JPH07158427A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To suppress the discharge of harmful elements to a minimum by providing a current carrying means for carrying a current to a heating device from the time of detecting the intention of start by a start intention detecting means to the specified period after the start of the engine. CONSTITUTION:A first catalyst device 15 is disposed at the intermediate part of the exhaust pipe 14 of an engine 1, and a second catalyst device 16 is disposed under the floor of the engine, downstream of the first catalyst device 15. The first catalyst device 15 has a three-way catalyst part 17 and a heater part 18. The heater part 18 is connected to an ECU (specified period setting means) 5 through a heater control part 19 and current-controlled by a control signal from the heater control part 19. A catalyst temperature sensor 30 is mounted on the first catalyst device 15, and its output signal is supplied to the ECU 5. The concentration of oxygen in exhaust gas is detected by an oxygen concentration sensor 21 and supplied to the ECU 5. The discharge of harmful components can be thus suppressed to a minimum even immediately after the start of the engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to a catalytic converter with a heating device which is disposed in an exhaust system of an internal combustion engine and purifies unburned gas in the exhaust gas. The present invention relates to an exhaust gas purification device for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in order to accelerate the temperature rise of a catalyst device arranged in an exhaust system of an internal combustion engine and to activate the catalyst device early, there has already been a technique in which a heater is attached to the catalyst device. Proposed (for example, JP-A-5-214927)
Issue).

In the above conventional technique, the residual energy remaining in the catalyst with a heater is calculated based on the integrated value of the engine speed, and the heater is turned on / off by comparing the energy with a predetermined value. That is, when the residual energy is below a predetermined value, the heater is energized, while when the residual energy is above the predetermined value, the heater is de-energized to prevent unnecessary power consumption. That is, in the above-mentioned conventional technique, a predetermined temperature higher than the activation temperature of the catalyst is set as the target temperature that the heater should reach, and when the heater reaches the target temperature, the energization of the heater is stopped and the catalyst device When the temperature falls below the activation temperature, the heater is energized again and the heater is on / off controlled to maintain the activated state of the catalyst.

[0004]

However, in the above prior art, since the heater is energized after the engine is started, purification of harmful components such as HC in the catalyst device immediately after the engine is started is sufficient. There was a problem that it was not done.

The present invention has been made in view of the above problems, and purifies exhaust gas of an internal combustion engine equipped with a catalyst device with a heating device capable of suppressing discharge of harmful components as much as possible even immediately after the engine is started. The purpose is to provide a device.

[0006]

In order to achieve the above object, the present invention comprises a heating device disposed in an exhaust system of an internal combustion engine for purifying unburned gas in exhaust gas and electrically heating the same. In an exhaust gas purifying apparatus for an internal combustion engine having a catalyst device, a start intention detecting means for detecting a driver's start intention before the starter of the engine is activated, and a temperature state detecting means for detecting a temperature state of the catalyst device. Further, when the starting intention of the driver is detected by the starting intention detecting means and the temperature state value detected by the temperature state detecting means is a low temperature state equal to or lower than a first predetermined value, the starting is performed. It is characterized in that it comprises an energizing means for energizing the heating device for a predetermined period after the engine is started from the time when the intention to detect is detected by the intention detecting means. .

Further, the predetermined period is provided with a predetermined period setting means for setting the temperature period value detected by the temperature state detecting means to be longer as the temperature state value is lower.

Further, the invention is characterized in that the apparatus further comprises an operation prohibiting means for prohibiting the operation of the starter when the temperature is lower than the second predetermined value which is lower than the first predetermined value.

The temperature condition detecting means of the catalyst device is preferably a water temperature detecting means for detecting the temperature of the cooling water of the engine.

[0010]

According to the above construction, even if the driver's intention to start is detected, the heating device is energized when the engine temperature state value (detected by the water temperature detecting means or the like) is not less than the first predetermined value. However, the heating device is energized when the driver's intention to start is detected and the engine temperature state value is equal to or lower than the first predetermined value.

Further, the lower the temperature state value, the longer the predetermined period is set.

Further, when the engine temperature state value is equal to or lower than the second predetermined value which is lower than the first predetermined value, the operation of the starter is prohibited.

[0013]

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

FIG. 1 is an overall configuration diagram showing an embodiment of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention.

In the figure, reference numeral 1 denotes a DOHC in-line 4-cylinder internal combustion engine (hereinafter referred to as "engine") in which each cylinder is provided with an intake valve and an exhaust valve (not shown).
A throttle body 3 is provided in the middle of the intake pipe 2 of the engine 1.
Is provided therein, and a throttle valve 3'is arranged therein. A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3 ', and an electronic control unit (hereinafter referred to as "ECU") outputs an electric signal corresponding to the opening of the throttle valve 3'. Supply to 5.

