Transmission unit, actuator, and robot

Abstract

This technology provides a way to reduce the range of change in the actuator's natural frequency when adjusting the output compliance of the actuator. [Solution] An actuator comprising a prime mover 12, a transmission 14 that receives the rotation output from the prime mover 12, changes the speed of that rotation and outputs it to drive a driven device 18, and can change the gear ratio, which is the ratio of the output rotation speed to the input rotation speed, and an input-side elastic element 32 provided on a power transmission path 30 from the output shaft 20 of the prime mover 12 to the input shaft 22 of the transmission 14.

Description

Technical Field

[0001] The present disclosure relates to an actuator.

Background Art

[0002] Patent Document 1 discloses an actuator including a prime mover and a speed reducer that receives the rotation output from the prime mover, reduces the rotation, and drives a driven device by outputting the reduced rotation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An actuator may be provided with a compliance adjustment mechanism that can adjust the output-side compliance (described later) of the actuator. This compliance adjustment mechanism includes an output-side elastic element provided on the output side rather than a speed reducer with a constant gear ratio, and is configured to be able to change the compliance of the output-side elastic element.

[0005] The inventor of the present application has studied an actuator using the above-described compliance adjustment mechanism. As a result, it has been recognized that such an actuator has a problem that the change range of the natural frequency of the actuator becomes large when adjusting the output-side compliance of the actuator. When the change range of the natural frequency is large in this way, there is a problem that it is likely to overlap with the resonance point of the fixed device or the driven device that is the fixing partner of the actuator.

[0006] Therefore, one object of the present disclosure is to provide a technique capable of reducing the change range of the natural frequency of an actuator when adjusting the output-side compliance of the actuator. [Means for solving the problem]

[0007] One aspect of the present disclosure is a transmission unit which is capable of driving a driven device by receiving rotation output from a prime mover, changing the speed of that rotation and outputting it, and which has a changeable gear ratio, which is the ratio of the output rotation speed to the input rotation speed, and an input-side elastic element provided on the power transmission path from the output shaft of the prime mover to the input shaft of the transmission.

[0008] Another aspect of the present disclosure is an actuator comprising: a prime mover; a transmission that receives rotation output from the prime mover as input, changes the speed of the rotation and outputs it, thereby driving a driven device, and which can change the gear ratio, which is the ratio of the output rotation speed to the input rotation speed; and an input-side elastic element provided on a power transmission path from the output shaft of the prime mover to the input shaft of the transmission.

[0009] Another aspect of the present disclosure is a robot comprising at least one joint and an actuator of the aforementioned aspect incorporated into the joint. [Effects of the Invention]

[0010] According to this disclosure, the range of change in the actuator's natural frequency can be reduced when adjusting the output compliance of the actuator. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram showing the actuator of the first embodiment. [Figure 2] This is a schematic diagram showing the actuator of the second embodiment. [Figure 3] This is a model diagram showing a reference form of the actuator. [Figure 4] This is a model diagram showing the actuator of the first embodiment. [Figure 5] This graph shows the results of vibration analysis using a reference actuator configuration. [Figure 6] This graph shows the results of vibration analysis using the actuator of the first embodiment. [Figure 7] Figure 7(A) is a schematic side view showing the input-side elastic element of the first example, Figure 7(B) is a schematic front view thereof, and Figure 7(C) shows the operating state of the input-side elastic element in Figure 7(B). [Figure 8] This figure schematically shows the input-side elastic element in the second example. [Figure 9] Figure 9(A) is a schematic top view showing the input-side elastic element of the third example, and Figure 9(B) is a schematic side view thereof. [Figure 10] This is a schematic diagram showing the input-side elastic element in the fourth example. [Figure 11] Figure 11(A) is a schematic top view showing the input-side elastic element of the fifth example, and Figure 11(B) is a side cross-sectional view thereof. [Figure 12] This is a block diagram showing a part of the actuator configuration of the first embodiment. [Figure 13] This is a schematic diagram illustrating a robot that uses actuators. [Figure 14] This is a side cross-sectional view showing an example of a transmission. [Modes for carrying out the invention]

[0012] Embodiments for implementing the actuator of this disclosure are described below. The same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted. For the sake of clarity, components are omitted, enlarged, or reduced in each drawing. The drawings should be viewed in accordance with the orientation of the reference numerals.

[0013] Refer to Figure 1. The actuator 10 of the first embodiment will be described. The actuator 10 comprises a prime mover 12, a transmission 14, and a transmission actuator 16.

[0014] The actuator 10 is used to drive the driven device 18. The specific examples of the driven device 18 are not particularly limited and may include, for example, (1) robots such as industrial robots, service robots, and assist robots (assist suits, etc.), (2) industrial machinery such as machine tools and construction machinery, (3) conveying machinery such as conveyors and film transport devices, (4) vehicles such as automated guided vehicles, and (5) various machines such as welfare equipment.

[0015] The prime mover 12 is equipped with an output shaft 20 (hereinafter also referred to as the prime mover output shaft 20). The prime mover 12 rotates the prime mover output shaft 20 by torque generated internally, and can output rotation from the prime mover output shaft 20. The prime mover 12 in this embodiment is an electric motor that rotates the prime mover output shaft 20 using electrical energy. The specific example of the prime mover 12 is not particularly limited, and for example, it may be an engine that rotates the drive shaft using thermal energy.

[0016] The transmission 14 receives rotational speed output from the prime mover 12. The transmission 14 can drive the driven device 18 by changing the speed of this rotational speed before outputting it. The transmission 14 is fixed to a fixed device (not shown).

[0017] The transmission 14 comprises an input shaft 22 (hereinafter referred to as the transmission input shaft 22), a transmission mechanism 24, and an output shaft 26 (hereinafter referred to as the transmission output shaft 26). The rotation output from the prime mover 12 is input to the transmission input shaft 22. The transmission mechanism 24 changes the speed of the rotation input to the transmission input shaft 22. The transmission output shaft 26 drives the driven device 18 by outputting the rotation changed by the transmission mechanism 24.

