JPS63306274A - Vapor generation detector for fuel injection type engine - Google Patents

Abstract

PURPOSE:To detect generation of vapor reliably by judging generation of vapor when a detection output of physically variable quantity concerning to pressure variation of fuel in delivery pipe deviates from specific range. CONSTITUTION:Upon judgement of engine stall, a control unit 15 reads in a fuel temperature signal fed from a temperature sensor 19 and a fuel pressure signal fed from a pressure sensor 20. Then temperature rise rate of fuel is operated and compared with a setting level. (Minimum temperature rise rate obtainable upon generation of vapor in fuel in the delivery pipe 2). If the temperature rise rate is higher than the setting level, it is judged that vapor is generated in fuel, and if the temperature rise is not higher than the setting level and the fuel temperature is not starting to lower, it is judged that vapor is not produced. When the temperature rise rate is higher than the setting level and the fuel temperature is not higher than saturation temperature, it is judged that vapor has been eliminated. Consequently, erroneous or non-detection of vapor can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vapor generation detection device for a fuel injection type engine, and more particularly to a vapor generation detection device utilized to take measures against fuel vapor lock during warm startup.

[Prior art]

Conventionally, the fuel supply system of a fuel injection engine includes a fuel tank, a pump, a fuel supply pipe, a delivery pipe, multiple fuel injection nozzles connected to the delivery pipe, a pulsation damper also connected to the delivery pipe, and a fuel pressure A regulator, a recirculation pipe that recirculates fuel overflowing from the fuel pressure regulator to the fuel tank, and an outside air introduction pipe that introduces outside air into the fuel tank are provided.

Particularly when the outside temperature is high such as in the summer, when a fuel injection engine is operated under high load, or after high load operation, heat radiation from the engine causes the fuel temperature in the fuel supply system to rise above the saturation temperature, causing the fuel to vaporize. This poses a problem in that it may cause problems with fuel supply or warm starting of the engine.

Conventionally, vapor generation detection devices that can accurately and reliably detect vapor generation in the fuel supply system have not yet been put into practical use, and vapor generation is roughly detected based on the ambient temperature and fuel temperature in the engine room. was common.

Incidentally, Japanese Unexamined Patent Publication No. 60-43163 describes a system in which vapor generation is estimated based on the fuel temperature at the time of engine startup and fuel control is performed.

(Problems to be Solved by the Invention) In conventional fuel injection engines, it is not possible to reliably detect vapor generation in the fuel in the fuel supply system, so vapor generation may not be detected at all, or vapor generation may be falsely detected. The problem is that you end up doing it.

During a warm start, if vapor is generated but is not detected and countermeasures are not taken, it will be difficult to start the engine, and if vapor is falsely detected even though no vapor is generated, the engine will fail. There is also a problem in that unnecessary measures such as circulating fuel for a predetermined period of time before starting are required.

Even though vapor is generated during engine operation, if it is not detected and countermeasures are not taken, there are problems such as engine malfunction or engine stalling.

[Means for solving problems]

A vapor generation detection device for a fuel injection engine according to the present invention includes a detection means for detecting a physical change amount related to fuel pressure fluctuation in a delivery pipe in an engine having a fuel injection valve, and a detection means for detecting an amount of physical change related to fuel pressure fluctuation in a delivery pipe, and receiving an output of the detection means. The apparatus includes vapor generation determining means for determining that vapor generation has occurred when the output or the rate of change in the output is out of a predetermined range.

Note that the physical change amount related to the above-mentioned fluctuation in fuel pressure includes the temperature or pressure of the fuel in the delivery pipe, the power consumption of the fuel pump, and the like.

For example, when vapor is generated in the fuel in the delivery pipe, the specific heat decreases due to vaporization, so the rate of change in fuel temperature becomes significantly large, and pressure fluctuations become irregular due to vapor generation. The fuel pressure increases and the load on the fuel pump increases, and when a large amount of vapor is generated, the load on the fuel pump is significantly reduced.

