Variable speed increaser and control method thereof

There is provided a variable speed increaser including a planetary gear transmission device which changes the speed of a rotational driving force of the electric driving device and transmits the changed rotation driving force to a driving target, and a rotation rate controller. The electric driving device includes a constant-speed motor having a constant-speed rotor, and a variable-speed motor having a variable-speed rotor and driven in a regenerative mode and in a power mode. A rotation rate of the output shaft varies within an operation range between a maximum rotation rate and a minimum rotation rate. The constant-speed motor has a rated torque which allows the output shaft to have the maximum rotation rate by itself. The rotation rate controller changes the rotation rate of the output shaft rotating within the operation range by driving the variable-speed motor only in the regenerative mode.

CROSS-REFERENCE TO RELATED APPLICATION

Priority is claimed on Japanese Patent Application No. 2018-032922, filed Feb. 27, 2018, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a variable speed increaser and a control method thereof.

Description of Related Art

As an apparatus for driving a rotary machine such as a compressor, there is an apparatus including an electric driving device for generating a rotational driving force and a transmission device for changing the speed of a rotational driving force generated by the electric driving device and then transmitting the speed-changed rotational driving force to the rotary machine.

Patent Document 1 discloses a variable speed increaser in which a constant-speed motor and a variable-speed motor for speed change are used as the electric driving device and a planetary gear transmission device is used as the transmission device to accurately control a gear ratio. In this apparatus, it is possible to change a rotation rate of an output shaft of the transmission device connected to the rotary machine by changing a rotation rate of the variable-speed motor.

PATENT DOCUMENTS

However, in the variable speed increaser, a rotation direction of the output shaft is always a constant direction, and due to mechanical properties of the planetary gear transmission device, a reverse torque constantly acts on planetary gears. Therefore, when the variable-speed motor rotates forward, a power mode is set, and when the variable-speed motor rotates in reverse, a regenerative mode is set. When the power mode and the regenerative mode are switched, a gear in the planetary gear transmission device rotating by the variable-speed motor also rotates in reverse. When a rotation direction of the gear is switched, transmission of a torque from the electric driving device to the output shaft becomes discontinuous, and thus instability of control may be caused or efficiency may be reduced due to loss.

The present invention provides a variable speed increaser capable of operating efficiently, and a control method thereof.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a variable speed increaser includes an electric driving device which generates a rotational driving force, and a planetary gear transmission device which changes the speed of the rotational driving force transmitted from the electric driving device to a constant-speed input shaft and a variable-speed input shaft and transmits the changed rotation driving force to a driving target through an output shaft. The electric driving device includes a constant-speed motor having a constant-speed rotor which rotates the constant-speed input shaft of the planetary gear transmission device, and a variable-speed motor having a variable-speed rotor which rotates the variable-speed input shaft of the planetary gear transmission device and driven in a regenerative mode in which the variable-speed motor serves as a generator and in a power mode in which the variable-speed motor serves as an electric motor. The variable speed increaser further includes a rotation rate controller which adjusts a rotation rate of the variable-speed motor. A rotation rate of the output shaft varies within an operation range between a maximum rotation rate and a minimum rotation rate. The constant-speed motor has a rated torque which allows the rotation rate of the output shaft to be the maximum rotation rate by itself. The rotation rate controller changes the rotation rate of the output shaft rotating within the operation range by driving the variable-speed motor only in the regenerative mode.

According to the above configuration, the variable-speed motor is not brought into a non-controlled state by the operation mode being switched from the regenerative mode to the power mode while the output shaft is being rotated. As a result, in the transmission device, a rotation direction of various gears is not switched in the middle. Therefore, it is possible to minimize instability of control and loss between the gears when the rotation direction of the gears in the transmission device is switched.

According to a second aspect of the present invention, in the first aspect, the rotation rate controller may set the rotation rate of the output shaft within the operation range to an intermediate rotation rate between the maximum rotation rate and the minimum rotation rate when the rotation rate of the variable-speed motor in the regenerative mode in a constant-torque region in which constant torque control is possible in the variable-speed motor becomes a maximum value.

According to a third aspect of the present invention, in the first or second aspect, the rotation rate controller may set the output shaft to have the minimum rotation rate by increasing the rotation rate of the variable-speed motor in the regenerative mode to a range beyond a constant-torque region in which the constant torque control is possible in the variable-speed motor.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the rotation rate controller may adjust the rotation rate of the variable-speed motor in the regenerative mode so that a torque of the variable-speed motor does not fall below a torque of the output shaft.

According to above configurations, it is possible to prevent the operation of the variable-speed motor from becoming unstable due to the torque of the output shaft becoming larger than the torque of the variable-speed motor during the adjustment of the rotation rate in the regenerative mode of the variable-speed motor.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the variable-speed motor may have a rated torque larger than a maximum torque of the output shaft.

According to the above configuration, it is possible to reliably prevent the torque of the variable-speed motor from falling below the torque of the output shaft during the adjustment of the rotation rate of the variable-speed motor in the regenerative mode, and thus it is possible to reliably minimize unstable operation of the variable-speed motor.

