JPH0435611B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention relates to an internal combustion engine in which fuel injection timing, fuel injection amount, and fuel injection pressure can be easily adjusted without stopping the internal combustion engine and independent of the rotational speed of the internal combustion engine. The present invention relates to a fuel injection control device.

BACKGROUND ART In general, in internal combustion engines, and in diesel engines in particular, fuel injection timing greatly affects engine performance, particularly fuel consumption rate. In addition, the fuel injection pressure can be increased to make the fuel spray finer and the injection period shorter, increasing combustion efficiency and reducing the fuel consumption rate. However, when the internal combustion engine is under low load, high-pressure injection This causes knocking and puts strain on the internal combustion engine, leading to a shortened engine life and excessive noise. The optimum injection timing and pressure vary greatly depending on the operating conditions of the internal combustion engine and the quality of the fuel oil.
If the fuel injection timing and fuel injection pressure could be freely adjusted while the internal combustion engine is running, it would be possible to significantly save fuel without forcing the internal combustion engine to overdo it, and given the current situation where oil prices are soaring, this would generate large profits.

Conventionally, a fuel injection system for an internal combustion engine is constructed by directly connecting a fixed stroke fuel injection pump that is activated in synchronization with the operation of the internal combustion engine and an automatic injection nozzle with a shutoff valve via a fuel injection pipe. Widely adopted around the world. In this conventional fuel injection device,
The fuel injection timing is determined by the set position of the cam, and when changing the fuel injection timing, it is necessary to change the set position of the cam on the camshaft, and the internal combustion engine must be temporarily stopped. Furthermore, the fuel injection pressure is determined by the rotational speed of the internal combustion engine and the dimensions of the injection nozzle, and cannot be freely adjusted.

On the other hand, in a fuel injection device already known in Japanese Patent Application Laid-Open No. 143344/1983, an injection nozzle with a shutoff valve is equipped with an electro-hydraulic servo valve, and the fuel flow path is switched using liquid pressure other than the fuel. There is a fuel injection device that injects and supplies fuel accumulated in a high-pressure fuel source into a cylinder from an injection nozzle, and the start and end of the injection is controlled by an electric pulse signal applied to the electrohydraulic servo valve. According to such a device, the fuel injection timing and fuel injection amount are determined by the transmission timing and pulse width of the electric pulse signal, and the fuel injection pressure is determined by the fuel pressure accumulated in the high-pressure fuel source. The fuel injection timing, fuel injection amount, and fuel injection pressure can be freely adjusted regardless of the speed of the internal combustion engine or the installation of the cam. However, in such a device,
Regardless of the injection period, it is necessary to maintain a state in which high-pressure fuel equivalent to the injection pressure is stored in the high-pressure fuel source at all times, and pressure loss due to piping between the high-pressure fuel source and the fuel valve and during fuel injection must be maintained. Unless the instantaneous pressure drop caused by the discharge of fuel is compensated for, a high fuel injection rate from the fuel valve cannot be maintained and a high injection pressure cannot be achieved.

Fuel injection pressure in marine engines is usually 600 to 1500
Because it is a combustible material and has a very high pressure of Kg/cm ² , the means to alleviate pressure fluctuations in high-pressure fuel sources uses the bulk elasticity of the fuel itself, rather than the gas-pressure accumulator normally used in hydraulic pipeline systems. There is no choice but to use a pressure vessel with a high temperature.

Therefore, the volume of the pressure vessel is determined by how much pressure fluctuation range is allowed in the balance between the maximum discharge amount and the supply amount. The fuel injection period in a marine engine is approximately 30 degrees crank angle, so if the engine speed is 500 rpm, it will take approximately 10 degrees.
When considering pressure fluctuations within such a short period of time, the supply amount can be ignored in practice, so for example 1
If the discharge amount per cycle is 15ml and the allowable pressure fluctuation range within the injection period is 30Kg/ ^cm2 , then
A simple calculation requires a volume of approximately 8.5.

