JP2799207B2 - Engine valve timing control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing control device for an engine, and more particularly, to an activation of a catalytic converter provided near an exhaust manifold collecting portion and prevention of thermal deterioration. About what you did.

(Prior art)

2. Description of the Related Art Conventionally, in automobile engines, an exhaust system provided with a catalytic converter for purifying exhaust gas has been widely put into practical use. Recently, however, in order to improve purification performance by shortening the time required for activating the catalytic converter. It has also been proposed to provide a catalytic converter near the junction of the exhaust manifold.

After the engine is started, the catalytic converter is brought to the specified temperature (approximately 250
Until the temperature exceeds 300 ° C.), the catalyst is not activated, and the exhaust gas purification performance is significantly reduced. On the other hand, when the exhaust gas flow rate increases and the exhaust temperature rises in the high speed range, the catalytic converter becomes hot.However, to prevent thermal degradation of the catalytic converter, it is necessary to keep the exhaust temperature in the high speed range as low as possible. desirable.

By the way, in order to improve the intake performance of the engine, a variable valve timing mechanism that can change the closing timing of the intake valve is provided, and the closing timing of the intake valve is set later in the high rotation range than in the low rotation range. A control device has been put into practical use, and a variable valve timing mechanism that can change the opening timing of the exhaust valve has been provided to improve the exhaust performance of the engine. A valve timing control device that is set earlier is now in practical use.

Japanese Unexamined Utility Model Publication No. 61-58605 and Japanese Unexamined Patent Publication No. 1-247724 disclose, although not directly related to the above-described prior art, a variable valve timing mechanism and an intake / exhaust overlap according to the operating state of the engine. Techniques for controlling the amount are described.

[Problems to be solved by the invention]

The exhaust gas purification performance of the catalytic converter is low and the emission deteriorates until the temperature of the catalytic converter rises and becomes active after the engine is started.

The temperature drop of the exhaust gas in the exhaust pipe
Since the temperature is about 100 ° C per meter, when a catalytic converter is installed near the exhaust manifold, the thermal load of the catalytic converter in the high rotation range becomes extremely large.
Due to the thermal deterioration, the durability and purification capacity of the catalytic converter are significantly reduced.

In the conventional valve timing control device that switches the closing timing of the intake valve, the closing timing is advanced in the low rotation range, and the effective compression ratio is increased and the combustion speed is increased as compared with the case where the closing timing is delayed. The exhaust temperature is lowered. Therefore, there is a problem that the time required until the catalytic converter is activated becomes longer, and the emission becomes worse by the amount of time required.

In the conventional valve timing control device that switches the opening timing of the exhaust valve, the opening timing is delayed in a low rotation range, so that the exhaust gas temperature is lower than when the opening timing is advanced. Therefore, similarly to the above, there is a problem that the time required until the catalytic converter is activated becomes long, and the emission time deteriorates by the amount of time required.

SUMMARY OF THE INVENTION An object of the present invention is to provide an engine valve timing control device that can suppress thermal deterioration of a catalytic converter at a high rotation speed and a high load while activating the catalyst converter at a low rotation speed and a low load state. To provide.

[Means for solving the problem]

The engine valve timing control device according to claim 1,
Operating state detecting means for detecting the number of revolutions and load of the engine in an engine equipped with a catalytic converter provided near the collecting portion of the exhaust manifold, and a variable valve timing mechanism capable of changing the valve timing of the intake valve;
Receiving the output of the operating state detecting means, the closing timing of the intake valve is delayed to increase the exhaust gas temperature at least in the low load region of the low rotation region, and at least in the high load region of the high rotation region. And control means for controlling the variable valve timing mechanism so as to slow down the exhaust gas temperature.

The engine valve timing control device according to claim 2 is
The invention according to claim 1 is characterized in that the control means performs control for delaying the closing timing of the intake valve when the engine is in a low load range in a low rotation range during warm-up.

