JPH07119517A - Fuel injection device for engine - Google Patents

Abstract

PURPOSE:To start an engine rapidly without reducing starting performance of the engine even if starting of the engine fails once at the time of hot start. CONSTITUTION:In a fuel injection type engine CE, fuel pressure is maintained at normal fuel pressure of comparatively low pressure, when a solenoid valve 32 is opened by a control unit 13, and fuel pressure is maintained at pressure increasing fuel pressure of comparatively high pressure when the solenoid valve 32 is closed. When an engine rotational speed is not increased to a complete explosion rotational speed at the time of hot start and thus engine start fails the solenoid valve 32 is closed so as to enhance fuel pressure, when the engine CE is started again. Fuel vapor in a fuel supplying passage 28 is therefore eliminated rapidly so as to improve starting performance at the time of restarting the engine CE.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine fuel injection system for increasing fuel pressure during a hot start.

[0002]

2. Description of the Related Art Generally, in a fuel injection engine, fuel in a fuel tank is supplied to a fuel injection valve through a fuel passage by a fuel pump, and when the fuel injection valve is intermittently opened, the fuel inside the fuel passage is opened. Fuel is injected into the intake passage to form an air-fuel mixture. Here, the valve opening time (injection pulse width) at each injection timing of the fuel injection valve is set according to the intake air amount and the like. Further, the fuel supply pressure to the fuel injection valve, that is, the fuel pressure is controlled by a pressure regulator valve (fuel pressure control valve) provided in the fuel passage.

In such a fuel injection type engine, a part of the fuel passage is arranged in the engine room. However, after the engine is stopped, the temperature in the engine room rises sharply, and during this time, in the vicinity of the engine. The fuel in the fuel passage is vaporized and the fuel vapor stays in the passage.
Therefore, when the engine is stopped for a short time, and therefore the engine is started when the engine room is still hot (at the time of hot start), fuel vapor is supplied to the fuel injection valve, The fuel injection valve does not inject an amount of fuel commensurate with the valve opening time (injection pulse width), resulting in a problem that the mixture becomes extremely lean and the startability of the engine deteriorates.

Therefore, when the engine has been stopped for a short time, and therefore when the engine room is in a high temperature state, when starting the engine, that is, when hot starting, the fuel pressure is increased as compared to when normal engine starting, A fuel injection engine has been proposed in which the fuel vapor in the fuel passage is quickly removed during cranking (see, for example, Japanese Patent Publication No. 63-38537). In this case, a means for detecting whether or not at the time of hot start is required, but since the cost is increased if such means is newly provided, in such a conventional fuel injection engine, an existing sensor, For example, an intake air temperature sensor is used to detect whether or not a hot start is being performed. Specifically, for example, when the intake air temperature difference represented by the difference between the intake air temperature at the time when the ignition switch is turned on at the engine start and the intake air temperature at the time when the engine was stopped last time exceeds a predetermined reference intake air temperature difference, The fuel pressure is increased on the assumption that it is during the start.

[0005]

However, in the conventional fuel injection type engine in which the fuel pressure at the time of starting the engine is increased based on the intake air temperature difference, the engine does not reach a complete explosion due to cranking at the time of hot starting. When the engine starts, that is, when the engine fails to start, the fuel pressure cannot be increased even if the cranking is performed again thereafter, so that there is a problem that the engine does not start easily and the commercial property is deteriorated. That is, in this case, since almost no time has passed from the time when the ignition switch was turned off last time, that is, the time when the engine failed to start, the intake temperature difference becomes very small, and therefore the intake temperature difference exceeds the reference intake temperature difference. Since there is no fuel pressure, it cannot be increased.

The present invention has been made in order to solve the above-mentioned conventional problems. Even if the engine fails to start once at the time of hot start, the startability of the engine is not deteriorated after that, and the start is promptly performed. It is an object of the present invention to provide an engine fuel injection device capable of starting an engine.