The structural dimensions of a pressure vessel that holds such a large amount of fuel under ultra-high pressure must be considerably larger than the dimensions of a conventional fuel injection pump for an internal combustion engine due to its strength, which increases manufacturing costs and reduces the impact on the engine. There is a problem with the installation method. Furthermore, due to the size of the pressure vessel, it is necessary to install it separately from the cylinder head where the fuel injection valve is installed.
Ultra-high pressure fuel is passed through a pressure vessel and a fuel injection valve by an injection pipe, but it is necessary to improve the strength and sealing performance of the injection pipe and joints to withstand the ultra-high pressure. Furthermore, it is necessary to supply ultra-high pressure fuel within a very short period of time through a relatively long injection pipe, and as the flow velocity in the pipe increases, as mentioned above, the pressure loss increases, and the pressure drop in the pressure vessel becomes higher than the predetermined injection pressure. Not only is it necessary to increase the original pressure, but pressure pulsations within the injection pipe can cause the pressure inside the injection pipe to become abnormally high or low, creating a risk of damage to the injection pipe and joints. There is a problem that irregular injection such as tertiary injection occurs. Furthermore, as the container holding the high-pressure fuel becomes larger and the injection pipe through which the high-pressure fuel passes becomes longer, the chances of fuel leaking increase. When high-pressure fuel leaks, it often becomes atomized, increasing the risk of fire. A fire on a ship causes great damage to the ship and the lives of its crew.

On the other hand, in order to solve the above-mentioned problem, there is a prior art that employs a pressure increasing structure using a booster applying Pascal's principle as a means for increasing the fuel injection pressure to an ultra-high pressure. In this prior art, the amount of hydraulic oil supplied to the drive-side pressure chamber at low pressure is greater than the amount of fuel injection by the pressure increase ratio.

For example, the required injection amount of fuel with an injection pressure of 1500Kg/cm ² is
If the injection time is 15 ml, if the pressure increase ratio is 7, then by simple calculation, approximately 214 kg/cm ² of hydraulic oil will be
This means that only 105 ml of water needs to be supplied within 0. Since the start of fuel injection is achieved by communicating the hydraulic oil between the pressure source and the drive side pressure chamber of the booster through the solenoid valve, the flow rate of the pressure oil through the solenoid valve is about 630/min.

Direct-acting type solenoid valves use electromagnetic force to move the spool to switch the pressure oil flow path. Direct-acting type solenoid valves use the driving force of the switched pressure oil to move the main spool and switch the pressure oil flow path. There is a pilot type. For large flow rates, when switching with direct acting type,
Since fluid force acts on the spool, making it impossible to switch, a pilot type is usually adopted. However, in the case of a pilot type, there is a limit to how fast response can be achieved due to its structure, since it requires multiple steps of operation. On the other hand, the control accuracy required for fuel injection in an internal combustion engine is 1 to 2 degrees of crank angle, and 0.3 to 0.7 degrees at a rotation speed of 500 rpm.
The time precision of 〓 is extremely small. Therefore, with the solenoid valve that handles high pressure and large flow rate as mentioned above,
It is impossible with current technology to perform highly accurate fuel injection control for internal combustion engines.

Purpose: In view of the above-mentioned problems of the prior art, the present invention provides a solenoid valve for controlling a large flow of pressurized oil to be fed to a booster with a pressure increasing structure required to increase the pressure of fuel to an ultra-high pressure, and a highly accurate fuel for an internal combustion engine. This problem is solved by sharing the fuel injection function with a small-flow solenoid valve that performs injection control, without stopping the internal combustion engine, and without depending on the rotational speed of the internal combustion engine. First, fuel injection timing and fuel injection amount,
It is an object of the present invention to provide a highly reliable and inexpensive fuel injection control device for an internal combustion engine that can easily adjust fuel injection pressure and increase the fuel pressure.

