JP7376069B2 - transmission structure - Google Patents

Description

The present invention relates to a transmission structure having a hydrostatic/mechanical continuously variable transmission structure (HMT structure) including a hydrostatic continuously variable transmission mechanism (HST) and a planetary gear mechanism.

A transmission structure including an HST structure and an HMT structure formed by a planetary gear mechanism is described in, for example, Patent Document 1, and is suitably used in a drive system transmission path of a work vehicle such as a combine harvester or a tractor.

FIG. 8 shows a transmission schematic diagram of a work vehicle to which the conventional transmission structure 500 described in Patent Document 1 is applied.
As shown in FIG. 8, the transmission structure 500 includes an HST 510 and a planetary gear mechanism 530.

The HST 510 includes a pump shaft 512 that operatively inputs rotational power from the drive source 210 of the work vehicle, a pump body 514 supported by the pump shaft 512, and a capacity of the pump body 514 that changes steplessly. It has a pump-side output adjustment member 520, a motor shaft 516 that outputs an HST output, and a motor main body 518 supported by the motor shaft 516 and fluidly connected to the pump main body 514. By changing the capacity of the pump main body 514 with the pump side output adjustment member 520 in a fixed capacity state, the rotation speed of the motor shaft 516 is continuously variable with respect to the rotation speed of the pump shaft 512. It is configured to obtain.

The planetary gear mechanism 530 includes a sun gear 532, a planet gear 534 that meshes with the sun gear 532, an internal gear 536 that meshes with the planet gear 534, and supports the planet gear 534 rotatably around an axis and supports the planet gear 534. It has a carrier 538 that rotates about the same axis as the sun gear 532 in conjunction with the revolution of the gear 534 around the sun gear 532, and the sun gear 532, the carrier 538, and the internal gear 536 rotate the three planetary elements. is forming.

As shown in FIG. 8, in the conventional transmission structure 500, the reference rotational power from the drive source 210 is operatively input to the internal gear 536, and the HST from the motor shaft 516 is input to the sun gear 532. The output is operatively input, and the carrier 538 outputs a composite rotational power obtained by combining the reference rotational power and the HST output.

Incidentally, the required maximum traction force and required maximum speed of the work vehicle are determined according to specifications, and the transmission structure is required to cover the required maximum traction force and required maximum speed.

FIG. 9 shows the relationship between the required maximum tractive force Tmax, the required maximum speed Smax, and the HST capacity (HST pump capacity) in an example of a work vehicle to which the conventional transmission structure 500 is applied.

Here, in the conventional transmission structure 500, in the HST 510, the capacity of the motor body 518 is fixed, and only the capacity of the pump body 514 is variable, and the capacity of the pump body 514 cannot be changed. The rotation speed of the HST output is changed by this.

However, it is difficult to cover the range of the required maximum tractive force Tmax and the required maximum vehicle speed Smax only by changing the speed change range of the rotational speed of the HST output.

Therefore, as shown in FIG. 8, the conventional transmission structure 500 includes an auxiliary transmission mechanism 570 that multi-stages the combined rotational power output from the planetary gear mechanism 530 and outputs the same to the driving wheels 220. In addition, by setting the number of gears of the sub-transmission mechanism 570 to three, it is configured to cover the required maximum tractive force Tmax and the required maximum speed Smax.
Note that the reference numeral 550 in FIG. 8 is a forward/reverse switching mechanism.

10(a) to (c), in a work vehicle to which the conventional transmission structure 500 is applied, the auxiliary transmission mechanism 570 is in a low gear transmission state, a middle gear transmission state, and a high gear transmission state, respectively. It shows the relationship between the vehicle speed and tractive force that can be produced and the HST capacity (HST pump capacity) when

As shown in FIGS. 9 and 10(a) to (c), in the example of FIG. The range of the required maximum tractive force Tmax and the required maximum vehicle speed Smax is covered by the three gears including the third gear (high speed gear) and the third gear (high speed gear).

Japanese Patent Application Publication No. 2010-076748

The present invention has been made in view of the above-mentioned prior art, and an object of the present invention is to provide a transmission structure having an HST forming an HMT structure and a planetary gear mechanism, which is capable of expanding the shiftable range of the HMT output. shall be.

In order to achieve the above object, a first aspect of the present invention provides a transmission structure that is inserted into a drive system transmission path of a working vehicle, the transmission structure including a pump that operatively inputs rotational power from a drive source of the working vehicle. a shaft, a pump body supported by the pump shaft, a pump-side output adjustment member capable of steplessly changing the capacity of the pump body between first and second pump capacities, a motor shaft, supported by the motor shaft; an HST having a motor body fluidly connected to the pump body, and a motor-side output adjustment member capable of changing the capacity of the motor body between a low-speed motor capacity and a high-speed motor capacity smaller than the low-speed motor capacity; has first to third elements, and synthesizes a reference rotational power operatively input to the first element from the drive source and an HST output operatively input to the second element from the motor shaft. , a planetary gear mechanism that outputs synthetic rotational power from the third element, wherein the output of the third element is adjusted according to a change in the HST output due to a change in the HST output from the first pump capacity to the second pump capacity of the pump body. a planetary gear mechanism set to increase speed; a manually operable speed change operation member; a vehicle speed sensor that directly or indirectly detects the vehicle speed of the work vehicle; and a vehicle speed sensor that directly or indirectly detects the capacity of the pump body The control device includes a pump sensor that detects the capacity, a motor sensor that directly or indirectly detects the capacity of the motor main body, and a control device that controls the operation of the pump side output adjustment member and the motor side output adjustment member. appears when the vehicle speed detected by the vehicle speed sensor is set to the low-speed motor capacity of the motor body and to the predetermined pump switching capacity between the first and second pump capacities. When the speed is below the switching speed, the motor side output adjustment member is operated so that the motor body is fixed at the low speed motor capacity, and the vehicle speed is increased in accordance with the speed increase and deceleration operations of the speed change operation member. and operates the pump-side output adjustment member to decelerate, and when the vehicle speed exceeds the switching speed, the capacity of the pump body is adjusted to the pump switching capacity in response to the speed increase operation of the speed change operation member. speed increasing operation of the pump side output adjusting member to change the capacity from the low speed motor capacity side to the high speed motor capacity side; the pump-side output adjustment member that synchronizes the speed operation and changes the capacity of the pump main body from the second pump capacity side to the pump switching capacity side in response to the deceleration operation of the speed change operation member; and a deceleration operation of the motor-side output adjustment member that changes the capacity of the motor main body from a high-speed motor capacity side to a low-speed motor capacity side are executed in synchronization , and the pump switching capacity is To provide a transmission structure having a neutral capacity that makes the rotation of the motor shaft zero regardless of the rotational state of the pump shaft .

