Patent Description:
In a construction machine such as an excavator, actuators are hydraulically controlled via a pump using an engine as a drive source. In recent years, it has been proposed to replace the engine as a drive source with a battery used as a drive source for driving the pump. Further, as disclosed in <CIT>, it has been proposed to use electric motors for electrically driving the actuators on a battery.

Since an electric motor tends to have a larger size than a hydraulic motor, an electric motor employed is required to rotate at a high speed for downsizing. However, when an electric motor rotates at a high speed, heating tends to occur particularly at a first-stage speed reducing unit that is directly connected to the motor shaft. Therefore, the heated portion needs to be cooled. <CIT>, for example, discloses that a fan and a hood are provided on the input shaft side for forcible air cooling to cool the heated portion. However, the cooling system with a fan is open for intake and exhaust of the air, and thus dirt enters the cooling system in the service environment of the construction machines. Therefore, with the cooling system with a fan, it is difficult to install a downsized electric motor on the construction machines. This drawback needs to be overcome. <CIT> and <CIT> disclose a speed reducer according to the preamble of claim <NUM>.

The present invention provides a speed reducer and a construction machine, the speed reducer using a fluid to inhibit heating of the speed reducing unit, thereby permitting both high speed rotation and downsizing and also facilitating installation on the construction machines. The above mentioned drawback is solved by the invention as claimed in claim <NUM>. The latter defines a speed reducer for which protection is sought. The dependent claims concern particular embodiments of the invention as claimed in claim <NUM>.

With the speed reducer and the construction machine according to the present invention, it is possible to inhibit heating of the speed reducing unit, thereby permitting both high speed rotation and downsizing and also facilitating installation on the construction machines.

The following describes embodiments of the present invention with reference to the drawings. In the following embodiments and modifications, like elements will be denoted by the same reference signs and redundant descriptions will be partly omitted.

<FIG> is a side view of an excavator <NUM> (construction machine) including an electric motor <NUM> with a speed reducer <NUM> in a driving unit. The excavator <NUM> of the embodiment travels by a crawler, which is a form of an undercarriage <NUM>. The excavator <NUM> includes the undercarriage <NUM> and a turning upper structure <NUM> disposed on the undercarriage <NUM> so as to be turnable.

The turning upper structure <NUM> includes a cab <NUM>, a boom <NUM>, an arm <NUM>, and a bucket <NUM>. The cab <NUM> houses an operator, the boom <NUM> is rotatably supported at its proximal end portion on the front portion of the cab <NUM>, the arm <NUM> is rotatably connected at its proximal end portion to the distal end portion of the boom <NUM>, and the bucket <NUM> is rotatably connected to the distal end portion of the arm <NUM>. Joints of the cab <NUM>, the boom <NUM>, the arm <NUM>, and the bucket <NUM> have drive devices installed therein (not shown). The drive devices in these joints are driven by operation of the operator in the cab <NUM>. The undercarriage <NUM> includes a crawler body <NUM> (vehicle body) and a drive wheel <NUM> rotatably supported on the crawler body <NUM>. The undercarriage <NUM> is provided with an electric motor <NUM> including a speed reducer <NUM> for driving the drive wheel <NUM>.

<FIG> is a sectional view of the speed reducer <NUM> with the electric motor <NUM> (cut along a plane including the rotational axis O). The shapes and dimensions of the speed reducer <NUM> shown in <FIG> are examples and do not correspond to actual ones.

The speed reducer <NUM> is connected to the electric motor <NUM> that can rotate both positively and negatively. The rotational driving force of the electric motor <NUM> is decelerated at the speed reducer <NUM> and output as a rotational motion that is transmitted to an axle provided on the drive wheel <NUM>.

The speed reducer <NUM> includes three speed reducing units <NUM> each formed of a planetary gear mechanism provided between a motor shaft <NUM> of the electric motor <NUM> and the axle. In the following description, the central axis of the motor shaft <NUM> is referred to as the rotational axis O. Further, the motor shaft <NUM> side in the direction along the rotational axis O is referred to as "the input side," while the side opposite thereto is referred to as "the output side.

