JP4368018B2 - Friction transmission type rotary drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a friction transmission type rotary drive device including a simple planetary roller mechanism having a sun roller, a planetary roller, and a ring roller as friction rollers, and a motor with a braking mechanism that rotationally drives the sun roller.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, many friction transmission type rotational drive devices including a simple planetary roller mechanism that transmits rotational power by frictional force and a motor have been proposed.
[0003]
FIG. 6 shows a friction transmission type rotary drive device 100 devised by the present inventor (unknown at the time of filing). The rotation drive device 100 is held by the sun roller 30 and the carrier 32 as friction rollers, and the planetary roller 34 that is in rolling contact with the outer periphery of the sun roller 30, and the planetary roller 34 is in contact with the inner periphery of the planetary roller 34. A simple planetary roller mechanism 28 having a ring roller 36 whose rotation is restricted, and a motor 102 which is connected to the sun roller 30 and drives the sun roller 30.
[0004]
Specifically, the motor shaft 102A of the motor 102 is connected to the sun roller 30 via a parallel key, and the motor 102 itself is fixed to the flange portion 38B of the casing 38 that houses the simple planetary roller mechanism 28 by bolts. ing.
[0005]
On the inner peripheral surface side of the casing 38, a ring-shaped fixing portion 38A protruding radially inward is formed, and the ring roller 36 is fixed thereto by a bolt 40.
[0006]
The simple planetary roller mechanism 28 in the rotary drive device 100 configured as described above has a sun roller 30 as an input element, a carrier 32 as an output element, and a ring roller 36 as a fixed element, and has a deceleration function as a whole. Have. That is, the rotary drive device 100 has a structure in which the rotational power of the motor 102 is transmitted to the sun roller 30 and is output from the carrier 32 side with a predetermined reduction ratio.
[0007]
The simple planetary roller mechanism 28 transmits the rotational power of the motor 102 using the frictional force generated on the contact surface between the friction rollers, and can be operated more smoothly and quietly than a transmission structure using gears or the like. It is.
[0008]
Therefore, in order to ensure a predetermined transmission capability (transmittable torque) by the simple planetary roller mechanism 28, it is necessary to generate a sufficient frictional force between the friction rollers. This frictional force generally causes the inner diameter of the ring roller 36 to be smaller than the sum of the diameter of the planetary roller 34 and the diameter of the sun roller 30, and applies a so-called tightening force to elastically deform the ring roller 36. Is granted by. When the tightening force is large, the frictional force between the friction rollers also increases. This frictional force also increases the transmittable torque of the simple planetary roller mechanism 28. Conversely, when the tightening force is small, the transmittable torque decreases. When the transmittable torque is large (the tightening force is large), the rotational resistance of each friction roller is also increased, the transmission efficiency of the rotary drive device 100 is reduced, and the simple planetary roller mechanism due to rolling fatigue Decrease in durability of 28 becomes a problem.
[0009]
The rotary drive device 100 has two main advantages by adopting the simple planetary roller mechanism 28 described above. First, as already shown, as a result of being able to transmit power smoothly and silently compared to a transmission structure such as a gear, the transmission efficiency of rotational power is increased and the power consumption of the motor 102 is reduced, so-called “energy saving”. To contribute. The other is that the friction roller is relatively easy to manufacture as compared with a gear or the like, so that the manufacturing cost is reduced and the entire rotary drive device 100 becomes “inexpensive”.
[0010]
On the other hand, the disadvantage of adopting the friction transmission type simple planetary roller mechanism 28 is that the rotational power is transmitted by the frictional force, so that a slight slip is always generated between the contact surfaces of the rotating friction rollers. The rotational speed of the sun roller 30 and the rotational speed of the carrier 32 are not necessarily in a “strict” reduction ratio relationship. Therefore, it can be said that the transmission structure such as a gear is superior in this respect.
[0011]
However, considering the situation where a motor (rotary drive device) of such a reduction gear mechanism is actually used, when an induction motor or the like is used in the first place, a certain slip occurs between the rotor and the rotating magnetic field. Therefore, it is not necessary to require a strict reduction ratio for the reduction mechanism itself. That is, in order to maintain the rotational speed of the partner machine to be connected at a predetermined value, it is common to measure the rotational speed of the counterpart machine or the like and feedback-control the motor. It can be said that the simple planetary roller mechanism that is “energy saving” and “cheap” is more in line with the current market needs than the gear reduction structure that is ratio-wise but also expensive.