[0018] The transmission 14 can change the gear ratio of the transmission mechanism 24 by means of a transmission actuator 16. Here, the gear ratio means the ratio of the output rotational speed to the input rotational speed (= output rotational speed / input rotational speed). The input rotational speed is the rotational speed of the transmission input shaft 22, and the output rotational speed is the rotational speed of the transmission output shaft 26. The transmission 14 of this embodiment is a continuously variable transmission that can change the gear ratio continuously. The transmission 14 can change the gear ratio within a predetermined gear ratio range. The transmission 14 of this embodiment is an infinitely variable transmission (IVT), and zero (= 1 / ∞) is included in the gear ratio range. The gear ratio range of this embodiment includes a reduction ratio. Here, the reduction ratio refers to a value where the gear ratio i satisfies -1 < i < 0 or 0 < i < 1. In addition to this, the gear ratio range may also include a speed increase ratio. Here, the speed increase ratio refers to a value where the gear ratio i satisfies i < -1 or 1 < i. The gear ratio range of this embodiment includes both a positive range and a negative range. An example of the transmission 14 will be described later.

[0019] The transmission actuator 16 can change the gear ratio of the transmission 14 by inputting power to the transmission 14. The transmission actuator 16 of this embodiment is a linear actuator, and inputs power along the axial direction of the transmission 14 to the transmission 14. The specific type of the transmission actuator 16 is not particularly limited as long as it can change the gear ratio of the transmission 14, and a rotary actuator or the like may also be used.

[0020] Here, the actuator 10 includes an input-side elastic element 32 provided on a first power transmission path 30 from the prime mover output shaft 20 to the transmission input shaft 22. The first power transmission path 30 includes a first input member 34 that inputs the rotation output from the prime mover output shaft 20 to the input-side elastic element 32, the input-side elastic element 32, and a first output member 36 that outputs rotation from the input-side elastic element 32. The first power transmission path 30 is part of the actuator 10. The first input member 34 may also be the prime mover output shaft 20, or it may be separate from the prime mover output shaft 20. The first output member 36 may also be the transmission input shaft 22, or it may be separate from the transmission input shaft 22. The first power transmission path 30 may also include other power transmission elements. The specific examples of these power transmission elements are not particularly limited and may include, for example, a rotating shaft, gears, belts, pulleys, chains, sprockets, universal joints, etc.

[0021] The input-side elastic element 32 receives rotation from the prime mover output shaft 20 via the first input member 34 from the input side of the first power transmission path 30. The input-side elastic element 32 undergoes its own elastic deformation and outputs the input rotation to the output side of the first power transmission path 30 via the first output member 36. As a result, the rotation output from the prime mover output shaft 20 is input to the transmission input shaft 22 via the input-side elastic element 32.

[0022] The input-side elastic element 32 is required to be easily elastically deformed when rotation is applied. From this viewpoint, the spring constant of the input-side elastic element 32 is preferably 100 N·m / ° or less. Power transmission elements that are generally assumed to be constructed as rigid bodies for power transmission are excluded from the concept of the input-side elastic element 32. These power transmission elements include, for example, gears, rotating shafts, pulleys, sprockets, etc., which are constructed entirely of the same material. Power transmission elements such as belts and chains that transmit power using tension are also excluded from the concept of the input-side elastic element 32. Furthermore, sealing members such as oil seals are also excluded from the concept of the input-side elastic element 32. The input-side elastic element 32 has a larger angular change due to elastic deformation in the rotational direction caused by the applied torque than the first input member 34 and the first output member 36, respectively. This angular change refers to the angular change of each individual element when the same magnitude of torque is applied to only the individual elements of the input-side elastic element 32, the first input member 34, and the first output member 36.

[0023] The input-side elastic element 32 is constructed using at least one of a spring material or an elastomer material. Here, the spring material refers to, for example, a leaf spring, a coil spring, a conical spring, a torsion bar, etc. The elastomer material may be made of either a thermosetting elastomer or a thermoplastic elastomer. An example of the input-side elastic element 32 will be described later.

[0024] Refer to Figure 2. The actuator 10 of the second embodiment will be described. The actuator 10 of the second embodiment differs from the actuator 10 of the first embodiment in that it includes the following output-side elastic element 40.

[0025] The output-side elastic element 40 is provided on the second power transmission path 42 from the transmission output shaft 26 to the driven device 18. The second power transmission path 42 includes a second input member 44 that inputs the rotation output from the transmission output shaft 26 to the output-side elastic element 40, the output-side elastic element 40, and a second output member 46 that outputs rotation from the output-side elastic element 40. In the second power transmission path 42, elements other than the driven device 18 become part of the actuator 10. The second input member 44 may also be the transmission output shaft 26, or it may be separate from the transmission output shaft 26. The second output member 46 may also be the driven device 18, or it may be separate from the driven device 18. The second power transmission path 42 may also include other power transmission elements. The specific examples of these power transmission elements are not particularly limited, and for example, the various power transmission elements mentioned in the description of the first power transmission path 30 may be applied.

[0026] The output-side elastic element 40 receives the rotation output from the transmission output shaft 26 via the second input member 44 from the input side of the second power transmission path 42. The output-side elastic element 40, accompanied by its own elastic deformation, outputs the input rotation to the output side of the second power transmission path 42 via the second output member 46. As a result, the rotation output from the transmission output shaft 26 is input to the driven device 18 via the output-side elastic element 40.

[0027] The details described regarding the input-side elastic element 32 (spring constant, specific examples, etc.) may also be applied to the output-side elastic element 40. For example, power transmission elements such as gears, which are entirely made of the same material, are excluded from the concept of the output-side elastic element 40, and the output-side elastic element 40 may be made of either spring material or elastomer material.

[0028] Refer to Figures 1 and 2. In both the first and second embodiments of the actuator 10 described above, a compliance adjustment mechanism is configured by the input-side elastic element 32 and the transmission mechanism 24 of the transmission 14 to adjust the overall compliance of the actuator 10 (hereinafter also referred to as output-side compliance). Compliance here refers to mechanical compliance. This compliance is an indicator of how easily the object in question deforms in response to torque, and is the reciprocal of the spring constant.

