Patent Description:
There are some work vehicles including a gear transmission that vary power from a power source and outputs the power to a traveling device, and a transmission case that contains the gear transmission therein. Examples of work vehicles of this type include a tractor discussed in Patent Literature <NUM>. The tractor includes a transmission case and a gear transmission (transmission device) contained in the transmission case.

Japanese Unexamined Patent Application Publication, <CIT> <CIT> and <CIT> disclose other examples of work vehicles including a gear transmission.

In some cases, the work vehicle includes an oil outlet port opening to a bottom portion of the transmission case, and is configured so that a lubricating oil stored in the transmission case can be taken out from the oil outlet port. At that time, if a vehicle body is inclined and the transmission case is inclined, the lubricating oil stored in an interior of the transmission case flows toward a side opposite to a side where the oil outlet port is located. Then, if only a part of the oil outlet port is located above an oil surface due to a decrease in the amount of the lubricating oil remaining at a portion where the oil outlet port is located, air may be sucked by a pump connected to the oil outlet port, or the like.

The present invention provides a work vehicle making it possible to take out the lubricating oil while ensuring that the air is less likely to be sucked from the oil outlet port even when the vehicle body is inclined, by employing measures that is easy to carry out while maintaining rigidity of the transmission case.

A work vehicle according to the present invention is defined in claim <NUM>, while preferred embodiments are described in the dependent claims.

With this configuration, the lubricating oil does not enter the first space zone in the sealed state. Therefore, even if the transmission case is inclined in the vehicle body front-back direction due to a longitudinal inclination of the vehicle body, or is inclined in the left-right direction due to a left/right inclination of the vehicle body, and the lubricating oil flows from the side where the oil outlet port is located toward an opposite side, the amount of the lubricating oil staying on the side opposite to the side where the oil outlet port is located becomes smaller than in cases where the first space zone is not present. Consequently, the amount of the lubricating oil remaining at the location where the oil outlet port is located increases. That is, even if the vehicle body is inclined in the longitudinal direction or in the left-right direction when the lubricating oil is taken out of the transmission case, the oil outlet port is less likely to be located above an oil surface, thereby preventing air from being sucked from the oil outlet port.

Additionally, the first space zone in the internal space of the transmission case is brought into the sealed state by separating from the second space zone. It is therefore possible to take simple measures only by adding the partition part. It is also possible to maintain rigidity of the transmission case because there is no need to decrease an outer diameter of the transmission case in order to decrease the internal space of the transmission case on the side opposite to the side where the oil outlet port of the transmission case is located.

The oil outlet port may open to a bottom portion in one end side of the transmission case in the vehicle body front-back direction and the vehicle body left-right direction. The partition part may divide the internal space of the transmission case into the first space zone along the sidewall portion of the transmission case, and the second space zone other than the first space zone on another end side in the vehicle body front-back direction and the vehicle body left-right direction of the transmission case.

With this configuration, the lubricating oil does not enter the first space zone in the sealed state. Therefore, in cases where the transmission case is inclined in the vehicle body front-back direction due to a longitudinal inclination of the vehicle body, and is inclined in the left-right direction due to a left/right inclination of the vehicle body, even if the lubricating oil flows from the side where the oil outlet port is located toward an opposite side, the amount of the lubricating oil staying on the side opposite to the side where the oil outlet port is located becomes smaller than in cases where the first space zone is not present. Consequently, the amount of the lubricating oil remaining at the location where the oil outlet port is located increases. That is, even if the vehicle body is inclined in the vehicle body front-back direction or the left-right direction when the lubricating oil is taken out of the transmission case, the oil outlet port is less likely to be located above an oil surface, thereby preventing air from being sucked from the oil outlet port.

In the present invention, the gear transmission preferably includes a planetary gear device configured to vary power from the power source and output the power, and a clutch disposed displacedly to a side where the sidewall portion is located relative to the planetary gear device, on a location closer to a side where the oil outlet port is located than the planetary gear device. Output of the planetary gear device is inputted to the clutch. The first space zone is preferably disposed at a location located on a lateral side of the planetary gear device, on a location closer to a side where the planetary gear device is located than the clutch.

With this configuration, the transmission case is formed in a state where the sidewall portion of the transmission case passes in the front-back direction on a lateral outer side of the clutch, and dead space formed on the lateral side of the planetary gear device is used for the first space zone. It is therefore easy to form the first space zone.

In the present invention, a differential mechanism configured to transmit output of the gear transmission to the traveling device is preferably contained on one end side of the transmission case in the vehicle body front-back direction.

With this configuration, even if the vehicle body is inclined in the front-back direction, and the lubricating oil flows toward a side opposite to the side where the oil outlet port is located, the amount of the lubricating oil remaining on one end side in the front-back direction of the transmission case is larger than that in the case where there is no first space zone in the sealed state. Consequently, the differential mechanism remains entering deeply the lubricating oil, and the differential mechanism can be lubricated and cooled.

