JPH0463929A - Fuel injector - Google Patents

Abstract

PURPOSE:To supply enough fuel at the time of high speed of an internal combustion engine, and prevent excess of an injection quantity of fuel at the time of low speed by increasing fuel pressure to an injector in accordance with the increase in engine speed of the engine. CONSTITUTION:There is provided a fuel pressure controller 10 which increasingly controls fuel pressure to an injector 2 in accordance with increase in engine speed of an internal combustion engine 1. A fuel pressure set signal Vps for providing a set value of the fuel pressure in the engine speed detected by an engine speed detection means 12 is outputted from a fuel pressure set means 13, to control driving voltage or current which is given from a power supply 15 to a fuel pump 5 by a pump controller 14 so that the fuel pressure detected by a fuel pressure detection means 11 corresponds to the set value of the fuel pressure. Excess of an injection quantity in a low range of the engine speed is prevented so as to respond to requirement of increase in the injection quantity at the time of high speed of the engine.

Description

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

[Prior Art] Fig. 19 shows the overall configuration of a fuel injection device used in an internal combustion engine. An injector 2 that injects fuel into 1a (inside the fuel injection space), a fuel pump 5 that pumps up fuel from a fuel tank 3 and pressure-feeds the fuel to a fuel supply pipe 4 leading to the injector 2, and a fuel supply pipe 4. A pressure regulator 6 is provided between the fuel tank 3 and the fuel tank 3.

In the conventional fuel injection device, the fuel pump 5 operates using a battery as a power source to supply fuel to the injector 2. The injector 2 is equipped with a needle valve that is driven to open and close by an electromagnet and a nozzle that injects fuel when the needle valve is opened. 1
The pressure difference between the pressure in the intake pipe and the pressure in the intake pipe is constantly applied as fuel pressure.

The pressure regulator 6 is supplied with the pressure in the intake pipe of the internal combustion engine in addition to the pressure normally supplied from the fuel pump, and when the difference in side pressure exceeds a set value, part of the fuel supplied from the fuel pump is supplied to the pressure regulator 6. part is returned to the fuel tank 3.

With this pressure regulator, the fuel pressure P applied to the injector is kept almost constant with respect to the rotational speed N, as indicated by the straight line a in FIG. 13.

The excitation coil of the electromagnet that drives the injector 2 is given an injection command signal with a predetermined time width in a predetermined rotation angle section of the engine by an electronic control device using a microcomputer. While this injection command signal is being applied, the needle valve of the injector opens and atomized fuel is injected into the intake pipe.

The amount of fuel injected from the injector 2 is determined by the fuel pressure and injection time. Further, when the injection time is constant, the injection amount increases as the fuel pressure increases. FIG. 14 shows an example of the relationship between the injection amount Q from the injector and the injection time T. In the figure, the curve (■) shows the case where the fuel pressure is high, and the curve (2) shows the case where the fuel pressure is low.

In this way, the amount of fuel injected from the injector 2 is determined by the fuel pressure and injection time, but in order to stabilize the operation of the injector and facilitate control, it is necessary to It is necessary to use a region where a linear relationship exists between Q and injection time T. That is, when the fuel pressure is increased as shown by curve (2), it is necessary to set the injection time to T1 or more and use it in a region where an injection amount of 01 or more is obtained. In this case, it is necessary to avoid usage that would result in an injection amount smaller than Q1. In addition, when the fuel pressure is reduced as shown in curve ■, the injection time is set to T0 or more and Q
It is necessary to use it in a region where an injection amount of O (<Ql) or more is obtained, and it is necessary to avoid usage where an injection amount is less than QO.

Since fuel needs to be supplied to the engine within a predetermined rotation angle range of the engine, the period during which fuel injection from the injector is effective (referred to as the effective injection period).

) becomes shorter as the engine speed N increases, as shown in FIG. In other words, as the engine speed increases, it becomes necessary to inject a predetermined amount of fuel within a short period of time, and in order to secure the necessary amount of fuel injection when the engine is running at high speed, the fuel pressure must be set to a certain level. I don't get it.

The amount of fuel injected from the injector can be adjusted by changing the length of time the injection command signal is given, but the fuel efficiency (fuel consumption) [l/Hr] required by the engine is generally shown in Figure 17. As the rotational speed N [rpm] increases and the throttle opening increases, the length of time for giving an injection command signal to the injector increases as the rotational speed increases. Therefore, it is necessary to increase the length as the throttle opening increases.

