JPH04269345A - Method and device for starting heating of internal combustion engine - Google Patents

Abstract

PURPOSE: To positively-determine need for hot starting by using bubbles of fuel formed in a fuel supply apparatus. CONSTITUTION: This hot starting method for an internal combustion engine includes measuring starting intake temperature TA, i.e., air temperature of an intake system in turning on a power switch before starting, comparing the starting intake temperature TA with a threshold intake temperature SW, and activating hot starting (s6) if the temperature exceeds the threshold intake temperature. In comparison with the conventional method where an engine temperature is used so as to be compared with the engine threshold temperature so that it may be determined whether hot starting should be activated, the time characteristic of the intake temperature is more suitable to that of a fuel supply system. By using the intake temperature instead of the engine temperature, bubbles of fuel are formed in a fuel intake apparatus, it is thus possible to positively-determine whether hot starting is needed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for warm-starting an internal combustion engine for determining whether or not to warm-start the engine.

0002

BACKGROUND OF THE INVENTION A typical warm start condition is air bubbles in the fuel supply system of an internal combustion engine. The fuel metering device thus supplies the internal combustion engine not only with the essentially desired fuel, but also with gas. In order to maximize the amount of fuel that is reduced by the presence of gas, during a warm start, the fuel metering device is activated to increase the amount of fuel delivered to the internal combustion engine. Other starts, and therefore those that do not presuppose the presence of air bubbles in the fuel supply, are collectively referred to below as cold starts. However, in reality, a wide range of variations is possible even in the case of cold starting, and in particular cold starting varies according to the engine temperature.

[0003] In this application, the expression "before starting" is often used to express the time. It can be thought of as the period from the time you turn on the ignition to the time you drive the starter.

[0004] In a previously known method of determining whether a warm start is to be performed in an internal combustion engine, the engine temperature is measured before starting. If this temperature is below the engine threshold temperature, a cold start will occur, otherwise a warm start will occur. This method is based on the fact that vapor bubbles in the fuel supply can only form when the engine has stored a certain minimum amount of heat, which is related to the engine temperature. Typically, the threshold temperature is about 96-97°C. When an engine, initially running under full load at approximately 90° C., is shut down, the above-mentioned threshold temperature is exceeded within a few minutes, and shortly thereafter the temperature typically reaches approximately 110° C. In contrast, the time characteristics of the part of the fuel supply system attached to the engine block are significantly longer and the temperatures are initially lower. Normal maximum temperature is about 90-115℃
, the value of the time constant is approximately 10-30 minutes. However, this value varies significantly depending on specifically how the fuel supply device is attached to the engine block.

[0005] When the engine, which has previously been operated at an engine temperature of approximately 90° C., is shut off and restarted after a few minutes, the threshold for determining whether a warm start should be carried out is established, as already explained. Exceed the temperature. The fuel supply device is accordingly driven to increase the fuel to compensate for the air bubbles being supplied instead of fuel. However, in the above example, more fuel is actually supplied to the engine. This is because the fuel supply system warms up only slightly during the short period mentioned and no bubbles are formed or only a small volume of bubbles is formed. However, if too much fuel is supplied to the engine, the engine may not start at all, or may stop abruptly.

[0006]

SUMMARY OF THE INVENTION In order to at least partially avoid this problem, it has been proposed to make the drive of the fuel supply system, which is additionally carried out during a warm start, related to the air temperature in the intake system. It is being This air temperature also increases after switching off the engine, in particular with a time constant that is longer than the time constant of the engine temperature increase and often longer than the time constant of the fuel supply temperature increase. If the conditions for a warm start are met, but it is detected that the intake air temperature is still quite low, the engine has only been off for a short time and therefore only a few air bubbles can form. It is thought that The fuel supply is therefore only slightly activated, unlike when the intake air temperature is high, which indicates that the engine has been stationary for a long time.

[0007] Even with the above-described method of making the additional actuation of the fuel supply system dependent on the intake air temperature, problems still arise when starting the internal combustion engine.

It is an object of the present invention to eliminate the above-mentioned conventional drawbacks and to make it possible to reliably determine that a warm start is necessary.

[0009]

[Means for Solving the Problems] In the method of the present invention for determining whether or not to perform a warm start in an internal combustion engine, the starting intake air temperature, that is, the air in the intake system when the internal combustion engine is turned on, is determined before starting. The temperature is measured and then the starting intake air temperature is compared to the intake air threshold temperature and if the threshold temperature is exceeded, a warm start is initiated.

0010

This method is based on the recognition that some of the difficulties in conventional methods are related to the fact that the engine temperature rises and falls much more rapidly than the fuel supply temperature. That is, the engine temperature is 90°C in advance.
to approximately 110° C., the engine temperature may drop below a threshold temperature of, for example, 97° C., for example 15 minutes after switching off the internal combustion engine. In such a case,
If the threshold temperature is still exceeded, the fuel supply will be operated much longer than in the case of a cold start. This is because the intake air temperature during that period exhibits a relatively high value. However, if the engine temperature drops even slightly below the engine's threshold temperature, a false cold start will occur.

In contrast, according to the method of the present invention, it is detected that a warm start should be performed. This is because the intake air temperature is still at a high value. The advantage of comparing the intake air temperature instead of the engine temperature to a threshold value to determine whether a warm start should be performed is that the temporal characteristics of the intake air temperature are much smaller than those of the engine temperature. It is well consistent with the temporal characteristics of the fuel supply device. If it is determined that a warm start should be performed,
The actual actuation of the fuel supply device is carried out as in the prior art, thus preferably taking into account the intake air temperature.

As described above, it has been shown that a warm start is activated when the starting intake air temperature exceeds a threshold value. In the basic embodiment of the invention described above, this start-up is equated with actually performing a warm start. Particularly preferably, however, the above-mentioned conditions are combined with other conditions. In that case, the warm start will not take place despite the start, since the start performed in the step described above will be canceled again due to other conditions.

Particular preference is given to a combination with conventional methods and therefore with a comparison of the starting engine temperature and an engine threshold value. However, in that case the engine threshold temperature can be selected significantly lower than before, for example below 90°C. If the engine temperature is below this low threshold temperature, it can basically be seen that the heat content of the engine is not yet sufficient to heat the fuel supply and form bubbles. In that case, even if the comparison between the starting intake air temperature and the intake air threshold temperature indicates that a warm start is to be initiated, a warm start will not be performed.

[0014] The intake air threshold temperature is normally set at about 40°C. It has been found that this threshold temperature can be exceeded even when idling, especially if the engine has previously been operated at full load for a short period of time. It has been found that in such cases a warm start is often not necessary. This is because the engine has cooled significantly within the period required to bring the intake air temperature above the intake air threshold temperature.
This is because a sufficient amount of heat cannot be supplied to heat the fuel supply device and form bubbles therein. In that case, the intake air temperature will not rise further after the engine is shut off. Preferably, therefore, the cut-off intake air temperature is detected when the internal combustion engine is switched off, and the difference between the cut-off intake air temperature and the starting intake air temperature is calculated before starting, and if the difference is below a difference threshold, the cut-off intake air temperature is detected. No starting takes place.

In experiments, in special cases the intake air threshold temperature is preferably corrected according to the ambient temperature. A reference temperature, for example 15° C., can be used as a standard for determining whether correction should be made and, if so, to what extent. If the ambient temperature is, for example, in the range +/-10°C, no correction is made. For lower or higher temperatures, the intake threshold temperature is changed by an amount determined by the test stand.

[0016]No special sensors are usually used to measure the ambient air. Providing additional sensors of this type is not cost-effective. If an additional sensor is to be used in the first place, it is preferable to install a sensor of this type in the fuel supply device, so that the temperature of this device can be used to directly determine the formation of air bubbles in the fuel. Must be. According to a preferred embodiment of the invention, the lowest intake air temperature during operation of the internal combustion engine is detected since, for the reasons mentioned above, the control of many internal combustion engines does not permit the addition of other temperature sensors. It is assumed that this temperature is a good representation of the ambient temperature. Even if the ambient temperature fluctuates relatively widely over the course of a day, the minimum temperature is still a good value for the temperature range while the engine is running. Evaluating this temperature range is sufficient to determine whether the intake air threshold temperature should be changed, and if so, in which direction.

