JPH0241306Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to an exhaust timing control device for a two-stroke engine.

BACKGROUND ART In a two-stroke engine, there is an exhaust timing control device that controls the exhaust timing to a timing suitable for the operating condition of the engine by changing the position of the upper edge of the exhaust port. In such an exhaust timing control device, usually,
In order to change the position of the upper edge of the exhaust port between two positions, a flap valve is provided at the exhaust port as an exhaust timing adjustment mechanism. A biasing force is applied to the flap valve by a spring or the like to bring it into the first opening state. Further, a rotational driving force that resists the biasing force is supplied from the actuator to the shaft of the flap valve so that the flap valve enters the second opening state depending on the operating state of the engine. The actuator reduces the rotation of a DC motor (hereinafter simply referred to as a motor) using a reduction gear to obtain a rotational driving force to change the opening state of the flap valve.
However, when the flap valve reaches either the first or second opening position, it is difficult to immediately stop the motor rotation and maintain that position, and if the stopper in the actuator is used to stop the motor, the impact of a collision will be There was a problem that the durability of the mechanism inside the actuator was poor due to the force.

Summary of the invention Therefore, the purpose of the invention is to provide an exhaust timing control device that improves the durability of its mechanical parts.

The exhaust timing control device of the present invention is characterized in that a braking means is provided to short-circuit the terminals of the motor when the supply of power supply voltage to the motor is stopped, thereby speeding up the motor stop.

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

In the exhaust timing control device according to the present invention shown in FIGS. 1 to 7, 1 is a two-stroke engine body, 2 is a cylinder, 3 is a piston, and 4 is an exhaust port. The exhaust port 4 is provided with a flap plate 11, which is coupled to a shaft 12 and is rotatable relative to the inner wall surface of the exhaust port 4, with its tip located at the upper edge of the exhaust port 4. ing.
The flap plate 11, the shaft 12, and the inner wall surface of the exhaust port 4 form a flap valve. The tip of the flap plate 11 is a slide valve 15.
As a result, a biasing force is applied substantially from above the cylinder 2, and the flap plate 11 is brought into contact with a stopper (not shown). The slide valve 15 is embedded in the cylinder block 16, and its slide plate 17 is biased by a spring 18 to abut the tip of the flap plate 11 and close the upper part of the exhaust port 4 than the flap plate 11. It's getting old. Shaft 12
One end of the exhaust port 4 is located outside the exhaust port 4, and a pulley 19 is connected thereto. Rotational force is supplied to the pulley 19 from an actuator 21.

In the actuator 21, as shown in FIG. 6, a motor 24 is installed outside a rectangular housing 23.
is fixed. A shaft of the motor 24 is located within the housing 23, and a gear 2 is attached to the shaft.
5 are combined. This gear 25 and gears 26 to 28 form a speed reduction mechanism. Final gear 26
A disc-shaped rotating member 30 is coupled to one end of the deceleration output shaft 29 . An engagement pin 31 is implanted at an eccentric position of the rotating member 30. On the other hand, the drive output shaft 3 is connected parallel to the deceleration output shaft 29.
2 is rotatably provided in the housing 23. A swing arm 33 is coupled to the drive output shaft 29 . A longitudinal engagement hole 3 extending in the longitudinal direction of the swing arm 33 is provided at the free end of the swing arm 33.
4 is formed. An engagement pin 31 is engaged in the longitudinal engagement hole 34 so as to be movable only in the longitudinal direction of the swing arm 33 . A pair of shielding plates 38 and 39 are installed near the free end of the swing arm 33.
protrudes in the direction of swing. Also, the swing arm 3
A printed circuit board 35 is provided on the housing 23 so as to be parallel to the swing arm 33 in the vicinity of the swing arm 33 . Two position sensors 3 are installed on the printed circuit board 35.
6 and 37 are fixed. Position sensor 36,3
Reference numeral 7 is a photocoupler, which generates a position detection signal when the shielding plates 38 and 39 enter the grooves of the corresponding position sensors 36 and 37 in accordance with the swing of the swing arm 33. Drive output shaft 3
One end of the housing 23 is located outside the housing 23, and a pulley 40 is coupled to the one end. The rotational force of the pulley 40 is transmitted to the pulley 19 by a wire 41.

The rotational operation of the motor 24 of the actuator 21 is controlled by a control circuit 44. Control circuit 44
As shown in FIG. 7, there is a waveform shaping circuit 47 that shapes the pulse signal generated in the primary coil of the ignition coil of the CDI ignition system into a Ne pulse, and a Ne pulse.
A rotation speed determination circuit 48 that determines from the pulse whether the engine rotation speed is higher than a predetermined rotation speed, and a determination output of the rotation speed determination circuit 48 and a position sensor 3
The drive circuit 49 rotates the motor 24 according to the outputs of the motors 6 and 37.

