Gear change control device, straddle-type vehicle, and method of controlling gearbox

Riding comfort of a vehicle is improved by reducing deceleration and acceleration exceeding the expectation of a rider due to gear changes. A gear change control device calculates current torque being transmitted from a drive-side member of a clutch to a driven-side member of the clutch, and calculates post-completion torque estimated to be transmitted from the drive-side member to the driven-side member after the completion of engagement of the clutch. The gear change control device then controls the degree of engagement of the clutch according to the difference between the current torque and the post-completion torque, and receives a next gear change command according to the difference between the current torque and the post-completion torque.

RELATED APPLICATIONS

This application claims the benefit of priority under 35 USC 119 of Japanese patent application no. 2007-043645, filed on Feb. 23, 2007, and Japanese patent application no. 2007-231135, filed on Sep. 6, 2007, which applications are hereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technique for changing shift gears and engaging and disengaging a clutch using an actuator.

2. Description of Related Art

There have conventionally been vehicles that disengage a clutch and change shift gears by actuating an actuator according to a shift-up or a shift-down operation by a rider. In general, gear change control devices mounted on such vehicles start gradually engaging the clutch after the shift gears have completely been moved (changed).

The driver may occasionally make successive shift-up or shift-down operations in a short time while the vehicle is running. In order to respond to such quick gear change operations by the rider, the gear change control device disclosed in JP-B-3132358 allows the reception of a next gear change command even before the start of engagement of the clutch if the shift gears have completely been moved. When a next gear change command is inputted before the start of engagement of the clutch, this gear change control device does not engage the clutch but starts moving the shift gears according to the next gear change command while keeping the clutch disengaged. This gear change control device engages the clutch after the completion of the movement. This allows the rider to make quicker gear change operations than in the case where the reception of a next gear change command is started after the completion of engagement of the clutch.

However, the riding comfort of a vehicle provided with the gear change control device of JP-B-3132358 may be poor at gear changes. Specifically, when a next gear change command is inputted before the start of engagement of the clutch, the gear change control device of JP-B-3132358 changes the shift gears according to the next gear change command while keeping the clutch disengaged. Therefore, the shift gear corresponding to the gear change command inputted later is set without the rider sensing deceleration and acceleration at the shift gear corresponding to the gear change command inputted earlier at all. Therefore, deceleration and acceleration exceeding the expectation of the rider may occur when the shift gears are completely changed and the clutch is engaged, leading to poor riding comfort.

SUMMARY OF THE INVENTION

The present invention addresses the foregoing problem and provides a gear change control device for a straddle-type vehicle that improves riding comfort by reducing the occurrence of deceleration and acceleration exceeding the expectation of a rider due to successive gear changes.

The present invention is directed to a gear change control device including a clutch actuator for changing a degree of engagement of a clutch. A current torque obtaining section obtains torque transmitted from a drive-side member of the clutch to a downstream mechanism in a torque transmission path as current torque, the downstream mechanism including a driven-side member of the clutch. A post-completion torque obtaining section obtains torque estimated to be transmitted from the drive-side member to the downstream mechanism after completion of engagement of the clutch as post-completion torque. A control unit disengages the clutch by actuating the clutch actuator and changing shift gears in response to a gear change command by a rider, and then controls the degree of engagement of the clutch according to a difference between the current torque and the post-completion torque. The control unit receives a next gear change command according to the difference between the current torque and the post-completion torque.

The present invention is also directed to a straddle-type vehicle including the gear change control device.

The present invention is further directed to a method of controlling a gearbox, comprising: disengaging a clutch by actuating a clutch actuator and changing shift gears in response to a gear change command by a rider; obtaining torque transmitted from a drive-side member of the clutch to a downstream mechanism in a torque transmission path as current torque, the downstream mechanism including a driven-side member of the clutch; obtaining torque estimated to be transmitted from the drive-side member to the downstream mechanism after completion of engagement of the clutch as post-completion torque; controlling a degree of engagement of the clutch according to a difference between the current torque and the post-completion torque; and starting to receive a next gear change command according to the difference between the current torque and the post-completion torque.

The present invention allows the rider to sense deceleration and acceleration that will occur after completion of engagement of the clutch, even before the clutch is completely engaged. The next gear change command can then be received after the rider senses deceleration or acceleration at the shift gear corresponding to the first gear change command. As a result, riding comfort is improved by reducing the occurrence of deceleration and acceleration exceeding the expectation of the rider due to successive gear changes. The straddle-type vehicle may be a motorcycle (including a scooter), a four-wheeled buggy, a snowmobile or a two-wheeled electric vehicle, for example.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention is described below with reference to the drawings.FIG. 1is a side view of a motorcycle1provided with a gear change control device10according to an exemplary embodiment of the present invention.

FIG. 2is a schematic view of a mechanism located on a torque transmission path of motorcycle1.

As shown inFIGS. 1 and 2, in addition to gear change control device10, motorcycle1comprises an engine30, a primary speed reducing mechanism36, a clutch40, a secondary speed reducing mechanism50, a front wheel2and a rear wheel3.

Front wheel2is supported by a lower end of a front fork4, and handlebars5are connected to the top of front fork4. An accelerator grip5amounted to a right end of handlebars5is connected to a throttle valve37aprovided in a throttle body37(FIG. 2). Throttle valve37ais opened according to a rider's accelerator operation, and a certain amount of air, which depends on the opening of throttle valve37a, is delivered to engine30. Motorcycle1may be provided with an electronically-controlled throttle device. In this case, there are provided a sensor for detecting a rider's accelerator operation and an actuator for rotating throttle valve37aaccording to the accelerator operation detected by the sensor.

As shown inFIG. 2, engine30has a cylinder31, a piston32, an intake port33and a crankshaft34. Throttle body37is connected to intake port33via an intake pipe35.

