Patent Description:
Construction machines include running units for allowing their vehicle bodies to run even on rough roads, and the running units can be crawlers, instead of wheels used in passenger cars. A crawler is engaged with a drive wheel (sprocket) rotatable around an axis. The drive wheel can be driven and rotated by a drive unit, which is often a hydraulic drive unit using a hydraulic motor as such a motor can easily produce a large rotational torque. The hydraulic drive unit includes, in addition to the hydraulic motor, a hydraulic pump configured to feed hydraulic oil to the hydraulic motor and an engine configured to drive the hydraulic pump. The hydraulic oil discharged from the hydraulic pump is fed to the hydraulic motor through piping routed within the construction machine. <CIT> discloses a motor drive unit that is configured such that a rotor shaft rotating with a rotor arranged in a stator coaxially therewith is supported by a bearing at both sides of a case, and the rotation of the rotor is extracted by a gear arranged at one end of the rotor shaft. A cooling oil passage for the motor drive unit is constituted by an oil supply reservoir and an oil discharge reservoir separated from each other on both sides in the axial direction of the gear near the one end of the rotor shaft, an intermediate oil reservoir arranged near the other end of the rotor shaft, an oil supply passage arranged in the center of the rotor shaft so as to link the oil supply reservoir and the oil intermediate reservoir, and an oil discharge passage arranged on the rotor shaft around the oil supply passage to link the oil intermediate reservoir and the oil discharge reservoir. <CIT>describes a gearmotor with integrated brake for direct drive to the electric-traction vehicle wheel where the traction motor is integrated with a direct drive to the driving-wheel, wherein said traction motor includes a shaft that on the wheel side is integrated with a pinion that internally gears in an integrated reducer-transmission system for the traction motion to the wheel in the respective gear chamber, and on the other side opposite the wheel is keyed to a braking system also integrated and cased with the group, in the respective opposite braking chamber. <CIT> relates to an electrically-propelled tracked vehicle with a vehicle chassis and tracks which run on corresponding running gears and which may each be driven by at least one crown gear. Each crown gear is provided with a drive device with at least one electric motor and a transfer gear. The electric motor is arranged, at least partly above the track, in the axial space for the track and the transfer gear is arranged on the side of the crown gear and drive motor facing the middle of the vehicle and that the housing for the transfer gear is rigidly connected to the vehicle chassis. <CIT> shows a crawler drive unit.

Recent years has seen a growing demand for the use of electric drive units in place of hydraulic drive units for the purposes of simplifying construction machines. An electric drive unit includes a battery in place of an engine, and an electric motor to be driven by power provided by the battery. The electric drive unit no longer needs a hydraulic pump as well as piping routed within a construction machine.

Given that electric and hydraulic motors have the same size, the rotational torque of the electric motor tends to be less than that of the hydraulic motor. Accordingly, if an electric drive unit is used, an electric motor of a larger size is used and combined with a speed reduction mechanism, which slows down the rotation of the electric motor and outputs the resulting rotation.

The speed reduction mechanism has a plurality of gears provided in a housing in a rotatable manner. When provided in a running unit, the speed reduction mechanism may use the housing as the output part. Considering the above, the electric drive unit is desirably contained within the running unit as entirely as possible so that the electric drive unit does not stick out of the running unit, because the drive unit can avoid getting damaged by soil, sand, rocks and the like while the construction machine is in motion. For this reason, the speed reduction mechanism may be housed within the drive wheel such that they are aligned with each other. The drive wheel can rotate integrally with the housing (the output part).

If an attempt is made to simply replace a hydraulic drive unit with an electric drive unit, an electric motor and a speed reduction mechanism need to be fitted into the space that is originally occupied by n hydraulic motor. The speed reduction mechanism can be contained within the running unit in the width direction or within its width (within the width of the sprocket), but the electric motor cannot avoid protruding out of the running unit in the width direction. This may result in the electric motor coming into contact with soil, sand, rocks and the like while the construction machine is in motion, which could damage the electric motor. In particular, if the speed reduction mechanism and the electric motor are placed at a similar height, this means that the electric motor is positioned close to the road surface. As a result, the electric motor may have a higher chance of getting damaged.

It is an object of the present invention to provide a crawler drive unit and a construction machine that can lower the chance of an electric motor coming into contact with soil, sand, rocks and the like. According to the present invention said object is solved by a crawler drive unit having the features of the independent claim <NUM>. Preferred embodiments are laid down in the dependent claims.

The crawler drive unit and construction machine described above can lower the chance of the electric motor coming into contact with soil, sand, rocks and the like.

The following describes embodiments of the present invention with reference to the drawings.

<FIG> is a perspective view of a construction machine <NUM>. As shown in <FIG>, the construction machine <NUM> is designed to, for example, excavate soil and sand. The construction machine <NUM> performs various construction works, for example, transports excavated soil and sand to another vehicle. The construction machine <NUM> includes a vehicle body <NUM>, running units <NUM> for causing the vehicle body <NUM> to run, and crawler drive units <NUM> provided on the running units <NUM> and configured to drive the running units <NUM>. In the following description, the term "front-rear direction" refers to the direction in which the construction machine <NUM> runs forward and backward. The simple term "width direction" refers to the direction in which the width of the construction machine <NUM> is defined, which extends horizontally and is orthogonal to the front-rear direction.

