JP2893997B2 - Fuel pressure control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel pressure control device for an internal combustion engine, and more particularly to a fuel pressure control device for improving startability at a hot start.

[0002]

2. Description of the Related Art In an electronically controlled internal combustion engine, a pressure regulator is provided in order to regulate the pressure of fuel sent to a fuel injection valve by a fuel pump. In general, when the supplied fuel pressure is increased by using the intake pipe negative pressure, a part of the fuel is returned to the fuel tank side, thereby adjusting the supplied fuel pressure. .

As described above, in the ordinary pressure regulator, the intake pipe negative pressure is used as a control parameter. Therefore, when the intake pipe negative pressure sharply rises simultaneously with the start of the engine, the pressure regulator operates to supply fuel. Since the fuel is returned to the tank, the fuel pressure in the fuel passage rapidly decreases. Therefore, when the engine is started in a high engine temperature state, for example, during a hot restart after high-speed running, vapor is generated in the delivery pipe due to the rapid decrease in the fuel pressure, and vapor lock occurs, and the air-fuel ratio becomes lean. And restart may be difficult.

[0004] For this reason, the hot start is determined based on the fact that the engine is in the starting state, the cooling water temperature of the engine is a predetermined value, for example, 95 ° C or higher, and the intake air temperature of the engine is a predetermined value, for example, 60 ° C or higher. At the time of a hot start, there is a type in which the atmospheric pressure is applied instead of the application of the negative pressure of the intake pipe to the pressure regulator, that is, the diaphragm chamber of the pressure regulator is released to the atmosphere (see: Shokai 62).
-95167). As a result, the return of fuel to the return pipe is cut to increase the fuel pressure in the delivery pipe, thereby preventing vapor lock, sending appropriate fuel to the fuel injection valve, and ensuring startability.

[0005]

However, in the above-mentioned conventional type, the pressure regulator is released to the atmosphere when the cooling water temperature is equal to or higher than a predetermined value and the intake air temperature is equal to or higher than a predetermined value. It is a fixed value regardless of the properties. In other words, when the fuel is light, it has a good respiratory property, generates a large amount of vapor, easily locks the vapor even at a relatively low temperature, and it is necessary to lower the above-mentioned predetermined temperature for determining the pressure regulator to open to the atmosphere. On the other hand, in the case of heavy fuel, on the other hand, it is necessary to raise the predetermined temperature at which the pressure regulator is opened to the atmosphere.

[0006] Therefore, if the predetermined temperature of the above-described determination of the release to the atmosphere is set to a temperature suitable for the light fuel, if the fuel becomes heavy, the pressure regulator is released to the atmosphere regardless of the absence of the vapor lock, and the pressure in the delivery pipe is reduced. Increase fuel pressure. Therefore, there is a problem that the amount of fuel supplied to the fuel injection valve increases, the air-fuel ratio becomes over-rich, and the startability decreases.

On the other hand, if the predetermined temperature for the above-described determination of the release to the atmosphere is set to a temperature corresponding to the heavy fuel, when the fuel becomes light, the pressure regulator is not released to the atmosphere regardless of the occurrence of vapor lock. For this reason, there is a problem that the amount of fuel to the fuel injection valve decreases, the air-fuel ratio becomes over-lean, and the startability also decreases. Therefore, an object of the present invention is to improve the startability at the time of a hot start or the like even if the fuel property changes.

[0008]

The means for solving the above problems is shown in FIG. That is, the pressure regulator adjusts the fuel pressure of the fuel supply system of the engine according to the intake pipe pressure or the atmospheric pressure of the engine, and the valve selectively applies the intake pipe pressure or the atmospheric pressure of the engine to the pressure regulator. On the other hand, the engine start state determination means determines whether the engine is in a start state. Further, the fuel property detecting means detects the fuel property of the fuel supply system of the engine. As a result, the reference cooling water temperature calculating means calculates the reference cooling water temperature THW 0 when the fuel property is light and the fuel cooling property is large when the fuel property is heavy, and the cooling water temperature determining means determines whether the cooling water temperature THW of the engine is higher than the reference cooling water temperature THW 0. Is determined. In addition, the reference intake air temperature calculating means is small when the fuel property is light and large when the fuel property is heavy.
THA 0 is calculated, and the intake air temperature determining means calculates the intake air temperature TH of the engine.
It is determined whether or not A is larger than the reference intake air temperature THA0. Then, the engine is in the starting state, the cooling water temperature THW of the engine is larger than the reference cooling water temperature THW 0, and the intake air temperature TH of the engine is set.
When A is larger than the reference intake air temperature THA 0, the control means controls the valve to apply the atmospheric pressure to the pressure regulator instead of the intake pipe pressure.

