JPH0243022B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection device for a diesel engine.

[Conventional technology]

In a diesel engine, the fuel injection amount is calculated by detecting engine operating conditions such as engine speed, accelerator opening, engine water temperature, and engine load, and the spill actuator is electrically driven to achieve this calculated injection amount. There is a system to control it. In such a system, if there is a drop in battery voltage when the engine is started, the computer stops operating, making it impossible to control the spill actuator. In this case, since fuel injection is not performed, problems such as inability to start and engine stall occur.

As a method to solve this problem, a system has been proposed in which in a gasoline-powered internal combustion engine, when the computer fails, the fuel injection valve drive circuit is disconnected from the computer and connected to a monostable multivibrator. See Utility Model Application No. 55-131534. The pulse duration of the monostable multivibrator is controlled according to the amount of intake air, making it possible to run as an evacuee in the event of a computer failure. There is also a statement that the amount increases when starting. That is,
It is understood that the purpose is to control the pulse duration of the monostable multivibrator to be longer when the computer determines that there is a failure at startup.

[Problem to be solved by the invention]

However, this conventional device does not work to ensure startup during a power failure. That is, when the power supply voltage decreases, not only the computer but also the monostable multivibrator cannot be compensated for its original operation. Therefore, even if an attempt is made to increase the pulse width, there is a possibility that the signal that causes the fuel injection valve to increase the amount required cannot be obtained, and starting cannot be ensured.

In this invention, when the power supply voltage drops, the fuel injection amount adjusting means is directly driven by the power supply, bypassing the computer.

[Means to solve the problem]

According to this invention, the fuel pumping means that pumps and sucks fuel according to the reciprocating motion of the plunger, and the fuel pumping means that is driven to be able to increase the effective stroke of the plunger by applying electricity to increase the amount of fuel injected from the fuel pumping means. a fuel injection amount adjusting means, a drive circuit for driving the fuel injection amount adjusting means, and controlling energization of the drive circuit so that a desired amount of fuel is supplied to the engine according to operating conditions. In a diesel engine equipped with an electronic control circuit, a start detection means detects when the engine starts, and a power supply voltage abnormality detection means detects a state in which the power supply voltage is lower than the normal value and the operation of the electronic control circuit cannot be maintained normally. There is also provided a fuel injection device for a diesel engine, characterized in that it is equipped with a means for maintaining the drive circuit and the power supply in a connected state and continuously energizing with the power supply voltage only at the time of starting when the power supply voltage is lower than the normal power supply voltage. Ru.

[Effect]

The starting time is detected by the starting time detection means, and when the power supply voltage abnormality detection means detects that the power supply voltage is lower than normal, the drive circuit of the fuel injection amount adjustment means is kept energized by the power supply.

〔Example〕

The present invention will be explained below with reference to the drawings. In FIG. 1, 10 indicates a main body of a diesel engine, and 12 indicates a fuel injection valve. Reference numeral 14 denotes a well-known distribution type fuel injection pump, which plays the role of supplying fuel to the fuel injection valve 12.

The fuel injection pump 14 includes one plunger 16 and is rotationally driven by a drive shaft 18 . On the drive shaft is a vane pump 20 which, during its rotation, pumps fuel received from an inlet conduit 22 into a pump chamber 24 . (The vane pump 20 is shown turned 90 degrees from its actual position.) During the rotation of the drive shaft 18, the plunger 16 reciprocates from side to side in the figure by the action of the roller 30 and face cam 32, and moves to the left. When moving, fuel in the pump chamber 24 is drawn into the discharge chamber 38 through the passage 36. In addition, the plunger 16
When the pump moves to the right, fuel in the discharge chamber 38 is supplied to the fuel injection valve 12 via a passage 40 in the plunger 16, a discharge passage 42, a delivery valve 44, and a fuel supply pipe 46.

The fuel injection amount adjusting means includes a spill ring 48 on the plunger 16 and an actuator that controls the position of the spill ring 48 in accordance with an electric signal. Moving the spill ring 48 to the right in the figure lengthens the effective stroke of the plunger 16, increasing the fuel injection amount; moving it to the left shortens the effective stroke, thereby decreasing the fuel injection amount. The control lever 50 is pivoted about a fulcrum 52, its lower end fits into an annular groove in the spill ring 48, and its upper end is connected to an actuator of the spill ring. That is, the actuator is a piston 58 and a solenoid 60.
The piston 58 is in contact with the upper end of the lever 50. The spring 62 generates a biasing force that causes the piston 58 to move to the left in the figure (in the direction of decreasing the fuel injection amount). By energizing the solenoid 60, the lever 5 resists the force of the spring 66 until it reaches a position where the current is balanced.
0 rotates counterclockwise, and the spill ring 16 moves to the right in the figure to increase the fuel injection amount.