[0029] Output-side compliance refers to the ease with which the entire power transmission element used in the actuator 10 deforms when torque is input to the actuator 10 from the output side while the prime mover output shaft 20 is fixed. Output-side compliance can be expressed as angle change / torque (rad / (N·m)), using the torque acting on the output end of the actuator 10 and the amount of angle change in the rotational direction of the output end when that torque is applied. Here, the output end refers to the point where rotation is directly output from the actuator 10 to the driven device 18. In the first embodiment, when rotation is directly output from the transmission output shaft 26 to the driven device 18, the output end refers to the transmission output shaft 26. In contrast, in the second embodiment, when there is another element in the second power transmission path 42 from the transmission output shaft 26 to the driven device 18, it refers to the element at the output end of the second power transmission path 42 (for example, the second output member 46).

[0030] The output compliance, although details will be described later, can be expressed by the following equation (H): C out is output compliance, i is gear ratio, C b The compliance of the input side elastic element 32, C l This is the compliance of the output-side elastic element 40. As shown in equation (H), the output-side compliance can be adjusted by changing the gear ratio of the transmission 14. In the actuator 10 of the first embodiment, there is no output-side elastic element 40, so its compliance C l Treat it as zero. C out =i2 ×C h +C l ... (H)

[0031] The greater the output compliance, the easier it is for the actuator 10 to absorb the torque input from the driven device 18, which is advantageous in terms of improving safety. In addition, increasing the output compliance is advantageous for the actuator 10 to perform tracking movements more effectively. Conversely, the smaller the output compliance, the more difficult it is for the driven device 18 to move relative to the actuator 10, which is advantageous in terms of accurately positioning the driven device 18 at the target location.

[0032] For example, consider the case where the driven device 18 becomes part of the robot, as will be described later. In this case, when positioning a part gripped by the robot's gripper with high precision, the output compliance may be reduced to make it difficult for the part to move together with the gripper. Conversely, when transporting the part, the output compliance may be increased to enhance safety. Another example is the case where a shaft material gripped by the robot's gripper is inserted into a hole. In this case, when performing a probing motion to locate the hole using the shaft material, the output compliance may be increased to facilitate the probing motion. Conversely, when pushing the shaft material into the hole by press-fitting or the like, the output compliance may be reduced to suppress rattling of the shaft material.

[0033] The effects of the actuator 10 described above will now be explained. Here, we will mainly explain the effects of the actuator 10 of the first embodiment.

[0034] Figure 3 shows a model of the actuator 10 in the reference configuration. The actuator 48 in the reference configuration includes a transmission 14 and an output-side elastic element 40 in order from the input side to the output side along the power transmission path from the prime mover 12 to the driven device 18.

[0035] Figure 4 shows a model of the actuator 10 of the first embodiment. The actuator 10 of the first embodiment includes an input-side elastic element 32 and a transmission 14 in order from the input side to the output side along the power transmission path from the prime mover 12 to the driven device 18.

[0036] In the reference embodiment, the actuator 10 has a constant gear ratio for the transmission 14. Furthermore, the actuator 10 in the reference embodiment is configured to allow for changes in the compliance of the output-side elastic element 40, thereby enabling adjustment of the output-side compliance. In other words, the compliance adjustment mechanism is configured using the output-side elastic element 40. In contrast, as described above, the actuator 10 of the first embodiment allows for adjustment of the output-side compliance by changing the gear ratio of the transmission 14, and the compliance adjustment mechanism is configured using the transmission 14 and the input-side elastic element 32.

[0037] (a) With the actuator 10 of this first embodiment, the range of change in the natural frequency of the actuator 10 is smaller when adjusting the output compliance compared to the actuator 10 of the reference embodiment. This is a new finding discovered by the inventors of the present invention as a result of theoretical and analytical studies described later. When the range of change in the natural frequency of the actuator 10 is small, it is less likely to overlap with the resonance points of the fixed device and the driven device 18. Consequently, it becomes easier to avoid situations in which the power transmission part of the actuator 10 vibrates due to resonance with the fixed device and the driven device, which is advantageous in improving the controllability of the actuator 10. In this specification, the natural frequency of the actuator 10 refers to the natural frequency of the entire power transmission part of the actuator 10.

[0038] (b) The amount of change in output compliance due to a change in the gear ratio, as in the actuator 10 of the first embodiment, is larger than the amount of change in output compliance due to a change in the compliance of the output elastic element 40, as in the actuator 48 of the reference embodiment. This is a new finding discovered by the inventors of the present invention as a result of theoretical studies described later. By using the actuator 10 of the first embodiment, the adjustment range of output compliance can be widened compared to the actuator 48 of the reference embodiment.

[0039] (c) In the actuator 48 of the reference embodiment, the output compliance does not depend on the gear ratio of the transmission 14, and the output compliance and gear ratio can be changed independently. For this reason, when the gear ratio becomes very large and the output rotational speed of the transmission 14 can become very high, the output compliance can be set to a low state. In this respect, as in the first embodiment, when the output compliance is adjusted by changing the gear ratio, the output compliance depends on the gear ratio, and the output compliance can be set to a higher state as the gear ratio increases. Therefore, when the gear ratio becomes very large and the output rotational speed of the transmission 14 can become very high, the output compliance can be set to a high state, which is advantageous in terms of improving safety.

[0040] (d) In some cases, the output compliance may be reduced by increasing the frictional force between multiple components. In this case, the smaller the output compliance, the greater the increase in frictional force between multiple components, which leads to an increase in the energy consumption of the actuator 10. In this respect, according to the first embodiment, when adjusting the output compliance, it is only necessary to change the gear ratio, and it is not necessary to change the frictional force between multiple components. Therefore, it is possible to avoid a situation in which the energy consumption of the actuator 10 increases when the output compliance is reduced, which is advantageous in reducing energy consumption.

