Patent Description:
As a conventional technique related to a straddle-type vehicle, a technique of assisting with a rider's operation is available.

For example, a driver assistance system is disclosed in PTL <NUM>. Based on information detected by a sensor that detects an obstacle present in a travel direction or substantially in the travel direction, the driver assistance system warns a motorcycle rider that the motorcycle inappropriately approaches the obstacle.

By the way, as the technique of assisting with the rider's operation, it is considered to apply the following control to the straddle-type vehicle such as the motorcycle. In the control, the vehicle is made to execute automatic emergency deceleration operation when a collision possibility occurs to the vehicle. The straddle-type vehicle tends to have an unstable posture in comparison with a four-wheeled vehicle, for example. Accordingly, the straddle-type vehicle exhibits behavior unintended by the rider due to automatic exertion of a braking force on the straddle-type vehicle during execution of such control, which possibly worsens the rider's comfort. The rider's comfort can be improved by braking the straddle-type vehicle such that the braking force is only generated to a rear wheel. However, in such a case, braking efficiency is possibly worsens as a force remains in a front-wheel brake mechanism that is more favorable for braking of the straddle-type vehicle than a rear-wheel brake mechanism.

The present invention has been made with the above-described problem as the background and therefore obtains a controller and a control method capable of appropriately executing automatic emergency deceleration operation of a straddle-type vehicle.

A controller according to the present invention is defined in independent claim <NUM>.

A control method according to the present invention is defined in independent claim <NUM>.

In the controller and the control method according to the present invention, when the automatic emergency deceleration operation of the straddle-type vehicle is executed, at the braking start time point at which the braking force starts being generated on the wheels, the braking force distribution between the front and rear wheels is brought into the initial state where the braking force is generated on the front wheel. As a result, at the braking start time point, it is possible to prevent generation of a force remaining in a brake mechanism for the front wheel that is more favorable for braking of the straddle-type vehicle than a brake mechanism for the rear wheel. Therefore, the automatic emergency deceleration operation of the straddle-type vehicle can appropriately be executed.

A description will hereinafter be made on a controller according to the present invention with reference to the drawings. Hereinafter, a description will be made on the controller used for a two-wheeled motorcycle. However, the controller according to the present invention may be used for a straddle-type vehicle other than the two-wheeled motorcycle (for example, a three-wheeled motorcycle, an all-terrain vehicle, a bicycle, or the like). The straddle-type vehicle means a vehicle that a rider straddles. In addition, a description will hereinafter be made on a case where an engine is mounted as a drive source capable of outputting power for driving wheels of the motorcycle. However, as the drive source for the motorcycle, a drive source other than the engine (for example, a motor) may be mounted, or a plurality of the drive sources may be mounted.

A configuration, operation, and the like, which will be described below, merely constitute one example. The controller and the control method according to the present invention are not limited to a case with such a configuration, such operation, and the like. Modifications are possible within the scope of the invention, as defined in the appended claims.

The same or similar description will appropriately be simplified or will not be made below. In the drawings, the same or similar members or portions will not be denoted by a reference sign or will be denoted by the same reference sign. In addition, a detailed structure will appropriately be illustrated in a simplified manner or will not be illustrated.

A description will be made on a configuration of a motorcycle <NUM> to which a controller <NUM> according to an embodiment of the present invention is mounted with reference to <FIG>.

<FIG> is a schematic view of the outline configuration of the motorcycle <NUM> to which the controller <NUM> is mounted. <FIG> is a schematic view of an outline configuration of a brake system <NUM>. <FIG> is a block diagram of an exemplary functional configuration of the controller <NUM>.

As illustrated in <FIG>, the motorcycle <NUM> includes: a trunk <NUM>; a handlebar <NUM> that is held by the trunk <NUM> in a freely turnable manner; a front wheel <NUM> that is held by the trunk <NUM> in the freely turnable manner with the handlebar <NUM>; a rear wheel <NUM> that is held by the trunk <NUM> in a freely rotatable manner; an engine <NUM>; and the brake system <NUM>. In this embodiment, the controller (ECU) <NUM> is provided to a hydraulic pressure control unit <NUM> in the brake system <NUM>, which will be described later. As illustrated in <FIG> and <FIG>, the motorcycle <NUM> further includes a surrounding environment sensor <NUM>, an input device <NUM>, an inertial measurement unit (IMU) <NUM>, a master-cylinder pressure sensor <NUM>, and a wheel-cylinder pressure sensor <NUM>. The motorcycle <NUM> corresponds to an example of the "straddle-type vehicle" in the present invention.

The engine <NUM> corresponds to an example of a drive source for the motorcycle <NUM>, and can output power for driving the wheel (more specifically, the rear wheel <NUM>). For example, the engine <NUM> is provided with: one or multiple cylinders, each of which is formed with a combustion chamber therein; a fuel injector that injects fuel into the combustion chamber; and an ignition plug. When the fuel is injected from the fuel injector, air-fuel mixture containing air and the fuel is produced in the combustion chamber, and the air-fuel mixture is then ignited by the ignition plug and burned. Consequently, a piston provided in the cylinder reciprocates to cause a crankshaft to rotate. In addition, a throttle valve is provided to an intake pipe of the engine <NUM>, and an intake air amount for the combustion chamber varies according to a throttle opening amount as an opening degree of the throttle valve.

