JPS62247161A - Variable venturi type carburetor - Google Patents

Abstract

PURPOSE:To prevent the excessive supply of the concentrated mixed gas by installing a valve into an air intake passage for introducing the atmosphere into a negative pressure chamber formed on the back surface of the piston of the captioned carburetor and opening said valve when the environmental temperature is below a prescribed value and closing said valve after the lapse of a prescribed time. CONSTITUTION:A venturi part 2 on the upstream side of a throttle valve 1 is constituted of a fixed wall 3 and a piston 4, and the effective passage area of the venturi part 2 can be varied by advancing and retreating the piston 4 by the negative pressure introduced into a negative pressure chamber 8 formed on the back surface of the piston 4 from a negative pressure passage 7. In this case, an intake passage 13 for introducing the atmosphere into the negative pressure passage 8 is formed, and one edge is connected to an intake passage 12 on the upstream side of the venturi part 2. A solenoid valve 14 is installed into the intake passage 13, and said valve 14 is opened when the cooling water temperature is below a prescribed value by an electric control circuit 16 according to the output of a temperature sensor 15 for detecting the engine cooling water temperature, and closed after the lapse of a prescribed time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to a variable venturi type carburetor, and more specifically, to a variable venturi type carburetor.
This invention relates to a variable venturi type carburetor that is used to ensure engine starting without diluting the air-fuel mixture during cold starting.

(Prior art and its problems) FIG. 2 shows an example of a conventional variable venturi type carburetor. The venturi part 2 on the upstream side of the throttle valve 1 is fixed to the wall 3
and a piston 4 that serves as a movable wall. A fuel passage 6 is formed in the fixed wall 3, the opening of which is adjusted by fJI by a needle valve 5 fixed to the piston 4.

The piston 4 has a negative pressure passage 7 that opens to the venturi portion 2.
is provided, and the negative pressure passage 7 communicates with a negative pressure chamber 8 on the back surface of the piston 4. Negative pressure chamber 8 is created by case 9,
A positive pressure chamber 10 is created within the case 9 with the piston 4 as a boundary. Since the piston 4 is receiving the biasing force of the spring 11, the position of the piston 4 is determined by the balance between this biasing force, the negative pressure in the negative pressure chamber 8, and the positive pressure in the atmospheric chamber 10, and the venturi portion 2 The opening area of the fuel passage 6 and the opening degree of the fuel passage 6 by the needle valve are adjusted. The negative pressure chamber 8 is connected to the atmosphere through an intake passage 13, and the intake passage 13 is opened and closed by a temperature sensor 15 that detects the temperature of engine cooling water.

This type of carburetor is designed to close the intake passage at a predetermined temperature of the engine during a cold start.
Because the temperature sensor is made of wax or bimetal, and is not very sensitive, and because there is a difference between the engine temperature and the coolant temperature, it takes time for the valve to close. For this reason, during a cold start, the opening area of the venturi portion is made small and a rich air-fuel mixture is supplied for a long time, resulting in a problem of deterioration of acceleration performance.

(Technical Problem of the Present Invention) The technical problem of the present invention is to solve the above-mentioned conventional problems and to solve the problem that the supply time of rich air-fuel mixture becomes longer than necessary at the time of cold start. .

(Technical means of the present invention and its effects) The present invention opens the intake passage connected to the negative pressure chamber by detecting that the ambient temperature, for example, the cooling water temperature, is below a predetermined temperature, and then opens the intake passage after a predetermined time. It is characterized by providing a control device in the intake passage to close the intake passage.

When the ambient temperature is low, air is introduced into the negative pressure chamber on the back of the piston to suppress the movement of the screw 1 and reduce the opening degree of the venturi when starting the engine.

The period of time during which this state of introducing atmospheric air into the negative pressure chamber is continued is a certain period of time after the intake of atmospheric air is started, for example, after the key is turned on. Actual variable venturi vaporizer system operating time may be on the order of about 1 minute, for example 45 seconds. After this operating time has elapsed, it can be experimentally confirmed that the engine rotation becomes stable, so it is possible to shut off the introduction of the atmosphere into the negative pressure chamber without detecting the ambient temperature.

