JPH0463221B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field The present invention relates to a fuel supply amount control device for an internal combustion engine, and more specifically, to an internal combustion engine equipped with an operating section such as an electro-hydraulic converter that operates an operating member that determines the amount of fuel injection. The present invention relates to a fuel supply amount control device for an internal combustion engine.

(b) Prior Art In such a diesel internal combustion engine, the operating section is comprised of, for example, an electro-hydraulic converter and a hydraulic pressure adjusting piston. Conventional regulating devices are used to optimally control the injection pump according to various drive parameters, such as load, rotational speed, exhaust gas value, engine temperature or fuel, etc. If an abnormality occurs in the control circuit, especially if the signal from the position sensor that detects the position of the operating member is lost, it is no longer possible to accurately control the fuel supply amount. In this case, a safety device is installed to protect the internal combustion engine from destruction, and in the event of a failure, the load on the internal combustion engine is reduced and the engine is driven in a limited rotational speed range, thereby overloading the internal combustion engine. Devices that protect against this are known.

For example, DE 30 07 663 A1 discloses a hydraulic actuating device for actuating an actuating member of an injection pump, for example. The idea of this actuating device is that in the event of a failure of the regulator, the actuating member of the injection pump is displaced into a predetermined final position. In this way, if a failure occurs in the regulator or a failure occurs in the electronic circuit, the control moves the operating member to a predetermined final position,
This prevents the engine from suffering mechanical damage.

Furthermore, German Patent Publication No. 1962570 discloses a control device for an operating device for operating an injection pump of a diesel engine, in which case the actual value is made very large in the event of a failure of the control circuit, so that the operating device is Control is performed to automatically return the operating member to the zero position.

The function of such conventional control devices is to prevent the output of the internal combustion engine from becoming too large in the event that the control circuit is interrupted or a failure occurs in each component of the control circuit. When a failure occurs, the member that adjusts the fuel supply amount is moved to the position where the fuel supply amount is at its minimum value, so that the internal combustion engine can be rotated with an extremely small injection amount, or it can be stopped in the first place, thereby overloading the internal combustion engine. This is prevented.

It has been found that reducing the fuel supply in the event of a fault is not always advantageous. When such a control device is used in a car, this means that the engine stops driving, and the car can no longer move on its own. This situation must be avoided. This is because the driver of the vehicle must be left with the possibility to continue driving in emergency mode and drive the vehicle to the next repair location. An open-loop control circuit for emergency running is only possible if sufficiently precise position control is possible in a limited load and speed range in which the actuating member is stable under open-loop control.

Electromechanical transducers driven by pulsed signals are also known. The transient time is then chosen to be shorter than the minimum time required for the armature to move over its entire stroke. The electromechanical transducer then assumes an average position proportional to the duty ratio of the pulse signal, in which case a very small vibrating element is superimposed on the piston stroke. When an electromechanical transducer is driven on and off above a limiting frequency, an advantage is gained over driving below a limiting frequency by moving the piston of a hydraulic transducer by means of pulses over its entire stroke range. be able to. The wear of the material during operation above the limit frequency can be significantly reduced, and in the case of operation above the limit frequency, the control at the mechanical output of the transducer is reduced due to the small size of the vibrating element. It becomes possible to overcome the insensitivity of

(c) Purpose Therefore, the present invention has been made in view of the above points, and provides a fuel supply amount control device for an internal combustion engine that adjusts the output of the internal combustion engine to enable emergency running when a failure occurs. The purpose is to

(d) Examples The present invention will be described in detail below according to examples shown in the drawings.

FIG. 1 schematically shows a device for controlling the fuel supply of a diesel internal combustion engine. code 10
The amount of fuel supplied to the internal combustion engine indicated by is based on the accelerator pedal 11, accelerator pedal position sensor 12, control stage 13, regulator 14, pulse width modulator 15, output stage 16, electro-hydraulic transducer 17, It is controlled via a series of circuits consisting of a control unit 18 and an injection pump 19 connected via a pipe 20 to the internal combustion engine. A displacement sensor 21 is provided which detects the position of the operating piston 22 of the operating part 18 biased by a spring 22', the output signal of which is input to the regulator 14, whereby the control circuit is closed loop. Configure. The output signal of the movement amount sensor 21 is input to a fault identification circuit 23, and the output of this identification circuit 23 is connected to the pulse width modulator 15. In addition to the signal from the accelerator pedal position sensor 12, the control stage 13 also receives signals related to the engine, such as a load signal (L), a rotational speed signal (j), a temperature signal (T), and an exhaust gas composition (λ). , as well as other signals (not shown in detail). The control stage 13, the fault identification circuit 23, the regulator 14, the pulse width modulator 15 and the output stage 16 can be combined as a control device 13', as shown in dotted lines. An electromagnet 24 and an electrohydraulic transducer 17, which in this example is configured as a continuously operating 3/3 position control slide 25, are connected via a pipe 26 to a pressure tank 27 and via a pipe 28 to a collection tank 29. , further connected to the operating section 18 via a pipe 30.