As illustrated in <FIG> and <FIG>, the brake system <NUM> includes: a first brake operation section <NUM>; a front-wheel brake mechanism <NUM> that brakes the front wheel <NUM> in an interlocking manner with at least the first brake operation section <NUM>; a second brake operation section <NUM>; and a rear-wheel brake mechanism <NUM> that brakes the rear wheel <NUM> in an interlocking manner with at least the second brake operation section <NUM>. The brake system <NUM> also includes the hydraulic pressure control unit <NUM>, and the front-wheel brake mechanism <NUM> and the rear-wheel brake mechanism <NUM> are partially included in the hydraulic pressure control unit <NUM>. The hydraulic pressure control unit <NUM> is a unit that has a function of controlling a braking force to be generated on the front wheel <NUM> by the front-wheel brake mechanism <NUM> and a braking force to be generated on the rear wheel <NUM> by the rear-wheel brake mechanism <NUM>.

The first brake operation section <NUM> is provided to the handlebar <NUM> and is operated by the rider's hand. The first brake operation section <NUM> is a brake lever, for example. The second brake operation section <NUM> is provided to a lower portion of the trunk <NUM> and is operated by the rider's foot. The second brake operation section <NUM> is a brake pedal, for example.

Each of the front-wheel brake mechanism <NUM> and the rear-wheel brake mechanism <NUM> includes: a master cylinder <NUM> in which a piston (not illustrated) is installed; a reservoir <NUM> that is attached to the master cylinder <NUM>; a brake caliper <NUM> that is held by the trunk <NUM> and has a brake pad (not illustrated); a wheel cylinder <NUM> that is provided to the brake caliper <NUM>; a primary channel <NUM> through which a brake fluid in the master cylinder <NUM> flows into the wheel cylinder <NUM>; a secondary channel <NUM> through which the brake fluid in the wheel cylinder <NUM> is released; and a supply channel <NUM> through which the brake fluid in the master cylinder <NUM> is supplied to the secondary channel <NUM>.

An inlet valve (EV) <NUM> is provided to the primary channel <NUM>. The secondary channel <NUM> bypasses a portion of the primary channel <NUM> between the wheel cylinder <NUM> side and the master cylinder <NUM> side from the inlet valve <NUM>. The secondary channel <NUM> is sequentially provided with an outlet valve (AV) <NUM>, an accumulator <NUM>, and a pump <NUM> from an upstream side. Between an end of the primary channel <NUM> on the master cylinder <NUM> side and a portion of the primary channel <NUM> to which a downstream end of the secondary channel <NUM> is connected, a first valve (USV) <NUM> is provided. The supply channel <NUM> communicates between the master cylinder <NUM> and a portion of the secondary channel <NUM> on a suction side of the pump <NUM>. A second valve (HSV) <NUM> is provided to the supply channel <NUM>.

The inlet valve <NUM> is an electromagnetic valve that is opened in an unenergized state and closed in an energized state, for example. The outlet valve <NUM> is an electromagnetic valve that is closed in an unenergized state and opened in an energized state, for example. The first valve <NUM> is an electromagnetic valve that is opened in an unenergized state and is closed in an energized state, for example. The second valve <NUM> is an electromagnetic valve that is closed in an unenergized state and is opened in an energized state, for example.

The hydraulic pressure control unit <NUM> includes: components such as the inlet valves <NUM>, the outlet valves <NUM>, the accumulators <NUM>, the pumps <NUM>, the first valves <NUM>, and the second valves <NUM> used to control a brake hydraulic pressure; a base body <NUM> to which those components are provided and channels constituting the primary channels <NUM>, the secondary channels <NUM>, and the supply channels <NUM> are formed; and the controller <NUM>.

The base body <NUM> may be formed of one member or may be formed of multiple members. In the case where the base body <NUM> is formed of the multiple members, the components may separately be provided to the different members.

The controller <NUM> controls operation of each of the components of the hydraulic pressure control unit <NUM>. As a result, the braking force to be generated on the front wheel <NUM> by the front-wheel brake mechanism <NUM> and the braking force to be generated on the rear wheel <NUM> by the rear-wheel brake mechanism <NUM> are controlled.

For example, in a normal time (that is, when none of automatic emergency deceleration operation and anti-lock brake control, which will be described later, is executed), the controller <NUM> opens the inlet valves <NUM>, closes the outlet valves <NUM>, opens the first valves <NUM>, and closes the second valves <NUM>. When the first brake operation section <NUM> is operated in such a state, in the front-wheel brake mechanism <NUM>, the piston (not illustrated) in the master cylinder <NUM> is pressed to increase a hydraulic pressure of the brake fluid in the wheel cylinder <NUM>, the brake pad (not illustrated) of the brake caliper <NUM> is then pressed against a rotor 3a of the front wheel <NUM>, and the braking force is thereby generated on the front wheel <NUM>. Meanwhile, when the second brake operation section <NUM> is operated, in the rear-wheel brake mechanism <NUM>, the piston (not illustrated) in the master cylinder <NUM> is pressed to increase the hydraulic pressure of the brake fluid in the wheel cylinder <NUM>, the brake pad (not illustrated) of the brake caliper <NUM> is then pressed against a rotor 4a of the rear wheel <NUM>, and the braking force is thereby generated on the rear wheel <NUM>.

