JPH051525A - Exhaust purification device for internal combustion engine using catalyst converter - Google Patents

Abstract

PURPOSE:To provide an exhaust purification catalyst converter with which standing-up of an exhaust purification effect is performed earlier by using an electric heater having a high heat efficiency, a small increase of a ventilation resistance, and a good durability. CONSTITUTION:A ribbon heater of an electrically resistant metal belt formed zig-zag in the plate surface direction is disposed on the upstream of a catalyst converter installed to an exhaust passage 100 or a bypass in an internal combustion engine, and the ribbon heater is energized to heat catalyst to an activation temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of purification efficiency at cold start in an exhaust purification system of an internal combustion engine using a catalytic converter.

[0002]

2. Description of the Related Art In order to purify exhaust gas of an internal combustion engine, a catalytic converter in which a three-way catalyst is carried on a carrier made of ceramic and having a honeycomb shape is mounted in an exhaust passage, and an oxygen sensor for detecting the amount of residual oxygen in the exhaust gas. An exhaust gas purification device is often used in which the fuel is attached to control the supplied fuel to have a stoichiometric air-fuel ratio. However, the catalyst currently used in the exhaust emission control device does not reach a sufficiently activated state unless the temperature becomes higher than about 350 ° C. Therefore, in order to further improve the exhaust gas purification effect, it is desirable to heat and raise the temperature of the catalytic converter as rapidly as possible during cold start of the engine (cold start). It is most preferable that the temperature is raised to the activation temperature of (1). To meet these requirements, 1) A catalytic converter is installed in the upstream part of the exhaust passage near the engine combustion chamber so that exhaust gas with the highest temperature can flow into the catalytic converter. 2) A small catalytic converter having a small heat capacity is installed immediately before the catalytic converter, and the temperature of the small catalytic converter is first raised. 3) An electric heater is attached to heat the exhaust gas or the catalytic converter by energizing the engine at the same time when it is started. Things have been proposed.

[0003]

However, in the conventional structure, 1) during high-speed operation, the oxygen sensor and the catalyst undergo thermal deterioration due to high-temperature exhaust gas, and the durability deteriorates. 2) Exhaust gas purification effect starts up a little faster, but cannot meet strict exhaust gas regulations. 3) The electric heater requires a large amount of electric power, and the structure of the electric heater most suitable for heating the catalytic converter has not been devised. Therefore, heating efficiency, durability, ventilation resistance of exhaust gas increase, etc. Practical performance is not sufficient. There were drawbacks such as.

An object of the present invention is to provide an internal combustion engine using a catalytic converter that has a high heating efficiency, prevents an increase in ventilation resistance, and uses an electric heater having excellent durability, and that can sufficiently comply with stricter exhaust gas purification regulations. To provide an exhaust emission control device. Further, in addition to the above, another object of the invention of claim 4 is to purify exhaust gas of an internal combustion engine using a catalytic converter that can quickly start up an exhaust gas purification effect only by supplying a small electric power to a small electric heater. The equipment is provided.

[0005]

In order to achieve the above object, the present invention adopts the following constitutions 1) to 4). 1) A catalytic converter mounted on an exhaust passage of an internal combustion engine, a ribbon heater arranged upstream of the catalytic converter, the ribbon heater having a meandering shape bent in a plate surface direction, and a temperature sensor,
And a controller for energizing the ribbon heater, the controller energizing the heater when the catalytic converter is at a low temperature to raise the temperature of exhaust gas of the internal combustion engine or the front surface of the catalytic converter to a temperature at which the catalyst is activated. An exhaust gas purification device for an internal combustion engine using a catalytic converter. 2) A catalytic converter installed in an exhaust passage of an internal combustion engine, a bypass provided upstream of the catalytic converter and separated from the exhaust passage to return to the upstream side of the catalytic converter, a switching valve for the bypass, and a bypass switching valve. , A ribbon heater in which a strip made of an electric resistance metal is bent in a plate surface direction in a meandering shape, a cooling water temperature sensor of an engine, and a control device for controlling a switching valve and energizing the ribbon heater. When the cooling water is below the set temperature, the ribbon heater is energized to raise the temperature of the exhaust gas of the internal combustion engine or the catalytic converter to a temperature at which the catalyst is activated, and the bypass is opened to open the bypass for a predetermined time from the engine start. , An exhaust gas purification device for an internal combustion engine using a catalytic converter that closes a bypass after reaching a temperature at which a catalyst is activated. 3) Two catalytic converters mounted on the exhaust passage of the internal combustion engine, and a ribbon heater disposed between the catalytic converters and sandwiching the electrical resistance metal strip plate in a meandering shape bent in the plate surface direction. A controller having a temperature sensor and energizing the ribbon heater, the controller energizes the heater when the catalytic converter is at a low temperature and raises the end faces of both catalytic converters to a temperature at which the catalyst is activated. An exhaust gas purification device for an internal combustion engine using a catalytic converter for heating. 4) A main catalytic converter installed in the exhaust passage of the internal combustion engine,
A bypass provided upstream of the bypass, which returns from the exhaust passage to the upstream of the main catalytic converter, a switching valve for the bypass, and a strip plate made of an electric resistance metal, which is arranged in series with the bypass. The controller comprises a ribbon heater and a small catalytic converter bent in a meandering shape in the plate surface direction, a cooling water temperature sensor for the engine, and a control device for controlling the operation of the switching valve and energizing the ribbon heater. When the water temperature is equal to or lower than the set temperature, the bypass is opened for a predetermined time from the engine start and the exhaust gas is passed therethrough, and the ribbon heater is energized to a temperature at which the catalyst activates the small catalytic converter or the exhaust passing through the small catalytic converter. Exhaust of an internal combustion engine using a catalytic converter that closes the bypass after the temperature is raised and reaches a temperature at which the catalyst of the main catalytic converter is activated Apparatus.