The engine valve timing control device according to claim 3 is
An operating state detecting means for detecting an engine speed and a load in an engine including a catalytic converter provided near a collection portion of an exhaust manifold and a variable valve timing mechanism capable of changing a valve timing of an exhaust valve;
In response to the output of the operating state detecting means, the variable valve timing mechanism is controlled so that the opening timing of the exhaust valve is advanced in order to increase the exhaust gas temperature at least in a low load region during a warm-up period when the engine is warmed up. And control means for performing the control.

The engine valve timing control device according to claim 4 is:
Operating state detecting means for detecting the number of revolutions and load of the engine in an engine equipped with a catalytic converter provided near the collecting portion of the exhaust manifold, and a variable valve timing mechanism capable of changing the valve timing of the intake valve;
Controlling the variable valve timing mechanism so as to delay the closing timing of the intake valve in order to increase the exhaust gas temperature at least in the low load range of the low rotation range during warm-up, receiving the output of the operating state detection means And control means for performing the control.

[Action]

In the engine valve timing control apparatus according to the first aspect, the control means controls the variable valve timing mechanism that changes the valve timing of the intake valve, and raises the exhaust gas temperature at least in a low load region in a low rotation range. Therefore, the valve timing is set so as to delay the closing timing of the intake valve, and to delay the closing timing of the intake valve in order to lower the exhaust gas temperature, at least in a high-load region at a high engine speed.

It is necessary to increase the temperature of the catalytic converter to promote its activation in the low rotation range and low load state after the engine is started.However, if the intake closing control is performed as described above, the effective compression ratio becomes small. When the load is low, the amount of residual gas is large, so that the combustion speed becomes slow and the exhaust gas temperature rises. Therefore, the activation of the catalytic converter can be promoted, and the exhaust gas purifying ability can be enhanced.

On the other hand, when the engine is in a high load state in a high rotation range, the residual gas amount is small, and the intake density is large, so that the combustion speed is high. As the temperature increases, the temperature of the exhaust gas decreases due to the promotion of the action for expansion and cooling. Therefore, the thermal load of the catalytic converter can be reduced, its durability can be improved, and a decrease in exhaust gas purification ability can be suppressed. In the valve timing control device for an engine according to the second aspect of the present invention, the control of delaying the closing timing of the intake valve during a low load region in a low rotational speed region during warm-up is performed. And enhance the exhaust gas purification ability.

In the valve timing control device for an engine according to the third aspect, the control means controls a variable valve timing mechanism capable of changing the valve timing of the exhaust valve. The valve timing is set so that the opening timing of the exhaust valve is advanced in order to raise the gas temperature.

If the exhaust valve opening timing is advanced at least in the low-medium rotation range during warm-up, the exhaust gas temperature will increase accordingly, so the catalyst converter's temperature rise rate after startup is increased, and the activation of the catalytic converter is promoted. Exhaust gas purification capacity can be increased.

In the valve timing control device for an engine according to the fourth aspect, the control means controls a valve timing mechanism capable of changing the valve timing of the intake valve. Since the closing timing of the intake valve is controlled to be delayed in order to increase the temperature, the activation of the catalytic converter at least during warm-up is promoted and the exhaust gas purification is performed, as described in the section of operation of claim 1. You can improve your ability.

〔The invention's effect〕

According to the first aspect of the present invention, as described in the above section, the activation of the catalytic converter after the start can be promoted to enhance the exhaust gas purification capability, and the high load state in the high rotation region can be achieved. In this case, the thermal load of the catalytic converter can be reduced, its durability can be improved, and a decrease in exhaust gas purification ability can be suppressed.

According to the second aspect of the present invention, the activation of the catalytic converter during warm-up can be promoted, and the exhaust gas purifying ability can be enhanced.

According to the third aspect of the present invention, as described in the above section, the activation of the catalytic converter during warm-up after the engine is started can be promoted, and the exhaust gas purifying ability can be enhanced.

According to the invention of claim 4, activation of the catalytic converter at least during warm-up can be promoted, and the exhaust gas purification ability can be enhanced.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

This embodiment is an example in which the present invention is applied to a valve timing control device of a V-type six-cylinder engine with a mechanical supercharger for an automobile.

