JPH06100105B2 - Fuel injector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection device for an internal combustion engine, and more specifically, it is possible to control an injection waveform that directly affects combustion of the internal combustion engine, that is, an injection rate. Fuel injection device.

[Conventional technology]

In general, the performance greatly changes depending on the manner of fuel injection of the internal combustion engine, and in the case of a direct injection diesel engine, the injection rate injected from the fuel injection pump through the injection nozzle directly affects combustion.

For example, a diesel engine has a problem that the combustion noise during idling operation is large, whereas it is known that increasing the combustion injection time during idling operation is effective. Further, in the medium-speed rotation region, efficient combustion can be performed by reducing the injection rate until ignition and rapidly increasing the injection rate at ignition.

Therefore, conventionally, a fuel injection device that controls various injection rates,
For example, there are those disclosed in Japanese Patent Laid-Open No. 58-82060 and the like. However, since the fuel injection rate of these is controlled by mechanical operation of a step motor, etc., control at high speed is performed accurately. There is a problem that there is no.

In addition, according to the experiments conducted by the inventors of the present invention, there is a problem in such an accumulation type that, depending on the nozzle and the operating state, the injection from the injection valve is temporarily stopped midway and then re-injected, that is, causes two-stage injection. found.
The latter problem is that when the piston moves due to the fuel in the pump pressurizing chamber that is pressurized during the plunger pressure stroke, the moving speed of this piston becomes faster and the piston moves away from the plunger to temporarily pressurize the pump. This was due to the fact that the pressure in the room decreased and fuel was not delivered. Further, for the purpose of improving combustion at a low load, fuel injection devices for performing pilot injection have been proposed as disclosed in JP-A-60-125754 and JP-A-60-34559. ing. However, in such an injection mode, noise reduction is not reliably performed because the fuel period due to the low injection amount is still short. Further, in the case of this device, when pilot injection is performed, the hydraulic pressure in the pressurizing chamber flows out through the throttle of the adjacent piston or the like. Since this outflow amount depends on the lift amount, throttle, etc. of the balance piston urged by the spring, the outflow amount also changes with changes in the oil temperature, making it impossible to secure a stable low injection rate. There is.

Further, in JP-A-58-187537 and JP-A-56-154134, the injection of pressure oil in the pressurizing chamber is directly overflowed to the low pressure side by utilizing the opening / closing control of the solenoid valve. An injection device for adjusting and controlling the start timing and the end timing is shown. However, depending on the operating condition of the internal combustion engine, the low injection rate during the pumping process, the high injection rate, and the control such as arbitrarily adjusting the period are not performed, so that the deterioration of fuel efficiency and low load Was causing noise.

[Problems to be solved by the invention]

The present invention has been made based on such a situation, and by changing the oil feed rate of the plunger according to the operating state of the engine, a fuel injection pump that can obtain an optimum injection rate over the entire motion range of the engine. The present invention aims to provide the fuel injection device.

[Means for solving problems]

That is, to solve the above problems, the present invention provides a fuel injection device for reciprocally moving a plunger slidably inserted in a housing to pressurize and deliver fuel in a pump pressurizing chamber, wherein a cylinder is provided in the housing, A piston in the cylinder that moves in one direction by the fuel pressure of the pump pressurizing chamber is provided, and the plunger and the piston are locked at one end of the piston and a connecting portion at the tip of the plunger. An oil-tight chamber that is connected to the oil-tight chamber by the piston and the cylinder, a communication hole that opens to the oil-tight chamber and connects the oil-tight chamber and the low-pressure fuel section, the oil-tight chamber and the low-pressure chamber. A valve for controlling communication and blockage with the fuel section and an electric drive means for operating the valve are provided, and in the pressure feeding step by the plunger, the valve is Communicating the communication hole by the drive control by a gas drive means, by occlusion, and adopts a technical means that controls the movement of the piston.

