CROSS-REFERENCE OF RELATED APPLICATIONS

The present invention claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2019-76594 and Japanese Patent Application No. 2019-76595 both filed on Apr. 12, 2019, each of which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a drum-type transmission device.

A drum-type transmission device has been proposed as a transmission device used for a travelling system transmission path in a working vehicle such as a utility vehicle or a tractor.

The conventional drum-type transmission described in Japanese Patent No. 5909400 comprises a shift gear rotatably supported on a first transmission rotation shaft and a power transmission gear non-rotatably supported on a second transmission rotation shaft and directly or indirectly meshed to the shift gear, a shifter member supported on the first transmission rotation shaft in a relatively non-rotatable yet axially movable manner, a drum member having a fork guide groove and being rotated around the axis, and a shift fork having a fork shaft parallel to the drum member, and a shift fork having a boss portion supported by the fork shaft so as to be movable in the axial direction and having an engagement pin engaged with the fork guide groove and a fork portion engaged with the shifter member.

Specifically, shift concave/convex portions are provided on the opposite surfaces of the shifter member and the shift gear. By rotating the drum member about the axis, the shift fork, whose axial position is regulated by the fork guide groove, is moved in the axial direction to realize a concave-convex engagement between the shifter member and the shift gear. Thus, the gear train including the shift gear and the power transmission gear enters the power transmission state, and power transmission between the first and second transmission rotation shafts is performed at the gear ratio of the gear train.

In such a drum-type transmission device, in addition to the power transmission state provided by the gear train, a parking state in which the rotation is forcibly stopped is also desired to produce. In this regard, in addition to the above-described configuration, the conventional drum-type transmission device further comprises a parking gear supported by the first transmission rotation shaft in a relatively non-rotatable manner, and a parking lock mechanism for engaging the operating arm (referred to as a park pole or the like) with the parking gear to forcibly stop the rotation of the first transmission rotation shaft in accordance with the rotation of the drum member to the parking position around the axis.

The parking lock mechanism comprises a locking member provided on the drum member, and a plate member having a concave portion into which the locking member can enter. The locking member is rotated in accordance with the rotation of the drum member to the parking position around the axis, as the plate member swings due to the movement of the locking member entering the concave portion, and the parking gear is then locked by using the swing of the plate member.

In a conventional drum-type transmission device, at the time of a parking lock release operation, the parking operation arm is disengaged from the parking gear by using the spring force of a parking release spring that urges the parking operation arm toward the unlock position. However, there exited such defect that in the case where the parking operation arm is sagged or burred, for example, while the vehicle is running, or where the vehicle is parked on a slope, when the torque between the parking gear and the parking operation arm is confined, the parking operation arm will remain in place (the parking operation arm does not separate from the parking gear) even when the unlock operation is performed.

As a parking lock mechanism that solves such a problem, there is known a mechanism (for example, JP Patent Publication 2018-158619) that comprises a rotatably movable lock cam component having a park lock activation cam portion that presses the parking operation arm that engages with a parking gear toward a lock position, and a park lock deactivation cam portion that presses the parking operation arm toward the unlock position, and when the parking lock is released, the locked state is forcibly released by using the park lock deactivation cam portion.

However, since the function to forcibly release the locked state is provided in the locking cam component, there exited the risk where the operation of the locking cam component may fail to release the locked state, due to such reasons as the wearing of the locking cam component itself, breakage or deterioration of the spring supporting the locking cam part, etc.

Further, in the conventional drum-type transmission device, a member (a locking member provided on the drum member or a plate member having a concave portion with which the locking member can engage, or the like) becomes worn that is intended for restricting the displacement of the parking operation arm and maintaining the locked state where the parking operation arm is engaged with the parking gear, the parking operation arm is separated from the parking gear, releasing the locked state, especially under such occasions as where the vehicle is parked on a slope, there is a risk that the vehicle may start moving unexpectedly and cause danger.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-described conventional technology, and aims to improve the reliability of a parking lock mechanism in a drum-type transmission device.