The electric motor <NUM> includes a motor shaft <NUM>, a motor body <NUM>, a motor case <NUM> retaining the motor body <NUM>, and a motor flange <NUM> fixed to one end of the motor case <NUM>. The motor shaft <NUM> extends in the motor axis direction through the central portion of the motor body <NUM>. The distal end portion 20a of the motor shaft <NUM> positioned at one end side (the left side in the drawing) projects into the speed reducer <NUM>. The electric motor <NUM> is mounted to the speed reducer <NUM> via the motor flange <NUM>. The motor flange <NUM> is shaped like a plate. The motor flange <NUM> is mounted to the motor case <NUM> and projects radially outward relative to the motor case <NUM>. The electric motor <NUM> may be selected from various motors that drive on electricity, such as what is called brushed motors and brushless motors.

The speed reducer <NUM> includes a plurality of speed reducing units <NUM>. Specifically, the speed reducing units <NUM> of the speed reducer <NUM> include a first speed reducing unit 4A at the first stage, a second speed reducing unit 4B at the second stage, and a third speed reducing unit 4C at the third stage. The first speed reducing unit 4A, the second speed reducing unit 4B, and the third speed reducing unit 4C are arranged in the order in which the rotational driving force from the motor shaft <NUM> is transmitted. Specifically, these speed reducing units <NUM> are arranged in the order of the first speed reducing unit 4A, the third speed reducing unit 4C, and the second speed reducing unit 4B from the input side to the output side in the direction along the rotational axis O. That is, the third speed reducing unit 4C is interposed between the first speed reducing unit 4A and the second speed reducing unit 4B. The first speed reducing unit 4A is rotatably supported by a first ring gear 5A (gear). The second speed reducing unit 4B and the third speed reducing unit 4C share a second ring gear 5B and are rotatably supported by the second ring gear 5B. The first ring gear 5A and the second ring gear 5B constitute a ring gear <NUM>.

In the embodiment, as shown in <FIG>, the first ring gear 5A is connected to the crawler body <NUM>, and the second ring gear 5B is connected to the drive wheel <NUM> of the undercarriage <NUM>. However, the first ring gear 5A and the second ring gear 5B are not necessarily connected in this way to the excavator <NUM>. For example, it is also possible that the first ring gear 5A is connected to the drive wheel <NUM>, and the second ring gear 5B is connected to the crawler body <NUM>. In this configuration, the rotational driving force of the electric motor <NUM> is also transmitted to the undercarriage <NUM> via the speed reducer <NUM>.

The speed reducer <NUM> is fixed to an output-side end surface 23b of the motor flange <NUM> with a fixing bolt <NUM>. Specifically, the speed reducer <NUM> is mounted to the motor flange <NUM> such that an end portion of the first ring gear 5A on the input side (an input-side end surface 501a) is in tight contact with the output-side end surface 23b. Thus, a first speed reducer chamber 1A inside the speed reducer <NUM> is closed in an air-tight manner. The first speed reducer chamber 1A is filled with a lubricant.

The first ring gear 5A is shaped like a bottomed tube. The first ring gear 5A includes an inner tubular wall <NUM> and a bottom wall <NUM>. The inner tubular wall <NUM> is disposed coaxially with the rotational axis O, and the bottom wall <NUM> is opposed to the motor flange <NUM> and closes an output-side end portion of the inner tubular wall <NUM>. The input-side end surface 501a of the inner tubular wall <NUM> is fixed to the motor flange <NUM> with the fixing bolt <NUM>. That is, the first ring gear 5A is integrated with the electric motor <NUM> so as not to be rotatable relative to the electric motor <NUM>. In an opening of the inner tubular wall <NUM> on the electric motor <NUM> side, a first bearing <NUM> is provided to support the motor shaft <NUM> rotatably. A first internal gear <NUM> is provided on an inner peripheral surface of the inner tubular wall <NUM> on the input side. A plurality of first planetary gears <NUM> are disposed inside the inner tubular wall <NUM> so as to mesh with the first internal gear <NUM>.

The first ring gear 5A is not mounted to the motor shaft <NUM> that rotates, but is fixed to the motor flange <NUM> that is fixed to the motor case <NUM>. Thus, the first ring gear 5A operates as a fixed gear.

In the embodiment, the inner tubular wall <NUM> is provided with a first fixing portion <NUM> to be fixed to the crawler body <NUM> of the excavator <NUM>.

On the bottom wall <NUM> of the first ring gear 5A, there are provided a second bearing <NUM> and rotational support columns <NUM>. The second bearing <NUM> rotatably supports a speed reducing input shaft <NUM> that is formed of a shaft member, and the rotational support columns <NUM> rotatably support third gears <NUM> of the third speed reducing unit 4C. The rotational support columns <NUM> are provided on an output-side end surface 502a of the bottom wall <NUM> so as to project integrally in the direction of the rotational axis O.