In FIG. 17, the portion indicated by a broken line indicates a region where the engine operation becomes unstable or where the engine operation becomes impossible. Further, straight lines ``■'' and ``■'' indicate the case where the throttle opening degree is 1/4 and 2/4, respectively, and straight line ``■'' indicates the case where the throttle opening degree is 4/4 (fully open).

In an actual fuel injection system, a damper or the like may be inserted between the fuel pump 5 and the injector 2 to further reduce the pulsation of the fuel, but these are not shown in Fig. 19. .

[Problems to be Solved by the Invention] In conventional fuel injection devices, the fuel pressure P applied to the injector is always kept constant regardless of the rotation speed N, as shown by the straight line a shown in FIG. The amount of fuel supplied was adjusted by adjusting only the length of time that the injection command signal was given to the injector, but in this case,
It was not possible to obtain the ideal fuel injection amount in all engine speed ranges.

In other words, the fuel pressure is set appropriately taking into account the amount of injection required by the engine, but if the fuel pressure is set high as shown in curve ■ in Figure 14 to supply sufficient fuel when the engine is running at high speed, , Ql, it is no longer possible to obtain an injection amount smaller than , Ql, which causes problems such as excessive fuel being injected when the engine is running at low speed, resulting in poor fuel efficiency and an increase in CO in the exhaust gas. In addition, if the fuel pressure is set low as shown in curve ■ in Figure 14 in order to make the amount of fuel injected at low speeds of the engine ideal, a sufficient amount of fuel can be injected when the engine is at high speeds. become unable to do so.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel injection device for an internal combustion engine that is capable of supplying sufficient fuel when the engine is running at high speeds and also preventing the amount of fuel injected from becoming excessive when the engine is running at low speeds. .

[Means for Solving the Problems] The present invention includes an injector that injects fuel into a fuel injection space of an internal combustion engine when an injection command signal is given, and a fuel pump that supplies fuel from a fuel tank to the injector. The present invention relates to a fuel injection device, and is characterized in that it includes a fuel pressure control device that increases the fuel pressure applied to an injector as the rotational speed of an internal combustion engine increases.

The fuel injection space is a space into which an injector injects fuel, and differs depending on the engine. In the case of a four-cycle engine, the space within the intake pipe is usually the fuel injection space, but when fuel is injected directly into the cylinder of the engine, the space inside the cylinder is the fuel injection space. In the case of a two-cycle engine, there are cases in which fuel is injected into an intake pipe, cases in which fuel is injected into a scavenging pipe, and cases in which fuel is injected directly into a cylinder.

The fuel pressure control device includes a fuel pressure detection means for detecting fuel pressure;
a rotation speed detection means for detecting the rotation speed of the internal combustion engine; a fuel pressure setting means for providing a fuel pressure set value at the rotation speed detected by the rotation speed detection means; and a fuel pressure setting means for setting the fuel pressure detected by the fuel pressure detection means to the fuel pressure set value. and a pump control device that controls the rotation of the fuel pump so as to match the rotation of the fuel pump.

The fuel pressure control device also includes a fuel pressure adjustment means provided between the fuel pump and the injector, an actuator for operating the fuel pressure adjustment means, a fuel pressure detection means for detecting the fuel pressure, and a rotation speed for detecting the rotation speed of the internal combustion engine. a fuel pressure setting means for providing a fuel pressure setting value at the rotational speed detected by the rotational speed detection means, and an actuator operation necessary to match the fuel pressure detected by the fuel pressure detection means with the fuel pressure setting value. It can also be configured by a control calculation means that calculates the amount, and a drive circuit that supplies a drive current to the actuator according to the operation amount calculated by the control calculation means.

The fuel pressure regulating means may be a flow rate regulating valve inserted between the fuel pump and the injector, or may be a flow regulating valve inserted between the injector inlet pipe and the fuel tank so that the pressure applied to the injector exceeds a set value. It may also be a pressure regulator that maintains the pressure on the inlet side of the injector at a set value by returning a portion of the fuel supplied from the fuel pump to the fuel tank when the injector is injected. In this case, the pressure regulator used includes a set value adjusting means for adjusting the set value of the pressure, and the set value adjusting means is operated by an actuator.