Throttle valve37ais placed in an intake passage of throttle body37. A mixture of air, which flows through the intake passage of throttle body37, and fuel, which is supplied from a fuel supply device (for example, an injector or carburetor), is delivered to an interior of cylinder31. Burning the air-fuel mixture causes piston32to reciprocate within cylinder31. Reciprocating motion of piston32is converted into rotating motion by crankshaft34, thereby outputting torque from engine30.

Primary speed reducing mechanism36includes a drive-side primary reduction gear36athat operates in conjunction with crankshaft34; and a driven-side primary reduction gear36bthat meshes with primary reduction gear36a. Primary speed reducing mechanism36decelerates rotation of crankshaft34according to a gear ratio between these gears.

Clutch40transmits and shuts off torque outputted from engine30to the downstream side in the torque transmission path. Clutch40is a friction clutch, for example, and is provided with a drive-side member41and a driven-side member42. Drive-side member41includes a friction disk, for example, and rotates together with primary reduction gear36b. Driven-side member42includes a clutch disk, for example, and rotates together with a main shaft52. Drive-side member41and driven-side member42are pressed against each other by elastic force of a clutch spring44at the time of engaging clutch40, so that the torque of engine30is transmitted from drive-side member41to driven-side member42. Also, when clutch40is disengaged, driven-side member42is moved away from drive-side member41, so that torque transmission from drive-side member41is interrupted. Gear change control device10is provided with a clutch actuator14to be discussed later. Clutch actuator14performs engaging operation of clutch40(switching clutch40from the disengaged state to the engaged state) and disengaging operation thereof (switching clutch40from the engaged state to the disengaged state).

Secondary speed reducing mechanism50decelerates rotation of main shaft52and transmits the decelerated rotation to an axle3aof rear wheel3. Secondary speed reducing mechanism50is provided with a gearbox51and a transmission mechanism57. Gearbox51is a mechanism to change deceleration ratios, such as a constant-mesh gearbox and a selective-sliding gearbox.

Gearbox51has plural shift gears53a(for example, first-speed, second-speed, third/fourth-speed gears) and shift gears53b(for example, fifth-speed and sixth-speed gears) on main shaft52. Gearbox51also has plural shift gears54a(for example, first-speed, second-speed, third/fourth-speed gears) and shift gears54b(for example, fifth-speed and sixth-speed gears) on a countershaft55. Shift gears53aare spline-connected to and operate in conjunction with main shaft52. Shift gears54arun idle with respect to countershaft55and mesh with shift gears53a. Shift gears53brun idle with respect to main shaft52. Shift gears54bmesh with corresponding shift gears53band are spline-connected to and operate in conjunction with countershaft55.

Gearbox51also comprises a gearshift mechanism56. Gearshift mechanism56includes a shift fork and a shift drum, for example, and selectively moves shift gears53a,53b,54a,54bin the axial direction of main shaft52or countershaft55. Then, gearshift mechanism56causes shift gears53b,54a, which run idle with respect to the corresponding shafts, to connect with adjacent shift gears53a,54b, which operate in conjunction with the corresponding shafts. This changes shift gears53a,53b,54a,54bto transmit torque from main shaft52to countershaft55. Gearshift mechanism56is actuated by power inputted from a shift actuator16.

Transmission mechanism57decelerates rotation of countershaft55and transmits the decelerated rotation to axle3aof rear wheel3. Transmission mechanism57includes a drive-side member57a(for example, a drive-side sprocket) that operates in conjunction with countershaft55; a driven-side member57b(for example, a driven-side sprocket) that operates in conjunction with axle3a; and a transmission member57c(for example, a chain) that transmits torque from drive-side member57ato driven-side member57b.

The configuration of gear change control device10is now described. Motorcycle1is a semi-automatic vehicle that changes the shift gears of gearbox51without the need for the rider to operate the clutch. Gear change control device10controls the degree of engagement of clutch40(relative positions of drive-side member41and driven-side member42), and changes shift gears53a,53b,54a,54b.FIG. 3is a block diagram of gear change control device10. As shown inFIG. 3, gear change control device10comprises a control unit11, a storage unit12, a clutch actuator drive circuit13, a clutch actuator14, a shift actuator drive circuit15, a shift actuator16, an accelerator operation detector17, an engine speed detector18, a vehicle speed detector19, a gear position detector21, a clutch position detector22and clutch rotational speed detectors23a,23b. Control unit11is connected to a shift-up switch9aand a shift-down switch9b.

Control unit11includes a central processing unit (CPU), and controls the degree of engagement of clutch40and the speed reduction ratios of gearbox51in accordance with programs stored in storage unit12in response to a gear change operation by the rider (in this example, operation to turn on shift-up switch9aor shift-down switch9b).

Storage unit12includes a nonvolatile memory and a volatile memory. Storage unit12stores in advance programs executed by control unit11and tables and expressions used in the processing executed by control unit11.

Clutch actuator drive circuit13supplies drive voltage or drive current to clutch actuator14in accordance with a control signal inputted from control unit11. Clutch actuator14includes, for example, a motor and a power transmission mechanism (such as hydraulic path or wire), and is driven by electric power supplied from clutch actuator drive circuit13. In this example, clutch actuator14presses a push rod43and releases the pressed push rod43. When push rod43is pressed by clutch actuator14, push rod43moves drive-side member41and driven-side member42away from each other against the elastic force of clutch spring44, so that clutch40is disengaged. In contrast, when the pressed push rod43is released by clutch actuator14, push rod43returns to its original position (the position at the time when clutch40is engaged) using the elastic force of clutch spring44. Thus, drive-side member41and driven-side member42approach each other, so that clutch40is engaged. In addition, clutch actuator14brings clutch40into a half-clutch state during engaging operation of clutch40. When clutch40is in a half-clutch state, only part of the torque of engine30is transmitted from drive-side member41to driven-side member42.

