Patent Publication Number: US-2021162964-A1

Title: Controller and control method

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a controller for a motorcycle and a control method of the same. 
     As a controller for a vehicle, a controller that executes hill-hold control for retaining a brake force of a brake mechanism even when an occupant of the vehicle releases a brake pedal or the like has been available (for example, see PTL 1). The brake force that has been retained by the hill-hold control is reduced when a certain condition is satisfied. 
     CITATION LIST 
     Patent Literature 
     PTL1: JP-A-2007-246051 
     SUMMARY OF THE INVENTION 
     In regard to the conventional controller, depending on a condition of a road surface and the like, there is a case where a vehicle body starts moving and a posture of the vehicle body thereby becomes unstable in a process of reducing the brake force, which has been retained by the hill-hold control. In particular, a vehicle body of a motorcycle is more likely to become unstable than that of a four-wheeled vehicle or the like. 
     The invention has been made with a problem as described above as the background and therefore has a purpose of providing a controller and a control method capable of suppressing a posture of a motorcycle from becoming unstable in a process of reducing a brake force that has been retained by hill-hold control. 
     A controller according to the invention is a controller for controlling a brake mechanism that generates a brake force on a motorcycle, and includes: a detection section for detecting movement of the motorcycle; and a control section for executing hill-hold control that retains the brake force on an inclined road surface. In the cases where the brake force, which has been retained by the hill-hold control, starts to be reduced and it is then determined on the basis of a detection signal of the detection section that the motorcycle starts moving, the control section reduces a reduction amount of the brake force per time to make it smaller than the reduction amount of the brake force per time prior to the determination that the motorcycle starts moving. 
     A control method according to the invention is a control method of a motorcycle for executing hill-hold control that retains a brake force of a brake mechanism on an inclined road surface, and includes the steps of: starting to reduce the brake force, which has been retained by the hill-hold control; determining whether the motorcycle starts moving after the brake force starts to be reduced; and, in the case where it is determined that the motorcycle starts moving, reducing a reduction amount of the brake force per time to make it smaller than the reduction amount of the brake force per time prior to the determination that the motorcycle starts moving. 
     In the controller and the control method according to the invention, in the case where it is determined that the motorcycle starts moving, the reduction amount of the brake force per time is reduced to be smaller than the reduction amount of the brake force per time prior to the determination that the motorcycle starts moving. Therefore, the movement of the motorcycle can be made gentle, and a posture of the motorcycle can be suppressed from becoming unstable. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view that schematically depicts a motorcycle including a controller according to a first embodiment of the invention. 
         FIG. 2  is a schematic configuration diagram of a hydraulic pressure control system that includes the controller according to the first embodiment of the invention. 
         FIG. 3  is a functional block diagram of various sensors, a control section, and various actuators provided in the hydraulic pressure control system that includes the controller according to the first embodiment of the invention. 
         FIG. 4  is a functional block diagram of a control section of the controller according to the first embodiment of the invention. 
         FIG. 5  is a chart that indicates timing of each of various operations in hill-hold control by the controller according to the first embodiment of the invention. 
         FIG. 6  is an explanatory chart of a brake force of the motorcycle that includes the controller according to the first embodiment of the invention. 
         FIG. 7  is one example of a control flow of the controller according to the first embodiment of the invention. 
         FIG. 8  is a view that schematically depicts the motorcycle that is stopped on an uphill road surface. 
         FIG. 9  is one example of a control flow of a controller according to a modified example of the first embodiment of the invention. 
         FIG. 10  is a functional block diagram of various sensors, a control section, and various actuators provided in a hydraulic pressure control system that includes a controller according to a second embodiment of the invention. 
         FIG. 11  is one example of a control flow of the controller according to the second embodiment of the invention. 
         FIG. 12  is one example of a control flow of a controller according to a modified example of the second embodiment of the invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A description will hereinafter be made on a controller and a control method according to the invention by using the drawings. Each of a configuration, an operation, and the like, which will be described below, is merely one example, and each of the controller and the control method according to the invention is not limited to a case with such a configuration, such an operation, and the like. For example, the controller and the control method according to the invention may perform an operation other than brake control. 
     In addition, in each of the drawings, detailed portions are depicted in an appropriately simplified manner or are not depicted. Furthermore, overlapping descriptions are appropriately simplified or are not made. 
     First Embodiment 
     &lt;Overall Configuration of Hydraulic Pressure Control System  100 &gt; 
       FIG. 1  is a view that schematically depicts a motorcycle including a controller according to this first embodiment.  FIG. 2  is a schematic configuration diagram of a hydraulic pressure control system that includes the controller according to this first embodiment. 
     A hydraulic pressure control system  100  is mounted in a motorcycle  200  and includes a controller  1  that generates a brake force on a wheel W (a front wheel  20  and a rear wheel  30 ). 
     The motorcycle  200  is formed by combining the wheel W, a vehicle body B, and the controller  1 . The vehicle body B includes all components of the motorcycle  200  except for the controller  1  and the wheel W. In addition, the motorcycle  200  will be described as a two-wheeled vehicle in this embodiment. However, the motorcycle  200  is not limited thereto and may be a three-wheeled vehicle. 
     The motorcycle  200  includes the front wheel  20  and the rear wheel  30  as well as a handlebar lever  24  and a foot pedal  34  that are operated by an occupant. When this handlebar lever  24  is operated, the brake force on the front wheel  20  is changed. When the foot pedal  34  is operated, the brake force on the rear wheel  30  is changed. 
     The hydraulic pressure control system  100  includes: a front-wheel hydraulic circuit C 1  through which a brake fluid used to generate the brake force on the front wheel  20  flows; and a rear-wheel hydraulic circuit C 2  through which a brake fluid used to generate the brake force on the rear wheel  30  flows. 