[Action]

According to the present invention, with the above configuration, when the valve is electrically controlled by the electric drive means to communicate with the communication hole in the pressure feeding step, the oil-tight chamber communicates with the low-pressure fuel portion, so that the oil pressure in the oil-tight chamber decreases. Then, the piston moves integrally with the plunger via the connecting portion and the locking portion. Therefore, the actual pressing cross-sectional area by the plunger is reduced, and the injection rate is kept low. At this time, the injection rate is defined by the amount of movement of the plunger and the actual pressurization cross-sectional area, so a stable low injection rate can be secured without being affected by temperature or the like. Further, the oil-tight chamber is closed by controlling the valve to be closed by the electric drive means, the movement of the piston is stopped, the actual pressurization cross-sectional area of the plunger is increased, and the fuel delivery amount, that is, the injection rate is increased. it can. Therefore, the injection rate can be switched at any timing according to the operating conditions of the internal combustion engine, so that it can be optimally controlled over a wide range according to the operating conditions of the internal combustion engine. Since it is performed by controlling, it becomes possible to control at high speed.

〔Example〕

 Hereinafter, the present invention will be described based on examples.

1 to 7 relate to the first embodiment of the present invention. FIG. 1 is a partial cross-sectional side view showing a main part of a fuel injection device, and FIG. 2 shows a structure near the controller 30 of FIG. FIG. 3 is a detailed view, FIG. 3 is a perspective view showing the detailed structure of the tip portion of the plunger 2, FIG. 4 is a characteristic view showing the relationship between the pump cam rotation angle and the effective area of the plunger, and the injection rate. FIG. It is a characteristic view which shows the relationship between control timing and injection rate. Further, FIG. 6 is a characteristic diagram showing the relationship between the pump cam rotation angle and the oil feed amount, and FIG. 7 is a characteristic diagram showing the relationship between the pump cam rotation angle and the injection rate.

In FIGS. 1 and 2, reference numeral 1 denotes a housing, into which a plunger 2 is slidably inserted. Plunger 2
Is connected to a drive shaft 3 that rotates in synchronization with a diesel engine (not shown) via a coupling 4 and a face cam 5. The coupling 4 always transmits the rotation of the shaft 3 to the face cam 5 and the plunger 2, and allows the shaft 3 to move the face cam 5 and the plunger 2 in the axial direction.

By the sliding contact between the face cam 5 provided on the plunger 2 and the cam roller 6 provided so as to face the face cam 5, the plunger 2 is reciprocated in the number of times corresponding to the number of cylinders of the engine during one rotation thereof. When the plunger 2 in each reciprocating motion is in the suction stroke in which the plunger 2 is moved to the left in FIG. 1, the pump pressurizing chamber 7 formed at the end surface of the plunger 2 has a tip outer periphery of the plunger 2. The fuel in the pump chamber 10 is sucked through one of the plurality of suction grooves 8 provided and the suction hole 9 extending in the housing 1.
When the plunger 2 rotates, the communication between the suction groove 8 and the suction hole 9 is dropped, and at the same time, the compression stroke in which the plunger 2 moves to the right in the drawing starts, and the fuel in the pump pressurizing chamber 7 is provided inside the plunger 2. It is supplied to the discharge port 13 through the vertical hole 11 and one distribution groove 12 provided on the outer peripheral surface of the plunger 2, and reaches the fuel injection valve of the corresponding cylinder of the engine (not shown) through the discharge port 13. The spill ring 14, which is a member for adjusting the fuel injection amount, is movable on the plunger 2, opens the spill port 15 communicating with the vertical hole 11 during the compression stroke of the plunger 2, and the timing of opening this spill port 15. The fuel injection amount supplied from the discharge port 13 is determined by. When the spill port 15 is opened, the fuel in the pump pressurizing chamber 7 is returned to the pump chamber 10 through the vertical hole 11 and this hole 15.

The spill ring 14 is connected to a governor leaf 18 that responds to the movement of the flyweight 17 by a supporting lever 16, and is also connected to an adjusting lever 21 by a tension lever 19 and a main spring 20 to prevent vehicle speed or accelerator pedal depression. It is already known that the fuel injection amount control according to the above is performed.

The pump chamber 10 is filled with fuel pressurized by the feed pump 25 provided on the drive shaft 3,
Since this fuel pressure is controlled by a pressure control valve (not shown) in a known manner in relation to the engine speed, the fuel pressure in the pump chamber 10 increases as the rotation speed increases.

A controller 30 is attached to the position of the pump pressurizing chamber 7. That is, the pump pressurizing chamber 7 is substantially constituted by a space surrounded by the housing 1, the plunger 2 and the controller 30. controller
30 is shown in FIGS. Ie 34
Is a cylinder of the controller 30, which is positioned on the housing 1 by a spigot portion 32 and fixed by screwing a screw portion 33 of a body 31 of the controller onto the housing 1. The cylinder 34 of the controller 30 has a piston
35 is oiltightly and slidably inserted. Further, by fastening the body 31 to the housing 1 by the screw portion 33, the cylinder 34 is pressed against the housing 1 and the oil tightness is maintained on the surface 1a.