[0012]
[Problems to be solved by the invention]
Conventionally, there are many gear transmission type rotational drive devices (so-called geared motors) in which a braking mechanism is added to a motor or the like. As far as the present inventors know, friction transmission type rotational drive with a braking mechanism is present. The device is not on the market, and no proposal has been made to install a braking mechanism. This is expected because there are actually a number of difficulties as shown below.
[0013]
(1) There is no theoretical system established so far regarding an optimal combination of a simple planetary roller mechanism and a braking mechanism.
[0014]
More specifically, the simple planetary roller mechanism transmits power through frictional force generated between the contact surfaces of each friction roller. When a large rotational load is applied, the contact surface is slid. Is generated. On the other hand, a generally used braking mechanism also converts kinetic energy into heat energy by friction caused by tightening the brake wheel by the brake piece, that is, braking force is generated by "slip" between the brake wheel and the brake piece. Is generated.
[0015]
Therefore, since both the simple planetary roller mechanism and the brake device have a possibility of slipping, it is difficult to find the optimum combination from the viewpoint of reliable braking. When actually designing and manufacturing, It is necessary to set a high safety including such uncertain factors and to set a large transmittable torque (depending on the tightening force) of the simple planetary roller mechanism.
[0016]
For example, if the transmission capability (transmittable torque) of the simple planetary roller mechanism is too small with respect to the braking capability of the braking mechanism (braking torque generated during braking), the rotary drive device is connected. This is because it was thought that the counterpart machine (external load) could not be braked reliably.
[0017]
(2) On the other hand, the simple planetary roller mechanism must efficiently transmit the rotational driving force of the motor.
[0018]
Therefore, when the simple planetary roller mechanism is designed and manufactured to be larger (including the transmission capability) as in (1) above, the rotational resistance of each friction roller increases, and “highly efficient transmission of rotational power is achieved. The advantage of the frictional transmission type simple planetary roller mechanism is lost. Of course, the cost also increases. That is, from the viewpoint of transmission efficiency and cost, the simple planetary roller mechanism must be designed as small as possible (including the transmission capability).
[0019]
Due to the conflicting factors (1) and (2), it is considered that the braking mechanism cannot be easily attached to the friction transmission type rotary drive device, and as a result, the adoption of the braking mechanism has been postponed.
[0020]
The present invention has been made in view of the above-mentioned problems, and maintains the braking ability by combining the balance of the simple planetary roller mechanism, the motor, and the braking mechanism in the most suitable state. Another object of the present invention is to obtain a friction transmission type rotary drive device excellent in cost performance that achieves both high efficiency and low cost.
[0021]
[Means for Solving the Problems]
The present invention is a simple planetary roller mechanism having a sun roller, a planetary roller that is held by a carrier and is in rolling contact with the outer periphery of the sun roller, and a ring roller in which the planetary roller is in contact with its inner periphery as a friction roller, A friction transmission type rotary drive device comprising a motor coupled to the sun roller and driving the sun roller. The motor is provided with a braking mechanism, a static friction torque Yd that can be taken out by the braking mechanism, and the carrier In addition, the test torque is gradually increased and inputted to the sun roller while the ring roller is fixed, and the test torque value Xd when the first slip occurs in any of the friction rollers is Yd <Xd. Dynamic friction torque Ys that can be taken out by the braking mechanism at the rated rotational speed of the motor and the sun roller The above-mentioned object is achieved by setting the limit transmission torque Xs that the simple planetary roller mechanism can transmit with the sun roller when rotating at the rated rotational speed to be 0.65Ys <Xs <3.4Ys. Is.
[0022]
The present inventor considered the situation that this rotary drive device would actually be used in newly attaching a braking mechanism to a friction transmission type rotary drive device combining a simple planetary roller mechanism and a motor, We focused on the difference between the braking state at rest and the braking state at rotation.
[0023]
Specifically, in general, the braking mechanism is, for example, a brake wheel that is sandwiched between brake pieces and exerts a braking force by a frictional force, but the braking ability is prevented from fluctuating depending on the rotation speed of the brake wheel. Therefore, the relative difference between the static friction torque at rest (so-called holding torque) and the dynamic friction torque at rotation is set as small as possible (although the static friction torque is somewhat higher).