[0006]

The catalytic converter according to the first aspect of the present invention has the following effects because the ribbon heater is used as the electric heater. a) Since the heating element is flat, it has a large surface area, so that heat can be quickly conducted to the exhaust gas, and the heating efficiency of the exhaust gas is high. b) Since the heating element is flat, the front surface area is small, and the ventilation resistance of the exhaust flow is unlikely to occur. c) Since the heating element is flat, it is resistant to vibration and corrosion and has excellent durability.

In addition to the above effects, the catalytic converter according to the second aspect of the present invention can prevent the ribbon heater from deteriorating due to high temperature exhaust during high-speed operation of the engine, so that the durability can be further improved.

In addition to the effect of claim 1, the catalytic converter according to claim 3 of the present invention can more efficiently radiate the radiant heat generated by the ribbon heater to the catalyst body, so that the preheating time can be shortened and the heat generation capacity can be reduced. Can be reduced.

According to a fourth aspect of the present invention, in addition to the effects of the first to third aspects, if the small catalytic converter is heated by a small ribbon heater at the cold start, the temperature of the catalyst rises to the activation temperature. Can warm. This makes it possible to significantly reduce power consumption.

[0010]

FIG. 1 shows an exhaust gas purifying catalytic converter for an internal combustion engine according to the present invention. 1 is an exhaust passage 100 of the internal combustion engine
The honeycomb-shaped catalytic converter 2 mounted on the above is a ribbon heater installed upstream of the converter 1.

The converter 1 has a well-known structure, and a ceramic columnar body having a circular, elliptical or elliptical cross section in which ventilation holes penetrating in the axial direction and having a substantially square cross section are formed in a grid pattern ( A honeycomb catalyst main body 11 in which a three-way catalyst is supported on a honeycomb carrier, and a net-shaped spring 12 wrapping the outer periphery thereof are provided in a housing 13 made of a stainless steel plate.
It is stored inside.

The ribbon heater 2 is made of stainless steel and has a thickness of 1.0 in a frame 21 which is slightly larger than the exhaust passage 100.
A ribbon heating element 22 having a size of 10 mm and a thickness of 10 mm, made of an iron-chromium-based electric resistance metal, is bent in the surface direction, and is formed in a meandering shape at intervals of 10 mm to cover a surface substantially corresponding to the cross section of the exhaust passage 100. It will be arranged. The frame 21 of the heating element 22
The fixing to the terminals is fixed to the terminals 23 and 24 penetrating the frame body 21 by insulating both ends of the heat generating body 22 and holding the curved portions 2a ... 2b located on both sides in the plate width direction. , Holding members 25 and 26 made of ceramic having a semi-cylindrical recess and holding the holding members 25 and 26 into the frame 21.
It is fixed to the inner wall of the.

In this embodiment, the ribbon heater 2 is installed 70 mm upstream from the front surface of the honeycomb catalyst body 11 and has a heat generation capacity of 3 kilowatts. Further, a heater temperature sensor 27 for detecting the temperature of the heating element 22 is attached so as to penetrate the frame body 21.

Although this type of ribbon heater is practically used for heating the supply air of a diesel engine, since it is directly exposed to exhaust gas in the present invention, it can be used as a heating element in comparison with heating the supply air. The frame 21 and the exhaust pipe, as well as the bolts for attaching the catalytic converter to the housing 13 are made of stainless heat-resistant steel to improve durability.

