JPH06137140A - Electrification control device for electrification heating type catalyst - Google Patents

Abstract

PURPOSE:To activate an electrification heating type catalyst by small power in an early stage while reducing a battery load so as to reduce exhaust emission when battery voltage is lowered. CONSTITUTION:First and second electric heater catalysts (EHC) 19, 20 are arranged in the exhaust system of right and left banks 2, 3 of a V-type engine. Respective EHCs 19, 20 are electrically connected to a battery 29 in parallel, and electrified by respecctive relay switches 32, 33 selectively. When it is judged by an ECU 81 that voltage of the battery 29 is reduced on the basis of detection of a voltage sensor 63 it blocks, electrification to the first EHC 19 in which an introduced exhaust temperature is low relatively and controls respective relay switches 32. 33 so that electrification only to the second HEC 20 is allowed. Therefore, in the second EHC 20 to which electrification is allowed, power of the battery 29 whose voltage is reduced is used effectively for heating so as to promote heating and warming-up operation in parallel with exhaust of high temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrically heated catalyst which can be heated by energization in order to promptly purify exhaust gas from a cold start of an internal combustion engine, and particularly to control the energization of the catalyst. The present invention relates to an energization control device.

[0002]

2. Description of the Related Art Conventionally, a catalytic converter such as a three-way catalyst has been generally provided in an exhaust system for the purpose of reducing exhaust emission of an internal combustion engine. Here, at the time of cold starting of the internal combustion engine, it is necessary to immediately activate the catalyst to purify the exhaust gas, so a technique of electrically heating the catalyst itself has been proposed. For example, in the technique disclosed in Japanese Patent Publication No. 3-504405, a plurality of starter catalysts that can be heated by energization are arranged in an exhaust system, and these are connected in parallel to a power source to selectively energize them. It is supposed to be done.

[0003]

However, in the technique of the above-mentioned prior art publication, when each starting catalyst is to be energized by using a vehicle-mounted battery as a power source, the starting catalyst may be applied to each starting catalyst depending on the state of voltage drop of the battery. It becomes difficult to supply sufficient electricity, and it is difficult to heat them early. However, even in such a situation, prompt exhaust gas purification is still required at the cold start, and how to use each starting catalyst in accordance with the battery voltage drop to reduce the exhaust emission. Is an issue.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to control the energization of a plurality of electrically heated catalysts to reduce the load on the battery even when the voltage of the battery drops. It is an object of the present invention to provide an energization control device for an energization heating type catalyst which is capable of quickly activating the energization heating type catalyst with a small amount of electric power while reducing the exhaust emission.

[0005]

In order to achieve the above object, according to the present invention, a plurality of units arranged in an exhaust system of an internal combustion engine, electrically connected in parallel to a battery, and capable of being heated by energization. Of the energization heating type catalyst, a voltage detecting unit for detecting the voltage state of the battery, and when it is determined that the voltage of the battery is low based on the detection result of the voltage detecting unit, among the plurality of energization heating type catalysts, With the intent of providing an energization control means for interrupting energization to the electrically heated catalyst where the temperature of the exhaust gas to be introduced becomes relatively low and allowing only the remaining electrically heated catalyst to be energized. There is.

[0006]

According to the above construction, the energization of each electrically heated catalyst from the battery is allowed, whereby each electrically heated catalyst is heated and warmed up, and their activation is promoted. Further, the exhaust gas discharged from the internal combustion engine is purified by being introduced into each activated electrically heated catalyst.

Then, the energization control means determines that the temperature of the exhaust gas to be introduced is relatively low among the plurality of energization heating type catalysts when it is determined that the voltage of the battery is low based on the detection result of the voltage detection means. Control is performed so that the energization to the other electrically heated catalyst is cut off and only the remaining electrically heated catalyst is allowed to be energized. Therefore, the temperature of the exhaust gas to be introduced becomes relatively high in the electrically heated catalyst which is allowed to be energized. Then, in the energization heating type catalyst which is allowed to energize, heating is performed by effectively using electric power of a battery whose voltage has dropped and which is small, and heating / warming is promoted in combination with high exhaust heat. Further, since all the electrically heated catalysts are not energized by the battery at the same time, a large load is not applied to the battery.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which an energization control device for an electrically heated catalyst according to the present invention is embodied in an automobile will be described below with reference to FIGS.
It will be described in detail based on.

