JPH09195752A - Exhaust emission control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To early activate a catalytic converter by providing a precatalytic converter and a main catalytic converter in series in an exhaust passage, providing a catalyst passage leading exhaust to the precatalytic converter, and providing a bybass passage bypassing the precatalytic converter. SOLUTION: In an exhaust passage 1, a catalyst passage 21 receiving a precatalytic converter 2, and a bypass passage 22 bypassing the precatalytic converter 2 and leading exhaust to a main catalytic converter 3 are arranged. The precatalytic converter 2 is arranged close to an exhaust manifold 10, so as to promote activation of catalyst at low temperature. A catalyst valve 11 limiting introduction of exhaust into the catalyst passage 21, and a bypass valve 12 limiting introduction of exhaust into the bypass passage 22 are provided, the bypass valve 12 is operated to open interlocking with the closing operation of the catalyst valve 11, and the opening of the catalyst valve 11 is adjusted under the condition in which the bypass valve 12 is closed in the inactive territoy of catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an engine exhaust purification device.

[0002]

2. Description of the Related Art In some internal combustion engines for automobiles, a catalytic converter for purifying exhaust gas is installed immediately below an exhaust manifold of the engine to accelerate activation of the catalyst at low temperatures.

An example of this type of exhaust emission control device is shown in FIG.
(See Japanese Utility Model Laid-Open No. 1-66420).

Explaining this, the exhaust passage 51 is branched into two branch passages 52 and 53. A main catalytic converter 54 is installed in one branch passage 52, and a pre-catalyst converter 56 and a main catalytic converter 55 are installed in series in the other branch passage 53.
Is oxidized and NOx is reduced.

The pre-catalyst converter 52 is arranged as close as possible to the exhaust manifold that collects the exhaust gas discharged from each cylinder of the engine, so as to accelerate the activation at a low temperature of the catalyst.

A switching valve 58 for selectively opening / closing the branch passages 52, 53 is provided, and an opening / closing valve 59 for selectively communicating the upstream sides of the main catalytic converters 54, 55.
Is provided.

The branch passage 53 is opened through the switching valve 58 in the catalyst inactive region where the exhaust gas temperature is lower than a predetermined value, the on-off valve 59 is closed, and the exhaust gas is passed through the pre-catalytic converter 56 and the main catalytic converter 55. To accelerate the activation of the catalyst.

While closing the branch passage 53 through the switching valve 58 and opening the opening / closing valve 59 in the catalyst active region where the exhaust gas temperature becomes higher than a predetermined value, the exhaust gas bypasses the pre-catalyst converter 56. The heat resistance of the pre-catalyst converter 56 is ensured by guiding it to the main catalyst converters 54 and 55.

[0009]

In such a conventional engine exhaust emission control device, the exhaust gas is introduced into the pre-catalyst converter via the single switching valve 58, or the pre-catalyst converter is bypassed. The pre-catalyst converter 5 has a structure in which whether to guide the exhaust gas is selectively performed and the exhaust gas is guided to the pre-catalyst converter 56 with a uniform velocity distribution.
There is a problem that exhaust gas cannot be intensively guided to a part of No. 6 for early activation.

An object of the present invention is to solve the above problems and to provide an exhaust gas purifying apparatus for an engine which can adjust the speed distribution of the exhaust gas guided to the pre-catalytic converter according to the operating conditions.

[0011]

According to a first aspect of the present invention, there is provided an exhaust gas purifying apparatus for an engine, which guides exhaust gas to an exhaust gas purifying pre-catalytic converter and a main catalytic converter which are installed in series in an exhaust passage. A catalyst passage, a catalyst valve that is rotatably interposed in the catalyst passage, a bypass passage that bypasses the pre-catalyst converter to guide exhaust gas, a bypass valve that is rotatably interposed in the bypass passage, and a catalyst valve. A catalyst valve drive means for driving the opening and closing, and a return spring for urging the bypass valve in the valve closing direction,
A transmission mechanism that opens the bypass valve in conjunction with the closing operation of the catalyst valve in the range where the opening of the catalyst valve is smaller than a predetermined value, and opens the catalyst valve with the bypass valve closed in the inactive area of the catalyst. Control means for adjusting the degree.

According to a second aspect of the present invention, in the exhaust gas purifying apparatus for an engine according to the first aspect, the transmission mechanism is a transmission gear that rotates in conjunction with an opening / closing operation of a catalyst valve, and an opening / closing operation of a bypass valve. A bypass valve drive gear that rotates in conjunction with the above, and a notch formed by removing teeth that mesh with the transmission gear and the bypass valve drive gear in a range where the opening of the catalyst valve is smaller than a predetermined value.