During travel of the motorcycle <NUM>, the surrounding environment sensor <NUM> constantly detects an index value I that represents a collision possibility of the motorcycle <NUM> with a target (an obstacle, a vehicle, a person, an animal, or the like) within a detection range.

As the surrounding environment sensor <NUM>, a radar, a camera, or the like is used, for example. The radar, the camera, or the like can detect a relative distance Dr and a relative speed Vr of the target (the obstacle, the vehicle, the person, the animal, or the like) in a travel direction of the motorcycle <NUM> to the motorcycle <NUM>. The surrounding environment sensor <NUM> is provided to a front portion of the trunk <NUM>, for example. The configuration of the surrounding environment sensor <NUM> is not limited to the above example. For example, the surrounding environment sensor <NUM> may detect the relative distance Dr and the relative speed Vr of the target that is predicted to enter the travel direction of the motorcycle <NUM>, or may detect the relative distance Dr and the relative speed Vr of the target that possibly collides with a side portion of the motorcycle <NUM>. The surrounding environment sensor <NUM> may detect relative acceleration Ar in addition to the relative distance Dr and the relative speed Vr of the target. The surrounding environment sensor <NUM> may detect other physical quantities that can substantially be converted to the relative distance Dr, the relative speed Vr, the relative acceleration Ar, and the like of the target.

For example, the surrounding environment sensor <NUM> derives the index value I that represents the collision possibility as a value that is defined by Formula <NUM> or Formula <NUM> below. Here, it means that the collision possibility becomes higher as the index value I is increased. Alternatively, the index value I that represents the collision possibility may be derived by the controller <NUM>, which will be described later. <MAT><MAT>.

The input device <NUM> accepts a travel mode selecting operation by the rider, and outputs information on the travel mode selected by the rider. As will be described later, in the motorcycle <NUM>, the controller <NUM> can execute a mode in which the motorcycle <NUM> is made to execute the automatic emergency deceleration operation. The automatic emergency deceleration operation is operation to automatically decelerate the motorcycle <NUM> under a situation where it is determined that the collision possibility of the motorcycle <NUM> with the target (the obstacle, the vehicle, the person, the animal, or the like) is high. By using the input device <NUM>, the rider can input whether the rider desires to make the motorcycle <NUM> execute the automatic emergency deceleration operation. For example, as the input device <NUM>, a lever, a button, a touchscreen, or the like is used. The input device <NUM> is provided to the handlebar <NUM>, for example.

The IMU <NUM> includes a three-axis gyroscope sensor and a three-directional acceleration sensor, and detects a posture of the motorcycle <NUM>. For example, the IMU <NUM> detects a pitch angle of the motorcycle <NUM>, and outputs a detection result. The IMU <NUM> may detect another physical quantity that can substantially be converted to the pitch angle of the motorcycle <NUM>. The pitch angle corresponds to an angle that indicates an inclination of the trunk <NUM> of the motorcycle <NUM> in a pitch direction (that is, a rotational direction P around a rotation axis along a vehicle width direction illustrated in <FIG>) with respect to a horizontal direction. The IMU <NUM> is provided to the trunk <NUM>, for example. In the motorcycle <NUM>, a sensor only having a function of detecting the pitch angle may be used instead of the IMU <NUM>.

The master-cylinder pressure sensor <NUM> detects the hydraulic pressure of the brake fluid in the master cylinder <NUM>, and outputs a detection result. The master-cylinder pressure sensor <NUM> may detect another physical quantity that can substantially be converted to the hydraulic pressure of the brake fluid in the master cylinder <NUM>. The master-cylinder pressure sensor <NUM> is provided to each of the front-wheel brake mechanism <NUM> and the rear-wheel brake mechanism <NUM>.

The wheel-cylinder pressure sensor <NUM> detects the hydraulic pressure of the brake fluid in the wheel cylinder <NUM>, and outputs a detection result. The wheel-cylinder pressure sensor <NUM> may detect another physical quantity that can substantially be converted to the hydraulic pressure of the brake fluid in the wheel cylinder <NUM>. The wheel-cylinder pressure sensor <NUM> is provided to each of the front-wheel brake mechanism <NUM> and the rear-wheel brake mechanism <NUM>.

The controller <NUM> controls the travel of the motorcycle <NUM>.

For example, the controller <NUM> is partially or entirely constructed of a microcomputer, a microprocessor unit, or the like. Alternatively, the controller <NUM> may partially or entirely be constructed of a member in which firmware or the like can be updated, or may partially or entirely be a program module or the like that is executed by a command from a CPU or the like, for example. The controller <NUM> may be provided as one unit or may be divided into multiple units, for example.

As illustrated in <FIG>, the controller <NUM> includes an acquisition section <NUM> and an execution section <NUM>, for example.

The acquisition section <NUM> acquires information that is output from each of the devices mounted to the motorcycle <NUM>, and outputs the acquired information to the execution section <NUM>. For example, the acquisition section <NUM> acquires the information output from the surrounding environment sensor <NUM>, the input device <NUM>, the IMU <NUM>, the master-cylinder pressure sensor <NUM>, and the wheel-cylinder pressure sensor <NUM>.

The execution section <NUM> controls operation of each of the devices mounted to the motorcycle <NUM>, so as to control drive power and the braking force exerted on the motorcycle <NUM>.

