JPH0914113A - Ignition timing control device for engine - Google Patents

Abstract

PURPOSE: To attain a structure for suppressing an engine, revolution speed without installing a special sensor by supplying air-fuel mixture by means of an evaporator provided with a PTC type autochoke mechanism, and controlling an ignition timing of an engine according to a value of current applied to the PTC. CONSTITUTION: A CPU 33 is composed of an autochoke operation sensing means 39 and an ignition timing setting means 40. The sensing means 39 calculates current value of a PTC (thermistor heater) 15 while measuring voltage of a resistance R. When the current value is larger than a set value, a choke ON signal is output to the setting means 40. When the current value is smaller than the set value, an OFF signal is outputted. The ignition timing setting means 40 is connected to a pulser generator 32 from which a crank angle signal is outputted. Based on the crank angle signal, engine revolution speed and a crank angle of an engine 6 are sensed and an ignition timing is determined. When a piston reaches an ignition position, an ignition signal is outputted to an ignition unit 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine ignition timing control system for a motorcycle which transmits engine power to wheels via a V-belt type continuously variable transmission and a centrifugal clutch.

[0002]

2. Description of the Related Art Conventionally, there is a structure in which engine power is transmitted to a rear wheel through a V-belt type continuously variable transmission and a centrifugal clutch, such as a scooter type motorcycle. As a carburetor used in this type of motorcycle, there is a carburetor equipped with an auto choke mechanism that enhances ignitability by controlling the air-fuel ratio so that a large amount of fuel is obtained when the engine is cold. This auto choke mechanism has a structure in which a starting fuel passage is opened on the downstream side of intake air from a throttle valve of a carburetor, and the amount of fuel sucked into the intake passage from this fuel passage is increased by the start valve at the time of engine startup. There are things.

In controlling the starting valve, wax, which is heated by a PTC (thermistor heater) supplied from an engine generator or the like and thermally expanded, is used as a drive source, and the opening degree is automatically changed. Was doing. That is, when the engine is started in a cold state, the air-fuel mixture is rich, and as the warm-up progresses, the air-fuel mixture is gradually thinned.

[0004]

However, a carburetor equipped with the auto choke mechanism constructed as described above is
When used in an engine having a V-belt type continuously variable transmission used for scooters and a centrifugal clutch, there has been a problem that the life of the centrifugal clutch is shortened.

This is because when the ignition timing of the engine is set so as to optimize the fuel consumption during steady running, when the auto choke mechanism is operating (during warm-up operation).
This is because the engine speed becomes too high.
That is, even though the vehicle body is stopped, the shoe slides in contact with the drum in the centrifugal clutch, and this sliding contact portion wears early.

Such a problem can be solved by retarding the ignition timing and lowering the engine speed when the auto choke mechanism is operating. However, for example, a potentiometer may be provided as a throttle opening sensor and the ignition timing may be controlled by detecting this opening, but the sensor must be connected to the carburetor, which complicates the structure of the carburetor. turn into. Further, since the sensor must be arranged around the carburetor, it is difficult to secure a space for disposing the sensor. In addition, the number of parts increases and the cost increases.

The present invention has been made to solve such a problem, and the ignition timing of the engine can be set so that the fuel consumption is optimum during steady running, and the operation state of the auto choke mechanism is easy. Therefore, even if the carburetor with an auto choke mechanism is used in an engine having a V-type continuously variable transmission and a centrifugal clutch, the centrifugal clutch can be used for a long period of time.

[0008]

An engine ignition timing control device according to the present invention controls an engine ignition timing in accordance with a value of a current flowing through a PTC.

[0009]

In the engine ignition timing control device according to the present invention, the operating state of the auto choke mechanism can be detected by the PTC current value.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a starting device in an engine according to the present invention, FIG. 2 is an enlarged sectional view showing a PTC type auto choke mechanism of a carburetor,
3 is a graph showing the temperature / resistance characteristics of PTC, and FIG. 4 is P
FIG. 5 is a graph showing the temperature / current characteristics of TC, and FIG. 5 is a flowchart for explaining the operation of the ignition timing control device for the engine according to the present invention.

In these figures, 1 is a scooter according to this embodiment, and this scooter 1 has a conventionally known structure except for an engine ignition timing control device which will be described later. 2 is the front wheel,
3 is a rear wheel, 4 is a steering wheel, 5 is a seat, and 6 is a unit swing type engine (hereinafter, simply referred to as an engine) for rotationally driving the rear wheel 3.

