Patent Description:
Robots are widely-used automation mechanisms that increase operational efficiency and accuracy. A robot typically comprises robot arm links and joints. The robot arm link can be driven to rotate or move by a motor arranged in the joint or a base. To meet the reduction ratio requirements, a gearbox needs to be arranged between the motor and the robot arm links to be driven. The gearbox is a device that uses gears and gear trains to provide speed and torque conversions from a rotating power source to another device.

Oil is usually provided in the gearbox to provide lubrication for the gears and other components. Besides the lubrication function for the individual elements to substantially reduce friction, oil in the gearbox can also cool the heated subassemblies as well as mitigate and attenuate gear strokes. In addition, it reduces vibration, protects against corrosion, and keeps everything clean.

For robotic applications, a motor is typically coupled to a gearbox with the motor's shaft extending into an oil cavity of the gearbox. The aging of seals used to seal the oil cavity results in problems in preventing oil in the oil cavity from entering the motor and thereby adversely affecting the operation of the motor.

<CIT> discloses a gear oil leak detection arrangement.

The invention provides an apparatus for determining oil leakage of a gearbox and an associated robot to at least in part solve the above and other potential problems.

In a first aspect, an apparatus for determining oil leakage of a gearbox is provided as defined in claim <NUM>.

With the apparatus according to embodiments of the present invention, before oil leaks into the motor, the user already knows of the leakage or the motor has already been stopped. In this case, the user may only need to replace the damaged or aging seal ring to restore the robot joint to a normal operation state. In this way, maintenance costs can be reduced. More importantly, the robot using the apparatus according to embodiments of the present invention can be operated more safely.

In some embodiments, the apparatus further comprises a housing arrangeable on a fixed part of the motor and comprising a receiving portion for receiving the swellable ring. In this way, the apparatus can be more easily mounted on the motor.

In some embodiments, the swellable ring is arranged in contact with a side of the receiving portion away from the output shaft. This arrangement can easily achieve the radial force to be applied on the output shaft.

In some embodiments, the swellable ring comprises a swelling portion made of a functional oil-absorbing material such that the swelling portion swells when the swelling portion contacts oil. The oil swelling rubber can ensure the apparatus to swell and to apply radial force to the output shaft, improving the reliability of the apparatus.

In some embodiments, the swellable ring further comprises a contacting portion arranged on a side of the swelling portion adjacent to the output shaft in a radial direction, and wherein the contacting portion is made of a nitrile rubber. The contacting portion can ensure sufficient radial force to be applied to the output shaft, so that the torque change on the output shaft, or the change in the current for driving the motor can be detected. In this way, the reliability of the apparatus is further improved.

In some embodiments, the functional oil-absorbing material comprises an oil swelling rubber.

In some embodiments, the apparatus further comprises an additional sleeve arranged on the output shaft and adapted to rotate with the output shaft. This arrangement can improve the adaptability of the apparatus.

In some embodiments, the swellable ring is arranged between the additional sleeve and the housing.

In some embodiments, the apparatus further comprises a radial sealing arranged between the additional sleeve and the housing.

In some embodiments, the controller is coupled to a power cable or a driver of the motor to detect the change in the current for driving the motor.

In a second aspect, a robot is provided as defined in claim <NUM>. The robot comprises at least one j oint and at least one apparatus according to the first aspect as mentioned above.

It is to be understood that the Summary is not intended to identify key or essential features of embodiments of the present invention, nor is it intended to be used to limit the scope of the present invention. Other features of the present invention will become readily comprehensible through the description below.

The above and other objectives, features and advantages of the present invention will become more apparent through more detailed depiction of example embodiments of the present invention in conjunction with the accompanying drawings, wherein in the example embodiments of the present invention, the same reference numerals usually represent the same components.

The present invention will now be discussed with reference to several example embodiments. It is to be understood these embodiments are discussed only for the purpose of enabling those persons of ordinary skill in the art to better understand and thus implement the present invention, rather than suggesting any limitations on the scope of the subject matter.