With the configuration according to the invention, the oil outlet port at the lower portion communicates with the internal space of the transmission case via the communication chamber and the communication hole. The oil outlet port at the upper portion communicates with the internal space of the transmission case via the communication chamber and the communication hole. Therefore, though the oil outlet port at the upper portion is disposed at a higher position than the oil outlet port at the lower portion, a height position of a portion where the oil outlet port at the lower portion takes out the oil in the internal space of the transmission case can be made identical with a height position of a portion where the oil outlet port at the upper portion takes out the oil in the internal space of the transmission case.

An embodiment of the present invention is described with reference to the drawings.

The following description relates to a traveling vehicle body of a tractor (an example of "work vehicles"). In <FIG>, <FIG>, and <FIG>, and the like, a direction of an arrow F is "front vehicle body," a direction of an arrow B is "rear vehicle body," a direction of an arrow U is "above vehicle body," a direction of an arrow D is "below vehicle body," a direction of an arrow L is "left vehicle body" and a direction of an arrow R is "right vehicle body.

As illustrated in <FIG>, the traveling vehicle body of the tractor includes an engine <NUM>, a transmission case <NUM>, a vehicle body frame <NUM>, a pair of left and right front wheels <NUM> and a pair of left and right rear wheels <NUM>. A front portion of the transmission case <NUM> is connected to a flywheel housing <NUM> disposed in a rear portion of the engine <NUM>. The vehicle body frame <NUM> is configured by, for example, a front frame <NUM> connected to a lower portion of the engine <NUM>. The front wheels <NUM> are traveling devices disposed at a front portion of the vehicle body frame <NUM> so as to be steerably and drivably. The rear wheels <NUM> are traveling device disposed drivably at a rear portion of the vehicle body frame <NUM>. The tractor includes a driving section <NUM> including the engine <NUM>, which is disposed at a front portion of the traveling vehicle body. The tractor includes an operation section <NUM> at a rear portion of the traveling vehicle body. The operation section <NUM> includes an operation seat <NUM>, a steering wheel <NUM> to perform steering operation of the front wheels <NUM>, and a cabin <NUM> to cover a boarding space. The tractor includes a link mechanism <NUM> and a power take-off shaft <NUM>. The link mechanism <NUM> connects various types of working devices, such as a rotary tiller (not illustrated), to a rear portion of the vehicle body frame <NUM> so that they can be subjected to a lifting operation. The power take-off shaft <NUM> transmits power from the engine <NUM> to the working devices being connected.

<FIG> is a diagram illustrates a power transmission device <NUM> that transmits the power of the engine <NUM> to the front wheels <NUM>, the rear wheels <NUM>, and the power take-off shaft <NUM>. As illustrated in <FIG> and <FIG>, the power transmission device <NUM> includes the transmission case <NUM> whose front portion is connected to the flywheel housing <NUM> disposed in the rear portion of the engine <NUM>. The transmission case <NUM> is disposed in the traveling vehicle body in a state where a front-back direction of the transmission case <NUM> coincides with a front-back direction of the traveling vehicle body as illustrated in <FIG>. The transmission case <NUM> is configured so as to be divisible into a front case part 3a, an intermediate case part 3b, and a rear case part 3c. A front portion of the front case part 3a is connected to the flywheel housing <NUM>. The intermediate case part 3b is connected to a rear portion of the front case part 3a. A front portion of the rear case part 3c is connected to a rear portion of the intermediate case part 3b.

As illustrated in <FIG>, the transmission case <NUM> contains therein a gear transmission <NUM> to which the power from the engine <NUM> that is a power source is inputted and from which the inputted power whose varied by the transmission case <NUM> is outputted to the front wheels <NUM> and the rear wheels <NUM>, a rear wheel differential mechanism <NUM> (corresponding to the differential mechanism), and an operation power transmission device <NUM> to transmit the power from the engine <NUM> to the power take-off shaft <NUM>.

The gear transmission <NUM> includes an input shaft <NUM>, a major transmission part <NUM>, a staged transmission part <NUM>, a forward-reverse switching device <NUM>, a first gear interlock mechanism <NUM>, and a front wheel transmission device <NUM> as illustrated in <FIG>. Power of an output shaft 1a of the engine <NUM> is transmitted via a major clutch <NUM> to the input shaft <NUM>, and the input shaft <NUM> inputs the transmitted power to the transmission case <NUM>. The major transmission part <NUM> is connected to the input shaft <NUM>. Output of the major transmission part <NUM> is inputted to the staged transmission part <NUM>. Output of the staged transmission part <NUM> is inputted to the forward-reverse switching device <NUM>. The first gear interlock mechanism <NUM> transmits output of the forward-reverse switching device <NUM> to the rear wheel differential mechanism <NUM>. The output of the forward-reverse switching device <NUM> is transmitted via the first gear interlock mechanism <NUM> to the front wheel transmission device <NUM>.

