Transmission structure

Abstract

To provide a transmission structure that comprises a main transmission unit for performing continuous transmission and an auxiliary transmission unit for performing multistage transmission, and is able to prevent shock as much as possible when shifting transmission gears of the auxiliary transmission unit during running.SOLUTION: When a transmission gear shifting operation is performed using an auxiliary transmission operating member during running, a control device is configured to: disengage a pre-shifting engagement clutch mechanism of an auxiliary transmission unit to create a free-running state; during the free-running state, operate a transmission output device with a vehicle speed corresponding to an actual vehicle speed based on an engagement state of a post-shifting engagement clutch mechanism as a target vehicle speed; then engage the post-shifting engagement clutch mechanism; and control the operation of the transmission output device with a vehicle speed defined by the operating position of a main transmission operating member as a target vehicle speed.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a transmission structure that includes a main transmission unit including a planetary gear mechanism that combines and outputs rotational power from a drive source and rotational power from a transmission output device, and an auxiliary transmission unit that is connected in series to the main transmission and performs multi-stage gear changes. [Background technology]

[0002] A transmission structure equipped with a main speed change unit having a planetary gear mechanism that combines and outputs rotational power from a drive source and rotational power from a hydrostatic continuously variable transmission (HST) that acts as a speed change output device is suitably used, for example, in the traveling system transmission path of work vehicles such as combine harvesters and tractors, and various configurations have been proposed to expand the vehicle speed variable range.

[0003] For example, Patent Document 1 listed below discloses a transmission structure in which a hydrostatic-mechanical continuously variable transmission (HMT) formed by the HST and the planetary gear mechanism, which acts as a main transmission unit, and a multi-speed transmission having three speed stages, namely low speed, medium speed, and high speed, which acts as an auxiliary transmission unit, are arranged in series in a traveling system transmission path.

[0004] The transmission structure described in Patent Document 1 is useful in that it can expand the range of vehicle speed variations, but the sub-speed change operation using the multi-speed device must be performed while the vehicle is stopped, which has the disadvantage of being cumbersome to operate and reducing driving work efficiency.

[0005] Furthermore, Patent Document 2 below proposes a transmission structure in which an HST that acts as a main transmission unit and a multi-speed sub-transmission mechanism that acts as a sub-transmission unit are arranged in series, and which enables the sub-transmission mechanism to switch gear positions while the vehicle is traveling.

[0006] The transmission structure described in Patent Document 2 includes a forward / reverse switching mechanism in addition to the HST and the auxiliary transmission mechanism, and is configured so that when the auxiliary transmission operation means is operated, the traveling speed is detected by a traveling speed detection means, the forward / reverse switching mechanism is switched from a forward state or a reverse state to a neutral state, the HST is shifted so that the traveling speed in the gear position after the shift of the auxiliary transmission mechanism matches the traveling speed detected when the auxiliary transmission operation means is operated, and then a gear change operation of the auxiliary transmission mechanism is performed, and the forward / reverse switching mechanism is switched from the neutral state to a forward state or a reverse state.

[0007] The transmission structure described in Patent Document 2 can suppress to some extent the shift shock that occurs when the multi-stage sub-transmission mechanism shifts gears while the vehicle is traveling, but does not take into consideration changes in traveling speed (in many cases, deceleration changes) when the forward / reverse switching mechanism is shifted to a neutral state and the vehicle is in a free-running state, and therefore cannot fully prevent or reduce speed changes when the sub-transmission mechanism completes its gear stage switching operation. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 5822761 [Patent Document 2] Patent No. 4889600 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in view of the above-mentioned conventional technology, and aims to provide a transmission structure including a main transmission unit that performs continuously variable speed change and an auxiliary transmission unit that performs multi-stage speed change, which enables the auxiliary transmission unit to change gear positions while the vehicle is traveling, and which can prevent or reduce, as much as possible, the change-over shock that occurs when the auxiliary transmission unit changes gear positions. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention provides a transmission structure that continuously changes the speed of a reference rotational power of a drive shaft operatively connected to a drive source and transmits the power to a traveling output shaft that determines the vehicle speed, the transmission structure including a transmission output device that outputs a transmission rotational power that is continuously variable between at least first and second speeds, and a planetary gear mechanism that combines the reference rotational power and the transmission rotational power, a main transmission unit that outputs the combined output of the planetary gear mechanism as traveling rotational power, and an auxiliary transmission unit that can change the speed of the traveling rotational power from the main transmission unit in multiple stages and transmit it to the traveling output shaft. The present invention provides a sub-transmission unit including a low-speed stage transmission path and a high-speed stage transmission path that transmit the traveling rotational power from the main transmission unit to the traveling output shaft at a forward low speed ratio and a forward high speed ratio, respectively, and low-speed stage and high-speed stage clutch mechanisms that engage and disengage the low-speed stage and high-speed stage transmission paths, a main speed change operating member and an sub-transmission operating member for operating the main transmission unit and the sub-transmission unit, respectively, and a control device, and the control device controls the low-speed stage state by engaging the low-speed stage clutch mechanism and the high-speed stage clutch mechanism in response to operation of the sub-transmission operating member. and controls the operation of the main speed change unit so that a target vehicle speed defined by the operation position of the main speed change operating member is obtained for each of the low speed stage state and the high speed stage state, and further controls the operation of the main speed change unit so that when a gear stage switching operation is performed by the main speed change operating member while the traveling output shaft is being driven and rotated, a pre-switching engagement clutch mechanism, which was engaged before the switching operation of the sub-speed change operating member among the low speed stage and high speed stage clutch mechanisms, is shifted to a released state to create a free running state, and and thereafter, the post-switching engagement clutch mechanism is shifted to an engaged state, and the operation of the shift output device is controlled in the post-switching gear state with the vehicle speed defined by the operating position of the main gear change operating member at that time as a target vehicle speed.

[0011] In order to achieve the above object, the present invention provides a transmission structure that continuously changes the speed of a reference rotational power of a drive shaft operatively connected to a drive source and transmits the same to a traveling output shaft that determines the vehicle speed, the transmission structure including a main transmission unit that has a transmission output device that outputs a transmission rotational power that is continuously changed between at least first and second speeds, and a planetary gear mechanism that combines the reference rotational power and the transmission rotational power, and outputs the combined output of the planetary gear mechanism as traveling rotational power, and an auxiliary transmission unit that can change the speed of the traveling rotational power from the main transmission unit in multiple stages and transmit it to the traveling output shaft. The present invention is provided with an auxiliary transmission unit including a low-speed stage transmission path and a high-speed stage transmission path that transmit the traveling rotational power from the main transmission unit to the traveling output shaft at a forward low-speed transmission ratio and a forward high-speed transmission ratio, respectively, and low-speed stage and high-speed stage clutch mechanisms that engage and disengage the low-speed stage and high-speed stage transmission paths, a main transmission operating member and an auxiliary transmission operating member for operating the main transmission unit and the auxiliary transmission unit, respectively, and a control device, and the main transmission unit is configured to change the combined output power of the planetary gear mechanism as the speed-change rotational power is changed from the first speed side to the second speed side. and a second speed stage transmission state in which the maximum speed of the first speed stage transmission state is made the lowest speed and the combined output of the planetary gear mechanism is increased as the speed of the speed-changing rotational power is changed from the second speed side to the first speed side, and the control device controls the operation of the sub-speed change unit so that a low speed stage state is achieved by engaging the low speed stage clutch mechanism and a high speed stage state is achieved by engaging the high speed stage clutch mechanism in response to operation of the sub-speed change operating member, and further, when the vehicle speed reaches a low speed stage switching speed in the low speed stage state and when the vehicle speed reaches a high speed stage state, and when the vehicle speed is up to the high-speed stage switching speed, a first speed stage state is displayed, and when the vehicle speed exceeds the low-speed stage switching speed in the low-speed stage state and when the vehicle speed exceeds the high-speed stage switching speed in the high-speed stage state, a second speed stage transmission state is displayed, and operation control of the main transmission unit is performed with the vehicle speed defined by the operation position of the main speed change operating member as a target vehicle speed for each of the low-speed stage state and the high-speed stage state, and further, when the traveling output shaft is driven to rotate and a speed change operation is performed by the auxiliary speed change operating member when the vehicle speed is equal to or lower than the low-speed stage switching speed, the control deviceA transmission structure configured to transition a pre-switching engagement clutch mechanism, of the low-speed and high-speed clutch mechanisms, that was engaged before the switching operation of the auxiliary speed change operating member, to a released state to create a free-running state, and during the free-running state, control the operation of the gear shift output device so that a vehicle speed corresponding to the actual vehicle speed at that time is created in a post-switching gear state created by a post-switching engagement clutch mechanism, of the low-speed and high-speed clutch mechanisms, that should be engaged after the switching operation of the auxiliary speed change operating member, is achieved, and then transition the post-switching engagement clutch mechanism to an engaged state, and control the operation of the gear shift output device in the post-switching gear state with the vehicle speed defined by the operating position of the main speed change operating member at that time as a target vehicle speed.

[0012] In order to achieve the above object, the present invention provides a transmission structure that continuously changes the speed of a reference rotational power of a drive shaft operatively connected to a drive source and transmits the power to a traveling output shaft that determines the vehicle speed, the transmission structure including a transmission output device that outputs a transmission rotational power that is continuously changed between at least first and second speeds, and a planetary gear mechanism that combines the reference rotational power and the transmission rotational power, a main transmission unit that outputs the combined output of the planetary gear mechanism as traveling rotational power, and an auxiliary transmission unit that can change the speed of the traveling rotational power from the main transmission unit in multiple stages and transmit it to the traveling output shaft. The vehicle is equipped with a sub-transmission unit including a low-speed stage transmission path and a high-speed stage transmission path that transmit the traveling rotational power from the main transmission unit to the traveling output shaft at a forward low-speed transmission ratio and a forward high-speed transmission ratio, respectively, and low-speed stage and high-speed stage clutch mechanisms that engage and disengage the low-speed stage and high-speed stage transmission paths, a main transmission operating member and an sub-transmission operating member for operating the main transmission unit and the sub-transmission unit, respectively, and a control device, and the main transmission unit is configured such that the combined output of the planetary gear mechanism increases as the speed-changing rotational power is changed from the first speed side to the second speed side. and a second speed stage transmission state in which the maximum speed of the first speed stage transmission state is made the lowest speed and the combined output of the planetary gear mechanism is increased as the speed-changing rotational power is changed from the second speed side to the first speed side, and the control device controls the operation of the sub-transmission unit in accordance with the operation of the sub-speed change operating member so that a low speed stage state is achieved by engaging the low speed stage clutch mechanism and a high speed stage state is achieved by engaging the high speed stage clutch mechanism, and further, when the vehicle speed in the low speed stage state reaches a low speed stage switching speed and when the vehicle speed in the high speed stage state reaches a low speed stage switching speed, When the vehicle speed is up to the high-speed stage switching speed, a first speed stage state is displayed, and when the vehicle speed exceeds the low-speed stage switching speed in the low-speed stage state and when the vehicle speed exceeds the high-speed stage switching speed in the high-speed stage state, a second speed stage transmission state is displayed, and operation of the main transmission unit is controlled with the vehicle speed defined by the operating position of the main speed change operating member as the target vehicle speed for each of the low-speed stage state and the high-speed stage state, and further, when the traveling output shaft is driven to rotate and a speed change operation is performed by the auxiliary speed change operating member when the vehicle speed is equal to or higher than the low-speed stage switching speed and lower than the high-speed stage switching speed, the control device:a pre-switching engagement clutch mechanism of the low-speed and high-speed clutch mechanisms that was engaged before the auxiliary speed change operating member was switched to a released state to create a free-running state, and during the free-running state, operation of the speed change output device is controlled so that the switch speed in the pre-switching gear state that was created by the pre-switching engagement clutch mechanism is created, and then switching is performed between the first gear transmission state and the second gear transmission state, and further operation of the speed change output device is controlled so that a vehicle speed corresponding to the actual vehicle speed at that time is created in a post-switching gear state that is created by a post-switching engagement clutch mechanism of the low-speed and high-speed clutch mechanisms that should be engaged after the auxiliary speed change operating member is switched, and then the post-switching engagement clutch mechanism is switched to an engaged state, and operation of the speed change output device is controlled in the post-switching gear state, with the vehicle speed defined by the operating position of the main speed change operating member at that time being set as a target vehicle speed.

