JPS595779B2 - electronic fuel supply system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to low pressure (fuel pressure 03 to 1
The present invention relates to an electronic fuel supply device that appropriately controls the amount of fuel supplied in a unit injection type diesel engine used in the range of 5 Klj/crtl.

In diesel engines using the low-pressure unit injection system, fuel is injected by each injector, and the amount of fuel injected per injector (injection amount per stroke) is a function of the fuel pressure applied to the injector and the engine rotation speed. given by.

That is, when the fuel pressure increases, the flow rate per unit time flowing into the injector increases, and the amount of fuel injected per time increases.

Furthermore, as the rotational speed of the engine increases, the time required for metering by the injector decreases, so the amount of fuel injected per time decreases.

Therefore, the pressure of fuel supplied to each injector is controlled according to engine operating conditions such as engine speed, intake air temperature, intake pressure, exhaust temperature, etc., and the amount of fuel injected from each injector at one time is set to an appropriate value. It must be kept in place.

Conventionally, a mechanical device such as a so-called PT pump has been used as a fuel supply device for controlling the fuel supplied to each injector.

This device uses mechanical governors such as PTG governors and MVS governors that control the amount of fuel supplied by utilizing the balance between centrifugal force and spring pressure in response to engine rotation, and is extremely complex and requires adjustment elements. Not only that, but the production cost was also high.

Additionally, since it is mechanical, there is a problem with response time accuracy, and it is extremely expensive to perform precise control based on not only engine speed, but also engine intake air temperature, intake pressure, exhaust temperature, etc. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel supply device that is inexpensive and has a simple configuration and can control the amount of fuel supplied with high precision in accordance with not only the rotational speed of the engine but also various conditions of the engine. shall be.

In the present invention, electromagnetic pulp is arranged in the fuel supply path to each injector of the engine, and the electromagnetic pulp is used as a control signal from an electronic circuit that forms a control signal according to engine rotational speed, intake/exhaust temperature, intake pressure, etc. so that it is controlled by
It does not require any complicated mechanical control equipment, and allows the amount of fuel supplied to be precisely controlled according to various engine conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electronic fuel supply system of the present invention will be described in detail below with reference to an embodiment of the accompanying drawings.

FIG. 1 shows an embodiment of the electronic fuel supply system of the present invention.

The fuel in the fuel tank 1 passes through the filter 2 to the fuel pump 3.
added to.

The fuel pump 3 is controlled so that the discharged fuel pressure is always constant, and the fuel pump 3 can be either an electric pump or a mechanical pump driven by an engine.

Fuel at a constant pressure discharged from the fuel pump 3 is applied to the electromagnetic pulp 4.

The electromagnetic pulp 4 is an on/off pulp and is controlled by a control signal C8 applied from an electronic circuit 5.

The electronic circuit 5 forms a control signal C8 for controlling the electromagnetic pulp 4 according to various engine conditions such as engine speed, intake and exhaust temperature, intake pressure, etc., and an example of the detailed circuit is shown in FIG. Shown in block diagram.

In FIG. 2, the engine rotation sensor 6 is disposed at an appropriate location such as the crankshaft of the engine (not shown).
Pulse signal Pa with a frequency corresponding to the rotational speed of the engine
occurs.

The pulse signal Pa from the engine rotation sensor 6 has a frequency of -
It is applied to a voltage converter I and converted into a voltage corresponding to its frequency, that is, a voltage vb corresponding to the rotational speed of the engine.

This voltage vb is added to the addition point 14 to which the command rotation speed voltage Vc (throttle signal) set by the variable resistor 9 is added, and at the addition point 14 it indicates the deviation between the engine rotation speed and the command rotation speed Vc. Signal Vc is applied to comparator 10 via correction circuit 8.

Note that the compensation circuit 8 is a series compensation circuit commonly used in servo systems.

On the other hand, the pulse signal Pa generated from the engine rotation sensor 6 is applied to the frequency dividing circuit 11.

If the engine has n cylinders, the frequency dividing circuit 11 divides the applied pulse signal Pa into n for two revolutions of the crankshaft.
The frequency is divided into three pulse signals.

For example, if the engine has six cylinders, the output of the frequency dividing circuit 11 will be as shown in Figure 3.

The output pulse signal Pc of this frequency dividing circuit 11 is
Added to 2.

The function generator 12 also includes various sensors (
(not shown) is added.

The function generator 12 uses each pulse of the pulse signal Pe as a trigger pulse to generate a waveform signal Vf whose rising portion is controlled by a predetermined time constant as shown in FIG. Controlled in response to signals from sensors.