The vapor generation detection device of the present invention is designed to detect vapor generation by focusing on changes in the above-mentioned various physical changes at the time of vapor generation.

[Function] ゛In the vapor generation detection device for a fuel injection engine according to the present invention, the detection means detects the amount of physical change (for example, fuel pressure or temperature) related to the pressure fluctuation of the fuel in the delivery pipe. be done.

The vapor generation determination means receives the output from the detection means, and determines that vapor generation has occurred when the output or the rate of change in the output is out of a predetermined range.

〔Effect of the invention〕

According to the vapor generation detection device for a fuel injection engine according to the present invention, vapor generation can be reliably detected with a simple configuration consisting of the detection means and the vapor generation determination means as described above.

If vapor generation in the fuel supply system can be detected reliably in this way, it will be possible to take appropriate measures in response to vapor generation, and it will be possible to eliminate various problems associated with false detection or non-detection of vapor generation. can.

〔Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall configuration of the fuel supply system and vapor generation detection device of a fuel injection engine. and a fuel supply pipe 3 extending from the fuel tank 1 to the delivery pipe 2.
, a fuel pump 4 and a fuel filter 5 interposed in the middle of the fuel supply pipe 3 , and a reflux pipe 6 for refluxing the fuel relieved from the delivery pipe 2 to the fuel tank 1 .
A pulsation damper 7 is provided at the inlet to the delivery pipe to absorb pulsations in fuel pressure, and a pressure regulator 8 is provided to control the fuel pressure in the delivery pipe 2 to a set pressure. On the upstream side, the fuel supply pipe 3 is provided with a check valve 4a for preventing a drop in fuel pressure within the fuel pump 4 and suppressing vapor generation.

Furthermore, outside air may be introduced into the fuel tank 1, or the fuel tank 1 may be
An air introduction pipe 9 is connected to the fuel tank 1 for sucking the fuel vapor generated inside the intake manifold into the intake manifold. A charge control valve 13 is interposed in a vapor supply pipe 14 extending from the charcoal canister 11 to the intake manifold.

The control valve 10, the on-off valve 12, and the charge control valve 13 are electromagnetic valves each controlled by a signal from a control unit 15.

The motor that drives the fuel pump 4 is connected to a power supply line 17 from a battery 16, and a pump switch 18 that is opened and closed by a signal from a control unit 15 is interposed in the power supply line 17.

As will be described later, as sensors for detecting the presence or absence of vapor generation in the fuel in the fuel supply system, there is a temperature sensor 19 that detects the fuel temperature in the delivery pipe 2, and a temperature sensor 19 that detects the fuel pressure in the delivery pipe 2. a pressure sensor 20 connected to the power supply line 17 of the fuel pump 4, an ammeter 21 and a voltmeter 22 interposed in the power supply line 17 of the fuel pump 4, a rotation speed sensor 23 connected to the crankshaft of the engine, and a An air flow meter 24 for detecting the amount of intake air is provided, and detection signals from these sensors 19 to 24 are output to the control unit 15, respectively.

The control unit 15 includes sensors 19 to 24.
an A/D converter that receives a detection signal from the A/D converter and performs A/D conversion; an input/output ink face connected to the A/D converter;
CPU (central processing bag W) connected to the input/output ink face, ROM (read only memory) and RAM (random access memory) connected to the CPU
A control program for vapor generation detection control, a memory map, etc., which will be described later, are input and stored in the ROM in advance.

The control unit 15 outputs control signals to the pump switch 18, control valve 10, on-off valve 12, and charge control valve 13, respectively.

By the way, the present invention is designed to prevent heat from the engine body during engine operation or when the engine is stopped after operation, such as when the engine is operated under high load for a long period of time or when the outside temperature is high such as in the summer. This system is characterized by vapor generation detection control that detects whether vapor is generated in the fuel inside the delivery pipe 2 or the fuel supply pipe 3, which is easily heated. An example of occurrence detection control will be explained based on a flowchart and drawings.