The major transmission part <NUM> includes a planetary gear device 18A and a continuously variable transmission device 18B as illustrated in <FIG>.

The planetary gear device 18A includes two planetary gear device sections disposed side by side in the front-back direction of the transmission case <NUM>. Hereinafter, a description is given where one of these two planetary gear device sections which is disposed on a front side is referred to as a first planetary gear device section <NUM>, and one of these two planetary gear device sections which is disposed on a rear side is referred to as a second planetary gear device section <NUM>.

The first planetary gear device section <NUM> includes a planetary gear <NUM> and a transmission gear (not illustrated) that meshes with the planetary gear <NUM>. The second planetary gear device section <NUM> includes a planetary gear <NUM>. A coupling member (not illustrated) that interlockingly couples the transmission gear and the planetary gear <NUM> is disposed across the first planetary gear device section <NUM> and the second planetary gear device section <NUM>. A carrier <NUM> of the first planetary gear device section <NUM> and a carrier <NUM> of the second planetary gear device section <NUM> are integrally rotatably coupled to each other. With this configuration, the planetary gear device 18A is configured as a complex planetary gear device.

The continuously variable transmission device 18B is configured by a hydrostatic continuously variable transmission device, and includes a variable displacement hydraulic pump P and a hydraulic motor M.

Power of the input shaft <NUM> is inputted via a front rotating shaft <NUM> and a second gear interlock mechanism <NUM> to the hydraulic pump P in the major transmission part <NUM>. By performing a gear shift operation to change a swash plate angle of the hydraulic pump P in the continuously variable transmission device 18B, the inputted power is shifted to forward rotation power and reverse rotation power, and the forward rotation power and the reverse rotation power are shifted steplessly. The shifted power is outputted from the hydraulic motor M. Output of the continuously variable transmission device 18B is inputted via a third gear interlock mechanism <NUM> to a sun gear <NUM> of the first planetary gear device section <NUM>. Power of the input shaft <NUM> is inputted via a fourth gear interlock mechanism <NUM> to an internal gear <NUM> of the first planetary gear device section <NUM>. Power transmitted from the engine <NUM> via the continuously variable transmission device 18B, and power transmitted from the engine <NUM> not via the continuously variable transmission device 18B are synthesized by the first planetary gear device section <NUM> and the second planetary gear device section <NUM> in the planetary gear device 18A. Synthetic power is outputted from a first output shaft 37a, a second output shaft 37b, and a third output shaft 37c included in the second planetary gear device section <NUM>.

The staged transmission part <NUM> includes four staged clutches to which the synthetic power from the planetary gear device 18A, and an output shaft <NUM> as illustrated in <FIG>. These four staged clutches are a first clutch CL1, a second clutch CL2, a third clutch CL3, and a fourth clutch CL4 illustrated in <FIG>, which are disposed on the output shaft <NUM>.

The synthetic power from the planetary gear device 18A is staged in four speed ranges and then outputted from the output shaft <NUM> by appropriate operations of the continuously variable transmission device 18B and the four staged clutches (the first clutch CL1, the second clutch CL2, the third clutch CL3, and the fourth clutch CL4) in the staged transmission part <NUM>.

<FIG> is an explanatory drawing illustrating a relationship among a speed change state of the continuously variable transmission device 18B, a speed range and a rotational velocity V of the output shaft <NUM> of the staged transmission part <NUM>. An ordinate in <FIG> represents the rotational velocity V of the output shaft <NUM>. An abscissa in <FIG> represents the speed change state of the continuously variable transmission device 18B, in which "N" represents a neutral state, "-MAX" represents a speed change state at a maximum speed in a reverse rotation direction, and "+MAX" represents a speed change state at a maximum speed in a forward rotation direction.

If the first clutch CL1 of the four staged clutches is brought into an engaged state and the continuously variable transmission device 18B is subjected to a gear shift operation, the power of the first output shaft 37a is varied by a first speed gear interlock mechanism 39a and the first clutch CL1, and the varied power is outputted from the output shaft <NUM>. As illustrated in <FIG>, the rotational velocity V of the output shaft <NUM> reaches a rotational velocity of a first speed range, and the rotational velocity V of the output shaft <NUM> increases steplessly from a velocity "<NUM>" to the maximum velocity "V1" of the first speed range along with a shift from "-MAX" to "+MAX" in the continuously variable transmission device 18B.

If the second clutch CL2 of the four staged clutches is brought into an engaged state and the continuously variable transmission device 18B is subjected to a gear shift operation, the power of the third output shaft 37c is varied by a second speed gear interlock mechanism 39b and the second clutch CL2, and the varied power is outputted from the output shaft <NUM>. As illustrated in <FIG>, the rotational velocity V of the output shaft <NUM> reaches a higher rotational velocity of a second speed range than the first speed range, and the rotational velocity V of the output shaft <NUM> increases steplessly from a minimum velocity "V1" of the second speed range to the maximum velocity "V2" of the second speed range along with a shift from "+MAX" to "-MAX" in the continuously variable transmission device 18B.

