A throttle valve control device for an internal combustion engine

Abstract: A motor-driven throttle valve control device has a throttle shaft (2) and a coupling lever (5) rotatably provided on the shaft (2), both being coupled by a spring. There is provided a default spring (7) which energizes the coupling lever (5) toward a position of the default opening of the throttle valve (1). The throttle shaft (2) rotates separately from the coupling lever (5) in the direction of a full open of the throttle valve (1) from a point at which the coupling lever (5) comes into contact with a stopper (103) defining the default position, and together with the coupling lever (5) in the direction of a full close of the throttle valve (1) from the point. Thereby, the throttle valve (1) can be kept at the default position by the default spring (7) through the coupling lever (5), when a motor (4) driving the throttle valve (1) is not fed.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a throttle valve control device for an internal combustion engine, and more particularly to a throttle valve control device with a motor-driven throttle valve. Description of the Prior Art A conventional device of this kind is typically disclosed in prior publications such as JP-A-63-150449 (1988), as well as USP Nos. 4,947,815 and 4,735,179 (the last one being owned by the same assignee as this application). As discussed in the prior publications as above, one of the most important things in a throttle valve device of the type that a throttle valve is driven by an actuator, such as a DC motor or a step motor, is that the minimum safety can be secured even against a trouble in the actuator. With the aforesaid "minimum safety", the following is meant; i.e., even in the event of occurrence of a trouble in a throttle valve actuator, an engine can produce torque of a certain magnitude, whereby an automobile can travel at a predetermined speed, e.g. 30 km/h or so, to reach a nearby repair shop. According to circumstances, however, the higher speed, e.g., 80 km/h, may be required for such an emergency speed. That is, it is desired that even in the event of occurrence of a trouble in a throttle valve actuator, a throttle valve is always kept at a certain opening so that an engine can produce torque large enough to allow an automobile to travel at a desired emergency speed. By way of example, let us assume a case where electric power for a throttle valve actuator is abruptly cut off. In such a case, a throttle valve is rapidly returned by a return spring to a full close position or an idle position, with the result that a traveling automobile is decelerated drastically. Further, with respect to "a full close position" and "an idle position", more detailed explanation will be given in relation to the description of the embodiment of the present invention, later. For the present, however, only "a full close position (or opening)" is used. Then, after the throttle valve is returned to the full close position, the automobile can no longer continue to travel at a desirable speed, because an engine can not produce sufficient torque with such opening of the throttle valve. Further, in an motor-driven throttle valve device, an initial position of a throttle valve when an engine does not operate, i.e., a full close position, is necessary to be selected at such a value that re-start torque of a driving motor never becomes large. The reason therefor is as follows. If the throttle valve is allowed to stand at the full close position for a long period of time after the engine stops, combustion products, such as tar and carbon, accumulate and adhere between the throttle valve and an inner wall of an intake pipe so that the throttle valve is fixed to the inner wall and becomes difficult to be opened by the torque of the driving motor, again. Therefore, the throttle valve device as disclosed in the aforesaid prior publications was provided with a stopper called a default stopper. This stopper serves to prevent a throttle valve from being at the full close position, when a trouble occurs in the driving motor and the throttle valve is rotated by a return spring in the closing direction. Therefore, the default stopper is different in its function from a stopper called a full close stopper (or an idle stopper), which is provided at a certain position to prevent a throttle valve from sticking into an inner wall of an intake pipe to secure a rotational speed for idling. Even if a driver releases his foot from an acceleration pedal to temporarily stop an automobile because of a traffic signal, the throttle valve must be slightly opened to keep a rotational speed for idling so that the engine is prevented from stalling. With such a rotational speed of the engine, however, an automobile can never travel at the speed of 30 km/h, for example. As already mentioned, in order to attain the aforesaid minimum safety, an automobile is required to be able to still travel at a desired emergency speed, even if a throttle valve driving motor has a trouble. Usually, a full close stopper (or idle stopper) is provided at the position of 1° ∼ 2° prior to the completely closed position of a throttle valve. Here, it is meant with the "completely closed position" of a throttle valve that the throttle valve completely chokes an intake pipe so as to flow no air therethrough. On the other hand, the default stopper is provided at the position that is further shifted by 3° ∼ 11° in the opening direction from the position of the full close stopper. With the opening of the throttle valve defined by the default stopper as above, an automobile can travel at the speed of 30 to 80 km/h (the travel under such a condition as described above is often called a limp-home travel (or operation)). Under the condition of the limp-home travel, the opening of the throttle valve is maintained at a value that the aforesaid minimum safety can be attained, but the opening can be no longer adjusted, even if an acceleration pedal is operated. Therefore, the control of the engine output is done by switching over a control mode of the ignition timing to one prepared for the limp-home operation, and/or by switching over a control mode of the fuel supply to one prepared for the same. If an automobile temporarily stops because of the traffic signal, for example, the rotational speed of the engine will become very high. Namely, the engine gets into a runaway condition. This is because under the limp-home operation, the throttle valve is kept at the opening which is much larger than that of the full close position. Therefore, an adequate instruction for the ignition timing and/or the fuel supply must be provided so as not to cause such a runaway condition in the engine, taking account of the fact that the automobile stands still, a rotational speed of the engine, an information of a trouble in a throttle valve motor, and so on. By the way, if a throttle valve motor operates normally, the default stopper is unnecessary and awkward, because desirably the motor can control the opening of a throttle valve without any limitation between the position defined by the full close stopper and the full open position, in proportion to the depression amount of an acceleration pedal. In the prior art, this point was dealt with in the following manner. Namely, the position of a default stopper is biased by putting it on some kind of elastic body like a spring or rubber. This elastic body has the elastic force being capable of balancing with the force of a return spring, when the throttle valve is at the position defined by the default stopper. Therefore, the throttle valve is never closed further by force of the return spring only. Then, in the prior art device, the throttle valve device is so designed that if a throttle valve motor operates normally, a throttle