JP3147585B2 - Exhaust control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust control system 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 in accordance with the rotational speed.

[0002]

2. Description of the Related Art In an exhaust pipe of an internal combustion engine, pressure oscillations (compression waves) occur in the exhaust stroke with the propagation of pressure applied from the cylinder side. When the frequency of this vibration matches the vibration frequency inherent in the exhaust pipe, the interior of the exhaust pipe resonates and a standing wave is generated in the exhaust pipe. It is known that when a standing wave of pressure vibration occurs in the exhaust pipe, the exhaust efficiency increases, and as a result, the air supply efficiency improves and the output of the engine improves. A region in which the exhaust efficiency can be improved by the pressure oscillation of the exhaust system is called a tuning rotation region.

[0003] In general, since the natural vibration frequency of the exhaust system is determined by its mechanical configuration, in an engine having no means for adjusting the natural vibration frequency of the exhaust system, only a part of the operating rotational speed region is tuned. In this synchronized rotation region, the exhaust efficiency increases and the air supply efficiency improves,
Outside the tuning rotation region, the exhaust efficiency is reduced, and the air supply efficiency is deteriorated.

Therefore, in an internal combustion engine requiring particularly high output, a valve (exhaust characteristic adjusting valve) for adjusting the characteristics of the exhaust system is provided, and the position of the valve is adjusted to the rotational speed [rpm] of the engine. Attempts have been made to generate a plurality of synchronous rotation regions in the operating rotation speed region by controlling the rotation speed in accordance with the rotation speed, thereby improving the air supply efficiency in a wide rotation speed region and improving the output of the engine.

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 FIG. 1A shows the configuration of an exhaust system that is often employed in a two-stroke engine. In FIG. 2A, S is a cylinder of an internal combustion engine, and EX is an exhaust gas connected to an exhaust port of the cylinder. Tube. Exhaust pipe E shown
X is, in order from the entrance side to the exit side, a straight portion e1 connected to the exhaust port of the cylinder, and a divergent portion e2 whose diameter gradually increases toward the exhaust port side.
, A straight portion e3, a convergent portion e4 whose diameter gradually decreases toward the exhaust port, and a straight portion e5 connected to the exhaust port. In this example, a valve a for adjusting the characteristics of the exhaust system by adjusting the cross-sectional area of the opening of the straight part e1 is provided in the straight part e1 on the inlet side of the exhaust pipe EX. When the valve a is not provided, the natural vibration frequency of the exhaust system shows a constant value determined by the mechanical configuration. However, when the valve a is provided and the cross-sectional area of the entrance of the exhaust system is changed, the acoustic impedance of the exhaust system is changed. Changes, the natural vibration frequency changes. In the example of FIG. 5A, the valve a is squeezed to reduce the straight portion e1.
When the opening cross-sectional area of the straight portion e1 is reduced, the natural vibration frequency at which a standing wave is generated decreases. When the valve a is opened to increase the opening cross-sectional area of the straight portion e1, the natural vibration frequency increases. Therefore, in this case, the valve a is squeezed to reduce the natural vibration frequency in the low-speed region of the engine so as to open the valve a and increase the natural vibration frequency in the high-speed region of the engine. Control according to. In this case, the position of the valve a may be controlled so as to be continuously changed according to the rotational speed. However, in practice, the operating rotational speed region of the engine is divided into, for example, a low speed region, a medium speed region, and a high speed region. The opening degree of the valve is controlled stepwise so that each of these regions is set as a tuning rotation region.

Next, in the example shown in FIG.
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 opening cross-sectional area of the branch pipe b is reduced by narrowing the valve a, the tuning rotation region shifts to the low-speed side, and the opening cross-sectional area of the branch pipe b is expanded by opening the valve a. 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 way of providing the valve is not limited to the above example.

Heretofore, the above-described exhaust control device has been operated using a battery as a power source, and has been applied only to internal combustion engines such as vehicles equipped with the battery. However, recently, it has been considered to perform exhaust control even in a vehicle or the like without a battery in order to improve the performance of the engine.

