JPH03956A - Fuel cut device - Google Patents

Abstract

PURPOSE:To improve responsibility in detecting acceleration and deceleration by constituting the negative pressure switch of a fuel cut system to be differential pressure type, and so controlling the system as to apply minimum negative pressure to one chamber of the switch when a throttle valve is open, and slightly deeper negative pressure than the aforesaid minimum negative pressure at the time of deceleration. CONSTITUTION:A fuel cut device 10 fitted to a slow fuel system comprising a slow fuel passage 8 having a solenoid valve 32, outputs a fuel cut signal from a fuel cut control circuit 31 to a solenoid valve 32 when an engine decelerates with a negative pressure switch 13 turned on, and when an engine speed is equal to or more than the predetermined value. In this case, the first negative pressure port 11 for reducing negative pressure according to an increase in the opening of a throttle valve and the second negative pressure port 12 for contrarily increasing the negative pressure are provided, and the second negative pressure port 12 is made continuous to the chamber 13b of the negative pressure switch 13. Also, the chamber 13c of the negative pressure switch 13 is applied with the shallow minimum negative pressure of the first negative pressure port 11 when a throttle valve is open, and with negative pressure slightly deeper than the minimum negative pressure during deceleration, via a working negative pressure control device 20.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fuel cut device that stops fuel supply in a vehicle engine as a measure against fuel consumption and emissions during deceleration. Regarding sexual improvement measures.

[Conventional technology]

In general, fuel cut devices for engines with carburetors,
A solenoid valve is installed in the slow fuel system of the carburetor, and during deceleration, the solenoid valve is closed to temporarily cut off fuel. Then, at a predetermined engine speed or acceleration, the solenoid valve is opened to restore the original fuel supply.

Here, a negative pressure switch is provided to detect the acceleration/deceleration, and the negative pressure switch is turned on and off by the suction negative pressure accompanying the change in the throttle valve. Therefore, the detection accuracy of acceleration/deceleration by the negative pressure switch directly affects the responsiveness of fuel cut or its recovery.In this point, the setting value of the negative pressure switch is reduced, and acceleration/deceleration is performed in this state. It is necessary to detect it reliably and quickly. Furthermore, since the negative pressure changes at high altitudes, the operation of the negative pressure switch may also change, but it is desirable to configure the system so that altitude compensation is not required.

Conventionally, regarding this type of fuel cut device, there is a prior art, for example, disclosed in Japanese Patent Laid-Open No. 119149/1983. Here, during sudden deceleration, negative pressure downstream of the throttle valve is immediately introduced into the pressure switch and opened, and the solenoid valve shuts off the slow fuel passage to cut off fuel. Next, the negative pressure delay valve is shown to introduce negative pressure into the other chamber of the pressure switch after a certain time delay and close it, thereby restarting the slow fuel supply.

[Problem to be solved by the invention]

By the way, in the prior art described above, since the fuel is cut only for a certain period of time immediately after deceleration, the fuel cut state does not continue during continuous descent, and the effects on fuel efficiency, emissions, etc. cannot be fully exerted.

Furthermore, since the pressure switch is configured to operate only with suction negative pressure downstream of the throttle valve, the set value of the spring needs to be large, resulting in poor response and requiring altitude compensation for use at high altitudes.

The present invention has been made in view of the above points, and its purpose is to improve the responsiveness of fuel cut and recovery accompanying acceleration/deceleration detection using a negative pressure switch, and to eliminate the need for altitude compensation. The object of the present invention is to provide a fuel cut device that can perform the following steps.

[Means to solve the problem]

In order to achieve the above object, the fuel cant device of the present invention includes:
A first negative pressure port that reduces negative pressure in accordance with an increase in the throttle valve opening of the carburetor brake, and a second negative pressure port that increases negative pressure conversely.
and a negative pressure port, the second negative pressure port is connected to one chamber of the differential pressure type negative pressure switch, and under the condition that the throttle valve is opened to the other chamber of the negative pressure switch, the second negative pressure port is connected to the first chamber.
A shallow minimum negative pressure is selectively applied to the negative pressure port, and a predetermined negative pressure slightly deeper than the minimum negative pressure is selectively applied during deceleration.

[For production]

Based on the above configuration, the negative pressure of the second negative pressure port is applied to the contact OFF side of the differential pressure type negative pressure switch in the fuel cut system when the throttle valve opens and closes, and the negative pressure switch contact ON side during deceleration. The fuel is cut by detecting deceleration based on the pressure difference between the predetermined negative pressure and the predetermined negative pressure applied to the engine. Further, during acceleration, acceleration is detected based on the differential pressure between the minimum negative pressure of the first negative pressure port that acts on the contact ON side of the negative pressure switch, and recovery is performed with good response.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, reference numeral 1 denotes a carburetor, and a throttle valve 4 is provided downstream of a venturi 3 in the air-fuel mixture passage 2, and a main nozzle 5 from a main fuel passage 6 opens in the venturi 3. Further, near the fully open position of the throttle valve 4, there is a slow port 7a.