Shift actuator drive circuit15supplies drive voltage or drive current to shift actuator16in accordance with a control signal inputted from control unit11. Shift actuator16includes, for example, a motor and a power transmission mechanism (such as hydraulic path or wire), and is actuated by driving power outputted from shift actuator drive circuit15. Shift actuator16actuates gearshift mechanism56to change shift gears53a,53b,54a,54bto transmit torque from main shaft52to countershaft55, in order to change the deceleration ratios.

Accelerator operation detector17detects the amount of an accelerator operation by the rider (hereinafter referred to as accelerator displacement (for example, throttle opening)). Examples of accelerator operation detector17are a throttle position sensor for detecting the throttle opening and an accelerator position sensor mounted to accelerator grip5ato detect the rotation angle of accelerator grip5a. Control unit11detects accelerator displacement by the rider based on a signal outputted from accelerator operation detector17.

Engine speed detector18detects rotational speed of engine30(hereinafter referred to as engine speed). Examples of engine speed detector18are a crank angle sensor for outputting a pulse signal with a frequency according to the rotational speed of crankshaft34or primary reduction gears36a,36band a tachogenerator for outputting a voltage signal according to the rotational speed thereof. Control unit11calculates engine speed based on a signal inputted from engine speed detector18.

Vehicle speed detector19detects vehicle speed, and outputs a signal to control unit11according to, for example, the rotational speed of axle3aof rear wheel3or that of countershaft55. Control unit11calculates the vehicle speed based on the signal. Vehicle speed detector19may output a signal according to the rotational speed of main shaft52. In this case, control unit11calculates vehicle speed not only based on the input signal, but also based on the deceleration ratio of gearbox51and that of transmission mechanism57.

Gear position detector21detects the positions of shift gears53a,53b,54a,54bprovided movably in the axial direction of countershaft55or main shaft52. An example of gear position detector21is a potentiometer mounted to gearshift mechanism56or shift actuator16. Gear position detector21outputs a signal to control unit11according to positions of shift gears53a,53b,54a,54b. Based on the input signal, control unit11detects that movements of shift gears53a,53b,54a,54bthat are associated with the gear change have been completed.

Clutch position detector22detects the degree of engagement of clutch40. Examples of clutch position detector22are a potentiometer for outputting a signal according to the position of push rod43and a potentiometer for outputting a signal according to the position or rotation angle of the output shaft of clutch actuator14. Control unit11detects the degree of engagement of clutch40based on the signal inputted from clutch position detector22.

Clutch rotational speed detector23adetects the rotational speed of drive-side member41of clutch40. Examples of clutch rotational speed detector23aare a rotary encoder for outputting a pulse signal with a frequency according to the rotational speed of drive-side member41and a tachogenerator for outputting a voltage signal according to the rotational speed of drive-side member41. Also, clutch rotational speed detector23bdetects the rotational speed of driven-side member42of clutch40. Examples of clutch rotational speed detector23bare a rotary encoder and a tachogenerator similar to those for clutch rotational speed detector23a.

Shift-up switch9aand shift-down switch9ballow the rider to give gear change control device10a command to change speed reduction ratios of gearbox51. Switches9a,9boutput a signal to control unit11according to the gear change command. Control unit11actuates shift actuator16according to the input signal to change shift gears53a,53b,54a,54bto transmit torque from main shaft52to countershaft55. Shift-up switch9aand shift-down switch9bare provided adjacent to accelerator grip5a, for example.

The processing executed by control unit11is now described. When a signal indicating a gear change command by the rider is inputted from shift-up switch9aor shift-down switch9b, control unit11disengages clutch40and moves shift gears53a,53b,54a,54b. Then, control unit11gradually engages clutch40after shift gears53a,53b,54a,54bhave completely been moved. In the example described herein, during engaging operation of clutch40, control unit11calculates torque Tpre (hereinafter referred to as current transmission torque) currently being transmitted from drive-side member41to a downstream mechanism in the torque transmission path including driven-side member42, such as driven-side member42, secondary speed reducing mechanism50and axle3a. Also, control unit11calculates torque Tfin (hereinafter referred to as post-completion transmission torque) estimated to be transmitted from drive-side member41to the downstream mechanism after completion of engagement of clutch40(when engaging operation of clutch40is finished). Control unit11then controls the degree of engagement of clutch40during engaging operation thereof based on the calculated current transmission torque Tpre and the calculated post-completion transmission torque Tfin.

Control unit11receives a next gear change command according to the difference between current transmission torque Tpre and post-completion transmission torque Tfin, even during engaging operation of clutch40. When a next gear change command is received during engaging operation of clutch40, control unit11does not complete gear change control corresponding to the gear change command inputted earlier, but disengages clutch40again, moves shift gears53a,53b,54a,54b, and then engages clutch40again according to the gear change command inputted later. The processing executed by control unit11is discussed in detail below.

FIG. 4is a functional block diagram of processing executed by control unit11. As shown inFIG. 4, control unit11includes a current torque obtaining section11a, a post-completion torque obtaining section11d, a clutch actuator control section11g, a shift actuator control section11hand a reception permission determination section11i. Current torque obtaining section11aincludes an EG torque obtaining section11band an inertia torque obtaining section11c, and post-completion torque obtaining section11dincludes a post-completion EG torque obtaining section11eand a post-completion inertia torque obtaining section11f.

Current torque obtaining section11ais first described. Current torque obtaining section11aexecutes processing for obtaining current transmission torque Tpre. Specifically, current torque obtaining section11acalculates current transmission torque Tpre based on torque TEpre currently being outputted from engine30(hereinafter referred to as EG torque) and based on inertia torque TIpre (hereinafter referred to as inertia torque) produced in a mechanism upstream of drive-side member41in the torque transmission path, such as crankshaft34, piston32and primary speed reducing mechanism36. Current torque obtaining section11aexecutes this processing in a preset sampling cycle (for example, several milliseconds) during engaging operation of clutch40. Current transmission torque Tpre is described herein as torque being transmitted to driven-side member42in the downstream mechanism described above.