The fuel injection valve 6 is provided for each cylinder in the middle of the intake pipe 2 between the engine 1 and the throttle valve 3 ', is connected to a fuel pump (not shown), and is connected to the ECU.
The valve opening time of the fuel injection is controlled by a signal from the ECU 5 which is electrically connected.

A branch pipe 7 is provided on the downstream side of the throttle valve 3 ', and an absolute pressure (PB
A) The sensor 8 is attached. The PBA sensor 8
Is electrically connected to the ECU 5, and the absolute pressure PBA in the intake pipe 2 is converted into an electric signal by the PBA sensor 8 and supplied to the ECU 5.

An intake air temperature (TA) sensor 9 is mounted on the pipe wall of the intake pipe 2 on the downstream side of the branch pipe 7, and the intake air temperature TA detected by the TA sensor 9 is converted into an electric signal and the ECU 5 Is supplied to.

An engine water temperature (TW) sensor 10 including a thermistor or the like is mounted on the peripheral wall of the cylinder filled with the cooling water of the cylinder block of the engine 1, and the engine cooling water temperature TW detected by the TW sensor 10 is converted into an electric signal. It is converted and supplied to the ECU 5.

An engine speed (NE) sensor 11 and a cylinder discrimination (CYL) sensor 12 are mounted around a cam shaft or a crank shaft (not shown) of the engine 1.

The NE sensor 11 outputs a signal pulse (hereinafter referred to as "TDC signal pulse") at a predetermined crank angle position every 180 degrees rotation of the crankshaft of the engine 1, and C
The YL sensor 12 outputs a signal pulse (hereinafter, referred to as “CYL signal pulse”) at a predetermined crank angle position of a specific cylinder, and each of these signal pulses is supplied to the ECU 5.

The spark plug 1 of each cylinder of the engine 1
3 is electrically connected to the ECU 5, and the ignition timing is controlled by the ECU 5.

A first catalyst device 15 is arranged in the exhaust pipe 14 of the engine 1, and the first catalyst device 15 is further provided.
A second catalyst device 16 is disposed below the engine floor on the downstream side of the.

The first catalyst device 15 has a three-way catalyst section 17 and a heater section 18, and the heater section 18 is connected to the ECU 5 via a heater control section 19 and receives a control signal from the heater control section 19. The energization is controlled by.

The second catalytic device 16 is composed of a three-way catalyst having a larger capacity than the first catalytic device 15, and the second catalytic device 16 mainly discharges HC, CO, NOx in exhaust gas after engine warm-up. Hazardous components such as are purified.

A catalyst temperature (TCAT) sensor 30 is mounted on the first catalyst device 15, and an output signal detected by the TCAT sensor 30 is supplied to the ECU 5.

Further, the first catalyst device 1 of the exhaust pipe 14
An oxygen concentration sensor 21 (hereinafter, referred to as “O ₂ sensor”) is provided on the upstream side of 5, and the oxygen concentration in the exhaust gas is detected by the O ₂ sensor 21 and the output signal is output from the ECU.
5 is supplied.

A battery 22 is connected to the heater control section 19 to supply electric power to the heater control section 19.

An ignition (IG) switch 23 and a starter (ST) switch 24 are electrically connected to the ECU 5. The IG switch 23 supplies an on / off signal indicating the starting intention state of the engine 1 to the ECU 5, and the ST switch 24 supplies an on / off signal indicating the operating state of the starter of the engine 1 to the ECU 5 and also from the ECU 5. Can supply an ON signal generation prohibition command to the ST switch 24.

Further, an oil temperature (TOIL) sensor 25 is attached to a lubricating oil passage or an oil reservoir (not shown) of the engine, and a detection signal detected by the TOIL sensor 25 is supplied to the ECU 5.

Therefore, the ECU 5 shapes the input signal waveforms from the various sensors, corrects the voltage level to a predetermined level, and converts the analog signal value into a digital signal value. Processing circuit (hereinafter "C
PU ”), a storage means 5c for storing various calculation programs executed by the CPU 5b and calculation results, and an output circuit 5d for supplying a drive signal to the fuel injection valve 6 and the ignition plug 13.

The CPU 5b discriminates various engine operating states such as a feedback control operating region and an open loop control operating region according to the oxygen concentration in the exhaust gas based on the various engine parameter signals described above, and determines the engine operating state. Accordingly, based on the equation (1), the TDC
Fuel injection time To of the fuel injection valve 6 synchronized with the signal pulse To
Calculate ut.