The present invention supplies hydraulic oil from the first pressure source 1 to one end of the movable bodies 7 and 8 in the booster 3 via the first electromagnetic valve 5 that is open for at least a period W2 that is longer than the fuel injection period W1. Fuel oil is introduced from the second pressure source 2 into the pressure chamber 10 on the side of the small diameter pressure receiving surface 72 at the other end of the moving bodies 7 and 8 through the first check valve 13. The fuel oil from this pressure chamber 10 passes through the second check valve 11 to the pressure accumulation chamber 12.
The fuel oil from the pressure accumulation chamber 12 is supplied to the first end of the valve body 100 that opens and closes the nozzle hole 106 of the injection valve 4.
Facing the pressure receiving surface, the first
The second of the closing piston 111 on the opposite side of the pressure receiving surface
The control piston 109 faces the pressure receiving surface 112 and operates the valve body 100.
The pressure chamber 3 on the valve body 100 side of the control piston 109 is connected to the closing piston 111 and opens during the fuel injection period W1.
8 is a conduit 43 from the first pressure source 1 and a relief conduit 45
The first pressure-receiving surface of the valve body 100 has a diameter of d1, and the second pressure-receiving surface has a diameter of d1.
The diameter of the pressure receiving surface 112 is d2, and the control piston 10
When the diameter of the valve 9 is D, D>d2>d1>d0, and the pressure Pf of the fuel oil in the pressure accumulation chamber 12 and the pressure Pa of the hydraulic oil via the conduit 43 are as follows: When closed, the nozzle hole 106
When the diameter facing the side is d0, each diameter D, d1, d
2, regarding d0, π/4(d1 ² −d0 ² )Pf+π/4(D ² −d1 ² )Pa>π/4
・This is a fuel injection control device for an internal combustion engine characterized by selecting a value such that d2 ²・Pf holds true.

Embodiments Embodiments of the present invention will be described with reference to the drawings. 1st
The figure is a configuration diagram showing a first embodiment of the present invention.
The first pressure source 1 is connected to the pressure chamber 9 from a connection port 19 of the booster 3 by a conduit 15 via a conduit 55, a check valve 17, and a first electromagnetic valve 5, and is connected to the pressure chamber 9 by a conduit 43 branching from the conduit 55. Connection port 3 of fuel injection valve 4 via check valve 42 and second solenoid valve 6
9 can be connected to the pressure chamber 38 via a passage 41. Connected to the conduits 15, 43 are accumulators 18, 44 for absorbing pressure pulsations within the conduits. The second pressure source 2 is connected to the pressure chamber 10 via a conduit 27 from the connection 21 of the booster 3 via a spring-loaded check valve 13 .

A plunger 8 that slides on an upper cylinder 67 is disposed within the booster 3, and the piston 7 and the plunger 8 are pressed against each other. The pressure chamber 9 formed by the cylinder 66 and the top 71 which is a large-diameter pressure receiving surface at the upper end of the piston 7 includes a first pressure source 1
Hydraulic oil can be supplied from the first electromagnetic valve 5 through the first electromagnetic valve 5. A check valve 11 with a spring is provided in the pressure chamber 10 formed by the cylinder 67 and a surface 72 which is a small diameter pressure receiving surface at the lower end of the plunger 8.
Pressure accumulator 12 arranged at the bottom of booster 3 via
It is connected to the. The pressure accumulation chamber 12 is connected to the fuel injection valve 4 through a passage 22 . The passage 22 communicates with a fuel reservoir 48 by a passage 35.

The fuel injection valve 4 is composed of a control section A and a valve section B.

2 is an enlarged sectional view of the section of FIG. 1; FIG. The valve body 100 includes a shaft portion 101 and a stepped portion 102.
, a small diameter portion 103 , and a tip portion 104 . The tip portion 104 is seated on the seat surface 105 to open the nozzle hole 1.
06 can be closed to bring the valve into a closed state. Fuel from the nozzle hole 106 is injected into the cylinder chamber of the diesel engine. The shaft portion 101 is the cylinder 1
07 in the axial direction.