According to one aspect of the drum-type transmission device according to the present invention, the drum-type transmission device comprises a transmission shaft which is configured to drive a vehicle wheel, a drum member which is configured to perform a shift operation, a transmission operation shaft which is configured to rotate the drum member, and a parking lock mechanism. The parking lock mechanism comprises a parking gear which is configured to be provided on the transmission shaft so as to be relatively non-rotatable, a parking operation arm which is configured to be displaceable between a lock position at which the parking operation arm engages with the parking gear and an unlock position at which the parking operation arm separates from the parking gear, a parking release spring which is configured to urge the parking operation arm toward the unlock position, and a parking pushing member which is configured to push the parking operation arm according to the rotation of the drum member from a shift position or a neutral position to a parking position. One end of the transmission operation shaft is located near the parking operation arm. At the one end of the transmission operation shaft, there is provided an arm restraining portion which is capable of urging the parking operation arm toward the unlock position when the drum member rotates from the parking position to the shift position or the neutral position.

According to one aspect of the drum-type transmission device of the present invention, when the drum member rotates from the parking position to the shift position or the neutral position, the lock release mechanism by the spring force of the parking release spring and the lock release mechanism by the transmission operation shaft will function, so that even if the parking state cannot be released only with the reaction force received by the parking operation arm from the parking gear and the spring force of the parking release spring, the parking state will be reliably released by the operation of the arm restraining portion. Thereby, the reliability of the parking lock mechanism in the drum-type transmission device can be improved.

Further, in a configuration in which the parking pushing member is provided with a forced release function of a parking state as disclosed in Japanese Patent Application Publication No. 2018-158619, even if the parking pushing member fails to perform its release function sufficiently due to such reasons as wearing or the like, the parking state can be released by the arm restraining portion that is provided at a location (transmission operation shaft) separated from the parking pushing member, thereby improving the reliability of the parking lock mechanism in the drum-type transmission device.

Furthermore, by providing an arm restraining portion on the transmission operation shaft that is interlocked with the drum member and the parking pushing member, two lock release mechanisms can be operated with one operation system (operation of the transmission operation shaft). That is, a lock release mechanism using an arm restraining portion can be provided without introducing any additional operation system to an operation system that operates the rotation of the drum member and the parking pushing member using the transmission operation shaft. With a simple configuration and at a low cost, the reliability of the parking lock mechanism in the drum-type transmission device can be improved.

Further, in the drum-type transmission device of the embodiment of the present invention, the arm restraining portion is provided on the transmission operation shaft that is located upstream of the rotational force transmission path for rotating the drum member. Therefore, when the drum member is turned from the parking position to the shift position or the neutral position, the release operation force input to the transmission operation shaft can be transmitted to the parking operation arm without decreasing the release operation force, and therefore suppressing distinctive increase in the release operation force.

According to another aspect of the drum-type transmission device of the present invention, the drum-type transmission device comprises a transmission shaft which is configured to drive a vehicle wheel, a drum member which is configured to perform a shift operation, a transmission operation shaft which is configured to rotate the drum member, and a parking lock mechanism. The parking lock mechanism comprises a parking gear which is configured to be provided on the transmission shaft so as to be relatively non-rotatable, a parking operation arm which is configured to be displaceable between a lock position at which the parking operation arm engages with the parking gear and an unlock position at which the parking operation arm separates from the parking gear, a parking release spring which is configured to urge the parking operation arm toward the unlock position, and a parking pushing member which is configured to push the parking operation arm according to the rotation of the drum member from a shift position or a neutral position to a parking position. One end of the transmission operation shaft is located near the parking operation arm. At the one end of the transmission operation shaft, there is provided an arm restraining portion which is configured to restrict the movement of the parking operation arm toward the unlock position when the drum member is at the parking position.

According to another aspect of the drum-type transmission device of the present invention, when the drum member is located at the parking position, the lock mechanism by the parking pushing member and the lock mechanism by the arm restraining portion that restricts the movement of the parking operation arm toward the unlock position will function so that by having two lock mechanisms provided on separate members, even does occur such a situation where one of the lock mechanisms fails, the other lock mechanism can maintain the parking state, and the reliability of the parking lock mechanism is improved.

