ACCELERATOR PEDAL DEVICE

Abstract: The present apparatus comprises an accelerator pedal 10, a pedal arm 20, a pedal shaft 30 which supports the pedal arm 20 free to swing, a return spring 40, a friction generating mechanism 50 which generates friction force in accordance with the movement of the pedal arm 20, an accelerator position sensor 60 and a control segment 70 which controls an opening of a throttle valve 110 in accordance with an output signal of the sensor 60, wherein a play range in which friction force equal to or larger than a specific level is not generated is set to the friction generating mechanism in the range where the pedal arm moves from the resting position by a specific amount, and in the play range, an output signal of the accelerator position sensor 60 is kept constant resulting in that the throttle valve is kept at a specific opening. In this manner, desirable operating feeling without unsuitable feeling with the accelerator pedal operation is obtained while the accelerator apparatus is being compact and so on.

Description: TECHNICAL FIELD The present invention relates to an accelerator pedal apparatus which is utilized for a vehicle etc. with a drive-by-wire system, and especially relates to an accelerator pedal apparatus having a sensor to detect depressing amount of the accelerator pedal. An apparatus in accordance with the features of the preamble of claim 1 is known from JP-A-11182268. BACKGROUND ART An electronic controlled throttle system, namely, a drive by wire system is well-known as a system to control a combustion state, power, revolution and etc. of an engine mounted to a vehicle especially an automobile, more accurately and precisely than a driver intends to control the accelerator. With this electronic controlled throttle system (the drive-by-wire system), an accelerator pedal and a throttle valve are not connected by an accelerator cable. The engine power is controlled based on electronic signals converted from the depressing amount of the accelerator pedal. As shown in Fig. 6, with a conventional accelerator pedal apparatus utilized for this system, depressing force and sensor output increase linearly from a resting position to a maximum depressing position. Consequently, there is no play at the beginning of depressing the accelerator pedal with this structure. Here, without a play to the operation of the accelerator pedal, a vehicle, with an automatic transmission for example, may have a possibility to start abruptly in case the throttle valve opens when the driver puts his foot on the accelerator pedal unconsciously without an intention of depressing. Accordingly, to prevent this phenomenon, the driver needs extra care for the accelerator operation, which causes unsuitable feeling with the operation of the accelerator pedal in comparison with the conventional accelerator pedal apparatus. The present invention is devised in the light of the abovementioned viewpoints, and the purpose is to provide an accelerator pedal apparatus which is easy to operate and has no unsuitable feeling with the accelerator pedal operation, with the structure being simple, compact and so on. DISCLOSURE OF THE INVENTION The accelerator pedal apparatus of the present invention comprises the features of claim 1. With this structure, when the accelerator pedal is depressed, the pedal arm firstly moves in the specific play range following the depression. Then when it moves further in excess of the play range, the friction force equal to or larger than a specific level is generated in accordance with the movement. Here, the throttle valve is kept at a specific opening in the play range of the pedal arm (the accelerator pedal) by the signal of the control means. In the range over the play range, the signal of the control means increases in accordance with the depressing amount of the accelerator pedal, and then the throttle valve is controlled appropriately at the opening in accordance with the depressing amount of the accelerator pedal. Here, in the play range of the pedal arm (the accelerator pedal), the signal of the control means is kept constant, resulting in that the throttle valve is kept at a specific opening. In this manner, desirable operating feeling without unsuitable feeling with the accelerator pedal operation is obtained while the structure is being simplified. Further details are part of the dependent claims. BRIEF DISCRIPTION OF THE DRAWINGS Fig. 1 is a schematic of an accelerator pedal apparatus of the present invention. Fig. 2 shows depressing force characteristics and throttle valve opening characteristics of the accelerator pedal. Fig. 3 (a) and (b) are basic circuit diagrams of an accelerator position sensor. Fig. 4 shows output characteristics of the sensor corresponding to Fig. 2 (a). Fig. 5 shows output characteristics of the sensor corresponding to Fig. 2 (b). Fig. 6 is a graph showing depressing force characteristics and accelerator position sensor output characteristics of a conventional accelerator pedal apparatus. BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention is explained with reference to the attached drawings. As shown in Fig. 1, the accelerator pedal apparatus of the embodiment