JPS62223453A - Fuel injection system for internal combustion engine - Google Patents

Abstract

PURPOSE:To simplify a unit injector itself in structure, and aim at miniaturization and low-unit cost of production as well as to improve the reliability of injection timing, by controlling a fuel high-speed pressure control valve, using an electrostrictive element, with a control unit. CONSTITUTION:Fuel is fed to a pressure chamber at each unit injector 1 from a fuel feeding source 14 via each inlet check valve 15. Next, a plunger 3 is pushed up by a cam 7 rotating synchronously with rotation of a crankshaft whereby the pressure chamber 4 is filled up with pressurized fuel, and a part of this fuel passes through each outlet check valve 21, then it is led into a high-speed pressure control valve 31 alone. An electrostrictive element is built in this high-speed pressure control valve 31, and it expands or contracts with an actuating signal for injection timing setting use to be emitted by a control unit 41, opening or closing the control valve 31. Therefore, injection timing of the pressurized fuel in each high-pressure chamber 4 comes to be controlled by the high-speed pressure control valve 31 alone is consequence so that reliability is improved and simultaneously the unit injector 1 is simplified in structure, thus miniaturization and low-unit cost of production are well promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention mainly relates to a fuel injection device for a pressurized combustion type internal combustion engine such as a diesel engine.

(Prior Art) As a fuel injection device for a diesel engine, there is a conventional one disclosed in Japanese Patent Application Laid-open No. 155568/1983.

This fuel injection device is installed in a cylinder so as to be able to reciprocate, forms a pressure chamber into which fuel from a fuel supply source flows, and is driven by a cam linked to a crankshaft to fill the pressure chamber. A plunger that pressurizes, an injection nozzle that injects fuel when the pressure in the pressure chamber reaches a predetermined pressure, an on-off valve provided in a fuel passage connecting the fuel supply source and the pressure chamber, and fuel downstream of the on-off valve. The fuel pressure control means is provided in the fuel passage and controls the pressure within the fuel passage.

(Problems to be Solved by the Invention) However, the conventional fuel injection device not only needs to be equipped with an on-off valve for each cylinder, that is, each unit injector, but also is driven by a linear motor as a fuel pressure control means. Since a pressure control valve is used, the structure is complicated and manufacturing costs are high. Also, since the on-off valve is built into the unit injector, the unit injector becomes large and its installation in the engine room is restricted. There was a problem with being exposed.

Furthermore, since a plurality of on-off valves and pressure control valves have to be controlled, it is difficult to control the injection timing, resulting in low reliability.Furthermore, the piping is complicated, and installation work on the vehicle is troublesome.

Structure of the Invention (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention includes a plunger that is reciprocatably inserted into a cylinder, and a pressure at which fuel from a fuel supply source flows into the cylinder. A unit injector comprising an injection nozzle forming a chamber and injecting fuel when the plunger is pressurized by a driving device operated in synchronization with rotation of a crankshaft and the pressure in the pressure chamber reaches a predetermined pressure or higher. an inlet check valve disposed in a fuel supply passage communicating between the fuel supply source and the pressure chamber of the unit injector; an inlet check valve disposed in a fuel control passage communicating the pressure chamber and the fuel supply source; a pressure control valve for controlling the pressure within the fuel control passage; an outleft check valve disposed upstream of the pressure control valve with respect to the fuel control passage; and an outleft check valve provided with respect to the fuel control passage; a pressure sensor disposed upstream of the pressure control valve; outputting an operation signal for setting the injection timing in synchronization with the rotation of the crankshaft to close the pressure control valve; and a control device for opening the pressure control valve when the pressure in the fuel control passage becomes equal to or higher than a predetermined pressure by a sensor.

(Operation) When the internal combustion engine is operated, fuel at a predetermined pressure is supplied from the fuel supply source to the pressure chamber of the unit injector via the in-left check valve, and the plunger is reciprocated at a predetermined cycle by the driving device.

When an operation signal for setting injection timing is input from the control device to the pressure control valve, the fuel control passage is closed by the pressure control valve. As a result, the pressure chamber is pressurized by the pressurizing operation of the plunger, the pressurized fuel in the pressure chamber acts on the injection nozzle, and fuel is injected from the injection nozzle into the combustion chamber.