     The hydraulic pressure control system  100  includes: a front brake pad  21  that is attached to the front wheel  20 ; a front wheel cylinder  22  in which a front brake piston (not depicted) for causing movement of the front brake pad  21  is provided in a freely slidable manner; and a brake fluid pipe  23  that is connected to the front wheel cylinder  22 . 
     The hydraulic pressure control system  100  includes: a first master cylinder  25  that is attached to the handlebar lever  24 ; a first reservoir  26  that stores the brake fluid; and a brake fluid pipe  27  that is connected to the first master cylinder  25 . Note that a master cylinder piston (not depicted) is provided in a freely slidable manner in the first master cylinder  25 . When the handlebar lever  24  is operated, the master cylinder piston in the first master cylinder  25  moves. 
     The hydraulic pressure control system  100  includes: a rear brake pad  31  that is attached to the rear wheel  30 ; a rear wheel cylinder  32  in which a rear brake piston (not depicted) for causing movement of the rear brake pad  31  is provided in a freely slidable manner; and a brake fluid pipe  33  that is connected to the rear wheel cylinder  32 . 
     The hydraulic pressure control system  100  includes: a second master cylinder  35  that is attached to the foot pedal  34 ; a second reservoir  36  that stores the brake fluid; and a brake fluid pipe  37  that is connected to the second master cylinder  35 . Note that a master cylinder piston (not depicted) is provided in a freely slidable manner in the second master cylinder  35 . When the foot pedal  34  is operated, the master cylinder piston in the second master cylinder  35  moves. 
     &lt;Description on Configuration of Controller  1 &gt; 
     The controller  1  includes: an internal channel  4  through which the brake fluid flows; and a pump device  2  that is used to feed the brake fluid in the internal channel  4  to the first master cylinder  25  side and the second master cylinder  35  side. Note that the internal channel  4  includes: an internal channel  4 A that constitutes a part of the front-wheel hydraulic circuit C 1 ; and an internal channel  4 B that constitutes a part of the rear-wheel hydraulic circuit C 2 . 
     In addition, the controller  1  includes a freely openable/closable regulating valve  3 . Note that the regulating valve  3  includes a first pressure boosting valve  3 A, a first pressure reducing valve  3 B, a second pressure boosting valve  3 C, and a second pressure reducing valve  3 D. The regulating valve  3  is, for example, a valve that is opened or closed when brake control such as control of an antilock brake system (an ABS) is executed. 
     Furthermore, the controller  1  includes a switching valve  10 , an opening degree of which can freely be adjusted, and freely openable/closable inlet valve  11 . The switching valve  10  includes: a switching valve  10 A that is provided in the front-wheel hydraulic circuit C 1 ; and a switching valve  10 B that is provided in the rear-wheel hydraulic circuit C 2 . When the switching valve  10 A is closed, a hydraulic pressure of the brake fluid in the front wheel cylinder  22  is retained, and retention of the brake force on the front wheel  20  is thereby realized. In addition, when the switching valve  10 B is closed, a hydraulic pressure of the brake fluid in the rear wheel cylinder  32  is retained, and retention of the brake force on the rear wheel  30  is thereby realized. 
     The inlet valve  11  includes: an inlet valve  11 A that is provided in the front-wheel hydraulic circuit C 1 ; and an inlet valve  11 B that is provided in the rear-wheel hydraulic circuit C 2 . The inlet valve  11 A is opened when the pressure of the front wheel cylinder  22  is boosted. The inlet valve  11 B is opened when the pressure of the rear wheel cylinder  32  is boosted. Note that each of the regulating valve  3 , the switching valve  10 , and the inlet valve  11  is an electromagnetic valve that includes a solenoid, for example. 
     The controller  1  includes a control section  7  that controls opening/closing and the like of the regulating valve  3 , the switching valve  10 , and the inlet valve  11 . Note that a part or a whole of the control section  7  may be constructed of a microcomputer, a microprocessor unit, or the like, may be constructed of a member in which firmware and the like can be updated, or may be a program module or the like that is executed by a command from a CPU or the like, for example. 
     The controller  1  includes a detection mechanism  8  that outputs detection signals to the control section  7 . The detection mechanism  8  includes: a switch  8 A (see  FIG. 3 ) that outputs an on/off signal to the control section  7 ; a position detection sensor  8 B 1  (see  FIG. 3 ) that is used to detect an operation state of the handlebar lever  24 ; a position detection sensor  8 B 2  (see  FIG. 3 ) that is used to detect an operation state of the foot pedal  34 ; a detection section  8 C 1  (see  FIG. 3 ) and a detection section  8 C 2  (see  FIG. 3 ) that are used to detect initiation of movement of the motorcycle  200 ; and a pressure sensor  8 D that detects a hydraulic pressure of the brake fluid in the internal channel  4 . Note that the detection section  8 C 1  is a front-wheel speed sensor and the detection section  8 C 2  is a rear-wheel speed sensor. In addition, the switch  8 A is attached to the vehicle body of the motorcycle  200 , for example. The occupant turns the switch  8 A on when permitting execution of hill-hold control. 
     The controller  1  includes various ports P that are connected to corresponding fluid pipes such as the brake fluid pipe  23 . In addition, the controller  1  includes: a float restrictor  5  that restricts a flow rate of the brake fluid flowing through the internal channel  4 ; and an accumulator  6  that can store the brake fluid. 