[0009]

According to the above-described means, the air-fuel ratio becomes appropriate at the time of a hot start and the like, regardless of the fuel property, and the startability is improved.

[0010]

FIG. 2 is an overall schematic diagram showing an embodiment of a fuel pressure control device for an internal combustion engine according to the present invention. In FIG. 2, 1 is a fuel tank, 2 is a fuel pump, and a delivery pipe 3 is connected to the fuel pump 2, and a fuel filter 4 is interposed in the delivery pipe 3. Pipe 3
Is connected to a delivery pipe 5, which communicates with a fuel injection valve 7 provided in an intake pipe 6. By driving the fuel pump 2, the fuel in the fuel tank 1 is sent to the fuel injection valve 7 and injected for a predetermined time. The fuel injection amount from the fuel injection valve 7 is configured to be proportional to the fuel injection time. For this reason, the pressure difference between the fuel pressure (also referred to as fuel pressure) of the fuel injection valve 7 and the negative pressure in the intake pipe is determined. A pressure regulator 8 for setting a value (for example, 2.55 kg / cm ² ) is provided.

The pressure regulator 8 is defined by a diaphragm 81 into a fuel chamber 82 and a diaphragm chamber 83, and the fuel chamber 82 communicates with the delivery pipe 5. The diaphragm chamber 83 is connected to a negative pressure control valve (vacuum switching valve) 11 via a pipe 9, and the negative pressure control valve 11 further includes an intake pipe 6 (intake pipe negative pressure) and a filter 12.
Connected to atmospheric pressure via The negative pressure control valve 11 is controlled by the control circuit 10, and the negative pressure control valve
When the pressure 11 is off, the negative pressure of the intake pipe 6 is applied to the diaphragm chamber 83 of the pressure regulator 8, while when the negative pressure control valve 11 is on, the atmospheric pressure is applied to the diaphragm chamber 83 of the pressure regulator 8. .

The other end of the return pipe 13 whose one end is connected to the fuel tank 1 is open to the fuel chamber 82 of the pressure regulator 8. A valve 84 is attached to the diaphragm 81 of the pressure regulator 8. A spring 85 interposed in the diaphragm chamber 83 urges the diaphragm 81 by the valve 84 in a direction to close the return pipe 13.

When the negative pressure control valve 11 is turned on and the diaphragm chamber 83 of the pressure regulator 8 is open to the atmosphere, the fuel pressure in the fuel chamber 24 becomes a predetermined value, for example, 2.55 kg / cm.
^{When the} pressure exceeds ^2, the valve 84 is pushed up against the spring 85, and the fuel is returned to the fuel tank 1 through the return pipe 13. On the other hand, the negative pressure control valve 11 is turned off and the fuel is returned to the diaphragm chamber 83. When the intake pipe negative pressure is introduced,
The fuel tank 13 is returned to the fuel tank 13 at a fuel pressure lower by the intake pipe negative pressure than at the time of release to the atmosphere.

A water temperature sensor 14 for detecting the temperature of cooling water is provided on a water jacket (not shown) of a cylinder block of the engine body. Water temperature sensor
Numeral 14 generates an analog voltage electric signal corresponding to the cooling water temperature THW. This output THW is supplied to an A / D converter 101 with a built-in sulplexer of the control circuit 10. Reference numeral 15 denotes an intake air temperature sensor that detects the temperature of air taken into the intake pipe 6, and is provided at an inlet of the intake pipe 6. The output THA of the intake air temperature sensor 15 is also supplied to the A / D converter 101.