comprises a pedal arm 20 which is movable from a resting position to a maximum depressing position by depressing force transmitted from an accelerator pedal 10, a pedal shaft 30 which supports the pedal arm 20 free to swing, a return spring 40 which urges the pedal arm 20 to return toward the resting position, a friction generating mechanism 50 which generates friction force in accordance with the movement of the pedal arm 20, an accelerator position sensor 60 as a detecting means which detects the depressing amount of the accelerator pedal 10, and so on. Then, a control means (a control segment) 70 drives a motor 100 appropriately based on the accelerator position sensor 60 output signals and so on, so that the opening of a throttle valve 110, which is disposed at an engine intake system, is controlled. As shown in Fig. 1, a friction force generating mechanism 50 comprises a first movable friction member 52 and a second movable friction member 53 disposed in a sliding guide member 51 having an inclined surface respectively that faces each other, a play load spring 54 disposed between the first movable friction member 52 and the second movable friction member 53, a return spring to push back the second movable friction member 53 to a resting position, and so on. Here, it is designed so that the urging force of the return spring 55 at a full-extended state is larger than that of the play load spring 54 at a full-pressed state. With this structure, when the accelerator pedal 10 is depressed, the pedal arm 20 rotates. Then the end portion 21 of the pedal arm 20 pushes the first movable friction member 52, to make it have contact with the second movable friction member 53 while compressing the play load spring 54. When the accelerator pedal 10 is depressed further, the first movable friction member 52 and the second movable friction member 53 move integrally while compressing the return spring 55. With this movement, the first movable friction member 52 and the second movable friction member 53 push each other with the inclined surface respectively causing wedge effect. The component of the force pushes the first movable friction member 52 and the second movable friction member 53 to the inside surface of the sliding guide member 51, so that friction force is generated in proportion to the pushing force. Consequently, in the beginning range of the depressing, while the play load spring 54 is compressed until the first movable friction member 52 has contact with the second movable friction member 53, the generation of the friction force is minimized (to or below a specific level). On the whole, the depressing force characteristics are as shown in Fig. 2. The control segment (the control means) 70 consists of a control unit in which a CPU is integrated. It controls the throttle valve 110 to be at the desired opening, by calculating variously based on programs or data maps stored in a memory segment 120 and transmitting control signals appropriately to the motor 100, after taking in signals of the accelerator position sensor 60, signals of various sensors to detect engine operating state, and so on. As shown in Fig. 3, the accelerator position sensor 60 is a contact type position sensor with a variable resistor. A slider 61 moves in the range between B and C where a resistor 63 exists, as shown in Fig. 3 (a). The range between B and C corresponds to the movable range of the accelerator pedal 10 (the pedal arm 20), which is between the resting position and the maximum depressing position, namely, all of the play range and the friction generating range. Therefore, the output signal increases linearly upward slant to the right in accordance with the depressing amount (pedal stroke) of the accelerator pedal 10, as shown in Fig. 4. Here, a threshold V0 of the sensor output is set to the memory segment 120 in advance, so that the control segment 70 controls the throttle valve 110 to stay at idling opening when the output signal is equal to or less than the threshold. In this manner, the control segment 70 holds the opening of the throttle valve 110 constant (idling opening) in the play range, where the friction force that is equal to or larger than a specific level is not generated. Furthermore, the contact type position sensor shown in Fig. 3 (b) can be adopted as another accelerator position sensor 60'. As shown in Fig. 3 (b), with this contact type position sensor 60', the slider 61 moves in the range between A and B where no resistor exists, and the range between B and C where the resistor 63 exists. When the slider 61 positions at point B, it is designed to correspond to the ending position of the play range, where the first movable friction member 52 contacts the second movable friction member 53. Consequently, the range between A and B corresponds to the play range of the friction force generating mechanism 50 (accelerator pedal 10), and the range between B and C corresponds to the range where the friction force being in excess of the play range is generated. Therefore, as shown in Fig. 5, an almost constant voltage signal V1 is output in the play range where the resistance change with sliding is small. In the range over the play range, output