Patent Description:
A power transmission device that transmits the respective outputs of a first motor and a second motor to an output shaft at speed reduction ratios different from each other has been known. For example, Patent Literature <NUM> discloses a power transmission device in which a first motor is coupled to an input shaft and a second motor is coupled to an intermediate shaft. The rotation of the input shaft driven by the first motor is transmitted to an output shaft via a first gear train and a second gear train, and the rotation of the intermediate shaft driven by the second motor is transmitted to the output shaft via the second gear train. As another example, Patent Literature <NUM> discloses a drive device, in particular for a wheel axle of a motor vehicle, with an output shaft, with a first electric motor and a second electric motor and with a gearbox device. It is provided that in a first operating mode of the gearbox device there is an operative connection between the first electric motor and the output shaft with a first gear ratio when the second electric motor is decoupled from the output shaft and in a second operating mode of the gearbox device there is an operative connection between the second electric motor and the output shaft with a second gear ratio when the first electric motor is decoupled from the output shaft, and that in a third operating mode of the gearbox device there is an operative connection between the first electric motor and the output shaft with a first coupling ratio and at the same time an operative connection between the second electric motor and the output shaft with a second coupling ratio different from the first coupling ratio. As a further example, Patent Literature <NUM> discloses a drive system, including a first electric motor and a second electric motor configured as a power source, first and second reduction gears connected to the first electric motor and the second electric motor and having different reduction ratios, a drive shaft transmitting output power of the first and second reduction gears, and a motor control device configured to drive a first drive point wherein the first electric motor responds according to a request torque of a driver and a running state of the vehicle and to determine a second drive point at which the second electric motor responds according to the request torque of the driver and the driving state of the vehicle, and the driving system uses at least one output torque from an output torque of the first electric motor and / or an output torque of the second electric motor in accordance with the determined drive point.

However, in the technique disclosed in Patent Literature <NUM>, the output from the second motor to the output shaft depends on the gear ratio of the second gear train, so that there is a problem that the torque that the second motor outputs to the output shaft cannot be increased.

The present invention has been made to solve the above problem, and an object of the present invention is to provide a power transmission device that can increase a torque that a second motor outputs to an output shaft.

To achieve this object, a power transmission device of the present invention includes alle the features of independent claim <NUM>.

In accordance with the power transmission device of Claim <NUM> of the present invention, the first input shaft and the second input shaft coupled to the first motor and the second motor, respectively, are disposed on the same axis. The first speed reduction mechanism transmits the rotation of the first input shaft to the output shaft via the intermediate shaft, and the first clutch disconnects or connects the transmission of the power by the first speed reduction mechanism. The second speed reduction mechanism transmits the rotation of the second input shaft to the output shaft via the intermediate shaft at a speed reduction ratio different from the speed reduction ratio of the first speed reduction mechanism. Thus, there is an effect of capable of increasing the torque that the second motor coupled to the second input shaft outputs to the output shaft.

In accordance with the power transmission device of the present invention, the first clutch consists of a one-way clutch interposed between the gear and the intermediate shaft. Since the first clutch is disposed to the intermediate shaft that may be able to lower the rotation speed as compared with the input shafts and the output shaft, the lubrication failure of the first clutch can be made unlikely to occur. Thus, with the present invention, there is an effect of capable of securing the durability of the first clutch.

In accordance with the power transmission device of Claim <NUM> of the present invention, the first input shaft and the second input shaft are disconnected or connected by a second clutch. When the the first input shaft and the second input shaft are connected by the second clutch, the first input shaft and the second input shaft can be rotated by the first motor and the second motor, respectively. Thus, in addition to the effect of the first or Claim <NUM> of the present invention, there is an effect of capable of increasing the torque outputted to the output shaft via the second speed reduction mechanism.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. First, a power transmission device <NUM> according to a first embodiment of the present invention will be described with reference to <FIG> is a skeleton diagram of the power transmission device <NUM> according to the first embodiment. According to this embodiment, the power transmission device <NUM> is mounted on a vehicle.

As illustrated in <FIG>, the power transmission device <NUM> includes a first input shaft <NUM>, a second input shaft <NUM>, an intermediate shaft <NUM>, and an output shaft <NUM>. The first input shaft <NUM> and the second input shaft <NUM> are disposed on the same axis. A first motor <NUM> is coupled to the first input shaft <NUM>, and a second motor <NUM> is coupled to the second input shaft <NUM>. The first input shaft <NUM> (the second input shaft <NUM>), the intermediate shaft <NUM>, and the output shaft <NUM> are disposed in parallel.