Here, the execution section <NUM> controls the operation of each of the devices mounted to the motorcycle <NUM>, and can thereby execute the automatic emergency deceleration operation. More specifically, the execution section <NUM> executes the automatic emergency deceleration operation in the case where a desire for making the motorcycle <NUM> execute the automatic emergency deceleration operation is input to the input device <NUM> and it is determined that the collision possibility of the motorcycle <NUM> with the target (the obstacle, the vehicle, the person, the animal, or the like) is high. The execution section <NUM> cancels the automatic emergency deceleration operation in the case where it is determined that the collision possibility of the motorcycle <NUM> with the target becomes low due to a change in the travel direction by the rider, movement of the target, or the like, for example.

In the automatic emergency deceleration operation, the motorcycle <NUM> is controlled to be stopped in front of the target (the obstacle, the vehicle, the person, the animal, or the like). A degree of deceleration may be limited to be equal to or lower than a certain magnitude of the deceleration.

More specifically, the execution section <NUM> acquires the index value I that represents the collision possibility and is acquired by the acquisition section <NUM>. Then, in the case where the index value I is larger than a reference index value, the execution section <NUM> calculates a target value of the deceleration (hereinafter referred to as target deceleration) on the basis of the index value I, and controls the drive power and the braking force to be exerted on the motorcycle <NUM> on the basis of a calculation result. For example, the execution section <NUM> increases the target deceleration as the index value I is increased. The target deceleration may be set to a fixed value.

The execution section <NUM> includes a drive control section 62a and a brake control section 62b, for example.

The drive control section 62a controls the drive power that is transmitted to the wheel of the motorcycle <NUM> during the automatic emergency deceleration operation. More specifically, during the automatic emergency deceleration operation, the drive control section 62a outputs a command to an engine control unit (not illustrated), which outputs a signal used to control operation of each of the components of the engine <NUM> (the throttle valve, the fuel injector, the ignition plug, and the like). In this way, the drive control section 62a controls operation of the engine <NUM>. As a result, during the automatic emergency deceleration operation, the drive power that is transmitted to the wheel is controlled.

In the normal time, the operation of the engine <NUM> is controlled by the engine control unit such that the drive power is transmitted to the wheel in response to the rider's accelerator operation.

Meanwhile, during the automatic emergency deceleration operation, the drive control section 62a controls the operation of the engine <NUM> such that the drive power is transmitted to the wheel without relying on the rider's accelerator operation. More specifically, during the automatic emergency deceleration operation, the drive control section 62a controls the operation of the engine <NUM> to reduce the drive power that is transmitted to the wheel, and controls the drive power that is transmitted to the wheel.

The brake control section 62b controls the operation of each of the components of the hydraulic pressure control unit <NUM> in the brake system <NUM>, so as to control the braking force generated on each of the wheels of the motorcycle <NUM>.

In the normal time, as described above, the brake control section 62b controls the operation of each of the components of the hydraulic pressure control unit <NUM> such that the braking force is generated on each of the wheels in response to the rider's brake operation.

Meanwhile, during the automatic emergency deceleration operation, the brake control section 62b controls the operation of each of the components such that the braking force is generated on each of the wheels without relying on the rider's brake operation. More specifically, during the automatic emergency deceleration operation, the brake control section 62b controls the operation of each of the components of the hydraulic pressure control unit <NUM> such that the deceleration of the motorcycle <NUM> becomes the target deceleration, which is calculated on the basis of the index value I representing the collision possibility, and controls the braking force generated on each of the wheels.

For example, during the automatic emergency deceleration operation, the brake control section 62b brings the motorcycle <NUM> into a state where the inlet valves <NUM> are opened, the outlet valves <NUM> are closed, the first valves <NUM> are closed, and the second valves <NUM> are opened, and drives the pumps <NUM> in such a state, so as to increase the hydraulic pressure of the brake fluid in each of the wheel cylinders <NUM> and generate the braking force on each of the wheels. In addition, the brake control section 62b adjusts the hydraulic pressure of the brake fluid in each of the wheel cylinders <NUM> by controlling an opening amount of the first valves <NUM>, for example. In this way, the brake control section 62b can control the braking force generated on each of the wheels.

Here, during the automatic emergency deceleration operation, the brake control section 62b separately controls operation of each of the front-wheel brake mechanism <NUM> and the rear-wheel brake mechanism <NUM>, so as to separately control the hydraulic pressure of the brake fluid in the wheel cylinder <NUM> of each of the front-wheel brake mechanism <NUM> and the rear-wheel brake mechanism <NUM>. In this way, the brake control section 62b can control braking force distribution between the front and rear wheels (that is, distribution of the braking force generated on the front wheel <NUM> and the braking force generated on the rear wheel <NUM>). More specifically, the brake control section 62b controls the braking force distribution between the front and rear wheels such that a total target value of the braking forces generated on the wheels becomes a requested braking force (that is, the braking force that is requested at the time of braking during the automatic emergency deceleration operation) corresponding to the target deceleration. More specifically, the requested braking force is a required braking force for bringing the deceleration of the motorcycle <NUM> to the target deceleration that is calculated on the basis of the index value I representing the collision possibility.

In the case where at least one of the wheels is locked or possibly locked, the brake control section 62b may execute the anti-lock brake control. The anti-lock brake control is control for adjusting the braking force of the wheel, which is locked or possibly locked, to such a magnitude of the braking force with which locking of the wheel can be avoided.