(First example of vapor generation detection control) This vapor generation detection control is for detecting whether vapor has occurred in the fuel in the delivery pipe 2 while the engine is stopped after the engine has been operated. This method attempts to detect vapor generation by focusing on the fact that when vapor occurs, the specific heat of the gas-liquid mixture of fuel decreases and the fuel temperature rises rapidly.

That is, FIG. 2 is a diagram showing the fuel temperature inside the delivery pipe 2. After the engine is stopped, the delivery pipe 2 is heated by heat from the engine body and the fuel temperature gradually rises. When vapor generation occurs at point B, the specific heat decreases and the fuel temperature rises rapidly. Thereafter, the temperature of the engine body decreases (so, after the fuel temperature reaches the maximum temperature T2 at point C, the fuel temperature begins to decrease).

Note that the fuel temperature within the delivery pipe 2 changes as shown in FIG. 3 while the engine is running and after the engine is stopped.

As the engine starts operating, the temperature of the engine body also rises, so the fuel temperature rises, but since the fuel is circulated by the operation of the fuel pump 4, the fuel temperature does not rise above temperature T1.

After the engine stops, the fuel pump 4 stops, so the fuel temperature rises further, but the temperature of the engine body does not rise any further and instead falls, so the fuel temperature is reduced to temperature T2.
The temperature will not rise above this level.

The rate of temperature rise when the fuel temperature rises above depends on the engine operating conditions and outside temperature, but the rate of temperature rise when the temperature rises rapidly due to vapor generation is the same as the temperature rise rate when no vapor is generated. Since this is much larger than the above, vapor generation can be detected based on the rate of increase in fuel temperature.

Next, the fourth section regarding this vapor generation detection control routine will be explained.
This will be explained using the flowchart shown in the figure.

Incidentally, in FIG. 4, 51 to S10 indicate each step. When control is started under predetermined conditions, it is determined at Sl whether or not the engine is to be stopped. This determination is made based on the signal from the rotation speed sensor 23 or the signal from the ignition switch, etc. When the determination is No, the process returns to Sl, and when the determination is Yes, the fuel temperature from the temperature sensor 19 and the fuel pressure from the pressure sensor 20 are determined in S2. The signal is read, and then the temperature increase rate dT/dt is calculated in step 83, and then in S4 it is determined whether the temperature increase rate is greater than or equal to a set value. This set value is the minimum value of the temperature increase rate that can occur when vapor generation occurs in the fuel in the delivery pipe 2, and is higher than the maximum value of the temperature increase rate when vapor generation does not occur. This is set to a large value and is input into the control program in advance.

As a result of the determination in S4, if the temperature increase rate is not equal to or higher than the set value, that is, if no vapor is generated in the fuel, the process moves from S4 to S5, and in S5, the fuel temperature is determined based on the temperature increase rate calculated in S3 above. It is determined whether or not the value has started to decrease, and if it has not started to decrease, then S5 to S8
Return to step 2, and if the fuel temperature starts to drop again, turn S
6, it is determined that no vapor is generated, and then the control ends.

In other words, when the fuel temperature is rising and no vapor is generated, steps S2 to 85 are repeated, and when the fuel temperature reaches the maximum temperature (0 point in Figure 2) and the fuel temperature starts to decrease, no vapor is generated. Since the occurrence of
In S6, it is determined that no vapor is generated.

By the way, if vapor generation occurs while the fuel temperature is rising, the temperature rise rate will rise rapidly and the determination of S4 will be Yes.
7, it is determined in S7 that vapor has occurred, then the fuel temperature (T) and fuel pressure (P) are read again in 88, and then the saturation temperature (T) is determined based on the fuel pressure in 39. T3) is calculated.

In order to calculate the saturation temperature (T3) of the fuel mentioned above, a table containing the relationship between fuel pressure and saturation temperature is prepared in advance in the ROM.
The saturation temperature (T, ) is calculated based on the table.