valve is controlled by force to the full close position against the elastic force as described above. That is to say, the elastic body, on which the default stopper is provided, is displaced by the torque of the motor in the direction of the full close position, and the throttle valve can be closed at the full close position. During an engine is in the idling operation, the throttle valve motor is necessary to produce the torque overcoming the force of the elastic body, whereby the throttle valve can be rotated from the opening of 4° ∼ 13° to the opening of 1° ∼ 2°. For the throttle valve motor, therefore, force caused by the elastic body is preferable to be as small as possible. If the elastic force is small, the throttle valve motor can produce only the small torque as much, which reduces the burden of a battery. This is desirable especially during the idling operation of the engine, because a charging generator does not produce sufficient output power in that duration. Namely, the throttle valve motor must continue to produce torque in order to keep the throttle valve at the full close position or the idle position against the default spring. Therefore, it is desirable that the spring force of the default spring is as small as possible. US 5 060 613 discloses an electromechanical device for adjusting a throttle valve out of its position of response in opposite directions. The device comprises an intermediate element which is capable of coming to rest on a repose position stop and a control element for operating a throttle valve. The control element and the intermediate element are connected by a spring which is actuated when the intermediate element stops at the position stop. From the position stop towards the opening direction of the throttle valve the intermediate element and the control element are moved together against a force of a spring disposed between the casing and the intermediate element. EP 0 651 147 A1 discloses a device according to the first part of claim 1. This document shows an accelerator pedal and an electromotive drive, the latter acting upon a motor lever which, in the neutral position, assumes an emergency running position which is fixed by a clamping spring and adjusts a throttle lever in such a way that the throttle valve undergoes a corresponding emergency running opening. The particular advantage of the control device according to this document is the use of a single spring having two ends jointly embracing a motor level journal and a housing journal to provide a corresponding force in both directions, the opening and the closing direction from the emergency position. EP 0 704 609 A1 discloses a simple structure of an electronically actuated throttle valve having a biasing member which operates to position the throttle valve at a default airflow position between the minimum and the maximum airflow positions across the entire range of positions. DE 41 41 104 A1 discloses a control device for a throttle valve comprising two return springs, a default spring, a coupling member, a control member, and a control element. The first return spring and the second return spring act on the control element and on the coupling member, while the default spring is disposed between the coupling member and the control member. The control member is operated by an electromotive drive for driving a throttle valve shaft which is fixed to the control element. EP-A-0651147 discloses a throttle control apparatus having an accelerator-pedal and an electro-motive drive. The electro-motive drive is acting upon a motorlever which in neutral position assumes an emergency running position which is fixed by spring action and adjusts a throttle lever in such a way that the throttle valve undergoes a corresponding emergency running operation. The electro-motive drive is capable of displacing the motor-levercounter to the spring action in the direction of an opening or closing position of the throttle valve. The spring action is provided by a simple clamping spring which with its two ends jointly embraces a motorlever journal and a housing journal. SUMMARY OF THE INVENTION An object of the present invention is to provide a small-sized motor-driven throttle valve control device for an internal combustion engine, in which torque required to be produced by a throttle valve motor can be reduced. The object is accomplished by a control device according to claim 1. The application of the present invention is not limited to such a type of the throttle valve control device that as described before, the limp-home function is attained by the electrical control. The present invention can also be applied to a throttle valve of the type that the limp-home function is performed by transmitting the depression amount of an acceleraton pedal to a throttle valve through links of a wire. According to the present invention, a return spring serves to put back a throttle valve to a default position, at which the aforesaid minimum safety can be secured. When the throttle valve moves in the closing direction from the default position, it is operably separated from the return spring and moves against force caused by another spring (default spring) provided separately. With the construction as mentioned above, a spring with weak spring force can be used as a default spring, compared with the conventional default spring, because force of the return spring acting in the closing direction does not need to be taken into consideration. One of the embodiments according to the present invention is provided with a coupling lever, which rotates together with a throttle valve and stops at a stopper (a default stopper) provided at the default position of the throttle valve. In such an arrangement, only the throttle valve is rotated by the throttle valve motor in the opening direction from the default position. In another embodiment, the throttle valve is rotated by the throttle valve motor only in the closing direction from the default position. In every embodiment, the rotation of the coupling lever is limited by the default stopper provided at the default position. That is, rotating torque of the throttle valve motor is transmitted to a throttle valve shaft through gears. The coupling lever is detachably coupled with the throttle valve shaft and rotates together therewith until it is caught by the default stopper. After the coupling lever and the default stopper contact with each other, only the throttle valve shaft continues to rotate. In the one embodiment, there is provided a return spring between the coupling lever and the throttle valve. A default spring is provided to energize the coupling lever in the direction of the default stopper. In the another embodiment, there is provided a default spring between the coupling lever and the throttle valve. A return spring is provided to energize the coupling lever in the direction of the default stopper. For springs in every case as above, the expansion force of a contracted spring or the contracting force of a stretched spring, and the combination thereof, can be used. In the embodiment of the invention, the return spring is preferably constructed by a spiral spring, the innermost end of which is fixed to a sleeve of the coupling lever. The sleeve is formed in a united body with the coupling lever and rotatably provided on a throttle valve shaft. The outermost end of the spiral spring is fixed to a member (a reduction gear, for example) fixedly provided on the throttle valve shaft. Further preferably, a gear fixed on the throttle valve shaft has a flat and circular depressed space or room in a body part thereof with the throttle valve shaft centered. The spiral spring, which is usually formed flat, too, i.e., in a disk-like form, is accommodated in the space or room defined by the flat and circular depression. Gear