Abstract:
A golf car operated by a prime mover under the control of an accelerator control a brake capable of being set in a locked condition for retaining the car from movement. Upon original operation of the prime mover the brake is not released until after a predetermined condition is established to insure against unwanted movement of the car before the prime mover is able to drive the car in the intended direction.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a golf car and more particularly to a brake releasing system and method for such cars. 
         [0002]    A typical golf car, which has been traditionally used on golf courses, is disclosed in published Japanese Application, JP-A-2001-17589. Such a traditional golf car may be powered by a prime mover such as either an electric motor or an internal combustion engine. As is typical this golf car is provided with a parking brake for preventing car movement at desired times. Typically, in order to start such a golf car, an accelerator pedal is depressed, and accordingly, the parking brake that is mechanically connected to the accelerator pedal, is released. However, there is a time lag between depression of the accelerator pedal or release of the parking brake and the actual start of vehicle movement. For example, with an internal combustion engine driven vehicle, there is a time lag between the engine start-up and the achievement of a predetermined level of engine power in order to effect vehicle movement. 
         [0003]    This may be best understood by reference to  FIG. 1  which is a chart illustrating vehicle conditions when an engine driven golf car, provided with the conventional brake release mechanism, starts moving on a sloping road. The traces A to E indicate respectively ON/OFF state of an accelerator switch (A), engine speed (B), engine ignition output (C), ON/OFF state of the parking brake (D), and vehicle&#39;s behavior (E). Time is shown along the horizontal axis 
         [0004]    As shown by (A), when a driver depresses the accelerator pedal at the time t 0 , the accelerator switch is turned ON. Upon turning ON the accelerator switch at t 0 , the parking brake is released as shown by (D). Thus, as shown by (E), the vehicle that has been stationary on the sloping road starts reversing in the down slope direction at t 0 . After a small time lag after depressing the accelerator pedal, operation of the starter generator begins at t 1  to start engine cranking as shown by (B). After cranking, an ignition output begins at t 2  as shown by (C), and ignition starts at t 3 , resulting in an increase in engine speed. 
         [0005]    However it is not until t 4 , that the engine torque reaches a level required for driving the vehicle forward on the sloping road, so that the vehicle starts running forward. Thus, under these conditions, the vehicle keeps reversing on the sloping road between t 0  and t 4 . That is that when the accelerator pedal is depressed to start driving the golf car that has been stationary on the sloping road, the parking brake is released even though the golf car is not yet in a condition for running forward on the sloping road due to insufficient levels of engine speed and torque. This causes the golf car to reverse in the down slope direction. 
         [0006]    In order to solve the aforementioned problem, one it has been proposed to use a mechanical structure for delaying the timing of release of the parking brake after the accelerator pedal is depressed. However, even using this mechanical structure, the parking brake may be released before sufficient engine power is obtained because of the extremely short time lag between depression of the accelerator pedal and release of the parking brake. In addition, the parking brake is released depending on the angle by which the accelerator pedal is depressed, or the like. Thus, the timing to release the parking brake differs depending on the quickness of driver&#39;s accelerating operation, and therefore drivers cannot always obtain consistent effects. 
         [0007]    It is, therefore, a principal object of this invention to provide a brake releasing system and method for golf cars that upon desired vehicle start from a braked condition the brake is not released until the prime mover is generating sufficient power to drive the car in the desired direction. 
       SUMMARY OF THE INVENTION 
       [0008]    This invention is adapted to be embodied in a prime mover driven golf car having a brake for selected retention of the car in a stationary position. The prime mover is operated in response to an accelerator control. 
         [0009]    In accordance with a car embodying the invention, the brake is released only when the prime mover is generating sufficient power to move the car in the desired direction. 
         [0010]    In accordance with a method of operating the car, the brake is released only when the prime mover is generating sufficient power to move the car in the desired direction 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a graphical time diagram showing a prior art type of automatic golf car brake release mechanism and method. 