The vehicle body <NUM> includes a swivel body <NUM> and a lower frame <NUM> provided below the swivel body <NUM> and pivotably supporting the swivel body <NUM>. The swivel body <NUM> has a cab <NUM> on which an operator can board, and a boom <NUM> that is swingably connected at one end thereof to the swivel body <NUM>. Although not shown in <FIG>, an arm is swingably provided at the other end of the boom <NUM>. A bucket or the like is attached to the end of the arm that is opposite to the end having the boom <NUM>. The running units <NUM> are provided on the respective sides of the lower frame <NUM> in the width direction.

The running units <NUM> each include a track frame <NUM> connected to the lower frame <NUM> and long in the front-rear direction, an idler rotatably provided in the front portion of the track frame <NUM> although not shown, a drive wheel (sprocket) <NUM> rotatably provided in the rear portion of the track frame <NUM>, a plurality of rolling wheels rotatably provided in the lower portion of the track frame <NUM> although not shown, and a crawler <NUM> wound over the idler, drive wheel <NUM> and rolling wheels. The crawler <NUM> is made of hard rubber, or metals such as iron. The crawler drive unit <NUM> is provided to rotate and drive the drive wheel <NUM>.

<FIG> is a plan view of the running units <NUM>, lower frame <NUM> and crawler drive units <NUM>, viewed in the front-rear direction. <FIG> is a sectional view showing the crawler drive unit <NUM>. As shown in <FIG> and <FIG>, the crawler drive unit <NUM> has an electric motor <NUM>, a transmission mechanism <NUM> connected to the electric motor <NUM>, and a speed reduction mechanism <NUM> connected to the transmission mechanism <NUM>.

The electric motor <NUM> includes a stator fixedly attached within a motor case <NUM>, although not shown, and a rotor <NUM> rotatable relative to the stator. The electric motor <NUM> is driven by the power fed thereto from an external power supply (battery) provided in the vehicle body <NUM>. The electric motor <NUM> can be any one of a variety of motors as long as they are driven by power fed thereto, such as so-called brush motors and brushless motors.

The motor case <NUM> has a connector <NUM> on the outer peripheral surface thereof, which is designed to feed power to the not-shown stator. To the connector <NUM>, an external connector extending from the not-shown external power supply is connected. The connector <NUM> has a receiving port 50a to which the not-shown external connector is connected.

The motor case <NUM> rotatably supports a motor shaft <NUM> of the rotor <NUM>. A part of the motor shaft <NUM> protrudes out of the motor case <NUM> in the direction along the rotational axis Jm of the motor shaft <NUM>. A tip end 7a of the protruding portion of the motor shaft <NUM> has splines on the outer peripheral surface thereof. To the tip end 7a, the transmission mechanism <NUM> is connected. The receiving port 50a of the connector <NUM> on the motor case <NUM> is oriented away from the tip end 7a of the motor shaft <NUM>.

The portion of the motor shaft <NUM> that protrudes out of the motor case <NUM> is surrounded by a cylindrical support case <NUM>. The support case <NUM> protrudes out of the motor case <NUM> in the direction along the rotational axis Jm and terminates before the tip end 7a of the motor shaft <NUM>. The support case <NUM> has, on the inner peripheral surface thereof, a seal member <NUM> on the side opposite to the motor case <NUM>. The seal member <NUM> ensures the seal between the support case <NUM> and the motor shaft <NUM>. The end of the support case <NUM> opposite to the motor case <NUM> is also connected to the transmission mechanism <NUM>.

The transmission mechanism <NUM> includes a transmission-side housing <NUM> and two spur gears <NUM> and <NUM> (a first spur gear <NUM>, a second spur gear <NUM>) rotatably housed in the transmission-side housing <NUM>. The transmission-side housing <NUM> has a housing body <NUM> shaped like a box open toward the electric motor <NUM>, and a closing plate <NUM> closing an opening 21a of the housing body <NUM>. The support case <NUM> is fixedly attached to the closing plate <NUM>. The closing plate <NUM> has a shaft insertion hole <NUM> formed therein into which the motor shaft <NUM> is inserted. The tip end 7a of the motor shaft <NUM> is inserted into the housing body <NUM> through the shaft insertion hole <NUM>.

An outer peripheral wall <NUM> b of the housing body <NUM> has a working oil inlet <NUM> formed therein. A bottom wall 21c of the housing body <NUM> has a connection port <NUM> formed therein. The housing body <NUM> has a transmission-side oil channel <NUM> formed therein, which establishes communication between the connection port <NUM> and the working oil inlet <NUM> and extends from the outer peripheral wall 21b to the bottom wall 21c. The working oil inlet <NUM>, the connection port <NUM>, and the transmission-side oil channel <NUM> are used to inject a lubricant oil into the speed reduction mechanism <NUM>.