[0007]

In order to achieve the above object, as shown in the configuration of FIG. 1, the first invention is the intake air temperature at the time when the ignition switch is turned on at the time of starting the engine, and the previous ignition switch. When the intake air temperature difference represented by the difference between the intake air temperature at the time when the engine is turned off exceeds a predetermined reference intake air temperature difference, a fuel pressure increase correction means a for increasing the fuel pressure at the time of starting the engine.
In the fuel injection device c of the engine b provided with
Engine rotation speed detection means d for detecting the rotation speed of the engine b is provided, and the fuel pressure increase correction means a is
When the fuel pressure was increased at the previous engine start and the engine speed did not rise to the predetermined reference speed, the fuel pressure is increased even when the intake temperature difference is less than or equal to the reference intake temperature difference at the current engine start. A fuel injection device for an engine is provided.

According to a second aspect of the present invention, in the engine fuel injection device according to the first aspect, the reference number of revolutions is the engine number of revolutions reached when the engine b reaches a complete explosion at the time of engine start. A fuel injection device for an engine is provided.

A third aspect of the present invention is the engine fuel injection apparatus according to the first aspect, wherein the fuel pressure increase correction means a increases the fuel pressure for a predetermined fuel pressure correction time when increasing the fuel pressure. If the fuel pressure is increased at the previous engine start and the engine speed has not risen to the reference speed, and the intake temperature difference is below the reference intake temperature difference, but the fuel pressure is increased, the intake temperature difference becomes the reference value. A fuel injection device for an engine, wherein the fuel pressure correction time is changed when the fuel pressure is increased by exceeding the intake air temperature difference.

[0010]

EXAMPLES Examples of the present invention will be specifically described below.
As shown in FIG. 2, in a fuel injection type engine CE using gasoline as a fuel, when the intake valve 1 is opened, the air-fuel mixture is sucked from the intake port 2 into the combustion chamber 3, and the air-fuel mixture is drawn by the piston 4 Are compressed and ignited and burned by the spark plug 5, and when the exhaust valve 6 is opened, the combustion gas is discharged to the exhaust passage 8 through the exhaust port 7. The exhaust passage 8 is provided with an O ₂ sensor 9 for detecting the oxygen concentration (air-fuel ratio) in the exhaust gas and a catalytic converter 10 for purifying the exhaust gas in order from the upstream side. Further, the spark plug 5 is connected to the distributor 11 and the ignition control device 12.
Thus, high-voltage ignition power is supplied at a predetermined timing set by the control unit 13. The distributor 11 can detect the crank angle (engine speed). The distributor 11 corresponds to "engine speed detecting means" described in the claims.

In order to supply air for fuel combustion to the engine CE (combustion chamber 3), an intake passage 14 having a downstream end communicating with the intake port 2 is provided, and the intake passage 14 is provided from the upstream side. In order, a hot wire type air flow sensor 15 for detecting the intake air amount, a throttle valve 16 opened / closed corresponding to the depression amount of an accelerator pedal (not shown), and the air flow in the intake passage 14 are stabilized. A surge tank 17 is provided. A fuel injection valve 18 for injecting fuel into the intake passage 14 is provided in the vicinity of the intake port 2 with its injection port facing the intake port 2 direction. Here, the fuel injection amount (injection pulse width) and the injection timing of the fuel injection valve 18 are set by the control unit 13 according to the intake air amount detected by the air flow sensor 15 and the like. The fuel injection valve 18 corresponds to the "fuel injection device" described in the claims.

A bypass intake passage 19 for guiding the air in the intake passage 14 upstream of the throttle valve 16 to the surge tank 17 by bypassing the throttle valve 16 is provided. An ISC valve 20 for controlling the intake air amount is installed. This ISC valve 20 is a control unit 1
In accordance with a signal applied from No. 3, it is opened / closed according to load characteristics, for example, ON / OFF of a compressor of an air conditioner. The engine CE is provided with an intake air temperature sensor 23 that detects the intake air temperature, a water temperature sensor 24 that detects the engine water temperature, and a throttle opening sensor 25 that detects the throttle opening.

A fuel supply system is provided for supplying fuel to the fuel injection valve 18. In this fuel supply system,
The fuel (gasoline) stored in the fuel tank 26 is
The fuel pump 27 supplies the fuel injection valve 18 through the fuel supply passage 28, and the surplus fuel that is not injected by the fuel injection valve 18 is returned to the fuel tank 26 through the fuel return passage 29.