As shown in FIG. 1, the left bank 1A and the right bank 1B of the engine E are each provided with three cylinders 2, and each cylinder 2 is provided with two intake valves 3 and two exhaust valves 4, bank
A camshaft 5 for driving the intake valves 3 and exhaust valves 4 of 1A and 1B is provided, and the pulleys 6 of these two camshafts 5 are linked to the crankshaft via a timing belt.

The intake passage 9 includes a common intake passage 10 and this common intake passage
A left bank intake passage 11A and a right bank intake passage 11B branching left and right from 10, and an independent intake passage branching from the left bank intake passage 11A to an intake port of each cylinder 2 of the left bank 1A.
12 and each cylinder 2 of the right bank 1B from the right bank intake passage 11B
An independent intake passage 12 branches to an intake port of the common intake passage 10, and an air cleaner 13 and an air flow meter 14 are provided in the common intake passage 10.
The throttle valves 16 are provided in the left and right bank intake passages 11A and 11B, and the left and right throttle valves 16 are connected to an accelerator pedal.

An intake control valve 17 is provided in each independent intake passage 12, and the three intake control valves 17 of the left bank 1A and the three intake control valves 17 of the right bank 1B are fixed to a common support shaft 18, respectively. Opening / closing is controlled by rotating the support shaft 18. The control valves 20 and 21 for variable intake are for increasing the intake filling rate by a resonance effect, and the control valve 20 is used in a predetermined low rotation range and the control valve 21 is used in a predetermined high rotation range by an actuator (not shown). It is being opened.

A left bank exhaust passage 23A extending from the exhaust manifold 22A of the left bank 1A and a right bank exhaust passage 23B extending from the exhaust manifold 22B of the right bank 1B are connected to a combined exhaust pipe 24.

A catalyst converter 15A is provided near the exhaust manifold 22A in the left bank exhaust passage 23A as a collection part of the exhaust manifold 22A, and the exhaust manifold 22B
A catalyst converter 15B is provided near the exhaust manifold 23B in the right bank exhaust passage 23B as an assembly part of.

A valve timing changing mechanism 30 for changing the valve timing of the intake valve 3 of each of the banks 1A and 1B is disclosed in Japanese Patent Application Laid-Open No. 1-2477.
Since it is similar to that described in Japanese Patent Publication No. 24, it will be briefly described.

2 and 3 show a valve timing changing mechanism 30 incorporated in the valve operating mechanism of the left bank 1A. A rocker for driving a pair of exhaust valves 4 is provided on a rocker shaft 7 on the left side of the cam shaft 6. An arm 31 is pivotally mounted, and a rocker arm 32 for driving a pair of intake valves 3 and an auxiliary rocker arm 33 are pivotally mounted on the rocker shaft 8 on the right side of the cam shaft 6, and a roller 31a at the tip of the rocker arm 31 is a cam. The roller 32a at the tip of the rocker arm 32 is in sliding contact with the first cam 6a of the cam shaft 6, and the roller 33a at the tip of the auxiliary rocker arm 33 is in contact with the second cam 6b of the cam shaft 6. Is in sliding contact.

A pair of cylinder holes 34 are formed over the pair of rocker arms 32 and the auxiliary rocker arm 33, and each cylinder hole 34
Inside, a pin 35 is slidably mounted in an oil-tight manner, and each pin 35 is urged toward an oil chamber 38 by a compression coil spring 37 via a receiving member 36, and a pair of oil chambers 38 are communicated. These oil chambers 38 are communicated with an oil passage 8a in the rocker shaft 8, oil pressure is supplied to the oil passage 8a from an oil pump 39 of the engine E via an oil passage 40, and the oil passage 40 is provided with an electromagnetic three-way valve. The electromagnetic three-way valve 41 is driven by a drive signal from the control unit 25.