FIG. 1 is a schematic configuration diagram showing a gasoline engine system in this embodiment. In an engine body 1 that constitutes a V-type engine as an internal combustion engine, each cylinder is divided into a left bank 2 and a right bank 3. Intake manifolds 4L and 4R and exhaust manifolds 5L and 5R are connected to the left and right banks 2 and 3, respectively.
Each intake manifold 4L, 4R has a common surge tank 6
Also, an air cleaner 8 is provided on the inlet side of the intake pipe 7 and communicates with the intake pipe 7. An intake system is constituted by the intake manifolds 4L and 4R, the surge tank 6, the intake pipe 7 and the like, and the air taken from the outside from the air cleaner 8 through the intake system is the combustion chambers 2a of the left and right banks 2 and 3, respectively. , 3a. Intake pipe 7
A throttle valve 9 for adjusting the amount of air introduced into each of the combustion chambers 2a and 3a is provided in the middle of.
The throttle valve 9 is opened and closed in conjunction with the operation of an accelerator pedal (not shown). Also, each intake manifold 4
L and 4R are injectors 10L and 10 for fuel injection.
R is provided for each. As is well known, the injectors 10L and 10R are opened by energization to inject fuel fed from a fuel tank (not shown) through a fuel pump into the vicinity of the intake port. Then, the fuel injected from each injector 10L, 10R becomes an air-fuel mixture with air and each combustion chamber 2a, 3a.
Will be introduced to. In each combustion chamber 2a, 3a, the introduced air-fuel mixture is exploded / combusted by the operation of the spark plugs 11L, 11R.

On the other hand, each exhaust manifold 5L, 5R constitutes a part of the exhaust system, and exhausts the exhaust gas after combustion from each combustion chamber 2a, 3a. In order to purify the discharged exhaust gas and discharge it into the atmosphere, each exhaust manifold 5
L and 5R have first and second three-way catalytic converters 1
2 and 13 are respectively connected. Exhaust pipes 14 and 15 are connected to the three-way catalytic converters 12 and 13, respectively. Further, as shown in FIG. 2, a common third three-way catalytic converter 16 is connected to each of the exhaust pipes 14 and 15, and an exhaust pipe 17 is further connected to the three-way catalytic converter 16. As is well known, the first to third three-way catalytic converters 12, 13, 16 oxidize hydrocarbons (HC) and carbon monoxide (CO) in exhaust gas, and
This is for purifying exhaust gas by reducing nitric oxide (NOx).

Further, since the cylinders of the left and right banks 2 and 3 are bank offset as a feature of the V-type engine, as can be seen from FIG. 2, the exhaust manifold 5L of the left bank 2 is the exhaust of the right bank 3. It is located slightly ahead of the manifold 5R. The first and second three-way catalytic converters 12 and 13 are arranged symmetrically on the rear side of the engine body 1. Therefore, the length L1 of the collecting portion 5a in the exhaust manifold 5L of the left bank 2 is
It is relatively larger than the length L2 of the collecting portion 5b in the exhaust manifold 5R of the right bank 3. From this, the first three-way catalytic converter 1 corresponding to the left bank 2
The temperature of the exhaust gas introduced into the second three-way catalytic converter 13 corresponding to the right bank 3 is relatively higher than the temperature of the exhaust gas introduced into the second bank 3. That is, each three-way catalytic converter 1 by the exhaust heat of the engine body 1
When considering warm-up of Nos. 2 and 13, the second three-way catalytic converter 13 corresponding to the right bank 3 is relatively easier to warm up.

First and second three-way catalytic converters 12,
13 are configured the same as each other. That is, as shown in FIG. 3, each of the three-way catalytic converters 12 and 13 is configured such that the casing 18 contains a three-way catalyst divided into three small and large sizes. Of these three three-way catalysts, the smaller ones on the upstream side are respectively provided with an electric heater and serve as a first electric heater-equipped catalyst 19 and a second electric heater-equipped catalyst 20 which can be heated by energization. Further, the middle-sized and large-sized ones on the downstream side are the main catalysts 21 and 22, respectively. Each of the catalysts with electric heaters 19 and 20 has a center electrode 23 arranged at the center of a honeycomb core forming a metal catalyst by adhering a three-way catalyst, and by supplying electricity between the center electrode 23 and the rim 24. , Is designed to heat its own metal catalyst. Further, each of the main catalysts 21 and 22 is composed of a metal catalyst to which a three-way catalyst is simply attached. The catalysts with electric heaters 19 and 20 are arranged on the upstream side of the other main catalysts 21 and 22, and are mainly operated when the engine is cold-started. On the other hand, the third three-way catalytic converter 16 is composed of only a large main catalyst.

It should be noted that the engine body 1 of this embodiment has a crankshaft 25 by cranking at the time of starting.
A starter 26 is provided to apply a rotational force to the. Further, the starter 26 is provided with a starter switch 61 for detecting its on / off operation. As is well known, the starter 26 is connected to an ignition switch 62 and is turned on / off by operating the switch 62. The ignition switch 62 can be switched to an off position, an on position and a starter position by key operation. Then, while the ignition switch 62 is switched to the starter position through the ON position, the starter 26 is turned on and the starter switch 61 outputs the starter signal STS of “ON”.