For example, during the anti-lock brake control, the brake control section 62b brings the motorcycle <NUM> into a state where the inlet valves <NUM> are closed, the outlet valves <NUM> are opened, the first valves <NUM> are opened, and the second valves <NUM> are closed, and drives the pumps <NUM> in such a state, so as to reduce the hydraulic pressure of the brake fluid in each of the wheel cylinders <NUM> and reduce the braking force generated on each of the wheels. In addition, the brake control section 62b closes both of the inlet valves <NUM> and the outlet valves <NUM> from the above state, for example. In this way, the brake control section 62b can keep the hydraulic pressure of the brake fluid in each of the wheel cylinders <NUM>, and thus can keep the braking force generated on each of the wheels. Furthermore, the brake control section 62b opens the inlet valves <NUM> and closes the outlet valves <NUM> from the above state, for example. In this way, the brake control section 62b can increase the hydraulic pressure of the brake fluid in each of the wheel cylinders <NUM>, and thus can increase the braking force generated on each of the wheels.

As described above, in the controller <NUM>, the execution section <NUM> can execute the automatic emergency deceleration operation. When executing the automatic emergency deceleration operation, at a braking start time point at which the braking force starts being generated on each of the wheels, the execution section <NUM> brings the braking force distribution between the front and rear wheels into an initial state where the braking force is generated on the front wheel <NUM>. Then, with a lapse of time, the execution section <NUM> increases a distribution ratio for the rear wheel <NUM> in the braking force distribution. In this way, the automatic emergency deceleration operation of the motorcycle <NUM> is appropriately executed. A detailed description will be made later on processing related to braking control for the wheels during such automatic emergency deceleration operation that is executed by the controller <NUM>.

The description has been made above on the example in which the drive control section 62a controls the operation of the engine <NUM> via the engine control unit. However, the drive control section 62a may output a signal for controlling the operation of each of the components of the engine <NUM>, so as to directly control the operation of each of the components of the engine <NUM>. In such a case, similar to the operation of the engine <NUM> during the automatic emergency deceleration operation, the drive control section 62a controls the operation of the engine <NUM> in the normal time.

A description will be made on operation of the controller <NUM> according to the embodiment of the present invention with reference to <FIG>.

<FIG> is a flowchart of an exemplary processing procedure that is executed by the controller <NUM>. More specifically, the control flow illustrated in <FIG> is repeatedly executed in the case where the desire for making the motorcycle <NUM> execute the automatic emergency deceleration operation is input to the input device <NUM>. In addition, step S510 and step S590 in <FIG> respectively correspond to initiation and termination of the control flow illustrated in <FIG>.

When the control flow illustrated in <FIG> is initiated, in step S511, the acquisition section <NUM> executes an acquisition step of acquiring the index value I that represents the collision possibility of the motorcycle <NUM>, and thereafter the execution section <NUM> determines whether a request to initiate the automatic emergency deceleration operation of the motorcycle <NUM> is made on the basis of the index value I. If the execution section <NUM> determines that the request to initiate the automatic emergency deceleration operation of the motorcycle <NUM> is made (step S511/YES), the processing proceeds to step S513. On the other hand, if the execution section <NUM> determines that the request to initiate the automatic emergency deceleration operation of the motorcycle <NUM> is not made (step S511/NO), the determination processing in step S511 is repeated.

For example, in the case where the execution section <NUM> determines that the index value I is larger than the reference index value, the execution section <NUM> determines that the request to initiate the automatic emergency deceleration operation of the motorcycle <NUM> is made. The reference index value may be a fixed value or a variable that varies according to a travel state of the motorcycle <NUM>, a road surface condition, or the like.

If it is determined YES in step S511 and the drive power that is transmitted to the wheel is present, in step S513, the drive control section 62a reduces such drive power. The brake control section 62b also starts braking the wheels of the motorcycle <NUM>. More specifically, during braking of the wheels, as described above, the brake control section 62b controls the braking force generated on each of the wheels such that the deceleration of the motorcycle <NUM> becomes the target deceleration that is calculated on the basis of the index value I representing the collision possibility.

Here, at the braking start time point at which the braking force starts being generated on each of the wheels, the brake control section 62b brings the braking force distribution between the front and rear wheels into the initial state where the braking force is generated on the front wheel <NUM>.

At the braking start time point, the braking force distribution is brought into the initial state where the braking force is generated on the front wheel <NUM>. Thus, at the braking start time point, it is possible to suppress generation of the force remaining in the brake mechanism for the front wheel <NUM> that is more favorable for braking of the straddle-type vehicle than the brake mechanism for the rear wheel <NUM>. In addition, from a perspective of further effectively suppressing the generation of the force that remains in the brake mechanism for the front wheel <NUM> at the braking start time point, in the above initial state, the brake control section 62b preferably causes the braking force to be only generated on the front wheel <NUM>. In addition, from a perspective of suppressing a forward tilt of the motorcycle <NUM> at the braking start time point, the brake control section 62b preferably causes the braking force to be generated on the rear wheel <NUM> in addition to the front wheel <NUM> in the above initial state.

