IDLING-UP CONTROLLER

Abstract: An idling-up control constituted by an idling-up control mechanism for moving a throttle valve (6) of a carburetor to a predetermined idling-up position by means of an actuator (14), and a fuel-cut mechanism having a fuel-cut valve (28) disposed at an intermediate portion of a slow-system passage (26) of the carburetor. The fuel-cut mechanism shuts off the supply of fuel by using a throttle-opening switch (32) when the rotational speed of the engine is reduced. The idling-up controller is provided with a first conductor (36) for effecting fuel-cut operation which connects the fuel-cut valve (28) of the fuel-cut mechanism and the throttle-opening switch (32) to each other, and a second conductor (40) for effecting idling-up operation which has an electromagnetic valve (22) for operating the actuator (14) and which is connected to the first conductor (36).

Description: The invention relates to an idling-up controller according to the preamble of claim 1. US-A-4 008 696 discloses a carburetor for optimum control of an air-fuel mixture supply to the engine during deceleration, according to which addition of most fuel is electrically prevented during breaking by the engine at a high engine speed. Below a certain engine speed, the electric signal is stopped and a vacuum-operated valve allows additional air-fuel mixture to enter the engine, even though the throttle valves are closed. Traditionally, in an internal combustion engine, the idling engine speed is set to be low in order to clarify exhaust gases and reduce fuel consumption. When the idling engine speed is low, even a slight increase in the load of the engine results in a reduction in the rotational speed of the engine and, hence, malfunction of the engine. For instance, an increase in the electrical load due to headlamps or the like being switched on reduces the rotational speed of the engine, resulting in malfunction of the engine. If cooling water for cooling the engine is circulated through a heat exchanger when the occupant wishes to use the heater in cold weather, the warming-up operation cannot be performed adequately since the rotational speed of the engine is low. For the purpose to solve this problem, a type of idling-up controller has been proposed in which a throttle valve of the carburetor is maintained at a set idle-opening so as to compensate for any reduction in the rotational speed of the engine when an electrical load such as that mentioned above is applied. In the conventional idling-up controller, the throttle opening is adjusted by an idling-up controlling screw at the time of idling-up control operation as shown in US-A- 4 060 063. This type of idling-up controller lacks any throttle-opening switch for limiting the throttle opening. If the throttle opening is accidentally set at an excess setting by the idling-up adjusting screw, the degree of idling-up exceeds a desired throttle opening at which the fuel-cut operation starts. Therefore, the fuel-cut operation is not performed even when the engine is in a state which requires a fuel-cut (for example, in a deceleration range), thus hindering the fuel-cut operation. If the fuel-cut operation is hindered, there is a risk of overheating catalysts and a lowering of the function of the catalysts. Also there is a problem of increase in the amount of discharged unburnt gas and, hence, deterioration of the fuel consumption. It is the object of the present invention to provide an idling-up controller of the above-mentioned kind which limits the degree of idling-up at a predetermined opening without hindering the fuel-cut control, and which ensures that overheating of catalysts is prevented. This object is achieved according to the invention by the features in the characterizing part of claim 1. The idling-up controller has an idling-up control mechanism and a fuel-cut control mechanism, in which a second conductor for idling-up control which has an electromagnetic valve for operating an actuator is connected to a first conductor for fuel-cut control which connects a fuel-cut valve of the fuel-cut control mechanism and a throttle-opening switch, and which, by using a detection signal from the throttle-opening switch for fuel-cut control as a signal for limiting the degree of idling-up, is capable of limiting the degree of idling-up when the throttle opening is set at an excess position while ensuring the fuel-cut operation and the prevention of catalyst overheating. To this end, the present invention provides an idling-up controller having: an idling-up control mechanism for moving a throttle valve of a carburetor to a predetermined idling-up position by means of an actuator; a fuel-cut mechanism having a fuel-cut valve disposed at an intermediate portion of a slow-system passage of the carburetor, the fuel-cut mechanism being adapted to cut the supply of fuel by means of a throttle-opening switch at the time of deceleration of the engine; a first conductor for effecting fuel-cut operation and connecting the fuel-cut valve of the fuel-cut mechanism and the throttle-opening switch to each other; and a second conductor for effecting idling-up operation having an electromagnetic valve for operating the actuator, the second conductor being connected to the first conductor. This arrangement makes it possible to use a detection signal from the throttle-opening switch for fuel-cut control as a signal for limiting the degree of idling-up so that degree of idling-up can be limited to a desired opening while ensuring the fuel cut operation and the prevention of catalyst overheating. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1 to 3 show an embodiment of the present invention in which: Fig. 1 is a schematic illustration of an idling-up controller; Fig. 2 is a graph of a fuel-cut control region relative to the throttle opening and the rotational speed of the engine; and Fig. 3 is a schematic illustration of a condition setting switch. DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will be described below in detail with reference to the accompanying drawings with respect to an preferred embodiment thereof. Figs. 1 to 3 illustrate an embodiment of the present invention. Referring first to Fig. 1, a carburetor 2, an inlet passage 4 and a carburetor throttle valve 6 are shown. An idling-up control mechanism will be described first. The carburetor throttle valve 6 is provided with a throttle lever 8 and a free lever 10. An idling-up control screw 12 which contacts the free lever and functions to adjust the throttle opening is disposed on the throttle lever 8. A controlling rod 16 of a diaphragm type actuator 14 is connected to the end of the free lever 10, and a negative-pressure passage 18 is connected to a pressure chamber (not shown) of the actuator 14. A port 20 which is the starting end opening of the negative passage 18 communicates with the inlet passage 4 at the downstream side relative to the carburetor throttle valve 6. The negative-pressure passage has two parts which are interconnected by an electromagnetic valve 22 which changes over and introduces a negative pressure and the atmospheric pressure. Next, a fuel-cut control mechanism will be described below. A slow system fuel passage 26 through which a float chamber 24 of the carburetor 2 and the inlet passage 4 communicate with each other is provided. A cut valve 28 for shutting off slow fuel is disposed at an intermediate portion of the fuel passage 26, and an idle mixing ratio controlling screw 30 is also disposed at another portion of the fuel passage 26. A throttle-opening switch 32 which is normally closed is adapted to operate in association with the carburetor throttle valve 6. The switch 32 opens when the throttle opening is greater than a predetermined degree. One end of the throttle-opening switch 32 is connected to a rotational speed sensor 34 which is supplied with ignition pulses, and the other end of the switch is connected to a first conductor 36 for fuel-cut control whereby the cut valve 28 is controlled so as to be opened or closed. A rotary switch 38 which is opened or closed by the rotational speed sensor 34 in accordance with the rotational speed of the engine is disposed at an intermediate portion of the first conductor 36 so as to connect this conductor. A second conductor 40 for idling-up control is connected to the first conductor 36 at a position between the rotary switch 38 and the throttle-opening switch 32. The electromagnetic valve 22 is controlled through the second conductor 40 so as to operate the actuator 14 in accordance with the throttle opening. A condition setting switch unit 42 which is turned on by an electrical load caused by the on-operation of a passenger-compartment cooler or an air conditioner is disposed at an intermediate portion of the second conductor 40. As shown in Fig. 3, this condition setting switch unit 42 is constituted by a switch SW1 which is turned on when a first electrical load is produced by the operation of the cooler or air conditioner, and a second SW2 which is turned on when a second electrical load is caused by other factors. The system shown in Fig. 1 also includes a filter 44 through which atmospheric-pressure air is introduced by the electromagnetic valve 22, and a battery 46. The operation of the idling-up controller in accordance with the present invention will now be described. When the opening of the carburetor throttle valve 6 is reduced below a predetermined degree at which the fuel-cut idling switch is operated, the throttle-opening switch 32 is turned on. If the rotational speed of the engine is higher than a predetermined level, that is, the speed at which the fuel-cut operation is performed, the rotary switch 38 is turned on by the rotary sensor 34 which is supplied with ignition pulses and which detects the rotational speed of the engine, thereby connecting the first conductor. At this time, a fuel cut region is defined, as represented by the hatched area in Fig. 2. After the rotary switch 38 has been turned on, the cut valve 28 operates so as to close the fuel passage of the slow system and shut off the supply of slow fuel from the float chamber 24 of the carburetor 2 to the inlet passage 4, thereby preventing discharge of unburnt gas at the time of deceleration and, hence, improving the fuel consumption. During the time of idling, the condition setting switch 42 is turned on in response to the application of the first electrical load effected when the cooler