Patent Publication Number: US-6981486-B2

Title: Vehicular accelerator pedal device

Description:
FIELD OF THE INVENTION 
   The present invention relates to a vehicular accelerator pedal device designed to accurately adjust generation timing of a predetermined pedal reaction force to timing of a desired throttle opening, so as to permit accurate agreement between transmission kickdown and pedal reaction force generation. 
   BACKGROUND OF THE INVENTION 
   Levers, pedals, etc. in various automotive and other types of vehicles are input devices operable by human operators or drivers, and, generally, as any one of these input devices is operated by the driver, a certain reaction force is imparted to a hand or foot of the driver through the input device. There has been known a technique that positively generates such a reaction force in response to driver&#39;s operation of the lever or pedal, i.e. that allows the lever or pedal to function not only as an input device but also as an output device. Devices using such a technique are called “haptic devices”, one example of which is known from Japanese Patent Laid-Open Publication No. 2001-105926 (JP-A-2001-105926) disclosing a vehicular operation apparatus provided with a haptic device. 
     FIG. 5  shows the vehicular operation apparatus disclosed in the above-mentioned No. 2001-105926 publication. This vehicular operation apparatus includes a pedal  101  connected via an actuator shaft  102  to a stroke simulator  103 . With a stroke sensor  104  provided on the actuator shaft  102 , the stroke simulator  103  generates and imparts a reaction force to the pedal  101  in accordance with a stroke of the pedal  101 . The stroke sensor  104  is operatively connected via an ECU  105  to a throttle device  106 , and the ECU  105  supplies the throttle device  106  with an instruction signal such that the throttle opening is varied in accordance with a detected pedal stroke. 
   In order to allow kickdown of an automatic transmission to be performed in the vehicle by the driver stepping on or depressing the pedal  101  rapidly and deeply for rapid acceleration, there may be provided a kickdown switch  109  rearwardly of the pedal  101  for generating a kickdown signal. Namely, once the pedal  101  is depressed to a predetermined stroke position, the kickdown switch  109  is turned on to generate an ON signal, and the instructed kickdown of the automatic transmission is executed in response to the ON signal from the switch  109 . 
   With the conventional devices using the haptic technique, however, the driver would feel uncomfortable when returning the pedal  10  from a depressed position in a predetermined reaction-force increasing control region where control is performed to increase the pedal reaction force in accordance with increase in the depression amount of the pedal, because the stroke simulator  103  generates the pedal reaction force in accordance with a stroke of the pedal. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing prior art problems, it is an object of the present invention to provide an improved vehicular accelerator pedal device which can significantly reduce an uncomfortable feeling of a human driver when returning the accelerator pedal from a depressed position in a predetermined reaction-force increasing control region. 
   In order to accomplish the above-mentioned object, the present invention provides an improved vehicular accelerator pedal device, which comprises: a depression amount detection section for detecting an amount of depression, by a human operator, of an accelerator pedal and generating a depression amount signal indicative of the detected amount of depression; a throttle control section for controlling a throttle opening on the basis of the depression amount signal; a pedal reaction impartment section for imparting the accelerator pedal with a reaction force on the basis of the amount of depression of the accelerator pedal; and a pedal reaction control section for, when operation has been performed by a human operator for returning the accelerator pedal from a depressed position, controlling the reaction force to be imparted to the accelerator pedal on the basis of the amount of depression of the accelerator pedal. 
   With the arrangement that, when the accelerator pedal is being returned from a depressed position, the pedal reaction control section controls the reaction force on the basis of the amount of depression of the accelerator pedal and irrespective of the traveling state of the vehicle, the reaction force does not vary greatly while the accelerator pedal is in the returning stroke; the arrangement can thus significantly reduce an uncomfortable feeling of the driver when returning the accelerator pedal from a depressed position in the reaction-force increasing control region. 
   Preferably, when the accelerator pedal is being returned from a depressed position, the pedal reaction control section controls the reaction force to be imparted in such a manner that the reaction force varies by a substantially uniform amount relative to variation in the amount of depression of the accelerator pedal. Thus, it is possible to reduce the uncomfortable feeling of the driver even more effectively when returning the accelerator pedal from a depressed position in the reaction-force increasing control region. 