According to a seventh aspect of the present invention, there is provided a method of controlling a variable speed increaser which includes an electric driving device which generates a rotational driving force, and a planetary gear transmission device which changes the speed of the rotational driving force transmitted from the electric driving device to a constant-speed input shaft and a variable-speed input shaft and transmits the changed rotation driving force to a driving target through an output shaft, and in which the electric driving device includes a constant-speed motor having a constant-speed rotor which rotates the constant-speed input shaft of the planetary gear transmission device, and a variable-speed motor having a variable-speed rotor which rotates the variable-speed input shaft of the planetary gear transmission device and being driven in a regenerative mode in which the variable-speed motor serves as a generator and in a power mode in which the variable-speed motor serves as an electric motor, wherein a rotation rate of the output shaft varies within an operation range between a maximum rotation rate and a minimum rotation rate, and wherein the constant-speed motor has a rated torque which allows the rotation rate of the output shaft within the operation range to be a maximum value by itself, the method including changing the rotation rate of the output shaft rotating within the operation range by driving the variable-speed motor only in the regenerative mode.

According to the variable speed increaser and the control method thereof described above, efficient operation is possible.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

Hereinafter, a variable speed increaser1according to a first embodiment of the present invention will be described in detail with reference to the drawings.

As shown inFIG. 1, the variable speed increaser1of the embodiment includes an electric driving device50which generates a rotational driving force, and a transmission device10which changes the speed of a rotational driving force generated by the electric driving device50and then transmits the speed-changed rotational driving force to a driving target. The variable speed increaser1can be applied to, for example, a fluid mechanical system such as a compressor system. The driving target of the variable speed increaser1of the embodiment is a compressor C.

The transmission device10is a planetary gear transmission device. The electric driving device50includes a constant-speed motor51having a constant-speed rotor52which rotates at a constant speed, and a variable-speed motor71having a variable-speed rotor72which rotates at an arbitrary rotation rate. Each of the constant-speed rotor52and the variable-speed rotor72is connected to the transmission device10.

The electric driving device50is supported on a frame90by an electric driving device support portion50S. The transmission device10is supported on the frame90by a transmission device support portion10S. The electric driving device50and the transmission device10which are heavy objects can be securely fixed by these support portions.

As shown inFIG. 2, the transmission device10includes a sun gear11which rotates about an axis Ar extending in a horizontal direction, a sun gear shaft12fixed to the sun gear11, a plurality of planetary gears15which mesh with the sun gear11, revolve around the axis Ar and rotate about their own center lines Ap, an internal gear (gear)17in which a plurality of teeth are arranged in an annular shape around the axis Ar and which meshes with the plurality of planetary gears15, a planetary gear carrier21which supports the plurality of planetary gears15to allow the plurality of planetary gears15to revolve around the axis Ar and to rotate about their own center lines Ap, an internal gear carrier (gear carrier)31which supports the internal gear17to allow the internal gear17to rotate about the axis Ar, and a transmission casing41which covers these elements.

Hereinafter, a direction in which the axis Ar extends is defined as an axial direction, one side in the axial direction is defined as an output side, and a side opposite to the output side is defined as an input side. Also, a radial direction around the axis Ar is simply referred to as a radial direction. In the variable speed increaser1of the embodiment, the electric driving device50is disposed on the input side in the axial direction, and the transmission device10is disposed on the output side of the electric driving device50. The compressor C is disposed on the output side of the variable speed increaser1.

The sun gear shaft12has a circular column shape centered on the axis Ar and extends from the sun gear11toward the output side in the axial direction. A connection flange13is formed at the output-side end of the sun gear shaft12. For example, a rotor of the compressor C which serves as a driving target is connected to the connection flange13. The sun gear shaft12is supported to be rotatable about the axis Ar by a sun gear bearing42disposed on the output side of the sun gear11. The sun gear bearing42is installed at the transmission casing41.

The planetary gear carrier21includes a planetary gear shaft22provided for each of the plurality of planetary gears15, a planetary gear carrier main body23which fixes the relative positions of the plurality of planetary gear shafts22, and an output-side planetary gear carrier shaft27owhich extends in the axial direction centered on the axis Ar. The output-side planetary gear carrier shaft27ois fixed to an inner side of the planetary gear carrier main body23in the radial direction.

The planetary gear shaft22passes through the center lines Ap of the planetary gears15in the axial direction and supports the planetary gears15to allow the planetary gears15to rotate about a center line Ap thereof. The planetary gear carrier main body23extends outward in the radial direction from the plurality of planetary gear shafts22.

The output-side planetary gear carrier shaft27oextends from the planetary gear carrier main body23toward the output side. The output-side planetary gear carrier shaft27ois formed in a cylindrical shape centered on the axis Ar.