Tout = Ti × KCMDM × KO2 × K1 + K2 (1) where Ti is the basic fuel injection time, specifically, the basic fuel injection determined according to the engine speed NE and the intake pipe absolute pressure PBA. It is time, and a Ti map for determining this Ti value is stored in the storage means 5c.

KCMDM is a corrected target air-fuel ratio coefficient, which is a target air-fuel ratio coefficient KC set according to the engine operating conditions such as the engine speed NE and the intake pipe absolute pressure PBA.
It is calculated by multiplying MD by the fuel cooling correction coefficient KETV.

[0035] KO2 is an air-fuel ratio correction coefficient calculated on the basis of the O ₂ sensor 21, air-fuel ratio feedback control is matched to the air-fuel ratio (oxygen concentration) of the target air-fuel ratio detected by the O ₂ sensor 21 And is set to a predetermined value according to the operating state of the engine during open loop control.

K1 and K2 are other correction coefficients and correction variables calculated according to various engine parameter signals, respectively, to optimize various characteristics such as fuel consumption characteristics and engine acceleration characteristics according to engine operating conditions. Is set to a value like

Further, as shown in FIG. 2, the heater control section 19 is connected to the ECU 5 and is a control circuit 2 including a microcomputer for controlling energization of the heater section 18.
6, a transistor 27 that performs a switching operation according to a command from the control circuit 26, and a current sensor 28 that detects a current value from the transistor 27 and outputs an electric signal to the control circuit 26. The base electrode of the transistor 27 is connected to the control circuit 26, and the emitter electrode of the battery 2 has a negative electrode terminal grounded.
0 is connected to the positive electrode terminal, and the collector electrode is connected to the resistor 29 of the heater unit 18 via the current sensor 28.

In the heater control section 19 thus constructed, the ECU 5 which receives the engine parameter signal from the PBA sensor 8 and the NE sensor 10 is operated by the heater section 18.
When it is determined that the heater 27 should not be energized, the transistor 27 is turned off through the control circuit 23, while when it is determined that the heater portion 18 should be energized, the control circuit 23 is turned off.
An energization start signal is input to and a low level signal is supplied to the base electrode of the transistor 27. Then, the transistor 27 is turned on, current is supplied from the battery 22 to the resistor 29 of the heater section 18 via the transistor 27 and the current sensor 28, the heater section 18 generates heat, and the catalyst bed temperature of the three-way catalyst section 17 is increased. TCAT rises.

However, the exhaust gas purifying apparatus has an energizing means for energizing the heater portion 18 for a predetermined time after the engine is started after the ON state of the IG switch 23 is detected in a predetermined low temperature state. The first catalyst device 15 is preheated before starting the engine.

FIG. 3 is a flow chart of a preheat control routine for preheating the first catalyst device 15. This program is executed by the CPU 5b in synchronization with the generation of the ON signal of the IG switch 23.

First, when the IG switch 23 is turned on, step S1 is executed to determine whether or not the engine cooling water temperature TW is below a first predetermined temperature TW1 (for example, 85 ° C.). Then, when the answer is negative (No), it is determined that the first catalyst device 15 is already in the activated state, and this program is terminated.

On the other hand, the answer to step S1 is affirmative (Yes).
In this case, the process proceeds to step S2, the TmHEATER table is searched, the predetermined energization time TmHEATER for preheating the first catalyst device 15 is calculated, and the timer is set.

As shown in FIG. 4, the TmHEATER table is given table values TmHEATER0 to TmHEATER5 for engine cooling water temperatures TW0 to TW5. The predetermined energization time TmHEATER is read by searching the TmHEATER table. Or calculated by an interpolation method. As is clear from FIG. 4, the predetermined energization time TmHEATER is
The higher the engine cooling water temperature TW, the shorter the time is set. This is because the higher the engine cooling water temperature TW is,
This is because it takes a short time to activate the first catalyst device 15.

Next, in step S3, the predetermined energization time T
It is determined whether mHEATER is "0". Then, in this case, in step S2, the predetermined energization time TmHEATER
Since step S3 has just been set, the answer to step S3 is negative (No), and it is determined in step S4 whether the current engine cooling water temperature TW is lower than the second predetermined temperature TW2 (<TW1) (for example, 20 ° C.). To determine. When the answer is affirmative (Yes), the first catalyst device 15 is set to "1" in the flag FST to prohibit the ST switch 24 from being turned on (step S5), and then the heater control unit 19 An energization command is issued to the heater section 18 via (step S6), and the process returns to step S3. That is, the heater unit 18
Is energized to start preheating of the first catalyst device 15. That is, in this case, in order to improve the exhaust gas purification characteristic after the engine is started, the engine start is prohibited, and the catalyst is activated early after the engine is started.

