JPH0217182Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an ignition timing control device that can change the ignition timing of an engine when it is cold and when it is warmed up.

Conventionally, 2-stroke engines in particular have had their compression ratios increased in order to obtain high output, but due to the structure of the 2-stroke engine, in 2-stroke engines with increased compression ratios, the engine is cold immediately after startup. If you suddenly open the throttle fully in this situation, you will end up with too much output. This phenomenon causes engine troubles such as piston seizure due to insufficient lubrication when the engine is cold, and this type of trouble is particularly common in snowmobiles.

Conventionally, the methods to prevent this kind of trouble are as follows:
One method is to attach a temperature-sensitive element such as a bimetal to the cylinder or crankcase, and when the engine temperature exceeds a certain set temperature, it will be displayed with a lamp or thermometer, and the driver will be warned not to drive until then. However, this method cannot be said to be perfect because the driver does not necessarily act in accordance with this warning. Here, we will consider the relationship between engine temperature and output. The output of an engine usually differs between when it is cold when started and when it is warmed up. That is, when the engine is cold, the intake air is not exposed to the heat emitted by the engine, so the temperature is naturally low, and therefore the density of the air is high, and the efficiency with which it is filled into the cylinder is high. On the other hand, after the engine has sufficiently warmed up, the intake air receives heat radiated from the engine, which reduces its density and reduces the efficiency with which it fills the cylinder, resulting in lower output than when the air is cold. This can be seen from the fact that the output is higher in winter than in summer. Note that this phenomenon is a general phenomenon that does not distinguish between 4-cycle and 2-cycle engines, but 2-stroke engines The difference is more noticeable than with a 4-stroke engine.

In the case of a 4-cycle engine, the viscosity of the engine oil is high when it is cold, and because it has valve mechanisms such as intake valves and exhaust valves, there is more mechanical loss when it is cold than a 2-cycle engine. , the difference in output from the time of warm-up when these mechanical losses are reduced is small. On the other hand, in the case of a 2-stroke engine, lubricating oil does not lead to power loss, and it does not have a valve mechanism, so it is mechanically similar to a 4-stroke engine when it is cold and when it is warm. There is no difference in output depending on the timing, so the influence of the density of the intake air as described above appears immediately. The reason why the engine outputs too much when it is cold is as mentioned above. The present invention was developed in view of this point.

In addition to this, two-stroke engines have the following problems. In other words, due to the structure of a 2-stroke engine, the cylinder has large holes for scavenging ports and exhaust ports, so the expansion rate when warmed up is not uniform compared to when it is cold, and piston seizure is more likely than in a 4-stroke engine. may be likely to occur. For this reason, in 2-stroke engines, the clearance between the cylinder and piston is set larger than that in 4-stroke engines, and measures are taken such as making the planar shape of the piston slightly oval rather than a perfect circle. is being taught. For this reason, in the present invention, the engine output is suppressed as much as possible when the engine is cold to prevent seizure due to rapid thermal deformation of the cylinder. Then, the ignition timing is forcibly delayed from the time the engine starts until the temperature of the cylinder or crankcase reaches a certain level or higher, regardless of the opening degree of the throttle valve.
The purpose of the present invention is to provide an ignition timing control device that can prevent engine troubles due to excessive rise in output or combustion temperature.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows an example in which the present invention is applied to a CDJ (capacitor discharge ignition) circuit. In the same figure,
1 is a capacitor charge coil for low speed, and 2 is a capacitor charge coil for high speed. These coils generate alternating current electromotive force by rotation of the flywheel. The primary side 6 of the capacitor charge coils 1 and 2, the diode 3, the capacitor 4, the diode 5, and the ignition coil 6
A charging circuit for the capacitor 4 is formed by a.

Reference numeral 7 denotes a thyristor as a switching element, which captures the polarity change of the AC electromotive force induced in the capacitor charge coils 1 and 2 as a timing input signal, and rapidly transfers the charge in the capacitor 4 to the ignition coil primary side 6a. It functions to flow to. When a sudden current flows through the primary side 6a, a high voltage is induced on the secondary side 6b, causing the spark plugs 8 and 9 to spark.

A gate circuit for firing the thyristor 7 is formed by diodes 10, 11, 12, a transformer 13, a bias resistor 14, and a temperature sensing element 15.
The temperature sensing element 15 is made of bimetal, for example, and has a contact point that is closed in a low temperature state, and is embedded in a suitable location in the cylinder or crankcase. Diode 1 is connected to the gate G of thyristor 7.
The secondary side 13b of the transformer 13 is connected to the secondary side 13b of the transformer 13 through the gate 0, and a resistor 14 which is grounded through the temperature sensing element 15 is connected in parallel with the secondary side 13b of the transformer 13. It is designed to give an appropriate bias level to the
Note that 16 is an engine stop switch.

Next, the operation of this device will be explained.