In order to energize the catalysts 19 and 20 with electric heaters, the power source lines 27 and
It is connected to the plus electrode 29a of the on-vehicle battery 29 via the 28 and the ignition switch 62.
The rim 24 side of the catalysts 19 and 20 with electric heaters is connected to the negative electrode 29b of the battery 29 via the power supply lines 30 and 31, respectively. Further, a first relay switch 32 and a second relay switch 33 are provided in the middle of the power supply lines 27 and 28 in order to control the power supply from the battery 29 to the catalysts 19 and 20 with electric heaters. ing. Then, the ignition switch 62
Is switched to the on position, and the first and second relay switches 32 and 33 are turned on by an electric signal, whereby the power supply lines 27 and 28 are closed and the catalysts 19 and 20 with electric heaters are closed. Power is supplied from the battery 29. In addition, the first and second relay switches 32, 33
Is turned off, the power supply lines 27 and 28 are opened, and the electricity supplied from the battery 29 to the catalysts 19 and 20 with electric heaters is stopped. Here, the battery 29
In the vicinity of the power supply line 27, the voltage sensor 6 for detecting the voltage (battery voltage) Vb of the battery 29 is provided.
3 is provided.

First and second three-way catalytic converters 12,
Reference numeral 13 denotes a first and second electric heater-equipped catalysts 19, 20.
There are provided a first catalyst temperature sensor 64 and a second catalyst temperature sensor 65 for detecting the respective temperatures (catalyst temperature) THC1 and THC2. Further, in the first and second three-way catalytic converters 12 and 13, each catalyst temperature sensor 6
A first oxygen sensor 66 and a second oxygen sensor 67 for detecting the oxygen concentration OX in the exhaust gas are provided on the upstream side of 4, 65.

Next, the structure of the secondary air supply device for supplying the secondary air to the exhaust system will be described. In this embodiment, an electric air pump 34 driven by energization is provided to supply secondary air to the exhaust system.
The electric air pump 34 has a built-in electric motor, and when driven, sucks and discharges outside air through the silencer 35. One end of an air pipe 36 for supplying secondary air is connected to the discharge port of the electric air pump 34, and the other end of the pipe 36 has two air pipes 36.
L and 36R are branched into three-way catalytic converters 12 and 1
The exhaust manifolds 5L and 5R upstream of the No. 3 are connected to each other. Battery 29 to electric air pump 34
The positive terminal of the pump 34 is connected to the positive electrode 29a of the battery 29 via the power supply lines 37, 27 and the ignition switch 62 in order to energize the battery.
The negative terminal of the electric air pump 34 is connected to the negative electrode 29 of the battery 29 via the power lines 38 and 30.
connected to b. Further, a third relay switch 39 is provided in the middle of the power supply line 37 in order to control the power supply to the electric air pump 34. When the ignition switch 62 is switched to the ON position and the third relay switch 39 is turned on by an electric signal, the power supply line 37 is closed and the electric air pump 34 is energized from the battery 29. Be seen. Then, the electric air pump 34 is driven by the energization, so that the sucked outside air causes the air pipe 3 to flow.
Through 6, 36L and 36R, secondary air can be introduced into the exhaust system from the upstream side of each three-way catalytic converter 12, 13. Further, when the third relay switch 39 is turned off, the power supply line 37 is closed, and the power supply from the battery 29 to the electric air pump 34 is stopped.

On the other hand, the air pipe 36 branched into two
In the middle of L and 36R, the diaphragm type first air control valve 40 and the second
Each air control valve 41 is provided. As is well known, each of these air control valves 4
0 and 41 are provided with diaphragm chambers 40a and 41a, and when negative pressure is introduced into the diaphragm chambers 40a and 41a, the valves are opened and the air pipes 36L and 36R are opened midway. Meanwhile, each air control valve 4
In order to open 0, 41, each diaphragm chamber 40
One ends of vacuum pipes 42 and 43 are connected to a and 41a, respectively. Also, these vacuum pipes 4
The other ends of 2, 43 are connected to the surge tank 6 through a common vacuum pipe 44. Then, the intake negative pressure generated in the surge tank 6 is changed to the vacuum pipe 4
Each diaphragm chamber 40a, 41 through 4, 42, 43
It can be introduced into a. Furthermore, each diaphragm chamber 4
In order to control the introduction of the negative pressure to 0a and 41a, a first three-system vacuum switching valve (hereinafter simply referred to as "VSV") is opened and closed by an electric signal in the middle of each vacuum pipe 42 and 43. 45) and a second VSV 46. Each of these V
When the SVs 45 and 46 are turned on by an electric signal, the middle of each vacuum pipe 42 and 43 is opened. Thereby, each air control valve 40, 41
Negative pressure is allowed to be introduced into the diaphragm chambers 40a and 41a, and the air control valves 40 and 41 are opened. On the other hand, when the VSVs 45 and 46 are turned off by non-energization, the vacuum pipes 4
The diaphragm chambers 40a and 41a are opened to the atmosphere while the middle of the diaphragms 2 and 43 are closed. As a result, the air control valves 40 and 41 are closed.

