JPH0361021B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a warm-up completion determination device for an internal combustion engine, and particularly relates to a warm-up completion determination device for an internal combustion engine. The present invention relates to a warm-up completion determination device for an internal combustion engine that derives a completion determination temperature and determines that warm-up is complete when the engine temperature reaches the warm-up completion determination temperature.

(Conventional technology) Conventionally, engine temperature, for example, engine cooling water temperature, which is representative of warm-up, has been measured using TW.
It is common to detect the temperature with a sensor and determine that warm-up is complete when the temperature value exceeds a predetermined value.

The reason why it is necessary to judge whether warm-up is complete is that internal combustion engines do not achieve the desired operating performance immediately after starting, but only after warming up to a certain temperature do they respond to engine operating conditions. This is because the control operation (open loop control or feedback control after starting) can be properly obtained.

When the ambient temperature of the engine at startup is normal temperature, as described above, if the temperature detected by the TW sensor is equal to or higher than a predetermined value (for example, 70° C.), it can be determined that warm-up is complete. That is, at room temperature, the warm-up completion determination temperature can be set to a certain specific value.

For this reason, conventionally, after the TW sensor detects the specific value, warm-up is assumed to have been completed, and, for example, scheduled air-fuel ratio control of the internal combustion engine (open-loop control or feedback control after starting) is performed. ).

However, if this warm-up completion judgment temperature is set in advance to match the ambient temperature at room temperature, when the ambient temperature drops and a cold start occurs, the TW sensor Even if the detected temperature reaches the warm-up completion determination temperature, a situation may occur in which the actual warm-up state of the engine is not yet completed.

This is because during a cold start, the detected temperature of the TW sensor does not represent the actual engine temperature during the warm-up process due to the mounting position of the TW sensor, etc., and the detected temperature rises first. This is because the actual engine temperature rises after a delay.

Therefore, when it is determined that warm-up has been completed based on the temperature detected by the TW sensor and the air-fuel ratio control device of the internal combustion engine starts the scheduled control operation, it is determined that warm-up has not actually been completed. Therefore, proper air-fuel ratio control cannot be performed.

Specifically, the engine rotation may become unstable, the rotation may become too low, or in some cases the engine may stop.

Therefore, in order to prevent the above-mentioned situation from occurring, conventionally, the warm-up completion determination temperature has been set high in consideration of cold starting. That is, the warm-up completion determination temperature is set to match the temperature at cold start (for example, -40°C).

Specifically, one example is raising the warm-up completion determination temperature at room temperature, 70°C, by 20°C to 90°C.

However, in this case, when the engine is started at room temperature, warm-up is performed more than necessary, which delays the start at zero start and causes a deterioration in the exhaust gas purification efficiency.

(Problems to be Solved by the Invention) The above-described conventional techniques had the following problems.

That is, as described above, if the warm-up completion determination temperature is set to match the normal temperature start, the engine operation will be poor during the cold start, making it difficult to achieve the planned stable running.

Further, if the setting is made for a cold start, the start at room temperature will be delayed and the exhaust gas purification efficiency will be deteriorated.

The present invention has been made to solve the above-mentioned problems.

(Means and effects for solving the problem) In order to solve the above problem, the present invention provides that, at each startup, depending on the sensor signal of the TW sensor at the beginning of startup, which represents the temperature of the internal combustion engine, Deriving the warm-up completion judgment temperature in advance, which is the criterion for judging completion of warm-up,
The system is characterized in that the warm-up completion determination is made when the value of the sensor signal reaches the warm-up completion determination temperature. Furthermore, in this case, since accurate engine temperature measurement cannot be performed when the TW sensor is in a transient state, the sensor signal is captured after confirming that the TW sensor is in a steady state.

(Example) First, in order to properly implement the present invention, as a prerequisite, it is necessary to accurately detect the temperature of the internal combustion engine at the time of starting. Specifically, this is done using a TW sensor, as described in the conventional example.

However, immediately after starting, the TW sensor is in a transient state (a state in which it cannot accurately detect engine temperature), so its output does not accurately display the engine temperature.

Therefore, in this embodiment, in general, in the transient state of the TW sensor, the absolute value of the difference between the previous sampling value and the current sampling value of the sensor signal is
Paying attention to the fact that the absolute value of the difference is larger than a certain reference value and is smaller than the reference value in its steady state, it is determined when the absolute value of the difference becomes smaller than the reference value. This time, the sampled value is read and recorded (retained) as a valid signal,
The warm-up completion determination temperature is determined based on the read memory value.

