JP4258578B2 - Vehicle transmission structure with HST - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmission structure in a vehicle such as a work vehicle provided with an HST (hydrostatic continuously variable transmission).
[0002]
[Prior art]
It is known to branch the front wheel drive HST output and output the rear wheel drive force. Such a transmission structure is disclosed, for example, in JP-A-9-66749.
[0003]
However, as shown in FIG. 10, the conventional transmission structure is a vehicle in which the differential gear device 140, the HST 120, and the drive source 110 are arranged from the front to the rear of the vehicle, and between the HST 120 and the differential gear device 140. Since the transmission 130 is provided in between, and the front wheel driving force and the rear wheel driving force are branched in the transmission 130, there are the following disadvantages. In the figure, reference numeral 131 denotes a front wheel drive shaft, which is connected to a differential gear device 140 that drives the front axle 151. Reference numeral 132 denotes a rear wheel drive shaft, which is connected to the rear axle 152 via a transmission shaft (not shown).
[0004]
That is, in the transmission structure shown in FIG. 10, the transmission 130 is indispensable, resulting in an increase in cost due to an increase in the number of parts. In addition, the provision of the transmission 130 has a problem that the reliability of the vehicle is lowered. That is, since the transmission 130 serves as a transmission path for both the front wheel driving force and the rear wheel driving force, a large load is applied to the components of the transmission. Therefore, components such as gears are easily damaged, and this leads to a decrease in the reliability of the vehicle. Further, since the transmission 130 is disposed in a limited space between the differential gear device 140 and the HST 130, it is difficult to perform the mounting operation, thereby deteriorating the assembly efficiency of the entire vehicle. there were.
[0005]
[Problems to be solved by the invention]
The present invention has been made to solve the above-mentioned problems, and is a transmission structure for a front wheel and a rear wheel in a work vehicle equipped with an HST, and an excessive load is imposed on the members constituting the transmission structure. The object is to provide a simple and inexpensive transmission structure that can be prevented.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention transmits a power from a drive source installed in a vehicle body to a differential gear device for driving a front axle via an HST disposed in front of the drive source. The HST includes a hydraulic pump having a pump shaft extending in the longitudinal direction of the vehicle, a hydraulic motor having a motor shaft arranged in parallel with the pump shaft, and cooperating with the hydraulic pump; A housing for housing the hydraulic pump and the hydraulic motor, wherein the hydraulic pump inputs power from the drive source from a rear end portion of the pump shaft, and the hydraulic motor drives a front wheel to the differential gear device. outputting a force from the motor shaft front end, and the rear wheel drive force is configured to be output from the motor shaft rear end portion, detachable to a rear portion of the HST housing A case having an inner part to be mounted and an outer part extending from the inner part to one side in the vehicle width direction and positioned away from the housing from the one side; and a front end part accommodated in the inner part of the case Is connected to the motor shaft so as not to rotate relative to the axis, accommodated in an outer portion of the case, and a rear wheel drive shaft with a rear end protruding rearward from the case, and accommodated in the case. A transmission structure further comprising a rear wheel drive device having a power transmission mechanism for transmitting power from the input shaft to the rear wheel drive shaft is provided.
[0008]
The outer portion of the case has a bulging portion that bulges forward, and the bulging portion includes a clutch mechanism that constitutes a part of the power transmission mechanism. An outer ring body that is rotatably supported by the rear wheel drive shaft and receives power from the input shaft, and is interposed between the outer ring body and the rear wheel drive shaft, and only forward force is transmitted to the rear wheel drive shaft. And a lock member that is supported by the rear wheel drive shaft so as not to rotate relative to the rear wheel and is slidable in the axial direction, and is detachable from the outer ring body. .
[0009]
Preferably, the housing and the case communicate with each other, and a suction path for introducing the oil in the housing into the case and a discharge path for discharging the oil in the case can be provided.