In the middle of each air pipe 36L, 36R,
Check valves 47 and 48 are provided respectively.
These check valves 47 and 48 are connected to the air pipes 36 from the exhaust manifolds 5L and 5R due to exhaust pulsation.
This is to prevent the exhaust gas from flowing back to L and 36R. Similarly, a check valve 49 is also provided in the middle of the vacuum pipe 44, so that even if the negative pressure of the surge tank 6 is lower than the operating negative pressure of the air control valves 40 and 41, the negative pressures of the diaphragm chambers 40a and 41a are reduced. It can be held.

In addition, the engine body 1 is provided with a water temperature sensor 68 for detecting the temperature (cooling water temperature) THW of the cooling water. The engine body 1 is provided with a rotation speed sensor 69 for detecting the rotation speed of the crankshaft 25 as an engine rotation speed NE.
The left and right banks 2 and 3 of the engine body 1 have camshafts 50L and 50L that interlock with the crankshaft 25.
Based on the rotation of R, the first cylinder discrimination sensor 70 and the second cylinder discrimination sensor 71 for detecting the cylinder discrimination and crank angle reference positions G1, G2 such as the top dead center position, respectively.
Is provided. Further, on the inlet side of the intake pipe 7, an air flow meter 72 for detecting the intake air flow rate Q taken into each combustion chamber 2a, 3a of the engine body 1 is provided.

In this embodiment, each injector 10L,
10R, first and second electric heater-equipped catalysts 19, 20,
The electric air pump 34 and the first and second VSVs 45,
Each of 46 is drive-controlled by an electronic control unit (hereinafter simply referred to as “ECU”) 81. To that end, the ECU
Reference numeral 81 denotes each injector 10L, 10R, first to third relay switches 32, 33, 39 and first and second Vs.
The SVs 45 and 46 are electrically connected to each other.
Further, the ECU 81 includes a starter switch 61, an ignition switch 62, a voltage sensor 63, first and second catalyst temperature sensors 64 and 65, a first and second oxygen sensor 6
6, 67, a water temperature sensor 68, a rotation speed sensor 69, first and second cylinder discrimination sensors 70, 71, and an air flow meter 72 are electrically connected to each other. And E
The CU 81 has the switches 61 and 62 and the sensors 63.
˜71 and various signals from the air flow meter 72 are executed to execute various calculation and judgment processes. This allows
Each injector 10L, 10R, the first to third relay switches 32, 33, 39 and the first and second VSV4s.
Driving control is preferably performed on each of 5, and 46.

FIG. 4 is a block diagram showing the electrical configuration of the ECU 81. ECU 81 is a central processing unit (CPU)
82, a read-only memory (ROM) 83 in which predetermined control programs and the like are stored in advance, and a random access memory (RAM) 8 in which the calculation results of the CPU 82 and the like are temporarily stored.
4. Backup RA that saves pre-stored data
Equipped with M85. Then, the ECU 81 includes the respective units 82 to 85, the external input circuit 86, and the external output circuit 87.
And the like are connected as a logical operation circuit by a bus 88. The CPU 82 of this embodiment also has the function of a free running counter.

The switches 61 and 62, the sensors 63 to 71, the air flow meter 72, etc. are connected to the external input circuit 86, respectively. The external output circuit 87 includes the injectors 10L and 10R described above, the first to third relay switches 32, 33 and 39, and the first output switch circuit.
And the second VSVs 45, 46 and the like are connected to each other. Then, the CPU 82 reads various signals from the switches 61 and 62, the sensors 63 to 71, the air flow meter 72 and the like as input values via the external input circuit 86. Further, the CPU 82, based on these input values, sends the respective injectors 10L and 10R to the first output via the external output circuit 87.
~ Drive control of 3rd relay switch 32, 33, 39, 1st and 2nd VSV45, 46 grade | etc., Is carried out suitably.

In this embodiment, the ECU 81 constitutes an energization control means. When the engine is cold-started, the ECU 81 activates the first and second electric heater-equipped catalysts 19 and 20 based on various signals from the switches 61 and 62, the sensors 63 to 71, and the like, and drives them electrically. The air pump 34 is driven. Further, the ECU 81 controls each injector 1 in order to control the fuel injection of the engine.
Drive 0L and 10R. Further, the ECU 81 executes air-fuel ratio feedback control (FB control) of the engine based on signals from the oxygen sensors 66 and 67.

Next, in the gasoline engine system configured as described above, the ECU 8 is started when the engine is started.
The processing operation for purifying the exhaust gas executed by No. 1 will be described.

FIG. 5 shows a "secondary air supply control routine" executed by the ECU 81, in which the starter signal STS from the starter switch 26 is switched from "OFF" to "ON" by operating the ignition switch 62. Be started.

When the processing of this routine is started, first in step 101, the battery voltage Vb and the cooling water temperature THW are read based on the detection signals of the voltage sensor 63 and the water temperature sensor 68, respectively. In addition, a cumulative intake flow rate TQAI, a post-start time CAST, and each flag XST described later.
EFI, FOTP, XBATOFF, XEHC1, XE
Read HC2 respectively.

