JPH06323142A - Exhaust control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide an exhaust control device for an internal combustion engine wherein next time starting the engine is facilitated by resetting a valve for adjusting a characteristic in an exhaust system, when stopped the internal combustion engine, to a position suited for the time of starting the engine. CONSTITUTION:A valve 12, operated by an actuator 16 to adjust a characteristic in an exhaust system, is provided, and a position of the valve 12 is controlled in accordance with a rotational speed by a microcomputer 23 actuated with a permanent-magnet generator 4, mounted on internal combustion engine 1, serving as the power supply. By the microcomputer 23, an engine stop detecting means for detecting stopping the internal combustion engine and a valve resetting means for resetting the valve 12 to a position suited for the time of starting the engine by driving the actuator 16, when detected the internal combustion engine stopped, are realized, and the position of the valve 12 in the case of stopping the engine is reset to the position suited for the time of starting the engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust control device for an internal combustion engine, which controls the position of a valve provided for adjusting the characteristics of the exhaust system of the internal combustion engine according to the rotational speed.

[0002]

2. Description of the Related Art In an exhaust pipe of an internal combustion engine, pressure oscillation (compression wave) is generated along with the propagation of pressure applied from the cylinder side in the exhaust stroke. When the frequency of this vibration matches the natural vibration frequency of the exhaust pipe, the inside of the exhaust pipe becomes in a resonance state, and a standing wave is generated in the exhaust pipe. It is known that when a standing wave of pressure oscillation occurs in the exhaust pipe, the exhaust efficiency increases, and as a result, the air supply efficiency improves and the engine output improves. The area where the exhaust efficiency can be improved by the pressure vibration of the exhaust system is called the tuning rotation area.

In general, the natural vibration frequency of the exhaust system is determined by its mechanical structure. Therefore, in an engine that does not have a means for adjusting the natural vibration frequency of the exhaust system, only a part of the operating speed range is tuned to rotate. Region, and in this synchronized rotation region, exhaust efficiency becomes higher and air supply efficiency improves,
If it goes out of the synchronous rotation region, the exhaust efficiency will decrease and the air supply efficiency will deteriorate.

Therefore, in an internal combustion engine that requires a particularly high output, a valve for adjusting the characteristics of the exhaust system (exhaust characteristic adjusting valve) is provided, and the position of the valve is adjusted to the engine speed [rpm]. It has been attempted to improve the output of the engine by generating a plurality of tuning rotation regions in the use rotation speed region by improving the air supply efficiency in a wide rotation speed region.

FIGS. 5A and 5B conceptually show the structure of an exhaust system provided with a valve for adjusting the characteristics of the exhaust system. The example shown in (A) of the figure shows the configuration of an exhaust system that is often adopted in a two-cycle engine. In the figure, S is a cylinder of an internal combustion engine, and EX is an exhaust connected to an exhaust port of the cylinder. It is a tube. Exhaust pipe E shown
X is a straight portion e1 connected to the exhaust port of the cylinder in order from the inlet side to the outlet side, and a divergent portion e2 whose diameter gradually increases toward the exhaust port side.
A straight portion e3, a convergent portion e4 having a diameter that gradually decreases toward the exhaust port side, and a straight portion e5 connected to the exhaust port. In this example, the straight portion e1 on the inlet side of the exhaust pipe EX is provided with a valve a for adjusting the characteristics of the exhaust system by adjusting the opening cross-sectional area of the straight portion e1. When the valve a is not provided, the natural vibration frequency of the exhaust system shows a constant value determined by its mechanical structure. However, when the valve a is provided and the cross-sectional area of the inlet of the exhaust system is changed, the acoustic impedance of the exhaust system is changed. Changes, its natural vibration frequency changes. In the example of FIG. 5 (A), the valve a is squeezed and the straight portion e1
When the opening cross-sectional area of (1) is reduced, the natural vibration frequency for generating a standing wave becomes low, and when the valve a is opened and the opening cross-sectional area of the straight portion e1 is expanded, the natural vibration frequency becomes high. Therefore, in this case, the valve a is set to the rotational speed of the engine so that the valve a is throttled to reduce the natural vibration frequency in the low speed region of the engine and the valve a is opened to increase the natural vibration frequency in the high speed region of the engine. Control accordingly. In this case, the position of the valve a may be controlled so as to be continuously changed according to the rotation speed, but in practice, the engine rotation speed range is divided into, for example, a low speed range, a medium speed range and a high speed range. The valve opening is controlled stepwise so that each of these areas is set as a synchronized rotation area.