The thus configured control device operates as follows. That is, when the actual value of the controlled variable and the target value match, the electro-hydraulic converter 17 has a predetermined duty ratio, that is, the control slider 25 is located at the center position shown in FIG. A pulsed voltage is applied with a duty ratio such that the connection between tank 27 and collection tank 29 remains in a position where it is broken. The pulse frequency of the input pulses is chosen to be large so that the control slider does not oscillate accordingly when driven in pulses due to its mechanical inertia, but is driven to assume a position corresponding to the average current. (Hereinafter, this will be referred to as driving with a frequency higher than the limit frequency).
When the target value changes or due to the influence of external disturbances, the duty ratio of the signal input to the converter changes, so that the control slider changes between the pipes 30 and 2.
8 is connected to weaken the pressing force of the operating portion 18 against the operating piston 22, or the pipe 30 and 2
6 can be connected to increase the pressing force. The operating piston 22 of the operating part 18 moves in a predetermined direction depending on the force acting on it, and changes the fuel supplied to the diesel engine 10 via the injection pump 19 accordingly. This continues until the actual value of the controlled variable detected by the movement amount sensor 21 takes a value that matches the target value. When the control function of the control device is reliable and normal, the electro-hydraulic converter 17 is driven in a region exceeding the limit frequency to perform accurate injection control to obtain an optimum injection amount.

Such control becomes completely different when the control circuit is interrupted, especially when a failure occurs in the movement amount sensor 21. A fault in the displacement sensor 21 is identified by the fault identification circuit 23 and when the fault occurs the pulse width modulator 15 is activated by the electro-hydraulic transducer 1.
The pulse frequency of the signal input to 7 is controlled to be a value below the limit frequency.

The control device according to the invention can be used not only in the case of a failure of the displacement sensor, but also in the case of a failure of the control device 13' or the regulator 14. Furthermore, in the case of a device that determines the amount of fuel supplied using a needle movement sensor or a piezo sensor, for example, the control device according to the present invention can be used when a failure occurs.
Furthermore, the control device according to the invention can be used not only for controlling the amount of fuel to be injected, but also for control involving noise, such as control of the injection point.

If the electrohydraulic transducer 17 is driven below the limit frequency, the pulse frequency of the signal input to the transducer is chosen to be small, so that the control slider 25 can be moved at each It can be made to move according to the pulse. Next, this will be explained in more detail with reference to FIG. FIGS. 2a to 2e show waveform diagrams showing the relationship of movement.

FIG. 2a shows how the duty ratio T of the signal input to the electrohydraulic converter 17 changes stepwise. FIGS. 2b to 2e show regions in which the stroke of the electrohydraulic transducer or the manipulated variable of the actuator 18 falls below or exceeds the limit frequency, respectively. FIG. 2b shows the electrohydraulic transducer 1 in the region above the limit frequency.
The variation of the stroke H ₂₅ of the control slider 25 of No. 7 as a function of time is illustrated. According to the definition of drive exceeding the limit frequency, the control slider 25 is determined by the duty ratio and the electromagnetic force 2
4 assumes its position according to the average current supplied to it. In this way the stroke of the electrohydraulic transducer 17 is controlled with respect to the duty ratio of the input signal.
FIG. 2c shows the position S ₂₂ of the actuating piston 22 as a function of time. The amount of movement of the control slider takes a positive value until t= _t1 . That is, the pressure tank 27 is connected to the pipe 30 via the pipe 26, and as a result, the pressure P _D of the pressure tank is applied to the operating piston 22. For the time t< _t1 , the operating piston is pushed to the leftmost end by the pressure P _D against the biasing force of the spring. This state is shown in Figure 2c.
Illustrated in S _nax . Control slider 25 is continuously acted upon for times t ₁ < t < t ₂
occupies exactly the center position. That is, in this state, the operating section is not connected to the pipes 26 to 28, so its position remains unchanged. At t>t ₂ the actuating piston 22 is released from the hydraulic pressure by connecting the pipes 28 and 30. In this case, the operating piston is pushed to the right end position by the biasing force of the spring. The speed of movement of the actuating piston is then determined according to various parameters such as mechanical friction, spring constant, etc.

In this way, the operating section exhibits different characteristics depending on the duty ratio, that is, the electrohydraulic transducer 17
When the internal combustion engine is driven at a frequency higher than the limit frequency, the fuel injected will differ depending on the duty ratio, but if the control circuit is cut off due to a failure of the travel sensor, the output obtained from the internal combustion engine will be unstable. This poses a significant risk to drivers of vehicles equipped with such internal combustion engines.