The pressure regulator is configured to maintain the pressure on the inlet side of the injector at a set value in response to the differential pressure between the pressure in the pipe line between the fuel pump and the injector and the pressure in the fuel injection space of the internal combustion engine. Alternatively, the pressure at the inlet of the injector may be maintained at a set value in response to only the pressure at the inlet of the injector.

Strictly speaking, the fuel pressure applied to the injector is the difference between the pressure of the fuel supplied to the injector from the fuel pump and the pressure within the fuel injection space of the engine.
A pressure sensor is installed in the pipe between the fuel pump and the injector and outputs an electrical signal proportional to the pressure in the pipe, and a pressure sensor is installed in the pipe between the fuel pump and the injector to output an electrical signal proportional to the pressure in the pipe. It can be configured by a pressure sensor that generates a signal and a means for calculating fuel pressure from the output of the side pressure sensor.

Alternatively, a pressure sensor may be attached near the inlet of the injector, and the output of the pressure sensor may be used as the fuel pressure detection signal.

In the above configuration, the fuel pressure is controlled by feedback control, but in the present invention, it is sufficient to control the fuel pressure to increase as the engine speed increases, and it is not necessarily necessary to control the fuel pressure by feedback control. do not have.

For example, by using an alternator that is driven by an internal combustion engine as a power source to drive a fuel pump and has the characteristic that its output voltage or output current increases as the engine's rotational speed increases, it is possible to increase or decrease the internal combustion engine's rotational speed. Accordingly, the discharge pressure of the fuel pump may be increased or decreased to increase the fuel pressure applied to the injector as the engine speed increases.

Note that it is not necessarily necessary to increase the fuel pressure as the engine speed increases in the entire engine speed range, but it is necessary to increase the fuel pressure as the engine speed increases only in the range below a predetermined engine speed to maintain the specified engine speed. The fuel pressure may be kept constant in the region exceeding .

In addition, it is not necessary to control the fuel pressure as the rotation speed increases, but it is not necessary to continuously control the fuel pressure as the rotation speed increases.
The fuel pressure may be changed stepwise at each set rotation speed.

[Function] With the above configuration, when the rotational speed is low, the fuel pressure is lowered and a linear relationship can be maintained between the injection amount and the injection time up to the region where the injection amount is small, and the rotational speed increases. When the fuel pressure is high, the fuel pressure can be increased to increase the injection amount.

Therefore, it is possible to prevent the injection amount from becoming excessive in a region where the engine speed is low. Further, since the fuel pressure is increased as the rotational speed increases, it is possible to meet the request for an increase in the injection amount when the engine is running at high speed without any problem.

Furthermore, when the fuel pressure is changed according to the engine speed as described above, the injection amount is determined by the product of the fuel pressure and the injection time. In order to obtain this, it is necessary to detect the fuel pressure and calculate the injection time according to the detected value, but this calculation of the injection time may be performed by using a microcomputer or an analog calculation circuit. Furthermore, if the fuel pressure at each rotational speed can be predicted in advance, the injection time may be determined from a non-arithmetic formula by determining the injection time using the rotational speed as a variable without detecting the fuel pressure.

[Examples] Examples of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 schematically shows the configuration of an embodiment of the present invention, in which 1 is an internal combustion engine, 2 is an injector, and 3 is a fuel tank, which are the conventional ones shown in FIG. 19. It is similar to

In the present invention, a fuel pressure control device 10 is provided that controls the fuel pressure applied to the injector 2 to increase as the rotational speed of the internal combustion engine 1 increases.

This fuel pressure control device can take various configurations, but
In the example shown in FIG. 1, fuel pressure detection means 1 detects the fuel pressure on the inlet side of the injector 2 and outputs the fuel pressure detection signal Vp.
1, and rotation speed detection means 12 for detecting the rotation speed of the internal combustion engine.
and a fuel pressure setting means 13 for outputting a fuel pressure setting signal Vps giving a fuel pressure setting value at the rotational speed detected by the rotational speed detection means 12; The fuel pressure control device 1 includes a pump control device 14 that controls the rotation of the fuel pump.
0 is configured.