teeth are formed on the outer periphery of the body part of the gear. Furthermore, a sleeve is formed in the center of a gear. The sleeve is fitted to the throttle valve shaft to fix the gear thereon. An outer sleeve further cover the outer periphery of the sleeve rotatably. The coupling lever is fixed on the outer sleeve. An end of the default spring is supported by the coupling lever fixed on the outer sleeve. The coupling lever is preferably provided with an arm having a surface contacting with the default stopper. Further, the coupling lever is preferably provided with an arm having a surface contacting with a member (a gear member, for example), which rotates together with the throttle valve, when the throttle valve rotates in the closing direction from the default position. Furthermore, that member is provided with a surface contacting with a stopper, which defines the end of the rotation of the throttle valve in the closing direction. In the another embodiment of the invention, a default spring is constructed by a spiral spring, the innermost end of which is fixed to a throttle valve shaft and the outermost end thereof to a coupling lever rotatably fixed on the throttle valve shaft. Further, in this embodiment, the coupling lever preferably supports the end of the return spring, and is provided with an arm having a surface contacting with the default stopper. Preferably, the coupling lever is provided with another arm, which contacts with a member fixed on the throttle valve shaft, when the throttle valve rotates in the opening direction from the default position. The coupling lever is further provided with an arm, on which an end of the default spring is fixed. Moreover, in every of the aforesaid embodiments of the present invention, the throttle valve never rotates under the condition that it is hold at the default position, even if an acceleration pedal is operated. Under such condition, the fuel injection amount and the ignition timing are controlled by switching over the control mode to that for the minimum safety, whereby the output (rotational speed) of an engine is controlled. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1A to 1C are explanatory drawings of the operational principle of an electronically controlled motor-driven throttle valve device according to a first embodiment of the present invention; Fig. 2 shows the cross-section of the throttle valve device according to the first embodiment, which is sectioned along the line intersecting a path of air; Fig. 3 shows the throttle valve device of Fig. 2, removing an end cover therefrom and viewing from the left side on the same figure; Fig. 4 is a plane view showing a subassembly composed of a driving gear and a coupling lever; Fig. 5 is a sectional view of the subassembly as shown in Fig. 4; Figs. 6A to 6D are perspective views of various parts decomposed of the subassembly as shown in Fig. 4; Fig. 7 is a schematic diagram for explaining the operation of the first embodiment as shown in the foregoing drawings; Fig. 8 is a perspective view for showing the detailed structure of a part of the first embodiment; Fig. 9 is a schematic diagram for explaining the operation of an electronically controlled motor-driven throttle valve device according to a second embodiment of the present invention; Fig. 10 is a perspective view for showing the detailed structure of the second embodiment; Fig. 11 is a diagram showing the concept of an automobile control system which adopts an electronic control throttle valve according to the present invention; and Fig. 12 is a flow chart for explaining the operation of the automobile control system as shown in Fig. 11. DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, detailed description will be made of preferred embodiments of the present invention, referring to the accompanying drawings. Referring at first to Figs. 7 and 8, a basic construction and its operational principle of a first embodiment of the present invention will be explained. In Fig. 7, air flowing through intake pipe 100 is adjusted by the throttle valve 1, which is fixed to the throttle valve shaft 2. Reduction gears are attached at the end of the throttle shaft 2. Rotating torque of the throttle valve motor 4 is transmitted to the throttle valve 1 through the gears, whereby the opening of the throttle valve 1 can be adjusted. The rotation of the motor 4 is controlled in proportion to the depression amount of the acceleration pedal and therefore the opening of the throttle valve 1 is adjusted by the acceleration pedal. Coupling lever 5 is supported by the throttle shaft 2, but can rotate independently therefrom. The lever 5 is energized toward the default stopper 103 by the default spring 7. The default spring 7 may be of an extension type or a compression type. If the throttle valve motor 4 is not fed, there is no rotating force acting on the throttle shaft 2. Therefore, force of the default spring 7 acts on the throttle shaft 2 through the coupling end 3A of the movable member 3 fixed on the throttle valve 1, whereby the throttle valve 1 is opened at the default opening (4° ∼ 13°, for example) defined by the default stopper 103. In order to further open the throttle valve 1 beyond the default position, the motor 4 must be energized so as to rotate the throttle valve 1 counterclockwise. At this time, the throttle valve 1 rotates, extending the return spring 6 provided between the throttle valve 1 and the coupling lever 5 presently located at the default position. Thereafter, the coupling lever 5 is left behind the operation of the throttle valve 1. On the other hand, in order to further close the throttle valve 1 beyond the default position, the motor 4 must be energized so as to rotate the throttle valve 1 clockwise. At this time, the throttle valve 1 pushes the coupling lever 5 at the default position by means of the coupling end 3A of the movable member 3 to rotate the coupling lever 5 clockwise. While extending the default spring 7, the coupling lever 5 rotates until the defining end 3B of the movable member 3 comes into contact with the full close stopper or the idle stopper. Explanation will be made of the definition of the full close stopper and the idle stopper, or of the full close position and the idle opening. A certain type of a throttle valve device is necessary to be kept at the minimum opening, in order that an engine continues to rotate without any operation of an acceleration pedal. With this minimum opening, the engine can take a minimum amount of air necessary for continuing to rotate at the number of rotation for idling without engine stalling. For the convenience of explanation, this type is called a first type of a throttle valve device, here. There is another type, i.e., a second type, of throttle valve device, in which an auxiliary air path is provided to by-pass a throttle valve in a main air path and the desired number of rotation for idling can be attained by the amount of air flowing through the auxiliary path. In this second type of a throttle valve device, the minimum opening of the throttle valve can be set substantially at 0°. In the first type of the throttle valve device, the minimum opening is usually set at 1° ∼ 2°. Generally, this opening of 1° ∼ 2° is called "idle opening (or position)". On the other hand, as in the second type of the throttle valve device, the opening of substantially 0° is called "full close opening (or position)". Further, when taking the spirit of the present invention into account, there can be considered a third type of a throttle valve device, in which the first type and the second type as mentioned above are combined with each other. Namely, in the third type, the minimum opening of the throttle valve is set at 1° ∼ 2°, and in addition there is provided a path by-passing the throttle