According to a third aspect of the present invention, in the exhaust gas purifying apparatus for an engine according to the second aspect, the transmission mechanism includes a hook that rotates in conjunction with an opening / closing operation of a catalyst valve and an opening / closing operation of a bypass valve. A stopper that rotates in conjunction with the hook and that engages with the hook when the opening of the catalyst valve is smaller than a predetermined value.

According to a fourth aspect of the present invention, there is provided an exhaust emission control system for an engine according to any one of the first to third aspects, wherein a catalyst valve shaft for rotatably supporting the catalyst valve and a bypass valve are rotated. A bypass valve shaft movably supported is arranged on the same axis.

[0015]

In the engine exhaust emission control device according to the first aspect of the present invention, the bypass passage is closed in the inactive region of the catalyst through the bypass valve, while the catalyst valve is inclined at a predetermined angle with respect to the passage center line of the catalyst passage. The exhaust gas guided to the pre-catalytic converter is deflected by hitting the catalytic valve by adjusting the half-open position so that the speed distribution of the exhaust gas with respect to the pre-catalytic converter is partially enhanced. This allows
The pre-catalytic converter is partially activated, exhaust gas is purified through the pre-catalytic converter, and the activation of the main catalytic converter is accelerated.

By opening the bypass passage through the bypass valve and closing the catalyst passage through the catalyst valve in the active region of the catalyst, the exhaust gas is guided around the precatalyst converter, so that the heat resistance of the precatalyst converter is improved. And the exhaust gas is purified through the main catalytic converter.

As described above, the structure can be simplified by opening and closing the bypass valve via the single catalyst valve drive means and adjusting the opening of the catalyst valve independently of the bypass valve.

In the exhaust gas purifying apparatus for an engine according to a second aspect of the present invention, in the active region of the catalyst, the catalyst gear is driven to the fully closed position via the transmission gear via the catalyst valve drive means. By engaging the bypass valve drive gear, the drive force from the catalyst valve drive means is transmitted to the bypass valve and is driven to the fully open position against the biasing force of the return spring.

In the inactive area of the catalyst, the transmission gear and the bypass valve drive gear are opposed to each other via the notch while the catalyst valve is driven to the half-open position by the catalyst valve drive means via the transmission gear. The bypass valve is held at the fully closed position by the urging force of the return spring without being transmitted with the driving force from the catalyst valve driving means.

Therefore, the opening of the catalyst valve can be adjusted independently of the bypass valve via the catalyst valve driving means composed of a single step motor or the like, and the structure can be simplified.

In the engine exhaust emission control device according to the third aspect, the hook engages with the stopper and rotates in a state where the catalyst valve is driven to the fully closed position by the catalyst valve drive means in the active region of the catalyst. Thus, the drive force from the catalyst valve drive means is transmitted to the bypass valve, and the bypass valve is driven to the fully open position against the biasing force of the return spring.

In the inactive area of the catalyst, the hook is not engaged with the stopper and the bypass valve is driven from the catalyst valve driving means while the catalyst valve is driven to the half-open position via the transmission gear via the catalyst valve driving means. The driving force of
It is held in the fully closed position by the biasing force of the return spring.

Therefore, the opening of the catalyst valve can be adjusted independently of the bypass valve via the catalyst valve drive means composed of a single step motor or the like, and the structure can be simplified.

According to a fourth aspect of the present invention, there is provided an engine exhaust gas purification apparatus having a structure in which a catalyst valve shaft for rotatably supporting a catalyst valve and a bypass valve shaft for rotatably supporting a bypass valve are arranged on the same axis. The device can be downsized.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the exhaust passage 1 of the engine
A pre-catalytic converter 2 and a main catalytic converter 3 are installed in series in the exhaust gas, to oxidize HC and CO in the exhaust gas and NOx.
Is reduced.

The control unit 5 receives detection signals such as the engine intake air amount Q and the engine speed N and inputs the basic fuel injection amount Tp (= K) which brings the air-fuel ratio close to the stoichiometric air-fuel ratio.
X Q / N; K is a constant) and the detection signals of the O ₂ sensors 8 and 9 are input, and the fuel is adjusted so that the air-fuel ratio falls within a narrow range around the target value in a predetermined stoichiometric range. The injection amount Ti is calculated by the following equation and feedback control is performed.

Ti = Tp × α × COEF + Ts ...
(1) where α is the air-fuel ratio feedback correction coefficient, COEF
Is the sum of various correction coefficients using the coolant temperature Tw and the like detected by the coolant temperature sensor 19 as parameters, and Ts is the invalid injection pulse width.