   In a preferred embodiment, when operation has been performed for returning the accelerator pedal from a depressed position in a predetermined reaction-force increasing control region where control is performed to increase the pedal reaction force in accordance with increase in the depression amount of the pedal, the pedal reaction control section controls the reaction force to be imparted in accordance with a predetermined map such that the reaction force to be imparted varies in proportional relation to the depression amount of the accelerator pedal or varies relative to the depression amount of the accelerator pedal only within a predetermined variation range (or width) smaller than a predetermined value. Thus, it is possible to reduce the uncomfortable feeling of the driver even more effectively when returning the accelerator pedal from a depressed position in the reaction-force increasing control region. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Certain preferred embodiments of the present invention will hereinafter be described in detail, by way of example only, with reference to the accompanying drawings, in which: 
       FIG. 1  is a schematic view of a vehicle employing an accelerator pedal device of the present invention; 
       FIG. 2  is a block diagram showing an example general setup of the accelerator pedal device of the present invention; 
       FIG. 3  is a block diagram showing an example setup of a pedal reaction control unit of the accelerator pedal device; 
       FIG. 4  is a graph explanatory of the behavior of the accelerator pedal device of the present invention; and 
       FIG. 5  is a block diagram explanatory of a conventional pedal device as a vehicular operator device. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a schematic view of a vehicle, such as an automotive vehicle, employing an accelerator pedal device of the present invention. The vehicle  10  is of the mid-ship type where an engine  13  is located between front and rear road wheels  11  and  12  closer to the rear road wheel  12 . By manipulation of an accelerator pedal  15  that is disposed underneath a front portion of a driver&#39;s seat, an opening of a not-shown throttle valve (i.e., throttle valve opening) in a throttle body  17 , provided on an upper portion of the engine  13  via an engine control unit (hereinafter referred to simply as an “ECU”)  16 , can be varied to control an output of the engine  13 . The manipulation of the accelerator pedal  15  can also control speed-changing operation of an automatic transmission  18  on the basis of an instruction from the ECU  16 . 
   Generally, the accelerator pedal and the throttle valve are mechanically interconnected via a throttle cable or otherwise. However, the vehicle  10  of  FIG. 1  employs the so-called DBW (Drive By Wire) construction where the accelerator pedal  15  and the throttle body  17  (specifically, throttle valve section provided in the body  17  for driving the throttle valve in a manner to be detailed later) are interconnected through electric wiring. 
   With the DBW or electric wiring drive construction, the throttle valve can be opened/closed very quickly in response to operation, by the human driver or driver, of the accelerator pedal  15 , so that the engine output can be controlled with a further enhanced response. Also, electrical signals from the accelerator pedal  15  can be used not only to drive the throttle valve, but also to control the above-mentioned speed-changing operation of the automatic transmission  18  and operation of other components. 
   The accelerator pedal  15  and ECU  16  are among components constituting the accelerator pedal device  21  of the present invention that will be detailed with reference to  FIG. 2 . 
     FIG. 2  is a block diagram showing an example general setup of the accelerator pedal device  21  of the present invention. The accelerator pedal device  21  includes the above-mentioned accelerator pedal  15 , and a pedal depression amount detection section  25  connected to one end of a pedal shaft  24 , functioning as a pivot shaft of the accelerator pedal  15 , for detecting a depression amount of the pedal  15  to generate a signal FS indicative of the detected depression amount of the pedal  15  (depression amount signal FS). The accelerator pedal device  21  also includes a pedal reaction impartment section  26  connected to the other end of the pedal shaft  24 , and, on the basis of the pedal depression amount signal FS, the pedal reaction impartment section  26  generates a reaction force to be imparted to the accelerator pedal  15  in accordance with the detected pedal depression amount; the reaction force is opposite in direction to the pedal depression force. The accelerator pedal device  21  also includes a pedal reaction control unit  27  for controlling the reaction force of the accelerator pedal  15  by giving a reaction force signal RS to the pedal reaction impartment section  26 . Further, in the accelerator pedal device  21 , the above-mentioned ECU  16  functions as a throttle control section that receives the pedal depression amount signal FS from the pedal reaction control unit  27 , and a speed change (transmission shift) instruction TS generated by the ECU  16  on the basis of the received pedal depression amount signal FS is passed to a transmission control section  28 . 
   Once the ECU  16  supplies the throttle valve drive section  32  with a drive signal DS based on the pedal depression amount signal FS, the drive section  32  opens or closes the throttle valve to vary the throttle opening. On the basis of the speed change instruction TS, the transmission control section  28  generates and supplies speed change information TJ to a speed change section  33  of the automatic transmission  18  of  FIG. 1 , in response to which the speed change section  33  executes a desired speed change. 