The pump control device 14 includes a circuit for determining the deviation between the fuel pressure detection signal Vp and the fuel pressure setting signal Vps, and a circuit for controlling the drive voltage or drive current applied to the fuel pump 5 from the power source 15 so as to reduce the deviation to zero. It can be configured by

The fuel pressure setting means 11 may be a circuit that calculates a set value of fuel pressure according to the number of revolutions using a predetermined calculation formula (or a circuit that reads out a set value of fuel pressure at each number of revolutions from a memory in a microcomputer). It is also possible to use

In this embodiment, as the fuel pump 5, a pump having a characteristic that the discharge pressure changes depending on the drive voltage or drive current is used. FIG. 7 shows an example of the fuel pump 5 that can be used in this embodiment, so in this example, the housing 5
A DC motor includes a stator-side field (magnet) 501 provided in a housing 500 and a rotor 503 attached to a rotating shaft 502 supported by a housing 500 via a bearing.
The pump 504 is provided at one end of the housing 500 and is driven by an electric motor.

The pump 504 consists of a pump casing 505 and an impeller 506 disposed inside the pump casing 505.
is coupled to the rotating shaft 502.

A suction port 507 is provided at the end of the casing of the pump 504, and a discharge port 508 is provided at the other end of the housing 500. A power supply terminal 509 is also provided at the other end of the housing 500, from which power is supplied to the windings of the rotor 503 via a brush 510 and a commutator 511.

The above fuel pump is located inside the fuel tank and has an inlet port 5.
07 is inserted into the fuel. Further, a discharge port 508 is connected to an injector through a pipe (not shown).

When power is supplied to the rotor 503 of the fuel pump, the rotor rotates, and the impeller of the pump 504 rotates. As a result, fuel is sucked from the suction port 507. The sucked fuel passes through the housing 500 and is delivered from the discharge port 508. The discharge pressure of this fuel pump increases as the voltage supplied to the rotor increases.

Next, an example of the injector 2 is shown in FIG.

In the same figure, 201 is an injector main body, and one end of this main body includes a valve body 204 having a valve seat 203 around an injection port 202, and a needle 205 provided in the valve body to open and close the injection port 202. A needle valve 206 is attached. Main body 2
01 contains an excitation coil 207, an iron core 208, and an iron core 20.
An electromagnet 21 consisting of an armature 209 attracted to
0 is placed and the armature 209 is connected to the needle 205. A return spring 211 is also provided within the main body 201, and this return spring always urges the needle 205 to close the injection port 202. Main body 201
A fuel inlet 212 is provided on the other end side, and a filter 213 is attached to this inlet side. Main body 201
A connector 214 is also attached to the coil 207, and power is supplied to the coil 207 from a terminal 215 of the connector.

The injector 2 described above is attached to, for example, an intake pipe of an engine, and the injection port 202 is directed into the intake pipe (inside the fuel injection space). The inlet 212 of the injector 2 is connected to the discharge port of the fuel pump by a pipe (not shown).
Fuel is supplied to the fuel tank at a predetermined pressure (fuel pressure). Further, a cable (not shown) is connected to the connector 214, and is connected to an injector drive device via the cable.

When the injection command signal is given, a drive current is given to the excitation coil 207 from an injector drive device (not shown). When a driving current is applied to the excitation coil 207, the iron core 2
08 is excited, the armature 209 is attracted to the iron core, the needle 205 moves toward the electromagnet, and the needle valve opens (.

As a result, fuel is atomized and injected into the intake pipe from the injection port 202. When the injection command signal disappears and the drive current of the excitation coil disappears, the coil 207 is demagnetized and the needle 205 is moved to the injection port 20 by the biasing force of the return spring 211.
2 returns to the closed position.

In the embodiment shown in FIG. 1, the fuel pressure applied to the injector 2 is controlled so as to match the set value set for each rotational speed of the engine, and the fuel pressure increases as the rotational speed increases. . If the fuel pressure set value is determined to increase linearly as the engine speed increases, the characteristic of the fuel pressure P with respect to the engine speed N will be as shown by the straight line in FIG.

If the fuel pressure is increased as the engine speed increases as described above, when the engine is running at high speed, the characteristic of the injection amount Q with respect to the injection time T will be as shown by the curve (■) in Figure 14, for example. Sometimes a sufficiently large injection quantity can be obtained.

Furthermore, when the engine speed is low, the characteristic of the injection amount Q versus the injection time T becomes, for example, as shown in the curve (■) in FIG. I can do it. Therefore, the injection amount when the engine is running at low speed can be set to a necessary amount, and it is possible to prevent excessive fuel from being supplied when the engine is running at low speed.

In addition, in order to meet the demand for accurate engine control under any load conditions, it is preferable to have a wide dynamic range for the injector, but if the fuel pressure is varied according to the rotation speed as described above, the injector Dynamic range can be increased.