A control piston 109 housed in a cylinder 108 in the control section A is fixed to the shaft section 101 . The control piston 109 includes a cylinder 110
The closing piston 111 is fixed by.

In the fuel storage 48, the shaft portion 101 and the stepped portion 1
02 and the small diameter portion 103 constitute a first pressure receiving surface. The outer diameter of the shaft portion 101 and the small diameter portion 103 is d.
1, d0. Top surface 1 of the closing piston 111
12 is a side opposite to the first pressure receiving surface and constitutes a second pressure receiving surface. The outer diameter of the closing piston 111 is d2
shall be. The surface of the control piston 109 facing the pressure chamber 38 constitutes a third pressure receiving surface 113. The third pressure receiving surface is oriented in the same direction as the first pressure receiving surface, and in this embodiment, facing the top surface 112, the outer diameter d1 of the shaft portion 101 is configured to be smaller than that of the closing piston.

The cylinder 107 is connected via a conduit 114 to a chamber 11 on the opposite side of the cylinder 108 from the pressure chamber 38.
5 is communicated with a tank 117 via a conduit 116.

In the first pressure source 1, the hydraulic oil is supplied from the tank 61,
The pressure is increased by a pump 58 through a filter 59. The pressure oil whose pressure has been adjusted by the pressure adjustment whip 7 is supplied to the conduit 55 via the filter 56. Second
In the pressure source 2 , fuel oil is increased in pressure from a tank 65 through a filter 64 by a pump 63 , and the pressure oil whose pressure is regulated by a valve 62 is supplied to a conduit 27 .

The maximum strokes of the piston 7 and the plunger 8 are selected such that the maximum stroke volume of the plunger 8 is slightly larger than the sum of the maximum injection amount per injection and the compressed volume of fuel required for high-pressure accumulation. By appropriately limiting this maximum stroke volume, the maximum injection amount can be specified.
For example, when the second solenoid valve 6 fails, it is possible to prevent more fuel than permissible from being supplied to the internal combustion engine.

The pressure chamber 38 of the control piston 109 is connected by means of a second solenoid valve 6 to the first pressure source 1 via a conduit 43 and to the tank via a relief conduit 45 .

A safety valve 120 is provided in communication with the pressure accumulation chamber 12 . This safety valve 120 includes a piston 121 and a spring 123 that biases the volume of the buffer chamber 122 defined by the piston 121 in a direction that reduces the volume of the buffer chamber 122.
including. When the pressure in the pressure storage chamber 12 becomes abnormally high, the piston 121 is displaced downward in FIG. It communicates with tank 65 via 125. The space 20 defined by the cylinder 66, the piston 7, and the plunger 8 is connected to the tank 65 from the connection port 26 via a conduit 28.

The operation will be explained. When the left-hand solenoid of the first solenoid 5 is energized and in position 5b, a throttle valve 60 is interposed with respect to the pressure chamber 9. The flow path is switched so that the connection port 19 of the booster 3 is communicated with the tank 61 via the return conduit 16. At this time, a check valve 13 is installed in the pressure chamber 10 of the booster 3.
Fuel is supplied from the second pressure source 2 through the conduit 27, the connection port 22 of the booster 3, and the check valve 13 at a pressure higher than the cracking pressure of is pushed up in the direction of making the top part 7 of the piston 7 smaller.
1 comes into pressure contact with the end surface 74 of the cylinder 66 and stops. The moving speed of the plunger 8 and the piston 7 is controlled by a throttle valve 60 disposed midway through the return conduit 16.
This prevents the piston 7 from running out of control due to the fuel made highly pressurized by the pump 63, and reduces the impact force at the end of the stroke.