The second ring gear 5B includes an outer tubular wall <NUM> that is fitted on an outer peripheral surface 501b of the inner tubular wall <NUM> of the first ring gear 5A via a third bearing <NUM> so as to be rotatable in the circumferential direction. A lid <NUM> is mounted to an opening positioned on the output side (the left side in the drawing) of the outer tubular wall <NUM>. The lid <NUM> closes tightly a second speed reducer chamber 1B filled with the lubricant.

A second internal gear <NUM> is provided on an inner peripheral surface of the outer tubular wall <NUM>. A plurality of second planetary gears <NUM> and the third gears <NUM> (described later) are disposed inside the outer tubular wall <NUM>. Both the plurality of second planetary gears <NUM> and the third gears <NUM> are disposed so as to mesh with the second internal gear <NUM>. The second ring gear 5B is associated with both the second planetary gears <NUM> and the third gears <NUM>. The second ring gear 5B is a stepped gear having a large-diameter gear 57A and a small-diameter gear 57B. The large-diameter gear 57A, which is a portion of the second internal gear <NUM> meshed with the second planetary gears <NUM>, has a larger inner diameter than the small-diameter gear 57B, which is a portion of the second internal gear <NUM> meshed with the third gears <NUM>. In the embodiment, the outer tubular wall <NUM> is provided with a second fixing portion <NUM> to be fixed to the drive wheel <NUM> of the excavator <NUM>. The large-diameter gear 57A meshed with the second speed reducing unit 4B and the small-diameter gear 57B meshed with the third speed reducing unit 4C are not capable of relative rotation.

The speed reducing input shaft <NUM>, which extends through the bottom wall <NUM> of the first ring gear 5A, and the rotational support columns <NUM>, which are fixed to the bottom wall <NUM>, are inserted in the second speed reducer chamber 1B.

As described above, the speed reducer <NUM> contains the first speed reducer chamber 1A, which forms space inside the first ring gear 5a, and the second speed reducer chamber 1B, which forms space inside the second ring gear 5B. The firsts speed reducer chamber 1A and the second speed reducer chamber 1B are partitioned by the bottom wall <NUM> of the first ring gear 5A. The output-side portion of the motor shaft <NUM> is inserted and positioned in the first speed reducer chamber 1A. The distal end portion 20a of the motor shaft <NUM> is connected with the speed reducing input shaft <NUM> positioned coaxially with the motor shaft <NUM>.

The first speed reducing unit 4A includes a first sun gear <NUM>, a plurality of first planetary gears <NUM>, and a first carrier <NUM>. The first sun gear <NUM> is connected coaxially to the motor shaft <NUM>. The plurality of first planetary gears <NUM> are arranged at regular intervals in the circumferential direction around the first sun gear <NUM>. The first planetary gears <NUM> are disposed to mesh with the first internal gear <NUM> of the first ring gear 5A and supported rotatably on the shaft portions <NUM> provided on the first carrier <NUM>. That is, the first planetary gears <NUM> are disposed to mesh with both the first sun gear <NUM> and the first ring gear 5A.

The shaft portions <NUM> of the first planetary gears <NUM> are coupled to the first carrier <NUM> by press-fitting. The first carrier <NUM> is shaped like a flat plate ring. The first carrier <NUM> is positioned on the output side of the first planetary gears <NUM> in the direction of the rotational axis O and fixed coaxially with the motor shaft <NUM> so as to be prohibited from rotating relative to the speed reducing input shaft <NUM>. The connection portion between the motor shaft <NUM> and the speed reducing input shaft <NUM> is positioned between the first sun gear <NUM> and the first carrier <NUM>.

In the first speed reducing unit 4A, the rotational driving force of the electric motor <NUM> is decelerated through the motor shaft <NUM>, the first sun gear <NUM>, the first planetary gears <NUM>, and the first carrier <NUM> and transmitted to the speed reducing input shaft <NUM>.

