Planetary gear assembly, HMT device and transmission structure

Abstract

To provide a planetary gear assembly capable of attaining downsizing of an entire device while expanding a gear change range of an HMT device to be formed in cooperation with an HST.SOLUTION: A planetary gear assembly comprises: a cylindrical transmission shaft; an output shaft interpolated to the transmission shaft; first and second planetary gear mechanisms in which a sun gear is supported on the transmission shaft so as not to be relatively rotated around an axis; first and second clutch mechanisms which are disposed coaxially with the transmission shaft and engage / disengage power transmission to reference rotation speed power input parts of the first and second planetary gear mechanisms; and a coupling member extrapolated to the transmission shaft so as to be freely relatively rotated around the axis. The output shaft makes the coupling member non-rotatable relatively around the axis in a state where a planetary element other than planetary elements in the first planetary gear mechanism forming the sun gear and the reference rotation speed power input part is coupled with a planetary element other than planetary elements in the second planetary gear mechanism forming the sun gear and the reference rotation speed power input part relatively non-rotatable around the axis.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a planetary gear assembly having two planetary gear mechanisms, a hydrostatic-mechanical continuously variable transmission (HMT device) including the planetary gear assembly, and a transmission structure including the HMT device. [Background technology]

[0002] Various HMT devices that combine a hydrostatic continuously variable transmission (HST) and a planetary gear mechanism have been proposed and are suitably used in the transmission structures of work vehicles such as combine harvesters and tractors.

[0003] For example, Patent Document 1 below discloses an HMT device (hereinafter referred to as the first conventional example) that includes an HST in which a pump shaft is operatively connected to a drive source and a motor shaft is arranged parallel to the pump shaft, a drive shaft coaxially connected to the pump shaft so as to be non-rotatable relative to the pump shaft, a first transmission shaft coaxially connected to the motor shaft so as to be non-rotatable relative to the pump shaft, a second transmission shaft arranged parallel to both the drive shaft and the first transmission shaft, a first planetary gear mechanism having a first sun gear, a first carrier, and a first internal gear and arranged coaxially with the first transmission shaft, a second planetary gear mechanism having a second sun gear, a second carrier, and a second internal gear and arranged coaxially with the second transmission shaft, an output shaft arranged coaxially and rotatable relative to the second transmission shaft, and first to fourth clutch mechanisms.

[0004] The first sun gear is supported on the first transmission shaft so as to be unable to rotate relative to it around its axis, the first carrier is operatively connected to the first transmission shaft (i.e., the motor shaft) via the first clutch mechanism and to the drive shaft (i.e., the pump shaft) via the second clutch mechanism, and the first internal gear is operatively connected to the output shaft.

[0005] In addition, the second internal gear is operatively connected to the drive shaft (i.e., the pump shaft) via the third clutch mechanism, the second carrier is operatively connected to the first transmission shaft (i.e., the motor shaft) via the fourth clutch mechanism, the second sun gear is supported on the second transmission shaft so as not to be able to rotate relative to it around its axis, and the second transmission shaft is operatively connected to the output shaft.

[0006] The first conventional example can selectively produce a first transmission state in which the first clutch mechanism is engaged and the second to fourth clutch mechanisms are released, a second transmission state in which the second clutch mechanism is engaged and the first, third and fourth clutch mechanisms are released, and a third transmission state in which the third and fourth clutch mechanisms are engaged and the first and second clutch mechanisms are released.

[0007] In the first transmission state, the HST output from the motor shaft is input to both the first sun gear and the first carrier, and rotational power is output from the first internal gear to the output shaft.

[0008] In the second transmission state, the reference rotational speed power from the drive source is input to the first carrier and the HST output from the motor shaft is input to the first sun gear, and the resultant rotational power by the first planetary gear mechanism is output from the first internal gear to the output shaft.

[0009] In the third transmission state, the reference rotational speed power from the drive source is input to the second internal gear and the HST output from the motor shaft is input to the second carrier, and the resultant rotational power by the second planetary gear mechanism is output from the second sun gear to the second transmission shaft and operatively transmitted to the output shaft.

[0010] The first conventional example having such a configuration is useful in that it can expand the range of speed changes that can be made to the rotational speed of the output shaft. However, it requires three shafts (the drive shaft, the first transmission shaft, and the second transmission shaft) that are arranged in an overlapping state in the axial direction, and further requires a gear train to transmit power between the three shafts. Therefore, there is room for improvement in terms of installation space, transmission efficiency, and cost.

[0011] Furthermore, the following Patent Document 2 discloses an HST including a drive shaft operatively connected to a drive source, a pump shaft operatively connected to the drive shaft with the drive shaft disposed parallel to the drive shaft, and a motor shaft disposed parallel to the drive shaft and the pump shaft at positions displaced from the drive shaft and the pump shaft, a first transmission shaft disposed parallel to the drive shaft, the pump shaft, and the motor shaft at positions displaced from the drive shaft, a first planetary gear mechanism having a first sun gear, a first carrier, and a first internal gear and disposed coaxially with the first transmission shaft, and a first planetary gear mechanism disposed coaxially with the first planetary gear mechanism. An HMT device (hereinafter referred to as the second conventional example) is disclosed which includes an intermediate shaft, a second transmission shaft coaxially connected to the motor shaft so as to be unable to rotate relative to the motor shaft about its axis, a second planetary gear mechanism having a second sun gear, a second carrier, and a second internal gear and arranged coaxially with the second transmission shaft, a second intermediate shaft arranged coaxially with the second planetary gear mechanism, an output shaft, a first clutch mechanism which engages and disengages power transmission from the first intermediate shaft to the output shaft, and a second clutch mechanism which engages and disengages power transmission from the second intermediate shaft to the output shaft (see, for example, Figure 1 of Patent Document 2).

[0012] The second conventional example requires many shafts, including the drive shaft, the first transmission shaft, the second transmission shaft, the first intermediate shaft, and the second intermediate shaft, which is very disadvantageous in terms of installation space, transmission efficiency, and cost.

[0013] Furthermore, Patent Document 2 also discloses an HMT device (hereinafter referred to as a third conventional example) that includes an HST and first and second planetary gear mechanisms arranged in series (see, for example, Figure 5 of Patent Document 2).

[0014] In the third conventional example, three shafts are arranged in an overlapping manner in the axial direction, including a drive shaft that is coaxially connected to the pump shaft and unable to rotate relative to it around its axis, a transmission shaft that is coaxially connected to the motor shaft and unable to rotate relative to it around its axis and supports the first and second planetary gear mechanisms and the first to third clutch mechanisms, and an output shaft that is operatively connected to the transmission shaft via a gear train, and there is room for improvement in terms of installation space, transmission efficiency, and cost. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Patent No. 4194709 [Patent Document 2] International Publication No. WO2020 / 097650 Summary of the Invention [Problem to be solved by the invention]

[0016] The present invention has been made in consideration of the above-mentioned conventional technology, and has as its first object to provide a planetary gear assembly that cooperates with an HST to form an HMT device, which can increase the speed range of the HMT output while reducing the size of the entire HMT device.

[0017] A second object of the present invention is to provide an HMT device including an HST and first and second planetary gear mechanisms, which can be made smaller while widening the speed change range of the HMT output.

[0018] A third object of the present invention is to provide a transmission structure equipped with an HMT device including an HST and first and second planetary gear mechanisms, which can reduce the size of the HMT device while widening the speed change range of the HMT output, and which can output the HMT output with good controllability. [Means for solving the problem]

[0019] In order to achieve the first object, a first aspect of the present invention is a planetary gear assembly that forms an HMT device in cooperation with an HST that continuously changes the speed of a reference rotational speed power operatively input from a drive source to a pump shaft between a first HST speed and a second HST speed and outputs the speed-changed HST output from a motor shaft, the planetary gear assembly including a cylindrical transmission shaft to which the HST output can be input, an output shaft that is inserted into the transmission shaft so as to be relatively rotatable about its axis with at least a portion of the output shaft extending outward from the transmission shaft, a first sun gear, a first carrier, and a first planetary gear mechanism having three planetary elements including a first internal gear, the first sun gear being supported on the transmission shaft so as not to be rotatable relative to the first carrier around its axis, one of the first carrier and the first internal gear forming a reference rotational speed power input section to which reference rotational speed power can be input; and a second planetary gear mechanism having three planetary elements including a second sun gear, a second carrier and a second internal gear, the second sun gear being supported on the transmission shaft so as not to be rotatable relative to the first carrier around its axis, one of the second carrier and the second internal gear forming a reference rotational speed power input section to which reference rotational speed power can be input. a second planetary gear mechanism forming a reference rotational speed power input portion to which a planetary element different from a planetary element forming a reference rotational speed power input portion of the first planetary gear mechanism is capable of inputting reference rotational speed power; a first clutch mechanism arranged coaxially with the transmission shaft and engaging and disengaging power transmission of the reference rotational speed power to the reference rotational speed power input portion of the first planetary gear mechanism; a second clutch mechanism arranged coaxially with the transmission shaft and engaging and disengaging power transmission of the reference rotational speed power to the reference rotational speed power input portion of the second planetary gear mechanism; and a connecting member rotatably inserted on the output shaft, the connecting member connecting planetary elements forming the planetary output portion other than the first sun gear and the planetary elements forming the reference rotational speed power input portion among the three planetary elements in the first planetary gear mechanism and planetary elements forming the planetary output portion other than the second sun gear and the planetary elements forming the reference rotational speed power input portion among the three planetary elements in the second planetary gear mechanism so as to be unable to rotate relative to the output shaft about the axis.

[0020] Preferably, the planetary gear assembly can further include a first driven gear that is supported directly or indirectly on an outwardly extending portion of the output shaft so as to be rotatable relative to the output shaft about its axis, and to which a reference rotational speed power can be input, and a second driven gear that is supported directly or indirectly on the transmission shaft so as to be rotatable relative to the output shaft about its axis, and to which a reference rotational speed power can be input.

[0021] In this case, the first clutch mechanism is supported on an outward extending portion of the output shaft so as to be able to engage and disengage power transmission from the first driven gear to the reference rotational speed power input portion of the first planetary gear mechanism, and the second clutch mechanism is supported on the transmission shaft so as to be able to engage and disengage power transmission from the second driven gear to the reference rotational speed power input portion of the second planetary gear mechanism.

[0022] The planetary gear assembly according to one embodiment of the first aspect may further include a third driven gear supported directly or indirectly on the transmission shaft so as to be rotatable relative to the transmission shaft about its axis and to which a reference rotational speed power can be input, the third driven gear having a pitch diameter smaller than that of the second driven gear, and a third clutch mechanism supported on the transmission shaft so as to be able to engage and disengage power transmission from the third driven gear to the reference rotational speed power input portion of the second planetary gear mechanism.

[0023] In various configurations of the first aspect, the first internal gear and the second carrier form the reference rotational speed power input portions of the first and second planetary gear mechanisms, respectively. In this case, the connecting member connects the first carrier and the second internal gear so as to be unable to rotate relatively about the axis.

[0024] Preferably, the first clutch mechanism includes: a first clutch housing supported directly or indirectly on an outwardly extending portion of the output shaft so as to be rotatable relative to the first clutch housing about its axis; a first friction plate group including first driving-side friction plates supported on the first clutch housing so as to be non-rotatable relative to the first clutch housing but movably in the axial direction, and first driven-side friction plates arranged opposite the first driving-side friction plates; a first rotating member that is extrapolated onto the outwardly extending portion of the output shaft so as to be rotatable relative to the first driving-side friction plates but movably in the axial direction; and a first piston that frictionally engages the first friction plate group by pressurized oil supplied to an oil chamber in the first clutch housing; and the first clutch housing is connected to the first driven gear so as to be non-rotatable relative to the first driven gear about its axis, and the first rotating member is connected to the first internal gear so as to be non-rotatable relative to the first driving-side friction plates about its axis.

[0025] Preferably, the second clutch mechanism includes: a second clutch housing supported directly or indirectly on the transmission shaft so as to be rotatable relative to the transmission shaft about its axis; a second friction plate group including second driving-side friction plates supported on the second clutch housing so as to be non-rotatable relative to the transmission shaft but movably in the axial direction, and second driven-side friction plates arranged opposite the second driving-side friction plates; a second rotating member that is extrapolated onto the transmission shaft so as to be rotatable relative to the transmission shaft about its axis and supports the second driven-side friction plates so as to be movably in the axial direction but non-rotatable relative to the transmission shaft; and a second piston that frictionally engages the second friction plate group by pressurized oil supplied to an oil chamber in the second clutch housing, and the second clutch housing is connected to the second driven gear so as to be non-rotatable relative to the transmission shaft about its axis, and the second rotating member is connected to the second carrier so as to be non-rotatable relative to the transmission shaft about its axis.

[0026] The first carrier may have a first carrier pin that meshes with both the first sun gear and the first internal gear and supports a first planetary gear that revolves around the first sun gear so as to be rotatable about an axis. The first carrier pin has an intermediate portion that supports the first planetary gear, and first and second extending portions that extend from the intermediate portion to one side and the other side in the axial direction, respectively.

[0027] In a configuration in which the first internal gear and the second carrier form the reference rotational speed power input portion, the connecting member is preferably cylindrical and has a first annular portion located on one axial side, a second annular portion spaced apart from the first annular portion on the other axial side, and a connecting portion connecting the first and second annular portions.

[0028] The first and second annular portions are respectively provided with a first engagement hole into which the first extension portion is inserted and a second engagement hole into which the second extension portion is inserted, and the connecting portion is supported by an intermediate portion of the first carrier pin. No. 1 The first and second annular portions are connected together while leaving a space for installing the planetary gears.

[0029] Furthermore, the inner and outer surfaces of the cylindrical body formed by the first annular portion, the connecting portion, and the second annular portion are each provided with a concave-convex engaging portion that engages with the outer surface of the outwardly extending portion of the output shaft, and an external tooth portion that meshes with the second internal gear.

[0030] In a configuration in which the first internal gear and the second carrier form the reference rotational speed power input portion, the gear ratio of the first planetary gear mechanism is preferably set so that, under a transmission state, the first carrier rotates at an increased speed in a first rotational direction, which is one side around the axis, as the HST output changes from the first HST speed side to the second HST speed side, and so that when the HST output is set to an HST speed for a predetermined first gear stage maximum speed, the first carrier rotates in the first rotational direction at a predetermined first gear stage maximum speed.

