JPS63134838A - Overrun preventing method for diesel engine - Google Patents

Abstract

PURPOSE:To limit a rotational speed of a Diesel engine to a permissible speed or less without interfering with another injection quantity control, by reducing a fuel injection rate when the rotational speed of the engine becomes greater than a predetermined value. CONSTITUTION:An engine speed sensor 70 detects a rotational speed of a Diesel engine 1 to feed the same to an electronic control circuit 40. When the engine speed exceeds a permissible speed, the electronic control circuit 40 reduces current flowing in a coil 36 of an injection pressure control solenoid valve 30. As a result, a fuel injection pressure is reduced, and a fuel injection rate is therefore reduced, thereby reducing the engine speed. Thus, the fuel injection rate may be reduced so that the engine speed of the Diesel engine 1 may not exceed the permissible speed, independently of fuel injection quantity control, that is, control of a spill ring 54. Accordingly, the engine speed control may be carried out without interfering with the injection quantity control. Further, in the case of adjusting a maximum injection quantity by providing an intake air pressure sensor 82 or the like, abnormality may be avoided.

Description

[Detailed Description of the Invention] Menhada Gokoma [Field of Industrial Application] The present invention is directed to the overrun of a diesel engine, that is,
This invention relates to a method for preventing a diesel engine from rotating beyond its allowable rotation speed.

[Prior Art] In a diesel engine, the load is controlled, in other words, the speed is controlled, by controlling the fuel injection amount, without controlling the intake air amount.

However, at extremely high speeds, the durability of each part of the diesel engine and each auxiliary machine becomes a problem. Therefore, an allowable rotation speed is set, and the control device uses a map etc. to ensure that the maximum injection amount is not exceeded. is set to control the actual injection amount so that it does not exceed this value.

[Problems to be Solved by the Invention] However, due to variations in mechanisms that control the fuel injection amount, such as injection pumps, injection nozzles, etc., the torque generated by the engine may vary greatly. In addition, due to aging of the injection pump and injection nozzle (injection nozzle valve opening pressure decrease), the fuel injection amount further changes, further expanding the variation in generated torque.On the other hand, engine load also increases due to engine friction. There are variations in the load of each auxiliary component, power steering, etc., and it is not constant.

As described above, conventional diesel engines have had the problem that, due to variations in both the fuel injection amount and the engine load, the engine maximum rotational speed, which is determined by the balance between the two, varies greatly.

As a solution to this problem, the applicant has already proposed an invention in which the maximum injection amount is determined by learning the rotational speed, and the upper limit of the injection amount is regulated using that value.
No. 4).

However, in systems that limit the maximum fuel amount in this way, even if the relationship between the diesel engine's allowable rotational speed and the maximum fuel injection amount is set to prevent overrun, the partial load injection amount and full load It is conceivable that this may interfere with the area in which other control factors such as the maximum injection amount are considered, resulting in complicated and difficult control. Additionally, if there are other factors that limit the maximum injection amount, for example, if the passage for measuring the intake pressure of the intake pressure sensor that detects the intake pressure is clogged, the maximum injection amount will also remain high, and such an overrun cannot be prevented. The problem of disappearing was also considered.

Therefore, the present invention has adopted the following configuration for the purpose of solving the above-mentioned problems.

[Means for Solving the Problems] That is, the gist of the present invention is that, as illustrated in FIG. Pl) In a diesel engine overrun prevention method in which the rotational speed is controlled by injecting the amount of fuel (P4), when the rotational speed of the diesel engine exceeds a predetermined speed (P2), the fuel injection rate A diesel engine overrun prevention method characterized by reducing (P3).

Here, the predetermined speed may be the allowable rotational speed of the diesel engine, or a value in the vicinity thereof, for example, a value lower or higher than the allowable rotational speed by a predetermined value.

[Operation] To determine the fuel injection amount, first, the accelerator operation amount and engine rotation speed of the diesel engine are detected, and the detected values are used to determine the fuel injection amount based on a predetermined pattern.

The predetermined pattern is a pattern that determines the fuel injection amount of the diesel engine to be injected using the accelerator operation amount and engine rotation speed as parameters, and for example,
This is a pattern as shown in FIG. 7, which will be described later.