valve. The by-pass path is used when the number of rotation for idling can not be maintained even at the minimum opening. As understood from the foregoing, through the specification of the present application, a full close position (or stopper) or an idle position (or stopper) means a minimum opening position of a throttle valve under the usual control situation, and a stopper provided at such a position. If there is no full close (or idle) stopper, a throttle valve can further rotate in the closing direction. However, this is not desirable, since the throttle valve may possibly stick in an inner wall of an intake pipe. To prevent this, therefore, there is provided a full close stopper even in the second type of a throttle valve device with a by-pass path. Incidentally, the default stopper for securing the minimum safety is provided at the position that is further progressed by 4° ∼ 13° in the opening direction of the throttle valve. Returning to the explanation of the embodiment, the basic construction embodying on the operational principle as shown in Fig. 7 will be described, referring to Fig. 8. The intake pipe (manifold) 100 rotatably supports the throttle valve shaft 2, to which the throttle valve 1 is attached. The throttle valve 1 rotates together with the throttle shaft 2 to vary the effective cross-sectional area of the intake manifold, whereby the amount of air sucked can be adjusted. The throttle shaft 2 goes through the wall of the manifold 100 and extends outside, at end of which a gear as the movable member 3 is provided. The gear-side sleeve 301 is formed in the center of the gear 3 as a unitary body. Around the center of the sleeve 301, there is formed a hole having the cross-sectional form which fits a notched portion for detent provided on the end portion of the throttle shaft 2. With such a construction, the throttle shaft 2 and the gear 3 always rotates together. The coupling lever 5 is rotatably provided on the outer periphery of the sleeve 301. To the center of the coupling lever 5, there is fixed the lever-side sleeve 501, in which the gear-side sleeve 301 is rotatably inserted. The gear 3 is made from sintered alloy in a sectorial form, on the outer arced periphery of which gear teeth are formed. A body of the gear 3 has the thickness in the axial direction, and there is formed a circular flat depressed space or room having the depth in the direction of the thickness of the gear body. In the circular flat space or room defined in the gear body, the return spring 6 in the spiral form is accommodated. The end 601 of the return spring 6 is hooked at the slit 502, which is cut on the outer periphery of the lever-side sleeve 501. The supporting pin 302 is projected from the gear 3, at which the other end 602 of the return spring 6 is hooked. The coupling lever 5 has three arms 51, 52, 53 extending radially. The arm 51 is provided with the surface 510 which receives the contacting end 3A formed on the periphery of the gear 3. The arm 52 is provided with the surface 520 which comes into contact with the default stopper 103 formed on the throttle valve body. The arm 53 holds one end of the spiral default spring 7. The other end of the default spring 7 is hooked at a supporting pin, which serves as the default stopper 103, too. One of both side ends of the gear 3 in the sectorial form serves as the defining end 3B, which comes into contact with the full close stopper (or idle stopper) 101 provided at the full close position (or idle position) of the throttle valve. The full close stopper 101 is a screw adjustably screwed in the throttle valve body. In the following, description will be made of the operation of the first embodiment constructed as above. When it is stopped to feed a throttle valve driving motor stops because of the engine stall or any trouble of the motor control circuit, the surface 520 of the arm 52 is kept contacting with the default stopper (pin) 103 by the force of the default spring 7 acting between the arm 53 of the coupling lever 5 and the default pin 103. At this time, the force of the return spring 6 does not act on the default spring 7 at all, which is one of the major differences from the conventional device. When the engine is prepared for start and the throttle valve motor is fed, the throttle valve 1 is required to keep the idle opening in order for the engine to continue the operation at the rotational speed for idling. When the motor 4 starts the rotation, it rotates the throttle shaft 2 through the reduction gear 3 counterclockwise. At this time, the coupling lever 5 rotates together counterclockwise, because the contacting end 3A comes into contact with the surface 510 formed on the arm 51 of the coupling lever 5. This rotational movement continues, until the defining end 3B located at the top end in the rotating direction of the movable member (gear) 3 comes into contact with the full close stopper 101. In this manner, the throttle valve motor 4 rotates the throttle shaft 2 from the default position to the full close (or idle) position, against the force of the default spring 7. The motor 4 has to continue to produce torque counterclockwise to keep the throttle valve 1 at the full close opening, until an acceleration pedal is depressed and an instruction for a predetermined opening is issued. When the acceleration pedal is depressed and the automobile becomes ready to start, the motor 4 receives an instruction for clockwise rotation (opening direction of the throttle valve 1) in proportion to the depressed amount of the pedal. Torque produced by the motor is large enough to rotate the throttle shaft 2 clockwise and open the throttle valve at the full open position. The mechanism of this part is possible to be constructed in such a manner that the tensile force of the default spring 7 is cooperatively added to the rotational movement by the motor 4. When the throttle valve 1 is opened at the default position, the coupling lever 5, which has rotated together, is prevented from further rotation. Accordingly, in the direction of the opening operation beyond that position, only the throttle shaft 2 rotates clockwise to open the throttle valve 1. At this time, the inner end 601 of the return spring 6 can not rotate, because it is held by the sleeve 501 of the coupling lever 5 which is stopped at the default position. Only the outer end 602 of the return spring 6 rotates together with the gear 3 clockwise, since the outer end 602 is held by the pin 302 provided on the gear 3, whereby as the diameter of the spring 6 increases, the spring 6 can store the energy to rotate the shaft 2 counterclockwise. If the acceleration pedal continues to be constantly depressed by a certain amount, the motor 4 continues to give the force corresponding to the stored energy to the throttle shaft 2 through the gear 3. If, however, the acceleration pedal is released, it is stopped to feed the motor 4. As a result, the force stored in the return spring 6 acts on the throttle shaft 2 through the gear 3 and the throttle valve 1 rotates counterclockwise (in the closing direction). At this time, the inertia caused by the mass of a rotor of the motor 4 is amplified by the gear 3 to act on the throttle shaft 2 in the closing direction of the throttle valve 1. In addition, the air flow blowing against the throttle valve 1 effects force in the closing direction thereof. When the contact end 3A of the gear 3 comes into contact with the surface 510 of the arm 51 of the coupling lever 5 staying at the default position, the coupling lever 5 rotates together with the gear 3 counterclockwise. Force caused by the default spring 7 hardly becomes the resistance against the counterclockwise rotation of the gear 3. This rotation stops, when the defining end 3B contacts with the full close stopper. It is of course that