[0031] The gear ratio of the second planetary gear mechanism is set so that, under a transmission state, when the HST output is set to the HST speed for the first gear stage maximum speed, the second internal gear rotates in the first rotational direction at the first gear stage maximum speed, and as the HST output is changed from the HST speed for the first gear stage maximum speed toward the first HST speed to a predetermined HST speed for the second gear stage maximum speed, the rotational speed of the second internal gear increases from the first gear stage maximum speed to the second gear stage maximum speed.

[0032] Preferably, the gear ratio of the first planetary gear mechanism is set so that, in a transmission state, the first carrier is at zero speed when the HST output is set to a predetermined HST speed for zero speed. Preferably, the zero speed HST speed is a speed shifted from the first HST speed toward the second HST speed by a predetermined speed.

[0033] The planetary gear assembly according to the present invention may preferably include an HST driven gear that is supported on the transmission shaft so as not to be rotatable relative to the transmission shaft and that can receive the HST output.

[0034] In order to achieve the second object, a second aspect of the present invention provides an HST that continuously changes the speed of a reference rotational speed power operatively input from a drive source to a pump shaft between a first HST speed and a second HST speed, and outputs the changed HST output from a motor shaft; a drive shaft to which the reference rotational speed power is operatively transmitted from the drive source; a cylindrical transmission shaft to which the HST output is operatively transmitted from the motor shaft; an output shaft that is inserted into the transmission shaft so as to be relatively rotatable about its axis with at least a portion of the output shaft extending outward from the transmission shaft; a first sun gear, a first carrier, and a first a first planetary gear mechanism having three planetary elements including an internal gear, the first sun gear being supported on the transmission shaft so as not to be rotatable relative to the first carrier around its axis, and one of the first carrier and the first internal gear forming a reference rotational speed power input section to which reference rotational speed power can be input; a first transmission gear train including a first drive gear supported on the drive shaft so as not to be rotatable relative to the first carrier around its axis, and a first driven gear operatively meshed with the first drive gear while being supported directly or indirectly on an outward extending portion of the output shaft so as to be rotatable relative to the first carrier around its axis; and the transmission shaft. The reference rotational speed power input device has a first clutch mechanism that is arranged on the same axis and that engages and disengages the power transmission of the reference rotational speed power from the first driven gear to the reference rotational speed power input portion of the first planetary gear mechanism, and three planetary elements that include a second sun gear, a second carrier, and a second internal gear, the second sun gear being supported on the transmission shaft so as not to be able to rotate relatively around its axis, and the reference rotational speed power input device is configured so that the reference rotational speed power can be input to one of the planetary elements that form the reference rotational speed power input portion of the first planetary gear mechanism, among the second carrier and the second internal gear. a second transmission gear train including a second driving gear supported on the drive shaft so as not to be rotatable relative to the drive shaft about its axis, and a second driven gear supported on the transmission shaft directly or indirectly so as to be rotatable relative to the transmission shaft about its axis and operatively meshed with the second driving gear; a second clutch mechanism arranged coaxially with the transmission shaft and configured to engage and disengage power transmission of the reference rotational speed power from the second driven gear to the reference rotational speed power input portion of the second planetary gear mechanism; and a connecting member fitted onto the transmission shaft so as to be rotatable relative to the transmission shaft about its axis,The present invention provides an HMT device in which the planetary elements forming the planetary output portion other than the first sun gear and the planetary elements forming the reference rotational speed power input portion among the three planetary elements in the first planetary gear mechanism and the planetary elements forming the planetary output portion other than the second sun gear and the planetary elements forming the reference rotational speed power input portion among the three planetary elements in the second planetary gear mechanism are connected so as not to rotate relative to the output shaft about their axes, and are not allowed to rotate relative to the output shaft about their axes.

[0035] In the HMT device according to the first aspect, the first internal gear forms the reference rotational speed power input portion of the first planetary gear mechanism, and the second carrier forms the reference rotational speed power input portion of the second planetary gear mechanism, and the connecting member is configured to connect the first carrier and the second internal gear so that they cannot rotate relative to each other around their axes.

[0036] In this case, the gear ratio of the first planetary gear mechanism is set so that, under a transmission state, when the HST output is set to a predetermined HST speed for zero speed, the first carrier reaches zero speed, and as the HST output changes from the first HST speed side to the second HST speed side, the first carrier rotates at an increased speed in a first rotational direction, which is one side around the axis, and when the HST output is set to a predetermined HST speed for the first gear stage maximum speed, the first carrier rotates in the first rotational direction at the predetermined first gear stage maximum speed.

[0037] The gear ratio of the second planetary gear mechanism is set so that, under a transmission state, when the HST output is set to the HST speed for the first gear stage maximum speed, the second internal gear rotates in the first rotational direction at the first gear stage maximum speed, and as the HST output is changed from the HST speed for the first gear stage maximum speed toward the first HST speed to a predetermined HST speed for the second gear stage maximum speed, the rotational speed of the second internal gear increases from the first gear stage maximum speed to the second gear stage maximum speed.

[0038] Preferably, the first clutch mechanism includes: a first clutch housing supported directly or indirectly on an outwardly extending portion of the output shaft so as to be rotatable relative to the first clutch housing about its axis; a first friction plate group including first driving-side friction plates supported on the first clutch housing so as to be non-rotatable relative to the first clutch housing but movably in the axial direction, and first driven-side friction plates arranged opposite the first driving-side friction plates; a first rotating member that is extrapolated onto the outwardly extending portion of the output shaft so as to be rotatable relative to the first driving-side friction plates but movably in the axial direction; and a first piston that frictionally engages the first friction plate group by pressurized oil supplied to an oil chamber in the first clutch housing; and the first clutch housing is connected to the first driven gear so as to be non-rotatable relative to the first driven gear about its axis, and the first rotating member is connected to the first internal gear so as to be non-rotatable relative to the first driving-side friction plates about its axis.

[0039] Preferably, the second clutch mechanism includes: a second clutch housing supported directly or indirectly on the transmission shaft so as to be rotatable relative to the transmission shaft about its axis; a second friction plate group including second driving-side friction plates supported on the second clutch housing so as to be non-rotatable relative to the transmission shaft but movably in the axial direction, and second driven-side friction plates arranged opposite the second driving-side friction plates; a second rotating member that is extrapolated onto the transmission shaft so as to be rotatable relative to the transmission shaft about its axis and supports the second driven-side friction plates so as to be movably in the axial direction but non-rotatable relative to the transmission shaft; and a second piston that frictionally engages the second friction plate group by pressurized oil supplied to an oil chamber in the second clutch housing, and the second clutch housing is connected to the second driven gear so as to be non-rotatable relative to the transmission shaft about its axis, and the second rotating member is connected to the second carrier so as to be non-rotatable relative to the transmission shaft about its axis.

[0040] Compared to the HMT device of the first embodiment, the HMT device of the second embodiment may further include a third transmission gear train including a third drive gear supported on the drive shaft so as not to be rotatable relative to the drive shaft around its axis, and a third driven gear operatively meshed with the third drive gear while supported directly or indirectly on the transmission shaft so as to be rotatable relative to the drive shaft around its axis, and a third clutch mechanism arranged coaxially with the transmission shaft and engaging and disengaging the power transmission of the reference rotational speed power from the third driven gear to the reference rotational speed power input portion of the second planetary gear mechanism. The third transmission gear train has a higher speed ratio than the second transmission gear train.

[0041] In order to achieve the third object, a third aspect of the present invention provides a transmission structure comprising: an HMT device according to the first aspect; a speed change operating member that can be manually operated within a speed change operating range between a zero speed position and a maximum speed position; an operating position sensor that detects the operating position of the speed change operating member; a first clutch operating member that switches the engagement and disengagement operation of the first clutch mechanism; a second clutch operating member that switches the engagement and disengagement operation of the second clutch mechanism; an HST operating member that operates an output adjustment member of the HST; an output sensor that directly or indirectly detects the rotational speed of the output shaft; and a control device that controls the operation of the first and second clutch operating members and the HST operating member.

[0042] In the transmission structure according to the third aspect, the gear shift operation range is divided into a first gear operation region on the low speed side, which is set in a range from the zero speed position to the first gear maximum speed position, and a second gear operation region on the high speed side, which is set in a range from the first gear maximum speed position to the maximum speed position.

[0043] The control device operates the first and second clutch operating members so that, when the speed change operating member is operated in the first gear operation range, the first clutch mechanism is engaged and the second clutch mechanism is disengaged to create a first gear transmission state, and when the speed change operating member is positioned at the first gear maximum speed position, one of the first and second clutch mechanisms is engaged and the other is disengaged, and when the speed change operating member is operated in the second gear operation range, the control device operates the first and second clutch operating members so that the first clutch mechanism is disengaged and the second clutch mechanism is engaged to create a second gear transmission state.

[0044] Furthermore, the control device operates the HST operating member so that, in response to operation of the speed change operating member to the zero speed position, the HST output becomes an HST speed for zero speed, in response to operation of the speed change operating member to the speed-increasing side in the first gear stage transmission state, the HST output is shifted from the first HST speed side to the second HST speed side, in response to operation of the speed change operating member to the first gear stage maximum speed position, the HST output becomes an HST speed for first gear stage maximum speed, in response to operation of the speed change operating member to the speed-increasing side in the second gear stage transmission state, the HST output is shifted from the second HST speed side to the first HST speed side, and in response to operation of the speed change operating member to the maximum speed position, the HST output becomes an HST speed for second gear stage maximum speed.

[0045] In order to achieve the third object, a fourth aspect of the present invention provides a transmission structure comprising: an HMT device according to the second aspect; a speed change operating member that can be manually operated within a speed change operating range between a zero speed position and a maximum speed position; an operating position sensor that detects the operating position of the speed change operating member; a first clutch operating member that switches the engagement and disengagement operation of the first clutch mechanism; a second clutch operating member that switches the engagement and disengagement operation of the second clutch mechanism; a third clutch operating member that switches the engagement and disengagement operation of the third clutch mechanism; an HST operating member that operates an output adjustment member of the HST; an output sensor that directly or indirectly detects the rotational speed of the output shaft; and a control device that controls the operation of the first to third clutch operating members and the HST operating member.

[0046] In the transmission structure according to the fourth aspect, the gear shift operation range is divided into a first gear operation region on the low speed side, which is set in a range from the zero speed position to the first gear maximum speed position, a second gear operation region on the intermediate speed side, which is set in a range from the first gear maximum speed position to the second gear maximum speed position, and a third gear operation region on the high speed side, which is set in a range from the second gear maximum speed position to the maximum speed position.

[0047] The control device operates the first to third clutch operating members so that, when the speed change operating member is operated in the first gear operation range, the first clutch mechanism is engaged and the second and third clutch mechanisms are disengaged, thereby realizing a first gear transmission state; when the speed change operating member is positioned in the first gear maximum speed position, one of the first and second clutch mechanisms is engaged and the remaining clutch mechanism is disengaged; when the speed change operating member is operated in the second gear operation range, the control device operates the first to third clutch operating members so that, when the speed change operating member is positioned in the second gear maximum speed position, the control device operates the first to third clutch operating members so that, when the speed change operating member is operated in the third gear operation range, the first and second clutch mechanisms are disengaged and the third clutch mechanism is engaged, thereby realizing a third gear transmission state.

[0048] Furthermore, the control device is configured so that, in response to operation of the speed change operating member to a zero speed position, the HST output becomes an HST speed for zero speed, and, in response to operation of the speed change operating member to a speed-up side in a first gear stage transmission state, the HST output is shifted from the first HST speed side to the second HST speed side, and, in response to operation of the speed change operating member to a first gear stage maximum speed position, the HST output becomes an HST speed for first gear stage maximum speed, and, in response to operation of the speed change operating member to a speed-up side in a second gear stage transmission state, the HST output is shifted from the second HST speed side to the first HST speed side, In response to operation of the speed change operating member to the second gear maximum speed position, the HST output becomes the HST speed for the second gear maximum speed, and when transitioning from the second gear transmission state to the third gear transmission state, the HST output becomes the HST speed for the second gear maximum speed from the HST speed for the third gear minimum speed, and in response to operation of the speed change operating member to the speed increase side in the third gear transmission state, the HST output is shifted from the second HST speed side to the first HST speed side, and in response to operation of the speed change operating member to the maximum speed position, the HST operating member is operated so that the HST output becomes the predetermined HST speed for the third gear maximum speed.

[0049] The HST speed for the third gear stage lowest speed is set so that the rotational speed of the output shaft when the HST output is set to the second gear stage highest speed in the second gear stage transmission state matches the rotational speed of the output shaft when the HST output is set to the third gear stage lowest speed HST speed in the third gear stage transmission state.

[0050] The transmission structure according to the first example of the present invention further includes a forward / reverse switching mechanism that can selectively take a forward output state in which the HMT power operatively input from the output shaft is output without changing the rotation direction, and a reverse output state in which the HMT power is output by reversing the rotation direction, and replacement and a forward / reverse actuating member for actuating the mechanism.

[0051] In the transmission structure according to the first example, the speed change operation range of the speed change operation member includes a forward operation range from the zero speed position to the forward maximum speed position, and a reverse operation range from the zero speed position to the reverse maximum speed position.

[0052] The control device operates the forward / reverse operating member so that the forward / reverse switching mechanism is in a forward rotation output state when the speed change operating member is positioned in a forward side operating range, and so that the forward / reverse switching mechanism is in a reverse rotation output state when the speed change operating member is positioned in a reverse side operating range.

[0053] The transmission structure according to the second example of the present invention may further include a forward / reverse switching mechanism that can selectively take a forward output state in which the HMT power operatively input from the output shaft is output without changing the rotational direction, and a reverse output state in which the HMT power is output by reversing the rotational direction, and a forward / reverse switching operating member that is manually operated.

[0054] The output state of the forward / reverse switching mechanism is switched mechanically by utilizing a manual operating force on the forward / reverse switching operation member, or by an operating member whose operation is controlled by the control device, in response to the operation of the forward / reverse switching operation member.

[0055] The transmission structure according to the present invention may further include an auxiliary transmission mechanism capable of changing the HMT power operatively input from the output shaft to a plurality of speed stages including a low speed stage and a high speed stage. [Effects of the Invention]

[0056] The planetary gear assembly according to the present invention can increase the speed range of the HMT output in the HMT device formed in cooperation with the HST, while also reducing the size of the entire HMT device.

[0057] According to the HMT device of the present invention, it is possible to increase the speed range of the HMT output while reducing the size. The transmission structure according to the present invention makes it possible to reduce the size of the HMT device while widening the speed range of the HMT output, and further improve the controllability of the HMT output. [Brief explanation of the drawings]

[0058] [Figure 1]FIG. 1 is a schematic diagram of a transmission structure of a working vehicle to which a planetary gear assembly according to a first embodiment of the present invention is applied. [Figure 2] FIG. 2 is a hydraulic circuit diagram of the transmission structure. [Figure 3] FIG. 3 is a partial vertical cross-sectional view of an HMT device including the planetary gear assembly according to the first embodiment. [Figure 4] FIG. 4 is a vertical cross-sectional view of the planetary gear assembly according to the first embodiment. [Figure 5] FIG. 5 is an exploded perspective view of the output shaft and the connecting member in the planetary gear assembly according to the first embodiment. [Figure 6] FIG. 6 is a graph showing the relationship between the HST output and the HMT output in an HMT device including the planetary gear assembly according to the first embodiment. [Figure 7] FIG. 7 is a graph showing the relationship between the HST output and the HMT output in a modified example of an HMT device including the planetary gear assembly according to the first embodiment. [Figure 8] FIG. 8 is a schematic diagram of a transmission structure of a working vehicle to which a planetary gear assembly according to a comparative example is applied. [Figure 9] FIG. 9 is a schematic diagram of a transmission structure of a working vehicle to which a planetary gear assembly according to the second embodiment of the present invention is applied. [Figure 10] FIG. 10 is a graph showing the relationship between the HST output and the HMT output in an HMT device including the planetary gear assembly according to the second embodiment. [Figure 11] FIG. 11 is a schematic diagram of another transmission structure to which the planetary gear assembly according to the first embodiment is applied. [Figure 12] FIG. 12 is a graph showing the relationship between the HST output and the output of the auxiliary transmission mechanism in the transmission structure shown in FIG. [Figure 13] FIG. 13 is a vertical cross-sectional view of a planetary gear assembly according to the fourth embodiment of the present invention. [Figure 14]FIG. 14 is a partially enlarged vertical cross-sectional view of the planetary gear assembly according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0059] Embodiment 1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a planetary gear assembly according to the present invention will now be described with reference to the accompanying drawings. 1 and 2 respectively show a transmission schematic diagram and a hydraulic circuit diagram of a transmission structure 200A in a working vehicle to which a planetary gear assembly 1A according to this embodiment is applied.

[0060] As shown in Fig. 1, the work vehicle includes a drive source 410, main drive wheels 420, and the transmission structure 200A interposed in a traveling system power transmission path from the drive source 410 to the main drive wheels 420. Note that reference numeral 411 in Figs. 1 and 2 denotes a flywheel included in the drive source 410.

[0061] The planetary gear assembly 1A cooperates with a hydrostatic continuously variable transmission (HST) 110, which continuously changes the speed of a reference rotational speed power operatively input from the drive source 410 and outputs it, to form an HMT device (hydrostatic-mechanical continuously variable transmission) 100A, and is used as one component of the transmission structure 200A.

[0062] That is, as shown in FIG. 1, the transmission structure 200A includes the HMT device 100A including the HST 110 and the planetary gear assembly 1A.

[0063] In this embodiment, as shown in FIG. 1, the transmission structure 200A includes, in addition to the HMT device 100, a forward / reverse switching mechanism 220 that can switch the rotation direction of the output (HMT output) of the HMT device 100A between a forward direction and a reverse direction, and a differential mechanism 230 that differentially transmits the output of the forward / reverse switching mechanism 220 to a pair of left and right main drive wheels 320.

[0064] The transmission structure 200A further includes a traveling brake mechanism 240 that selectively applies braking force to the pair of main drive wheels 320, a differential lock mechanism 235 that forcibly drives the pair of main drive wheels 320 synchronously, and a drive force take-off mechanism 250 for auxiliary drive wheels that can selectively output the output of the forward / reverse switching mechanism 220 to the auxiliary drive wheels.

[0065] The transmission structure 200A also has a PTO shaft 260 that outputs rotational power to the outside, and a PTO multi-stage transmission mechanism 270 that includes a PTO clutch 265 interposed in the PTO transmission path from the drive source 410 to the PTO shaft 260. The transmission structure 200A, the differential mechanism 230, the auxiliary drive wheel drive force takeoff mechanism 250, and the PTO multi-stage speed change mechanism 270 are housed in a transmission case (not shown).

[0066] The HST 110 is configured to continuously change the speed of the reference rotational speed power from the drive source 410 between a first HST speed and a second HST speed, and to output an HST output after the speed change.

[0067] Specifically, as shown in FIGS. 1 and 2, the HST 10 includes a pump shaft 112 that operatively inputs reference rotational speed power from the drive source 410, a hydraulic pump 114 that is supported on the pump shaft 112 so as not to be rotatable relative to the pump shaft 112, a hydraulic motor 118 that is fluidly connected to the hydraulic pump 114 via a pair of hydraulic oil lines 115 and is hydraulically driven to rotate by the hydraulic pump 114, a motor shaft 116 that supports the hydraulic motor 118 so as not to be rotatable relative to the hydraulic motor, and an output adjustment member 120 that changes the volume of at least one of the hydraulic pump 114 and the hydraulic motor 118.

[0068] The output adjustment member 120 operates within an operable range defined by first and second operating end positions, and the HST 10 is capable of continuously changing the ratio of the rotational speed of the HST output output from the motor shaft 116 to the reference rotational speed input to the pump shaft 112 (i.e., the speed ratio of the HST 110) between a first HST speed and a second HST speed depending on the operating position of the output adjustment member 120 within the operable range. In this embodiment, the output adjusting member 120 is configured to change the volume (discharge amount) of the hydraulic pump 114.

[0069] In this embodiment, the HST 110 is capable of switching the rotation direction of the HST output between forward and reverse.

[0070] That is, in the HST 110, when the rotation direction of the reference rotation speed power is set to a first rotation direction (e.g., forward rotation direction), the rotation speed of the HST output (first HST speed) when the output adjustment member 120 is positioned at the first operating end position is set to the maximum speed (-max) in a second rotation direction (e.g., reverse direction) opposite to the first rotation direction, and the rotation speed of the HST output (second HST speed) when the output adjustment member 120 is positioned at the second operating end position is set to the maximum speed (+max) in the first rotation direction (e.g., forward rotation direction).

[0071] In this case, when the output adjusting member 120 is positioned at a neutral position between the first and second operating end positions, the rotational speed of the HST output becomes neutral speed (zero speed).

[0072] The HST 110 can take a variety of forms, including axial piston and radial piston types. When the HST 110 is an axial piston type, the output adjustment member 120 may be a movable swash plate. When the HST 110 is a radial piston type, the output adjustment member 120 may be a movable cam ring.

[0073] The output adjusting member 120 can be operated in response to a human operation. That is, as shown in FIG. 1, the transmission structure 200A is provided with a gearshift operating member 310 that can be manually operated within a gearshift operating range between a zero speed position and a maximum speed position, an operating position sensor 315 that detects the operating position of the gearshift operating member 310, an HST operating member 320 that operates the output adjustment member 120, and a control device 300 that controls the operation of the HST operating member 320 in accordance with the operating position of the gearshift operating member 310. In this embodiment, the gear shift operating member 310 is a lever type.

[0074] The HST operating member 320 can take various forms, such as a hydraulic actuator or an electric actuator, including a hydraulic servomechanism and an electromagnetic valve that switches the supply and discharge of pressure oil to the hydraulic servomechanism, as long as it can operate the output adjustment member 120 by a control signal from the control device 300.

[0075] FIG. 3 shows a partial vertical cross-sectional view of the HMT device 100A including the planetary gear assembly 1A. FIG. 4 shows a vertical cross-sectional view of the planetary gear assembly 1A.

[0076] As shown in Figures 1 to 4, the planetary gear assembly 1A includes a cylindrical transmission shaft 15, an output shaft 90 inserted into the transmission shaft 15, first and second planetary gear mechanisms 20, 30, and first and second clutch mechanisms 180(1), 180(2).

[0077] In this embodiment, the transmission shaft 15 is adapted to operatively receive the HST output. Specifically, the transmission shaft 15 operatively receives the HST output from the motor shaft 116 via an HST transmission gear train 130 .

[0078] The HST transmission gear train 130 includes an HST drive gear 132 connected to the motor shaft 116 so as not to rotate relative to it about its axis, and an HST driven gear 134 operatively meshed with the HST drive gear 132.

[0079] As shown in Figures 1 and 3, the transmission shaft 15 is arranged parallel to the motor shaft 116, supports the HST driven gear 134 so that it cannot rotate relative to the HST driven gear 134 about its axis, and supports the first planetary gear mechanism 20 on a first axial side of the HST driven gear 134 (the side away from the motor shaft 116 in the axial direction, and on the right side in Figures 1 and 3).

[0080] The output shaft 90 is inserted into the transmission shaft 15 so as to be relatively rotatable about its axis, with at least a portion of the output shaft 90 extending outward from the transmission shaft 15 as an outward extending portion.

[0081] As shown in Figures 3 and 4, in this embodiment, the output shaft 90 has outward extending portions at both ends thereof, namely, a first end side on one axial side (right side in Figures 3 and 4) and a second end side on the other axial side (left side in Figure 3).

[0082] As shown in Figures 3 and 4, the first planetary gear mechanism 20 has a first sun gear 22, a first planetary gear 24 meshing with the first sun gear 22, a first internal gear 26 meshing with the first planetary gear 24, and a first carrier 28 that supports the first planetary gear 24 so as to be rotatable about its axis and rotates about the axis of the first sun gear 22 in conjunction with the revolution of the first planetary gear 24 about the first sun gear 22, and the first sun gear 22, the first carrier 28 and the first internal gear 26 form a planetary triad.

[0083] As shown in FIGS. 3 and 4, the first sun gear 22, which is the first element of the three planetary elements, is supported by the transmission shaft 15 so as to be non-rotatable relative to the transmission shaft 15. As described above, in this embodiment, the HST output is input to the transmission shaft 10. Therefore, in this embodiment, the first sun gear 22 acts as a variable power input section that receives the HST output.

[0084] The second element of the three planetary elements acts as a reference rotational speed power input section that inputs a reference rotational speed power, and the third element acts as a planetary output section that outputs a composite rotational power (HMT power) that is a combination of the rotational powers input to the first and second elements. In this embodiment, the first internal gear 26 and the first carrier 28 form the second element (reference rotational speed power input portion) and the third element (planetary output portion) of the first planetary gear mechanism 20, respectively.

[0085] In this embodiment, the HMT device 100A is provided with a drive shaft 125 to which a reference rotational speed power is operatively transmitted from the drive source 410, and the reference rotational speed power can be operatively input from the drive shaft 125 to the first internal gear 26.

[0086] More specifically, in this embodiment, as shown in Figures 1 and 3, the drive shaft 125 is connected coaxially with the pump shaft 112 so as to be unable to rotate relative to it about the axis, and the HMT device 100A is provided with the drive shaft 125 and a first transmission gear train 135(1) that forms a power transmission path from the drive shaft 125 to the first internal gear 26.

[0087] In this embodiment, as shown in FIGS. 1 and 3, the first transmission gear train 135(1) has a first drive gear 136(1) supported on the drive shaft 125 so as not to be rotatable relative to the drive shaft 125 about its axis, and a first driven gear 137(1) supported on an outwardly extending portion on the first end side of the output shaft 90 so as to be rotatable relative to the drive shaft 125 about its axis while being operatively meshed with the first drive gear 136(1).

[0088] The first clutch mechanism 180(1) is disposed coaxially with the transmission shaft 15 and is configured to engage and disengage the power transmission of the reference rotational speed power to the reference rotational speed power input portion of the first planetary gear mechanism 20.

[0089] As described above, in this embodiment, the first internal gear 26 forms the reference rotational speed power input portion of the first planetary gear mechanism 20, and the first clutch mechanism 180(1) is configured to engage and disengage power transmission from the first driven gear 137(1) to the first internal gear 26.

[0090] As shown in FIGS. 1 to 3, in this embodiment, the first clutch mechanism 180(1) is a hydraulic multi-plate clutch.

[0091] In detail, as shown in FIGS. 3 and 4, the first clutch mechanism 180(1) includes a first clutch housing 181(1) supported on an outward extending portion on the first end side of the output shaft 90 so as to be relatively rotatable about the axis, a friction plate group 182(1) including first driving-side friction plates supported on the first driven gear 137(1) so as not to be relatively rotatable, and first driven-side friction plates supported on the first clutch housing 181(1) so as not to be relatively rotatable while facing the first driving-side friction plates, and a first piston 183(1) that frictionally engages the first friction plate group 182(1) with pressure oil supplied to the first clutch housing. 3 and 4 denotes a return spring that biases the first piston 183(1) in a direction that separates it from the first friction plate group 182(1), and when the first friction plate group 182(1) is brought into frictional engagement, the first piston 183(1) is pushed by the force of pressure oil toward the first friction plate group 182(1) against the biasing force of the return spring 184(1).

[0092] The first clutch housing 181(1) is connected to the first internal gear 26, which forms a reference rotational speed power input portion, so as to be non-rotatable relative to the first internal gear 26 about its axis. In this embodiment, as shown in FIGS. 3 and 4, the first clutch housing 181(1) is provided with an external tooth portion 180a that meshes with the first internal gear .

[0093] As shown in Figures 3 and 4, the second planetary gear mechanism 30 has a second sun gear 32, a second planetary gear 34 meshing with the second sun gear 32, a second internal gear 36 meshing with the second planetary gear 34, and a second carrier 38 that supports the second planetary gear 34 so as to be rotatable about its axis and rotates about the axis of the second sun gear 32 in conjunction with the revolution of the second planetary gear 34 about the second sun gear 32, and the second sun gear 32, the second carrier 38 and the second internal gear 36 form three planetary elements.

[0094] As shown in FIGS. 3 and 4, the second sun gear 32, which is the first element of the three planetary elements, is supported by the transmission shaft 15 so as to be non-rotatable relative to the transmission shaft 15. As described above, in this embodiment, the HST output is input to the transmission shaft 15. Therefore, in this embodiment, the second sun gear 32 acts as a variable power input section that receives the HST output.

