JP3446806B2 - Rotation direction switching control method 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 a rotation direction switching control method for an internal combustion engine, which switches the rotation direction of a spark ignition type reciprocating piston type internal combustion engine.

[0002]

2. Description of the Related Art In vehicles such as scooters and snowmobiles where importance is placed on simplicity, a small 2-cycle internal combustion engine or 4-cycle internal combustion engine is used as a drive source. Centrifugal clutch type continuously variable transmissions are often used as power transmission devices for transmitting output to drive wheels. This kind of vehicle is small, lightweight,
Since it is important to be inexpensive, as an unauthorized transmission,
Often used without back gear.

As described above, in a vehicle or the like using a transmission that does not have a back gear, it is not possible to reverse (reverse), so when it is necessary to reverse the traveling direction in a narrow place. Moreover, it was necessary to lift the entire vehicle body and change its direction, which made the operability poor.

As described above, in order to make it possible to reverse the traveling direction of a vehicle not equipped with a back gear, it is sufficient to be able to switch the rotation direction of the internal combustion engine when necessary.

As a method of switching the rotation direction of the internal combustion engine, the method described in the specification of US Pat. No. 3,036,802 and the drawings has been proposed. In this proposed rotation direction switching method, when it becomes necessary to switch the rotation direction of the engine, the operation of the ignition device is stopped to cause the engine to misfire, thereby reducing the rotation speed of the crankshaft of the engine. , When the crankshaft rotation speed has dropped to the set value and is on the verge of stoppage, the ignition operation is performed at a sufficiently advanced rotation angle position to push back the piston and reverse the engine rotation direction. . After reversing the rotation direction of the engine in this way, immediately after changing the ignition position to a rotation angle position suitable for maintaining the rotation in the reversed direction, the engine in the state in which the rotation direction is reversed Continue driving.

[0006]

Problems to be Solved by the Invention US Pat. No. 3,033
In the previously proposed method shown in No. 6,802, the engine is misfired when the rotational speed of the engine is decreased, and therefore a large amount of unburned gas (particularly HC component) is generated when the rotational direction of the engine is reversed. There was a problem of being emitted and polluting the atmosphere.

In the proposed method, the ignition operation is restarted in the state where the unburned exhaust gas is accumulated in the exhaust pipe when the engine rotation direction is reversed, so that the unburned gas is ignited in the exhaust pipe. After-fire may occur, and at that time, a loud explosion may occur to make the driver uneasy, or the impact generated when the after-fire occurs may damage the engine body or the exhaust pipe.

An object of the present invention is to propose a rotation direction switching control method for an internal combustion engine, which is capable of reversing the rotation direction of the crankshaft without discharging unburned gas.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a spark ignition which is equipped with a piston reciprocating in a cylinder and a crankshaft connected to the piston, and which is ignited by an ignition device capable of controlling an ignition position. The present invention relates to a rotation direction switching control method for switching the rotation direction of a reciprocating piston type internal combustion engine.

According to the present invention, when a reversing command for reversing the rotational direction of the internal combustion engine is given, the internal combustion engine is kept in a state where the opening of the throttle valve is maintained near the opening during idling. The retarding process of gradually decreasing the ignition position of the internal combustion engine to decrease the rotation speed of the internal combustion engine, and the ignition position set when the rotation speed of the internal combustion engine decreases to the set over-advance start rotation speed. When an over-advance process of advancing to an advance position is performed and it is detected that the rotation direction of the internal combustion engine is reversed in the over-advance process,
The ignition position is shifted to a rotational angle position suitable for maintaining the rotation of the internal combustion engine in the reversed direction.

In order to detect the rotation direction of the engine, an appropriate rotation direction detecting means is provided. The rotation direction detecting means includes, for example, a rotation sensor that generates a pulse signal differently when the crankshaft of the engine rotates in one direction and in another direction, and a pulse signal that is generated by the rotation sensor. It can be configured by a pulse generation form identification means for identifying a form.

The ignition position of the internal combustion engine is represented by the rotational angle position of the crankshaft of the engine. The ignition position of the engine is changed (advanced) to a position advanced from the top dead center (the rotation angle position of the crankshaft when the piston reaches the top dead center) according to the operating condition of the engine. The ignition position at each rotational speed during steady operation is set to a position required to extract a predetermined output from the engine and stably rotate the engine.

In the present invention, "over-advancing angle" of the ignition position means advancing the ignition position further to the advance side than the proper ignition position at each rotational speed during steady operation.

As described above, when the ignition position of the internal combustion engine is gradually retarded, the position where the pressure in the cylinder after ignition becomes maximum shifts to the retard side, and with the retard of the ignition position. As a result, the force that drives the piston becomes weaker, and the rotational speed of the engine gradually decreases. When the engine rotation speed drops to a preset over-advanced start rotation speed, the ignition position is advanced to the set over-advanced position and the ignition operation is performed at the over-advanced position. The engine reverses because the force that pushes back the piston comes to overcome the force of the piston that rises toward top dead center. In this way, when it is detected that the rotation direction of the engine is reversed, the ignition position should be shifted to a rotation angle position suitable for maintaining the rotation of the internal combustion engine (for example, a position near the top dead center). If so, the rotation of the internal combustion engine in the reversed direction can be maintained.

According to the above method, the direction of rotation of the internal combustion engine can be reversed without causing misfire, so that unburned gas is prevented from being discharged when the direction of rotation of the engine is switched. Therefore, it is possible to eliminate the risk of generating afterfire and polluting the atmosphere when switching the rotation direction.

As a method of gradually decreasing the rotational speed of the internal combustion engine and finally reversing its rotational direction, the ignition position is gradually advanced to the over-advanced side when a reversal command is given. There is also a method of reversing the rotation direction of the engine when the ignition position reaches a predetermined over-advanced position. However, when the method of gradually advancing the ignition position to the over-advanced side in this way is adopted, in the process of advancing the ignition position, the knocking state (the piston moves in the opposite direction to the advancing direction). Since a period in which a directional force is applied) is long, a problem arises in that an impact time around the piston and the crankshaft is long.

On the other hand, as in the present invention, by retarding the ignition position, the engine rotation speed is reduced to a predetermined rotation speed, and then the ignition position is advanced by a predetermined angle. Then, the time for over-advancing the ignition position is short, and since knocking does not occur in the process of retarding the ignition position, the period in which knocking occurs can be shortened. Therefore, when reversing the rotation direction of the engine, it is possible to prevent giving unnecessary impact to the engine.

