JP2002195110A - Fuel heating heater control method based on input electric energy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly quickly control operation of a heater without overheating fuel and the heater by feedforward control for estimating a heating degree of the fuel obtained thereby from heating electric energy inputted to the heater. SOLUTION: Target input electric energy to be inputted to the heater for setting the fuel to a prescribed heating degree is estimated on the basis of an engine starting time fuel injection quantity, a cooling water temperature, an intake air temperature, intake pipe negative pressure, fuel properties, system fuel pressure, atmospheric pressure, an engine speed, a fuel injection valve operation frequency per a crank angle, and heat conductivity around the heater, and when actual input electric energy reaches the target input electric energy, current-carrying to the heater is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system for an engine of a vehicle such as an automobile, and more particularly to controlling the operation of a heater for heating the fuel of the engine.

[0002]

2. Description of the Related Art In an engine for the above use, a heater is provided for a fuel injection valve for injecting fuel into an engine combustion chamber,
Injecting while heating the fuel by heating the fuel injection valve with such a heater has been already performed for a long time. Further, the overheating of the heater is prevented to improve the durability thereof, and the heater is used. Various inventions have been proposed for controlling the heating of fuel based on the atmosphere, the temperature state of the engine, the combustion state of the fuel, and the like. Examples of such inventions are disclosed in JP-A-5-288131 and JP-A-11-14.
No. 8441, and the like. Particularly, the latter publication describes that the fuel heating heater is shut off when the fuel temperature or the engine cooling water temperature exceeds a predetermined value.

Japanese Patent Application No. 2000-340907, which is filed by the same applicant as the present applicant, discloses a method for controlling the operation of a heater for heating a fuel injection valve of an engine, in which the degree of heating of the fuel injection valve is controlled to a predetermined value. It is described that it is determined whether or not the temperature is equal to or more than a threshold value, and when it is determined that the value is equal to or more than a predetermined threshold value, the operation of the heater is blocked. The fact that the threshold value has been reached means that the drive current waveform changes with the temperature rise of the fuel injection valve, the fuel injection amount in response to the valve opening instruction signal increases with the temperature rise of the fuel injection valve, or the fuel injection It has been proposed to make a determination based on an increase in the operating noise of the valve as the temperature of the valve increases.

[0004]

The present invention also provides a heater for heating a fuel so as to improve the engine startability and the exhaust characteristics at the time of starting the engine by appropriately controlling the heating of the engine fuel by the heater. Is controlled by directly detecting the degree of heating of the fuel by the heater based on the fuel temperature, as described in the above-mentioned publications, or by the fuel injection by the heater as in the above-mentioned prior application. Prior to controlling the operation of the heater by judging the degree of heating performed by the heater by detecting a parameter that changes as a result of actually heating the valve, if the heating energy is directly applied to the heater, the fuel is thereby reduced. By controlling the operation of the heater in a feed-forward manner based on the assumption that it should be heated to the bareest temperature, a greater control agility is achieved. It is and achieving the control of the engine fuel heater.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method for controlling the operation of an electric heater for heating fuel of an engine. Estimating a target input power amount to be input to the heater, and correcting the power supply to the heater to be reduced when it is estimated that the effective input power amount input to the heater has reached the target input power amount. Is proposed.

In the above-described heater control method, the correction for reducing the power supply to the heater may be to stop the power supply as one embodiment.

In the above-described heater control method, the predetermined heating degree of the fuel includes a cooling water temperature at engine start, an intake air temperature, an intake pipe negative pressure, a fuel property, a system fuel pressure, an atmospheric pressure,
Engine speed, number of fuel injector actuations per crank angle,
It may be modified according to at least one of the thermal conductivity around the heater.

[0008]

The heating of the engine fuel by the heater, if controlled properly, is particularly effective in improving the startability of the engine at cold start and improving the exhaust characteristics at engine start. It demonstrates. However, the heating of the fuel by the heater at the time of starting the engine is a short time of at most ten and several seconds. On the other hand, heat transfer is a rather slow phenomenon compared to the agility that is possible to control the heater current. When the engine starts,
Pulsating sudden changes occur in the fuel flow. In such a situation,
The operation control of the heater for heating the fuel is feed-forward control that controls the amount of power to be supplied to the heater with the target of the heating temperature of the fuel, in addition to the feedback control that considers the fuel temperature and the degree of heating of the heater section. There is a situation where is suitable. At this point, in controlling the operation of the electric heater for heating the engine fuel as described above, the target amount of electric power to be supplied to the heater in order to bring the fuel to a predetermined heating degree is estimated. When it is estimated that the effective input power input to the target has reached the target input power, if the power supply to the heater is corrected to be reduced at least, it is necessary to supply the engine fuel in a short time at the time of starting the engine. Only enough heating and not too much heating.