As used herein, the term "comprises" and its variants are to be read as open terms that mean "comprises, but is not limited to. " The term "based on" is to be read as "based at least in part on. " The term "one embodiment" and "an embodiment" are to be read as "at least one embodiment. " The term "another embodiment" is to be read as "at least one other embodiment. " The terms "first," "second," and the like may refer to different or same objects. Other definitions, explicit and implicit, may be comprised below. A definition of a term is consistent throughout the description unless the context clearly indicates otherwise.

Gearboxes and motors are common components in the joints of a robot. A motor <NUM> usually comprises a brake mechanism to reduce a rotation speed of an arm of a joint quickly or to hold arms of a joint in position. A gearbox <NUM> is typically provided with an oil cavity for receiving oil to lubricate the individual elements to substantially reduce friction and to fulfill other necessary functions. To make the joint more compact, a motor's shaft is usually inserted into the oil cavity to engage with gears arranged in the oil cavity.

A seal is provided around the motor <NUM> shaft to prevent oil from entering the motor <NUM>. However, with long periods of operation, the seal surrounding the motor <NUM> shaft may fail due to long-term wear, which will result in oil entering into the motor <NUM>. The oil entering the motor <NUM> will accelerate the aging of insulating parts in the motor <NUM>. In addition, and more importantly, once oil enters the motor's brake mechanism, there is a risk of failure of the brake mechanism, which may cause a major accident. For example, if the motor's brake mechanism for stopping or holding the second and third arms fails, the third arm may slip off due to the brake mechanism failure, which may damage surrounding equipment and/or threaten personal safety.

Conventional solutions to prevent oil from entering the motor <NUM> are to employ a double-seal structure, which comprises two seals. A detection hole is provided between the two seals for an operator to observe oil leaking through one of the seals adjacent to the oil cavity. If the oil is observed through the detection hole, it means that at least one of the two seals is damaged, and the motor <NUM> or double-seal structure needs to be replaced in time. However, there is currently no way to know if an oil leakage has occurred for the motor <NUM> wrapped inside a joint.

In order to at least partially address the above and other potential problems, embodiments of the present disclosure provide an apparatus for determining oil leakage of a gearbox <NUM>. <FIG> and <FIG> show simplified cross-sectional views of an apparatus for determining oil leakage of a gearbox <NUM> arranged between a gearbox <NUM> and a motor <NUM> according to embodiments of the present disclosure.

As shown in <FIG> and <FIG>, in general, the apparatus comprises a swellable ring <NUM> and a controller <NUM>. The swellable ring <NUM> is arranged surrounding an output shaft <NUM> of a motor <NUM> which is coupled to the gearbox <NUM>. That is, the swellable ring <NUM> is arranged outside the gearbox <NUM> but surrounding the output shaft <NUM>. When the oil does not leak from the gearbox <NUM>, the swellable ring <NUM> will not contact the output shaft. When contacting oil, the swellable ring <NUM> can swell to contact the output shaft and apply a radial force to the output shaft <NUM>.

It can be seen from the above that when there is no oil leaking from the gearbox <NUM>, the swellable ring <NUM> does not contact the output shaft and the motor <NUM> can drive the gearbox <NUM> via the output shaft <NUM> to operate normally. When the oil leakage of the gearbox <NUM> occurs, the swellable ring <NUM> is arranged so that the oil leaking from the gearbox <NUM> will first contact the swellable ring <NUM>. As a result, the swellable ring <NUM> swells to apply the radial force to the output shaft <NUM>.

Accordingly, the torque on the output shaft <NUM> will be changed in response to the radial force applied by the swellable ring <NUM>. Compared to the case where there is no radial force applied, current for driving the motor <NUM> will be increased accordingly. The controller <NUM> can detect the torque change on the output shaft <NUM> and/or the change in the current for driving the motor <NUM>. In response to a detection of the torque change on the output shaft <NUM> and/or the change in the current for driving the motor <NUM>, the controller <NUM> can determine or detect the oil leakage of the gearbox <NUM>.