The second electromagnetic valve 6 switches the flow path so that the right solenoid is energized and is in position 6a, so that the connection port 39 of the pressure chamber 38 communicates with the tank 61 via the relief conduit 45. In the fuel injection valve 4, the fuel oil from the passage 22 acts on the first pressure receiving surface of the valve body 100 in the fuel reservoir 48 and the upper surface of the closing piston 111 in the back pressure chamber 126. Valve body 1
The diameter of the pressure receiving surface of 00 is d1, and the closing piston 11
When the diameter of the pressure receiving surface 112 of No. 1 is d2, d2>d1 (1), so the small diameter portion 103 seats on the seat surface 105 and the valve portion B is in a closed state.

The pressure storage chamber 12 of the booster 3 stores fuel at an extremely high pressure higher than the supply pressure from the second pressure source 2 . This pressure accumulation chamber 12 has a check valve 11 and a safety valve 120.
And the valve part B makes it airtight.

Next, the solenoid on the right side of the first solenoid valve 5 is energized, and as shown in FIG.
When the flow path of the first electromagnetic valve 5 is switched to position 5a, the conduit 15 and the connection port 19 communicate with each other, and pressure oil is supplied from the first pressure source 1 to the pressure chamber 9. Therefore, the piston 7 and the plunger 8 are pushed downward in FIG. 1, compressing the fuel filling the pressure chamber 10. At this time, the accumulator 18 effectively works to prevent the pressure of the pressure oil within the conduit 15 from dropping momentarily. If the area ratio of the top surface 71 of the piston 7 to the surface 72 of the plunger 8 is K (K>1), a pressure K times the pressure in the pressure chamber 9 is generated in the pressure chamber 10 . K is called the pressure increase ratio. Increasing the pressure increase ratio and increasing the injection pressure improves the injection rate and atomizes the fuel, which improves fuel performance and is effective in reducing fuel consumption. However, if the pressure increase ratio is increased, the amount of hydraulic oil passing through the first solenoid valve 5 increases proportionally, and the first solenoid valve 5 becomes larger. The pressure in the pressure chamber 10 and the pressure in the pressure accumulation chamber 12 are almost the same, so the check valve 1
Valve 1 is closed by spring force. Second solenoid valve 6
maintains position 6a, and the valve portion is closed.

Thereafter, the second electromagnetic valve 6 operates during the fuel injection period W1 from time t2 to time t3 (however, W1<W
When the flow path is switched by 2) to position 6b, the pressure chamber 38 is connected to the first pressure source 1 and the control piston 109 is urged upward. Therefore, the resultant force of the fuel pressure acting upward on the first pressure receiving surface and the force pushing the control piston 109 upward exceeds the force pushing the closing piston 111 downward.
moves upward, and valve portion B opens. That is, the second equation holds true. Here, the pressure of the fuel oil in the pressure accumulation chamber 12 is
Let Pf be the pressure of the hydraulic oil passing through the conduit 43 and Pa. The diameter of the control piston 109 is D, and the valve body 1
00 closes the nozzle hole 106, the nozzle hole 1
When the diameter of the small diameter portion 103 facing the 06 side is d0, π/4(d1 ² −d0 ² )Pf+π/4(D ² −d1 ² )Pa>π/4d
2 ² Pf (2) Therefore, the valve body 100 is displaced upward in FIG. 1, and the fuel from the passage 35 is injected from the fuel reservoir 48 through the nozzle hole 106 during the fuel injection period W1.

After the start of injection, fuel is supplied and discharged from the pressure accumulation chamber 12 to the nozzle hole 106 via the passage 22, and
The check valve 11 opens and the pressure storage chamber 12 is supplied with high pressure fuel from the pressure chamber 10 . Upon receiving sufficient pressure oil from the first pressure source 1, the piston 7 moves to the plunger 8.
move. Therefore, the pressure chamber 10 is maintained at a high pressure, and fuel is injected and replenished into the cylinder chamber from the nozzle hole 106 while the injection pressure is maintained at a high pressure.

After the predetermined injection period W1 has elapsed, at time t3, the second solenoid valve 6 is switched to the switched position 6a, and the connection port 39 is connected to the tank 61. is tank 6
1 and loses its power. Since the cross-sectional area of the shaft portion 101 is smaller than that of the closing piston 111, the force of the closing piston 111 exceeds the force that drives the valve body 100 upward, and the valve body 100 moves downward in FIG. 1 to enter the valve closed state. becomes.