Next, in the example shown in FIG. 5B, the exhaust pipe E
A cavity (cavity resonator) CV is connected to X via a branch pipe b, and an exhaust characteristic adjusting valve a is attached to the branch pipe b. In this example, when the valve a is narrowed to reduce the opening cross-sectional area of the branch pipe b, the tuning rotation region shifts to the low speed side, and the valve a is opened to increase the opening cross-sectional area of the branch pipe b. The tuning rotation region shifts to the high speed side.

In order to adjust the vibration characteristics of the exhaust system, it is sufficient to adjust the acoustic impedance of the exhaust system, and the method of installing the valve is not limited to the above example.

Conventionally, since the exhaust control device as described above is operated by using the battery as a power source, it has been applied only to an internal combustion engine such as a vehicle equipped with the battery. However, recently, even in a vehicle or the like which is not equipped with a battery, it has been studied to perform exhaust control in order to improve the performance of the engine.

Therefore, in order to enable the exhaust control device to be applied to an internal combustion engine of a vehicle or the like which does not have a battery,
It has been proposed to drive an actuator that operates a valve for adjusting the characteristics of the exhaust system with the output of a magneto coil installed in a magneto generator attached to the engine.
Also, paying attention to the fact that only the output of the half cycle of the ignition power supply coil provided in the magnet generator is used to supply the ignition energy. Attempts have been made to construct a DC power supply using the output and to drive a control means such as a microcomputer with the output of the DC power supply.

[0010]

When an actuator for operating a valve for adjusting the characteristics of the exhaust system is driven by using a magnet generator as a power source, electric power for driving the actuator cannot be obtained when the engine is started. ,
The position of the exhaust characteristic adjusting valve when the engine is started is the position when the engine was stopped last time. Therefore, if the engine is stopped while the valve is in a position other than the position suitable for the starting rotation region, there is a problem that the air supply efficiency is reduced and the engine startability is deteriorated when the engine is started next time. .

An object of the present invention is to, when an actuator for operating an exhaust characteristic adjusting valve is driven by using a magnet generator as a power source, ensure that the valve is always in a position suitable for starting at the time of starting the engine. It is an object of the present invention to provide an exhaust control device for an internal combustion engine, which is capable of facilitating the starting of the engine.

[0012]

SUMMARY OF THE INVENTION The present invention is a valve for adjusting the characteristics of an exhaust system of an internal combustion engine, and an electric type that is driven by the output of a magneto generator attached to the internal combustion engine to operate the valve. The invention relates to an exhaust control device for an internal combustion engine, comprising: the actuator; and a valve control device for controlling the actuator according to the rotation speed of the internal combustion engine to adjust the valve position to a position adapted to each rotation speed of the engine. In the present invention, engine stop detection means for detecting the stop of the internal combustion engine, and when the engine stop detection means detects the stop of the internal combustion engine, the actuator is driven to return the valve to a position suitable for starting the engine. And a valve returning means for allowing the valve to return.

In the present invention, "detection of the stop of the internal combustion engine" means detecting that the internal combustion engine will soon stop, that is, predicting the stop when the internal combustion engine is in a rotating state. And detecting that the internal combustion engine is in a stopped state or in a state close to a stopped state.

Prediction of engine shutdown can be accomplished in a variety of ways. For example, in the case of an internal combustion engine in which the engine stop switch is operated when the engine is stopped, this can be done by detecting that the engine stop switch is operated. Further, in the case of an internal combustion engine that is designed to stop the internal combustion engine when an abnormality occurs in the engine, the stop of the engine can be predicted from the output of the sensor for detecting the abnormality. Further, the disappearance of the voltage (for example, the induced voltage of the primary coil of the ignition coil) that is periodically generated in the ignition device when the ignition operation is normally performed is detected (the engine is in a misfire state). It is possible to predict the stoppage of the engine also by detecting ().