The output-side planetary gear carrier shaft27ois supported to be rotatable about the axis Ar by a first planetary gear carrier bearing43. The first planetary gear carrier bearing43is installed at the transmission casing41. The sun gear shaft12is inserted through the inner circumferential side of the output-side planetary gear carrier shaft27o.

The transmission device10further includes an input-side planetary gear carrier shaft27iwhich is connected to the variable-speed rotor72of the variable-speed motor71, and a transmitting shaft25which transmits rotation of the input-side planetary gear carrier shaft27ito the planetary gear carrier21.

The input-side planetary gear carrier shaft27iis formed in a cylindrical shape centered on the axis Ar. The input-side planetary gear carrier shaft27iis disposed on the input side of the transmission device10and is supported by a second planetary gear carrier bearing44to be rotatable about the axis Ar. The second planetary gear carrier bearing44is installed at the transmission casing41. An internal gear carrier shaft (gear carrier shaft)37for driving the internal gear carrier31of the transmission device10is inserted through the inner circumferential side of the input-side planetary gear carrier shaft27i.

An annular planetary gear flange28which expands outward in the radial direction is formed at the input-side end of the input-side planetary gear carrier shaft27i. An input-side arm portion26which extends outward in the radial direction is formed on the output-side end of the input-side planetary gear carrier shaft27i.

The transmitting shaft25is supported to be rotatable about the axis At. The transmitting shaft25is installed at the transmission casing41via a bearing (not shown). An input-side transmitting gear29iand an output-side transmitting gear290are fixed to both ends of the transmitting shaft25.

The input-side transmitting gear29imeshes with a gear formed on the outer circumference of the input-side arm portion26. The output-side transmitting gear29omeshes with a gear formed on the outer circumference of the planetary gear carrier main body23. Accordingly, the rotation of the input-side planetary gear carrier shaft27iis transmitted as rotation in a direction opposite to that of the planetary gear carrier21via the transmitting shaft25.

The internal gear carrier31includes an internal gear carrier main body33to which the internal gear17is fixed, and the internal gear carrier shaft37which is fixed to the internal gear carrier main body33and extends in the axial direction centered on the axis Ar.

The carrier main body33includes an internal gear cylindrical portion35which has a cylindrical shape centered on the axis Ar and has the internal gear17fixed to the inner circumferential side thereof, and an internal gear input-side arm portion36which extends inward from an input-side end of the internal gear cylindrical portion35in the radial direction.

The internal gear carrier shaft37having a column shape centered on the axis Ar is disposed on the input side of the sun gear shaft12having a column shape centered on the axis Ar. The internal gear input-side arm portion36of the internal gear carrier main body33is fixed to the internal gear carrier shaft37. The internal gear carrier shaft37is inserted through the inner circumferential side of the cylindrical input-side planetary gear carrier shaft27i.

The internal gear carrier shaft37is a constant-speed input shaft Ac which rotates at a constant speed under a driving force of the constant-speed motor51. The input-side planetary gear carrier shaft27iis a variable speed input shaft Av which rotates at an arbitrary rotation rate under a driving force of the variable-speed motor71. The variable speed increaser1can change the rotation rate of sun gear shaft12which is an output shaft Ao of the transmission device10connected to the driving target by changing the rotation rate of the variable-speed motor71.

At the time of normal operation, except for the time of startup, the output shaft Ao has a variable rotation rate within an operation range Ro (refer toFIG. 6) between a maximum rotation rate and a minimum rotation rate. The output shaft Ao is rotated with a rotation rate necessary for operating the compressor C with high efficiency as an intermediate rotation rate. The intermediate rotation rate is an intermediate rotation rate between the maximum rotation rate and the minimum rotation rate of the output shaft Ao. For example, when a rated rotation rate is 100%, the intermediate rotation rate is set to a rotation rate of about 90%, which is lower than the rated rotation rate. In this case, the maximum rotation rate is a rotation rate which exceeds the rated rotation rate, for example, a rotation rate of about 105%. Further, the minimum rotation rate is a rotation rate of about 75%.

As shown inFIG. 3, the constant-speed motor51rotationally drives the internal gear carrier shaft37of the transmission device10. The constant-speed motor51has a rated torque which allows the rotation rate of the output shaft Ao within the operation range Ro to be the maximum rotation rate by itself. The variable-speed motor71rotationally drives the input-side planetary gear carrier shaft27iof the transmission device10. The electric driving device50further includes a cooling fan91which cools the constant-speed motor51and a fan cover92which covers the cooling fan91.

In the embodiment, the constant-speed motor51is, for example, a four-pole three-phase induction motor. Further, the variable-speed motor71is an eight-pole three-phase induction motor having more poles than the constant-speed motor51. The specifications of the constant-speed motor51and the variable-speed motor71are not limited to these and can be appropriately changed.

The constant-speed motor51includes a constant-speed rotor52which rotates about the axis Ar and is connected to the internal gear carrier shaft37which is the constant-speed input shaft Ac of the transmission device10, a constant-speed stator66disposed on the outer circumferential side of the constant-speed rotor52, and a constant-speed motor casing61in which the constant-speed stator66is fixed to the inner circumferential side thereof.