The second speed reducing unit 4B includes a second sun gear <NUM>, a plurality of second planetary gears <NUM>, and a second carrier <NUM>. The second sun gear <NUM> is connected coaxially with a distal end portion 3a of the speed reducing input shaft <NUM> positioned on the output side (the left side in the drawing). The plurality of second planetary gears <NUM> are arranged at regular intervals in the circumferential direction around the second sun gear <NUM>. The second planetary gears <NUM> are disposed to mesh with the second internal gear <NUM> (the large-diameter gear 57A) of the second ring gear 5B and supported rotatably on the shaft portions <NUM> provided on the second carrier <NUM>. That is, the second planetary gears <NUM> are disposed to mesh with both the second sun gear <NUM> and the second ring gear 5B.

The shaft portions <NUM> of the second planetary gears <NUM> are coupled to the second carrier <NUM> by press-fitting. The second carrier <NUM> is shaped like a flat plate ring. The second carrier <NUM> is positioned on the input side of the second planetary gears <NUM> in the direction of the rotational axis O and fixed coaxially with the motor shaft <NUM> so as to be rotatable relative to the speed reducing input shaft <NUM>. The second carrier <NUM> is positioned between the second sun gear <NUM> and a third sun gear <NUM> in the direction of the motor axis.

In the second speed reducing unit 4B, the rotational driving force decelerated at the first speed reducing unit 4A is decelerated through the speed reducing input shaft <NUM>, the second sun gear <NUM>, the second planetary gears <NUM>, and the second carrier <NUM> and transmitted to the third sun gear <NUM> of the third speed reducing unit 4C.

The third speed reducing unit 4C includes a third sun gear <NUM> and a plurality of third gears <NUM>. The third sun gear <NUM> has a hollow portion penetrated by the speed reducing input shaft <NUM>. The speed reducing input shaft <NUM> penetrates both the first carrier <NUM> and the third sun gear <NUM>. The speed reducing input shaft <NUM> penetrating the third sun gear <NUM> has the distal end portion 3a to which the second sun gear <NUM> is fixed coaxially. The output side of the third sun gear <NUM> is unrotatably engaged and thus integrated with an inner periphery 46a of the second carrier <NUM>. Accordingly, the third sun gear <NUM> rotates with the second carrier <NUM>.

The plurality of third gears <NUM> are arranged at regular intervals in the circumferential direction around the third sun gear <NUM>. The third gears <NUM> are disposed to mesh with the second internal gear <NUM> (the small-diameter gear 57B) of the second ring gear 5B and supported rotatably on the rotational support columns <NUM> projecting toward the output side from the bottom wall <NUM> of the first ring gear 5A. That is, the third gears <NUM> are disposed to mesh with both the third sun gear <NUM> and the second ring gear 5B.

In the third speed reducing unit 4C, the rotational driving force decelerated at the second speed reducing unit 4B is decelerated through the third sun gear <NUM> and the third gears <NUM> and transmitted to the second ring gear 5B.

As shown in <FIG> and <FIG>, the first ring gear 5A is provided with a water-cooling channel <NUM> (channel) for cooling the first speed reducing unit 4A by water cooling. The motor flange <NUM> is provided with an inlet port <NUM> and an outlet port <NUM> connected to the water-cooling channel <NUM>. The water-cooling channel <NUM> is disposed in the first ring gear 5A and connected to the inlet port <NUM> and the outlet port <NUM>.

Each of the inlet port <NUM> and the outlet port <NUM> extends from an outer peripheral surface 23a of the motor flange <NUM> and bent in an L-shape toward the output-side end surface 23b. The inlet port <NUM> receives cooling water W (fluid) from the outside into the water-cooling channel <NUM>. The outlet port <NUM> discharges the cooling water W flowing through the water-cooling channel <NUM> to the outside. The inlet port <NUM> and the outlet port <NUM> are connected by piping to a water supply (not shown) installed on a portion of the excavator <NUM> described above.

As shown in <FIG>, the water-cooling channel <NUM> is disposed in the input-side end surface 501a of the inner tubular wall <NUM> of the first ring gear 5A facing the motor flange <NUM>. On an outer peripheral edge 501c positioned on the outer peripheral side of the water-cooling channel <NUM> as viewed from the direction of the rotational axis O, a waterproof member (not shown) such as an O-ring is provided so as to be in contact with the motor flange <NUM> in a liquid tight manner. The water-cooling channel <NUM> extends in a C-shape as viewed from the direction of the rotational axis O. The water-cooling channel <NUM> includes a first groove <NUM> having a small depth and a plurality (four in this embodiment) of second grooves <NUM> formed in a portion of the first groove <NUM> and having a larger depth than the first groove <NUM>. The C-shape of the water-cooling channel <NUM> mentioned above is a substantially circular shape with a portion thereof in the circumferential direction cut off. The length of the portion cut off is not particularly limited. The substantially circular shape of the water-cooling channel <NUM> may be an ellipse or a polygon, for example. In this embodiment, the portion of the C-shape of the water-cooling channel <NUM> having no groove (the portion in which an inlet 63a and an outlet 63b (described later) are positioned) faces upward, but this is not limitative. This portion may face downward or laterally, for example.