The idle port 7b is open and communicates with the slow fuel passage 8, and the carburetor l is connected to the intake manifold 9.
It communicates with the engine body through.

A fuel cut device IO is provided in the slow fuel system, and an operating negative pressure control device 2 is provided in the intake system downstream of the throttle valve 4.
0 is set.

The fuel cut device 10 has a first negative pressure port 11 in the mixture passage 2 at a position downstream of the throttle valve 4 when the throttle valve 4 is fully opened, and at a position upstream of the throttle valve 4 when the opening is a predetermined opening or more. 4 is fully closed, the second negative pressure port 1 is located upstream, and when the opening is over a predetermined degree, the second negative pressure port 1 is located downstream.
It has 2. Here, the negative pressure Pa of the first negative pressure port 11 is large when the throttle valve 4 is fully closed, as shown in FIG. 2(a).
It decreases rapidly as the throttle opening increases. The negative pressure PC at the second negative pressure port 2 is equal to the atmospheric pressure when the throttle valve 4 is fully open, and rises rapidly as the throttle opening increases, and when the throttle opening exceeds a predetermined throttle opening, the negative pressure PC at the second negative pressure port 21. It has the same characteristics as the negative pressure Pb and Pc of the negative pressure port 22, and has the same characteristics as the negative pressure Pb and Pc of the negative pressure port 11. The negative pressures Pa and Pf of the second negative pressure port 12 are set to have opposite characteristics.

The negative pressure switch 13 has one chamber 13b and the other chamber 13c partitioned by a diaphragm 13a.
A contact 13d operated by the diaphragm 13a is provided in the chamber 3b, and a return spring 13e is biased in the other chamber 13c. One chamber 13b communicates with the second negative pressure port 12 through a passage 14, and the other chamber 13c communicates with the first negative pressure port 11 through a passage 16 having a first check valve 15, thereby creating a differential pressure system. configured. The first check valve 15 opens when the negative pressure in the other chamber 13c is deep. Therefore, when the throttle valve 4 opens and the negative pressure in the first negative pressure port 11 decreases, the other chamber 13c opens. 13G of negative pressure is leaked, and the negative pressure Pa of the first negative pressure port 11 is reset to the minimum value Pam.

On the other hand, the negative pressure responsive valve 25 includes a negative pressure chamber 25c communicating with the negative pressure port 21 via the passage 23, and a negative pressure chamber 25b partitioned by a diaphragm 25a having an orifice 25e.
Negative pressure chamber 25 communicating with negative pressure port 22 via passage 24
d, and an operating negative pressure setting chamber 251 further having an orifice 25h on the inlet side of the valve body 25g, and the diaphragm 25
A spring 25j provided in a negative pressure chamber 25c is biased and a valve body 25g is fixed to port 2.
Open and close 5r. When the valve body 25g of the negative pressure responsive valve 25 opens immediately after deceleration, the atmospheric pressure in the operating negative pressure setting chamber 25i becomes
The orifice 25h generates a negative pressure Pd that is shallower than the negative pressures Pb and Pc and deeper than the negative pressure Pam.

This operating negative pressure setting chamber 251 is connected to the other chamber 13 of the negative pressure switch 13 by a passage 18 having a second check valve 17.
The second check valve 17 opens when the negative pressure in the operating negative pressure setting chamber 251 is deep. Therefore, immediately after deceleration, when the negative pressure responsive valve 25 opens and generates negative pressure Pd, the other chamber 13c is set to negative pressure Pd and reset.

Furthermore, a negative pressure switch 13. The signal from the engine rotation speed sensor 3° is input to a fuel cut control circuit 31 and processed. Further, a solenoid valve 32 is provided in the slow fuel passage 8, and at least at a predetermined engine speed or higher during deceleration, an output signal from the fuel cut control circuit 31 is used to control the solenoid valve 32.
2 is closed.

Next, the operation of the tM fuel cut device will be described.

First, when driving with the throttle valve 4 in steady operation with a predetermined opening degree, the negative pressures in the negative pressure chambers 25c and 25d are equal, so the negative pressure responsive valve 25 closes and the operating negative pressure setting chamber 25+ becomes atmospheric pressure. , and the second check valve 17 is closed. At this time, the negative pressure Pa of the first negative pressure port 11 is as shown in FIG.
is the minimum value Pam due to the characteristics of the first check valve 1
5 is also closed, and the negative pressure Pe in the other chamber 13c of the negative pressure switch 13 is confined to a value equal to the minimum value Pam as shown in FIG. 3(b). Further, the negative pressure Pr of the second negative pressure port 12 is a value larger than the minimum value Pam depending on the throttle opening, and this is a value that is larger than the minimum value Pam of the negative pressure switch 13
3b, resulting in the relationship lPam1<lPf'l,
The contact 13d of the negative pressure switch 13 is turned off.