A rotation speed detector (tachometer) is used to detect that the engine is in a stopped state or a state close to a stopped state.
Can be monitored or the primary induced voltage of the ignition coil of the internal combustion engine ignition device can be monitored.

[0016]

As described above, the engine stop detecting means for detecting the stop of the internal combustion engine, and the actuator driven when the stop of the internal combustion engine is detected by the engine stop detecting means to position the valve at a position suitable for starting the engine. If a valve returning means for returning to the internal combustion engine is provided, the valve position can be always returned to a position suitable for starting when the internal combustion engine is stopped, so that the next engine starting can be easily performed. it can.

[0017]

1 shows the overall construction of an embodiment of the present invention, in which 1 is an internal combustion engine having an intake pipe 2 and an exhaust pipe 3, and 4 is attached to an output shaft 1a of the internal combustion engine 1. It is a magnet generator composed of a magnet rotor 4A and a stator 4B attached to the case of the engine.

A throttle valve 5 is provided on the inlet side of the intake pipe 2.
The injector 6 is attached so as to inject fuel into a space (fuel injection space) on the downstream side of the throttle valve 5 in the intake pipe. The injector 6
It is equipped with a valve for opening and closing the injection port and an electromagnet for operating the valve. The injection command signal V is supplied to the control input terminal 6a.
While ij is given, the electromagnet is excited to open the valve.

A fuel pump 7 is composed of a pump motor (electric motor) 7A and a pump 7B driven by the motor. The suction port of the pump 7B is connected to a fuel tank 9 through a pipe 8.
The discharge port of the pump 7B is connected to the fuel supply port of the injector 6 via the pipe 10.

Reference numeral 11 denotes a pressure regulator connected between the fuel supply port of the injector 6 and the fuel tank 9, and this pressure regulator has a set value for the pressure of the fuel supplied to the fuel supply port of the injector 6. By returning a part of the fuel to the fuel tank 9 when it exceeds, the pressure (fuel pressure) of the fuel supplied to the injector 6 is kept constant.

When an injection command signal is given to the injector 6, the valve of the injector 6 opens, so that fuel is injected from the injection port into the intake pipe 2. The amount of fuel given to the engine is determined by the fuel pressure and the injection time. The time for giving the injection command signal to the injector 6 is controlled so that the mixed gas having the optimum air-fuel ratio is given into the cylinder of the engine at each rotational speed of the engine.

The exhaust pipe 3 is provided with a cavity 3A having a divergent part e2, a straight part e3 and a convergent part e4, and changes the opening cross-sectional area of the straight part e1 on the upstream side of the cavity 3A. Thus, the exhaust characteristic adjusting valve 12 is provided. The exhaust characteristic adjusting valve 12 of the present embodiment is a linear displacement type valve that moves in and out of the exhaust pipe 3 from a direction perpendicular to the axial direction of the exhaust pipe 3 to change the opening cross-sectional area of the exhaust pipe 3. The exhaust valve is driven by an actuator 16 including a rack 13 connected to the exhaust valve, a pinion 14 meshed with the rack, and an electric motor 15 that rotationally drives the pinion 14.

The exhaust characteristic adjusting valve 12 need not be of the linear displacement type, but may be of the rotary type.

At each rotational speed, a valve position sensor for detecting the position of the valve 12 and generating an electric signal (valve position detection signal) is provided in order to control the position of the valve 12 to match the target position. The actuator 16 is controlled so that the position of the exhaust valve detected by the valve position sensor matches the target position. Further, according to the present invention, a valve position detecting sensor at the time of starting (not shown) for detecting the position of the valve 12 at the time of starting.
Is provided and is detected by this sensor when the engine is stopped (valve position suitable for starting the engine)
The valve 12 is reset.

The valve position sensor may be a single position sensor (potentiometer or differential transformer) whose output changes in an analog manner according to the opening of the valve, and detects a plurality of valve positions. As described above, it may be an assembly of a plurality of position detection switches arranged side by side along the displacement direction of the valve. Alternatively, the position of the valve may be detected by counting the pulses obtained from a rotary encoder attached to the output shaft of the electric motor that is the drive source of the actuator.