If the third clutch CL3 of the four staged clutches is brought into an engaged state and the continuously variable transmission device 18B is subjected to a gear shift operation, the power of the second output shaft 37b is varied by a third speed gear interlock mechanism 39c and the third clutch CL3, and the varied power is outputted from the output shaft <NUM>. As illustrated in <FIG>, the rotational velocity V of the output shaft <NUM> reaches a higher-side rotational velocity of a third speed range than the second speed range, and the rotational velocity V of the output shaft <NUM> increases steplessly from a minimum velocity "V2" of the third speed range to the maximum velocity "V3" of the third speed range along with a shift from "-MAX" to "+MAX" in the continuously variable transmission device 18B.

If the fourth clutch CL4 of the four staged clutches is brought into an engaged state and the continuously variable transmission device 18B is subjected to a gear shift operation, the power of the third output shaft 37c is varied by the fourth speed gear interlocking mechanism 39d and the fourth clutch CL4, and the varied power is outputted from the output shaft <NUM>. As illustrated in <FIG>, the rotational velocity V of the output shaft <NUM> reaches a higher-side rotational velocity of a fourth speed range than the third speed range, and the rotational velocity V of the output shaft <NUM> increases steplessly from a minimum velocity "V3" of the fourth speed range to the maximum velocity "V4" of the fourth speed range along with a shift from "+MAX" to "-MAX" in the continuously variable transmission device 18B.

As illustrated in <FIG>, the forward-reverse switching device <NUM> includes an input shaft <NUM> connected to the output shaft <NUM> of the staged transmission part <NUM>, a forward clutch CLF and a reverse clutch CLR disposed on the input shaft <NUM>, and an output shaft <NUM>. The output shaft <NUM> is connected via a forward gear mechanism 41f to the forward clutch CLF, and is connected via a reverse gear mechanism 41r to the reverse clutch CLR. As illustrated in <FIG>, the reverse gear mechanism 41r includes a reverse gear <NUM> configured to mesh with a tooth part of an output rotary member of the reverse clutch CLR. The reverse gear <NUM> is relatively rotatably supported on an input shaft 22a of the rear wheel differential mechanism <NUM>.

In the forward-reverse switching device <NUM>, if the forward clutch CLF is brought into an engaged state, power transmitted from the staged transmission part <NUM> to the input shaft <NUM> is converted to forward movement power by the forward clutch CLF and the forward gear mechanism 41f, and the forward movement power is outputted from the output shaft <NUM>. If the reverse clutch CLR is brought into an engaged state, power transmitted from the staged transmission part <NUM> to the input shaft <NUM> is converted to reverse movement power by the reverse clutch CLR and the reverse gear mechanism 41r, and the reverse movement power is outputted from the output shaft <NUM>. The forward movement power and the reverse movement power outputted from the output shaft <NUM> are transmitted to the first gear interlock mechanism <NUM> and are then transmitted to the input shaft 22a of the rear wheel differential mechanism <NUM> by the first gear interlock mechanism <NUM>.

The forward movement power and the reverse movement power outputted from the forward reverse switching device <NUM> are inputted via the first gear interlock mechanism <NUM> to the input shaft 22a, and the rear wheel differential mechanism <NUM> outputs the inputted powers to the left and right rear wheels <NUM>. Output of the rear wheel differential mechanism <NUM> is transmitted via a reduction device <NUM> to the rear wheels <NUM>. The reduction device <NUM> is configured by a planetary gear device. A steering brake <NUM> is disposed on a transmission system from the rear wheel differential mechanism <NUM> to the rear wheels <NUM>.

The front wheel transmission device <NUM> includes an input shaft <NUM>, a constant velocity clutch CLT and a speed-up clutch CLH disposed on the input shaft <NUM>, and an output shaft <NUM> as illustrated in <FIG>. The forward movement power and the reverse movement power from the forward reverse switching device <NUM> are transmitted via the first gear interlock mechanism <NUM> to the input shaft <NUM>. The output shaft <NUM> is connected via a constant velocity gear mechanism 44a to the constant velocity clutch CLT, and is connected via a speed-up gear mechanism 44b to the speed-up clutch CLH. A parking brake <NUM> is connected to the input shaft <NUM>.