The device of the present invention for determining whether or not to perform a warm start in an internal combustion engine includes a temperature sensor that measures the starting intake air temperature, that is, the air temperature in the intake system when the internal combustion engine is turned on; a comparator that compares the starting intake air temperature with an intake air threshold temperature and outputs a comparison signal; It consists of a sequence control device that activates the engine start.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below according to embodiments shown in the drawings.

The method shown in FIG. 1 begins by turning on the ignition of the internal combustion engine. Then step s1
After passing through s6, the internal combustion engine rotates. These steps are explained in detail below.

[0020] While the internal combustion engine is rotating, the air temperature within the intake system, ie, the intake air temperature, is continuously measured. In step s7, the lowest intake air temperature TA_MIN is detected. This is done by comparing the then measured intake air temperature with the lowest intake air temperature detected since the start of the internal combustion engine. If the newly measured intake air temperature is lower than the stored minimum temperature, the new intake air temperature is stored as T_MIN. Otherwise, the value already stored is retained. This process is repeated until ignition off is detected in step s8.

As soon as the ignition off is detected in step s8 mentioned above, the last measured value of the intake air temperature is stored as the value TA_ALT in step s9. If the respective measured intake air temperature is stored as is for further processing, it is sufficient to ensure that the stored value is retained after the ignition is switched off. This means that the value TA_
Make sure the MIN is held. The process is then terminated.

The stored values TA_ALT and TA_
MIN is read from memory after the ignition is turned on in a first step s1. Further, in step s1, the engine temperature TM and the intake air temperature TA at that time are measured. The difference value TDIFF=TA-TA_ALT is formed from the values TA and TA_ALT, which is required in a later processing step. Further, the intake air temperature threshold value SW_TA is corrected according to the deviation between the minimum intake air temperature TA_MIN and the reference temperature TA_B.

In this embodiment, the above-mentioned intake air threshold temperature SW_TA is 40°C, and the reference temperature TA_B is 1.
The temperature is 5°C. If TA_MIN is in the range 5°C to 25°C, and thus moves within +/-10°C of the reference temperature, the intake threshold temperature is unchanged. Above and below, the intake air threshold temperature is raised or lowered, respectively, by 1°C for every 5°C change in TA_MIN. The optimum values for the respective internal combustion engine are determined on the test stand in such a way that the warm start takes place optimally in practice.

As soon as all initial values have been read out, measured or calculated in step s1, in step s2 the intake air temperature TA is adjusted to the above-mentioned intake air threshold temperature S.
Compare with W_TA. If the intake air temperature does not exceed the intake air threshold temperature, a cold start is performed in step s3, after which the engine rotates, and the step s7 described above is performed.
s9 continues. A condition in which the intake air temperature is lower than the intake air threshold temperature means that the internal combustion engine has been turned on for the first time recently, or has been turned off for a significant period of time, and the intake air temperature was initially high but then stopped. This indicates that the temperature has become lower than the critical temperature. In that case, the fuel supply device is also being cooled, and the bubbles that may have formed during that time are thought to have liquefied and returned to fuel.

If in step s2 it is detected that the intake air temperature exceeds the intake air threshold temperature, then in step s4 the engine temperature TM also exceeds the associated threshold, ie, the engine temperature threshold SW_TM. It will be determined whether there is. If it does not exceed
A cold start is performed in step s3. The engine threshold temperature can also be chosen low since the intake air temperature is also checked, so that there is no risk of frequent warm starts. In this example, the threshold engine temperature is 89°C. If this temperature is not exceeded, it can be assumed that the amount of heat stored in the internal combustion engine is so small that it is not possible to warm up the entire configuration to the extent that bubbles form in the fuel supply system. In this case, therefore, a cold start is performed.

Following the conditions of step s2, step s4
If the condition is also satisfied, it is determined in step s5 whether the above-mentioned difference TDIFF exceeds the difference threshold value SW_TDIFF. If not, a cold start is performed in step s3, and if not, a warm start is performed in step s6. The warm start then takes place as usual depending on the intake air temperature, but this is not important for the invention. This is because the intake air temperature is a condition that determines whether or not a warm start should be performed in the first place.