On the other hand, the answer to step S4 is negative (No),
That is, the engine cooling water temperature TW is the second predetermined temperature TW.
If it is 2 or more, the flag FST is set to "0" in step S7.
And permitting the ST switch 24 to be turned on, the process proceeds to step S6 to start energizing the heater portion 18, and then returns to step S3. That is, when the engine cooling water temperature TW is equal to or higher than the second predetermined temperature TW2, the time required for the first catalyst device 15 to be in the activated state is short and the battery power consumption can be suppressed.
To enable the engine to be started at any time, avoiding unnecessarily limiting engine startup.

Then, returning to step S3, it is again determined whether or not the predetermined energization time TmHEATER is "0", and when the predetermined energization time TmHEATER is not yet "0",
Similar to the above, each step after step S4 is executed.

On the other hand, the answer in step S3 is affirmative (Yes
s), that is, the first when the timer times out
This program is terminated by determining that the catalyst device 15 has been activated.

FIG. 5 is a time chart when the preheat control routine is executed, in which the horizontal axis represents time (T) and the vertical axis represents engine cooling water temperature TW.

That is, as indicated by the broken line P, when the IG switch 23 is turned on, that is, when the engine cooling water temperature TW at time A is higher than the first predetermined temperature TW1, the first catalyst device 15 is in the activated state. Therefore, the heater section 18 is not energized.

When the engine cooling water temperature TW is lower than the first predetermined temperature TW1 but higher than the second predetermined temperature TW2, that is, the engine cooling water temperature TW is TW1 <T.
When in the range of W <TW2, the first catalyst device 15 is activated in a short time, so that the engine can be started and the timer set to the predetermined energization time TmHEATER ″ is set to the time A ( The operation is started from the time when the IG switch 23 is turned on. The dashed-dotted line Q shows the characteristic in this case. That is, the timer is counted up at the time B ″ at which the first predetermined temperature TW1 can be reached and the heater unit 1
Stop energizing 8.

When the engine cooling water temperature TW is lower than the second predetermined temperature TW2, the cooling water temperature TW is the second temperature.
The engine start is prohibited until the temperature reaches the predetermined temperature TW2 of the first catalyst device 1 in a short time after the engine start.
Activate 5 That is, a prohibition time for prohibiting engine start is provided, and the starter operation is prohibited during the prohibition time. Then, the heater portion 18 is energized for a predetermined time period including the prohibition time, and the timer sets the first predetermined temperature TW.
1 is counted up at the time when the heater unit 1 can be reached.
Stop energizing 8. The solid line S and the chain double-dashed line R show the characteristics in this case. That is, in this case, the engine start is prohibited during the prohibition times t1 and t1 ′ when the engine cooling water temperatures TWL and TWL ′ reach the second predetermined temperature TW2, and the predetermined energization time is from the time A when the IG switch 23 is turned on. The heater section 18 is energized over TmHEATER and TmHEATER ', and the energization to the heater section 18 is stopped at times B and B'when the timer is counted up.

As a result, it becomes possible to heat the first catalytic device 15 before the engine is started, and the first catalytic device 1 can be heated.
5 can be quickly raised, and the exhaust gas purification characteristics can be improved when the engine is cold. And
When the engine cooling water temperature TW is between the first predetermined temperature TW1 and the second predetermined temperature TW2, it is considered that the first catalyst device 15 is activated early after the engine is started. The prohibition on starting the vehicle has been lifted to avoid the driver's waiting for starting as much as possible.

It is needless to say that the present invention is not limited to the above-mentioned embodiment and can be modified within the scope not departing from the gist. In the above embodiment, the TW sensor 10 is used as the means for detecting the temperature state of the first catalyst device 15, but the detection value of the TOIL sensor 25 may be used. Also, instead of the TW sensor 10, a TCA
The temperature of the first catalyst device 15 may be directly detected by the T sensor 30. However, it is necessary to perform processing for directly attaching the TCAT sensor to the first catalyst device 15,
Moreover, such processing is not preferable in consideration of the durability of the catalyst, and heat resistance is required because it is in a high temperature atmosphere (maximum 1000 ° C.), so that it may be relatively expensive. Therefore, it is more realistic to perform the heater control based on the detection value of the TW sensor 10 which has a relatively low temperature substantially correlating with the temperature characteristic of the first catalyst device 15 and can be used also with another system. .