In some embodiments, to improve the reliability of the apparatus, reference values for the torque on the output shaft <NUM> and/or the current for driving the motor <NUM> may be provided. For example, under normal conditions, that is, without oil leakage, when the robot performs certain predetermined operations, the torque of the output shaft <NUM> of the motor <NUM> or a value of current for driving the motor <NUM> can be recorded as the reference values. The predetermined operations may be some operations routinely performed by the robot.

The controller <NUM> will detect the torque and/or the current during each subsequent predetermined operation. If differences between the torque and/or current and the reference values exceed corresponding threshold values, the controller <NUM> can determine that the swellable ring <NUM> has exerted a radial force on the output shaft <NUM>. The radial force applied by the swellable ring <NUM> implies that the swellable ring <NUM> is in contact with oil leaking from the gearbox <NUM>. Thus, the controller <NUM> can then determine or detect the oil leakage by detecting the torque change on the output shaft <NUM> and/or the change in the current for driving the motor <NUM>.

The controller <NUM> may also determine that the increase in the torque or the current is not caused by other factors. For example, in some embodiments, the controller <NUM> may also employ other sensors, such as load sensors, coupled to the robot to determine that the increase in the torque or the current is caused by the radial force exerted by the swellable ring, rather than other factors such as an increase in loads applied on the robot.

In some embodiments, the apparatus can also inform users about the determined oil leakage. For example, when the controller <NUM> determines that an oil leakage of the gearbox <NUM> has occurred, the controller <NUM> may directly, or indirectly through other controllers <NUM>, push notification or warning of the oil leakage to an external device such as a cell phone used by the user. Alternatively or additionally, the controller <NUM> may also be configured to stop the motor <NUM> when determining an oil leakage before notifying or warning users. In some embodiments, the controller <NUM> may be a controller <NUM> of a robot in which the apparatus is used. In some alternative embodiments, the controller <NUM> may also be a controller <NUM> independent of the controller <NUM> of the robot.

In this way, before oil leaks into the motor <NUM>, the user already knows, or the motor <NUM> has already been stopped. In this case, the user may only need to replace the damaged seal ring to restore the robot joint to a normal operation state. In this way, maintenance costs can be reduced. More importantly, the robot using the apparatus according to embodiments of the present disclosure can be operated more safely.

In some embodiments, the motor <NUM> may detect the change in the current for driving the motor <NUM> by being coupled to a power cable of the motor <NUM>. As mentioned above, the current for driving the motor <NUM> varies depending on the torque of the motor's output shaft <NUM>. In some embodiments, the controller <NUM> may be coupled to a driver of the motor <NUM> to detect the change in the current. In this way, the controller <NUM> can detect or determine the oil leakage of the gearbox <NUM> more easily.

In some embodiments, the apparatus may also comprise a housing <NUM> arranged on a fixed part <NUM> of the motor <NUM>, as shown in <FIG> and <FIG>. The fixed part <NUM> of the motor <NUM> means an external stationary part of the motor <NUM>. For example, the fixed part <NUM> of the motor <NUM> may be an enclosure of the motor <NUM>. The housing <NUM> may be arranged on the enclosure of the motor <NUM> in any suitable way, for example, by interference fits, fastener connections, etc. The housing <NUM> comprises a receiving portion <NUM> for receiving the base. As a result, the apparatus can be easily mounted between the motor <NUM> and the gearbox <NUM>.

To ensure that a sufficient radial force can be applied to the output shaft <NUM> by the swellable ring <NUM>, in some embodiments, the swellable ring <NUM> is arranged in contact with a side of the receiving portion <NUM> away from the output shaft <NUM>, as shown in <FIG> and <FIG>. In this way, the swellable ring <NUM> is able to expand more towards the output shaft <NUM> to exert the sufficient radial force on the output shaft <NUM>.

In some embodiments, the swellable ring <NUM> may comprise a swelling portion <NUM> made of a functional oil-absorbing material that can swell when contacting oil. For example, in some embodiments, the functional oil-absorbing material comprises an oil swelling rubber. That is, the swelling portion <NUM> may be made of an oil swelling rubber. The oil swelling rubber is a type of polymer functional oil-absorbing material, which mainly comprises a rubber matrix and lipophilic functional groups or lipophilic components. The swelling portion <NUM> made of the oil swelling rubber can swell when contacting oil. Further, the swelling portion <NUM> can act as a further seal to prevent oil from entering the motor <NUM>.