Therefore, in order to be able to apply the exhaust control device to an internal combustion engine such as a vehicle without a battery,
It has been proposed to drive an actuator that operates a valve for adjusting characteristics of an exhaust system with an output of a power generation coil provided in a magnet generator mounted on an engine.
Also, noting that only the output of the half cycle of the ignition power supply coil provided in the magnet generator is used for supplying the ignition energy, the half cycle of the ignition power supply coil not used for the supply of the ignition energy is used. Attempts have been made to construct a DC power supply using the output, and to drive control means such as a microcomputer with the output of the DC power supply.

[0010]

When an actuator that operates a valve that adjusts the characteristics of an 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. ,
When the engine is started, the position of the exhaust characteristic adjusting valve is the position when the engine was stopped last time. Therefore, when the engine is stopped in a state where the valve is located at a position other than the position suitable for the start rotation region, there is a problem that the air supply efficiency is reduced at the next start of the engine and the startability of the engine is deteriorated. .

[0011] An object of the present invention is to provide an engine for operating an exhaust characteristic adjusting valve by using a magnet generator as a power source so that the valve is always in a suitable position when the engine is started. It is an object of the present invention to provide an internal combustion engine exhaust control device capable of facilitating the start of the engine.

[0012]

According to the present invention, there is provided a valve for adjusting the characteristics of an exhaust system of an internal combustion engine, and an electric system for operating the valve driven by an output of a magnet generator mounted on the internal combustion engine. The present invention relates to an exhaust gas control device for an internal combustion engine, comprising: an actuator of claim 1; In the present invention, the engine stop detecting means for detecting the stop of the internal combustion engine, and the actuator is driven when the stop of the internal combustion engine is detected by the engine stop detecting means to return the valve to a position suitable for starting the engine. And a valve return means for causing the valve to return.

In the present invention, "detecting the stop of the internal combustion engine" includes detecting that the internal combustion engine is about to stop, that is, predicting the stop when the internal combustion engine is rotating. And detecting that the internal combustion engine has come to a stopped state or a state close to a stopped state.

Predicting that the engine will be stopped can be performed in various ways. For example, in the case of an internal combustion engine that operates an engine stop switch when stopping the engine, the operation can be performed by detecting that the engine stop switch has been operated. Further, in the case of an internal combustion engine that stops the internal combustion engine when an abnormality occurs in the engine, it is possible to predict the stop of the engine from the output of the abnormality detection sensor. Further, it detects the disappearance of the voltage (for example, the induced voltage of the primary coil of the ignition coil) periodically generated in the ignition device when the ignition operation is performed normally (when the engine is in a misfire state). ) Can also predict the stop of the engine.

The detection that the engine has come to a stopped state or a state close to a stopped state is performed by detecting a rotation speed detector (tachometer).
Or by monitoring the primary induced voltage of the ignition coil of the ignition device for the internal combustion engine.

[0016]

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

[0017]

1 shows an overall configuration of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an internal combustion engine having an intake pipe 2 and an exhaust pipe 3; This is a magnet generator comprising a magnet rotor 4A provided and a stator 4B attached to an engine case.

A throttle valve 5 is provided on the inlet side of the intake pipe 2.
Is mounted, and an injector 6 is mounted so as to inject fuel into a space (fuel injection space) downstream of the throttle valve 5 in the intake pipe. The injector 6
It has a valve for opening and closing the injection port, and an electromagnet for operating the valve.
While ij is being provided, the electromagnet is energized to open the valve.

A fuel pump 7 includes 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 via a pipe 8.
, And a discharge port of the pump 7B is connected to a fuel supply port of the injector 6 via a pipe 10.