[0013] Further, in order to achieve the above object, the present invention provides a transmission structure that continuously changes the speed of a reference rotational power of a drive shaft operatively connected to a drive source and transmits the reference rotational power to a traveling output shaft that defines a vehicle speed, the transmission structure including a main transmission unit having a transmission output device that outputs a transmission rotational power that is continuously changed between at least a first speed and a second speed, and a planetary gear mechanism that combines the reference rotational power and the transmission rotational power, and outputs a combined output of the planetary gear mechanism as traveling rotational power; and an auxiliary transmission unit that can change the speed of the traveling rotational power from the main transmission unit in multiple stages and transmit it to the traveling output shaft, The vehicle is equipped with an auxiliary transmission unit including a low-speed stage transmission path and a high-speed stage transmission path that transmit the traveling rotational power from the main transmission unit to the traveling output shaft at a forward low-speed transmission ratio and a forward high-speed transmission ratio, respectively, and low-speed stage and high-speed stage clutch mechanisms that engage and disengage the low-speed stage and high-speed stage transmission paths, a main transmission operating member and an auxiliary transmission operating member for operating the main transmission unit and the auxiliary transmission unit, respectively, and a control device, and the main transmission unit is a second transmission unit that is configured to increase the speed of the combined output of the planetary gear mechanism as the speed-changing rotational power is changed from the first speed side to the second speed side. and a second speed stage transmission state in which the maximum speed of the first speed stage transmission state is set to the minimum speed and the combined output of the planetary gear mechanism is increased as the speed-changing rotational power is changed from the second speed side to the first speed side, and the control device controls the operation of the sub-transmission unit in accordance with the operation of the sub-speed change operating member so that a low speed stage state is achieved by engaging the low speed stage clutch mechanism and a high speed stage state is achieved by engaging the high speed stage clutch mechanism, and further, when the vehicle speed reaches a low speed stage switching speed in the low speed stage state and when the vehicle speed reaches a high speed stage switching speed in the high speed stage state, and when the vehicle speed exceeds the low-speed stage switching speed in the low-speed stage state or when the vehicle speed exceeds the high-speed stage switching speed in the high-speed stage state, a first speed stage state is displayed, and when the vehicle speed exceeds the low-speed stage switching speed in the high-speed stage state, a second speed stage transmission state is displayed, and operation control of the main transmission unit is performed with a vehicle speed defined by the operation position of the main speed change operating member as a target vehicle speed for each of the low-speed stage state and the high-speed stage state, and further, when the traveling output shaft is driven to rotate and a speed change operation is performed by the auxiliary speed change operating member when the vehicle speed is equal to or higher than the high-speed stage switching speed and lower than the maximum vehicle speed in the low-speed stage state, the control deviceA transmission structure characterized in that it is configured such that a pre-switching engagement clutch mechanism of the low-speed and high-speed clutch mechanisms that was engaged before the switching operation of the auxiliary speed change operating member is shifted to a released state to create a free-running state, and during the free-running state, operation of the gear shift output device is controlled so that a vehicle speed corresponding to the actual vehicle speed at that time is created in a post-switching gear state created by a post-switching engagement clutch mechanism of the low-speed and high-speed clutch mechanisms that should be engaged after the switching operation of the auxiliary speed change operating member, and then the post-switching engagement clutch mechanism is shifted to an engaged state, and operation of the gear shift output device is controlled in the post-switching gear state with the vehicle speed defined by the operating position of the main speed change operating member at that time as a target vehicle speed.

[0014] Furthermore, in order to achieve the above object, the present invention provides a transmission structure that continuously changes the speed of a reference rotational power of a drive shaft operatively connected to a drive source and transmits the power to a traveling output shaft that determines the vehicle speed, the transmission structure including a transmission output device that outputs a transmission rotational power that is continuously variable between at least first and second speeds, a main transmission unit that has a planetary gear mechanism that combines the reference rotational power and the transmission rotational power, and outputs the combined output of the planetary gear mechanism as traveling rotational power, and an auxiliary transmission unit that can change the speed of the traveling rotational power from the main transmission unit in multiple stages and transmit it to the traveling output shaft. the transmission includes a low-speed stage transmission path and a high-speed stage transmission path that transmit the traveling rotational power from the main transmission unit to the traveling output shaft at a forward low-speed speed ratio and a forward high-speed speed ratio, respectively, and an auxiliary transmission unit including low-speed stage and high-speed stage clutch mechanisms that engage and disengage the low-speed stage and high-speed stage transmission paths, respectively; a main transmission operating member and an auxiliary transmission operating member for operating the main transmission unit and the auxiliary transmission unit, respectively; and a control device, wherein the main transmission unit adjusts the synchronism of the planetary gear mechanism as the speed-changing rotational power is changed from the first speed side to the second speed side. and a second speed stage transmission state in which the maximum speed of the first speed stage transmission state is made the lowest speed and the composite output of the planetary gear mechanism is increased as the speed of the speed-changing rotational power is changed from the second speed side to the first speed side, and the control device controls the operation of the sub-speed change unit so that a low speed stage state is achieved by engaging the low speed stage clutch mechanism and a high speed stage state is achieved by engaging the high speed stage clutch mechanism in response to operation of the sub-speed change operating member, and further ... when the vehicle speed is up to a low speed stage switching speed in the low speed stage state and when the vehicle speed is up to a low speed stage switching speed in the high speed stage state. When the vehicle speed is up to the high-speed stage switching speed in the low-speed stage state, a first speed stage state is displayed, and when the vehicle speed exceeds the low-speed stage switching speed in the low-speed stage state and when the vehicle speed exceeds the high-speed stage switching speed in the high-speed stage state, a second speed stage transmission state is displayed, and operation of the main transmission unit is controlled with the vehicle speed defined by the operation position of the main speed change operating member as the target vehicle speed for each of the low-speed stage state and the high-speed stage state, and further, when the traveling output shaft is driven to rotate and the vehicle speed is equal to or higher than the maximum vehicle speed in the low-speed stage state, a switching operation from the high-speed stage to the low-speed stage is performed by the auxiliary speed change operating member,A transmission structure characterized in that the operation of the gear change output device is controlled so that the vehicle speed is decelerated to the maximum vehicle speed in the low-speed stage state while maintaining the engaged state of the high-speed stage clutch mechanism, the high-speed stage clutch mechanism is shifted to a released state after the deceleration to create a free-running state, and during the free-running state, the operation of the gear change output device is controlled so that a vehicle speed corresponding to the actual vehicle speed at that time is created in the low-speed stage state created by the low-speed stage clutch mechanism, and then the low-speed stage clutch mechanism is shifted to an engaged state, and the operation of the gear change output device is controlled in the low-speed stage state with the vehicle speed defined by the operating position of the main gear change operating member at that time as the target vehicle speed.

[0015] In the various configurations described above, preferably, when a gear change operation is performed using the auxiliary shift operating member, the control device controls the operation of the shift output device so as to present a constant speed running state in which the vehicle speed at that time is maintained for a predetermined period of time, and thereafter presents the free running state.

[0016] In one embodiment, the main transmission unit includes a speed change transmission path that transmits the speed change rotational power to a third element of the three planetary elements of the planetary gear mechanism, input-side first and second transmission paths that transmit the reference rotational power to a first element and a second element of the three planetary elements of the planetary gear mechanism, respectively, input-side first and second clutch mechanisms that engage and disengage the input-side first and second transmission paths, respectively, output-side first and second transmission paths that transmit the rotational power of the second element and the first element, respectively, to a traveling intermediate shaft, and output-side first and second clutch mechanisms that engage and disengage the output-side first and second transmission paths, respectively, and is configured to realize a first speed stage transmission state by engagement of the input-side and output-side first clutch mechanisms and to realize a second speed stage transmission state by engagement of the input-side and output-side second clutch mechanisms, and the sub-transmission unit is arranged to change speeds in multiple stages between the traveling intermediate shaft and the traveling output shaft.

[0017] In one embodiment, the planetary gear mechanism, the input side first and second transmission paths, and the output side first and second transmission paths are preferably configured so that the rotational speed of the second element when the output of the transmission output device is set to second speed in the first speed transmission state is substantially the same as the rotational speed of the second element when the output of the transmission output device is set to second speed in the second speed transmission state, and so that the rotational speed of the first element when the first speed transmission state is substantially the same as the rotational speed of the first element when the output of the transmission output device is set to second speed in the second speed transmission state.

[0018] In another embodiment, the main transmission unit includes a first speed stage planetary gear mechanism and a second speed stage planetary gear mechanism acting as the planetary gear mechanism, a first speed change transmission path that transmits the speed change rotational power to a sun gear of the three planetary elements of the first speed stage planetary gear mechanism, a first reference power transmission path that transmits the reference rotational power to a first element and a second element of the three planetary elements of the first speed stage planetary gear mechanism that act as a reference power input portion, a first clutch mechanism that engages and disengages the first reference power transmission path, a first output transmission path that transmits planetary elements that form a planetary output portion other than the sun gear and the planetary elements that form the reference power input portion of the three planetary elements of the first speed stage planetary gear mechanism to a traveling intermediate shaft, and a second transmission path for shifting power that transmits the reference rotational power to a sun gear among the three planetary elements of the second-speed planetary gear mechanism, a second transmission path for reference power that transmits the reference rotational power to a first element and a second element of the three planetary elements of the second-speed planetary gear mechanism that act as a reference power input portion, a second clutch mechanism that engages and disengages the second transmission path for reference power, and a second transmission path for output that transmits planetary elements that form a planetary output portion other than the sun gear and the planetary elements that form the reference power input portion among the three planetary elements of the second-speed planetary gear mechanism to the traveling intermediate shaft, wherein a first speed transmission state is realized by engagement of the first clutch mechanism and a second speed transmission state is realized by engagement of the second clutch mechanism, and the sub-transmission unit is arranged to change speeds in multiple stages between the traveling intermediate shaft and the traveling output shaft. [Effects of the Invention]

[0019] According to the transmission structure of the present invention, it is possible to prevent or reduce as much as possible the shock that may occur when the sub-transmission unit switches gear positions while the vehicle is traveling. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram of a power transmission of a working vehicle to which a transmission structure according to one embodiment of the present invention is applied. [Figure 2] FIG. 2 is a graph showing the relationship between the rotational speed (vehicle speed) of the driving rotational power output by the transmission structure and the output rotational speed of the HST in the transmission structure. [Figure 3] Figures 3(a) and (b) are a graph and a table, respectively, showing an example of the relationship between the operating position (opening) of the main shift operating member in the transmission structure and the target output speed (target vehicle speed) of the transmission structure when the engine serving as the driving source is at a predetermined rotation speed (e.g., 2200 rpm). [Figure 4] FIG. 4 is a graph showing the relationship between the passage of time and the engaged / disengaged state of the high-speed and low-speed clutch mechanisms, the output state of the gear shift output device (the gear shift state of the HST), and the vehicle speed (the rotational speed of the traveling output shaft) in Example 1 of the transmission structure. [Figure 5] FIG. 5 is a graph showing the relationship between the passage of time and the engaged / disengaged state of the high-speed and low-speed clutch mechanisms, the output state of the shift output device (shift state of the HST), and the vehicle speed (rotation speed of the traveling output shaft) in Example 2 of the transmission structure. [Figure 6] FIG. 6 is a graph showing the relationship between the engagement / disengagement states of the input side first and second clutch mechanisms and the output side first and second clutch mechanisms and the output state of the shift output device (shift state of the HST) during the free running state period of Example 2. [Figure 7]FIG. 7 is a graph showing the relationship between the passage of time and the engaged / disengaged state of the high-speed and low-speed clutch mechanisms, the output state of the shift output device (shift state of the HST), and the vehicle speed (rotation speed of the traveling output shaft) in Example 3 of the transmission structure. [Figure 8] FIG. 8 is a graph showing the relationship between the passage of time and the engaged / disengaged state of the high-speed and low-speed clutch mechanisms, the output state of the shift output device (shift state of the HST), and the vehicle speed (rotation speed of the traveling output shaft) in Example 4 of the transmission structure. [Figure 9] FIG. 9 is a schematic diagram of an example of a display monitor that cooperates with the transmission structure, as well as an example of the main and auxiliary gearshift operating members. [Figure 10] FIG. 10 is a schematic diagram of a power transmission in a working vehicle to which a transmission structure according to a modification of the above embodiment is applied. DETAILED DESCRIPTION OF THE INVENTION

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a transmission structure according to the present invention will now be described with reference to the accompanying drawings. FIG. 1 shows a schematic diagram of power transmission in a working vehicle 200A to which a transmission structure 1A according to this embodiment is applied.