Of course, it is to be understood that the embodiments where the functional oil-absorbing material comprises an oil swelling rubber are merely for illustrative purposes, without suggesting any limitation as to the scope of the present invention. Any other suitable material that can swell when exposed to or contacting oil is also possible. For example, in some alternative embodiments, the functional oil-absorbing material may also comprise a polymer material such as resins that swell when exposed to oil.

In some embodiments, the entire body of the swellable ring <NUM> may be composed of the oil swelling rubber. To ensure sufficient radial force is applied to the output shaft <NUM>, in some embodiments, the oil swelling rubber can be modified to be able to exert sufficient radial force during expansion.

In some embodiments, as shown in <FIG>, besides the swelling portion <NUM>, the swellable ring <NUM> may further comprise a contacting portion <NUM>. The contacting portion <NUM> is arranged on a side of the swelling portion <NUM> adjacent to the output shaft <NUM> in a radial direction. The contacting portion <NUM> may be made of a nitrile rubber, which has higher hardness and lower deformability than oil swelling rubber. By means of the contacting portion <NUM>, the swellable ring <NUM> can exert sufficient radial force on the output shaft <NUM>.

Of course, it is to be understood that the embodiments where the contacting portion <NUM> made of the nitrile rubber are merely for illustrative purposes, without suggesting any limitation as to the scope of the present invention. Other material or structure that has higher hardness and/or lower deformability than oil swelling rubber is also possible. For example, the contacting portion <NUM> may also be made of a metal or a plastic material, etc. In some embodiments, the contacting portion <NUM> may comprise a plurality of segments, uniformly disposed on the radial inner side of the swelling portion <NUM>.

In some embodiments, the apparatus may also comprise a radial sealing <NUM> between the output shaft <NUM> of the motor <NUM> and the housing <NUM>, as shown in <FIG> and <FIG>. The radial sealing <NUM> can provide an additional sealing protection to the oil cavity of the gearbox <NUM>. The oil leaking from the gearbox <NUM> will be first blocked from leaking outside of the apparatus due to the radial sealing <NUM>, without affecting the motor <NUM>. Even if the radial sealing <NUM> is damaged, the oil leakage can be known in time before it enters the motor <NUM>. It is only necessary to replace seals of the gearbox <NUM> and the radial sealing <NUM> of the apparatus, without replacing the motor <NUM> or the entire joint, which significantly reduces the cost.

In some embodiments, in order to improve adaptability, the apparatus may further comprise an additional sleeve <NUM>, as shown in <FIG>. The additional sleeve <NUM> may be arranged on the output shaft <NUM> of the motor <NUM> and can rotate with the output shaft <NUM>. In those embodiments, the radial sealing <NUM> and the swellable ring <NUM> are arranged between the additional sleeve <NUM> and the housing <NUM>. In this way, no matter the structure of the output shaft <NUM> of the motor <NUM>, the apparatus can be applied to it. As a result, the apparatus can be applied to various motors, which significantly improves the adaptability of the apparatus.

According to other aspects of the present invention, a robot is provided. The robot comprises at least one joint and at least one apparatus as mentioned above. With the apparatus according to embodiments of the present invention, the oil leakage of the gearbox <NUM> can be determined in time before affecting the performance of the motor <NUM>. In this way, the reliability of the robot is improved.

Claim 1:
An apparatus for determining oil leakage of a gearbox (<NUM>), comprising:
a swellable ring (<NUM>) arrangeable to surround an output shaft (<NUM>) of a motor (<NUM>) coupled to the gearbox (<NUM>), characterized in that the swellable ring (<NUM>), when contacting oil, swells to apply a radial force to the output shaft (<NUM>); and
a controller (<NUM>) configured to detect the oil leakage by detecting at least one of the following caused by the applied radial force: a torque change on the output shaft (<NUM>), or a change in a current for driving the motor (<NUM>).