In this case, the over-advanced angle starting rotation speed is set to a sufficiently low value so that the impact generated when the ignition position is advanced to the over-advanced angle can be limited to a range that does not interfere. To do.

When the internal combustion engine is determined, the relationship between the ignition position and the rotation speed of the engine is substantially determined, so that the ignition position corresponding to the above-mentioned over-advanced angle starting rotation speed can be obtained in advance. Therefore, the ignition position corresponding to the over-advanced start rotation speed is set as the over-advanced start position, and the ignition position is set when the ignition position of the internal combustion engine is retarded to the set over-advanced start position. Alternatively, the rotation direction of the engine may be reversed by advancing to the over-advanced position.

That is, according to the present invention, when the reversing command is given, the ignition position of the internal combustion engine is gradually retarded while the throttle valve opening is maintained near the opening during idling. The retarding process that lowers the rotation speed of the internal combustion engine by the following, and the over-advanced angle that advances the ignition position to the set over-advanced position when the ignition position of the internal combustion engine is retarded to the set over-advanced start position. When it is detected that the rotation direction of the internal combustion engine is reversed in the over-advanced angle process, the rotation angle position suitable for maintaining the rotation of the internal combustion engine in the direction in which the ignition position is reversed is detected. It may be changed.

Further, according to the present invention, when the reversing command is given, the ignition position of the internal combustion engine is gradually retarded while the throttle valve opening is maintained near the opening during idling. The retarding process of lowering the rotation speed of the internal combustion engine and the ignition position when the rotation speed of the internal combustion engine decreases to the set over-advance starting rotation speed or when the ignition position retards to the over-advance starting position. An over-advance process of advancing to a set over-advance position and igniting at least one cylinder at the over-advance position, and an ignition position of each cylinder after the over-advance process ends near the top dead center. It is also possible to shift to the set ignition position set to the above and perform the rotational direction determination process of determining whether or not the rotational direction of the engine is reversed.

Since the rotation speed at the time of reversing the rotation of the engine is very low and is unstable, it is not always easy to detect that the rotation direction of the engine has reversed, but
As described above, if the rotation direction of the engine is confirmed after the ignition position is returned to near the top dead center, the rotation direction of the engine can be easily determined.

In order to ensure the reversal of the engine, when it is detected that the revolving direction of the engine has not been reversed in the above-described process of determining the revolving direction, it is delayed until it is confirmed that the revolving direction of the engine has been reversed. A series of processes from the angular process to the rotation direction determination process are repeated, and after it is detected that the rotation direction of the engine is reversed in the rotation direction determination process, the engine is operated with the rotation direction being reversed. Preferably.

The number of ignitions during the over-advancing process is set to an appropriate number for reversing the rotation direction of the engine. Since the engine may stop if the number of ignitions in the over-advancing process is too large, it is preferable to set the number of ignitions in the over-advancing process to a necessary minimum value.

Further, in the case of permitting repeating a series of processes from the retarding process to the rotational direction determining process a plurality of times,
The initial advance amount in the over-advance process is set to be small, and the over-advance position in the over-advance process is set to the previous over-advance angle each time the series of processes from the retard process to the rotation direction determination process is repeated. If the position is advanced further than the over-advanced angle position in the process, it is possible to reliably reverse the rotation direction of the engine.

Further, when a series of processes from the retarding process to the rotational direction discriminating process is repeated a plurality of times, ignition is performed at the over-advanced position and overposition every time the series of processes from the retarding process to the rotational direction discriminating process are repeated. If the number of times is increased, it is possible to reliably invert the rotation direction of the engine.

In order to inform the driver that the engine has been reversed, display means for displaying that the engine rotation direction has been reversed is provided, and it has been detected that the engine rotation direction has been reversed during the above rotation direction determination process. At times, it is desirable to cause the display means to perform a display operation.

In the internal combustion engine, the higher the temperature of the air-fuel mixture, the faster the propagation speed of the flame generated when the fuel is ignited, and the shorter the time until the explosive force applied to the piston after ignition reaches the maximum value. . Therefore, when advancing the ignition position to the over-advanced side and reversing the rotation direction of the engine, when the temperature of the air-fuel mixture at the time of reversing the engine is high, the advancing amount at the time of advancing the ignition position is set. Can be reduced.
Further, when the temperature of the air-fuel mixture is low, it is necessary to increase the advance amount when the ignition position is excessively advanced.

Therefore, in the present invention, at least one of the engine temperature sensor for detecting the temperature of the internal combustion engine and the intake air temperature sensor for detecting the intake air temperature of the internal combustion engine is provided, and the temperature detected by the temperature sensor is It is preferable to change the over-advanced position according to the temperature detected by the temperature sensor so as to increase the advance amount when the ignition position is over-advanced as the ignition position increases.

Further, in the present invention, when the ignition position of the internal combustion engine is gradually retarded after the inversion command signal is given, the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is set to the lean side or the rich side. It is preferable that the output torque of the internal combustion engine is reduced by changing the value of the engine speed to 1 to suppress the impact generated when the rotation direction of the engine is switched.

In the present invention, it is preferable that the ignition position is over-advanced in the over-advanced angle process (stepwise advanced to the ignition position and the over-advanced position). Alternatively, the ignition position may be advanced to the over-advanced position over a predetermined time (a sufficiently short time).

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the configuration of an internal combustion engine control device used to carry out a rotational direction switching control method according to the present invention. In FIG. 1, reference numeral 1 denotes an internal combustion engine to be controlled. An engine 2, a fuel injection valve (injector) that supplies fuel to the internal combustion engine 1, 3 is a fuel pump that supplies fuel to the fuel injection valve 2, 4 is a fuel injection control device that controls the fuel injection valve, and 5 is the internal combustion engine 1 Is an ignition device that ignites the. Further, 6 is a rotation sensor for detecting the rotation of the internal combustion engine 1, 7 is a reversal command generation unit for generating a reversal command, and 8 is for reversing the rotation direction of the internal combustion engine when the reversal command generation unit generates a reversal command. It is a rotation direction switching control device that controls the ignition device 5 and the fuel injection control device 4.

Here, the fuel injection control device 4, the ignition position control device 5B and the rotation direction switching control device 8 are realized by causing a microcomputer to execute a predetermined program. Each control device may be realized by using an individual microcomputer or may be realized by using the same microcomputer.

The internal combustion engine 1 is a spark ignition type reciprocating piston type internal combustion engine having a piston reciprocating in a cylinder and a crankshaft connected to the piston. The internal combustion engine to be controlled by the present invention may be a two-cycle engine or a four-cycle engine, but in this example, it is assumed to be a two-cycle engine.

