JPS6115249B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exhaust gas control actuator, and in particular to an exhaust gas control actuator for an automobile internal combustion engine (hereinafter referred to as an engine) that uses a three-way catalytic converter. ) relates to an improvement in an exhaust gas control actuator suitable for controlling the air-fuel ratio of exhaust gas flowing into the catalyst within a certain range.

[Conventional technology and its problems]

Generally, in the gases exhausted from the engine.
In order to reduce HC, CO and NOx at the same time,
It is known that it is necessary to maintain the air-fuel ratio of exhaust gas flowing into a three-way catalytic converter provided in the exhaust system within a narrow range around the stoichiometric air-fuel ratio. Therefore, the air-fuel ratio of the carburetor in the engine's intake system is set to be richer than the stoichiometric air-fuel ratio, and secondary air is supplied to the exhaust system manifold from an air pump or air suction valve, and then passed through the downstream exhaust pipe. Oxygen concentration detector (hereinafter referred to as oxygen concentration detector) installed at the entrance of the three-way catalytic converter
If feedback is given to the secondary air supply amount control to keep the exhaust air-fuel ratio of the gas flowing into the three-way catalyst within a narrow range centered on the stoichiometric air-fuel ratio based on the signal from the _O2 sensor, HC in the exhaust gas, It is possible to simultaneously reduce CO and NOx and improve vehicle power performance.

However, in the conventional secondary air supply system to the exhaust system, there are problems such as difficulty in ensuring the durability of the catalyst due to the influence of the output characteristics of the O ₂ sensor, as described below.

In other words, in the exhaust system, secondary air is supplied and the apparent air-fuel ratio is adjusted to the stoichiometric air-fuel ratio, and the exhaust that comes out when the mixture at the stoichiometric air-fuel ratio is combusted in the engine has the same air-fuel ratio. However, the composition of the exhaust gas is different, with the former exhaust containing more H ₂ ,
The concentration of CO, O ₂ increases. In addition, O ₂ sensors that use zirconia (ZrO ₂ ) are affected not only by O ₂ concentration, but also by H ₂ and CO, especially H ₂ concentration, and the air-fuel ratio when the electromotive force suddenly rises is leaner than the stoichiometric air-fuel ratio. It's starting to shift to the side. Therefore, the signal change point of the O ₂ sensor installed in the exhaust system that is supplied with secondary air exhibits an output characteristic that shifts to the leaner side than the stoichiometric air-fuel ratio.

In addition, since the catalyst has some O ₂ storage effect, the exhaust air-fuel ratio will be ± around the stoichiometric air-fuel ratio.
Even if the ratio fluctuates by about 0.5, it is possible to simultaneously purify HC, CO, and NOx at a high purification rate, similar to exhaust gas at the stoichiometric air-fuel ratio, but when the H ₂ , CO, and HC concentrations in the exhaust composition are high The average operating temperature of the catalyst increases. Therefore, this causes a problem of catalyst overheating during long-term high-load operation, and the carrier supporting the catalyst,
Care must be taken to protect containers, etc. from overheating.

Furthermore, three-way catalysts are durable under conditions of use where they are constantly exposed alternately to reducing atmospheres (rich exhaust gas) and oxidizing atmospheres (lean exhaust gases), and their purification performance does not deteriorate much; As the rate of exposure to the atmosphere increases, durability decreases,
The deterioration of purification performance accelerates, and the durability generally decreases to about tens of thousands of kilometers in terms of mileage. As described above, the lean shift of the O ₂ sensor signal change point increases the exposure of the catalyst to the oxidizing atmosphere, and also causes the operating temperature to increase when the exhaust gas at the normal stoichiometric air-fuel ratio increases due to heat generation due to oxidation. Coupled with the fact that it is higher than in the case of treatment, it becomes even more difficult to ensure the durability of the catalyst.