The engine 6 is of a two-cycle single cylinder type, and a carburetor 7 having an electric PTC type auto choke mechanism is connected to the upper part of a cylinder 6a and an exhaust pipe 8 is connected to the lower part thereof to form a crankshaft. The drive pulleys of the generator 9 and the V-belt type continuously variable transmission 10 are mounted on a shaft (not shown). A centrifugal clutch (not shown) is interposed between the V-belt type continuously variable transmission 10 and the rear wheel 3, and
Power is transmitted from the crankshaft to the rear wheels 3 via the belt type continuously variable transmission 10 and the centrifugal clutch.

As shown in FIG. 2, the PTC type auto choke mechanism of the carburetor 7 includes a main body 11 of the carburetor 7 and a starting fuel passage 13 provided in a lower cover 12 which forms a starting fuel chamber S together with the main body 11. A starting valve 14 for opening and closing
PTC1 for heating the wax of the start valve 14 described later.
5 are formed. The starting fuel passage 13 has an upstream side communicating with the starting fuel chamber S, a downstream side opening to a downstream side of a throttle valve in an intake passage (not shown), and a starting valve 14 is interposed in the middle. . In addition,
The starting fuel chamber S has a structure in which fuel is supplied from a fuel tank (not shown).

The starting valve 14 includes a cylindrical bottomed valve case 16 supported and fixed to the main body 11 of the carburetor 7, a needle 17, a plunger 18, and a spring seat 19.
And a valve body 20 supported by the valve case 16 and the carburetor main body 11 so as to be movable in the vertical direction in the figure, and a compression for biasing the valve body 20 upward (in the opening direction) in the figure. A coil spring 21 and a wax unit 23 connected to the upper portion of the valve body 20 via a push rod 22 are formed. The wax unit 23 has a conventionally known structure in which the thermal expansion of the wax 25 in the wax case 24 is transmitted to the push rod 22 via the diaphragm 26, the semi-fluid substance 27 and the rubber 28.

The PTC 15 is closely attached to the upper surface of the wax case 24. The PTC 15 has a structure that generates heat when energized. In FIG. 2, a lead wire 15a is connected to a power source (generator 9), and a lead wire 15b is grounded. That is, when the crankshaft of the engine 6 rotates and the generator 9 generates power, the PTC 15 generates heat and the wax 25
Will be heated. The wax 25 has a certain heat capacity, and the cylinder 6a of the engine 6
Since it is arranged in the vicinity of, the temperature of the engine 6 gradually decreases after the engine 6 is stopped after traveling.

In the PTC type auto choke mechanism constructed as described above, the needle 17 closes the needle hole 13a of the starting fuel passage 13 as shown in FIG. It is set not to. Therefore, when the engine is started, a large amount of fuel flows in the starting fuel passage 13, and a rich air-fuel mixture is sucked into the engine 6 from the intake passage to improve ignitability.

Further, when the wax 25 is heated by the PTC 15 and extends, the push rod 22 and the valve body 20 move downward in FIG. 2 when the force to extend becomes larger than the spring force of the compression coil spring 21. Moving. At this time, the needle 17 of the valve body 20 gradually closes the needle hole 13a, and the fuel flowing through the starting fuel passage 13 gradually decreases. As a result, the air-fuel mixture becomes gradually thinner than in the above-mentioned state, and when the thermal expansion of the wax 25 becomes the largest, the needle hole 13a is completely closed and the air-fuel ratio at the time of steady running is obtained.

Reference numeral 31 is a starting device for an engine according to the present invention. The engine starting device 31 is the PTC 15
And a pulsar generator 32 provided in the generator 9.
And a CPU 33 as a control device, a CDI ignition unit 34, an ignition coil 35, and the like. A reference numeral 36 in FIG. 1 is a regulator,
37 is a battery. The PTC is a regulator 36
It is structured to be powered from.

The pulsar generator 32 has a structure for outputting a crank angle signal to the CPU 33 every time the pulsar rotor 38 mounted on the rotor (not shown) of the generator 9 rotates. This crank angle signal is configured to be generated when the crank shaft rotates by a predetermined crank angle. In this embodiment, the crankshaft is 1
A signal for one pulse is generated each time it rotates.