Further, in order to achieve the above object, a second aspect of the present invention is a transmission structure that is inserted into a drive system transmission path of a working vehicle, and which operatively inputs rotational power from a drive source of the working vehicle. a pump shaft, a pump body supported by the pump shaft, a pump-side output adjustment member that can steplessly change the capacity of the pump body between first and second pump capacities, a motor shaft, a pump body supported by the motor shaft; and an HST having a motor body fluidly connected to the pump body, and a motor-side output adjustment member capable of changing the capacity of the motor body between a low-speed motor capacity and a high-speed motor capacity smaller than the low-speed motor capacity. , has first to third elements, and synthesizes the reference rotational power operatively input to the first element from the drive source and the HST output operatively input to the second element from the motor shaft. and a planetary gear mechanism that outputs synthetic rotational power from the third element, wherein the output of the third element is adjusted according to a change in the HST output due to a change in the HST output from the first pump capacity to the second pump capacity of the pump body. a planetary gear mechanism set to increase the speed of the pump; a manually operable speed change operation member; a vehicle speed sensor that directly or indirectly detects the vehicle speed of the work vehicle; a motor sensor that directly or indirectly detects the capacity of the motor main body, and a control device that controls the operation of the pump-side output adjustment member and the motor-side output adjustment member, When the vehicle speed detected by the vehicle speed sensor is less than the switching speed that appears when the motor body is set to a low-speed motor capacity and the pump body is set to a predetermined pump switching capacity, the device While operating the motor-side output adjustment member so that the motor body is fixed at a low-speed motor capacity, the pump-side output is adjusted so that the vehicle speed increases and decelerates in accordance with the speed increase and deceleration operations of the speed change operation member. At the same time, actuating the motor side output adjusting member so that when the vehicle speed reaches the switching speed from the low speed side by actuating the adjusting member, the capacity of the motor body changes from the low speed motor capacity to the high speed motor capacity. , the pump-side output adjustment member is operated so that the capacity of the pump body becomes a pump adjustment capacity that can maintain the vehicle speed at the switching speed in a state where the motor body is set to the high-speed motor capacity, and the vehicle speed exceeds the switching speed; While operating the motor-side output adjustment member so that the motor body is fixed at the high-speed motor capacity, the vehicle speed increases and decreases in accordance with the speed increase and deceleration operations of the speed change operation member. When the vehicle speed reaches the switching speed from the high speed side, the motor side output adjustment member is operated to change the capacity of the motor body from the high speed motor capacity to the low speed motor capacity. To provide a transmission structure configured to actuate the pump-side output adjusting member to change the capacity of the pump body from the pump adjustment capacity to the pump switching capacity at the same time as the member is actuated.

In the second aspect , preferably, the pump switching capacity is a second pump capacity.

The transmission structure according to the present invention has a forward transmission state in which the combined rotational power operatively inputted from the third element is output as rotational power for moving the vehicle forward, and a forward transmission state in which the combined rotational power is outputted as rotational power for moving the vehicle backward. The vehicle may include a forward/reverse switching mechanism that can selectively switch between a reverse transmission state and a reverse transmission state.

In this case, in the planetary gear mechanism, when the motor body is set to a low speed motor capacity and the pump body is set to a predetermined planetary zero output capacity, the output of the third element becomes zero speed, and the pump body The output of the third element is set so that as the capacity is changed from the planetary zero output capacity to the second pump capacity, the output of the third element increases from zero speed to one side around the axis.

The control device operates the motor side output adjustment member so that when the speed change operation member is located at the zero speed position, the motor body has a low speed motor capacity, and the pump body has a planetary zero output. The pump-side output adjustment member is operated so that the capacity is reached.

Preferably, the planetary zero output capacity is a first pump capacity.

In one form, the speed change operation member is operable from a zero speed position to a forward drive side and a reverse drive side.
In this case, the control device controls the forward/reverse movement so that the forward/reverse switching mechanism enters the forward transmission state and the reverse transmission state, respectively, in response to the operation of the speed change operating member from the zero speed position to the forward and reverse sides. Activate the switching mechanism.

In another embodiment, the transmission structure includes a forward/reverse switching operation member that can be manually operated.
In this case, the control device operates the forward/reverse switching mechanism so that the forward/reverse switching mechanism is in a forward transmission state and a reverse transmission state in response to an operation on the forward/reverse switching operation member.

Preferably, the transmission structure according to the present invention may include a sub-transmission mechanism that changes the rotational power operatively input from the third element in multiple stages.

According to the transmission structure according to the present invention, the shiftable range of the output of the HMT formed by the HST and the planetary gear mechanism can be expanded without causing sudden speed changes.
Therefore, for example, when a multi-stage auxiliary transmission mechanism is provided, the number of gears of the auxiliary transmission mechanism can be reduced from the number of gears required in a conventional transmission structure.

FIG. 1 is a schematic transmission diagram of a work vehicle to which a transmission structure according to Embodiment 1 of the present invention is applied. FIG. 2 is a control block diagram of the control device in the transmission structure according to the first embodiment. 3(a) and (b) are graphs showing the relationship between vehicle speed, tractive force, and HST capacity (capacity of the pump body and motor body) in a work vehicle to which the transmission structure according to the first embodiment is applied. 1 and 2 are graphs, respectively, when the auxiliary transmission mechanism provided in the transmission structure is engaged in the first gear (low gear) and engaged in the second gear (high gear). FIG. 4 is a control block diagram of a control device according to a modification of FIG. 2. 5(a) and (b) show the relationship between vehicle speed, tractive force, and HST capacity (capacity of the pump body and motor body) in a work vehicle to which the transmission structure according to Embodiment 2 of the present invention is applied. 2A and 2B are graphs, respectively, when the auxiliary transmission mechanism provided in the transmission structure is engaged in the first gear (low gear) and when the second gear (high gear) is engaged. 6(a) and (b) show the relationship between vehicle speed, tractive force, and HST capacity (capacity of the pump body and motor body) in a working vehicle to which the transmission structure according to the modification of the second embodiment is applied. These graphs are graphs when the auxiliary transmission mechanism included in the transmission structure is engaged in the first gear (low gear) and when the second gear (high gear) is engaged, respectively. FIGS. 7(a) and (b) are graphs showing the relationship between vehicle speed, tractive force, and HST capacity (capacity of the pump body and motor body) in a work vehicle to which the transmission structure according to the third embodiment is applied. 1 and 2 are graphs, respectively, when the auxiliary transmission mechanism provided in the transmission structure is engaged in the first gear (low gear) and engaged in the second gear (high gear). FIG. 8 is a schematic transmission diagram of a work vehicle to which a conventional transmission structure is applied. FIG. 9 is a graph showing the relationship between the required maximum tractive force, the required maximum vehicle speed, and the HST capacity (HST pump capacity) in an example of a work vehicle to which the conventional transmission structure shown in FIG. 8 is applied. FIGS. 10(a) to (c) show, respectively, when the auxiliary transmission mechanism in a work vehicle to which the conventional transmission structure is applied is in a low gear transmission state, a middle gear transmission state, and a high gear transmission state. It is a graph showing the relationship between the vehicle speed and tractive force that can be produced and the HST capacity (HST pump capacity).

Embodiment 1
DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a transmission structure according to the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows a transmission schematic diagram of a work vehicle 200 to which a transmission structure 1 according to the present embodiment is applied.

As shown in FIG. 1, the work vehicle 200 includes a drive source 210, a drive wheel 220, and the transmission structure 1 inserted in a traveling system transmission path from the drive source 210 to the drive wheels 220. ing. Note that the reference numeral 210a in FIG. 1 is a flywheel included in the drive source 210.

As shown in FIG. 1, the transmission structure 1 includes a hydrostatic continuously variable transmission mechanism (HST) 10 and a planetary planet that cooperates with the HST 10 to form an HMT structure (hydrohydraulic/mechanical continuously variable transmission structure). A gear mechanism 30 is provided.

The HST 10 includes a pump shaft 12 that operatively inputs rotational power from the drive source 210, a pump body 14 supported by the pump shaft 12, and a pump that can change the capacity of the pump body 14 steplessly. A side output adjustment member 20, a motor shaft 16, a motor body 18 supported by the motor shaft 16 and fluidly connected to the pump body 14, and a motor side output adjustment member 25 capable of changing the capacity of the motor body 18. It is equipped with

As shown in FIG. 1, in this embodiment, a speed increasing gear train 214 is interposed between the drive source 210 and the pump shaft 12, so that the rotational power of the drive source 210 is transferred to the pump shaft 12. It is operatively input to the first end of the pump shaft 12 on one end side in the axial direction via the speed increasing gear train 214 .
Alternatively, it is also possible to connect the drive source 210 and the pump shaft 12 directly.

The pump body 14 includes a pump-side cylinder block (not shown) supported by the pump shaft 12 so as not to be relatively rotatable around the axis, and housed in the pump-side cylinder block so as to be unrotatable relative to the axis and movable back and forth in the axial direction. This is a variable displacement axial piston machine having a pump side piston (not shown), and is configured so that the capacity changes according to the range of movement of the pump side piston. The piston pump type can take various forms, such as a swash plate type, an oblique shaft type, and a radial type.

The pump-side output adjustment member 20 is configured to be able to steplessly change the capacity of the pump body 14 between a first pump capacity and a second pump capacity, and is configured to be able to steplessly change the capacity of the pump body 14 between a first pump capacity and a second pump capacity, and is configured to control a control device provided in the transmission structure 1. The operation is controlled by 100.

FIG. 2 shows a control block diagram of the control device 100.
As shown in FIG. 2, the pump-side output adjustment member 20 is connected directly to a pump-side control shaft 21a disposed on a pump-side swing axis perpendicular to the pump shaft 12, and to a free end of the pump-side piston. Alternatively, the pump-side control shaft 21a is operably connected to the pump-side control shaft 21a so as to swing about the pump-side swing axis in response to the rotation of the pump-side control shaft 21a about the axis in an indirectly engaged state; The pump-side movable swash plate 21b defines a range of movement of the pump-side piston according to the swing position about the pump-side swing axis, and the pump-side actuator 21c rotates the pump-side control shaft 21a about the axis. ing.

The pump-side actuator 21c may take various forms as long as its operation can be controlled by the control device 100, such as an electric/hydraulic actuator including a solenoid valve and a hydraulic cylinder, or an electric actuator including an electric motor.

The first pump capacity is, for example, a normal rotation side in which the pump side movable swash plate 21b rotates the motor shaft 16 in the normal rotation direction with respect to the rotation direction of the pump shaft 12 around the pump side swing axis. and the pump capacity when the pump is swung to the swing end of one of the reverse rotation sides (for example, the reverse side) to be rotated in the reverse direction, and the second pump capacity is the other of the normal rotation side and the reverse rotation side (for example, the reverse rotation side). This is the pump capacity when the pump is swung to the swing end (normal rotation side).

In this case, when the pump-side movable swash plate 21b is positioned at a neutral position around the pump-side rocking axis, the pump body 14 has a neutral capacity (zero capacity), and the pump shaft 12 rotates. The rotation of the motor shaft 16 becomes zero regardless of whether the motor shaft 16 is present or not.

In the present embodiment, the pump capacity when the pump side movable swash plate 21b is positioned at the swing end on the reverse side (maximum capacity on the reverse side) is the first pump capacity, and the pump side movable swash plate 21b The pump capacity when the pump is positioned at the normal rotation side swing end (normal rotation side maximum capacity) is the second pump capacity.

The motor main body 18 includes a motor-side cylinder block (not shown) supported by the motor shaft 16 so as not to be relatively rotatable around the axis, and housed in the motor-side cylinder block so that it cannot rotate relative to the axis and can move back and forth in the axial direction. This is a variable displacement axial piston machine having a motor-side piston (not shown), and the displacement is configured to change according to the range of movement of the motor-side piston. The piston motor type can take various forms, such as a swash plate type, an oblique shaft type, and a radial type.

The motor-side output adjustment member 25 adjusts the capacity of the motor body 18 between a predetermined low-speed motor capacity (L) and a predetermined high-speed motor capacity (H) that is smaller than the low-speed motor capacity. It is configured so that it can be changed.

As shown in FIG. 2, the motor-side output adjustment member 25 is directly connected to a motor-side control shaft 26a disposed on a motor-side swing axis perpendicular to the motor shaft 16, and a free end of the motor-side piston. or is operably connected to the motor-side control shaft 26a so as to swing about the motor-side swing axis in response to the rotation of the motor-side control shaft 26a about the axis in an indirectly engaged state; The motor-side movable swash plate 26b defines a range of movement of the motor-side piston according to the swing position about the motor-side swing axis, and the motor-side actuator 26c rotates the motor-side control shaft 26a about the axis. ing.

The motor-side actuator 26c may take various forms as long as its operation can be controlled by the control device 100, such as an electric/hydraulic actuator including a solenoid valve and a hydraulic cylinder, or an electric actuator including an electric motor.

As the capacity of the motor body 18 becomes smaller, the rotational speed of the motor shaft 16 relative to the pump shaft 12 increases.
Therefore, as the capacity of the motor body 18 is changed from a low speed motor capacity (large capacity) to a high speed motor capacity (small capacity), the rotational speed of the motor shaft 16 increases.

As shown in FIG. 1, the second end of the pump shaft 12 on the other end side in the axial direction is operatively connected to a PTO shaft 280 provided in the work vehicle 200.

Specifically, as shown in FIG. 1, the work vehicle 200 has the PTO shaft 280 and a PTO transmission structure forming a PTO system transmission path from the pump shaft 12 to the PTO shaft 280.

In the present embodiment, the PTO transmission structure includes a PTO drive shaft 260 that is connected to the second end of the pump shaft 12 on the other end side in the axial direction so as not to rotate relative to the axis, and a first PTO transmission shaft 261 and a second PTO transmission shaft 262 operatively connected via a reduction gear train 217; a PTO clutch mechanism 265 that engages and disengages power transmission from the first PTO shaft 261 to the second PTO shaft 262; It has a PTO transmission mechanism 270 that can change the rotational power of the second PTO transmission shaft 262 in multiple stages and transmit it to the PTO shaft 280.

As shown in FIG. 1, the planetary gear mechanism 30 includes a sun gear 32, a planet gear 34 that meshes with the sun gear 32, an internal gear 36 that meshes with the planet gear 34, and rotates the planet gear 34 about an axis. It has a carrier 38 that freely supports and rotates around the axis of the sun gear 32 in conjunction with the revolution of the planetary gear 34 around the sun gear 32, and the sun gear 32, the carrier 38, and the internal gear. 36 forms three planetary elements.

In the planetary gear mechanism 30, the reference rotational power from the drive source 210 is operatively inputted to the first element of the three planetary elements, and the HST output from the motor shaft 16 is operatively inputted to the second element. input, and outputs a composite rotational power that is a combination of the reference rotational power and the HST output from the third element, and further includes an HST output due to a change in volume of the pump body 14 from the first pump capacity to the second pump capacity. The composite rotational power output from the third element is configured to increase in speed according to a change in the rotational power.

As shown in FIG. 1, in this embodiment, the internal gear 36 acts as the first element, the sun gear 32 acts as the second element, and the carrier 38 acts as the third element. It is acting as.

Specifically, the sun gear 32, which acts as the second element, is supported by a sun gear shaft 32a so as not to be relatively rotatable, and the sun gear shaft 32a is operatively connected to the motor shaft 16 via a gear train 215.

A cylindrical power transmission shaft 36a is fitted onto the sun gear shaft 32a so as to be relatively rotatable.
The transmission shaft 36a is operatively connected to the PTO drive shaft 260 via a gear train 216.
The internal gear 36, which acts as the first element, is operatively connected to the transmission shaft 36a, and is connected to the drive source via the pump shaft 12, the PTO drive shaft 260, the gear train 216, and the transmission shaft 36a. Rotational power from 210 is input.

A cylindrical planetary output shaft 39 is relatively rotatably inserted into the sun gear shaft 32a at a different position in the axial direction from the transmission shaft 36a, and the carrier 38, which acts as the third element, It is connected to a planetary output shaft 39.

As shown in FIG. 2, the transmission structure 1 further includes a manually operable speed change operation member 110, a vehicle speed sensor 120 that directly or indirectly detects the vehicle speed of the work vehicle 200, and a capacity of the pump body 14. The motor sensor 140 includes a pump sensor 130 that directly or indirectly detects the capacity of the motor body 18, and a motor sensor 140 that directly or indirectly detects the capacity of the motor body 18.
Note that reference numeral 112 in FIG. 2 is a sensor that detects the operating state (operating position) of the speed change operating member 110.

The vehicle speed sensor 120 is configured to detect the rotational speed of any rotating member on the transmission path from the third element of the planetary gear mechanism 30 to the drive wheel 220, as long as the control device 100 can recognize the vehicle speed. can be done.

The pump sensor 130 and the motor sensor 140 can take various configurations as long as the control device 100 can recognize the capacities of the pump body 14 and the motor body 18, respectively.

The pump sensor 130 may be, for example, a sensor that detects the operating state of the pump-side actuator 21c or a sensor that detects the rotation angle of the pump-side control shaft 21a around the axis.
Similarly, the motor sensor 140 may be, for example, a sensor that detects the operating state of the motor-side actuator 26c or a sensor that detects the rotation angle of the motor-side control shaft 26a around the axis.

As shown in FIG. 1, the transmission structure 1 according to the present embodiment includes a forward/reverse switching mechanism 50 capable of switching the rotational direction of the rotational power output from the third element of the planetary gear mechanism 30 between forward and reverse directions. It is equipped with

That is, the HST 10 and the planetary gear mechanism 30 in the transmission structure 1 are set so that the rotational direction of the combined rotational power output from the third element is only on one side around the axis.

The forward/reverse switching mechanism 50 has a forward transmission state in which the combined rotational power operatively inputted from the third element is output as rotational power for forward movement of the vehicle, and a forward transmission state in which the combined rotational power is outputted as rotational power for backward movement of the vehicle. The vehicle is configured to be able to selectively take on a reverse transmission state in which it outputs as follows.

Specifically, as shown in FIG. 1, the transmission structure 1 has a running transmission shaft 45 downstream of the planetary gear mechanism 30 in the transmission direction.
The forward/reverse switching mechanism 50 includes a forward transmission mechanism 55F capable of transmitting the combined rotational power outputted from the third element to the travel transmission shaft 45 as rotational power for forwarding the vehicle; A reverse transmission mechanism 55R capable of operating and transmitting rotational power for reversing the vehicle to the traveling transmission shaft 45, a forward clutch mechanism 60F for engaging and disengaging power transmission from the forward transmission mechanism 55F, and a forward clutch mechanism 60F for engaging and disengaging power transmission from the forward transmission mechanism 55F; It includes a reverse clutch mechanism 60R that engages and disengages, and a forward/reverse switching actuator 65 that operates the forward clutch mechanism 60F and the reverse clutch mechanism 60R.

The forward transmission mechanism 55F includes a forward drive gear 56F that is relatively rotatably supported by the planetary output shaft 39, and a forward drive gear 56F that is relatively rotatably supported by the traveling power transmission shaft 45 while being meshed with the forward drive gear 56F. It has a forward driven gear 57F.

The reverse transmission mechanism 55R includes a reverse drive gear 56R that is relatively rotatably supported by the planetary output shaft 39, a reverse driven gear 57R that is relatively rotatably supported by the travel transmission shaft 45, and the reverse drive gear 56R. and a reverse gear train 58R that reverses the rotational power of and transmits it to the reverse driven gear 57R.

In this embodiment, the reversing gear train 58R includes a cylindrical intermediate shaft 58a that is relatively rotatably fitted onto the PTO drive shaft 260, and a cylindrical intermediate shaft 58a that is meshed with the reverse drive gear 56R. 58a, and a second intermediate gear 58c, which is supported in a relatively non-rotatable manner on the intermediate shaft 58a while being meshed with the reverse driven gear 57R. .

In this embodiment, the forward clutch mechanism 60F and the reverse clutch mechanism 60R are friction plate clutch mechanisms.

Specifically, as shown in FIG. 1, the forward clutch mechanism 60F includes a forward clutch housing 62F that is relatively non-rotatably supported by the traveling transmission shaft 45, and a forward clutch housing 62F that is relatively non-rotatably supported by the forward clutch housing 62F. a forward friction plate group 64F including a driven side friction plate and a forward drive side friction plate connected to the forward driven gear 57F in a state where it is opposed to the forward driven side friction plate and is non-rotatably connected to the forward driven gear 57F; and the forward friction plate group 64F. and a forward piston (not shown) that frictionally engages.

The reverse clutch mechanism 60R includes a reverse clutch housing 62R that is supported in a relatively non-rotatable manner on the travel transmission shaft 45, a reverse driven side friction plate that is supported on the reverse driven clutch housing 62R in a relatively non-rotatable manner, and the reverse driven side friction plate. A reverse friction plate group 64R including a reverse drive-side friction plate that is connected to the reverse driven gear 57R in a relatively non-rotatable manner while facing the reverse drive gear 57R, and a reverse piston that frictionally engages the reverse friction plate group 64R. are doing.
In this embodiment, the forward clutch housing 62F and the reverse clutch housing 62R are a single common housing.

The operation of the forward/reverse switching mechanism 50 is controlled by the control device 100.
In this embodiment, as shown in FIG. 2, the forward/reverse switching actuator 65 has a forward line 66F and a reverse line fluidly connected to the oil chamber of the forward clutch housing 62F and the oil chamber of the reverse clutch housing 62R, respectively. line 66R, and an electromagnetic valve 67 for switching the supply and discharge of pressure oil to and from the forward line 66F and the reverse line 66R.

The solenoid valve 67 has a forward position where it supplies pressure oil from a hydraulic source to the forward line 66F and fluidly connects the reverse line 66R to a drain line, and a forward position where it supplies pressure oil from the hydraulic source to the reverse line 66R. It can also have a reverse position in which the forward line 66F is fluidly connected to the drain line, and a power cutoff position in which the forward and reverse lines 66F and 66R are opened.

The operation of the electromagnetic valve 67 is controlled by the control device 100 in response to an operator's manual operation.
As shown in FIG. 2, in this embodiment, the speed change operation member 110 is in the form of a manual lever, and can be operated from a stop position (zero speed position) to the forward and reverse sides.
In this case, the control device 100 positions the solenoid valve 67 at the forward position and the reverse position in response to the operation of the speed change operation member 110 to the forward and reverse sides, respectively.

In this embodiment, the forward/reverse switching actuator 65 is an electric/hydraulic actuator, but instead, the forward/reverse switching actuator 65 may be an electric actuator such as an electric motor.

As shown in FIGS. 1 and 2, the transmission structure 1 includes an auxiliary transmission mechanism 70 that changes the composite rotational power of the planetary gear mechanism 30 that is operatively inputted in multiple stages and outputs it to the drive wheels 220. It is equipped with
In the present embodiment, the sub-transmission mechanism 70 is configured to perform two-stage gear shifting: a first gear, which is a low gear, and a second gear, which is a high gear.

In the present embodiment, the auxiliary transmission mechanism 70 is configured to perform two-step speed change between the traveling power transmission shaft 45 and the traveling output shaft 47 disposed downstream of the traveling power transmission shaft 45 in the transmission direction. It is configured.

Specifically, as shown in FIG. 1, the sub-transmission mechanism 70 includes a first gear train 71(1) capable of transmitting rotational power from the traveling transmission shaft 45 to the traveling output shaft 47 at a predetermined gear ratio. and a second speed gear train 71 capable of transmitting rotational power from the traveling power transmission shaft 45 to the traveling output shaft 47 at a gear ratio higher than the predetermined gear ratio (a gear ratio at which the traveling output shaft 47 rotates at high speed). (2), a first speed clutch mechanism 75(1) that engages and disengages power transmission from the first speed gear train 71(1), and a first speed clutch mechanism 75(1) that engages and disengages power transmission from the first speed gear train 71(2); It has a second speed clutch mechanism 75(2) that engages and disengages.

In the present embodiment, the first speed gear train 71(1) includes a first speed drive gear 72(1) supported by the traveling transmission shaft 45, and a first speed drive gear 72(1) supported by the traveling transmission shaft 45. 1) and a first speed driven gear 73(1) supported by the traveling output shaft 47 in a meshed state.

The second speed gear train 71(2) is supported by the traveling transmission shaft 45 and includes a second speed drive gear 72(2) having a larger diameter than the first speed drive gear 72(1). , a second speed driven gear 73 supported by the traveling output shaft 47 in a state of meshing with the second speed drive gear 72(2), and having a smaller diameter than the first speed driven gear 73(1). (2).

A drive side gear group formed by the first speed and second speed drive gears 72(1) and 72(2), and the first speed and second speed driven gears 73(1) and 73. One of the driven gear groups formed by (2) is supported by the corresponding shaft in a relatively non-rotatable manner, and the other is supported by the corresponding shaft in a relatively rotatable manner.

In addition, the first speed and second speed clutch mechanisms 75(1) and 75(2) engage and disengage gears that are relatively rotatably supported by the corresponding shafts. It is composed of

In this embodiment, as shown in FIG. 1, the driving side gear group is relatively rotatably supported by the corresponding traveling transmission shaft 45, and therefore, the first gear clutch mechanism 75(1) is configured to selectively engage and disengage the first speed drive gear 72(1) from the traveling transmission shaft 45, and the second speed clutch mechanism 75(2) 72(2) can be selectively engaged with and disengaged from the traveling transmission shaft 45.

In this embodiment, the first speed clutch mechanism 75(1) and the second speed clutch mechanism 75(2) are of a dog clutch type.

Specifically, the first speed clutch mechanism 75(1) includes a first speed slider that is supported on a corresponding shaft (in this embodiment, the traveling transmission shaft 45) so as to be non-rotatable and movable in the axial direction. and a first speed stage including one of the uneven portions provided on the opposing surface of the first speed step drive gear 72(1) and the other of the uneven engaging portions provided on the opposing surface of the first speed slider. It has an uneven portion.

The second speed clutch mechanism 75(2) includes a second speed slider supported by a corresponding shaft (in this embodiment, the traveling transmission shaft 45) so as to be non-rotatable and movable in the axial direction; a second gear stage uneven portion including one of the uneven parts provided on the opposing surface of the second gear stage drive gear 72 (2) and the other of the uneven engaging portions provided on the opposing surface of the second gear slider; have.
In this embodiment, the first gear slider and the second gear slider are a single common slider.

In this embodiment, as shown in FIG. 2, the operation of the auxiliary transmission mechanism 70 is controlled by the control device 100 in response to the operation of a manual lever-shaped auxiliary transmission operating member 115 that can be manually operated. It is configured.

That is, the sub-transmission mechanism 70 includes a sub-transmission mechanism formed by an electric/hydraulic actuator or an electric actuator that operates the first gear slider and the second gear slider (in this embodiment, the common slider). A speed change actuator is provided.
Then, the control device 100 controls the operation of the auxiliary transmission switching actuator based on a signal from a sensor 117 that detects the operation state (operation position) of the auxiliary transmission operation member 115.

Alternatively, the sub-shift switching actuator may be configured to be operated via a mechanical link in response to a manual operation on the sub-shift operating member 115.
The mechanical link operates the first gear slider and the second gear slider (in this embodiment, the common slider) by using mechanical movement of the sub-shift operation member 115 by human operation. It is configured as follows.
In this case as well, it is possible to configure the controller 100 to recognize the operating state (operating position) of the auxiliary shift operating member 115 using the sensor 117.

In the present embodiment, the work vehicle 200 includes a pair of main drive wheels that act as the drive wheels 220, a pair of main drive axles 250 that respectively drive the pair of main drive wheels, and a differential gear mechanism 300. The rotational power of the traveling output shaft 47 is differentially transmitted to the pair of main drive axles 250 via the differential gear mechanism 300.

The reference numeral 255 in FIG. 1 is a travel brake mechanism that selectively applies braking force to the main drive axle 250, and the reference numeral 310 is a travel brake mechanism that selectively applies braking force to the main drive axle 250. This is a differential lock mechanism that forcibly drives the 250 in synchronization.

The control structure by the control device 100 will be explained below.
3(a) and (b) show vehicle speed, tractive force, and HST capacity (pump body 14 and motor The relationship between the figure and the capacity of the main body 18 is shown.

As shown in FIGS. 3(a) and (b), the control device 100 is configured such that the vehicle speed detected by the vehicle speed sensor 120 is such that the motor body 18 has a low-speed motor capacity and the pump body 14 has a predetermined pump capacity. When the switching speed is lower than the switching speed that appears when the switching capacity is set, the speed change operation member 110 is operated while operating the motor side output adjustment member 25 so that the motor main body 18 is fixed at the low speed motor capacity. A normal control mode is executed in which the pump side output adjustment member 20 is operated so that the vehicle speed increases and decelerates in accordance with the speed increasing and decelerating operations.

Then, when the vehicle speed exceeds the switching speed, the control device 100 operates the pump side output adjustment member 20 so that the pump body 14 is fixed at the pump switching capacity, and controls the speed change. A high-speed control mode is executed in which the motor side output adjustment member 25 is operated so that the vehicle speed increases and decelerates in accordance with the speed increasing and decelerating operations of the operating member 110.

According to such a configuration, it is possible to expand the shiftable range of the HMT structure formed by the HST 10 and the planetary gear mechanism 30 while preventing vehicle speed changes from occurring when switching between normal operation control and high-speed operation control. .

Therefore, in the conventional transmission structure (see FIGS. 8 to 10), the range of the required maximum tractive force Tmax and the required maximum speed Smax, which could not be covered unless the auxiliary transmission mechanism 570 having three gear stages is provided, is covered by 2. This can be covered by simply providing the auxiliary transmission mechanism 70 for each gear, and the transmission structure of the work vehicle 200 can be made more compact and inexpensive.

In the present embodiment, the vehicle speed sensor 120 detects the rotational power in a state after the sub-transmission mechanism 70 performs multi-stage shifting (i.e., the traveling output shaft 47 or the downstream side of the traveling output shaft 47 in the transmission direction). The control device 100 is configured to detect the speed of a rotating member such as a drive axle 250 of It has a first gear switching speed (FIG. 3(a)) and a second gear switching speed (FIG. 3(b)), which are respectively used in the gear transmission state.

Instead, the vehicle speed sensor 120 detects the rotational power of the state before multi-speed shifting by the auxiliary transmission mechanism 70 (for example, the rotational power of the third element 38, the planetary output shaft 39, or the traveling transmission shaft 45). ), the control device 100 controls the operation using a single switching speed regardless of the gear engagement state of the sub-transmission mechanism 70. configured to do so.

As shown in FIGS. 3(a) and 3(b), in this embodiment, by setting the second pump capacity to the pump switching capacity, the speed of the planetary gear can be changed by changing the capacity of the pump body 14. Although the speed range of the combined rotational power of the mechanism 30 is expanded, the present invention is not limited to such a configuration. Can be set as switching capacity.

Further, as shown in FIGS. 3(a) and 3(b), in this embodiment, when the pump main body 14 is set to the first pump capacity, the combined rotational power of the planetary gear mechanism 30 is at zero speed ( The planetary gear mechanism 30 is set so that the vehicle speed is zero), thereby expanding the speed range of the combined rotational power of the planetary gear mechanism 30 that can be changed in speed by changing the capacity of the pump body 14. However, the present invention is not limited to such a configuration, and the planetary gear mechanism 30 is configured so that the resultant rotational power becomes zero speed at a predetermined pump capacity, such as a pump capacity of 90% of the first pump capacity. It is also possible to set

Further, in this embodiment, as shown in FIG. 2, the shift operation member 110 is operable from the stop position (zero speed position) to the forward and reverse sides. In place of the operating member 110, as shown in FIG. 4, it is also possible to use a foot pedal-shaped shift operating member 150 that can be operated only in one direction from the stop position (zero speed position).

In this case, an independent manual lever-type forward/reverse switching operation member 160 that is separate from the speed change operating member 150 is provided, and the control device 100 controls the operation state of the forward/reverse switching operation member 160 ( It is configured to control the operation of the forward/reverse switching mechanism 70 based on a signal from a sensor 162 that detects the operating position).

Embodiment 2
Other embodiments of the transmission structure according to the present invention will be described below with reference to the accompanying drawings.
FIGS. 5(a) and 5(b) show vehicle speed, traction force, and HST in a state where the sub-transmission mechanism 70 is engaged in the first gear and the second gear, respectively, in the transmission structure according to the present embodiment. The relationship with capacity (capacity of pump body 14 and motor body 18) is shown.
Note that a transmission schematic diagram of a working vehicle to which the transmission structure according to the present embodiment is applied is similar to that shown in FIG. 1, and a control block diagram is similar to that shown in FIG. 2.

The transmission structure according to the present embodiment differs from the transmission structure 1 according to the first embodiment only in the control structure executed by the control device 100.
Below, only the differences will be explained.

In the transmission structure 1 according to the first embodiment, the control device 100 includes:
- When the vehicle speed is below the switching speed that appears when the motor main body 18 is set to the low speed motor capacity and the pump main body 14 is set to the pump switching capacity, the motor main body 18 is fixed at the low speed motor capacity. The capacity of the pump main body 14 is changed from the first pump capacity side to the pump switching capacity side in response to the speed increase operation of the speed change operation member 110, and the capacity of the pump body 14 is changed in response to the speed change operation of the speed change operation member 110. changing the capacity of the main body 14 from the pump switching capacity side to the first pump capacity side to the pump switching capacity side;
- When the vehicle speed exceeds the switching speed, with the pump main body 14 fixed at the pump switching capacity, the capacity of the motor main body 18 is changed to the low speed motor capacity in response to the speed increasing operation of the speed change operation member 110. The capacity of the motor main body 18 is changed from the high speed motor capacity side to the low speed motor capacity side in response to the deceleration operation of the speed change operation member 110.

On the other hand, in the transmission structure according to the present embodiment, as shown in FIGS. 5(a) and 5(b), the control device 100
- When the vehicle speed is less than or equal to the switching speed that appears when the motor main body 18 is set to the low-speed motor capacity and the pump main body 14 is set to the predetermined pump switching capacity between the first and second pump capacities. The vehicle speed increases and decreases in accordance with speed increasing and decelerating operations of the speed change operation member 110 while operating the motor side output adjustment member 25 so that the motor main body 18 is fixed at a low speed motor capacity. Executing the normal control mode in which the pump-side output adjustment member 20 is operated as shown in FIG.
- When the vehicle speed exceeds the switching speed, the pump changes the capacity of the pump body 14 from the pump switching capacity side to the second pump capacity side in response to the speed increasing operation of the speed change operation member 110. Synchronizing the speed increasing operation of the side output adjusting member 20 and the speed increasing operation of the motor side output adjusting member 25 that changes the capacity of the motor main body 18 from a low speed motor capacity side to a high speed motor capacity side, and a deceleration operation of the pump side output adjustment member 20 that changes the capacity of the pump body 14 from the second pump capacity side to the pump switching capacity side in response to the deceleration operation of the speed change operation member 110, and the motor body. 18 from the high speed motor capacity side to the low speed motor capacity side.

Also in this embodiment having such a configuration, the same effects as in the first embodiment can be obtained.

As shown in FIGS. 5(a) and 5(b), in this embodiment, the pump switching capacity is a neutral capacity (neutral capacity) that makes the rotation of the motor shaft 16 zero regardless of the rotational state of the pump shaft 12. zero capacity).
According to such a configuration, it is possible to smoothly switch between the normal control mode and the high-speed control mode.

Note that the pump switching capacity can be set to a desired capacity other than the neutral capacity (zero capacity).
For example, when the first pump capacity is the maximum capacity on the reverse rotation side (-100%) and the second pump capacity is the maximum capacity on the forward rotation side (+100%), FIGS. 6(a) and (b) As shown, it is also possible to set the pump switching capacity to a normal rotation side intermediate capacity (for example, +50%) between the neutral capacity and the second pump capacity.

Embodiment 3
Hereinafter, further embodiments of the transmission structure according to the present invention will be described with reference to the accompanying drawings.
7(a) and (b) show vehicle speed, tractive force, and HST in a state where the sub-transmission mechanism 70 is engaged in the first gear and the second gear, respectively, in the transmission structure according to the present embodiment. The relationship with capacity (capacity of pump body and motor body) is shown.
Note that a transmission schematic diagram of a working vehicle to which the transmission structure according to the present embodiment is applied is similar to that shown in FIG. 1, and a control block diagram is similar to that shown in FIG. 2.

The transmission structure according to this embodiment differs from the transmission structure according to the first and second embodiments only in the control structure executed by the control device 100.

That is, in the transmission structure according to the present embodiment, as shown in FIGS. 7(a) and (b), the control device controls the vehicle speed so that the motor main body 18 has a low-speed motor capacity and the pump main body 14 The switching speed that appears when the pump switching capacity is set to a predetermined pump switching capacity (the first gear switching speed when the sub-transmission mechanism 70 is engaged in the first gear (FIG. 7(a)), and the sub-shift When the mechanism 70 is engaged in the second gear, the motor-side output adjustment member is adjusted so that the motor main body 18 is fixed at the low-speed motor capacity when the speed is less than the second gear switching speed (FIG. 7(b)). 25, the pump is configured to increase the vehicle speed by changing the capacity of the pump main body 14 from the first pump capacity to the pump switching capacity side in response to the speed increasing operation of the speed change operation member 110. The vehicle speed is reduced by activating the side output adjustment member 20 and changing the capacity of the pump body 14 from the pump switching capacity side to the first pump capacity side in response to the deceleration operation of the speed change operation member 110. A normal control mode is executed in which the pump side output adjustment member 20 is operated so as to cause the pump side output adjustment member 20 to operate.

In this embodiment, as shown in FIGS. 7(a) and 7(b), by setting the second pump capacity to the pump switching capacity, the speed of the planetary gear can be changed by changing the capacity of the pump body 14. Although the speed range of the combined rotational power of the mechanism 30 is expanded, the present invention is not limited to such a configuration. Can be set as switching capacity.

Then, when the vehicle speed reaches the switching speed from the low speed side, the control device 100 operates the motor side output adjustment member 25 so that the capacity of the motor main body 18 changes from the low speed motor capacity to the high speed motor capacity. At the same time, the pump-side output adjustment member 20 is operated so that the capacity of the pump body 14 becomes a pump adjustment capacity that can maintain the vehicle speed at the switching speed when the motor body 18 is set to the high-speed motor capacity. Executes time switching control mode.

Furthermore, when the vehicle speed exceeds the switching speed, the control device 100 operates the motor-side output adjustment member 25 so that the motor main body 18 is fixed at the high-speed motor capacity, and operates the speed change operation member. In response to the speed increasing operation of step 110, the pump side output adjustment member 20 is operated to increase the vehicle speed by changing the pump capacity from the pump adjustment capacity side to the second pump capacity side, and A high speed mode in which the pump side output adjustment member 20 is operated to reduce the vehicle speed by changing the pump capacity from the second pump capacity side to the pump adjustment capacity side in response to the deceleration operation of the speed change operation member 110. Run control mode.

Then, when the vehicle speed reaches the switching speed from the high speed side, the control device 100 operates the motor side output adjustment member 25 so that the capacity of the motor main body 18 changes from the high speed motor capacity to the low speed motor capacity. At the same time, a normal transition switching control mode is executed in which the pump side output adjustment member 20 is operated so that the capacity of the pump main body 14 changes from the pump adjustment capacity to the pump switching capacity.

Also in this embodiment having such a configuration, the same effects as in the first and second embodiments can be obtained.