π/4d1 ² Pf<π/4d2 ² Pf ...(3) When valve part B is closed, pressure accumulator 12 and pressure chamber 1
At zero, high pressure is instantaneously generated due to the acceleration of the piston 7 and plunger 8. At this time, the pressure chamber 122 of the safety valve 120 that is open to the pressure accumulation chamber 12
The volume of is increased by the displacement of the piston 121 sliding against the spring force of the spring 123, so that the impact pressure is absorbed. In other words, the pressure chamber 122
acts as a buffer volume. When the piston 14 moves downward in FIG. 1 by more than a certain value due to some abnormality, the passage 124 communicates with the pressure chamber 122 and high pressure fuel is discharged from the flow pipe 125 to the tank 65. Therefore, the pressure accumulation chamber 12 is prevented from becoming abnormally high pressure. As the pressure in the pressure storage chamber 12 is equalized as the piston 7 and plunger 8 stop, the piston 121 is pushed back by the spring 123.

After the fuel injection ends, at time t4 in FIG. 3(1), the first solenoid valve 5 is switched to position 5b, and the flow path is switched so that the connection port 19 and the return conduit 16 communicate with each other, and the pressure chamber is closed. 9 is discharged from the return conduit 16 to the tank 61 via the throttle valve 60. At this time, as the pressure oil is discharged from the pressure chamber 9, the piston 7 and the plunger 8 move upward due to the driving force of the fuel in the pressure chamber 10, the volume of the pressure chamber 10 increases, and the pressure decreases. . Since the pressure chamber 10 is isolated from the pressure accumulation chamber 12 by the check valve 11, a high pressure is maintained in the pressure accumulation chamber 12. When the pressure in the pressure chamber 10 becomes lower than the pressure in the connection port 21 by the cracking pressure of the check valve 13, the check valve 13 opens, high-pressure fuel is supplied and removed from the second pressure source, and the piston top surface 71 becomes the cylinder. It is pressed against the seat surface 74 of 66 and stops. The opening degree of the throttle valve 60 disposed midway through the return conduit 16 is adjusted so as to limit the movement speed of the piston 7 and the plunger 8 due to the driving force of the pressure oil in the pressure chamber 10.

The flow rate of the hydraulic oil passing through the first electromagnetic valve 5 is large because the pressure increase ratio is large in order to improve combustion performance and a large injection amount is produced in a short time. When injecting 11 cc of fuel at a rotation speed of 500 rpm and a crank angle of 25 degrees, if the pressure increase ratio is 8, then Q = 6 x 500/25 x 11 x 60/1000 x 8 = 633/min... (4) This Therefore, the first solenoid valve 5 has to be of a pilot operation type, and although a pilot operation type solenoid valve has poor response, it is possible to replenish the pressure chamber 10 with fuel within a sufficiently long period of time outside the injection period. Generally, switching of the first solenoid valve 5 does not require high-speed switching as the second solenoid valve 6 does. In fact, when controlling the injection period and injection timing in units of 1 degree of crank angle in an internal combustion engine rotating at 500 rpm, the second solenoid valve 6 is required to have a responsiveness of the order of 100/500×6=0.33〓 ……(5) However, if the injection timing is 25 degrees, the first solenoid valve 5 switches the flow path between (360-25) x 1000/500 x 6 = 112 = (6), and the second solenoid valve The response should be 1/10 or more compared to 6.

In the embodiment configured as described above, ultra-high pressure fuel is accumulated for each injection cycle,
Since the booster 3 acts to constantly replenish fuel within the injection period, a stable injection rate can be obtained. A large-capacity ultra-high-pressure pressure vessel is not required.