The exhaust passage 1 is provided with a catalyst passage 21 in which exhaust gas from the engine is housed in the pre-catalyst converter 2 and a bypass passage 22 which bypasses the pre-catalyst converter 2 and leads to the main catalyst converter 3.

The pre-catalyst converter 2 is arranged as close as possible to the exhaust manifold 10 that collects the exhaust gas discharged from each cylinder of the engine so as to accelerate the activation at a low temperature of the catalyst.

A catalyst valve 11 for restricting the introduction of exhaust gas into the catalyst passage 21 and a bypass passage 2 are provided in the middle of the exhaust passage 1.
A bypass valve 12 is installed side by side to limit the introduction of the exhaust gas to the two.

As shown in FIG. 1, a chamber 20 is connected to the outlet of the exhaust manifold 10, and a catalyst valve 11 and a bypass valve 12 are housed in the chamber 20, respectively. The opening diameter of the catalyst passage 21 is smaller than the opening diameter of the bypass passage 22.

The catalyst valve 11 is formed in a disc shape and is rotatably supported via a catalyst valve shaft 13.

As shown in FIG. 2, the step motor 1 is used as a catalyst valve driving means for opening and closing the catalyst valve 11.
7 are provided.

A catalyst valve drive gear 14 is connected to one end of the catalyst valve shaft 13. Catalyst valve drive gear 14
Meshes with a pinion gear 16 via a transmission gear 15, and the pinion gear 16 is connected to a rotation shaft of a step motor 17. Rotation of the step motor 17 causes the pinion gear 1
6, the catalyst valve shaft 13 rotates via the transmission gear 15, the catalyst valve drive gear 14.

The rotation of the step motor 17 is controlled by a signal sent from the control unit 5. The opening of the catalyst valve 11 is continuous between the fully closed position that is substantially orthogonal to the passage centerline of the catalyst passage 21 and the fully opened position that is substantially parallel to the passage centerline due to the rotation of the step motor 17. It is adjusted to.

The bypass valve 12 is formed in a disc shape,
It is rotatably supported via the bypass valve shaft 23.

The bypass valve shaft 23 is arranged coaxially with the catalyst valve valve shaft 13. The catalyst valve shaft 13 is formed in a tubular shape, and the catalyst valve shaft 1
A bypass valve shaft 23 is provided so as to penetrate inside 3.

When the opening of the catalyst valve 11 is smaller than a predetermined value, a bypass valve drive is provided at one end of the bypass valve shaft 23 as a transmission mechanism for opening the bypass valve 12 in conjunction with the closing operation of the catalyst valve 11. Gear 2
4 is connected, and a transmission gear 25 that meshes with the bypass valve drive gear 24 is coupled to the transmission gear 15. That is, the transmission gear 25 rotates together with the transmission gear 15 as the catalyst valve 11 opens and closes, and the bypass valve 12 opens and closes via the bypass valve drive gear 24 that meshes with the transmission gear 25.

In order to open / close the catalyst valve 11 independently of the bypass valve 12 within a range where the opening of the catalyst valve 11 is smaller than a predetermined value, a notch 26 is formed on the outer periphery of the transmission gear 25. The notch 26 is formed by removing the teeth that mesh with the bypass valve drive gear 24. The notch portion 26 is formed in a predetermined angle range so that the transmission gear 25 and the bypass valve drive gear 24 mesh with each other in an opening range in which the catalyst valve 11 is smaller than a predetermined opening degree.

A return spring 27 for urging the bypass valve 12 in the valve closing direction is provided. One end of the coiled return spring 27 is connected to the bypass valve shaft 23, and the other end thereof is connected to the chamber 20 side via the connecting member 28.

The control unit 5 receives the starter switch signal, the intake air amount Q, the engine speed N, the cooling water temperature Tw, and other detection signals to control the opening / closing operations of the catalyst valve 11 and the bypass valve 12.

In the inactive area of the catalyst, the bypass passage 22 is closed through the bypass valve 12, while the catalyst valve 11 is closed.
The opening degree of the exhaust gas is adjusted so that the speed distribution of the exhaust gas with respect to the pre-catalytic converter 2 is gradually made uniform as the activation of the catalyst progresses due to the rectifying action of the catalyst valve 11.

The rotation of the step motor 17 causes the catalyst valve shaft 13 to rotate via the pinion gear 16, the transmission gear 15, and the catalyst valve drive gear 14, and the catalyst valve 11
Is driven to the half open position. As described above, the cutout portion 26 of the transmission gear 25 faces the bypass valve drive gear 24 in the state where the catalyst valve 11 is held in the half open position. As a result, the bypass valve 12 is held in the fully closed position by the urging force of the return spring 27 without the driving force of the step motor 17 being transmitted.