[0010]
More preferably, the discharge path communicates with the case and the casing of the differential gear device for driving the front axle , and the suction path further includes a meshing point of a gear constituting the power transmission mechanism. The gear that forms the meshing point communicates with the case on the downstream side in the rotational direction when the vehicle moves forward, and the discharge path is located upstream of the meshing point and on the upstream side in the rotational direction when the gear moves forward with the vehicle. It can be communicated to.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a transmission structure according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic perspective view of a vehicle to which the transmission structure according to the present embodiment is applied, and FIG. 2 is a view as seen from an arrow A in FIG. In the figure, reference numeral 10 denotes an HST, and power is input from an engine (not shown) disposed behind the HST. The front wheel driving force is transmitted to the front axle 61 via the differential gear device 50 disposed in front of the HST 10. On the other hand, the rear wheel driving force is transmitted from the rear wheel drive device 20 provided behind the HST 10 to the rear axle 62 via the transmission shaft 63. In the figure, 40 is a hydraulic block, 45 is a charge pump, 31 is a PTO shaft for mower drive disposed in front of the vehicle, and 35 is a mower drive pump.
[0012]
FIG. 3 is a developed cross-sectional view of a portion where the HST, PTO unit, and rear wheel drive device are disposed, and FIGS. 4 and 5 are cross-sectional views taken along lines BB and CC in FIG. 3, respectively.
[0013]
The HST 10 includes a housing 11 and a hydraulic pump 12 and a hydraulic motor 15 accommodated in the housing. The housing 11 includes a main body portion 11a located at substantially the same position as the differential gear device 50 in the vehicle body width direction, and an extending portion 11b extending leftward from the main body portion 11a. The hydraulic pump 12 and the hydraulic motor 15 are accommodated in the housing body 11a. On the other hand, a PTO unit 30 for mower driving is accommodated in the housing extension 11b. In the present embodiment, the left side and the right side are the left side and the right side, respectively, facing the front of the vehicle.
[0014]
The main body portion 11a of the housing is open at the front and closed at the rear by the rear wall, while the extending portion 11b is closed at the front by the front wall and opened at the rear. The front opening of the main body 11a is closed by a hydraulic block 40, and the rear opening of the extending part 11b is closed by a closing member 19, thereby obtaining the following effects. That is, in the configuration having the extending portion 11b in addition to the main body portion 11a, if the front of both the main body portion 11a and the extending portion 11b is an opening, the length in the vehicle body width direction of the hydraulic block 40 that closes the opening is increased. This causes a cost increase due to an increase in materials and the like. Since the hydraulic block 40 needs to have a certain thickness in order to secure the amount of oil, the amount of material that increases by increasing the length in the width direction of the block 40 increases. The housing 11 according to the above configuration can be easily cast by pulling the mold of the main body 11a forward and pulling the mold of the extension 11b backward.
[0015]
The hydraulic pump 12 has a pump shaft 13 extending along the longitudinal direction of the vehicle body, as shown in FIG. 6, which is a sectional view taken along the line DD in FIGS. 3 and 3. The rear end of the pump shaft 13 projects rearward from the housing 11 and is connected to an output shaft of an engine (not shown). The front end of the pump shaft 13 protrudes forward from the housing 11, penetrates the hydraulic block 40, and enters the case of the charge pump 45. Further, a gear 14 is supported on a portion of the pump shaft 13 located behind the hydraulic pump main body so as not to be relatively rotatable.
[0016]
The PTO unit 30 is supported by the front wall of the housing extension 11b and the closing member 19 as shown in FIG. 3 and FIG. 8 which is a cross-sectional view taken along line FF in FIG. Has a PTO shaft 31 projecting forward, a driven member 32 supported relative to the PTO shaft so as not to rotate relative to the PTO shaft, and to be rotatable relative to the PTO shaft 31 and not slidable in the axial direction. And a driving side member 33 supported and connected to the gear 14. The clutch ON / OFF operation of the PTO unit is performed by the hydraulic pressure of the hydraulic oil sent from the charge pump 45 through the oil passages formed in the hydraulic block 40, the housing 11 and the closing member 19.
[0017]
On the other hand, the hydraulic motor 15 includes a motor shaft 16 disposed substantially parallel to the right side of the pump shaft 13 as shown in FIG. 7 which is a cross-sectional view taken along line EE in FIGS. Have. A front end portion of the motor shaft 16 projects forward from the housing 11, passes through the hydraulic block 40, and is connected to the input gear 51 of the differential gear device 50. And the rear-end part of this motor shaft 16 protrudes back from the said housing 11, and it has the structure which can take out a rear-wheel drive force from this protrusion part.