the motor 4 is fed to produce torque of rotating the throttle shaft 2 clockwise (in the closing direction), after the throttle valve 1 passes through the default position. The returning force (counterclockwise force) of the spring 6 becomes substantially zero, when the throttle valve 1 passes through the default position. Since, however, the throttle shaft 2 receives force counterclockwise (in the closing direction) because of the inertia of the motor rotor and the torque produced thereby, the throttle shaft 2 continues to rotate until the full close position. Of course, if the opening of the throttle valve 1 is large, the inertia of the motor rotor, which causes the throttle shaft 2 to rotate in the closing direction, becomes also large as much. Contrary, if the throttle valve 1 is opened slightly, the energy stored in the return spring 6 is small and therefore the inertia of the motor rotor is also small. At this time, the throttle shaft 2 rotates until the full close position by the motor torque. The inertia of the motor rotor operates also in the case where the motor 4 and/or the control circuit thereof have a trouble and torque produced by the motor 4 disappears. However, the motor 4 can not produce torque in the closing direction, even after the default position is passed through. Therefore, even if the throttle shaft 2 once passed through the default position, it is returned by the tensile force of the default spring 7 finally. This is the reason why the minimum safety can be attained with the default position, since the default opening is larger than the full close opening. The first embodiment as mentioned above will be explained further in details later, referring to Figs. 1 to 6. Referring next to Fig. 9, description will be made on the principle of the second embodiment, hereinafter. In Fig. 9, the throttle valve 1 is attached to the throttle valve shaft 2, which is rotated by the throttle valve motor 4 clockwise or counterclockwise through the reduction gear 3, in the same manner as in Fig. 7. The coupling lever 5 is arranged rotatably in relation to the throttle shaft 2, which is also the same as in Fig. 7. The following are the differences from Fig. 7: (1) the throttle valve 1 is closed at the default position by the return spring 6 through the coupling lever 5; and (2) the default spring 7 is provided between the throttle valve 1 and the coupling lever 5. The structural differences as mentioned above cause the following operational differences: (a) from the default position to the full close stopper, the throttle shaft 2 rotates independently, separated from the coupling lever 5. At this time, force of the default spring 7 acts directly on the throttle shaft 2; and (b) in the opening direction beyond the default position, the throttle shaft 2 rotates together with the coupling lever 5. At this time, force of the return spring 6 acts on the throttle shaft 2 through the coupling lever 5. Fig. 10 shows an basic structure of the second embodiment of the present invention. Rotating torque of the throttle valve motor 4 is amplified by the reduction gear 3 and transmitted to the throttle shaft 2 rotatably supported by the bearing 2 of the intake manifold 100. Accordingly, the throttle shaft 2 rotates clockwise or counterclockwise in accordance with the rotational direction of the motor 4, whereby the throttle valve 1 closes or opens to adjust the effective cross-section of the intake air path. The partially flattened portion for detent is formed on the throttle shaft 2 at the end portion, which is opposite to the gear 3 with respect to the throttle valve 1. The throttle lever 3 as the movable member is provided with a hole fitting the flattened portion of the throttle shaft 2. The throttle shaft 2 is inserted through the hole, whereby the throttle lever 3 is attached to the throttle shaft 2. In the same manner, the fixed sleeve 701 is also attached to the throttle shaft 2. The coupling lever 5 is rotatably supported by the throttle shaft 2 through the sleeve 505. The lever 5 is provided with the arm 506 formed as a unitary body, which has the surface 506a coming into contact with the throttle lever 3 when the coupling lever 5 rotates clockwise. The default spring 7 is formed by a spiral spring, the outer end 704 of which is hooked at the arm 506 of the coupling lever 5 (hence, the outer end 704 will be called an outer hook end, hereinafter). The spiral default spring 7 starts from the inner end 703 and then is wound up by a few turns counterclockwise, viewed from the left-hand side of the figure, and finally reaches the outer hook end 704. When the coupling lever 5 rotates counterclockwise, the arm 506 is received by the outer hook end 704. The inner end 703 of the default spring 7 is stopped by the projection 702, which is projected radially from the outer periphery of the fixed sleeve 701. The coupling lever 5 has the second arm 507, which comes into contact with the default stopper 103 at the default position, when the coupling lever 5 rotates clockwise. The default stopper 103 is adjustably screwed directly into the intake manifold 100 or into an appropriate member attached thereat. Further, the coupling lever 5 has the third arm 508, at which one end of a coil spring serving as the return spring 6 is hooked. The other end of the return spring 6 is hooked at the intake manifold 100 or directly into the intake manifold 100. Further, the throttle lever 3 is arranged to come into contact with the full close stopper 101 provided at the full close position of the throttle valve 1, when it rotates in the closing direction. In the following, description will be made of the operation of the second embodiment constructed as above. When an engine is out of operation and hence a throttle valve motor 4 is not fed, the coupling lever 5 is kept by the return spring 6 at the position of the default stopper 103. This situation is held, since neither force in the closing direction nor force in the opening direction acts on the throttle shaft 2, When the engine is started, but an acceleration pedal is not depressed, a control system requires the throttle valve 1 to be in the full close opening, taking the operational condition of the engine into consideration. Therefore, the throttle valve motor 4 is fed to rotate the throttle shaft 2 clockwise, i.e., in the direction of closing the throttle valve 1. When the throttle shaft 2 rotates in this direction, the throttle lever 3 separates from the arm 506, because the coupling lever 5 is stopped at the default position. Since the outer hook end 704 of the default spring 7 is supported by the arm 506, on one hand, and the inner end 703 thereof rotates clockwise together with the sleeve 701, as the throttle shaft 2 rotates, on the other hand, the default spring 7 is wound up tightly to store energy. The throttle valve 1 is needed to be kept at the full close position, until the acceleration pedal is depressed. Through that duration, therefore, the throttle valve motor 4 has to continuously apply counter force corresponding to the energy stored in the default spring 7, to the throttle shaft 2. The throttle lever 3 continues to come into contact with the full close stopper 101 through the whole duration. When the acceleration pedal is depressed and the automobile begins to run, the throttle valve 1 is controlled in response to the depression amount of the acceleration pedal. At this time, the polarity of feeding the throttle valve motor 4 is switched over, whereby the motor 4 produces torque of rotating the throttle shaft 2 counterclockwise. Until the default position, the energy stored in the default spring 7 acts on the throttle shaft 2 in the same direction and aids the throttle shaft 2 to rotate counterclockwise. When the throttle shaft 2 rotates to reach the default position, the