In the inactive region of the catalyst, the bypass passage 22 is closed through the bypass valve 12, while the catalyst valve 11 is closed.
Is held at a half-open position that is inclined at a predetermined angle with respect to the passage center line of the catalyst passage 21, so that the exhaust gas passing from the intake manifold 10 through the catalyst passage 21 to the pre-catalyst converter 2 hits the catalyst valve 11 and is deflected. Thus, the velocity distribution of the exhaust gas with respect to the pre-catalytic converter 2 is partially enhanced. As a result, the pre-catalyst converter 2 is partially activated, and the activated portion gradually expands as the catalyst valve 11 opens, so that activation can be accelerated. Thereby, the pre-catalyst converter 2
The exhaust gas is purified via the valve and the activation of the main catalytic converter 3 is accelerated.

In the active region of the catalyst, the bypass passage 22 is opened via the bypass valve 12, the catalyst passage 21 is closed via the catalyst valve 11, and the exhaust gas is guided by bypassing the precatalyst converter 2.

The rotation of the step motor 17 causes the catalyst valve shaft 13 to rotate via the pinion gear 16, the transmission gear 15, and the catalyst valve drive gear 14, and the catalyst valve 11
Is driven to the fully closed position. As the catalyst valve 11 is driven to the fully closed position in this way, the cutout portion 26 of the transmission gear 25 moves out of the position facing the bypass valve drive gear 24, and the transmission gear 25 and the bypass valve drive gear 24
Are engaged with each other, the driving force of the step motor 17 is transmitted to the bypass valve 12, and the bypass valve 12 is driven to the fully closed position against the biasing force of the return spring 27.

Exhaust gas is guided to the active area of the catalyst while bypassing the pre-catalyst converter 2, so that the heat resistance of the pre-catalyst converter 2 is ensured and the exhaust gas is purified through the main catalyst converter 3.

The bypass valve drive gear 2 is attached to the transmission gear 25.
With the structure in which the notch portion 26 facing 4 is provided, the bypass valve 12 can be opened / closed via the single step motor 17, and the opening degree of the catalyst valve 11 can be adjusted independently of the bypass valve 12. This is possible and the structure can be simplified.

Next, the embodiment shown in FIGS. 4 and 5 will be described. 1 and 2 are denoted by the same reference numerals.

A catalyst valve drive gear 34 is connected to one end of the catalyst valve shaft 13. Catalyst valve drive gear 34
Meshes with the pinion gear 16, and the pinion gear 16 is connected to the rotation shaft of the step motor 17. The rotation of the step motor 17 causes the catalyst valve shaft 13 to rotate via the pinion gear 16 and the catalyst valve drive gear 34.

As a transmission mechanism for opening the bypass valve 12 in conjunction with the closing operation of the catalyst valve 11, a hook 31 is connected to one end of the bypass valve shaft 23, and a stopper 30 engaging with the hook 31 is a catalyst valve. It is coupled to the drive gear 34. The stopper 30 is rotated as the catalyst valve 11 is closed, and the bypass valve 12 is opened via the hook 31 engaging with the stopper 30.

The stopper 30 and the hook engage with each other in the opening range of the catalyst valve 11 smaller than a predetermined opening.

A return spring 27 for urging the bypass valve 12 in the valve closing direction is provided. One end of the coiled return spring 27 is connected to the bypass valve shaft 23, and the other end thereof is connected to the chamber 20 side via the connecting member 28.

Next, the operation will be described.

In the inactive area of the catalyst, the step motor 17
Rotation of the pinion gear 16, the catalyst valve drive gear 3
The catalyst valve shaft 13 rotates via 4 and the catalyst valve 11 is driven to the half open position.

Since the stopper 30 does not engage with the hook 31 while the catalyst valve 11 is held in the half-open position in this way, the drive force of the step motor 17 is not transmitted to the bypass valve 12 and the return spring 27 is attached. It is held in the fully closed position by power.

In the active area of the catalyst, the pinion gear 16 and the catalyst valve drive gear 34 are rotated by the rotation of the step motor 17.
The catalyst valve shaft 13 is rotated via the, and the catalyst valve 11 is driven to the fully closed position.

As the catalyst valve 11 is driven to the fully closed position in this way, the stopper 30 engages with the hook 31, whereby the driving force of the step motor 17 is transmitted to the bypass valve 12, and the bypass valve 12 is transmitted. 12 is driven to the fully open position against the biasing force of the return spring 27. In order to adjust the opening of the catalyst valve 11 independently of the bypass valve 12 via the single step motor 17,
The structure can be simplified.