Since the booster 3, which is a pressure accumulating container, can be miniaturized, the booster 3 can be placed close to or directly connected to the injection valve 4. Therefore, the pressure accumulator 12 which is a pressure vessel
The injection passage from the injection valve to the injection valve 4 can be shortened, pressure loss in the injection passage can be reduced, and the occurrence of fuel leakage can be suppressed by omitting piping.
Fire outbreak can be prevented.

A large-capacity ultra-high-pressure pressure vessel is not required, and pressure piping that is smaller than the injection pressure is sufficient from the hydraulic oil pressure source to the booster, so conventional piping and joints can be used and are inexpensive.

In conventional hydraulically actuated pressure booster fuel injection devices, the impact force generated when the booster piston or plunger is seated has been a problem, but in the case of the present invention, the pressure increaser has a shock absorbing piston disposed in the pressure accumulation chamber 12 and Piston 12 constituting the safety valve
1 can prevent overpressure in the pressure accumulation chamber.

By disposing the check valves 11 and 13 in the pressure accumulation chamber 12, fuel can be supplied and a small amount of fuel can be injected.

A large-capacity solenoid valve is required to supply high-pressure hydraulic oil for pressure increase, but in the past, a single injection timing system required extremely high control accuracy as well as responsiveness and reproducibility. Since this is done using a solenoid valve, it is not possible to achieve both large capacity and accuracy. In the present invention, fuel injection by hydraulic operation can be achieved by having individual electromagnetic valves 5 and 6 share the function of generating the hydraulic driving force required for pressure increase and the function of controlling the injection period.

A booster 3 and an injection valve 4 are provided for each cylinder, and the injection system is independent for each cylinder, so interference between cylinders can be prevented as in a high-pressure injection system, and
Even if such a configuration for one cylinder fails, operation of the internal combustion engine can be continued in other cylinders, so the reliability of the engine is high.

FIG. 4 is a block diagram showing a second embodiment of the present invention. This embodiment is similar to the first embodiment, and corresponding parts are provided with the same reference numerals. What should be noted is that a four-way solenoid valve is used as the second solenoid valve 6, and the pressure chambers 38a and 38b arranged on both sides of the control piston 109 are connected to the first pressure source 1 by the second solenoid valve 6. The control pistons 109 can be alternately connected to the conduits 45, and are urged downwardly in the switching position 6a and upwardly in the switching position 6b by the hydraulic fluid of the first pressure source 1. In FIG. 4, the first solenoid valve 5 is in the switching position 5c (during period W2), and the second solenoid valve 6 is in the switching position 6a, and in FIG.
It shows a state between 2. High pressure fuel oil whose pressure has been increased by the booster 3 is held in the pressure chamber 10 and the pressure accumulation chamber 12, and the valve portion B of the injection valve 4 is not yet opened. In other words, the force of the fuel oil pressure that urges the valve body 100 upward in the fuel reservoir 48 is the same as the fuel pressure that urges the closing piston 111 downward in the back pressure chamber 126, and the force that forces the control piston 109 downward in the pressure chamber 38b. Since the force is smaller than the resultant force of the force due to the urging hydraulic oil pressure, the valve body is pressed against the valve seat 105 and the valve portion B is closed.

At time T2, the second solenoid valve 6 is switched,
In the position shown at 6b, the pressure chamber 38b is connected to the relief conduit 45, the pressure chamber 38a is connected to the pressurized conduit 43, and the control piston 109 is urged upward by the hydraulic fluid of the first pressure source. fuel storage 4
The resultant force of the force of the fuel oil that urges the valve body upward at 8 and the upward force of the control piston 109 exceeds the force that urges the closing piston 111 downward in the back pressure chamber 126, and the valve body 100 moves. and valve part B
The valve opens and fuel is injected into the cylinder chamber (not shown).