Note that the reference value here is a value corresponding to the maximum absolute value of the difference between the previous value and the current value in a steady state of the TW sensor (a state in which the engine temperature can be accurately detected).

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

Figure 2a is a characteristic diagram of the output (sensor signal) of the engine temperature sensor (TW sensor) that detects the engine cooling water temperature, which is representative of the engine temperature, and Figure 2b is the previous sampling value (previous value) of the sensor signal. ) and the current sampling value (current value) (|previous value−current value|) is a change characteristic diagram.

In addition, in FIG. 2b, ST indicated by a broken line indicates the level of the reference value described above.

In FIG. 1, the ignition switch 15
When turned on and the starting state begins, the potential at point A rises with a predetermined time constant, and then maintains a constant potential. Therefore, the output of the inverter 7 is the output of the ignition switch 15.
It becomes a pulse signal that rises as soon as the voltage is turned on, and then falls when the supplied voltage reaches a predetermined level.

Then, the pulse signal is sent to the flip-flop 8.
and 12 reset terminals, so their Q terminal outputs are at high level. The high level signal is supplied to one terminal of each of AND gates 10 and 11. Therefore, the AND gates 10 and 11 are connected to the flip-flop 8
and 12 remain open until subsequently set.

Further, a pulse signal is applied to the other terminal of the AND gate 10 from the pulse generating circuit 9 at a scheduled timing.

Therefore, the AND gate 10 operates to supply the pulse signal to the gate circuit 2 as it is. As a result, the gate circuit 2 is in an open state during the pulse application period.

On the other hand, the A/D conversion circuit 1 samples the sensor signal (engine temperature signal) output as an analog signal from the TW sensor 16 in synchronization with the pulse output timing of the pulse generation circuit 9,
Digitize and output.

Therefore, when the ignition switch 15 is turned on at time t0 in FIG. The digitized engine temperature signal passes through a gate circuit 2 and is supplied to a previous value register 3.
It will be remembered temporarily.

Next, at time t1, the engine temperature signal at time t0, which is the value stored in the previous value register 3, is supplied to the subtracter 4. At the same time, the engine temperature signal sampled and digitized at time t1 is supplied from the A/D conversion circuit 1 to the subtracter 4.

The subtracter 4 detects the absolute value of the difference between the engine temperature signal at time t0 from the previous value register 3 and the engine temperature signal at time t1 supplied from the A/D conversion circuit 1, and The value is fed to the comparator 5. That is, the subtracter 4 supplies the comparator 5 with the absolute value of the difference between the previous value and the current value.

The comparator 5 stores the absolute value in a reference value register 6.
It is detected whether or not it is smaller than the reference value ST supplied from ST. If it is smaller than the standard value ST,
Sensor has fully started up (ends transient state)
As a result, a high level signal (engine temperature sensor stable state signal) is output to the set terminal of flip-flop 8.

Note that after the engine temperature signal at time t0 is supplied from the previous value register 3 to the subtracter 4, the pulse signal from the pulse generation circuit 9 is sent to the AND gate 10.
The signal is supplied to the gate circuit 2 via. For this purpose,
At approximately time t1, the stored value in the previous value register 3 is updated to the engine temperature signal at time t1.

As is clear from FIG. 2b, at time t1, the absolute value of the difference between the previous value and the current value is greater than the reference value ST, so no high level signal is output from the comparator 5 at this time.

Therefore, flip-flop 8 is not set and a high level signal is still output from its Q terminal. For this reason, the AND gate 10 remains open.

Therefore, the pulse signal from the pulse generation circuit 9 is
The signal is supplied to the gate circuit 2 through the AND gate 10, and as a result, as described above, the comparator 5 determines whether the absolute value of the difference between the previous value and the current value is smaller than the reference value ST. Detected.

Note that this detection is performed until the absolute value becomes smaller than the reference value ST.

At time t11, as is clear from Fig. 2b,
When the absolute value of the difference between the previous value and the current value becomes smaller than the reference value ST and a high level signal is output from the comparator 5, the flip-flop 8 is set.

Therefore, the Q terminal output becomes low level and the Q terminal output becomes high level. As a result, the AND gate 10 is closed.

Therefore, the pulse signal from the pulse generating circuit 9 is not supplied to the gate circuit 2, and therefore the stored value in the previous value register 3 is not updated.

Further, since the high level signal which is the Q terminal output of the flip-flop 8 is supplied to the other terminal of the AND gate 11, the AND gate 11 outputs a high level signal.