FIG. 2 shows the configuration on the engine side and the configuration on the load side, taking as an example the case where the internal combustion engine 1 is used to drive a snowmobile. The illustrated internal combustion engine 1 includes an engine body 100 having a cylinder 100a and a crankcase 100b, a piston 101 fitted in the cylinder 100a, and a connecting rod 1 attached to the piston 101.
2 is a piston valve type two-cycle internal combustion engine having a crankshaft 103 connected via a No. 02. The cylinder 100a is provided with an intake port 104, an exhaust port 105, and a scavenging port (not shown), and an exhaust pipe 106 is connected to the exhaust port 105. Although not shown, a scavenging passage is provided so as to connect a space inside the crankcase 100b and a scavenging port (not shown) hidden behind the piston 101. The intake port 104 is connected to an intake manifold (not shown) via a check valve.

In FIG. 2, reference numerals 10 and 11 denote a primary pulley and a secondary pulley, respectively, which constitute a belt type continuously variable transmission (CVT), and 12 denotes a steel belt wound around the pulleys 10 and 11. Pulleys 10 and 11
Can change the width of each V-shaped groove to change the radial position of the slope contact with the belt.
The primary pulley 10 is attached to the crankshaft 103, and the drive wheel of the snowmobile is attached to the rotating shaft of the secondary pulley 11.

The primary pulley 10 is connected to the centrifugal clutch mechanism. The centrifugal clutch mechanism uses the belt 1 when the rotation speed of the crankshaft of the internal combustion engine is lower than a certain value.
The width of the V-shaped groove for engaging 2 is widened so that the belt 12 is not driven, and the width of the V-shaped groove for engaging the belt is narrowed in a region where the rotation speed of the crankshaft exceeds a certain value. Is driven, and the radial position of the slope contact between the belt 12 and the pulley 10 is changed according to the rotation speed. The secondary pulley 11 can also change the width of the V-shaped groove that engages the belt 12 according to the rotation speed, and by changing the position of the slope contact with the belt 12 according to the rotation speed, Pulley 1
The speed reduction ratio between 0 and the secondary pulley 11 is changed.

In this specification, in FIG. 2, the rotation of the crankshaft 103 in the clockwise direction (direction of the arrow CL) is defined as the forward rotation, and the rotation of the crankshaft in the counterclockwise direction is defined as the reverse rotation.

The fuel injection valve (injector) 2 shown in FIG. 1 is provided with, for example, a valve body having an injection port at its tip, a valve for opening and closing the injection port, and an electromagnet for driving the valve. The fuel is supplied from the fuel pump 3 into the valve body at a predetermined pressure. The fuel injection valve 2 opens the valve while a drive current is applied to the electromagnet, and injects fuel into a fuel injection space such as a space in an intake manifold of an internal combustion engine or a space (combustion chamber) in a cylinder. The amount of fuel injected from the fuel injection valve 2 (fuel injection amount) is determined by the product of the fuel pressure applied from the fuel pump into the valve body and the time the valve is open. Generally, the pressure of the fuel supplied from the fuel pump 3 to the fuel injection valve 2 is kept constant so that the injection amount can be controlled only by the time when the valve of the fuel injection valve 2 is open.

The fuel injection control device 4 controls the fuel injection valve 2 according to various control conditions such as engine temperature, intake air temperature, atmospheric pressure, throttle valve opening, engine rotational speed, presence of a reversal command, and the like. The fuel injection amount from the fuel injection valve 2 is controlled by controlling the timing of applying the drive current and the time of applying the drive current.

The ignition device 5 includes an ignition circuit 5A which generates a high voltage for ignition when an ignition signal is given, and an ignition position control device 5B which gives an ignition signal to the ignition circuit 5A at an ignition position of an internal combustion engine. A spark plug 5C attached to a cylinder of the internal combustion engine 1 is provided.

The ignition circuit 5A is provided with an ignition coil and a primary current control circuit that causes a rapid change in the primary current of the ignition coil when an ignition signal is applied. The change induces a high voltage for ignition in the secondary coil of the ignition coil. As the ignition circuit 5A, various types such as a capacitor discharge type circuit and a current interruption type circuit are known, but in the present invention, the ignition position control device 5B is generated at the ignition position of the internal combustion engine. Any type of ignition circuit may be used as long as it outputs a high voltage for ignition in response to the ignition signal.

The ignition position control device 5B is equipped with a microcomputer, and obtains engine rotation speed information and rotation angle information from a signal generated by the rotation sensor 6 to determine whether the engine rotation speed, engine temperature, or reverse command is present. The ignition position of the engine is calculated according to various control conditions such as, and an ignition signal is given to the ignition circuit 5A when the calculated ignition position is detected.

The ignition plug 5C is connected to the output terminal of the ignition circuit 5A, and when the ignition circuit 5A generates a high voltage for ignition, a spark is generated to ignite the engine.

The rotation sensor 6 generates a pulse signal containing information on the rotation speed, rotation angle and rotation direction of the internal combustion engine. As the rotation sensor, for example, an inductor type signal generator shown in FIG. 3 is used. Can be used. In FIG. 3, reference numeral 600 denotes a rotor including a rotary yoke 601 attached to the crankshaft 103 of the engine and a two-stage reluctor 602 formed on the outer periphery of the rotary yoke 601. The two-stage reluctor 602 has a first portion 602a located near one end in the circumferential direction and a second portion 6 located near the other end.
02b, the height of the second portion 602b is set higher than the height of the first portion 602a, and the arc length (circumferential length) of the first portion 602a is the second portion 60b.
It is set shorter than the arc length of 2b. In the illustrated example, the rotor 600 is provided so that the first portion 602a of the reductor is located on the front side in the rotation direction when the engine is rotating normally. As the yoke 601, a flywheel or the like attached to the engine can be used.

Reference numeral 603 denotes a signal generator which is arranged on the outer peripheral side of the rotor 601 and is attached to a fixed portion such as a case of the engine. The signal generator 603 has a magnetic pole portion 603a1 at the tip.
An iron core 603a, a signal coil 603b wound around the iron core, and a permanent magnet 603c magnetically coupled to the iron core.
And a magnetic pole portion 603a1 is provided in the rotor 60.
It is arranged so as to be opposed to the outer peripheral surface of 0 through a predetermined gap.