The ribbon heater 2 is controlled by the energization control device 3 shown in FIG. The energization control device 3 includes the heater temperature sensor 27, an indicator light 31 that lights up when the heater temperature sensor 27 reaches a set temperature, an exhaust temperature sensor 32 installed downstream of the catalytic converter 1, and an upstream of the ribbon heater 2. It comprises an attached oxygen sensor 4 with a heater 41, an engine cooling water temperature sensor 35, a switch 37 interposed between the vehicle-mounted power source 36 and the ribbon heater 2, and an exhaust control unit 30.

Reference numeral 5 denotes a fuel injection device attached to the air supply passage 200 of the engine, and a mixing ratio (air-fuel ratio) of fuel and air supplied to the engine in accordance with the output of the oxygen sensor 4.
Is controlled to approach the stoichiometric air-fuel ratio at which the fuel can be completely burned.

The energization control device 3 energizes the ribbon heater 2 and the heater 41 of the oxygen sensor as shown in the time chart of FIG. As soon as you insert the key switch,
Alternatively, when the key switch is set to the accessory (ACC) position, the energization control device 3 is activated, and when the output of the engine cooling temperature sensor 34 is less than or equal to the set value, that is, when a considerable amount of time has passed after cold start or engine stop. When it is present, the heater 41 of the oxygen sensor and the ribbon heater 2 are energized. The ribbon heater 2 is set to a set temperature (for example, 9
When the temperature is raised to 00 ° C.), the indicator light 31 is turned on to inform the driver that the engine start preparation is completed. In this state, the oxygen sensor 4 is set so that the heater 41 has completed heating to the operating temperature of 400 ° C. By this lighting, the driver recognizes that the preheating (preheating) of the ribbon heater 2 and the oxygen sensor 4 is completed,
Turn on the key switch to the starter motor operating position via the on position (energization of the engine electrical system).

The time for energizing the heater 41 of the oxygen sensor and the ribbon heater 2 is determined by a timer in addition to the temperature of the ribbon heater 2 itself directly detected by the heater temperature sensor 27 as described above. A certain time,
Alternatively, it may be a set time set by a timer according to the engine water temperature detected by the cooling water temperature sensor 35. The power supply to the ribbon heater 2 is stopped when the engine water temperature reaches the set value. After that, when the engine water temperature falls below the set value, electricity may be supplied again to allow afterheating.

FIG. 5 shows a second embodiment. In this embodiment, the ribbon heater 2 is installed immediately in front of the honeycomb catalyst main body 11. With this configuration, the honeycomb-shaped catalyst body 11
Is heated by the radiant heat generated by the ribbon heater 2. Therefore, the heating efficiency is good, and the front surface of the catalyst body 11 can be quickly heated to 350 ° C. or higher at which the catalyst is locally activated by the heater having a small heat generation capacity. In this state, the exhaust gas having a relatively low flow rate and a large amount of unburned components in the idling operation performed at the cold start of the engine is reacted to generate reaction heat from the beginning of the engine, and then the catalytic heat is applied to the catalytic converter 1. It becomes possible to maintain the exhaust gas purification temperature.

In this case, in order to prevent the catalyst on the front surface of the honeycomb catalyst main body 11 from being deteriorated by the heat of the ribbon heater 2, the temperature of the ribbon heater 2 is controlled so as not to exceed about 600 ° C. Is desirable.

FIG. 6 shows a third embodiment. In this embodiment, a bypass 6 and a switching valve 7 that branch from the exhaust passage 100 and return to the exhaust passage 100 are provided immediately before the catalytic converter 1, and the ribbon heater 2 is attached to the bypass 6.

In this structure, all or part of the exhaust gas is caused to flow to the bypass 6 only during the initial cold start operation, for example, and the exhaust valve 100 is operated to flow all the exhaust gas to the exhaust passage 100 during the subsequent operation. To do so.
This allows the ribbon heater 2 to be heated by high-temperature exhaust gas during high-speed operation.
Can be prevented from deteriorating, and the ventilation resistance does not increase at all.

FIG. 7 shows a fourth embodiment. In this embodiment, the honeycomb catalyst main body 11 is divided into a short front honeycomb catalyst main body 11A and a long rear honeycomb catalyst main body 11B, and the ribbon heater 2 is mounted between the two. .

With this structure, the radiant heat from the ribbon heater 2 can be radiated to the end faces of the front and rear honeycomb catalyst bodies 11A and 11B, and the heating by the radiant heat can be effectively performed. Therefore, in this embodiment, the preheating time can be further shortened and the heater capacity can be reduced as compared with the effect of the second embodiment.