[0024]
On the other hand, the simple planetary roller mechanism is not intended to generate a rotational load because of its function, but focuses on smooth rotation by applying a predetermined tightening force between the friction rollers. Therefore, the limit transmission torque Xs during rotation may be “relatively” much smaller than the test torque Xd at rest (also referred to as holding torque).
[0025]
Therefore, the present inventor has paid attention to the fact that the relative difference in transmission (braking) capability between stationary and rotating greatly differs between the braking mechanism and the simple planetary roller mechanism. Therefore, in order to make good use of this difference, a new concept of “test torque Xd” indicating the transmission capability of the simple planetary roller mechanism when stationary and “limit transmission torque Xs” indicating the transmission capability during rotation is introduced. From these numerical values measured from an actual simple planetary roller mechanism, it was found that an optimum balance of the simple planetary roller mechanism, the braking mechanism and the motor can be set.
[0026]
As a result, it has become possible to set the test torque Xd, the limit transmission torque Xs, and the braking torque (static friction torque, dynamic friction torque) of the braking mechanism in the above magnitude relationship. According to this friction transmission type rotary drive device, the static friction torque that can be taken out by the braking mechanism when stationary is reliably transmitted to the counterpart machine connected via the simple planetary roller mechanism, and the counterpart machine is reliably kept stationary. Hold Can. In addition, the dynamic friction torque generated by the braking mechanism can be reliably transmitted to the rotating counterpart machine through the simple planetary roller mechanism to a certain extent, and the rotational speed of the counterpart machine can be reliably reduced.
[0027]
In other words, because of the function of the braking mechanism, it is necessary to make sure that the counterpart machine is finally stopped, but it is considered that the braking mechanism itself is in a state of braking while sliding, The planetary roller mechanism does not necessarily have to transmit its braking force “completely” to the counterpart machine, and it can be said that the planetary roller mechanism may have the possibility of sliding. Therefore, it is sufficient that the rotational drive device exerts a predetermined braking force to reduce the rotational speed of the counterpart machine within the limit range that the simple planetary mechanism can transmit. Since the limit transmission capability of the simple planetary roller mechanism gradually increases as it gradually decreases due to braking (confirmed by the inventor), the braking capability ( The configuration that the braking ability that can be transmitted to the other machine is also improved is adopted. As a result, the counterpart machine can be surely braked finally, and once the counterpart machine stops, the counterpart machine does not start to rotate freely.
[0028]
On the other hand, when considering the relation of the combination of a general motor and a braking mechanism, if the configuration of the rotary drive device according to the present invention is used, the transmission capability of the simple planetary roller mechanism with respect to the drive capability of the motor at the rated rotational speed is It is neither too large nor too small, and can be said to be optimally set. That is, the friction transmission type characteristic of quiet and smooth rotational power transmission (highly efficient transmission) is sufficiently maintained in spite of surely exerting the braking function as described above.
[0029]
As a result, according to the present invention, a three-way balance between the simple planetary roller mechanism, the braking mechanism, and the motor is optimally set, and a rotary drive device with excellent cost performance can be obtained.
[0030]
In this rotary drive device, the specific motor drive capability may be set so that the rated torque T of the motor is T <Xs with respect to the limit transmission torque Xs of the simple planetary roller mechanism. preferable. In this way, in terms of the driving ability in addition to the braking ability, the counterpart machine connected to the friction transmission type rotary drive device can be driven more reliably.
[0031]
In the above invention, the limit transmission torque Xs of the simple planetary roller mechanism is set to be 0.65 Ys <Xs <3.4 Ys, but preferably 0.8 Ys <Xs <1.7 Ys, and the best is that Ys and Xs are almost equal. It is set to match.
[0032]
In general, as a power transmission mode of the simple planetary roller mechanism, there is a fixed / input / output relationship as shown below.
[0033]
1) When the sun roller is an input element, the ring roller is a fixed element, the carrier holding the planetary roller is the output element, and the ring roller is the output element and the carrier holding the planetary roller is the fixed element. Yes,
2) When the carrier holding the planetary roller is used as an input element, there are cases where the ring roller is a fixed element, the sun roller is an output element, and the ring roller is an output element and the sun roller is a fixed element.