When the pressure in the fuel control passage rises above a predetermined pressure, the operating signal from the control device is stopped and the pressure control valve is opened, so that the pressure chamber is connected to the fuel tank of the fuel supply source via the fuel control passage. The pressure inside the pressure chamber decreases and fuel injection from the injection nozzle is stopped.

(Example) Hereinafter, a first example in which the present invention is embodied as a fuel injection device for a diesel engine will be described based on FIGS. 1 to 3.

FIG. 1 shows the entire unit injector 1 that is installed in each cylinder of a diesel engine and injects fuel into a combustion chamber. A plunger 3 is inserted into a bore 2a of a cylinder 2 formed in the upper part of the unit injector 1 so as to be movable up and down, and the lower end surface of the plunger 3 and the pore 2a are inserted into the bore 2a.
A pressure chamber 4 is formed by the bottom of the pressure chamber 4 . A retainer 5 is fixed to the upper end of the plunger 3, and the housing 2
It is urged upward by a spring 6 interposed between. A cam 7 that rotates in synchronization with the rotation of a crankshaft (not shown) is always in contact with the upper surface of the retainer 5. In order to sequentially change the fuel injection timing for each cylinder, the cams 7 are installed at different phases as shown in FIG.

A housing 8 is integrally formed on the outside of the cylinder 2, and a fuel supply passage 9 is formed in the housing 8, and the passage 9 is connected to a fuel tank 11, a fuel pump 12, and a low pressure relief valve by a fuel supply pipe 10. The fuel supply source 14 is connected to the pump 12 and is configured to supply low-pressure fuel (for example, 4 to 8 kg/co!) to the pressure chamber 4. The housing 8 includes an in-left check valve 15 for preventing the fuel in the pressure chamber 4 from flowing back toward the fuel pump 12 side.

The check valve 15 includes a main body 16, a ball valve 17 housed in the main body 16, and a spring 18 that urges the ball valve 17 to a closed position. Similarly,
A fuel control passage 19 is formed in the housing 8 , and the passage 19 is connected to the fuel tank 11 via a fuel control line 20 . The control passage 19 has a built-in outlet check valve 21 configured similarly to the check valve 15 for preventing backflow of fuel from the fuel tank 11 to the pressure chamber 4.

Next, the fuel injection nozzle 22 attached to the lower end of the cylinder 2 will be explained. A nozzle body 23 is fixed to the lower end of the cylinder 2 by a holding cylinder 24, and a needle valve is provided inside the nozzle body 23. 25 are accommodated. A stopper 26 is interposed between the cylinder 2 and the nozzle body 23 to restrict the upward movement of the needle valve 25, and a retainer 27 is fixed to the upper end of the needle valve 25 and a housing hole is formed in the lower half of the cylinder 2. A spring 28 is installed between the needle valve 2b and the bottom surface, which always biases the needle valve 25 downward, that is, in the closing direction.

A fuel reservoir chamber 29 is formed in the nozzle body 23, and the outer peripheral surface of the needle valve 25 corresponding to the classroom 29 is connected to a pressure receiving surface 25a.
It is said that The fuel reservoir chamber 29 includes a fuel pressure feeding passage 3 formed in the cylinder 2, the stopper 26, and the nozzle body 23.
0 communicates with the pressure chamber 4. When the plunger 3 is moved downward and the pressure within the pressure chamber 4 becomes a high pressure equal to or higher than a predetermined pressure, this high pressure is applied to the pressure receiving surface 25.
a, the needle valve 25 is moved upward against the biasing force of the spring 28, and fuel is injected into the combustion chamber from the injection port 23a. The accommodation hole 2b is communicated with the fuel tank 11 through a leak pipe.

