JPH0526945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic yoke device for internal combustion engines, particularly for general-purpose small internal combustion engines.

[Conventional technology]

An example of a conventional autochoke device for a general-purpose small internal combustion engine is shown in FIG. In the figure, 1 is a throttle valve;
2 is a bench lily, 3 is a main nozzle for ejecting the main fuel, 4 is a choke bore, 5 is a choke valve, 6 is a choke rod, 7 is a bimetal, 8 is a choke case, 9 is a heater, and 10 is the amount of electricity to the heater 9. It is a control device.

In an internal combustion engine with a carburetor, during normal operation, the choke valve 5 is open and in the position shown in FIG. After passing through the choke bore 4, the fuel is throttled by the bench lily 2, and at the same time, negative pressure is generated in the main nozzle 3 to suck up the fuel, and the fuel is ejected from the tip of the main nozzle 3. The jetted fuel and air become a mixture, and the flow rate is controlled by the throttle valve 1.
It is fed into a cylinder (not shown) and burned.

On the other hand, when the engine is at low temperature, the fuel supplied from the main nozzle 3 is not sufficiently vaporized (evaporated).
The air-fuel mixture fed into the cylinder often has excess air and is not within the flammable limit of the air-fuel mixture, so in order to avoid this by suppressing the amount of intake air, the chiyoke valve 5
is installed. Therefore, the chiyoke valve 5
It is necessary to change the degree of opening of the valve according to the temperature. Conventionally, the valve 5 is connected to a valve rod 6 to transmit the temperature-induced displacement of a bimetal 7, which is a temperature sensor, to the valve 5. The heater 9 also serves to increase the temperature variation of the bimetal 7, and the energization amount control device 10 serves to prevent the bimetal 7 from being overheated by the heater 9.

[Problems to be Solved by the Invention] However, in such a conventional autochoke device, since the displacement of the bimetal 7 due to temperature is small, a device such as a heater 9 for heating the bimetal 7 is required. , a device for controlling overheating of the bimetal 7 is also required. For this reason, there are problems in that the autochoke device becomes larger and inevitably becomes more expensive.

The present invention has been made in view of the above, and it is an object of the present invention to provide an automatic yoke device that has a simplified structure and is inexpensive to manufacture.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention is characterized in that a yoke spring that adjusts the opening degree of the yoke valve according to changes in engine temperature is made of a polymeric urethane elastomer material.

[Effect]

Since the present invention has the above-mentioned configuration, the yoke spring itself has the function of controlling the opening and closing of the yoke valve in accordance with changes in engine temperature. No temperature control device is required.

〔Example〕

One embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, and FIG. 4. FIG. 1 is a schematic diagram of the main part, and FIG. 2 is a sectional view taken along the - arrow in FIG. 1. . In the figure, 11 is a chiyoke valve, 12
1 is a spiral spring for a chiyoke made of a polymeric urethane elastomer material, and 13 is a main nozzle. 15
is fixed to the teak yoke shaft 19 by a plate and rotates together with it. One end of the spiral spring 12 is fixed or rotatably attached to the plate 15 with a rivet 16, and the other end is attached to the carburetor main body 20.
It is supported by being press-fitted or slid onto. 18
is a floating chamber, and 17 is a rolling chamber.

In the auto-choke device having the above configuration, the chi-yoke shaft 1 of the chi-yoke valve 11
9, with respect to the center 14a of the chiyoke bore 14
If the piston is made eccentric by a certain amount, a rotation couple M is generated because the pressure receiving area of the yoke valve 11 differs with respect to the center of rotation of the intake air due to the downward movement of a piston (not shown). A reaction force against this M is generated in the spiral spring 12, and the spring force T of the spiral spring 12 is expressed as T=Θ×bh ³ E/12l (1). However, b is the width of the spring 12, h is the thickness, l is the total length, E is the longitudinal elastic modulus, and Θ is the rotation angle.

When the spring force T is large with respect to the rotating force couple M (see FIG. 1), the yoke valve 11 closes, and conversely, when the above-mentioned T is small, the yoke valve 11 opens. FIG. 4 shows the characteristics of the temperature and longitudinal elastic modulus E of the material of the spring 12 according to the present invention. It is generally known that polymeric urethane elastomer materials have a glass transition point Tg at which the modulus of longitudinal elasticity E changes rapidly with temperature. The glass transition point Tg can be set around room temperature (10 to 20°C).

That is, in equation (1), since the longitudinal elastic modulus E of the spring 12 changes depending on the temperature, the spring force T changes with Tg as a boundary. Therefore, at a temperature where the engine does not require a choke, the temperature of the spiral spring 12 is higher than Tg, so the spring force T is small, and the rotational force M of the choke valve 11 caused by the intake air is larger. , the check valve 11 is opened. On the other hand, when the engine is cold, at a temperature that requires the choke, the temperature of the spiral spring 12 is below Tg, so the spring force T is large, and T is greater than the rotation couple M of the choke valve 11 caused by the intake air. Due to its large size, the chiyoke valve 11 remains closed.
Further, after the engine has finished operating, since there is no intake air, a closing force T by the spiral spring 12 acts on the choke valve 11, and the spring 12 is held in the closed state. If the engine temperature continues to drop and becomes below Tg, check valve 1 when restarting the engine.
1 is kept closed, and if the engine is restarted at a temperature higher than Tg, where the engine temperature cannot be lowered enough, the rotary couple M will open the engine yoke valve 11 and start the engine, causing problems such as overarching yoke. There isn't.

In the above embodiment, a spiral spring 12 is used, but even if a plate spring, coil spring, torsion bar, etc. are used, the effect is exactly the same as described above.

〔Effect of the invention〕

The present invention is constructed as described above, and according to the present invention, the automatic opening and closing of the check valve is controlled only by the check spring, so that the heater for heating and overheating of the bimetal can be prevented, unlike the conventional automatic check valve using a bimetal. No additional equipment such as a device is required, which simplifies the device and reduces manufacturing costs. The present invention also provides a spring made of a polymeric urethane elastomer material such as a urethane elastomer made by polymerizing irifluorone diisocyanate and bisphenol. In this polymeric urethane elastomer material, the glass transition point Tg, which is the temperature at which the longitudinal elastic modulus E changes, is a physical property of the material itself. (the temperature at which E changes) can be stably obtained without being affected by temperature or humidity.

Therefore, the auto-chitch yoke device of the present invention, which includes a yoke spring made of a polymeric urethane elastomer material, can freely set the yoke valve opening/closing temperature required by the engine and has high operational stability.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention,
Figure 1 is a schematic outline drawing, and Figure 2 is the − of Figure 1.
It is a sectional view along a line. FIG. 3 is a schematic external view showing an example of a conventional automatic yoke device, and FIG. 4 is a diagram for explaining the operation. 11... Chiyoke valve, 12... Spiral spring for chiyoke, 19... Chiyoke shaft.

Claims (1)

[Claims] 1. An internal combustion engine equipped with an auto-choke device that automatically opens and closes a chi-yoke valve depending on the engine temperature, characterized by comprising a chi-yoke spring made of a polymeric urethane elastomer material and adjusting the opening degree of the chi-yoke valve according to changes in engine temperature. Autochoke device for internal combustion engines.