3) When the ring roller input element is used, there are cases where the carrier holding the planetary roller is a fixed element and the sun roller is an output element, and the carrier holding the planetary roller is an output element and the sun roller is a fixed element. is there.
[0034]
The simple planetary roller mechanism of the present invention employs the above-described aspect (1), and the present invention can be applied regardless of whether the ring roller or the carrier is used as an output element.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.
[0036]
FIG. 1 shows a friction transmission type rotary drive device 101 according to an embodiment of the present invention. The rotary drive device 101 is a friction roller that is held by a sun roller 130 and a carrier 132, and a planetary roller 134 that is in rolling contact with the outer periphery of the sun roller 130, and the planetary roller 134 that is in contact with the inner periphery of itself. A simple planetary roller mechanism 128 having a ring roller 136 whose rotation is restricted, and a motor 126 that is connected to the sun roller 130 and drives the sun roller 130.
[0037]
Further, the motor 126 of the rotary drive device 101 is provided with a braking mechanism 122. The static friction torque Yd that can be taken out by the braking mechanism and the test torque Xd that the simple planetary roller mechanism 128 has (details will be described later). Are set so that Yd <Xd and the dynamic friction torque Ys that can be taken out by the braking mechanism 122 at the rated rotational speed of the motor 126 and the simple planetary roller mechanism 128 when the sun roller 130 rotates at the rated rotational speed. Is set so that 0.65Ys <Xs <3.4Ys.
[0038]
The limit transmission torque Xs is preferably set within a range of 0.8 Ys <Xs <1.7 Ys, and the rated torque Ts of the motor 126 and the limit transmission torque Xs are set to satisfy T <Xs. Is set to This numerical value is based on the knowledge obtained as a result of the inventors creating a large number of prototypes and actually conducting application tests in many scenes.
[0039]
As a specific structure, the simple planetary roller mechanism 128 is accommodated in a casing 138 having a two-part structure, and a ring roller 136 is sandwiched between the casings 138 having the two-part structure. The three parties are connected together. That is, the ring roller 136 also constitutes a part of the casing 138. Further, an output shaft 133 projects from the axial center position of the carrier 132 so that it can be connected to a counterpart machine (driven machine) via a coupling or the like.
[0040]
A motor casing 126A of the motor 126 is integrally connected to the casing 138 on the sun roller 130 side. One end of a motor shaft 148 that rotates integrally with the rotor of the motor 126 is connected to the sun roller 130 by a key structure, and a braking mechanism 122 is connected to the other end side.
[0041]
The braking mechanism 122 includes a ring-shaped exciting coil 144 provided integrally with the motor casing 126A, and a ring that is slidable in the axial direction in a state where the braking mechanism 122 cannot rotate in the circumferential direction with respect to the motor casing 126A. And a brake wheel 150 connected to the motor shaft 148 and rotating integrally with the sun roller 130, and a coil spring 152 that constantly biases the brake piece 146 toward the brake wheel 150.
[0042]
When the exciting coil 144 is in the excited state, the brake piece 146 is attracted to the exciting coil 144, and the brake piece 146 is separated from the brake wheel 150 against the urging force of the coil spring 152 to be in a non-braking state. When the exciting coil 144 is in a non-excited state, the brake piece 146 is pressed against the brake wheel 150 by the coil spring 152 to enter a braking state.
[0043]
Next, “test torque Xd” and “limit transmission torque Xs” will be described.
[0044]
FIG. 2 schematically shows a state in which the test torque Xd is measured. A torque generator 62 (which can generate rotational power) is connected to the sun roller 130 via a torque measuring device 60. On the other hand, the carrier 132 is connected to the fixing member 64 and its rotation is completely restricted. The ring roller 136 is similarly fixed to the fixing member 64 via the casing 138.
[0045]
In this state, torque is gradually increased from the torque generator 62 and input to the sun roller 130. This gradually increasing input torque is the “test torque X” referred to in the present invention. In this case, the reaction torque Xo is generated on the simple planetary roller mechanism 128 side by the frictional force on the contact surface of each friction roller. Then, the detected torque Xr detected by the torque detector 60 also gradually increases following this (X = Xo = Xr). However, when the reaction force torque Xo generated by the friction force reaches the limit, sliding rotation occurs in any of the friction rollers, and even if the test torque X is further increased, the reaction force torque Xo rapidly decreases due to this slip. Therefore, the detected torque Xr detected by the torque detector 60 also decreases rapidly. From the above data obtained by the torque detector 60 (see FIG. 3), when the detected torque Xr rapidly decreases (corresponding to P in FIG. 3), the value of the test torque that has been applied until then is obtained. This corresponds to the “test torque value Xd” used for this setting. That is, this value is equal to the detected torque Xr immediately before it decreases.