In addition, the response speed when an O ₂ sensor is installed in the exhaust system is as follows: when the air-fuel ratio becomes larger than the stoichiometric air-fuel ratio and the transition occurs from a rich signal indicating that the fuel is rich to a lean signal indicating that the fuel is lean, time T is plotted on the horizontal axis. As shown in characteristic line A in Figure 1, where the output voltage V of the O ₂ sensor is plotted on the vertical axis, it shows a gradual falling characteristic.
On the contrary, a sharp rise characteristic as shown by characteristic line B is shown. In other words, the time delay characteristics of the O ₂ sensor vary depending on the switching direction of the output signal, but in order to accurately control the air-fuel ratio of the catalyst-containing gas around the stoichiometric air-fuel ratio, it is necessary to Adjust the control amplitude centered on the air-fuel ratio to the + side and -
It is desirable to set the range to be as small as possible.

Furthermore, in such a secondary air control system, the following requirements are made from the aspect of engine operation. In other words, in order to meet the output requirements without increasing the engine capacity of the vehicle, reduce the weight of the vehicle, and improve fuel efficiency, the air-fuel ratio of the carburetor is set to, for example, about 12.5 to 11.5 when the vehicle accelerates or has high output. It is desirable to make it as rich as possible. In addition, if an air pump whose supply amount is proportional to the engine speed is used as the secondary air supply surface, the secondary air supply amount will be adjusted in response to changes in the intake air amount of the engine even when the engine speed is constant. Furthermore, it is desired to purify the exhaust gas by controlling the secondary air supply amount as quickly and appropriately as possible in various engine situations such as when the engine is started in a cold state with insufficient warming up. Furthermore, if the catalyst overheats due to high-load, long-term operation, etc., the supply of secondary air should be stopped to protect the catalyst, or if there is a risk of catalyst overheating due to engine braking from high-speed driving, etc. It is desirable to lower the catalyst bed temperature and easily realize catalyst protection by fully opening the supply of secondary air or by stopping the supply of secondary air.