When the electromagnetic three-way valve 41 is switched to the non-supply position, the oil pressure in the oil chamber 38 decreases, each pin 35 retreats toward the oil chamber 38, the auxiliary rocker arm 33 and the rocker arm 32 are separated, and the intake valve 3
Is driven to open and close via the first cam 6 a of the cam shaft 6 and the rocker arm 32. When the electromagnetic three-way valve 41 is switched to the supply position, hydraulic pressure is supplied to the oil chamber 38, and each pin 35 is switched to the position shown in FIG. 2, and the auxiliary rocker arm 33 and the pair of rocker arms 32 The intake valve 3 is interlocked and connected via 35, and is driven to open and close via the second cam 6b of the camshaft 6, the auxiliary rocker arm 33 and the rocker arm 32. The valve train of the right bank 1B is the same as that of the left bank 1A.

FIG. 4 shows the valve timings of the intake valve 3 and the exhaust valve 4. When the first cam 6a is selected, the intake valve 3
Theta ₁ crank angle after the closing timing BDC (e.g., theta ₁
≒ 50 °), the closing timing BDC after theta ₂ crank angle of the intake valve 3 when selecting the second cam 6b (e.g., theta ₂ ≒ 8
0 ゜), and the intake is lately closed.

Control unit for controlling the engine E
25, an air flow meter 14, a throttle opening sensor (not shown) for detecting the opening of the throttle valve 16, an idle switch 26, a crank angle sensor 29 provided in a distributor, and a reference crank angle sensor 2.
8, and other signals from various sensors and switches (not shown) are input to the control unit 25, and the control unit 25 sends the fuel to the ignition unit and the intake port of each cylinder 2 (not shown). ), A drive signal is output to the actuator 19, the electromagnetic three-way valve 41, and the like.

The control unit 25 includes a microcomputer having an input / output interface, a CPU (central processing unit), a ROM (read only memory) and a RAM (random access memory), and an intake air amount signal from the air flow meter 14. A / D converter for AD conversion, A / D for AD conversion of throttle opening signal from throttle valve opening sensor
It includes a converter, a drive circuit for an injector, a drive circuit for an ignition unit, a drive circuit for an actuator 19, a drive circuit for an electromagnetic three-way valve 41, and the like.

The ROM stores a control program for ignition timing control, a control program for fuel injection control, and a first program via an electromagnetic three-way valve 41.
A control program for valve timing switching control for switching the closing timing of the intake valve 3 by switching between the cam 6a and the second cam 6b, a map accompanying the program, and the intake control valve 17 via the actuator 19 when in the idle state. A control program for controlling the closing of the motor and various other control programs are input and stored in advance.

FIG. 6 shows the setting of an early closing region in which the intake valve 3 is closed early and a late closing region in which the intake valve 3 is closed late, using the engine speed and the load as parameters. Is preliminarily input and stored in the ROM as a map to be executed.

Since the control for switching the closing timing of the intake valve 3 is a simple control, a description will be given without using a flowchart. In the following description, the engine rotation is performed using the crank angle signal from the crank angle sensor 29 over the entire period during which the engine E is operating. Calculate the number,
The load is calculated from the amount of intake air read from the air flow meter 14 and the engine speed, and the operating state of the engine E is determined based on the engine speed and the load. The actuator 16 is controlled to select the first cam 6a when it is in the intake valve early closing area, and to select the second cam 6b when it is in the intake valve late closing area. Control.

On the other hand, regarding the control for the intake control valve 17, it is determined whether or not the engine is in the idle state based on signals from the idle switch 26, the neutral switch of the transmission, and the like. When the idle state is reached, the actuators of the left and right banks 1A and 1B are actuated.
The intake control valve 17 is switched from open to closed via 19. However,
Even if the intake control valve 17 is switched to the closed state, the intake air required for the idling operation flows.

Next, the operation of the valve timing control device for the engine will be described.

FIG. 5 shows the relationship between the closing timing of the intake valve 3 and the exhaust gas temperature. In the low rotation speed region, the exhaust temperature increases as the closing timing is slow, and in the high rotation speed region, the exhaust temperature increases as the closing timing is delayed. Temperature drops.

That is, in the low rotation range, the intake speed is low because the intake density is small and the residual gas is large, and if the intake valve closing timing is delayed, the effective compression ratio is reduced and the combustion speed is reduced. The later the valve closing timing, the higher the exhaust gas temperature. In the high rotation range, the intake speed is high because the intake density is large and the residual gas amount is small, and if the intake valve closing timing is delayed, the effective compression ratio decreases and the expansion ratio increases. The later the valve closing timing, the lower the exhaust gas temperature.