[0046]
This test torque value Xd can be expressed as a limit torque that the simple planetary roller mechanism 128 can hold an external load converted to a torque value on the sun roller 130 side. When the external load connected to the carrier 132 side tries to rotate while the roller 130 is fixed, the limit capability that the simple planetary roller mechanism 128 can withstand (can hold) is quantified on the sun roller 130 side. It can be said that.
[0047]
Next, the limit transmission torque of the simple planetary roller mechanism 128 will be described with reference to FIG.
[0048]
In order to measure the limit transmission torque Xs, a load generator 80 (which can generate a rotational load) is connected to the sun roller 130 via a torque measuring device 60. On the other hand, a motor shaft 84A of a test motor 84 fixed to a fixing member (base material) 64 is connected to the carrier 132 via a coupling. The ring roller 136 is similarly fixed to the fixing member 64 via the casing 138.
[0049]
First, in a state where the rotational load of the load generator 80 is not generated, the carrier 132 is rotated by the test motor 84, and the motor to be connected in the future. 126 The sun roller 130 is rotated at the rated rotation speed (see FIG. 1).
[0050]
The driving torque of the test motor 84 is sufficiently larger than the torque that can be transmitted by the simple planetary roller mechanism 128 to be measured or the braking torque of the braking mechanism 122, and even if there is some load fluctuation on the sun roller side. , A predetermined rotational speed of the sun roller 130 126 The driving force is sufficient to continue the rotation at the rated rotation speed of In this state, when the rotational load (load torque Xn) of the sun roller 130 is gradually increased and inputted by the load generator 80, the test motor 84 continues to rotate at a constant speed regardless of the increase in the load. The reaction torque Xo corresponding to the load torque Xn applied from the load generator 80 side is returned to 130, and as a result, the detected torque Xr is detected by the torque detector 60 (Xn = Xo = Xr). The detected torque Xr increases with an increase in the load torque Xn. However, if the load torque Xn input by the load generator 80 is further increased, the reaction force torque Xo cannot follow the increase in the load torque Xn due to the slip between the friction rollers, and the slip increases, resulting in a product. The allowable slip rate (approximately 0.2%) is reached (see FIG. 5). As a result, the detected torque value Xr (corresponding to the point Q in FIG. 5) detected from the torque detector 60 when this limit is reached is the “limit transmission torque Xs” in the present invention.
[0051]
In this embodiment, the carrier 132 is an output element. However, when the ring roller is an output element, the load generator 80 may be connected to the ring roller and the measurement may be performed in the same manner.
[0052]
This limit transmission torque Xs is an allowable limit torque that can drive an external load of the counterpart machine when the simple planetary roller mechanism 128 is driven by a motor 102 that can be connected in the future and is rotating at a rated speed. It represents a value. In other words, from the standpoint of braking of the counterpart machine, in the state where the sun roller 130 is rotating at the rated speed, this simple planetary roller mechanism 128 permits the braking ability (torque) that can be transmitted to the counterpart machine. It can be said that it is a limit value.
[0053]
In the rotary drive device 101, the test torque value Xd, the limit transmission torque Xs, the static friction torque Yd, and the dynamic friction torque Ys of the braking mechanism measured as described above are set as described above. The simple planetary roller mechanism 128 has an optimal size (transmission capability) with respect to the mechanism 122, and sufficiently exhibits the basic function of “finally stopping the counterpart machine finally”.
[0054]
At the time of braking during rotation, there is a possibility that each friction roller of the simple planetary roller mechanism 128 may slip, but the braking torque (dynamic friction torque) of the braking mechanism 122 (the limit that the simple planetary mechanism 128 can transmit) to the counterpart machine side. (Within) can be reliably transmitted to reduce the rotational speed of the counterpart machine. If this state continues, the rotational speed of the counterpart machine will eventually decrease, and the limit transmission torque of the simple planetary roller mechanism 128 will increase accordingly (experiment and verification by the present inventor), so that the braking torque of the braking mechanism 122 Can be transmitted more reliably, and finally, the counterpart machine can always be stationary.