If the constant velocity clutch CLT is brought into an engaged state in the front wheel transmission device <NUM>, power transmitted from the forward reverse switching device <NUM> to the input shaft <NUM> is transmitted via the constant velocity clutch CLT and the constant velocity gear mechanism 44a to the output shaft <NUM>, and the power is transmitted from the output shaft <NUM> via a rotating shaft <NUM> to the front wheel differential mechanism <NUM>. This leads to a situation where the pair of left and right front wheels <NUM> and the pair of left and right rear wheels <NUM> are driven in a state where an average peripheral speed of the pair of left and right front wheels <NUM> is approximately equal to an average peripheral speed of the pair of left and right rear wheels <NUM>, namely, a so-called four-wheel drive state at an equal velocity of the front and rear wheels. If the speed-up clutch CLH is brought into an engaged state, power transmitted from the forward reverse switching device <NUM> to the input shaft <NUM> is transmitted via the speed-up clutch CLH and the speed-up gear mechanism 44b to the output shaft <NUM>, and the power is transmitted from the output shaft <NUM> to the front wheel differential mechanism <NUM>. This leads to a situation where the pair of left and right front wheels <NUM> and the pair of left and right rear wheels <NUM> are driven in a state where the average peripheral speed of the pair of left and right front wheels <NUM> is higher than the average peripheral speed of the pair of left and right rear wheels <NUM>, specifically, a so-called four-wheel drive state where the front wheels have a higher speed.

The operation power transmission device <NUM> is connected via the front rotating shaft <NUM> and a rear rotating shaft <NUM> to the input shaft <NUM> as illustrated in <FIG>. The operation power transmission device <NUM> includes an operation clutch <NUM> (corresponding to a clutch) to which power from the engine <NUM> is inputted, and an operation power transmission mechanism <NUM> that varies the output of the operation clutch <NUM> and transmits the output to the power take-off shaft <NUM>. The front rotating shaft <NUM> is disposed behind the input shaft <NUM> so as to be located on the same straight line as the input shaft <NUM>. The rear rotating shaft <NUM> is disposed behind the front rotating shaft <NUM> so as to be located on the same straight line as the front rotating shaft <NUM>.

The operation clutch <NUM> in the operation power transmission device <NUM> performs switching between a state where the power from the engine <NUM> is transmitted to the power take-off shaft <NUM> and a state where a power transmission from the engine <NUM> to the power take-off shaft <NUM> is discontinued. That is, if the operation clutch <NUM> is switched to an engaged state, the rear rotating shaft <NUM> and the operation power transmission mechanism <NUM> are interlockingly connected to each other by the operation clutch <NUM>, so that the power from the input shaft <NUM> is transmitted to the power take-off shaft <NUM>. If the operation clutch <NUM> is switched to a disengaged state, the interlocking connection between the rear rotating shaft <NUM> and the operation power transmission mechanism <NUM> is disconnected by the operation clutch <NUM>, so that the power transmission from the input shaft <NUM> to the power take-off shaft <NUM> is disconnected.

As illustrated in <FIG>, a power take-off gear <NUM> is configured to be engaged with a transmission gear 35a in the second gear interlock mechanism <NUM> to interlock the front rotating shaft <NUM> and the hydraulic pump P of the continuously variable transmission device 18B. A first hydraulic pump <NUM>, a second hydraulic pump <NUM> and a third hydraulic pump <NUM> are connected to the power take-off gear <NUM>. As illustrated in <FIG> and <FIG>, the first hydraulic pump <NUM>, the second hydraulic pump <NUM>, and the third hydraulic pump <NUM> are supported on a lateral upper portion of the transmission case <NUM>.

The first hydraulic pump <NUM> is driven by power that the power take-off gear <NUM> takes off from the second gear interlock mechanism <NUM>. The first hydraulic pump <NUM> pumps the lubricating oil stored in the transmission case <NUM>, and supplies, as a hydraulic oil, the pumped lubricating oil to the continuously variable transmission device 18B via a first filler pipe member <NUM> extending from the first hydraulic pump <NUM>. The second hydraulic pump <NUM> is driven by power that the power take-off gear <NUM> takes off from the second gear interlock mechanism <NUM>. The second hydraulic pump <NUM> pumps the lubricating oil stored in the interior of the transmission case <NUM>, and supplies, as a hydraulic oil, the pumped lubrication oil to the major transmission part <NUM> and the forward-reverse switching device <NUM> via a second oil filler pipe member <NUM> extending from the second hydraulic pump <NUM> and a preferential switching valve <NUM>. The preferential switching valve <NUM> is disposed on two lateral portions of the transmission case <NUM>. The third hydraulic pump <NUM> is driven by power that the power take-off gear <NUM> takes off from the second gear interlock mechanism <NUM>. The third hydraulic pump <NUM> pumps the lubricating oil stored in the interior of the transmission case <NUM>. The pumped lubricating oil is fed to a lubrication release valve <NUM> via a third oil filler pipe member <NUM> extending from the third hydraulic pump <NUM>, and is then fed into the transmission case <NUM> as a lubricating oil.