[0022] As shown in Fig. 1, the work vehicle 200A includes a drive source 210, a drive shaft 212 operatively connected to the drive source 210, drive wheels 220, a traveling output shaft 47 that outputs rotational power for traveling toward the drive wheels 220, and the transmission structure 1A that transmits the rotational power from the drive shaft 212 to the traveling output shaft 47 at a continuously variable speed. Note that reference numeral 210a in Fig. 1 denotes a flywheel included in the drive source 210.

[0023] The work vehicle 200A has a pair of left and right main drive wheels as the drive wheels 220. Therefore, as shown in FIG. 1, the work vehicle 200A further has a pair of main drive axles 250 that respectively drive the pair of main drive wheels 220, and a differential mechanism 260 that differentially transmits the rotational power of the traveling output shaft 47 to the pair of main drive axles 250.

[0024] As shown in FIG. 1, the work vehicle 200A further includes a traveling brake mechanism 255 that selectively applies braking force to the main drive axles 250, a differential lock mechanism 265 that forcibly synchronously drives the pair of main drive axles 250 using rotational power from the traveling output shafts 47, and an auxiliary drive wheel driving force take-off mechanism 270 that can selectively output rotational power taken from the traveling output shafts 47 to the auxiliary drive wheels.

[0025] The work vehicle 200A also has a PTO shaft 280 that outputs rotational power to the outside, and a PTO clutch mechanism 285 and a PTO multi-stage transmission mechanism 290 that are interposed in a PTO transmission path from the drive source 210 to the PTO shaft 280.

[0026] As shown in FIG. 1, the transmission structure 1A includes a transmission output device and a planetary gear mechanism 30, and is equipped with a main transmission unit 3A that can continuously change the speed of a reference rotational power from the drive source 210, an auxiliary transmission unit 5 that can change the speed of the traveling rotational power from the main transmission unit 3A in multiple stages, a main transmission operating member 180 and an auxiliary transmission operating member 185 for operating the main transmission unit 3A and the auxiliary transmission unit 5, respectively, and a control device 100.

[0027] The speed-changing output device is configured to output speed-changing rotational power whose speed is continuously variable between at least first speed and second speed. The operation of the speed change output device is controlled by the control device 100.

[0028] As shown in FIG. 1, the transmission structure 1A according to this embodiment includes a hydrostatic continuously variable transmission (HST) 10 as the speed change output device. The HST 10 cooperates with the planetary gear mechanism 30 to form an HMT (hydrostatic-mechanical continuously variable transmission structure). It is also possible to provide the transmission structure 1A with an electric motor that can output infinitely variable speed rotation by manual operation, instead of the HST 10, as the speed change output device.

[0029] As shown in FIG. 1, the HST 10 includes a pump shaft 12 that is operatively rotationally driven by the drive source 210, an HST pump 14 that is supported on the pump shaft 12 so as not to be rotatable relative to the pump shaft 12, an HST motor 18 that is fluidly connected to the HST pump 14 via a pair of first and second HST lines 11 and is hydraulically rotationally driven by the HST pump 14, a motor shaft 16 that supports the HST motor 18 so as not to be rotatable relative to the HST motor 18, and an output adjustment member 20 that changes the capacity of at least one of the HST pump 14 and the HST motor 18.

[0030] The HST 10 is capable of continuously changing the ratio of the rotational speed of the HST output output from the motor shaft 16 to the rotational speed of the power input to the pump shaft 12 (i.e., the gear ratio of the HST 10) depending on the operating position of the output adjustment member 20.

[0031] In other words, when the rotational speed of the rotational power operatively input from the drive source 210 to the pump shaft 12 is defined as a reference input speed, the HST 10 continuously changes the rotational power of the reference input speed to a rotational power at least between the first speed and the second speed depending on the operating position of the output adjustment member 20, and outputs the rotational power from the motor shaft 16. In addition, reference numeral 190a in FIG. 1 denotes a gear shift output sensor that detects the output rotation speed of the gear shift output device (the HST 10 in this embodiment).

[0032] In this embodiment, as shown in FIG. 1, the pump shaft 12 is connected to the drive shaft 212 operatively connected to the drive source 210 via an HST input gear train 214 .

[0033] FIG. 2 shows the relationship between the output rotation speed of the HST 10 and the rotation speed (vehicle speed) of the driving rotational power of the transmission structure 1A. Although details will be described later, the sub-transmission unit 5 is capable of realizing a high-speed stage state and a low-speed stage state, and the solid line in FIG. 2 indicates the relationship between the HST output rotation speed and the vehicle speed in the low-speed stage state, and the two-dot chain line indicates the relationship between the HST output rotation speed and the vehicle speed in the high-speed stage state.

[0034] As shown in FIG. 2, in this embodiment, the HST 10 is capable of switching the rotation direction of the HST output between forward and reverse. In other words, when the rotation direction of the reference input speed is the forward direction, the HST 10 is configured so that when the output adjustment member 20 is positioned in the first operating position, it outputs rotational power at a first speed (e.g., maximum speed in the forward direction + max) in which the rotation direction is set to one side of the forward or reverse direction (e.g., the forward direction) from the motor shaft 16, and when the output adjustment member 20 is positioned in the second operating position, it outputs rotational power at a second speed (maximum speed in the reverse direction - max) in which the rotation direction is set to the other side of the forward or reverse direction (e.g., the reverse direction) from the motor shaft 16. In this case, when the output adjusting member 20 is positioned at a neutral position between the first and second operating positions, the rotational speed of the HST output becomes neutral (zero speed).

[0035] In this embodiment, the HST 10 has, as the output adjustment member 20, a movable swash plate that changes the volume of the HST pump 14 by swinging about a swing axis, as is common in axial piston pumps, and that is capable of swinging to one side and the other side about the swing axis around a neutral position where the discharge volume from the HST pump 14 is zero.

[0036] When the movable swash plate is positioned in the neutral position, the HST pump 14 stops discharging pressure oil, and the HST 10 enters a neutral state in which the output of the HST motor 18 is zero.

[0037] When the movable swash plate is swung from the neutral position to one of the forward rotation sides around the sway axis, pressure oil is supplied from the HST pump 14 to one of the pair of HST lines, with the first HST line becoming the high-pressure side and the second HST line becoming the low-pressure side. As a result, the HST motor 18 is rotated in the forward direction, and the HST 10 is brought into a forward rotation output state.

[0038] Conversely, when the movable swash plate is swung from the neutral position to the other reverse side around the swing axis, pressurized oil is supplied from the HST pump 14 to the other second HST line of the pair of HST lines, so that the other second HST line becomes the high-pressure side and one first HST line becomes the low-pressure side. As a result, the HST motor 18 is rotated in the reverse direction, and the HST 10 is put into a reverse output state. In the HST 10, the volume of the HST motor 18 is fixed by a fixed swash plate.

[0039] The output adjusting member 20 is actuated and controlled by the control device 100 in response to the operation of the main speed change operating member 180 .

[0040] That is, as shown in FIG. 1, the transmission structure 1A according to this embodiment has an HST shift actuator 192 that operates the output adjustment member 20, and the control device 100 operates the output adjustment member 20 via the HST shift actuator 192 in response to operation of the main shift operating member 180.

[0041] The HST speed change actuator 192 can have various configurations, such as an electric motor or a hydraulic mechanism (for example, a hydraulic servo mechanism), as long as its operation can be controlled by the control device 100.

[0042] As shown in FIG. 1, the planetary gear mechanism 30 has a sun gear 32, planetary gears 34 meshing with the sun gear 32, an internal gear 36 meshing with the planetary gears 34, and a carrier 38 that supports the planetary gears 34 rotatably about their axes and rotates about the axis of the sun gear 32 in conjunction with the revolution of the planetary gears 34 about the sun gear 32, and the sun gear 32, the carrier 38 and the internal gear 36 form three planetary elements.

[0043] In this embodiment, as shown in FIG. 1, the main change gear unit 3A includes, in addition to the speed change output device and the planetary gear mechanism 30, a speed-changing transmission path 40 that transmits the speed-changing rotational power to a third element of the three planetary elements of the planetary gear mechanism 30; an input-side first transmission path 50(1) and an input-side second transmission path 50(2) that transmit the reference rotational power to a first element and a second element of the three planetary elements of the planetary gear mechanism 30, respectively; an input-side first clutch mechanism 60(1) and an input-side second clutch mechanism 60(2) that engage and disengage the input-side first and second power transmission paths 50(1), 50(2), respectively; an output-side first transmission path 70(1) and an output-side second transmission path 70(2) that transmit the rotational power of the second element and the rotational power of the first element to a traveling intermediate shaft 45 disposed between the drive shaft 212 and the traveling output shaft 47 in the transmission direction, respectively; an output-side first clutch mechanism 80(1) and an output-side second clutch mechanism 80(2) that are respectively engaged with and disengaged from the output-side first and second power transmission paths 70(1) and 70(2); It has the following characteristics.

[0044] In this embodiment, the sun gear 32 serves as the third element, and acts as a variable power input portion that inputs the speed-changing rotational power.

[0045] As described above, in this embodiment, the HST 10 is provided as the speed change output device, and therefore the speed change transmission path 40 is configured to operatively connect the motor shaft 16 to the sun gear 32, as shown in FIG. 1.

[0046] In this embodiment, the internal gear 36 is the first element, and the carrier 38 is the second element. Therefore, the input side first transmission path 50(1) is configured to operatively connect the drive shaft 212 to the internal gear 36, and the input side second transmission path 50(2) is configured to operatively connect the drive shaft 212 to the carrier 38.

[0047] As shown in FIG. 1, the transmission structure 1A according to this embodiment includes a first transmission shaft 150 operatively connected to the first element (the internal gear 36), a second transmission shaft 152 operatively connected to the second element (the carrier), an input side first drive gear 52(1) operatively connected to the first transmission shaft 150 and supported so as to be rotatable relative to the drive shaft 212, and an input side second drive gear 52(2) operatively connected to the second transmission shaft 152 and supported so as to be rotatable relative to the drive shaft 212.

[0048] In this configuration, the input side first drive gear 52(1) and the first transmission shaft 150 form the input side first transmission path 50(1), and the input side second drive gear 52(2) and the second transmission shaft 152 form the input side second transmission path 50(2).

[0049] In this embodiment, as shown in FIG. 1, the second transmission shaft 152 is arranged coaxially with the planetary gear mechanism 30, and the first transmission shaft 150 is extrapolated to the second transmission shaft 152 in a state where it can rotate relative to the second transmission shaft 152.

[0050] As shown in Figures 1 and 2, the transmission structure 1A according to this embodiment further includes an input-side first driven gear 54(1) that is supported on the first transmission shaft 150 so as not to rotate relative to the first transmission shaft 150 and is operatively connected to the input-side first drive gear 52(1), and an input-side second driven gear 54(2) that is supported on the second transmission shaft 152 so as not to rotate relative to the second transmission shaft 152 and is operatively connected to the input-side second drive gear 52(2).

[0051] The input-side first and third driven gears 54(1), 54(2) form part of the input-side first and second power transmission paths 50(1), 50(2), respectively.

[0052] The input side first and second clutch mechanisms 60(1), 60(2) are respectively interposed in the input side first and second power transmission paths 50(1), 50(2).