[0018]
Thus, the following effects can be obtained by connecting the front end portion of the motor shaft 16 to the differential gear device 50 that drives the front axle and projecting the rear end portion rearward from the housing 11. That is, in the conventional transmission structure, a transmission is provided between the HST and the differential gear device, and the front wheel driving force and the rear wheel driving force are branched in the transmission (see FIG. 10). Therefore, a transmission is indispensable, and the cost increases due to an increase in the number of parts. In addition, since both the front wheel driving force and the rear wheel driving force are output via the transmission, the load applied to the components of the transmission is large and the components of the transmission are easily damaged. Therefore, there is a risk of reducing the reliability of the vehicle. Furthermore, since the transmission was installed in a limited space between the HST and the differential gear device, the assembly efficiency was poor.
[0019]
On the other hand, in the present embodiment, as described above, the front wheel driving force and the rear wheel driving force are extracted from the front end portion and the rear end portion of the motor shaft 16, respectively. Therefore, the cost can be reduced and the vehicle reliability can be improved by reducing the number of parts. Further, since the rear wheel driving force is extracted from the rear of the HST 10 having a relatively large space, the assembly efficiency of the vehicle can be improved as compared with the conventional transmission structure. Further, since the rear wheel driving force is taken out from the rear end portion of the motor shaft 16, the connecting shaft with the rear axle can be shortened as compared with the conventional transmission structure.
[0020]
Further, in the present embodiment, the pump 13 shaft and the motor shaft 16 are arranged in substantially the same horizontal plane as shown in FIG. 3 and FIG. The engine to be connected can be installed below, and the vehicle stability is improved by downsizing the vehicle and lowering the center of gravity of the vehicle. That is, in the conventional configuration in which the pump shaft connected to the engine drive shaft is disposed above the motor shaft, the engine is disposed above the vehicle body, thereby increasing the size of the vehicle and the center of gravity of the vehicle. Although the vehicle stability is deteriorated due to the rise, such an inconvenience does not occur in the present embodiment.
[0021]
On the other hand, a rear wheel drive device 20 is disposed near the right side behind the HST 10. The rear wheel drive device 20 has a case 21 connected to the housing 11. In the case, the inner portion 21a overlaps the portion of the rear wall of the housing that bears the rear end of the motor shaft, and the outer portion 21b extends from the inner portion to the right and is detached from the housing 11 in the vehicle width direction. It is like that. The outer portion 21b has a bulging portion 21c that bulges forward.
[0022]
The case 21 supports an input shaft 22, an intermediate shaft 23 and a rear wheel drive shaft 24 along the longitudinal direction of the vehicle in order from the inner portion 21a toward the outer portion 21b. The front end of the input shaft 22 is connected to the motor shaft 16 so as not to rotate relative to the motor shaft 16. Further, an input gear 25 is provided on the input shaft 22 so as not to be relatively rotatable. An intermediate gear 26 that meshes with the input gear 25 is supported on the intermediate shaft 23 so as to be relatively rotatable.
[0023]
On the other hand, the rear wheel drive shaft 24 has a rear end portion protruding rearward from the case 21 and is configured such that a rear wheel drive force can be taken out from this portion. Further, a clutch mechanism 27 is supported on the rear wheel drive shaft 24 by utilizing the bulging portion 21c of the case. In the present embodiment, the input gear 25, the intermediate shaft 23, the intermediate gear 26, and the transmission mechanism 27 constitute a power transmission mechanism that transmits power from the input shaft 22 to the rear wheel drive shaft 24.
[0024]
The clutch mechanism 27 includes a one-way clutch 28 and a lock member 29 of the clutch. The one-way clutch 28 is interposed between an outer ring body 28a having a gear meshing with the intermediate gear 26 on the outer periphery, and between the outer ring body 28a and the rear wheel drive shaft 24, and only the forward force is transmitted to the rear wheel drive shaft 24. And a clutch element 28b for transmitting to the motor. On the other hand, the lock member 29 is provided with a shifter 29a which is provided on the rear wheel drive shaft 24 so as not to rotate relative to the rear wheel and is slidable in the axial direction.
[0025]
The clutch mechanism 27 prevents the rear wheel from slipping due to a difference in turning radius between the front wheel and the rear wheel during forward travel, and provides four-wheel drive during reverse travel. That is, when the vehicle moves forward, the one-way clutch 28 is operated to allow the rear wheel drive shaft 24 to rotate faster than the outer ring body 28a. Therefore, it is possible to prevent the rear wheel from slipping due to a difference in turning radius between the front wheel and the rear wheel. On the other hand, when the vehicle moves backward, the one-way clutch 28a is locked by the lock member 29, so that the rear wheel driving force can be output effectively.
[0026]
Further, in the present embodiment, the clutch mechanism 27 is installed on the right side of the HST 10 using the empty space existing behind the differential gear device 50. The vehicle will not be large.
[0027]
Further, since the rear wheel drive shaft 24 is displaced to the right from the motor shaft 22 as described above, the engine can be installed below. That is, when the rear wheel drive shaft 24 is arranged coaxially with the motor shaft 22, in order to avoid a conflict between the connecting shaft 63 connecting the rear wheel drive shaft 24 and the rear axle 62 and the engine, Must be installed upward (see FIG. 1). Such an upward installation of the engine leads to an increase in the size of the vehicle and a deterioration in running stability due to an increase in the center of gravity of the vehicle. On the other hand, if the rear wheel drive shaft 24 is displaced from the axial position of the motor shaft 22 to the right as in the present embodiment, the connecting shaft can be connected even if the engine is installed at substantially the same height as the HST 10. There is no interference between the engine 63 and the engine. Therefore, there is no inconvenience that the size of the vehicle is increased and the running stability is deteriorated.
[0028]
Further, in the present embodiment, a lubricating oil suction passage 41 that communicates the inside of the housing 11 and the inside of the case 21, and a lubricating oil discharge passage 42 that communicates the inside of the case 21 and the inside of the casing 52 of the differential gear device. And.
[0029]
The suction passage 41 communicates with the inside of the case 21 in the vicinity of the meshing point of the plurality of gears in the rear wheel drive device 20 and downstream in the rotation direction when the gear that forms the meshing point moves forward. . On the other hand, the discharge passage 42 communicates with the inside of the case 21 in the vicinity of the meshing point and upstream in the rotation direction of the gear that forms the meshing point. In the present embodiment, as well represented in FIG. 4, the suction hole 41 is in the vicinity of the meshing point 43 between the input gear 25 and the intermediate gear 26 and downstream in the rotational direction when these gears are moving forward. Is connected to the case 21 and the discharge hole 42 is connected to the case 21 upstream, so that the lubricating oil of the rear wheel drive device 20 and the hydraulic oil of the HST 10 can be used together, and the temperature of the HST hydraulic oil is increased. Is cheaply and effectively prevented. The reason is as follows.
[0030]
That is, consider the flow of oil in the case 21 in the vicinity of the meshing point of the gear. For example, in FIG. 4, when the rotation direction of the input gear 25 when the vehicle moves forward is the counterclockwise direction, the intermediate gear 26 meshing with the input gear 25 rotates clockwise. Therefore, on the downstream side in the rotational direction of the input gear 25 and the intermediate gear 26 (X portion in FIG. 4), oil flows inward of the case 21 as the gears 25 and 26 rotate (solid arrow in FIG. 4). ). On the other hand, on the upstream side in the rotation direction (Y portion in FIG. 4), the oil flows outward from the case 21 as the gears 25 and 26 rotate (broken arrows in FIG. 4). Therefore, as described above, if the suction hole 41 and the discharge hole 42 are provided on the downstream side and the upstream side in the rotation direction, respectively, the hydraulic oil in the housing 11 is supplied to the case 21 by the pump action by the rotation of the gears 25 and 26. It is possible to efficiently inhale and the lubricating oil in the case 21 can be efficiently discharged. The reason why the rotation at the time of forward movement is set as a reference is that the vehicle is usually moved forward for a longer time than the backward movement.
[0031]
Further, in the present embodiment, the communication position of the suction path 41 and the discharge path 42 to the case 21 is determined with reference to the input gear 25 and the intermediate gear 26, but naturally the communication position is within the case 21. Any gear may be used as a reference. For example, the suction path 41 may be provided downstream in the rotation direction of the input gear 25 and the intermediate gear 26, and the discharge path 42 may be provided upstream in the rotation direction of the intermediate gear 26 and the outer ring body 28a.
[0032]
Further, it is preferable that the suction path 41 is opened in the case 21 on the lower side in the vertical direction, and the discharge path 42 is opened in the case 21 on the upper side in the vertical direction. By forming in this way, the oil in the housing 11 can be easily sucked into the case 21 and the oil is supplied from above the differential gear device 50 via the oil passage 42a formed in the upper wall of the housing. It becomes easy to discharge. Therefore, the oil discharged from the case 21 can be effectively used as the lubricating oil for the differential gear device.
[0033]
By the way, instead of communicating the discharge hole 42 with the casing 53 of the differential gear device, it is possible to communicate with the housing 11. In such a case, oil that has been sucked into the case 21 from the housing 11 and used as lubricating oil in a limited space in the case 21 is returned to the HST 10 again. The oil temperature in the housing 11 is raised. The increase in the oil temperature leads to a change in the pressure of the HST hydraulic oil, and this can be solved by additionally providing a device for cooling the oil in the housing 11.
[0034]
On the other hand, in the present embodiment, oil sucked from the housing 11 and used as lubricating oil is discharged to the differential gear device 50. The oil discharged to the differential gear device 50 is sucked by the charge pump 45 through the filter 55 (see FIGS. 6 to 8) and returned to the hydraulic circuit of the HS 10T. Thus, by circulating the oil that has been used as the lubricating oil for the rear wheel drive device and has reached a high temperature, the oil can be naturally cooled. Therefore, in this embodiment, it is not necessary to provide the above-described cooling device.
[0035]
In the present embodiment, rear wheel drive device 20 is housed in case 21 that is detachably attached to HST housing 11, but the present invention is not limited to such a form. For example, as shown in FIG. 9, a bulging portion 11c 'is provided on the right side of the HST housing, and a lid member 21' is detachably attached to the housing 11 'so that the bulging portion 11c' and the rear wall of the housing 11 ' It is also possible to accommodate the rear wheel drive device 20 in a space defined by the lid member 21 '. In such an embodiment, the bulging portion 11c ′ formed in the HST housing, the housing rear wall, and the lid member 21 ′ correspond to the case 21 in the present embodiment.
[0036]
Furthermore, the relationship between the left side and the right side in the present embodiment can of course be reversed.
[0037]
【The invention's effect】
According to the present invention, there is provided a transmission structure in a vehicle that transmits power from a drive source installed in a vehicle body to a differential gear device for driving a front axle via an HST disposed in front of the drive source. Since the front end of the motor shaft of the HST protrudes forward from the housing of the HST and is connected to the differential gear device, and the rear end of the motor shaft protrudes from the rear of the housing, the HST and the differential A transmission that is arranged between the gear device and branches the front wheel driving force and the rear wheel driving force can be made unnecessary, whereby the cost can be reduced. Furthermore, by eliminating the need for the transmission, which is a transmission path for both the front wheel driving force and the rear wheel driving force, it is possible to improve vehicle reliability and assembly efficiency.
[0038]
Further, if a rear wheel drive device extending in one vehicle width direction is provided behind the HST housing and a rear wheel drive shaft is provided at one end in the vehicle width direction of the rear wheel drive device, A drive source disposed behind can be installed below. Therefore, it is possible to reduce the size of the vehicle and improve the running stability.
[0039]
In addition, a bulging portion that bulges forward is provided at one end in the vehicle width direction of the rear wheel drive device, and the vehicle reverses while allowing the rear wheels to rotate faster than the front wheels when the vehicle moves forward. In some cases, if a clutch mechanism that provides the same speed rotation of the front and rear wheels is provided, an increase in the size of the vehicle due to the installation of the clutch mechanism can be prevented.
[0040]
Furthermore, if the housing and the case communicate with each other, and a suction path for introducing drain oil in the housing into the case and a discharge path for discharging the oil in the case are provided, It can also be used as a lubricant for the rear wheel drive device.