The oil outlet port, which permits pumping the oil from the transmission case <NUM> by the first hydraulic pump <NUM>, the second hydraulic pump <NUM>, and the third hydraulic pump <NUM>, is formed by opening a bottom portion 3e on one end side of the transmission case <NUM> in a vehicle body front-back direction and a vehicle body left-right direction. If the traveling vehicle body is inclined in a front-back direction, the transmission case <NUM> enters an inclined state where the other end side in the vehicle body front-back direction (the side opposite to the side where the oil outlet port is located) is lowered. Consequently, the lubricating oil staying in the interior of the transmission case <NUM> flows from one end side in the vehicle body front-back direction of the transmission case <NUM> toward the other end side in the vehicle body front-back direction. If the traveling vehicle body is inclined in the left-right direction, the transmission case <NUM> enters an inclined state where the other end side in the vehicle body left-right direction (the side opposite to the side where the oil outlet port is located) is lowered. Consequently, the lubricating oil staying in the interior of the transmission case <NUM> flows from one end side of the transmission case <NUM> in the vehicle body front-back direction toward the other end side in the vehicle body left-right direction. With the present embodiment, a volume of a region where the lubricating oil stays in the interior of the transmission case <NUM> is made smaller than a volume of the internal space of the transmission case <NUM> on the other end side of the transmission case <NUM> in the vehicle body front-back direction and the vehicle body left-right direction. With this configuration, even if the traveling vehicle body is inclined in the front-back direction or in the left-right direction, the amount of the lubricating oil staying in the region where the oil outlet port is located in the transmission case <NUM> can be increased. This prevents the oil outlet port from being located above the oil surface, thereby preventing the first hydraulic pump <NUM>, the second hydraulic pump <NUM>, and the third hydraulic pump <NUM> from sucking air through the oil outlet port.

Specifically, as illustrated in <FIG>, an oil outlet part <NUM> is disposed at a right lateral portion of the transmission case <NUM> on a rear end side of the transmission case <NUM>. The oil outlet part <NUM> is formed at a part of the transmission case <NUM> which is located ahead of a rear axle case 7a (refer to <FIG>) extending from the transmission case <NUM>. As illustrated in <FIG> and <FIG>, the oil outlet part <NUM> includes a first oil output port <NUM>, a second oil outlet port <NUM>, and a third oil outlet port <NUM>, which are configured to take out the lubricating oil from the interior of the transmission case <NUM>, and open into the bottom portion 3e of the transmission case <NUM>. The first oil outlet port <NUM> is connected to the first hydraulic pump <NUM> with a first suction pipe member <NUM> interposed therebetween. The second oil outlet port <NUM> is connected to the second hydraulic pump <NUM> with a second suction pipe member <NUM> interposed therebetween. The third oil outlet port <NUM> is connected to the third hydraulic pump <NUM> with a third suction pipe member <NUM> interposed therebetween. The first oil outlet port <NUM>, the second oil outlet port <NUM>, and the third oil outlet port <NUM> in the oil outlet part <NUM> open into the bottom portion 3e of the transmission case <NUM>.

As illustrated in <FIG> and <FIG>, the first oil outlet port <NUM> and the third oil outlet port <NUM> are individually disposed at lower portions of the bottom portion 3e, and the second oil outlet port <NUM> is disposed at an upper portion of the bottom portion 3e in the present embodiment.

The bottom portion 3e includes a communication chamber formation member <NUM> attached to an outer surface of the right sidewall portion 3d of the transmission case <NUM>. The communication chamber formation member <NUM> is attached to the right sidewall portion 3d in a state where a reentrant space in the right sidewall portion 3d is closed. A communication chamber <NUM> located between the communication chamber formation member <NUM> and the right sidewall portion 3d is formed by the communication chamber formation member <NUM> and the right sidewall portion 3d. The first oil outlet port <NUM> and the third oil outlet port <NUM>, which are disposed side by side in the vehicle body front-back direction, are opened below the communication chamber formation member <NUM>. The second oil outlet port <NUM> is opened above the communication chamber formation member <NUM>. The second oil outlet port <NUM> is located at a higher position than the first oil outlet port <NUM> and the third oil outlet port <NUM>. The first oil outlet port <NUM>, the second oil outlet port <NUM> and the third oil outlet port <NUM> communicate with the communication chamber <NUM>. A first communication hole <NUM>, which allows the communication chamber <NUM> to communicate with an internal space 3f of the transmission case <NUM>, opens to a portion of the right sidewall portion 3d which is opposed to the first oil outlet port <NUM>. A second communication hole <NUM>, which allows the communication chamber <NUM> to communicate with the internal space 3f of the transmission case <NUM>, opens to a portion of the right sidewall portion 3d which is opposed to the third oil outlet port <NUM>. The first communication hole <NUM> includes a first strainer <NUM>, and the second communication hole <NUM> includes a second strainer <NUM>.

The first oil outlet port <NUM> communicates with the internal space 3f of the transmission case <NUM> via the communication chamber <NUM>, the first communication hole <NUM>, the first strainer <NUM>, the second communication hole <NUM>, and the second strainer <NUM>. The second oil outlet port <NUM> communicates with the internal space 3f of the transmission case <NUM> via the communication chamber <NUM>, the first communication hole <NUM>, the first strainer <NUM>, the second communication hole <NUM>, and the second strainer <NUM>. The third oil outlet port <NUM> communicates with the internal space 3f of the transmission case <NUM> via the communication chamber <NUM>, the second communication hole <NUM>, the second strainer <NUM>, the first communication hole <NUM>, and the first strainer <NUM>.