In the housing body <NUM>, the two spur gears <NUM> and <NUM> are stored while meshing with each other. Of the two spur gears <NUM> and <NUM>, the first spur gear <NUM> is fixedly fitted onto the tip end 7a of the motor shaft <NUM>. The splines on the tip end 7a allows the motor shaft <NUM> and the first spur gear <NUM> to rotate integrally with each other.

Of the two spur gears <NUM> and <NUM>, the second spur gear <NUM> is rotatable on the axis Jh, which is parallel to and offset from the rotational axis Jm of the motor shaft <NUM> in the radial direction with respect to the motor shaft <NUM> (the second spur gear <NUM>). The second spur gear <NUM> has a larger number of teeth than the first spur gear <NUM>. Accordingly, the rotation of the second spur gear <NUM> is slower than the rotation of the first spur gear <NUM>.

Into the second spur gear <NUM>, an end 16a of an input shaft (an example of an input part recited in the claims) <NUM> of the speed reduction mechanism <NUM> is fixedly fitted. The end 16a has splines, so that the second spur gear <NUM> and the input shaft <NUM> are rotatable integrally with each other. The rotational axis Jn of the input shaft <NUM> is aligned with the rotational axis Jh of the second spur gear <NUM>. Since the rotational axis Jh of the second spur gear <NUM> is parallel to the rotational axis Jm of the motor shaft <NUM>, the rotational axis Jn of the input shaft <NUM> is also parallel to the rotational axis Jm of the motor shaft <NUM>.

The input shaft <NUM> is solid. The input shaft <NUM> is inserted into the housing body <NUM> from the speed reduction mechanism <NUM> side through a shaft insertion hole <NUM> formed in the bottom wall <NUM> c of the housing body <NUM>. In the shaft insertion hole <NUM>, a seal member <NUM>, and a bearing <NUM> are provided. The seal member <NUM> seals between the bottom wall 21c of the housing body <NUM> and the input shaft <NUM>. The bearing <NUM> rotatably supports the input shaft <NUM> on the transmission mechanism <NUM> side thereof.

The speed reduction mechanism <NUM> includes, in addition to the input shaft <NUM>, a reduction-side housing <NUM> that rotatably supports the input shaft <NUM>, and a plurality of stages (two stages in the present embodiment) formed by gear mechanism 18A and 18B (the first and second stages are respectively formed by the gear mechanisms 18A and 18B) connected to the reduction-side housing <NUM>. In the following description of the speed reduction mechanism <NUM>, the simple term "radial direction" refers to the radial direction of the input shaft <NUM>.

The reduction-side housing <NUM> is fixedly attached to the bottom wall 21c of the housing body <NUM> constituting the transmission-side housing <NUM>. The reduction-side housing <NUM> has a base part <NUM> and a bearing housing <NUM> that form a single piece. The base part <NUM> is stacked on the bottom wall 21c of the housing body <NUM>, and the bearing housing <NUM> protrudes from the base part <NUM> away from the electric motor <NUM>. A plurality of first fastener seats <NUM> are integrally formed on an outer peripheral surface 19a of the base part <NUM> such that the first fastener seats <NUM> protrude outwardly in the radial direction. The first fastener seats <NUM> are used to secure the crawler drive unit <NUM> to the running unit <NUM>. The base part <NUM> has a through hole 19b formed therein through which the input shaft <NUM> runs.

The bearing housing <NUM> has a depression <NUM>, which is continuous from the through hole 19b formed in the base part <NUM>. At the bottom of the depression <NUM> (on the side opposite to the transmission mechanism <NUM>), a shaft insertion hole <NUM> is formed through the bearing housing <NUM> in the direction extending along the rotational axis Jn. Through the shaft insertion hole <NUM>, another end 16b of the input shaft <NUM> projects away from the transmission mechanism <NUM>. In the shaft insertion hole <NUM>, a bearing <NUM> and a seal member <NUM> are provided. The bearing <NUM> rotatably supports the input shaft <NUM>, and the seal member <NUM> seals between the bearing housing <NUM> and the input shaft <NUM>.

A parking brake <NUM> is provided in the depression <NUM> in the bearing housing <NUM>. The parking brake <NUM> is configured to restrict or allow the rotation of the input shaft <NUM>. The parking brake <NUM> includes a plate 32a, which is constantly pressed by a not-shown spring. This restricts the rotation of the input shaft <NUM>. To release the parking brake <NUM>, a working oil is supplied to the parking brake <NUM>. This allows the working oil to produce pressure to compress and deform the not-shown spring. This resultantly releases the plate 32a from being pressed by the spring, thereby releasing the input shaft <NUM>.

