JP3640883B2 - Heater heater control method based on input power - Google Patents

Description

[0001]
BACKGROUND 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]
[Prior art]
In the engine for the above-mentioned use, it has been practiced for a long time to provide a fuel injection valve for injecting fuel into the engine combustion chamber and to inject fuel while heating the fuel injection valve with such a heater. In addition, various inventions have been proposed in which overheating of the heater is prevented and its durability is improved, and heating of the fuel by the heater is controlled based on the atmosphere, the engine temperature state, the fuel combustion state, or the like. ing. Examples of such inventions are shown in Japanese Patent Application Laid-Open Nos. 5-288131 and 11-148441. In particular, the latter publication describes that the fuel heating heater is shut off when the fuel temperature or the engine coolant temperature exceeds a predetermined value.
[0003]
In Japanese Patent Application No. 2000-340907, which is filed by the same applicant as the present applicant, as a method for controlling the operation of a heater for heating the fuel injection valve of the engine, the heating degree of the fuel injection valve exceeds a predetermined threshold value. It is described that the operation of the heater is prevented when it is determined that the fuel injection valve is greater than or equal to a predetermined threshold value, and the heating degree of the fuel injection valve is set to the predetermined threshold value. That the drive current waveform changes with the temperature rise of the fuel injection valve, the fuel injection amount with respect to the valve opening instruction signal increases with the temperature rise of the fuel injection valve, or the temperature of the fuel injection valve It has been proposed to make a judgment based on an increase in the operating sound as it rises.
[0004]
[Problems to be solved by the invention]
The present invention also controls the operation of the fuel heater so that the engine fuel is heated properly by the heater and is controlled appropriately so as to improve the engine startability and the exhaust characteristics at engine start. However, as described in the above publications, etc., the degree of fuel heating by the heater is directly detected by the fuel temperature, or the fuel injection valve is actually heated by the heater as in the previous application. If the heating energy is input to the heater before the heater operation is controlled by determining the degree of heating performed by the heater by detecting the parameter, the fuel is heated to the specific temperature. By controlling the heater operation in a feed-forward manner based on the estimation that the engine is heated, it is possible to control the heater for engine fuel heating, which is superior in control agility. Is an object of the present invention to achieve.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a method for controlling the operation of an electric heater for heating engine fuel,
Estimating a target input power amount to be input to the heater in order to make the fuel have a predetermined heating degree,
The present invention proposes a method characterized in that when the effective input power amount input to the heater is estimated to have reached the target input power amount, the heater is energized to be reduced.
[0006]
In the heater control method described above, the reduction correction of energization to the heater may be to stop energization as one embodiment.
[0007]
In the heater control method described above, the predetermined heating degree of the fuel is determined by the engine starting coolant temperature, intake air temperature, intake pipe negative pressure, fuel properties, system fuel pressure, atmospheric pressure, engine speed, and crank angle. The correction may be made according to at least one of the number of times of operation of the fuel injection valve and the thermal conductivity around the heater.
[0008]
[Action and effect of the invention]
The heating of the engine fuel by the heater is particularly effective in improving the startability when the engine is cold and improving the exhaust characteristics when starting the engine, if it is accurately controlled. 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 gradual phenomenon compared to the agility that can be controlled by the heater current. Further, when the engine is started, a pulsating sudden change occurs in the fuel flow. In such a situation, the operation control of the heater for heating the fuel is performed by controlling the amount of electric power to be input to the heater with the fuel heating temperature as a target, in addition to the feedback control in consideration of the fuel temperature and the heating degree of the heater unit. There is a situation where feedforward control is suitable. In this respect, in controlling the operation of the electric heater that heats the engine fuel as described above, a target input power amount to be input to the heater in order to make the fuel a predetermined heating degree is estimated, and the heater When it is estimated that the effective input electric energy input to the target electric input electric energy has been reached, the engine fuel is required in a short period of time when the engine is started if it is corrected so that the energization to the heater is at least reduced. Can be heated sufficiently and not to be overheated.