The dynamic range of the injector is the maximum injection amount Qm
It is defined by the ratio QmaX/Qmin between ax and the minimum injection amount Qmin. For example, when the fuel pressure is set so as to obtain a sufficient injection amount Q at high speeds and the fuel pressure is held constant, the characteristic of the injection amount with respect to the injection time is as shown by the curve (2) in FIG. In FIG. 15, the horizontal axis indicates the duty Td of the injection time. As shown in FIG. 16(A), the injection command signal Vc
When i is given, the drive current Ii flows through the excitation coil of the injector 2 to open the injector as shown in FIG.
From i and the time t1 of one cycle of the injection command signal, Td =
It is given by (ti/lf)xlOO[%].

When the fuel pressure is kept constant and the characteristics of curve ■ in Fig. 15 are obtained,
Since the only characteristics that can be used are those in the region where a linear relationship is maintained, the dynamic range of the injector is
Qmax/Q1min.

On the other hand, when the fuel pressure is changed as in the present invention, the characteristic of the injection time Q with respect to the duty Td of the injection time is the characteristic of the curve ■ in Fig. 15 at high speed, and the characteristic of the curve ■ in the same figure at low speed. Therefore, the maximum value of the injection amount is Qmax.

The minimum value is Q omin (<Q 1m1n).

Therefore, the dynamic range of the injector is Qma
x/Qomin, and the dynamic range of the injector can be made larger than when the fuel pressure is constant.

In the above embodiment, the fuel pressure is controlled by controlling the rotation of the fuel pump 5, but in the present invention, elements that can change the fuel pressure in the fuel supply system are controlled according to the engine speed. The fuel pressure can be controlled by

FIG. 2 shows another embodiment of the present invention. In this embodiment, a valve 20 as a fuel pressure adjusting means is inserted between the discharge port of the fuel pump 5 and the injector 2, and this valve is controlled. By doing this, the fuel pressure is controlled.

That is, the fuel pressure control device 10 shown in FIG.
1, a fuel pressure detection means 22 for detecting the fuel pressure, a rotation speed detection means 23 for detecting the rotation speed of the internal combustion engine, and a fuel pressure setting means 24 for providing a set value of the fuel pressure at the rotation speed detected by the rotation speed detection means. , a manipulated variable calculation means 25 that calculates the manipulated variable of the actuator necessary to make the fuel pressure detected by the fuel pressure detection means coincide with the set value of the fuel pressure; A drive circuit 26 supplies a drive current to the drive circuit 26.

In this embodiment, the valve 20 is operated according to the deviation between the detected fuel pressure and the set value of the fuel pressure at each rotational speed, and the fuel pressure is made to match the set value.

FIG. 3 shows still another embodiment of the present invention, in which the inlet side of the pressure regulator 30 is connected in the middle of the pipe connecting the fuel pump 5 and the injector 2, The outlet side of the pressure regulator is connected to the fuel tank 3. The pressure regulator 30 maintains the pressure at the inlet side of the injector at the set value by returning part of the fuel supplied from the fuel pump 5 to the fuel tank 3 when the pressure applied to the injector 2 exceeds the set value. This pressure regulator is equipped with a set value adjusting means for adjusting the set value of the pressure.

In this embodiment, a pressure regulator 30 is used as a fuel pressure regulating means, and the fuel pressure control device 10 detects the pressure regulator, the rotation speed of the internal combustion engine 1, and the fuel pressure of the injector 2, and sets the detected value of the fuel pressure. The control section 31 changes the setting value of the pressure regulator 30 according to the deviation from the pressure regulator 30.

This control section 31, similar to that shown in FIG. a fuel pressure setting means for providing a set value of fuel pressure at the rotational speed detected by the number detecting means; and a manipulated variable for calculating the manipulated variable of the actuator necessary to match the fuel pressure detected by the fuel pressure detecting means with the set value of the fuel pressure. It can be configured by a calculation means and a drive circuit that supplies a drive current to the actuator according to the operation amount calculated by the operation amount calculation means.

FIG. 9 shows an example of a pressure regulator 30, which has a fuel chamber 32 and a spring chamber 33, with a diaphragm 34 separating the fuel chamber 32 and the spring chamber 33. has been done.