A connection between the first suction pipe member <NUM> and the first oil outlet port <NUM> is made by inserting an end portion of the first suction pipe member <NUM> into the first oil outlet port <NUM>. The lubricating oil is taken out by the first suction pipe member <NUM> mainly via the first oil outlet port <NUM>, the communication chamber <NUM>, the first communication hole <NUM>, and the first strainer <NUM>. The lubricating oil can also be taken out by the first suction pipe member <NUM> via the first oil outlet port <NUM>, the communication chamber <NUM>, the second communication hole <NUM>, and the second strainer <NUM>.

A connection between the third suction pipe member <NUM> and the third oil outlet port <NUM> is made by inserting an end portion of the third suction pipe member <NUM> into the third oil outlet port <NUM>. The lubricating oil is taken out by the third suction pipe member <NUM> mainly via the third oil outlet port <NUM>, the communication chamber <NUM>, the second communication hole <NUM>, and the second strainer <NUM>. The lubricating oil can also be taken out by the third suction pipe member <NUM> via the third oil outlet port <NUM>, the communication chamber <NUM>, the first communication hole <NUM>, and the first strainer <NUM>.

A connection between the second suction pipe member <NUM> and the second oil outlet port <NUM> is made by inserting an end portion of the second suction pipe member <NUM> into the second oil outlet port <NUM>. The lubricating oil is taken out by the second suction pipe member <NUM> via the second oil outlet port <NUM>, the communication chamber <NUM>, the first communication hole <NUM>, the first strainer <NUM>, the second communication hole <NUM>, and the second strainer <NUM>. The second oil outlet port <NUM> is located at a higher position than the first oil outlet port <NUM> and the third oil outlet port <NUM>. A height position of a region where the second oil outlet port <NUM> takes out the lubricating oil in the interior of the transmission case <NUM> is the same as a height position of a region where the first oil outlet port <NUM> and the third oil outlet port <NUM> take out the lubricating oil in the interior of the transmission case <NUM>.

A volume of the region where the lubricating oil stays in the interior of the transmission case <NUM> is made smaller than a volume of the internal space of the transmission case <NUM> on a front end side of the transmission case <NUM> (the side opposite to the side where the first oil outlet port <NUM>, the second oil outlet port <NUM>, and the third oil outlet port <NUM> are located in the vehicle body front-back direction), and on a left end side of the transmission case <NUM> (the side opposite to the side where the first oil outlet port <NUM>, the second oil outlet port <NUM>, and the third oil outlet port <NUM> are located in the vehicle body left-right direction).

As illustrated in <FIG> and <FIG>, a partition part <NUM> is disposed in the interior of the transmission case <NUM>, specifically at a region toward the front end of the transmission case <NUM>, namely, at a region located closer to the front of the vehicle body than the oil outlet part <NUM>. The partition part <NUM> divides the internal space 3f of the transmission case <NUM> into a first space zone A1 along a left sidewall portion <NUM> of the transmission case <NUM> and a second space zone A2 other than the first space zone A1. The first space zone A1 is sealed with the partition part <NUM> and the left sidewall portion <NUM> in order to prevent the lubricating oil stored in the interior of the transmission case <NUM> from entering the first space zone A1. A volume in which the lubricating oil can be stored in the interior of the transmission case <NUM> at the region toward the front end of the transmission case <NUM>, namely, at the region located closer to the front of the vehicle body than the oil outlet part <NUM> is smaller than a volume of the internal space 3f at the region toward the front end of the transmission case <NUM> by the amount of a volume of the first space zone A1.

As illustrated in <FIG>, the left sidewall portion <NUM> and the partition part <NUM> include an opening <NUM> that enables integral casting of the partition part <NUM> with the transmission case <NUM>, and a closing member <NUM> that closes the opening <NUM> so as to seal the first space zone S1.

The lubricating oil is stored in the internal space 3f of the transmission case <NUM> so as to lubricate the gear transmission <NUM> and the rear wheel differential mechanism <NUM>. The lubricating oil is preferably stored in a state where the height position of the oil surface S of the lubricating oil is the same as a height position between the rotation axis of the ring gear 22b of the rear wheel differential mechanism <NUM> and a lower end of the ring gear 22b. An upper end T of the first space zone A1 is located above the oil surface S.