The oil temperature TOIL may also be used as a parameter for the predetermined energization time TmHEATER. Further, the predetermined energization time TmHETER may use an integrated value from the fuel injection time Tout before starting, and by changing the integrated value according to the temperature state of the first catalyst device 15 before starting, It is possible to accurately determine the engine warm-up state and efficiently determine the energization time.

[0055]

As described above in detail, the present invention has a catalytic device provided with an exhaust system of an internal combustion engine for purifying unburned gas in exhaust gas and electrically heating it. In an exhaust gas purification device for an internal combustion engine,
The engine includes a starting intention detecting means for detecting a starting intention of the driver before the starter of the engine is activated, and a temperature state detecting means for detecting a temperature state of the engine, and the driver is operated by the starting intention detecting means. When the starting intention is detected and the temperature state value detected by the temperature state detecting means is a low temperature state equal to or lower than a first predetermined value, the engine starting is started from the time when the starting intention is detected by the starting intention detecting means. Since the energizing means is energized to energize the heating device for a predetermined later period, the catalyst device can be preheated when the engine is cold, and the catalyst device is activated early when the engine is cold-started. Therefore, it is possible to improve the exhaust gas purification characteristic at the low temperature start. Further, it is possible to stop the execution of the energizing means when the temperature state value is equal to or higher than the first predetermined value.
It is possible to avoid unnecessary power consumption.

Further, the predetermined period is provided with a predetermined period setting means for setting the temperature state value detected by the temperature state detecting means to be longer, so that the predetermined period is preheated only in accordance with the temperature state of the engine. Therefore, it is possible to avoid unnecessary power consumption without being preheated more than necessary.

Further, by providing the operation inhibiting means for inhibiting the operation of the starter when the temperature is lower than the second predetermined value which is lower than the first predetermined value, the starter is used when the cooling water temperature of the engine is extremely low. While it is possible to effectively start preheating by prohibiting the start of the engine, it is possible to release the prohibition of the starter operation when the temperature of the cooling water of the engine becomes high to some extent, which is inconvenient for the driver. It is possible to avoid such a start waiting period as much as possible.

Further, since the temperature state detecting means of the catalyst device is a water temperature detecting means for detecting the cooling water temperature of the engine, the energization control can be performed without directly detecting the temperature state of the catalyst device. Therefore, the cost of the device can be reduced.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an exhaust gas purification device according to the present invention.

FIG. 2 is an electric circuit diagram showing details of a heater controller of FIG.

FIG. 3 is a flowchart of a preheat control routine for preheating the first catalyst device.

FIG. 4 is a TmHEATER table diagram for calculating a predetermined energization time TmHEATER.

FIG. 5 is a time chart when the preheat control routine is executed.

[Explanation of symbols]

 1 Internal Combustion Engine 5 ECU (Predetermined Period Setting Means) 10 TW Sensor (Temperature State Detection Means) 18 Heater Section (Heating Device) 19 Heater Control Section (Electrification Means) 23 IG Switch (Actuation State Detection Means) 24 ST Switch 25 TOIL Sensor (Temperature condition detecting means)

Claims (4)

[Claims] 1. An exhaust gas purifying apparatus for an internal combustion engine, comprising a catalyst device provided in an exhaust system of an internal combustion engine for purifying unburned gas in exhaust gas and electrically heating the catalyst. The engine has a start intention detecting means for detecting a start intention of the driver before the starter of the engine is activated, and a temperature state detecting means for detecting a temperature state of the catalyst device. When the starting intention is detected and the temperature state value detected by the temperature state detecting means is a low temperature state equal to or lower than a first predetermined value, the engine starting is started from the time when the starting intention is detected by the starting intention detecting means. An exhaust gas purifying apparatus for an internal combustion engine, comprising: an energizing means for energizing the heating device for a predetermined period thereafter. 2. The internal combustion engine according to claim 1, further comprising a predetermined period setting means for setting the predetermined period to be longer as a temperature state value detected by the temperature state detecting means is lower. Exhaust gas purification device. 3. An operation inhibiting means for inhibiting the operation of the starter when the temperature is lower than a second predetermined value lower than the first predetermined value, and the operation inhibiting means is provided. 2. An exhaust gas purification device for an internal combustion engine according to 2. 4. The exhaust gas of an internal combustion engine according to claim 1, wherein the temperature state detecting means of the catalyst device is a water temperature detecting means for detecting a cooling water temperature of the engine. Purification device.