The second grooves <NUM> are deeper than a bottom 63c of the first groove <NUM>. As shown in <FIG>, in the direction of the rotational axis O, the second grooves <NUM> are positioned to run close to the first internal gear <NUM> meshed with the first planetary gears <NUM> of the first speed reducing unit 4A. The inlet 63a positioned at one end of the water-cooling channel <NUM> in the extension direction thereof is connected with the inlet port <NUM>. The outlet 63b positioned at the other end of the water-cooling channel <NUM> in the extension direction thereof is connected with the outlet port <NUM>. The cooling water W received through the inlet 63a of the water-cooling channel <NUM> flows toward the outlet 63b (in the direction of the arrows shown in <FIG> and <FIG>) and are discharged through the outlet 63b. At this time, the cooling water W flowing into the first groove <NUM> enters the four second grooves <NUM>.

As shown in <FIG>, the speed reducer <NUM> thus configured receives the rotational driving force input from the motor shaft <NUM> rotated by the electric motor <NUM>. The rotational driving force causes the first planetary gears <NUM> to rotate while revolving around the rotational axis O, in accordance with the differences in the number of teeth between the first sun gear <NUM> and the first planetary gears <NUM> and between the first planetary gears <NUM> and the first internal gear <NUM> of the first ring gear 5A, in the first speed reducing unit 4A. Further, the decelerated rotational driving force is transmitted from the first speed reducing unit 4A to the speed reducing input shaft <NUM> through the first carrier <NUM> supporting the first planetary gears <NUM>.

When the rotational driving force is input from the first speed reducing unit 4A to the speed reducing input shaft <NUM> connected to the motor shaft <NUM>, the second planetary gears <NUM> rotate while revolving around the rotational axis O, in accordance with the differences in the number of teeth between the second sun gear <NUM> and the second planetary gears <NUM> and between the second planetary gears <NUM> and the second ring gear 5B (the large-diameter gear 57A), in the second speed reducing unit 4B fixed to the distal end portion 3a of the speed reducing input shaft <NUM>. Further, the decelerated rotational driving force is transmitted from the second speed reducing unit 4B to the third sun gear <NUM> of the third speed reducing unit 4C through the second carrier <NUM> supporting the second planetary gears <NUM>.

When the rotational driving force is input from the second carrier <NUM> of the second speed reducing unit 4B to the third sun gear <NUM> of the third speed reducing unit 4C, the third gears <NUM> rotate and the second ring gear 5B meshing with the third gears <NUM> rotate around the rotational axis O, in accordance with the differences in the number of teeth between the third sun gear <NUM> and the third gears <NUM> and between the third gears <NUM> and the second ring gear 5B (the small-diameter gear 57B), in the third speed reducing unit 4C. That is, the decelerated rotational driving force is transmitted from the third speed reducing unit 4C to the second ring gear 5B through the third gears <NUM>. Further, the decelerated rotational driving force can be output to the drive wheel <NUM> of the excavator <NUM> fixed to the second fixing portion <NUM> of the second ring gear 5B.

As described above, in the speed reducer <NUM> of the embodiment, the speed reducing units <NUM> decelerate the rotational driving force of the electric motor <NUM> and transmit the decelerated rotational driving force to the rotational driving unit, and the water-cooling channel <NUM> is provided in the first ring gear 5A to communicate a fluid (the cooling water W). Therefore, the first speed reducing unit 4A, which meshes with the first ring gear 5A cooled by the water-cooling channel <NUM>, is also cooled, making it possible to inhibit heating of the first speed reducing unit 4A connected directly to the motor shaft <NUM>. Thus, the first speed reducing unit 4A can handle high speed rotation of the electric motor <NUM>, and the electric motor <NUM> can be downsized. Further, the water-cooling is accomplished with the water-cooling channel <NUM>. This prevents entrance of dirt unlike the conventional air-cooling system with a fan which is open for intake and exhaust of the air, thus facilitating installation on the construction machines that are apt to entrance of dirt.