The processing for obtaining EG torque TEpre is first described. Storage unit12stores in advance a table (hereinafter referred to as EG torque table) that correlates EG torque TEpre with engine speed and accelerator displacement. Then, EG torque obtaining section11bdetects accelerator displacement based on the signal inputted from accelerator operation detector17, and detects engine speed based on the signal inputted from engine speed detector18. EG torque obtaining section11bthen refers to the EG torque table to obtain EG torque TEpre corresponding to the detected accelerator displacement and detected engine speed.

In place of the EG torque table, storage unit12may store in advance an expression (hereinafter referred to as EG torque relational expression) that defines the relationship among engine speed, accelerator displacement, and EG torque TEpre. In this case, EG torque obtaining section11bsubstitutes the detected engine speed and detected accelerator displacement into the EG torque relational expression to calculate EG torque TEpre.

Alternatively, EG torque obtaining section11bmay obtain EG torque TEpre based on the pressure of air (hereinafter referred to as intake pressure) flowing through the interior of intake pipe35. For example, storage unit12may store a table that correlates EG torque TEpre with intake pressure and engine speed. In addition, a pressure sensor for outputting a signal according to the intake pressure is disposed in intake pipe35. In this case, EG torque obtaining section11bdetects engine speed, and intake pressure based on the signal inputted from the pressure sensor, at the time when the crank angle becomes a predetermined value (for example, at the end of intake stroke). EG torque obtaining section11bthen refers to the table stored in storage unit12to obtain EG torque TEpre corresponding to the detected intake pressure and detected engine speed.

Inertia torque TIpre is determined according to the variation in engine speed Ωe per unit time (dΩe/dt, hereinafter referred to as rate-of-change of EG speed). Storage unit12stores in advance an expression that associates inertia torque TIpre and the rate-of-change of EG speed (dΩe/dt). Specifically, storage unit12stores an expression that defines inertia torque TIpre as a value (I×(dΩe/dt)) obtained by multiplying the inertial moment I of the mechanism upstream of drive-side member41by the rate-of-change of EG speed (dΩe/dt). In this case, inertia torque obtaining section11ccalculates the rate-of-change of EG speed (dΩe/dt) based on the signal inputted from engine speed detector18. Inertia torque obtaining section11cthen multiplies the rate-of-change of EG speed (dΩe/dt) by inertial moment I of the mechanism upstream of drive-side member41(hereinafter simply referred to as inertial moment), and defines the multiplication result (I×(dΩe/dt)) as inertia torque TIpre. Storage unit12may store a table that correlates the rate-of-change of EG speed (dΩe/dt) and inertia torque TIpre. In this case, inertia torque obtaining section11crefers to the table to obtain inertia torque TIpre corresponding to the rate-of-change of EG speed (dΩe/dt).

As described above, current torque obtaining section11aobtains current transmission torque Tpre based on EG torque TEpre and inertia torque TIpre. For example, storage unit12may store in advance an expression that defines the relationship among current transmission torque Tpre, EG torque TEpre, and inertia torque TIpre, and current torque obtaining section11amay substitute EG transmission torque TEpre and inertia torque TIpre obtained by the processing described above into the expression, in order to calculate current transmission torque Tpre. For example, storage unit12may store the following expression (1):
Tpre=(TEpre−TIpre)×Pratio  (1)
where Pratio is the gear ratio of primary speed reducing mechanism36(Pratio=the number of teeth of driven-side primary reduction gear36b/the number of teeth of drive-side primary reduction gear36a).

The processing for calculating current transmission torque Tpre is not limited to the aforementioned processing. For example, storage unit12may store a table or an expression that correlates current transmission torque Tpre with engine speed, accelerator displacement, and the rate-of-change of EG speed. In this case, current torque obtaining section11acan use the table or expression to directly obtain current transmission torque Tpre from engine speed, the rate-of-change of EG speed, and accelerator displacement.

The processing executed by post-completion torque obtaining section11dis now described. Post-completion torque obtaining section11dexecutes processing for obtaining post-completion transmission torque Tfin described above. Specifically, post-completion torque obtaining section11dobtains post-completion transmission torque Tfin based on torque TEfin (hereinafter referred to as post-completion EG torque) estimated to be outputted from engine30after completion of engagement of clutch40and inertia torque TIfin (hereinafter referred to as post-completion inertia torque) estimated to be produced in the mechanism upstream of drive-side member41in the torque transmission path after completion of clutch engagement.

The processing for estimating post-completion EG torque TEfin is first described. Post-completion EG torque obtaining section11eestimates engine speed after completion of clutch engagement based on the rotational speed of driven-side member42or a mechanism downstream of driven-side member42. Post-completion EG torque obtaining section11ethen estimates post-completion EG torque TEfin based on the estimated engine speed and based on accelerator displacement.

For example, post-completion EG torque obtaining section11edetects the current rotational speed of driven-side member42and the rotational speed of drive-side member41, in order to calculate the difference in rotational speed between these members (hereinafter referred to as clutch rotational speed difference Ωdiff). Post-completion EG torque obtaining section11ealso calculates current engine speed Ωe. Then, post-completion EG torque obtaining section11esubstitutes the calculated clutch rotational speed difference Ωdiff and the calculated engine speed Ωe into the expression stored in advance in storage unit12, to define the obtained value as engine speed Ωfin after completion of clutch engagement. For example, post-completion EG torque obtaining section11emay substitute the current clutch rotational speed difference Ωdiff and engine speed Ωe into the following expression (2), to define the obtained value as engine speed Ωfin after completion of clutch engagement.
Ωfin=Ωe−(Ωdiff×Pratio)  (2)

Post-completion EG torque obtaining section11ealso detects accelerator displacement based on the signal inputted from accelerator operation detector17. Post-completion EG torque obtaining section11ethen defines torque corresponding to engine speed Ωfin and accelerator displacement as post-completion EG torque TEfin using, for example, the EG torque table described above.