As described above, the heating of the engine fuel by the heater is a short period at the time of starting the engine, and the heater and the fuel passage means such as the fuel injection valve heated by the heater naturally have a certain heat capacity. As described above, even if the reduction of the power supply to the heater when the effective input power input to the heater reaches the target input power amount is performed in a manner of stopping, the undesirable sudden change in the heating of the fuel does not occur. .

The degree of heating desired for the fuel at the time of starting the engine includes the temperature of the engine at the time of starting the engine, the intake air temperature, the negative pressure of the intake pipe, the fuel properties, the system fuel pressure, the atmospheric pressure, the engine speed, and the heat conduction around the fuel heater. Since it varies depending on the degree and the like, if it is modified according to at least one of these parameters, and possibly more, the fuel heating at the time of starting the engine can be more favorable. . The effect of these parameters on the degree of heating of the fuel, that is, the amount of electric power supplied to the heater is shown in FIG.
As shown in FIG.

That is, as shown in FIG. 1, the correction coefficient K1 for the cooling water temperature of the engine as the correction coefficient for the heating degree desired for the fuel at the time of starting the engine may be smaller as the warming degree of the engine is higher. The higher the temperature of the air taken into the engine, the lower the degree of heating of the fuel may be. Therefore, the correction coefficient K2 for the intake air temperature may be smaller as the intake air temperature is higher. Further, since the fuel is more likely to be atomized if the intake pipe negative pressure is large, the correction coefficient K3 of the fuel heating degree with respect to the intake pipe negative pressure may be reduced as the intake pipe negative pressure increases. The correction of the fuel heating degree with respect to the fuel property may be such that the correction coefficient K4 is increased in accordance with the increase in the fuel heaviness.

If the degree of heating of the fuel injected by the engine is too high, vapor lock of the fuel may occur in the fuel passage due to vaporization of the fuel. However, this possibility becomes weaker as the fuel pressure becomes higher. The fuel heating degree correction coefficient K5 may be increased in accordance with an increase in the system fuel pressure. Similarly, even if the correction of the fuel heating degree with respect to the system fuel pressure is not performed, the higher the atmospheric pressure is, the less the possibility of causing a vapor lock in the fuel passage is reduced. It is preferable to prepare K6 to increase as the atmospheric pressure increases as shown in the figure.

Further, the rapidity of the intermittent fuel flow in the fuel supply system due to the intermittent injection of the fuel corresponding to the rotation of the engine increases with an increase in the engine speed. It is desirable that the higher the fluidity, the higher the fluidity of the fuel. Therefore, from this viewpoint, it is preferable to correct the fuel heating degree with respect to the engine speed. The correction coefficient K7 increases as the engine speed increases. May be performed. Although not shown in the figure for the same reason as the correction of the fuel heating degree with respect to the engine speed, the fuel injection valve is operated twice per 720 ° of crank rotation angle for group injection, or independent injection is performed. Depending on whether it operates once per 720 ° of crank rotation,
It is preferable that the fuel heating degree is also corrected for the intermittent flow rapidity of the fuel in the fuel supply system.

Further, as described above, the heating of the fuel by the heater at the time of starting the engine is a short time of at most ten and several seconds, and the degree of heating generated by the supply of electric power to the heater depends on the thermal conductivity around the heater. Since it is greatly affected, the effect of this difference may be prepared as a correction coefficient K8 for the thermal conductivity as shown in the figure.

Thus, the standard value of the electric energy to be supplied to the heater per unit fuel injection amount for heating the fuel is Wto
Assuming that the fuel injection amount is Vf, the input power amount Wt at each start of the engine is determined by the correction coefficients K1, K2,. . . Wt = K1, K2, K3, K4, K5, K6, K7, K
It is obtained by calculation as 8 · Wto · Vf. The setting of the map for each correction coefficient as shown in FIG. 1 can be performed based on experiments for each type of engine, and it is not possible to store such a map as digital data and calculate the input electric energy based on the map. The operation can be performed without any problem by using an electric vehicle operation control device having a microcomputer which is incorporated in a vehicle such as a current automobile as a standard.

Then, the amount of electric power We supplied to the heater is obtained as an integrated value of voltage × current during energization of the heater.
If correction is made to reduce the power supply to the heater when e reaches Wt, such feedforward control can achieve rapid fuel heating during engine start without causing excessive heating of the heater.