The fuel chamber 32 is provided with a pipe 35 whose one end is open toward the diaphragm 34, and a valve seat 35a is formed at one end of the pipe 35. A valve 36 is attached to the diaphragm 34, and one end of the pipe 35 is opened and closed by the valve 36. The fuel chamber 32 is provided with an inlet 37 that communicates with the space around the pipe 35, and the other end of the pipe 35 is connected to an outlet 38.
It becomes. A diaphragm 3 is located inside the spring chamber 33.
A coil spring 39 is disposed to bias the spring 4, and the end of the spring 39 opposite to the diaphragm is stopped by a plate 40, which is movable in the axial direction of the spring. An operating rod 41 is provided slidably and airtightly penetrating the end wall of the spring chamber 33.
One end of the spring holder is connected to the plate 40.

An intermediate portion of a lever 44 is supported by a support portion 42 provided on an end wall of the spring chamber 39 via a pin 43, and one end of the lever 44 is connected to a rod 41 via a pin 45. The other end of the lever 44 is provided with a coupling part 44a to an actuator, and the coupling part 44a is connected to an output part of an actuator (not shown).

The inlet 37 of the pressure regulator is connected to the middle of a pipe connecting the discharge port of the fuel pump 5 and the injector, and the outlet 38 is connected to the fuel tank 3 via a predetermined pipe. An intake pipe connection port 46 is also provided in the spring chamber 33, and the connection port 46 is connected to an intake pipe of the internal combustion engine.

In this pressure regulator, when the difference (fuel pressure) between the pressure of fuel supplied from the fuel pump and the pressure in the intake pipe exceeds the pressure set by the spring 39, the valve 36
opens to communicate the inlet 37 and the outlet 38, returning a portion of the fuel supplied to the injector from the fuel pump to the fuel tank. The set value of the pressure can be changed as appropriate by moving the spring plate 40 via the lever 44 and adjusting the biasing force of the spring 39 applied to the diaphragm 34.

In the embodiment shown in FIG. 3, the control unit 31 adjusts the pressure setting value of the pressure regulator 30 according to the deviation between the detected value of the fuel pressure and the set value of the fuel pressure at each rotation speed, so that the fuel pressure is adjusted at each rotation speed. Match the setting value in number.

As in the embodiment shown in Fig. 3, providing a path for returning part of the fuel flowing between the fuel pump and the injector to the fuel tank prevents the temperature of the fuel supplied to the injector from rising. It also has a preventive effect.

FIG. 4 shows another embodiment of the present invention. In this embodiment, a generator 50 is attached to the output shaft of the internal combustion engine 1, and the output of the generator 50 is fed to the fuel via a rectifier circuit 51. A voltage is applied to the power terminal of the pump 5.

As the generator 50, for example, a magnetic AC generator including a magnetic rotor and a stator having an armature coil can be used.

When a magnetic alternating current generator is used as the generator 50, the characteristics of its output voltage Vo versus output current Io are as shown in, for example, FIG. 10 or FIG. 11.

In these figures, curves a to d show characteristic curves at different rotational speeds, respectively.

The rotation speed N increases in the order of b, c, and d.

In the embodiment shown in FIG. 4, when the generator 50 having the characteristics shown in FIG. 10 is used, the load line of the fuel pump (
If the relationship between the input voltage and the input current is L, then the relationship between the generator rotation speed (engine rotation speed) N and fuel pressure is as shown by the curve ■ in Figure 12, and the engine rotation speed N is compared. A characteristic is obtained in which the fuel pressure P rises suddenly in a low target range, and then becomes saturated and becomes almost constant. In this case, the fuel pressure increases as the rotational speed increases only in a relatively low rotational speed range, and the fuel pressure remains almost constant in a speed range above a predetermined rotational speed.

In this case, as in the example shown in Fig. 19, a pressure regulator is provided between the fuel tank and the pipe line between the fuel pump and the injector, so that when the engine fuel pressure exceeds the set value, By returning part of the fuel to the fuel tank through the pressure regulator, the fuel pressure may be controlled to be constant in a speed range above a predetermined number of revolutions. In this case,
A characteristic is obtained in which the fuel pressure increases as the engine speed increases in a region where the engine speed is below the set value, and the fuel pressure becomes approximately constant in a region where the engine speed exceeds the set speed.

In addition, when using the generator 50 with the characteristics shown in FIG. 11, the fuel pressure P with respect to the rotational speed N is
A characteristic that increases linearly is obtained.