First, when the engine is started and immediately after starting, the engine is in a cold state, so the contacts of the temperature sensing element 15 are closed. In this case, an alternating current electromotive force is induced in the low-speed capacitor charge coil 1 and the high-speed capacitor charge coil 2 due to the rotation of the flywheel, and the positive side of this alternating current electromotive force is half-wave rectified by the diode 3. capacitor 4
to charge. In other words, the capacitor charge current is as follows: capacitor charge coil 1 → capacitor charge coil 2 → diode 3 → capacitor 4 →
The current flows from the parallel circuit of the primary side 6a of the ignition coil 6 and the diode 5 to the ground, charging the capacitor 4.

Next, when the AC electromotive force of the capacitor charge coils 1 and 2 becomes negative, the diode 3 is cut off and the capacitor 4 is maintained in a charged state. In this case, the electromotive force of the capacitor charge coil 1 is short-circuited by the diode 12, but the electromotive force of the capacitor charge coil 2 is changed from the capacitor charge coil 2 to the capacitor charge coil 1.
→ Earth → Primary side 13a of transformer 13 → Diode 11, and current will flow through the circuit formed by this. This current flows through the primary side 1 of the transformer 13.
3b, and this electromotive force causes the secondary side 13b of the transformer → the diode 10 → the resistance between the gate G and the cathode K of the thyristor 7, and the resistance 14
Current flows from the parallel circuit with the temperature sensing element 15 to the ground. As a result, when the gate voltage of the thyristor 7 reaches the ignition voltage, the thyristor 7 becomes conductive and transfers the charge of the capacitor 4 from the capacitor 4 to
Thyristor 7 → Earth → Ignition coil 6
A high voltage is induced in the secondary side 6b of the ignition coil 6, causing the spark plugs 8 and 9 to spark.

Now, when the engine is in a cold state as described above, that is, when the contact of the temperature sensing element 15 is closed and the resistor 14 is inserted into the gate circuit of the thyristor 7, the ignition timing characteristics of the engine are as normal as when warmed up. The bias level of the gate G of the thyristor 7 is set by the resistor 14 to a suitable bias level that is later than the ignition timing of the thyristor 7, and its ignition timing characteristic becomes a curve as shown in FIG. 2a. Note that such a characteristic can be obtained relatively arbitrarily by appropriately selecting the resistance value of the resistor 14, and this characteristic can be obtained by combining the temperature sensing element 15 and the resistor 14 in this way. Thyristor 7
Since this is performed by intervening in the gate G, the ignition timing can be retarded over the entire range regardless of the opening degree of the throttle valve.

Next, when the engine is warmed up and the temperature of the cylinder or crankcase reaches a certain set point or higher, the contacts of the temperature sensing element 15 are opened, which causes the resistance 14
is separated from the gate circuit of the thyristor 7 to change the bias level of the gate G.
Then, the signal current of the capacitor charge coil 2 flows to the primary side 13a of the transformer 13, and the output of the secondary side 13b is applied as it is to the gate of the thyristor 7, and as a result, it is biased by the resistor 14. The gate voltage of the thyristor 7 reaches the ignition voltage earlier than when the ignition timing is reached, and as a result, the ignition timing becomes earlier. Figure 2 b
shows this ignition timing characteristic, which is the regular engine ignition timing characteristic. In this way, the ignition timing characteristic instantaneously switches from curve a to curve b when the engine changes from a cold state to a warm state during operation.

In addition to this embodiment, another method of inserting a resistor into the gate circuit of the thyristor 7 is to insert two resistors in parallel with the gate G and connect one side to the temperature sensing element 15.
It may be of a type that can be turned on and off.

Due to the above-mentioned functions and effects, the present invention can automatically change the ignition timing characteristics according to changes in the temperature of the engine cylinder or crankcase. This means that engine troubles can be prevented by delaying the magneto's ignition timing characteristics when the engine is cold.

According to the present invention, the driver can handle the engine with peace of mind compared to conventional methods that call for attention using lamps, etc., and it is also less expensive than conventional lamp displays and meter displays. Become.

Also, in the case of a cold start, the engine speed at which sparks start will be higher, which will help prevent sagging.

Furthermore, if such a mechanism is not required, normal ignition timing characteristics can be obtained by simply disconnecting the temperature sensing element.

[Brief explanation of drawings]

FIG. 1 shows an example in which the present invention is applied to a CDJ circuit, and FIG. 2 shows an ignition timing characteristic diagram. 1, 2... Capacitor charge coil, 3, 5,
10, 11, 12... Diode, 4... Capacitor, 6... Ignition coil, 6a... Primary side of ignition coil, 7... Thyristor, 13...
Transformer, 14...Resistor, 15...Temperature sensing element.

Claims (1)

[Scope of utility model registration request] In a two-cycle engine ignition system that intermittently controls the current flowing to the primary side of an ignition coil by a switching element that is turned on and off by a timing input signal, a temperature sensing element is attached to at least one of the engine cylinder or crankcase, A resistor that determines the bias level on the input signal terminal side of the switching element is connected to the temperature-sensing element, and the temperature-sensing element turns on and off the current flowing through the resistor, changing the bias level between when the engine is cold and when the engine is warm. This ignition timing control device is characterized by controlling the ignition timing to be changed depending on engine timing, to delay the ignition timing over the entire range regardless of the opening degree of the throttle valve when the engine is cold, and to advance the ignition timing when the engine is warmed up.