throttle lever 3 comes into contact with the surface 506a of the arm 506 of the coupling lever 5. If the throttle shaft 2 further rotates counterclockwise, the coupling lever 5 rotates together. In such a situation, the return spring 6 hooked at the arm 508 of the coupling lever 5 is extended, whereby the spring 6 stores energy. If the acceleration pedal is released, feeding of the throttle valve motor 4 is stopped. Only the tensile force stored in the return spring 6 acts on the throttle shaft 2 through the arm 506 of the coupling lever 5 and the throttle lever 3, whereby the throttle shaft 2 rotates counterclockwise, i.e., in the closing direction. At this time, in the same manner as in the first embodiment, inertia force caused by mass of the motor rotor is amplified by the gear 3 and acts on the throttle shaft 2 in the closing direction. When the default stopper 103 at the default position receives the arm 507 of the coupling lever 5, the rotation of the coupling lever 5 stops there. Thereafter, the throttle shaft 2 solely rotates in the closing direction by the inertia force of the motor rotor. During this, the default spring 7 is wound up tightly to store energy. After the throttle shaft 2 passes through the default position, the throttle valve motor 4 is fed, again, whereby torque of the motor 4 is added to rotate the throttle shaft 2 in the closing direction. Also in this embodiment, the clockwise returning force of the spring 6 does no longer act on the throttle shaft 2 at the default position. Therefore, the throttle shaft 2 is rotated by the inertia force of the motor rotor and the torque produced by the motor 4 until the full close position. As already described with respect to the first embodiment, also in this embodiment, the larger the throttle valve opening is, the larger the inertia force of the motor rotor is. If the throttle shaft 2 rotates only slightly from the default position, energy stored in the return spring 6 is small, too, and hence the inertia force of the motor rotor is small. At this time, as in the first embodiment, the throttle shaft 2 is rotated by torque produced by the motor 4 clockwise until the full close position. Even in the case where the throttle valve motor 4 can not be fed because of any trouble, the inertia force of the motor rotor is applied to the throttle shaft 2. Since, however, the motor 4 does not produce torque in the closing direction after the throttle shaft 2 passes through the default position, the throttle shaft 2 is finally returned to the default position by the energy stored in the default spring 7. Further, in both the first and the second embodiments, if when the throttle shaft 2 is positioned at the closing side with respect to the default position, feeding of the throttle valve motor 4 is interrupted because of any trouble, it is of course that the throttle shaft 2 is rotated to the default position by the energy stored in the default spring 7. As shown in Figs. 11 and 12, the engine control unit ECU receives the acceleration pedal depression amount signal APS and the throttle valve opening signal  T from the throttle sensor 201 to thereby calculate the throttle valve motor signal V M . The throttle valve motor 4 is controlled in accordance with the signal V M and adjusts the opening of the throttle valve 1. It is discriminated at step 120 that an automobile falls into the emergency traveling condition, if the following conditions occur: i.e., the throttle valve opening signal  T does not reach a predetermined value, although the acceleration pedal depression amount signal APS changes; and the throttle valve motor 4 is not fed normally. If the emergency traveling condition is discriminated to occur, the warning lamp is on at step 125 and the fuel supply signal T P for emergency traveling is calculated and output at step 126. At step 127, the ignition timing  Ad is compensated so as to be delayed, compared with that in the normal operation. When no depression of the acceleration pedal occurs and the speed V S of the automobile is zero, the engine has to be kept at the number of rotation for idling. Since, however, the throttle valve opening is as large as 4° ∼ 13° under the emergency traveling condition, the number N e of rotation of the engine becomes much higher than the usual number of rotation for idling. To prevent this and keep a predetermined number of rotation for idling, in this embodiment, the number N e of rotation of the engine is compared with the predetermined number of rotation for idling and the amount of fuel to be injected is decreased so that the former follows the latter. Further, the ignition timing is delayed so as to be at the ignition timing in the operation for low load and low speed. In Fig. 12, if it is discriminated that no emergency traveling occur, the engine control unit ECU, at step 121, calculates the basic fuel injection pulse T P on the basis of the intake air amount Q a and the number of rotation N e of the engine, and at step 122, calculates the ignition timing  Ad corresponding to the number of rotation N e of the engine, and finally at steps 123, 124, outputs control signals to an fuel injector and a ignition control circuit IgN, respectively. Receiving these signals, the injector injects a predetermined amount of fuel into cylinders and the ignition coil IgC produces spark at spark plugs IgP. Further, in Fig. 12, the number of rotation pick-up N e P is actuated by a crank shaft of the engine and detects the number of rotation N e of the engine. Returning to Figs. 1 to 6, description will be made of the more detailed structure of the first embodiment. Figs. 1A to 1C are explanatory diagrams schematically showing the operational principle of an electronic control throttle valve according to the first embodiment of the present invention. As shown in the drawing, the throttle valve 1 is attached to the throttle valve shaft 2, which is rotatably supported by the body 100 of the throttle valve device. To one end of the throttle shaft 2 is attached to the movable member 3, which is mainly composed of gears. The throttle valve 1 is opened or closed by the throttle valve motor 4 through the movable member 3. There is provided the contacting member 5 formed by a lever made of thin plate, and when the movable member 3 moves in the direction of closing the throttle valve 1, the member 5 comes into contact with the member 3. Between the members 3 and 5, there is provided the spring 6, which energizes both the members in the opposite direction to each other. Further, between the contacting member 5 and the body of the throttle valve device, there is provided the spring 7 which energizes the member 5 in the direction of opening the throttle valve 1. On the body of the throttle valve device, the full close stopper 101 for defining the position of full close of the throttle valve 1, the full open stopper 102 for defining the position of full open of the throttle valve 1, and the default stopper 103 for defining a predetermined small opening of the throttle valve 1, which allows an automobile travel at the speed for the emergency travel, even if the throttle valve motor 4 has a trouble. With this construction, during the usual travel of an automobile, the throttle valve 1 and the contacting member 3 conduct the opening and closing operation in the range between the full close position (as shown in Fig. 1A) and the full open position (as shown in Fig. 1C). In the event of failure of the throttle valve motor 4 or during no operation of the engine, the throttle valve 1 and the contacting member 5 are held by the springs 6 and 7 at the position of the default stopper 103 (as shown in Fig. 1B). Thereby, even in the event of failure of the throttle valve motor 4, it is possible to keep a necessary air flow rate to let the automobile travel to a