     The switching valve  10 A, the inlet valve  11 A, the first pressure boosting valve  3 A, the first pressure reducing valve  3 B, and the like are provided in the internal channel  4 A. The internal channel  4 A is connected to the brake fluid pipe  23  and the brake fluid pipe  27  via the ports P. The switching valve  10 B, the inlet valve  11 B, the second pressure boosting valve  3 C, the second pressure reducing valve  3 D, and the like are provided in the internal channel  4 B. The internal channel  4 B is connected to the brake fluid pipe  33  and the brake fluid pipe  37  via the ports P. 
     The pump device  2  includes: a drive mechanism  2 A that can be constructed of a DC motor and the like, for example; and two pump elements  2 B, to each of which drive power is provided by the drive mechanism  2 A. The drive mechanism  2 A includes a stator, a rotor, and the like, and a rotational frequency thereof is controlled by the control section  7 . One of the pump elements  2 B is used to feed the brake fluid in the front-wheel hydraulic circuit C 1  and is provided in the internal channel  4 A. The other of the pump elements  2 B is used to feed the brake fluid in the rear-wheel hydraulic circuit C 2  and is provided in the internal channel  4 B. 
     The control section  7  executes the hill-hold control under a certain condition. In the hill-hold control, the brake force of the motorcycle  200  is retained in the case where the occupant of the motorcycle  200  releases the handlebar lever  24  and the foot pedal  34  in a state where the motorcycle  200  is stopped on an inclined road surface. After a lapse of a certain time, the control section  7  cancels retention of the brake force and reduces the brake force. 
     &lt;Configuration Example of Control Section  7 &gt; 
       FIG. 3  is a functional block diagram of the various sensors, the control section, and various actuators provided in the hydraulic pressure control system that includes the controller according to this first embodiment.  FIG. 4  is a functional block diagram of the control section of the controller according to this first embodiment. A description will be made on a configuration example of the control section  7  with reference to  FIG. 3  and  FIG. 4 . 
     Note that the first pressure boosting valve  3 A and the second pressure boosting valve  3 C are opened and the first pressure reducing valve  3 B and the second pressure reducing valve  3 D are closed in the following description. The handlebar lever  24  and the foot pedal  34  are also collectively referred to as a brake operation section. The detection section  8 C 1  and the detection section  8 C 2  are also collectively referred to as a detection section WS. The position detection sensor  8 B 1  and the position detection sensor  8 B 2  are also collectively referred to as a position detection sensor SW. The pressures of the front wheel cylinder  22  and the rear wheel cylinder  32  are also collectively referred to as a cylinder pressure. 
     A brake mechanism means a configuration of generating the brake force on the motorcycle  200 . For example, the switching valve  10 , the inlet valve  11 , the pump device  2 , and the like correspond to the brake mechanism. 
     The control section  7  includes: an input section  7 A that receives the signals from the detection mechanism  8 ; a processor section  7 B that makes various determinations and the like; and a memory section  7 C in which various types of data are stored. 
     (Input Section  7 A) 
     The input section  7 A is, for example, constructed of a circuit that includes an input circuit for receiving the signals from the detection mechanism  8 , and the like. The signals received by the input section  7 A are output to the processor section  7 B. 
     (Processor Section  7 B) 
     The processor section  7 B includes an arithmetic section T 1  and an actuator control section T 2 . The arithmetic section T 1  includes a determination section  7 B 1 , a decision section  7 B 2 , a timer section  7 B 3 , and a computation section  7 B 4 . The processor section  7 B can be constructed of a microcontroller and the like, for example. 
     The determination section  7 B 1  determines whether to execute the hill-hold control. Here, the hill-hold control includes a retention mode and a cancellation mode. The retention mode is a mode of retaining the brake force of the motorcycle  200 . The cancellation mode is a mode of cancelling the retention of the brake force in the retention mode and reducing the brake force. Thus, timing at which the brake force, which has been retained by the hill-hold control, starts to be reduced is shift timing from the retention mode to the cancellation mode. 
     The determination section  7 B 1  determines whether the execution of the hill-hold control is permitted, determines whether the motorcycle  200  is stopped, and determines whether the brake operation section is released. 
     When determining that the execution of the hill-hold control is permitted, that the motorcycle  200  is stopped, and that the brake operation section is released, the determination section  7 B 1  determines to execute the retention mode of the hill-hold control. 
     Note that the on/off signal of the switch  8 A is used to determine whether the execution of the hill-hold control is permitted. In addition, a wheel speed that is computed by the computation section  7 B 4  is used to determine whether the motorcycle  200  is stopped. Furthermore, a detection signal of the position detection sensor SW is used to determine whether the brake operation section is released. 
     Note that, when the brake operation section is released, pressures of the first master cylinder  25  and the second master cylinder  35  are reduced, for example. The pressures of the front wheel cylinder  22  and the rear wheel cylinder  32  are also reduced. For this reason, a pressure that is computed by the computation section  7 B 4  on the basis of a detection signal of the pressure sensor  8 D can also be used to determine whether the brake operation section is released. 
     In addition, on the basis of a signal from the timer section  7 B 3 , the determination section  7 B 1  determines whether the certain time has elapsed since initiation of the retention mode. When the certain time elapses, the control section  7  shifts from the retention mode to the cancellation mode. The certain time is set to approximately a few seconds, for example. 
     In the case where the cancellation mode is executed, the determination section  7 B 1  determines whether the motorcycle  200  starts moving on the basis of a detection signal of the detection section WS. More specifically, movement (rotation) of the wheels W is detected by the detection section WS, and the control section  7  determines whether the motorcycle  200  starts moving. Note that, because the wheel speed of the motorcycle  200  at the initiation of the movement is extremely low, it is assumed that the computation section  7 B 4  cannot compute the wheel speed. For this reason, the determination section  7 B 1  uses the detection signal of the detection section WS instead of that of the computation section  7 B 4 . 