[0009]
As described above, the heating of the engine fuel by the heater is a short period when the engine is started, and the fuel passage means such as the heater and the fuel injection valve heated by the heater naturally has a certain heat capacity. Even if the reduction of energization to the heater when the input effective input electric energy reaches the target input electric energy is performed in a manner of stopping, there is no sudden change unfavorable for heating the fuel.
[0010]
In addition, the degree of heating desired for the fuel when starting the engine depends on the engine temperature, intake air temperature, intake pipe negative pressure, fuel properties, system fuel pressure, atmospheric pressure, engine speed, thermal conductivity around the fuel heater, etc. Since it varies accordingly, fuel heating at engine start-up can be made more favorable if it is modified in response to at least one of these parameters, possibly more. The influence of each of these parameters on the degree of heating of the fuel, that is, the amount of electric power supplied to the heater is as shown in FIG.
[0011]
That is, as shown in FIG. 1, the correction coefficient K1 for the engine coolant temperature as the correction coefficient for the heating degree desired for the fuel at the time of starting the engine may be smaller as the engine warm-up degree is higher. The higher the temperature of the intake air, the smaller the degree of heating with respect to the fuel. Therefore, the correction coefficient K2 for the intake air temperature may be smaller as the intake air temperature is higher. Further, if the intake pipe negative pressure is large, the fuel is more easily atomized. Therefore, the fuel heating degree correction coefficient K3 for the intake pipe negative pressure may be decreased 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 heavyness.
[0012]
If the degree of heating of the engine-injected fuel is too high, vaporization of the fuel may cause vapor lock in the fuel passage, but this possibility becomes weaker as the fuel pressure increases. The correction coefficient K5 may be increased as the system fuel pressure increases. Similarly, even if the fuel heating degree is not corrected for the system fuel pressure, the higher the atmospheric pressure, the less the possibility of causing vapor lock in the fuel passage. It is preferable to prepare K6 so as to increase as the atmospheric pressure increases as shown in the figure.
[0013]
Further, the rapidity of the intermittent flow of fuel in the fuel supply system accompanying the intermittent injection of fuel corresponding to the rotation of the engine increases as the engine speed increases, and the rapidity of the intermittent flow of fuel is high. As the fuel fluidity is desired to be higher, it is preferable to correct the fuel heating degree with respect to the engine speed from this point of view, and the correction coefficient K7 increases as the engine speed increases. It may be. 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 operates twice per 720 ° of the crank rotation angle for group injection, or independent injection is not performed. Therefore, it is preferable that the fuel heating degree is corrected for the intermittent flow rapidity of the fuel in the fuel supply system, depending on whether the crank is operated once per 720 °.
[0014]
Furthermore, as described above, the heating of the fuel by the heater at the time of starting the engine is a short time of at least a few tens of seconds, and the degree of heating generated in the fuel when the power is supplied to the heater is greatly influenced by the thermal conductivity around the heater. Therefore, the influence of this difference may also be prepared as a correction coefficient K8 for thermal conductivity as shown in the figure.
[0015]
Thus, assuming that the standard value of the amount of electric power to be supplied to the heater per unit fuel injection amount for the fuel heating is Wto and the fuel injection amount is Vf, the input electric power at each engine start-up The amount Wt is determined by the correction coefficients K1, K2,. . . Wt = K1, K2, K3, K4, K5, K6, K7, K8, Wto, Vf
As obtained by calculation. 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 possible to store such a map as digital data and calculate the input power amount based on it. This can be done without problems by using an electric vehicle operation control device equipped with a microcomputer that is built in a standard vehicle such as an automobile.
[0016]