Then, in step 102, it is judged whether or not the preconditions for supplying the secondary air are satisfied. That is, whether or not the start mode flag XSTEFI indicating that the engine is in the start mode is "0",
That is, it is determined whether or not the start mode has been exited. The start mode flag XSTEFI is set by a separate routine, and the engine speed NE is "200 rp".
It is set to "1" when it has dropped to "m", and to "0" when the engine speed NE has exceeded "400 rpm". In addition, it is determined whether the cooling water temperature THW is "-10 ° C" or higher and "35 ° C" or lower. Here, the start mode flag XSTEFI is "1" and the cooling water temperature T
If the HW is not higher than "-10 ° C" and lower than "35 ° C", the precondition is not satisfied, and it is determined that the secondary air is not supplied, and the process proceeds to step 108. On the other hand, when the start mode flag XSTEFI is “0” and the cooling water temperature THW is “−10 ° C.” or higher and “35 ° C.” or lower, it is determined that the precondition is satisfied, the process proceeds to step 103, and the secondary The air supply flag XAIpre is set to "1".

Next, at step 104, it is judged if the execution condition for the secondary air supply is satisfied. That is, it is determined whether or not the start mode flag XSTEFI is "0", and whether or not the post-start time CAST, which is timed by a separate routine, has exceeded "3 seconds" or more. Also, it is determined whether or not the battery voltage Vb is "11.5 V" or higher. Further, it is determined whether or not the startup amount increase flag F0TP set in a separate routine is "0". The startup amount increase flag FOTP is set to "1" when the fuel injection amount is being increased when the engine is started, and is set to "0" when the fuel amount is not increased. Then, if all the above conditions are not satisfied, it is determined that the secondary air is not supplied, and step 10 is performed.
8. If all the conditions are satisfied, the process proceeds to step 105.

In step 105, it is determined whether or not the cumulative intake air flow rate TQAI after the start, which is obtained by a separate routine, is smaller than the maximum integrated intake air flow rate TQAImax. The integrated intake air flow rate TQAI is obtained based on the intake air flow rate Q obtained by the detection of the air flow meter 72. Then, if the integrated intake air flow rate TQAI is not smaller than the maximum integrated intake air flow rate TQAImax, it is determined that the secondary air is not supplied, and the routine proceeds to step 108. On the other hand, the cumulative intake flow rate TQAI is the maximum cumulative intake flow rate T
If it is smaller than QAImax, the process proceeds to step 106.

In step 106, the operating time (pump operating time) CAP of the electric air pump 34, which will be described later, is set.
It is determined whether R is smaller than the standard time "120 seconds". Then, the pump operating time CAPR is "120.
If it is not smaller than "second", it means that the supply of the secondary air is stopped because the standard time has been exceeded, and the routine proceeds to step 108. On the other hand, when the pump operating time CAPR is smaller than "120 seconds", the standard time has not been exceeded, so that the secondary air is supplied, and the routine proceeds to step 107.

Then, step 102 and step 10
4, in step 108 after moving from step 105 or step 106, the third relay switch 39
Is turned off to stop the power supply from the battery 29 to the electric air pump 34, thereby turning off the pump 34. Next, the process proceeds from step 108 to step 109, the first VSV 45 is turned off, and step 1
In 10, the second VSV 46 is turned off, and the subsequent processing is temporarily ended. In this way, the electric air pump 34
Is turned off, and the first and second VSVs 45 and 46 are
Is turned off, the supply of the secondary air to the first and second catalytic converters 12 and 13 is stopped.

On the other hand, step 102, step 1
When all the determination conditions of 04, step 105, and step 106 are satisfied, the process proceeds from step 106 to step 107, the third relay switch 39 is turned on, and the battery 29 is energized to the electric air pump 34. The pump 34 is turned on. Next, in step 111, the pump operating time CAPR is incremented by "1".

After that, in step 112, it is judged whether or not the voltage drop flag XBATOFF is "0". The voltage drop flag XBATOFF is for instructing the voltage drop of the battery 29, and is set in the "catalyst energization control routine" described later. If the voltage drop flag XBATOFF is "0", it means that the voltage of the battery 29 is not dropped and it is determined that the electricity supply to the catalysts 19 and 20 with electric heaters is not stopped. Then, in the same step 113, the first VSV 45 is turned on, and the second VSV 46 is turned on in step 114, and the subsequent processing is temporarily terminated. In this way, the electric air pump 34 is turned on, and the first and second VSVs 45,
By turning on 46, secondary air is supplied to the first and second catalytic converters 12, 13.

On the other hand, if the voltage drop flag XBATOFF is not "0" in step 112, it is determined that the voltage of the battery 29 has dropped and step 11
Go to 5. Then, in step 115, it is determined whether or not the pump operating time CAPR is shorter than a predetermined delay time (less than "120 seconds") α. And
When the pump operating time CAPR is not smaller than the delay time α, it is determined that the delay time α has already elapsed, the process proceeds to step 113 to turn on the first VSV 45, and at step 114, turn on the second VSV 46. .