In order to avoid such an unpleasant situation for the driver of a motor vehicle, if the control circuit is interrupted, the actuating element is adjusted to the minimum value so that the fuel supplied to the internal combustion engine is minimized, thereby allowing the internal combustion engine to operate normally. There are known methods to bring it to a standstill state. However, in the case of such a conventional control device, emergency running becomes impossible.

According to the present invention, when the movement amount sensor fails, the pulse frequency of the signal input to the electrohydraulic converter 17 by the fault identification circuit 23 is adjusted to the control slider 2.
5 is reduced to a value that allows driving below the limit frequency. The stroke of the control slider 25 below the limit frequency is shown in FIG. 2d when the duty ratio changes as shown in FIG. 2a. The control slider varies between two extreme values, where the ratio of the time convection to the maximum as well as the minimum stroke is given by the duty ratio. The ability of the actuating piston 22 to respond to this sudden pressure change depends on the adjustment speed of the actuating piston 22, which is characterized by the time constant _Ts . The amplitude or pulse frequency of the signal input to the electrohydraulic transducer is therefore matched to the adjustment speed of the actuating element. FIG. 2e shows the displacement of the actuating piston with a well-chosen pulse frequency and time constant. It can be seen that the average amount of movement of the operating piston always corresponds to the amount of movement of the duty ratio. However, an alternating current component that vibrates minutely with an amplitude related to T _s is superimposed on this average movement amount.

As is clear from FIG. 2e, if the displacement sensor fails, the control of the operating piston 22 and therefore the fuel supply amount will change the duty ratio of the input signal when the electro-hydraulic transducer 17 is driven below the limit frequency. It can be understood that it is possible to control the Furthermore, by limiting the usable range of the duty ratio, it is also possible to limit the amount of fuel to be injected. The degree to which micro-vibrations superimposed on the average position of the actuating piston 22 can be tolerated varies depending on the type of internal combustion engine used. The magnitude of this microvibration can be varied according to the frequency of the input signal of the electrohydraulic transducer, and can also be varied according to the amplitude of the input signal. Continuously operating control slider 25
If the piston 22 is not used over its entire available stroke range, it is also possible to reduce the minute vibrations of the operating piston 22.

In order to further understand the above, the theoretical relationship between the duty ratio and the manipulated variable will be explained.
In the following explanation, each symbol means the following. T ₁ is the period when the operation is hydraulically energized;
T ₂ is the period when the hydraulic pressure of the operating part is released, P _D is the pressure in the pressure tank, A is the control cross section of the control slider (proportional to the stroke of the control slider), and K is the aperture of the control slider. coefficient,
A _p is the cross section of the operating piston, F is the return force of the spring that biases the operating piston, and is expressed as F=F _p +C·y (C is the spring constant and y is the amount of movement).

When the internal pressure governing the operating section is P _i = F/A _p , the amount m ₁ flowing from the pressure tank 27 to the operating section ₁₈ at time T 1 is m ₁ = A・K・T ₁・√ _D − _i On the other hand, if the operating unit is connected to the collection tank 29 via the control slider 25, the time
The amount m ₂ flowing from the operation unit 18 to the collection tank 29 during T ₂ is m ₂ =A·K·T ₂ · _√i . Equilibrium is obtained when m ₁ = m ₂ ,
After a few slight deformations, a proportional relationship yP _D・T ₁ ² /(T ₁ ² +T ₂ ² ) according to an addition constant is obtained between the operation amount y of the operation unit 18 and the times T ₁ and T ₂ . It will be done. Due to this relationship, the pressure in the pressure tank
When P _D is given, it is possible to calculate the duty ratio T ₁ /T ₂ corresponding to the desired manipulated variable y, and thereby set or limit the injection amount during emergency running in proportion to the manipulated variable y. .

By operating the electro-hydraulic transducer 17 below the limit frequency, it is possible to adjust the fuel supply amount or the injection timing during emergency driving, but this open-loop control of the fuel supply amount is dependent on the rotational speed. It has been found preferable to provide a closed loop control. The control of the fuel supply amount in relation to the rotational speed will be explained with reference to FIG. In the figure, the fuel supply amount control circuit is composed of a pulse width modulator 15 driven by a regulator 14, an output stage 16, an electrohydraulic converter 17, an operating section 18, an injection pump 19, and an internal combustion engine 10. Ru. At this point, the control system described above is the same as the control system shown in FIG. 1 in the case where the movement amount sensor 21 fails. But the third
In the illustrated embodiment, a rotational speed-related output signal from a rotational speed sensor 40 connected to the internal combustion engine 10 is input to a characteristic signal generator 41 . The output signal from this signal generator 41 is input together with the output signal from the pulse width modulator 15 via an output stage 16 to an electrohydraulic transducer 17 .