repair shop. In addition, since the throttle valve 1 is slightly opened from the full close position (default position) during no operation of the engine, it is possible to improve re-starting capability of the engine and to prevent sticking of the throttle valve. As for the spring load applied to the throttle valve motor 4, only the spring 7 is active in the range between the full close position and the default position, and only the spring 6 is active in the range between the default position and the full open position. Force caused by the respective springs 6 and 7 acts on the motor 4 separately. As a result, the difference in the spring characteristics and the resistance against the sliding movement are never added to each other, whereby the load applied to the throttle valve motor 4 can be determined by the characteristic of one of the springs. In addition, each of the spring 6, 7 can be made small in size and the load of the motor 4 can be reduced, because it only operates in the narrow range of operation. A throttle valve device according to the first embodiment of the present invention will be explained, referring to Fig. 2 to Figs. 6A to 6D, wherein Fig. 2 shows a cross-sectional view of principal parts of the device sectioned in the direction intersecting the air intake path, Fig. 3 is a front view showing the driving portion, Figs. 4, 5 and 6A to 6B show a plane view, a sectional view and perspective views of decomposed parts, of the subassembly mainly composed of the movable member 3 and the contacting member 5. In this embodiment, the movable member 3 is a sectorial gear with the hollow cylindrical sleeve 3b in its center. A space or room for accommodating the spring 6 is formed in a body portion of the gear, on the outer-side periphery of which body gear portion (gear teeth) 3h is formed. Driving torque of the throttle valve motor 4 is transmitted from output gear 11 to the throttle shaft 2 through the intermediate gear 12 and the gear portion 3h of the movable member 3, with the rotational speed reduced (i.e., with the torque amplified). Further, the movable member 3 and the contacting member 5 are energized by the spring 6 in the opposite direction to each other, and the contacting member 5 and the gear portion 3h rotates together after the arm 35 of the former and the end surface 3f of the later establish contact with each other. The spiral spring 6 is accommodated in the space or room formed in the movable member 3. The outer hook portion 6a of the spring 6 is hooked at the hooking portion 3a provided on the movable member 3. In this embodiment, the low friction coefficient member 3c made of nylon resin is arranged between the inner surface of the movable member 3 and the spring 6 to reduce the frictional resistance caused by the sliding movement. The projection 3d is engaged with the dent 3e formed inside the outer-side periphery of the gear portion 3h to serve as a slip stopper. The plane plate portion 3i serves to reduce the friction between the end surface of the spring 6 and the plane plate portion 3j of the body portion of the movable member 3. The inner hook portion 6b of the spiral spring 6 is hooked at the slit 5d provided in the bearing member 5a which is formed as a unitary body with the contacting lever 5. In the embodiment shown, the bearing member 5a is made of metal, and its body portion is inserted in the inner circular space defined by the spiral spring 6. The projecting portion is formed at the central portion thereof, which is inserted in a central hole provided in the contacting lever 5. The projecting portion is folded toward the outside, whereby the lever 5 is fixed by caulking to the end surface of the body portion of the bearing member 5a. The contacting lever 5 is rotatably supported by the hollow sleeve 3b formed as a unitary body with the movable member 3, in which the inner peripheral wall of the bearing member 5a serves as a bearing. In this embodiment, the frictional resistance by sliding movement is reduced by press-fitting the cylindrical sleeve 5c made of metal into the bearing member 5a, in which the sleeve 5c is coated with low friction coefficient material such as nylon or Teflon resin. The contacting lever 5 is made of thin metal plate, which has the three arms 35, 36, 37, each extending radially. The arm 35 provides the contacting portion, on which the contacting lever 5 and the movable member 3 contact with each other. The arm 36 serves to keep the throttle valve 1 at a predetermined small opening by its end surface 36a coming into contact with the stopper 103 provided on the throttle valve body, when the throttle valve motor 4 produces no torque. The arm 37 has the grommet 5d at its top portion, at which the spring 7 is hooked by the hook 71 formed on one end thereof. The hook 72 provided at the other end of the spring 7 is hooked at the projection 104 formed on the throttle valve body. Thereby, the movable member 3 and the contacting lever 5 can be formed as a subassembly in a unitary body, with the result that both the members become easy to be assembled in the throttle valve body. Further, the movable member 3 and the contacting lever 5 moves together when the throttle valve 1 rotates between the full close position and the default position, and hence no frictional resistance occurs in the bearing portion of the contacting lever 5. As a result, the characteristic in controlling the opening especially in the small angle can be much improved and the controllability for idling operation is also improved. In this embodiment, in which the spring 7 operable during the small opening is formed by an extension spring, there can be reduced the frictional resistance of the sliding movement of the spring itself when it operates. Further, since it is not necessary to arrange the spring around the whole periphery of the throttle valve 2, different from the case of a torsion spring, it can be arranged at a position juxtaposed with the intermediate gear 12 and accordingly size of the throttle valve body can be reduced. Furthermore, in this embodiment, the full close stopper 101 is a metallic pin adjustably screwed into a gear cover integrated in the throttle valve body. The full open stopper 102 is a stepped portion formed on the throttle valve body and the default stopper 103 is formed by a projection integrally provided on the throttle valve body. The end portion 3k of the gear portion 3h is brought into contact with the stopper 101 at the full close position of the throttle valve 1. The end portion 3g of the gear portion 3h is brought into contact with the stopper 102 at the full open position of the throttle valve 1. The end surface 30a of the arm 36 is brought into contact with the stopper 103 at a predetermined small opening position. In addition, in this embodiment, the rotational angle sensor 20 for detection of the throttle valve opening is arranged between the movable member 3 and the throttle valve body. The sensor 20 can be located between the resin mold housing 21 and the wall of the throttle valve body, whereby the sensor 20 can be made thin in width as a whole and detecting portion can be protected from abrasion powder produced from the gear etc.. The contact lever 5 can be fixed at the bearing member 5a by resin-molding. Since in that case the bearing member itself can also be formed with resin, the sleeve 5c can be omitted. The sleeve 5c may be integrally formed of resin such as nylon. In this embodiment, the spring 6 may be accommodated inside the cover 202 as a so-called return spring. The spring 7 can also be accommodated in the cover 201. The rotation angle sensor 20 can be protected form moisture by the double cover structure composed of the cover 202 and the housing 21. As described above, according to the first and the second embodiments of the present