[0053] As shown in FIG. 1, in this embodiment, the input-side first and second clutch mechanisms 60(1), 60(2) are configured to engage and disengage power transmission from the drive shaft 212 to the input-side first and third drive gears 52(1), 52(2), respectively.

[0054] In this embodiment, the input side first and third clutch mechanisms 60(1), 60(2) are hydraulic friction plate clutches.

[0055] The input side first and second clutch mechanisms 60(1), 60(2) have a common clutch housing that is supported on the drive shaft 212 so as not to be rotatable relative to each other.

[0056] In detail, the input side first clutch mechanism 60(1) has an input side common clutch housing 62, an input side first friction plate group 64(1) including a first driving side friction plate supported on the input side common clutch housing 62 so as not to be rotatable relative to the input side, and a first driven side friction plate supported on the input side first driving gear 52(1) so as not to be rotatable relative to the input side common clutch housing 62 and facing the first driving side friction plate, and an input side first piston (not shown) that frictionally engages the input side first friction plate group 64(1).

[0057] The input side second clutch mechanism 60(2) has the input side common clutch housing 62, an input side second friction plate group 64(2) including second driving side friction plates supported on the input side common clutch housing 62 so as not to be rotatable relative to each other and second driven side friction plates supported on the input side second driving gear 52(2) so as not to be rotatable relative to each other in a state facing the second driving side friction plates, and an input side third piston (not shown) that frictionally engages the input side third friction plate group 64(2).

[0058] The output side first transmission path 70(1) is configured to transmit the rotational power of the second element to the traveling intermediate shaft 45, and the output side second transmission path 70(2) is configured to transmit the rotational power of the first element to the traveling intermediate shaft 45.

[0059] As shown in FIG. 1, the transmission structure 1A according to this embodiment has an output-side first gear 72(1) operatively connected to the second transmission shaft 152 and supported on the traveling intermediate shaft 45 so as to be rotatable relative to the second transmission shaft 152, and an output-side second gear 72(2) operatively connected to the first transmission shaft 150 and supported on the traveling intermediate shaft 45 so as to be rotatable relative to the first transmission shaft 152.

[0060] In this embodiment, the output side first gear 72(1) is meshed with the input side second driven gear 54(2) and is operatively connected to the second transmission shaft 152 via the input side second driven gear 54(2).

[0061] In this configuration, the second transmission shaft 152, the input-side second driven gear 54(2), and the output-side first gear 72(1) form the output-side first transmission path 70(1). That is, in this embodiment, the input side second driven gear 54(2) forms part of the input side second power transmission path 50(2) and also forms part of the output side first power transmission path 70(1).

[0062] In this embodiment, the output side second gear 72(2) is meshed with the input side first driven gear 54(1) and is operatively connected to the first transmission shaft 150 via the input side first driven gear 54(1).

[0063] In this configuration, the first transmission shaft 150, the input-side first driven gear 54(1), and the output-side second gear 72(2) form the output-side second transmission path 70(2). That is, in this embodiment, the input side first driven gear 54(1) forms part of the input side first power transmission path 50(1) and also forms part of the output side second power transmission path 70(2).

[0064] The output-side first and second clutch mechanisms 80(1), 80(2) are respectively interposed in the output-side first and second power transmission paths.

[0065] As shown in FIG. 1, in the present embodiment, the output-side first and second clutch mechanisms 80(1), 80(2) are configured to engage and disengage power transmission from the output-side first and second gears 72(1), 72(2) to the traveling intermediate shaft 45, respectively.

[0066] In this embodiment, the output side first and second clutch mechanisms 80(1), 80(2) are hydraulic friction plate clutches. The output-side first and second clutch mechanisms 80(1), 80(2) have a common clutch housing that is supported on the intermediate shaft 155 so as not to be rotatable relative to each other.

[0067] In detail, the output-side first clutch mechanism 80(1) has an output-side common clutch housing 82 supported on the traveling intermediate shaft 45 so as not to be rotatable relative to the traveling intermediate shaft 45, an output-side first friction plate group 84(1) including a first driving-side friction plate supported on the output-side common clutch housing 82 so as not to be rotatable relative to the traveling intermediate shaft 45, and a first driven-side friction plate supported on the output-side first gear 72(1) so as to be opposed to the first driving-side friction plate, and an output-side first piston (not shown) that frictionally engages the output-side first friction plate group 84(1).

[0068] The output side second clutch mechanism 80(2) has the output side common clutch housing 82, an output side second friction plate group 84(2) including second driving side friction plates supported on the output side common clutch housing 82 so as not to be rotatable relative to each other and second driven side friction plates supported on the output side second gear 72(2) so as not to be rotatable relative to each other in a state facing the second driving side friction plates, and an output side second piston (not shown) that frictionally engages the output side second friction plate group 84(2).

[0069] The transmission structure 1A further has a main speed change transmission state switching actuator 194 that switches between engagement and disengagement of the input side first and second clutch mechanisms 60(1), 60(2) and the output side first and second clutch mechanisms 80(1), 80(2).

[0070] The main speed change transmission state switching actuator 194 may have various configurations such as an electric motor or a hydraulic mechanism, as long as its operation can be controlled by the control device 100 .

[0071] The sub-transmission unit 5 has a low-speed stage transmission path 400L and a high-speed stage transmission path 400H that transmit the rotational power of the traveling intermediate shaft 45 to the traveling output shaft 47 at a forward low-speed transmission ratio and a forward high-speed transmission ratio, respectively, and a low-speed stage clutch mechanism 410L and a high-speed stage clutch mechanism 410H that engage and disengage the low-speed stage and high-speed stage transmission paths 400L, 400H, respectively.

[0072] As shown in FIG. 1, the low-speed transmission path 410L includes a low-speed driving gear 402L supported on the traveling intermediate shaft 45, and a low-speed driven gear 404L supported on the traveling output shaft 47 and meshed with the low-speed driving gear 402L.

[0073] In this embodiment, the low-speed drive gear 402L is supported by the traveling intermediate shaft 45 so as not to be rotatable relative to the traveling intermediate shaft 45, and the low-speed driven gear 404L is supported by the traveling output shaft 47 so as to be rotatable relative to the traveling output shaft 47.

[0074] As shown in FIG. 1, the high-speed stage transmission path 410H includes a high-speed stage driving gear 402H supported by the traveling intermediate shaft 45, and a high-speed stage driven gear 404H supported by the traveling output shaft 47 and meshed with the high-speed stage driving gear 402H.

[0075] In this embodiment, the high-speed stage drive gear 402H is supported by the traveling intermediate shaft 45 so as not to be rotatable relative to the traveling intermediate shaft 45, and the high-speed stage driven gear 404H is supported by the traveling output shaft 47 so as to be rotatable relative to the traveling output shaft 47.

[0076] The low-speed stage clutch mechanism 410L and the high-speed stage clutch mechanism 410H are supported by the traveling output shaft 47 so as to engage and disengage the low-speed stage driven gear 404L and the high-speed stage driven gear 404R with the traveling output shaft 47, respectively.

[0077] In this embodiment, the low-speed stage clutch mechanism 410L and the high-speed stage clutch mechanism 410H are hydraulic friction plate clutches.

[0078] The low-speed clutch mechanism 410L has a low-speed clutch housing 412L supported on the traveling output shaft 47 so as not to rotate relative to the driving output shaft 47, a low-speed friction plate group 414L including a low-speed driven side friction plate supported on the low-speed clutch housing 412L so as not to rotate relative to the driving output shaft 47, and a low-speed drive side friction plate supported on the low-speed driven gear 404L so as not to rotate relative to the low-speed driven side friction plate and facing the low-speed driven side friction plate, and a low-speed piston (not shown) that frictionally engages the low-speed friction plate group 414L.

[0079] The high-speed stage clutch mechanism 410H has a high-speed stage clutch housing 412H supported on the traveling output shaft 47 so as not to rotate relative to the driving output shaft 47, a high-speed stage friction plate group 414H including a high-speed stage driven side friction plate supported on the high-speed stage clutch housing 412H so as not to rotate relative to the driving output shaft 47, and a high-speed stage drive side friction plate supported on the high-speed stage driven gear 404H so as not to rotate relative to the high-speed stage driven side friction plate, facing the high-speed stage driven side friction plate, and a high-speed stage piston (not shown) that frictionally engages the high-speed stage friction plate group 414H.

[0080] In this embodiment, the auxiliary transmission unit 5 is capable of realizing a reverse state in addition to a high-speed state and a low-speed state.

[0081] Specifically, the sub-transmission unit 5 further includes a reverse transmission path 400R that transmits the rotational power of the traveling intermediate shaft 45 to the traveling output shaft 47 as a reverse driving force, and a reverse clutch mechanism 410R that engages and disengages the reverse transmission path 400R.

[0082] The reverse transmission path 400R has a reverse drive gear 402R supported by the traveling intermediate shaft 45, and a reverse driven gear 404R supported by the traveling output shaft 47 and meshed with the reverse drive gear 402R via an idle gear 403 (see Figure 1).

[0083] In this embodiment, the reverse drive gear 402R is supported by the traveling intermediate shaft 45 so as not to be rotatable relative to the traveling intermediate shaft 45, and the reverse driven gear 404R is supported by the traveling output shaft 47 so as to be rotatable relative to the traveling output shaft 47.

[0084] The reverse clutch mechanism 410R has a reverse clutch housing 412R, a reverse friction plate group 414R including a reverse driven side friction plate supported on the reverse clutch housing 412R so as not to be rotatable relative to the reverse clutch housing 412R and a reverse drive side friction plate supported on the reverse driven gear 404R so as not to be rotatable relative to the reverse driven side friction plate and facing the reverse driven side friction plate, and a reverse side piston (not shown) that frictionally engages the reverse friction plate group 414R. In this embodiment, the reverse clutch housing 412R is formed integrally with the low-speed clutch housing 412L.

[0085] As shown in FIG. 1, the transmission structure 1A further includes an auxiliary speed change transmission state switching actuator 196 that switches between engagement and disengagement of the low-speed stage clutch mechanism 410L and the high-speed stage clutch mechanism 410R. In this embodiment, the auxiliary speed change transmission state switching actuator 196 is configured to also switch the engagement and disengagement of the reverse clutch mechanism 410R.

[0086] The auxiliary speed change transmission state switching actuator 196 may have various configurations, such as an electric motor or a hydraulic mechanism, as long as its operation can be controlled by the control device 100 .

[0087] The control device 100 controls the operation of the main transmission unit 3A and the sub transmission unit 5. That is, the control device 100 controls the operation of the sub-transmission unit 5 in accordance with the operation of the sub-transmission operating member 185 so that a low-speed stage state is achieved by engagement of the low-speed stage clutch mechanism 410L and a high-speed stage state is achieved by engagement of the high-speed stage clutch mechanism 410H, and is further configured to control the operation of the input side first and second clutch mechanisms 60(1), 60(2) and the output side first and second clutch mechanisms 80(1), 80(2) in accordance with the vehicle speed, while controlling the operation of the transmission output device (the HST 10 in this embodiment) in accordance with the operation of the main transmission operating member 180.

[0088] In this embodiment, the control device 100 also controls the operation of the subtransmission unit 5 in response to the operation of the forward / reverse switching member so that a reverse state is realized by engaging the reverse clutch mechanism 410R.

[0089] Here, the gear ratios of the input side first and second power transmission paths 50(1), 50(2), the planetary gear mechanism 30, and the output side first and second power transmission paths 70(1), 70(2) are set as follows:

[0090] In a first speed transmission state which is achieved by bringing the input side first clutch mechanism 60(1) and the output side first clutch mechanism 80(1) into an engaged state and the input side second clutch mechanism 60(2) and the output side second clutch mechanism 80(2) into a released state, the rotational power of the drive shaft 212 is transmitted to the traveling intermediate shaft 45 via the input side first transmission path 50(1), the planetary gear mechanism 30, and the output side first transmission path 70(1).

[0091] In this first speed stage transmission state, the first element (the internal gear 36 in this embodiment) of the planetary gear mechanism 30 acts as a reference power input part that inputs reference rotational power from the drive shaft 212, and the second element (the carrier 38 in this embodiment) acts as a composite power output part that outputs running rotational power toward the running intermediate shaft.

[0092] As shown in FIG. 2 , the input-side first transmission path 50(1) and the output-side first transmission path 70(1), which serve as power transmission paths in the first speed stage transmission state, and the planetary gear mechanism 30 are set so that when the output of the speed change output device (the HST 10 in this embodiment) is set to first speed, the rotational speed of the second element (i.e., the rotational speed of the traveling output shaft 47) becomes the lowest speed, and as the output of the speed change output device is shifted from first speed to second speed, the rotational speed of the second element (i.e., the rotational speed of the traveling intermediate shaft 47) increases.

[0093] In a second speed transmission state which is achieved by bringing the input side second clutch mechanism 60(2) and the output side second clutch mechanism 80(2) into an engaged state and bringing the input side first clutch mechanism 60(1) and the output side first clutch mechanism 80(1) into a released state, the rotational power of the drive shaft 212 is transmitted to the traveling intermediate shaft 47 via the input side second transmission path 50(2), the planetary gear mechanism 30, and the output side second transmission path 70(2).

[0094] In this second speed transmission state, the second element of the planetary gear mechanism 30 acts as the reference power input portion, and the first element acts as the combined power output portion.

[0095] Here, the input-side first and second transmission paths 50(1), 50(2), the planetary gear mechanism 30, and the output-side first and second transmission paths 70(1), 70(2) are set so that the rotational speed of the second element when the output of the transmission output device is set to second speed in the first speed transmission state is substantially the same as the rotational speed of the second element rotated by the driving force transmitted via the input-side second transmission path 50(2) in the second speed transmission state; and further, the rotational speed of the first element rotated by the driving force transmitted via the input-side first transmission path 50(1) in the first speed transmission state is substantially the same as the rotational speed of the first element when the output of the transmission output device is set to second speed in the second speed transmission state. Note that "substantially the same" refers not only to a case where this is achieved by setting strict gear ratios for each of the power transmission paths 50(1), 50(2), 70(1), 70(2) and the planetary gear mechanism 30, but also to a state where there is a difference in rotational speed to an extent that can be absorbed by slippage between friction plates when the components forming each of the traveling system power transmission paths, for example, a hydraulic friction plate clutch described below, engage.

[0096] As shown in FIG. 2, the speed changeable range of the first element acting as a combined power output unit in the second speed transmission state is set to be faster than the speed changeable range of the second element acting as a combined power output unit in the first speed transmission state, and in the second speed transmission state, as the output of the speed change output device is shifted from second speed to first speed, the rotational speed of the first element (i.e., the rotational speed of the traveling intermediate shaft 47) increases.

[0097] As shown in FIG. 2, the control device 100 changes the rotation speeds of the first element and the second element in accordance with the vehicle speed as follows. For example, when the absolute value of the vehicle speed recognized based on the vehicle speed sensor 190b or the engine rotation speed sensor 190c and the transmission output sensor 190a (see FIG. 1) is in a range up to the switching speed (i.e., a range up to a low-speed switching speed a1 when the sub-transmission unit 5 is in a low-speed state, and a range up to a high-speed switching speed b1 when the sub-transmission unit 5 is in a high-speed state), the control device 100 causes the first speed transmission state to occur, and when the main transmission operating member 180 is operated to the lowest speed position (0% opening position), the control device 100 shifts the output of the transmission output device to first speed to make the rotational speed of the second element the lowest speed, and shifts the output of the transmission output device toward second speed in response to the speed-increasing operation of the main transmission operating member 180 to increase the rotational speed of the second element. When the absolute value of the vehicle speed is in the range from the switching speed to the maximum speed (i.e., in the range from low-speed switching speed a1 to low-speed maximum speed a2 when the sub-transmission unit 5 is in the low-speed state, and in the range from high-speed switching speed b1 to high-speed maximum speed b2 when the sub-transmission unit 5 is in the high-speed state), the control device 100 causes the second gear transmission state to occur, and changes the output of the gear shift output device toward the first gear in accordance with the speed-up operation of the main gear shift operating member 180, thereby increasing the rotational speed of the first element.

[0098] Figures 3(a) and (b) respectively show a graph and a table of an example of the relationship between the operating position (opening) of the main transmission operating member 180 and the target vehicle speed when the engine acting as the driving source 210 is set to a predetermined rotation speed (e.g., 2200 rpm). In the example shown in FIGS. 3(a) and 3(b), the sub-transmission unit 5 has a speed ratio in a high speed stage state that is twice the speed ratio in a low speed stage state.

[0099] Specifically, when the main shift operating member 180 is positioned at the lowest speed position (0% opening), the target vehicle speed is 2 km / h in the low speed state and 4 km / h in the high speed state, and when the main shift operating member 180 is positioned at the highest speed position (100% opening), the target vehicle speed is 20 km / h in the low speed state and 40 km / h in the high speed state.

[0100] The transmission structure 1A according to this embodiment has the following configuration so that the gear change operation of the sub-transmission unit 5 in response to the operation of the sub-transmission operating member 185 when the vehicle is running (i.e., when the running output shaft 45 is being driven and rotated) can be performed while preventing or reducing gear change shock as much as possible.

[0101] First, the gear shifting operation of the sub-transmission unit 5 while the vehicle is traveling at a speed equal to or lower than the low-speed shifting speed a1 will be described using an example (hereinafter referred to as Example 1) in which the sub-transmission operating member 185 is operated from a high-speed selection state to a low-speed selection state while the vehicle is traveling with the main transmission operating member 180 operated to a 10% opening position.

[0102] Figure 4 shows the relationship between the passage of time and the engagement / disengagement state of the high-speed stage clutch mechanism 410H and the low-speed stage clutch mechanism 410L, the output state of the transmission output device (the transmission state of the HST 10), and the vehicle speed (the rotational speed of the traveling output shaft 47) in Example 1. The relationship between the operating position (opening) of the main speed change operating member 180 and the vehicle speed follows the example shown in FIG.

[0103] In the high-speed state, when the main speed change operating member 180 is operated to a 10% opening position, the target vehicle speed (4 km / h) is equal to or lower than the high-speed switching speed b1 (14 km / h in this example), so the control device 100 brings about a first-speed transmission state and controls the operation of the transmission output device so that the target vehicle speed (4 km / h) is obtained in the first-speed transmission state. In the first embodiment, the control device 100 controls the operation of the HST 10 to an output state (speed ratio X11) that brings about the target vehicle speed (see (I) in FIG. 4).

[0104] In this state, when the auxiliary speed change operating member 185 is operated from the high speed selection state to the low speed selection state at time T1, the control device 100 transitions the pre-switching engagement clutch mechanism (the high speed stage clutch mechanism 410H in Example 1) of the low speed and high speed stage clutch mechanisms 410L, 410H that was engaged before the auxiliary speed change operating member 185 was switched to a disengaged state, thereby creating a free-running state in which power transmission from the drive source 210 to the traveling output shaft 47 is cut off.

[0105] Next, during the free running state, the control device 100 controls the operation of the transmission output device so that a vehicle speed corresponding to the actual vehicle speed at that time is produced in a post-switching gear state (low-speed state in Example 1) produced by a post-switching engagement clutch mechanism (low-speed clutch mechanism 410L in Example 1) of the low-speed and high-speed clutch mechanisms 410L, 410H that should be engaged after switching operation of the auxiliary speed change operating member 185. In Example 1, the control device 100 controls the operation of the HST 10 to an output state (speed ratio X12) that produces the actual vehicle speed (see (II) in Figure 4). In the free-running state, power transmission from the drive source 210 to the traveling output shaft 47 is interrupted, so the vehicle speed changes depending on the traveling conditions (gradually decelerates in the first embodiment).

[0106] Thereafter, the control device 100 transitions the post-switching engagement clutch mechanism (low-speed clutch mechanism 410L in Example 1) to an engaged state, and is configured to control the operation of the shift output device in the post-switching gear state (low-speed state in Example 1) with the vehicle speed defined by the operating position of the main shift operating member 180 at that time as the target vehicle speed.

[0107] In the first embodiment, the operating position (opening) of the main transmission operating member 180 is not changed (maintained at 10% opening) before and after the operation of the auxiliary transmission operating member 185, and therefore the control device 100 controls the operation of the HST 10 to the output state (speed ratio X11) before the switching operation of the auxiliary transmission operating member 180 (see (III) in Figure 4).

[0108] As a result, the vehicle speed smoothly transitions to the target vehicle speed (2 km / h) when the main speed change operating member 180 is operated to the 10% opening position in the low gear state.

[0109] Next, the gear shifting operation of the sub-transmission unit 5 while the vehicle is traveling at a speed equal to or higher than the low-speed shifting speed a1 (7 km / h in this example) and equal to or lower than the high-speed shifting speed b1 (14 km / h in this example) will be described using an example (hereinafter referred to as Example 2) in which the sub-transmission operating member 185 is operated from a low-speed selection state to a high-speed selection state while the vehicle is traveling with the main transmission operating member 180 operated to an opening position of 30%.

[0110] Figure 5 shows the relationship between the passage of time and the engagement / disengagement state of the high-speed stage clutch mechanism 410H and the low-speed stage clutch mechanism 410L, the output state of the transmission output device (the transmission state of the HST 10), and the vehicle speed (the rotational speed of the traveling output shaft 47) in Example 2. The relationship between the operating position (opening) of the main speed change operating member 180 and the vehicle speed follows the example shown in FIG.

[0111] In the low-speed state, when the main speed change operating member 180 is operated to a 30% opening position, the target vehicle speed (6.5 km / h) is equal to or higher than the low-speed changeover speed a1, so the control device 100 brings about a second-speed transmission state and controls the operation of the gear change output device so that the target vehicle speed (6.5 km / h) is obtained in the second-speed transmission state. In the second embodiment, the control device 100 controls the operation of the HST 10 to an output state (speed ratio X21) that brings about the target vehicle speed (see (I) in FIG. 5).

[0112] In this state, when the auxiliary transmission operating member 185 is operated from the low-speed selection state to the high-speed selection state at time T1, the control device 100 transitions the pre-switching engagement clutch mechanism (the low-speed clutch mechanism 410L in Example 2) of the low-speed and high-speed clutch mechanisms 410L, 410H that was engaged before the auxiliary transmission operating member 185 was switched to a disengaged state, thereby creating a free-running state in which power transmission from the drive source 210 to the traveling output shaft 47 is cut off.

[0113] In the second embodiment, when the sub-transmission unit 5 is switched between different speed stages, it is necessary to change the speed stage of the main transmission unit 3A. In this regard, the transmission structure 1A according to this embodiment has the following configuration.

[0114] That is, the control device 100 controls the operation of the gear change output device so that a switching speed (low-gear stage switching speed a1 in the second embodiment) in a pre-switching gear stage state (low-gear stage state in the second embodiment) that has been realized by the pre-switching engagement clutch mechanism (low-gear stage clutch mechanism 410L in the second embodiment) is realized during a free running state. In the second embodiment, the control device 100 controls the operation of the HST 10 to an output state (second speed in the second embodiment) that realizes the low-gear stage switching speed a1 (see (II) in FIG. 5).

[0115] FIG. 6 shows the relationship between the engaged and disengaged states of the input side first and second clutch mechanisms 60(11), 60(2) and the output side first and second clutch mechanisms 80(1), 80(2) and the output state of the shift output device (shift state of the HST 10) during the idle running state period of the second embodiment.

[0116] The control device 100 determines whether the transmission state capable of realizing the switched speed in the post-switched gear stage state is the first speed stage transmission state or the second speed stage transmission state. In the second embodiment, the transmission state for obtaining the switching speed (low-speed switching speed a1 in the second embodiment) in the post-switching speed state (high-speed state in the second embodiment) is the first-speed transmission state.

[0117] Therefore, the control device 100 controls the operation of the input side first and second clutch mechanisms 60(1), 60(2) and the output side first and second clutch mechanisms 80(1), 80(2) so that the transmission state of the main change gear unit 3A becomes the first speed stage transmission state, which is the transmission state for obtaining the low speed stage switching speed a1 in the high speed stage state.

[0118] Specifically, as shown in FIG. 6, while the transmission output device is in an output state that produces a low-speed stage switching speed a1 (i.e., while the HST 10 is in second speed), the control device 100 transitions the input-side first clutch mechanism 60(1) and the output-side first clutch mechanism 80(1), which produce the speed stage state before switching of the sub-transmission unit 5, from an engaged state to a released state, and transitions the input-side second clutch mechanism 60(2) and the output-side second clutch mechanism 80(2), which produce the speed stage state that should be produced after switching of the sub-transmission unit 5, from a released state to an engaged state.

[0119] 5, the control device 100 controls the operation of the transmission output device so that a vehicle speed corresponding to the actual vehicle speed at that time is produced in a post-switching gear state (high-speed state in the second embodiment) produced by a post-switching engagement clutch mechanism (high-speed clutch mechanism 410H in the second embodiment) among the low-speed and high-speed clutch mechanisms 410L, 410H that should be engaged after the auxiliary shifting operation member 185 is switched. In the second embodiment, the control device 100 controls the operation of the HST 10 to an output state (speed ratio X22) that produces the actual vehicle speed (see (II) in FIG. 5). In the free-running state, power transmission from the drive source 210 to the traveling output shaft 47 is cut off, so the vehicle speed changes depending on the traveling conditions (gradually decelerates in the second embodiment).

[0120] Thereafter, the control device 100 transitions the post-switching engagement clutch mechanism (high-speed stage clutch mechanism 410H in Example 2) to an engaged state, and is configured to control the operation of the shift output device in the post-switching gear stage state (high-speed stage state in Example 2) with the vehicle speed defined by the operating position of the main shift operating member 180 at that time as the target vehicle speed.

[0121] In the second embodiment, the operating position (opening) of the main transmission operating member 180 is not changed (maintained at 30% opening) before and after the operation of the auxiliary transmission operating member 185, and therefore the control device 100 controls the HST to operate in the output state (speed ratio X21) (see (III) in Figure 5).

[0122] As a result, the vehicle speed smoothly transitions to the target vehicle speed (13 km / h) when the main transmission operating member 180 is operated to the 30% opening position in the high speed gear state.

[0123] Furthermore, switching between the first and second gear stage transmission states is performed after the gear change output device is shifted so that the output state of the main transmission unit 3A becomes an output state corresponding to the switching speed in the speed stage state engaged at that time (low gear stage switching speed a1 in Example 2), so the burden on the components of the main transmission unit 3A can be reduced as much as possible.

[0124] Next, the gear shifting operation of the sub-transmission unit 5 while the vehicle is traveling at a speed equal to or higher than the high-speed shifting speed b1 (14 km / h in this example) and equal to or lower than the low-speed maximum speed a2 (20 km / h in this example) will be described using an example (hereinafter referred to as Example 3) in which the sub-transmission operating member 185 is operated from a low-speed selection state to a high-speed selection state while the vehicle is traveling with the main transmission operating member 180 operated to an opening position of 70%.

[0125] Figure 7 shows the relationship between the passage of time and the engagement / disengagement state of the high-speed stage clutch mechanism 410H and the low-speed stage clutch mechanism 410L, the output state of the transmission output device (the transmission state of the HST 10), and the vehicle speed (the rotational speed of the traveling output shaft 47) in Example 3. The relationship between the operating position (opening) of the main speed change operating member 180 and the vehicle speed follows the example shown in FIG.

[0126] The target vehicle speed (15.5 km / h) when the main speed change operating member 180 is operated to a 70% opening position in the low-speed state is equal to or greater than the high-speed switching speed b1 (14 km / h in this example) and is also equal to the maximum speed in the low-speed transmission state (20 km / h in this example), so the control device 100 controls the operation of the transmission output device to realize the second-speed transmission state and obtain the target vehicle speed (15.5 km / h) in the second-speed transmission state. In the third embodiment, the control device 100 controls the operation of the HST 10 to an output state (speed ratio X31) that realizes the target vehicle speed (see (I) in FIG. 7).

[0127] In this state, when the auxiliary transmission operating member 185 is operated from the low-speed stage selection state to the high-speed stage selection state at time T1, the control device 100 transitions the pre-switching engagement clutch mechanism (the low-speed stage clutch mechanism 410L in Example 3) of the low-speed and high-speed stage clutch mechanisms 410L, 410H that was engaged before the auxiliary transmission operating member 185 was switched to a disengaged state, thereby creating a free-running state in which power transmission from the drive source 210 to the traveling output shaft 47 is cut off.

[0128] Next, during the free running state, the control device 100 controls the operation of the transmission output device so that a vehicle speed corresponding to the actual vehicle speed at that time is produced in a post-switching gear state (high-speed state in Example 3) produced by a post-switching engagement clutch mechanism (high-speed clutch mechanism 410H in Example 3) of the low-speed and high-speed clutch mechanisms 410L, 410H that should be engaged after switching operation of the auxiliary speed change operating member 185. In Example 3, the control device 100 controls the operation of the HST 10 to an output state (speed ratio X32) that produces the actual vehicle speed (see (II) in Figure 7). In the free-running state, power transmission from the drive source 210 to the traveling output shaft 47 is cut off, so the vehicle speed changes depending on the traveling conditions (gradually decelerates in the third embodiment).

[0129] Thereafter, the control device 100 transitions the post-switching engagement clutch mechanism (high-speed stage clutch mechanism 410H in Example 3) to an engaged state, and is configured to control the operation of the shift output device in the post-switching gear stage state (high-speed stage state in Example 3) with the vehicle speed defined by the operating position of the main shift operating member 180 at that time as the target vehicle speed.

[0130] In Example 3, the operating position (opening) of the main transmission operating member 180 is not changed (maintained at 70% opening) before and after the operation of the auxiliary transmission operating member 185, and therefore the control device 100 controls the operation of the HST 10 to the output state (speed ratio X31) before the switching operation of the auxiliary transmission operating member 180 (see (III) in Figure 7).

[0131] As a result, the vehicle speed smoothly transitions to the target vehicle speed (31 km / h) when the main transmission operating member 180 is operated to a position of 70% opening in the high speed stage state.

[0132] Finally, the gear shifting operation of the sub-transmission unit 5 while the vehicle is traveling at a speed equal to or higher than the maximum low-speed speed a2 (20 km / h in this example) will be described using an example (hereinafter referred to as Example 4) in which the sub-transmission operating member 185 is operated from a high-speed selection state to a low-speed selection state while the vehicle is traveling with the main transmission operating member 180 operated to a 100% opening position.

[0133] Figure 8 shows the relationship between the passage of time and the engagement / disengagement state of the high-speed stage clutch mechanism 410H and the low-speed stage clutch mechanism 410L, the output state of the transmission output device (the transmission state of the HST 10), and the vehicle speed (the rotational speed of the traveling output shaft 47) in Example 4. The relationship between the operating position (opening) of the main speed change operating member 180 and the vehicle speed follows the example shown in FIG.

[0134] In the high-speed state, the target vehicle speed (40 km / h) when the main speed change operating member 180 is operated to the 100% opening position is equal to or greater than the high-speed switching speed b1 (14 km / h in this example), so the control device 100 brings about a second-speed transmission state and controls the operation of the speed change output device so that the target vehicle speed (40 km / h) is obtained in the second-speed transmission state. In Example 4, the control device 100 controls the operation of the HST 10 to an output state that brings about the target vehicle speed. In Example 4, because the main speed change operating member 180 is at a 100% opening, the target output state of the HST 10 is first speed (maximum speed in the forward rotation direction + max).

[0135] In this state, when the auxiliary transmission operating member 185 is operated from the high-speed selection state to the low-speed selection state at time T1, the control device 100 determines that the vehicle speed at that time exceeds the low-speed maximum speed a2 and therefore cannot immediately transition from the high-speed state to the low-speed state.

[0136] Therefore, the control device 100 first controls the operation of the gear shift output device so that the vehicle speed is reduced to the low-speed maximum vehicle speed a2 while maintaining the high-speed clutch mechanism 410H in an engaged state (in Example 4, the control device 100 controls the operation of the HST 10 so that the output state (gear ratio X41) is such that the low-speed maximum vehicle speed a2 is realized in the high-speed state (see (II) in Figure 8)).

[0137] After the deceleration, the control device 100 shifts the high speed stage clutch mechanism 410H to a release state, thereby creating a free running state.

[0138] Next, the control device 100 controls the operation of the gear output device during the free running state so that a vehicle speed corresponding to the actual vehicle speed at that time is produced in the low gear state produced by the low gear clutch mechanism 410L. In the fourth embodiment, the control device 100 controls the operation of the HST 10 to an output state (speed ratio X42) that produces the actual vehicle speed (see (III) in FIG. 8). In the free-running state, power transmission from the drive source 210 to the traveling output shaft 47 is cut off, so the vehicle speed changes depending on the traveling conditions (gradually decelerates in the fourth embodiment).

[0139] Thereafter, the control device 100 transitions the low-speed clutch mechanism 410L to an engaged state, and in the low-speed state, controls the operation of the shift output device with the target vehicle speed being determined by the operating position of the main shift operating member 180 at that time.

[0140] In the fourth embodiment, the operating position (opening) of the main transmission operating member 180 remains unchanged (maintained at 100% opening) before and after the operation of the auxiliary transmission operating member 185, and therefore the control device 100 controls the operation of the HST 10 to the output state (first speed (maximum speed in the forward direction +max)) before the switching operation of the auxiliary transmission operating member 180 (see (III) in Figure 8).

[0141] As a result, the vehicle speed smoothly transitions to the target vehicle speed (20 km / h) when the main speed change operating member 180 is operated to the 100% opening position in the low gear state.

[0142] Preferably, in the first to fourth embodiments, when a gear change operation is performed using the auxiliary transmission operating member 185 while the vehicle is traveling, the control device 100 controls the operation of the transmission output device so as to present a constant speed traveling state that maintains the vehicle speed at that time for a predetermined period of time, and thereafter presents the free-running state. The predetermined time is set in advance through experiments or the like, and is preferably changeable by a manually operable setting member so as to suit the riding feeling of each user.

[0143] With this configuration, it is possible to reduce the shock caused by fluctuations in vehicle speed when the power transmission of the pre-switching engagement clutch mechanism, which is one of the low-speed stage clutch mechanism 410L and the high-speed stage clutch mechanism 410H and is engaged before the sub-speed change operating member 185 is switched, is cut off and the vehicle transitions to a free-running state.

[0144] That is, if the pre-engagement clutch mechanism is disengaged while the vehicle is accelerating or decelerating, a large shock occurs due to the fluctuation in vehicle speed, which may cause discomfort to the user, especially when the vehicle is traveling at high speeds.

[0145] In this regard, if the vehicle is configured to travel at a constant speed for a predetermined period of time before the pre-switching engagement clutch mechanism is disengaged, the shock caused when the pre-switching engagement clutch mechanism is disengaged can be alleviated, improving the driving feel.

[0146] In addition, in Example 4, the control device 100 is configured to reduce the vehicle speed to the low-speed stage maximum speed a2 in response to operation of the auxiliary transmission operating member 185 to the low-speed stage selection state, and then control the operation of the transmission output device so that the vehicle travels at a constant speed for a predetermined period of time, and to disengage the high-speed stage clutch mechanism 410H after the constant-speed travel.

[0147] FIG. 9 shows a schematic diagram of an example of a display monitor 205 that can be provided in the driver's seat of the work vehicle 200A to which the transmission structure 1A of this embodiment is applied, as well as an example of the main transmission operating member 180 and the auxiliary transmission operating member 185.

[0148] In the example shown in FIG. 9, the auxiliary speed change operating member 185 has a high-speed switch 185H and a low-speed switch 185L.

[0149] The display monitor 205 has an area 205a that displays the current vehicle speed, an area 205b that displays the operating position (opening) of the main transmission operating member 180, and an area 205c that displays the gear state (low gear state or high gear state) of the sub-transmission unit 5.

[0150] Furthermore, the display monitor 205 is provided with a notification means 206 for notifying the user whether or not the gear position of the sub-transmission unit 5 can be changed at the present time. The notification means 206 may be, for example, a lamp, and the control device 100 may be configured to turn on the lamp when the vehicle is traveling in a state in which the sub-transmission unit 5 can be shifted, and to turn off the lamp when the vehicle is traveling in a state in which the sub-transmission unit 5 cannot be shifted.

[0151] In addition, the control device 100 can be configured to determine whether or not the speed difference between the vehicle speed before the shifting operation and the vehicle speed after the shifting operation exceeds a predetermined threshold value when the sub-shifting operation member 185 is operated to shift the gear stage at that time.

[0152] In this case, the display monitor 205 is provided with a determination display area, and whether or not the sub-transmission unit 5 can be switched between gear positions is always displayed in the determination display area.

[0153] Alternatively, or in addition, when the control device 100 determines that the speed difference between the vehicle speed before and after the gear shift operation of the auxiliary transmission operating member 185 actually occurs exceeds a predetermined threshold, it can display a warning message on the display monitor 205.

[0154] The work vehicle may also be provided with audio means, and may be configured to issue a warning to the user by the audio means instead of or in addition to the warning displayed on the display monitor.

[0155] FIG. 10 shows a schematic diagram of power transmission in a working vehicle 200B to which a transmission structure 1B according to a modified example of this embodiment is applied. In FIG. 10, the same members as those in this embodiment are denoted by the same reference numerals.

[0156] The transmission structure 1B differs from the transmission structure 1A in that the main speed change unit 3A is changed to a main speed change unit 3B.

[0157] That is, the transmission structure 1B has the main speed change unit 3B, the sub-speed change unit 5, the main speed change operating member 180, the sub-speed change operating member 185, and the control device 100.

[0158] As shown in FIG. 10, the main transmission unit 3B has: The HST 10 that functions as the speed change output device; a first gear stage planetary gear mechanism 310(1) and a second gear stage planetary gear mechanism 310(2); a first transmission path 330(1) for transmission of the speed-change rotational power to a sun gear 312(1) of the three planetary elements of the first-speed planetary gear mechanism 310(1); and a first transmission path 340(1) for reference power for transmission of the reference rotational power to a planetary element (e.g., an internal gear 316(1)) of the first and second planetary elements of the three planetary elements of the first-speed planetary gear mechanism 310(1), which acts as a reference power input portion. a first clutch mechanism 350(1) that engages and disengages the reference power first transmission path 340(1); a first output transmission path 360(1) that transmits power from planetary elements (e.g., carrier 318(1)) that form a planetary output portion other than the sun gear 312(1) and the planetary elements (e.g., internal gear 316(1)) that form the reference power input portion, among the three planetary elements of the first-speed planetary gear mechanism 310(1), to the traveling intermediate shaft 45; a second transmission path 330(2) for speed change that transmits the speed change rotational power to the sun gear 312(2) of the three planetary elements of the second speed stage planetary gear mechanism 310(2); a reference power second transmission path 340(2) that transmits the reference rotational power to a planetary element (e.g., carrier 318(2)) that acts as a reference power input portion among the first element and the second element of the three planetary elements of the second-speed planetary gear mechanism 310(2); a second clutch mechanism 350(2) that engages and disengages the reference power second transmission path 340(2); and a second output transmission path 360(2) that transmits the planetary elements (e.g., the internal gear 316(2)) that form the planetary output portion other than the sun gear 312(2) and the planetary element (318(2)) that forms the reference power input portion out of the three planetary elements of the second-speed planetary gear mechanism 310(2) to the traveling intermediate shaft 45.

[0159] In the transmission structure 1B, the control device 100 engages the first clutch mechanism 350(1) and disengages the second clutch mechanism 350(2) when the absolute value of the vehicle speed recognized based on, for example, the vehicle speed sensor 190b or the engine revolution number sensor 190c and the transmission output sensor 190a (see FIG. 10) is in a range up to a switching speed (i.e., a range up to a low-speed stage switching speed a1 when the sub-transmission unit 5 is in a low-speed stage state, and a range up to a high-speed stage switching speed b1 when the sub-transmission unit 5 is in a high-speed stage state). The first gear stage transmission state is realized by disengaging the first clutch mechanism 350(1) and engaging the second clutch mechanism 350(2), while the absolute value of the vehicle speed is in the range from the switching speed to the maximum speed (i.e., in the range from low-speed stage switching speed a1 to low-speed stage maximum speed a2 when the sub-transmission unit 5 is in the low-speed stage state, and in the range from high-speed stage switching speed b1 to high-speed stage maximum speed b2 when the sub-transmission unit 5 is in the high-speed stage state).

[0160] In the present embodiment and the modified example, the transmission structures 1A, 1B are applied to the vehicles 200A, 200B having the drive source 210 of an internal combustion engine type, but the transmission structures 1A, 1B can also be applied to work vehicles equipped with an electric motor drive source. [Explanation of symbols]

[0161] 1A, 1B transmission structure 3A, 3B main transmission unit 5 Sub-transmission unit 10 HST (speed change output device) 30 Planetary gear mechanism 32 Sun gear (third element) 36 Internal gear (first element) 38 Carrier (second element) 40 Transmission path for speed change 45 Travelling intermediate shaft 47 Travel output shaft 50(1), 50(2) Input side first and second transmission paths 60(1), 60(2) Input side first and second clutch mechanisms 70(1), 70(2) Output side first and second transmission paths 80(1), 80(2) Output side first and second clutch mechanisms 100 control device 180 Main transmission operating member 185 Auxiliary speed change operating member 210 Drive source 212 Drive shaft 310(1), 310(2) Planetary gear mechanism for 1st and 2nd gears 312(1), 312(2) Sun gear 316(1), 316(2) Internal gear 318(1), 318(2) Carrier 330(1), 330(2) First and second transmission paths for speed change 340(1), 340(2) First and second transmission paths for reference power 350(1), 350(2) First and second clutch mechanisms 360(1), 360(2) First and second power transmission paths for output 400L Low-speed transmission path 400H high speed transmission path 410L Low-speed clutch mechanism 410H high-speed step clutch mechanism

Claims

1. A transmission structure that continuously changes the speed of a reference rotational power of a drive shaft operatively connected to a drive source and transmits it to a traveling output shaft that determines the vehicle speed, a main transmission unit including a speed change output device that outputs speed change rotational power that is continuously variable between at least first speed and second speed, and a planetary gear mechanism that combines the reference rotational power and the speed change rotational power, and that outputs a combined output of the planetary gear mechanism as running rotational power; an auxiliary transmission unit capable of transmitting the traveling rotational power from the main transmission unit to the traveling output shaft after multi-stage speed change, the auxiliary transmission unit including a low-speed stage transmission path and a high-speed stage transmission path that transmit the traveling rotational power from the main transmission unit to the traveling output shaft at a forward low-speed transmission ratio and a forward high-speed transmission ratio, respectively, and low-speed stage and high-speed stage clutch mechanisms that engage and disengage the low-speed stage and high-speed stage transmission paths, respectively; a main speed change operating member and an auxiliary speed change operating member for operating the main speed change unit and the auxiliary speed change unit, respectively; a control device; The control device In response to operation of the auxiliary speed change operating member, the operation of the auxiliary speed change unit is controlled so as to realize a low-speed stage state by engaging the low-speed stage clutch mechanism and a high-speed stage state by engaging the high-speed stage clutch mechanism, and the operation of the main speed change unit is controlled so as to obtain a target vehicle speed defined by the operating position of the main speed change operating member for each of the low-speed stage state and the high-speed stage state, Furthermore, when the gear shift operation is performed by the auxiliary speed change operating member while the traveling output shaft is being driven to rotate, a pre-switching engagement clutch mechanism of the low-speed and high-speed clutch mechanisms that was engaged before the switching operation of the auxiliary speed change operating member is transitioned to a released state to create a free-running state, and during the free-running state, operation of the gear shift output device is controlled so that a vehicle speed corresponding to the actual vehicle speed at that time is created in a post-switching gear state created by a post-switching engagement clutch mechanism of the low-speed and high-speed clutch mechanisms that should be engaged after the switching operation of the auxiliary speed change operating member, and then the post-switching engagement clutch mechanism is transitioned to an engaged state, and in the post-switching gear state, operation of the gear shift output device is controlled with the vehicle speed defined by the operating position of the main speed change operating member at that time as a target vehicle speed.

2. A transmission structure that continuously changes the speed of a reference rotational power of a drive shaft operatively connected to a drive source and transmits it to a traveling output shaft that determines the vehicle speed, a main transmission unit including a speed change output device that outputs speed change rotational power that is continuously variable between at least first speed and second speed, and a planetary gear mechanism that combines the reference rotational power and the speed change rotational power, and that outputs a combined output of the planetary gear mechanism as running rotational power; an auxiliary transmission unit capable of transmitting the traveling rotational power from the main transmission unit to the traveling output shaft after multi-stage speed change, the auxiliary transmission unit including a low-speed stage transmission path and a high-speed stage transmission path that transmit the traveling rotational power from the main transmission unit to the traveling output shaft at a forward low-speed transmission ratio and a forward high-speed transmission ratio, respectively, and low-speed stage and high-speed stage clutch mechanisms that engage and disengage the low-speed stage and high-speed stage transmission paths, respectively; a main speed change operating member and an auxiliary speed change operating member for operating the main speed change unit and the auxiliary speed change unit, respectively; a control device; the main transmission unit is configured to be capable of taking a first speed stage transmission state in which the combined output of the planetary gear mechanism is increased as the speed of the speed-changing rotational power is changed from the first speed side to the second speed side, and a second speed stage transmission state in which the maximum speed in the first speed stage transmission state is set to the minimum speed, and the combined output of the planetary gear mechanism is increased as the speed of the speed-changing rotational power is changed from the second speed side to the first speed side, The control device In response to operation of the auxiliary speed change operating member, the operation of the auxiliary speed change unit is controlled so that a low-speed state is achieved by engaging the low-speed clutch mechanism and a high-speed state is achieved by engaging the high-speed clutch mechanism, and further, a first speed state is achieved when the vehicle speed in the low-speed state is up to the low-speed switching speed and when the vehicle speed in the high-speed state is up to the high-speed switching speed, and a second speed state is achieved when the vehicle speed in the low-speed state exceeds the low-speed switching speed and when the vehicle speed in the high-speed state exceeds the high-speed switching speed, and operation of the main speed change unit is controlled with the vehicle speed defined by the operating position of the main speed change operating member as a target vehicle speed for each of the low-speed state and the high-speed state, Furthermore, when the traveling output shaft is driven to rotate and a gear change operation is performed using the auxiliary speed change operating member when the vehicle speed is below a low-speed change speed, a pre-switching engagement clutch mechanism of the low-speed and high-speed clutch mechanisms that was engaged before the switching operation of the auxiliary speed change operating member is transitioned to a released state to create a free-running state, and during the free-running state, operation of the gear change output device is controlled so that a vehicle speed corresponding to the actual vehicle speed at that time is created in a post-switching gear state created by a post-switching engagement clutch mechanism of the low-speed and high-speed clutch mechanisms that should be engaged after the switching operation of the auxiliary speed change operating member, and then the post-switching engagement clutch mechanism is transitioned to an engaged state, and in the post-switching gear state, operation of the gear change output device is controlled with the vehicle speed defined by the operating position of the main speed change operating member at that time as a target vehicle speed.