Next, in step S515, the execution section <NUM> determines whether the rider's riding posture is appropriate as a posture during the deceleration. If the execution section <NUM> determines that the rider's riding posture is inappropriate as the posture during the deceleration (step S515/NO), the processing proceeds to step S517. On the other hand, if the execution section <NUM> determines that the rider's riding posture is appropriate as the posture during the deceleration (step S515/YES), the processing proceeds to step S519. More specifically, in the case where the execution section <NUM> determines that the rider's riding posture is inappropriate as the posture during the deceleration, the execution section <NUM> reduces the distribution ratio for the front wheel <NUM> in comparison with the case where the execution section <NUM> does not determine that the rider's riding posture is inappropriate. The execution section <NUM> may determine whether the rider's riding posture is appropriate as the posture during the deceleration prior to step S513. Then, at a time point at which the braking force distribution is brought into the initial state, the execution section <NUM> may reduce the distribution ratio for the front wheel <NUM>.

More specifically, the riding posture that is inappropriate as the posture during the deceleration means such a posture that the rider is not ready for behavior of the motorcycle <NUM> during the deceleration and thus the rider possibly falls off the motorcycle <NUM>.

For example, when determining that the rider does not grasp the handlebar <NUM>, the execution section <NUM> determines that the rider's riding posture is inappropriate as the posture during the deceleration. The determination on whether the rider grasps the handlebar <NUM> can be made by using a proximity sensor provided to the handlebar <NUM>, for example.

In addition, for example, when determining that the rider does not hold the trunk <NUM> between both of his/her legs, the execution section <NUM> determines that the rider's riding posture is inappropriate as the posture during the deceleration. The determination on whether the rider holds the trunk <NUM> between both of his/her legs can be made by using a proximity sensor provided to the trunk <NUM>, for example.

In addition, for example, when determining that the rider's line of sight is not oriented to the front, the execution section <NUM> determines that the rider's riding posture is inappropriate as the posture during the deceleration. The determination on whether the rider's line of sight is oriented to the front can be made by using a device that captures an image of the rider's face and performs image processing on the acquired image to detect the rider's line of sight, for example.

If it is determined NO in step S515, in step S517, the brake control section 62b increases the distribution ratio for the rear wheel <NUM> in the braking force distribution between the front and rear wheels with the lapse of time.

In a process of increasing the distribution ratio for the rear wheel <NUM> in the braking force distribution between the front and rear wheels, as described above, the braking force distribution between the front and rear wheels is controlled such that the total value of the target values of the braking forces generated on the wheels becomes the requested braking force. Accordingly, for example, under a situation where the deceleration of the motorcycle <NUM> remains constant (that is, the requested braking force remains constant) for a specified period from the braking start time point, in such a specified period, the braking force generated on the rear wheel <NUM> is increased with the lapse of time while the braking force generated on the front wheel <NUM> is reduced with the lapse of time.

In the case where the braking force distribution is maintained in the initial state, the motorcycle <NUM> is more likely to be tilted forward in a manner that a rear portion of the motorcycle <NUM> is lifted. Thus, it is considered to change the braking force distribution from the initial state. However, in the case where the braking force distribution is abruptly changed at this time, pitching of the motorcycle <NUM> is likely to occur. Thus, as described above, after the braking force distribution is brought into the initial state, the distribution ratio for the rear wheel <NUM> is increased with the lapse of time. In this way, it is possible to suppress the forward tilt of the motorcycle <NUM> while suppressing occurrence of the pitching that is caused by the abrupt change in the braking force distribution.

Here, from a perspective of further stabilizing the posture of the motorcycle <NUM> after the braking force distribution is brought into the initial state, the brake control section 62b preferably brings the braking force distribution into the initial state, and thereafter preferably controls the braking force distribution between the front and rear wheels on the basis of information on the behavior of the motorcycle <NUM>.

For example, after bringing the braking force distribution into the initial state, the brake control section 62b may control a change rate of the braking force distribution on the basis of a pitch angle of the motorcycle <NUM>. For example, in the case where the pitch angle is large, the brake control section 62b may increase the change rate of the braking force distribution to be higher than the change rate of the braking force distribution at the time when the pitch angle is small. Alternatively, for example, in the case where a change rate of the pitch angle is high, the brake control section 62b may increase the change rate of the braking force distribution to be higher than the change rate of the braking force distribution at the time when the change rate of the pitch angle is low.

After bringing the braking force distribution into the initial state, the brake control section 62b may control the change rate of the braking force distribution on the basis of a slip amount of the front wheel <NUM> of the motorcycle <NUM>. For example, the slip amount may be defined as a ratio (a slip rate) of a rotational frequency of the front wheel <NUM> to a body speed of the motorcycle <NUM>, or may be defined by another physical quantity that is substantially equivalent to such a ratio. Calculation of the slip amount of the front wheel <NUM> is well known. Thus, a description thereon will not be made. For example, in the case where the slip amount of the front wheel <NUM> is large, the brake control section 62b may increase the change rate of the braking force distribution to be higher than the change rate of the braking force distribution at the time when the slip amount of the front wheel <NUM> is small. Alternatively, for example, in the case where a change rate of the slip amount of the front wheel <NUM> is high, the brake control section 62b may increase the change rate of the braking force distribution to be higher than the change rate of the braking force distribution at the time when the change rate of the slip amount of the front wheel <NUM> is low.