[0041] (e) Consider the case where the compliance adjustment mechanism is constituted by the output-side elastic element 40 and the reduction ratio is included in the speed ratio range. In this case, the elastic element 40 constituting the compliance adjustment mechanism is provided on the second power transmission path 42 from the transmission output shaft 26 to the driven device 18, as referred to in the second embodiment. On this second power transmission path 42, the rotation of the large torque output from the transmission output shaft 26 is transmitted, rather than the rotation of the small torque output from the prime mover output shaft 20. Therefore, the load on the output-side elastic element 40 increases, and the output-side elastic element 40 is likely to be enlarged and heavier together with the peripheral structure. In this regard, consider the case where the compliance adjustment mechanism is constituted by the transmission 14 and the input-side elastic element 32 as in the first embodiment. In this case, it can be realized by providing the elastic element 32 constituting the compliance adjustment mechanism on the first power transmission path 30 where the rotation of the small torque is transmitted, rather than on the second power transmission path 42 where the rotation of the large torque is transmitted. Therefore, compared with the case where the compliance adjustment mechanism is constituted by the output-side elastic element 40, the load on the elastic element 32 can be reduced, which is advantageous for downsizing and weight reduction of the elastic element 32 together with the peripheral structure.

[0042] In relation to such an effect, the speed ratio range that the transmission 14 can obtain may include only the reduction ratio without including the increase ratio. That is, the speed ratio range may be defined only within the range of -1 < i < 0 or 0 < i < 1 using the speed ratio i of the transmission 14. Also, in relation to the same effect, the actuator 10 may not include the output-side elastic element 40.

[0043] (f) In the reference embodiment of the actuator 10, the output compliance is adjusted by adjusting the compliance of the output elastic element 40. In this case, the greater the output compliance by increasing the compliance of the output elastic element 40, the easier it becomes for the power transmission unit (for example, the prime mover output shaft 20) located on the input side of the transmission 14 to rotate, and the more easily that power transmission unit vibrates. In contrast, the actuator 10 of the first embodiment does not have an output elastic element 40, and the output compliance is adjusted by changing the gear ratio of the transmission 14. In this case, even if the output compliance is increased by increasing the gear ratio of the transmission 14, the ease with which the power transmission unit located on the input side of the transmission 14 rotates does not change, and vibration in that power transmission unit can be suppressed.

[0044] (g) The range of possible gear ratios for the transmission 14 includes zero. Therefore, the transmission 14 can switch between a first state where the gear ratio is zero and a second state where the gear ratio is greater than or less than zero. In the first state, the input-side elastic element 32 has no effect on the output-side compliance, and in the second state, it is possible to change the output-side compliance according to the spring constant of the input-side elastic element 32 (see also equation (H) above). In other words, with respect to the state of the actuator 10, it is possible to switch between a first state where the input-side elastic element 32 has no effect on the output-side compliance and a second state in which the output-side compliance can be changed according to the spring constant of the input-side elastic element 32. In particular, if the actuator 10 does not have an output-side elastic element 40, it is possible to achieve a flexible-rigidity switch between a first state with zero output-side compliance and high rigidity, and a second state with greater than zero output-side compliance and flexibility.

[0045] The effects described in (a) to (e) and (g) above can also be obtained by the actuator 10 of the second embodiment.

[0046] (h) The actuator 10 of the second embodiment includes an output-side elastic element 40 provided on the second power transmission path 42. By including the output-side elastic element 40, the output-side compliance of the actuator 10 can be further increased.

[0047] Next, one of the theoretical considerations that supports the findings described in (a) will be explained.

[0048] Refer to FIG. 3. Examine the natural frequency of the actuator 10 of the reference embodiment. Let the moment of inertia and the rotation angle of the prime mover 12 be I m , θ m , the gear ratio of the transmission 14 be i, the rotation angle of the transmission output shaft 26 be θ2, the spring constant of the output-side elastic element 40 be k, and the moment of inertia and the rotation angle of the driven device 18 be I l , θ l . Here, the moment of inertia or the rotation angle refers to the moment of inertia or the rotation angle of the rotating part of the object being referred to. θ m = θ2 / i.

[0049] When the rotating parts of the entire actuator 10 of the reference embodiment perform free vibration in the rotational direction, the following equations of motion (1) and (2) hold.

[0050]

Equation

[0051]

Equation

[0052] In this case, the natural frequency ω can be expressed by the following equation (3) by solving the equations of motion (1) and (2).

Equation

[0053] Refer to Figure 4. The natural frequency of the actuator 10 of the first embodiment is examined. Let the spring constant of the input-side elastic element 32 be k. Other symbols (I m θ m The definition of ...) is the same as in Figure 3. θ² = θ l / i

[0054] When the entire rotating part of the actuator 10 in the first embodiment vibrates freely in the rotational direction, the following equations of motion (4) and (5) hold true.

[0055]

number

[0056]

number

[0057] In this case, the natural frequency ω can be expressed by the following equation (6) by solving the equations of motion in equations (4) and (5).

number

[0058] Let's consider a case where the output compliance is adjusted by changing the compliance of the output elastic element 40, as in the reference actuator 10. In this case, the spring constant k of the output elastic element 40 is changed by changing the compliance of the output elastic element 40. In this case, as shown in equation (3), the natural frequency ω of the actuator 10 changes in proportion to the square root of the spring constant k.

[0059] In contrast, we consider the case where the output compliance is changed by changing the gear ratio i, as in the first embodiment. In this case, as shown in equation (6), the natural frequency ω of the actuator 10 is 1 / I m +1 / (i 2 ×I lIt changes in proportion to the square root of the value of (hereinafter referred to as the specific value). Here, the moment of inertia I of the prime mover 12 is usually m The moment of inertia I of the driven device 18 relative to l The ratio (I l / I m ) becomes very large, for example, more than 100. In this way I l / I m If the value is very large, the second term of the specific value (1 / (i 2 ×I l )) for the first term (1 / I m The ) becomes very large, and even if the gear ratio i changes, the effect on a specific value becomes very small. As a result, the range of change in natural frequency ω is smaller compared to the range of change in natural frequency ω when the compliance of the output-side elastic element 40 changes. In other words, as in this embodiment, when the output-side compliance is changed by changing the gear ratio i, the range of change in the actuator's natural frequency ω can be made smaller compared to when the output-side compliance is adjusted by changing the compliance of the output-side elastic element 40.