In the present invention, the auxiliary generator driving power generation coil 4a common to the pump motor 7A and the actuator 16 is provided in the magnet generator 4, and the output of the auxiliary machinery driving power generation coil 4a is the power supply circuit. It is supplied to the pump motor 7 A via 17 and is supplied to the electric motor 15 of the actuator 16 via the valve drive circuit 18.

An ignition power supply coil 4b for supplying ignition energy to the ignition device for an internal combustion engine is also provided in the magnet generator 4, and a power generation coil for driving a lighting load or the like is further provided as necessary.

The positive half cycle output of the ignition power supply coil 4b is given to the ignition circuit 19 of the internal combustion engine ignition device, and the negative half cycle output of the ignition power supply coil 4b is supplied to the power supply circuit 2.
It is given to 0. Reference numeral 21 is a diode which constitutes a return path of current from the ignition circuit 19 to the ignition power supply coil 4b side, and 2
Reference numeral 2 is a diode that constitutes a return path of a current from the power supply circuit 20 to the ignition power supply coil 4b side.

The power supply circuit 20 is composed of a power supply capacitor charged by the negative half cycle output of the ignition power supply coil 4b, and a voltage adjusting circuit for maintaining the voltage across the power supply capacitor at a constant value. This power supply circuit is used as a power supply for the microcomputer 23 and the valve control circuit 24.

FIG. 2 shows a specific configuration example of the ignition circuit 20, the power supply circuit 17, the valve drive circuit 18, and the power supply circuit 20. The power supply circuit 17 of FIG.
From the full-wave rectifier 25 that rectifies the output of a, the smoothing power supply capacitor 26 that is connected between the output terminals of the rectifier 25, and the voltage regulator 27 that controls the voltage across the capacitor 26 to maintain a constant value. The DC voltage obtained across the capacitor 26 is applied to the pump motor 7A, and the actuator 16 is driven through the valve drive circuit 18.
Is being supplied to.

The voltage regulator 27 is, for example, a capacitor 2
When the voltage across both ends of 6 exceeds the rated value, the magneto coil 4a
Is short-circuited to lower the output voltage of the magneto coil 4a, and when the voltage across the capacitor 26 is below the rated value, the short circuit of the magneto coil 4a is released to recover the output voltage of the magneto coil 4a. The generator coil 4a so as to limit the voltage across the capacitor 26 to below the rated value.
Control the output voltage of.

The ignition circuit 20 is a known capacitor discharge type circuit, and the illustrated ignition circuit includes an ignition coil IG, an ignition energy storage capacitor C1 provided on the primary side of the ignition coil, and a charge of the capacitor C1. The ignition coil 1
A thyristor Th1 as a discharging switch for discharging the next coil, diodes D1 and D2 forming a charging circuit for charging the capacitor C1 with the positive half cycle output of the ignition power coil 4b, and a gate cathode of the thyristor Th1 are connected in parallel. A resistor R1 and a capacitor C2 connected to
An ignition plug P attached to a cylinder of an internal combustion engine and connected to a secondary coil of an ignition coil IG. The cathode of the thyristor Th1 is grounded together with one ends of the primary coil and the secondary coil of the ignition coil IG, and one end and the other end of the ignition power supply coil 4b are connected to the cathodes of the diodes 19 and 21 whose anodes are grounded, respectively.

In the above ignition circuit, when the ignition power supply coil 4b induces a positive half cycle voltage, the diodes D1 and D2 and the diode 19 are discharged from the ignition power supply coil 4b.
Capacitor C1 is charged to the polarity shown in the drawing through and.
When the ignition signal Vig is applied to the gate of the thyristor Th1 at the ignition timing of the internal combustion engine, the thyristor Th1 becomes conductive, and the electric charge of the capacitor C1 is discharged through the thyristor Th1 and the primary coil of the ignition coil IG. As a result, a high voltage is induced in the secondary coil of the ignition coil IG, and the engine is ignited.