As shown in FIG. 2, a direct type high-speed pressure control valve 31 is disposed in the middle of the fuel control line 20. The high-speed pressure control valve 31 is connected to the control line 20 as shown in FIG. A holder 35, a poppet 36 fixed to the holder 35 of 32 valve chambers, and the valve body 34.
a housing tube 37 connected to the housing tube 37; an electrostrictive element 38 built in the housing tube 37 and held by the holder 35;
Furthermore, it comprises an adjustment bolt 39 which is screwed into the housing cylinder 37 and adjusts the positions of the electrostrictive element 38 and the poppet 36, that is, the initial position of the valve. The electrostrictive element 38 is connected to the control device 4 by a lead wire 40.
1, and quickly expands and closes the control pipe 20 in response to a voltage as an operation signal for setting the injection timing from the control device 41, and conversely contracts when the voltage is cut off. The control conduit 20 is opened. In addition, when the strain force of the electrostrictive element 38 is <50μ, the diameter of the valve seat 33 is 5φ, and the fuel pressure is 250 kg/cd, 7//
About min of fuel is leaked.

Further, a pressure control valve 31 is provided in the fuel control pipe 20.
A pressure sensor 42 is arranged so as to be located upstream of the
A detection signal from the sensor 42 is input to the control device 41 via a lead wire 43. and,
When the pressure in the control pipe 20 reaches a predetermined pressure or higher, the voltage supplied from the control device 41 to the electrostrictive element 38 of the pressure control valve 31 via the lead wire 40 is cut off, and the electrostrictive element 38 The poppet 36 is moved away from the valve seat 33 to open the fuel control pipe 20 and allow fuel to leak from the pressure chamber 4.

Note that the low-pressure fuel supply source 14 and high-speed pressure control valve 3 described above
1. The control device 41 is installed at an arbitrary position in the vehicle, etc., not far from the engine body.

Next, the operation of the diesel engine fuel injection device configured as described above will be explained.

When the engine is started and the fuel is pressurized to a predetermined pressure by the low-pressure fuel supply source 14, when the plunger 3 of the unit injector 1 is in the suction process in relation to the cam 7,
The in-left check valve 15 is opened, and the fuel is guided to the pressure chamber 4 through the fuel supply line 10.

When the plunger 3 of the unit injector 1 is pressed by the cam 7, the plunger 3 moves downward and the pressure chamber 4 is pressurized, the pressure inside the pressure chamber 4 is increased and fuel can be injected. . However, at times other than the fuel injection time, the operating voltage is not applied to the electrostrictive element 38 from the control device 41.
Since the high-speed pressure control valve 31 is open, the control pipe 2 is supplied from the pressure chamber 4 of the gold cylinder through the control passage 19 and the outlet check valve 21.
0, the fuel is returned to the tank 11, and therefore no fuel is injected from the injection nozzle 22 in any cylinder.

Now, when an operating voltage is supplied from the control device 41 to the high-speed pressure control valve 31 at a timing suitable for combustion based on a signal from an engine rotation angle sensor (not shown), etc., the pressure control valve 31 20 is closed, high pressure is generated in the pressure chamber 4 by the lower pressure of the plunger 3 by the cam 7 of the uppermost unit injector 1 shown in FIG. 2, and high pressure fuel passing through the fuel passage 30 causes
The needle valve 25 is moved upward and fuel is injected into the combustion chamber.

During fuel injection, the fuel pressure is monitored by the pressure sensor 42, and the detection signal of the pressure sensor 42 is fed back to the control device 41, and the control device 41 determines the timing at which the high-speed pressure control valve 31 opens the control pot 20. By controlling the above, it is possible to control the desired fuel pressure, that is, the injection rate.

Then, when the control line 20 is opened again by the high-speed pressure control valve 31, the fuel is returned to the tank 11 again, and fuel injection is completed.

In the case of a four-cycle engine, the operation of the unit injector 1 installed in each cylinder of the engine requires two rotations of the engine shift, that is, one injection per rotation G of the cam 7. Therefore, in the case of a four-cylinder engine, the high-speed pressure control valve 31 intermittently sequentially injects fuel four times per two rotations.

Further, when any one of the unit injectors 1 is injecting fuel, the outlet check valve 21 prevents high-pressure fuel from flowing into the pressure chamber 4 of the other unit injector 1.