The fuel return passage 29 is provided with a pressure control valve 30 (fuel pressure control valve) for controlling the fuel supply pressure to the fuel injection valve 18, that is, the fuel pressure. The pressure control valve 30 is a negative pressure inside the surge tank 17. Is being supplied to the pressure chamber 36 through the negative pressure supply passage 31 and the solenoid valve 32, the fuel pressure is maintained at a relatively low normal-time fuel pressure, while the solenoid valve 3
When the supply of the negative pressure to the pressure chamber 36 is cut off by 2, the fuel pressure is maintained at the pressure increasing fuel pressure higher than the normal pressure fuel pressure. The solenoid valve 32
Are controlled by the control unit 13.

Specifically, in the pressure control valve 30, a diaphragm 33 for partitioning the internal space of the pressure control valve into a pressure chamber 36 and a fuel chamber 37 is provided, and the end face of the diaphragm 33 on the fuel chamber side is arranged. A valve body 35 for increasing or decreasing the passage cross section of the fuel return passage 29 is attached. Here, the diaphragm 33 is moved toward the fuel chamber side by the spring 34 provided in the pressure chamber 36, that is, in the direction in which the valve body 35 reduces the passage cross section of the fuel return passage 29 (hereinafter, referred to as the valve body closing direction). That is, the opposite direction is called the valve body opening direction). As described above, the negative pressure or the atmospheric pressure is supplied to the pressure chamber 36, while the fuel chamber 37 is filled with the fuel.

Here, when the solenoid valve 32 is opened by the control unit 13 and the negative pressure in the surge tank 17 is being supplied into the pressure chamber 36, the diaphragm 33 has a negative pressure in the pressure chamber 36 and a fuel chamber. The fuel pressure in 37 applies a force in the valve opening direction, while the spring 34 applies a force in the valve closing direction.
Therefore, the diaphragm 33 (valve body 35) is held at a position where the force in the valve body opening direction due to the fuel pressure and the negative pressure and the force in the valve body closing direction due to the spring 34 are balanced. The fuel pressure increases as the valve body 35 moves in the valve closing direction because the cross section of the fuel return passage 29 is narrowed. That is, the fuel pressure is maintained at a relatively low pressure corresponding to a value obtained by subtracting the force in the valve opening direction due to the negative pressure in the pressure chamber 36 from the force in the valve closing direction due to the spring 34, that is, the fuel pressure for normal time. Will be.

On the other hand, when the control unit 13 closes the solenoid valve 32 to shut off the supply of negative pressure to the pressure chamber 36 and supply atmospheric pressure into the pressure chamber 36, the diaphragm 33 is operated by the negative pressure valve. Since the force in the body opening direction does not act, the valve body 35 is held at the position moved in the valve body closing direction, and therefore the fuel pressure is kept in the spring 3
Therefore, the fuel pressure is maintained at a relatively high pressure corresponding to the force of the valve body 4 in the valve closing direction, that is, the fuel pressure for pressure increase. That is, the solenoid valve 32 interrupts the supply of the negative pressure to the pressure chamber 36, so that the fuel pressure is increased in two stages (normal pressure, normal pressure,
It is possible to switch to the fuel pressure for boosting).

The control unit 13 is a comprehensive control device for the engine CE, which is composed of a microcomputer and includes the "fuel pressure increase correction means" recited in the claims, and is detected by the O ₂ sensor 9. Oxygen concentration in the exhaust gas (air-fuel ratio), crank angle signal (engine speed) output from the distributor 11, intake air amount detected by the air flow sensor 15, intake air temperature detected by the intake air temperature sensor 23, water temperature Engine water temperature detected by sensor 24, throttle sensor 25
Various predetermined controls are performed using control information such as the throttle opening detected by the ignition switch and the ignition switch signal output from the ignition switch 39, but general control of the engine CE is well known. The description of the general control is omitted because it is not the gist of the present invention, and only the fuel pressure control according to the gist of the present invention will be described below with reference to FIG. The control method will be described.