According to the above pattern, the maximum injection amount is naturally determined by considering the allowable rotation speed, but due to errors or failures in the mechanism, the rotation speed of the diesel engine may rise abnormally and the allowable rotation speed may be exceeded. If it exceeds the limit, the fuel injection rate is reduced, resulting in a reduction in the output of the diesel engine and overrun can be prevented.

In the present invention, for example, normally the spill timing of the pump plunger of the fuel injection pump is adjusted to control the fuel injection amount, but in order to prevent overrun, the injection amount is adjusted in addition to changing the spill timing. It changes the injection rate (fuel supply per hour) based on pressure, etc.

Next, the present invention will be described in detail.The present invention is not limited to these, but includes various embodiments without departing from the gist thereof.

[Embodiment] FIG. 2 is a block diagram showing an embodiment of the present invention, in which the method of the present invention is applied to a Bosch type distribution fuel injection pump.

The four-stroke diesel engine 1 transmits a portion of its rotational output to the drive shaft 4 of the fuel injection pump 3. The drive shaft 4 obtains its driving force and rotates at 1 of the crankshaft rotational speed.
It is rotating at a rotation speed of /2. The rotational force from the drive shaft 4 is transmitted to the vane pump 6. The vane pump 6 sucks fuel from the fuel tank FT via the fuel filter FF, and pumps it through the hydraulic supply path 7 to a fuel reservoir.

The fuel pressure in the fuel reservoir is maintained at a predetermined pressure by a pressure regulating valve 10.

The face cam 12 and the pump plunger 14 are integrated, and are connected to the drive shaft 4 through a coupling 15 to apply rotational force to the face cam 12. The face cam 12 is pressed against a roller 19 by a pair of plunger springs 17 (one not shown).

Therefore, as the pump drive shaft 4 rotates, the plunger 14 performs both rotational movement and reciprocating movement in the axial direction.
During intake, the fuel in the fuel reservoir is transferred from the intake port 21 to the high pressure chamber 23.
At the same time, when the distributor slit 25 rotates during pressure feeding, the outlet passage 2 corresponding to a predetermined cylinder is
The high-pressure fuel is distributed from the outlet passage 27 to the injection nozzle (not shown) through the delivery valve 29 and injected into the combustion chamber of the predetermined cylinder of the diesel engine 1.

The solenoid valve protruding from the tip of the high pressure chamber 23 controls the injection pressure f!
g A seat portion 33 which is a solenoid valve 30 and determines a pressure receiving area on which internal pressure from the high pressure chamber 23 acts on the housing 31 ladle;
The high pressure chamber 2 can be seated on and removed from the seat portion 33 at will.
a valve body 34 that adjusts the pressure of high-pressure fuel in the valve body 3 ;
4, an electromagnetic coil 36 that provides driving force to the moving core 35, and the valve body 34.
When the high pressure chamber 2 is separated from the seat portion 33, that is, opened,
3, and a flow path 37 for returning the fuel of No. 3 to the fuel reservoir 9 in the pump housing.

A return spring 45 is disposed between the moving core 35 and the housing 31, and a threaded portion 46 and a spring retainer 47 that directly receives the spring 45 are provided on the side of the housing 31 that receives the spring 45. By adjusting the insertion amount of the retainer 47, the set load of the spring 45 is made variable. The relief pressure by the valve body 34 of the injection pressure control solenoid valve 30 is set by the added force of the electromagnetic force generated by the current flowing through the coil 36 and the return spring 45. Here, when the valve element 34 relieves fuel, the spring constant and air gap of the return spring 45 are selected so that the change in the acting force of the valve element 34 with respect to the lift amount is small.

That is, as shown in FIG. 3, the set load FR, which is the sum of the spring force FS of the return spring 45 and the electromagnetic force FB, is made approximately constant with respect to the lift amount of the valve body 34. Here, the relationship between the relief pressure PR and the set load FR is expressed as PR=FRX (4/πd2). Here, d is the opening diameter of the seat portion 33.