In the valve timing control device of the present embodiment, as shown in FIG. 6, the intake air is supplied at least when the engine E is warmed up and the catalyst converters 15A and 15B are activated at least in a low rotational speed region in a low load state. Since the valve closing timing is delayed, the exhaust gas temperature increases as described above, and the catalytic converter 15
The heating rate of A / 15B increases, and the catalytic converter 15A / 1
The time required for 5B to be activated at about 280 ° C. is reduced. Thus, the exhaust gas purifying performance when the catalytic converters 15A and 15B are activated can be enhanced, and the emission can be improved.

On the other hand, since the intake valve closing timing is delayed during low, medium, and high load conditions in the high rotation range, the exhaust temperature is reduced as described above, and the thermal load on the catalytic converters 15A and 15B is reduced, and the durability is improved. In addition, it is possible to suppress a decrease in exhaust gas purification performance.

In the case where a valve timing changing mechanism capable of switching the closing timing of the intake valve 3 to a plurality of stages of three or more or continuously and continuously can be provided, the intake valve closing timing has characteristics as shown in FIG. It is desirable to control
Note that a plurality of lines in FIG. 7 indicate equal closing timing lines having the same intake valve closing timing. Further, as the valve timing changing mechanism of the intake valve 3, various mechanisms other than those in the above embodiment can be used.

<Another embodiment> The above embodiment may be partially modified to be configured as follows. In the above-described embodiment, the valve timing of the intake valve 3 is configured to be changeable. In this embodiment, while the valve timing of the intake valve 3 is fixed, a mechanism corresponding to the valve timing change mechanism 30 is replaced with an exhaust valve of a valve mechanism. By providing the four drive systems, the opening timing of the exhaust valve 4 can be changed.

Figure 8 is shows the valve timing of the intake valve 4 and the intake valve 3, the opening timing of the exhaust valve 4 is when first select cam BDC before theta ₃ crank angle (e.g., theta ₃ ≒ 7
0 °), the opening timing BDC before theta ₄ crank angle of exhaust valve 4 when selecting the second cam (e.g., theta ₄ ≒ 100
゜) and the exhaust is quickly opened.

FIG. 10 shows the setting of an exhaust valve early opening region in which the exhaust valve 4 is opened earlier and an exhaust valve late opening region in which the exhaust valve 4 is opened later, using the engine speed and load as parameters. Is previously input and stored in the ROM as in the case of the map. Further, in the ROM, a valve timing switching control program for switching the opening timing of the exhaust valve 4 by switching between the first cam and the second cam via an electromagnetic three-way valve according to the operating state of the engine E is previously stored. Input is stored. This valve timing switching control is performed in substantially the same manner as the valve timing switching control of the above embodiment.

Next, the operation of the valve timing control device will be described.

FIG. 9 shows the relationship between the exhaust valve opening timing and the exhaust gas temperature. In the low rotation speed region, the exhaust gas temperature increases as the exhaust valve opening timing is advanced, whereas the high rotation speed particularly in the high rotation speed region In this state, the exhaust gas temperature does not always increase as the exhaust valve opening timing is advanced. That is, in this operating state, the exhaust gas temperature is often lowered because the exhaust gas flow rate becomes very large, and if the exhaust valve opening timing is advanced, the effective pumping time becomes longer, so that the exhaust pumping is reduced. .

In the valve timing control device of the present embodiment,
As shown in FIG. 10, the exhaust valve opening timing is advanced at least in the low-rotation region where the engine E is warmed up and the catalytic converters 15A and 15B are activated and the catalyst converters 15A and 15B are activated at least in a low load state. The exhaust gas temperature rises and the catalytic converter 15
The heating rate of A / 15B increases, and the catalytic converter 15A / 1
The time required for 5B to be activated at about 280 ° C. is reduced. Thus, the exhaust gas purifying performance when the catalytic converters 15A and 15B are activated can be enhanced, and the emission can be improved.