If the pump operating time CAPR is smaller than the delay time α in step 115, it is determined that the delay time α has not yet passed, and step 11
Go to 6. Then, in step 116, the first
Catalyst energization flag XEHC1 and second catalyst energization flag XE
It is determined whether both HC2 are "0". Both of these flags XEHC1 and XEHC2 are set in a "catalyst energization control routine" described later. The first catalyst energization flag XEHC1 is set to "0" when the first electric heater-equipped catalyst 19 is not energized, and similarly the second catalyst energization flag XEHC1 is set to the second value.
The catalyst energization flag XEHC2 is the catalyst 1 with the first electric heater.
Set to "0" when 9 is not energized. Here, when both the first and second catalyst energization flags XEHC1 and XEHC2 are not "0" in step 116, it is assumed that only the second catalyst with electric heater 20 is energized, and step 114 To the second V
Only SV46 is turned on. As a result, the secondary air is supplied only to the second three-way catalytic converter 13. on the other hand,
In step 116, when both the first and second catalyst energization flags XEHC1 and XEHC2 are “0”, it is determined that the first and second catalysts with electric heaters 19 and 20 are not energized. , Jump to step 108, execute the processes of step 108, step 109, and step 110, and then once terminate the process. That is, the supply of the secondary air to both the first and second three-way catalytic converters 12 and 13 is stopped.

The processing is executed as described above, and the supply of the secondary air to the first and second three-way catalytic converters 12 and 13, and further to the first and second catalysts with electric heaters 19 and 20 is controlled. To be done.

FIG. 6 shows a "catalyst energization control routine" executed by the ECU 81, which is started at the timing when the starter signal STS switches from "OFF" to "ON" as in the above.

When the process of this routine is started, first in step 201, the battery voltage Vb, each of the battery voltage Vb, is detected based on the detection signals of the voltage sensor 63, the first catalyst temperature sensor 64 and the second catalyst temperature sensor 65. Catalyst temperature THC1, TH
Read C2 respectively. Further, the start mode flag XSTEFI and the secondary air supply flag XAIpre described above are read.

Next, at step 202, it is judged if the start mode flag XSTEFI is "0". Here, when the start mode flag XSTEFI is not "0", it is determined that the start mode is not exited,
Go to step 210. Also, the start mode flag XS
If TEFI is “0”, it is determined that the start mode has been exited, and the process proceeds to step 203.

At step 203, it is judged if the secondary air supply flag XAIpre is "1".
Then, when the secondary air supply flag XAIpre is not "1", it is determined that the precondition for the secondary air supply is not satisfied, and the routine proceeds to step 210. on the other hand,
If the flag XAIpre is "1", it is determined that the precondition for the secondary air supply is satisfied, and the routine proceeds to step 204.

In step 204, it is determined whether or not the battery voltage Vb is higher than the reference "10.5V". The battery voltage Vb is "10.5V"
If not, the voltage drop flag XBATOFF is set to "1" in step 205 on the assumption that the voltage of the battery 29 has dropped. In step 206, it is determined whether the first catalyst energization flag XEHC1 is "1". If the first catalyst energization flag XEHC1 is not "1", the battery 2
Assuming that power is not being supplied to the first catalyst with electric heater 19 from 9, the process proceeds to step 210. on the other hand,
When the first catalyst energization flag XEHC1 is “1”, it is determined that the battery 29 is energized to the first catalyst with electric heater 19, and the process proceeds to step 213. Then, in step 213, the first relay switch 32 is turned off to turn off the first catalyst with electric heater 1
By stopping the power supply to 9, the catalyst 19 is turned off. At the same time, the first catalyst energization flag XEHC1 is set to "0", and then the process is temporarily terminated. As a result, only the heating / warming of the first catalyst with electric heater 19 corresponding to the exhaust system of the left bank 2 where the temperature of the exhaust gas from the engine body 1 becomes relatively low is stopped.

On the other hand, in step 204, when the battery voltage Vb is higher than "10.5V", it is determined that the voltage of the battery 29 is sufficient, and the process proceeds to step 207, and the first catalyst energization flag XEHC1 and It is determined whether or not the second catalyst energization flags XEHC2 are both "0". Here, both catalyst energization flags XEHC1,
If both XEHC2 are not “0”, it is determined that only the second catalyst with electric heater 20 is energized, and the process proceeds to step 209. If both catalyst energization flags XEHC1 and XEHC2 are both "0",
Assuming that both the electric heater-attached catalysts 19 and 20 are not energized, the process proceeds to step 208. Then, in step 208, each catalyst with electric heater 1
The target energization time Tonb to be energized to 9 and 20 is corrected and calculated. The target energization time Tonb is corrected and calculated according to the respective catalyst temperatures THC1 and THC2 at that time.

Then, step 207 or step 20
In step 209 after shifting from 8, it is determined whether the actual energization time (actual energization time) Cehcon exceeds the target energization time Tonb obtained in step 208. If the actual energization time Cehcon does not exceed the target energization time Tonb, step 214
The actual energization time Cehcon is changed to the target energization time To.
If it exceeds nb, the process proceeds to step 210.