The constant-speed rotor52includes a constant-speed rotor shaft53which has a column shape centered on the axis Ar, and a conductive body56fixed to the outer circumference of the constant-speed rotor shaft53. The cooling fan91is fixed to the input-side end of the constant-speed rotor shaft53.

The constant-speed stator66is disposed outward from the conductive body56of the constant-speed rotor52in the radial direction. This constant-speed stator66is formed of a plurality of coils.

The constant-speed motor casing61includes a constant-speed casing main body62having a cylindrical shape centered on the axis Ar and in which the constant-speed stator66is fixed to the inner circumferential side thereof, and covers63iand63owhich close both axial ends of the cylindrical constant-speed casing main body62. Constant-speed rotor bearings65iand65oare installed at the respective covers63iand63oto rotatably support the constant-speed rotor shaft53about the axis Ar. A plurality of openings64axially passing through the respective covers63iand63oat positions outward from the constant-speed rotor bearing65iin the radial direction are formed in the respective covers63iand63o.

The input-side end of the constant-speed rotor shaft53protrudes toward the input side from the input-side cover63iof the constant-speed motor casing61. The cooling fan91is fixed to the input-side end of the constant-speed rotor shaft53. The fan cover92is fixed to the input-side cover63iof the constant-speed motor casing61.

The variable-speed motor71includes a variable-speed rotor72which rotates about the axis Ar and is connected to the input-side planetary gear carrier shaft27iwhich is the variable-speed input shaft Av, a variable-speed stator86disposed on the outer circumferential side of the variable-speed rotor72, and a variable-speed motor casing81in which the variable-speed stator86is fixed to the inner circumferential side thereof.

The variable-speed rotor72has a variable-speed rotor shaft73and a conductive body76fixed to the outer circumference of the variable-speed rotor shaft73. The variable-speed rotor shaft73has a cylindrical shape around the axis Ar and has a shaft insertion hole74passing through the variable-speed rotor shaft73in the axial direction. The internal gear carrier shaft37as the constant-speed input shaft Ac is inserted through the shaft insertion hole74of the variable-speed rotor shaft73. An annular variable-speed flange73oexpanding outward in the radial direction is formed at the output-side end of the variable-speed rotor shaft73.

The variable-speed stator86is disposed outward from the conductive body76of the variable-speed rotor72in the radial direction. The variable-speed stator86is formed of a plurality of coils.

The variable-speed motor casing81includes a casing main body82having a cylindrical shape around the axis Ar and to the inner circumferential side of which the variable-speed stator86is fixed, an output-side cover83owhich covers the output-side end of the cylindrical casing main body82, and an inlet-side cover83idisposed on the input side of the variable-speed stator86and fixed to the inner circumferential side of the cylindrical casing main body82. Variable-speed rotor bearings85iand85owhich rotatably support the variable-speed rotor shaft73about the axis Ar are installed at the respective covers83iand83o. In the respective covers83iand83o, a plurality of openings84passing through the respective covers83iand83oin the axial direction are formed at positions outward from the variable-speed rotor bearings85iand85oin the radial direction.

A space in the variable-speed motor casing81and a space in the constant-speed motor casing61communicate with each other through the plurality of openings84formed in the respective covers83iand83oof the variable-speed motor casing81and the plurality of openings64formed in the respective covers63iand63oof the constant-speed motor casing61.

Further, in the variable speed increaser1of the present embodiment, the constant-speed rotor52, the variable-speed rotor72and the sun gear shaft12are disposed on the same axis Ar.

As shown inFIG. 4, the constant-speed motor51rotates the constant-speed rotor52only in a second direction R2when electric power is supplied. The second direction R2is a direction toward one side in the circumferential direction of the axis Ar and is a drive rotation direction of the constant-speed motor51. As the constant-speed rotor52rotates in the second direction R2, the internal gear carrier shaft37, the internal gear carrier31, and the internal gear17rotate in the second direction R2. Therefore, the planetary gear15is rotated in the second direction R2via the internal gear17. As a result, the constant-speed rotor52rotates in the second direction R2, and thus the output shaft Ao rotates in a first direction R1opposite to the second direction R2.

Therefore, the forward rotation of the constant-speed motor51is the second direction R2, and the forward rotation of the output shaft Ao of the transmission device10is the first direction R1. The compressor C operates normally as the output shaft Ao rotates forward.

In the following description, a rotation direction of the first direction R1is a minus (negative) rotation direction, and a rotation direction of the second direction R2is a plus (positive) rotation direction. Therefore, for example, the rotation rate of the constant-speed rotor52which rotates in the second direction R2in the constant-speed motor51is +1800 rpm and is constant.