The processing for estimating post-completion inertia torque TIfin is now described. Post-completion inertia torque obtaining section11festimates post-completion inertia torque TIfin based on the current rate-of-change of rotational speed (variation in rotational speed per unit time, hereinafter referred to as rate-of-change of rotational speed) of the mechanism provided downstream of drive-side member41in the torque transmission path, such as driven-side member42, countershaft55, and axle3a.

The processing for estimating post-completion inertia torque TIfin is described herein using driven-side member42in the mechanism downstream of drive-side member41as an example. Post-completion inertia torque obtaining section11fcalculates the current rate-of-change of rotational speed (dΩcl/dt) of driven-side member42. Then, post-completion inertia torque obtaining section11fsubstitutes the calculated rate-of-change of rotational speed (dΩcl/dt) of driven-side member42into the following expression (3), for example, to calculate post-completion inertia torque TIfin.
TIfin=I×(dΩcl/dt)×Pratio  (3)

Storage unit12stores in advance an expression that defines the relationship between the rate-of-change of rotational speed (dΩcl/dt) and post-completion inertia torque TIfin.

Post-completion inertia torque obtaining section11fmay estimate post-completion inertia torque TIfin based on the rate-of-change of rotational speed of a component such as countershaft55or axis3arather than based on the rate-of-change of rotational speed (dΩcl/dt) of driven-side member42. In this case, post-completion inertia torque obtaining section11fmultiplies the rate-of-change of rotational speed of such a component by the gear ratio of the mechanism located between the component and engine30(for example, the gear ratio of gearbox51and the gear ratio of primary speed reducing mechanism36after completion of engagement of clutch40), in order to calculate post-completion inertia torque TIfin.

Post-completion inertia torque obtaining section11fcalculates the rate-of-change of rotational speed (dΩcl/dt) of driven-side member42by the processing described above in a predetermined sampling cycle during engaging operation of clutch40, in order to sequentially calculate post-completion inertia torque TIfin based on the calculated rate-of-change of rotational speed (dΩcl/dt). Alternatively, post-completion inertia torque obtaining section11fmay continuously use the rate-of-change of rotational speed (dΩcl/dt) calculated immediately before clutch40is disengaged (for example, several hundred milliseconds before clutch40starts being disengaged) in the processing executed by clutch actuator control section11g, rather than calculating the rate-of-change of rotational speed (dΩcl/dt) in a predetermined sampling cycle. The processing executed by clutch actuator control section11gwill be discussed later.

The processing for calculating post-completion transmission torque Tfin is now described. Post-completion torque obtaining section11dsubstitutes post-completion EG torque TEfin and post-completion inertia torque TIfin calculated as described above into an expression that defines the relationship between these torques and post-completion transmission torque Tfin, in order to calculate post-completion transmission torque Tfin. For example, post-completion torque obtaining section11dsubstitutes post-completion EG torque TEfin and post-completion inertia torque TIfin into the following expression (4) to calculate post-completion transmission torque Tfin.
Tfin=(TEfin−TIfin)×Pratio  (4)

Post-completion torque obtaining section11dmay calculate post-completion transmission torque Tfin based on the calculation result of expression (4) and a preset correction value. For example, post-completion torque obtaining section11dmay define the value obtained by multiplying (TEfin−TIfin)×Pratio in expression (4) by a correction value k as post-completion transmission torque Tfin. For example, correction value k is determined according to accelerator displacement by the rider, and set so as to increase in proportion to accelerator displacement.

The processing executed by clutch actuator control section11gis now described. Clutch actuator control section11gactuates clutch actuator14to control the degree of engagement of clutch40based on current transmission torque Tpre obtained by current torque obtaining section11aand post-completion transmission torque Tfin estimated by post-completion torque obtaining section11d. Clutch actuator control section11gexecutes the following processing, for example.

Storage unit12stores in advance an expression (hereinafter referred to as actuation amount relational expression) that defines the relationship between the difference (hereinafter referred to as torque deviation) between current transmission torque Tpre and post-completion transmission torque Tfin and the actuation amount of clutch actuator14. Clutch actuator control section11gcalculates the torque deviation (Tfin−Tpre) every time current torque obtaining section11acalculates current transmission torque Tpre. Clutch actuator control section11gthen substitutes the torque deviation (Tfin−Tpre) into the actuation amount relational expression in order to calculate the amount by which clutch actuator14is to be actuated (hereinafter referred to as command actuation amount) and outputs a control signal to clutch actuator drive circuit13according to the command actuation amount. Clutch actuator drive circuit13supplies driving power to clutch actuator14according to the input control signal.

FIG. 5is a graph showing the relationship between the torque deviation (Tfin−Tpre) and the command actuation amount obtained from the actuation amount relational expression. InFIG. 5, the actuation amount relational expression is established such that if the torque deviation (Tfin−Tpre) is positive, clutch actuator14is actuated in the direction to engage clutch40. In contrast, the actuation amount relational expression is established such that if the torque deviation (Tfin−Tpre) is negative, clutch actuator14is actuated in the direction to disengage clutch40. In addition, the actuation amount relational expression is established such that the command actuation amount increases in proportion to the torque deviation (Tfin−Tpre).

Storage unit12stores two actuation amount relational expressions. One expression (hereinafter referred to as engagement actuation amount relational expression) is to actuate clutch actuator14in the direction to engage clutch40when the torque deviation (Tfin−Tpre) is positive as shown inFIG. 5. The other expression (hereinafter referred to as disengagement actuation amount relational expression) is to actuate clutch actuator14in the direction to disengage clutch40.FIG. 6is a graph showing the relationship between the torque deviation (Tfin−Tpre) and the command actuation amount obtained from the disengagement actuation amount relational expression. InFIG. 6, the actuation amount relational expression is established such that if the torque deviation (Tfin−Tpre) is positive, clutch actuator14is actuated in the direction to disengage clutch40, in contrast to the graph shown inFIG. 5.

