JPH0143150B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates particularly to a negative pressure operating mechanism of a negative pressure type two-stage carburetor in which a throttle valve of a secondary vaporizer is operated by a vent valve negative pressure.

(Prior art and its problems) A lever fixed to the diaphragm and the throttle valve shaft of the secondary carburetor applies a composite negative pressure of the primary carburetor's bench lily negative pressure and the secondary carburetor's vent lily negative pressure to the diaphragm. In the negative pressure operation mechanism, in which the secondary throttle valve is opened by a composite negative pressure above a certain level by connecting the valves with a connecting rod, a return spring acts on the diaphragm against the composite negative pressure. When the negative pressure overcomes the spring force, the diaphragm is attracted by the combined negative pressure and moves to open the secondary throttle valve. In other words, the secondary throttle valve is mechanically opened when the combined negative pressure exceeds a certain level, so if the engine is operated in a cold state where the secondary carburetor is activated immediately after starting, for example, the engine will not run properly. Even though a highly concentrated mixture is required compared to when the engine is warmed up, the mixture supplied to the engine becomes considerably leaner due to the addition of the mixture from the secondary carburetor. Kernock is likely to occur when the device starts operating.

As a countermeasure, it is proposed to fix the secondary throttle valve in the closed position by letting the atmosphere act on the diaphragm when the engine is not warmed up.
-121952), but the configuration is extremely complicated because it requires an air introduction passage and a temperature-sensitive valve, and it is also troublesome as it requires consideration to prevent dust from entering the atmosphere. It is.

The present invention eliminates the need for special equipment or parts and processing for their attachment, and has a simple configuration in which a locking spring made of shape memory alloy is inserted into the negative pressure operating mechanism. To provide a negative pressure type two-stage vaporizer that does not require operation of the vaporizer.

(Means for Solving the Problems) The present invention provides a diaphragm of a negative pressure operating mechanism that is connected to the throttle valve shaft of a secondary carburetor and operates with a ventilator negative pressure, and a coil-shaped coil that acts in the direction of closing the secondary throttle valve. A return spring and a coiled lock spring made of a shape memory alloy are actuated, and the lock spring expands and contracts in coil length so as to fix the diaphragm in the secondary throttle valve closing position below a predetermined temperature. This is a means to solve the above problem.

Shape memory alloys, that is, metal materials with a shape memory effect, are known as materials that reversibly change shape with temperature changes due to thermoelastic martensitic transformation, and the alloy that is the material is heated to a temperature at which the reverse transformation ends.
By heat-treating at a temperature higher than A _f to memorize the original shape, and processing and deforming it into a desired shape at a temperature lower than the martensitic transformation end temperature M _f , the original shape and the deformed shape can be changed within the transition temperature range. It is also known that the shape reversibly changes between

Figure 1 shows the minimum T _L and maximum T _H of the dislocation temperature of a material made of shape memory alloy, and the temperatures in between.
It is a characteristic curve diagram showing the relationship between the amount of deformation and load at T ₁ , T ₂ , and T ₃ , where stress is linearly related to load and strain is directly proportional to the amount of deformation. The temperature is T _L
When the material changes from A to T _H when no load is applied,
It deforms by B under a constant load P.
When a bias member made of a metal material that does not have a shape memory effect is applied, it deforms by C. Furthermore, when the temperature changes, the temperature at which the same amount of deformation is reached is different when the temperature is raised and when the temperature is lowered, and the bias member helps to reduce or eliminate this difference due to hysteresis.

Furthermore, as can be seen from Figure 1, the amount of deformation of shape memory alloys due to temperature changes is small in the high temperature range close to T _H.
It is large in the temperature range close to T _L. Therefore, the bias member is also effective in stably maintaining the secondary throttle valve in an inoperative state at low temperatures.

