Patent Description:
As a shift device for a straddle type vehicle, a shift device in which a lost motion mechanism is provided on a shift pedal is known (for example, see <CIT>). In a shift device disclosed in <CIT>, one end of a shift shaft protrudes from an upper side surface of a crankcase, a shift pedal extends rearward from a lower side surface of the crankcase, and one end of the shift shaft and an intermediate portion of the shift pedal are coupled via a shift rod. While a load of a dog of a transmission device acts on the shift pedal during a shift operation, an operation feeling of the shift operation is improved by absorbing the load with the lost motion mechanism of the shift pedal.

<CIT> discloses a power transmission apparatus including a shift drum, a clutch, a clutch lifter, and a transmission body. The shift drum makes a dowel be extracted/inserted between a shifter and a shift gear. The clutch has first friction plates and second friction plates. The first friction plates rotate around a main shaft by receiving power from a crankshaft. The second friction plates are disposed alternately with the first friction plates and are relatively non-rotatably supported by the main shaft. The clutch lifter is displaced between a connection position at which power is transmitted by the clutch and a disconnection position at which the transmission of the power is disconnected. The transmission body transmits a driving force to the shift drum while the clutch lifter moves from the connection position to the disconnection position, in accordance with rotation of a shift spindle that rotates in accordance with a driving force.

<CIT> discloses a shift position changing drive member for a transmission including an arm member capableof turning around theaxis of a shift spindle for drivingly turning a shift drum in response to the turning of the shift spindle wherein the shift drum is prevented from coming into a neutral position even if the shifting speed is stopped in midstream. A lost motion spring includes gripping portions gripping a pressing portion from both sides of a coil portion surrounding the shift spindle. An arm member of shift position changing drive member is provided with a pressure-receiving member which is gripped by both gripping portions in such a manner that when the turning member is turned, if, in response to the turning direction, the pressing portion abuts against one of the gripping portions for turning, the other of the gripping portions abuts against the pressure-receiving member.

However, since the lost motion mechanism disclosed in <CIT> is provided on the shift pedal outside the engine, there is a problem that the shift pedal is increased in size and a degree of freedom of a layout of the shift device is reduced.

It is an object of the present claims to provide a shift device capable of improving convenience of a user with a compact structure and a transmission device and an engine with such a shift device.

According to a shift device according to the present invention, a shift shaft rotates in response to a shift operation, but immediately after the shift operation, a drive plate does not move due to a reaction force of a shift cam, and the rotation of the shift shaft is absorbed by a lost motion mechanism. A further shift operation causes the rotation of the shift shaft to be transmitted to the drive plate with a delay, and the drive plate moves the shift cam. Accordingly, immediately after a shift operation with a large operating load, depression of the shift pedal is not transmitted to the shift cam, thereby improving a feeling of the shift operation. Further, by attaching the lost motion mechanism to one end of the shift shaft, a structure becomes compact and a degree of freedom of a layout of the shift device is improved.

A shift device according to an aspect of the present claims causes a transmission device to shift in response to a shift operation of a shift pedal. A shift shaft rotates in response to the shift operation of the shift pedal, the shift cam is moved by a drive plate in response to the rotation of the shift shaft, and a coupling state of a shift gear of the transmission device is changed by the shift cam. The lost motion mechanism is interposed between the shift shaft and the drive plate, the rotation of the shift shaft is absorbed by the lost motion mechanism, and power transmission to the drive plate is delayed. Accordingly, the shift shaft rotates in response to the shift operation, but immediately after the shift operation, the drive plate does not move due to reaction force of the shift cam, and the rotation of the shift shaft is absorbed by the lost motion mechanism. A further shift operation causes the rotation of the shift shaft to be transmitted to the drive plate with a delay, and the drive plate moves the shift cam. Accordingly, immediately after a shift operation with a large operating load, depression of the shift pedal is not transmitted to the shift cam, thereby improving a feeling of the shift operation. Further, by attaching the lost motion mechanism to one end of the shift shaft, a structure becomes compact and a degree of freedom of a layout of the shift device is improved.

