed by drilling in the valve 51 to be smaller than that of the control port 52 of the pressure control device 11 connected thereto, the passage 51 has a throttling effect. This is to prevent the same high fuel pressure as in the common rail 5 from acting on the control port 52 when the valve is moved to the valve opening position. Thereby, when the valve closing operation of the pressure control device is performed, even if the valve spring 44 is weak, the valve body 43 can be moved to the valve closing position with good responsiveness, and by extension, the solenoid coil 49. It is possible to further reduce the size of the solenoid coil 49, etc., by reducing the required suction force (electromagnetic force). The passage 51 is connected to the control port 52.
Instead of smaller diameter than passage 51 and control port 52
Another diaphragm may be provided inside.

The operation of the pressure-accumulation type fuel injection device using the pressure control device of the present invention will be described with reference to FIG. 6 which is a time chart. FIG. 6 shows that when the engine is operating under a high load and the common rail pressure is high, the accelerator opening is set to 0 at time t ₁ to perform rapid deceleration, and the common rail pressure is also rapidly reduced. A solid line shows an actual change in the common rail pressure by the pressure control device 11 of the present invention when the common rail pressure is to be maintained at a value of a certain low pressure after the time t _{2 is changed} to the light load operation. For comparison with this, in the same drawing, a change in the common rail pressure in the case of the prior art that does not use the pressure control device 11 is shown by a chain line, and a command injection pressure (control target pressure) is shown by a broken line. There is.

In the case of the conventional pressure-accumulation type fuel injection device without the pressure control device 11, when the accelerator opening is set to 0 and the vehicle is rapidly decelerated, even if the high-pressure fuel supply from the high-pressure pump 4 is cut off, the common rail 5 Since there is no escape place for the high-pressure fuel accumulated in the fuel cell, the pressure is gradually reduced due to slight leakage of sliding parts, etc.
_{Also in 2} , the actual injection pressure greatly exceeds the command injection pressure. If the common rail pressure is too high as described above, problems such as generation of acceleration shock, deterioration of emission, and increase of noise cannot be avoided.

On the other hand, in the fuel injection device according to the present invention in which the common rail 5 is provided with the pressure control device 11 as shown in FIG. 1, the pressure control device 11 is opened during the rapid deceleration at time t _1. Then, by directly discharging the high-pressure fuel from the common rail 5 to the drain port 47, the actual injection pressure can be promptly reduced. As a result, when the light load operation is started next at time t ₂ , the actual injection pressure sufficiently follows the command injection pressure,
Since the fuel injection can be performed with the injection pressure most suitable for the operating state, it is possible to solve all the problems as in the case of the above-mentioned conventional technique.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a pressure accumulation type fuel injection device using a pressure control device of the present invention.

FIG. 3 is a conceptual diagram of a fuel injection device using a conventional three-way valve type directional control valve.

FIG. 4 is a partially enlarged and simplified cross-sectional view showing a main part structure of a two-way valve injector in a pressure accumulation type fuel injection device as an object to which the pressure control device of the present invention is attached.

FIG. 5 is a diagram showing the relationship between the force acting on the valve element and the fuel pressure of the common rail in the pressure control device of the present invention.

FIG. 6 is a time chart showing the operation of a pressure accumulation type fuel injection device using the pressure control device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Accumulation type fuel injection device 2 ... Fuel tank 4 ... High pressure pump 5 ... Common rail (accumulation container) 6 ... Multi-cylinder engine main body 7 ... Two-way valve injector 9 ... Pressure sensor 10 ... ECU 11 ... Pressure control device 14 ... Valve needle 15 ... Oil sump chamber 16 ... First orifice 17 ... Back pressure chamber 19 ... Hydraulic control valve 32 ... Second orifice 39 ... Fuel injection port 43 ... Valve body of pressure control device 44 ... Valve spring 45 ... Conical shape Valve portion 46 ... Valve seat portion 47 ... Drain port 49 ... Solenoid coil 50 ... Armature 52 ... Control port 54 ... Balance rod 55 ... Balance pressure chamber 56 ... Communication passage

Claims (4)

[Claims] 1. A pressure-accumulation fuel injection device in which high-pressure fuel is housed in a pressure accumulator container, and the fuel is injected into each cylinder of an internal combustion engine by an electrically controlled fuel injection valve. A control port that forms a seat and can communicate between the inside of the accumulator and the low pressure side, a valve body that opens and closes the control port at the tip, and a valve that urges the valve body toward a closed position. A spring, and a solenoid coil that attracts the valve element to open the valve when energized,
A cylinder formed inside the valve body with a diameter smaller than the valve seat of the control port, a balance rod slidably inserted into the cylinder in a liquid-tight manner, and formed by the cylinder and the balance rod. A pressure control device that is mounted on the pressure accumulating container, comprising: a balance pressure chamber that is configured as described above; and a communication passage that is provided at a tip end portion of the valve body and that always communicates the control port with the balance pressure chamber. 2. The set load of the valve spring is such that the hydraulic acting force acting on the valve body at the maximum pressure of the pressure accumulator container overcomes the biasing force of the valve spring to move the valve body to the valve opening position. The pressure control device according to claim 1, wherein the pressure control device is set to. 3. The attraction force of the solenoid coil is set to be equal to the sum of the hydraulic force acting on the valve element at the lowest common rail pressure in the normal range and the urging force of the valve spring. Item 1. The pressure control device according to item 1. 4. The pressure control device according to claim 1, wherein a throttle is provided between the pressure accumulating container and the valve seat of the control port.