(Example) An example of the present invention will be described with reference to the drawings.
The lever 3 is fixed to the throttle valve shaft 2 of the secondary throttle valve 1 of the secondary carburetor S arranged in parallel with the primary carburetor P, and the lever 3 is fixed to the center of the diaphragm 5 of the negative pressure actuation mechanism 4 in the operating direction. The extending arm 6 is connected by a connecting rod 7. Diaphragm 5 of negative pressure actuation mechanism 4
The negative pressure chamber 8 into which negative pressure is introduced is connected to a negative pressure passage 9 which applies a composite negative pressure of the negative pressure of the primary vaporizer P and the negative pressure of the secondary vaporizer S. , a coiled return spring 10 made of ordinary metal material without shape memory effect.
is built in and acts on the diaphragm 5.

In the embodiment shown in FIG. 2, a coiled lock spring 11 made of a shape memory alloy is returned to a negative pressure chamber 8.
0, and this lock spring 11 is heat-treated at a temperature higher than the above-mentioned A _f .
The material used is one that has been stretched and deformed at a temperature lower than M _f .

In this embodiment, the lock spring 11 presses the diaphragm 5 at low temperatures to fix the secondary throttle valve 1 in the closed position, but contracts at temperatures above a predetermined temperature and returns the spring force of the spring 10 and the negative pressure of the negative pressure chamber 8. Move the diaphragm 5 to a balanced position and open the secondary throttle valve 1.
to open.

In the embodiment shown in FIG. 3, a coiled lock spring 13 made of a shape memory alloy is built into the atmospheric chamber 12 on the opposite side of the negative pressure chamber 8, and is applied to the diaphragm 5 in opposition to the return spring 10. This lock spring 13 is heat treated at a temperature higher than the above Af.
It is used that has been compressed and deformed at a lower temperature than Mf. Further, the return spring 10 used has a larger load than those conventionally used.

In this embodiment, the locking spring 13 contracts at low temperatures and pushes the diaphragm 5 by the heavily loaded return spring 10, fixing the secondary throttle valve in the closed position.
When the temperature exceeds a predetermined temperature, it expands and reduces the load on the return spring 10. That is, when the temperature exceeds the predetermined temperature, the return spring 1
The diaphragm 5 is moved to a position where the spring force of 0, the negative pressure of the negative pressure chamber 8, and the spring force of the lock spring 13 are balanced, and the secondary throttle valve is opened. Works as a bias member.

(Effects of the Invention) According to the present invention, a lock spring made of a shape memory alloy is applied to a diaphragm of a negative pressure operating mechanism,
The diaphragm is fixed with a locking spring at temperatures below a certain temperature, and the secondary throttle valve remains closed even when high negative pressure is applied, so the secondary vaporizer operates immediately after starting in cold weather. Even if the engine is operated forcibly, the air-fuel mixture will be supplied only from the primary carburetor, which will not cause car lock, and will not cause the inconvenience of putting a heavy burden on an engine that has not been sufficiently warmed up and affecting its life. It is. In addition, a coiled lock spring made of shape memory alloy can increase the amount of change in length due to temperature changes and has high operational reliability, so it is possible to properly secure the secondary throttle valve and open and close it using negative pressure. Not only can the lock spring be installed, but it also eliminates the need for special equipment, parts, and machining for its attachment, and can achieve its purpose with a simple configuration of simply inserting the lock spring into the negative pressure operating mechanism.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram of a shape memory alloy, and FIGS. 2 and 3 are longitudinal sectional views showing different embodiments of the present invention. P...Primary vaporizer, S...Secondary vaporizer, 1...Secondary throttle valve, 4...Negative pressure operation mechanism, 5...Diaphragm, 8
... Negative pressure chamber, 10... Return spring, 11, 13... Lock spring.

Claims (1)

[Claims] 1 The diaphragm of the negative pressure operating mechanism connected to the throttle valve shaft of the secondary carburetor and operated by the bench lily negative pressure,
A coiled return spring that acts in the direction of closing the secondary throttle valve and a coiled lock spring made of a shape memory alloy act on the diaphragm to close the secondary throttle valve when the temperature is below a predetermined temperature. A negative pressure two-stage vaporizer characterized by having a structure in which the length of the coil expands and contracts so as to be fixed in position.