In the signal generator shown in FIG. 3, the first portion 6 of the two-stage reluctor 602 is provided during the forward rotation of the engine.
When 02a faces the magnetic pole portion 603a1 of the signal emitting electron, the magnetic flux linked to the signal coil 603b increases, and when the second portion 602b of the reluctor faces the magnetic pole portion 603a1 of the signal emitting electron, The interlinking magnetic flux is further increased. The signal coil 603b generates pulse signals having different polarities when the interlinking magnetic flux increases and when the interlinking magnetic flux decreases.

4 (A) and 4 (B) respectively show the signal coil 6 when the engine is rotating forward and in the reverse direction.
The waveform of the pulse signal induced in 03b is shown with respect to the rotation angle θ of the engine. The signal coil 603b is
When the engine is rotating normally, the first portion 6 of the reluctor
The angle θ at which 02a starts facing the magnetic pole of the signal-generating electron
Pulse signals S1 and S2 of one polarity (positive polarity in the illustrated example) are generated at the position 1 and at the angle θ2 where the second portion 602b of the reluctor starts to face the magnetic pole portion of the signal-generating electron, The pulse signal S3 of another polarity (negative polarity in the illustrated example) is generated at the position of the angle .theta.3 at which the second portion 602b of the reluctor ends the facing of the magnetic pole portion of the signal emitting electron.

The signal coil 603b also has an angle θ3 at which the second portion 602b of the reluctor faces the magnetic pole portion of the signal generating electron when the engine is rotating in the reverse direction, as shown in FIG. 4B. Generate a positive pulse signal S3 'at the position,
The position of the angle θ2 at which the second portion 602b of the reluctor ends the facing of the magnetic pole portion of the signal emitting electron, and the first portion 60
The negative signals S2 'and S1' are generated at the position of the angle .theta.1 at which 2a finishes facing the magnetic pole of the signal-generating electron.

Strictly speaking, the generation position of each pulse signal is a position where each pulse signal reaches a threshold level (a level that can be recognized by a circuit that receives the pulse signal). Is sufficiently narrow that
In the above, for convenience, the peak position of each pulse signal is used as its generation position.

As described above, in the signal generator shown in FIG. 3, the polarity of the signal induced in the signal coil and the generation order are different between when the engine is rotating normally and when the engine is rotating reversely. Since they are different, the rotational direction of the engine can be determined by identifying the polarity of the signal obtained from the signal coil and the generation order.

The rotation direction detecting means can be constituted by the rotation sensor 6 and the pulse generation mode identifying means for identifying the generation order of the pulse signals generated by the rotation sensor.

That is, in the illustrated example, the signal coil 603b
However, when pulse signals are generated in the order of the positive polarity pulse S1, the positive polarity pulse S2, and the negative polarity pulse S3, it can be determined that the engine is rotating normally, and the signal coil has the positive polarity pulse S3 ′, When the pulse signals are generated in the order of the negative polarity pulse S2 'and the negative polarity pulse S1', it can be determined that the engine is rotating in the reverse direction.

Further, the rotational speed of the engine can be detected from the pulse generation interval, for example, the time from the generation of the pulse signal S1 to the generation of the pulse signal S3.

Further, the polar arc angle α of the reluctor 602 is appropriately set, and when the piston of the engine reaches the top dead center, the center position of the reluctor 602 in the circumferential direction opposes the center of the magnetic pole portion of the signal generator 603. Signal generator 60 so that
By arranging No. 3, the pulse signals S1 and S3 'are transmitted before the top dead center α during the forward rotation and the reverse rotation of the engine.
/ 2 can be generated at symmetrical positions, and the positions where these signals S1 and S3 'are generated are the minimum advance position of the ignition position during forward rotation and the minimum advance position of the ignition position during reverse rotation. You can Here, the "minimum advance position" is the ignition position closest to the top dead center among the ignition positions during steady operation of the engine, and is usually the ignition position during idling.
The polar arc angle α of the reluctor 602 is set to, for example, 10 degrees.
When the polar arc angle of the reluctor is 10 degrees, the minimum advance angle position (ignition position during idling) during normal rotation and reverse rotation of the engine is a position 5 degrees before top dead center.

The angle that determines the generation position of each pulse signal needs to be measured with reference to a fixed position, but normally the generation position of each pulse signal is measured with reference to the top dead center of the engine.

The pulse signal obtained from the rotation sensor 6 is
A waveform shaping circuit (not shown) converts the signal into a waveform that can be recognized by the microcomputer and applies the signal to a predetermined input port of the microcomputer.

The microcomputer obtains the rotation angle information, the rotation speed information, and the rotation direction information of the engine from the signal given by the rotation sensor. Processing for obtaining the fuel injection control device 4, the ignition position control device 5B, and the rotation direction switching control device 8 by obtaining information such as the temperature (cooling water temperature), the opening of the throttle valve, and the atmospheric pressure. I do.

In the example shown in FIG. 1, the inversion command generator 7 has a resistor 7A whose one end is connected to the positive output terminal of a constant voltage DC power supply circuit (not shown) and between the other end of the resistor 7A and the ground. It is composed of a switch 7B for inversion command connected. The output terminal on the negative side of the constant voltage DC power supply circuit (not shown) is grounded, and the output voltage of the power supply circuit is applied to both ends of the series circuit of the resistor 7A and the switch 7B. Resistance 7
The output terminal is derived from the connection point between A and the switch 7B,
A signal obtained between the output terminal and the ground is input to a microcomputer (not shown), and the rotation direction switching control device 8
It is used as a signal that gives an inversion command to. Switch 7
For example, B is kept in an off state when the engine is rotating normally, and is turned on when the engine is rotating in the reverse direction. The switch 7B is kept in the ON state while the engine is rotating in the reverse direction, and is kept in the OFF state when rotating the engine in the forward direction.

The signal generated by the inversion command generator 7 is in a high level state when the switch 7B is in an off state, and is in a zero level state when the switch 7B is in an on state. The rotation direction switching control device 8 determines that a reversal command is issued to invert the rotation direction of the engine each time the level of the signal supplied from the reversal command generation unit changes.

When reversing the direction of rotation of the engine, first, the throttle operating member such as the throttle lever is operated so that the opening of the throttle valve is set to a value near the minimum value (a value near the opening during idling). , The switch 7B of the inversion instruction generator 7 is operated.

The rotation direction switching control device 8 includes a switch 7B.
Is operated and a reversal command is given from the reversal command generator 7, various controls (control of the ignition device and the fuel injection device) performed by the microcomputer are switched to the control mode at the time of reversal. Let the engine perform the processing for reversing the engine.