Further, the speed reducer <NUM> of the embodiment includes the plurality of speed reducing units <NUM>. Among the plurality of speed reducing units <NUM>, the first speed reducing unit 4A is positioned at the end on the input side, and the gear of the first speed reducing unit 4A (the first ring gear 5A) is provided with the water-cooling channel <NUM>. This makes it possible to efficiently cool the first speed reducing unit 4A on the input side which rotates at the highest speed and tends to heat.

Further, in the speed reducer <NUM> of the embodiment, the speed reducing units <NUM> include the sun gear that receives the rotational driving force input from the electric motor <NUM>, the ring gear <NUM> encircling the sun gear and having internal teeth, and the planetary gears provided between the sun gear and the ring gear <NUM> and meshing with the sun gear and the ring gear <NUM>. The gear is the first ring gear 5A. Therefore, the first ring gear 5A can be fixed unrotatably, making it possible to simplify the piping structure extending from the water supply installed on a construction machine such as the excavator <NUM> of the embodiment to the water-cooling channel <NUM>.

Further, in the speed reducer <NUM> of the embodiment, the water-cooling channel <NUM> has a C-shape as the first ring gear 5A is viewed from the direction of the rotational axis O of the electric motor <NUM>. The water-cooling channel <NUM> includes the first groove <NUM> having a small depth and at least one second groove <NUM> formed in a portion of the first groove <NUM> and having a larger depth than the first groove <NUM>. Therefore, in the region of the first speed reducing unit 4A (a portion of the first internal gear <NUM>) where meshing strength of the gears (the first planetary gears <NUM>) is needed, the grooves are not provided in the entire circumference, and the second groove <NUM> having a larger depth can be provided in a part of the circumference. That is, in the regions where the meshing strength mentioned above is less affected, the first groove <NUM> having a small depth can be provided to allow the cooling water W to flow therein. In addition, a portion of the first internal gear <NUM> where cooling is needed can be cooled using the cooling water W entering the second groove <NUM>.

Further, in the speed reducer <NUM> of the embodiment, a plurality of second grooves <NUM> are arranged at predetermined intervals. Since the second grooves having a larger depth than the first groove reduce the rigidity of the first ring gear 5A (the fixed gear), it is supposed that the first ring gear 5A should have a larger outer diameter. However, in the embodiment, the second grooves are provided in a part of the circumference, making it possible to inhibit the first ring gear 5A from having a reduced rigidity or having a larger outer diameter.

Further, in the speed reducer <NUM> of the embodiment, the first planetary gears <NUM> are provided to mesh with the first ring gear 5A, and the number of the second grooves <NUM> is different from the number of the first planetary gears <NUM>. That is, in the embodiment, four second grooves <NUM> are provided in the circumferential direction of the first groove <NUM>, and one planetary gear <NUM> meshes with the first ring gear 5A. Since the number of the second grooves <NUM> and the number of the first planetary gears <NUM> are different, it can be prevented that the second grooves and the planetary gears are in phase for causing vibration as in the case where the number of the second grooves and the number of the planetary gears are the same.

Further, in the speed reducer <NUM> of the embodiment, the motor flange <NUM> is disposed on the first ring gear 5A. The motor flange <NUM> is provided with the inlet port <NUM> and the outlet port <NUM> connected to the water-cooling channel <NUM>. Therefore, the cooling water W received through the inlet port <NUM> flows through the water-cooling channel <NUM> in one direction and is discharged through the outlet port <NUM>. In this way, the cooling water W flows in one direction in the water-cooling channel <NUM>. In addition, it is possible to connect the inlet port <NUM>, the outlet port <NUM>, and an external water supply (not shown) by piping. This configuration allows efficient circulation of the cooling water W.

Further, in the speed reducer <NUM> of the embodiment, the motor flange <NUM> is mounted to the electric motor <NUM>, and thus it is also possible to cool the electric motor <NUM> connected to the motor flange <NUM>. Therefore, heating of the electric motor <NUM> itself can also be inhibited.