Clutch actuator control section11gselects either the engagement or disengagement actuation amount relational expression depending on whether the clutch rotational speed difference is positive or negative. Specifically, if the clutch rotational speed difference is positive, clutch actuator control section11gselects the engagement actuation amount relational expression to substitute the torque deviation (Tfin−Tpre) into the engagement actuation amount relational expression. On the contrary, if the clutch rotational speed difference is negative, clutch actuator control section11gselects the disengagement actuation amount relational expression to substitute the torque deviation (Tfin−Tpre) into the disengagement actuation amount relational expression.

By allowing clutch actuator control section11gto selectively use the engagement and disengagement actuation amount relational expressions depending on the clutch rotational speed difference, an engine brake can be applied on a downhill slope, for example. For example, as a result of accelerator displacement being set to zero on a downhill slope, the post-completion transmission torque Tfin is occasionally negative. At this time, if clutch40is disengaged, current transmission torque Tpre is zero, and therefore the torque deviation (Tfin−Tpre), which is the difference between post-completion transmission torque Tfin and current transmission torque Tpre, is negative. Also, when the rotational speed of driven-side member42is faster than that of drive-side member41, the disengagement actuation amount relational expression is selected. As a result, the command actuation amount corresponding to the torque deviation (Tfin−Tpre) is a value in the direction to engage clutch40, thereby applying an engine brake.

Alternatively, in place of the engagement and disengagement actuation amount relational expressions, storage unit12may store a table that correlates the command actuation amount with post-completion transmission torque Tfin and current transmission torque Tpre. In this case, clutch actuator control section11grefers to the table to directly obtain the command actuation amount corresponding to post-completion transmission torque Tfin and current transmission torque Tpre, without calculating the difference between post-completion transmission torque Tfin and current transmission torque Tpre.

When a gear change command is inputted in the state where execution of gear change control is permitted in the processing executed by reception permission determination section11i, clutch actuator control section11gfirst disengages clutch40to temporarily interrupt torque transmission from drive-side member41to driven-side member42. The processing executed, by reception permission determination section11iwill be discussed later. After that, clutch actuator control section11gdetects that some shift gears53a,53b,54a,54bcorresponding to the gear change command have completely been moved based on the signal inputted from gear position detector21, and then starts the aforementioned control to engage clutch40.

The processing executed by shift actuator control section11his now described. When a gear change command by the rider is inputted in the state where execution of gear change control is permitted in the processing executed by reception permission determination section11i, shift actuator control section11hactuates shift actuator16to change shift gears53a,53b,54a,54b. The processing executed by reception permission determination section11iwill be discussed later. Specifically, after detecting that clutch40has been disengaged based on the signal inputted from clutch position detector22, shift actuator control section11houtputs a control signal to shift actuator drive circuit15according to the gear change command. Shift actuator16is actuated by driving power supplied from shift actuator drive circuit15according to the control signal in order to move some of the shift gears53a,53b,54a,54b.

The processing executed by reception permission determination section11iis now described. When a next gear change command is inputted subsequently to a first gear change command during engaging operation of clutch40, reception permission determination section11idetermines whether or not to receive the next gear change command and perform gear change control according to the gear change command according to the difference between current transmission torque Tpre and post-completion transmission torque Tfin, that is, the torque deviation (Tfin−Tpre). Specifically, reception permission determination section11idetermines whether or not the torque deviation (Tfin−Tpre) satisfies a predetermined condition (hereinafter referred to as reception permission condition).

The reception permission condition herein is that the torque deviation (Tfin−Tpre) is less than a predetermined value (hereinafter referred to as reception permission torque deviation (for example, a value close to zero)), for example. Alternatively, the reception permission condition may be that the torque deviation (Tfin−Tpre) is continuously less than the reception permission torque deviation for a predetermined time (hereinafter referred to as reception permission condition time) or more during engaging operation of clutch40.

Different reception permission conditions may be adopted depending on whether the gear change command inputted during engaging operation of clutch40is a gear change command for a shift-up or a gear change command for a shift-down. For example, the reception permission condition time adopted for a shift-down may be longer than that adopted for a shift-up. This extends the time for which the rider senses deceleration at the shift gear corresponding to the first gear change command at a shift-down compared to a shift-up, thereby improving riding comfort of the vehicle at gear changes.

When current transmission torque Tpre and post-completion transmission torque Tfin satisfy the reception permission condition, reception permission determination section11istores in storage unit12information indicating that the start of gear change control according to the gear change command inputted subsequently is allowed even during execution of gear change control according to the first gear change command. For example, reception permission determination section11isets a flag (hereinafter referred to as permission flag) on indicating that the start of gear change control is allowed. In this case, reception permission determination section11isets the permission flag off when current transmission torque Tpre and post-completion transmission torque Tfin do not satisfy the reception permission condition any more.

When a first gear change command is inputted and gear change control is started, reception permission determination section11imay store in storage unit12information indicating that reception of a next gear change command is restricted. For example, reception permission determination section11imay set a flag (hereinafter referred to as prohibition flag) on indicating that reception of a gear change command is restricted. In this case, reception permission determination section11isets the prohibition flag off when current transmission torque Tpre and post-completion transmission torque Tfin have come to satisfy the reception permission condition.

The flow of processing executed by control unit11is now described.FIG. 7is a flowchart showing an example of processing executed by control unit11. Reception permission determination section11imeasures the elapsed time since the torque deviation (Tfin−Tpre) becomes less than the reception permission torque deviation using a variable i (hereinafter referred to as time measurement variable) that increments by one in each sampling cycle of current transmission torque Tpre. Time measurement variable i is initially set to zero. In this example, when current transmission torque Tpre and post-completion transmission torque Tfin do not satisfy the reception permission condition described above, storage unit12stores the prohibition flag indicating that reception of a next gear change command is restricted.