[0060] Next, we will explain one of the analytical studies that supports the findings described in (a). Figures 5 and 6 are graphs showing the results of vibration analysis to determine the natural frequencies of the models in Figures 3 and 4, respectively. In both cases, the moment of inertia I of the prime mover m Moment of inertia I of the driven device l The ratio (I l / I m The condition was set to 2000 times. In this vibration analysis, for each model in Figures 3 and 4, the natural frequencies of the actuator 10 were determined under four conditions in which the spring constant (N·m / rad), which is the reciprocal of the output compliance, was set to k0 (No. 1), 4k0 (No. 2), 9k0 (No. 3), and 16k0 (No. 4). In adjusting this spring constant, the compliance of the output elastic element 40 was changed in the reference model in Figure 3, and the gear ratio was changed in the embodiment model in Figure 4.

[0061] In the graphs of Figures 3 and 4, the peaks of each line indicate the natural frequencies. In the reference model, as shown in Figure 5, the range of natural frequencies varied within a range of approximately 2.5a (Hz). In contrast, in the embodiment model, as shown in Figure 6, the range of natural frequencies varied within a range of approximately 1a (Hz). This supports the idea that when the output compliance is changed by changing the gear ratio, as in the embodiment, the range of change in the natural frequency of the actuator 10 is smaller compared to when the output compliance is adjusted by changing the output elastic element 40, as in the reference model.

[0062] Next, I will explain one of the theoretical considerations that supports the findings described in (b).

[0063] Assume that there are both an input-side elastic element 32 and an output-side elastic element 40, as in the actuator 10 of the second embodiment. The compliance of the input-side elastic element 32 is set to C h The compliance of the output side elastic element 40 is C l Let's consider the case where a constant torque is input from the output terminal of actuator 10 to the entire power transmission element of actuator 10.

[0064] Change in rotation angle Δθ of the transmission output shaft 26 o This is the change in the rotation angle Δθ of the transmission input shaft 22. i When this is the case, it can be expressed by the following equation (A), where i is the gear ratio. Δθ o =i × Δθ i ... (A)

[0065] Torque T of transmission output shaft 26 o The torque of the transmission input shaft 22 is T i When this is the case, it can be expressed by the following equation (B). T o = (1 / i) × T i ...(B)

[0066] The twist angle of the input elastic element 32 is Δθ h The torque acting on the input elastic element 32 is the torque T of the transmission input shaft 22.i It is the same as this. Therefore, the compliance C of the input elastic element 32 h C h =Δθ h / T i It can be expressed as follows. Furthermore, assuming that all elements except the input-side elastic element 32 are rigid on the first power transmission path 30, the twist angle Δθ of the input-side elastic element 32 h This is the change in the rotation angle of the transmission input shaft 22, Δθ. i This is equivalent to the following. From these, the following equation (C) holds true. T i =(1 / C h ) × Δθ i ... (C)

[0067] Using equations (A) to (C), we can derive equation (D). T o =(1 / i 2 ) × (1 / C) h ) × Δθ o ... (D)

[0068] The twist angle of the output elastic element 40 is Δθ l The torque acting on the output elastic element 40 is the torque T of the transmission output shaft 26. o It is the same as this. Therefore, the compliance C of the output side elastic element 40 l C l =Δθ l / T o It can be expressed as follows. From this, we can derive the following equation (E). T o =(1 / C l ) × Δθ l ... (E)

[0069] Since the output elastic elements 40 are connected in series, the change in the rotation angle Δθ of the entire actuator 10 is due to this connection. out This can be expressed by the following equation (F). Δθ out =Δθ o +Δθ l ... (F)

[0070] From equations (D), (E), and (F), we can derive equation (G). Δθ out =i 2 ×C h ×T o +C l ×T o ... (G)

[0071] Overall output side compliance C of actuator 10 out is, Δθ out / T o It can be expressed as follows. From this and equation (G), we can derive the following equation (H). C out =i 2 ×C h +C l ... (H)

[0072] Actuator output side compliance C out As shown in equation (H), the ratio is the square of the gear ratio i and the compliance C of the output side elastic element. l It is proportional to the first power of . If the output compliance is adjusted by changing the compliance of the output elastic element 40, the output compliance is proportional to the compliance C of the output elastic element. l This results in a change proportional to the first power of the value, which narrows the adjustment range. In contrast, as in the first and second embodiments, the output compliance C can be changed by changing the gear ratio i. out When adjusting the output side compliance C out This can be changed in proportion to the square of the gear ratio i, and the adjustment range can be widened. This is because, as in the first and second embodiments, when adjusting the output side compliance by changing the gear ratio i, the compliance C of the output side elastic element 40 can be changed as in the reference embodiment. l This modification provides evidence that the adjustment range can be wider compared to adjusting the output compliance.

[0073] Next, a specific example of the input-side elastic element 32 will be described. Figures 7(A) to 7(C) show a first example in which the input-side elastic element 32 is composed of a leaf spring 50. The leaf spring 50 is plate-shaped and extends in the longitudinal direction X. A first input member 34 is connected to one end of the leaf spring 50 in the longitudinal direction X, and a first output member 36 is connected to the other end.

[0074] The first input member 34 includes a first shaft portion 34a that is rotatable around the rotation axis L1 by rotation input from the input side of the first power transmission path 30, and a first connecting portion 34b to which one end of the leaf spring 50 is connected at a position radially offset with respect to the rotation axis L1 of the first shaft portion 34a. The first output member 36 includes a second shaft portion 36a provided on the same axis as the first shaft portion 34a and rotatable around the rotation axis L1, and a second connecting portion 36b to which the other end of the leaf spring 50 is connected at a position radially offset with respect to the rotation axis L1.

[0075] The leaf spring 50 is provided with a width direction Y that intersects the length direction X of the leaf spring 50 and is parallel to the rotation axis L1. Rotation around the rotation axis L1 is input to the leaf spring 50 from the first input member 34. When rotation is input to the leaf spring 50 from the first input member 34, it undergoes elastic deformation that bends in the thickness direction Z and can output rotation around the rotation axis L1 to the first output member 36.