[0095] The second element of the three planetary elements acts as a reference rotational speed power input section that inputs a reference rotational speed power, and the third element acts as a planetary output section that outputs a composite rotational power (HMT power) that is a combination of the rotational powers input to the first and second elements. In this embodiment, the second carrier 38 and the second internal gear 36 form the second element (reference rotational speed power input portion) and the third element (planetary output portion) of the second planetary gear mechanism 30, respectively.

[0096] In this embodiment, a reference rotational speed power is operatively input to the second carrier 38 from the drive shaft 125 .

[0097] More specifically, as shown in FIGS. 1 and 3, the HMT device 100A further includes a second transmission gear train 135(2) that forms a power transmission path from the drive shaft 125 to the second carrier 38.

[0098] The second transmission gear train 135(2) has a second drive gear 136(2) supported on the drive shaft 125 so as not to be rotatable relative to the drive shaft 125 about its axis, and a second driven gear 137(2) supported on the transmission shaft 15 so as to be rotatable relative to the drive shaft 125 about its axis while being operatively meshed with the second drive gear 136(2).

[0099] The second clutch mechanism 180(2) is arranged coaxially with the transmission shaft 15 and is configured to engage and disengage the power transmission of the reference rotational speed power to the reference rotational speed power input portion of the second planetary gear mechanism 30.

[0100] As described above, in the present embodiment, the second carrier 38 forms the reference rotational speed power input portion of the second planetary gear mechanism 30, and the second clutch mechanism 180(2) is configured to engage and disengage power transmission from the second driven gear 137(2) to the second carrier 38.

[0101] As shown in FIGS. 1 to 3, in this embodiment, the second clutch mechanism 180(2) is also a hydraulic multi-plate clutch.

[0102] In detail, as shown in FIGS. 3 and 4, the second clutch mechanism 180(2) includes a second clutch housing 181(2) supported on the transmission shaft 15 so as to be relatively rotatable about its axis, a second friction plate group 182(2) including second driving-side friction plates supported on the second driven gear 136(2) so as not to be relatively rotatable, and second driven-side friction plates supported on the second clutch housing 181(2) so as to be relatively non-rotatable while facing the second driving-side friction plates, and a second piston 183(2) that frictionally engages the second friction plate group 182(2). 3 and 4 denotes a return spring that biases the second piston 183(2) in a direction to separate it from the second friction plate group 182(2), and when the second friction plate group 182(2) is brought into frictional engagement, the second piston 183(2) is pushed by the force of pressure oil toward the second friction plate group 182(2) against the biasing force of the return spring 184(2).

[0103] The second clutch housing 181(2) is connected to the second carrier 38, which forms a reference rotational speed power input portion, so as to be non-rotatable relative to the second carrier 38 about its axis.

[0104] In this embodiment, as shown in FIGS. 3 and 4, the second carrier 38 has a second carrier pin 39. The second carrier pin 39 has an intermediate portion 39a that supports the second planetary gear 34, and first and second extending portions 39b, 39c that extend from the intermediate portion 39a to one side and the other side in the axial direction, respectively.

[0105] The second clutch housing 181(2) has an annular main body portion 186(2) that is externally fitted and supported on the transmission shaft 15 so as to be relatively rotatable about the axis, an annular end wall portion 187(2) that faces the main body portion 186(2) in the axial direction across the second planetary gear 34, and a connecting portion 188(2) that connects the main body portion 186(2) and the end wall portion 187(2) while leaving an installation space for the planetary gear 34.

[0106] The end wall portion 187(2) is provided with a first engagement hole into which the first extension portion 39b of the second carrier pin 39 engages, and the main body portion 186(2) is provided with a second engagement hole into which the second extension portion 39c of the second carrier pin 39 engages. The second driven friction plate is supported by the main body portion 186(2) so as not to be rotatable relative to the main body portion 186(2).

[0107] As shown in FIGS. 1 to 4, the planetary gear assembly 1A further includes a connecting member 80 that is fitted onto the transmission shaft 15 so as to be relatively rotatable about its axis.

[0108] The connecting member 80 connects the planetary output portion of the three planetary elements in the first planetary gear mechanism 20 other than the first sun gear 22 and the planetary elements that form the reference rotational speed power input portion to the planetary output portion of the three planetary elements in the second planetary gear mechanism 30 other than the second sun gear 32 and the planetary elements that form the reference rotational speed power input portion so that they cannot rotate relative to each other around their axis, while being made non-rotatable relative to the output shaft 90 around its axis.

[0109] As described above, in this embodiment, the first sun gear 22 forms a variable power input portion that inputs HST power, the first internal gear 26 forms a reference rotational speed power input portion, and the first carrier 28 forms a planetary output portion in the first planetary gear mechanism 20.

[0110] In addition, the second sun gear 32 forms a variable power input section that inputs HST power, the second carrier 38 forms a reference rotational speed power input section, and the second internal gear 36 forms a planetary output section in the second planetary gear mechanism 30.

[0111] Therefore, the connecting member 80 is configured to be unable to rotate relative to the output shaft 90 around its axis while connecting the first carrier 28, which is the planetary output part of the first planetary gear mechanism 20, and the second internal gear 36, which is the planetary output part of the second planetary gear mechanism 30, so that they cannot rotate relative to each other around their axis.

[0112] The connecting member 80 acts as a composite rotational power transmission member that transmits the composite rotational power of the first planetary gear mechanism 20 and the composite rotational power of the second planetary gear mechanism 30 to the output shaft 90 .

[0113] FIG. 5 shows an exploded perspective view of the output shaft 90 and the connecting member 80. As shown in FIG.

[0114] As shown in FIGS. 3 to 5, the output shaft 90 has male spline-shaped engaging portions 90a, which open radially outward and are arranged in the circumferential direction, on the outer peripheral surface of the outwardly extending portion on the first end side.

[0115] As shown in FIGS. 3 and 4, the first carrier 28 has a first carrier pin 29. The first carrier pin 29 has an intermediate portion 29a that supports the first planetary gear 24, and first and second extending portions 29b, 29c that extend from the intermediate portion 29a to one side and the other side in the axial direction, respectively.

[0116] The connecting member 80 is cylindrical and has an engaging portion 80a in the form of a female spline on its inner circumferential surface that engages with the concave-convex engaging portion 90a of the output shaft 90 to fix the output shaft 90 so that it cannot rotate relative to the output shaft 90, and an external tooth portion 80b on its outer circumferential surface that meshes with the second internal gear 36 that acts as the planetary output portion of the second planetary gear mechanism 30. In addition to splines, the engaging portions 80a, 90a may be formed by knurling, keys, press fitting, shrink fitting, or cold fitting. When splines or keys are used, the connecting member 80 and the output shaft 90 can be easily disassembled and assembled.

[0117] As shown in FIG. 5, the connecting member 80 has first and second annular portions 81 and 82 located on one and the other sides in the axial direction, respectively, and a connecting portion 83 located between the first and second annular portions 81 and 82 in the axial direction.

[0118] The first annular portion 81 is formed with a first engagement hole 81a (see FIG. 5) into which the first extending portion 29b of the first carrier pin 29 is inserted. The second annular portion 82 is formed with a second engagement hole 82a (see FIG. 5) into which the second extending portion 29c of the first carrier pin 29 is inserted.

[0119] The connecting portion 83 connects the first and second annular portions 81, 82 while leaving an installation space between the first and second annular portions 81, 82 for the planetary gear 24 supported by the intermediate portion 29a of the first carrier pin 29.

[0120] In this embodiment, as shown in Figure 5, the inward concave-convex engagement portion 80a is formed on the inner surface of the first annular portion 81, and the external tooth portion 80b is formed on the outer surface of the second annular portion 82.

[0121] As shown in FIG. 2, the first and second clutch mechanisms 180(1), 180(2) are configured to engage and disengage power transmission by first and second clutch operating members 145(1), 145(2), respectively, whose operation is controlled by the control device 300.

[0122] That is, the transmission structure 200A further includes the first clutch operating member 145(1) that switches the engagement and disengagement operation of the first clutch mechanism 180(1) and the second clutch operating member 145(2) that switches the engagement and disengagement operation of the second clutch mechanism 180(2), and the control device 300 is configured to control the operation of the first and second clutch operating members 145(1), 145(2) in addition to controlling the operation of the HST operating member 320.

[0123] In this embodiment, the first and second clutch operating members 145(1), 145(2) are hydraulic actuators.

[0124] In detail, as shown in FIG. 2, the first clutch actuating member 145(1) includes a pressure oil supply line 146 whose upstream side is fluidly connected to a hydraulic pressure source 430 such as a hydraulic pump, a drain line 147, a first supply / discharge line 148(1) that supplies / discharges pressure oil to / from the first clutch mechanism 180(1), and a first clutch solenoid valve 150(1).

[0125] As shown in FIG. 3 , the first supply / discharge line 148(1) has a first hydraulic oil axial oil passage 149a(1) formed in the output shaft 90, and a first hydraulic oil radial oil passage 149b(1) formed in the output shaft 90 so as to have one end fluidly connected to the first hydraulic oil axial oil passage 149a(1) and the other end fluidly connected to an oil pressure chamber of the first clutch mechanism 180(1). Since a relative rotation difference occurs between the output shaft 90 and the first clutch housing 181(1), an annular groove is formed on either the inner or outer contact surface thereof, and the first hydraulic oil radial oil passage 149b(1) passes through this annular groove, thereby establishing an oil passage that is not interrupted.

[0126] The first clutch solenoid valve 150(1) is configured to selectively take a clutch engagement position in which the first supply / discharge line 148(1) is fluidly connected to the pressure oil supply line 146 and a clutch disengagement position in which the first supply / discharge line 148(1) is fluidly connected to the drain line 147 in response to a signal from the control device 300.

[0127] The second clutch operating member 145(2) includes the pressure oil supply line 146, the drain line 147, a second supply / discharge line 148(2) that supplies / discharges pressure oil to / from the second clutch mechanism 180(2), and a second clutch solenoid valve 150(2).

[0128] As shown in FIG. 3 , the second supply / discharge line 148(2) has a second hydraulic oil axial oil passage 149a(2) formed in the output shaft 90, and a second hydraulic oil radial oil passage 149b(2) formed in the output shaft 90 and the transmission shaft 15 so that one end is fluidly connected to the second hydraulic oil axial oil passage 149a(2) and the other end is fluidly connected to the oil pressure chamber of the second clutch mechanism 180(2). Since a relative rotation difference occurs between the output shaft 90 and the transmission shaft 15, and between the transmission shaft 15 and the second clutch housing 181(2), annular grooves are formed on either the inner or outer contact surface of each of them in a double arrangement, and the second hydraulic oil radial oil passage 149b(2) is made to pass through these annular grooves to form an oil passage that is not divided.

[0129] The second clutch solenoid valve 150(2) is configured to selectively take a clutch engagement position in which the second supply / discharge line 148(2) is fluidly connected to the pressure oil supply line 146 and a clutch disengagement position in which the second supply / discharge line 148(2) is fluidly connected to the drain line 147 in response to a signal from the control device 300.

[0130] 2 denotes a hydraulic oil relief valve that sets the clutch hydraulic pressure in the hydraulic oil supply line 146.

[0131] In this embodiment, the first and second clutch solenoid valves 150(1), 150(2) are proportional pressure valves, but instead, they may be ON-OFF valves.

[0132] Furthermore, in this embodiment, the first and second clutch operating members 145(1), 145(2) are hydraulic actuators that operate hydraulic multi-plate clutches. However, for example, if the first and second clutch mechanisms 180(1), 180(2) are dog clutches, the first and second clutch operating members 145(1), 145(2) can also be electric actuators such as electric motors that shift the dog clutches.

[0133] As described above, in this embodiment, the transmission structure 200A has the forward / reverse switching mechanism 220. In this case, the transmission structure 200A further includes the forward / reverse shift replacement A forward / reverse operating member 155 is provided to operate mechanism 220, and the speed change operating member 310 can be manually operated within a forward operation range from the zero speed position to the maximum forward speed position, and within a reverse operation range from the zero speed position to the maximum reverse speed position.

[0134] The control device 300 then operates the forward / reverse operating member 155 so that the forward / reverse switching mechanism 220 is in a forward output state (forward output state) when the speed change operating member 310 is positioned in the forward side operating range, and so that the forward / reverse switching mechanism 220 is in a reverse output state (reverse output state) when the speed change operating member 310 is positioned in the reverse side operating range.

[0135] It is also possible to provide the transmission structure 200A with a dedicated forward / reverse switching operation member for manually operating the forward / reverse switching mechanism 220. In this case, the forward / reverse switching operation member can have various configurations, such as a lever mechanically operably connected to the forward / reverse switching mechanism 220 or an electric switch type. When the forward / reverse switching operation member is provided, the speed change operation member 310 is, for example, a pedal-type member that can be operated from a zero speed position to a maximum speed position, and the transmission structure 200A is configured to output driving force from zero speed to maximum forward speed and from zero speed to maximum reverse speed in response to manual operation of the speed change operation member 310 and the forward / reverse switching operation member.

[0136] The forward / reverse actuation member 155 may take various forms, such as a hydraulic actuator or an electric actuator, as long as it can actuate the forward / reverse switching mechanism 220 in response to a control signal from the control device 300 .

[0137] In this embodiment, as shown in FIG. 2, the forward / reverse operating member 155 is also a hydraulic actuator.

[0138] As shown in FIG. 1, the forward / reverse switching mechanism 220 is configured to switch the rotation direction of the HMT output between the forward direction and the reverse direction between the intermediate drive shaft 210, which operatively inputs the HMT output from the output shaft 90, and the traveling output shaft 215, which is operatively connected to the differential mechanism 230.

[0139] In the present embodiment, the forward / reverse switching mechanism 220 includes a forward gear train 330F including a forward drive gear 331F supported by the intermediate drive shaft 210 and a forward driven gear 332F supported by the traveling output shaft 215 and meshed with the forward drive gear 331F, a reverse gear train 330R including a reverse drive gear 331R supported by the intermediate drive shaft 210 and a reverse driven gear 332R supported by the traveling output shaft 215 and meshed with the reverse drive gear 331R via an idle gear 333, a forward clutch mechanism 340F that engages and disengages power transmission of the forward gear train 330F, and a reverse clutch mechanism 340R that engages and disengages power transmission of the reverse gear train 330R.

[0140] As shown in FIG. 2, the forward / reverse operating member 155 includes the pressure oil supply line 146, the drain line 147, a forward supply / discharge line 156F that supplies / discharges pressure oil to / from the forward clutch mechanism 330F, a reverse supply / discharge line 156R that supplies / discharges pressure oil to / from the reverse clutch mechanism 330R, a forward solenoid valve 157F, and a reverse solenoid valve 158R.

[0141] The forward solenoid valve 157F is configured to selectively take a clutch engagement position that fluidly connects the forward supply / discharge line 156F to the pressure oil supply line 146 and a clutch disengagement position that fluidly connects the forward supply / discharge line 156F to the drain line 147 in response to a signal from the control device 300.

[0142] Similarly, the reverse solenoid valve 157R is configured to selectively take a clutch engaged position in which the reverse supply / discharge line 156R is fluidly connected to the pressure oil supply line 146 and a clutch disengaged position in which the reverse supply / discharge line 156R is fluidly connected to the drain line 147 in response to a signal from the control device 300.

[0143] In this embodiment, the transmission structure 200A is provided with a lubricating oil supply structure. As shown in Figures 2 to 4, the lubricating oil supply structure includes a lubricating oil supply line 161 that receives the oil discharged from the hydraulic oil relief valve 146a after pressure adjustment, and a lubricating oil guide line 162 that guides the oil received from the lubricating oil supply line 161 to the desired lubrication points, such as the friction plates of the forward clutch mechanism 340F and the reverse clutch mechanism 340R of the forward / reverse switching mechanism 220.

[0144] As shown in Figures 3 and 4, the lubricant oil guide line 162 has a lubricant oil axial oil passage 163 formed from the intermediate drive shaft 210 to the output shaft 90 to receive the oil received from the lubricant oil supply line 161, and a plurality of lubricant oil guide oil passages that receive the lubricant oil from the lubricant oil axial oil passage 163 and guide it to a plurality of desired lubrication locations, respectively.

[0145] As shown in FIG. 4, in this embodiment, the lubricating oil guide passage includes a first planetary gear lubricating oil guide passage 165 that guides lubricating oil to the first planetary gear transmission mechanism 20, a second planetary gear lubricating oil guide passage 166 that guides lubricating oil to the second planetary gear transmission mechanism 30, a first clutch lubricating oil guide passage 167 that guides lubricating oil to the first clutch mechanism 180(1), and a second clutch lubricating oil guide passage 168 that guides lubricating oil to the second clutch mechanism 180(2).

[0146] As shown in FIG. 4, the first planetary gear lubricating oil guide passage 165 includes: a first planetary gear lubricating oil take-out passage 165a formed in the output shaft 90 so that one end is fluidly connected to the lubricating oil axial passage 163 and the other end opens to the outer surface of the outwardly extending portion on the first end side of the output shaft 90; a first planetary gear lubricating oil connection passage 165b (see FIG. 5) formed in the first annular portion 81 so that one end is fluidly connected to the first planetary gear lubricating oil take-out passage 165a and the other end opens to the first engaging hole 81a; and a first carrier pin lubricating oil passage 165c formed in the first carrier pin 29 so as to receive lubricating oil from the first planetary gear lubricating oil connection passage 165b and guide the lubricating oil to the desired lubrication portion.

[0147] In the present embodiment, the first carrier pin lubricating oil passage 165c is configured to guide lubricating oil to the outer peripheral surface of the intermediate portion 29a of the first carrier pin 29 that supports the first planetary gear 24.

[0148] Furthermore, the first carrier pin lubricating oil passage 165c is configured to guide the lubricating oil also to the end face of the second extending portion 29c of the first carrier pin 29.

[0149] As shown in FIG. 4, the second planetary gear lubricating oil guide passage 166 includes: a second planetary gear lubricating oil take-out passage 166a formed in the output shaft 90 and the transmission shaft 15 so as to have one end fluidly connected to the lubricating oil axial oil passage 163 and the other end opening to the outer surface of a portion of the transmission shaft 15 that supports the main body 186(2) of the second clutch housing 181(2); a second planetary gear lubricating oil connection passage 166b formed in the main body 181(2) so as to have one end fluidly connected to the second planetary gear lubricating oil take-out passage 166a and the other end opening to a second engagement hole of the main body 181(2); and a second carrier pin lubricating oil passage 166c formed in the second carrier pin 39 so as to receive lubricating oil from the second planetary gear lubricating oil connection passage 166b and guide the lubricating oil to a desired lubrication location. Since a relative rotation difference occurs between the output shaft 90 and the transmission shaft 15, and between the transmission shaft 15 and the second clutch housing 181(2), annular grooves are formed on either the inner or outer contact surface of each of them in a double arrangement, and the lubricating oil extraction oil passage 166a is connected to the lubricating oil connection oil passage 166b without interruption by passing through these annular grooves.

[0150] In this embodiment, the second carrier pin lubricating oil passage 166c is configured to guide lubricating oil to the outer peripheral surface of the intermediate portion 39a of the second carrier pin 39 that supports the second planetary gear .

[0151] Furthermore, the second carrier pin lubricating oil passage 166c is configured to guide the lubricating oil also to the end face of the second carrier pin 39 on the first end side.

[0152] The first clutch lubricating oil guide oil passage 167 has one end fluidly connected to the lubricating oil axial oil passage 163 and the other end opening to the outer surface of the portion of the outward extending portion on the first end side of the output shaft 90 that supports the installation cylindrical portion of the first clutch housing 181(1), and has a first clutch lubricating oil extraction oil passage 167a formed in the installation cylindrical portion and the output shaft 90 so as to pass through the installation cylindrical portion and release oil toward the friction plates of the first clutch. Since a relative rotation difference occurs between the output shaft 90 and the first clutch housing 181(1), an annular groove is formed on either the inner or outer contact surface thereof, and the lubricating oil extraction oil passage 167a passes through this annular groove, thereby forming an oil passage that is not interrupted.

[0153] The second clutch lubricating oil guide oil passage 168 has one end fluidly connected to the lubricating oil axial oil passage 163 and the other end opening to the outer surface of a portion of the transmission shaft 15 that supports the installation cylindrical portion of the main body 186(2) of the second clutch housing 181(2), and has a second clutch lubricating oil extraction oil passage 168a formed in the installation cylindrical portion, the output shaft 90, and the transmission shaft 15 so as to pass through the installation cylindrical portion and release oil toward the friction plates of the second clutch. Since a relative rotation difference occurs between the output shaft 90 and the transmission shaft 15, and between the transmission shaft 15 and the second clutch housing 181(2), annular grooves are formed on either the inner or outer contact surface of each of them in a double arrangement, and the lubricating oil extraction oil passage 168a passes through these annular grooves to form an uninterrupted oil passage.

[0154] As shown in FIG. 4, in this embodiment, the lubricating oil guide passage further includes a transmission shaft lubricating oil guide passage 169 that guides lubricating oil to a bearing member interposed between the transmission shaft 15 and the output shaft 90, and a thrust bearing lubricating oil guide passage 170 that guides lubricating oil to a thrust bearing arranged between the outward extending portion on the first end side of the output shaft 90 and the first end of the transmission shaft 15.

[0155] 2 denotes a lubricating oil relief valve that sets the oil pressure of the lubricating oil supply line 161.

[0156] Here, the set gear ratios of the first and second planetary gear mechanisms 20, 30 will be explained. FIG. 6 shows a graph showing the relationship between the HST output (the rotation speed of the motor shaft 116) and the HMT output (the rotation speed of the output shaft 90) in the HMT device 100A.

[0157] As shown in FIG. 6, the first planetary gear mechanism 20 has a gear ratio set so that in a first planetary transmission state (first gear transmission state) in which the HST output is input to the first sun gear 22 and the reference rotational speed power is input to the first internal gear 26, when the HST output is set to an HST speed for zero speed, the HMT output presented to the first carrier 28 (i.e., the connecting member 80 and the output shaft 90) becomes zero speed, and as the HST output changes from the first HST speed side to the second HST speed side, the HMT output presented to the first carrier 28 rotates at an increased speed in a first rotational direction, which is one side about the axis, and when the HST output is set to an HST speed for a predetermined first gear maximum speed, the HMT output presented to the first carrier 28 rotates in the first rotational direction at a predetermined first gear maximum speed.

[0158] In this embodiment, the zero speed HST speed is a speed shifted by a predetermined speed from the first HST speed, which is one end of the variable range of the HST output, toward the second HST speed.

[0159] This is due to the following reasons. In other words, in theory, it is possible to set the zero speed HST speed to the first HST speed, but in this case, depending on the running load of the work vehicle, etc., it is possible that the HST output will not reach the first HST speed even if the output adjustment member 120 is positioned at the first operating end position corresponding to the first HST speed. Taking this into consideration, the control device 300 sets the zero speed HST speed to a speed that is a predetermined speed away from the first HST speed, which is one speed end of the variable range of the HST output, toward the second HST speed.

[0160] For the same reason, in this embodiment, the control device 300 sets the speed shifted from the second HST speed, which is the other speed end of the variable range of the HST output, to the first HST speed by a predetermined speed as the HST speed for the first gear stage maximum speed. That is, in this embodiment, the "highest speed HST speed" refers to the adjusted output value by the control device 300, not the mechanical limit output value of the HST 110.

[0161] As shown in Figure 6, the second planetary gear mechanism 30 has a gear ratio set so that in a second planetary transmission state (second gear transmission state) in which the HST output is input to the second sun gear 32 and the reference rotational speed power is input to the second carrier 38, when the HST output is set to an HST speed for the first gear maximum speed, the HMT output produced at the second internal gear 36 (i.e., the connecting member 80 and the output shaft 90) becomes the first gear maximum speed, and as the HST output changes from the second HST speed side to the first HST speed side, the HMT output produced at the second internal gear 36 rotates at an increased speed in a first rotational direction, which is one side around the axis, and when the HST output is set to a predetermined HST speed for the second gear maximum speed, the HMT output produced at the second internal gear 36 rotates in the first rotational direction at a predetermined second gear maximum speed.

[0162] In this embodiment, the HST speed for the second gear stage maximum speed is also set to a speed shifted from the first HST speed, which is one end of the variable range of the HST output, to the second HST speed by a predetermined speed.

[0163] If the maximum vehicle speed that can be output in the second planetary transmission state (second gear stage transmission state) is too fast for the specifications of the work vehicle, the control device 300 can be adjusted to set the speed that is shifted significantly from the first HST speed toward the second HST speed (preferably to the neutral position N or close to the neutral position) as the HST speed for the second gear stage maximum speed, as shown in FIG.

[0164] In this embodiment, the control device 300 is configured to perform the following control to produce the HMT output shown in FIG.

[0165] That is, the transmission structure 200A further includes an output sensor 50 (see FIG. 1) that directly or indirectly detects the rotation speed of the output shaft 90. In this embodiment, the output sensor 50 detects the rotational speed of the output shaft 90 at the outward extending portion on the second end side of the output shaft 90, but instead, it is also possible to position the output sensor 50 so as to detect the rotational speed of the connecting member 80.

[0166] As shown in FIG. 6, the speed change operation range of the speed change operation member 310 is divided into a first speed operation region on the low speed side and a second speed operation region on the higher speed side than the first speed operation region. The first gear stage operation region is set in a range from a zero speed position to a first gear stage maximum speed position, and the second gear stage operation region is set in a range from a first gear stage maximum speed position to a second gear stage maximum speed position.

[0167] The control device 300 executes the following operation control for the first and second clutch operating members 145(1), 145(2).

[0168] That is, the control device 300: When it is determined that the speed change operating member 310 is operated in the first gear operating range based on a signal from the operating position sensor 315, the first and second clutch operating members 145(1), 145(2) are operated so as to obtain a first gear transmission state which is achieved by bringing the first clutch mechanism 180(1) into an engaged state and the second clutch mechanism 180(2) into a disengaged state; When it is determined that the speed change operating member 310 is positioned at the first gear maximum position based on a signal from the operating position sensor 315, the first and second clutch operating members 145(1), 145(2) are operated so that one of the first and second clutch mechanisms 180(1), 180(2) is in an engaged state and the other is in a disengaged state; When it is determined based on a signal from the operating position sensor 315 that the speed change operating member 310 is being operated in the second gear operating range, the first and second clutch operating members 145(1), 145(2) are operated so as to obtain a second gear transmission state which is achieved by bringing the first clutch mechanism 180(1) into a disengaged state and the second clutch mechanism 180(2) into an engaged state.

[0169] Furthermore, the control device 300 executes the following operation control for the HST operating member 320.

[0170] That is, the control device 330: When it is determined that the gear shift operating member 310 has been operated to the zero speed position based on a signal from the operating position sensor 315, the HST operating member 320 is operated so that the HST output becomes an HST speed for zero speed, When it is determined based on a signal from the operation position sensor 315 that the gear shift operating member 310 is being operated to increase the speed within the first gear stage operation range, the HST operating member 320 is operated so that the HST output is shifted from the first HST gear side to the second HST gear side, When it is determined that the gearshift operating member 310 has been operated to the first gear maximum speed position based on a signal from the operating position sensor 315, the HST operating member 320 is operated so that the HST output becomes the HST speed for the first gear maximum speed, When it is determined that the gear shift operating member 310 is being operated to increase the speed within the second gear stage operating range based on a signal from the operating position sensor 315, the HST operating member 320 is operated so that the HST output is shifted from the second HST gear side to the first HST gear side, When it is determined that the gearshift operating member 310 has been operated to the highest speed position based on a signal from the operating position sensor 315, the HST operating member 320 is operated so that the HST output becomes the HST speed for the second gear stage highest speed.

[0171] Furthermore, the control device 300 executes the following operation control for the forward / reverse operation member 155.

[0172] That is, the control device 300: When it is determined that the speed change operating member 310 is positioned in the forward operation range based on a signal from the operating position sensor 315, the forward / reverse operating member 155 is actuated so that the forward / reverse switching mechanism 220 is in a normal rotation output state; When it is determined that the speed change operating member 310 is positioned in the reverse operation range based on a signal from the operating position sensor 315, the forward / reverse operating member 155 is operated so that the forward / reverse switching mechanism 220 is in a reverse output state.

[0173] As described above, in this embodiment, the first clutch mechanism 180(1) is arranged coaxially with the transmission shaft 15 so as to be able to engage and disengage power transmission from the first driven gear 137(1) to the reference rotational speed power input portion of the first planetary gear mechanism 20 (the first internal gear 26 in this embodiment), and the second clutch mechanism 180(2) is arranged coaxially with the transmission shaft 15 so as to be able to engage and disengage power transmission from the second driven gear 137(2) to the reference rotational speed power input portion of the second planetary gear mechanism 30 (the second carrier 38 in this embodiment).

[0174] Here, the effect of arranging the first and second clutch mechanisms 180(1), 180(2) in this manner will be described.

[0175] FIG. 8 shows a schematic diagram of a power transmission of a working vehicle to which a planetary gear assembly 1X according to a comparative example is applied. In the planetary gear assembly 1X, a first clutch mechanism 140(1) that engages and disengages the transmission of the reference rotational speed power to the reference rotational speed power input portion of the first planetary gear mechanism 20, and a second clutch mechanism 140(2) that engages and disengages the transmission of the reference rotational speed power to the reference rotational speed power input portion of the second planetary gear mechanism 30 are arranged on the drive shaft 125. In FIG. 8, the same members as those in this embodiment are denoted by the same reference numerals.

[0176] In detail, as shown in FIG. 8, the planetary gear assembly 1X includes the transmission shaft 10 to which the HST output can be operatively input, the drive shaft 125, the first planetary gear mechanism 20 including the first sun gear 22 supported on the transmission shaft 10 so as not to be rotatable relative to the transmission shaft 10 about its axis, the second planetary gear mechanism 30 including the second sun gear 32 supported on the transmission shaft 10 so as not to be rotatable relative to the transmission shaft 10 about its axis, the first transmission gear train 135(1) capable of operatively transmitting a reference rotational speed power from the drive shaft 125 to a reference rotational speed power input portion of the first planetary gear mechanism 20 (the first internal gear 26 in the configuration shown in FIG. 8), and a front carrier 38 (2) capable of operatively transmitting a reference rotational speed power from the drive shaft 125 to a reference rotational speed power input portion of the second planetary gear mechanism 30 (the second carrier 38 in the configuration shown in FIG. 8). The second transmission gear train 135(2) includes a connecting member 40 that connects the planetary output portion of the first planetary gear mechanism 20 (the first carrier 28 in the configuration shown in FIG. 8) and the planetary output portion of the second planetary gear mechanism 30 (the second internal gear 36 in the configuration shown in FIG. 8) so as to be non-rotatable relative to each other about their axes; an output shaft 45 that is connected to the connecting member 40 so as to be non-rotatable relative to each other about their axes; the first clutch mechanism 140(1) that is supported by the drive shaft 125 so as to engage and disengage power transmission from the drive shaft 125 to the first drive gear 136(1) of the first transmission gear train 135(1); and the second clutch mechanism 140(2) that is supported by the drive shaft 125 so as to engage and disengage power transmission from the drive shaft 125 to the second drive gear 136(2) of the second transmission gear train 135(2).

[0177] In the planetary gear assembly 1X, the first clutch mechanism 140(1) is disposed between the drive shaft 125 and the first drive gear 136(1) supported on the drive shaft 125 so as to be rotatable relative to the drive shaft 125 about its axis in the transmission direction, and the second clutch mechanism 140(2) is disposed between the drive shaft 125 and the second drive gear 136(2) supported on the drive shaft 125 so as to be rotatable relative to the drive shaft 125 about its axis in the transmission direction.

[0178] For this reason, in the planetary gear assembly 1X, when one of the clutch mechanisms (for example, the first clutch mechanism 140(1)) is engaged, the drive gear on the non-engagement side (in this example, the second drive gear 136(2)) is reversely driven by the driven gear (in this example, the second driven gear 137(2)) that receives the rotation of the connecting member 40. At this time, if the relative rotation difference between the drive gear on the non-engagement side (in this example, the second drive gear 136(2)) and the drive shaft 125 exceeds an allowable value, abnormal wear or seizure may occur.

[0179] In contrast to this, in the planetary gear assembly 1A according to this embodiment, as shown in FIG. 1 etc., in a state in which the first and second drive gears 136(1), 136(2) are unable to rotate relatively about their axes on the drive shaft 125, the first clutch mechanism 180(1) is disposed between the first driven gear 137(1) and the reference rotational speed power input portion of the first planetary gear mechanism 20 (the first internal gear 26 in this embodiment) in terms of the transmission direction, and the second clutch mechanism 180(2) is disposed between the second driven gear 137(2) and the reference rotational speed power input portion of the second planetary gear mechanism 30 (the second carrier 38 in this embodiment) in terms of the transmission direction.

[0180] Therefore, in the planetary gear assembly 1A, when one of the clutch mechanisms (for example, the first clutch mechanism 180(1)) is engaged, the rotation of the connecting member 80 is not transmitted to the non-engaged driven gear (in this example, the second driven gear 137(2)), which allows for an advantageous design around the drive shaft 125.

[0181] Embodiment 2 Hereinafter, another embodiment of the planetary gear assembly according to the present invention will be described with reference to the accompanying drawings. FIG. 9 shows a schematic diagram of a transmission structure 200B for a working vehicle to which a planetary gear assembly 1B according to this embodiment is applied. In the drawings, the same members as those in the first embodiment are given the same reference numerals, and the description thereof will be omitted as appropriate.

[0182] As shown in FIG. 9, the planetary gear assembly 1B according to this embodiment further includes a third driven gear 137(3) and a third clutch mechanism 180(3) in comparison with the planetary gear assembly 1 according to the first embodiment.

[0183] The third driven gear 137(3) is supported directly or indirectly by the transmission shaft 15 so as to be relatively rotatable about its axis in a state in which a reference rotational speed power can be input.

[0184] The third driven gear 137(3) cooperates with a third drive gear 136(3) supported on the drive shaft 125 so as not to be able to rotate relatively about its axis, to form a third transmission gear train 135(3).

[0185] The third transmission gear train 135(3) forms a power transmission path from the drive shaft 125 to the reference rotational speed power input portion of the second planetary gear mechanism 30 (the second carrier 38 in this embodiment).

[0186] 9, the third driven gear 137(3) has a smaller pitch diameter than the second driven gear 137(2), and the third transmission gear train 135(3) has a higher speed ratio than the second transmission gear train 135(2). That is, the third transmission gear train 135(3) rotates the reference rotational speed power input portion (the second carrier 38 in this embodiment) of the second planetary gear mechanism 30 at a higher speed than the second transmission gear train 135(2).

[0187] The third clutch mechanism 180(3) is supported by the transmission shaft 15 so as to be able to engage and disengage power transmission from the third driven gear 137(3) to the reference rotational speed power input portion of the second planetary gear mechanism 30 (the second carrier 38 in this embodiment).

[0188] As shown in FIG. 9, in this embodiment, the third clutch mechanism 180(3) is also a hydraulic multi-plate clutch.

[0189] In detail, as shown in FIG. 9, the third clutch mechanism 180(3) includes a third clutch housing 181(3) supported on the transmission shaft 15 so as to be relatively rotatable about its axis, a third friction plate group 182(3) including second driving-side friction plates supported on the third driven gear 137(3) so as not to be relatively rotatable, and second driven-side friction plates supported on the third clutch housing 181(3) so as to be relatively non-rotatable while facing the third driving-side friction plates, and a third piston (not shown) that frictionally engages the third friction plate group 182(3).

[0190] The third clutch housing 181(3) is connected to the second carrier 38, which forms a reference rotational speed power input portion, so as to be non-rotatable relative to the second carrier 38 about its axis. In this embodiment, the third clutch housing 181(3) is integrally formed with the second clutch housing 181(2).

[0191] The third clutch mechanism 180(3) is configured to engage and disengage power transmission by a third clutch operating member (not shown) whose operation is controlled by the control device 300.

[0192] FIG. 10 shows a graph showing the relationship between the HST output and the HMT output in an HMT device 100B equipped with the planetary gear assembly 1B.

[0193] As shown in FIG. 10, in the HMT device 100B, the second planetary transmission state includes a second speed stage transmission state and a third speed stage transmission state.

[0194] The second speed transmission state is a transmission state that is achieved when the first clutch mechanism 180(1) is disengaged, the second clutch mechanism 180(2) is engaged, and the third clutch mechanism 180(3) is disengaged.

[0195] The third speed transmission state is a transmission state that is realized when the first clutch mechanism 180(1) is disengaged, the second clutch mechanism 180(2) is disengaged, and the third clutch mechanism 180(3) is engaged.

[0196] In this case, the gear shift operation range of the gear shift operation member 310 includes a first gear operation region from the zero speed position to the first gear maximum speed position, a second gear operation region from the first gear maximum speed position to the second gear maximum speed position, and a third gear operation region from the second gear maximum speed position to the third gear maximum speed position, as shown in FIG. 10.

[0197] When the speed change operating member 310 is operated within a range from the zero speed position to the second gear maximum speed position, the control device 300 executes the same operation control as in the first embodiment for the HST operating member 320 and the first and second clutch operating members 145(1), 145(2).

[0198] On the other hand, when the speed change operating member 310 is positioned in the second gear maximum speed position, the control device 300 engages one of the second clutch mechanism 180(2) and the third clutch mechanism 180(3) and disengages the other clutch mechanism; when the speed change operating member 310 is positioned in the third gear operating range, the control device 300 operates the first to third clutch operating members 145(1) to 145(3) so that the first and second clutch mechanisms 180(1), 180(2) are disengaged and the third clutch mechanism 180(3) is engaged, thereby achieving a third gear transmission state.

[0199] In this embodiment, the control device 300 executes the following operational control to prevent a sudden speed change from occurring in the HMT output when transitioning between the second speed transmission state and the third speed transmission state.

[0200] That is, when the speed change operating member 310 is operated to increase the speed to the second gear maximum speed position within the second gear operating range, the control device 300 operates the HST operating member 320 so that the HST output becomes the HST speed for the second gear maximum speed, and the HMT output becomes the second gear maximum speed.

[0201] Here, in the third speed transmission state, the reference rotational speed power is input to the second element (the second carrier 38 in the illustrated embodiment) of the second planetary gear mechanism 30 via the third transmission gear train 135(3) which has a higher speed ratio than the second transmission gear train 135(2).

[0202] Therefore, when the HST output is maintained at the HST speed for the second-speed maximum speed and the transmission state is shifted from the second-speed transmission state to the third-speed transmission state, a large speed change occurs in the HMT output.

[0203] Taking this into consideration, in the present embodiment, when the gear change operating member 310 is operated from the second gear operating range to the third gear operating range, the control device 300 operates the second and third clutch operating members 145(2), 145(3) so that the second clutch mechanism 180(2) is disengaged and the third clutch mechanism 180(3) is engaged, thereby transitioning from the second gear transmission state to the third gear transmission state, while operating the HST operating member 320 so that the HST output changes from the second gear highest speed HST speed to the third gear lowest speed HST speed, thereby preventing or reducing speed changes in the HMT output when transitioning between the second gear transmission state and the third gear transmission state.

[0204] The HST speed for the third gear stage lowest speed is set to a speed that makes the HMT output the second gear stage highest speed under the third gear stage transmission condition.

[0205] Thereafter, the control device 300 When it is determined based on a signal from the operation position sensor 315 that the gear shift operating member 310 is being operated to increase the speed within the third gear operation range, the HST operating member 320 is operated so that the HST output is shifted from the second HST gear side to the first HST gear side, When it is determined that the gearshift operating member 310 has been operated to the third gear maximum speed position based on a signal from the operating position sensor 315, the HST operating member 320 is operated so that the HST output becomes the HST speed for the third gear maximum speed.

[0206] The third gear maximum speed HST speed is set appropriately according to the vehicle speed specifications of the work vehicle. In this embodiment, as shown in Fig. 10, the third gear maximum speed HST speed is set to a speed shifted from the first HST speed, which is one end of the variable range of the HST output, toward the second HST speed side rather than the second gear maximum speed HST speed.

[0207] Embodiment 3 In this embodiment, the planetary gear assembly 1A according to the first embodiment is applied to a transmission structure 200C that is different from the transmission structure 200A. FIG. 11 shows a schematic diagram of the transmission structure 200C. In the drawings, the same members as those in the first and second embodiments are given the same reference numerals, and the description thereof will be omitted as appropriate.

[0208] As shown in FIG. 11, the transmission structure 200C is different from the transmission structure 200A in the first embodiment in that it includes an auxiliary transmission mechanism 280 that can change the output of the HMT device 100A in multiple stages.

[0209] In this embodiment, the sub-transmission mechanism 280 is disposed between the HMT device 100A and the forward / reverse switching mechanism 220 in terms of the power transmission direction, and is capable of shifting between two stages: low speed L and high speed H.

[0210] The sub-transmission mechanism 280 is configured to switch between the low speed stage L and the high speed stage H via a mechanical link mechanism or via a sub-transmission operating member such as a hydraulic actuator or an electric actuator whose operation is controlled by the control device 300, in response to manual operation of a sub-transmission operating member (not shown) configured as a lever or an electric switch.

[0211] FIG. 12 is a graph showing the relationship between the HST output and the output of the auxiliary transmission mechanism 280.

[0212] The transmission structure 200C is provided with an auxiliary transmission sensor 285 (see FIG. 11) that can detect the transmission state of the auxiliary transmission mechanism 280 and transmit a detection signal to the control device 300. The auxiliary transmission sensor 285 can take various forms, such as a sensor that detects the operating position of the auxiliary transmission operating member, a sensor that detects the operating state of the auxiliary transmission mechanism 280, or a sensor that detects the movement of the auxiliary transmission operating member.

[0213] In this embodiment, as shown in FIG. 12, the control device 300 is configured so that, in the auxiliary L-stage engaged state, the HST output is set to an HST speed for second gear maximum speed when auxiliary L-stage is engaged in response to operation of the gearshift operating member 310 to the second gear maximum speed position, while in the auxiliary H-stage engaged state, the HST output is set to an HST speed for second gear maximum speed when auxiliary H-stage is engaged, which is a predetermined speed lower than the HST speed for second gear maximum speed when auxiliary L-stage is engaged, in response to operation of the gearshift operating member 310 to the second gear maximum speed position.

[0214] The HST speed for second gear maximum speed when auxiliary transmission L stage is engaged and the HST speed for second gear maximum speed when auxiliary transmission H stage is engaged are set appropriately according to the specifications of the working vehicle.

[0215] Embodiment 4 Hereinafter, still another embodiment of the planetary gear assembly according to the present invention will be described with reference to the accompanying drawings. FIG. 13 shows a vertical cross-sectional view of a planetary gear assembly 1D according to this embodiment. FIG. 14 shows a partially enlarged vertical cross-sectional view of the planetary gear assembly 1D. In the drawings, the same components as those in the above-described embodiments are given the same reference numerals, and the description thereof will be omitted as appropriate.

[0216] The planetary gear assembly 1D according to this embodiment differs from the planetary gear assembly 1A according to the first embodiment only in that the first clutch mechanism 180(1) is changed to a modified first clutch mechanism 180D(1).

[0217] As shown in FIGS. 13 and 14 , the modified first clutch mechanism 180D(1) includes: a first clutch housing 181D(1) supported directly or indirectly on an outward extending portion of the output shaft 90 so as to be relatively rotatable about the axis; a first friction plate group 182D(1) including first driving-side friction plates supported on the first clutch housing 180D(1) so as to be non-rotatable relative to the first clutch housing 180D(1) and movable in the axial direction; and first driven-side friction plates arranged opposite the first driving-side friction plates; a first rotating member 185D(1) that is extrapolated onto the outward extending portion of the output shaft 90 so as to be relatively rotatable about the axis and supports the first driven-side friction plates so as to be non-rotatable relative to the first driving-side friction plates and movable in the axial direction; and a first piston 183D(1) that frictionally engages the first friction plate group 182D(1) by pressurized oil supplied to an oil chamber in the first clutch housing 181D(1).

[0218] Note that the symbol 184D(1) in FIG. 14 is a return spring that biases the first piston 183D(1) in a direction to move it away from the first friction plate group 182D(1), and when the first friction plate group 182D(1) is frictionally engaged, the first piston 183D(1) is pushed by the force of pressurized oil toward the first friction plate group 182D(1) against the biasing force of the return spring 184D(1).

[0219] The first clutch housing 181D(1) is connected to the first driven gear 137(1) so as to be unable to rotate relatively about its axis. In the present embodiment, as shown in FIG. 14, a ball bearing is interposed between the output shaft 90 and the first driven gear 137(1) in order to smoothly rotate the first driven gear 137(1) relative to the output shaft 90, and further, a needle bearing is interposed between the output shaft 90 and the first clutch housing 181D(1) in order to smoothly rotate the first clutch housing 181D(1) relative to the output shaft 90. In addition, in this embodiment, as shown in FIG. 14, two rows of needle bearings are interposed between the second clutch housing 181(2) and the transmission shaft 15, thereby improving the smoothness of relative rotation of the second clutch housing 181(2) with respect to the transmission shaft 15.

[0220] The first rotating member 185D(1) is provided with the external tooth portion 180a that meshes with the first internal gear 26, and is connected to the first internal gear 26 via the external tooth portion 180a so as to be unable to rotate relative to the first internal gear 26 around the axis.

[0221] Compared to the planetary gear assembly 1A according to the first embodiment, the planetary gear assembly 1D equipped with the modified first clutch mechanism 180D(1) can effectively prevent or reduce energy loss in a double transmission state, abnormal wear and seizure of the first friction plate group 182D(1), and temperature rise of the hydraulic oil due to absorption of frictional heat of the first friction plate group 182D(1) in the second planetary transmission state (second gear transmission state).

[0222] That is, as shown in FIG. 4 and the like and as described above, in the first clutch mechanism 180(1) in the first embodiment, the first driving-side friction plates are supported by the first driven gear 137(1) so as to be non-rotatable relative to each other and movable axially, and the first driven-side friction plates are supported by the first clutch housing 181(1) so as to be non-rotatable relative to each other and movable axially in a state facing the first driving-side friction plates, and the first clutch housing 181(1) is connected to the first internal gear 26 that forms the reference rotational speed power input portion so as to be non-rotatable relative to each other about the axis.

[0223] In the planetary gear assembly 1A equipped with the first clutch mechanism 180(1) having such a configuration, the following phenomenon may occur in the second planetary transmission state (second speed transmission state) which is established when the first clutch mechanism 180(1) is in a disengaged state and the second clutch mechanism 180(2) is in an engaged state.

[0224] That is, in the second planetary transmission state (second gear transmission state), the second internal gear 36, which acts as a planetary output section, is rotated by a combined rotational power of a reference rotational power operatively transmitted to the second carrier 38 via the second driven gear 137(2) and the second clutch mechanism 180(2) and an HST output operatively transmitted to the second sun gear 32 via the HST driven gear 134 and the transmission shaft 15.

[0225] The rotation of the second internal gear 36 due to the combined rotational power is transmitted to the output shaft 90 via the connecting member 80, and at this time, the rotation of the connecting member 80 is also transmitted to the first internal gear 26 via the first carrier 28 and the first planetary gear 24, and the first clutch housing 181(1) is rotated in a driven manner via the first internal gear 26.

[0226] Here, since the connecting member 80 rotates at a higher speed in the second planetary transmission state (second gear transmission state) than in the first planetary transmission state (first gear transmission state), the driven rotation of the first clutch housing 181(1) in the second planetary transmission state (second gear transmission state) becomes relatively fast, and centrifugal force acts on the oil in the oil chamber of the first clutch housing 181(1), which can cause a phenomenon in which the first piston 183(1) is pushed against its will in the direction of the first friction plate group.

[0227] Such a phenomenon leads to problems such as energy loss, abnormal wear of the first friction plate group 182(1), and hydraulic oil.

[0228] In contrast to this, in the modified first clutch mechanism 180D(1), the first internal gear 26 is connected to the first rotating member 185D(1) instead of the first clutch housing 181D(1).

[0229] Therefore, in the second planetary transmission state (second gear transmission state), the first clutch housing 181D(1) is not rotated at high speed via the first internal gear 26, and the above-mentioned inconveniences can be effectively prevented or reduced.

[0230] In addition, a similar phenomenon may occur in the second clutch mechanism 180(2) in the first planetary transmission state (second gear transmission state), but the rotational speed of the connecting member 80 in the first planetary transmission state (first gear transmission state) is slower than the rotational speed in the second planetary transmission state (second gear transmission state).

[0231] Therefore, although it is unlikely that the above-mentioned inconvenience will occur in the second clutch mechanism 180(2) during the first planetary transmission state (second gear transmission state), it is also possible to provide a modified second clutch mechanism (not shown) having a configuration similar to that of the modified first clutch mechanism 180D(1) instead of the second clutch mechanism 180(2).

[0232] That is, the modified second clutch mechanism includes: a second clutch housing supported directly or indirectly on the transmission shaft 15 so as to be rotatable relative to the transmission shaft 15 about its axis; a second friction plate group including second driving-side friction plates supported on the second clutch housing so as to be non-rotatable relative to the transmission shaft 15 but movably in the axial direction; and second driven-side friction plates arranged opposite the second driving-side friction plates; a second rotating member that supports the second driven-side friction plates so as to be non-rotatable relative to the transmission shaft 15 but movably in the axial direction; and a second piston that frictionally engages the second friction plate group by pressurized oil supplied to an oil chamber in the second clutch housing; and the second clutch housing is connected to the second driven gear 135(2) so as to be non-rotatable relative to the transmission shaft 15 about its axis, and the second rotating member is connected to the second carrier 38 so as to be non-rotatable relative to the second sun gear 32 about its axis. The modified second clutch mechanism may also be provided with a return spring that biases the second piston in a direction that moves it away from the second friction plate group. [Explanation of symbols]

[0233] 1A~1D Planetary gear assembly 15 Transmission shaft 20. First planetary gear mechanism 22 First sun gear 26 1st internal gear 28 First Carrier 30 Second planetary gear mechanism 32 Second sun gear 36 Second internal gear 38 Second Carrier 50 Output Sensor 80 Connecting member 90 output shaft 100A~100B HMT device 110 HST 112 Pump shaft 116 Motor shaft 125 drive shaft 134 HST driven gear 135(1)~135(3) 1st~3rd transmission gear train 136(1)~136(3) 1st~3rd drive gears 137(1)~137(3) 1st~3rd driven gears 180(1)~180(3) 1st~3rd clutch mechanism 180D(1) Modified first clutch mechanism 181D(1) First clutch housing 182D(1) 1st friction plate group 183D(1) First piston 185D(1) First rotating member 200A~200C Transmission Structure 220 Forward / reverse switching mechanism 280 Sub-transmission mechanism 300 control device 310 Gear shift operating member 315 Operation position sensor 320 HST operating member 410 Drive source

Claims

1. A planetary gear assembly that forms an HMT device in cooperation with an HST that continuously changes the speed of a reference rotational speed power operatively input from a drive source to a pump shaft between a first HST speed and a second HST speed, and outputs the changed HST output from a motor shaft, a cylindrical transmission shaft to which HST output can be input; an output shaft inserted into the transmission shaft so as to be relatively rotatable about its axis, with at least a portion of the output shaft extending outward from the transmission shaft; a first planetary gear mechanism having three planetary elements including a first sun gear, a first carrier, and a first internal gear, the first sun gear being supported on the transmission shaft so as not to be rotatable relative to the transmission shaft about its axis, and one of the first carrier and the first internal gear forming a reference rotational speed power input section to which a reference rotational speed power can be input; a second planetary gear mechanism having three planetary elements including a second sun gear, a second carrier, and a second internal gear, the second sun gear being supported on the transmission shaft so as to be unable to rotate relatively about its axis, and one of the second carrier and the second internal gear, which is different from a planetary element that forms a reference rotational speed power input portion in the first planetary gear mechanism, forms a reference rotational speed power input portion to which reference rotational speed power can be input; a first clutch mechanism that is disposed coaxially with the transmission shaft and that engages and disengages power transmission of the reference rotational speed power to the reference rotational speed power input portion of the first planetary gear mechanism; a second clutch mechanism that is arranged coaxially with the transmission shaft and that engages and disengages power transmission of the reference rotational speed power to the reference rotational speed power input portion of the second planetary gear mechanism; a connecting member fitted onto the transmission shaft so as to be relatively rotatable about the axis thereof, a planetary gear assembly including a connecting member that connects the planetary elements of the three planetary elements in the first planetary gear mechanism that form the planetary output portion other than the first sun gear and the planetary elements that form the reference rotational speed power input portion to the planetary elements of the three planetary elements in the second planetary gear mechanism that form the planetary output portion other than the second sun gear and the planetary elements that form the reference rotational speed power input portion so that they cannot rotate relative to each other around their axis, and that is also configured to be unable to rotate relative to the output shaft around its axis.

2. a first driven gear that is directly or indirectly supported on an outwardly extending portion of the output shaft so as to be relatively rotatable about its axis, and to which a reference rotational speed power can be input; a second driven gear that is directly or indirectly supported on the transmission shaft so as to be relatively rotatable about its axis and to which a reference rotational speed power can be input; the first clutch mechanism is supported on an outwardly extending portion of the output shaft so as to be able to engage and disengage power transmission from the first driven gear to the reference rotational speed power input portion of the first planetary gear mechanism, 2. The planetary gear assembly according to claim 1, wherein the second clutch mechanism is supported by the transmission shaft so as to be able to engage and disengage power transmission from the second driven gear to the reference rotational speed power input portion of the second planetary gear mechanism.

3. a third driven gear that is directly or indirectly supported on the transmission shaft so as to be relatively rotatable about its axis and to which a reference rotational speed power can be input, the third driven gear having a pitch diameter smaller than that of the second driven gear; 3. The planetary gear assembly according to claim 2, further comprising a third clutch mechanism supported on the transmission shaft so as to be able to engage and disengage power transmission from the third driven gear to the reference rotational speed power input portion of the second planetary gear mechanism.

4. the first internal gear and the second carrier form the reference rotational speed power input portion, 4. The planetary gear assembly according to claim 2, wherein the connecting member connects the first carrier and the second internal gear so as not to rotate relative to each other about an axis line.

5. the first clutch mechanism includes: a first clutch housing supported directly or indirectly on an outwardly extending portion of the output shaft so as to be relatively rotatable about the axis; a first friction plate group including first driving-side friction plates supported on the first clutch housing so as to be relatively rotatable but axially movable; and first driven-side friction plates disposed opposite the first driving-side friction plates; a first rotating member that is externally inserted onto the outwardly extending portion of the output shaft so as to be relatively rotatable about the axis and that supports the first driven-side friction plates so as to be relatively rotatable but axially movable; and a first piston that frictionally engages the first friction plate group by pressurized oil supplied to an oil chamber in the first clutch housing, the first clutch housing is connected to the first driven gear so as to be unable to rotate relative to the first driven gear about an axis; 5. The planetary gear assembly according to claim 4, wherein the first rotating member is connected to the first internal gear so as not to rotate relative to the first internal gear about its axis.

6. the second clutch mechanism includes: a second clutch housing supported directly or indirectly on the transmission shaft so as to be relatively rotatable about the axis; a second friction plate group including second driving side friction plates supported on the second clutch housing so as to be relatively rotatable but axially movable; and second driven side friction plates disposed opposite the second driving side friction plates; a second rotating member that is inserted onto the transmission shaft so as to be relatively rotatable about the axis and supports the second driven side friction plates so as to be relatively rotatable but axially movable; and a second piston that frictionally engages the second friction plate group by pressurized oil supplied to an oil chamber in the second clutch housing, the second clutch housing is connected to the second driven gear so as to be unable to rotate relative to the second driven gear about an axis; 6. The planetary gear assembly according to claim 4, wherein the second rotating member is connected to the second carrier so as to be non-rotatable relative to the second sun gear about the axis of the second sun gear.

7. the first carrier has a first carrier pin that meshes with both the first sun gear and the first internal gear and supports a first planetary gear that revolves around the first sun gear so as to be rotatable about an axis; the first carrier pin has an intermediate portion that supports the first planetary gear, and first and second extending portions that extend from the intermediate portion to one side and the other side in the axial direction, respectively; the connecting member is cylindrical and has a first annular portion located on one side in the axial direction, a second annular portion spaced apart from the first annular portion on the other side in the axial direction, and a connecting portion connecting the first and second annular portions, The first and second annular portions are provided with a first engagement hole into which the first extension portion is inserted and a second engagement hole into which the second extension portion is inserted, respectively; the connecting portion is configured to connect the first and second annular portions while leaving an installation space for the first planetary gear supported by an intermediate portion of the first carrier pin, 7. A planetary gear assembly as described in any one of claims 4 to 6, characterized in that the inner and outer surfaces of the cylindrical body formed by the first annular portion, the connecting portion, and the second annular portion are respectively provided with a concave-convex engaging portion that engages with the outer surface of the outwardly extending portion of the output shaft and an external tooth portion that meshes with the second internal gear.