Now, in the first embodiment of the present invention, fuel can be supplied from the fuel pump 12 of the fuel supply source 14 to the pressure chamber 4 of each unit injector 1 via the fuel supply pipe 10. An inlet check valve 15 is interposed, the pressure chamber 4 and the fuel tank 11 are communicated through a control pipe 20, and a pressure control valve 31 is provided in the middle of the cough pipe 20.
Further, a pressure sensor 42 is disposed in the control pipe 20 so as to be located upstream of the pressure control valve 31,
a control device 41 for cutting off voltage to the pressure control valve 31 when the pressure of the pressure sensor 42 reaches a predetermined pressure;
As a result, the structure of the unit injector 1 itself can be simplified, the engine can be made smaller, and costs can be significantly reduced. At the same time, installation in the engine room has been improved, and pressure control according to the fuel injection timing has been achieved. Since only one valve 31 needs to be controlled, fuel injection timing can be easily managed and reliability can be improved.

Furthermore, since the outlet check valve 21 is provided between the pressure control valve 31 and the unit injector 1, the fuel pressure chamber 4 in the control pipe 20
It is also possible to eliminate backflow and prevent irregular injection due to pressure waves.

Further, in the first embodiment, since the pressure control valve 31 can be closed according to the operation command from the control device 41 to accurately control the injection timing, the machining accuracy of the shape of the cam 7 can be reduced. It also has the advantage of not having to be raised.

Furthermore, in the first embodiment, only two piping systems, the fuel supply pipe lO and the fuel control pipe 20, are required, so the piping system is simplified, and from this point of view as well, the ease of installation in the engine room is improved.

Furthermore, in this first embodiment, the electrostrictive element 38 is used in the pressure control valve 31, and a feedback system using the pressure sensor 42 is adopted, so the responsiveness of the pressure control is very fast.
- Injection rate control during the injection period becomes difficult, and it is possible to improve controllability.

Next, a second embodiment of the present invention will be described based on FIGS. 4 and 5.

This embodiment uses the plunger 3 described in the first embodiment.
As the drive device, a solenoid valve system is used instead of a cam system. The difference between this second embodiment and the first embodiment is that a housing 45 is installed on the upper surface of the cylinder 2, and a piston 46 fitted into the plunger 3 is housed inside the housing 45. . A working chamber 47 is formed in the upper part of the piston 46, and a low pressure chamber 48 is formed in the lower part.
A spring 49 is interposed between the two and always urges the plunger 3 upward. The working chamber 47 is a conduit 50
The fuel pump 12 is connected to the fuel supply pipe 10 by a fuel injection timing setting operation signal output from a control device 41 via a lead wire 51 to the pipe 50.
An electromagnetic valve 52 is interposed to be switched between a communication port 52a communicating with the fuel tank 11 and a cutoff port 52b communicating with the fuel tank 11 via a leak pipe 53.

The low pressure chamber 48 is connected to the fuel tank 11 by a leak pipe 54.
are in constant communication. Moreover, this low pressure chamber 48 is connected to the communication path 5.
5 communicates with the accommodation hole 2b.

Therefore, in this second embodiment, when an operation signal is output from the control device 41 to the solenoid valve 52, the solenoid valve 52 is switched from the cutoff port 52b to the communication port 52a, and fuel is supplied to the working chamber 47. Since the plunger 3 is moved downward against the biasing force of the spring 49 and pressurizes the pressure chamber 4, fuel injection is performed thereafter in the same manner as in the first embodiment described above.

In this second embodiment, the driving of the plunger 3 is controlled by the solenoid valve 52, so compared to the cam method of the first embodiment described above, flexible control is possible, excellent controllability, and stable idling operation. It is possible to achieve low vibration, low vibration, and low noise.

Further, in the second embodiment, the power transmission mechanism can be omitted compared to the cam type, and as a result, the device can be made more compact than the first embodiment, and the area where it can be placed in the engine room is wider.

Other functions and effects in this second embodiment are similar to those in the first embodiment.

Note that the present invention can also be embodied as follows.

(1) The electrostrictive element 38 is a piezoelectric element.

(2) The inlet check valve 15 and the outlet check valve 21 are arranged in the middle of the fuel supply pipe 10 and the fuel control pipe 20.

(3) The high-speed pressure control valve 31 should be a solenoid valve (path shown).