The CPU 33 comprises an auto choke operation detecting means 39 and an ignition timing setting means 40. As shown in FIG. 1, the auto choke operation detecting means 39 measures the voltage across the resistor R interposed in the power feeding path of the PTC 15 to calculate the current value of the current flowing through the PTC 15, and this current value is calculated in advance. When it is larger than the predetermined value, a choke ON signal is output to the ignition timing setting means 40.
On the other hand, when the current value is smaller than the set value, the choke OFF signal is output to the ignition timing setting means 40. When the current value is larger than the set value, the automatic choke mechanism is operating, and when the current value is smaller than the set value, the automatic choke mechanism is not operating. This will be described with reference to FIGS. 3 and 4.

As shown in FIG. 3, it is known that the resistance of the PTC 15 gradually increases as the temperature rises. Here, needle 1 of auto choke mechanism
When 7 and T ₁ the temperature at which no longer is the fuel flow in the starting fuel passage 13 closes substantially a needle hole 13a (when the operation of the automatic choke mechanism is completed), the resistance R ₁ when reaching this temperature T ₁ of Can be obtained from the characteristic diagram of PTC 15 (FIG. 3).

On the other hand, since the voltage supplied from the regulator 36 and applied to the PTC 15 is constant, the temperature-resistance curve of FIG. 3 can be replaced with the temperature-current curve of FIG. That is, the current I _{1 at} the temperature T ₁ becomes the current value at the end of the operation of the auto choke mechanism.
_When more current is flowing than _1, it can be determined that the auto choke mechanism is operating. This current value is detected by the auto choke operation detecting means.

The ignition timing setting means 40 is connected to the pulsar generator 32 of the generator 9, detects the rotational speed and crank angle of the engine 6 by the crank angle signal output from the pulsar generator 32, and determines the ignition timing. The ignition signal is output to the CDI ignition unit 34 when the piston position reaches the ignition position. To determine the ignition timing, the choke ON input from the automatic choke operation detecting means 39,
Performed based on the choke OFF signal. That is, when the choke ON signal is input from the auto choke operation detecting means 39, the ignition timing is retarded by a predetermined angle from the ignition timing during steady traveling, and when the choke OFF signal is input, ignition during steady traveling is performed. It is time. It should be noted that the ignition timing at the time of steady running is the ignition timing that provides the highest fuel economy.

The CDI ignition unit 34 includes a generator 9
A part of the electric power generated by is charged, and when the ignition timing setting means 40 outputs an ignition signal, the charged electric power is supplied to the primary coil of the ignition coil 35. Also, the ignition coil 3
Reference numeral 5 is a conventionally well-known structure, and a large voltage is generated in the secondary coil when the primary coil is energized, and this large voltage is applied to the spark plug 41 of the engine 6.

Next, the operation of the ignition timing control device for the engine configured as described above will be described with reference to FIG. First, when a main switch (not shown) is turned on,
As shown in step S ₁ in FIG. 5, the CPU 33 detects the engine speed, the crank angle, and the value of the current flowing through the PTC 15. Then, as shown in step S ₂ , the auto choke operation detecting means 39 of the CPU 33 determines from the current value whether or not the auto choke mechanism is operating.

When the engine 6 is started by a starter motor or kick type starter (not shown) while the engine 6 is cold, the temperature of the PTC 15 immediately after the start will be T in FIGS. 3 and 4.
_It is lower than ₁ and the wax 25 of the starting valve 14 is also PT at low temperature.
Since it is difficult to raise the temperature of C15, the auto choke operation detecting means 39 outputs a choke ON signal to the ignition timing setting means 40. And step S in FIG.
_{In 3} , the ignition timing setting means 40 sets the ignition timing to a value that is retarded from a predetermined timing from the ignition timing during steady running.

The ignition timing setting means 40 outputs an ignition signal to the CDI ignition unit 34 based on the ignition timing set on the retard side as described above, and the CDI ignition unit 34 performs ignition control (step S ₄ ). . After the engine is started, the engine ignition timing control device returns from step S ₄ to step S ₁ and repeats the above control.

On the other hand, when the engine 6 is in a cold state, the wax 25 of the starting valve 14 is also in the most contracted state at a low temperature, and even if it is heated by the PTC 15 from the beginning of starting, the expansion due to thermal expansion is small. The start valve 14 is substantially fully opened and a large amount of fuel flows into the start fuel passage 13.
Therefore, a rich air-fuel mixture is supplied to the engine 6.

However, since the ignition timing is retarded as described above, the engine speed does not become higher than necessary even if such a rich air-fuel mixture is supplied. That is, even if the engine 6 is cold when the engine is started, the centrifugal clutch of the V-belt type continuously variable transmission 10 idles, and power is not transmitted from the engine 6 to the rear wheels 3.