Reference numeral 11 denotes a pressure regulator connected between the fuel supply port of the injector 6 and the fuel tank 9. The pressure regulator adjusts the pressure of the fuel supplied to the fuel supply port of the injector 6 to a set value. 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 during which an injection command signal is supplied to the injector 6 is controlled so that a mixed gas having an optimum air-fuel ratio is supplied 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 portion e2, a straight portion e3, and a convergent portion e4, and changes the opening cross-sectional area of the straight portion e1 upstream of the cavity 3A. As described above, the exhaust characteristic adjusting valve 12 is provided. The exhaust characteristic adjusting valve 12 of this embodiment is a linear displacement type valve that enters and exits the exhaust pipe from a direction perpendicular to the axial direction of the exhaust pipe 3 and changes 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 for driving the pinion 14 to rotate.

The exhaust characteristic adjusting valve 12 need not be a linear displacement type, but may be a 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 coincide with 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, in the present invention, a start-time valve position detection sensor (not shown) for detecting the position of the valve 12 at the time of start-up.
The position detected by this sensor when stopping the engine (valve position suitable for starting the engine)
The valve 12 is returned to the initial position.

The valve position sensor may be a single position sensor (a potentiometer or a differential transformer) whose output changes in an analog manner according to the opening of the valve, and detects a plurality of positions of the valve. As a result, an aggregate of a plurality of position detection switches provided side by side along the displacement direction of the valve may be used. Further, the position of the valve may be detected by counting pulses obtained from a rotary encoder attached to an output shaft of a motor as a drive source of the actuator.

In the present invention, the auxiliary generator driving 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 driving generator coil 4a is supplied to the power supply circuit. The motor 17 of the actuator 16 is supplied to the pump motor 7 </ b> A through the valve driving circuit 17 and supplied to the electric motor 15 of the actuator 16 through the valve driving circuit 18.

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

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

The power supply circuit 20 is composed of a power supply capacitor charged by the output of the negative half cycle 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.
a full-wave rectifier 25 for rectifying the output of a, a smoothing power supply capacitor 26 connected between the output terminals of the rectifier 25, and a voltage regulator 27 for controlling the voltage across the capacitor 26 to a constant value. The DC voltage obtained at both ends of the capacitor 26 is supplied to the pump motor 7A, and the actuator 16
Supplied to

The voltage regulator 27 includes, for example, the capacitor 2
6 when the voltage at both ends exceeds the rated value.
To reduce the output voltage of the power generation coil 4a, and when the voltage across the capacitor 26 falls below the rated value, the short circuit of the power generation coil 4a is released to recover the output voltage of the power generation coil 4a. Then, the power generation coil 4 a
Control the output voltage.

The ignition circuit 20 is a known capacitor discharge type circuit. 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 constituting a charging circuit for charging the capacitor C1 with the output of the positive half cycle of the ignition power supply coil 4b, and a gate and a cathode of the thyristor Th1 in parallel. A resistor R1 and a capacitor C2 connected to
The ignition plug P is attached to the cylinder of the internal combustion engine and connected to the secondary coil of the ignition coil IG. The cathode of the thyristor Th1 is grounded together with one end of the primary coil and one end of 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 diodes 19 and 21, respectively, whose anodes are grounded.

In the above ignition circuit, when the ignition power supply coil 4b induces a voltage of a positive half cycle, the diodes D1 and D2 and the diode 19 from the ignition power supply coil 4b.
, The capacitor C1 is charged to the polarity shown.
When the ignition signal Vig is given to the gate of the thyristor Th1 at the ignition timing of the internal combustion engine, the thyristor Th1 conducts, so that 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 comprises a power supply capacitor C3 charged to the polarity shown through a diode D3 at the output of the negative half cycle of the ignition power supply coil 4b, and a capacitor C3.
And a thyristor Th2 which conducts when the voltage across the terminal reaches a set value and which conducts when a trigger signal is given through the Zener diode Z1 to bypass 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 in the drawing by the negative half cycle output voltage of the ignition power supply coil 4b. When the voltage between both ends of the capacitor C3 reaches the set value, the Zener diode Z1 is turned on, so that the thyristor Th2 is turned on and the capacitor C3 is turned on.
To prevent filling. By these operations, a substantially constant DC voltage is obtained across the power supply capacitor C3. This DC voltage is supplied 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.
, Information about the rotation angle of the engine and information about the rotation speed are obtained. The microcomputer 23 also has an output of a valve position sensor 31 for detecting the position of the valve 12 for adjusting the characteristics of the exhaust system, and a start position for detecting that the position of the valve 12 has reached a position suitable for starting the engine. The output of the sensor 32 is provided.