On an outer peripheral wall 20a of the bearing housing <NUM>, a reduction-side oil channel <NUM> is formed to establish connection between the depression <NUM> and the connection port <NUM> of the transmission-side housing <NUM>. Through the reduction-side oil channel <NUM>, the connection port <NUM> of the transmission-side housing <NUM>, the transmission-side oil channel <NUM> and the working oil inlet <NUM>, the working oil is fed from outside into the depression <NUM>. This activates the parking brake <NUM>. A plurality of second pillars <NUM>, which are integrally formed on the bearing housing <NUM>, project from the side away from the transmission mechanism <NUM>. The second pillars <NUM> constitute part of the gear mechanisms 18A and 18B.

The gear mechanisms 18A and 18B are located on the opposite side to the transmission mechanism <NUM> with the bearing housing <NUM> being provided therebetween, and aligned with the rotational axis Jn. The gear mechanisms 18A and 18B are arranged next to each other in the order of the gear mechanism 18A of the first stage and the gear mechanism 18B of the second stage, such that the gear mechanism 18B is closer to the bearing housing <NUM> than is the gear mechanism 18A.

The gear mechanism 18A of the first stage is a so-called planetary gear mechanism. The gear mechanism 18A of the first stage includes a first sun gear <NUM>, a first planetary gear <NUM>, an internal gear <NUM>, and a first planetary gear <NUM>. The first sun gear <NUM> is coupled to the other end 16b of the input shaft <NUM> via a coupling <NUM>, the first planetary gear <NUM> meshes with the first sun gear <NUM>, the internal gear <NUM> meshes with the first planetary gear <NUM>, and the first planetary carrier <NUM> supports the first planetary gear <NUM>. The first sun gear <NUM> is rotatable integrally with the input shaft <NUM>. A plurality of (for example, three) first planetary gears <NUM> are provided. The first planetary gears <NUM> are arranged at equal intervals around the first sun gear <NUM>.

The internal gear <NUM> is cylindrically shaped to surround the gear mechanisms 18A and 18B and the bearing housing <NUM>. An end 37a of the internal gear <NUM> facing the transmission mechanism <NUM> is close to the base part <NUM> of the reduction-side housing <NUM>. Between the base part <NUM> and the end 37a of the internal gear <NUM>, a mechanical seal (floating seal) <NUM> is provided. The mechanical seal <NUM> can prevent grease (lubricating oil) stored in the internal gear <NUM> from leaking out through between the end 37a of the internal gear <NUM> and the base part <NUM>.

At another end 37b of the internal gear <NUM> facing away from the transmission mechanism <NUM>, an end plate <NUM> is provided to close an opening 37c of the internal gear <NUM>. A plurality of second fastener seats <NUM> are integrally formed on the outer peripheral surface of the internal gear <NUM>, positioned near the transmission-side housing <NUM>, and protrude outwardly in the radial direction. The second fastener seats <NUM> are configured to transmit the driving force produced by the crawler drive unit <NUM> to the running unit <NUM> (see the below for more details).

The internal gear <NUM> is rotatably supported on the bearing housing <NUM> via two bearings 39a and 39b. The internal gear <NUM> has internal teeth 37d positioned correspondingly to the gear mechanisms 18A and 18B. The internal teeth 37d mesh with the first planetary gears <NUM>.

The first planetary carrier <NUM>, which supports the first planetary gears <NUM>, is located on the side facing the bearing housing <NUM>. The first planetary carrier <NUM> has, on a surface 38a thereof facing the first planetary gears <NUM>, first pillars <NUM> protruding and rotatably supporting the first planetary gears <NUM>. The first planetary carrier <NUM>, on another surface 38b thereof facing the bearing housing <NUM>, a second sun gear <NUM> integrated therewith. The second sun gear <NUM> constitutes the second-stage gear mechanism 18B.

The gear mechanism 18B of the second stage includes, in addition to the second sun gear <NUM>, a carrier gear <NUM>, and the internal gear <NUM>. The carrier gear <NUM> meshes with the second sun gear <NUM>, and the internal gear <NUM> meshes with the carrier gear <NUM>. The internal gear <NUM> is shared between the gear mechanism 18B of the second stage and the gear mechanism 18A of the first stage. The second sun gear <NUM> is shaped like a cylinder. The coupling <NUM> is inserted into the second sun gear <NUM> such that the coupling <NUM> is rotatable relative to the second sun gear <NUM>. A plurality of (for example, three) carrier gears <NUM> are provided. The carrier gears <NUM> are arranged at equal intervals around the second sun gear <NUM>. The carrier gears <NUM> are rotatably supported by the second pillars <NUM> integrated with the bearing housing <NUM>.

With the above arrangement, the crawler drive unit <NUM> is arranged such that the internal gear <NUM> of the speed reduction mechanism <NUM> is contained within the drive wheel <NUM> in the radial direction. The electric motor <NUM> is positioned inside the speed reduction mechanism <NUM> in the width direction. The second fastener seats <NUM> of the internal gear <NUM> are fixedly attached to the drive wheel <NUM>. The internal gear <NUM> is rotatable integrally with the drive wheel <NUM>. On the other hand, the first fastener seats <NUM> of the reduction-side housing <NUM> are fixedly attached to the track frame <NUM>.