[0060]

As described above, in the engine exhaust gas purification apparatus according to the first aspect of the present invention, the bypass passage is closed through the bypass valve in the inactive region of the catalyst, while the catalyst valve causes the passage center line of the catalyst passage to pass through. Is adjusted to a half-open position that is inclined at a predetermined angle with respect to, and the speed distribution of the exhaust gas relative to the pre-catalytic converter is partially increased, so that the pre-catalytic converter is partially activated and exhaust gas purification is performed via the pre-catalytic converter. As well as being done, the activation of the main catalytic converter can be accelerated. Further, by opening and closing the bypass valve via a single catalyst valve drive means and adjusting the opening of the catalyst valve independently of the bypass valve, the apparatus can be simplified and downsized.

According to a second aspect of the present invention, there is provided an exhaust emission control device for an engine, wherein the catalyst gear is driven to a half-open position by the catalyst valve drive means via the transmission gear in the inactive region of the catalyst, and the transmission gear and the bypass valve are provided. The drive gear faces the notch so that the bypass valve does not receive the driving force from the catalyst valve drive means, and the opening of the catalyst valve is independent of the bypass valve via a single step motor or the like. Can be adjusted, and the structure can be simplified.

According to the third aspect of the present invention, in the exhaust gas purifying apparatus for an engine, the hook is a stopper when the catalyst valve is driven to the half-open position in the inactive region of the catalyst via the transmission gear via the catalyst valve drive means. The drive force from the catalyst valve drive means is not transmitted to the bypass valve and the opening degree of the catalyst valve can be adjusted independently of the bypass valve via a single step motor or the like. Can be simplified.

According to another aspect of the engine exhaust emission control device of the present invention, the catalyst valve shaft for rotatably supporting the catalyst valve and the bypass valve shaft for rotatably supporting the bypass valve are arranged on the same axis. The device can be downsized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a chamber and the like showing an embodiment of the present invention.

FIG. 2 is a side view of the chamber and the like.

FIG. 3 is a system diagram of an exhaust emission control device.

FIG. 4 is a cross-sectional view of a chamber and the like showing another embodiment.

FIG. 5 is a side view of the chamber and the like.

FIG. 6 is a system diagram of an exhaust gas purification device showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust passage 2 Pre-catalyst converter 3 Main catalytic converter 4 Bypass passage 5 Control unit 10 Exhaust manifold 11 Catalyst valve 12 Bypass valve 13 Catalyst valve shaft 14 Catalyst valve drive gear 15 Transmission gear 16 Pinion gear 17 Step motor 21 Catalyst passage 22 Bypass passage 23 Bypass Valve Shaft 24 Bypass Valve Drive Gear 25 Transmission Gear 26 Notch 27 Return Spring 30 Stopper 31 Hook

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikio Matsumoto 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd.

Claims (4)

[Claims] 1. A pre-catalyst converter and a main catalytic converter for exhaust purification installed in series in an exhaust passage, a catalyst passage for guiding exhaust gas to the pre-catalyst converter, and a catalyst valve rotatably interposed in the catalyst passage. A bypass passage for bypassing the pre-catalyst converter to guide the exhaust gas, a bypass valve rotatably installed in the bypass passage, a catalyst valve driving means for opening and closing the catalyst valve, and a bypass valve in the closing direction. A return spring that energizes, a transmission mechanism that opens the bypass valve in conjunction with the closing operation of the catalyst valve when the opening of the catalyst valve is smaller than a predetermined value, and closes the bypass valve in the inactive area of the catalyst. An exhaust emission control device for an engine, comprising: a control unit that adjusts the opening of a catalyst valve while the valve is open. 2. As the transmission mechanism, a transmission gear that rotates in conjunction with the opening / closing operation of the catalyst valve, a bypass valve drive gear that rotates in conjunction with the opening / closing operation of the bypass valve, and an opening degree of the catalyst valve of a predetermined value. The exhaust emission control device for an engine according to claim 1, further comprising: a notch formed by removing teeth that mesh with the transmission gear and the bypass valve drive gear in a smaller range. 3. The transmission mechanism includes a hook that rotates in conjunction with the opening / closing operation of a catalyst valve, and a hook that rotates in conjunction with the opening / closing operation of a bypass valve and that has a degree of opening of the catalyst valve smaller than a predetermined value. The engine exhaust gas purification apparatus according to claim 1, further comprising: a stopper that engages with the stopper. 4. The catalyst valve shaft for rotatably supporting the catalyst valve and the bypass valve shaft for rotatably supporting the bypass valve are arranged on the same axis. The exhaust gas purification device for an engine according to any one of the above.