[0017]

FIG. 2 is a flow chart showing a control process for controlling the operation of the heater for fuel heating as described above according to one embodiment of the present invention. The operation control of the heater in this control process is started with the start of the engine by a program incorporated in the microcomputer unit of the electronic vehicle operation control device (not shown).

When the control is started, first, at step 10, data necessary for controlling the engine cooling water temperature, the intake air temperature, and the like is read. Control then proceeds to step 2
The process proceeds to 0, and it is determined whether the condition for heating the fuel is satisfied based on the read data, that is, whether the heater operation is necessary. If the answer is yes, the control proceeds to step 30, where the heater is energized for fuel heating.

After energization of the heater is started, the control proceeds to step 4
Going to 0, in addition to the fuel injection amount based on the data read in step 10, the engine cooling water temperature, intake air temperature, intake pipe negative pressure, fuel heaviness, system fuel pressure, atmospheric pressure, engine speed, heater circumference At least one of the thermal conductivity of the
If possible, correction factors K1 and K
2,. . . And the like are obtained from the above-described maps, and based on them, the target input power amount Wt to be input to the heater is calculated.

Next, the control proceeds to step 50, at which the effective input power We, which is a temporal integration of the product of the heater current and the voltage based on the data read at step 10, is also given.
Is calculated.

Next, the control proceeds to a step 60, wherein it is determined whether or not We reaches Wt. If the answer is no and the answer is no, the control returns to step 10 and the heater is continuously energized while updating the read data as needed.

If the control is continued through steps 10 to 60 while energizing the heater in this way, We eventually reaches Wt, and the answer to step 60 changes from yes to no. It only has to be corrected in the direction. In the embodiment of FIG. 2, the power supply to the heater is stopped here. Thus, one heater operation control ends.

FIG. 3 is a flowchart similar to FIG. 2 showing a control process for performing the operation control of the fuel heating heater as described above according to another embodiment of the present invention. In FIG. 3, the steps for performing the same control as the steps in FIG. 2 are indicated by the same step numbers as in FIG. In this embodiment, in step 10,
In addition to the data in the embodiment of FIG. 2, the presence / absence of a command to increase the fuel pressure of the fuel supply system is read, and when the command is issued, the fuel of the system is pressurized in step 25. It is. The pressurization of the system fuel is, of course, achieved by changing the correction coefficient K5 to the target input power W
is reflected in t. In this case, after the power supply to the heater is stopped in step 70, it is preferable to take some buffer time to return the pressurized system fuel pressure to the original pressure.
At step 80, a predetermined time has elapsed, and after that, at step 90, the system fuel pressure is returned to the normal pressure.
Here, one heater control ends.

In the above, the present invention has been described in detail with respect to two examples of the correction of the amount of electric power supplied to the heater for several parameters and the control process. However, these embodiments are within the scope of the present invention. It will be apparent to those skilled in the art that various modifications are possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing an engine temperature state, an intake air temperature, an intake pipe negative pressure, a fuel property, a system fuel pressure, an atmospheric pressure, an engine rotation speed, and a heater periphery with respect to a heating degree desired for fuel heating at the time of engine start of the present invention. Map showing the effect of thermal conductivity on the surface.

FIG. 2 is a flowchart showing a control process for controlling the operation of the fuel heating heater according to the present invention for one embodiment.

FIG. 3 is a flowchart showing a control process for performing operation control of a fuel heating heater according to another embodiment of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuhiko Koga 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Kazuki Sato 1-1-1, Showa Town, Kariya City, Aichi Prefecture Denso Corporation (72) Inventor Hideki Suzuki 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside DENSO Corporation

Claims (3)

[Claims] 1. A method for controlling the operation of an electric heater for heating fuel of an engine, comprising the steps of: estimating a target amount of electric power to be supplied to the heater in order to bring the fuel to a predetermined heating degree; A method comprising: modifying the heater to reduce the power supply to the heater when it is estimated that the supplied actual input power has reached the target input power. 2. The method according to claim 1, wherein the correction of the power supply to the heater comprises stopping the power supply. 3. The predetermined heating degree of the fuel includes a cooling water temperature at the time of engine start, an intake air temperature, an intake pipe negative pressure, a fuel property, a system fuel pressure, an atmospheric pressure, an engine speed, a number of times of operating a fuel injector per crank angle, 3. Modified according to at least one of thermal conductivity around the heater.
The method described in.