An example of a change in the waveform Vf generated from the function generator 12 is shown by a dotted line in FIG. 3C.

In other words, the frequency of the waveform signal generated from the function generator 12 corresponds to the engine rotational speed, and the rise time constant corresponds to other engine conditions such as the engine intake air temperature, intake air pressure, and exhaust temperature. .

Such a function generator 12 includes a sawtooth wave generation circuit whose rise time constant is controlled by signals from the various sensors using the pulse signal Pe as a trigger pulse, and a limiter which limits the upper limit level of this sawtooth wave generation circuit. It can be easily constructed by combining it with a circuit.

The waveform signal Vf generated from the function generator 12 is applied to the comparator 10.

The comparator 10 compares the output of the correction circuit 8 and the output Vf of the function generator 12, and if vd>vf, outputs a high level signal, and if Vd≦Vf, outputs a low level signal.

That is, if the output of the compensation circuit 8 is a value as shown by the dashed line in FIG. 3C, the output of the comparator circuit 10 is a pulse signal Pg as shown in FIG. 3D.

Further, when the output of the function generator 12 changes as shown by the dotted line in FIG. 3C, the output of the comparator 10 becomes as shown by the dotted line in FIG. 3D.

As is clear from the graph, the pulse width of the signal Pg output from the comparator 10 increases as the output Vd of the compensation circuit 8 increases, decreases as it decreases, and also depends on the time constant of the rise of the output Vf of the function generator 12. comparator 10 according to the increase or decrease of
The pulse width of the output pulse signal Pg increases and decreases.

The output Pg of the comparator 10 is applied to the electromagnetic pulp 4 (FIG. 1) as a control signal C8 via a pulp drive circuit 13.

The electromagnetic pulp 4 is turned on while the control signal C8 is at -.-level, and supplies fuel to each injector.

FIG. 4 shows the relationship between the open time of the metering orifice (not shown) of the injector of each cylinder of the engine, that is, the metering area, and the control signal C8 from the electronic circuit 5.

In Fig. 4, Fig. 4 a '' f shows the metering area of 1 cylinder, 5 cylinder, 3 cylinder, 6 cylinder, 2 cylinder, and 4 cylinder, respectively, and Fig. 4 g shows the control signal C8. There is.

As mentioned above, the control signal C8 is formed from six pulses for two revolutions of the engine crankshaft, so the metering area for each cylinder includes two pulses of the control signal C8. , each cylinder is supplied with fuel on average.

Furthermore, it is not necessary to accurately time the top dead center, bottom dead center, etc., due to this method.

FIG. 5 shows a characteristic curve showing the relationship between the engine speed and the amount of fuel injected per injector (this value is proportional to torque) when using the electronic fuel supply system according to the same embodiment. It is something that

By varying the throttle (variable resistor 9 (Fig. 2)), this characteristic curve can be changed as shown by arrow A in the same way as when using a mechanical governor, and can also be changed as shown by arrow B depending on the output of each sensor. It can be changed as follows.

As explained above, according to the present invention, one of each injector
The injection amount of the stroke can be easily set to an appropriate value, and since no mechanical governor control element is included, maintenance is easy, and characteristics can be easily changed to take measures against exhaust gas.

In addition, since it is an electronic type, the response is good, so ideal governor characteristics and starting characteristics can be obtained, and manufacturing costs can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the electronic fuel supply device of the present invention, FIG. 2 is a partially detailed block diagram of the same embodiment,
3 and 4 are graphs explaining the operation of the same embodiment, and FIG. 5 is a graph showing the characteristics of the engine according to the same embodiment. 3... Fuel pump, 4... Electromagnetic pulp, 5... Electronic circuit.

Claims (1)

[Claims] 1. In a unit injection type diesel engine fuel supply device having a plurality of unit injectors in which the fuel injection amount is controlled in accordance with the applied fuel pressure, each unit injector is connected to the fuel supply path to the unit injector. an electromagnetic pulp that is commonly arranged for the engine, and a circuit that generates a first signal corresponding to the engine rotational speed, whose period corresponds to the engine rotational speed, and whose rise time constant is the intake and exhaust temperature and the intake pressure. a function generator that generates a second signal that is controlled according to other conditions of the engine, such as a function generator that compares the first signal and the second signal, and compares the first signal with the second signal; and a comparator generating a signal that controls the electromagnetic pulp to open when the signal is greater than the signal and controls the electromagnetic pulp to close when the signal is smaller than the signal.