Next, in the SIO, it is determined whether the fuel temperature is equal to or higher than the saturation temperature, and when the result is No, the process moves to S6, and when the result is Yes, the process returns to S7. In other words, even if vapor is generated once, there is a possibility that the fuel temperature will decrease due to the temperature of the engine body starting to decrease, etc., so after steps S8 and S9, it is determined in S10 whether the fuel temperature is equal to or higher than the saturation temperature. If the fuel temperature has decreased, it is determined in S6 that the vapor generation has been eliminated.

In S7 above, if it is determined that vapor is generated, control is performed such that, for example, the fuel pump 4 is automatically operated to circulate the fuel and the vapor in the fuel supply pipe 3 and delivery pipe is returned to the fuel tank 1. It will be done.

When the fuel is recirculated as described above, the gas pressure in the fuel tank 1 increases, so a control signal is output from the control unit 15 to the control valve 10, the on-off valve 12, and the charge control valve 13, and the control valve 10 is opened. Close the on-off valve 12 and charge control valve 13
By opening the fuel tank 1, fuel vapor in the fuel tank 1 is supplied to the intake manifold.

Note that while the engine is running, the on-off valve 12 is kept open, and the control valve 10 reduces the pressure in the fuel tank 1 as the fuel decreases, so that the differential pressure is approximately 0°3 kg/cJ.
It functions as a check valve that automatically opens every time the

When the intake negative pressure in the intake manifold increases and exceeds a predetermined value, the charge control valve 13 automatically opens to suck the fuel components trapped in the charcoal canister 11 into the intake manifold.

(Second example of vapor generation detection control) This vapor generation detection control detects vapor generation during engine operation, and detects vapor generation in the fuel inside the delivery pipe 2 or the fuel supply pipe 3. When the fuel pressure starts, the load on the fuel pump 4 increases, and when a large amount of vapor is generated in the fuel, the load on the fuel pump 4 decreases markedly. It is.

That is, the fuel injection amount is set according to the operating state determined by the engine speed and load, and the load on the fuel pump 4 is determined according to the fuel injection amount, so the engine operating state and the load on the fuel pump 4 ( A memory map that sets the relationship with power consumption) is input and stored in the ROM in advance.

FIG. 5 shows, for example, the power consumption (W) of the fuel pump 4 when the engine is in any operating state, and when no vapor is generated, the power consumption (W) is approximately linear. When the power consumption (W) is kept constant and vapor starts to be generated, the power consumption (W) increases as shown by curve E, and when a large amount of vapor is generated, the compressibility of the fuel containing a large amount of vapor by the fuel pump 4 increases. , the power consumption (W) is as shown by curve F. As shown in these curves E and F, the power consumption (W
) deviates from the setting data of the memory map, it is determined that vapor generation has occurred.

Next, we will discuss the vapor generation detection control routine in the sixth section.
This will be explained based on the flowchart shown in the figure.

Incidentally, in FIG. 6, 81 to S6 indicate each step.

When control is started under predetermined conditions, the engine rotation speed (N) from the engine rotation speed sensor 23 and the intake air from the air flow meter 24 are detected at 31! i (Q), voltage (V) from voltmeter 22 and current (A) from ammeter 21
is read, and then at 32 the voltage (V) and current (
The power consumption (W) of the fuel pump 4 is calculated based on A), and then in step 33, the pump setting power consumption (Wo) is calculated from the memory map based on the engine speed (N) and intake air ffi (Q). is calculated, and then in 84 the pump power consumption (W) is calculated as the pump setting power consumption (Wo).
It is determined whether or not it is substantially equal to W=W0 with no vapor generated, the process moves to S5, where it is determined that no vapor is generated, and the process returns from S5 to 31.

If vapor starts to be generated while steps S1 to 35 are repeated, the pump power consumption (W) becomes almost no longer equal to the pump setting power consumption (Wo), so S4
The process moves from to 36, and in S6 it is determined that vapor is generated.
Return from S6 to 81.

The control performed after it is determined that vapor has occurred as described above is the same as the control described above, and therefore the description thereof will be omitted.