[0076] Figure 8 shows a second example in which the input elastic element 32 is composed of a mainspring 52. The mainspring 52 is made of a spirally wound plate, wire, or the like. A first input member 34 is connected to one end of the mainspring 52, and a first output member 36 is connected to the other end. The first input member 34 inputs rotation to the mainspring 52 about a rotation axis L1 along the centerline of the spiral shape formed by the mainspring 52. When rotation is input to the mainspring 52 from the first input member 34, it undergoes elastic deformation that bends radially and can output rotation to the first output member 36.

[0077] Figures 9(A) and 9(B) show a third example in which the input-side elastic element 32 is composed of a coil spring 54. Figure 9(B) is also a view of a part of the input-side elastic element 32, etc., from the direction of arrow V in Figure 9(A). The coil spring 54 is composed of a wire or the like that is wound in a spiral shape. The coil spring 54 is placed between a disc-shaped first input member 34 and a first output member 36. The first input member 34 is connected to one end of the coil spring 54. For example, rotation is input to the first input member 34 in one direction around the rotation axis L1 (hereinafter referred to as the positive rotation direction D1). The coil spring 54 is positioned such that its center line L3 is located at a position radially offset with respect to the rotation axis L1. A roller member 56 is connected to the other end of the coil spring 54. The first output member 36 is provided with an inclined surface 36c on which the roller member 56 can roll. The inclined surface 36c is inclined with respect to a plane perpendicular to the rotation axis L1 such that it approaches the first input member 34 as it moves toward the positive rotation direction D1.

[0078] When rotation in the forward rotation direction D1 is input to the coil spring 54 from the first input member 34, the roller member 56 rolls on the inclined surface 36c of the first output member 36 in the forward rotation direction D1, causing the coil spring 54 to elastically deform and compress in the axial direction. A component force F2 of the axial restoring force F1 caused by the elastic deformation of the coil spring 54, which is perpendicular to the inclined surface 36c, acts on the first output member 36, and this component force F2 causes rotation to be output from the coil spring 54 to the first output member 36. In other words, when rotation is input to the coil spring 54 from the first input member 34, the coil spring 54 undergoes elastic deformation in the axial direction and can output rotation to the first output member 36.

[0079] Here, an example is described in which an inclined surface 36c is provided on the first output member 36 to compress and deform the coil spring 54 in the axial direction when the first input member 34 rotates in the forward rotation direction D1. In addition, other inclined surfaces may be provided on the first output member 36 to compress the coil spring 54 in the axial direction when the first input member 34 rotates in the reverse rotation direction D2, which is opposite to the forward rotation direction D1. These other inclined surfaces only need to be inclined with respect to a plane perpendicular to the rotation axis L1 so that they approach the first input member 34 as they move toward the reverse rotation direction D2.

[0080] Figure 10 shows a fourth example in which the input elastic element 32 is composed of a coil spring 54. The coil spring 54 is made of a wire or the like that is wound in a spiral shape. A first input member 34 is connected to one end of the coil spring 54, and a first output member 36 is connected to the other end. The coil spring 54 receives rotation around a rotation axis L1 along the center line of the spiral shape formed by the coil spring 54 from the first input member 34. When rotation is input from the first input member 34, the coil spring 54 undergoes elastic deformation that bends radially, and can output rotation to the first output member 36.

[0081] Figure 11 shows a fifth example in which the input-side elastic element 32 is made of an elastomer material 58. In this embodiment, the elastomer material 58 is planar, but its specific shape is not particularly limited. The elastomer material 58 is placed between the first input member 34 and the first output member 36. The elastomer material 58 is attached to the first input member 34 and the first output member 36 by adhesive or the like. Rotation around the rotation axis L1 is input to the elastomer material 58 from the first input member 34. When rotation is input to the elastomer material 58 from the first input member 34, it undergoes a twisting elastic deformation and can output rotation to the first output member 36.

[0082] In either example, the first input member 34 and the first output member 36 may be rotatable around a common axis of rotation L1. Furthermore, the details regarding the input-side elastic element 32 described so far may also be applied to the output-side elastic element 40. When applying these details, the terms "input-side elastic element 32," "first input member 34," and "first output member 36" may be replaced with "output-side elastic element 40," "second input member 44," and "second output member 46" in the descriptions provided so far.

[0083] Refer to Figure 12. Each block consists of a combination of hardware and software elements, or either hardware and software elements. Each block may be implemented in various ways through the coordination of these elements. Each block may be implemented by common or separate hardware or software elements. The actuator 10 includes a rotation detector 60 and a control device 62.

[0084] The rotation detector 60 detects the rotation of the transmission output shaft 26. The rotation detector 60 is composed of an encoder, resolver, etc. When detecting the rotation of the transmission output shaft 26, the rotation detector 60 may directly detect its rotation, or it may indirectly detect it by detecting the rotation of another component that rotates at the same rotational speed as the transmission output shaft 26.

[0085] The hardware elements of the control device 62 include, for example, a processor, ROM (Read Only Memory), and RAM (Random Access Memory). The software elements of the control device 62 include, for example, an operating system and application programs. The control device 62 comprises a gear shift actuator control unit 64 that controls the operation of the gear shift actuator 16, a prime mover control unit 66 that controls the operation of the prime mover 12, and a storage unit 68 that stores data used by the control device 62.

[0086] The gear shift actuator control unit 64 can change the gear ratio of the transmission 14 by controlling the operation of the gear shift actuator 16. The gear shift actuator control unit 64 can change the gear ratio of the transmission 14 to a command value by controlling the gear shift actuator 16. Various methods, including known methods, may be employed to achieve this. The command value of the gear ratio is commanded by operation on the user's control unit or by an external controller. The external controller refers to, for example, a higher-level controller that comprehensively controls the operation of multiple actuators 10. The control unit consists of, for example, switches provided on a control panel, as well as information processing terminals such as touch panels.