The variable-speed motor71is capable of rotating the variable-speed rotor72in the first direction R1and the second direction R2in the circumferential direction of the axis Ar. That is, the variable-speed motor71is capable of rotating the variable-speed rotor72forward and in reverse. As the variable-speed rotor72rotates in the first direction R1, the input-side planetary gear carrier shaft27iand the planetary gear carrier21rotate in the first direction R1. As the variable-speed rotor72rotates in the second direction R2, the input-side planetary gear carrier shaft27iand the planetary gear carrier21rotate in the second direction R2.

The variable-speed motor71serves as a generator by rotating the variable-speed rotor72by an external force (constant-speed motor51). Here, a state in which the variable-speed motor71serves as a generator is referred to as a regenerative mode. In the regenerative mode, the variable-speed motor71is driven by an external torque. As the variable-speed motor71is driven in the regenerative mode, a torque in a direction to decelerate the rotation rate of the output shaft Ao acts on the variable-speed rotor72, and the rotation rate of the output shaft Ao decreases.

Further, the variable-speed motor71serves as an electric motor by the electric power being supplied. Here, a state in which the variable-speed motor71serves as an electric motor is referred to as a power mode. In the power mode, the variable-speed motor71is driven by the supplied electric power. As the variable-speed motor71is driven in the power mode, a torque in a direction in which the rotation rate of the output shaft Ao increases acts on the variable-speed rotor72, and the rotation rate of the output shaft Ao increases.

The rotation direction of the variable-speed rotor72of the variable-speed motor71is not limited to a structure in which the first direction R1is a rotation direction in the regenerative mode and the second rotation direction is a rotation direction in the power mode.

The torque acts on the variable-speed rotor72to decelerate the output shaft Ao and the rotation rate of the output shaft Ao decreases from the maximum rotation rate, for example, by increasing the rotation rate of the variable-speed motor71in the regenerative mode from 0% (from 0% to −200% inFIG. 6).

The variable speed increaser1of the embodiment includes a rotation rate controller100which adjusts the rotation rate of the variable-speed motor71and an electric driving device controller120which controls an operation of the rotation rate controller100.

The electric driving device controller120is configured of a computer. The electric driving device controller120includes a receiving portion121which directly receives an instruction from an operator or receives an instruction from a host control device, an interface122which provides instructions to the rotation rate controller100, and a calculating portion123which creates an instruction for the rotation rate controller100according to the instructions received by the receiving portion121or the like.

The rotation rate controller100changes a frequency of the supplied electric power or the torque in the variable-speed motor71. The rotation rate controller100changes the rotation direction of the variable-speed motor71by changing a phase of a voltage applied to the variable-speed motor71. That is, the rotation rate controller100is capable of rotating the variable-speed rotor72forward and in reverse.

The rotation rate controller100supplies the electric power having the frequency instructed from the electric driving device controller120to the variable-speed motor71. In the variable-speed motor71, the variable-speed rotor72rotates at a rotation rate corresponding to this frequency. Since the rotation rate of the variable-speed rotor72changes in this manner, the rotation rate of the planetary gear carrier21of the transmission device10connected to the variable-speed rotor72also changes. As a result, the rotation rate of the output shaft Ao of the transmission device10also changes.

As shown inFIG. 6, specifically, the rotation rate controller100adjusts the rotation rate of the variable-speed motor71in the regenerative mode within a range of 0% to −200% (within the operation range Ro of the output shaft Ao) during the normal operation except for the time of startup. That is, the rotation rate controller100drives the variable-speed motor71only in the regenerative mode, without driving the variable-speed motor71in the power mode, except at the time of startup.

The rotation rate controller100reduces the rotation rate of the output shaft Ao from the maximum rotation rate by increasing the rotation rate of the variable-speed motor71in the regenerative mode to approach −200%. At this time, when the rotation rate of the variable-speed motor71in the regenerative mode is −100% (when the rotation rate of the variable-speed motor71in the regenerative mode becomes the maximum value within a constant-torque region Rt in which constant torque control is possible in the variable-speed motor71), the rotation rate of the output shaft Ao is the intermediate rotation rate. Therefore, the rotation rate controller100adjusts the rotation rate of the variable-speed motor71in the regenerative mode so that the rotation rate of the output shaft Ao is set to the minimum rotation rate within a range in which the torque of the variable-speed motor71reduces beyond the constant-torque region Rt. Specifically, when the rotation rate controller100sets the rotation rate of the variable-speed motor71in the regenerative mode to −200% of the maximum value, the rotation rate of the output shaft Ao becomes the minimum rotation rate.

The rotation rate controller100increases the rotation rate of the output shaft Ao to approach the maximum rotation rate by decreasing the rotation rate of the variable-speed motor71in the regenerative mode to approach 0%. Therefore, when the rotation rate controller100sets the rotation rate of the variable-speed motor71in the regenerative mode to 0% which is the minimum value, the rotation rate of the output shaft Ao becomes the maximum rotation rate.

Meanwhile, the rotation rate controller100adjusts the rotation rate of the variable-speed rotor72so that the torque of the variable-speed motor71does not fall below the torque of the output shaft Ao in a state in which the rotation rate of the variable-speed motor71in the regenerative mode is within the range from 0% to −200%.

Next, a control method of the variable speed increaser1according to the embodiment will be described.

In the variable speed increaser1in which the compressor C is operated at a rated point at which it can operate with high efficiency and the rotation rate of the output shaft Ao is the intermediate rotation rate, a case in which the rotation rate of the output shaft Ao is adjusted will be described as an example. As shown inFIG. 5, when the electric driving device controller120receives an instruction to increase the rotation rate of the output shaft Ao (S11), an instruction to lower the rotation rate of the variable-speed motor71in the regenerative mode is output to the rotation rate controller100(S12). Therefore, the rotation rate of the variable-speed motor71in the regenerative mode decreases from −100% to approach 0%. As a result, in the transmission device10, a speed of the output shaft Ao is increased, and the rotation rate of the output shaft Ao is increased.

Conversely, when the electric driving device controller120receives an instruction to lower the rotation rate of the output shaft Ao (S13), an instruction to increase the rotation rate of the variable-speed motor71in the regenerative mode is outputted to the rotation rate controller100(S14). Therefore, the rotation rate of the variable-speed motor71in the regenerative mode increases from −100% to approach −200%. As a result, in the transmission device10, the output shaft Ao is decelerated, and the rotation rate of the output shaft Ao is reduced.

At the time of starting the constant-speed motor51and rotating the constant-speed rotor52from a stopped state, it is necessary to drive the variable-speed motor71in the power mode (for example, rotation rate of +10%) and to prevent the variable-speed rotor72from over-rotating. Specifically, when the constant-speed motor51is started with the variable-speed motor71in a non-controlled state, the torque is transmitted in a direction to accelerate the output shaft Ao, but since inertial energy of the output shaft Ao connected to the compressor C is large, the variable-speed rotor72is over-accelerated in a reverse rotation direction. Therefore, occurrence of abnormal behavior of the variable-speed rotor72is suppressed by controlling the variable-speed rotor72at a low speed rotation in the same rotation direction as a direction in which the output shaft Ao is accelerated so that the variable-speed rotor72does not over-rotate.

According to the above-described variable speed increaser, when the output shaft Ao is rotating within the operation range Ro, the variable-speed motor71is driven only in the regenerative mode. Therefore, while the compressor C is being operated by rotating the output shaft Ao, the variable-speed motor71is prevented from being brought into the non-controlled state by the operation mode being switched from the regenerative mode to the power mode. As a result, in the transmission device10, the rotation direction of the various gears such as the internal gear carrier31and so on is not switched in the middle. Therefore, it is possible to suppress instability of control and loss between the gears when the rotation direction of the gears in the transmission device10is switched. Accordingly, it is possible to efficiently operate the variable speed increaser1and the compressor C connected to the variable speed increaser1.

Further, in the transmission device10, since the rotation direction of the various gears such as the internal gear carrier31and so on is not switched, the transmission of the torque from the electric driving device50to the compressor C is continuously performed in the transmission device10. That is, it is possible to prevent the transmission device10from being in an unloaded state due to discontinuous transmission of the torque in the transmission device10, thereby preventing the operation of the transmission device10from becoming unstable. Accordingly, it is possible to operate the variable speed increaser1and the compressor C connected to the variable speed increaser1in a stable state.

Further, the constant-speed motor51has a rated torque which allows the rotation rate of the output shaft Ao to be the maximum rotation rate by itself. Due to such a configuration, the variable-speed motor71is operated only in the regenerative mode. Therefore, the variable-speed motor71is operated within a range in which the output shaft Ao rotating at the maximum rotation rate is decelerated. Thus, the variable-speed motor71is operated within a range in which the torque required in the compressor C is reduced. Accordingly, it is possible to adjust the rotation rate of the output shaft Ao in a wide range required for operating the compressor C without increasing the rated torque of the variable-speed motor71. Furthermore, since the rated torque of the variable-speed motor71is not increased, it is possible to minimize an increase in cost of the variable speed increaser1.

Further, since it is driven only in the regenerative mode, it is possible to recover energy generated in the constant-speed motor51. Specifically, it is possible for the constant-speed motor51to mainly apply a load on the compressor C, and thus it is possible for the variable-speed motor71to recover extra energy which is not consumed by the compressor C on a load side as regenerative energy. Accordingly, it is possible to recover the extra energy in the variable-speed motor71in a form of applying a brake to the constant-speed motor51rotating at a maximum speed.

Also, in the operation range Ro of the output shaft Ao, the rotation rate of the variable-speed motor71in the regenerative mode is adjusted by the rotation rate controller100so that the torque of the variable-speed motor71does not fall below the torque of the output shaft Ao even in a range beyond the constant-torque region Rt of the variable-speed motor71. Therefore, it is possible to prevent the operation of the variable-speed motor71from becoming unstable by the torque of the output shaft Ao becoming larger than the torque of the variable-speed motor71during the adjustment of the rotation rate of the variable-speed motor71in the regenerative mode.