FIG. 8 shows a fifth embodiment. In this embodiment, a bypass 6 and a switching valve 7 that are separated from the exhaust passage and return to the upstream of the main catalytic converter are provided upstream of the main catalytic converter 10 mounted in the exhaust passage 100 of the internal combustion engine.
A small ribbon heater 20 and a small catalytic converter 8 are arranged adjacent to the bypass 6, and when the cooling water temperature of the engine is low, the bypass 6 is opened for a short time after starting the engine to exhaust all or part of exhaust gas. The small ribbon heater 20 is energized and the small catalytic converter 8 or the exhaust gas passing through the small catalytic converter 8 is heated to a temperature at which the catalyst is activated.

According to this structure, both the ribbon heater 20 and the catalytic converter 8 can be small in size and have a small heat capacity, and the ribbon heater has a size of about 1.5 which is about half that of the structure shown in FIG.
Equivalent effect is obtained with a heating capacity of kilowatts. The switching valve 7 closes the bypass after reaching the temperature at which the catalyst of the main catalytic converter 10 is activated. As a result, the ribbon heater 20 and the small catalytic converter 8 can be prevented from being deteriorated by high temperature exhaust after warming up.

[Brief description of drawings]

FIG. 1 is a sectional view of an exhaust gas purifying catalytic converter for an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a ribbon heater.

FIG. 3 is a schematic diagram of a power supply control device for a ribbon heater.

FIG. 4 is a time chart of energization of a ribbon heater.

FIG. 5 is a sectional view of a catalytic converter according to a second embodiment of the present invention.

FIG. 6 is a sectional view of a catalytic converter according to a third embodiment of the present invention.

FIG. 7 is a sectional view of a catalytic converter according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view of a catalytic converter according to a fifth embodiment of the present invention.

[Explanation of symbols]

1 Honeycomb catalyst converter 2 Ribbon heater 3 energization control device 4 oxygen sensor 5 Fuel injection device 6 bypass 7 Switching valve (switching valve) 8 Small catalytic converter 10 Main catalytic converter 20 Small ribbon heater 100 exhaust path

Claims (4)

[Claims] 1. A catalytic converter mounted in an exhaust passage of an internal combustion engine, a ribbon heater disposed upstream of the catalytic converter, the ribbon heater formed in a meandering shape by bending a strip plate of an electric resistance metal in a plate surface direction, and a temperature sensor. A controller for energizing the ribbon heater, the controller energizing the heater when the catalytic converter is at a low temperature to raise the temperature of exhaust gas of the internal combustion engine or the front surface of the catalytic converter to a temperature at which the catalyst is activated. An exhaust gas purification device for an internal combustion engine using a catalytic converter for heating. 2. A catalytic converter mounted in an exhaust passage of an internal combustion engine, a bypass provided upstream of the catalytic converter and separated from the exhaust passage to return to the upstream side of the catalytic converter, a switching valve for the bypass, and the bypass. A ribbon heater, which is arranged and has a meandering shape in which a strip made of an electric resistance metal is bent in the plate surface direction, and a cooling water temperature sensor for the engine, which comprises a control device for operating a switching valve and energizing the ribbon heater, When the cooling water is below a set temperature, the control device energizes the ribbon heater to raise the temperature of the exhaust gas of the internal combustion engine or the catalytic converter to a temperature at which the catalyst is activated, and opens the bypass for a predetermined time from engine start. An exhaust gas purification device for an internal combustion engine that uses a catalytic converter that closes a bypass after passing a temperature of exhaust gas through which a catalyst is activated. 3. A two catalytic converter mounted in an exhaust passage of an internal combustion engine, and a ribbon which is disposed so as to be sandwiched between the two catalytic converters and which has a strip plate made of an electric resistance metal and bent in a plate surface direction to meander. A heater and a controller having a temperature sensor and energizing the ribbon heater are energized. The controller energizes the heater when the temperature of the catalytic converter is low, and the catalyst activates the end faces of both catalytic converters. An exhaust gas purification device for an internal combustion engine using a catalytic converter that raises the temperature. 4. A main catalytic converter mounted in an exhaust passage of an internal combustion engine, a bypass provided upstream of the main catalytic converter and separated from the exhaust passage to return to the upstream of the main catalytic converter, and a bypass switching valve. A ribbon heater and a small catalytic converter, which are arranged in series in a bypass and are made of an electric resistance metal and bent in a plate surface direction, meandering, and are provided with an engine cooling water temperature sensor. When the cooling water temperature is equal to or lower than a preset temperature, the controller opens the bypass to allow exhaust gas to pass through and to energize the ribbon heater to energize the small-sized catalyst when the cooling water temperature is equal to or lower than a set temperature. Exhaust gas passing through the converter or the small catalytic converter is heated to a temperature at which the catalyst is activated and reaches a temperature at which the catalyst of the main catalytic converter is activated. After that, an exhaust gas purification device for an internal combustion engine using a catalytic converter that closes the bypass.