A connecting portion 70 for preventing the piston 35 from separating is provided at the tip of the plunger 2 and has a shape as shown in detail in FIG. Piston 35 is spring 71
Since it is urged to the right in FIG. 2 by the lock lever 78 of the piston 35 as shown in FIG.
Are connected to the connecting portion 70 at the tip of the.

72 is a communication hole that connects the suction groove 8 and the vertical hole 11 to the piston
When the locking portion 78 of the 35 blocks the spring storage hole 73,
It is provided to prevent the hydraulic lock of the pressurizing chamber.

Further, as described above, the body 31 presses and fixes the cylinder 34 to the housing 1 at the contact surface 31a of the body 31.

Further, the valve housing 100 is mounted inside the body 31, and the threaded portion 108 of the solenoid housing 107 is attached to the body 31.
The left end face of the valve housing 100 is pressed against the right end face of the cylinder 34 by being fastened to. The valve housing 100 is provided with a valve chamber 109 and a valve chamber 119.
The ball valve 101 is installed in the 09, and the ball valve 10 is installed by the spring 103.
1 is biased to the right and the ball valve 101 is the valve housing
The control hole 106 provided in 100 is closed.

A check valve 49 is mounted in the valve chamber 119, and the check valve 49 is biased to the right by a spring 48 to close the feed hole 116 provided in the valve housing 100. Further, the valve housing 100 is provided with a communication hole 104, and the control hole 106 and the feed hole 116 are connected to the communication hole 10.
It communicates with the pump chamber 10, that is, the low-pressure fuel portion via 4, 41, and 42.

The valve chamber 109 and the valve chamber 119 communicate with each other through the communication groove 111.
09 communicates with the oiltight chamber 38.

As can be seen from the above, in the state shown in FIG. 2 in which the valve ball 101 closes the control hole 106 and the check valve 49 closes the feed hole 116, the oil-tight chamber 38 and the valve chambers 109 and 119 are oil-tightly closed. It becomes a space.

Reference numeral 200 is a solenoid which is an electric drive means, 107 is a solenoid housing, 110 is a coil, 203 is a spool, 20
1 is a rear plate, 202 is a connector, and 120 is a terminal for an electrode. Further, 105 is a core, 102 is a pin, the right end of the pin 102 is press-fitted into the core 105, and the left end of the pin 102 is the ball valve 101.
The pin 102 and the inner surface of the solenoid housing 107 are slidably fitted together. The rear plate 201 is fixed by caulking at the right end of the solenoid housing 107. 67 is an O-ring for sealing.

As shown in FIG. 2, when voltage is applied to the terminal 120, the core 105
And the pin 102 moves to the left, and the left end surface of the pin 102 is the ball valve 10
When 1 is pushed to the left, the control hole 106 is opened, and the communication hole 104 and the valve chamber 109 communicate with each other.

A communication hole 102a is provided inside the pin 102 so that the core 105 can move smoothly.

The operation of the first embodiment based on the above configuration will be described.

Now, when a voltage is applied to the terminal 120 and the plunger 2 is moved to the right in the drawing to pressurize the fuel in the pump processing chamber 7 while the control hole 106 is opened, the piston 35 applies the fuel pressure to the left end surface. As it receives, the plunger 2 and the piston 35 are connected
It is moved integrally to the right without being separated by the 70 and the locking portion 78.

At this time, the fuel in the oil-tight chamber 38 is transferred to the valve chamber 10 by the piston 35.
9, passing through the control hole 106, the communication holes 104 and 41, 42, and escaped into the pump chamber 10 by an amount corresponding to the movement amount of the piston 35. When the current to the coil 110 is cut off, the core 105 and pin 10
2.The ball valve 101 moves to the right by the biasing force of the spring 103, and when the ball valve 101 reaches the position where it closes the control hole 106,
Since the fuel in the oil-tight chamber 38 has no escape, the piston 35
Almost all movements are stopped.