(Third Example of Vapor Generation Detection Control) In this vapor generation detection control, when vapor is not generated, the pressure is increased almost regularly according to the difference between the discharge amount of the fuel pump 4 and the injection amount from the injection nozzle 2a. Since the regulator 8 performs a relief operation, the fuel pressure within the delivery pipe 2 fluctuates periodically, but when vapor starts to be generated, the vapor generation occurs without any periodicity, so the above-mentioned periodicity is disturbed. The aim is to detect the occurrence of vapor.

That is, as shown in FIG. 7, when no vapor is generated, the fuel pressure (P) fluctuates periodically as shown by curve G within a predetermined pressure difference (ΔP) range, for example, at a period t0.

On the other hand, when vapor starts to be generated, it fluctuates irregularly as shown by curve H. Next, this vapor generation detection control routine will be explained based on the flowchart of FIG. 8.

Incidentally, reference numerals 31 to S5 in the figure indicate each step.

When control is started under predetermined conditions, the fuel pressure (P) from the pressure sensor 20 is read at sl, and then the period of pressure fluctuation is calculated at 32.

Next, in S3, it is determined whether or not there is periodicity in the pressure fluctuation, and if no vapor is generated and there is periodicity in the pressure fluctuation, the process moves to S4, where it is determined that no vapor is generated, and s
Return from 4 to 81. On the other hand, when vapor begins to be generated and the periodicity of pressure fluctuation disappears, the process moves from S3 to 85, and in s5 it is determined that vapor has occurred, and from s5 to 81
Return to

The control after it is determined in S5 that vapor has occurred is the same as the control described above, and therefore the description thereof will be omitted.

In addition, when the fuel pump 4 is operated for a predetermined period of time before turning on the starter switch as a measure against vapor lock during a warm start of the engine, when it is determined that vapor is generated by the vapor generation detection control described above, the gas in the fuel tank 1 is In order to prevent the pressure from rising, the on-off valve 12 is closed and the control valve 10 and charge control valve 13 are opened in the same manner as described above, thereby controlling the fuel vapor to be supplied from the inside of the fuel tank 1 to the intake manifold. It is also possible.

As explained above, in the vapor generation detection control device of the present invention, vapor generation can be detected by relatively simple control based on the temperature rise rate of the fuel, the fluctuation of the power consumption of the fuel pump 4, or the periodicity of the fuel pressure. can be reliably detected, and can be effectively used to solve various problems associated with erroneous detection or non-detection of vapor generation.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is an overall configuration diagram of the fuel supply system and vapor generation detection control device of a fuel injection type engine; FIG. 2 is a diagram showing the fuel temperature after the engine is stopped; Fig. 3 is a diagram showing the fuel temperature when the engine is running and when the engine is stopped, and Fig. 4 is a diagram showing the fuel temperature when the engine is running and when the engine is stopped.
FIG. 5 is a flowchart showing the example routine; FIG. 5 is a diagram showing the power consumption of the fuel pump; FIG. 6 is a flowchart of the second example routine of vapor generation detection control; FIG. FIG. 8 is a flowchart of a third example routine of vapor generation detection control. 2. Delivery pipe, 15. Control unit, 19. Temperature sensor, 20. Pressure sensor, 21. Ammeter, 22. Voltmeter. Patent applicant: Mazda Motor Corporation Figure 2 Figure 3

Claims (3)

[Claims] (1) In an engine having a fuel injection valve, a detection means for detecting the amount of physical change related to the pressure fluctuation of the fuel in the delivery pipe; What is claimed is: 1. A vapor generation detection device for a fuel injection engine, comprising: vapor generation determination means for determining that vapor generation has occurred when the amount of vapor is outside a predetermined range. (2) The vapor generation detection device for a fuel injection engine according to claim 1, wherein the detection means is a pressure detection means for detecting the fuel pressure within the delivery pipe. (3) The vapor generation detection device for a fuel injection engine according to claim 1, wherein the detection means is a temperature detection means for detecting the temperature of the fuel in the delivery pipe.