As shown in detail in <FIG>, with the crawler drive units <NUM> being mounted on the running units <NUM>, the entire speed reduction mechanism <NUM> and almost the entire transmission mechanism <NUM> are contained within the running units <NUM> in the width direction or within the width of the running units <NUM>. More specifically, in <FIG>, it is only the closing plate <NUM> of the transmission mechanism <NUM> that protrudes inwardly in the width direction out of the running unit <NUM>.

The rotational axis Jm of the motor shaft <NUM> is immediately higher than the rotational axis In of the input shaft <NUM> (the rotational axis Jh of the second spur gear <NUM>). The electric motor <NUM> is entirely positioned higher than the bottom surface 104a of the lower frame <NUM>. The entire electric motor <NUM> here refers to the connector <NUM>, motor case <NUM>, and support case <NUM> that form the outline of the electric motor <NUM>. The term "higher" means higher in the direction of gravity. If something is higher, it is more distant from the surface of road. To be specific, the electric motor <NUM> and the lower frame <NUM> are positioned relative to each other such that, by referring to <FIG>, the lower edge of the motor case <NUM> is aligned with the bottom surface 104a as seen in the front-rear direction.

The following describes how the crawler drive unit <NUM> works. As shown in <FIG> and <FIG>, the motor shaft <NUM> of the rotor <NUM> is rotated as the electric motor <NUM> is driven. As the motor shaft <NUM> rotates, the rotation of the motor shaft <NUM> is transmitted to the input shaft <NUM> of the speed reduction mechanism <NUM> via the first and second spur gears <NUM> and <NUM> of the transmission mechanism <NUM>. Here, the two spur gears <NUM> and <NUM> reduces the rotation of the motor shaft <NUM> and transmits the reduced rotation to the input shaft <NUM>.

As the motor shaft <NUM> is rotated, the first sun gear <NUM> is rotated integrally with the motor shaft <NUM>. The first planetary gears <NUM> meshing with the internal gear <NUM> and the first sun gear <NUM> rotate on their own axes on the first pillars <NUM>, while orbiting around the first sun gear <NUM>. The first planetary carrier <NUM> supporting the first planetary gears <NUM> rotates around the rotational axis In of the input shaft <NUM>. The second sun gear <NUM> is rotated integrally with the first planetary carrier <NUM>. The second sun gear <NUM> is formed in a cylindrical shape. Since the second sun gear <NUM> has the coupling <NUM> inserted therein in the radial direction, the rotation of the second sun gear <NUM> does not interfere with the rotation of the input shaft <NUM>.

As the second sun gear <NUM> rotates, the carrier gears <NUM> meshing with the internal gear <NUM> and the second sun gear <NUM> rotate on their own axes on the second pillars <NUM>. The rotation of the carrier gears <NUM> rotates the internal gear <NUM>. The drive wheel <NUM> rotates integrally with the internal gear <NUM>. In other words, the internal gear <NUM> reduces the rotation of the motor shaft <NUM> and outputs the reduced rotation to the drive wheel <NUM>. The rotation of the drive wheel <NUM> actuates the crawler <NUM>, as a result of which the construction machine <NUM> runs. In this way, the speed reduction mechanism <NUM> transmits the driving force to the crawler <NUM> via the drive wheel <NUM>. The electric motor <NUM> applies the driving force to the speed reduction mechanism <NUM> via the transmission mechanism <NUM>.

In the crawler drive unit <NUM>, the rotational axis Jm of the motor shaft <NUM> is immediately higher than the rotational axis Jn of the input shaft <NUM> (the rotational axis Jh of the second spur gear <NUM>). The electric motor <NUM> is entirely positioned higher than the bottom surface 104a of the lower frame <NUM>. With such arrangement, the electric motor <NUM> can be positioned higher than the speed reduction mechanism <NUM> in the crawler drive unit <NUM>. In this way, the electric motor <NUM> can be spaced away as much as possible from the road surface even if the electric motor <NUM> and the speed reduction mechanism <NUM> constitutes the crawler drive unit <NUM>, which is used in the running unit <NUM>, and the electric motor <NUM> protrudes out of the running unit <NUM> in the width direction. Therefore, the possibility of the electric motor <NUM> coming into contact with soil, sand, rocks, etc. while the construction machine <NUM> is in motion can be reduced. The construction machine <NUM> can run well.

In particular, since the electric motor <NUM> is entirely positioned higher than the bottom surface 104a of the lower frame <NUM>, the possibility of the electric motor <NUM> coming into contact with soil, sand, rocks, etc. while the construction machine <NUM> is in motion can be certainly reduced. Since the electric motor <NUM> is positioned as high as possible, a working space can be left below the electric motor <NUM>. This allows the crawler drive unit <NUM> to be maintained in a better manner.