In FIG. 12, the straight line {circle around (2)} shows the characteristics of a conventional fuel injection system in which the fuel pressure was controlled to be constant.

In the embodiment of FIG. 4, a voltage regulator may be provided on the output side of the generator to control the voltage applied to the fuel pump so that it does not exceed a set value.

Even when a voltage regulator is installed in this way, the fuel pressure increases as the engine speed increases when the engine speed is below the set value, and remains almost constant when the engine speed exceeds the set value. The following characteristics can be obtained.

In the above example, by using a generator whose output voltage increases as the rotational speed increases, the output of the fuel pump increases as the rotational speed increases, thereby increasing the fuel pressure. Similar results can be obtained by using a generator having a characteristic in which the output current increases as the rotational speed increases.

In the above example, an alternating current generator is used as the generator 50, but a direct current generator can also be used as the generator, and in that case, the rectifier circuit is omitted.

In the embodiment shown in FIG. 4, when an alternating current generator is used as the generator 50, an alternating current motor without brushes can be used as the electric motor for driving the fuel pump.
In that case, the rectifier circuit 51 is omitted. Particularly when the fuel pump is disposed inside the fuel tank, driving the fuel pump with an electric motor without brushes can eliminate the risk of sparks, thereby increasing safety.

In each of the above embodiments, the fuel pressure is changed by electrical means, but as shown in FIG. By adjusting the pressure setting value of the pressure regulator 30, the fuel pressure can also be increased or decreased depending on the rotation speed. In this case, the fuel pressure control device 10 is configured by the centrifugal governor 51 and the pressure regulator 30.

Furthermore, by operating the valve 20 shown in FIG. 2 using a centrifugal governor, it is also possible to increase or decrease the fuel pressure in accordance with the rotational speed.

FIG. 6 shows still another embodiment of the present invention. In this embodiment, a pressure accumulator 52 is provided between the fuel pump 5 and the injector 2, and a predetermined pressure supplied from the fuel pump 5 is provided. The fuel is stored in the pressure accumulator 52, and the fuel is supplied to the injector 2 from the pressure accumulator 52. Other points are similar to the embodiment shown in FIG.

If a configuration is adopted in which the fuel pump 5 is driven by the output of the generator 50 when starting the engine manually or kickstarting the engine, if the starting operation is performed with the fuel pressure at zero, the predetermined amount will be lost in one starting operation. The engine may not start because fuel pressure is not available. If a pressure accumulator 52 is provided between the fuel pump and the injector, the fuel pressure generated by the starting operation can be stored in the pressure accumulator 52, so that the starting operation is performed when the fuel pressure is initially zero. Even in this case, by repeating the starting operation, a predetermined fuel pressure can be generated and the engine can be started.

Furthermore, by providing a pressure accumulator 52, residual pressure can be applied to the injector using the pressure in the pressure accumulator 52 when the engine is stopped, thereby ensuring fuel pressure in the injector when the engine is next started. This makes it easier to start the engine.

In the embodiments shown in FIG. 1, FIG. 2, FIG. 4, and FIG. 6, a path is not provided for returning part of the fuel flowing through the fuel supply system to the fuel tank 3. In this example, in order to prevent the temperature of the fuel supplied to the injector 2 from rising, a path may be provided for returning part of the fuel flowing between the fuel pump and the injector to the fuel tank. Furthermore, it is also possible to load a pressure regulator to these embodiments and control the fuel pressure so that it does not rise above a set value (setting an upper limit of the fuel pressure).

The configurations of the fuel pump, injector, and pressure regulator shown in the above description are merely examples, and there is no use of devices having configurations other than those shown in the above description. Not hinder.

[Effects of the Invention] As described above, according to the present invention, the fuel pressure is increased or decreased according to the increase or decrease in the engine speed, so when the engine speed is low, the fuel pressure is lowered and the injection amount is reduced. A linear relationship can be maintained between the injection amount and the injection time up to the region, and when the engine speed is high, the fuel pressure can be increased (and the injection amount can be increased).Therefore, injection can be performed in the region where the engine speed is low. It is possible to prevent the injection amount from becoming excessive.Furthermore, since the fuel pressure is increased as the rotational speed increases, it is possible to meet the request for an increase in the injection amount when the engine is running at high speed without any problem.