When the engine 6 is started, the PTC 15 is energized to heat the wax 25. As the warm-up progresses, the wax 25 receives not only the heat of the PTC 15 but also the heat of the engine 6. Then, the wax 25 is thermally expanded and the needle 17 of the starting valve 14 is inserted into the needle hole 13
The engine 6 is warmed up by closing a.
At this time, almost no fuel flows into the starting fuel passage 13, and the air-fuel ratio of the air-fuel mixture becomes the ratio during steady running.

Further, at this time, the temperature of the PTC 15 reaches T ₁ in FIG. 4, and the current flowing through the PTC 15 becomes smaller than I _1. Therefore, step S _{2 in} FIG.
The CPU33 proceeds to step S ₅ from automatic choke operation detecting unit 39 outputs a choke OFF signal to the ignition timing setting section 33. Then, the ignition timing setting means 33 sets the ignition timing to a value during steady running, and the CDI ignition unit 34 performs ignition control in step S ₄ . That is,
After warming up, the engine 6 will be operated with the ignition timing during steady running.
Will be driven.

Further, after running, the engine 6 is stopped,
If it is restarted before it cools down, the wax 25 is also kept at a high temperature and the PTC15
Since the value of the electric current flowing through is smaller than I _{1 in} FIG. 4, the ignition timing becomes the value during steady running. That is, the ignition timing is not retarded when such an auto choke mechanism does not operate.

Therefore, since the PTC 15 substantially serves as a sensor for detecting the operation state of the auto choke mechanism, it is not necessary to attach a special sensor to the carburetor to detect the operation of the auto choke mechanism, and the simple construction is possible. I'm done. Therefore, it is possible to easily realize a configuration in which the ignition timing is retarded to suppress the engine speed when the auto choke mechanism is operating.

It should be noted that, as described above, the engine ignition timing can be controlled in consideration of the engine temperature. With such a configuration, the ignition timing can be controlled so as to be an appropriate timing in any engine state. Since the wax provided in the auto choke mechanism is easier to cool than the engine, the wax may harden and return to the initial state while it is still warm after the engine is stopped. When the engine is started in such a state, the auto choke mechanism operates in the same way as when the engine is completely cooled down. At this time, the engine speed becomes higher than when it is cold because the engine has reached a temperature at which it can be easily operated.

That is, when it is determined that the engine is in an easy-to-operate state by taking the engine temperature into consideration, PT
By adding the ignition timing control amount based on the engine temperature to the ignition timing control amount based on the current value at C, it is possible to prevent the engine speed from increasing as described above.
When detecting the temperature of the engine, the temperature of the engine cylinder or cylinder head is directly detected by the temperature sensor, or in the case of a water-cooled engine, the temperature of the engine cooling water is detected by the temperature sensor, or the oil pan is used. If the engine has it, the oil temperature can be detected by a temperature sensor.

[0036]

As described above, the engine ignition timing control device according to the present invention controls the ignition timing of the engine in accordance with the value of the current flowing through the PTC.
TC becomes a sensor that substantially detects whether or not the auto choke mechanism is operating.

Therefore, it is possible to easily realize a structure in which the ignition timing is retarded to suppress the engine speed when the auto choke mechanism is operating, without attaching a special sensor to the carburetor. For this reason, with a very simple structure, it is possible to prevent the degree of contact at the sliding contact portion of the centrifugal clutch from increasing at the time of starting and to extend the life of the centrifugal clutch.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a starting device in an engine according to the present invention.

FIG. 2 is an enlarged sectional view showing a PTC type auto choke mechanism of a vaporizer.

FIG. 3 is a graph showing temperature / resistance characteristics of PTC.

FIG. 4 is a graph showing temperature / current characteristics of PTC.

FIG. 5 is a flowchart for explaining the operation of the engine ignition timing control device according to the present invention.

[Explanation of symbols]

6 ... Engine, 7 ... Vaporizer, 14 ... Start valve, 15 ... PT
C, 25 ... Wax, 31 ... Engine starter, 33 ...
CPU, 34 ... CDI ignition unit, 39 ... Auto choke operation detecting means, 40 ... Ignition timing setting means.

Claims (1)

[Claims] 1. Power of an engine is transmitted to wheels via a V-belt type continuously variable transmission and a centrifugal clutch, and an air-fuel mixture is supplied to the engine by a carburetor provided with a PTC type auto choke mechanism. In a motorcycle, an ignition timing control device for an engine, which controls an ignition timing of the engine according to a value of a current flowing through the PTC.