In order to satisfy the above requirements, the applicant has already proposed an exhaust gas control actuator as disclosed in Japanese Patent Application Laid-Open No. 121323/1983. this is,
As shown in FIGS. 2 and 3, the O ₂ sensor 14 provided in the exhaust pipe 12 of the engine 10
A three-way catalytic converter 18 downstream of the exhaust system controls the amount of secondary air supplied to the secondary air supply port 16 connected to the exhaust port of the engine 10.
An exhaust gas control actuator 20 that maintains the air-fuel ratio of exhaust gas flowing into the exhaust gas within a certain range,
It has a flow control valve 22 and a flow control device 24 that controls the flow control valve 22.
is provided with a valve body 26, an inflow port 30 that communicates with an air pump 28, an outflow port 34 that communicates with an exhaust manifold 32, and a bypass port 38 that communicates with an air cleaner 36. A negative pressure is communicated to the intake manifold 44 by an electromagnetic on-off valve 43 that is partitioned by a diaphragm 40 that operates the valve body 26 and is operated by an electronic control circuit 42 in response to the output signal of the O ₂ sensor 14. A working chamber 50 is provided with an inlet 46 and an atmosphere inlet 48 that is constantly communicated with the atmosphere, and an O ₂
A nozzle flapper mechanism is provided that changes the flow resistance of the negative pressure inlet 46 and the atmosphere inlet 48 in accordance with the operating position of the valve body so as to provide negative feedback of the output signal of the sensor 14 to the secondary air supply amount. The nozzle flapper mechanism is supported by the control core 52 through a support 54 and a control core 52 that moves in connection with the valve body 26 of the flow control valve 22 and whose axis can be tilted within its movement range, and is supported by the control core 52 through a support 54. The axis of the control core 52 is controlled by a flapper 56 disposed between the port 46 and the atmosphere inlet 48, and a lock coil 57 connected to the flapper 56 and energized by the electronic control circuit 42 in accordance with the output signal of the O ₂ sensor 14. The armature 5 is attracted to the side and controls the operating state of the flapper 56.
8 is disclosed. In the figure, 70 is a carburetor, 72 is an air cleaner 3
6 is an air inlet pipe that introduces air into the air pump 28; 74 is an air inlet pipe that allows air sent out by the air pump 28 to flow into the inlet port 30 of the flow control valve 22 of the exhaust gas control actuator 20; 76 is a flow control pipe; The secondary air flowing out from the outflow port 34 of the valve 22 is transferred to the secondary air supply port 16.
78 is a bypass conduit for returning excess air discharged from the bypass port 38 of the flow control valve 22 to the air cleaner 36; 82 and 84 are led out from the intake manifold 44; Negative pressure is applied via the electromagnetic on-off valve 43,
A negative pressure conduit 86 feeding the flow control device 24 is
A valve body 88 and a diaphragm 8 directly connect the inflow port 30 of the flow control valve 22 and the bypass port 38.
9, a communication passage 100 in which a negative pressure control valve 87 having an atmospheric chamber 90, a negative pressure chamber 92 connected to the intake manifold 44, and a compression spring 94 is disposed;
is a rod connecting the valve body 26 of the flow control valve 22 and the diaphragm 40 of the flow control device 24;
102 is an atmospheric chamber formed on the lower side of the diaphragm 40; 104 is a plate that is fixed to the upper surface of the diaphragm 40 and forms a sliding surface with the control core 52; 106 and 108 are respectively attached to the control core 52 A stay for supporting the upper and lower ends of the housing 110 of the flow control device 24; 112 is a compression spring for urging the control core 52 downward; 114 is an adjustment stay for supporting the upper end of the compression spring 112; 118 is a leaf spring that biases the middle part of the flapper 56 upward; 120 is a spring plate whose vertical position can be adjusted by a screw 116; A fulcrum screw 122 is used to adjust the gap between the arms, a fixed spring biases the left side of the armature 58 in a direction in which it comes into close contact with the flapper 56, and 124 is a filter. The electronic control circuit 42 also includes a comparator 42 that compares the output of the O ₂ sensor 14 and the output of the reference voltage source 42a.
b, and a timer circuit 42C. Furthermore,
The electromagnetic on-off valve 43 includes a solenoid 43 that is energized by the output of the electronic control circuit 42, and a plunger 43b that is attracted by the solenoid 43a.
, a valve body 43C fixed to the lower end of the plunger 43b, and a compression spring 43d that urges the valve body 43C downward in the figure.

According to such an exhaust gas control actuator, when the lock coil 57 is de-energized and the flapper 56 and control core 52 are disconnected, the amount of secondary air supplied is adjusted according to the output request from the engine. It is possible to control in a wide range from the maximum to the minimum, and on the other hand, when the lock coil 57 is energized and the control core 52 and flapper 56 are connected by magnetic force, the rotational position of the axis of the control core 52, i.e. Since the vertical position of the diaphragm 40 is controlled by the nozzle flapper mechanism formed by the flapper 56, the gap between the negative pressure inlet 46 and the atmosphere inlet 48, the position of the diaphragm 40 in the vertical direction is a minute amount during steady operation of the engine. The control amplitude of the air supply amount is maintained within a narrow range. However, in this exhaust gas control actuator, not only is the configuration complicated, but also the axis of the control core 52 is inclined, so that the plate 104 of the diaphragm 40 and the lower end of the control core 52 come into sliding contact. Therefore, the sticking phenomenon is likely to occur, and there are problems with reduced reliability such as variations in durability, responsiveness, and control width.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional art, and it is possible to obtain the required characteristics with a simple configuration, and furthermore, the control core moves linearly in the axial direction of the control core, so that it does not cause the sticking phenomenon, etc. The purpose is to provide an exhaust gas control actuator without any exhaust gas control actuator.

