Motorcycle

A motorcycle includes: a front wheel brake that brakes a front wheel that is supported by a front fork; a rear wheel brake; a control unit that controls an ABS modulator connected to the front wheel brake and the rear wheel brake on the basis of front wheel speed and rear wheel speed; and a front wheel rise detection unit that detects whether the front wheel is likely to rise from a road surface, wherein when the front wheel rise detection unit detects that the front wheel is likely to rise, the control unit operates the front wheel brake through the ABS modulator.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-051383 filed on Mar. 19, 2019, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a motorcycle that prevents an occurrence of a wheelie (front wheel lifted) travel state.

Description of the Related Art

For example, Japanese Laid-Open Patent Publication No. 2012-144240 (hereinafter, referred to as JP 2012-144240 A) discloses a technique regarding a two-wheeled vehicle control device that performs brake control of a motorcycle. In this technique, a slip ratio is calculated on the basis of the front wheel speed and the rear wheel speed. If the calculated slip ratio is more than a predetermined threshold, a front wheel brake and a rear wheel brake are operated through an ABS modulator so that a lock of wheels is prevented (in the paragraph [0018] of JP 2012-144240 A).

Moreover, J P 2012-144240 A discloses the following technique. If a wheelie travel state in which a front wheel rises has occurred, engine output is decreased to suppress the wheelie travel or a TCS (Traction Control System) control is performed to brake a rear wheel (in the paragraph of JP 2012-144240 A).

SUMMARY OF THE INVENTION

By the technique disclosed in JP 2012-144240 A, if the wheelie travel state has occurred, it is expected that the front wheel will land on a road surface.

However, in a structure described in JP 2012-144240 A, the control is performed on the premise that the wheelie can occur. Thus, in consideration of a driving characteristic that is peculiar to the motorcycle, such as steering performance or braking performance, it is desired that the control is performed to prevent the wheelie travel.

The present invention has been made to solve the above problem, and an object thereof is to provide a motorcycle that can prevent an occurrence of a wheelie travel state with a simple structure.

A motorcycle according to one aspect of the present invention includes: a front wheel brake configured to brake a front wheel (FW) that is supported by a front fork including a suspension; a rear wheel brake configured to brake a rear wheel (RW) supported by a swing arm; an ABS modulator connected to the front wheel brake and the rear wheel brake; a control unit configured to control the ABS modulator on a basis of front wheel speed and rear wheel speed; and a front wheel rise detection unit configured to detect whether the front wheel (FW) is likely to rise from a road surface, wherein when the front wheel rise detection unit detects that the front wheel (FW) is likely to rise, the control unit operates the front wheel brake through the ABS modulator.

In the present invention, if it has been detected that the front wheel of the motorcycle is likely to rise from the road surface (wheelie travel is likely to occur), the front wheel brake is operated through the ABS modulator. Thus, the suspension operates in a direction in which the front fork sags. Therefore, it is possible to prevent the wheelie travel state of the motorcycle from occurring with a simple structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a motorcycle according to the present invention is hereinafter described in detail with reference to the attached drawings.

Embodiment

FIG. 1is a side view of a motorcycle (hereinafter, also referred to as two-wheeled vehicle or vehicle)10according to the embodiment.FIG. 2is a plan view of the two-wheeled vehicle10.

As illustrated inFIG. 1andFIG. 2, the two-wheeled vehicle10includes a vehicle body frame12. The vehicle body frame12includes a head pipe14, a pair of left and right main frames16that obliquely extends rearward and downward from the head pipe14, a pair of left and right pivot plates18that is attached to rear ends of the main frames16, a pair of left and right down frames17that obliquely extends rearward and downward from the head pipe14below the main frames16, a pair of left and right seat rails20that extends rearward from upper parts of the pivot plates18, and a sub frame22that bridges between a rear part of the seat rail20and a rear part of the pivot plate18.