Further, the embodiment is provided with the crawler body <NUM> (vehicle body), the drive wheel <NUM> for traveling of the crawler body <NUM>, and the electric motor <NUM> and the speed reducer <NUM> for driving the drive wheel <NUM>. In the speed reducer <NUM>, the speed reducing units <NUM> decelerate the rotational driving force of the electric motor <NUM> and transmit the decelerated rotational driving force to the rotational driving unit, and the water-cooling channel <NUM> is provided in the first ring gear 5A to communicate the cooling water W. The first ring gear 5A is fixed to the crawler body <NUM> or the drive wheel <NUM>. The rotational driving force of the electric motor <NUM> is transmitted to the drive wheel <NUM> via the speed reducer <NUM>. The water-cooling channel <NUM> is connected to the water supply provided on at least one of the crawler body <NUM> or the drive wheel <NUM>. Therefore, the speed reducer <NUM> can be installed such that the water-cooling channel <NUM> is connected to the water supply provided on the construction machine such as the excavator <NUM>.

The present invention is not limited to the above-described embodiments. For example, in the above embodiments, the speed reducer <NUM> includes the three speed reducing units 4A, 4B, and 4C, but the number of the speed reducing units is not limited to three. For example, a speed reducer including two or one speed reducing unit may be provided with the water-cooling channel <NUM>. Further, in the embodiment, the cooling water W is used as an example of the fluid, but the fluid is not limited to water. For example, use of fluids such as oil or other coolant is also possible.

Further, in the above embodiment, the water-cooling channel <NUM> (channel) is provided to the first ring gear 5A, but the water-cooling channel <NUM> is not necessarily provided to the first ring gear 5A that is a fixed gear. The channel may be provided to any gear. For example, with the planetary gear mechanism as in the above embodiment, the channel may be provided to the sun gear or the planetary gears instead of the ring gear, if the channel has structure for dynamic path alteration. This configuration also accomplishes the purport of the present invention.

Further, in the above embodiment, the second ring gear 5B is disposed on the output side of the first ring gear 5A in the direction of the rotational axis O, and the second ring gear 5B is rotatably supported on the first ring gear 5A, but this configuration with the second ring gear 5B is not limitative.

Further, in the above embodiment, the water-cooling channel <NUM> extends in a C-shape and includes the first groove <NUM> having a small depth and at least one second groove <NUM> formed in a portion of the first groove <NUM> and having a larger depth than the first groove <NUM>. The water-cooling channel <NUM> is not limited to this two-stage groove shape but may have other shapes. It is also possible that the water-cooling channel <NUM> includes grooves in three or more stages, instead of two stages.

Further, in the above embodiment, the motor flange <NUM> mounted to the first ring gear 5A is provided with the inlet port <NUM> and the outlet port <NUM>. It is also possible that the inlet port <NUM> and the outlet port <NUM> are provided in, for example, the first ring gear 5A instead of the motor flange <NUM>.

Further, the speed reducer <NUM> of the embodiment is formed of the planetary gear mechanism as an example, but the speed reducer <NUM> is not necessarily formed of the planetary gear mechanism. For example, an eccentric oscillating speed reducer included in the planetary gear mechanism or a speed reducer with a center crank mechanism may be provided with the channel for cooling described above. An eccentric oscillating speed reducer includes a plurality of crankshafts arranged in the circumferential direction around the central axis of the speed reducer, and the eccentric oscillating speed reducer is configured such that an external gear oscillates and a carrier takes out rotation. A speed reducer with a center crank mechanism includes a crankshaft positioned coaxially with the central axis of the speed reducer, and is configured such that the crankshaft causes an external gear to oscillate and the rotation of the external gear is taken out from a pin of a carrier. The present invention can also be applied to a speed reducer including both an eccentric oscillating speed reducer and a center crank mechanism.

Further, in the embodiment, the transmission mechanism is based on speed reducing relationship (speed reducer), but the speed may also be maintained or increased.

Claim 1:
A speed reducer (<NUM>) that is connectable to an electric motor (<NUM>), the speed reducer (<NUM>) comprising:
at least one speed reducing unit (<NUM>) for decelerating a rotational driving force of the electric motor (<NUM>) and transmitting the decelerated rotational driving force to a rotational driving unit; and
a channel (<NUM>) provided in a gear (<NUM>) of the at least one speed reducing unit (<NUM>) and configured to communicate a fluid,
characterized in that
the channel (<NUM>) has a C-shape as the gear (<NUM>) is viewed from a direction of a rotational axis of the electric motor (<NUM>).