voltage signal increases linearly in accordance with the depressing amount of the accelerator pedal 10. In consequence, even though the accelerator pedal 10 is operated in the play range, the sensor output signal does not change, resulting in that the control segment 70 holds the throttle valve 110 at idling opening. In this manner, the control segment 70 holds the opening of the throttle valve 110 constant (idling opening) in the play range, where the friction force that is equal to or larger than a specific level is not generated. With either accelerator position senor 60 or 60', when a driver depresses the accelerator pedal 10 from the resting position, it is possible to recognize the position where the increasing characteristic of the depressing force changes caused by the generation of the friction force, namely the ending position of the play range, by the depressing feeling. The engine power control begins from that position. Hence, an operation without unsuitable feeling is obtained, and the accelerator pedal 10 can be operated safely. In the abovementioned embodiment, a contact type position sensor is adopted as the accelerator position sensor 60, 60'. However, not limited to this type, it is possible to adopt a non-contact type position sensor which outputs position signals by utilizing magnetic flux. In this case, by utilizing a programmable Hall IC, output gradient to the magnetic flux is easily set with an external interface. Specifically, the characteristic of constant output in the play range and that of linear output are possible to obtain. Therefore, being similar to the abovementioned embodiment, either the method to control by the control means with a previously set threshold or the method to control by utilizing the sensor output signals as they are, can be adopted. Further, either a rotary type or a linear type is applicable to the type of the accelerator position sensor. Furthermore, in the abovementioned embodiment, the friction force generating mechanism 50 is performed with a linear movement. However, not limited to this, it is possible to generate friction force with an arc-shaped movable friction member being coupled to an arc-shaped sliding surface. In addition, the play load spring 54 can be disposed between the first movable friction member 52 and the end portion 21 of the pedal arm 20. In this case, the play range is until the end portion 21 of the pedal arm 20 has contact with the first movable friction member 52. INDUSTRIAL APPLICABILITY With the accelerator pedal apparatus of the present invention, a play range is set to a depressing operation of an accelerator pedal (a pedal arm), and in this range, friction force equal to or larger than a specific level is not generated and an opening of a throttle valve is kept constant, so that desirable operating feeling without unsuitable feeling with the accelerator pedal operation can be obtained.

Claims: An accelerator pedal apparatus, comprising: a pedal arm (20) which is supported movably from a resting position to a maximum depressing position, by depressing force transmitted from an accelerator pedal (10); a return spring (40) which urges said pedal arm (20) to return toward said resting position; a detecting means (60) which detects the depressing amount of said accelerator pedal (10); and a control means (70) to control the opening of a throttle valve (110) disposed at an intake system of an engine based on an output signal of said detecting means (60); wherein a play range is set in a range where said pedal arm (20) moves from said resting position by a specific amount, characterized in that it furthermore comprises a friction generating mechanism (50) which generates friction force in accordance with the movement of said pedal arm (20); wherein in said play range a friction force equal to or larger than a specific level is not generated by said friction generating mechanism (50), and wherein an opening of said throttle valve (110) is kept constant in said play range. An accelerator pedal apparatus according to claim 1, characterized in that said friction generating mechanism (50) comprises a sliding guide member (51), a first movable friction member (52) disposed in said sliding guide member (51) and a second movable friction member (53) disposed in said sliding guide member (51), and in that a play load spring (54) is disposed between said first movable friction member (52) and said second movable friction member (53). An accelerator pedal apparatus according to any of the preceding claims, characterized in that said detecting means (60) is a non-contact type position sensor for outputting position signals by utilizing magnetic flux. An accelerator pedal apparatus according to claim 3, characterized in that said detecting means (60) is arranged to output a constant signal in said play range.

Inventors: HOSONO TSUYOSHI, KUMAMOTO MASATO, OIKAWA TAKUMI, HOSONO, TSUYOSHI, KUMAMOTO, MASATO, OIKAWA, TAKUMI, HOSONO, Tsuyoshi, c/o MIKUNI CORPORATION, KUMAMOTO, Masato, c/o MIKUNI CORPORATION, OIKAWA, Takumi, c/o MIKUNI CORPORATION
Applicants: MIKUNI KOGYO KK, MIKUNI CORPORATION
Application year: 2001
Main classification: B60K26
IPC codes: B60K26, F02D9, F02D11, G05G1