JP2502301Y2 - Fuel injection device for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a fuel injection device for a diesel engine.

(Prior Art) In order to achieve low fuel consumption, high output, and low pollution of a diesel engine, there is a fuel injection device that controls the injection timing and injection rate by changing the prestroke (static injection start) of the fuel injection pump. Yes (Motor Vehicle Vol. 39, No. 1, January 1, 1989, published by Kudan Shobo, see).

(Problems to be solved by the invention) In this injection rate variable fuel injection device, when a failure occurs in the power supply circuit of the control unit, high-load high-speed operation is performed with the prestroke largely shifted from the target value. It is possible that If fuel is increased through the boost compensator provided in the fuel injection pump at the time of this failure, the internal pressure of the nozzle tube becomes excessive and causes a secondary failure of the injection system, or the internal pressure of the engine becomes excessive. Therefore, there is a problem that the engine body may be damaged. Especially when the actuator is fixed at the pre-stroke maximum position due to the disconnection of the power circuit,
Since the cam that drives the plunger of the fuel injection pump always uses the nose portion to inject fuel, cam wear is promoted and the injection pump is likely to deteriorate.

The present invention aims to solve these conventional problems.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an actuator for adjusting a prestroke of a fuel injection pump, and a fuel injection by sending a prestroke drive signal to the actuator according to an engine operating state. In a fuel injection device for a diesel engine, which includes a control unit for controlling the fuel injection rate and the injection timing, and a boost compensator for adjusting the fuel injection amount by the boost pressure introduced from the intake pipe, the control unit is closed when the power circuit of the control unit is energized. And a three-way solenoid valve that cuts off the boost pressure introduced to the boost compensator and releases it to the atmosphere when the control unit is not energized via the relay.

(Operation) Based on the above configuration, when the power supply circuit of the control unit is disconnected, the relay opens to shut off the boost pressure introduced to the boost compensator by the three-way solenoid valve and release it to the atmosphere. It is possible to prevent a secondary failure of the fuel system without increasing the amount.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, 1 is a direct injection diesel engine, 2
Is a fuel injection pump provided with an injection rate variable mechanism, and 3 is an actuator for driving the injection rate variable mechanism. The control unit 4 inputs a rack position signal, a water temperature signal, a rotation signal, a prestroke position signal, etc., and sends a prestroke drive signal to the actuator 3 according to the engine operating state to control the fuel injection rate and the injection timing. .

The fuel injection pump 2 is provided with a boost compensator 8 as a fuel increasing mechanism required for an engine with a supercharger.
The boost compensator 8 receives a boost pressure from the air supply pipe 7 through the pipe 10, and when the boost pressure overcomes the tension of the spring incorporated therein, the diaphragm and the push rod are pushed to increase the fuel injection amount. It has become.

Actuator 3 connected to control unit 4
A normally closed relay 6 is provided in the middle of the power supply circuit 5.
The control unit 4 energizes and opens the relay 6 when the actuator 3 fails or the sensors fail.
A control means for stopping the energization of the actuator 3 is provided.

Further, a normally open relay 16 that is closed when the power supply circuit 15 of the control unit 4 is energized is provided. A fuse 17 and a key switch 18 are provided in the middle of the power supply circuit 15.

Piping 10 that guides boost pressure to boost compensator 8
A three-way solenoid valve 9 is installed in the middle of the
Is energized and controlled via a relay 6 provided in the actuator power supply circuit 5 and a relay 16 driven by a control unit power supply circuit 15.

With such a configuration, the relay 16 is closed when the power supply circuit 15 of the control unit 4 is energized, and the relay 6 is closed when the actuator 3 and the sensors are normal. The three-way solenoid valve 9 has its valve body 12
Closes the atmosphere release port 11 and opens the pipe 10, and boost pressure increases fuel at high speed.

On the other hand, if the current supplied to the control unit 4 is stopped due to some cause such as disconnection of the power supply circuit 15 or disconnection of the fuse 17, the relay 16 is opened.

In addition, as shown in FIG. 4, when the sensor 3 is disconnected or short-circuited and the position of the actuator 3 cannot be detected, the actuator 3 is further disconnected, shorted, stuck or stuck, and the prestroke When the target value is no longer followed, the prestroke position control by the control unit 4 is stopped and the relay 6 of the power supply circuit 5 is opened.

In either case, energization of the three-way solenoid valve 9 is stopped, and as shown in FIG. 3, the valve body 12 of the three-way solenoid valve 9 is opened to the atmosphere release port.
Open 11 and shut off the intake pipe side of the pipe 10. Therefore, the boost pressure is not introduced into the boost compensator 8, and the diaphragm and the push rod are held in the initial position by the tension of the spring incorporated in the boost compensator 8, and the fuel injection amount is not increased. As a result, it is possible to reduce the pressure of the nozzle tube that guides the injected fuel from the fuel injection pump 2 and prevent a secondary failure in the fuel injection system and the engine body.

(Effect of the Invention) As described above, according to the present invention, the control unit is provided with a relay that closes when the power circuit of the control unit is energized, and the boost pressure introduced to the boost compensator is cut off via this relay when the control unit is not energized. Since it is equipped with a three-way solenoid valve that releases air to the atmosphere, the fuel injection pump will not be fixed at the maximum injection position when the power supply circuit of the control unit is disconnected due to a blown fuse, etc. It is possible to prevent the deterioration of the injection pump and the secondary failure of the injection system and the engine body.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 and 3 are diagrams showing the operating state of a three-way solenoid valve, and FIG. 4 is a flow chart showing the operation. 1 ... Engine, 2 ... Fuel injection pump, 3 ... Prestroke actuator, 4 ... Control unit, 8 ... Boost compensator, 9 ... Three-way solenoid valve, 15 ... Control unit power circuit, 16 ... Relay .

Claims (1)

(57) [Scope of utility model registration request] 1. An intake pipe, comprising: an actuator for adjusting a prestroke of a fuel injection pump; and a control unit for sending a prestroke drive signal to the actuator to control a fuel injection rate and an injection timing according to an engine operating state. In a fuel injection device of a diesel engine equipped with a boost compensator for adjusting a fuel injection amount by a boost pressure derived from, a relay that is closed when the power supply circuit of the control unit is energized is provided, and the control unit is de-energized through this relay. A fuel injection device for a diesel engine, comprising a three-way solenoid valve for interrupting the boost pressure sometimes introduced to the boost compensator and releasing it to the atmosphere.