Effects of the Invention As detailed above, the present invention simplifies the structure of the unit injector itself, downsizes the engine, significantly reduces costs, and requires only one pressure control valve to be controlled. Therefore, fuel injection timing can be easily managed and reliability can be improved. Furthermore, since there is an outleft check valve between the pressure control valve and the unit injector, it is possible to prevent fuel from flowing back into the pressure chamber from the control passage at the start of injection, thereby eliminating irregular injection due to pressure waves.

Furthermore, since the piping system of the present invention is simplified, it has a very advantageous effect when mounted on a vehicle.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of only the central part of a unit injector showing a first embodiment embodying the present invention, Fig. 2 is a road body circuit diagram showing the entire fuel injection system, and Fig. 3 is a diagram of a high-speed pressure control valve. FIG. 4 is a longitudinal sectional view of the central portion of only a unit injector showing a second embodiment of the present invention, and FIG. 5 is a circuit diagram showing the whole. Unit injector 11 cylinder 2, plunger 3,
Pressure chamber 4, spring 6, cam 7, housing 8, fuel supply passage 9, fuel supply pipe 10° fuel tank 11, fuel pump 12, low pressure relief valve 13, fuel supply source 14, inlet check valve 15, fuel control passage゛19
, fuel control line 20, out-left check valve 21, injection nozzle 22, nozzle body 23, needle valve 2
5, Spring 28, Fuel reservoir chamber 29, High speed pressure control valve 3
1. Valve body 34, electrostrictive element 38, lead wire 40°43.
51, control device 41, pressure sensor 42, housing 45
, piston 46, working chamber 47, low pressure chamber 48, conduit 50,
Solenoid valve 52, fuel leak pipe 53.54°

Claims (1)

[Claims] 1. A drive system in which a plunger is reciprocatably inserted into a cylinder, a pressure chamber is formed in the cylinder into which fuel from a fuel supply source flows, and the plunger is operated in synchronization with the rotation of a crankshaft. a unit injector equipped with an injection nozzle that injects fuel when the plunger is pressurized by a device and the pressure chamber becomes equal to or higher than a predetermined pressure; and a fuel unit that communicates the fuel supply source with the pressure chamber of the unit injector. an inlet check valve disposed in the supply passage; a pressure control valve disposed in a fuel control passage communicating the pressure chamber and the fuel supply source for controlling the pressure in the fuel control passage; an outlet check valve located upstream of the pressure control valve with respect to the fuel control passage; and a pressure sensor similarly located upstream of the pressure control valve with respect to the fuel control passage. , when the pressure control valve is closed by outputting an operation signal for setting the injection timing in synchronization with the rotation of the crankshaft, and when the pressure in the fuel control passage becomes equal to or higher than a predetermined pressure by the pressure sensor; A fuel injection device for an internal combustion engine, which includes a control device for opening a pressure control valve. 2. The fuel injection device for an internal combustion engine according to claim 1, wherein the drive device that pressurizes the plunger is a cam mechanism rotated in synchronization with rotation of a crankshaft. 3. The drive device that pressurizes the plunger includes a housing attached to the cylinder of the unit injector, a piston attached to the plunger that divides the housing into a working chamber and a low pressure chamber, and a piston that connects the working chamber and the fuel supply source. a solenoid valve that is disposed in the middle of a communicating fuel supply pipe and can be switched between two ports: a communication port that communicates the working chamber with the fuel supply pipe; and a cutoff port that communicates with a fuel tank of a fuel supply source; The fuel injection device for an internal combustion engine according to claim 1, comprising a fuel leak pipe communicating the low pressure chamber and the fuel tank. 4. The pressure control valve includes a valve body having a valve seat and a valve chamber;
a housing cylinder attached to the valve body; a housing cylinder housed within the housing cylinder;
an electrostrictive element that is expanded and contracted by a current from a control device;
It is composed of a poppet that is fixed to the electrostrictive element and opens and closes the valve seat, and an adjustment bolt that is screwed into the housing cylinder and adjusts the position of the electrostrictive element, that is, the amount of opening and closing of the poppet. A fuel injection device for an internal combustion engine according to claim 1.