   The pedal depression amount detection section  25 , which is, for example, in the form of a rotational angle sensor for detecting a rotational angle of the pedal shaft  24 , detects a depression amount of the accelerator pedal  15  as a pivot angle of the accelerator pedal  15 . The pedal reaction impartment section  26  is, for example, in the form of an electric motor having an output shaft connected to the pedal shaft  24 . 
   On the basis of the depression amount signal FS, the pedal reaction control unit  27  controls a range of depressed positions of the pedal  15  where a reaction force is to be generated and imparted to the pedal  15  and an intensity value (particularly, maximum value) of the pedal reaction force. The pedal reaction control unit  27  and transmission control section  28  together constitute a reaction/transmission control section  35 . The pedal shaft  24  is provided with a reaction sensor  36  for detecting the pedal reaction force. 
     FIG. 3  is a block diagram showing an example setup of the pedal reaction control unit  27 , which receives the depression amount signal FS from the pedal depression amount detection section  25  to control the electric motor  29 . The pedal reaction control unit  27  includes a target-pedal-reaction setting section  40 , an offset calculation section  41 , a PI setting section  42 , a motor drive circuit  43 , a pedal reaction detection section  44 , and a pedal depressing/returning operation determination section  45 . 
   The target-pedal-reaction setting section  40  calculates a target pedal reaction force Ft on the basis of the depression amount signal FS from the pedal depression amount detection section  25 , and it sends the calculated target pedal reaction force Ft to the offset calculation section  41  and also passes the depression amount signal FS to the ECU  16 . Specifically, when the output signal from the pedal depressing/returning operation determination section  45  is indicative of returning (operation) of the accelerator pedal  15  from a depressed position, the target-pedal-reaction setting section  40  outputs a target pedal reaction force Ft on the basis of a target pedal reaction map stored in a storage section  40   a . Specifically, the target pedal reaction map is prestored in the storage section  40   a  as a predetermined function of the pedal depression amount Fs, in accordance with which the target pedal reaction force Ft varies in proportional relation to the pedal depression amount Fs or in accordance with which the target pedal reaction force Ft varies relative to the pedal depression amount Fs only within a variation range (or width) smaller than a predetermined value (i.e., variation in the target pedal reaction force Ft relative to the pedal depression amount Fs is limited within the predetermined range). 
   More specifically, when the output signal from the pedal depressing/returning operation determination section  45  is indicative of the returning operation of the accelerator pedal  15  while the reaction force of the accelerator pedal  15  falls within a predetermined reaction-force increasing control region where control is performed to increase the pedal reaction force in accordance with increase in the depression amount of the pedal, the target-pedal-reaction setting section  40  outputs a given target pedal reaction force Ft on the basis of the target pedal reaction map that defines various values of the target pedal reaction force Ft varying in proportional relation to various possible values of the pedal depression amount Fs or varying relative to the various possible values of the pedal depression amount Fs only within the variation range (or width) smaller than the predetermined value. The offset calculation section  41  calculates a difference or offset DF by subtracting, from the value of the target pedal reaction force Ft output from the setting section  40 , the value of the pedal reaction detected by the pedal reaction detection section  44  (i.e., pedal reaction detection value Fd), and it outputs the calculated offset DF to the PI setting section  42 . The PI setting section  42  performs a predetermined arithmetic operation using the offset DF to thereby calculate a target voltage Vt such that the pedal reaction detection value Fd follows the target pedal reaction force Ft, and it feeds the thus-calculated target voltage Vt to the motor drive circuit  43 . The motor drive circuit  43  generates a motor drive current for driving the motor  29  on the basis of the target voltage Vt fed from the PI setting section  42 . The pedal reaction detection section  44  determines the pedal reaction detection value Fd on the basis of an output signal from the reaction sensor  36  that is, for example, in the form of a torque sensor, and it passes the pedal reaction detection value Fd to the offset calculation section  41 . 
   The pedal depressing/returning operation determination section  45  makes a determination, on the basis of the depression amount signal FS from the pedal depression amount detection section  25 , as to whether the accelerator pedal  15  is currently in a going state (or stroke) or in a returning state (or stroke), and it outputs a result of the determination to the target-pedal-reaction setting section  40 . The pedal depressing/returning operation determination section  45  includes a differentiation circuit  46  and a determining section  47 . The differentiation circuit  46  calculates a temporal differentiated value of the depression amount FS detected by the pedal depression amount detection section  25  and passes the calculated temporal differentiated value to the determining section  47 . The determining section  47  determines, on the basis of the temporal differentiated value from the differentiation circuit  46 , whether the accelerator pedal  15  is currently in the going state or in the returning state, and a result of the determination is given to the target-pedal-reaction setting section  40 . If the accelerator pedal  15  is currently in the going state, the pedal depressing/returning operation determination section  45  outputs a signal of a value “0”, while, if the accelerator pedal  15  is currently in the returning state, the determination section  45  outputs a signal of a value “1”. 