In order to achieve this objective, the exhaust gas control actuator of the present invention provides a
a flow rate control valve disposed in the air supply flow path; an oxygen concentration detector that detects the oxygen concentration in the exhaust gas;
It has a diaphragm that operates the valve body of the flow rate control valve, a negative pressure inlet and an atmosphere inlet are provided in the working chamber partitioned by the diaphragm, and the flow rate control valve operates in accordance with the output signal of the oxygen concentration detector. a flow control device provided with a nozzle flapper mechanism that changes the flow resistance of the air inlet port in conjunction with the position of the valve body, the nozzle flapper mechanism being in contact with the diaphragm and interlocking with the valve body of the flow rate control valve; a control core supported so as to be movable linearly in the same direction as the valve body, and a distal end slidably fitted into the control core and extending substantially perpendicular to the axis of the control core. The tip is disposed opposite to the air inlet, and when connected to the control core, the tip is displaced to change the flow resistance of the air inlet, while when not connected, the tip is disposed opposite to the air inlet. a flapper held with a predetermined gap therebetween; a magnetic force concentration means provided between the flapper and the control core; and a flapper arranged around the control core, which is energized when the oxygen concentration detector detects a rich state. and a lock coil that concentrates magnetic force on a part of the flapper and electromagnetically connects it to the control core.

According to the above configuration, during normal operation, when the oxygen concentration detector detects a lean state, the lock coil is cut off, the control core and flapper are disconnected, and only the control core is interlocked with the valve body. At the same time, negative pressure is introduced into the working chamber, so the diaphragm operates the valve body in a direction that reduces the flow area of the flow control valve, thereby reducing the amount of secondary air. On the other hand, when the oxygen concentration detector detects a rich state, the lock coil is energized, and the magnetic flux density increases locally between the control core and the flapper due to the magnetic force concentration means, and the flapper is strongly attracted to the control core and integrated. be converted into At the same time, since the introduction of negative pressure is cut off, air is introduced into the working chamber from the air inlet. Then, the diaphragm operates the valve body in the direction of increasing the flow area, which is opposite to that when negative pressure is applied, and increases the amount of secondary air. At this time, the control core is displaced in conjunction with the valve body, but the amount of displacement is limited by the distance between the tip of the flapper and the atmosphere inlet. That is,
As the valve body moves in the direction of increasing flow rate, the control core also moves linearly. When the control core is displaced to a position where the tip of the flapper closes the air inlet, the flow resistance of the air inlet becomes large, blocking the introduction of air, and the valve body is held at that position.

In this way, since the control core moves linearly in the axial direction when the amount of secondary air is controlled by the amount of displacement of the flapper, slippage does not occur at the contact area between the lower end of the control core and the diaphragm. The movement of the valve body is reliably transmitted to the flapper via the control core. Therefore, since the exhaust system is supplied with an amount of secondary air proportional to the amount of displacement of the flapper in accordance with the output of the oxygen concentration detector, the air-fuel ratio is optimally controlled within a certain range.

Embodiments of the present invention will be described in detail below with reference to the drawings. The exhaust gas control actuator 200 according to this embodiment includes a flow rate control valve 22 and a flow rate control device 202, as shown in FIG.

The flow rate control valve 22 is the same as that of the conventional example, so the same symbol will be given and the explanation will be omitted.