According to another aspect of the drum-type transmission device of the present invention, an arm restraining portion is provided on a transmission operation shaft that is interlocked with a drum member and a parking pushing member, so that one operation system can operate two lock mechanisms. That is, a lock release mechanism using an arm restraining portion can be provided without introducing any additional operation system to an operation system that operates the rotation of the drum member and the parking pushing member using the transmission operation shaft. With a simple configuration and at a low cost, the reliability of the parking lock mechanism in the drum-type transmission device can be improved.

In the drum-type transmission device according to the embodiment of the present invention, the arm restraining portion is formed by cutting out the one end of the transmission operation shaft, and is eccentric with respect to an axis of the transmission operation shaft; the portion of the parking operation arm facing the arm restraining portion overlaps with a part of a cutout portion of the transmission operation shaft when viewed from the axial direction of the transmission operation shaft at the lock position, whereas the portion of the parking operation arm facing the arm restraining portion is shaped so as not to hinder the displacement of the arm restraining portion accompanying the rotation of the transmission operation shaft at the unlock position.

According to another aspect of the drum-type transmission device of the present invention, the arm restraining portion can be provided to the transmission operation shaft without increasing the number of parts. Therefore, the reliability of the parking lock mechanism of the drum-type transmission device can be improved at a low cost and with a compact configuration by avoiding a significant increase in the manufacturing cost.

Further, the drum-type transmission device according to the embodiment of the present invention may also comprise a transmission operation arm which is configured to rotate the drum member via a shift gear train, and a parking lock holding mechanism, which is configured to engage a gear lock member with a lock member engagement portion which is provided to one of the plurality of shift gears constituting the shift gear train so as to inhibit the rotation of the shift gear, when the drum member is at the parking position.

According to this aspect, when the drum member is located at the parking position, the gear lock member can be engaged with the lock member engagement portion provided on the shift gear of the shift gear train to inhibit the rotation of the shift gear. It can be prevented for the shift lever that is provided on the vehicle from being unexpectedly operated avoiding the parking state being released during parking of the vehicle on which the drum-type transmission device is mounted.

In the drum-type transmission device of the embodiment of the present invention, the parking lock holding mechanism may comprise an electric actuator which is configured to slide the gear lock member in a direction in which the gear lock member is disengaged from the lock member engagement portion; the parking lock holding mechanism is configured to urge the gear lock member in a direction in which the gear lock member engages with the lock member engagement portion, at the time when the electric actuator is de-energized.

According to this aspect, with just a simple configuration of the electric actuator, even at the time when the power supply to the electric actuator cannot be performed due to, for example, running out of a battery, the gear lock member is engaged with the lock member engagement portion so that the operation of the shift gear train can be reliably inhibited when the drum member is at the parking position.

Further, in the drum-type transmission according to the embodiment of the present invention, the electric actuator may comprise a solenoid which is configured to have a plunger that makes linear movement; wherein the gear lock member may be provided at a distal end of the plunger. According to this aspect, the parking lock holding mechanism can be realized with a simple configuration, while an increase in manufacturing cost can be suppressed.

Provided in the embodiment of the present invention is a vehicle, which comprises a drive source, which is configured to be supported by a vehicle body, front wheels and rear wheels, which are configured to be supported by the vehicle body, and a transmission, which is configured to transmit the power of from the drive source to the front and rear wheels; wherein the transmission comprises the drum-type transmission device, an axle drive device, which is configured to drive the front wheels or the rear wheels, and a power take-out device, which is configured to drive the front wheels or the rear wheels; wherein the power take-out device comprises a parking brake mechanism, which is configured to selectively brake the rotation of the transmission shaft of the drum-type transmission device.

According to the vehicle of the embodiment of the present invention, the parking brake mechanism which brakes the rotation of the transmission shaft of the drum-type transmission device is provided within the power take-out device, hence it can be realized for the parking brake mechanism to be provided in the transmission, without making additional modifications to the configurations of the drum-type transmission device as well as the axle drive device.