The two-wheeled vehicle10includes a power unit PU including a transmission TM and an engine E supported between the pivot plate18and the down frame17.

A front fork32is attached to the head pipe14in a steerable manner. The front fork32supports a front wheel FW by a spring and a damper (neither are shown). A bar handle34is attached to an upper end of the front fork32.

A swing arm36that supports a rear wheel RW is attached to the pivot plate18through a pivot shaft35.

The swing arm36houses a shaft that transmits motive power from the transmission TM to the rear wheel RW in a hollow part. A rear cushion unit38is provided between the swing arm36and the pivot plate18.

Exhaust pipes45,46extend downward from a front side cylinder and a rear side cylinder of the engine E so as to connect to a muffler51.

Note that in the example of the present embodiment, a shaft drive is described as a structure of a motive power transmission mechanism. However, the motive power may be transmitted by a chain from the transmission TM to the rear wheel RW.

FIG. 3illustrates a structure of a brake system100provided to the vehicle10.

The brake system100includes a front disc brake device (front brake device or front wheel brake)53that brakes the front wheel FW, a rear drum brake device (rear brake device or rear wheel brake)57that brakes the rear wheel RW, and an ABS modulator64.

The front wheel brake53includes a brake disc53a(also seeFIG. 1) that is integrally attached to the front wheel FW and a brake caliper53bthat is attached to the front fork32. The brake caliper53bholds the brake disc53a, so that the front wheel FW is braked.

The rear wheel brake57includes a brake drum57athat is integrally attached to the rear wheel RW, and a wheel cylinder57band a brake shoe57cprovided to the inside of the brake drum57a. The wheel cylinder57bpushes the brake shoe57cto the brake drum57a, so that the rear wheel RW is braked (also seeFIG. 1).

The front wheel brake53and the rear wheel brake57are connected to the anti-lock brake system modulator (ABS modulator)64that forms an anti-lock brake system (ABS)60.

As it is commonly known, the ABS modulator64includes an electric motor, a pump that is driven by the electric motor, a plurality of fluid pressure pipes (fluid paths) connected to the pump, a solenoid valve that is provided in the middle of the fluid pressure pipes (fluid paths), and the like. As illustrated inFIG. 1, the ABS modulator64is an assembly that is disposed between the seat rail20and the sub frame22in the side view.

On a right grip side of the bar handle34(FIG. 1), a throttle grip80, a front wheel brake lever82, and a front master cylinder58illustrated inFIG. 3are provided. The front master cylinder58supplies fluid pressure (hydraulic pressure) to the brake caliper53bthrough a fluid path158, the ABS modulator64, and a fluid path153.

A rear wheel brake pedal83and a rear master cylinder59illustrated inFIG. 3are provided near a main step of a lower part of a vehicle body. The rear master cylinder59supplies the fluid pressure (hydraulic pressure) to the wheel cylinder57bthrough a fluid path159, the ABS modulator64, and a fluid path157.

The ABS60includes a front wheel speed sensor61that detects the wheel speed of the front wheel FW, a rear wheel speed sensor62that detects the wheel speed of the rear wheel RW, and an ECU (electronic control unit)63as a control unit (control device) that transmits a control signal to the ABS modulator (fluid pressure unit)64so as to determine a slip state of the wheels in the braking on the basis of wheel speed signals from the front wheel speed sensor61and the rear wheel speed sensor62and keep an appropriate slip ratio.

The ECU63executes programs that are stored in an internal storage device so as to operate as various function achievement units. In the present embodiment, the ECU63functions as a front wheel rise detection unit (front wheel rise possibility detection unit or wheelie state occurrence possibility detection unit)63aor the like.

The ABS modulator64increases or decreases the fluid pressure (hydraulic pressure) for braking the front wheel FW by the brake caliper53bof the front disc brake device53from the front master cylinder58through the fluid path158and the fluid path153on the basis of the control signal from the ECU63. On the other hand, the ABS modulator64increases or decreases the fluid pressure (hydraulic pressure) for braking the rear wheel RW by the wheel cylinder57band the brake shoe57cof the rear drum brake device57from the rear master cylinder59through the fluid path159and the fluid path157.