Reception permission determination section11ifirst determines whether or not a gear change command is inputted from shift-up switch9aor shift-down switch9b(S101). If a gear change command is not inputted, control unit11waits for a gear change command. On the other hand, if a gear change command is inputted, reception permission determination section11idetermines whether or not the prohibition flag is set on (S102). If the prohibition flag is set on, reception permission determination section11ireturns to S101. If the prohibition flag is set off, reception permission determination section11isets on the prohibition flag (S103). In addition, clutch actuator control section11gactuates clutch actuator14to disengage clutch40, and shift actuator control section11hmoves some of the shift gears53a,53b,54a,54bcorresponding to the gear change command after detecting that clutch40has been disengaged (S104).

Next, post-completion torque obtaining section11dcalculates post-completion transmission torque Tfin, and current torque obtaining section11acalculates current transmission torque Tpre (S105). Clutch actuator control section11gthen substitutes the torque deviation (Tfin−Tpre) into the engagement or disengagement actuation amount relational expression described above (seeFIG. 5or6) to calculate the command actuation amount for clutch actuator14(S106). As described above, if the clutch rotational speed difference is positive (if the rotational speed of drive-side member41is more than that of driven-side member42), clutch actuator control section11gsubstitutes the torque deviation (Tfin−Tpre) into the engagement actuation amount relational expression. If the clutch rotational speed difference is negative (if the rotational speed of drive-side member41is less than that of driven-side member42), clutch actuator control section11gsubstitutes the torque deviation (Tfin−Tpre) into the disengagement actuation amount relational expression. Clutch actuator control section11goutputs a control signal to clutch actuator drive circuit13according to the command actuation amount to change the degree of engagement of clutch40(step S107). This brings clutch40into a half-clutch state, in which the degree of engagement is gradually changed.

Reception permission determination section11inext performs processing for determining whether or not the reception permission condition is satisfied. Specifically, reception permission determination section11ifirst determines whether or not the torque deviation (Tfin−Tpre) is less than the reception permission torque deviation (S108). If the torque deviation (Tfin−Tpre) is less than the reception permission torque deviation, reception permission determination section11iincrements time measurement variable i (S109), and determines whether or not time measurement variable i exceeds a predetermined value (hereinafter referred to as reception permission condition value) (S110). If time measurement variable i has already exceeded the reception permission condition value, reception permission determination section11ijudges that the torque deviation (Tfin−Tpre) has continuously been less than the reception permission torque deviation for the reception permission condition time described above or more, and sets the prohibition flag off in storage unit12(S111). Reception permission determination section11ithen determines whether or not a next gear change command is inputted (S112).

On the other hand, if the torque deviation (Tfin−Tpre) is not less than the reception permission torque deviation in S108, the reception permission condition is not satisfied. Therefore, reception permission determination section11iresets time measurement variable i to zero (S116), and proceeds to the processing in S112without setting the prohibition flag off in storage unit12. If time measurement variable i has not exceeded the reception permission condition value yet in S110, the reception permission condition is not satisfied. Therefore, reception permission determination section11iproceeds to the processing in S112without setting the prohibition flag off.

If a next gear change command is not inputted in S112, clutch actuator control section11gcalculates the clutch rotational speed difference, and determines whether or not the calculated rotational speed difference is less than the rotational speed difference for discontinuing half-clutch (step S114). If the clutch rotational speed difference is less than the rotational speed difference for discontinuing half-clutch, clutch actuator control section11gcompletely engages drive-side member41and driven-side member42, and discontinues the half-clutch state (S115), to complete the gear change control.

On the other hand, if a gear change command is inputted in S112even during engaging operation of clutch40, the reception permission determination section11idetermines whether or not the prohibition flag in storage unit12is set off (S113). If the prohibition flag in storage unit12is still set on, the operating state of the vehicle (the degree of engagement of clutch40) is not suitable to start gear change control according to the gear change command inputted in S112. Therefore, control unit11proceeds to the processing in S114without responding to the gear change command. On the other hand, if the prohibition flag in storage unit12is set off in S113, control unit11returns to the processing in S103to start gear change control according to the gear change command. Control unit11repeats the above processing in a predetermined cycle (for example, several milliseconds) until the half-clutch state is discontinued in S115. The aforementioned processing is an example of processing executed by control unit11at gear changes.

The results of the processing executed by control unit11are now described.FIG. 8is a time chart showing examples of the results of processing executed at gear changes, whereinFIG. 8(a) shows changes over time in the degree of engagement of clutch40,FIG. 8(b) shows changes over time in post-completion transmission torque Tfin,FIG. 8(c) shows changes over time in current transmission torque Tpre, andFIG. 8(d) shows the ON/OFF state of the prohibition flag. In the example to be described, the rider commands a shift-down, and an engine brake is applied, that is, current transmission torque Tpre transmitted from drive-side member41to driven-side member42of clutch40is negative. Also, in the example to be described, a shift-down is commanded twice during engaging operation of clutch40.

When a signal to command a gear change is inputted from shift-down switch9bat time t1, clutch actuator control section11gexecutes processing to disengage clutch40as shown inFIG. 8(a). At this time, reception permission determination section11iexecutes processing to set the prohibition flag on as shown inFIG. 8(d). In addition, current transmission torque Tpre transmitted from drive-side member41to driven-side member42of clutch40becomes zero as shown inFIG. 8(c).