In a preferred mode, when a reversal command is generated, a fuel injection amount reduction command is first given to the fuel injection control device 4 to decrease or increase the fuel injection amount below a specified amount (amount during steady operation). As a result, the air-fuel ratio of the air-fuel mixture is changed to the lean side or the rich side within the range where the internal combustion engine is not stopped.

FIG. 8 shows the relationship between the air-fuel ratio of the air-fuel mixture and the rotation speed of the engine. As shown in FIG. 8, when the air-fuel ratio is changed to the lean side or the rich side, the rotation speed of the engine changes. It will decrease. In FIG. 8, A1 is the lean limit value of the air-fuel ratio at which the engine rotation can be maintained,
If the air-fuel ratio is changed further to the lean side than this limit value A1, the engine will stop. A2 is an air-fuel ratio when the engine produces maximum torque, and A3 is a rich-side limit value of the air-fuel ratio at which the engine can be kept rotating. If the air-fuel ratio is changed to a rich side than A3, the engine will stop.

After the fuel injection amount is decreased or increased to change the air-fuel ratio to the lean side or the rich side, the ignition position of the internal combustion engine is gradually increased with the throttle valve opening kept at the minimum value. A retarding process is performed in which the engine is retarded to reduce the rotation speed of the engine.

When it is detected that the rotation speed of the internal combustion engine has reached the over-advanced start rotation speed, an over-advance process for advancing the ignition position of the internal combustion engine to the set over-advance position is performed, When it is detected that the rotation direction of the internal combustion engine is reversed in the over-advanced angle process, the ignition position is shifted to a rotation angle position suitable for maintaining the rotation of the internal combustion engine in the reversed direction.

FIG. 5 shows the relationship between the ignition position and the rotation angle of the engine. In the figure, CL indicates the normal rotation direction of the engine, TDC indicates the top dead center of the engine (the piston is at the top dead center). The rotation angle position of the crankshaft is shown. When the engine is rotating in the direction indicated by the arrow CL, the ignition position is slightly advanced from the top dead center TDC, and
Further, the position between the advanced angle θb and the advanced angle range during steady operation is set as the advanced angle range, and the ignition position is changed within this advanced angle range in accordance with the change in the rotational speed. The range more advanced than the ignition position θb is the over-advanced range, and the position of θd is the over-advanced position of the ignition position when reversing the rotation direction of the normally rotating engine by the method of the present invention. is there.

Further, in FIG. 5, θa ′ to θb ′ are advancing ranges in a steady state in the state where the engine is rotating in the direction opposite to the arrow CL direction shown in the figure, and θd ′ is rotating in the opposite direction. It is the over-advanced position when reversing the rotating direction of the engine.

In FIG. 5, BTDC is the top dead center TD.
It means that the rotation angle range is more advanced than C, and A
TDC means a rotation angle range on the retard side with respect to the top dead center.

In a preferred embodiment of the present invention, referring to FIGS. 6 (A) and 6 (B), the change of the ignition position and the change of the rotational speed of the engine at the time of reversing the rotation direction of the internal combustion engine which is rotating normally. Will be described in detail. FIG. 6A shows time t.
6B shows the change in the ignition position θi, and FIG. 6B shows the change in the engine rotation speed N with respect to time t.

In order to reverse the rotation of the internal combustion engine, FIG.
At time t0 shown in (A) and (B), if the opening of the throttle valve is reduced to the minimum value, the ignition position θi of the engine becomes
It is the position θa closest to top dead center in the advance range during steady operation.

When the reversal command is given at time t1, the ignition position changes to the top dead center TDC side, and gradually changes to the retard side beyond the top dead center TDC.

FIG. 7 shows the relationship between the rotation angle θ of the engine and the pressure P in the cylinder. In FIG. 7, the curve a shows the case where ignition is performed at the proper position, and the curve b shows the proper position. It shows a case where ignition is performed at a position retarded from the above. As shown in the figure, the pressure in the cylinder when the ignition operation is performed becomes lower as the ignition position retards, and the position where the pressure in the cylinder becomes maximum after ignition is on the retard side (the engine It shifts to the side away from the dead center TDC). Therefore, as the ignition position is retarded, the force that drives the piston becomes weaker, and the rotational speed of the engine gradually decreases.

At time t2 shown in FIG. 6, the ignition position is set when the ignition position θi is retarded to a certain position θs and the engine rotation speed N drops to the set overadvance start rotation speed Ns. Is advanced by an advanced amount βx (x = 1, 2, ...) And the ignition position is over-advanced θdx (x = 1,
2, ...).

When ignition is performed at the over-advanced position θdx, the force to push back the piston acts, and the force to push back the piston at time t3 rises toward the top dead center TDC. When the force of is overcome, the rotation direction of the engine is reversed. When it is detected that the rotation direction of the engine is reversed at time t4, the ignition position shifts to an ignition position (top dead center TDC in the illustrated example) suitable for maintaining the rotation direction of the engine in the reversed direction. To be made. It is preferable that the over-advancement of the ignition position is performed stepwise as shown.

Here, the magnitude of the advance amount βx when the ignition position is excessively advanced is appropriately selected according to the temperature of the air-fuel mixture. In an internal combustion engine, the higher the temperature of the air-fuel mixture,
When the fuel is ignited, the flame propagation speed increases,
The time until the explosive force applied to the piston after ignition reaches the maximum value becomes shorter. Therefore, when the temperature of the air-fuel mixture at the time of reversing the engine is high, the advance amount βx at the time of overadvancing the ignition position can be reduced as β1 shown in FIG. 6 (A). Further, when the temperature of the air-fuel mixture is low, it is necessary to increase the advance amount when the ignition position is excessively advanced, as shown by β3 in FIG. 6 (A).

As described above, in order to change the magnitude of the step advance amount βx according to the temperature of the air-fuel mixture, the engine temperature sensor for detecting the temperature of the internal combustion engine and the intake air temperature sensor for detecting the intake air temperature of the internal combustion engine. At least one of the above is provided, and when the temperature detected by the temperature sensor is lower, the advance amount βx for advancing the ignition position is increased, and the temperature is detected according to the temperature detected by the temperature sensor. The advance angle position θdx may be changed.

According to the above method, the direction of rotation of the internal combustion engine can be reversed without causing misfire, so that unburned gas is prevented from being discharged when the direction of rotation of the engine is switched. Therefore, it is possible to eliminate the risk of generating afterfire and polluting the atmosphere when switching the rotation direction.