To the ECU63of the brake system100, a throttle grip opening sensor122that detects opening θg of the throttle grip80(grip opening θg), a throttle valve opening sensor124that detects opening θv of a throttle valve, a rotation speed sensor (Ne sensor)126that detects an engine rotation speed (rotation speed of crank shaft) Ne of the engine E, a roll angle sensor (bank angle detection unit)128that detects a roll angle (bank angle) θr corresponding to a bank angle of the motorcycle10, a stroke sensor132that detects a stroke amount L of the front fork32, and an acceleration sensor134that detects front-rear acceleration A are further connected.

An occurrence prevention control process for a wheelie travel state of the motorcycle10according to the present embodiment basically structured as above is described with reference to flowcharts inFIG. 4toFIG. 7. Note that the ECU63mainly executes the programs according to the flowcharts; however, referring to this description in each process is complicate, and thus the description is appropriately omitted.

FIG. 4is an overall flowchart for describing operation of the occurrence prevention control process for the wheelie travel state.

In the travel of the two-wheeled vehicle10, an acceleration posture control condition determination process inFIG. 5is repeatedly performed at predetermined time intervals in step S10. In step S20, a front brake pressurization control (FR brake pressurization control) process inFIG. 6is performed. If necessary, for example, in accordance with the kind of the vehicle, a front suspension damper control (FR suspension damper control) process inFIG. 7is performed in step S30.

FIG. 5illustrates the detail of the acceleration posture control condition determination process in step S10.

In step S11, it is determined whether the roll angle θr detected by the roll angle sensor128is less than or equal to a setting value that is set in advance at which a wheelie can occur.

If the roll angle θr is less than or equal to the setting value (step S11: YES), in step S12, the front wheel rise detection unit63adetermines whether the wheelie travel state can occur (wheelie determination) at a position where the motorcycle10rises from a corner (curve), for example.

FIG. 8is a characteristic diagram (map) that expresses the relation between a burden rate Br of the front wheel FW (burden rate of front wheel) and the stroke amount L (expansion and contraction amount) of the front fork32.

The burden rate Br of the front wheel is a ratio of a burden (load) applied to the front wheel FW to an entire burden (entire load) applied to the front wheel FW and the rear wheel RW. The total of the burden rate Br of the front wheel FW and a burden rate of the rear wheel RW is one. In the front wheel-burden rate map inFIG. 8, if the burden rate Br of the front wheel satisfies Br=0, it is the wheelie state (front wheel lifted state). Thus, the stroke amount L becomes a maximum value (a rise amount from a reference becomes the maximum) Lmax. On the other hand, if the burden rate Br of the front wheel FW satisfies Br=1, it is a rear wheel lifted state. Thus, the stroke amount L becomes the minimum (a sag amount from the reference becomes the maximum).

In the present embodiment, in order to detect whether the wheelie travel state can occur, it is assumed that the stroke amount L at a predetermined burden rate Brth before the burden rate Br of the front wheel FW becomes zero is regarded as a threshold Lth, and then, in step S12, it is determined whether the stroke amount L detected by the stroke sensor132becomes more than or equal to the threshold Lth (L≥Lth).

If the stroke amount L has become the threshold Lth (step S12: NO), it is determined that the current state is not the wheelie state but the state is likely to be changed to the wheelie travel state. Next, in step S13, it is determined whether the front-rear acceleration A detected by the acceleration sensor134is more than or equal to a predetermined setting value in which the wheelie state can occur.

If the front-rear acceleration A is more than or equal to the setting value (step S13: YES), in step S14, it is determined whether driving force of the rear wheel RW by the engine E (value that is obtained by multiplying engine torque by gear ratio) is more than or equal to a predetermined setting value in which the wheelie state can occur.

If the driving force is more than or equal to the setting value (step S14: YES), in step S15, the slip ratio is calculated on the basis of the front wheel speed sensor61, the rear wheel speed sensor62, and vehicle body speed, and it is determined whether the calculated slip ratio is less than or equal to a predetermined setting value expressing that the front wheel FW and the rear wheel RW grip a road surface.

If the slip ratio is less than or equal to the setting value (step S15: YES) (grip state), in step S16, it is determined whether request torque of a driver is less than or equal to a predetermined setting value in which the wheelie state is not desired on the basis of a detected value of the grip opening θg from the throttle grip opening sensor122.

If the request torque of the driver is less than or equal to the setting value (step S16: YES), the front brake pressurization control in step S20is permitted in order to prevent an occurrence of the wheelie state.

FIG. 6illustrates the detail of the front brake pressurization control process.

In step S21, if the acceleration posture control is permitted (step S21: YES), in step S22, braking force using the front-rear acceleration A as a parameter, that is, close duty of the brake caliper53bof the front wheel brake53is calculated.

In this case, in step S23, the ECU63controls the ABS modulator64so as to perform opening/closing control for the brake caliper53bof the front wheel brake53(perform fluid pressure control for front brake) in accordance with the calculated close duty from the ABS modulator64through the fluid path153. Thus, since the braking force is applied to the front wheel FW through the brake disc53a, the front fork32can be operated in the direction in which the front fork32sags (direction in which front suspension shrinks) in accordance with deceleration of the vehicle10and acceleration behavior by the driving force of the rear wheel RW. Therefore, the occurrence of vehicle body pitch, that is, the wheelie state can be prevented.

As a result, the posture of the two-wheeled vehicle10is controlled so that the wheelie is less likely to occur, and acceleration loss can be reduced compared to a conventional case in which control is performed after the wheelie occurs (engine torque is controlled so as to be reduced by TBW (throttle by wire) technique or the like).

Next, the process returns to step S17in the flowchart inFIG. 5, and it is determined whether the front-rear acceleration A is less than or equal to a predetermined setting value in which the wheelie state does not occur. If the front-rear acceleration A is less than or equal to the setting value (step S17: YES), a designation timer (not shown) is started, and if the time for which the front-rear acceleration A is less than or equal to the setting value has become a time designated by the designation timer in step S18(step S18: YES), it is determined that the wheelie state does not occur. Thus, the acceleration posture control is prohibited in step S19.

Therefore, the acceleration posture control is prohibited in step S21inFIG. 6, and the control of FR brake fluid pressure in the front wheel brake53from the ECU63through the ABS modulator64is canceled in step S24.

Note that if the acceleration posture control in step S20is permitted, in addition to the front pressurization control in steps S21to S24, front suspension damper control in step S30in the flowchart inFIG. 7may be simultaneously performed, if necessary.

That is to say, if the acceleration posture control regarding the front suspension damper control is permitted in step S31(step S31: YES), in step S32, the damping amount (FR damping amount) of a front suspension damper using the front-rear acceleration A as a parameter is calculated and the front suspension damper is controlled through the ECU63.

In this case, the front suspension damper that is housed in the front fork32is electronically controlled and the damping amount of the front suspension damper is controlled by a predetermined amount stepwise from the normal damping amount on the basis of the calculated damping amount so that the front suspension is weakened. Thus, the front fork32sags in accordance with the predetermined amount, so that the occurrence of the wheelie state is suppressed.

In this case, the process returns to step S17in the flowchart inFIG. 5, and it is determined whether the front-rear acceleration A is less than or equal to the predetermined setting value in which the wheelie state does not occur. If the front-rear acceleration A is less than or equal to the setting value, the designation timer (not shown) is started, and if the time for which the front-rear acceleration A is less than or equal to the setting value has become the time designated by the designation timer in step S18, it is determined that the wheelie state does not occur. Thus, the acceleration posture control is prohibited in step S31.

As illustrated inFIG. 7, if the acceleration posture control is prohibited in step S31, the FR damping amount is changed from the FR damping mount regarding the acceleration posture control to the normal FR damping amount gradually in step S33.

In this manner, the process ends. Note that if step S11: NO, step S12: YES, steps S13to S16: NO, or steps S17, S18: NO, the process returns to step S10.

FIG. 9is an explanatory diagram that compares the prior art (upper side) and the present embodiment (lower side).

In a motorcycle200according to the prior art, if the wheelie state in which the front wheel is lifted due to the large driving force of the rear wheel has been detected, wheelie behavior is relieved by restricting engine output by the TBW technique or the like. Thus, the state is returned to the normal travel state.

On the other hand, in the motorcycle10according to the embodiment, if it is detected that the wheelie state is likely to occur due to the large driving force of the rear wheel RW, the vehicle body posture is controlled so that the pitching in a wheelie direction is suppressed by using the FR brake (front suspension damper control may be also used). Thus, the occurrence of the wheelie state can be prevented, and both the easiness of the driver's operation and the reduction of the acceleration loss can be achieved.

[The Invention that can be Obtained from the Embodiment]

Here, the invention that can be obtained from the above embodiment is described. Note that the reference symbol used in the above embodiment is added to a structure component with parentheses to help understanding; however, the structure component is not limited thereto.

The motorcycle (10) according to the present invention includes: the front wheel brake (53) configured to brake the front wheel (FW) that is supported by the front fork (32) including the suspension; the rear wheel brake (57) configured to brake the rear wheel (RW) supported by the swing arm (36); the ABS modulator (64) connected to the front wheel brake (53) and the rear wheel brake (57); the control unit (63) configured to control the ABS modulator (64) on the basis of the front wheel speed and the rear wheel speed; and the front wheel rise detection unit (63a,132, step S12) configured to detect whether the front wheel (FW) is likely to rise from the road surface, wherein when the front wheel rise detection unit (63a,132, step S12) detects that the front wheel (FW) is likely to rise, the control unit (63) operates the front wheel brake (53) through the ABS modulator (64).

In this structure, if it has been detected that the front wheel (FW) of the motorcycle (10) is likely to rise from the road surface (wheelie travel is likely to occur), the front wheel brake (53) is operated through the ABS modulator (64). Thus, the suspension operates in the direction in which the front fork (32) sags. Therefore, it is possible to prevent the wheelie travel state of the motorcycle (10) from occurring with the simple structure.

In addition, in the motorcycle (10), the front wheel rise detection unit (63a,132, step S12) may be the stroke sensor (132) provided to the front fork (32) and configured to detect the expansion and contraction amount of the front fork (32).

The stroke sensor (132) can detect the expansion and contraction amount of the front fork (32) easily and precisely.

Moreover, in the motorcycle (10), when the expansion and contraction amount becomes more than or equal to the threshold (Lth), the front wheel rise detection unit (63a,132, step S12) may detect that the front wheel (FW) is likely to rise.

In this structure, when the expansion amount is more than or equal to the predetermined threshold (Lth), it is detected that the front wheel (FW) is likely to rise. Thus, it is possible to precisely detect that the front wheel (FW) is likely to rise.

Furthermore, in the motorcycle (10), when the front wheel rise detection unit (63a,132, step S12) detects that the front wheel (FW) is likely to rise, the control unit (63) may calculate the damping amount of the front suspension damper using the acceleration (A) as the parameter.

In this structure, the damping amount of the front suspension damper is controlled in accordance with the acceleration (A) when the motorcycle (10) is accelerated, so that the front suspension damper can be contracted. Thus, it is possible to further prevent the wheelie travel state from occurring.

The present invention is not limited to the above embodiment and may employ various structures on the basis of the description in the present specification.