In such a configuration, when the engine rotation speed is a low rotation speed below a predetermined rotation speed, the swing arm 3
3 is in the position shown by the solid line in FIG. 5, and the flap plate 11 is biased by the slide valve 15 so that the upper part of the exhaust port 4 is in the position shown in FIG. 17
It is occluded at the tip. When the engine speed increases and exceeds the specified speed, the engine speed becomes high.
The output level of the rotation speed determination circuit 48 is inverted from low level to high level. This high level is the drive circuit 4
9, the drive circuit 49 drives the motor 24 in reverse rotation. The rotation of the shaft of the motor 24 is reduced in speed by gears 25 to 28 and transmitted to the rotating member 30. The rotating member 30 rotates in the direction of arrow A in FIG.
It reciprocates within the longitudinal engagement hole 34 of No. 3. Then,
When the swing arm 33 swings around the drive output shaft 32 and moves to a position near the broken line in FIG. 6, the shielding plate 38 enters the groove of the position sensor 36, and the output level of the position sensor 36 becomes high. Flip to level. Since this high level is supplied as a position detection signal to the drive circuit 49, the drive circuit 49 stops driving the motor 24. Then, as will be described later, dynamic braking occurs in the motor 24, and the swinging arm 33 moves gently to the position indicated by the broken line in FIG. The dowel pin 31 abuts and the movement of the swing arm 33 is stopped. The swinging motion of the swinging arm 33 is transmitted from the drive output shaft 32 to the flap plate 11 via the pulley 40, wire 41, pulley 19, and shaft 12. The flap plate 11 moves together with the slide plate 17 against the biasing force of the spring 20, and the tip of the flap plate 11 is positioned on the inner wall surface of the exhaust port 4 as shown in FIG. Therefore, when the engine speed is high, the upper edge of the exhaust port 4 becomes higher, so that the exhaust timing is earlier than when the engine speed is low.

As the rotating member 30 rotates approximately 180 degrees, the swing arm 33 is located at the solid line position when the engine speed is low and at the broken line position when the engine speed is high, as shown in FIG. In these two positions, pulley 4
Even if an external force is applied to the rotating member 30, the external force only applies a force in the direction of the central axis of the rotating member 30 to the engaging pin 31, and almost no force is generated to rotate the rotating member 30, resulting in a locked state.

FIG. 8 shows a specific configuration of the rotation speed determination circuit 48. In this circuit, a one-shot pulse generating circuit 51 is provided. The one shot pulse generation circuit 51 generates a one shot pulse of a predetermined time width in response to the rising edge of the Ne pulse. A charging/discharging circuit 52 and a shot trigger generating circuit 60 are connected to the output terminal of the one shot pulse generating circuit 51. The charging/discharging circuit 52 consists of resistors 53, 54, a capacitor 55, and a transistor 56. When the transistor 56 is off, a voltage _Vcc is supplied to the capacitor 55 via the resistor 54 to charge the capacitor 55, and the transistor 56 receives a one-shot pulse. The accumulated charge in the capacitor 55, which is turned on in response to this, is discharged. A comparator circuit 57 is connected to the output end of the charge/discharge circuit 52, that is, one end of the capacitor 55. Comparison circuit 57 compares the terminal voltage of capacitor 55 and the voltage divided by resistors 58 and 59 of voltage _Vcc . A D-latch circuit 61 is connected to the output terminal of the comparison circuit 57, and the D-latch circuit 61 holds the output level of the comparison circuit 57 in response to the Schmitt trigger supplied from the Schmitt trigger generation circuit 60 and outputs it to the drive circuit 49.