     When determining that the motorcycle  200  starts moving, the determination section  7 B 1  determines whether a prescribed time TM 1  has elapsed on the basis of the signal from the timer section  7 B 3 . These determinations are used to obtain timing for opening/closing the switching valve  10  when a reduction amount α per time, which will be described below, is set to a prescribed value α 2 . 
     In the case where the cancellation mode is executed, the determination section  7 B 1  determines whether the cylinder pressure that is computed by the computation section  7 B 4  is higher than a first prescribed pressure. The determination is made in consideration of a case where the brake force cannot be secured timely in the state where the cylinder pressure is lower than the first prescribed pressure and thus the posture of the motorcycle  200  cannot be stabilized. 
     In the case where the cancellation mode is executed, the determination section  7 B 1  determines whether the cylinder pressure, which is computed by the computation section  7 B 4 , is lower than a second prescribed pressure. Note that the second prescribed pressure is lower than the first prescribed pressure. The determination is used to obtain timing for terminating the cancellation mode. 
     The decision section  7 B 2  decides parameters that are used during the execution of the cancellation mode. (1) Initially, the decision section  7 B 2  decides the reduction amount α per time to a prescribed value α 1 . Here, the reduction amount α per time represents a magnitude of the brake force that is reduced per unit time. 
     (2) Next, the decision section  7 B 2  decides the reduction amount α of the brake force per time to the prescribed value α 2 , the reduction amount α of the brake force per time being used in the case where the determination section  7 B 1  determines that the motorcycle  200  starts moving. Here, the prescribed value α 2  is smaller than the prescribed value α 1 . Note that the prescribed value α 2  may be a negative value. That is, when the cancellation mode is executed, the prescribed value α 2  can be decided so as to increase the brake force. On the other hand, the prescribed value α 1  is a positive value so as to reduce the brake force. 
     (3) Next, the decision section  7 B 2  decides a time TM, in which the reduction amount α of the brake force per time is set to the prescribed value α 2 , to the prescribed time TM 1 . 
     In this first embodiment, the parameters, such as the prescribed value α 1 , that are used during the execution of the cancellation mode are decided in advance. Note that the parameters may appropriately be changed. 
     The timer section  7 B 3  counts a period from the initiation of the retention mode until the lapse of the certain time, a period from the time, at which the reduction amount α of the brake force per time is set to the prescribed value α 2 , until a lapse of the prescribed time period TM 1 , and the like, for example. 
     The computation section  7 B 4  computes the wheel speed on the basis of the detection signal of the detection section WS. The computation section  7 B 4  also computes the cylinder pressure on the basis of the detection signal of the pressure sensor  8 D. In addition to the above, the computation section  7 B 4  can compute the pressures of the first master cylinder  25  and the second master cylinder  35  on the basis of the detection signal of the pressure sensor  8 D. 
     The actuator control section T 2  includes a drive mechanism control section  7 B 5  and a valve control section  7 B 6 . 
     The valve control section  7 B 6  controls opening/closing operations of the regulating valve  3 , the switching valve  10 , and the inlet valve  11 . When the determination section  7 B 1  determines to execute the hill-hold control, the valve control section  7 B 6  closes the switching valve  10  so as to retain the brake force of the motorcycle  200 . In addition, when the determination section  7 B 1  determines that the certain time has elapsed from the initiation of the retention mode, the valve control section  7 B 6  opens/closes the switching valve  10  on the basis of a content of a decision of the decision section  7 B 2 . 
     The drive mechanism control section  7 B 5  controls the rotational frequency of the drive mechanism  2 A in correspondence with the opening/closing operation of the inlet valve  11 . Note that, in the case where the prescribed value α 2 , use of which is decided by the decision section  7 B 2 , is the negative value, the valve control section  7 B 6  opens the inlet valve  11  and closes the switching valve  10 . Then, the drive mechanism control section  7 B 5  operates the drive mechanism  2 A, so as to increase the cylinder pressure and increase the brake force. 
     (Memory Section  7 C) 
     The memory section  7 C stores data related to the detection signals of the detection mechanism  8 , values of the parameters that are decided by the decision section  7 B 2 , and the like. The memory section  7 C can be constructed of a random access memory (a RAM) and the like, for example. 
     &lt;Brake Force in Retention Mode and Cancellation Mode&gt; 
       FIG. 5  is a chart that indicates timing of each of the various operations in the hill-hold control by the controller according to this first embodiment.  FIG. 6  is an explanatory chart of the brake force of the motorcycle that includes the controller according to this first embodiment. 
     A line L 1  in  FIG. 5  indicates timing t 1  at which the retention mode is shifted to the cancellation mode in the hill-hold control. The retention mode is executed in a period before the timing t 1 , and the cancellation mode is executed in a period after the timing t 1 . 
     A line L 2  in  FIG. 5  indicates timing t 2  at which it is determined that the motorcycle  200  starts moving in the cancellation mode. In reality, the motorcycle  200  possibly starts moving at timing that is after the timing t 1  and is before the timing t 2 . Thus, the timing t 2  merely indicates the timing at which the determination section  7 B 1  determines that the motorcycle  200  starts moving in the cancellation mode. 
     A line L 3  in  FIG. 5  indicates timing at which the prescribed time TM 1  elapses from the timing t 2 , at which it is determined that the motorcycle  200  starts moving. 
     A line F 1  in  FIG. 6  indicates a temporal change of the brake force in the hill-hold control by the controller  1 . A line F 2  in  FIG. 6  indicates a temporal change of the brake force in the hill-hold control by the conventional controller. Note that each of the line F 1  and the line F 2  also corresponds to a temporal change of the cylinder pressure. 