Hereinafter, an engine according to the present embodiment will be described with reference to the accompanying drawings. <FIG> is a right side view of the engine according to the present embodiment. <FIG> is a left side view of the engine according to the present embodiment. Further, in the following drawings, an arrow FR indicates a vehicle front side, an arrow RE indicates a vehicle rear side, an arrow L indicates a vehicle left side, and an arrow R indicates a vehicle right side.

As shown in <FIG>, the engine <NUM> includes a crankcase <NUM> including a vertically split structure including an upper case <NUM> and a lower case <NUM>. The upper case <NUM> is integrated with a cylinder, and a cylinder head <NUM> and a cylinder head cover <NUM> are attached to an upper portion of the upper case <NUM>. A valve gear (not shown) that operating an intake and exhaust valve is accommodated inside the cylinder head <NUM> and the cylinder head cover <NUM>. An oil pan <NUM> that stores oil for lubrication and cooling is attached to a lower portion of the lower case <NUM>. A clutch cover <NUM> that covers a clutch <NUM> from a side is attached to a right side surface of the crankcase <NUM>.

As shown in <FIG>, a magnet cover <NUM> that covers a magnet (not shown) from the side is attached to a left side surface of the crankcase <NUM>. A sprocket cover <NUM> that covers a part of a drive chain (not shown) that drives a rear wheel and a drive sprocket <NUM> (see <FIG>) from the side is attached to a rear side of the magnet cover <NUM>. An oil control valve <NUM> that controls an oil pressure of the engine <NUM> is attached above the sprocket cover <NUM>. A transmission device <NUM> that transmits power from a crankshaft <NUM> (see <FIG>) and a shift device <NUM> that causes the transmission device <NUM> to shift are accommodated inside the engine <NUM>.

Such an engine <NUM> employs a quick shift that detects the shift operation of a driver and is capable of shifting without clutch operation. In the general quick shift, an operation stroke of the shift pedal is detected by a stroke sensor provided outside the engine <NUM>. In this case, a layout of the stroke sensor is restricted by other parts outside the engine <NUM>, and the stroke sensor is exposed to the outside, and thus a weatherability requirement such as rust prevention is increasing. Therefore, a method for detecting the shift operation in the engine <NUM> using a gear position sensor has also been studied.

In the quick shift using the gear position sensor, in a state in which a load is applied to a dog of the shift gear, rotation of the shift cam is detected by the gear position sensor, and an engine output is controlled to reduce the load applied to the dog. However, there is a time lag between detecting the rotation of the shift cam and controlling the engine output, and the load continues to be applied to the dog for a certain period of time immediately after the shift operation, and thus the operation feeling becomes stiff. Therefore, in the present embodiment, a lost motion mechanism <NUM> is provided in the shift device <NUM> to delay the power transmission from the shift pedal to the shift cam immediately after the shift operation.

The transmission device and the shift device will be described with reference to <FIG>. <FIG> is a schematic view of the transmission device and the shift device according to the present embodiment. <FIG> is a perspective view of the shift device according to the present embodiment. <FIG> is a sectional perspective view of the shift device according to the present embodiment.

As shown in <FIG>, the transmission device <NUM> is provided with a counter shaft <NUM> and a drive shaft <NUM> parallel to the crankshaft <NUM> (see <FIG>). The clutch <NUM> is provided at one end portion of the counter shaft <NUM>, and the power from the crankshaft <NUM> to the counter shaft <NUM> is transmitted and blocked by the clutch <NUM>. The counter shaft <NUM> and the drive shaft <NUM> are coupled to each other via a plurality of shift gears <NUM> and <NUM>. The drive sprocket <NUM> is provided at one end portion of the drive shaft <NUM>, and the power is transmitted to the rear wheel (not shown) by the drive sprocket <NUM>.

The shift gears <NUM> and <NUM> respectively provided on the counter shaft <NUM> and the drive shaft <NUM> includes a fixed gear that rotates integrally with the shaft and an idler gear that idles with respect to the shaft. A claw called the dog is formed on each of a side surface of the fixed gear and the idler gear, and the fixed gear is moved in an axial direction by shift forks <NUM>, <NUM>, and the fixed gear and the idler gear which are adjacent to each other in the axial direction are coupled or separated. A shift cam <NUM> and a shift shaft <NUM> are provided below the transmission device <NUM> in a manner of being parallel to the shafts <NUM> and <NUM>. A cam groove that causes the shift forks <NUM>, <NUM> to slide in the axial direction is formed on an outer peripheral surface of the shift cam <NUM>.