As described above, if the transmission case <NUM> enters an inclined state where the front end side of the transmission case <NUM> in the vehicle body front-back direction is lowered, the lubricating oil staying in the interior of the transmission case <NUM> flows from the rear end side of the transmission case <NUM> (the side where the first oil outlet port <NUM>, the second oil outlet port <NUM>, and the third oil outlet port <NUM> are located) toward the front end side of the transmission case <NUM> (the side opposite to the side where the first oil outlet port <NUM>, the second oil outlet port <NUM>, and the third oil outlet port <NUM> are located). Even if the lubricating oil flows toward the front end side of the transmission case <NUM>, the amount of the lubricating oil staying on the front end side of the transmission case <NUM> becomes smaller under the presence of the first space zone A1 than in the cases where the first space zone A1 is not present. Consequently, the amount of the lubricating oil remaining on the front end side of the transmission case <NUM> decreases, and the amount of the lubricating oil remaining on the rear end side of the transmission case <NUM> increases, so that the first oil outlet part <NUM>, the second oil outlet port <NUM>, and the third oil outlet port <NUM> remain entering the lubricating oil.

Similarly, if the transmission case <NUM> enters an inclined state where a left end side in the vehicle body left-right direction is lowered, the lubricating oil staying in the interior of the transmission case <NUM> flows from the a right end side of the transmission case <NUM> (the side where the first oil outlet port <NUM>, the second oil outlet port <NUM>, and the third oil outlet port <NUM> are located) toward the left end side of the transmission case <NUM> (the side opposite to the side where the first oil outlet port <NUM>, the second oil outlet port <NUM>, and the third oil outlet port <NUM> are located). Even if the lubricating oil flows toward the left end side of the transmission case <NUM>, the amount of the lubricating oil staying on the left end side of the transmission case <NUM> becomes smaller under the presence of the first space zone A1 than in the cases where the first space zone A1 is not present. Consequently, the amount of the lubricating oil remaining on the left end side of the transmission case <NUM> decreases, and the amount of the lubricating oil remaining on the right end side of the transmission case <NUM> increases, so that the first oil outlet part <NUM>, the second oil outlet port <NUM>, and the third oil outlet port <NUM> remain entering the lubricating oil.

In the present embodiment, as illustrated in <FIG> and <FIG>, the first clutch CL1, the second clutch CL2, the third clutch CL3, and the fourth clutch CL4 (staged clutches) are disposed in the staged transmission part <NUM>, and output of the planetary gear device 18A is inputted thereto. The first clutch CL1, the second clutch CL2, the third clutch CL3, and the fourth clutch CL4 are disposed displacedly to the side where the left sidewall portion <NUM> is located relative to the planetary gear device 18A, from portions closer to a side where the first oil outlet port <NUM>, the second oil outlet port <NUM>, and the third oil outlet port <NUM> are located, to the left end side of the transmission case <NUM> (the side where the first oil outlet port <NUM>, the second oil outlet port <NUM>, and the third oil outlet port <NUM> are located). The first space zone A1 is disposed toward the lateral side of the planetary gear device 18A at a location closer to the side where the planetary gear device 18A is located than the first clutch CL1, the second clutch CL2, the third clutch CL3, and the fourth clutch CL4, on the lateral side of the planetary gear device 18A. The first space zone A1 is disposed using a dead space formed between the planetary gear device 18A and the left sidewall portion <NUM> as an installation space for the first space zone A1.

Claim 1:
A work vehicle comprising:
a gear transmission (<NUM>) configured to vary power from a power source (<NUM>) and output the power to a traveling device (<NUM>, <NUM>);
a transmission case (<NUM>) containing the gear transmission (<NUM>);
a first oil outlet port (<NUM>) disposed at a lower portion in a bottom portion (3e) in one end side of the transmission case (<NUM>) in a vehicle body front-back direction or in a vehicle body left-right direction, the first oil outlet port (<NUM>) being configured to take out a lubricating oil from an interior of the transmission case (<NUM>); and
a second oil outlet port (<NUM>) disposed at an upper portion in the bottom portion (3e) in the one end side of the transmission case (<NUM>) in the vehicle body front-back direction or in the vehicle body left-right direction, the second oil outlet port (<NUM>) being configured to take out the lubricating oil from the interior of the transmission case (<NUM>), wherein
the work vehicle includes a partition part (<NUM>) dividing an internal space (3f) of the transmission case (<NUM>) into a first space zone (A1) along a sidewall portion (<NUM>) of the transmission case (<NUM>), and a second space zone (A2) other than the first space zone (A1) on another end side in the vehicle body front-back direction of the transmission case (<NUM>), the partition part (<NUM>) keeping the first space zone (A1) in a sealed state;
characterized in that the bottom portion (3e) includes a communication chamber formation member (<NUM>) disposed on an outer surface of a sidewall portion (3d) of the transmission case (<NUM>), the communication chamber formation member (<NUM>) being configured to form a communication chamber (<NUM>) between itself and the sidewall portion (3d);
the first oil outlet port (<NUM>) at the lower portion opens to a lower portion of the communication chamber formation member (<NUM>);
the second oil outlet port (<NUM>) at the upper portion opens to an upper portion of the communication chamber formation member (<NUM>); and
a communication hole (<NUM>) allowing the communication chamber (<NUM>) to communicate with an internal space (3f) of the transmission case (<NUM>) opens to a portion of the sidewall portion (3d) which is opposed to the first oil outlet port (<NUM>) at the lower portion.