     The control section  7  executes the retention mode in the period before the timing t 1 . Thus, the brake force is retained to be higher than that after the timing t 1 . 
     At the timing t 1 , the control section  7  shifts from the retention mode to the cancellation mode. The control section  7  controls the switching valve  10  such that the reduction amount α of the brake force per time becomes the prescribed value α 1 . For example, in the case where opening/closing times of the switching valve  10  each time is set to be constant, the control section  7  increases number of opening/closing of the switching valve  10  per time as the prescribed value α 1  is increased. On the other hand, in the case where the opening/closing times of the switching valve  10  are set to be variable, the control section  7  extends the opening time of the switching valve  10  per time as the prescribed value α 1  is increased. 
     At the timing t 2 , the control section  7  determines that the motorcycle  200  starts moving. Accordingly, the control section  7  controls the switching valve  10  such that the reduction amount α of the brake force per time becomes the prescribed value α 2 . In an example of  FIG. 6 , the prescribed value α 2  is zero. Thus, the control section  7  closes the switching valve  10  during the prescribed time TM 1 . 
     At a timing t 3 , the control section  7  determines that the certain time has elapsed since the initiation of the retention mode. Accordingly, the control section  7  controls the switching valve  10  such that the reduction amount α of the brake force per time becomes the prescribed value α 1  from the prescribed value α 2 . 
     &lt;Control Flow Example of First Embodiment&gt; 
       FIG. 7  is one example of a control flow of the controller according to this first embodiment. A description will be made on the hill-hold control that is executed by the control section  7  of the controller  1  with reference to  FIG. 7 . 
     (Step S 0 : Start) 
     The control section  7  executes the control flow that includes the hill-hold control. 
     (Step S 1 : Determination Related to Execution Permission of Hill-Hold Control) 
     On the basis of the on/off signal of the switch  8 A, the determination section  7 B 1  of the control section  7  determines whether the execution of the hill-hold control is permitted. 
     If it is determined that the execution is permitted, the process proceeds to step S 2 . 
     If it is determined that the execution is not permitted, step S 1  is repeated. 
     (Step S 2 : Determination Related to Stop of Motorcycle  200 ) 
     On the basis of the wheel speed that is computed by the computation section  7 B 4 , the determination section  7 B 1  of the control section  7  determines whether the motorcycle  200  is stopped. 
     If it is determined that the motorcycle  200  is stopped, the process proceeds to step S 3 . 
     If it is determined that the motorcycle  200  is not stopped, the process returns to step S 1 . 
     (Step S 3 : Determination Related to Brake Operation Section) 
     On the basis of the detection signal of the position detection sensor SW, the determination section  7 B 1  of the control section  7  determines whether the brake operation section is released. 
     If it is determined that the brake operation section is released, the process proceeds to step S 4 . 
     If it is determined that the brake operation section is not released, the process returns to step S 1 . 
     (Step S 4 : Execution of Retention Mode of Hill-Hold Control) 
     The control section  7  executes the retention mode of the hill-hold control. The control section  7  closes the switching valve  10  for the certain time such that the brake force of the motorcycle  200  is retained. 
     (Step S 5 : Execution of Cancellation Mode of Hill-Hold Control) 
     The control section  7  executes the cancellation mode of the hill-hold control. In addition, the decision section  7 B 2  of the control section  7  decides the reduction amount α of the brake force per time to the prescribed value α 1 . Then, the control section  7  controls the switching valve  10  such that the reduction amount α of the brake force per time becomes the prescribed value α 1 . 
     (Step S 6 : Determination Related to Initiation of Movement of Motorcycle  200 ) 
     The determination section  7 B 1  of the control section  7  determines whether the cylinder pressure is higher than the first prescribed pressure, and also determines whether the motorcycle  200  starts moving. 
     If it is determined that the cylinder pressure is higher than the first prescribed pressure and it is determined that the motorcycle  200  starts moving, the process proceeds to step S 7 . 
     If it is determined that the cylinder pressure is higher than the first prescribed pressure and it is determined that the motorcycle  200  does not start moving, the process returns to step S 5 . 
     If it is determined that the cylinder pressure is not higher than the first prescribed pressure, the process proceeds to step S 9  regardless of the determination related to the initiation of the movement. 
     (Step S 7 : Change in Reduction Amount α of Brake Force Per Time) 
     The decision section  7 B 2  of the control section  7  changes the reduction amount α of the brake force per time to the prescribed value α 2 . Then, the control section  7  controls the switching valve  10  such that the reduction amount α of the brake force per time becomes the prescribed value α 2 . 
     (Step S 8 : Determination Related to Prescribed Time TM 1 ) 
     After controlling the switching valve  10  by setting the reduction amount α of the brake force per time to the prescribed value α 2  on the basis of the signal from the timer section  7 B 3 , the determination section  7 B 1  of the control section  7  determines whether the prescribed time TM 1  has elapsed. 
     If it is determined that the prescribed time TM 1  has elapsed, the process proceeds to step S 9 . 
     If it is determined that the prescribed time TM 1  has not elapsed, the process returns to step S 7 . 
     (Step S 9 : Set Back Reduction Amount α of Brake Force Per Time) 
     The decision section  7 B 2  of the control section  7  makes a decision to set back the reduction amount α of the brake force per time from the prescribed value α 2  to the prescribed value α 1 . Then, the control section  7  controls the switching valve  10  such that the reduction amount α of the brake force per time becomes the prescribed value α 1 . 