[Brief explanation of the drawing]

1 to 6 are block diagrams showing different embodiments of the present invention, FIGS. 7 to 9 are sectional views showing structural examples of a fuel pump, an injector, and a pressure regulator, and FIGS. Fig. 11 is a diagram showing different characteristic examples of generators that can be used in the embodiments of the present invention, and Fig. 12 is a diagram showing fuel pressure versus rotation speed characteristics obtained by the embodiment of Fig. 4. , FIG. 13 is a diagram comparing the conventional fuel pressure vs. rotation speed characteristic and an example of the fuel pressure vs. rotation speed characteristic obtained by the present invention, and FIG. 14 is a graph showing the relationship between the injection amount and injection time of the injector. A diagram showing an example for different fuel pressures, Fig. 15 is a diagram showing an example of the relationship between the injection amount and injection time duty of the injector for different fuel pressures, and Fig. 16 shows the injection given to the injector. A waveform diagram showing an example of the command signal and drive current, Figure 17 is a diagram showing an example of the relationship between engine fuel efficiency and engine speed, and Figure 18 is a relationship between engine fuel injection effective engine and engine speed. FIG. 19 is a block diagram showing the configuration of a conventional fuel injection device. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Injector, 3... Fuel tank, 5... Fuel pump, 10... Fuel pressure control device, 11... Fuel pressure detection means, 12... Fuel pressure detection means , 13...Fuel pressure setting means, 14...Pump control device, 22...Fuel pressure detection means, 23...Rotational speed detection means, 24...Fuel pressure setting means, 25...Manipulation amount calculation means , 26... Drive circuit, 30... Pressure regulator, 31...
...Control unit, 50... Generator. Figure 2 Figure 1 + Denta I. m-rotational speed N [rI) m] m-rotational speed N [rom]

Claims (7)

[Claims] (1) A fuel injection device including an injector that injects fuel into a fuel injection space of an internal combustion engine when an injection command signal is given, and a fuel pump that supplies fuel from a fuel tank to the injector. A fuel injection device comprising a fuel pressure control device that increases the applied fuel pressure as the rotational speed of an internal combustion engine increases. (2) The fuel pressure control device includes a fuel pressure detection means for detecting the fuel pressure, a rotation speed detection means for detecting the rotation speed of the internal combustion engine, and a set value of the fuel pressure at the rotation speed detected by the rotation speed detection means. and a pump control device that controls the rotation of the fuel pump so that the fuel pressure detected by the fuel pressure detection means matches the set value of the fuel pressure. The fuel injection device described in . (3) The fuel pressure control device includes a fuel pressure adjusting means provided between the fuel pump and the injector, an actuator for operating the fuel pressure adjusting means, a fuel pressure detecting means for detecting the fuel pressure, and a rotation of the internal combustion engine. a rotation speed detection means for detecting a rotation speed; a fuel pressure setting means for providing a set value of fuel pressure at the rotation speed detected by the rotation speed detection means; and a fuel pressure setting means for matching the fuel pressure detected by the fuel pressure detection means to the set value of the fuel pressure. and a drive circuit that supplies a drive current to the actuator according to the operation amount calculated by the operation amount calculation means. The fuel injection device according to claim 1. (4) The fuel injection device according to claim 3, wherein the fuel pressure adjustment means comprises a flow rate adjustment valve inserted between the fuel pump and the injector. (5) The fuel pressure adjusting means is provided between a pipe on the inlet side of the injector and the fuel tank, and is configured to adjust a portion of the fuel supplied from the fuel pump when the pressure applied to the injector exceeds a set value. a pressure regulator that maintains the pressure on the inlet side of the injector at a set value by returning the pressure to the fuel tank, and the pressure regulator includes a set value adjusting means for adjusting the set value of the pressure, and adjusts the set value 4. A fuel injection device according to claim 3, characterized in that the means are operated by the actuator. (6) The pressure regulator maintains the pressure on the inlet side of the injector at a set value in response to the differential pressure between the pressure in the pipe line between the fuel pump and the injector and the pressure in the fuel injection space. The fuel injection device according to claim 5, configured as follows. (7) In a fuel injection device equipped with an injector and a fuel pump that supplies fuel from a fuel tank to the injector, the fuel pump is driven by an internal combustion engine as a power source to drive the fuel pump, and as the rotational speed of the engine increases. A fuel injection device characterized in that the discharge pressure of the fuel pump is increased or decreased in accordance with an increase or decrease in the rotational speed of an internal combustion engine, using an alternator that has a characteristic of increasing output voltage or output current.