As a result, the gate circuit 13 is in an open state, so the digitized engine temperature signal at this time t11 passes from the A/D conversion circuit 1 to the gate circuit 13, and is passed through the warm-up completion determination temperature deriving device 1.
7 will be supplied.

That is, at this time, the initial engine temperature in the TW sensor steady state is supplied to the warm-up completion determination temperature deriving device 17.

Incidentally, at this time t11, the high level signal output from the AND gate 11 is also supplied to the set terminal of the flip-flop 12 via the delay circuit 21. For this reason, the Q of the flip-flop 12 is
The terminal output becomes low level after the scheduled time delay.

Therefore, the output of the AND gate 11 with the gate circuit 13 in the open state falls with a slight delay from time t11. As a result, the warm-up completion determination temperature deriving device 17 is supplied with only the digitized engine temperature signal when the TW sensor 16 transitions from the transient state to the steady state.

FIG. 3 shows the value of the engine temperature signal supplied to the warm-up completion determination temperature deriving device 17 and the value of the engine temperature signal supplied to the warm-up completion determination temperature deriving device 17 using this as a parameter.
FIG. 3 is a characteristic diagram showing an example of the relationship between warm-up completion determination temperatures stored in advance in engine temperature at startup and warm-up completion determination temperature;

The relationship between the engine temperature at startup and the warm-up completion determination temperature can be determined experimentally or empirically.

As described above, when the engine temperature signal is supplied to the warm-up completion determination temperature deriving device 17, the third
The warm-up completion determination temperature determined according to the characteristic diagram shown in the figure is read out and supplied to the latch circuit 18.

The latch circuit 18 holds the warm-up completion determination temperature and supplies it to the comparator 19.

On the other hand, the comparator 19 is supplied with an engine temperature signal sampled at a scheduled sampling period and digitized from the A/D conversion circuit 1 .

Therefore, the comparator 19 determines whether or not the value of the engine temperature signal supplied from the A/D conversion circuit 1 has become equal to or higher than the warm-up completion determination temperature supplied from the latch circuit 18. For example, a high level signal (warm-up completion signal) is generated.

As a result, the engine operating state determination circuit 20:
By supplying the high level signal,
It can be determined that warm-up has been completely completed.

That is, according to this embodiment, it is possible to accurately measure the temperature of the internal combustion engine at the time of starting, and depending on the temperature of the engine thus measured,
Deriving a predetermined warm-up completion determination temperature,
When the engine temperature reaches the warm-up completion determination temperature, it is determined that warm-up is complete.

The above-mentioned determination of the completion of warm-up of the internal combustion engine is carried out using a general microcomputer.
This can also be achieved by executing the determination and processing in steps S1 to S12 in the figure.

Step S1...The sensor signal (engine temperature signal) from the TW sensor 16 is read and stored.

Step S2...In step S6, which will be described later,
Determine whether the valid signal stored flag is set. If it has been set, proceed to step S7. Since it is not set at the time of startup, proceed to step S3.

Step S3: The absolute value of the difference between the previous value of the engine temperature signal stored in step S5, which will be described later, and the current value of the engine temperature signal read and stored in step S1 is calculated.

Step S4: It is determined whether the absolute value is smaller than a predetermined (pre-stored) reference value ST.

When it is smaller than the reference value ST, the process advances to step S6. The process proceeds to step S6 when the TW sensor 16 has finished its transient state and has completely risen, and its output, the sensor signal, properly indicates the engine temperature.

When the engine is first started, as is clear from Fig. 2 a and b, the judgment in step S4 is not established.
Proceed to step S5.

Step S5: The current value of the sensor signal read and stored in step S1 is stored as the previous value. Then return to the main program.

While the steps S1 to S5 are cycled through several times, the TW sensor 16 completes the transient state and rises completely, and as a result, the determination in the previous step S4 is established. That is, the state corresponds to time t11 in FIG. 2b.

As a result, the process proceeds to step S6.

Step S6...Set the valid signal stored flag. After that, proceed to step S7.

Step S7...In step S9, which will be described later,
It is determined whether the engine temperature memorized flag at startup is set. If it has been set, proceed to step S10. Initially, it is not set, so proceed to step S8.

Step S8... Corresponding to the current value of engine temperature TW read and stored in the previous step S1, warm-up completion judgment temperature that is predetermined (for example, stored in a table) and serves as a criterion for judging completion of warm-up. Read and store. An example of the characteristic of the warm-up completion determination temperature corresponding to the engine temperature TW at the time of starting is shown in FIG. 3, as described above.