invention, there can be realized a small-sized throttle valve device, which can maintain a desirable rotational speed of an engine even in a case of a trouble of a throttle valve motor and allows an automobile to travel at a desired speed for emergency traveling. With the structure of the present invention, the accurate control of the throttle valve can be performed especially during the small opening of the throttle valve. In the embodiments, the two kinds of springs (the default spring and the return spring) are operably influenced with each other through the coupling lever, in which one of the springs is active for the closing operation of the throttle valve and the other for the opening operation thereof. As a result, there exists no operational range in which force of both the springs acts together at the same time, which makes it possible to reduce the variation in the applied load and the frictional resistance of sliding movement. Further, the range, in which the respective springs must operate, is narrow, since the range corresponds to only a part of the full operation range of the throttle valve. Therefore, it is possible to make the spring constant large without increasing the maximum load applied to the throttle valve motor, with the result that the spring can be made small in size (reduction in the number of turns). On the contrary, if the spring constant is not changed, the maximum load applied to the motor can be reduced, whereby the throttle valve motor can be made small in size. If, otherwise, the reduction ratio is reduced, the gear can be made small in size. Further, in the first embodiment, because an extension spring having a small interwire friction (a small sliding resistance) is employed as a default spring, the control accuracy in the small opening range is improved. Moreover, since the extension spring is not required to be arranged around the whole periphery of the throttle shaft, the throttle valve body can be made small in size. Furthermore, by arranging a guide portion of the contacting member on the side of the movable member, a sliding portion of the contacting member can be omitted in the small opening range and accordingly the control accuracy in the small opening range can be improved. Further, by making the shape of the movable member nearly cylindrical, a return spring can be accommodated on the inside of the cylindrical portion and teeth of the gear operably engaged with the throttle valve motor can be formed on the outside of the cylindrical portion, whereby the throttle valve body can be decreased its size. Furthermore, by employing a spiral spring as the return spring, which is operable in the range of the large opening of the throttle valve, and by hooking the outer hook end of the spiral spring at the movable member and the inner end thereof at the contacting member, the control accuracy in the range of the large opening can be improved, since the movable member can serve as an outer radial guide of the spiral spring and the frictional resistance of slide caused by the relative movement of the outer periphery of the spiral spring and the outer radial guide can be suppressed as small as possible. Moreover, by integrating the guide portion of the contacting member and the movable member together, the contacting member, the movable member and the return spring can be formed as a subassembly in a unitary body, whereby the throttle valve device can be easily assembled. If at least one of surfaces of a case accommodating the angle sensor is formed by a part of a main body of the throttle valve device and the remaining surfaces thereof are formed integratedly with a housing of the angle sensor, the throttle valve body can be made thinner, in addition to the protection of the detecting portion, compared with the structure that the whole surfaces are covered by the housing. Further, since the angle sensor can be arranged even at a position near gears which more or less produce abrasion powder, it is possible to make a throttle valve device small in size without losing any reliability. As described above, it is possible to construct a small-sized throttle valve device capable of performing the highly accurate control, which can perform traveling in emergency since the desirable rotational speed is kept even in the event of failure of a throttle valve driving motor.

Claims: A throttle valve control device for controlling an amount of intake air of an internal combustion engine, comprising: a main body (100) in which an intake air path is formed, a throttle shaft (2) which is rotatably supported by the main body (100), a throttle valve (1) being disposed in the intake air path and operatively secured to the throttle shaft (2), an electric motor (4) for driving the throttle valve (1), which is housed in a motor casing portion of the main body, gears (3h, 11, 12) for transmitting a rotating torque of the motor (4) to the throttle shaft (2), a sensor (20) for detecting a throttle valve opening, a movable member (3) disposed on the throttle shaft (2) and fixed thereto for transmitting a torque of the motor (4), a contacting member (5) rotatably disposed on the throttle shaft for coming into contact with said movable member (3) and for stopping at a default stopper (103) provided at a default position of the throttle valve (1), a default spring (7) for acting a force on the throttle valve in an opening direction towards said default position defined by said stopper (103), a return spring (6) for acting a force on the throttle valve in a closing direction towards the default position, wherein during the movement in the closing direction from the default position, the throttle valve (1) is operably separated from the return spring (6), when the contacting member (5) is stropped by the default stopper (103), and, after the contacting member (5) is stopped, the throttle valve (1) moves against the force caused by the default spring (7) so that only the default spring (7) is active in the range between the full close position and the default position (103) and only the return spring (6) is active between the default position and the full open position, characterized in that the contacting member (5) is rotatably supported by a sleeve (3b) which is formed as a unitary body with the movable member (3), said movable member (3) comprises a sectional gear (3h) at an outer periphery of a cylindrical portion for transmitting the torque of the electric motor (4) to the throttle shaft (2), wherein the movable member (3) is driven by said electric motor (4) through said gears (3h, 11, 12). Throttle valve control device according to claim 1, characterized in that the default spring (7), the return spring (6), the sensor (20) and the gears (3h, 11, 12) are accommodated in a space composed of a portion of the main body and a cover (101) removably attached to the main body, and an opening of the motor casing portion is arranged in the space. Throttle valve control device according to claim 1 or 2, characterized in that the movable member (3) is disposed on one end portion of the throttle shaft (2), a gear (11) is mounted to one end portion of a shaft of the electric motor (4), and an intermediate gear (12) is engaged with the movable member (3) and said gear (11). Throttle valve control device according to any of claims 1-3, characterized in that said intermediate gear (12) comprises a first reduction gear engaging with said gear (11) mounted to one end portion of a shaft of the electric motor (4), and a second reduction gear engaging with the movable member (3).

Inventors: ISOZAKI NORIHIRO, KAMIMURA YASUHIRO, ONO KENJI, YAMADA HIROYUKI, ISOZAKI, NORIHIRO, KAMIMURA, YASUHIRO, ONO, KENJI, YAMADA, HIROYUKI
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1997
Main classification: F02D11
IPC codes: F02D11, F02D9, F02B75