In the rotational speed determination circuit 48, Ne pulses whose generation intervals become shorter as the engine rotational speed increases are supplied from the waveform shaping circuit 47 to the one-shot pulse generation circuit 51 as shown in FIG. 9a. The one shot pulse generating circuit 51 generates a one shot pulse of a predetermined time width as shown in FIG. 9b in response to the rising edge of the Ne pulse.
The one-shot pulse is supplied to the base of transistor 56 via resistor 53, so transistor 56 is turned on. By turning on the transistor 56, both ends of the capacitor 55 are short-circuited, and the accumulated charge in the capacitor 55 is discharged. When the one-shot pulse disappears, transistor 56 is turned off.
When the transistor 56 is turned off, the voltage V _cc is applied to the resistor 5.
The terminal voltage of the capacitor 55 gradually rises as shown in FIG. 9c until just before the next one-shot pulse is generated. That is, the terminal voltage of the capacitor 55 increases in proportion to the engine speed. When the engine speed reaches a high speed higher than a predetermined speed, the terminal voltage of the capacitor 55 changes to the resistor 58,
59, the output level of the comparator _circuit 57 is inverted from a low level to a high level as shown in FIG. 9d. The output level of the comparator circuit 57 is held in the latch circuit 61 at the rising timing of the one-shot pulse.As shown in FIG. The level remains high until it is determined that the engine speed is low, and if it is determined that the engine speed is low, the level remains low until it is determined that the engine speed is high.

FIG. 10 shows a specific configuration of the drive circuit 49. In this circuit, position sensors 36, 37
Latch circuits 65 and 66 are provided which are connected to the output terminals of the circuits. The latch circuit 65 is the position sensor 36
The output level of the position sensor 37 is maintained and is reset in response to the high level output of the position sensor 37. Similarly, the latch circuit 66 holds the output level of the position sensor 37,
It is reset in response to the high level output of position sensor 36. In addition, in the drive circuit 49, AND circuits 67, 68, NOR circuit 69, OR circuits 70, 7
1. Inverter 72, transistors 73 to 8
0 and diodes 81 to 84 are provided. The AND circuit 67 takes the logical product of the output levels of the rotation speed determination circuit 48 and the latch circuit 66,
The AND circuit 68 calculates the logical product of the inverted level by the inverter 72 of the rotation speed determining circuit 48 and the output level of the latch circuit 65. NOR circuit 69 is AND
Take the logical sum of each output level of the circuits 67 and 68,
OR circuit 70 is AND circuit 68 and NOR circuit 69
The OR circuit 71 calculates the logical sum of each output level of
The logical sum of each output level of the AND circuit 67 and the NOR circuit 69 is taken. The output terminal of AND circuit 67 is NPN
The emitter of the transistor 74 is grounded, and the collector is connected to the base of the transistor 74.
Connected to the base of PNP transistor 73. A voltage V _B is supplied to the emitter of the transistor 73, and a diode 81 is connected between the collector and emitter of the transistor 73.
A transistor 75 is connected to the output terminal of the AND circuit 68.
76 and a diode 82 are connected in the same configuration as the transistors 73, 74 and diode 81 described above. Also, at the output end of the OR circuit 70
NPN transistors 77 and 78 are connected in Darlington, a diode 83 is connected between the collector and emitter of transistor 78, and similarly NPN transistors 79 and 8 are connected to the output terminal of OR circuit 70.
0 is Darlington connected, and a diode 84 is connected between the collector and emitter of the transistor 80. The collectors of the transistors 81 and 83 are both connected to the negative terminal of the motor 24, and the collectors of the transistors 82 and 84 are both connected to the positive terminal of the motor 24.

In this drive circuit 49, when the engine speed is low and the swing arm 33 is at the position indicated by the solid line in FIG. Then, since the output level of the position sensor 37 becomes high level, both the AND circuits 67 and 68 become low level outputs, and the transistors 73 to 76 are turned off. On the other hand, the NOR circuit 69 outputs a high level and makes the output levels of the OR circuits 70 and 71 high, so that the transistors 77 to 80
turns on. Therefore, both ends of the motor 24 are short-circuited and rotation is stopped. When the engine speed increases from this state and the engine speed discrimination circuit 48 determines that the engine speed is high and outputs a high level signal,
The output level of the AND circuit 67 becomes high level,
Since the output level of the AND circuit 68 remains at a low level, the NOR circuit 69 becomes a low level. Also
The output level of the OR circuit 70 becomes a low level,
The output level of the OR circuit 71 becomes high level due to the high level output of the AND circuit 67. Therefore, transistors 73, 74, 79, and 80 are turned on,
Since the transistors 75, 76, 77, and 78 are turned on, the voltage V _B is supplied to the motor 24 with the opposite polarity. The motor 24 rotates in the opposite direction to rotate the rotary member 30 in the direction of arrow A as described above, thereby moving the swinging arm 33 toward the position indicated by the broken line in FIG. Due to this movement, the shielding plate 39 comes off the groove of the position sensor 37, and the output level of the position sensor 37 becomes a low level immediately after the movement of the swing arm 33 starts. However, since the latch circuit 66 maintains the high level output, the motor 24 Continue to rotate in reverse. When the oscillating ohm 33 moves close to the position indicated by the broken line in FIG. The latch circuit 65 then outputs a high level, and the latch circuit 66 outputs a low level. Therefore, AND circuits 67 and 68 both have low level outputs, transistors 73 to 76 are turned off, and the supply of voltage V _B to motor 24 is stopped. Further, the NOR circuit 69 has a high level output, causing the output levels of the OR circuits 70 and 71 to be high level, so that the transistors 77 to 80 are turned on. Therefore, even after the supply of voltage V _B to motor 24 is stopped, motor 24 continues to rotate due to inertial force, so motor 24 operates as a generator and an electromotive force is generated between its positive and negative terminals. A current due to this electromotive force flows through the transistor 78 and the diode 84.
Since the current flows and the terminals of the motor 24 are short-circuited, a braking force is applied to the motor 24.