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

The microcomputer 23 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. The 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 in accordance with the rotational speed N of the engine. The valve control circuit 24 gives a predetermined trigger signal to the valve drive circuit 18 in accordance with the drive signal Ve to operate the actuator 16.

FIG. 3 shows an example of the configuration of the valve drive circuit 18. The valve drive circuit 18 includes transistors Tr1 to Tr4 connected in a bridge, and the valve control circuit 24 sends a trigger signal (TRG) to the transistors Tr1 to Tr4. Base current).

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

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

FIG. 4 is a flowchart showing a process at the time of engine stop when the internal combustion engine is provided with a stop switch composed of a push button switch. In this case, when the stop switch is pressed, the valve 12 is first returned to a 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 reduce the fuel injection amount to zero, and the supply of the ignition signal Vig to the ignition circuit 19 is stopped. Extinguish ignition sparks.

In the flow chart shown in FIG. 4, after the operation of returning the valve 12 to a suitable position at the time of starting is performed, the operation of stopping the engine (the operation of setting the fuel injection amount to zero and extinguishing the ignition spark) is performed. Although the engine was stopped, the engine did not stop immediately even if the operation of stopping the engine was performed. For a while, the magnet generator 4 generated an output and continued to supply power to the microcomputer, and the engine stopped. Since the power supply capacitor C3 continues to supply the power supply voltage to the microcomputer for a considerable period of time thereafter, the operation of returning the position of the valve 12 is performed after the operation of stopping the engine or simultaneously with the operation of stopping the engine. You may do so.

In the flowchart 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-described embodiment, a series of operations are performed by detecting that the stop switch has been pressed to predict that the engine will be stopped. Alternatively, when it is detected that the engine is in a state close to a stopped state, the valve 12 may be returned to a position suitable for starting.

In the above embodiment, since the position of the valve is controlled by using the microcomputer, the valve return means is realized by using the microcomputer.
In the case where the position of the valve is controlled using an analog circuit, the valve return means can be configured.

In order to control the position of the valve using an analog circuit, for example, a valve position setting signal for giving a set position of the valve in each rotation speed region of a start region, a low speed region, a medium speed region, and a 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 the instantaneous position of the valve with the selected valve position setting signal. What is necessary is just to control an actuator so that it may be performed. When a control circuit using such an analog circuit is used, a valve position setting signal that gives a position of a valve in a start region when the stop of the engine is detected is selected, and the output of the valve position sensor is output. Valve return 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 a 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 the drawings]

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

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

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 processes performed when the engine is stopped in the embodiment of the present invention.

FIGS. 5A and 5B are configuration diagrams conceptually showing different configuration examples of an exhaust system.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Exhaust pipe 6 Injector 7 Fuel pump 12 Exhaust characteristic adjustment 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)

(57) [Claims] 1. A valve for adjusting characteristics of an exhaust system of an internal combustion engine, an electric actuator driven by an output of a magnet generator mounted on the internal combustion engine to operate the valve, and a rotation of the internal combustion engine An exhaust control device for an internal combustion engine, comprising: a valve control device for controlling a position of the valve according to each rotational speed of the engine by controlling the actuator according to a speed. A stop detecting unit; and a valve returning unit that drives the actuator to return the valve to a position suitable for starting the engine when the stop of the internal combustion engine is detected by the engine stop detecting unit. Exhaust control device for an internal combustion engine.