The power supply circuit 22 includes a power supply capacitor C3 and a capacitor C3, which are charged to the illustrated polarity through a diode D3 by the negative half cycle output of the ignition power supply coil 4b.
Zener diode Z1 which conducts when the voltage across both ends of the capacitor reaches a set value, and a thyristor Th2 which conducts when a trigger signal is applied through the zener diode Z1 and bypasses the charging current of the capacitor C3 from the capacitor.
And a resistor R2 and a capacitor C4 connected between the gate and cathode of the thyristor Th2.

In this power supply circuit 22, the power supply capacitor C3 is charged to the polarity shown by the negative half cycle output voltage of the ignition power supply coil 4b. When the voltage across the capacitor C3 reaches the set value, the Zener diode Z1 becomes conductive, so the thyristor Th2 becomes conductive and the capacitor C3
Prevent filling. By these operations, a substantially constant DC voltage is obtained across the power supply capacitor C3. This DC voltage is given to the microcomputer 23 and the valve control circuit 24 as a power supply voltage.

The microcomputer 23 takes in the output of the signal generator SG that generates a signal at a predetermined rotation angle of the engine through the waveform shaping circuit 30, and outputs the signal generator SG.
The information about the rotation angle of the engine and the information about the rotation speed are obtained from the output of. The microcomputer 23 also includes an output of a valve position sensor 31 that detects the position of the valve 12 that adjusts the characteristics of the exhaust system, and a start position that detects that the position of the valve 12 has reached a position suitable for starting the engine. The output of the sensor 32 is given.

The microcomputer 23 calculates the ignition position by an interpolation method using a map that gives the relationship between each rotational speed and the ignition position (angle) of the engine, and ignites the thyristor Th1 of the ignition circuit 19 at the calculated ignition position. The signal Vig is given.

The microcomputer 23 also calculates the injection time at each rotation speed using a map giving the relationship between each rotation speed and the fuel injection time, and based on the rotation angle information obtained from the output of the signal generator SG. , An injection command signal Vij having a predetermined time width (injection time) is given to the injector 6 at a predetermined rotation angle position. The injector 6 injects fuel while the injection command signal is given.

The microcomputer 23 also supplies a valve drive signal Ve to the valve control circuit 24 according to the engine speed N. The valve control circuit 24 gives a predetermined trigger signal to the valve drive circuit 18 according to the drive signal Ve to operate the actuator 16.

FIG. 3 shows an example of the configuration of the valve drive circuit 18. This valve drive circuit 18 is composed of transistors Tr1 to Tr4 which are bridge-connected, and the valve control circuit 24 sends a trigger signal (transistor Tr1 to Tr4) to the transistors Tr1 to Tr4. Base current).

Now, as shown in FIG. 5, the position θ of the valve 12
With respect to the rotation speed N. In the figure, No is the starting rotation speed of the engine, and θo is the valve position suitable for starting. In this case, the microcomputer sends a valve drive signal Ve for instructing to move the valve 12 in the opening direction or the closing direction when it is detected that the rotation speed is in the range of N1 to N2 or N3 to N4. Give to 24. The valve control circuit 24 applies a trigger signal to the transistors Tr1 and Tr2 to rotate the electric motor 15 in the forward direction when a valve drive signal instructing to move the valve in the opening direction is supplied, and moves the valve 12 in the opening direction. Let When a valve drive signal Ve for instructing to move the valve in the closing direction is given, a trigger signal is given to the transistors Tr3 and Tr4 to reverse the electric motor 15 and move the valve 12 in the closing direction. The microcomputer stops the output of the valve drive signal Ve and stops the electric motor 15 when it is detected that the position of the valve 12 has reached the set position at each rotation speed.

In the present invention, when the engine stop is detected, the valve 12 is moved to the position θo suitable for starting the engine.
Return to. Therefore, an engine stop detection means for detecting the stop of the internal combustion engine, and a valve return for returning the valve to a position suitable for starting the engine by driving an actuator when the engine stop detection means detects the stop of the internal combustion engine Means are provided. These means can be realized by a microcomputer.