One end portion of the shift cam <NUM> is provided with a cam plate <NUM>, and the shift shaft <NUM> is provided with a drive plate <NUM> coupled to the cam plate <NUM>. The lost motion mechanism <NUM> is provided at one end portion of the shift shaft <NUM>, and the shift shaft <NUM> and the drive plate <NUM> are coupled via the lost motion mechanism <NUM>. A shift pedal <NUM> is coupled to the other end portion of the shift shaft <NUM> via a link mechanism (not shown) or the like. As described above, the engine <NUM> is provided with the shift device <NUM> in which the lost motion mechanism <NUM> is interposed in a power transmission path from the shift pedal <NUM> to the shift cam <NUM>.

When the shift pedal <NUM> is operated by the driver, the shift shaft <NUM> is rotated by a predetermined angle, and rotation of the shift shaft <NUM> is transmitted to the shift cam <NUM> via the lost motion mechanism <NUM> and the like. When the shift cam <NUM> is rotated by a predetermined angle, the shift forks <NUM> and <NUM> slide in the axial direction, and a coupling state between the shift gears <NUM> and <NUM> respectively provided on the counter shaft <NUM> and the drive shaft <NUM> is changed. The shift stage is switched depending on the coupling state between the shift gears <NUM> and <NUM> respectively provided on the counter shaft <NUM> and the drive shaft <NUM>, and driving force of the crankshaft <NUM> is transmitted to the rear wheel in a state in which a rotation speed and torque are changed.

A shift sensor <NUM> is provided in the shift device <NUM>, and the shift operation is detected by the shift sensor <NUM>. For example, the shift operation is detected from the operation of the shift pedal <NUM>, the rotation of the shift shaft <NUM>, and actuation of the lost motion mechanism <NUM>, by the shift sensor <NUM>. A detection signal of the shift sensor <NUM> is input to a control device <NUM> of the engine <NUM> (see <FIG>), and engine torque input to the transmission device <NUM> is controlled by the control device <NUM>. Since the engine torque is temporarily reduced by the control device <NUM> after the shift operation, the load applied to the dog of the shift gears <NUM> and <NUM> is reduced.

As described above, there is a time lag between the detection of the shift operation and the reduction of the engine torque, and the load applied to the dogs of the shift gears <NUM> and <NUM> is not sufficiently decreased immediately after the shift operation. Therefore, the rotation of the shift shaft <NUM> is absorbed by the lost motion mechanism <NUM> until the engine torque is temporarily reduced by the control device <NUM> after the shift operation, and the power transmission from the shift shaft <NUM> to the drive plate <NUM> is delayed. Further, since the power is transmitted from the shift pedal <NUM> to the shift cam <NUM> after an operating load of the shift operation becomes small, the operation feeling of the shift operation is improved.

As shown in <FIG> and <FIG>, the drive plate <NUM>, a shift arm <NUM>, and the lost motion mechanism <NUM> are attached to one end side of the shift shaft <NUM> of the shift device <NUM>. Operation force is input to the shift shaft <NUM> from the shift pedal <NUM> (see <FIG>), and the shift shaft <NUM> rotates in response to the shift operation of the shift pedal <NUM>. The drive plate <NUM> is supported by the shift shaft <NUM> in a manner of being rotatable relative to the shift shaft <NUM>. The rotation of the shift shaft <NUM> is input to the drive plate <NUM> via the lost motion mechanism <NUM>, and the shift cam <NUM> (see <FIG>) is moved by the drive plate <NUM> in response to the rotation of the shift shaft <NUM>.

The drive plate <NUM> extends from the shift shaft <NUM> toward the shift cam <NUM>. An opening <NUM> is formed in the drive plate <NUM>, and a camshaft <NUM> of the shift cam <NUM> enters the opening <NUM>. The shift cam <NUM> is provided with the cam plate <NUM> in a manner of facing the drive plate <NUM>. A claw <NUM> is formed on a distal side of the drive plate <NUM>, and a plurality of shift pins <NUM> are formed on the cam plate <NUM>. The claw <NUM> of the drive plate <NUM> hits the shift pin <NUM> of the cam plate <NUM>, and the drive plate <NUM> swings about the shift shaft <NUM> to rotate the shift cam <NUM>.