           [0012]      FIG. 2  is a partially schematic top plan view of a golf car constructed and operated in accordance with the invention. 
           [0013]      FIG. 3  is a schematic view showing the controls for the golf car. 
           [0014]      FIG. 4  is a graphical time diagram in part similar to  FIG. 1  showing a first embodiment of the invention. 
           [0015]      FIG. 5  is a graphical time diagram in part similar to  FIGS. 1 and 4  and showing a second embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Referring again in detail to the drawings and initially to  FIG. 2 , A golf car embodying the invention is identified generally by the reference numeral  11  is comprised of a body portion  12  that may have any desired configuration and construction. This body portion  12  dirigibly supports, in a desired manner and through a suspension system, not shown, front wheels  13 . In addition the body portion  12  further supports, again through any desired suspension structure, rear wheels  14 . 
         [0017]    The front wheels  13  are steered by an operator of the car  11  by a suitable steering mechanism by means of a steering wheel  15 . The rear wheels  14  are driven through a transmission  16  from a prime mover such as a fuel injected internal combustion engine, indicated generally by the reference numeral  17 . However those skilled in the art will readily understand that the prime mover may also comprise an electric motor. 
         [0018]    At least the rear wheels  14  are provided with brakes  18  of a suitable type operated by means of a brake pedal  19  positioned in proximity to the operator. The brake pedal  19  has a parking brake function to lock up in a braking condition by depressing a parking brake pedal  19  to stop the vehicle. When stopped, the vehicle is made immovable by locking the parking brake. Its release will be described shortly. 
         [0019]    The engine  17  includes an ignition system  21  of any desired type for firing spark plugs (not shown) in accordance with any desired control routine. The engine  17  is supplied with fuel via one or more fuel injectors (not shown). The engine operation is under the control of an accelerator pedal  23  that is disposed adjacent the brake pedal  19 . An accelerator position detector  24  detects depressing operation of the accelerator pedal  23  by the operator. In the illustrated embodiment, when the operator depresses the accelerator pedal  23  the detector  24  outputs a signal so that the engine  17  and car  11  is driven at a constant speed. Of course those skilled in the art will readily understand how the invention can be practiced with systems wherein the prime mover and car speed may be variable, 
         [0020]    The accelerator position detector  24  and a key operated main switch  25  are connected to an engine controller, indicated generally at  26 . The controller  26  is supplied with power from a battery  27 . For charging the battery  27  and providing electrical power for operation of the car  11  there is provided a starter generator  28 . 
         [0021]    As has been noted, the brake pedal  19  has a parking brake function to lock up in a braking condition by depressing a parking brake pedal to stop the vehicle. The brake pedal  19  is provided with a brake release mechanism  29 . While the vehicle is stationary with parking brakes applied, the brake pedal  19  is depressed again to initiate release of the parking brakes. The brake release mechanism is operated in according with the invention, as will be described shortly. 
         [0022]    Referring now to  FIG. 3 , this is a circuit block diagram of the golf car  11 . When the main switch  25  is turned ON, the battery  27  supplies power to the controller  26  and when the accelerator switch  24  is turned ON, an acceleration input signal is sent to the controller  26 . When the main switch  25  and the accelerator switch  24  are both ON, the starter generator  28  starts-up via a relay or power on circuit  34 . The starter generator  28  charges the battery  27  through a regulator  31  for electric power generation. 
         [0023]    Rotation of the starter generator  28  cause the engine  17  to start. Attached for rotation to the engine crankshaft or any other shaft that rotates with the crankshaft is a rotor  32  having one or more timing marks that cooperates with a sensor  33  that sends pulser signals to the controller  26 . The controller  26  calculates the rotational speed of the crankshaft and a crank angle based on these pulser signals. Upon determining the engine start-up, the controller  26  sends ignition signals to the engine ignition system  21 . Further, determining a predetermined condition, for example in this embodiment that the engine speed reaches a certain preset value, the controller  26  sends a signal to initiate parking brake release by the break release mechanism  29 . 