[0087] The prime mover control unit 66 can control the rotational speed of the prime mover output shaft 20 (hereinafter referred to as prime mover rotational speed). Various methods, including known methods, may be employed to achieve this. The prime mover control unit 66 controls the prime mover rotational speed so that the output rotational speed of the transmission 14 approaches a target value. This target value of the output rotational speed is commanded, for example, by operation on the user's control unit or by an external controller. To achieve this, the prime mover control unit 66 may use the detected value of the output rotational speed of the transmission output shaft 26 as follows. Specifically, the rotation detector 60 may detect the output rotational speed of the transmission output shaft 26, and the prime mover control unit 66 may perform feedback control to control the prime mover rotational speed so that the detected value of the output rotational speed obtained thereby approaches the target value.

[0088] In addition, the engine control unit 66 may control the engine speed according to the command value of the gear ratio, as follows. Specifically, there is a relationship between the engine speed, the gear ratio of the transmission 14, and the output speed of the transmission 14. This relationship can be expressed, for example, by the equation: engine speed × gear ratio = output speed. The memory unit 68 stores relationship information such as relationship equations and tables that show this relationship. Based on the relationship information stored in the memory unit 68, the command value of the gear ratio, and the target value of the output speed, the engine control unit 66 may derive an engine speed corresponding to the command value of the gear ratio that can achieve the target value, and control the engine speed to achieve that derived value.

[0089] Let's consider the case where the gear ratio of the transmission 14 is changed by the transmission actuator control unit 64 in order to adjust the output compliance of the actuator 10. In this case, the output rotational speed of the transmission 14 may fluctuate as a result of the change in the gear ratio of the transmission 14. Even in this case, the effect of the fluctuation can be suppressed by controlling the engine speed with the engine control unit 66 of the control device 62 so that the output rotational speed of the transmission 14 approaches the target output rotational speed.

[0090] Refer to Figure 13. An example of the use of actuator 10 will be described. Here, an example of actuator 10 being used in robot 70 is shown. The robot 70 in this embodiment is a collaborative robot for working in cooperation with humans, but its specific example is not particularly limited and may be various types of robots.

[0091] The robot 70 comprises at least one joint 72 and a plurality of link members 74 connected by the joint 72. The robot 70 in this example is a multi-joint robot with three joints and is constructed using a serial link mechanism. Alternatively, the multi-joint robot may be constructed using a parallel link mechanism. The number of joints is not particularly limited and may be one to two or four or more.

[0092] In this example, the multiple link members 74 form elongated arm members. The link member 74 at the base end also serves as a base placed on the floor, but it may be provided separately from the base and fixed to the base. An attachment 76, such as a gripper, is detachably mounted on the link member 74 at the tip end.

[0093] An actuator 10 is incorporated into the joint 72. The actuator 10 is capable of connecting adjacent link members 74 and rotating them relative to each other. At least one of the multiple joints 72 incorporates an actuator 10 equipped with the aforementioned input-side elastic element 32. To satisfy this condition, the actuator 10 equipped with the input-side elastic element 32 may be incorporated into all of the joints 72, or into only two or more joints 72. In the other joints 72 in which an actuator 10 equipped with the input-side elastic element 32 is not incorporated, an actuator 10 without the input-side elastic element 32 may be incorporated.

[0094] In this example, the driven devices driven by the actuator 10 are the components (link members 74, joints 72, etc.) located on the tip side of the robot 70 beyond the joints 72 of the actuator 10. Furthermore, the fixed devices to which the actuator 10 is attached are the components (link members 74, joints 72, etc.) located on the base end side of the robot 70 beyond the joints 72 of the actuator 10.

[0095] The effects of the robot 70 described above are explained below. As explained in (b), the actuator 10 has a wide range of adjustment for output compliance. By incorporating such actuators 10 with a wide range of adjustment for output compliance into multiple joints of the robot 70, the range of adjustment for output compliance around multiple directional axes can be expanded. Consequently, it becomes easier to absorb impact loads when impact loads are applied to the end of the robot, which is advantageous in terms of improving safety. It is also advantageous when the robot performs tracking movements. Furthermore, it is advantageous when multiple robots perform coordinated movements.

[0096] As described in (e), the actuator 10 is advantageous in miniaturizing and lightening the input elastic element 32 together with the surrounding structure. When such an actuator 10 is incorporated into the robot 70, it is advantageous in increasing the payload capacity and working range of the robot 70.

[0097] Refer to Figure 14. An example of the transmission 14 will be described. In addition to the transmission input shaft 22, transmission mechanism 24, and transmission output shaft 26 mentioned above, the transmission 14 includes a transmission ratio changing mechanism 100 that can change the transmission ratio of the transmission mechanism 24 using power output from the transmission actuator 16.

[0098] The transmission input shaft 22 comprises an input-side member 22a to which rotation is input, a shaft 22b connected to the input-side member 22a, and a sleeve 22c fixed to the shaft 22b. The transmission input shaft 22 only needs to be able to transmit the input rotation to the transmission mechanism 24, and its specific structure is not particularly limited. The transmission input shaft 22 shown here is an example composed of multiple members, but it may also be composed of a single member, and the number of members is not particularly limited.

[0099] The transmission mechanism 24 includes an input raceway 102 that is rotatably mounted integrally with the transmission input shaft 22, a first support raceway 104 that is rotatably supported on the transmission input shaft 22, a second support raceway 108 that is axially movable within the casing 106 of the transmission 14, an output raceway 110 that is rotatably mounted integrally with the transmission output shaft 26, and a plurality of planetary rolling elements 112 that roll on each of the raceway 102, 104, 108, and 110. The plurality of planetary rolling elements 112 are pressed toward the output raceway 110 by a pressing force applied from the second support raceway 108 by a pressing force applying mechanism (not shown).

[0100] As the input raceway 102 rotates, the planetary rolling elements 112 rotate on their own axis L112 while revolving around the rotation axis L22 (orbital axis) of the transmission input shaft 22. As the planetary rolling elements 112 revolve, the output raceway 110 follows suit and rotates around the rotation axis L22. Ideally, the output raceway 110 rotates at an output speed obtained by multiplying the input rotation speed of the transmission input shaft 22 by the gear ratio. This gear ratio is determined according to the inclination angle of the rotation axis L112 with respect to the rotation axis L22 and is changed by the gear ratio changing mechanism 100.