On the other hand, the flow rate control device 202 is connected to the lower housing 2
A diaphragm 40 is provided on the inner lower end side of the 04. This diaphragm 40 has a support rod 100 for the valve body 26 of the flow control valve 22 provided on its lower surface, and a spring receiver 2 provided on its upper surface.
06, the diaphragm 40 is
It is urged downward in the figure by a compression spring 208. Further, the lower housing 204 is divided by the diaphragm 40 into a lower working chamber 210 and an atmospheric chamber 90 which is constantly communicated with the atmosphere. An upper working chamber 212 is provided in the upper part of the lower housing 204.
An upper housing 214 is fixed, and an upper working chamber 212 in the upper housing 214 and a lower working chamber 210 in the lower housing 204 communicate with each other through a communication port 216. A control core 218 is disposed inside the upper housing 214 and whose upper and lower ends are supported by the upper housing 214 so as to be slidable in the vertical direction. A spring receiver 220 is fixed to the upper end of the control core 218, and the control core 2
The lower end of 18 is urged downward so as to come into contact with diaphragm 40 . control core 218
Around the electronic control circuit 4 similar to the conventional example
A lock coil 226 is provided which is energized and controlled by the lock coil 226. Further, a negative pressure inlet 228 through which intake negative pressure is introduced via an electromagnetic on-off valve 43 similar to the conventional one is provided in the middle part of the upper housing 214 in a direction perpendicular to the axial direction of the control core 218. Further, an atmosphere inlet 232 that constantly introduces the atmosphere through a filter 230 is formed in the upper part of the upper housing 214 in an upward direction parallel to the axial direction of the control core 218.
Further, a flapper 234 is disposed near the air inlet 232, the tip of which is perpendicular to the air inlet 232, and the center of which is slidably supported by the control core 218. This flapper 234 is always urged upward in the figure by a compression spring 236.

Further, as shown in detail in FIG. 5, a crescent-shaped shim 238 made of a non-magnetic material is inserted between the central part of the flapper 234 and the control core 218, and is made of a magnetic material. The apparent magnetic permeability of the flapper 234 is partially changed so that the magnetic force generated by the lock coil 226 is concentrated on one side, thereby increasing the coupling force between the control core 218 and the flapper 234. Note that the shape of the shim 238 is not limited to the crescent shape, but may be approximately C-shaped with a rectangular recess as shown in FIG.

The specific configuration of the electromagnetic on-off valve 43 that introduces the intake negative pressure of the intake manifold into the negative pressure inlet 228, and the electronic control circuit 42 that controls the energization state of the electromagnetic on-off valve 43 and the energization state of the lock coil 226 is as described above. Since this is the same as the example, the explanation will be omitted.

The action will be explained below. When the engine has reached a steady operating state, if it is necessary to reduce the amount of secondary air, the electronic control circuit 42 de-energizes the lock coil 226 and connects the control core 218 and flapper 234. Release. Then, the diaphragm 40 is sucked upward in the figure by the intake negative pressure supplied from the electromagnetic on-off valve 43 to the working chamber 212 through the negative pressure inlet 228 against the compression spring 208, and the control core 226 and the slave The valve body 26 is connected to the O ₂ sensor 14
Move to the upper position until a leaner signal is received to reduce the flow rate of secondary air.

On the other hand, when the flow rate is increased in the same steady operating state, the electronic control circuit 42 energizes the lock coil 226, so that the control core 218 and flapper 234 are brought together by magnetic force. At this time, since the electromagnetic on-off valve 43 is turned off by the electronic control circuit 42, the negative pressure inlet 228
No negative pressure is introduced into the chamber, and only atmospheric air is supplied from the atmospheric air inlet 232 via the filter 230. Therefore, the action of the compression springs 208 and 224 causes the control core 218 to close to the atmosphere inlet 2.
32 and the tip of the flapper 234 to close the atmosphere inlet 232 and prevent the control core 218 from descending. This series of movements moves the valve body 26 through the diaphragm 40 and the rod 100.
The flow rate increases by the stroke corresponding to the gap L. By the above-mentioned movements, the control width of the flow rate in the steady operating state of the engine is set to L.
It is possible to control the control amplitude of the secondary air supply amount within a narrow range and improve control accuracy.

On the other hand, when load responsiveness is required in which the amount of secondary air supplied quickly changes in response to changes in the amount of intake air of the engine, the lock coil 226 is controlled by the electronic control circuit 42 in the same way as in the conventional example.
The time is controlled so that the lock is released when the energization time exceeds a certain level.
Able to achieve purpose.