         [0024]    The operation of this embodiment will now be described by reference to  FIG. 4  which should be compared with Prior Art  FIG. 1  to show the improved result. The respective traces (A to E) are the of the same characteristics as those of  FIG. 1 . That is traces (A) to (E) indicate respectively ON/OFF state of the accelerator switch, engine speed, engine ignition output, ON/OFF state of the parking brake, and vehicle&#39;s behavior, respectively, while the horizontal axis represents lapse of time. 
         [0025]    When operating in accordance with the circuit as shown in  FIG. 3 , and as shown by trace (A), the driver depresses the accelerator pedal  23  and then the accelerator switch  24  is ON at t 0 . With a small time lag after the accelerator switch  24  is ON, the starter generator  28  starts-up at t 1  while the engine starts cranking. Then, ignition output begins at t 2 , followed by ignition at t 3 , so that the engine speed starts increasing, as shown by traces (B) and (C) respectively. However the brakes  18  are not released at the same time, as with the prior art. Then when the engine speed reaches a certain preset value at t 4 , the parking brake is released as shown by the trace (D). This time delay in brake release insures that the engine is developing sufficient power to actually effect movement of the car  12 . Thus, the vehicle starts moving at t 4 , and soon moves forward in the upslope direction. However, the vehicle may reverse slightly by an extremely short distance in the down slope direction after t 4 , depending on the slope angle and/or engine power, as shown by trace (E). 
         [0026]    As described above, the engine speed required for releasing the parking brake is predetermined depending on, for example, the characteristics of the golf course. This prevents the parking brake from being released, if sufficient drive power has not yet been obtained after the accelerator pedal  23  was depressed. Thereby, the distance the vehicle move in reverse on the sloping road can thus be reduced or totally eliminated. 
         [0027]    Referring now to  FIG. 5 , this shows another embodiment that delays brake release for a predetermined time after engine start up rather than actual engine speed. Like  FIGS. 1 and 4  this figure is a chart illustrating different vehicle conditions when the golf car of the invention starts moving on the sloping road. (A) to (E) indicate the same characteristics as shown in  FIGS. 1 and 4  and the horizontal axis again represents lapse of time. 
         [0028]    As shown by trace (A), the driver depresses the accelerator pedal and then the accelerator switch is ON at t 0 . With a small time lag after the accelerator switch is ON, the starter generator starts-up at t 1  while the engine starts cranking, and then, ignition output begins at t 2 , as shown by traces (B) and (C), respectively. According to the second embodiment, at t 2  when an ignition signal is first generated, the parking brake is released as shown by trace (D). 
         [0029]    Thus, the vehicle starts moving at t 2 , and reverses slightly in the down slope direction, as shown by (E). However, after that, the engine ignition is started at t 3 , and the engine speed thus starts increasing. Therefore, at t 4 , the engine power reaches a level sufficient to enable the vehicle to move forward in the up slope direction. 
         [0030]    In this embodiment, since the engine power at the time of releasing the parking brake is not sufficient to enable the vehicle to move forward in the upslope direction, the vehicle reverses slightly. However, the reverse distance is shorter compared to the conventional art ( FIG. 1 ) using the parking brake that is released concurrently with depressing the accelerator pedal. 
         [0031]    In addition, as in the first embodiment, increasing the engine power for releasing the parking brake may cause the vehicle on the flat road to start suddenly. Therefore, as noted in the second embodiment, releasing the parking brake with low engine power allows the vehicle on the flat road to start smoothly. Thus, the second embodiment may be more suitable for gently undulating courses, for example. 
         [0032]    It should be obvious to those skilled in the art that the present invention may apply to any vehicles driven by a fuel injection engine or a carbureted engine having a controller, or in fact even an electric motor. Of course those skilled in the art will readily understand that the described embodiments are only of a exemplary forms that the invention may take and that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.