Fig. 4 shows the relief pressure PR with respect to the current flowing through the electromagnetic coil 36 of the injection pressure control valve 30, where PN indicates the injection nozzle opening pressure, and the relief pressure when the current I is zero (left end) is the return Set load F of spring 45
This corresponds to S. The set load corresponding to the magnetic force increases linearly with the coil current I. That is, by adjusting the amount of current flowing through the coil 36 according to the operating conditions of the diesel engine 1, the maximum injection pressure can be controlled and the fuel injection pressure can be freely changed.

Returning to FIG. 2, the pumping of fuel begins after the plunger 14 moves in the direction of arrow C and closes the intake port 21, and the high-pressure fuel compressed in the high-pressure chamber 23 flows through the distributor slit 25 to a predetermined outlet passage 27. The fuel is distributed, exits the delivery valve 29, passes through the high-pressure pipe 50, and is injected from a predetermined injection nozzle of the diesel engine 1 into the combustion chamber of a predetermined cylinder.

When the pressure in the high pressure chamber 23 exceeds the relief pressure of the injection pressure control solenoid valve 30 as the plunger 14 moves, the valve body 34 of the injection pressure control valve 30 lifts, increasing the maximum pressure in the high pressure chamber 23. Hold at relief set pressure. Further, when the plunger 14 moves in the direction of arrow C and the spill boat 52 is opened to the fuel reservoir 9 from the end surface of the spill ring 54 in the C direction, the pumping of fuel ends. Therefore, by adjusting the movement position of the spill ring 54 in the axial direction of the plunger 14, it is possible to adjust the fuel injection amount.

The movement position of the spill ring 54 is adjusted by an electromagnetic actuator 60. The actuator 60 determines the position of the moving core 65 by balancing the force in the direction of the arrow generated by the current flowing through the coil 61 and the force in the opposite direction to the direction of the arrow generated by the spring 63. The moving core 65 moves the spill ring 54 via the link machine tII 66 to adjust the fuel injection amount. The moving position of the moving core 65 is detected by a moving position detector 69 constituted by a differential transformer 68. The moving position of the moving core 65 is determined by the amount of insertion of the moving core 65 into the differential transformer 68.
It is detected by the change in the impedance of the

Further, the drive shaft 4 described above is equipped with a rotation speed detector 70 for detecting the rotation speed of the drive shaft 4.

The rotational speed detector 70 is a pulser 7 directly connected to the drive shaft 4.
2 is detected by an electromagnetic pickup 74 fixed to the roller ring 73, and this electric signal is input to the electronic control circuit 40 as a rotational speed signal of the diesel engine 1. Since the rotation ratio of the drive shaft 4 is 1/2 that of the crankshaft of the diesel engine 1, the rotation ratio of the drive shaft 4 is 1/2 that of the crankshaft of the diesel engine 1, so in the end
It serves as a rotation speed detector.

The roller ring 73 is driven by a timer 76, and displaces the position of the roller 19 to change the phase at which the face cam 12 rides on it. That is, the fuel injection timing is controlled according to the rotational speed of the diesel engine 1.

The vane pump 6 and the timer 76 are shown unfolded at 90° in FIG. 2 for the sake of explanation.

The electronic control circuit 40 includes a central processing unit (CPU) 40a, a waveform shaping circuit 40b, an analog/digital (A/D) conversion circuit 40c, a read-only memory (ROM) 40d, and a random access memory (RAM).
) 40e, an actuator servo circuit 40f, and a solenoid valve drive circuit 40g.

Of these, the ROM 40d includes a control program as shown in FIG. 6, which will be described later, which is executed by the CPU 40a, a governor characteristic map, etc., as shown in FIG. 7, which will be described later.

The actuator servo circuit 40f operates according to the output of the CPU 40a in order to control the spill ring 54 to a desired position so as to supply the required amount of fuel to the combustion chamber according to the operating state of the diesel engine 1. This circuit controls the current flowing through the coil 61 of the electromagnetic actuator 6o while referring to the output value of the movement position detector 69.