[0055]
Once the counterpart machine is stationary, the holding torque (test torque value Xd) of the simple planetary roller mechanism 128 exceeds the braking torque of the braking mechanism 122 (static friction torque Yd). The planetary roller mechanism 128 does not slide out first, and the counterpart machine can be sufficiently held.
[0056]
On the other hand, the rotational drive device 101 is more sensitive to the motor 126 as apparent from the relationship between the limit transmission torque Xs and the static friction torque Ys when considering the general balance of performance of the motor 126 and the braking mechanism 122. The simple planetary roller mechanism 128 has an optimal size (transmission capability), and the simple planetary roller mechanism 128 is not too large. Therefore, the rotational power of the motor 126 can be transmitted to the counterpart machine side with high efficiency.
[0057]
As a result, the contradictory requirements for the simple planetary roller mechanism 128 of braking characteristics and transmission efficiency are balanced in an optimal state, so that the rotary drive device 101 is excellent in cost performance as a whole.
[0058]
In the above example, the limit transmission torque Xs of the simple planetary roller mechanism and the rated torque T of the motor are set so that T <Xs, but more preferably, T <0.8Xs. The best is T≈0.6Xs.
[0059]
In the embodiment described above, the case where the braking mechanism is attached to the tail of the motor is shown. However, the present invention is not limited to this, and the braking mechanism is provided between the simple planetary roller mechanism and the motor. The structure of the braking mechanism is not limited to the above disk type. For example, a drum type in which a brake wheel is pressed in a radial direction by a brake piece may be used, and an on / off switching method may be a hydraulic type, a mechanical type, a pneumatic type, or the like.
[0060]
Further, in this embodiment, a rotary drive device in which a simple planetary roller mechanism, a motor, and a braking mechanism are combined is shown. It may be provided with a reduction gear.
[0061]
【The invention's effect】
According to the friction transmission type rotary drive device according to the present invention, the counterpart machine can be reliably braked, and in particular, the friction transmission type rotation excellent in both cost and transmission efficiency (energy saving). A drive device can be obtained.
[Brief description of the drawings]
FIG. 1 is a partial sectional view showing a friction transmission type rotary drive device according to an embodiment of the present invention;
FIG. 2 is a schematic diagram showing a state in which a test torque of a simple planetary roller mechanism is measured in the rotation drive device.
FIG. 3 is a schematic diagram showing detected torque data in the same measurement state.
FIG. 4 is a schematic diagram showing a state in which a limit transmission torque of a simple planetary roller mechanism is measured in the rotation driving device.
FIG. 5 is a schematic diagram showing detected torque data in the same measurement state.
FIG. 6 is a schematic view showing a conventional friction transmission type rotary drive device;
[Explanation of symbols]
101 ... Rotary drive device
122 ... Braking mechanism
128 ... Simple planetary roller mechanism
126 ... Motor
130 ... Sun Roller
132 ... Career
134 ... Planetary roller
136 ... Ring roller

Claims (2)

A simple planetary roller mechanism having a sun roller, a planet roller that is held by a carrier and that is in rolling contact with the outer periphery of the sun roller, and a ring roller that is in contact with the inner periphery of the planet roller, as the friction roller, and the sun roller A friction transmission type rotary drive device comprising: a motor coupled to the motor for driving the sun roller;
Attaching a braking mechanism to the motor,
The static friction torque Yd that can be taken out by the braking mechanism and the test torque are gradually increased and input to the sun roller while the carrier and the ring roller are fixed, and the sliding rotation is first applied to one of the friction rollers. The test torque value Xd at the time of occurrence is set such that Yd <Xd, and the dynamic friction torque Ys that can be extracted by the braking mechanism at the rated rotational speed of the motor, and the sun roller is at the rated rotational speed And a limit transmission torque Xs that the simple planetary roller mechanism can transmit with the sun roller when rotating at a speed of 0.65 Ys <Xs <3.4 Ys. In claim 1,
The friction transmission device characterized in that the limit transmission torque Xs of the simple planetary roller mechanism and the rated torque T of the motor are set such that T <Xs.

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