In this embodiment, the first input shaft <NUM> is a main shaft directly receiving the driving force of the first motor <NUM>, and the second input shaft <NUM> is a main shaft directly receiving the driving force of the second motor <NUM>. Also, the output shaft <NUM> is a vehicle axis, a differential gear <NUM> is disposed at the center of the output shaft <NUM>, and wheels <NUM> are respectively disposed at both ends of the output shaft <NUM>. A plurality of wheels (not illustrated) other than the wheels <NUM> are disposed on the vehicle on which the power transmission device <NUM> is mounted, and the vehicle can run by the rotation driving of the output shaft <NUM> and the wheels <NUM>.

The first input shaft <NUM> and the second input shaft <NUM> are relatively rotatably coupled to each other via a pilot bearing (not illustrated). With this, as compared with the case where the first input shaft <NUM> and the second input shaft <NUM> are respectively supported by bearings, the number of bearings can be reduced.

The first motor <NUM> is a device providing the rotation driving force to the first input shaft <NUM>, and the second motor <NUM> is a device providing the rotation driving force to the second input shaft <NUM>. In this embodiment, the first motor <NUM> and the second motor <NUM> are electrically operated motors. The first motor <NUM> and the second motor <NUM> have the same torque characteristic.

A first speed reduction mechanism <NUM> is a mechanism transmitting the rotation of the first input shaft <NUM> to the output shaft <NUM> via the intermediate shaft <NUM>. The first speed reduction mechanism <NUM> includes a first gear <NUM> coupled to the first input shaft <NUM>, and a second gear <NUM> disposed to the intermediate shaft <NUM> and engaging with the first gear <NUM>. The first speed reduction mechanism <NUM> is set to a speed reduction ratio by the engaging of the first gear <NUM> and the second gear <NUM>.

A first clutch <NUM> is disposed to the intermediate shaft <NUM>. In this embodiment, the first clutch <NUM> is a one-way clutch transmitting the power in the forward direction from the second gear <NUM> to the intermediate shaft <NUM>. The first clutch <NUM> is interposed between the intermediate shaft <NUM> and the second gear <NUM>. When the first clutch <NUM> is connected, the second gear <NUM> is coupled to the intermediate shaft <NUM>, and when the first clutch <NUM> is disconnected, the second gear <NUM> idles the intermediate shaft <NUM>. While the first clutch <NUM> interceptably transmits the rotation of the second gear <NUM> to the intermediate shaft <NUM>, the first clutch <NUM> intercepts the transmission of the rotation from the intermediate shaft <NUM> to the second gear <NUM>.

A second speed reduction mechanism <NUM> is a mechanism transmitting the rotation of the second input shaft <NUM> to the output shaft <NUM> via the intermediate shaft <NUM>. The second speed reduction mechanism <NUM> includes a third gear <NUM> coupled to the second input shaft <NUM>, a fourth gear <NUM> coupled to the intermediate shaft <NUM> and engaging with the third gear <NUM>, a fifth gear <NUM> coupled to the intermediate shaft <NUM>, and a sixth gear <NUM> coupled to the differential gear <NUM> and engaging with the fifth gear <NUM>. The second motor <NUM> can always transmit the power to the output shaft <NUM> via the second speed reduction mechanism <NUM>.

The second speed reduction mechanism <NUM> is set to a speed reduction ratio different from the speed reduction ratio of the first speed reduction mechanism <NUM> by the engaging of the third gear <NUM>, the fourth gear <NUM>, the fifth gear <NUM>, and the sixth gear <NUM>. In this embodiment, the speed reduction ratio of the second speed reduction mechanism <NUM> is lower than the speed reduction ratio of the first speed reduction mechanism <NUM>. To the second speed reduction mechanism <NUM>, a gear train different from a gear train configuring the first speed reduction mechanism <NUM> is set.

The power transmission device <NUM> drives at least the first motor <NUM> at the time of starting and during running at low speed. The output of the first motor <NUM> is transmitted to the output shaft <NUM> via the first speed reduction mechanism <NUM> having a higher speed reduction ratio than the second speed reduction mechanism <NUM>, so that the large driving torque is obtained from the low speed to enable powerful starting and running at low speed. At the time of the change from the low-speed running to the high-speed running, at least the second motor <NUM> is driven.

When the first motor <NUM> is driven at this time, the first motor <NUM> is brought into the high rotation range, so that the torque of the first motor <NUM> is typically reduced. However, the output of the second motor <NUM> is transmitted to the output shaft <NUM> at the speed reduction ratio of the second speed reduction mechanism <NUM> lower than the speed reduction ratio of the first speed reduction mechanism <NUM>, so that the sufficient driving torque is obtained even at high speed to enable stable acceleration.

Also, the second speed reduction mechanism <NUM> transmits the rotation of the second input shaft <NUM> to the output shaft <NUM> at the speed reduction ratio different from the speed reduction ratio of the first speed reduction mechanism <NUM>, so that the torque that the second motor <NUM> coupled to the second input shaft <NUM> outputs to the output shaft <NUM> can be increased. Thus, the sufficient driving torque can be obtained from the low speed to the high speed.

To the second speed reduction mechanism <NUM>, the gear train different from the gear train configuring the first speed reduction mechanism <NUM> is set, so that the first speed reduction mechanism <NUM> and the second speed reduction mechanism <NUM> can be set to any speed reduction ratio without affecting each other. Thus, the torque that the second motor <NUM> outputs to the output shaft <NUM> can be increased by the second speed reduction mechanism <NUM> without receiving the restriction of the first speed reduction mechanism <NUM>.

When the power transmission device <NUM> drives the first motor <NUM> so that the rotation speed of the second gear <NUM> is relatively higher than the rotation speed of the intermediate shaft <NUM>, the first clutch <NUM> is connected, and the first motor <NUM> outputs the torque to the output shaft <NUM> via the first speed reduction mechanism <NUM>. On the other hand, when the rotation speed of the second gear <NUM> is relatively lower than the rotation speed of the intermediate shaft <NUM>, the first clutch <NUM> is disconnected, so that the rotation speed of the first motor <NUM> can be prevented from being excessive. Further, it is possible to prevent the drag loss by the first motor <NUM> and the first speed reduction mechanism <NUM> when the power transmission device <NUM> is driven by the second motor <NUM> and the second speed reduction mechanism <NUM>. Since the first clutch <NUM> is the one-way clutch, an actuator switching the disconnection and the connection of the clutch can be unnecessary.

The first clutch <NUM> is disposed to the intermediate shaft <NUM> that may be able to lower the rotation speed as compared with the first input shaft <NUM>, the second input shaft <NUM>, and the output shaft <NUM>, so that the lubrication failure of the first clutch <NUM> can be made unlikely to occur. Thus, the durability of the first clutch <NUM> can be secured.

A comparative example will be described with reference to <FIG>. In the first embodiment, the power transmission device <NUM> including the first clutch <NUM> including the one-way clutch has been described. On the contrary, in the comparative example, a power transmission device <NUM> including a first clutch <NUM> including an engaging clutch will be described. It should be noted that the same portions as the portions described in the first embodiment are indicated by the same reference numerals, and the description thereafter is omitted. <FIG> is a skeleton diagram of the power transmission device <NUM> according to the comparative example.

As illustrated in <FIG>, in the power transmission device <NUM>, the first clutch <NUM> is disposed to the intermediate shaft <NUM>. In this embodiment, the first clutch <NUM> is the engaging clutch that can switch the coupling of the second gear <NUM> to the intermediate shaft <NUM> and the releasing of the second gear <NUM> from the intermediate shaft <NUM>. As the engaging clutch, a gear clutch, a tooth clutch, a dog clutch, and the like are given. The first clutch <NUM> operates the actuator (not illustrated) to switch the disconnection and the connection.

In the power transmission device <NUM>, when the first clutch <NUM> is connected, the first motor <NUM> outputs the torque to the output shaft <NUM> via the first speed reduction mechanism <NUM>. When the first clutch <NUM> is disconnected, it is possible to prevent the drag loss by the first motor <NUM> and the first speed reduction mechanism <NUM> when the power transmission device <NUM> is driven by the second motor <NUM> and the second speed reduction mechanism <NUM>. Since the first clutch <NUM> is made to be the engaging clutch, the configuration of the clutch can be simplified as compared with the case of using a multiple disc clutch and the like.

A second embodiment will be described with reference to <FIG>. In the first embodiment, the case where the first input shaft <NUM> and the second input shaft <NUM> are relatively rotatably coupled to each other via the pilot bearing (not illustrated) has been described. On the contrary, in the second embodiment, the case where a second clutch <NUM> disconnecting or connecting the first input shaft <NUM> and the second input shaft <NUM> will be described. It should be noted that the same portions as the portions described in the first embodiment are indicated by the same reference numerals, and the description thereafter is omitted. <FIG> is a skeleton diagram of a power transmission device <NUM> according to the second embodiment.

As illustrated in <FIG>, in the power transmission device <NUM>, the second clutch <NUM> is disposed between the first input shaft <NUM> and the second input shaft <NUM> disposed on the same axis. The second clutch <NUM> disconnects or connects the first input shaft <NUM> and the second input shaft <NUM>. The second clutch <NUM> adopts any clutch, such as the engaging clutch and a friction clutch. Of course, synchromesh can be incorporated into the second clutch <NUM>.

When the first input shaft <NUM> and the second input shaft <NUM> are connected by the second clutch <NUM>, the power transmission device <NUM> can rotate the first input shaft <NUM> and the second input shaft <NUM> by the first motor <NUM> and the second motor <NUM>, respectively. Thus, the second motor <NUM> and the first motor <NUM> that can always transmit the power to the output shaft <NUM> via the second speed reduction mechanism <NUM> are driven, so that the torque outputted to the output shaft <NUM> can be increased. In particular, since the torque during the high-speed running in which the torque of the first motor <NUM> is reduced can be increased, the sufficient driving torque is obtained even at high speed to enable acceleration.

The present invention has been described above based on the embodiments, but the present invention is not limited to the embodiments at all, and it can be easily inferred that various modifications can be made within the scope of the present invention, which is defined by the claims.

In the respective embodiments, the case where one intermediate shaft <NUM> is disposed between the first input shaft <NUM>, the second input shaft <NUM>, and the output shaft <NUM> has been described, but the present invention is not necessarily limited to this. Of course, a plurality of intermediate shafts <NUM> can be provided, a gear can be disposed to each of the intermediate shafts <NUM>, and a gear train configuring part of each of the first speed reduction mechanism <NUM> and the second speed reduction mechanism <NUM> can be provided to each of the intermediate shafts <NUM>.

In the respective embodiments, the case where the electrically operated motors having the same torque characteristic are used for the first motor <NUM> and the second motor <NUM> has been described, but the present invention is not necessarily limited to this. Of course, motors having different torque characteristics can be used. For example, the motor having a torque characteristic for low speed is the first motor <NUM>, and the motor having a torque characteristic for high speed is the second motor <NUM>. The first motor <NUM> having the torque characteristic for low speed is a motor in which the torque peak value is on the low rotation side. The second motor <NUM> having the torque characteristic for high speed is a motor in which the torque peak value is on the high rotation side with respect to the rotation speed in which the torque of the first motor <NUM> is peak.

In the respective embodiments, the case where the electrically operated motors are used for the first motor <NUM> and the second motor <NUM>, but the present invention is not necessarily limited to this. Of course, one of the first motor <NUM> and the second motor <NUM> can be an oil hydraulic motor, or both of the first motor <NUM> and the second motor <NUM> can be oil hydraulic motors.

In the respective embodiments, the case where the first input shaft <NUM> directly receives the driving force of the first motor <NUM> and the second input shaft <NUM> directly receives the driving force of the second motor <NUM>, but the present invention is not necessarily limited to this. Of course, a gear train, a belt, and the like can be interposed between the first motor <NUM>, the second motor <NUM>, the first input shaft <NUM>, and the second input shaft <NUM>.

In the respective embodiments, although not described, when the power transmission device <NUM>, <NUM>, or <NUM> is mounted on the vehicle, the front wheels or the rear wheels can be driven by the first motor <NUM> and the second motor <NUM>, and the remaining wheels are applicable to a four-wheel drive vehicle that is driven by an engine. Also, of course, the front wheel or the rear wheel is applicable to a two-wheel drive vehicle that is driven by the first motor <NUM> and the second motor <NUM>.

In the respective embodiments, the case where the wheels <NUM> are disposed at both ends of the output shaft <NUM> of the power transmission device <NUM>, <NUM>, or <NUM> (when the power transmission device <NUM>, <NUM>, or <NUM> is mounted on the vehicle) has been described, but the present invention is not necessarily limited to this. Of course, the power transmission device <NUM>, <NUM>, or <NUM> can be used for a machine tool, a construction machine, an agricultural machine, and the like.

Claim 1:
A power transmission device(<NUM>,<NUM>) comprising:
a first input shaft(<NUM>) and a second input shaft(<NUM>) coupled to a first motor(<NUM>) and a second motor(<NUM>), respectively, and disposed on the same axis; and
a first speed reduction mechanism(<NUM>) transmitting the rotation of the first input shaft(<NUM>) to an output shaft(<NUM>) via an intermediate shaft(<NUM>) and a gear(<NUM>);
characterized in that the power transmission system (<NUM>,<NUM>) further comprises:
a second speed reduction mechanism(<NUM>) transmitting the rotation of the second input shaft(<NUM>) to the output shaft(<NUM>) via the intermediate shaft(<NUM>) at a speed reduction ratio lower than the speed reduction ratio of the first speed reduction mechanism(<NUM>); and
a first clutch(<NUM>) consisting of a one-way clutch interposed between the gear(<NUM>) and the intermediate shaft (<NUM>) on which the gear(<NUM>) is disposed,
wherein, when the power transmission device (<NUM>,<NUM>) drives the first motor (<NUM>) so that the rotation speed of the second gear (<NUM>) is relatively higher than the rotation speed of the intermediate shaft (<NUM>), the first clutch(<NUM>) is connected and the first motor (<NUM>) outputs the torque to the output shaft (<NUM>) via the first speed reduction mechanism (<NUM>), and the first clutch (<NUM>) is disconnected when the speed of rotation of the second gear (<NUM>) is relatively lower than the speed of rotation of the intermediate shaft (<NUM>).