When some of the shift gears53a,53b,54a,54bhave completely been moved in the processing executed by shift actuator control section11hat time t2, torque estimated to be transmitted to driven-side member42after completion of engaging operation of clutch40(when drive-side member41and driven-side member42have completely been engaged) corresponding to the first gear change command (the gear change command inputted at time t1) is set as post-completion transmission torque Tfin in processing executed by post-completion torque obtaining section11d, as shown inFIG. 8(b). Clutch actuator control section11gthen executes processing to actuate clutch actuator14according to the difference between post-completion transmission torque Tfin and current transmission torque Tpre, in order to bring clutch40into a half-clutch state as shown inFIG. 8(a). The difference between current transmission torque Tpre being transmitted to drive-side member42and post-completion transmission torque Tfin becomes gradually smaller as shown inFIGS. 8(b) and8(c).

when another gear change command is inputted at time t3, gear change control corresponding to this gear change command is not started at this time because the prohibition flag is still set on as shown inFIG. 8(d). When current transmission torque Tpre reaches post-completion transmission torque Tfin at time t4, and the torque deviation, or the difference between them, becomes less than reception permission torque deviation, reception permission determination section11imeasures the time since the torque deviation becomes less than the reception permission torque deviation. Then, when it is judged that the elapsed time has become the reception permission condition time or more at time t5, the prohibition flag is set off as shown inFIG. 8(d). Since current transmission torque Tpre has reached post-completion transmission torque Tfin at time T4, the rider can sense deceleration at the shift gear corresponding to the gear change command inputted first (the command inputted at time t1) after time t4.

When a gear change command is inputted again at time t6, gear change control corresponding to the gear change command is started since the prohibition flag is set off. As a result, clutch actuator control section11gdisengages clutch40again as shown inFIG. 8(a), and current transmission torque Tpre becomes zero again as shown inFIG. 8(c). Also, at this time, reception permission determination section11isets the prohibition flag on again as shown inFIG. 8(d).

When some of the shift gears53a,53b,54a,54bhave completely been moved at time t7, post-completion torque obtaining section11dsets post-completion transmission torque Tfin estimated to be transmitted via clutch40after completion of engagement of clutch40(at time t10inFIG. 8), as shown inFIG. 8(b). Clutch actuator control section11gthen executes processing to actuate clutch actuator14according to the difference between current transmission torque Tpre and post-completion transmission torque Tfin, in order to bring clutch40closer to an engaged state. When accelerator displacement has been varied during the gear change control, a post-completion transmission torque Tfin different from that set when the first gear change command is inputted is set at time t7, as shown inFIG. 8(b). After that, clutch40is brought into a half-clutch state as shown inFIG. 8(a), and the difference between current transmission torque Tpre and post-completion transmission torque Tfin becomes gradually smaller as shown inFIGS. 8(b) and8(c).

When current transmission torque Tpre reaches post-completion transmission torque Tfin at time t8, and the torque deviation becomes less than reception permission torque deviation, reception permission determination section11imeasures the elapsed time since time t8. When the elapsed time since time t8exceeds the reception permission condition time at time t9, reception permission determination section11iexecutes the processing to set the prohibition flag off again as shown inFIG. 8(d). If current transmission torque Tpre and post-completion transmission torque Tfin coincide with each other at time t8, the degree of engagement of clutch40is maintained thereafter as shown inFIG. 8(a).

When the clutch rotational speed difference becomes less than the rotational speed difference for discontinuing half-clutch at time t10, clutch actuator control section11gcompletely engages drive-side member41and driven-side member42. Gear change control by control unit11is thus finished.

In gear change control device10described above, after a first gear change command is inputted, a next gear change command is received according to the difference between current transmission torque Tpre and post-completion transmission torque Tfin. This allows the rider to sense deceleration and acceleration that will occur after completion of engagement of clutch40, even before clutch40is completely engaged. Gear change control device10can then receive the next gear change command after the rider senses deceleration or acceleration at the shift gear corresponding to the first gear change command. As a result, riding comfort is improved by reducing the occurrence of deceleration and acceleration exceeding the expectation of the rider. For example, the rider can sense deceleration and acceleration at the shift gear corresponding to the gear change command inputted first, to judge the necessity for another gear change and expect deceleration and acceleration at another gear change. Consequently, riding comfort is improved by reducing the occurrence of deceleration and acceleration exceeding the expectation of the rider.

In addition, in gear change control device10, current torque obtaining section11acalculates current transmission torque Tpre based on EG torque TEpre being outputted from engine30and inertia torque TIpre of the mechanism upstream of drive-side member41in the torque transmission path. This allows calculation of current transmission torque Tpre by simple processing without using a sensor for directly detecting torque or the like.

Further, in gear change control device10, post-completion torque obtaining section11destimates post-completion EG torque TEfin to be outputted from engine30after completion of engagement of clutch40and post-completion inertia torque TIfin of the mechanism upstream of drive-side member41after completion of engagement of clutch40, and calculates post-completion transmission torque Tfin based on the estimated EG torque TEfin and the estimated post-completion inertia torque TIfin. This allows calculation of current transmission torque Tpre by simple processing. Gear change control device10may also execute the processing described above when gear change commands for a shift-up are successively inputted, for example, rather than when gear change commands for a shift-down are inputted as in the example described herein.

Moreover, in gear change control device10, control unit11starts receiving a next gear change command according to the time when the difference between current transmission torque Tpre and post-completion transmission torque Tfin becomes a predetermined value (in the above description referred to as reception permission torque deviation) or less. This allows the rider to sense deceleration and acceleration that will occur after completion of engagement of clutch40, even before clutch40is completely engaged, by setting the reception permission torque deviation to a small value, for example. Gear change control device10then receives the next gear change command after the rider senses deceleration or acceleration at the shift gear corresponding to the first gear change command. As a result, riding comfort is improved by reducing the occurrence of deceleration and acceleration exceeding the expectation of the rider.

The present invention is not limited to the embodiments of gear change control device10and motorcycle1described above, and can be modified variously. For example, although motorcycle1is provided with engine30as a driving source, the driving source may be an electric motor or a hybrid engine combining an electric motor and an engine.

In addition, in the above description, gear change control device10and clutch40are applied to motorcycle1. However, the gear change control device described above may be applied to other vehicles such as an automobile.

While particular embodiments of the invention have been described, it should be understood that these embodiments are exemplary, and not restrictive. Various modifications will be apparent to those of skill in the art and are within the scope of the present invention as set forth in the following claims.