AUTOMATIC CONTROL APPARATUS FOR ENGINE THROTTLE VALVES

Abstract: The invention concerns an automatic control apparatus for engine throttle valves (1) which are provided rotatably in the intake line (2) and are driven by a motor (3), the downstream side of the throttle valve being connected to the engine. Means for opening forcedly the throttle valve when the engine is shut down are provided so as not to allow tar components in the fuel to deposit on the outer peripheral portion of the throttle valve.

Description: The present invention relates to the control of automobile internal combustion engines, and is particularly concerned with an automatic control apparatus for an engine throttle valve which is capable of minimizing the load of the motor for controlling the position of the throttle valve. Control apparatus for internal combustion engine throttle valves are already known (cf. for example "Control Apparatus for Internal Combustion Engine Throttle Valves", Japanese Patent Publication No. 25853/1983 and "Valve Driving Device", Japanese Patent Laid-Open No. 145867/1980). In these conventional apparatus the throttle valve is supported rotatably on a pipeline. A motor for driving the throttle valve is coupled directly to the throttle valve or connected thereto through a reduction gear. A return spring is provided on the throttle valve, and thus when the motor is not operated, the throttle valve is returned invariably to a position at which the engine comes to idling. A position sensor for detecting the opening degree is provided on the throttle valve, and information on the actual position of the throttle valve is obtained from the position sensor, which is used for a correction of the position control of the motor. Generally in automobile internal combustion engines with fuel injection downstream of the throttle valve, viscous deposits stick on the throttle valve due to a fuel scum return, backfiring and the like, which may lead to a clogging of the throttle valve at fullopen position. In the conventional apparatus, the torque of the return spring is loaded in addition to the torque for relieving the throttle valve from such a clogged state, and thus a considerable overall-torque is required for the driving motor. To obtain such a heavy torque, an increased reduction ratio is normally applied, however, such a measure deteriorates the response characteristic. On the other side, an enlarged motor therefor inevitably increases the weight of the apparatus which is, needless to say, also disadvantageous. It is an object of the invention to provide an automatic control apparatus for engine throttle valves operated by a small-sized motor wherein the throttle valve is prevented from being clogged at full-open position whithout deterio­ rating the response. The throttle valve is clogged by hardened deposits which are formed by leaving the throttle valve closed for a long time after the engine is shut down. Clogging of the throttle valve does not occur if it is kept open at a certain position after shutdown of the engine. The invention is based on that finding. According to the invention, means operating at the time of engine shutdown are provided at the throttle valve, which forcedly open the throttle valve by means of an actuator when the engine is shut down. The invention is described in the following with reference to the drawings. Fig. 1 represents one embodiment of the apparatus according to the invention, Fig. 2 represents another embodiment of the apparatus according to the invention, Fig. 3 is a drawing for illustrating in detail the magnetic coupling of Fig. 2, Fig. 4 is a drawing representing a further embodiment of the apparatus according to the invention, Fig. 5 is a drawing representing a further embodiment of the apparatus according to the invention. Fig. 6 is a drawing for illustrating in detail a lever of Fig. 5. Referring now to Fig. 1, a throttle valve 1 operated by a motor 3 is supported rotatably in an intake line 2, and a lever 11 is fixed on one end of its shaft. An actuator 12 pushes the lever 11 to open the throttle valve. The actuator 12 comprises a diaphragm 14 and a retainer 15 for holding the diaphragm 14; a shaft 13 is fixed on the retainer 15, and a case 17 is provided which supports the shaft slidably, holds down the diaphragm 14 and forms an airtight chamber on the side counter to the shaft 13. A spring 16 is provided for extruding the shaft on the airtight chamber side. The airtight chamber is connected to a check valve 18 which communicates with the intake line downstream of the throttle valve 1. The check valve 18 opens to a large orifice when the air pressure of the airtight chamber steps down, but to a small orifice when the air pressure steps up, thus preventing the air pressure from rising sharply. The arrow A in Fig. 1 indicates the air flow direction, and E indicates the engine side. When the engine starts, a negative suction pressure is produced and passes the check value 18. This leads to a dropping of the air pressure of the airtight chamber of the actuator 12, whereby the diaphragm 14 is pulled, the spring 16 is compressed, the shaft 13 is also drawn in, and thus the throttle valve 1 is closed. The spring 16 and the diaphragm 14 are dimensioned such that they operate even at the time of cranking. When the engine stops, the negative suction pressure downstream of the throttle valve 1 is turned to atmos­ pheric pressure and the air pressure within the actuator 12 is increased accordingly; however, the air pressure does not rise quickly because of the check valve 18 provided therefor, and the shaft 13 will not come out so suddenly, and thus the throttle valve 1 is not opened immediately after the engine has stoped. The check valve thus provided is effective enough to suppress hunting. Fig. 2 represents another embodiment. The throttle valve 1, the intake line 2 and the lever 11 are disposed as in the case of Fig. 1. Furthermore, a lever 21 is so disposed as to come in contact with the lever 11, and the throttle valve 1 can be opened by means of the tensile force of a spring 22 which is fixed to the same side of the lever 21. A wire 23 is mounted on the same side of the lever 21, and thus when the wire 23 is pulled, the lever 21 is detached from the lever 11. The wire 23 is wound on a drum 24. The drum 24 has a stopper 25, which prevents the lever 21 from being overdrawn. The drum 24 is connected to the engine shaft 27 through a magnetic coupling 26. The structure of the magnetic coupling 26 is shown in Fig. 3. The drum 24 is rotatable with respect to the engine shaft 27 through a bearing 28. A magnet 30 is fixed on the drum 24. The magnetic coupling 26 is fixed on the engine shaft 27, and an iron plate 29 is fixed further thereon. The magnetic flux from the magnet 30 penetrates the iron plate 29, and a torque is generated so as to rotate the drum in the same direction as that of engine rotation. The torque is generated in the direction R of Fig. 2, and the wire 23 is pulled thereby. The lever 21 is thus detached from the lever 11, and no action is exerted on the throttle valve if the engine is running. When the engine stops, no torque is generated, the tensile force of the wire 23 is removed, and the lever 21 pushes the lever 11 by the force of the spring 22 to open the throttle valve 1. In Fig. 4, the same construction is given as in the case of Fig. 2, and the same reference numerals are used however, no spring is provided directly on the lever 21, but a spring 31 is provided on the drum 24. Quite differently from the construction of Fig. 2, the lever 21 operates the lever 11 when the wire 23 is pulled, because the wire 23 is connected to the opposite side of the lever 21. The drum 24 generates a torque during rotation of the engine, but moves in the direction losing the tensile force of the wire 23 against the spring 31 and then stops at the stopper 25. The wire has the tensile force removed as above, therefore the lever 21 does not operate the lever 11. When the engine stops, the drum 24 loses the torque and pulls the wire 23 because of the torque of the spring 31 and the lever 21 operates the lever 11 to open the throttle valve 1. In the example of Fig. 4, when the wire 23 is cut, no action can be exerted on the throttle valve, and hence a car or engine can be prevented from running away. In the embodiment of Fig. 5, a return spring 4 and an actuator 41 for keeping the return spring 4 from operating at the time of motor actuation are provided with the construction of Fig. 1. As in the case of the actuator 12, the actuator 41 operates on a negative suction pressure. A three-way solenoid valve 42 is provided halfway of the line connecting the check valve 18 to the intake line 2. The solenoid valve 42 is connected to the actuator 41, and a negative suction pressure is introduced to the actuator 41 when the solenoid valve 42 is turned on, and atmospheric pressure is introduced to the actuator 41 when the solenoid valve 42 is turned off. The three-way solenoid valve 42 is turned on whenever the engine starts. However, when something is wrong with the motor to bring about an uncontrollable state, it is turned off upon decision of a controller 6, atmospheric pressure is introduced to the actuator 41, the return spring 4 operates the throttle valve 1, and thus the throttle valve 1 is closed until a position of idling. The return spring 4 of Fig. 5 and its periphery are shown in detail in Fig. 6. A drum 51 is rotatable with respect to the throttle valve shaft 50. An adjusting screw 52 is provided on the drum 51, which comes in contact with a lever 53 fixed on the throttle valve shaft 50, and thus the throttle valve 1 is closed by the torque of the return spring 4 mounted on the drum 51. A wire 54 is mounted on the drum 51, and when it is pulled, the adjusting screw 52 is detached from the lever 53, and the torque of the return spring 4 will not work on the throttle valve 1. The actuator 12 operates on the lever 53 likewise as in the case of Fig. 1. According to this embodiment, the load of the motor 3 is limited to the frictional force and the torque generated by the air stream acting on the throttle valve 1. As described above, according to the invention, since the throttle valve is never clogged at an idling position, it is not necessary to take an excessive torque into consideration, and accordingly, the load of the motor for the position control of the throttle valve can be decreased accordingly, a gear with a large reduction ratio is unnecessary, and further the motor can be miniaturized considerably.