Second Embodiment

Next, the variable speed increaser of a second embodiment will be described with reference toFIG. 7.

In the second embodiment, the same reference numerals are given to the same constituent elements as those in the first embodiment, and a detailed description thereof will be omitted. A capacity of the variable-speed motor of the second embodiment is different from that of the first embodiment.

A variable-speed motor71A has a rated torque larger than a maximum torque of the output shaft Ao. As shown inFIG. 7, a magnitude of the torque in the constant-torque region Rt of the variable-speed motor71A is larger than the maximum torque of the output shaft Ao. Further, even when the output shaft Ao has the lowest rotation rate and the torque of the output shaft Ao becomes the lowest, the torque of the variable-speed motor71A is higher than the torque of the output shaft Ao.

As a result, it is possible to reliably prevent the torque of the variable-speed motor71A from falling below the torque of the output shaft Ao during the adjustment of the rotation rate of the variable-speed motor71A in the regenerative mode, and it is possible to reliably suppress the unstable operation of the variable-speed motor71A.

Third Embodiment

Next, the variable speed increaser of a third embodiment will be described with reference toFIG. 8.

In the third embodiment, the same reference numerals are given to the same constituent elements as those in the first embodiment and the second embodiment, and a detailed description thereof will be omitted. An internal structure of the transmission device of the third embodiment is different from that of the first embodiment.

In a transmission device10A of the third embodiment, the gear which was the internal gear17in the first embodiment is an external gear17A. Therefore, the gear carrier shaft which was the internal gear carrier shaft37in the first embodiment is an external gear carrier shaft37A.

Specifically, as shown inFIG. 8, the transmission device10A of the third embodiment includes the sun gear11, the sun gear shaft12, a planetary gear15A, the external gear (gear)17A, a planetary gear carrier21A, an external gear carrier (gear carrier)31A, and the transmission casing41which covers these elements.

The planetary gear15A of the third embodiment includes a plurality of first planetary gears (primary gears)151A and a plurality of second planetary gears (secondary gears)152A.

The first planetary gear151A meshes with the external gear17A. The first planetary gear151A revolves around the axis Ar and also rotates about its own center line Ap.

The second planetary gear152A meshes with the sun gear11. The second planetary gear152A revolves around the axis Ar and also rotates about its own center line Ap which is the same as that of the first planetary gear151A. The second planetary gear152A is disposed on the output side in the axial direction with respect to the first planetary gear151A. One of the second planetary gears152A is rotatable integrally with one of the first planetary gears151A. That is, one first planetary gear151A is disposed in a pair with respect to one second planetary gear152A.

The planetary gear carrier21A of the third embodiment includes a planetary gear shaft22A, a planetary gear carrier main body23A, and a planetary gear carrier shaft27A.

The planetary gear shaft22A is provided for each of the planetary gears15A. The planetary gear shaft22A allows the first planetary gear151A and the second planetary gear152A connected to each other to rotate about the center line Ap. The planetary gear shaft22A connects one second planetary gear152A with one first planetary gear151A. Specifically, the first planetary gear151A is connected to the input side of the planetary gear shaft22A in the axial direction, and the second planetary gear152A is connected to the output side of the planetary gear shaft22A in the axial direction. The planetary gear shaft22A passes through the first planetary gear151A and the second planetary gear152A in the axial direction. Therefore, the input-side end of the planetary gear shaft22A in the axial direction is located on the input side with respect to the first planetary gear151A in the axial direction. Further, the output-side end of the planetary gear shaft22A in the axial direction is located on the output side with respect to the second planetary gear152A in the axial direction.

The planetary gear carrier main body23A fixes mutual positions of a plurality of planetary gear shafts22A. The planetary gear carrier main body23A includes a planetary gear output-side arm portion24A and a planetary gear input-side arm portion26A.

The planetary gear output-side arm portion24A rotatably supports the output-side ends of the plurality of planetary gear shafts22A in the axial direction. The planetary gear input-side arm portion26A rotatably supports the input-side ends of the plurality of planetary gear shafts22A in the axial direction. The planetary gear carrier21A coaxially supports the first planetary gear151A and the second planetary gear152A by supporting the planetary gear shafts22A via the planetary gear carrier main body23A in this manner.

The planetary gear carrier shaft27A fixes the planetary gear carrier main body23A. The planetary gear carrier shaft27A extends in the axial direction about the axis Ar. The planetary gear carrier shaft27A includes an output-side planetary gear carrier shaft27Ao which extends from the planetary gear output-side arm portion24A to the output side, and an input-side planetary gear carrier shaft27Ai which extends from the planetary gear input-side arm portion26A to the input side. Both the output-side planetary gear carrier shaft27Ao and the input-side planetary gear carrier shaft27Ai are formed in a cylindrical shape with the axis Ar as a center.

The output-side planetary gear carrier shaft27Ao is supported by the first planetary gear carrier bearing43to be rotatable about the axis Ar with respect to the transmission casing41. In the first planetary gear carrier bearing43, the sun gear shaft12is inserted through the inner circumferential side of the output-side planetary gear carrier shaft27Ao disposed on the output side with respect to the planetary gear output-side arm portion24A.