   The following paragraphs describe behavior of the accelerator pedal device constructed in the above-described manner. 
     FIG. 4  is a graph explanatory of the behavior of the accelerator pedal device of the present invention. The vertical axis of  FIG. 4  represents the depression amount signal FS from the pedal depression amount detection section  25 , throttle opening θTH, speed change information TJ from the transmission control section  28  and pedal reaction force RP 1  imparted by the motor to the accelerator pedal  15 , while the horizontal axis of  FIG. 4  represents the depression amount PS of the accelerator pedal  15 . 
   Once the pedal depression amount PS reaches a value S 1  as the human operator or driver of the vehicle steps on or depresses the accelerator pedal  15 , the depression amount signal FS starts increasing in value, in response to which the throttle opening θTH starts increasing. The throttle opening θTH is an amount that corresponds to (e.g. is proportionally related to) the depression amount FS. 
   By that time, the value “0” signal indicating that the accelerator pedal  15  is currently in the going state (or stroke) (i.e., going-state indicative signal) has been fed from the depressing/returning operation determination section  45  to the target-pedal-reaction setting section  40 . The pedal reaction force RP 1  rises sharply as the pedal depression amount PS increases from zero to the value S 1 , and then it increases progressively in response to increase in the pedal depression amount PS above the value S 1 . 
   Then, the pedal reaction force RP 1  starts increasing rapidly once the pedal depression amount PS reaches a value S 2  and the speed change information TJ rises from a LOW level to a HIGH level once the pedal depression amount PS reaches a greater amount S 3 , so that a speed change or transmission shift (in this case, “kickdown” operation) is initiated and the pedal reaction force RP 1  starts decreasing rapidly. The pedal reaction force RP 1  assumes the maximum value F 1  when the pedal depression amount PS is at the value S 3 . 
   Then, once the pedal depression amount PS reaches a still greater value S 4 , not only the speed change information TJ falls from the HIGH level to the LOW level, but also the pedal reaction force RP 1 , which has been decreasing so far, again starts increasing progressively. 
   If the accelerator pedal  15  is released in this condition, then the depressing/returning operation determination section  45  determines, on the basis of the output signal FS from the pedal depression amount detection section  25 , that the accelerator pedal  15  is currently in the returning state (or stroke), and it outputs the value “1” signal (i.e., returning-state indicative signal) to the target-pedal-reaction setting section  40 . The target-pedal-reaction setting section  40 , having received the value “1” signal, outputs a target pedal reaction force in accordance with the map prestored in the storage section  40   a  as the predetermined function of the pedal depression amount Fs, in accordance with which the target pedal reaction force Ft varies in proportional relation to the pedal depression amount Fs or in accordance with which the target pedal reaction force Ft varies relative to the pedal depression amount Fs only within the variation range (or width) smaller than the predetermined value. Thus, the electric motor  29  is controlled to generate and impart the target pedal reaction force to the accelerator pedal  15 . Particularly, when the accelerator pedal has been returned from a depressed position in the predetermined reaction-force increasing control region, the target-pedal-reaction setting section  40  outputs a given target pedal reaction force Ft on the basis of the target pedal reaction map prestored as the above-mentioned function. If the target pedal reaction map prestored in the storage section  40   a  is a map set such that the variation amount of the target pedal reaction force relative to the variation amount of the pedal depression amount is zero, the pedal reaction force RP 1  will vary in a manner as indicated by a solid straight line LR in  FIG. 4 . However, if the target pedal reaction map prestored in the storage section  40   a  is a map set such that the target pedal reaction force Ft varies in proportional relation to the pedal depression amount or varies relative to the pedal depression amount only within the variation range (or width) smaller than the predetermined value, the pedal reaction force RP 1  will vary in a manner as indicated by a dotted straight line LR″ in  FIG. 4 . 
   In the above-described manner, it is possible to significantly reduce an uncomfortable feeling of the driver when returning the accelerator pedal from a depressed position in the reaction-force increasing control region. 
   Further, whereas the reaction/transmission control section  35  has been described as being provided separately from the ECU  16 , it may be included in the ECU  16 . 
   Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.