After bringing the braking force distribution into the initial state, the brake control section 62b may control the change rate of the braking force distribution on the basis of a slip amount of the rear wheel <NUM> of the motorcycle <NUM>. For example, the slip amount may be defined as a ratio (a slip rate) of a rotational frequency of the rear wheel <NUM> to the body speed of the motorcycle <NUM>, or may be defined by another physical quantity that is substantially equivalent to such a ratio. Calculation of the slip amount of the rear wheel <NUM> is well known. Thus, a description thereon will not be made. For example, in the case where the slip amount of the rear wheel <NUM> is large, the brake control section 62b may reduce the change rate of the braking force distribution to be lower than the change rate of the braking force distribution at the time when the slip amount of the rear wheel <NUM> is small. Alternatively, for example, in the case where a change rate of the slip amount of the rear wheel <NUM> is high, the brake control section 62b may reduce the change rate of the braking force distribution to be lower than the change rate of the braking force distribution at the time when the change rate of the slip amount of the rear wheel <NUM> is low.

In addition, after bringing the braking force distribution into the initial state, the brake control section 62b may control an increase start time point, at which the distribution ratio for the rear wheel <NUM> in the braking force distribution starts being increased, on the basis of the pitch angle of the motorcycle <NUM>. For example, the brake control section 62b may determine a time point, at which the pitch angle exceeds a reference value, as the increase start time point. Then, at such an increase start time point, the brake control section 62b may start increasing the distribution ratio for the rear wheel <NUM> in the braking force distribution. Alternatively, for example, the brake control section 62b may determine a time point, at which a change rate of the pitch angle exceeds a reference value, as the increase start time point. Then, at such an increase start time point, the brake control section 62b may start increasing the distribution ratio for the rear wheel <NUM> in the braking force distribution.

After bringing the braking force distribution into the initial state, the brake control section 62b may control the increase start time point, at which the distribution ratio for the rear wheel <NUM> in the braking force distribution starts being increased, on the basis of the slip amount of the front wheel <NUM> of the motorcycle <NUM>. For example, the brake control section 62b may determine a time point, at which the slip amount of the front wheel <NUM> exceeds a reference value, as the increase start time point. Then, at such an increase start time point, the brake control section 62b may start increasing the distribution ratio for the rear wheel <NUM> in the braking force distribution. Such a reference value may correspond to a limit slip amount with which locking or possible locking of the front wheel <NUM> does not occur, or may correspond to the slip amount that is smaller than the limit slip amount. For example, the brake control section 62b may determine a time point, at which a change rate of the slip amount of the front wheel <NUM> exceeds a reference value, as the increase start time point. Then, at such an increase start time point, the brake control section 62b may start increasing the distribution ratio for the rear wheel <NUM> in the braking force distribution.

The brake control section 62b may set a time point at which the target deceleration calculated on the basis of the index value I representing the collision possibility at the time point exceeds a reference value, as the increase start time point, at which the distribution ratio for the rear wheel <NUM> in the braking force distribution starts being increased, or may set a time point at which a period determined according to a magnitude of the target deceleration used in step S513 elapses from the braking start time point, as the increase start time point. In the case where the target deceleration is high, such a period may be set shorter than that at the time when the target deceleration is low. Alternatively, the brake control section 62b may set a time point, at which body deceleration generated to the motorcycle <NUM> exceeds a reference value, as the increase start time point, at which the distribution ratio for the rear wheel <NUM> in the braking force distribution starts being increased.

The brake control section 62b may set a time point, at which an elapsed time from the braking start time point exceeds a reference value set in advance as a fixed value, as the increase start time point, at which the distribution ratio for the rear wheel <NUM> in the braking force distribution starts being increased.

A mode of increasing the distribution ratio for the rear wheel <NUM> in the braking force distribution, which is conducted after the braking force distribution is brought into the initial state, only needs to be the increase with the lapse of time, and thus is not particularly limited. For example, the brake control section 62b may increase the distribution ratio for the rear wheel <NUM> stepwise with the lapse of time. Alternatively, for example, the brake control section 62b may increase the distribution ratio for the rear wheel <NUM> continuously with the lapse of time. For example, the brake control section 62b may increase the distribution ratio for the rear wheel <NUM> such that a transition average of the distribution ratio for the rear wheel <NUM> in the braking force distribution is increased with the lapse of time. That is, the brake control section 62b may change the distribution ratio for the rear wheel <NUM> in the braking force distribution such that the distribution ratio for the rear wheel <NUM> is increased while being accompanied with a temporary reduction.

After step S517, or if it is determined YES in step S515, in step S519, the execution section <NUM> determines whether a request to terminate the automatic emergency deceleration operation of the motorcycle <NUM> is made. If the execution section <NUM> determines that the request to terminate the automatic emergency deceleration operation of the motorcycle <NUM> is made (step S519/YES), the processing proceeds to step S521. On the other hand, if the execution section <NUM> determines that the request to terminate the automatic emergency deceleration operation of the motorcycle <NUM> is not made (step S519/NO), the determination processing in step S519 is repeated.

For example, when determining that the collision possibility of the motorcycle <NUM> with the target (the obstacle, the vehicle, the person, the animal, or the like) becomes low, the execution section <NUM> determines that the request to terminate the automatic emergency deceleration operation of the motorcycle <NUM> is made.

If it is determined YES in step S519, in step S521, the brake control section 62b terminates braking of the wheels of the motorcycle <NUM>.

Next, the control flow illustrated in <FIG> is terminated.