On the other hand, the exhaust valve opening timing is advanced when the load is low, medium, and high in the high rotation range, so the exhaust temperature is reduced as described above, the thermal load on the catalytic converters 15A and 15B is reduced, and the durability is improved. In addition, it is possible to suppress a decrease in exhaust gas purification performance.

When a valve timing changing mechanism capable of switching the opening timing of the exhaust valve 4 to three or more stages or continuously switching continuously is provided, the exhaust valve opening timing with the characteristics shown in FIG. It is desirable to control
Note that a plurality of lines in FIG. 11 indicate equal opening timing lines having the same exhaust valve opening timing. Further, as the valve timing changing mechanism of the exhaust valve 4, various mechanisms other than those in the above embodiment can be used.

It is needless to say that the present invention can be applied not only to the V-type six-cylinder but also to a vertical four-cylinder engine or to a supercharged engine.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is an overall configuration diagram of an engine and a valve timing control device thereof, FIG. 2 is a plan view of a valve timing changing mechanism incorporated in a valve operating mechanism, FIG. FIG. 4 is an explanatory view of a valve timing, FIG. 5 is a characteristic diagram of exhaust gas temperature, FIG. 6 is an explanatory view of an intake valve early closing region and an intake valve late closing region, 7 is a characteristic diagram of intake valve closing timing, FIGS. 8 to 11 relate to another embodiment, FIG. 8 is a diagram corresponding to FIG. 4, FIG. 9 is a characteristic diagram of exhaust temperature, FIG. FIG. 11 is an explanatory diagram of an exhaust valve early opening region and an exhaust valve late opening region, and FIG. 11 is a characteristic diagram of exhaust valve opening timing. E ... Engine, 14 ... Air flow meter, 15A / 15B ...
… Catalytic converter, 22A / 22B …… Exhaust manifold, 25
…… Control unit, 29 …… Crank angle sensor,
30 …… Valve timing change mechanism.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-120820 (JP, A) JP-A-63-297729 (JP, A) JP-A-3-54307 (JP, A) JP-A-3- 57883 (JP, A) JP-A-3-64648 (JP, A) JP-A-59-103910 (JP, A) JP-A-2-161154 (JP, A) JP-A-3-138443 (JP, A) Hira 3-99844 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 13/02 F01L 13/00 F01N 3/20

Claims (4)

(57) [Claims] 1. An operation for detecting an engine speed and a load in an engine provided with a catalytic converter provided near a collection portion of an exhaust manifold and a variable valve timing mechanism capable of changing a valve timing of an intake valve. Receiving the output of the operating state detecting means, the closing timing of the intake valve is delayed to increase the exhaust gas temperature at least when the engine is in the low load area in the low engine speed area, and at least the high timing in the high engine speed area is A valve timing control device for an engine, further comprising control means for controlling a variable valve timing mechanism so as to slow down the exhaust gas temperature in a load range in order to lower the temperature. 2. The engine valve according to claim 1, wherein the control means performs control to delay the closing timing of the intake valve when the engine is in a low load range in a low rotation range during warm-up. Timing control device. 3. An operation for detecting an engine speed and a load in an engine provided with a catalytic converter provided near a collecting portion of an exhaust manifold and a variable valve timing mechanism capable of changing a valve timing of an exhaust valve. Receiving the output of the state detecting means and the operating state detecting means, and changing the opening timing of the exhaust valve earlier in order to increase the exhaust gas temperature at least in a low load region of a low rotation range during warm-up. A valve timing control device for an engine, further comprising control means for controlling a valve timing mechanism. 4. An operation for detecting an engine speed and a load in an engine provided with a catalytic converter provided near a collection portion of an exhaust manifold and a variable valve timing mechanism capable of changing a valve timing of an intake valve. Receiving the output of the state detecting means and the operating state detecting means, and changing at least the closing timing of the intake valve in order to increase the exhaust gas temperature at least in the low load range of the low rotation range during warm-up. A valve timing control device for an engine, further comprising control means for controlling a valve timing mechanism.