[0041]
Further, the discharge path communicates the case and the casing of the differential gear device, and further, the suction path of the gear that forms the mesh point from the mesh point of the gear that constitutes the power transmission mechanism. The HST is communicated with the case on the downstream side in the rotational direction when the vehicle moves forward, and the discharge path communicates with the case on the upstream side in the rotational direction when the vehicle moves forward from the meshing point. It is possible to effectively suppress an increase in the oil temperature in the HST housing while combining the working oil and the lubricating oil for the rear wheel drive device.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a vehicle to which a transmission structure according to a preferred embodiment of the present invention is applied.
FIG. 2 is a view taken in the direction of arrow A in FIG.
FIG. 3 is an exploded cross-sectional view of a portion where the HST, PTO unit, and rear wheel drive device are disposed in the embodiment.
4 is a cross-sectional view taken along line BB in FIG. 3. FIG.
FIG. 5 is a cross-sectional view taken along the line CC in FIG. 3;
FIG. 6 is a cross-sectional view taken along the line DD in FIG.
FIG. 7 is a cross-sectional view taken along line EE in FIG. 3;
FIG. 8 is a cross-sectional view taken along line FF in FIG. 3;
FIG. 9 is a cross-sectional view of a transmission structure according to another embodiment of the present invention.
FIG. 10 is a schematic diagram of a transmission structure according to the prior art.
[Explanation of symbols]
10 HST
11 Housing 12 Hydraulic pump 13 Pump shaft 15 Hydraulic motor 16 Motor shaft 20 Rear wheel drive device 21 Case 24 Rear wheel drive shaft 27 Clutch mechanism 30 PTO unit 40 Hydraulic block 50 Differential gear device 52 Casing

Claims (4)

A transmission structure in a vehicle for transmitting power from a drive source installed in a vehicle body to a differential gear device for driving a front axle via an HST disposed in front of the drive source,
The HST has a hydraulic pump having a pump shaft extending in the vehicle front-rear direction, a motor shaft disposed in parallel with the pump shaft, and a hydraulic motor cooperating with the hydraulic pump, the hydraulic pump and the hydraulic motor And a housing for housing
The hydraulic pump receives power from the drive source from the rear end of the pump shaft,
The hydraulic motor is configured to output a front wheel driving force to the differential gear device from the motor shaft front end, and to output a rear wheel driving force from the motor shaft rear end.
A case having an inner part that is detachably attached to a rear part of the HST housing, and an outer part that extends from the inner part to one side in the vehicle width direction and is located on the one side away from the housing;
An input shaft housed in the inner part of the case, the front end of which is connected to the motor shaft so as not to rotate relative to the motor shaft;
A rear wheel drive shaft housed in an outer portion of the case, and a rear end portion protruding rearward from the case;
A power transmission mechanism housed in the case and configured to transmit power from the input shaft to the rear wheel drive shaft;
A transmission structure , further comprising a rear wheel drive device having The outer portion of the case has a bulging portion that bulges forward,
The bulging portion is provided with a clutch mechanism that constitutes a part of the power transmission mechanism,
The clutch mechanism is supported on the rear wheel drive shaft so as to be relatively rotatable, and an outer ring body to which power from the input shaft is transmitted;
A clutch element interposed between the outer ring body and the rear wheel drive shaft and transmitting only forward force to the rear wheel drive shaft;
The transmission structure according to claim 1 , further comprising a lock member that is supported on the rear wheel drive shaft so as not to rotate relative to the rear wheel and is slidable in an axial direction, and is capable of being engaged with and disengaged from the outer ring body. . A suction path that communicates between the housing and the case and introduces oil in the housing into the case;
The power transmission structure according to claim 1, further comprising a discharge passage that discharges oil in the case. The discharge passage is adapted to communicate the case and the casing of the differential gear device for driving the front axle ,
Further, the suction path communicates with the case on the downstream side in the rotational direction of the gear that forms the meshing point when the vehicle moves forward from the meshing point of the gear that constitutes the power transmission mechanism, and the discharge path is The transmission structure according to claim 3 , wherein the transmission structure communicates with the case on the upstream side in the rotational direction of the gear when the vehicle moves forward from the meshing point.

Images