A spill sensor 68 generates a signal according to the position of the piston 58, in other words, the position of the spill ring 16 (=fuel injection amount).

Reference numeral 70 is a control circuit with a computer function, which includes various sensors representing the operating status, most basically a sensor 72 for indicating the amount of depression of the accelerator pedal, and a sensor 72 for indicating the rotation speed of the pump drive shaft corresponding to the engine rotation speed. A signal from sensor 74 indicating . Based on the signals from these sensors, the control circuit forms a control current to the solenoid 60 to control the fuel injection amount.

FIG. 2 is a block diagram showing details of the control circuit. First, reference numeral 80 is a computer which has the role of calculating the required fuel injection amount which changes as shown in FIG. 3 depending on the engine speed N and the accelerator opening. In practice, the mapping of the fuel injection amount to the combination of engine speed and accelerator position as shown in Figure 4, and the mapping of the spill ring position to the combination of engine speed and fuel injection amount as shown in Figure 5. Two are provided, and the relationship between the spill ring position and the combination of engine speed and accelerator opening is converted from these two. 8
2 is a servo circuit that includes a differential amplifier 821, an amplifier 822, a comparator 823, and an oscillator 824. One input of the differential amplifier 821 is the CPU 80
The other input is connected to a position detection sensor 68 of the spill ring 48. Reference numeral 84 denotes a drive circuit for the spill actuator, which is basically a current amplifier consisting of a transistor Tr, and plays the role of controlling energization to the solenoid 60 of the actuator.

According to the present invention, electric signal generating means is provided for generating an electric signal to enable fuel supply for starting to the fuel injection amount adjusting means when there is a possibility that the control circuit 82 may not operate normally. In this embodiment, this means includes a voltage drop detection circuit 96, a starter switch 94, and an AND gate 92, and the output of the AND gate 92 is connected to the drive circuit 84 via an OR gate 90. That is, one input a ₁ of the OR gate 90 is connected to the comparator output of the servo circuit 82 . Also the other input a ₂ is
Connected to the output of AND gate 92. One input _b1 of the AND gate is connected to the internal fuel engine power supply +B via the starter switch 94. Also
The other input of the AND gate 92 detects abnormal operation of the computer and outputs a logical output of "1" in the event of an abnormality.
Detection circuit 9 that outputs a logic output of “0” during normal operation
Connected to 9. In this embodiment of FIG.
Reference numeral 6 is configured as a voltage detection circuit for the power supply, and when a drop in the power supply voltage is detected, it is determined that there is an abnormality and a signal is generated.

The operation of the present invention will now be described. During normal operation of the engine, the starter switch 94 is OFF. On the other hand, the operational amplifier 821 of the servo circuit 82
is determined by the accelerator position, such as the engine rotation speed, from the CPU 80. Target spill ring position corresponding to target fuel injection amount and spill position sensor 6
8 and the actual spill ring position. This is connected to comparator 8 via amplifier 822.
23 and is compared with the triangular wave from the triangular wave oscillator 824, and as a result, a pulse signal with a duty ratio corresponding to the deviation of the set spill ring position from the target spill ring position is sent to the comparator 82.
The output of 3 is obtained. This pulse signal passes through the OR gate 90 and turns on and off the transistor Tr.
A current is generated in the solenoid 60 of the spill ring actuator that causes the actual spill ring position to deviate from the target spill ring position, and as a result, the spill ring 48 moves by that amount to adjust the fuel injection amount to the target value.

Next, regarding the time of starting, the starter switch 94 is ON at the time of starting. On the other hand, if there is a problem with the power supply and there is a possibility that the computer 80 may not function normally, an output is also output from the voltage drop detection circuit 96. Therefore, AND gate 92 is turned on,
As a result, the power supply voltage is directly applied from the OR gate 90 regardless of the voltage from the servo circuit 82, and the maximum current is allowed to flow through the spill actuator solenoid 60. Therefore, the piston 58 of the spill actuator is pulled as much as possible to the left in the drawing, resulting in the spill ring 48 moving to the right in the drawing, maximizing the effective stroke of the plunger 16. Thus, the fuel injection amount is maximized. Since the necessary amount of fuel injection can be obtained at the time of starting, a stable start can always be achieved even when the computer does not function properly due to a drop in the power supply voltage. When the power supply voltage returns to normal, the voltage drop detection circuit 96 is turned off, so the AND gate 92 does not generate an output, and as a result, the OR circuit 90 outputs the signal set by the servo circuit 82 and normal control is performed. It will be done.
Therefore, even if the driver turns the starter switch 94 for a long time during startup, overrun will not occur.