The input-side planetary gear carrier shaft27Ai is supported by the second planetary gear carrier bearing44to be rotatable about the axis Ar with respect to the transmission casing41. The second planetary gear carrier bearing44is disposed on the input side with respect to the planetary gear input-side arm portion26A. The external gear carrier shaft37A which will be described later is inserted through the inner circumferential side of the input-side planetary gear carrier shaft27Ai.

The external gear carrier31A supports the external gear17A to be rotatable about the axis Ar. The external gear carrier31A has the external gear carrier shaft37A connected to the external gear17A.

The external gear carrier shaft37A is fixed to the external gear17A around the axis Ar and extends in the axial direction. The external gear carrier shaft37A is formed in a circular column shape centered on the axis Ar. The external gear carrier shaft37A extends from the external gear17A to the input side in the axial direction. The input-side portion of the external gear carrier shaft37A is inserted through the inner circumferential side of the cylindrical input-side planetary gear carrier shaft27Ai.

Even with the variable speed increaser1having the above-described transmission device10A, like in the first embodiment, it is possible to stably and efficiently operate the variable speed increaser1and the compressor C connected to the variable speed increaser1.

Other Modified Examples of the Embodiments

Although the embodiments of the present invention have been described in detail with reference to the drawings, the constitutions and combinations in the respective embodiments are merely examples, and additions, omissions, substitutions, and other modifications of the constitutions are possible without departing from the scope of the present invention. Further, the present invention is not limited by the embodiments and is limited only by the claims.

The configuration of the transmission device10A is not limited to the gear constitution, like the above-described first or third embodiment. Specifically, the gear which meshes with the planetary gears15and15A may be one of the internal gear17like in the first embodiment and the external gear17A like in the third embodiment, and also the number thereof is not limited to the configuration like in this embodiment. Therefore, for example, the gear which meshes with the planetary gear15may have a configuration in which two or more internal gears17are provided, like the first embodiment. In addition, the gear which meshes with the planetary gear15A may have a configuration in which only one or three or more external gears17A are provided, like the third embodiment.

Further, in the above-described embodiment, a four-pole three-phase induction motor is exemplified as the constant-speed motor51suitable for rotating the compressor C at high speed, and an eight-pole three-phase induction motor is exemplified as the variable-speed motor71suitable for varying the rotation rate of the compressor C within a certain range. However, when it is unnecessary to rotate the driving target at high speed, other types of electric motors may be used as the constant-speed motor51and the variable-speed motor71.

Further, in the above-described embodiment, the shaft insertion hole74is formed in the variable-speed rotor72, and the constant-speed rotor52is inserted through the shaft insertion hole74. However, the shaft insertion hole74may be formed in the constant-speed rotor52, and the variable-speed rotor72may be inserted through the shaft insertion hole74.

Further, in the above-described embodiment, the constant-speed rotor52, the variable-speed rotor72, and the sun gear shaft12are disposed on the same axis Ar, but the present invention is not limited to such a structure. For example, the variable-speed motor71may be disposed so that the axis Ar of the variable-speed rotor72is parallel to the axis Ar of the constant-speed rotor52and is located at a different position. Also, for example, the variable-speed rotor72may be connected to the variable-speed input shaft Av via a connection structure such as another gear.

Further, the variable speed increaser1of the embodiment is not limited to a structure in which one variable-speed motor71is connected to one transmission device10or10A. For example, a plurality of variable-speed rotors72may be connected to one variable-speed input shaft Av so that a plurality of variable-speed motors71are connected to one transmission device10or10A.

Further, in the transmission device10of the embodiment, an idle gear may be provided at the input-side arm portion26. In this case, the variable-speed motor71can rotate the variable-speed rotor72(the planetary gear carrier21) in the first direction R1as the forward direction, like the constant-speed motor51.

Further, the operation range Ro of the output shaft Ao is not limited to the maximum rotation rate of 105% and the minimum rotation rate of 75% with respect to the rated rotation rate. The operation range Ro of the output shaft Ao may be appropriately set according to the operation conditions required for the driving target to which the output shaft Ao is connected.

Further, the rotation rate of the variable-speed motor71in the regenerative mode when the rotation rate of the output shaft Ao is the maximum rotation rate is not limited to 0%, like in the embodiment. The rotation rate of the variable-speed motor71in the regenerative mode when the rotation rate of the output shaft Ao is the maximum rotation rate may not be 0% as long as the variable-speed motor71is driven in the regenerative mode. Similarly, the rotation rate of the variable-speed motor71in the regenerative mode when the rotation rate of the output shaft Ao is the minimum rotation rate is not limited to −200%, like in the embodiment. The rotation rate of the variable-speed motor71in the regenerative mode when the rotation rate of the output shaft Ao is the minimum rotation rate may also not be −200% as long as the variable-speed motor71is driven in the regenerative mode.