A distributor (not shown) is provided with a crank angle sensor 16 whose axis generates a pulse signal for detecting a reference position every 30 ° in terms of a crank angle, for example. The pulse signal N of these crank angle sensors 16
e is supplied to the input / output interface 102 of the control circuit 10 and further supplied to the interrupt terminal of the CPU 103. 17 is a starter switch, and a key switch (not shown)
ST "position or starter (not shown)
Is turned on when is rotated. The output ST of the starter switch 17 is supplied to an input / output interface 102 of the control circuit 10.

Reference numeral 18 denotes a fuel property sensor provided in the fuel tank 1. The fuel property sensor 18 is, for example, a fuel flow rate sensor that determines based on the vapor flow rate of the fuel tank. Further, a temperature sensor is built in the fuel property sensor 18, and when the fuel temperature is low and the vapor flow rate is large, it is determined that the fuel is light fuel. On the contrary, when the fuel temperature is high and the vapor flow rate is small, it is possible to determine that the fuel is heavy fuel. . Further, the fuel property sensor 18 may be an RVP (lead vapor pressure) detection method or a fuel tank internal pressure detection method.

The control circuit 10 is configured as, for example, a microcomputer, and includes an A / D converter 101, an input / output interface 102, a CPU 103, a RAM 104, a ROM 105, a clock generation circuit 106, and the like. Note that the CPU 103 generates an interrupt after the A / D conversion of the A / D converter 101 is completed.
For example, when the input / output interface 102 receives the pulse signal of the crank angle sensor 16.

The operation of the control circuit shown in FIG. 2 will be described with reference to FIGS. FIG. 3 shows a VSV on control routine for turning on the negative pressure control valve 11, which is executed at predetermined intervals. In step 301, the output S of the starter switch 17
T is taken to determine whether or not the engine is in the starting state (ST = "1"). As a result, in the starting state (ST = "
1 "), the process proceeds to step 302, and if not in the starting state (ST =" 0 "), the process directly proceeds to step 317.

At step 302, the output of the fuel property sensor 18 is A / D converted and taken in. At steps 303 and 304, it is determined whether the fuel is light, heavy, or intermediate. As a result, if the fuel is light, the reference cooling water temperature THW 0 is set to X in step 305, and the reference intake air temperature THW is set in step 306.
Let A 0 be A. If the fuel is intermediate, step
At 307, the reference cooling water temperature THW 0 is set to Y, and step 308
Let B be the reference intake air temperature THA0. Further, if the fuel is heavy, the reference cooling water temperature THW 0 is set to Z in step 309, and the reference intake air temperature THA 0 is set to C in step 310. Here, there is a relationship of X <Y <ZA <B <C.

At step 311, the cooling water temperature THW is A / D converted and taken in from the water temperature sensor 14, and at step 312 it is determined whether THW ≧ THW0. Further, in step 313, the intake air temperature THA is A / D converted and taken in from the intake air temperature sensor 15, and in step 314, it is determined whether or not THA ≧ THA0. As a result, THW ≧ THW 0 and THA ≧
Only in the case of THA 0, proceed to step 315, turn on the negative pressure control valve 11 and turn on the diaphragm chamber of the pressure regulator 8.
Atmospheric pressure is introduced into 83, and a flag FV indicating that the negative pressure control valve 11 is on is set ("1") at step 316 and stored in the RAM 105. In other cases, that is, THW <THW 0
Alternatively, if THA <THA 0, the routine proceeds directly to step 317, where the negative pressure control valve 11 is kept off, and the intake pipe negative pressure is introduced into the diaphragm chamber 83 of the pressure regulator 8.