FIG. 4 is a flow chart showing the processing when the engine is stopped when the internal combustion engine is provided with a stop switch consisting of a push button switch. In this case, when the stop switch is pressed, the valve 12 is first returned to the position suitable for starting. After returning the position of the valve 12 to a position suitable for starting, the output of the injection command signal to the injector 6 is stopped to make the fuel injection amount zero, and the supply of the ignition signal Vig to the ignition circuit 19 is stopped. Extinguish the ignition spark.

In the flowchart shown in FIG. 4, the operation of stopping the engine (operation of making the fuel injection amount zero and extinguishing the ignition spark) is performed after the operation of returning the valve 12 to the position suitable for starting is performed. Although the engine is stopped, the engine does not stop immediately even if the operation to stop the engine is performed. For a while, the magnet generator 4 generates an output and continues to supply the power supply voltage to the microcomputer, and the engine stops. After that, since the power supply capacitor C3 continues to supply the power supply voltage to the microcomputer for a considerable time, after the operation of stopping the engine or the operation of stopping the engine, the operation of returning the position of the valve 12 is performed. You may do it.

In the flow chart of FIG. 4, the order of the process for reducing the fuel injection amount to zero and the process for extinguishing the ignition spark may be reversed.

Further, in the above embodiment, by detecting that the stop switch is pressed, the engine is predicted to stop, and a series of operations are performed. However, when the engine has stopped, Alternatively, the valve 12 may be returned to a position suitable for starting when it is detected that the engine is close to a stopped state.

In the above embodiment, since the valve position is controlled by using the microcomputer, the valve returning means is realized by using the microcomputer.
The valve return means can also be configured when controlling the valve position using an analog circuit.

In order to control the valve position using the analog circuit, for example, a valve position setting signal which gives the valve setting position in each rotation speed region of the starting region, the low speed region, the medium speed region and the high speed region is generated. Then, select one of the valve position setting signals according to the rotation speed, and match the output of the valve position sensor that detects each instantaneous valve position with the selected valve position setting signal. It suffices to control the actuator in such a way as to control the actuator. When a control circuit using such an analog circuit is used, a valve position setting signal that gives the position of the valve in the starting region is selected when the stop of the engine is detected, and the output of the valve position sensor is selected. The valve returning means can be realized by a circuit that controls the actuator so as to match the position setting signal.

[0049]

As described above, according to the present invention, when the stop of the engine is detected, the valve for adjusting the characteristics of the exhaust system is returned to the position suitable for starting the engine. Even when the exhaust control device is driven by the output of the magnet generator without using the engine, there is an advantage that the engine can always be easily started.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an overall configuration of an exemplary embodiment of the present invention.

FIG. 2 is a circuit diagram showing an electrical configuration example of a main part of the embodiment of FIG.

3 is a circuit diagram showing a configuration of a valve control circuit and a valve drive circuit used in the embodiment of FIG.

FIG. 4 is a flowchart showing an algorithm of a series of processing performed when the engine is stopped in the embodiment of the present invention.

5A and 5B are configuration diagrams conceptually showing configuration examples of different exhaust systems.

FIG. 6 is a diagram showing an example of changes in valve position with respect to rotation speed.

[Explanation of symbols]

 1 Internal Combustion Engine 3 Exhaust Pipe 6 Injector 7 Fuel Pump 12 Exhaust Characteristic Control Valve 16 Actuator 17 Power Supply Circuit 18 Valve Drive Circuit 19 Ignition Circuit 20 Power Supply Circuit 23 Microcomputer 24 Valve Control Circuit

Claims (1)

[Claims] 1. A valve for adjusting a characteristic of an exhaust system of an internal combustion engine, an electric actuator driven by an output of a magneto generator attached to the internal combustion engine to operate the valve, and a rotation of the internal combustion engine. An exhaust gas control device for an internal combustion engine, comprising: a valve control device that controls the position of the valve to a position adapted to each rotational speed of the engine by controlling the actuator according to the speed; A stop detection means; and a valve return means for returning the valve to a position suitable for starting the engine by driving the actuator when the stoppage of the internal combustion engine is detected by the engine stop detection means. An exhaust control device for an internal combustion engine.