     (Step S 10 : Determination Related to Cylinder Pressure) 
     The determination section  7 B 1  of the control section  7  determines whether the cylinder pressure is lower than the second prescribed pressure. 
     If it is determined that the cylinder pressure is lower than the second prescribed pressure, the process proceeds to step S 11 . 
     If it is determined that the cylinder pressure is not lower than the second prescribed pressure, the process returns to step S 9 . 
     (Step S 11 : End) 
     The control section  7  terminates the control flow that includes the hill-hold control. 
     Note that, in this first embodiment, the description has been made on the case where the determinations, which are described in step S 1  to step S 3  depicted in  FIG. 7 , are made prior to shifting to the hill-hold control; however, the invention is not limited thereto. For example, the determination on whether to shift to the hill-hold control may include a determination on whether the motorcycle  200  is in a low gear or the like. 
     &lt;Effects that Controller  1  According to this First Embodiment has&gt; 
     In the cases where the brake force, which has been retained by the hill-hold control, starts to be reduced and it is then determined on the basis of the detection signal of the detection section WS that the motorcycle  200  starts moving, the control section  7  of the controller  1  according to this first embodiment reduces the reduction amount α of the brake force per time to make it smaller than the reduction amount α of the brake force per time prior to the determination that the motorcycle  200  starts moving. In other words, the controller  1  according to this first embodiment can achieve gentle movement of the motorcycle  200  that starts moving on the inclined road surface. 
     For example, a normal force from the road surface that acts on the motorcycle  200  is smaller than that acting on the four-wheeled vehicle and the like, and a friction force between the wheel W and the road surface tends to be reduced. Accordingly, compared to the four-wheeled vehicle and the like, the initiation of the movement of the motorcycle  200  from the stopped state on the inclined road surface tends to become unstable. The control section  7  of the controller  1  according to this first embodiment can achieve the gentle movement of the motorcycle  200  that starts moving on the inclined road surface, and thus can suppress the posture of the motorcycle  200  from becoming unstable. Therefore, the controller  1  according to this first embodiment is particularly suited for use in the motorcycle  200 . 
     In addition, differing from the four-wheeled vehicle and the like, the occupant himself/herself needs to secure stability of the posture of the motorcycle  200  by using legs or the like. When the motorcycle  200 , which is stopped on an uphill road surface, suddenly starts moving, it becomes difficult to secure the stability of the posture of the motorcycle  200 . Therefore, the controller  1  according to this first embodiment is particularly effective for the hill-hold control that is executed on the uphill road surface. 
     Preferably, in the cases where it is determined that the motorcycle  200  starts moving on the basis of the detection signal of the detection section WS and the brake force is smaller than the prescribed value, the controller  1  according to this first embodiment does not reduce the reduction amount α of the brake force per time. Note that this prescribed value corresponds to the above-described first prescribed pressure (see step S 6  in  FIG. 7 ). It is because, when the brake force is smaller than the prescribed value, the movement of the motorcycle  200  cannot be made gentle and it is thus difficult to stabilize the posture of the motorcycle  200 . In other words, the controller  1  can avoid unnecessary extension of the time in the cancellation mode. 
     &lt;Modified Example of First Embodiment&gt; 
       FIG. 8  is a view that schematically depicts the motorcycle that is stopped on the uphill road surface. The prescribed value α 2  and the prescribed time TM 1 , both of which are defined in advance, are used in the first embodiment. In a modified example, an inclination value θ of the road surface is obtained, and the prescribed value α 2  and the prescribed time TM 1  are changed in accordance with the inclination value θ. 
     The computation section  7 B 4  computes the inclination value θ on the basis of the detection signal of the detection section WS as the wheel speed sensor, the signal being obtained immediately before the motorcycle  200  stops. Compared to a case where the inclination value θ is small, deceleration of the wheel speed is promoted in the case where the inclination value θ is large. Accordingly, the computation section  7 B 4  can compute the inclination value θ from a relationship between the detection signal of the detection section WS as the wheel speed sensor and the detection signal of another detection section (the position detection sensor SW, the pressure sensor  8 D, or the like). 
     When determining that the execution of the hill-hold control is permitted, that the motorcycle  200  is stopped, and that the brake operation section is released, the determination section  7 B 1  determines to execute the retention mode of the hill-hold control. 
     The decision section  7 B 2  computes the prescribed value α 2  and the prescribed time TM 1  in accordance with the inclination value θ that is computed by the computation section  7 B 4 . For example, compared to the case where the inclination value θ is small, a vehicle body speed of the motorcycle  200  at the time when it is determined that the motorcycle  200  starts moving is possibly high in the case where the inclination value θ is large. Accordingly, in the case where the inclination value θ is large, the decision section  7 B 2  reduces the prescribed value α 2  to make it smaller than that in the case where the inclination value θ is small. In other words, the reduction amount α of the brake force per time is reduced to a greater degree. In addition, in the case where the inclination value θ is large, the prescribed time TM 1  is extended to be longer than that in the case where the inclination value θ is small by the decision section  7 B 2 . Note that the decision section  7 B 2  may decide both of the reduction of the prescribed value α 2  and extension of the prescribed time TM 1  or may decide either one of them. 
     &lt;Control Flow Example of Modified Example of First Embodiment&gt; 
       FIG. 9  is one example of a control flow of the controller according to the modified example of this first embodiment. Note that  FIG. 9  differs from  FIG. 7  in points that step S 27  is added and contents of step S 28  and step S 29  are changed from those of step S 7  and step S 8 . Because step S 20  to step S 26  and step S 30  to step S 32  in  FIG. 9  are respectively the same as step S 0  to step S 6  and step S 9  to step S 11  in  FIG. 7 , the description thereon will not be made. 