Claims: 1. An automatic control apparatus for engine throttle valves comprising a motor for driving the throttle valve, characterized by means (11, 12, 18; 11, 21, 22, 23, 24; 11, 21, 23, 24, 31; 6, 12, 18, 41, 42) for opening the throttle valve (1) forcedly from a full-close position at the time of engine shutdown so as not to allow tar components of the fuel to stick on the outer peripheral portions of the throttle valve (1) (Figs. 1, 2, 4, 5). 2. An automatic control apparatus according to claim 1, characterized by means for forcedly opening the throttle valve (1) by the actuating force of a spring (16; 22; 31; 4) (Figs. 1, 2, 4, 5). 3. An automatic control apparatus according to claim 1 or 2, characterized by means (12, 18; 6, 41, 42) detecting whether or not the engine is shut down according to the presence of a negative suction pressure of the engine, driving the means for forcedly opening the throttle valve (1) (Figs. 1, 5). 4. An automatic control apparatus according to claim 1 or 2, characterized by means (11, 21, 22, 23, 24; 11, 21, 23, 24, 31) detecting whether or not the engine is shut down according to the rotation of the engine shaft, driving the means for forcedly opening the throttle valve (1) (Figs. 2, 4). 5. An automatic control apparatus, according to claim 1 or 2, characterized by a return mechanism (4) for returning the throttle valve (1) to an idling position, a controller (6) for detecting a trouble on the throttle valve driving motor (3), and a throttle valve reset mechanism (41, 42) for keeping said return mechanism (4) from operating normally but sending an output for returning said return mechanism (4) to the idling position according to a command from said controller (6) when a trouble of the motor (3) is detected by said controller (Fig. 5).

Inventors: EJIRI, YUKI, ITO, TOMOO
Applicants: HITACHI, LTD.
Application year: 1986
Main classification: F02D11
IPC codes: F02D41, F02D11, F02D9, F02M9