FIG. 6 shows a second embodiment of the abnormality detection circuit 96, which includes an F-V converter 960 connected to the engine rotation speed sensor 4 and a rotation speed discrimination circuit 961.
It consists of FV converter 960 converts engine speed to analog voltage. Rotation speed discrimination circuit 9
61 determines whether the engine speed is below or above a predetermined value, and if it is below, it is considered abnormal and outputs "1" within the desired range. If it is above, it is considered normal and outputs "0". Therefore, the AND gate 92 is opened only when the engine speed is low and the starter is being turned, and the amount of fuel is increased at the time of starting.

In the embodiment shown in FIG. 7, abnormality detection is performed by detecting whether the CPU 80 is working normally. That is, a smoothing circuit 963 made of C and R is connected at one end to the WDT terminal of the computer, and at the other end to the AND gate 92 via an inverter 964. A constant pulse signal is output from the WDT terminal during normal computer operation, so this is smoothed by the smoothing circuit 963, but the inverter 96
4, and “0” is input to the AND gate 92.
Enter as a signal. Therefore, AND gate 92
It is turned OFF and normal control is performed. When the computer 80 is not working, no output appears at the WDT terminal, so a signal of "1" is sent from the inverter 964 to the AND gate 92, and if the starter is ON, the AND gate 92 opens, as described above. Achieves fuel increase operation at startup.

〔effect〕

According to the present invention, when there is a possibility that the computer may not work properly due to a drop in the power supply voltage at the time of starting, the computer is bypassed and the drive circuit of the fuel injection amount means is kept connected to the power supply. By driving the injection amount adjusting means, fuel necessary for starting can be secured. Since the computer is bypassed only when its normal operation cannot be ensured, fuel supply is controlled by the control circuit during normal operation, which occupies most of the time.
That is, the uncontrolled range that is not controlled by the control circuit is reduced compared to the conventional system, and it is possible to approach an ideal fuel supply state.

Furthermore, in a diesel engine, the maximum amount of fuel injection is limited by the mechanical stroke of the plunger, and even with a simple configuration like the one in this invention where electricity is always applied at startup, the fuel injection valve will not open continuously. , the fuel injection amount is increased within the range up to its maximum value, and good startability can be maintained. Continuous energization of the actuator is only intended for temporary malfunctions during startup, so
Even if there is an abnormality in the calculation unit during normal driving, maximum fuel injection will not continue, and there is no risk of overrun, making the structure safe. That is,
Diesel engines use compression self-ignition when there is excess air, so combustion will occur even if the amount of fuel injected is greater than necessary, so if the amount of fuel injected is kept fixed at the maximum value during normal driving, overrun is likely to occur. By adopting the configuration of the present invention, it is possible to achieve the original purpose of improving startability in a diesel engine, while also meeting safety requirements during normal driving.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of the fuel injection amount control device according to the present invention, Fig. 2 is a block diagram of the control circuit, Fig. 3 is a graph of the relationship between engine speed and fuel injection amount, and Fig. 4 is an accelerator. Fig. 5 is a mapping diagram of fuel injection amount for combinations of position and engine rotation speed, Figure 5 is a mapping diagram of spill position command voltage for combinations of fuel injection amount and engine rotation speed, and Figures 6 and 7 are the above detection circuits. The figure which shows another Example. 48... Spill ring, 58... Spill ring actuator piston, 60... Spill ring actuator solenoid, 68... Spill ring position sensor, 70... Control circuit, 80... Computer, 82... Servo circuit, 84... Drive circuit ,90...
OR gate, 92...AND gate, 96...abnormality detection circuit.

Claims (1)

[Claims] 1. A fuel pumping means that pumps and sucks fuel according to the reciprocating motion of the plunger, and a fuel injection amount adjustment device that is driven to increase the amount of fuel injected from the fuel pumping means by increasing the effective stroke of the plunger when energized. a drive circuit for driving the fuel injection amount adjusting means; and an electronic control circuit for controlling energization of the drive circuit so that a desired amount of fuel is supplied to the engine according to operating conditions. In a diesel engine, a starting detection means detects when the engine is started, a power supply voltage abnormality detection means detects a state in which the power supply voltage is lower than the normal value and the operation of the electronic control circuit cannot be maintained normally; 1. A fuel injection device for a diesel engine, characterized by comprising means for continuously energizing with the power supply voltage by keeping the drive circuit and the power supply in a connected state only when the power supply voltage is lower than the normal starting time.