The coupling state of the shift gears <NUM> and <NUM> (see <FIG>) of the transmission device <NUM> is changed by the rotation of the shift cam <NUM>. Further, the shift shaft <NUM> is provided with the shift arm <NUM> on the other side in a vehicle width direction with respect to the drive plate <NUM>. When the shift shaft <NUM> is rotated, the shift arm <NUM> abuts against the shift pin <NUM> of the cam plate <NUM> to regulate a rotation angle of the shift cam <NUM>. A shaft return spring <NUM> is attached to the shift arm <NUM>, and after the shift operation, the shift shaft <NUM> is returned to an initial position by restoring force of the shaft return spring <NUM>. Thus, in the shift device <NUM>, the transmission device <NUM> shifts in response to the shift operation of the shift pedal <NUM>.

The lost motion mechanism <NUM> is interposed between the shift shaft <NUM> and the drive plate <NUM>, that is, in the middle of a transmission path from the shift shaft <NUM> to the drive plate <NUM>. The lost motion mechanism <NUM> transmits the power from the shift shaft <NUM> to the drive plate <NUM> via a lost motion plate <NUM>, a torsion coil spring <NUM>, and a pin <NUM> held by a pin holder <NUM>. Since the rotation of the shift shaft <NUM> is absorbed by the torsion coil spring <NUM> of the lost motion mechanism <NUM>, the power transmission from the shift shaft <NUM> to the drive plate <NUM> is delayed until a certain time elapses from immediately after the shift operation.

The lost motion plate <NUM> extends from the shift shaft <NUM> in a manner of facing the drive plate <NUM>. A tubular portion <NUM> is formed on a proximal end side of the lost motion plate <NUM>, the tubular portion <NUM> is fixed to the one end portion of the shift shaft <NUM>, and the lost motion plate <NUM> is integrally rotated with the shift shaft <NUM>. A long hole <NUM> extending along a rotation direction of the shift shaft <NUM> is formed in the lost motion plate <NUM>. The torsion coil spring <NUM> is attached to an outer peripheral surface of the tubular portion <NUM>, and both ends of the torsion coil spring <NUM> are hooked on a hook piece <NUM> at a distal of the lost motion plate <NUM>.

The pin holder <NUM> is attached to the shift shaft <NUM> between the lost motion plate <NUM> and the drive plate <NUM>. The pin holder <NUM> is supported by the shift shaft <NUM> via a needle bearing <NUM> such that the pin holder <NUM> rotates relative to the shift shaft <NUM>. The pin holder <NUM> extends along the lost motion plate <NUM>, and the pin <NUM> is press-fitted to a distal of the pin holder <NUM>. The pin <NUM> extends parallel to the shift shaft <NUM>, one end of the pin <NUM> is inserted into the long hole <NUM> of the lost motion plate <NUM>, and the other end of the pin <NUM> is coupled to the drive plate <NUM>.

One end side of the pin <NUM> is sandwiched between both ends of the torsion coil spring <NUM>, and the torsion coil spring <NUM> holds the pin <NUM> at a neutral position away from an end surface of the long hole <NUM>. When the pin <NUM> at the neutral position moves relative to the long hole <NUM> against elastic force of the torsion coil spring <NUM>, the rotation of the shift shaft <NUM> is absorbed by the lost motion mechanism <NUM>. Further, when the pin <NUM> moves against the elastic force of the torsion coil spring <NUM> and comes into contact with the end surface of the long hole <NUM>, the lost motion plate <NUM> and the drive plate <NUM> integrally rotate via the pin <NUM>, and the rotation of the shift shaft <NUM> is transmitted to the drive plate <NUM>.

The operation of the shift device will be described with reference to <FIG> are diagrams illustrating the operation of the shift device according to the present embodiment.