     (Step S 27 : Acquisition of Prescribed Value α 2  and Prescribed Time TM 1 ) 
     The decision section  7 B 2  of the control section  7  obtains the prescribed value α 2  and the prescribed time TM 1  from the memory section  7 C. Prior to step S 27 , the prescribed value α 2  and the prescribed time TM 1  are computed by using the inclination value θ, which is computed immediately before the motorcycle  200  is stopped, and are stored in the memory section  7 C. 
     (Step S 28 : Change in Reduction Amount α of Brake Force Per Time) 
     The decision section  7 B 2  of the control section  7  changes the reduction amount α of the brake force per time from the prescribed value α 1  to the prescribed value α 2  that is computed by the computation section  7 B 4 . Then, the control section  7  controls the switching valve  10  such that the reduction amount α of the brake force per time becomes the prescribed value α 2 . 
     (Step S 29 : Determination Related to Prescribed Time TM 1 ) 
     After controlling the switching valve  10  by setting the reduction amount α of the brake force per time to the prescribed value α 2 , the determination section  7 B 1  of the control section  7  determines whether the prescribed time TM 1 , which is computed by the computation section  7 B 4 , has elapsed. 
     If it is determined that the prescribed time TM 1  has elapsed, the process proceeds to step S 30 . 
     If it is determined that the prescribed time TM 1  has not elapsed, the process returns to step S 28 . 
     &lt;Effects that Controller  1  According to the Modified Example of this First Embodiment has&gt; 
     Preferably, in accordance with the inclination value θ of the road surface, the control section  7  decides the time TM, in which the reduction amount α of the brake force per time is reduced to be smaller than the reduction amount α of the brake force per time prior to the determination that the motorcycle  200  starts moving. In other words, the control section  7  decides the prescribed time TM 1  in accordance with the inclination value θ. 
     In addition, preferably, in accordance with the inclination value θ of the road surface, the control section  7  decides a degree of reducing the reduction amount α of the brake force per time to make it smaller than the reduction amount α of the brake force per time prior to the determination that the motorcycle  200  starts moving. 
     For example, even in the case where the wheel speed (the vehicle body speed) of the motorcycle  200  at the time when it is determined that the motorcycle  200  starts moving is changed in accordance with the inclination value θ of the uphill road surface, the movement of the motorcycle  200  can further reliably be made gentle. 
     Second Embodiment 
     In the following description, a description that overlaps that of the first embodiment will not be made, and only different portions will be described. 
       FIG. 10  is a functional block diagram of various sensors, a control section, and various actuators provided in a hydraulic pressure control system that includes a controller according to this second embodiment. A description will be made on the second embodiment with reference to  FIG. 10 . 
     In the first embodiment, it is determined whether to execute the hill-hold control by using the on/off signal of the switch  8 A. Instead of the above, in the second embodiment, it is determined whether to execute the hill-hold control by using a detection signal of an acceleration sensor (a detection section AS). In other words, instead of the switch  8 A, the acceleration sensor is provided in the controller  1 . 
     In addition, in the first embodiment, the initiation of the movement of the motorcycle  200  is determined on the basis of the detection section WS as the wheel speed sensor. Meanwhile, in the second embodiment, the initiation of the movement of the motorcycle  200  is determined on the basis of the detection section AS as the acceleration sensor. 
     On the basis of the inclination value θ that is computed by the computation section  7 B 4  from a detection signal of the detection section AS as the acceleration sensor, the determination section  7 B 1  determines whether the motorcycle  200  is on the inclined road surface. In addition, when determining that the motorcycle  200  is on the inclined road surface, that the motorcycle  200  is stopped, and that the brake operation section is released, the determination section  7 B 1  determines to execute the retention mode of the hill-hold control. Furthermore, when the cancellation mode is executed, the determination section  7 B 1  determines on the basis of the detection signal of the detection section AS whether the motorcycle  200  starts moving. 
     &lt;Control Flow Example of Second Embodiment&gt; 
       FIG. 11  is one example of a control flow of the controller according to this second embodiment.  FIG. 11  differs from  FIG. 7  in a point that contents of step S 41  and step S 46  are changed from those of step S 1  and step S 6 . Because step S 40 , step S 42  to step S 45 , and step S 47  to step S 51  in  FIG. 11  are respectively the same as step S 0 , step S 2  to step S 5 , and step S 7  to step S 11  in  FIG. 7 , the description thereon will not be made. 
     (Step S 41 : Determination Related to Inclination) 
     On the basis of the detection signal of the detection section AS as the acceleration sensor, the determination section  7 B 1  of the control section  7  determines whether the motorcycle  200  is on the inclined road surface. 
     If it is determined that the motorcycle  200  is on the inclined road surface, the process proceeds to step S 42 . 
     If it is determined that the motorcycle  200  is not on the inclined road surface, step S 41  is repeated. 
     (Step S 46 : Determination Related to Initiation of Movement of Motorcycle  200  and the Like) 
     The determination section  7 B 1  of the control section  7  determines whether the cylinder pressure is higher than the first prescribed pressure, and also determines on the basis of the detection signal of the detection section AS whether the motorcycle  200  starts moving. 
     If it is determined that the cylinder pressure is higher than the first prescribed pressure and it is determined that the motorcycle  200  starts moving, the process proceeds to step S 47 . 
     If it is determined that the cylinder pressure is higher than the first prescribed pressure and it is determined that the motorcycle  200  does not start moving, the process returns to step S 45 . 
     If it is determined that the cylinder pressure is not higher than the first prescribed pressure, the process proceeds to step S 49  regardless of the determination related to the initiation of the movement. 