The actual pressure cross-sectional area of the fuel in the pressure chamber 7 when the piston 35 was moving rightward together with the plunger 2 was [the cross-sectional area of the plunger 2]-[the cross-sectional area of the piston 35]. However, the actual pressure cross-sectional area when the piston 35 is in the stopped state is about the same as the [cross-sectional area of the plunger 2], so the actual pressure cross-sectional area suddenly increases after the piston 35 stops, For example, as shown by the broken line in FIG. 4 (A), the amount of fuel delivered from the pump pressurizing chamber 7 increases. Therefore, the injection rate increases as shown in FIG. 4 (B).

On the other hand, when the plunger 2 reaches the suction stroke after the fuel has been pumped, the fuel pressure in the pump pressurizing chamber 7 decreases and the plunger 2 moves to the left, so that the connecting portion 70 of the plunger 2 moves to the piston 35. Piston while pulling the locking part 78
35 moves leftward with the plunger 2. When the piston 35 moves to the left, the pressure in the oil-tight chamber 38 drops, so that the fuel in the pump chamber 10 moves along with the movement of the piston 35 and the communication hole 4
2, 41, 104, the feed hole 116, the valve chamber 119, the communication groove 111, the valve chamber 109, and is introduced into the oil-tight chamber 38. When a current is passed through the coil 110 and the control hole 106 is opened during the suction process, the fuel in the pump chamber 10 is introduced into the oil tight chamber 38 through the control hole 106 and the valve chamber 109. Therefore, the piston 35 returns to the initial position by the next pressurizing stroke.

However, as can be seen from the above-described operation, the time when the power supply to the coil 10 is cut off determines the time when the oil feed rate suddenly increases.

Now, when the time to cut off the current flowing through the coil 110 is delayed and the time to increase the oil transfer rate is delayed from A → B → C in FIG. 6,
If the amount of oil fed when the injection valve reaches the valve opening pressure is q, the injection rate is as shown in FIG. 7 in which the states under the same conditions in FIG. Since the oil feed rate is reduced by the amount corresponding to the reduction, the injection amount within the same period is reduced. Here, if the position of the adjusting lever 21 is adjusted to lengthen the injection period, the injection rate can be changed as shown by →→ in FIG. 7 with the same injection amount.

Also, by advancing the timing of turning off the current flowing through the coil 110 and advancing the timing of increasing the oil transfer rate as shown in A to D of FIG. 6, the valve opening timing of the injection valve can be advanced from A to E. It is also possible to advance the injection timing as shown by → in Fig. 7.

Specifically, in a low speed operation range such as when the engine is idling, the combustion noise during idle operation is reduced by lowering the injection rate and extending the injection timing as shown in FIG. In particular, in a small direct injection diesel engine, combustion at low speed can be greatly improved.

In the high engine speed range, good engine performance can be obtained by increasing the injection rate and advancing the injection timing as shown in FIG.

That is, as an actual operation in the first embodiment,
As shown in Fig. 5, the timing of turning off the solenoid current with respect to the rotational position signal is calculated by a microcomputer or the like and optimally controlled at high speed in accordance with the operating condition of the engine, thereby achieving a significant improvement in engine performance. it can.

The check valve 49 is for preventing the generation of bubbles in the oil tight chamber 38 when the piston 35 moves to the left.

Further, the solenoid 200 is energized in the pump suction stroke to open the ball valve 101, and maintains the ball valve 101 in the open state even in the initial state of the pump pressure stroke, but in the open state, the core 105 of the solenoid 200 is opened. Since it is at the leftmost side in the figure and the gap with the solenoid housing 107 is small, the open state of the ball valve 101 can be maintained even with a small electromagnetic force even during the pump pressure-feeding stroke. Therefore, the solenoid 200 can use a small one.

Next, a second embodiment will be described with reference to FIG.

In contrast to the first embodiment, this embodiment is an embodiment of a structure in which a current is passed through the coil 110 to close the control hole 106.

When no current flows through the coil 110, the valve 101 'closes the control hole 106 by the weak biasing force of the spring 103', so if the pressure in the oil-tight chamber 38 rises, the hydraulic pressure will bias the spring 103 '. And the control hole 106 is opened. When a current is applied to the coil 110, an electromagnetic force is applied to the biasing force of the spring 103 ', so that the valve 101' again closes the control hole 106,
The oil-tight chamber 38 has no escape place for oil, and the movement of the piston 35 is stopped. When the right urging force of the solenoid 200 is sufficiently larger than the oil pressure of the oil tight chamber 38 and the urging force for pushing the valve 101 'to the right, such a configuration can be adopted. Since the other structure and operation are the same as those of the above-described embodiment, the same reference numerals are given and the description thereof will be omitted.

