JPH0143148B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a carburetor accelerator device that automatically changes the amount of acceleration fuel in response to temperature changes to provide stable acceleration performance.

(Prior art and its problems) In an accelerator that supplies extra fuel to cope with the temporary increase in the amount of intake air during engine acceleration, the amount of fuel discharged per operation of the accelerator pump is reduced at high temperatures. There are some that are designed to reduce the amount and increase it when the temperature is low so that stable acceleration performance can always be obtained.

Conventionally, as a means of adjusting the discharge amount of an accelerator pump, the pump stroke is adjusted by changing the connection position of the reciprocating member consisting of the piston or diaphragm of the accelerator pump and the link mechanism that drives them, thereby adjusting the discharge amount. There is a way to do this, but you have to change the connection position manually, which is troublesome and often forgotten.
In reality, it is hardly ever adopted.

In addition, link mechanisms are provided with expandable parts using thermowax so that the length changes according to temperature changes (see Japanese Patent Application Laid-Open No. 1981-81831), and a bypass with a pump that operates at low temperatures is installed in the acceleration fuel passage. to adjust the amount of fuel injected from the acceleration nozzle into the intake passage according to the temperature (Japanese Patent Laid-Open No. 124133/1983).
There are some automatic adjustment methods available, such as (see Japanese Patent Publication No. 2003-111001), but the structure is complicated and requires special processing and attachment of parts.

The present invention utilizes a shape memory alloy for either the coiled return spring or the damper spring that acts directly or indirectly on the reciprocating member of the accelerator pump. The fuel discharge amount is automatically adjusted according to temperature changes with a simple configuration.

(Means for Solving the Problems) The present invention includes a coil-shaped return spring that acts in the direction of increasing the volume of the pump chamber of an acceleration pump, and a coil-shaped damper spring that acts in the direction of decreasing the volume of the pump chamber. In the accelerator device for a carburetor, either the return spring or the damper spring is made of a shape memory alloy, and the spring made of the shape memory alloy increases the pump stroke at low temperatures and the pump stroke at high temperatures. The coil length is expanded and contracted so as to reduce the stroke, thereby solving the above problem.

A material with a shape memory effect, that is, a shape memory alloy, is known as a material that reversibly changes shape with changes in temperature due to thermoelastic martensitic transformation.
By heat-treating at a temperature higher than Af to memorize the original shape, and processing and deforming it into the desired shape at a temperature lower than the martensitic transformation end temperature Mf, the transition between the original shape and the deformed shape is achieved within the transition temperature range. It is also known that the shape changes reversibly. When a coiled spring is made of a shape memory alloy, if the original memorized shape is compressed at a temperature lower than the Mf and deformed so that the coil length becomes shorter, the spring will elongate as the temperature rises. Shrinks as temperature decreases. Conversely, when the spring is stretched and deformed so that the coil length becomes longer, the spring contracts as the temperature rises and expands as the temperature falls.

Figure 1 shows the relationship between the minimum T _L and maximum transition temperature T _H of a coiled spring made of shape memory alloy, and the amount of deformation and load at temperatures T ₁ , T ₂ , and T ₃ between them. This is a characteristic curve diagram showing that the amount of deformation is very small in the high temperature region (Figure a).
It can be seen that the spring deforms to a practically effective amount only in a limited low temperature range. When the load of a bias spring made of a metal material without shape memory effect is applied to this spring, the spring deforms along the line S, and the amount of deformation is b, starting from the lowest T _L of the dislocation temperature. A practically effective deformation occurs in the entire temperature range up to T _H. Changing the initial load or spring characteristics of the bias spring results in a deformation along a line parallel to line S. 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 spring also helps to reduce or eliminate the difference due to hysteresis.

In the present invention, a spring made of a metal material that does not have a shape memory effect acts as a bias spring.

As stated at the beginning, the purpose of the present invention is to adjust the amount of accelerated fuel depending on the temperature, especially the engine temperature, and for this purpose, phase dislocation due to thermoelastic martensitic transformation of a material having a shape memory effect is performed. This phenomenon is used to control the stroke of the accelerator pump depending on the temperature, and springs made of shape memory alloys are used between temperatures below Mf and above Af, as well as between Mf and Af. It may also be used in a suitable temperature range between . Furthermore, depending on the installation location and direction of action, springs made of shape memory alloys can be selected and used by processing and deforming the original shape so that, for example, the coil length contracts or expands when the temperature drops. Needless to say.