Various characteristic curves can be considered for controlling the engine speed. The choice of characteristic curve depends on various factors, such as, for example, the type of internal combustion engine used, and also whether speed control is to be carried out over the entire speed range or only in the idling range. It is also related to individual issues. The characteristic signal generator 41 is capable of generating an output signal which increases the fuel in case of falling below a minimum rotational speed, thereby preventing the rotational speed from reaching a value so small as to stop the internal combustion engine. be able to. It is likewise possible to reduce the rotational speed of the internal combustion engine in the high rotational speed range, thereby protecting the internal combustion engine from mechanical damage resulting from overspeeding. If the high speed limit value is exceeded, the characteristic signal generator 41 can generate an output signal which reduces the fuel supply and acts to prevent the maximum permissible speed from being exceeded.

In this way, the rotational speed-related control that is used to control the amount of fuel supplied during emergency driving guarantees stability for the driver of a vehicle equipped with an internal combustion engine, and at the same time prevents the internal combustion engine from experiencing mechanical overload. It becomes possible to protect it from being damaged by the load.

(e) Effects As explained above, according to the present invention, when a failure occurs that makes closed-loop control of the fuel supply amount impossible, the pulse frequency of the electrical signal input to the converter is reduced to a value below the limit frequency. By using open-loop control to control the position of the operating member that adjusts the amount of fuel supplied, the output of the internal combustion engine can be ensured without the need for any additional mechanical equipment. , making reliable emergency driving possible.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a schematic configuration of the device of the present invention, Fig. 2 a to e are signal waveform diagrams explaining the operation of the device shown in Fig. 1, and Fig. 3 shows the number of rotations when the movement sensor fails. FIG. 2 is a block diagram showing an embodiment in which controls related to are superimposed. 10... Internal combustion engine, 11... Accelerator pedal,
12...Accelerator pedal position sensor, 13...Control stage, 14...Adjuster, 15...Pulse width modulator, 16...Output stage, 17...Electrohydraulic transducer, 18...Operation unit, 19 ...Injection pump, 21
...Movement sensor, 22...Operation piston, 23
...Fault identification circuit, 27...Pressure tank, 29...
...collection tank.

Claims (1)

[Scope of Claims] 1. A fuel supply amount control device for an internal combustion engine including an electrohydraulic converter that operates an operating member that adjusts the fuel supply amount, wherein the electrohydraulic converter is a movable part of the converter. It is driven by an electric signal of a predetermined pulse frequency that is pulse width modulated and is higher than a limit frequency characterized by inertia, and when a failure occurs that makes closed loop control impossible for the position control of the operating member, the pulse frequency of the electric signal is changed. A fuel supply amount control device for an internal combustion engine, characterized in that the fuel supply amount is reduced to a value below the limit frequency, and the position of the operating member is controlled in an open loop to enable emergency running. 2. The fuel supply amount control device for an internal combustion engine according to claim 1, wherein the pulse frequency is reduced to a value below a limit frequency when a failure occurs in a sensor that detects the fuel supply amount. 3 Movement amount sensor 21 that detects the position of the operating member
3. The fuel supply amount control device for an internal combustion engine according to claim 2, wherein the pulse frequency is reduced to a value below a limit frequency when a failure occurs in the internal combustion engine. 4. The fuel supply control device for an internal combustion engine according to claim 1, wherein the fuel supply amount is controlled according to the duty ratio of the signal input to the electrohydraulic converter 17. 5. Any one of claims 2 to 4 in which the amplitude of the signal input to the electro-hydraulic converter 17 is adjusted to the adjustment speed of the operating unit 18 when a failure occurs in the movement amount sensor. The fuel supply amount control device for an internal combustion engine according to item 1. 6. The internal combustion engine according to any one of claims 2 to 5, wherein when a failure occurs in the movement amount sensor 21, control of the fuel supply amount related to the rotation speed is superimposed. fuel supply amount control device. 7. The fuel supply amount control device for an internal combustion engine according to claim 6, wherein control characteristics of the fuel supply amount related to the rotational speed can be individually adjusted according to a characteristic signal generator. 8. Fuel supply for an internal combustion engine according to claim 7, wherein when the fuel supply amount is controlled in relation to the rotation speed in a low rotation speed region, the fuel supply amount is increased as the rotation speed decreases. Volume control device. 9 Claim 6: When controlling the fuel supply amount in relation to the rotation speed in a high rotation speed region, the fuel supply amount is decreased as the rotation speed increases.
9. The fuel supply amount control device for an internal combustion engine according to item 7 or 8. 10. The fuel supply amount of the internal combustion engine according to any one of claims 6 to 9, wherein control of the fuel supply amount according to the rotation speed is interrupted in an intermediate rotation speed region. Control device.