or air conditioner is used so that the switch SW1 is turned on. Since, at this time, the opening of the carburetor throttle valve 6 is, of course, below the predetermined degree, the throttle-opening switch 32 maintains the on state. In response to the on state of the throttle-opening switch 32, the second conductor 40 is connected so as to effect idling-up control. That is, the electromagnetic valve 22 is changed over under control so that a negative pressure in the inlet passage 4 at the downstream side relative to the carburetor throttle valve 6 acts on the pressure chamber of the diaphragm type actuator 14 via the negative-pressure passage 18; the free lever 10 is turned as the control rod 16 is pulled; and the opening of the carburetor throttle valve 6 is increased, thus effecting idling-up. If, at the time of idling-up control, the opening of the carburetor throttle valve 6 is above the predetermined degree, the throttle-opening switch 32 is turned off so that the first and second conductors 36 and 40 are shut off, thereby inhibiting the idling-up control. That is, the idling-up-possible region is set by the throttle-opening switch, as indicated in Fig. 2. It is thereby possible to use a detection signal from the throttle-opening switch for fuel-cut control as a signal for limiting the degree of idling-up, thereby enabling suitable idling-up in response to the throttle opening. The controller in accordance with the present invention is thus advantageous in terms of practice. When the throttle opening is accidentally set at an excess setting, the degree of idling-up can be limited to the predetermined throttle opening, that is, within the idling-up-possible region by the operation of the throttle-opening switch while ensuring the fuel cut control. It is thereby possible to prevent catalysts from overheating. The present invention is not limited to the above-described embodiment and can be modified and applied variously. For instance, in the embodiment of the present invention, the operation of the passenger-compartment cooler or air conditioner has exemplified the electrical load which turns on the condition setting switch, but it is also possible to design the controller such that the condition setting switch is turned on to connect the second conductor when electrical loads such as the on operations of a power transmission clutch for the cooler or air conditioner, a heater blower, headlamps, and a heater power source for a rear defogger are produced. As described above in detail, the idling-up controller in accordance with the present invention has the idling-up control mechanism and the fuel-cut control mechanism and, in this controller, the first conductor for fuel-cut control which connects the fuel-cut valve of the fuel-cut mechanism and the throttle-opening switch is connected to the second conductor for idling-up control which has the electromagnetic valve for operating the actuator. It is thereby possible to use a detection signal from the throttle-opening switch for fuel-cut control as a signal for limiting the degree of idling-up so as to enable suitable idling-up in response to the throttle opening. When the throttle opening is accidentally set at an excess setting, the degree of idling-up can be limited to the predetermined throttle opening, that is, within the idling-up-possible region by the operation of the throttle-opening switch while ensuring the fuel-cut control and preventing catalysts from overheating.

Claims: An idling-up controller comprising: a fuel-cut mechanism having a fuel-cut valve (28) disposed at an intermediate portion of a slow system passage (26) of said carburetor, said fuel-cut mechanism being adapted to cut the supply of fuel by means of a throttle-opening switch (32) at the time of deceleration of the engine which throttle opening switch (32) is operated by the opening position of the throttle valve (6) in the inlet passage (4); a first conductor (36) for effecting fuel-cut operation, said first conductor (36) connecting said fuel-cut valve (28) of said fuel-cut mechanism and said throttle-opening switch (32) to each other, and characterized by, an idling-up control mechanism for moving the throttle valve (6) in the inlet passage (4) of a carburetor to a predetermined idling-up position by means of an actuator (14); a second conductor (40), for effecting idling-up operation, connecting an electromagnetic valve (22), which operates said actuator (14), to said first conductor (36) over a second switch (42), the switch (42) being actuated when auxiliary loads are connected to the engine, so that an opening movement of the throttle valve (6) causing opening of the throttle opening switch (32), thereby interrupting the contact of the current source to said first and second conductor (36,40), causes the actuator (14) to decrease the opening degree of the throttle valve (6). An idling-up controller according to claim 1, wherein said second conductor (40) has a condition setting switch (42) disposed at its intermediate portion, said condition setting switch being turned on by an electrical load.

Inventors: DOI, MINORU
Applicants: SUZUKI JIDOSHA KOGYO KABUSHIKI KAISHA
Application year: 1987
Main classification: F02M3
IPC codes: F02M3, F02D9