Therefore, when the steady running described above is decelerated by releasing the accelerator at time t1 in Fig. 3, as the throttle valve 4 closes, the negative pressures Pb and Pc in the negative pressure ports 21 and 22 increase as shown in Fig. 3(b). suddenly increases, and at a predetermined time t2, the negative pressure responsive valve 2
A pressure difference is generated between the negative pressure chambers 25b and 25c of No. 5 by the orifice 25 for a predetermined delay time, and the port 25r of the negative pressure response valve 25 is opened and the negative pressure of the negative pressure chamber 25d is activated.The negative pressure setting chamber 251 In order to generate a predetermined negative pressure Pd, the second check valve 17 opens and the negative pressure Pe in the other chamber 13c of the negative pressure switch 13 becomes a negative pressure deeper than the minimum value Pam. Therefore, the negative pressure Pr of the second negative pressure port 12 is
As shown in Fig. 2(b), based on the characteristics of Fig. 2(a), it becomes deep once and then suddenly becomes shallow, and lPd l>lP''
At time t3 when the relationship I is reached, the negative pressure switch 13 is turned on as shown in FIG. 3(C) to detect deceleration. At this time, if the engine speed is higher than the set value, a fuel cut signal is output from the fuel cut control circuit 31 to the solenoid valve 32 to close it, and from then on, the slow system fuel is cut off as shown in Figure 3(d). afterburn is prevented.

After the deceleration is detected, the negative pressure P' in the second negative pressure port 12 becomes atmospheric pressure, and the negative pressure P' in the other chamber 1 of the negative pressure switch 13
Since negative pressure Pd is confined in 3c, lPd l
>lPf l continues, and the negative pressure switch 13 is kept in the on state.

Next, to describe the case where acceleration is performed by pressing the accelerator at time t4, the negative pressure Pa of the first negative pressure port hLl rapidly decreases to the minimum value PaII+, as shown in FIG. 3(b).
Therefore, when the first check valve 15 opens, the negative pressure Pe in the other chamber 13c of the negative pressure switch 13 also becomes Pd.
It becomes shallow from the minimum value Pam.

On the other hand, the negative pressure Pd of the second negative pressure port 12 increases rapidly, and at the time t of the relationship IPaIIIl < l Pf l.
5, the negative pressure switch 13 is turned off and acceleration is detected as shown in FIG. 3(C). Therefore, as shown in FIG. 3(d), time t5
Thereafter, a recovery signal is output from the fuel cut control circuit 31 to the solenoid valve 32 to open it, and the slow system fuel cut is recovered.

〔Effect of the invention〕

As described above, according to the present invention, the negative pressure switch of the fuel cut system is configured to be a differential pressure type, and the differential pressure setting value is set small, so that the responsiveness of acceleration/deceleration detection is improved.

In addition, by improving the responsiveness of the fuel cut-off fuel recovery based on acceleration detection in particular, fuel is quickly supplied, improving drivability and reducing shocks caused by delays in fuel supply.

Furthermore, since it is a differential pressure type negative pressure switch, the relative pressure is constant even when the suction negative pressure changes due to altitude, so altitude compensation is not required.

Furthermore, since the configuration is such that the differential pressure operation is performed using the port negative pressure of the throttle valve with reverse characteristics and the negative pressure associated with the introduction of atmospheric air from the negative pressure responsive valve, the structure is simplified.

During deceleration, the differential pressure set value is determined to be large based on the negative and positive values associated with the introduction of atmospheric air into the negative pressure responsive valve, so that deceleration can be detected quickly and the detected state can be maintained.

Furthermore, during acceleration, the differential pressure set value is set to a small value by the port negative pressure of the throttle valve, so acceleration can be similarly detected quickly and the detected state can be maintained.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the fuel cut device of the present invention, FIG. 2(a) is a graph of negative pressure characteristics with respect to throttle opening,
FIG. 2(b) is a negative pressure characteristic diagram of each part when opening and closing the negative pressure responsive valve, and FIG. 3 is a characteristic diagram showing the action during deceleration and re-acceleration.

Claims (2)

[Claims] (1) It has a first negative pressure port that reduces negative pressure in accordance with an increase in the throttle valve opening of the carburetor, and a second negative pressure port that increases the negative pressure, and The pressure port is connected to one chamber of the differential pressure type negative pressure switch, and under the condition that the throttle valve is opened to the other chamber of the negative pressure switch, the shallow minimum negative pressure of the first negative pressure port is applied, and during deceleration, the shallow minimum negative pressure is applied to the other chamber of the negative pressure switch. A fuel cut device that selectively applies a predetermined negative pressure that is slightly deeper than the minimum negative pressure. (2) A negative pressure responsive valve is provided to set the operating negative pressure of the negative pressure switch, and the operating negative pressure setting chamber formed in the negative pressure responsive valve is connected to the negative pressure switch via a second check valve. 2. The fuel cut device according to claim 1, wherein the first negative pressure port is connected to the other chamber of the first negative pressure port through a first check valve.