Next, when the engine rotation speed falls below a predetermined rotation speed and the output level of the rotation speed discrimination circuit 48 is reversed to a low level while the swing arm 33 is at the position indicated by the broken line in FIG. Since the output level of the AND circuit 67 becomes low level and the output level of the AND circuit 68 remains high level, the NOR circuit 69 becomes low level. Further, the output level of the OR circuit 70 becomes a high level, and the output level of the OR circuit 71 becomes a low level due to the low level output of the AND circuit 67. Therefore, transistors 73, 7
4, 79, and 80 are turned off, and transistor 7
5, 76, 77, and 78 are turned on, so motor 2
4 is supplied with voltage V _B of positive polarity. motor 2
4 rotates forward and rotates the rotating member 30 in a direction opposite to the direction of arrow A, thereby moving the swinging arm 33 toward the position indicated by the solid line in FIG. Furthermore, when the swinging arm 33 moves close to the position indicated by the solid line in FIG. Latch circuit 6
6 outputs a high level, and the latch circuit 65 outputs a low level. Therefore, the above-mentioned swing arm 33
As in the case where V _B moves to the vicinity of the broken line in FIG. 5, transistors 73 to 76 are turned off and transistors 77 to 80 are turned on.
An electromotive force is generated between the terminals. A current due to this electromotive force flows through the transistor 80 and the diode 83, and the terminals of the motor 24 are short-circuited.
The braking force acts on 4.

Effects of the Invention As described above, in the exhaust timing control device for a two-stroke engine of the present invention, when the supply of power supply voltage to the motor that drives the exhaust timing adjustment mechanism is stopped, the terminals of the motor are short-circuited, and the motor The brakes are starting to apply. Therefore, just before the exhaust timing adjustment mechanism reaches one of the two predetermined exhaust port upper edge positions, the supply of power supply voltage to the motor is stopped and a braking force is applied, thereby adjusting the exhaust timing to either of the two predetermined exhaust port upper edge positions. The impact force applied to members such as stoppers in the actuator when reaching the position can be made very small, and the durability of the mechanism in the actuator can be improved.
Furthermore, since the inertial force of the motor becomes braking energy, energy that would otherwise have been wasted can be effectively used, which has the advantage of saving energy compared to systems that employ mechanical brakes.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2 is a sectional view showing the exhaust timing adjustment mechanism portion, Fig. 3 is a - sectional view in Fig. 2, and Fig. 4 is a - sectional view in Fig. 2. 5 is a sectional view of FIG. 2, FIG. 6a is a side view showing the structure of the actuator, FIG. 6b is a plan view showing the structure of the actuator, and FIG. 7 is a structure of the control circuit. Block diagram, Fig. 8 is a circuit diagram showing the specific configuration of the rotation speed discrimination circuit, Fig. 9 is a waveform diagram showing the operation of the circuit shown in Fig. 8, and Fig. 10 shows the specific configuration of the drive circuit. It is a circuit diagram. Explanation of symbols of main parts, 1...Engine body,
4...Exhaust port, 13...Flap valve, 15...
... Slide valve, 21 ... Actuator, 2
4... Motor, 30... Rotating member, 31... Engagement pin, 33... Swinging arm, 36, 37... Position sensor, 44... Control circuit.

Claims (1)

[Scope of utility model registration request] An exhaust timing adjustment mechanism provided at an exhaust port for changing the position of the upper edge of the exhaust port of a two-cycle engine, a motor that drives the exhaust timing adjustment mechanism, and a power supply voltage supplied to the motor according to the operating state of the engine. and a voltage supply means for controlling the rotation of the motor, and the voltage supply means has a control means for short-circuiting between terminals of the motor when the supply of power supply voltage to the motor is stopped. Exhaust timing control device.