The electric motor <NUM> (motor shaft <NUM>) and the speed reduction mechanism <NUM> (input shaft <NUM>), which are connected together via the transmission mechanism <NUM>, are arranged such that their rotational axes Jm and In are parallel. This allows the driving power to be transmitted more efficiently from the electric motor <NUM> to the speed reduction mechanism <NUM> than in a case where the rotational axes Jm and Jn intersect. More specifically, the transmission mechanism <NUM> can be configured by the two spur gears <NUM> and <NUM> meshing with each other. The use of the spur gears <NUM> and <NUM> can contribute to transmit the rotation of the motor shaft <NUM> to the input shaft <NUM> efficiently.

The second spur gear <NUM> has a larger number of teeth than the first spur gear <NUM>. Accordingly, the rotation of the second spur gear <NUM> is slower than the rotation of the first spur gear <NUM>. This means that, in addition to the speed reduction mechanism <NUM>, the transmission mechanism <NUM> can also contribute to reduce the rotation of the motor shaft <NUM>. As a result, while the crawler drive unit <NUM> achieves a reduced size, it can also accomplish a high reduction ratio. The crawler drive unit <NUM> relating to the present aspect can achieve a high output.

With the crawler drive unit <NUM> being mounted on the running unit <NUM>, the entire speed reduction mechanism <NUM> and almost the entire transmission mechanism <NUM> are contained within the running unit <NUM> in the width direction or within the width of the running unit <NUM>. In this way, the speed reduction mechanism <NUM> can be covered with the running unit <NUM> (the drive wheel <NUM>). This can prevent the speed reduction mechanism <NUM> from coming into contact with soil, sand, rocks and the like. This can lower the chance of the speed reduction mechanism <NUM> breaking down.

In the above-described first embodiment, the electric motor <NUM> is entirely positioned higher than the bottom surface 104a of the lower frame <NUM>. The present embodiment, however, is not limited to such, and any configuration is acceptable as long as the entire electric motor <NUM> is positioned higher than the rotational axis In of the input shaft <NUM>. In this way, the electric motor <NUM> can be still positioned higher than the speed reduction mechanism <NUM>, contrary to the case where the rotational axis Jm of the motor shaft <NUM> is aligned with the rotational axis Jn of the input shaft <NUM>. This modification can produce the same effects as the first embodiment described above.

The following describes a second embodiment of the present invention with reference to <FIG> and <FIG> and by referring to <FIG>. <FIG> is a plan view of running units <NUM>, a lower frame <NUM> and crawler drive units <NUM> relating to a second embodiment, viewed in the front-rear direction. <FIG> schematically shows part of the running unit <NUM> and the crawler drive unit <NUM> relating to the second embodiment of the present invention, viewed in the width direction. <FIG> presents a view seen along the arrow A-A in <FIG>. The second embodiment has the same features as the first embodiment described above. In the following description of the second embodiment, those features are assigned with the same reference numerals as in the first embodiment and not described (this applies to a third embodiment described further below).

In the second embodiment, a construction machine <NUM> includes a vehicle body <NUM>, running units <NUM> for causing the vehicle body <NUM> to run, and crawler drive units <NUM> provided on the running units <NUM> and configured to drive the running units <NUM> (see also <FIG>). In terms of these features, the second embodiment is the same as the above-described first embodiment (so is the following third embodiment). The second embodiment is different from the first embodiment in terms of the following. The electric motors <NUM> are oriented differently between in the crawler drive units <NUM> relating to the second embodiment and in the crawler drive units <NUM> relating to the first embodiment.

Specifically, as shown in <FIG> and <FIG>, the electric motors <NUM> of the crawler drive units <NUM> provided on the running units <NUM> are offset from their speed reduction mechanisms <NUM> in the front-rear direction. The two electric motors <NUM> are arranged next to each other in the front-rear direction. The electric motors <NUM> are entirely accommodated on the projection of the running units <NUM>. In each crawler drive unit <NUM>, the rotational axis Jm of the motor shaft <NUM> and the rotational axis In of the input shaft <NUM> are aligned with the same horizontally extending line. In other words, the electric motor <NUM> and the speed reduction mechanism <NUM> are located at the same height.

With such arrangement, as shown in, for example, <FIG>, the respective crawler drive units <NUM> on the left and right running units <NUM> can be prevented from interfering with each other even when the running units <NUM> are arranged with a short distance being provided therebetween. Since the second embodiment eliminates the need of providing appropriate crawler drive units <NUM> for different spacings between the left and right running units <NUM>, the crawler drive units <NUM> can be more versatile.

<FIG> schematically shows part of the running unit <NUM> and the crawler drive unit <NUM> relating to a modification example of the second embodiment of the present invention, viewed in the width direction. <FIG> corresponds to <FIG> referred to in the above. According to the above-described second embodiment, in each crawler drive unit <NUM>, the rotational axis Jm of the motor shaft <NUM> and the rotational axis In of the input shaft <NUM> are aligned with the same horizontally extending line. The present embodiment, however, is not limited to such, and the rotational axis Jm of the motor shaft <NUM> may be positioned higher than the rotational axis In of the input shaft <NUM> as shown in <FIG>. Such arrangement can not only produce the same effects as the above-described second embodiment but also lower the possibility of the electric motors <NUM> coming into contact with soil, sand, rocks, etc. while the construction machine <NUM> is in motion.