[0101] The transmission output shaft 26 comprises an output raceway 110 and an output-side member 26a that is integrally connected to the output raceway 110 and outputs rotation. The transmission output shaft 26 only needs to be able to output the rotation that has been shifted by the transmission mechanism 24, and its specific structure is not particularly limited.

[0102] The gear ratio changing mechanism 100 in this embodiment can change the gear ratio by changing the position of the input raceway wheel 102. The gear ratio changing mechanism 100 includes a shaft 100a that is movable in the axial direction by power output from the gear actuator 16, and a ring member 100b that is movable in the axial direction integrally with the shaft 100a. The ring member 100b rotatably supports the transmission input shaft 22 via a bearing 100c and is movable in the axial direction integrally with the transmission input shaft 22 by a retaining ring or the like. The specific example of the gear ratio changing mechanism 100 is not particularly limited, and various similar mechanisms used in the transmission 14 may be adopted.

[0103] When axial power is input to the shaft 100a from the speed actuator 16, the transmission input shaft 22 (including the input raceway 102 and the first support raceway 104) moves axially as a whole together with the ring member 100b. As the input raceway 102 and the first support raceway 104 move axially relative to the second support raceway 108 and the output raceway 110, the inclination angle of the rotation axis L112 of the planetary rolling element 112 with respect to the rotation axis L22 is changed, and the gear ratio is changed according to that inclination angle. This gear ratio becomes zero (=1 / ∞) when the rotation axis L112 is parallel to the rotation axis L22, and increases continuously as the inclination angle of the rotation axis L112 with respect to the rotation axis L22 increases. In other words, the gear ratio can be changed steplessly (continuously), and the range of possible gear ratios includes zero. At this time, the sign of the gear ratio changes according to the inclination direction of the rotation axis L112.

[0104] The transmission 14 described here is merely an example, and its specific implementation is not particularly limited. The transmission 14 may be a continuously variable transmission such as a toroidal continuously variable transmission, a belt-type continuously variable transmission, or a chain-type continuously variable transmission. Furthermore, instead of a continuously variable transmission that can continuously change the gear ratio, the transmission 14 may be a transmission that can change the gear ratio in steps. Also, the range of gear ratios that the transmission 14 can take may not include reduction ratios, but only increase ratios. Moreover, the range of gear ratios may not include zero.

[0105] Refer to Figure 1. The actuator 10 described so far can also be considered as a transmission unit 120 comprising a transmission 14 and an input-side elastic element 32. The transmission unit 120 only needs to include at least the components on the first power transmission path 30 that are on the output side from the input-side elastic element 32. Here, we show an example in which the prime mover output shaft 20 and the first input member 34 are separate, and the first input member 34 is also part of the transmission unit 120.

[0106] Refer to Figure 2. The transmission unit 120 may also include an output-side elastic element 40, similar to the actuator 10. The transmission unit 120 only needs to include components on the second power transmission path 42 that are on the input side from the output-side elastic element 40. Here, we show an example where the driven device 18 and the second output member 46 are separate, and the second output member 46 is also part of the transmission unit 120.

[0107] The effects (a) to (h) listed above can also be seen as effects of the transmission unit 120 obtained by using the transmission unit 120 as part of the actuator 10.

[0108] The contents of each component described in the embodiments above are illustrative. The abstract technical ideas derived from these should not be interpreted restrictively to the contents of this specification. Many design changes, such as modifications, additions, and deletions, are possible for the contents of each component described in the embodiments. Any combination of the above components is also valid. Components composed of a single member in the description herein may be composed of multiple members. Similarly, components composed of multiple members may be composed of a single member. Furthermore, any substitution of any of the components and expressions of this disclosure between methods, apparatus, systems, etc., is also valid as an embodiment of this disclosure. [Explanation of symbols]

[0109] 10...Actuator, 12...Prime mover, 14...Transmission, 16...Transmission actuator, 18...Driven device, 20...Output shaft (prime mover output shaft), 22...Input shaft (transmission input shaft), 26...Output shaft (transmission output shaft), 32...Input side elastic element, 32...Elastic element, 40...Output side elastic element, 40...Elastic element, 48...Actuator, 64...Transmission actuator control unit, 66...Prime mover control unit, 70...Robot, 72...Joint, 120...Transmission unit.

Claims

1. A transmission that receives rotational speed output from a prime mover, changes the speed of that rotation, and outputs it to drive a driven device, and whose gear ratio, which is the ratio of the output rotational speed to the input rotational speed, A transmission unit comprising an input-side elastic element provided on the power transmission path from the output shaft of the prime mover to the input shaft of the transmission.

2. The aforementioned transmission is capable of changing the gear ratio within the gear ratio range. The transmission unit according to claim 1, wherein the gear ratio range includes a reduction ratio.

3. The aforementioned transmission is capable of changing the gear ratio within the gear ratio range. The transmission unit according to claim 1, wherein the gear ratio range includes zero.

4. The transmission unit according to claim 1, further comprising an output-side elastic element provided on the power transmission path from the output shaft of the transmission to the driven device.

5. The prime mover and A transmission that receives the rotation output from the prime mover as input, changes the speed of that rotation, and outputs it to drive a driven device, and whose gear ratio, which is the ratio of the output rotation speed to the input rotation speed, is changeable. An actuator comprising an input-side elastic element provided on the power transmission path from the output shaft of the prime mover to the input shaft of the transmission.

6. A transmission actuator capable of changing the gear ratio of the transmission, A transmission actuator control unit that can change the gear ratio of the transmission by controlling the operation of the transmission actuator, The actuator according to claim 5, further comprising a prime mover control unit capable of controlling the rotational speed of the output shaft so that the output rotational speed of the transmission approaches a target value.

7. At least one joint, A robot comprising the actuator according to claim 5, which is incorporated into the joint portion.

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