The solenoid valve drive circuit 40g controls the current flowing through the coil 36 of the injection pressure control 91I solenoid valve 30 so that fuel is supplied to the combustion chamber at a required fuel injection rate according to the operating state of the diesel engine 1. This is a circuit that controls the

The electronic control circuit 40 further connects the rotation speed detector 70 to the diesel engine 1 via the waveform shaping circuit 40b.
In addition to detecting the rotational speed of the A/D conversion circuit 4,
0c, the accelerator sensor 81 detects the depression of the accelerator pedal (corresponds to the accelerator operation position), the intake pressure sensor 82 detects the pressure of the intake air in the intake pipe of the diesel engine 1, and the intake air temperature sensor 83 indicates the intake air pressure in the intake pipe. The cooling water temperature sensor 84 detects the temperature of the cooling water of the diesel engine 1.

The electronic control circuit 40 calculates and processes these detected values, and injects fuel into the fuel chamber at a target injection amount and target injection rate determined by correlating these data with map data in the ROM 40d, etc. The injection pressure control valve 30 and electromagnetic actuator 60 are controlled.

Next, FIG. 5(A) shows a specific example of the electromagnetic valve drive circuit 409. The CPU 40a inputs the calculated target current value to a digital/analog (D/A) converter 91, where it is converted into an analog voltage corresponding to the target current value. Solenoid valve 3
The current flowing through the zero coil 36 is detected by a current detection resistor 92, passes through a current detection amplifier 93, and is input to an error correction amplifier 94 as an actual current signal. The error correction amplifier 94 controls the base current of the transistor 95 so that the target current value and the actual current signal match. In this way, the solenoid valve drive circuit 409 works so that the calculated target current value and the actual current flowing through the coil 36 of the solenoid valve 30 match. The capacitor 96 is for stably operating the above operation without oscillation.

Note that this solenoid valve drive circuit 40g is not limited to current value control, and may have the configuration shown in FIG. 5(B), for example. The value is input to the D/A converter 91s and converted into an analog signal. The analog signal is compared with the sawtooth wave signal generated by the sawtooth wave signal generation circuit 97 by a comparator 98, and converted into a duty-controlled pulse signal 6 Therefore, the target current value is converted to duty, and this Accordingly, the transistor 9 is switched and the solenoid valve 30 is driven.

Next, the electronic control circuit 4 that controls the system with the above configuration
The fuel injection and control of the diesel engine 1 carried out at 0 will be explained using the flowchart of FIG.

The flowchart in FIG. 6 is repeated after starting the diesel engine 1 as part of the main routine for controlling the diesel engine 1.
c), it is executed.

First, in step 100, the accelerator opening degree, that is, the accelerator pedal depression Accp is read from the accelerator sensor 81, and the diesel engine 1
The rotational speed NE is read from the rotational speed detector 70.

Next, in step 110, the fuel injection amount Qv is determined from the governor characteristics shown in FIG. 7 using the above Accp and NE. The fuel injection 1LQv corresponds to the moving position of the spill ring 54. That is, it is related to the current flowing through the coil 61 of the electromagnetic actuator 60. Note that the governor characteristics may be corrected by providing an intake pressure sensor in the intake pipe of the diesel engine 1 so that the higher the intake pressure is, the higher the upper limit value of the injection amount is.

Next, in step 120, the rotation speed NE read above is
It is determined whether or not the rotation speed exceeds the allowable rotation speed NUL. If the negative determination is made because the rotation speed NE is normal, the flag F indicating that the process for reducing the injection rate is the second or subsequent time is reset in step 125, and then the spill position setting is output in step 130. That is, the current flowing through the coil 61 of the electromagnetic actuator 60 is controlled so that the fuel injection ff1QV determined from the governor characteristics is injected once in each cylinder.

On the other hand, if an affirmative determination is made in step 120 because the rotational speed NE exceeds the allowable rotational speed NLIL, then in step 140 it is determined whether or not the flag F is set. Since it is O, a negative determination is made, and in step 150, the current value flowing through the coil 36 of the injection pressure control solenoid valve 30, which is currently set, is read into the memory D2 at a predetermined location. If the current is controlled by duty, the duty value is read into D2.

Next, in step 160, flag F is set to 0. Then, in stellar 7170, the value of D2 is decreased by ΔD2. The ΔD2 is a value for reducing the amount of current (or duty), and is set to several percent or several tens of percent of the initially read value of D2. Alternatively, the value may be a predetermined percentage of the value of D2, which is constantly rewritten.