In this example, the difference threshold is 5°C.
That is, in step s5, it is determined whether the intake air temperature TA measured when the ignition was turned on is at least 5° C. higher than the intake air temperature TA_ALT measured when the ignition was last turned off. If this condition does not exist, the engine will proceed to a warm start even if the engine is turned off slightly from idling after full load. When idling after full load, the engine cools down somewhat, but
Since the intake air temperature increases significantly, the intake air threshold temperature SW_
It is clear that the TA is exceeded. Conditions s2 and s4 may then be fulfilled already at the moment of switching off, or in any case within a short time after switching off. In that case, the condition of step s5 prevents a warm start.

The idea underlying this condition is that if the intake air temperature has not yet increased by at least 5° C. since turning off, there is still enough heat in the fuel supply system to vaporize a critical amount of fuel. There is a high probability that the supply is not available. This condition is met if the time since switching off the ignition has been too short to bring about a temperature increase by TDIFF, or if the heat capacity of the engine is no longer sufficient to provide this increase.

As explained above, steps s2 and s4
and s5, it is determined whether a warm start should be performed. Since they are coupled in series, the order of steps s2, s4 and s5 is arbitrary.

As explained at the beginning, instead of measuring the air temperature in the intake system with a temperature sensor installed in the intake system, the temperature of the fuel supply system should be better measured. A temperature sensor is required. It is advantageous to install the temperature measuring element in the intake system at a point where the temperature constant matches the temperature constant of the fuel supply device as best as possible.

FIG. 2 shows an internal combustion engine 10, in which an intake system 11 is provided with a temperature sensor 12. An output signal from this temperature sensor is supplied to a comparator 13 of a control device 14. The comparator compares the measured temperature to a threshold temperature and provides a comparison signal to the sequence controller 15. In this embodiment, the sequence control device implements the flow shown in FIG. 1 to control the injection valve device 16 for a normal injection time when starting the engine 10, or for an extended injection time in the case of a warm start. Drive with.

[0032]

Effects of the Invention As is clear from the above explanation, according to the present invention, since the intake air temperature is used instead of the engine temperature as the warm start condition, it is possible to prevent the formation of fuel bubbles. It is possible to more accurately identify whether a warm start is necessary, and thereby whether a warm start is necessary can be determined more reliably.

[Brief explanation of the drawing]

FIG. 1 is a flowchart diagram illustrating a method for comparing various conditions, in particular a starting intake air temperature and an intake air threshold temperature, to determine whether a warm start should be performed in an internal combustion engine.

FIG. 2 is a schematic block diagram illustrating a device for determining whether a warm start is to be performed in an internal combustion engine;

[Explanation of symbols]

12 Temperature sensor 13 Comparator 15 Sequence control device

Claims (5)

[Claims] [Claim 1] A warm starting method for an internal combustion engine that determines whether or not to perform a warm start in the internal combustion engine, comprising:
Before starting, measure the starting intake air temperature, that is, the air temperature in the intake system when the internal combustion engine is turned on, and then compare the starting intake air temperature with the intake air threshold temperature, and if it exceeds the threshold temperature, , a method for warm starting an internal combustion engine, characterized by activating a warm start. [Claim 2] Measuring the starting engine temperature before starting,
2. The method of claim 1, further comprising comparing the starting engine temperature with an engine threshold temperature and deactivating the warm start if the threshold temperature has not been reached. 3. When shutting down the internal combustion engine, detect the cutoff intake air temperature, calculate the difference between the cutoff intake air temperature and the starting intake air temperature before starting the engine, and perform a warm start if the difference is lower than the difference threshold. 3. The method according to claim 1 or 2, characterized in that no step is performed. 4. The system according to claim 1, wherein the lowest intake air temperature is detected when the internal combustion engine is being driven, and the intake air threshold temperature is corrected in a direction in which the lowest intake air temperature changes with respect to a reference temperature. The method described in any one of the above. 5. A warm start device for an internal combustion engine that determines whether or not to perform a warm start of the internal combustion engine, comprising:
A temperature sensor (12) that measures the starting intake air temperature, that is, the air temperature in the intake system when the internal combustion engine is turned on, and a comparator (12) that compares the starting intake air temperature with an intake air threshold temperature and outputs a comparison signal. 13) and a sequence control device (15) that controls the temporal flow and activates a warm start when the comparison signal indicates that the measured temperature exceeds a threshold temperature. Features: Warm starting device for internal combustion engines.