(Example) Embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows a case in which the present invention is implemented in a piston-type accelerator pump, and shows the pump arm 1 which is linked by a throttle valve (not shown) and a link mechanism.
An auxiliary rod 5 is inserted between the piston rod 4 connected to the piston 3 of the acceleration pump 2, and the piston rod 4
and the auxiliary rod 5 are connected to each other so as to be movable in the axial direction, and a coiled damper spring 6 is inserted between spring supports 4a and 5a provided thereon.
The pump chamber 7 of the accelerator pump 2 has a fuel inlet 8 and an outlet 9 and is fitted with a coiled return spring 10 .

The damper spring 6 acts on the piston 3 in the direction of decreasing the volume of the pump chamber 7, the return spring 10 acts on the piston 3 in the direction of increasing the volume of the pump chamber 7, and the pump arm 1 acts on the piston 3 in the direction of increasing the volume of the pump chamber 7. 3 to send the fuel in the pump chamber 5 from the outlet 9 to an accelerating nozzle (not shown) is the same as in the conventional case.

In this embodiment, the damper spring 6 was made of a normal metal material, and the return spring 10 was heat-treated at a temperature higher than Af and stretched at a temperature lower than Mf to deform the spring. Alternatively, the damper spring 6 may be heat-treated at a temperature higher than the above Af.
The same effect can be achieved even if the return spring 10 is made of a normal metal material and is compressed and deformed at a lower temperature.

As a result, the coil length of the return spring 10 is expanded or the coil length of the damper spring 6 is contracted at low temperatures, increasing the pump stroke and increasing the acceleration pump 2.
Increases fuel discharge amount.

FIG. 3 shows a case in which the present invention is implemented in a diaphragm type acceleration pump. In this acceleration pump 11, a negative pressure chamber 12 into which engine suction negative pressure is introduced and a pump chamber 13 are connected by a diaphragm 14. A coiled damper spring 15 is installed in the partitioned negative pressure chamber 12.
A coiled return spring 18 is inserted into the pump chamber 13, which has a fuel inlet 16 and an outlet 17.

The damper spring 15 acts on the diaphragm 14 in the direction of decreasing the volume of the pump chamber 13, and the return spring 18 acts on the diaphragm 14 in the direction of increasing the volume of the pump chamber 13, so that when the opening of the throttle valve increases, the suction negative pressure decreases. The diaphragm 14 then deflects toward the pump chamber 13 to send fuel from the outlet 177 to an accelerating nozzle (not shown), as in the conventional case.

In this embodiment, the damper spring 15 was heat-treated at a temperature higher than Af and compressed at a temperature lower than Mf to be deformed, and the return spring 18 was made of a normal metal material. Alternatively, the damper spring 15 may be made of a normal metal material, and the return spring 18 may be heat-treated at a temperature higher than Af and then stretched and deformed at a temperature lower than Mf.

As a result, the coil length of the return spring 18 is expanded or the coil length of the damper spring 15 is contracted at low temperatures, increasing the pump stroke and increasing the fuel discharge amount of the acceleration pump 11.

(Effects of the Invention) According to the present invention, since either the return spring or the damper spring is made of a shape memory alloy, it is not necessary to manually adjust the fuel discharge amount of the accelerator pump, and a special device is not required. This eliminates the need for springs, parts, and processing for their attachment, and by simply replacing conventional springs, it can automatically adjust according to temperature and provide stable acceleration performance. In addition, coiled springs made from shape memory alloys have the advantage of being able to change length due to temperature changes larger than bimetals, thermowaxes, etc. whose shape changes with heat, and are highly reliable in operation. . Furthermore, the other spring made of ordinary metal material acts as a bias spring for the spring made of shape memory alloy, reducing or eliminating hysteresis, allowing accurate and constant shape change at a constant temperature, and stable acceleration. can give performance.

[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. 2,11...acceleration pump, 3...piston, 6,1
5... Damper spring, 7, 13... Pump chamber, 10, 1
8...Return spring, 14...Diaphragm.

Claims (1)

[Claims] 1. In a carburetor accelerator device comprising a coiled return spring that acts in a direction to increase the volume of a pump chamber of an acceleration pump and a coiled damper spring that acts in a direction to decrease the volume of the pump chamber, the return spring Either one of the damper spring and the damper spring is made of a shape memory alloy, and the spring made of the shape memory alloy has a configuration in which the coil length expands and contracts so that the pump stroke becomes larger when the temperature is low and the pump stroke becomes smaller when the temperature is high. An accelerator device characterized by: