Control method for transmission for motorcycle

A control method for a transmission for a motorcycle having a plurality of shift gear trains such that the combination of gears meshing with each other is changed by driving an actuator to change a shift position. When a vehicle body inclination angle β as a sideward inclination angle of a vehicle body of the motorcycle during running of the motorcycle becomes greater than or equal to a predetermined angle, a change in shift position in the transmission is inhibited. The method controls the transmission for the motorcycle in order to reduce an operational load on a rider during turning of the motorcycle.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2006-035922, filed Feb. 14, 2006, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control method for a transmission for a motorcycle such that a shift position in the transmission is changed by driving an actuator.

2. Description of Background Art

An automatic shift mechanism for changing a shift position by driving an actuator in a transmission is generally adopted in a four-wheel vehicle, and in some case it is also adopted in a motorcycle (see Japanese Patent Laid-open No. 2002-67741).

The motorcycle disclosed in Japanese Patent Laid-open No. 2002-67741 includes an automatic transmission having a plurality of shift gear trains such that the combination of gears meshing with each other is changed by driving an actuator to thereby obtain a proper one of a plurality of shift positions. Further, the grip of a steering handle in this motorcycle is provided with an A/M selector switch for switching between an automatic mode and a manual mode and a shift switch for instructing upshift and downshift.

When the automatic mode is set by the A/M selector switch, a shift position is decided according to an operational condition of an internal combustion engine mounted on the motorcycle, and an actuator is driven under control to change the current shift position in the transmission into the shift position decided above.

On the other hand, when the manual mode is set, the actuator is driven according to an instruction from the shift switch operated by a rider, thereby upshifting or downshifting the shift position.

However, the vehicle body of a motorcycle is inclined sideward in turning. Accordingly, when the current shift position in the transmission is changed according to the operational condition of the internal combustion engine or according to the operation of the shift switch during turning of the motorcycle in the condition where a vehicle body inclination angle is large, an operational load on the rider is increased to cope with a vehicle body behavior due to fluctuations in drive torque.

SUMMARY AND OBJECTS OF THE INVENTION

It is accordingly an object of the present invention to provide a control method for a transmission for a motorcycle which can reduce an operational load on a rider during turning of the motorcycle.

In accordance with a first aspect of the present invention, there is provided a control method for a transmission for a motorcycle having a plurality of shift gear trains such that the combination of gears meshing with each other is changed by driving an actuator to change a shift position. When a vehicle body inclination angle as a sideward inclination angle of a vehicle body of the motorcycle during running of the motorcycle becomes greater than or equal to a predetermined angle, a change in shift position in the transmission is inhibited.

In accordance with a second aspect of the present invention, the actuator is driven according to a shift instruction from shift operating means operated by a rider on the motorcycle.

In accordance with a third aspect of the present invention, the actuator is driven according to a shift position decided by shift position deciding means according to at least a throttle angle, an engine rotation speed, and a vehicle speed.

In accordance with a fourth aspect of the present invention, the vehicle body inclination angle is calculated according to a vehicle speed and a steering angle.

In accordance with a fifth aspect of the present invention, the vehicle body inclination angle is detected by an inclination angle sensor.

EFFECTS OF THE INVENTION

According to the first aspect of the present invention, a change in shift position in the transmission is inhibited when the vehicle body inclination angle becomes greater than or equal to the predetermined angle. Accordingly, fluctuations in drive torque in such a running condition can be avoided to reduce an operational load on the rider.

According to the second aspect of the present invention, the actuator is driven according to a shift instruction from the shift operating means operated by the rider. Accordingly, during running in the condition where the vehicle body inclination angle is greater than or equal to the predetermined angle, a change in shift position is inhibited in spite of the shift operation performed by the rider, an operational load on the rider is reduced.

According to the third aspect of the present invention, the actuator is driven according to a shift position decided by the shift position deciding means according to at least a throttle angle, an engine rotation speed, and a vehicle speed. Accordingly, during running in the condition where the vehicle body inclination angle is greater than or equal to the predetermined angle, a change in shift position is inhibited in spite of the decision of a proper shift position made by the shift position deciding means, an operational load on the rider is reduced.

According to the fourth aspect of the present invention, the vehicle body inclination angle is calculated according to a vehicle speed and a steering angle. Accordingly, the vehicle body inclination angle can be calculated without the use of any special inclination angle sensor.

According to the fifth aspect of the present invention, the vehicle body inclination angle is detected by the inclination angle sensor. Accordingly, the vehicle body inclination angle can be directly obtained without the performance of any special computation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a side view of a motorcycle1mounted a transmission4according to the preferred embodiment, andFIG. 2is a front elevation of the motorcycle1in turning.

The motorcycle1has a vehicle body2, and an internal combustion engine3is suspended at a central portion of the vehicle body2. The transmission4is mounted on the rear side of the engine3. A steering shaft5is supported at a front portion of the vehicle body2so as to extend obliquely. A front fork6extends downward from the steering shaft5, and a front wheel7is supported to the lower ends of the front fork6. A steering handle8extends laterally from the upper end of the steering shaft5.

A rear fork10is supported at its front end to the vehicle body2at a position near a rear portion of the transmission4so as to extend rearward, and a rear wheel11is supported to the rear ends of the rear fork10.

A chain is connected between an output shaft projecting from the transmission4and an axle of the rear wheel11, thereby transmitting power from the transmission4to the rear wheel11. A seat12for a rider is provided above the rear wheel11.

In turning the motorcycle1, the steering handle8is turned to the right or left to incline the vehicle body2in the direction of turn as shown inFIG. 2, thereby keeping the balance of the vehicle body2.

As shown inFIG. 2, the angle β of inclination of the vehicle body2, or the vehicle body inclination angle will be hereinafter referred to as bank angle.

Although not shown inFIG. 1, a throttle sensor21for detecting a throttle angle θ as the opening angle of a throttle valve is mounted on a throttle body in an intake system of the internal combustion engine3. Further, an engine rotation speed sensor22for detecting an engine rotation speed n is provided at an end portion of a crankshaft.

A vehicle speed sensor23for detecting a vehicle speed v as the rotational speed of a wheel is provided on the front wheel7, and a steering angle sensor24for detecting a steering angle φ as the rotational angle of the steering shaft5is provided on the steering shaft5.

The transmission4is a multispeed transmission having a plurality of shift gear trains such that the combination of gears meshing with each other is changed to thereby change a shift position. The change of the combination of the gears is achieved by driving a shifting motor20. The shifting motor20is drive controlled by a shift control unit30as an electronic control unit using a computer.

The shift control unit30performs an automatic shifting method such that the transmission4is automatically shifted according to an operational condition of the internal combustion engine3.

FIG. 3is a schematic block diagram of a control system by the shift control unit30.

The shift control unit30inputs the throttle angle θ detected by the throttle sensor21, the engine rotation speed n detected by the engine rotation speed sensor22, the vehicle speed v detected by the vehicle speed sensor23, and the steering angle φ detected by the steering angle sensor24. The shift control unit30performs computation according to these detection signals from the sensors21to24to output a drive control signal for controlling the shifting motor20.

This control signal is output to a motor driving device35for driving the shifting motor20. Thus, the shifting motor20is driven by the motor driving device35according to the control signal.

By driving the shifting motor20, a shift drum in the transmission4is rotated to change the combination of the meshing gears in the shift gear trains, thereby changing the shift position.

The rotational angle of the shift drum in the transmission4is detected by shift position detecting means36, and the shift position detected by the shift position detecting means36is fed back to the motor driving device35, thus the shifting motor20is controlled by feedback controlling.

The shift control unit30is composed of bank angle computing means31, shift inhibition determining means32, and shift position deciding means33. The bank angle computing means31computes the bank angle β from the vehicle speed v and the steering angle φ detected above.

The bank angle β may be computed by a known method (as disclosed in Japanese Patent Laid-open No. Hei 5-637, for example). The shift inhibition determining means32determines whether or not shifting is to be inhibited according to the bank angle β calculated by the bank angle computing means31.

More specifically, if the bank angle β calculated is less than a predetermined angle B, shifting is permitted, whereas if the bank angle β calculated is not less than the predetermined angle B, shifting is inhibited.

The shift position deciding means33decides a proper shift position by using a preset shift map according to the throttle angle θ, the engine rotation speed n, and the vehicle speed v detected above. The shift position deciding means33also decides whether or not shifting is to be performed according to the result of determination by the shift inhibition determining means32.

FIG. 4is a flowchart showing a control process by the shift inhibition determining means32.

The vehicle speed v detected by the vehicle speed sensor23and the steering angle φ detected by the steering angle sensor24are read (step1), and in step2the bank angle β is calculated from the vehicle speed v and the steering angle φ.

It is determined whether or not the bank angle β calculated above is greater than or equal to the predetermined angle B (step3).

If the bank angle β is less than the predetermined angle B (β<B), the program proceeds to step4, in which a shift inhibition flag F is set to “0”. Conversely, if the bank angle β is greater than or equal to the predetermined angle B (β≧B), the program proceeds to step5, in which the shift inhibition flag F is set to “1”.FIG. 5is a flowchart showing a control process by the shift position deciding means33. In step11, the status of the shift inhibition flag F is determined. If the shift inhibition flag F is “0”, the program proceeds to step12, whereas if the shift inhibition flag F is “1”, the program is ended, that is, the shift control is not performed.

Accordingly, when the shift inhibition flag F is “1”, that is, when the bank angle β is greater than or equal to the predetermined angle B (β≧B), the current shift position is not changed, but it is maintained.

When the shift inhibition flag F is “0” and the program proceeds to step12, the throttle angle θ, the engine rotation speed n, and the vehicle speed v detected are read and the program proceeds to step13, in which a proper shift position is decided according to the shift map.

In step14, it is determined whether or not the shift position decided above is higher than the current shift position. If the decided shift position is higher than the current shift position, the program jumps to step16, in which a control signal instructing upshift is output.

If the decided shift position is not higher than the current shift position, the program proceeds from step14to step15, in which it is determined whether or not the decided shift position is lower than the current shift position. If the decided shift position is lower than the current shift position, the program proceeds to step17, in which a control signal instructing downshift is output.

If the decided shift position is not higher than the current shift position and not lower than the current shift position, that is, if the decided shift position is the same as the current shift position, the program is ended from step15and the current shift position is maintained.

Thus, the shift control for the transmission4in the motorcycle1is performed as mentioned above. Accordingly, during running in the condition where the bank angle β of the vehicle body2is less than the predetermined angle B, normal automatic shift control is performed to permit a change in shift position. However, during turning in the condition where the bank angle β is greater than or equal to the predetermined angle B, a change in shift position is inhibited to maintain the current shift position. Accordingly, fluctuations in drive torque in such a running condition can be avoided to thereby reduce an operational load on the rider.

While the bank angle β is calculated from the vehicle speed v and the steering angle φ in this preferred embodiment, the bank angle β may be directly detected by a bank angle sensor as an inclination angle sensor such as a gimbal or a gyroscope.

Another preferred embodiment of the present invention will now be described with reference toFIGS. 6 to 8.

The motorcycle according to this preferred embodiment adopts a manual shifting method such that shifting is performed according to an operational instruction by the rider. The motorcycle according to this preferred embodiment includes an upshift switch41and a downshift switch42as shift operating means for performing a shift instruction provided in the vicinity of one of the grops of the steering handle. The motorcycle further includes a bank angle sensor43such as a gimbal or a gyroscope for directly detecting the bank angle β.

FIG. 6is a schematic block diagram of a control system by a shift control unit50included in this motorcycle.

InFIG. 6, a shifting motor20and a drive control system therefore are the same as those in the previous preferred embodiment, so the same parts as those shown inFIG. 3are denoted by the same reference numerals.

The shift control unit50inputs on-signals from the upshift switch41and the downshift switch42and the bank angle β detected by the bank angle sensor43. The shift control unit50performs computation according to these detection signals from the switches41and42and the sensor43to output a control signal for controlling the shifting motor20.

The shift control unit50is composed of shift inhibition determining means51and shift position deciding means52. The shift inhibition determining means51performs shift inhibition determination according to the control flowchart shown inFIG. 7.

Referring toFIG. 7, the bank angle β detected above is read (step21), and it is determined whether or not the bank angle β detected above is greater than or equal to the predetermined angle B (step22).

If the bank angle β is less than the predetermined angle B (β<B), the program proceeds to step23, in which the shift inhibition flag F is set to “0”. Conversely, if the bank angle β is greater than or equal to the predetermined angle B (β≧B), the program proceeds to step24, in which the shift inhibition flag F is set to “1”.

The shift position deciding means52decides a proper shift position according to the control flowchart shown inFIG. 8to output a control signal.

In step31, the status of the shift inhibition flag F is determined. If the shift inhibition flag F is “0”, the program proceeds to step32, whereas if the shift inhibition flag F is “1”, the program is ended, that is, the shift control is not performed.

Accordingly, when the shift inhibition flag F is “1”, that is, when the bank angle β is greater than or equal to the predetermined angle B (β≧B), the current shift position is not changed, but it is maintained.

When the shift inhibition flag F is “0” and the program proceeds to step32, it is determined whether or not the upshift switch41is in the on state. If the upshift switch41is in the on state, that is, if the upshift operation is instructed by the rider, the program jumps to step34, in which a control signal instructing upshift is output.

If the upshift switch41is in the off state, the program proceeds to step33, in which it is determined whether or not the downshift switch42is in the on state. If the downshift switch42is in the on state, that is, if the downshift operation is instructed by the rider, the program jumps to step35, in which a control signal instructing downshift is output.

If both of the upshift switch41and the downshift switch42are in the off state, that is, if a change in shift position is not instructed by the rider, the program is ended from step33and the current shift position is maintained.

Thus, the shift control for the transmission according to this preferred embodiment is performed as mentioned above. Accordingly, during running in the condition where the bank angle β of the vehicle body2is less than the predetermined angle B, a change in shift position is performed according to the shift instruction by the rider. However, during turning in the condition where the bank angle β is greater than or equal to the predetermined angle B, a change in shift position is inhibited in spite of the shift instruction by the rider to maintain the current shift position. Accordingly, fluctuations in drive torque in such a running condition can be avoided to thereby reduce an operational load on the rider.

While the bank angle β is detected by the bank angle sensor43in this preferred embodiment, a vehicle speed sensor and a steering angle sensor may be provided instead as in the previous preferred embodiment to thereby calculate the bank angle β from the vehicle speed v and the steering angle φ.

Further, while the shifting method in this preferred embodiment is a manual shifting method, the shifting method may be modified to combine the manual shifting method adopted in this preferred embodiment and the automatic shifting method adopted in the previous preferred embodiment, wherein a manual mode using the manual shifting method and an automatic mode using the automatic shifting method may be switched therebetween. Also in this case, the shift inhibition control according to the bank angle β may be effected in both of the manual mode and the automatic mode.