1 Transmission structure 10 HST
12 Pump shaft 14 Pump body 16 Motor shaft 18 Motor body 20 Pump-side output adjustment member 25 Motor-side output adjustment member 30 Planetary gear mechanism 50 Forward/reverse switching mechanism 70 Sub-transmission mechanism 100 Control device 110 Shift operation member 120 Vehicle speed sensor 130 Pump sensor 140 Motor sensor 160 Forward/forward switching operation member 200 Work vehicle 210 Drive source

Claims (8)

A transmission structure inserted in a drive system transmission path of a work vehicle,
A pump shaft that operatively inputs rotational power from a drive source of the work vehicle, a pump body supported by the pump shaft, and a capacity of the pump body that can be varied steplessly between a first and a second pump capacity. A pump-side output adjustment member, a motor shaft, a motor body supported by the motor shaft and fluidly connected to the pump body, and a capacity of the motor body that is set to a low-speed motor capacity and a high-speed motor capacity smaller than the low-speed motor capacity. an HST having a motor side output adjustment member that can be changed between;
has first to third elements, and synthesizes a reference rotational power operatively input to the first element from the drive source and an HST output operatively input to the second element from the motor shaft. , a planetary gear mechanism that outputs synthetic rotational power from the third element, wherein the output of the third element is adjusted according to a change in the HST output due to a change in the HST output from the first pump capacity to the second pump capacity of the pump body. a planetary gear mechanism configured to increase speed;
a manually operable speed change operation member;
a vehicle speed sensor that directly or indirectly detects the vehicle speed of the work vehicle;
a pump sensor that directly or indirectly detects the capacity of the pump body;
a motor sensor that directly or indirectly detects the capacity of the motor body;
a control device that controls the operation of the pump-side output adjustment member and the motor-side output adjustment member,
The control device includes:
The vehicle speed detected by the vehicle speed sensor is a switching speed that appears when the motor body is set to a low-speed motor capacity and the pump body is set to a predetermined pump switching capacity between the first and second pump capacities. In the following cases, while operating the motor-side output adjustment member so that the motor body is fixed at a low-speed motor capacity, the vehicle speed increases and decreases in accordance with the speed increase and deceleration operations of the speed change operation member. activating the pump-side output adjustment member so as to
When the vehicle speed exceeds the switching speed, the pump side output changes the capacity of the pump main body from the pump switching capacity side to the second pump capacity side in response to the speed increasing operation of the speed change operation member. synchronously performing a speed increase operation of the adjustment member and a speed increase operation of the motor side output adjustment member that changes the capacity of the motor main body from a low speed motor capacity side to a high speed motor capacity side, and the speed change operation A deceleration operation of the pump side output adjustment member changes the capacity of the pump body from the second pump capacity side to the pump switching capacity side in accordance with the deceleration operation of the member, and the capacity of the motor body is changed to the high speed motor capacity side. synchronously with a deceleration operation of the motor-side output adjustment member to change the output from a low-speed motor capacity to a low-speed motor capacity ;
The transmission structure is characterized in that the pump switching capacity is a neutral capacity that makes the rotation of the motor shaft zero regardless of the rotational state of the pump shaft. A transmission structure inserted in a drive system transmission path of a work vehicle,
A pump shaft that operatively inputs rotational power from a drive source of the work vehicle, a pump body supported by the pump shaft, and a capacity of the pump body that can be varied steplessly between a first and a second pump capacity. A pump-side output adjustment member, a motor shaft, a motor body supported by the motor shaft and fluidly connected to the pump body, and a capacity of the motor body that is set to a low-speed motor capacity and a high-speed motor capacity smaller than the low-speed motor capacity. an HST having a motor side output adjustment member that can be changed between;
has first to third elements, and synthesizes a reference rotational power operatively input to the first element from the drive source and an HST output operatively input to the second element from the motor shaft. , a planetary gear mechanism that outputs synthetic rotational power from the third element, wherein the output of the third element is adjusted according to a change in the HST output due to a change in the HST output from the first pump capacity to the second pump capacity of the pump body. a planetary gear mechanism configured to increase speed;
a manually operable speed change operation member;
a vehicle speed sensor that directly or indirectly detects the vehicle speed of the work vehicle;
a pump sensor that directly or indirectly detects the capacity of the pump body;
a motor sensor that directly or indirectly detects the capacity of the motor body;
a control device that controls the operation of the pump-side output adjustment member and the motor-side output adjustment member,
The control device includes:
When the vehicle speed detected by the vehicle speed sensor is less than the switching speed that appears when the motor body is set to a low-speed motor capacity and the pump body is set to a predetermined pump switching capacity, the motor body While operating the motor-side output adjustment member so that the capacity is fixed at a low-speed motor capacity, the pump-side output adjustment member is operated so that the vehicle speed increases and decelerates in response to speed increase and deceleration operations of the speed change operation member. activate it,
When the vehicle speed reaches the switching speed from the low speed side, the motor side output adjustment member is operated so that the capacity of the motor body changes from the low speed motor capacity to the high speed motor capacity, and at the same time, the motor body changes from the high speed side to the high speed side. operating the pump side output adjustment member so that the capacity of the pump body becomes a pump adjustment capacity that can maintain the vehicle speed at the switching speed in a state where the motor capacity is set;
When the vehicle speed exceeds the switching speed, the motor side output adjustment member is operated so that the motor body is fixed at the high speed motor capacity, and the speed change operation member is operated in response to speed increase and deceleration operations. actuating the pump-side output adjustment member so that the vehicle speed increases and decreases;
When the vehicle speed reaches the switching speed from the high speed side, the motor side output adjustment member is operated so that the capacity of the motor body changes from the high speed motor capacity to the low speed motor capacity, and at the same time the capacity of the pump body is changed. A transmission structure characterized in that the pump side output adjustment member is operated so that the pump output adjustment member changes from a pump adjustment capacity to a pump switching capacity. 3. The transmission structure according to claim 2 , wherein the pump switching capacity is a second pump capacity. A forward transmission state in which the composite rotational power operatively inputted from the third element is outputted as rotational power for moving the vehicle forward, and a reverse transmission state in which the composite rotational power is outputted as rotational power for the vehicle to move backward are selectively selected. Equipped with a forward and backward switching mechanism,
In the planetary gear mechanism, when the motor body is set to a low speed motor capacity and the pump body is set to a predetermined planetary zero output capacity, the output of the third element becomes zero speed, and the pump body is set to a planetary zero output capacity. The output of the third element is set so that as the capacity is changed from the output capacity to the second pump capacity, the output of the third element increases from zero speed to one side around the axis,
The control device operates the motor side output adjustment member so that when the speed change operation member is located at the zero speed position, the motor body has a low speed motor capacity, and the pump body has a planetary zero output capacity. 4. The transmission structure according to claim 1, wherein the pump-side output adjusting member is operated so that the pump side output adjustment member is operated so as to achieve the following . 5. The transmission structure according to claim 4 , wherein the planetary zero output capacity is a first pump capacity. The speed change operation member is operable from a zero speed position to a forward drive side and a reverse drive side,
The control device operates the forward/reverse switching mechanism so that the forward/reverse switching mechanism enters a forward transmission state and a reverse transmission state, respectively, in response to an operation of the shift operating member from a zero speed position to a forward drive side and a reverse drive side. The transmission structure according to claim 4 or 5 , characterized in that the transmission structure is operated. Equipped with a manually operable forward and backward switching operation member,
The control device operates the forward/reverse switching mechanism so that the forward/reverse switching mechanism is in a forward transmission state and a reverse transmission state in response to an operation on the forward/reverse switching operation member. 5. Transmission structure according to 4 or 5 . 8. The transmission structure according to claim 1, further comprising an auxiliary transmission mechanism that shifts the rotational power operatively input from the third element in multiple stages.

Images