JPS6160971B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel control system for a diesel engine of direct injection type and having a unit injector.

As shown in Figure 1, a conventional fuel control system consists of a gear pump 2, a governor 4, a flyweight 5, and an MVS.
(Mechanical variable speed) governor 10,
It is equipped with a shaft off valve 13, an injector 15, etc., and has two main control functions. One is the gear pump 2 that pressurizes the fuel in the fuel tank 1, and the governor 4 that controls the flyweight 5, which is linked to engine rotation, the governor spring 6, and the fuel pressure (hereinafter referred to as fuel pressure).
A function that determines acceleration horsepower, maximum horsepower, maximum torque, or torque curve by regulating the fuel pressure at each rotation speed by balancing the three factors.
In the MVS governor 10, the fuel pressure from the gear pump 2 and the MVS governor spring 12 are balanced to keep the engine speed constant regardless of the load depending on the position of the throttle lever 11.

However, in the conventional fuel control device described above, there are many combinations of the characteristics of the governor spring 6, the size of the button 7, the governor plunger 8, etc., and it is difficult to change the characteristic curve of the engine torque, horsepower, etc. as desired. The disadvantage was that it was difficult to

The present invention was made for the purpose of eliminating the above-mentioned drawbacks, and it is possible to control the engine speed by controlling the supply pressure of the electric pump, and also to control black smoke during sudden acceleration, intake pressure or cooling water temperature. The present invention provides a fuel control device for a diesel engine that corrects horsepower based on the above.

Hereinafter, the present invention will be explained in detail based on one embodiment of the accompanying drawings.

FIG. 2 is a diagram illustrating the principle of the present invention. When controlling the engine rotation speed in a diesel engine equipped with a unit injector 31, the engine rotation is adjusted by adjusting the fuel pressure supplied to the injector 31. Focusing on the fact that it is possible to
The throttle sensor 4 detects the rotational speed of the throttle sensor 4.
2 detects the position of the throttle lever 41, and based on these detected values, the controller 50 controls the electric pump 2.
The rotational speed is controlled by controlling the fuel supply power of the engine 1.

FIG. 3 is a diagram showing an embodiment of a fuel control device 50 according to the present invention, in which an oil pump 22 of an electric pump 21 is rotationally driven by a motor 23 and is connected to an oil supply pipe 10 from a fuel tank 1 via a filter 20.
Fuel is pressurized to diesel engine 30.
are supplied to each of the injectors 31a to 31d. The pressure flow characteristics of this electric pump 21 are given by the following equation.

PQ=kVIa (1) where k is a proportionality constant, P is the pump discharge pressure, Q is the discharge flow rate, V is the motor terminal voltage, and Ia is the armature current.

As is clear from the above equation (1), the pressure P is proportional to the motor armature current Ia. Therefore, the pressure P can be limited by detecting the armature current Ia of the motor 23 and limiting the current. From this, it can be seen that it is sufficient to simply replace the mechanical engine speed-fuel pressure characteristic with the engine speed-armature current characteristic. Therefore, the engine rotation speed-armature current characteristic is created by the function generator 52, and while the engine rotation speed is being controlled, the set output of this function generator 52 is applied to the motor 2 of the electric pump 21.
Make sure that the armature current in step 3 does not exceed. In order to achieve this, a minor loop for controlling the rotational speed of the electric pump is created in the engine rotational speed control loop, and a current limit is applied to the motor 23 within this loop.

In addition, if the rotation speed of the electric pump cannot be detected, the rotation speed of the motor is calculated using the characteristics of the drive DC motor, and this value is used as the feedback amount for rotation control of the electric pump. do. By doing so, the responsiveness of the electric pump can be improved.

Now, the rotational speed of the motor is N, the terminal voltage is V,
If the armature current is Ia, and the sum of the armature resistance and the brush resistance is r, then the rotational speed N of the motor can be determined by the following equation.

N=V−rIa/K……(2) Here, K is the back electromotive force constant of the motor.

The throttle sensor 42 is the throttle lever 41
The position shown in FIG. 2 is detected and a corresponding position signal E _s is output.

Engine rotation sensor 40 detects the rotation speed of engine 30 and outputs a pulse signal P _o with a period proportional to the rotation speed. The frequency-voltage converter 51 outputs a voltage signal E _o according to the frequency of the pulse signal P _o .

The PID compensation circuit 53 inputs the deviation value between the signals Es and E _o , performs various compensations such as proportional, integral, and differential compensation on this input signal, and outputs a motor rotation speed command signal e _n corresponding to the deviation input.