Next, a third embodiment will be described with reference to FIG.

In this embodiment, the solenoid 20 which is an electric drive means
Instead of 0, use the piezoelectric actuator 300 to control holes
It controls the opening and closing of 106.

The piezoelectric actuator 300 includes a housing 307, a piezoelectric body 303 in which a plurality of electrostrictive elements such as PZTs are laminated, a case 304 for housing the piezoelectric body 303, and a housing 307 formed by expanding and contracting the piezoelectric body 303.
Piezoelectric piston 302 that can slide inside, hydraulic connection chamber 309, pin
It is mainly composed of 301 and. The piezoelectric body 303 is an electrode terminal
It expands and contracts when a voltage is applied to 120, but since its stroke is about several tens of microns, the piezoelectric piston 30
The hydraulic connection chamber 309 between 2 and the pin 301 is filled with oil for hydraulic connection, and the cross-sectional area of the pin 301 is made smaller than the cross-sectional area of the piezoelectric piston 302 to increase the small stroke of the piezoelectric body 303. Then, the structure is transmitted to the pin 301. A check valve 305 allows only oil sucked into the hydraulic connection chamber 309. Reference numeral 310 denotes a corrugated ring-shaped leaf spring provided in the hydraulic connection chamber 309, which constantly biases the piezoelectric piston 302 in the right direction in the drawing.

In addition, since the piezoelectric body has extremely good responsiveness, the piezoelectric body can be turned on and off during fuel injection, so for example, by increasing the injection rate during injection, the injection rate is close to the end of injection. It can also be operated to lower the injection rate. Alternatively,
In the case where the injection rate drops (breathing phenomenon) due to the opening of the nozzle at the beginning of injection, it is possible to easily perform control so as to increase the injection rate only when the injection rate drops.

〔The invention's effect〕

As described above, according to the configuration of the present invention, it is possible to accurately change the fuel injection rate and optimally control the injection rate switching timing over a wide range according to the operating conditions of the internal combustion engine. In particular, the period of low injection rate during idling can be lengthened, so that more reliable noise reduction can be realized.

[Brief description of drawings]

1 to 7 relate to the first embodiment of the present invention. FIG. 1 is a partial cross-sectional side view showing the main part of a fuel injection rate control device, and FIG. 2 is a view of the vicinity of the controller 30 of FIG. FIG. 3 is a detailed view showing the structure, FIG. 3 is a perspective view showing the detailed structure of the tip portion of the flanger 2, FIG. 4 is a characteristic view showing the relationship between the pump cam rotation angle and the effective area of the plunger, and the injection rate. FIG. 6 is a characteristic diagram showing the relationship between the solenoid control timing and the injection rate, FIG. 6 is a characteristic diagram showing the relationship between the pump cam rotation angle and the oil feed amount, and FIG. 7 is a characteristic showing the relationship between the pump cam rotation angle and the injection rate. FIG. 8 is a partial sectional view showing the second embodiment, and FIG. 9 is a partial sectional view showing the third embodiment. 1 …… Housing, 2 …… Plunger, 7 …… Pump pressurizing chamber, 34 …… Cylinder, 35 …… Piston, 38 …… Oiltight chamber, 70…
… Coupling part, 78 …… Locking part, 41,42,104,106 …… Communication hole, control hole, 101,101 ′ …… Ball valve, valve, 200,300 …… Solenoid and electrostrictive actuator that serve as electric drive means.

Claims (1)

[Claims] 1. A fuel injection device for reciprocally moving a plunger slidably inserted in a housing to pressurize and deliver fuel in a pump pressurizing chamber, wherein a cylinder is provided in the housing, and the pump is provided in the cylinder. A piston that moves in one direction by the fuel pressure in the pressurizing chamber is provided, and the plunger and the piston are connected via a connecting portion at the tip of the plunger and a locking portion at one end of the piston. An oil-tight chamber that is pressurized by the piston and the cylinder, a communication hole that opens in the oil-tight chamber and communicates the oil-tight chamber with the low-pressure fuel section, and a communication between the oil-tight chamber and the low-pressure fuel section. A valve for controlling the valve and an electric drive means for operating the valve, and in the pressure feeding step by the plunger, the valve is driven and controlled by the electric drive means. Communicating the communication hole, by blockage, fuel injection system and controlling the movement of the piston.