     &lt;Effects that Controller  1  According to this Second Embodiment has&gt; 
     Preferably, the detection section AS of the controller  1  is the acceleration sensor that detects acceleration acting on the motorcycle  200 . In other words, similar effects to those of the controller  1  according to the first embodiment can be obtained by using the acceleration sensor (the detection section AS) instead of the wheel speed sensor. 
     Note that, in the case where the controller  1  includes the detection section AS, the determination section  7 B 1  of the control section  7  can determine whether the road surface is inclined even when the occupant does not perform the operation of the switch  8 A or the like on the inclined road surface. Thus, a burden on the occupant can be reduced. 
     &lt;Modified Example of Second Embodiment&gt; 
     In the modified example of the first embodiment, it is determined whether to execute the hill-hold control by using the on/off signal of the switch  8 A. Instead of the above, in a modified example of the second embodiment, it is determined whether to execute the hill-hold control by using the detection signal of the acceleration sensor (the detection section AS). In addition, in the modified example of the second embodiment, the initiation of the movement of the motorcycle  200  is determined on the basis of the detection section AS as the acceleration sensor. Furthermore, in the modified example of the second embodiment, the inclination value θ of the road surface is obtained from the detection signal of the detection section AS. 
       FIG. 12  is one example of a control flow of a controller according to the modified example of this second embodiment. Note that  FIG. 12  differs from  FIG. 9  in a point that contents of step S 61 , step S 66 , and step S 67  are changed from those of step S 21 , step S 26 , and step S 27 . Because step S 60 , step S 62  to step S 65 , and step S 68  to step S 72  in  FIG. 12  are respectively the same as step S 20 , step S 22  to step S 25 , and step S 28  to step S 32  in  FIG. 9 , the description thereon will not be made. In addition, because step S 61  and step S 66  are respectively the same as step S 41  and step S 46  in  FIG. 11 , the description thereon will not be made. 
     (Step S 67 : Acquisition of Prescribed Value α 2  and Prescribed Time TM 1 ) 
     The decision section  7 B 2  of the control section  7  obtains the prescribed value α 2  and the prescribed time TM 1  from the memory section  7 C. Prior to step S 67 , the prescribed value α 2  and the prescribed time TM 1  are computed by using the inclination value θ, which is computed by using the detection signal of the acceleration sensor (the detection section AS), and are stored in the memory section  7 C. As the inclination value θ, the inclination value θ that is used for the determination in step S 61  is preferably used. 
     &lt;Effects that Controller  1  According to Modified Example of this Second Embodiment has&gt; 
     Similar effects to the effects obtained by the modified example of the first embodiment and the effects that the controller  1  according to the second embodiment has can be obtained. 
     Note that the brake force of either one of the front wheel  20  and the rear wheel  30  may be retained, or the brake forces of both of the front wheel  20  and the rear wheel  30  may be retained in the retention mode of the hill-hold control in each of the first embodiment, the modified example thereof, the second embodiment, and the modified example thereof. Whether to select either one of the front wheel  20  and the rear wheel  30  or both of the front wheel  20  and the rear wheel  30  may be switched in accordance with the inclination value θ that is obtained by the control section  7 , for example. 
     The description has been made so far on the first embodiment, the modified example thereof, the second embodiment, and the modified example thereof. However, the invention is not limited to the description of each of these. For example, a whole or a part of each of the embodiments and each of the modified examples may be combined. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 : Controller 
               2 : Pump device 
               2 A: Drive mechanism 
               2 B: Pump element 
               3 : Regulating valve 
               3 A: First pressure boosting valve 
               3 B: First pressure reducing valve 
               3 C: Second pressure boosting valve 
               3 D: Second pressure reducing valve 
               4 : Internal channel 
               4 A: Internal channel 
               4 B: Internal channel 
               5 : Float restrictor 
               6 : Accumulator 
               7 : Control section 
               7 A: Input section 
               7 B: Processor section 
               7 B 1 : Determination section 
               7 B 2 : Decision section 
               7 B 3 : Timer section 
               7 B 4 : Computation section 
               7 B 5 : Drive mechanism control section 
               7 B 6 : Valve control section 
               7 C: Memory section 
               8 : Detection mechanism 
               8 A: Switch 
               8 B 1 : Position detection sensor 
               8 B 2 : Position detection sensor 
               8 C 1 : Detection section 
               8 C 2 : Detection section 
               8 D: Pressure sensor 
               10 : Switching valve 
               10 A: Switching valve 
               10 B: Switching valve 
               11 : Inlet valve 
               11 A: Inlet valve 
               11 B: Inlet valve 
               20 : Front wheel 
               21 : Front brake pad 
               22 : Front wheel cylinder 
               23 : Brake fluid pipe 
               24 : Handlebar lever 
               25 : First master cylinder 
               26 : First reservoir 
               27 : Brake fluid pipe 
               30 : Rear wheel 
               31 : Rear brake pad 
               32 : Rear wheel cylinder 
               33 : Brake fluid pipe 
               34 : Foot pedal 
               35 : Second master cylinder 
               36 : Second reservoir 
               37 : Brake fluid pipe 
               100 : Hydraulic pressure control system 
               200 : Motorcycle 
             AS: Detection section 
             B: Vehicle body 
             C 1 : Front-wheel hydraulic circuit 
             C 2 : Rear-wheel hydraulic circuit 
             P: Port 
             SW: Position detection sensor 
             T 1 : Arithmetic section 
             T 2 : Actuator control section 
             W: Wheel 
             WS: Detection section 
             α: Reduction amount per time 
             α 1 : Prescribed value 
             α 2 : Prescribed value 
             θ: Inclination value