In the embodiment described above, the shim 238 made of a non-magnetic material was used to increase the coupling force between the control core 218 and the flapper 234, but the magnetic force concentration means is not limited to this. For example, as in the other variations shown in FIGS. 7 and 8,
It is also possible to form a coating 240 made of a nonmagnetic material on the half circumferential surface of the flapper 234 by copper plating or the like, or to form a thin film made of a nonmagnetic material by fixing a copper plate.

〔Effect of the invention〕

As described above, according to the present invention, the control core is supported to be movable linearly with respect to the axis, and the flapper is slidably fitted to the control core and supported so as to be electromagnetically coupled. Since the flapper is connected to the control core with strong adsorption force, the nozzle flapper function is not deteriorated due to vibration, and the flapper displacement position is always maintained in a constant relationship with respect to the valve body displacement position, so the control waveform is The variation in 2 is eliminated and stable 2
Next, the flow rate of air can be controlled. Also,
The flapper mechanism has a simplified structure with a reduced number of parts, which greatly improves assembly work efficiency, and the working chamber can be made smaller, allowing the pressure in the working chamber to rise and fall quickly. , the responsiveness of the diaphragm can be improved.

[Brief explanation of the drawing]

Fig. 1 is a line diagram showing the time output characteristics of the oxygen concentration detector, Fig. 2 is a partially cross-sectional system piping diagram showing the secondary air supply system to which the exhaust gas control actuator is applied, and Fig. 3 is a diagram showing the time output characteristics of the oxygen concentration detector. 4 is a partially cross-sectional system piping diagram showing a conventional example of an exhaust gas control actuator already proposed by the applicant; FIG. 4 is a sectional view showing an embodiment of the exhaust gas control actuator according to the present invention; FIG. 5 is a sectional view taken along line V-V in FIG. 4, FIG. 6 is a sectional view showing a modification of the shim for connecting the flapper and control core, and FIG. 7 is a sectional view showing the connection between the flapper and the control core. FIG. 8 is a longitudinal sectional view showing another modification of the section, and is a sectional view taken along the - line in FIG. 7. 10...Engine, 12...Exhaust pipe, 14...
O ₂ sensor, 18...Three-way catalytic converter, 22
...Flow control valve, 28...Air pump, 32...
Exhaust manifold, 36...Air cleaner, 40
...Diaphragm, 42...Electronic control circuit, 43
... Solenoid on-off valve, 44 ... Intake manifold, 7
0... Carburetor, 200... Exhaust gas control actuator, 202... Flow rate control device, 204,
214...Housing, 210, 212...Working chamber, 218...Control core, 226...Lock coil, 228...Negative pressure inlet, 232...
Air inlet, 234... flapper, 236... compression spring.

Claims (1)

[Claims] 1 A flow control valve disposed in a secondary air supply flow path to an exhaust system of an internal combustion engine, an oxygen concentration detector that detects the oxygen concentration in exhaust gas, and a diaphragm that operates the valve body of the flow control valve. A negative pressure inlet and an atmosphere inlet are provided in the working chamber partitioned by the diaphragm, and a flow resistance of the atmosphere inlet is adjusted to the valve body position in accordance with the output signal of the oxygen concentration detector. a flow rate control device provided with a nozzle flapper mechanism that changes the flow rate in conjunction with the flow rate control valve; a control core movably supported by the control core; and a tip slidably fitted into the control core and extending substantially perpendicularly to the axis of the control core, the tip being connected to the atmosphere inlet. Flappers are arranged facing each other, and when connected to the control core, displace the tip to change the flow resistance of the air inlet, and when unconnected, are held with a predetermined gap between them and the air inlet. , a magnetic force concentration means provided between the flapper and the control core; and a magnetic force concentration means arranged around the control core, which is energized when the oxygen concentration detector detects a rich state and concentrates the magnetic force on a part of the flapper. An exhaust gas control actuator consisting of a lock coil that is electromagnetically connected to a control core.