As described above, if the ignition position is retarded when the inversion command is given, the engine speed can be reduced without causing knocking. Further, as described above, if the ignition position is advanced to the over-advanced position after the engine speed has decreased to the set over-advanced starting rotation speed, the over-advanced starting rotation speed will be sufficient. By setting it low, the rotation direction of the engine can be switched without applying an excessive force to the engine.

When the internal combustion engine is determined, the relationship between the ignition position and the rotation speed of the engine is substantially determined, so that the ignition position θs corresponding to the overadvanced angle starting rotation speed Ns can be obtained in advance. Therefore, the ignition position θs corresponding to this over-advanced start rotation speed is set as the over-advanced start position,
The engine rotation direction may be reversed by advancing the ignition position to the set over-advanced position when the ignition position of the internal combustion engine is retarded to the set over-advanced start position θs.

Since the rotation speed when the rotation direction of the engine reverses is very low and is unstable, the rotation direction of the engine reverses when the ignition position of the internal combustion engine is in the over-advanced position θdx. It is not always easy to detect whether or not it has been done. Therefore, it is preferable to confirm that the rotation direction of the engine is reversed after the ignition position is shifted from the over-advanced position to the ignition position after the rotation direction is reversed.

To this end, when the reversing command is given, the ignition position of the internal combustion engine is gradually retarded while the opening of the throttle valve is maintained near the opening during idling. The ignition position is set when the retarding process of decreasing the rotation speed and when the rotation speed of the internal combustion engine decreases to the set over-advance start rotation speed Ns, or when the ignition position retards to the over-advance start position θs. To the above-mentioned over-advanced position and ignite at least one cylinder at the over-advanced position, and after the over-advanced process is completed, the ignition position of each cylinder is set near the top dead center. It is only necessary to shift to the set ignition position that is set to No. 1 and to perform a rotational direction determination process of determining whether or not the rotational direction of the engine is reversed.

The number of ignitions in the over-advancing process is not the number of ignitions for each cylinder of the engine, but the number of ignitions for the entire engine. The number of ignitions is set to an appropriate number in order to reverse the rotation direction of the engine. If the number of ignitions in the over-advance process is too large, the engine may stop, so
It is preferable to set the number of ignitions during the over-advance process to a necessary minimum value. This number of ignitions may be less than the number of cylinders in the engine. That is, when the engine has multiple cylinders, it is possible that only some of the cylinders are ignited during the over-advance process.

In the case of basically reversing the rotation direction of the engine by performing the series of processes from the retarding process to the rotating direction determining process only once, the advance amount of the ignition position in the over-advancing process is set. Is preferably made sufficiently large within the range where the engine is not stopped, and the limit is that ignition is performed once in at least one cylinder in the over-advanced position, or once in each cylinder.

In order to inform the driver that the engine has reversed, the display means (lamp) that indicates that the engine has reversed when it is detected that the engine has reversed during the above-described rotational direction determination process. It is desirable to have the display operation be performed by a sound generator, etc.). Further, in order to ensure that the engine is reversed, when it is detected that the engine rotation direction has not been reversed during the above-described rotation direction determination process, the retarding process is performed until it is confirmed that the engine rotation direction has been reversed. From the rotation direction determination process is repeated, and after it is detected that the rotation direction of the engine is reversed in the rotation direction determination process, the engine is operated with the rotation direction reversed. Is preferred.

FIG. 9 shows a program executed by the microcomputer when a method of repeating a series of processes from the retarding process to the rotational direction determining process is repeated until it is confirmed that the rotational direction of the engine has been reversed. , Shows an algorithm of an interrupt routine executed when a reverse command is given.

According to the algorithm of FIG. 9, when the reversal command is given, first, in step 1, the fuel injection amount is reduced to change the air-fuel ratio to the lean side within a range where the engine is not stopped. Next, in step 2, it is judged whether or not the throttle opening is kept at the minimum value. If the throttle opening is not minimum, the fuel injection amount is returned to the specified amount in step 2a, and the ignition position is set in step 2b. After returning to the normal position (stopping the process of reversing the rotation direction of the engine), the process returns to the main routine. When it is confirmed in step 2 that the throttle opening is kept at the minimum value, it is determined in step 3 whether the engine rotation speed N has decreased to the over-advanced start rotation speed Ns. If it is determined that the rotation speed N has not decreased to the over-advancement start rotation speed Ns, the process proceeds to step 4, the ignition position is retarded by Δθi, and the process returns to step 2.

When it is determined in step 3 that the rotation speed N has decreased to the over-advancement start rotation speed Ns, in step 5, the over-advancement angle that matches the detection value of the sensor detecting the intake air temperature. The amount βx is determined, and in step 6, the ignition position is advanced by the excessive advance amount βx. Thereafter, in step 7, it is determined whether or not a predetermined number of ignitions have been performed, and when it is confirmed that the predetermined number of ignitions have been performed, the process proceeds to step 8. In step 8, the fuel injection amount is the specified amount (the amount required to make the air-fuel ratio normal)
Then, in step 9, the ignition position is moved to near the top dead center. When the ignition position is near the top dead center, the engine can be rotated regardless of whether the rotation direction of the engine is reversed or not, so that the engine can be prevented from stopping.

After shifting the ignition position to the top dead center, the rotational direction of the engine is determined in step 10. As a result, when the rotation direction of the engine is reversed, the process returns to the main routine. When it is determined in step 10 that the rotation direction is not reversed, the number of ignitions performed at the over-advanced position in the over-advanced process performed next in step 11 is set to a predetermined number (for example, 1).
Number of times) and then returns to step 1 to repeat the same process as above.

In the example shown in FIG. 9, step 4 is the retarding process, and steps 5 and 6 are the over-advancing process. Further, steps 8 to 10 are the rotational direction determination process.

Although not shown in FIG. 9, step 1
When it is determined that the rotation direction is not reversed at 0, after the advance amount βx when the ignition position is advanced in step 11 is increased by a predetermined amount (after It is also possible to return to step 1 after advancing the over-advanced position in the process further than the over-advanced position in the previous over-advanced process).

Further, in step 11 of FIG. 9, the number of ignitions to be performed at the over-advanced position in the next over-advanced angle process is increased by a predetermined number, and the advancement amount for advancing the ignition position to the over-advanced side. βx may be increased by a predetermined amount.

In the example shown in FIG. 9, when the reversal command is given, the fuel injection amount is first decreased in step 1 to change the air-fuel ratio to the lean side, but in step 1, the fuel injection amount is changed. May be increased to change the air-fuel ratio to the rich side without stopping the engine.

In order to facilitate the reversal of the engine rotation direction, the air-fuel ratio of the air-fuel mixture is first changed to the lean side or the rich side when the reversal command is given as described above. Although preferable, this step of changing the air-fuel ratio may be omitted.

In the example shown in FIG. 9, the amount of advance angle βx when the ignition position is excessively advanced is changed according to the intake air temperature of the engine, but the temperature of the engine (cooling water of the engine Temperature) and the magnitude of the advance amount βx may be changed according to the temperature of the engine, and the magnitude of the advance amount βx may be set for both the intake air temperature and the engine temperature. You may decide.

Further, regardless of the intake air temperature and the engine temperature, the advance amount when the ignition position is excessively advanced is set to a constant value (a value that can reverse the rotational direction of the engine even when the temperature of the air-fuel mixture is low). Good.

In the example shown in FIG. 9, the number of ignitions in the over-advanced angle process is increased each time a series of processes from the retarded angle process to the rotational direction determination process is repeated. When repeating a series of processes up to the direction determination process, the number of ignitions in the over-advanced process performed each time may be constant. In that case, step 11 in FIG. 9 is omitted.

In the above example, the fuel injection valve (injector) is used as the means for supplying the fuel to the internal combustion engine, but the present invention can be applied to the case where the carburetor is used as the means for supplying the fuel to the internal combustion engine. Of course.

When a carburetor is used, in order to change the air-fuel ratio of the air-fuel mixture, for example, a valve is inserted between the float chamber of the carburetor and the nozzle, and the fuel is injected from the nozzle of the carburetor depending on the opening of the valve. The amount of fuel to be used may be changed.

In the above example, the driver keeps the opening of the throttle valve at the minimum value when reversing the rotation direction of the internal combustion engine. However, the throttle valve is operated by an electric actuator. The actuator may be controlled so that the opening of the throttle valve is maintained at the minimum value when the reversal command is given.

In the case of reversing the rotation direction of the engine and backing up the vehicle or the like, it is dangerous that the rotation speed of the engine rises indefinitely. Therefore, when the engine is rotated in the direction of backing the vehicle or the like, it is preferable to limit the rotation speed of the engine to a predetermined limit value or less. To limit the rotational speed of the engine, for example, the ignition position may be retarded when the rotational speed of the engine exceeds the limit value.

In order to shorten the time when knocking occurs,
In the over-advanced angle process, as shown in FIG.
It is preferable to advance i to the over-advanced position stepwise, but the present invention is not limited to the case where the ignition position is over-advanced in the stepwise manner as described above. Even if the ignition position is changed to the over-advanced position over a predetermined time (sufficiently short time) when it is retarded to the position or when the rotation speed decreases to the over-advanced start rotation speed. Good.

[0103]

As described above, according to the present invention, by gradually retarding the ignition position of the internal combustion engine, the rotational speed of the engine is reduced, and the engine speed is set to an excessively advanced start. Since the ignition position is advanced to the over-advanced position when the rotation speed is reached or when the ignition position is retarded to the set over-advanced start position, the internal combustion engine should be misfired even once. Instead, the direction of rotation can be reversed. Therefore, it is possible to prevent the unburned gas from being discharged when the rotation direction of the engine is switched, and it is possible to eliminate the risk of generating afterfire and polluting the atmosphere when switching the rotation direction.

Further, in the present invention, by retarding the ignition position, the engine rotation speed is reduced without causing knocking, and when the engine rotation speed is sufficiently reduced, the ignition position is advanced. Therefore, it is possible to prevent unnecessary impact from being applied to the engine when reversing the rotation direction of the engine.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a control device used to carry out a method according to the present invention.

FIG. 2 is an explanatory diagram showing an example of an internal combustion engine to which the method of the present invention is applied and an example of a transmission provided between the engine and drive wheels of a vehicle or the like.

FIG. 3 is a configuration diagram showing an example of a rotation sensor used to detect the rotation of the engine when carrying out the method of the present invention.

FIG. 4 is a waveform diagram showing a waveform of a signal obtained from the rotation sensor of FIG.

FIG. 5 is an explanatory diagram for explaining changes in the ignition position during normal rotation and reverse rotation of the engine.

FIG. 6 is a diagram showing a temporal change of an ignition position and a temporal change of an engine speed in an embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a pressure in a cylinder of an internal combustion engine and a rotation angle.

FIG. 8 is a diagram showing the relationship between the air-fuel ratio of the air-fuel mixture supplied to the engine and the rotational speed of the engine.

FIG. 9 is a flowchart showing an algorithm of an interrupt routine of a program executed by a microcomputer when an inversion command is given, according to an embodiment of the present invention.

[Explanation of symbols]

1 Internal combustion engine 2 fuel injection valve 3 fuel pump 4 Fuel injection control device 5 Ignition device for internal combustion engine 6 Rotation sensor 7 Reverse command generator 8 Rotation direction switching control device

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02P 5/15 F02P 5/15 B (72) Inventor Hiroyasu Nito 3744 Ooka, Numazu-shi, Shizuoka Domestic Electric Co., Ltd. (56) References: JP-A-3-64668 (JP, A) JP-A-2-207176 (JP, A) JP-A-11-82270 (JP, A) JP-B-50-225 (JP, B1) (58) Survey Fields (Int.Cl. ⁷ , DB name) F02D 27/00-27/02 F02D 43/00 F02P 5/15 F02D 17/02 F02D 41/04

Claims (11)

(57) [Claims] 1. Rotation of a spark ignition type reciprocating piston type internal combustion engine, which comprises a piston reciprocating in a cylinder and a crankshaft connected to the piston, and is ignited by an ignition device capable of controlling an ignition position. In a rotation direction switching control method for switching the direction, when a reversal command for reversing the rotation direction of the internal combustion engine is given, in a state where the opening of the throttle valve is maintained near the opening during idling, A retarding process of gradually reducing the ignition position of the internal combustion engine to decrease the rotation speed of the internal combustion engine, and the ignition position when the rotation speed of the internal combustion engine decreases to a set overadvance start rotation speed. And an over-advance process for advancing to a set over-advance position are performed, and when it is detected that the rotation direction of the internal combustion engine is reversed in the over-advance process. The ignition position, the rotation direction switching control method for an internal combustion engine, characterized in that shifting to the rotational angular position suitable for maintaining the rotation of the internal combustion engine to the inverted direction. 2. Rotation of a spark ignition type reciprocating piston type internal combustion engine which is equipped with a piston reciprocating in a cylinder and a crankshaft connected to the piston and is ignited by an ignition device capable of controlling an ignition position. In a rotation direction switching control method for switching the direction, when a reversal command for reversing the rotation direction of the internal combustion engine is given, in a state where the opening of the throttle valve is maintained near the opening during idling, A retardation process of gradually retarding the ignition position of the internal combustion engine to reduce the rotational speed of the internal combustion engine, and the ignition position when the ignition position of the internal combustion engine is retarded to a set over-advance start position. And an over-advance process for advancing to a set over-advance position, and when it is detected that the rotation direction of the internal combustion engine is reversed in the over-advance process, Position, the rotation direction switching control method for an internal combustion engine, characterized in that shifting to the rotational angular position suitable for maintaining the rotation of the internal combustion engine to the inverted direction. 3. Rotation of a spark ignition type reciprocating piston type internal combustion engine, which comprises a piston reciprocating in a cylinder and a crankshaft connected to the piston, and is ignited by an ignition device capable of controlling an ignition position. In a rotation direction switching control method for switching the direction, when a reversal command for reversing the rotation direction of the internal combustion engine is given, in a state where the opening of the throttle valve is maintained near the opening during idling, A retarding process of gradually reducing the ignition position of the internal combustion engine to decrease the rotation speed of the internal combustion engine, and the ignition position when the rotation speed of the internal combustion engine decreases to a set overadvance start rotation speed. Is advanced to a set over-advanced position, and an over-advanced process of igniting at least one cylinder of the internal combustion engine at the over-advanced position and the over-advanced process are performed. After that, the ignition position of each cylinder is moved to a set ignition position set near the top dead center to perform a rotation direction determination process of determining whether the rotation direction of the engine is reversed. Method for controlling rotation direction switching of internal combustion engine. 4. A rotation of a spark ignition type reciprocating piston type internal combustion engine, which comprises a piston reciprocating in a cylinder and a crankshaft connected to the piston, and is ignited by an ignition device capable of controlling an ignition position. In a rotation direction switching control method for switching the direction, when a reversal command for reversing the rotation direction of the internal combustion engine is given, in a state where the opening of the throttle valve is maintained near the opening during idling, In the retarding process of gradually reducing the ignition position of the internal combustion engine to reduce the rotation speed of the internal combustion engine, and in the retarding process, the ignition position of the internal combustion engine is retarded to the set over-advance start position. And an over-advance process for advancing the ignition position to a set over-advance position and igniting at least one cylinder of the internal combustion engine at the over-advance position. After the completion of the above, the ignition position of each cylinder is moved to a set ignition position set near the top dead center, and a rotation direction determination process for determining whether or not the rotation direction of the engine is reversed is performed. A method for controlling rotation direction switching of an internal combustion engine. 5. A rotation of a spark ignition type reciprocating piston type internal combustion engine, comprising a piston reciprocating in a cylinder and a crankshaft connected to the piston, and ignited by an ignition device capable of controlling an ignition position. In a rotation direction switching control method for switching the direction, when a reversal command for reversing the rotation direction of the internal combustion engine is given, in a state where the opening of the throttle valve is maintained near the opening during idling, A retarding process of gradually reducing the ignition position of the internal combustion engine to decrease the rotation speed of the internal combustion engine, and the ignition position when the rotation speed of the internal combustion engine decreases to a set overadvance start rotation speed. Is advanced to a set over-advanced position to ignite at least one cylinder of the internal combustion engine at the over-advanced position, and the over-advanced process is ended. After that, the ignition position of each cylinder is moved to a set ignition position set near the top dead center, and a rotation direction determination process of determining whether the rotation direction of the engine is reversed is performed, and the rotation direction determination is performed. When it is detected that the rotation direction of the engine is not reversed in the process, a series of processes from the retarding process to the rotation direction determination process is repeated until it is confirmed that the rotation direction of the engine is reversed, A rotation direction switching control method for an internal combustion engine, comprising: operating the engine in a state where the rotation direction is reversed after it is detected in the rotation direction determination process that the rotation direction of the engine is reversed. 6. A rotation of a spark ignition type reciprocating piston type internal combustion engine, comprising a piston reciprocating in a cylinder and a crankshaft connected to the piston, and being ignited by an ignition device capable of controlling an ignition position. In a rotation direction switching control method for switching the direction, when a reversal command for reversing the rotation direction of the internal combustion engine is given, in a state where the opening of the throttle valve is maintained near the opening during idling, A retarding process of gradually retarding the ignition position of the internal combustion engine to reduce the rotation speed of the internal combustion engine, and the ignition position is set when the ignition position of the internal combustion engine is retarded to an over-advance start position. An advanced angle position to advance to an over-advanced position and ignite at least one cylinder of the internal combustion engine at the over-advanced position; The ignition position of the engine is moved to a set ignition position set near the top dead center and a rotation direction determination process of determining whether the rotation direction of the engine is reversed is performed, and in the rotation direction determination process of the engine, When it is detected that the rotation direction is not reversed, the series of processes from the retarding process to the rotation direction determination process is repeated until it is confirmed that the rotation direction of the engine is reversed. A method for controlling rotation direction switching of an internal combustion engine, comprising: operating the engine in a state where the rotation direction is reversed after it is detected that the rotation direction of the engine is reversed. 7. The over-advanced position in the over-advanced process is advanced further than the over-advanced position in the previous over-advanced process each time a series of processes from the retardation process to the rotational direction determination process is repeated. 7. The rotation direction switching control method for an internal combustion engine according to claim 5 or 6, wherein. 8. The number of ignitions performed at the over-advanced position is increased each time a series of processes from the retarding process to the rotational direction determining process is repeated. A rotation direction switching control method for an internal combustion engine as described. 9. The display means for displaying that the rotation direction of the engine has been reversed is caused to perform a display operation when it is detected that the rotation direction of the engine has been reversed in the process of determining the rotation direction. Item 8. A rotation direction switching control method for an internal combustion engine according to any one of items 3 to 7. 10. An engine temperature sensor for detecting the temperature of the internal combustion engine and at least one of an intake air temperature sensor for detecting the intake air temperature of the internal combustion engine are provided, and the temperature detected by the temperature sensor is low. 9. The over-advanced position is changed according to the temperature detected by the temperature sensor so as to increase the advance amount in the over-advanced process in some cases. A rotation direction switching control method for an internal combustion engine as described. 11. When the ignition position of the internal combustion engine is gradually retarded after the inversion command signal is given, the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is lean within a range that does not stop the internal combustion engine. The rotation direction switching control method for an internal combustion engine according to any one of claims 1 to 9, wherein the output torque of the internal combustion engine is reduced by changing to a rich side or a rich side.