Also, in the case where the request to terminate the automatic emergency deceleration operation of the motorcycle <NUM> is made in the middle of the processing to increase the distribution ratio for the rear wheel <NUM> in the braking force distribution (that is, the processing in step S517), the brake control section 62b terminates braking of the wheels. Then, the control flow illustrated in <FIG> is terminated.

As described above, in the control flow illustrated in <FIG>, when determining that the rider's riding posture is appropriate as the posture during the deceleration, the execution section <NUM> prohibits the distribution ratio for the rear wheel <NUM> from being increased with the lapse of time after the braking force distribution between the front and rear wheels is brought into the initial state. The controller <NUM> may not make the determination in step S515, that is, may control the braking force distribution between the front and rear wheels regardless of the rider's riding posture.

A description will be made on effects of the controller <NUM> according to the embodiment of the present invention.

When executing the automatic emergency deceleration operation of the motorcycle <NUM>, at the braking start time point at which the braking force starts being generated on each of the wheels, the execution section <NUM> in the controller <NUM> brings the braking force distribution between the front and rear wheels into the initial state where the braking force is generated on the front wheel <NUM>. As a result, at the braking start time point, it is possible to prevent the generation of the force remaining in the brake mechanism for the front wheel (the front-wheel brake mechanism <NUM>) that is more favorable for braking of the straddle-type vehicle than the brake mechanism for the rear wheel (the rear-wheel brake mechanism <NUM>). Therefore, the automatic emergency deceleration operation of the motorcycle <NUM> can appropriately be executed.

Preferably, in the controller <NUM>, the execution section <NUM> causes the braking force to be generated only on the front wheel <NUM> in the initial state. In this way, it is possible to further effectively suppress the generation of the force remaining in the brake mechanism for the front wheel <NUM> at the braking start time point.

Preferably, in the controller <NUM>, in the initial state, the execution section <NUM> causes the braking force to be generated on the rear wheel <NUM> in addition to the front wheel <NUM>. In this way, it is possible to suppress the forward tilt of the motorcycle <NUM> at the braking start time point.

Preferably, in the controller <NUM>, when causing the braking force to be generated on each of the wheels in the automatic emergency deceleration operation, the execution section <NUM> brings the braking force distribution into the initial state at the braking start time point, and then increases the distribution ratio for the rear wheel <NUM> in the braking force distribution with the lapse of time. In this way, it is possible to suppress the forward tilt of the motorcycle <NUM> while suppressing the occurrence of the pitching that is caused by the abrupt change in the braking force distribution.

Preferably, in the controller <NUM>, after bringing the braking force distribution into the initial state, the execution section <NUM> controls the braking force distribution on the basis of the information on the behavior of the motorcycle <NUM>. For example, the information on the behavior includes: the slip amount of each of the wheels (the front wheel <NUM> and the rear wheel <NUM>), the target deceleration in the automatic emergency deceleration operation, the body deceleration generated to the motorcycle <NUM>, the pitch angle of the motorcycle <NUM>, and the like. In this way, it is possible to appropriately suppress unstable body behavior that is caused by bringing the braking force distribution into the initial state. As a result, it is possible to further stabilize the posture of the motorcycle <NUM> after the braking force distribution is brought into the initial state. Therefore, the rider's comfort can further appropriately be secured.

Preferably, in the controller <NUM>, after bringing the braking force distribution into the initial state, the execution section <NUM> controls the change rate of the braking force distribution on the basis of the information on the behavior of the motorcycle <NUM>. In this way, it is possible to further appropriately suppress the unstable body behavior that is caused by bringing the braking force distribution into the initial state. As a result, it is possible to further effectively stabilize the posture of the motorcycle <NUM> after the braking force distribution is brought into the initial state. Therefore, the rider's comfort can further appropriately be secured.

Preferably, in the controller <NUM>, after bringing the braking force distribution into the initial state, the execution section <NUM> controls the increase start time point, at which the distribution ratio for the rear wheel <NUM> in the braking force distribution starts being increased, on the basis of the information on the behavior of the motorcycle <NUM>. In this way, it is possible to further appropriately suppress the unstable body behavior that is caused by bringing the braking force distribution into the initial state. As a result, it is possible to further effectively stabilize the posture of the motorcycle <NUM> after the braking force distribution is brought into the initial state. Therefore, the rider's comfort can further appropriately be secured.

Claim 1:
A controller (<NUM>) that controls travel of a straddle-type vehicle (<NUM>), the controller comprising:
an acquisition section (<NUM>) that acquires an index value (I) representing a collision possibility of the straddle-type vehicle (<NUM>); and
an execution section (<NUM>) that initiates automatic emergency deceleration operation of the straddle-type vehicle (<NUM>) according to the index value (I), wherein
when executing the automatic emergency deceleration operation, at a braking start time point at which a braking force starts being generated on wheels (<NUM>, <NUM>) of the straddle-type vehicle (<NUM>), the execution section (<NUM>) brings braking force distribution between the front and rear wheels into an initial state where the braking force is generated on the front wheel (<NUM>),
characterized in that
in the case where the execution section (<NUM>) determines that a rider's riding posture is inappropriate as a posture during deceleration at a time point at which the braking force distribution is brought into the initial state or after the braking force distribution is brought into the initial state, the execution section (<NUM>) reduces a distribution ratio for the front wheel (<NUM>) in comparison with the case where the execution section (<NUM>) does not determine that the rider's riding posture is inappropriate.