The following describes a third embodiment of the present invention with reference to <FIG> schematically shows part of a running unit <NUM> and a crawler drive unit <NUM> relating to the third embodiment of the present invention, viewed in the width direction. <FIG> corresponds to <FIG> referred to in the above. As shown in <FIG>, the third embodiment is different from the second embodiment in that a transmission mechanism <NUM> of the third embodiment is different from the transmission mechanism <NUM> of the second embodiment (the first embodiment).

To be specific, the transmission mechanism <NUM> has a third spur gear <NUM> between the first spur gear <NUM> and the second spur gear <NUM>. The third spur gear <NUM> may have a different number of teeth than the first or second spur gear <NUM> or <NUM>. The third spur gear <NUM> may have the same number of teeth as the first spur gear <NUM>. In the third embodiment, the third spur gear <NUM> has the same number of teeth as the first spur gear <NUM>. In each crawler drive unit <NUM>, the rotational axis Jm of the motor shaft <NUM> and the rotational axis Jn of the input shaft <NUM> are aligned with the same horizontally extending line. In other words, the electric motor <NUM> and the speed reduction mechanism <NUM> are located at the same height.

Accordingly, the third embodiment produces the same effects as the second embodiment described above. Since the transmission mechanism <NUM> includes the three spur gears <NUM>, <NUM> and <NUM>, the rotational axis Jm of the motor shaft <NUM> can be significantly offset from the rotational axis In of the input shaft <NUM>. In this manner, the crawler drive unit <NUM> can benefit from more flexible layouts.

Since the third spur gear <NUM> has a different number of teeth than the first or second spur gear <NUM> or <NUM>, the transmission mechanism <NUM> can achieve a higher reduction ratio. As a result, while the crawler drive unit <NUM> achieves a reduced size, it can also accomplish a high reduction ratio. The crawler drive unit <NUM> can achieve a high output.

According to the third embodiment described above, the transmission mechanism <NUM> is constituted by the three spur gears <NUM>, <NUM> and <NUM>. The present embodiment, however, is not limited to such, and the transmission mechanism <NUM> may be constituted by four or more spur gears.

<FIG> schematically shows part of the running unit <NUM> and the crawler drive unit <NUM> relating to a modification example of the third embodiment of the present invention, viewed in the width direction. <FIG> corresponds to <FIG> referred to in the above. According to the above-described third embodiment, in the crawler drive unit <NUM>, the rotational axis Jm of the motor shaft <NUM> and the rotational axis In of the input shaft <NUM> are aligned with the same horizontally extending line. The present embodiment, however, is not limited to such, and the rotational axis Jm of the motor shaft <NUM> may be positioned higher than the rotational axis In of the input shaft <NUM> as shown in <FIG>. Such arrangement can not only produce the same effects as the third embodiment but also lower the possibility of the electric motor <NUM> coming into contact with soil, sand, rocks, etc. while the construction machine <NUM> is in motion.

The configuration of the transmission mechanism <NUM> relating to the third embodiment described above may be applied to the transmission mechanism <NUM> relating to the first embodiment described above. In this manner, the electric motor <NUM> can be positioned further higher than the speed reduction mechanism <NUM>. Therefore, the possibility of the electric motor <NUM> coming into contact with soil, sand, rocks, etc. while the construction machine <NUM> is in motion can be further reduced. The construction machine <NUM> can run further well.

The present invention is not limited to the above embodiments, but encompasses various modifications of the above embodiments within the purport of the present invention. For example, the foregoing embodiments provide the crawler drive units <NUM>, <NUM> and <NUM> configured to drive the running units <NUM> provided on the construction machine <NUM>. The present invention, however, is not limited to such, and the above-described crawler drive units <NUM>, <NUM> and <NUM> can be applied to various devices having the running units <NUM>.

In the above-described embodiments, the running unit <NUM> includes the track frame <NUM>, the idler, the drive wheel (sprocket) <NUM>, the rolling wheel, and the crawler <NUM> wound around the idler, driving wheel <NUM> and rolling wheel. The present invention, however, is not limited to such, and the running unit <NUM> may be configured in any manner as long as the rotation of the drive wheel <NUM> actuates the crawler <NUM>, as a result of which the construction machine <NUM> runs.

In the embodiments described above, the transmission mechanisms <NUM> and <NUM> are constituted by more than one spur gear (<NUM>, <NUM> and <NUM>). The present invention, however, is not limited to such, and the transmission mechanisms <NUM>, <NUM> can be configured in any manner as long as they can transmit the rotation of the motor shaft <NUM> of the electric motor <NUM> to the input shaft <NUM> of the speed reduction mechanism <NUM>. As another example, a pulley and a timing belt may constitute the transmission mechanisms <NUM> and <NUM>. As yet another example, a sprocket and a chain may constitute the transmission mechanisms <NUM> and <NUM>.