8. the first planetary gear mechanism has a gear ratio set such that, under a transmission state in which a reference rotational speed power is operatively input to the first internal gear forming the reference rotational speed power input portion and an HST output is operatively input to the first sun gear, the first carrier rotates at an increased speed in a first rotational direction which is one side about the axis as the HST output changes from the first HST speed side to the second HST speed side, and the first carrier rotates in the first rotational direction at a predetermined first gear maximum speed when the HST output is set to a predetermined first gear maximum speed HST speed; 8. The planetary gear assembly according to claim 4, wherein the second planetary gear mechanism has a gear ratio set so that, under a transmission state in which reference rotational speed power is operatively input to the second carrier forming the reference rotational speed power input portion and HST output is operatively input to the second sun gear, when the HST output is set to an HST speed for first gear maximum speed, the second internal gear rotates in the first rotational direction at the first gear maximum speed, and as the HST output is changed from the HST speed for first gear maximum speed toward the first HST speed to a predetermined HST speed for second gear maximum speed, the rotational speed of the second internal gear increases from the first gear maximum speed to the second gear maximum speed.

9. 9. The planetary gear assembly according to claim 8, wherein the gear ratio of the first planetary gear mechanism is set so that the first carrier is at zero speed when the HST output is set to a predetermined HST speed for zero speed under the transmission state.

10. 10. The planetary gear assembly according to claim 9, wherein the zero speed HST speed is a speed shifted from the first HST speed by a predetermined speed toward the second HST speed.

11. 11. The planetary gear assembly according to claim 1, further comprising an HST driven gear that is supported on the transmission shaft so as not to be rotatable relative to the transmission shaft and that can receive HST output.

12. an HST that continuously changes the speed of a reference rotational speed power operatively input from a drive source to a pump shaft between a first HST speed and a second HST speed, and outputs the changed HST output from a motor shaft; a drive shaft to which a reference rotational speed power is operatively transmitted from the drive source; a cylindrical transmission shaft to which the HST output is operatively transmitted from the motor shaft; an output shaft inserted into the transmission shaft so as to be relatively rotatable about its axis, with at least a portion of the output shaft extending outward from the transmission shaft; a first planetary gear mechanism having three planetary elements including a first sun gear, a first carrier, and a first internal gear, the first sun gear being supported on the transmission shaft so as not to be rotatable relative to the transmission shaft about its axis, and one of the first carrier and the first internal gear forming a reference rotational speed power input section to which a reference rotational speed power can be input; a first transmission gear train including a first drive gear supported on the drive shaft so as not to be rotatable relative to the drive shaft about its axis, and a first driven gear supported directly or indirectly on an outwardly extending portion of the output shaft so as to be rotatable relative to the drive shaft about its axis, and operatively meshed with the first drive gear; a first clutch mechanism that is disposed coaxially with the transmission shaft and that engages and disengages power transmission of the reference rotational speed power from the first driven gear to a reference rotational speed power input portion of the first planetary gear mechanism; a second planetary gear mechanism having three planetary elements including a second sun gear, a second carrier, and a second internal gear, the second sun gear being supported on the transmission shaft so as to be unable to rotate relatively about its axis, and one of the second carrier and the second internal gear, which is different from a planetary element that forms a reference rotational speed power input portion in the first planetary gear mechanism, forms a reference rotational speed power input portion to which reference rotational speed power can be input; a second transmission gear train including a second driving gear supported on the drive shaft so as not to be rotatable relative to the drive shaft about its axis, and a second driven gear supported directly or indirectly on the transmission shaft so as to be rotatable relative to the drive shaft about its axis and operatively meshed with the second driving gear; a second clutch mechanism that is disposed coaxially with the transmission shaft and that engages and disengages power transmission of the reference rotational speed power from the second driven gear to the reference rotational speed power input portion of the second planetary gear mechanism; a connecting member fitted onto the transmission shaft so as to be relatively rotatable about the axis thereof, the connecting member connects the planetary elements forming the planetary output portion other than the first sun gear and the planetary elements forming the reference rotational speed power input portion among the three planetary elements in the first planetary gear mechanism to the planetary elements forming the planetary output portion other than the second sun gear and the planetary elements forming the reference rotational speed power input portion among the three planetary elements in the second planetary gear mechanism so as to be unable to rotate relative to the output shaft about the axis,

13. the first internal gear and the second carrier form the reference rotational speed power input portion, the connecting member connects the first carrier and the second internal gear so as not to rotate relative to each other about an axis; The first planetary gear mechanism has a gear ratio set so that, under a transmission state, when the HST output is set to a predetermined HST speed for zero speed, the first carrier reaches zero speed, and as the HST output is changed from the first HST speed side to the second HST speed side, the first carrier rotates at an increased speed in a first rotation direction which is one side about the axis, and when the HST output is set to a predetermined HST speed for first gear stage maximum speed, the first carrier rotates in the first rotation direction at the predetermined first gear stage maximum speed, 13. The HMT device according to claim 12, wherein the gear ratio of the second planetary gear mechanism is set so that, in a transmission state, when the HST output is set to an HST speed for first gear maximum speed, the second internal gear rotates in a first rotational direction at the first gear maximum speed, and as the HST output is changed from the HST speed for first gear maximum speed toward the first HST speed to a predetermined HST speed for second gear maximum speed, the rotational speed of the second internal gear increases from the first gear maximum speed to the second gear maximum speed.

14. the first clutch mechanism includes: a first clutch housing supported directly or indirectly on an outwardly extending portion of the output shaft so as to be relatively rotatable about the axis; a first friction plate group including first driving-side friction plates supported on the first clutch housing so as to be relatively rotatable but axially movable; and first driven-side friction plates disposed opposite the first driving-side friction plates; a first rotating member that is externally inserted onto the outwardly extending portion of the output shaft so as to be relatively rotatable about the axis and that supports the first driven-side friction plates so as to be relatively rotatable but axially movable; and a first piston that frictionally engages the first friction plate group by pressurized oil supplied to an oil chamber in the first clutch housing, the first clutch housing is connected to the first driven gear so as to be unable to rotate relative to the first driven gear about an axis; 14. The HMT device according to claim 13, wherein the first rotating member is connected to the first internal gear so as not to rotate relative to the first internal gear about an axis.

15. the second clutch mechanism includes: a second clutch housing supported directly or indirectly on the transmission shaft so as to be relatively rotatable about the axis; a second friction plate group including second driving side friction plates supported on the second clutch housing so as to be relatively rotatable but axially movable; and second driven side friction plates disposed opposite the second driving side friction plates; a second rotating member that is inserted onto the transmission shaft so as to be relatively rotatable about the axis and supports the second driven side friction plates so as to be relatively rotatable but axially movable; and a second piston that frictionally engages the second friction plate group by pressurized oil supplied to an oil chamber in the second clutch housing, the second clutch housing is connected to the second driven gear so as to be unable to rotate relative to the second driven gear about an axis; 15. The HMT device according to claim 13, wherein the second rotating member is connected to the second carrier so as to be non-rotatable relative to the second carrier about the axis of the second sun gear.

16. a third transmission gear train including a third drive gear supported on the drive shaft so as not to be rotatable relative to the drive shaft about its axis, and a third driven gear operatively meshed with the third drive gear while being supported on the transmission shaft directly or indirectly so as to be rotatable relative to the drive shaft about its axis; a third clutch mechanism that is arranged coaxially with the transmission shaft and that engages and disengages power transmission of the reference rotational speed power from the third driven gear to the reference rotational speed power input portion of the second planetary gear mechanism, 16. The HMT device according to claim 13, wherein the third transmission gear train has a higher speed ratio than the second transmission gear train.

17. An HMT device according to any one of claims 13 to 15; a speed change operation member that can be manually operated within a speed change operation range between a zero speed position and a maximum speed position; an operation position sensor that detects the operation position of the gear shift operation member; a first clutch actuating member that switches between an engagement and disengagement operation of the first clutch mechanism; a second clutch actuating member that switches between an engagement and disengagement operation of the second clutch mechanism; an HST operating member that operates an output adjusting member of the HST; an output sensor that directly or indirectly detects the rotation speed of the output shaft; a control device that controls the operation of the first and second clutch operating members and the HST operating member, The speed change operation range is divided into a first gear operation region on the low speed side, which is set in a range from a zero speed position to a first gear maximum speed position, and a second gear operation region on the high speed side, which is set in a range from the first gear maximum speed position to a maximum speed position, The control device operates the first and second clutch operating members so that, when the speed change operating member is operated in the first gear operation range, the first clutch mechanism is engaged and the second clutch mechanism is disengaged, thereby realizing a first gear transmission state; when the speed change operating member is positioned at a first gear maximum speed position, one of the first and second clutch mechanisms is engaged and the other is disengaged; and when the speed change operating member is operated in the second gear operation range, the control device operates the first and second clutch operating members so that, when the speed change operating member is operated in the second gear operation range, the first clutch mechanism is disengaged and the second clutch mechanism is engaged, thereby realizing a second gear transmission state; Furthermore, the control device operates the HST operating member so that the HST output becomes an HST speed for zero speed in response to operation of the speed change operating member to the zero speed position, the HST output is shifted from the first HST speed side to the second HST speed side in response to operation of the speed change operating member to the speed increasing side in the first gear stage transmission state, the HST output becomes an HST speed for first gear stage maximum speed in response to operation of the speed change operating member to the first gear stage maximum speed position, the HST output is shifted from the second HST speed side to the first HST speed side in response to operation of the speed change operating member to the speed increasing side in the second gear stage transmission state, and the HST output becomes an HST speed for second gear stage maximum speed in response to operation of the speed change operating member to the maximum speed position.

18. an HMT device according to claim 16; a speed change operation member that can be manually operated within a speed change operation range between a zero speed position and a maximum speed position; an operation position sensor that detects the operation position of the gear shift operation member; a first clutch actuating member that switches between an engagement and disengagement operation of the first clutch mechanism; a second clutch actuating member that switches between an engagement and disengagement operation of the second clutch mechanism; a third clutch actuating member that switches between an engagement and disengagement operation of the third clutch mechanism; an HST operating member that operates an output adjusting member of the HST; an output sensor that directly or indirectly detects the rotation speed of the output shaft; a control device that controls the operation of the first to third clutch operating members and the HST operating member, The speed change operation range is divided into a first gear operation region on the low speed side, which is set in a range from a zero speed position to a first gear maximum speed position, a second gear operation region on the intermediate speed side, which is set in a range from the first gear maximum speed position to a second gear maximum speed position, and a third gear operation region on the high speed side, which is set in a range from the second gear maximum speed position to a maximum speed position, The control device operates the first to third clutch operating members so that, when the speed change operating member is operated in the first gear operation range, the first clutch mechanism is engaged and the second and third clutch mechanisms are disengaged, thereby realizing a first gear transmission state; when the speed change operating member is positioned at the first gear maximum speed position, one of the first and second clutch mechanisms is engaged and the remaining clutch mechanism is disengaged; when the speed change operating member is operated in the second gear operation range, the first and third clutch mechanisms are disengaged and the second clutch mechanism is engaged, thereby realizing a second gear transmission state; when the speed change operating member is positioned at the second gear maximum speed position, one of the second and third clutch mechanisms is engaged and the remaining clutch mechanism is disengaged; and when the speed change operating member is operated in the third gear operation range, the first and second clutch mechanisms are disengaged and the third clutch mechanism is engaged, thereby realizing a third gear transmission state; Furthermore, the control device is configured so that, in response to operation of the speed change operating member to a zero speed position, the HST output becomes an HST speed for zero speed, and, in response to operation of the speed change operating member to a speed-up side in a first gear stage transmission state, the HST output is shifted from the first HST speed side to the second HST speed side, and, in response to operation of the speed change operating member to a first gear stage maximum speed position, the HST output becomes an HST speed for first gear stage maximum speed, and, in response to operation of the speed change operating member to a speed-up side in a second gear stage transmission state, the HST output is shifted from the second HST speed side to the first HST speed side, In response to operation of the speed change operating member to a second gear maximum speed position, the HST output becomes a second gear maximum speed HST speed, and when transitioning from the second gear transmission state to the third gear transmission state, the HST output becomes from the second gear maximum speed HST speed to the third gear minimum speed HST speed, and in response to operation of the speed change operating member to the speed increase side in the third gear transmission state, the HST output is shifted from the second HST speed side to the first HST speed side, and in response to operation of the speed change operating member to the maximum speed position, the HST operating member is operated so that the HST output becomes a predetermined third gear maximum speed HST speed, A transmission structure characterized in that the HST speed for the third gear stage lowest speed is set so that the rotational speed of the output shaft when the HST output is set to the second gear stage highest speed in the second gear stage transmission state matches the rotational speed of the output shaft when the HST output is set to the third gear stage lowest speed HST speed in the third gear stage transmission state.

19. a forward / reverse switching mechanism that can selectively take a normal rotation output state in which the HMT power operatively input from the output shaft is output without changing the rotation direction, and a reverse rotation output state in which the HMT power is output by reversing the rotation direction; a forward / reverse operating member that operates the forward / reverse switching mechanism, the speed change operation range of the speed change operation member includes a forward operation range from a zero speed position to a forward maximum speed position, and a reverse operation range from the zero speed position to a reverse maximum speed position, 19. The transmission structure according to claim 17 or 18, wherein the control device operates the forward / reverse operating member so that the forward / reverse switching mechanism is in a forward rotation output state when the speed change operating member is positioned in a forward side operation range, and so that the forward / reverse switching mechanism is in a reverse rotation output state when the speed change operating member is positioned in a reverse side operation range.

20. a forward / reverse switching mechanism that can selectively take a normal rotation output state in which the HMT power operatively input from the output shaft is output without changing the rotation direction, and a reverse rotation output state in which the HMT power is output by reversing the rotation direction; A forward / reverse switching operation member is manually operated, 19. The transmission structure according to claim 17, wherein an output state of the forward / reverse switching mechanism is switched in response to operation of the forward / reverse switching operation member.

21. 21. The transmission structure according to claim 17, further comprising an auxiliary transmission mechanism capable of changing the HMT power operatively input from the output shaft to a plurality of speed stages including a low speed stage and a high speed stage.

Images