Voltage detection circuit 6 of motor rotation speed detection circuit 60
1 detects the terminal voltage V of the motor 23 and outputs a corresponding signal e _v . The armature current detection circuit 62 is a shunt resistor connected to the current circuit of the motor 23.
Detect the voltage across Rs and the actual armature current Ia
Outputs a voltage signal e _a corresponding to . Coefficient unit 6
3 multiplies the signal e _a by the coefficient r corresponding to the sum of the armature resistance and the brush resistance to obtain the signal e _a '(=r・e
_a ) is output. The coefficient unit 64 divides the deviation (e _v −e _a ′) between the signals e _v and _{e a} ′ by the back electromotive force constant K,
The calculation represented by the above equation (2) is performed to calculate the rotational speed N of the motor 23, and a corresponding rotational speed signal e _{o is} output.

The function generator 52 is for setting the rotational speed of the electric pump 21 at each engine rotational speed Ne, that is, the armature current Ia of the motor 23, along a preset torque curve of the engine 30.
An armature current setting signal E _as (Fig. 4) corresponding to the engine rotational speed signal E _o is output.

The PID compensation circuit 54 outputs a motor rotation speed command signal e.
The deviation between _n and the actual motor rotational speed signal e _o is
It compensates in the same way as the PID compensation circuit 53 and outputs it as a motor rotation speed command signal _En .

Integrator 56 integrates the difference between maximum armature current setting signal E _as and signal e _a corresponding to actual armature current I _a and outputs armature current command signal E _a .

The minimum signal priority circuit 55 gives priority to the smallest signal among the input signals and outputs it.
The smaller command signal between _n and E _a is output as the armature current command signal E. This minimum signal priority circuit 55 is configured as shown in FIG. 5, for example.

The amplifier 57 amplifies and outputs the command signal E, applies it to the motor 23, and controls the terminal voltage V of the motor 23. The armature current Ia of the motor 23 is the terminal voltage V
It changes depending on. The motor 23 rotates at a rotational speed N according to the terminal voltage V and the armature current Ia, thereby driving the pump 22 to rotate.

When the signal e _a exceeds the setting signal E _as , the output signal E _a of the integrator 56 decreases. Therefore, no matter how large the motor rotational speed command signal E _n becomes, the minimum signal priority circuit 55 outputs the signal E _a preferentially. Therefore, the output voltage of the amplifier 57 decreases, and as a result, the armature current Ia also decreases and is suppressed within the limit value.

The pump 22 supplies fuel to each injector 31a to 31d at a pressure P depending on the rotation speed. The engine 30 has these injectors 31a to 31d.
It rotates according to the fuel supplied to it.

Now, in a turbocharged diesel engine, when the engine is suddenly accelerated, the response of the supercharger is poor, so the amount of intake air cannot catch up with the amount of fuel injection, resulting in an oxygen deficiency and black smoke comes out from the exhaust pipe. Put it away. Therefore, in the present invention, black smoke is prevented by adjusting the fuel injection amount to match the intake air amount during acceleration. In this method, as shown in FIG. 3, a pressure switch 67 is disposed in the intake manifold 32 of the engine 30, which is turned on when the intake pressure is low and turned off when it is high.
Controls _p on and off. This output E _p is 0 when the pressure switch 67 is on, and becomes (R ₂ /R ₁ −R ₂ )×Vcc when it is off. This signal E _p is added to the output signal E _as of the function generator 52. Then, the signal E _as (curve I in FIG. 6) is shifted by the signal E _p (curve in the same figure).

Therefore, while the intake pressure is low during sudden acceleration, the signal E _p
The injection amount is reduced by the amount equivalent to , and black smoke can be prevented.

Furthermore, it is known that when the air becomes thinner at high altitudes or the specific gravity of fuel increases, the exhaust gas temperature increases if the injection amount limit value remains the same. If the exhaust gas temperature is too high, the durability of the engine will be impaired, so it is necessary to prevent the exhaust temperature from exceeding a permissible temperature.

In the present invention, as shown in FIG. 3, an exhaust gas temperature sensor, such as a thermistor 71, is disposed within the exhaust manifold 33 of the engine 30 to detect a signal e _t corresponding to the exhaust temperature. After this signal e _t is amplified by the exhaust sensor amplifier 72 of the exhaust temperature compensation circuit 70,
The deviation from the preset value E _T of the maximum exhaust temperature value setter 73 is calculated, and this deviation signal is applied to the integrator 74. The output signal E _t of the integrator 74 is applied to the minimum signal priority circuit 55 as a motor armature current command signal. Then, when the signal E _t is larger than the signal E _T , the signal E _t becomes smaller, and the minimum signal priority circuit 5
5 preferentially outputs this signal _Et , limits the armature current _Ia , lowers the pressure of the electric pump 21, suppresses the amount of fuel injected from the injectors 31a to 31d, and lowers the exhaust temperature.