For example, a universal joint may be used as the transmission mechanism. In this case, the rotational axis Jm of the motor shaft <NUM> does not need to be parallel to the rotational axis Jn of the input shaft <NUM>. If the rotational axis Jm of the motor shaft <NUM> intersects the rotational axis In of the input shaft <NUM>, it may be only required that the motor shaft <NUM> be positioned higher than the rotational axis In of the input shaft <NUM>. This arrangement produces the same effects as the above embodiments.

In the above-described embodiments, the transmission mechanisms <NUM> and <NUM> are also configured to reduce the rotation of the motor shaft <NUM>. The present invention, however, is not limited to such, and the transmission mechanisms <NUM>, <NUM> may be configured in any manner as long as they can transmit the rotation of the motor shaft <NUM> to the speed reduction mechanism <NUM>. For example, the transmission mechanisms <NUM> and <NUM> may be configured to keep or increase the rotation of the motor shaft <NUM> and transmit the resulting rotation to the speed reduction mechanism <NUM>.

In the above-described embodiments, the input shaft <NUM> is referred to as the input part in the claims. The present invention, however, is not limited to such, and the input part may be configured in any manner as long as it is capable of inputting the rotation of the electric motor <NUM> to the speed reduction mechanism <NUM>. For example, the input shaft <NUM> is solid in the above-described embodiments, but may be hollow.

In the above-described embodiments, the speed reduction mechanism <NUM> includes the gear mechanisms 18A and 18B forming two stages. The gear mechanism 18A of the first stage is a so-called planetary gear mechanism including the first sun gear <NUM>, the first planetary gears <NUM>, the internal gear <NUM> and the first planetary carrier <NUM>. The gear mechanism 18B of the second stage includes the second sun gear <NUM>, the carrier gears <NUM> and the internal gear <NUM>. The present invention, however, is not limited to such, and the speed reduction mechanism <NUM> can be configured in any manner as long as it can reduce the rotation of the motor shaft <NUM> of the electric motor <NUM> and output the reduced rotation. For example, a plurality of spur gears may mesh with each other, so that the rotational axis of the input part is offset from the rotational axis of the output part (the output side).

In the above-described embodiments, the speed reduction mechanism <NUM> is configured to transmit the rotation of the motor shaft <NUM> of the electric motor <NUM> transmitted thereto via the transmission mechanisms <NUM> and <NUM> from the internal gear <NUM> to the drive wheel <NUM>. The present invention, however, is not limited to such, and the speed reduction mechanism <NUM> may be configured in any manner as long as it can transmit the rotation of the motor shaft <NUM> to the drive wheel <NUM>. In other words, when the speed reduction mechanism is constituted by a plurality of spur gears, for example, it can be configured in any manner as long as the spur gear of the last stage can transmit the rotation of the motor shaft <NUM> to the drive wheel <NUM>.

In the above embodiments, the electric motor <NUM> protrudes in the width direction out of the running unit <NUM>. The present invention, however, is not limited to such, and the above-described crawler drive units <NUM>, <NUM> and <NUM> can be applied even if, for example, the crawler drive units <NUM>, <NUM> and <NUM> can be contained within the running unit <NUM> so that the electric motor <NUM> does not protrude in the width direction out of the running unit <NUM>. Note that the crawler drive units <NUM>, <NUM> and <NUM> described above can be suitably applied when the electric motor <NUM> protrudes in the width direction out of the running unit <NUM>.

Claim 1:
A crawler drive unit (<NUM>, <NUM>, <NUM>) comprising:
a speed reduction mechanism (<NUM>) suitable to be provided in a running unit (<NUM>) for causing a vehicle body (<NUM>) to run, the speed reduction mechanism (<NUM>) being suitable to transmit a driving force to a crawler (<NUM>) provided on the running unit (<NUM>);
a transmission mechanism (<NUM>, <NUM>) for transmitting the driving force to the speed reduction mechanism (<NUM>); and
an electric motor (<NUM>) for applying a rotational force to the transmission mechanism (<NUM>, <NUM>), wherein the electric motor (<NUM>) includes:
a motor case (<NUM>),
a motor shaft (<NUM>) which protrudes out of the motor case (<NUM>), and
a support case (<NUM>) which protrudes out of the motor case (<NUM>) in a direction that is the same as a direction in which the motor shaft (<NUM>) protrudes and supports the motor shaft (<NUM>)
wherein the speed reduction mechanism (<NUM>) includes an input part (<NUM>) for receiving the driving force input thereto from the transmission mechanism (<NUM>, <NUM>),
wherein the motor shaft (<NUM>) of the electric motor (<NUM>) is positioned higher than a rotational axis (Jn) of the input part (<NUM>), and
an end of the support case (<NUM>) opposite to a side of the motor case (<NUM>) is connected to the transmission mechanism (<NUM>).