In step 317, this routine ends. As described above, according to the routine of FIG. 3, the open-to-atmosphere temperature of the pressure regulator 8 is changed according to the fuel property. FIG. 4 shows a modification of FIG. In FIG. 4, steps 401 and 402 are provided instead of steps 303 to 310 in FIG. That is, in the routine of FIG. 3, the calculation of the reference cooling water temperature THW 0 and the reference intake air temperature THA 0 is performed by classifying the fuel properties into three types. However, in the routine of FIG. Continuous reference cooling water temperature TH
W 0 and the reference intake air temperature THA 0 are given. That is, in step 401, the reference cooling water temperature TH is determined using the one-dimensional map stored in the ROM 104 in advance based on the fuel properties.
In step 402, the reference intake air temperature THA0 is interpolated using a one-dimensional map stored in the ROM 104 in advance based on the fuel properties.

FIG. 5 shows that V
This is an SV-off control routine, which is executed at every predetermined crank angle, for example, at every 30 ° C. output cycle of the crank angle sensor 16. In step 501, it is determined whether or not the negative pressure control valve 11 is on based on the flag FV. As a result, the flow of steps 502 and 503 is executed only when the negative pressure control valve 11 is on, and when the negative pressure control valve 11 is off,
Go directly to 507.

In step 502, the counter N is incremented by +1. In step 503, N ≧ 1800 × 12. That is, after the engine is started (after the negative pressure control valve 11 is turned on), the engine is operated at 1800.
It is determined whether or not it has rotated. As a result, the flow proceeds to steps 504, 505, and 506 only when 1800 rotations are made. That is, in step 504, the negative pressure control valve 11 is turned off, and the intake pipe negative pressure is applied again to the diaphragm chamber 83 of the pressure regulator 8, and in step 505, the flag FV is reset ("0"). Clears the counter N and proceeds to step 507.

In step 507, this routine ends. As described above, according to the routine of FIG. 5, the time of the high fuel pressure can be determined in accordance with the state of vapor generation in the fuel supply pipe, for example, the delivery pipe 5.

[0025]

As described above, according to the present invention, since the pressure regulator is released to the atmosphere in accordance with the fuel properties, even if the fuel properties change, vapor lock does not occur, and the pressure at the time of hot restart is reduced. Startability can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is an overall schematic diagram showing an embodiment of a fuel pressure control device for an internal combustion engine according to the present invention.

FIG. 3 is a flowchart illustrating an operation of the control circuit of FIG. 2;

FIG. 4 is a flowchart illustrating an operation of the control circuit of FIG. 2;

FIG. 5 is a flowchart showing an operation of the control circuit of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel tank 2 ... Fuel pump 5 ... Delivery pipe 7 ... Fuel injection valve 8 ... Pressure regulator 11 ... Negative pressure control valve 13 ... Return pipe 18 ... Fuel property sensor

Continuation of the front page (56) References JP-A-63-113130 (JP, A) JP-A-62-168957 (JP, A) JP-A-62-168941 (JP, A) JP-A-62-258126 (JP) JP-A-62-206254 (JP, A) JP-A-2-308945 (JP, A) JP-A-63-272935 (JP, A) JP-A-57-51928 (JP, A) 62-95167 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/00-45/00

Claims (1)

(57) [Claims] A pressure regulator that adjusts a fuel pressure of a fuel supply system of an internal combustion engine according to an intake pipe pressure or an atmospheric pressure of the engine; and a pressure regulator that adjusts an intake pipe pressure or the atmospheric pressure of the engine to the pressure regulator. A valve (11) for selectively applying, an engine starting state determining means for determining whether or not the engine is in a starting state, a fuel property detecting means for detecting a fuel property of a fuel supply system of the engine; Means for calculating a reference coolant temperature (THW 0) which is small when the fuel property is light and large when the fuel property is heavy, and whether the coolant temperature (THW) of the engine is higher than the reference coolant temperature (THW 0). Cooling water temperature determining means for determining whether or not the detected fuel property is light, and calculating reference air temperature (THA 0) which is small when the detected fuel property is heavy; THA) Serial standard intake air temperature (THA
0) an intake air temperature determining means for determining whether or not the temperature is higher than the reference cooling water temperature (THW 0); and the intake air temperature of the engine is higher than the reference cooling water temperature (THW 0). Control means for controlling the valve to apply atmospheric pressure to the pressure regulator in place of the intake pipe pressure when (THA) is greater than the reference intake air temperature (THA 0). Control device.