Furthermore, if high output is produced when the cooling water temperature is low,
Because the entire engine has not been warmed up, there are problems such as lubricating oil not circulating smoothly.
It is necessary to suppress the engine output until the cooling water temperature rises. To achieve this, in the present invention, as shown in FIG. 3, a water temperature sensor, such as a thermistor 80, is attached to the cooling waterway to measure the cooling water temperature, and a signal e _c corresponding to the water temperature is detected. This signal e _c is amplified by a cooling water temperature sensor amplifier 82 of a cooling water temperature compensation circuit 81 and then applied to an upper limit circuit 83 . The output signal E _c of the upper limit circuit 83 does not change any further when the water temperature reaches a certain value t _a (FIG. 7). This signal E _c is added to the output signal E _as of the function generator 52. Then, the signal E _as (curve in FIG. 8) is shifted (increased) as the water temperature becomes higher (curve in FIG. 8).

The reason for limiting the upper limit of the signal E _c is that when the temperature exceeds a predetermined temperature t _a , the engine can reach its maximum output without any problem, and since it is a problem if the output changes depending on the water temperature, the upper limit of the signal E _c is limited. The value of the signal E _c is limited to a constant value.

Note that a temperature switch may be used instead of the water temperature sensor 80, and as shown in FIG. 9, the temperature switch 90 is turned on when the water temperature is low and turned off when the water temperature is high.
is placed in the cooling water passage, and controls the output E _c ' of the cooling water temperature compensation circuit 91 to be turned on or off. This output signal E _c ' is 0 when the temperature switch 90 is on, and becomes (R ₄ /R ₃ +R ₄ )×Vcc when it is off. This signal E _c ' is added to the output signal E _as of the function generator 52 instead of the signal E _c . When the water temperature is low, the temperature switch 90 is turned on and the armature current set value E _as is lowered by (R ₄ /R ₃ +R ₄ ) x Vcc (curve in Figure 10), and when the water temperature rises, the temperature switch 90 is turned on.
When 0 is turned off, it returns to the steady set value (the curve in the figure). By doing so, the engine output can be suppressed similarly to the cooling water temperature compensation circuit 80 described above.

As another method for limiting torque and horsepower, there is a method that detects the rotational speed of the motor instead of limiting the motor's armature current and suppressing fuel pressure, as described above, in which the discharge amount depends on the rotational speed of the pump. Using the proportional relationship, fuel pressure can be suppressed by changing the rotational speed of the motor.

FIG. 11 is a diagram showing another embodiment of the fuel control device of the present invention, and is an explanatory diagram of the main part of the fuel control device in which the fuel pressure is suppressed by the rotational speed of the motor.

In the figure, the output signal P _o of the engine rotation sensor 40 is converted into a corresponding voltage signal E _o by a frequency-voltage converter 51 as described above. Based on this signal E _o , the function generator 111 generates a pump rotation speed control signal E _p corresponding to the engine rotation speed Ne.
Outputs _s . Further, the PID compensation circuit 53 outputs an electric pump rotational speed command signal e _n according to the deviation between the position signal E _s of the throttle sensor 42 and the signal E _o . The minimum signal priority circuit 112 handles the signals e _n and E _ps
The smaller signal is given priority and output as the electric pump rotation speed command signal E.

On the other hand, the motor rotation speed sensor 115 detects the rotation speed of the motor 23 of the electric pump 21 and outputs a corresponding signal e _b . This signal e _b is converted and output as a corresponding voltage signal E _b by the frequency-voltage converter 116 . The PID compensation circuit 113 uses the command signal E
A command signal E' corresponding to the deviation ΔE between the signal E _b and the signal E b is output. This signal E' is amplified by an amplifier 114 and then applied to the motor 23 to control the rotation speed of the motor 23.

The pump 22 rotates according to the rotation speed of the motor 23 and pumps fuel to each injector via the pipe 101.

In addition, the PID compensation circuit 5 of the engine speed control system
Even if the output _en of No. 3 exceeds the set value E _ps of the function generator 111, the rotational speed of the motor 23 will not increase too much because the lower level voltage value has priority.

In this way, the rotational speed of the motor 23 is controlled to suppress the fuel pressure.