At time t3, the second electromagnetic valve 6 returns to the switching position 6a, and the control piston 109 is urged downward by the pressure of the hydraulic oil. As a result, the valve body 100 moves downward, the valve part B closes, and the injection ends. In this embodiment, the outer diameter d1 of the shaft portion 101
is made slightly smaller than the outer diameter d2 of the closing piston 111, so when the hydraulic oil pressure in the conduit 43 is lost, the force that urges the closing piston 111 downward is exceeded, and the valve part B closes. This prevents unexpected spraying. Unexpected injections can lead to engine failure and fire. Since there is only a slight difference between d1 and d2, the valve body 100 can be driven with a small force. Since the outer diameter D of the control piston 109 is made larger than d1 and d2, and it generates a large force, the valve body 100 is urged with a large force (and therefore a large acceleration), and the valve part B is closed. Since this is done extremely instantaneously, so-called ``fuel depletion'' is good, which is favorable in terms of fuel efficiency.

As described above, according to the present invention, the fuel injection timing, fuel injection amount, and fuel injection pressure can be easily adjusted without stopping the internal combustion engine and without depending on the rotational speed of the internal combustion engine. It becomes possible to increase the pressure. In particular, in the present invention, the diameter d1 of the first pressure receiving surface of the valve body 100 is selected to be smaller than the diameter d2 of the second pressure receiving surface 112 of the closing piston 111, so that unexpected injection of fuel can be prevented. .

Furthermore, since the diameter D of the control piston 109 is selected to be larger than the diameters d1 and d2, the valve body 100 is biased with a large force, and the valve can be opened instantaneously, allowing the valve to be refueled at precise timing. supply.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an enlarged sectional view of the section shown in FIG. 1, and FIG. 3 is a waveform diagram for explaining the operation of the embodiment shown in FIGS. 1 and 2. 4 are configuration diagrams of still another embodiment of the present invention. 1...First pressure source, 2...Second pressure source, 3...
Booster, 4... Injection valve, 5, 6... Solenoid valve, 7
... Piston, 8 ... Plunger, 10 ... Pressure chamber, 11, 13 ... Check valve, 12 ... Pressure accumulation chamber, 1
00... Valve body.

Claims (1)

[Scope of Claims] 1. Hydraulic oil from the first pressure source 1 is supplied to the movable bodies 7, 8 in the booster 3 via the first solenoid valve 5, which remains open for at least a period W2 that is longer than the fuel injection period W1. The pressure chamber 1 is guided to the large-diameter pressure-receiving surface 71 side at one end, and the pressure chamber 1 is guided to the small-diameter pressure-receiving surface 72 side at the other end of the movable bodies 7 and 8.
0, fuel oil is supplied from the second pressure source 2 to the first check valve 1.
3, the fuel oil from the pressure chamber 10 is supplied to the pressure accumulation chamber 12 via the second check valve 11, and the fuel oil from the pressure accumulation chamber 12 is introduced into the nozzle hole 10 of the injection valve 4.
The second pressure receiving surface 11 of the closing piston 111 faces the first pressure receiving surface at one end of the valve body 100 that opens and closes 6, and is further opposite to the first pressure receiving surface at one end of the valve body 100.
2, a control piston 109 is connected to the valve body 100 and the closing piston 111 to operate the valve body 100, and the fuel injection period W1
The pressure chamber 38 on the valve body 100 side of the control piston 109 can be selectively connected to the conduit 43 from the first pressure source 1 and the relief conduit 45 by the second solenoid valve 6 which is opened at . The diameter of the first pressure-receiving surface of the valve body 100 is d1, and the diameter of the second pressure-receiving surface is d1.
The diameter of the pressure receiving surface 112 is d2, and the control piston 10
When the diameter of the valve 9 is D, D>d2>d1>d0, and the pressure Pf of the fuel oil in the pressure accumulation chamber 12 and the pressure Pa of the hydraulic oil via the conduit 43 are as follows: When closed, the nozzle hole 106
When the diameter facing the side is d0, each diameter D, d1, d
2, regarding d0, π/4(d1 ² −d0 ² )Pf+π/4(D ² −d1 ² )Pa>π/4
・A fuel injection control device for an internal combustion engine, characterized in that a value is selected such that d2 ²・Pf holds true.