Then, the amount of electric power We supplied to the heater is obtained as an integrated value of voltage x current in the heater energization, and if the correction is made so as to reduce the energization to the heater when We reaches Wt, this feedforward control Thus, rapid fuel heating at the time of engine start can be achieved without causing excessive heating in the heater.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 is a flowchart showing a control process for controlling the operation of the fuel heating heater as described above according to the present invention. The heater operation control according to such a control process is started when the engine is started by a program incorporated in the microcomputer section of the electronic vehicle operation control apparatus (not shown).
[0018]
When the control is started, first, in step 10, data necessary for the control of the engine cooling water temperature, the intake air temperature, etc. is read. Next, the control proceeds to step 20, and it is determined whether or not a condition for heating the fuel is satisfied based on the read data, that is, whether or not the heater operation is necessary. When the answer is yes, control proceeds to step 30 and energization of the heater for heating the fuel is started.
[0019]
After starting energization of the heater, the control proceeds to step 40, and in addition to the fuel injection amount based on the data read in step 10, the engine coolant temperature, intake air temperature, intake pipe negative pressure, fuel severity, system fuel pressure , Atmospheric pressure, engine speed, thermal conductivity around the heater, etc., if possible, correction factors K1, K2,. . . Are obtained from the above map, and based on these values, the target input power amount Wt to be input to the heater is calculated.
[0020]
Next, the control proceeds to step 50, where an execution input power amount We which is a temporal integration of the product of the heater current and the voltage based on the data read in step 10 is calculated.
[0021]
Control then proceeds to step 60, where it is determined whether We has reached Wt. And while it has not yet reached that and the answer is no, control returns to before step 10 and continues energizing the heater while updating the read data as needed.
[0022]
If the control is continued through steps 10 to 60 while the heater is energized in this way, We reaches Wt and the answer to step 60 turns from yes to no, so the energization to the heater is corrected in the decreasing direction. It only has to be done. In the embodiment of FIG. 2, the energization of the heater is stopped here. Thus, one heater operation control is completed.
[0023]
FIG. 3 is a flowchart similar to FIG. 2 showing another embodiment of the control process for controlling the operation of the fuel heater according to 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 or absence of a command to pressurize the fuel pressure of the fuel supply system is read, and when that command is issued In step 25, the fuel of the system is pressurized. Such pressurization of the system fuel is naturally reflected in the target input power amount Wt by the change of the correction coefficient K5. In this case, after the energization of the heater is stopped in step 70, it is preferable to take some buffer time to restore the pressurized system fuel pressure. In step 90, the system fuel pressure is returned to the normal pressure, and one heater control is finished here.
[0024]
In the above, the present invention has been described in detail with respect to several examples of the correction of the input electric energy to the heater with respect to several parameters, and two embodiments relating to the control process. However, these embodiments are not limited within the scope of the present invention. It will be apparent to those skilled in the art that these modifications are possible.
[Brief description of the drawings]
FIG. 1 shows the engine temperature state, intake air temperature, intake pipe negative pressure, fuel properties, system fuel pressure, atmospheric pressure, engine speed, and heater surroundings with respect to the degree of heating desired for fuel heating at the time of starting the engine. A map showing the effect of thermal conductivity.
FIG. 2 is a flowchart showing a control process for performing operation control of a fuel heating heater according to the present invention in 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.

Claims (3)

In the method of controlling the operation of the electric heater that heats the engine fuel,
Estimating a target input power amount to be input to the heater in order to make the fuel have a predetermined heating degree,
A method of correcting to reduce energization to the heater when it is estimated that the execution input power amount input to the heater has reached the target input power amount. The method according to claim 1, wherein the correction of energization to the heater is to stop energization. The predetermined heating degree of the fuel is the engine cooling water temperature, intake air temperature, intake pipe negative pressure, fuel properties, system fuel pressure, atmospheric pressure, engine speed, number of fuel injection valve operations per crank angle, and heat conductivity around the heater. The method according to claim 1, wherein the method is modified in accordance with at least one of the following.

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