The process proceeds from step 202, step 203, step 206 or step 209 to step 21.
At 0, the second relay switch 33 is turned off to stop (turn off) the electricity supply from the battery 29 to the second catalyst with electric heater 20. At the same time, the second catalyst energization flag XEHC2 is set to "0". As a result, heating of the second electric heater-equipped catalyst 20 corresponding to the right bank 3 where the temperature of the exhaust gas from the engine body 1 becomes relatively high.
Warming up is stopped.

Then, at step 211, it is judged if the voltage drop flag XBATOFF is "0". Here, when the voltage drop flag XBATOFF is not "0", it is determined that the voltage of the battery 29 is low, and the process proceeds to step 213. On the other hand, if the voltage drop flag XBATOFF is “0”, it is determined that the voltage of the battery 29 has not dropped, and step 21
At 2, the count value of the actual energization time Cehcon is cleared.

Then, step 211 or step 21
In step 213 after shifting from 2, the first relay switch 32 is turned off to stop (turn off) the electricity supply from the battery 29 to the first catalyst with electric heater 19. At the same time, the first catalyst energization flag XEHC1 is set to "0", and then the process ends. As a result, heating of the catalyst 19 with the first electric heater corresponding to the left bank 2 where the temperature of the exhaust gas from the engine body 1 becomes relatively low.
Warming up is stopped.

On the other hand, in step 214 after shifting from step 209, it is determined whether or not the voltage drop flag XBATOFF is "0". If the voltage drop flag XBATOFF is "0", the battery 2
Assuming that the voltage of 9 has not dropped, step 215
At, the first relay switch 32 is turned on to energize the battery 29 from the battery 29 to the first catalyst with electric heater 19 (on). At the same time, the first catalyst energization flag X
Set EHC1 to "1". Further, at 216, the second relay switch 33 is turned on to energize the battery 29 from the battery 29 to the second catalyst with electric heater 20 (on). At the same time, the second catalyst energization flag XEHC2 is set to "1". Then, in step 217,
After adding the count value of the actual energization time Cehcon, the process is temporarily terminated. That is, when the voltage of the battery 29 has not dropped, both the first and second catalysts with electric heaters 19 and 20 are energized as needed.

On the other hand, when the voltage drop flag XBATOFF is not "0" in step 214,
Assuming that the voltage of the battery 29 has dropped, the process proceeds to step 216. Then, in step 216, the second relay switch 33 is turned on to turn on the battery 2
Power is supplied from 9 to the second catalyst with electric heater 20 (ON). At the same time, the second catalyst energization flag XEHC
Set 2 to "1". After that, in step 217, the count value of the actual energization time Cehcon is added, and then the process is temporarily terminated. That is, when the voltage of the battery 29 is low, the temperature of the exhaust gas from the engine body 1 becomes relatively high as necessary, and the right bank 3
That is, only the second catalyst with electric heater 20 corresponding to is energized to heat and warm up.

As described above, the catalyst energization control corresponding to the secondary air supply control at the time of starting is executed, and the first and second catalysts 19 and 20 with electric heaters are turned on and off, that is, the first and second catalysts. The energization from the battery 29 to the second electric heater-equipped catalysts 19 and 20 is controlled.

As described above, in this embodiment, V
The first catalyst with electric heater 19 is arranged in the exhaust system corresponding to the left bank 2 of the diesel engine, and the second catalyst with electric heater 20 is arranged in the exhaust system corresponding to the right bank 3.
Further, the catalysts 19 and 20 with electric heaters are used for the battery 2
9 are electrically connected in parallel with each other, and by selectively turning on and off the first and second relay switches 32 and 33, the catalysts 19 and 20 with electric heaters are selectively energized and heated.・ Warm up. When the voltage of the battery 29 has not dropped more than necessary, the first and second
Both of the electric heater-equipped catalysts 19 and 20 are allowed to be energized, and the respective catalysts 19 and 20 are heated and warmed up to promote activation. At this time, the exhaust gas discharged from the engine body 1 is the activated catalysts with electric heaters 19,
Each of them is introduced to 20 and purified.

On the other hand, when the voltage of the battery 29 is low, the first of the catalysts 19 and 20 with electric heaters is selected.
The power supply to the catalyst with electric heater 19 is cut off, and the power supply to only the second catalyst with electric heater 20 is allowed. That is,
The temperature of the exhaust gas introduced from the engine body 1 becomes relatively low, so that the electricity supply to the first catalyst with electric heater 19 is cut off and only the electricity to the remaining second catalyst with electric heater 20 is allowed. .