(Embodiment) An embodiment of the present invention is shown in FIG. 1. Since the basic structure of the carburetor is almost the same as the example shown in FIG. Omitted.

In FIG. 1, an intake passage 1 on the upstream side of the venturi section 2
An intake path 13 communicating from the negative pressure chamber 8 to the negative pressure chamber 8 is provided. Intake path 1
3 is connected to a solenoid valve 14 to control the introduction of atmospheric air into the negative pressure chamber 8 via the intake path 13.

A control device 16 such as an electric control circuit section is connected to the solenoid valve 14, and the opening and closing of the solenoid valve 14 is controlled by electric signals from the electric control circuit section 16.

The electric control circuit section 16 has a built-in timer, is connected to a temperature sensor 15 that detects the temperature of engine cooling water, and receives signals from the temperature sensor 15.

When the engine key is turned in and the engine is started, the temperature sensor 15 sends a signal corresponding to the engine coolant temperature to the electric control circuit section 16. At the same time as the engine starts, a timer in the electric control circuit 16 is set, and when the signal from the temperature sensor 15 indicates that the coolant temperature is below a predetermined value, the solenoid valve is activated for the time set by the timer. 1
4 is energized, the intake passage 13 is opened, and the atmosphere is drawn into the negative pressure chamber 8.
to be introduced. As a result, the pressure in the negative pressure chamber 8 increases, and the biasing force of the spring 11 and the pressure in the negative pressure chamber 8 cause the piston 4 to
The opening area of the venturi section 2 does not increase despite the suction effect at the time of engine startup, that is, despite the large negative pressure of the venturi section 2. . (As a result, the negative pressure applied to the fuel passage 6 increases, the amount of fuel injected increases, and a rich mixture can be supplied when starting the engine in cold weather. Set with a timer as shown in Figure 3. After the specified time, that is, after the engine rotation has stabilized,
The timer is released, power to the solenoid valve 14 is stopped,
The introduction of atmospheric air into the negative pressure chamber 8 is blocked and the vaporizer is used under the same operation as before. That is, after the timer is released, the negative pressure of the venturi section 2 is introduced into the negative pressure chamber 8 through the negative pressure passage 7, and the piston 4 is moved to the left in FIG.
Increase the aperture area.

An on/off type solenoid valve is used as the solenoid valve 14, and a timer built into the electric control circuit 16 is adjusted to set the ambient temperature (in the illustrated example, the engine cooling water temperature).
The valve opening time can be changed depending on the situation. The relationship between the opening time of the solenoid valve 14 and the set ambient temperature can be changed linearly as shown in FIG.

(Effects) In the present invention, the problem of continuing a cold start longer than necessary is solved by WIR control that supplies atmospheric air to the negative pressure chamber for a selected period of time during a cold start. Furthermore, since an ordinary carburetor is simply provided with an intake passage and a solenoid valve, the present invention can be easily applied to existing carburetors.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an example of the present invention, Fig. 2 is a cross-sectional view of a conventional carburetor, Fig. 3 is a view showing the relationship between the solenoid valve in the intake passage and the operation time, and Fig. 4 is a cross-sectional view of a conventional carburetor. It is a figure showing the relationship between valve temperature and valve opening time.

Claims (1)

[Claims] a fuel passage opening in a fixed wall of a venturi portion of the intake passage; a piston forming a movable wall facing the fixed wall;
a needle valve fixed to the piston and adjusting the opening degree of the fuel passage; a negative pressure passage provided in the piston for introducing negative pressure into the negative pressure chamber on the back surface of the piston; and connected to the negative pressure chamber. A variable venturi type carburetor having an intake passage for introducing atmospheric air, the variable venturi carburetor having a valve connected to the intake passage, a control device connected to the valve to control opening and closing of the valve, and an ambient temperature detection device. , wherein the control device has a built-in timer and controls to open the valve in response to a signal from the ambient temperature detection device indicating that the temperature is below a predetermined temperature, and close the valve after a predetermined time after opening. vessel.