In this fuel pressure control, basically, the solenoid valve 32 is normally opened to maintain the fuel pressure at a relatively low fuel pressure for normal use, while the intake air temperature at the time when the ignition switch 39 is turned on at the time of engine starting. In order to improve the startability of the engine CE when the intake air temperature difference defined by the difference between the intake air temperature at the time when the ignition switch 39 is finally turned off exceeds a predetermined reference intake air temperature difference, that is, at the hot start. In addition, when the engine is started, the solenoid valve 32 is closed for a predetermined time to maintain the fuel pressure at the relatively high pressure-increasing fuel pressure. In addition to this, when the fuel pressure was raised at the previous engine start and the engine speed did not rise to the predetermined reference speed (complete explosion speed), the intake temperature difference at the time of the engine start this time Even in the following cases, the fuel pressure is increased in order to reliably start the engine CE.

Specifically, when the control is started, first in step # 1, various signals such as an engine water temperature signal, an intake air temperature signal, a throttle opening signal, an engine speed signal, an ignition switch signal, etc. are read as control information. Be done.
Next, in step # 2, the engine water temperature is set to a set value a (for example,
90 ° C) is exceeded and the water temperature is set to the set value a
If it is determined that the intake air temperature exceeds the set value (YES), it is further determined in step # 3 whether the intake air temperature exceeds the set value b (for example, 90 ° C.). In the present embodiment, when the engine water temperature is relatively low or the intake air temperature is relatively low, it is unlikely that a large amount of fuel vapor is retained in the fuel supply passage 28, so other conditions are considered. Instead, the fuel pressure is maintained at the normal fuel pressure. However, if the fuel pressure is increased more than necessary when the fuel vapor is not staying in the fuel supply passage 28, not only the fuel efficiency is deteriorated, but also the air-fuel mixture becomes excessively rich and the ignitability is deteriorated. This is because the durability or reliability of the fuel supply system may decrease.

Thus, if it is determined in step # 2 that the engine water temperature is below the set value a (NO), or if it is determined in step # 3 that the intake air temperature is below the set value b (NO). In step # 10, the solenoid valve 32 is opened, and the pressure chamber 3 of the pressure control valve 30 is opened.
Negative pressure in the surge tank 17 is supplied to the surge tank 6, and the fuel pressure is maintained at a relatively low normal-time fuel pressure. Then, the process returns to step # 1.

On the other hand, if it is determined in step # 2 that the water temperature exceeds the set value a (YES) and in step # 3 that the intake air temperature exceeds the set value b (YE
S), and the intake air temperature difference ΔTHA is set to the set value c in step # 4.
Or not is determined. Where intake air temperature difference Δ
THA is a value obtained by subtracting the intake air temperature at the time when the ignition switch 39 is finally turned off from the intake air temperature at the time when the ignition switch 39 is turned on at the time of starting the engine this time.

For a while after the engine CE is stopped, the running wind does not hit the radiator fan, and the radiator fan is stopped. Therefore, the residual heat of the engine CE causes the temperature in the engine room to rise rapidly, and the intake air temperature accordingly. The intake air temperature detected by the sensor 23 also rises sharply. Therefore, when the intake air temperature difference ΔTHA is large, it is considered that not much time has passed since the engine was stopped. Therefore, in the present embodiment, basically, the intake air temperature difference ΔTHA at the time of engine starting.
Is greater than the set value c, it has not been long after the engine is stopped, and therefore the fuel supply passage 28
It is assumed that it is during a hot start in which a large amount of fuel vapor is retained, and the fuel pressure is maintained at a relatively high pressure-increasing fuel pressure. As will be described later, even when the intake air temperature difference ΔTHA exceeds the set value c, the fuel pressure is not increased except during idling.

If it is determined in step # 4 that ΔTHA> c (YES), step # 7 to be described later is executed. On the other hand, if it is determined in step # 4 that ΔTHA ≦ c is satisfied (NO), it is first determined in step # 5 whether or not the fuel pressure was increased at the previous engine start, and the fuel pressure was increased. If determined (YES), it is further determined in step # 6 whether or not the engine speed has risen to the predetermined reference speed of 500 rpm during the previous engine start. Here, the standard rotation speed is 500r.
pm is the number of revolutions obtained when the engine reaches the complete explosion at the time of starting the engine, that is, the so-called complete explosion number of revolutions.

In step # 5, it is judged that the fuel pressure was increased at the previous engine start (YES), and in step # 5
If it is determined in 6 that the engine speed has not risen to the reference speed of 500 rpm at the time of the previous engine start (YES), step # 7 described later is executed, and in step # 7, Except when it is determined that the engine is not idle, the fuel pressure is increased even when the engine is started this time. The reason why the fuel pressure is increased even in such a case is as follows.

That is, when the engine speed has not risen to the reference speed of 500 rpm (complete explosion speed) even though the fuel pressure was increased at the previous engine start, that is, the engine start fails. If so, it is considered that the fuel vapor still remains in the fuel supply passage 28. However, in this case, since almost no time has passed from the time when the ignition switch 39 was last turned off, that is, the time when the engine start failed last time, to the time when the ignition switch 39 was turned on at the time of this engine start, Intake temperature difference Δ
THA has become very small, and if it remains as it is (Step #
5, (without Step # 6), the fuel pressure cannot be increased,
This engine start may also fail. Therefore,
In such a case, the fuel pressure is increased to quickly remove the remaining fuel vapor, and this time the engine CE is reliably started.

On the other hand, if it is determined in step # 5 that the fuel pressure was not increased at the time of the previous engine start.
(NO), or if it is determined in step # 6 that the engine speed has risen to the reference speed of 500 rpm during the previous engine start (NO), there is no need to increase the fuel pressure, so step # At 10, the solenoid valve 32 is opened and the fuel pressure is maintained at the normal fuel pressure. Then, the process returns to step # 1.

At step # 7, it is judged if the engine CE is in the idle state. In this embodiment, when the engine CE is not in the idle state, that is, when the throttle valve 16 is opened, the valve opening time (injection pulse width) of the fuel injection valve 18 at each injection timing is long, and therefore the fuel supply passage Since the fuel vapor in 28 is promptly removed, the fuel pressure is not unnecessarily increased.

If it is determined in step # 7 that the engine CE is not in the idle state (NO), the solenoid valve 32 is opened in step # 10 and the fuel pressure is maintained at the normal fuel pressure. Then, the process returns to step # 1.

On the other hand, if it is determined in step # 7 that the engine CE is in the idle state (YES), it is determined in step # 8 whether it is within 120 seconds after the engine is started, that is, the ignition switch 39 is turned on. After 120
Whether it is within seconds or not is determined, and when it is determined that it is within 120 seconds (YES), the solenoid valve 32 is closed in step # 9, and the atmospheric pressure is supplied to the pressure chamber 36 of the pressure control valve 30. Then, the fuel pressure is maintained at a relatively high pressure-increasing fuel pressure, and then the process returns to step # 1.

As described above, since the fuel pressure is increased when the engine CE is started, the fuel vapor staying in the fuel supply passage 28 is promptly removed, and the startability of the engine CE is improved. On the other hand, if it is determined in step # 8 that the time exceeds 120 seconds after the engine is started (NO), the solenoid valve 32 is opened in step # 10, and the fuel pressure is maintained at the normal fuel pressure. Then, the process returns to step # 1. As described above, the reason why the fuel pressure is returned to the normal fuel pressure after 120 seconds have passed since the engine was started is that the fuel vapor is normally removed within 120 seconds.

In this way, the fuel pressure is increased at the time of hot start, and the startability of the engine CE is improved. Further, if the engine CE fails to start once at the time of hot start, the fuel pressure is increased at the time of restarting the engine regardless of the magnitude of the intake air temperature difference ΔTHA, so that the startability of the engine CE at the time of restart is improved. The engine CE can be reliably started.

In the above embodiment, the time for increasing the fuel pressure at the time of hot starting is constant (120 times).
However, if the engine CE fails to start once at the time of hot start, the time for increasing the fuel pressure may be set shorter than the first time when the engine CE is restarted. This is because, at the time of starting the engine for the first time, a part of the fuel vapor in the fuel supply passage 28 has already been removed, so it is considered that the fuel vapor is sufficiently removed even if the time for increasing the fuel pressure is shortened. .

FIG. 4 shows the logic of fuel pressure control when the fuel pressure is increased for 120 seconds at the first engine start and the fuel pressure is increased for 100 seconds at the second engine start at the hot start. A circuit diagram is shown. In FIG. 4, 41 and 42 are AND circuits,
43 is an OR circuit. In the fuel pressure control as shown in FIG. 4, it is possible to prevent the fuel pressure from being unnecessarily increased for a long time at the second engine start, improve the fuel efficiency, and enhance the durability or reliability of the fuel supply system.

[0035]

According to the first aspect of the present invention, when the fuel pressure is increased at the previous engine start and the engine speed has not risen to the predetermined reference speed, the intake air is started at the current engine start. The fuel pressure is increased even when the temperature difference is less than or equal to the reference intake air temperature difference. Therefore, at the time of hot start, the engine speed does not rise to the reference speed, and even if the engine start fails once, the fuel pressure is increased when the engine is started again, so the fuel vapor in the fuel supply system is increased. Can be promptly removed, and the engine can be reliably started.

According to the second invention, basically the same action and effect as the first invention can be obtained. Furthermore, since the reference rotation speed is the engine rotation speed that is reached when the engine reaches the complete explosion at the time of engine start, if the engine start fails at the time of hot start,
The fuel pressure is increased at the next engine start. Therefore, the startability of the engine can be further enhanced.

According to the third invention, basically, the same action and effect as those of the first invention can be obtained. Further, when the engine fails once at the time of hot starting, the time for increasing the fuel pressure can be changed to that at the time of starting the engine for the second time when starting the engine for the second time. Therefore, for example, if the engine fails once to start and the fuel pressure is increased when the engine is restarted, the time for increasing the fuel pressure is set to 1
By making it shorter than the first time, it is possible to prevent the fuel pressure from being unnecessarily increased for the second time the engine is started.
The fuel efficiency is improved, and the durability or reliability of the fuel supply system is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of first to third inventions corresponding to claims 1 to 3, respectively.

FIG. 2 is a system configuration diagram of an engine including a fuel injection device according to the present invention.

FIG. 3 is a flowchart showing a control method of fuel pressure control by a control unit.

FIG. 4 is a logic circuit diagram showing another control method of fuel pressure control.

[Explanation of symbols]

 CE ... Engine 11 ... Distributor 13 ... Control unit 14 ... Intake passage 18 ... Fuel injection valve 23 ... Intake temperature sensor 28 ... Fuel supply passage 29 ... Fuel return passage 30 ... Pressure regulator valve 32 ... Solenoid valve

Claims (3)

[Claims] 1. When the intake air temperature difference represented by the difference between the intake air temperature at the time when the ignition switch is turned on at the time of engine start and the intake air temperature at the time when the ignition switch is turned off last time exceeds a predetermined reference intake air temperature difference. In a fuel injection device for an engine, which is provided with a fuel pressure increase correction means for increasing the fuel pressure at the time of starting the engine, an engine rotation speed detection means for detecting the rotation speed of the engine is provided, and the fuel pressure increase correction means is provided. , When the fuel pressure was increased at the previous engine start and the engine speed did not rise to the predetermined reference speed, the fuel pressure is increased even if the intake temperature difference is equal to or less than the reference intake temperature difference at the current engine start. A fuel injection device for an engine, characterized in that 2. The fuel injection device for an engine according to claim 1, wherein the reference rotation speed is an engine rotation speed that is reached when the engine reaches a complete explosion at the time of engine start. Engine fuel injection system. 3. The fuel injection device for an engine according to claim 1, wherein the fuel pressure increase correction means is configured to increase the fuel pressure for a predetermined fuel pressure correction time when increasing the fuel pressure. At this time, when the fuel pressure is increased and the engine speed has not risen to the reference speed, the intake temperature difference exceeds the reference intake temperature difference when the fuel pressure is increased even though the intake temperature difference is equal to or less than the reference intake temperature difference. The fuel injection device for an engine is characterized in that the fuel pressure correction time is changed when the fuel pressure is increased by the above.