Therefore, in the second catalyst with electric heater 20 which is allowed to be energized, the temperature of the introduced exhaust gas becomes relatively high. Then, the second catalyst with electric heater 20
In the above, heating is performed by effectively using less electric power of the battery 29 whose voltage has dropped, and heating / warming is promoted in combination with high exhaust heat. As a result, the second catalyst with electric heater 20 is rapidly heated and warmed up. Further, since the two catalysts with electric heaters 19 and 20 are not energized by the battery 29 at the same time, a large load is not applied to the battery 29.

As a result, even when the voltage of the battery 29 is lowered, by controlling the energization of the two catalysts 19 and 20 with an electric heater, the load on the battery 29 is reduced and the second electric power is reduced. The catalyst 20 with an electric heater can be activated at an early stage, thereby reducing exhaust emission. Especially at cold start, in response to the demand for early exhaust gas purification,
Moreover, regardless of the voltage drop of the battery 29, the exhaust emission can be reduced by making full use of the second catalyst with electric heater 20.

The present invention is not limited to the above-described embodiment, but may be implemented as follows with a part of the configuration appropriately modified without departing from the spirit of the invention. (1) In the above embodiment, the first and second three-way catalytic converters 12 and 13 arranged in parallel corresponding to the exhaust systems of the left and right banks 2 and 3 of the V-type engine are provided. Two
It was embodied when the catalysts 19 and 20 with electric heaters of 1 were arranged respectively.

On the other hand, as shown in FIG. 7, the first three-way catalytic converter 53 and the second three-way catalytic converter 54 are arranged in series with the exhaust system 52 of the in-line engine 51.
It may be embodied in the case where the first catalyst 55 with an electric heater and the second catalyst 56 with an electric heater are respectively disposed in the above. Also in the case of this other embodiment, the upstream first catalyst 55 with an electric heater is rapidly heated and warmed up, and exhaust emission can be reduced early. (2) In the above embodiment, the first and second catalysts with electric heaters 19 and 20 have the same structure, but the catalysts with electric heaters may have different structures. For example,
The volume volumes of the catalysts with electric heaters may be different from each other, and the electric resistances of the catalysts with electric heaters may be different from each other.

(3) In the above-mentioned embodiment, the catalysts 19 and 20 with electric heaters are arranged such that the central electrode 23 is arranged at the center of the honeycomb core which constitutes the metal catalyst.
Although the electricity is supplied between the rim 24 and the rim 24, the structure of the catalyst with an electric heater is not limited to this, and it is sufficient that the catalyst itself can be heated by the electricity.

[0057]

As described above in detail, according to the present invention, when it is judged that the voltage of the battery is low, a plurality of electric heating type heaters are arranged in the exhaust system and electrically connected in parallel to the battery. Of the catalyst, shut off the energization to the electrically heated catalyst where the temperature of the exhaust gas introduced becomes relatively low,
Only the remaining energized heating type catalyst is allowed to be energized. Therefore, in the energization heating type catalyst which is allowed to energize, heating is performed by effectively using less electric power of the battery whose voltage has dropped, and in combination with high exhaust heat, heating / warming is promoted and There is no heavy load. Therefore, even when the voltage of the battery is lowered, the conduction heating type catalyst can be activated early with a small amount of electric power while reducing the load on the battery, and it is possible to reduce the exhaust emission. .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a gasoline engine system in an embodiment embodying the present invention.

FIG. 2 is a plan view showing first and second three-way catalytic converters arranged in parallel with an exhaust system corresponding to each of left and right banks of a V-type engine in one embodiment.

FIG. 3 is a cross-sectional view showing the structure of each three-way catalytic converter in one embodiment.

FIG. 4 is a block diagram showing a configuration of an ECU and the like in one embodiment.

FIG. 5 is a flowchart showing a “secondary air supply control routine” executed by the ECU in the embodiment.

FIG. 6 is a flowchart showing a “catalyst energization control routine” executed by an ECU in one embodiment.

FIG. 7 shows another embodiment embodying the present invention in which first and second units are arranged in series with an exhaust system of an in-line engine.
FIG. 3 is a plan view showing a three-way catalytic converter or the like.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine main body as internal combustion engine, 5L, 5R ... Exhaust manifold, 14, 15 ... Exhaust pipe, 19, 55 ... First electric heater-equipped catalyst, 20, 56 ... Second electric heater-equipped catalyst (19, 20) Constitute a plurality of electrically heated catalysts), 29 ... Battery, 63 ... Voltage sensor as voltage detecting means, 81 ... ECU as electricity controlling means.

Front Page Continuation (72) Inventor Masahiko Hibino 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (1)

[Claims] 1. A plurality of electrically heated catalysts arranged in an exhaust system of an internal combustion engine, electrically connected in parallel to a battery and capable of being heated by energization, and a voltage for detecting a voltage state of the battery. Of the plurality of electrically heated catalysts, the temperature of the exhaust gas to be introduced is relatively lower when it is determined that the voltage of the battery is low based on the detection result of the detection unit and the voltage detection unit. An energization control device for an energization heating type catalyst, comprising: an energization control means for interrupting energization to the energization heating type catalyst and permitting only energization to the remaining energization heating type catalyst.