As explained above, according to the present invention, it is possible to save fuel consumption by controlling the armature current of the electric pump motor or controlling the rotational speed of the motor to suppress the fuel pressure, and to reduce the amount of black smoke during sudden acceleration. It has the excellent effect of suppressing the generation of heat, correcting the engine horsepower depending on the intake pressure and water temperature, eliminating stress on the engine, and making it possible to always operate the engine in the best condition.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional fuel control device for a diesel engine, FIG. 2 is a diagram showing the principle of a fuel control device for a diesel engine according to the present invention, and FIG. 3 is a diagram showing a fuel control device for a diesel engine according to the present invention. FIG. 4 is a diagram showing an example of the characteristic diagram of the function generator shown in FIG. 3;
5 is a diagram showing an embodiment of the minimum signal priority circuit shown in FIG. 3, FIG. 6, FIG. 7, FIG. 8, and FIG.
The figure shows an example of each part signal of Fig. 3, and Fig. 9
This figure is a diagram showing another embodiment of the cooling water temperature compensation circuit shown in FIG. 3, and FIG. 11 is an explanatory diagram of main parts showing another embodiment of the fuel control device shown in FIG. 3. 1... Fuel tank, 20, 24... Filter,
21...Electric pump, 30...Engine, 31, 31
a to 31d... Injector, 40... Engine rotation speed sensor, 41... Throttle lever, 42... Throttle sensor, 50, 110... Fuel control device,
68...Black smoke prevention circuit, 70...Exhaust temperature compensation circuit, 8
0,91...Cooling water temperature compensation circuit, 90...Temperature switch.

Claims (1)

[Scope of Claims] 1. In a fuel control device for a unit injection diesel engine, an electric pump that drives an oil pump with a DC motor to supply fuel to an injector, and a means for outputting an electric pump rotational speed command signal; a function generator for outputting an armature current setting signal for the electric pump according to the engine rotational speed along a preset engine torque curve; and an armature for the electric pump. a motor rotation speed detection circuit that detects the current and outputs a corresponding armature current signal; and a motor rotation speed detection circuit that integrates the deviation between the armature current setting signal and the actual armature current signal as a second electric pump rotation speed command signal. The circuit includes an integrator that outputs an output, and a minimum signal priority circuit that outputs the smaller one of the first and second command signals preferentially to limit the armature current, and controls the electric pump according to the rotational speed of the engine. A diesel engine fuel control device that limits rotational speed and torque. 2. In a unit injection diesel engine fuel control device, an electric pump that drives an oil pump with a DC motor to supply fuel to an injector, and a first electric pump rotation speed command based on a throttle position and an engine rotation speed. means for outputting a signal; a function generator for outputting an armature current setting signal for the electric pump according to the engine speed along a preset torque curve of the engine; and a function generator for detecting and responding to the armature current for the electric pump. a motor rotation speed detection circuit that outputs an armature current signal; an integrator that integrates a deviation between the armature current setting signal and the actual armature current signal and outputs it as a second electric pump rotation speed command signal; an exhaust temperature compensation circuit that includes an exhaust temperature sensor disposed in the exhaust manifold of the engine and operates when the sensor output exceeds a preset value to output a third electric pump rotation speed command signal; 2. A minimum signal priority circuit that outputs a smaller signal among the third command signals preferentially to limit the armature current, and when the exhaust temperature exceeds the preset value, the exhaust temperature falls below the preset value. A diesel engine fuel control device that suppresses the armature current of the electric pump and reduces the amount of fuel injected until the electric pump's armature current decreases. 3. In a fuel control device for a unit injection diesel engine, an electric pump drives an oil pump using a DC motor to supply fuel to an injector, and a first electric pump rotational speed command is determined based on a throttle position and an engine rotational speed. means for outputting a signal; a function generator for outputting an armature current setting signal for the electric pump according to the engine speed along a preset torque curve of the engine; and a function generator for detecting and responding to the armature current for the electric pump. a motor rotation speed detection circuit that outputs an armature current signal; a cooling water temperature compensation circuit that detects the cooling water temperature with a cooling water temperature sensor and changes the set value of the armature current setting signal according to the detected value; and this armature current. an integrator that integrates the deviation between the set signal and the actual armature current signal and outputs it as a second electric pump rotation speed command signal; and an integrator that outputs the smaller one of the first and second command signals with priority. A fuel control device for a diesel engine that is equipped with a minimum signal priority circuit that limits the armature current by suppressing the armature current of an electric pump when the engine is cold, reducing the amount of fuel injection and lowering the engine output. .