As shown in <FIG>, when the operation of the shift pedal <NUM> (see <FIG>) is started, the shift shaft <NUM> rotates and the lost motion plate <NUM> starts to swing. At this time point, the shift pin <NUM> on the cam plate <NUM> and the claw <NUM> of the drive plate <NUM> are separated from each other, and the drive plate <NUM> is isolated from the load applied to the dog of the shift gears <NUM> and <NUM> (see <FIG>). Therefore, since resistance force of the pin <NUM> is small, in a state in which the pin <NUM> is held at the neutral position of the long hole <NUM> by the torsion coil spring <NUM>, the lost motion plate <NUM> and the drive plate <NUM> integrally swing around the shift shaft <NUM> via the pin <NUM>.

As shown in <FIG>, when the shift pedal <NUM> is further operated, the rotation of the shift shaft <NUM> starts to be absorbed by the lost motion mechanism <NUM>. At this time point, the shift pin <NUM> on the cam plate <NUM> and the claw <NUM> of the drive plate <NUM> are in contact with each other, and the load applied to the dog of the shift gears <NUM> and <NUM> also acts on the drive plate <NUM>. Therefore, the resistance force of the pin <NUM> increases, and the pin <NUM> is relatively moved with respect to the long hole <NUM> against the elastic force of the torsion coil spring <NUM>. Although the lost motion plate <NUM> swings, the drive plate <NUM> does not move the shift cam <NUM>.

As shown in <FIG>, when an operation amount of the shift pedal <NUM> further increases, the rotation of the shift shaft <NUM> starts to be transmitted to the drive plate <NUM>. At this time point, the engine torque is reduced by the control device <NUM> (see <FIG>), and the load acting on the drive plate <NUM> is reduced. When the pin <NUM> comes into contact with the end surface of the long hole <NUM>, the lost motion plate <NUM> and the drive plate <NUM> integrally swing about the shift shaft <NUM> via the pin <NUM>. Although the shift cam <NUM> is moved by the drive plate <NUM>, the operating load of the shift operation is sufficiently small due to the reduction of the engine torque.

As described above, in the shift device <NUM> according to the present embodiment, the engine torque is controlled by the control device <NUM> before the pin <NUM> comes into contact with the end surface of the long hole <NUM>. Therefore, the shift of the transmission device <NUM> (see <FIG>) is completed without increasing the operating load of the shift operation, and the operation feeling is improved. Further, after the operation of the shift pedal <NUM>, the shift shaft <NUM> is returned to the initial position by the restoring force of the shaft return spring <NUM> (see <FIG>), and the pin <NUM> is returned to the neutral position of the long hole <NUM> by the restoring force of the torsion coil spring <NUM>. A positional relationship between the drive plate <NUM> and the lost motion plate <NUM> is returned to an initial state.

A layout of the lost motion mechanism will be described with reference to <FIG> and <FIG>. <FIG> is a right side view of the crankcase according to the present embodiment. <FIG> is a cross-sectional view of the crankcase taken along a line A-A in <FIG>.

As shown in <FIG>, an accommodation chamber of the clutch <NUM> is formed on one side (right side) of the crankcase (case) <NUM> in the vehicle width direction. The accommodation chamber of the clutch <NUM> is extended rearward, and the lost motion mechanism <NUM> is accommodated in an extended portion of the accommodation chamber. By accommodating the lost motion mechanism <NUM> in the crankcase <NUM>, it is possible to lower a weatherability requirement such as rust prevention without affecting a layout of an outside of a vehicle body. Further, since the lost motion mechanism <NUM> is accommodated in the accommodation chamber of the clutch <NUM>, it becomes unnecessary to lubricate the lost motion mechanism <NUM> by splashing or immersion of engine oil during operation.

As shown in <FIG>, the clutch <NUM> is provided at one side of the transmission device <NUM> in the vehicle width direction, and the lost motion mechanism <NUM> is positioned behind the clutch <NUM>. The clutch <NUM> is provided with a driven gear <NUM> to which the power is input from the crankshaft <NUM> (see <FIG>). The pin holder <NUM>, the lost motion plate <NUM>, and the torsion coil spring <NUM> excluding the pin <NUM> of the lost motion mechanism <NUM> are provided in a manner of being accommodated in an entire length of the clutch <NUM> including the driven gear <NUM>. The lost motion mechanism <NUM> is provided by effectively utilizing a space behind the clutch <NUM>, and an increase in dimension of the crankcase <NUM> in the vehicle width direction is prevented.

As described above, according to the shift device <NUM> of the present embodiment, the shift shaft <NUM> rotates in response to the shift operation, but immediately after the shift operation, the drive plate <NUM> does not move due to reaction force of the shift cam <NUM>, and the rotation of the shift shaft <NUM> is absorbed by the lost motion mechanism <NUM>. A further shift operation causes the rotation of the shift shaft <NUM> is transmitted to the drive plate <NUM> with a delay, and the shift cam <NUM> is moved by the drive plate <NUM>. Accordingly, immediately after the shift operation with the large operating load, depression of the shift pedal <NUM> is not transmitted to the shift cam <NUM>, thereby improving the feeling of the shift operation. Further, since the lost motion mechanism <NUM> is attached to the one end portion of the shift shaft <NUM>, the layout flexibility of the shift device <NUM> is improved with the compact structure.

The lost motion mechanism using the torsion coil spring has been described in the above embodiment, the lost motion mechanism is configured to absorb the rotation of the shift shaft and delay the power transmission to the drive plate. For example, the lost motion mechanism may be a lost motion mechanism using a combination of a flat cam and a pressing spring provided in a circumferential direction as described in <CIT>, wherein such a lost motion mechanism is not part of the present invention.

Further, in the above-described embodiment, the shift shaft is coupled to the shift pedal via the link mechanism or the like, but the shift shaft may be directly coupled to the shift pedal.

In the above embodiment, the lost motion mechanism is provided behind the clutch, a positional relationship between the clutch and the lost motion mechanism is not particularly limited. It is sufficient if the lost motion mechanism is accommodated in the case of the transmission device.

The engine is not limited to the engine of the straddle type vehicle described above, and may be applied to an engine of another straddle type vehicle. The straddle type vehicle is not limited to general vehicles on which a rider rides in a posture of straddling a seat, and also includes small-sized scooter type vehicles on which a rider rides without straddling a seat.

According to the present invention, the lost motion plate rotates integrally with the shift shaft in response to the shift operation, but the drive plate does not move immediately after the shift operation with the large operating load. Therefore, the pin coupled to the drive plate and the long hole of the lost motion plate relatively move against the reaction force of the torsion coil spring, and the rotation of the shift shaft is absorbed by the lost motion mechanism. When the pin coupled to the drive plate and the end surface of the long hole of the lost motion plate are in contact with each other by the further shift operation, the rotation of the shift shaft is transmitted to the drive plate with the delay, and the shift cam is moved by the drive plate.

Claim 1:
A shift device (<NUM>) that is configured to cause a transmission device (<NUM>) to shift in response to a shift operation of a shift pedal (<NUM>), the shift device (<NUM>) comprising:
a shift shaft (<NUM>) configured to rotate in response to the shift operation of the shift pedal (<NUM>);
a shift cam (<NUM>) configured to rotate in a manner of being capable of changing a coupling state of shift gears (<NUM>, <NUM>) of the transmission device (<NUM>);
a drive plate (<NUM>) configured to move the shift cam (<NUM>) in response to the rotation of the shift shaft (<NUM>); and
a lost motion mechanism (<NUM>) interposed between the shift shaft (<NUM>) and the drive plate (<NUM>), wherein
the lost motion mechanism (<NUM>) is attached to one end portion of the shift shaft (<NUM>) and absorbs the rotation of the shift shaft (<NUM>) to delay power transmission to the drive plate (<NUM>), wherein
the lost motion mechanism (<NUM>) includes
a lost motion plate (<NUM>) configured to rotate integrally with the shift shaft (<NUM>),
a pin holder (<NUM>) configured to hold a pin (<NUM>) and rotate relative to the shift shaft (<NUM>), and
a torsion coil spring (<NUM>) attached to the lost motion plate (<NUM>),
a long hole (<NUM>) is formed in the lost motion plate (<NUM>) along a rotation direction,
one end of the pin (<NUM>) is inserted into the long hole (<NUM>),
the other end of the pin (<NUM>) is coupled to the drive plate (<NUM>), and
the one end of the pin (<NUM>) is held in a neutral position away from an end surface of the long hole (<NUM>) by the torsion coil spring (<NUM>).