Next, in step 180, a current corresponding to this value D2 is applied to the injection pressure control solenoid valve 30 from the solenoid valve drive circuit 4o9.
is output to.

Here, since the relationship between the current amount and the valve opening pressure of the valve body 34 is as shown in FIG. 8, as the current amount decreases, the leakage amount increases as shown in FIG. 9, and the fuel The injection pressure decreases and the injection rate (oil feeding rate) decreases. Even if the injection amount is constant, there is a difference between the injection rate and the output torque of the diesel engine 1.
Since there is a line shape relationship as shown in FIG. 10, lowering the injection rate can lead to a lower rotational speed.

Next, step 130 is executed, and the above-described injection process is performed. At this time, in the coil 61 of the electromagnetic actuator 60 for adjusting the spill ring position, a current corresponding to the injection amount determined from the above governor characteristics during normal operation is corrected using the above injection rate, and the total injection amount is calculated based on the above governor characteristics. The injection amount is adjusted to match the Of course, it is not necessary to specifically correct the injection rate, and in that case, the torque reducing effect of both the injection rate reduction and the injection amount reduction will be exerted.

In this way, the process once ends and moves on to other processes, but even if this routine is executed again, if an affirmative determination is made in step 120, an affirmative determination is made in step 140, and then the process of step 170 is performed again. executed. In this way, the fuel injection rate gradually decreases until a negative determination is made in step 120.

Since the present embodiment is configured as described above, in addition to controlling the injection amount, that is, controlling the spill ring 54, the rotational speed of the diesel engine does not exceed the allowable speed.
The fuel injection rate can be lowered, the control will not interfere with injection amount control (spill ring position control), and even if the maximum injection amount is adjusted by installing an intake pressure sensor, etc., it will not be affected by abnormalities. I can deal with it.

As described above, the present invention is characterized in that when the rotational speed of the diesel engine exceeds a predetermined speed, the fuel injection rate is reduced. Therefore, it is possible to limit the rotational speed of the diesel engine below the allowable speed, and there is no need to consider interference with other injection amount controls.Also, the data used to set the upper limit of the fuel injection pump is not abnormal. It is also possible to limit the rotational speed of the diesel engine to below the allowable speed.

[Brief Description of the Drawings] Fig. 1 is a diagram illustrating the basic configuration of the present invention, Fig. 2 is a configuration diagram of one embodiment, and Fig. 3 is a diagram showing the relationship between the spring force FS of the return spring and the lift amount of the valve body. A graph showing the change in the total electromagnetic force FE, Fig. 4 is a graph showing the relief pressure PR with respect to the current flowing in the electromagnetic coil of the injection pressure control valve, and Fig. 5 (A> is a graph showing the change in the electromagnetic valve drive circuit controlled by analog). Diagram,
FIG. 5 CB) is a configuration diagram of a duty-controlled electromagnetic valve drive circuit, FIG. 6 is a flowchart showing a fuel injection amount control routine, and FIG. 7 is a graph showing governor characteristics of the embodiment.
Figure 8 is a graph showing the relationship between the amount of current output to the injection pressure control solenoid valve and the opening pressure of the valve body, and Figure 9 is a graph showing the relationship between the amount of current output, injection rate, leak amount, and leak timing. , 1st
Figure 0 represents a graph showing the relationship between injection rate and output torque. 1...Diesel engine 3...Fuel injection pump 14...Pump plunger 30...Injection pressure control solenoid valve 34...Valve body 36...Solenoid coil 40...Electronic control circuit 60...・Electromagnetic actuator 61...Electromagnetic coil 70...Rotation speed detector 81...Accelerator sensor

Claims (2)

[Claims] 1. In a diesel engine overrun prevention method in which the rotation speed is controlled by injecting a fuel amount determined according to the accelerator operation amount and the engine rotation speed based on a predetermined pattern, the rotation speed of the diesel engine is controlled. A diesel engine overrun prevention method comprising reducing the fuel injection rate when the speed exceeds a predetermined speed. 2. 2. The method for preventing overrun of a diesel engine according to claim 1, wherein the predetermined speed is an allowable rotational speed of the diesel engine.