Step S9...Sets the engine temperature memorized flag at startup.

Step S10: It is determined whether the current value of the engine temperature TW read and stored in the previous step S1 is equal to or higher than the warm-up completion determination temperature read and stored in step S8. If the temperature is equal to or higher than the warm-up completion determination temperature, the process advances to step S12. When the engine is first started, the temperature is lower than the warm-up completion determination temperature, so the process advances to step S11.

Step S11...Set the warming up flag, then return to the main program.

While going through steps S1-2, S7 and S10-S11 several times, the current value of the engine temperature
TW becomes higher than the warm-up completion judgment temperature, and as a result,
The judgment in the previous step S10 is established. Therefore, the process advances to step S12.

Step S12: The warm-up flag set in step S11 is reset, and a warm-up completion flag is set instead. Then return to the main program.

The overall configuration of this embodiment described above is shown in FIG. 5 as a functional block diagram.

In the above description, as a prerequisite for properly implementing the present invention, in order to accurately detect the temperature of the internal combustion engine at the time of starting, the absolute value of the difference between the previous value and the current value in the steady state of the TW sensor 16 is calculated. As the maximum value of the reference value, compare the reference value with a similar absolute value in the transient state of the TW sensor 16, and enable the sensor signal when the absolute value becomes smaller than the reference value (at the end of the transient state). I decided to use it as a signal.

However, this is not the only method for accurately detecting the temperature of an internal combustion engine during startup. For example, the output (sensor signal value) is adopted after the elapsed time from the time when the ignition switch is turned on to start the engine and when the TW sensor 16 is expected to have completely started up after passing through the transient state. You can also.

Furthermore, in this embodiment, the warm-up completion determination temperature value is read out from a preset table in accordance with the engine temperature value at the time of starting. Substitute it into
It may be determined by calculation.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved.

(1) The setting of the warm-up completion judgment temperature, which is derived based on the output of the TW sensor, is appropriately selected according to the temperature of the internal combustion engine at the time of starting.
When the warm-up completion determination temperature is set to a fixed value as in the conventional example, engine malfunctions such as unstable engine rotation are likely to occur, as well as delayed start and deterioration of exhaust gas purification efficiency due to excessive warm-up. It is now possible to prevent this from happening.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
Figure a is an output characteristic diagram of the TW sensor at startup, Figure b is a change characteristic diagram of the absolute value of the difference between the previous sampling value and the current sampling value (|previous value - current value|), and Figure 3 is a diagram of the change characteristic during startup. FIG. 4 is a flowchart when the circuit operation of FIG. 1 is executed by a microcomputer, and FIG. 5 is a schematic block diagram showing the overall configuration of the present invention. It is a diagram. 1...A/D conversion circuit, 2, 13...Gate circuit, 3...Previous value register, 4...Subtractor, 5...
... Comparator, 6 ... Reference value register, 7 ... Inverter, 8, 12 ... Flip-flop, 9 ... Pulse generation circuit, 10, 11 ... AND gate, 1
5...Ignition switch, 16...TW sensor, 17...Warm-up completion determination temperature derivation device, 18
... Latch circuit, 19 ... Comparator, 20 ... Engine operating state determination circuit, 21 ... Delay circuit.

Claims (1)

[Scope of Claims] 1. An engine temperature sensor that detects engine temperature; a device that samples and stores the output signal of the engine temperature sensor at a predetermined period; , a warm-up completion determination temperature derivation device that derives a warm-up completion determination temperature that is a criterion for determining warm-up completion, and a warm-up completion determination temperature deriving device that compares the output of the engine temperature sensor and the warm-up completion determination temperature value, and determines that the engine temperature sensor output is A warm-up completion determination device for an internal combustion engine, comprising a device that generates a warm-up completion signal when a warm-up completion determination temperature is reached. 2. The above-mentioned patent characterized in that the warm-up completion determination temperature deriving device is a device that reads out the warm-up completion determination temperature stored in a memory in advance using a sampled stored value obtained at the time of starting the engine as a parameter. A warm-up completion determination device for an internal combustion engine according to claim 1. 3. The warm-up completion determination temperature deriving device is an arithmetic circuit that calculates the warm-up completion determination temperature by inputting a sampling memory value obtained at the time of starting the engine. Warm-up completion determination device for internal combustion engines. 4. Any one of claims 1 to 3, wherein the sampled memory value obtained at the time of starting the engine is the sampled memory value at the time when the output of the engine temperature sensor reaches a steady state. The internal combustion engine warm-up completion determination device according to claim 1.