3. A transmission structure that continuously changes the speed of a reference rotational power of a drive shaft operatively connected to a drive source and transmits it to a traveling output shaft that determines the vehicle speed, a main transmission unit including a speed change output device that outputs speed change rotational power that is continuously variable between at least first speed and second speed, and a planetary gear mechanism that combines the reference rotational power and the speed change rotational power, and that outputs a combined output of the planetary gear mechanism as running rotational power; an auxiliary transmission unit capable of transmitting the traveling rotational power from the main transmission unit to the traveling output shaft after multi-stage speed change, the auxiliary transmission unit including a low-speed stage transmission path and a high-speed stage transmission path that transmit the traveling rotational power from the main transmission unit to the traveling output shaft at a forward low-speed transmission ratio and a forward high-speed transmission ratio, respectively, and low-speed stage and high-speed stage clutch mechanisms that engage and disengage the low-speed stage and high-speed stage transmission paths, respectively; a main speed change operating member and an auxiliary speed change operating member for operating the main speed change unit and the auxiliary speed change unit, respectively; a control device; the main transmission unit is configured to be capable of taking a first speed stage transmission state in which the combined output of the planetary gear mechanism is increased as the speed of the speed-changing rotational power is changed from the first speed side to the second speed side, and a second speed stage transmission state in which the maximum speed in the first speed stage transmission state is set to the minimum speed, and the combined output of the planetary gear mechanism is increased as the speed of the speed-changing rotational power is changed from the second speed side to the first speed side, The control device In response to operation of the auxiliary speed change operating member, the operation of the auxiliary speed change unit is controlled so that a low-speed state is achieved by engaging the low-speed clutch mechanism and a high-speed state is achieved by engaging the high-speed clutch mechanism, and further, a first speed state is achieved when the vehicle speed in the low-speed state is up to the low-speed switching speed and when the vehicle speed in the high-speed state is up to the high-speed switching speed, and a second speed state is achieved when the vehicle speed in the low-speed state exceeds the low-speed switching speed and when the vehicle speed in the high-speed state exceeds the high-speed switching speed, and operation of the main speed change unit is controlled with the vehicle speed defined by the operating position of the main speed change operating member as a target vehicle speed for each of the low-speed state and the high-speed state, Furthermore, when the traveling output shaft is driven and rotated and a gear change operation is performed by the auxiliary speed change operating member when the vehicle speed is equal to or higher than the low-speed change speed and equal to or lower than the high-speed change speed, a pre-switching engagement clutch mechanism, of the low-speed and high-speed clutch mechanisms, that was engaged before the switching operation of the auxiliary speed change operating member is shifted to a released state to create a free-running state, and during the free-running state, operation of the speed change output device is controlled so that the switching speed in the pre-switching gear state that was created by the pre-switching engagement clutch mechanism is created, and then switching is performed between the first speed transmission state and the second speed transmission state. and further controlling the operation of the gear shift output device so that a vehicle speed corresponding to the actual vehicle speed at that time is realized in a post-switching gear stage state realized by a post-switching engagement clutch mechanism, of the low-speed and high-speed clutch mechanisms, that should be engaged after switching operation of the auxiliary gear shift operating member, and then transitioning the post-switching engagement clutch mechanism to an engaged state, and controlling the operation of the gear shift output device in the post-switching gear stage state with the vehicle speed defined by the operating position of the main gear shift operating member at that time as a target vehicle speed.

4. A transmission structure that continuously changes the speed of a reference rotational power of a drive shaft operatively connected to a drive source and transmits it to a traveling output shaft that determines the vehicle speed, a main transmission unit including a speed change output device that outputs speed change rotational power that is continuously variable between at least first speed and second speed, and a planetary gear mechanism that combines the reference rotational power and the speed change rotational power, and that outputs a combined output of the planetary gear mechanism as running rotational power; an auxiliary transmission unit capable of transmitting the traveling rotational power from the main transmission unit to the traveling output shaft after multi-stage speed change, the auxiliary transmission unit including a low-speed stage transmission path and a high-speed stage transmission path that transmit the traveling rotational power from the main transmission unit to the traveling output shaft at a forward low-speed transmission ratio and a forward high-speed transmission ratio, respectively, and low-speed stage and high-speed stage clutch mechanisms that engage and disengage the low-speed stage and high-speed stage transmission paths, respectively; a main speed change operating member and an auxiliary speed change operating member for operating the main speed change unit and the auxiliary speed change unit, respectively; a control device; the main transmission unit is configured to be capable of taking a first speed stage transmission state in which the combined output of the planetary gear mechanism is increased as the speed of the speed-changing rotational power is changed from the first speed side to the second speed side, and a second speed stage transmission state in which the maximum speed in the first speed stage transmission state is set to the minimum speed, and the combined output of the planetary gear mechanism is increased as the speed of the speed-changing rotational power is changed from the second speed side to the first speed side, The control device In response to operation of the auxiliary speed change operating member, the operation of the auxiliary speed change unit is controlled so that a low-speed state is achieved by engaging the low-speed clutch mechanism and a high-speed state is achieved by engaging the high-speed clutch mechanism, and further, a first speed state is achieved when the vehicle speed in the low-speed state is up to the low-speed switching speed and when the vehicle speed in the high-speed state is up to the high-speed switching speed, and a second speed state is achieved when the vehicle speed in the low-speed state exceeds the low-speed switching speed and when the vehicle speed in the high-speed state exceeds the high-speed switching speed, and operation of the main speed change unit is controlled with the vehicle speed defined by the operating position of the main speed change operating member as a target vehicle speed for each of the low-speed state and the high-speed state, Furthermore, when the traveling output shaft is driven to rotate and a gear change operation is performed using the auxiliary speed change operating member when the vehicle speed is equal to or greater than the high-speed changeover speed and equal to or less than the maximum vehicle speed in the low-speed state, a pre-switching engagement clutch mechanism of the low-speed and high-speed clutch mechanisms that was engaged before the switching operation of the auxiliary speed change operating member is transitioned to a released state to create a free-running state, and during the free-running state, operation of the gear change output device is controlled so that a vehicle speed corresponding to the actual vehicle speed at that time is created in a post-switching gear state created by a post-switching engagement clutch mechanism of the low-speed and high-speed clutch mechanisms that should be engaged after the switching operation of the auxiliary speed change operating member, and then the post-switching engagement clutch mechanism is transitioned to an engaged state, and in the post-switching gear state, operation of the gear change output device is controlled with the vehicle speed defined by the operating position of the main speed change operating member at that time as the target vehicle speed.

5. A transmission structure that continuously changes the speed of a reference rotational power of a drive shaft operatively connected to a drive source and transmits it to a traveling output shaft that determines the vehicle speed, a main transmission unit including a speed change output device that outputs speed change rotational power that is continuously variable between at least first speed and second speed, and a planetary gear mechanism that combines the reference rotational power and the speed change rotational power, and that outputs a combined output of the planetary gear mechanism as running rotational power; an auxiliary transmission unit capable of transmitting the traveling rotational power from the main transmission unit to the traveling output shaft after multi-stage speed change, the auxiliary transmission unit including a low-speed stage transmission path and a high-speed stage transmission path that transmit the traveling rotational power from the main transmission unit to the traveling output shaft at a forward low-speed transmission ratio and a forward high-speed transmission ratio, respectively, and low-speed stage and high-speed stage clutch mechanisms that engage and disengage the low-speed stage and high-speed stage transmission paths, respectively; a main speed change operating member and an auxiliary speed change operating member for operating the main speed change unit and the auxiliary speed change unit, respectively; a control device; the main transmission unit is configured to be capable of taking a first speed stage transmission state in which the combined output of the planetary gear mechanism is increased as the speed of the speed-changing rotational power is changed from the first speed side to the second speed side, and a second speed stage transmission state in which the maximum speed in the first speed stage transmission state is set to the minimum speed, and the combined output of the planetary gear mechanism is increased as the speed of the speed-changing rotational power is changed from the second speed side to the first speed side, The control device In response to operation of the auxiliary speed change operating member, the operation of the auxiliary speed change unit is controlled so that a low-speed state is achieved by engaging the low-speed clutch mechanism and a high-speed state is achieved by engaging the high-speed clutch mechanism, and further, a first speed state is achieved when the vehicle speed in the low-speed state is up to the low-speed switching speed and when the vehicle speed in the high-speed state is up to the high-speed switching speed, and a second speed state is achieved when the vehicle speed in the low-speed state exceeds the low-speed switching speed and when the vehicle speed in the high-speed state exceeds the high-speed switching speed, and operation of the main speed change unit is controlled with the vehicle speed defined by the operating position of the main speed change operating member as a target vehicle speed for each of the low-speed state and the high-speed state, Furthermore, when the traveling output shaft is driven to rotate and a switching operation from a high speed to a low speed is performed using the auxiliary shift operating member when the vehicle speed is equal to or higher than the maximum vehicle speed in the low speed state, the operation of the shift output device is controlled so that the vehicle speed is decelerated to the maximum vehicle speed in the low speed state while maintaining the engaged state of the high speed stage clutch mechanism, and after the deceleration, the high speed stage clutch mechanism is switched to a released state to create a free running state, and during the free running state, the operation of the shift output device is controlled so that a vehicle speed corresponding to the actual vehicle speed at that time is created in the low speed stage state created by the low speed stage clutch mechanism, and then the low speed stage clutch mechanism is switched to an engaged state, and in the low speed stage state, the operation of the shift output device is controlled so that the vehicle speed defined by the operating position of the main shift operating member at that time is used as a target vehicle speed.

6. 6. A transmission structure according to claim 1, wherein the control device controls the operation of the transmission output device so that, when a gear change operation is performed using the auxiliary transmission operating member, a constant speed traveling state in which the vehicle speed at that time is maintained is realized for a predetermined period of time, and then causes the free running state to be realized.

7. the main transmission unit includes a speed change transmission path that transmits the speed change rotational power to a third element of the three planetary elements of the planetary gear mechanism, input side first and second transmission paths that transmit the reference rotational power to a first element and a second element of the three planetary elements of the planetary gear mechanism, respectively, input side first and second clutch mechanisms that engage and disengage the input side first and second transmission paths, respectively, output side first and second transmission paths that transmit the rotational power of the second element and the first element to a traveling intermediate shaft, respectively, and output side first and second clutch mechanisms that engage and disengage the output side first and second transmission paths, respectively, and is configured to realize a first speed stage transmission state by engagement of the input side and output side first clutch mechanisms, and to realize a second speed stage transmission state by engagement of the input side and output side second clutch mechanisms, 6. The transmission structure according to claim 2, wherein the auxiliary transmission unit is arranged to change speeds in multiple stages between the intermediate shaft and the output shaft.

8. 8. The transmission structure according to claim 7, wherein the planetary gear mechanism, the input-side first and second transmission paths, and the output-side first and second transmission paths are configured so that the rotational speed of the second element when the output of the transmission output device is set to second speed in the first speed transmission state is substantially the same as the rotational speed of the second element when the output of the transmission output device is set to second speed in the second speed transmission state, and so that the rotational speed of the first element when the first speed transmission state is substantially the same as the rotational speed of the first element when the output of the transmission output device is set to second speed in the second speed transmission state.

9. The main transmission unit includes a first speed stage planetary gear mechanism and a second speed stage planetary gear mechanism acting as the planetary gear mechanism, a first speed change transmission path that transmits the speed change rotational power to a sun gear of the three planetary elements of the first speed stage planetary gear mechanism, a reference power first transmission path that transmits the reference rotational power to a first element and a second element of the three planetary elements of the first speed stage planetary gear mechanism that act as a reference power input portion, a first clutch mechanism that engages and disengages the reference power first transmission path, a first output transmission path that transmits planetary elements that form a planetary output portion other than the sun gear and the planetary elements that form the reference power input portion of the three planetary elements of the first speed stage planetary gear mechanism to a traveling intermediate shaft, and the second gear stage planetary gear mechanism includes a second transmission path for transmission of the reference rotational power to a sun gear of the three planetary elements of the second gear stage planetary gear mechanism; a second transmission path for reference power for transmission of the reference rotational power to a first element and a second element of the three planetary elements of the second gear stage planetary gear mechanism that act as a reference power input portion; a second clutch mechanism for engaging and disengaging the second transmission path for reference power; and a second transmission path for output for transmission of planetary elements that form a planetary output portion other than the sun gear and the planetary elements that form the reference power input portion of the three planetary elements of the second gear stage planetary gear mechanism to the traveling intermediate shaft, wherein a first gear stage transmission state is realized by engagement of the first clutch mechanism and a second gear stage transmission state is realized by engagement of the second clutch mechanism, 6. The transmission structure according to claim 2, wherein the auxiliary transmission unit is arranged to change speeds in multiple stages between the intermediate shaft and the output shaft.

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