Gear device

Abstract

The invention provides a gear device. A reduction gear (1) according to an embodiment is provided with: a housing (2); a speed reduction mechanism (4) which is housed inside the housing (2) together with a lubricant, and which has a plurality of gears that rotate by receiving power from the outside of the housing (2); a measurement chamber (40) that communicates with the inside and outside of the housing (2) and is blocked from outside air outside the housing (2); a pressure sensor (32) that detects the pressure inside the measurement chamber (40); and a control unit (34) that monitors the state of the lubricant inside the housing (2) on the basis of the detection result of the pressure sensor (32).

Description

Technical Field

[0001] The present invention relates to gear arrangements. Background Art

[0002] As a gear device, for example, a reducer is known that reduces the rotation of an electric motor and outputs the reduced speed. This reducer includes: a casing; and a transmission mechanism, which is housed in the casing and has a plurality of gears that receive the rotation of the electric motor and rotate. The plurality of gears also include, for example, an input shaft that transmits the rotation of the electric motor, an output shaft that reduces the rotation of the input shaft and outputs the reduced speed, and the like.

[0003] The housing is filled with lubricant to reduce the friction resistance of the transmission mechanism and suppress the temperature rise of the transmission mechanism. Therefore, for example, various sealing mechanisms have been proposed to prevent the lubricant from leaking from between the housing and the output shaft.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2008-286357 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] However, it is difficult to completely prevent the lubricant from leaking from the inside of the housing. Therefore, it is important to detect the leakage of the lubricant. For example, a method of using a tray or the like to receive the leaked lubricant and detecting the lubricant accumulated in the tray or the like is conceivable. However, in this case, it is difficult to quickly detect the leakage of the lubricant, and it is difficult to detect the leakage of the lubricant with high accuracy. In addition, it is also necessary to ensure a place for detecting the leakage of the lubricant.

[0009] In particular, when the state of the lubricant inside the housing is not appropriate, there is a possibility that the friction resistance of the transmission mechanism cannot be effectively reduced and the temperature increase of the transmission mechanism cannot be suppressed.

[0010] The present invention provides a gear device capable of monitoring the state of a lubricant quickly and accurately, appropriately maintaining the state of the lubricant, and suppressing an increase in the size of the device.

[0011] Solutions for solving problems

[0012] A gear device according to one aspect of the present invention comprises: a housing; a transmission mechanism housed inside the housing together with a lubricant, and having a plurality of gears that rotate by receiving power from outside the housing; a measuring chamber that is connected to the inside and outside of the housing and is blocked from external air outside the housing; a pressure sensor that detects the pressure inside the measuring chamber; and a control unit that monitors the state of the lubricant inside the housing based on the detection result of the pressure sensor.

[0013] For example, if the lubricant contained in the housing leaks, the pressure inside the housing changes in accordance with the amount of leakage. The measuring chamber is connected to the inside and outside of the housing, and is blocked from the outside air outside the housing. Therefore, by detecting the pressure in the measuring chamber, the control unit can determine whether the lubricant contained in the housing has leaked. In this way, the state of the lubricant inside the housing can be monitored quickly and with high precision. The state of the filling amount of the lubricant, etc. can be appropriately maintained based on the monitoring results. There is no need for a large-scale measuring device outside the gear device, so the size of the gear device can be suppressed.

[0014] In the above configuration, the gear device may include a housing that is provided independently of the casing and forms the measurement chamber that communicates with the interior of the casing.

[0015] In the above structure, the measurement chamber may be formed by using a part of the housing and the outer shell.

[0016] In the above structure, the gear device may include a temperature sensor, which is disposed in the measurement chamber and detects the temperature of a portion exposed to the measurement chamber. The control unit may determine the leakage of the lubricant from the inside of the housing based on the detection result of the temperature sensor and the detection result of the pressure sensor.

[0017] In the above structure, the control unit may include a table that associates the temperature rise value of the temperature of the portion exposed to the measurement chamber relative to the reference temperature with the pressure inside the measurement chamber. The control unit may compare the detection result of the temperature sensor and the detection result of the pressure sensor with the table, estimate the ratio of the lubricant to the total volume obtained by adding the volume of the inside of the housing and the volume of the measurement chamber, and judge whether the filling amount of the lubricant is appropriate based on the estimated result.

[0018] Effects of the Invention

[0019] According to the gear device of the present invention, the state of the lubricant inside the housing can be monitored quickly and with high accuracy. The state of the filling amount of the lubricant can be appropriately maintained based on the monitoring result. No large-scale measuring device is required outside the gear device, so the size of the gear device can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a cross-sectional view of a reduction gear transmission in an embodiment of the present invention.

[0021] Figure 2 It is a diagram showing a table of a control unit in the embodiment of the present invention.

[0022] Figure 3 This is an enlarged cross-sectional view of a part of a reduction gear transmission in a modified example of the embodiment of the present invention.

[0023] Description of Reference Numerals

[0024] 1. Speed ​​reduction device (gear device); 2. Housing; 4. Speed ​​reduction mechanism (transmission mechanism); 30. Measuring device; 31. Housing; 32. Pressure sensor; 33. Temperature sensor; 34. Control unit; 39. Table; 40. Measuring chamber; 41. Through hole. DETAILED DESCRIPTION

[0025] Next, embodiments of the present invention will be described based on the drawings.

[0026] <Reduction gear>

[0027] Figure 1 It is a cross-sectional view of the reduction gear 1 as a gear device.

[0028] like Figure 1 As shown, the reduction gear device 1 reduces the speed of rotation of an input shaft 101 provided integrally with an electric motor 100 and outputs the rotation. The reduction gear device 1 is a so-called eccentric oscillating type reduction gear device.

[0029] The reduction gear 1 includes: a cylindrical housing 2; a gear frame 3 rotatably provided radially inward of the housing 2; a reduction mechanism (an example of a transmission mechanism in the claims) 4 connected to the gear frame 3; and a measuring device 30 mounted on the housing 2. The central axis of the housing 2, the rotation axis of the gear frame 3, and the rotation axis of the input shaft 101 of the electric motor 100 are consistent.

[0030] In the following description, the center axis of the housing 2, the rotation axis of the gear frame 3, and the rotation axis of the input shaft 101 are defined as the first rotation axis A1 as a common name. The direction parallel to the first rotation axis A1 is defined as the axial direction. The rotation direction of the gear frame 3 is defined as the circumferential direction. The radial direction of the housing 2 that is orthogonal to the axial direction and the circumferential direction is simply defined as the radial direction.

[0031] The reduction gear device 1 and the electric motor 100 are arranged side by side in the axial direction.

[0032] <Housing>

[0033] An outer flange portion 2a extending radially outward is integrally formed on the outer peripheral surface of the housing 2. A plurality of bolt holes 2b for inserting bolts 103 are formed on the outer flange portion 2a. The bolt holes 2b are arranged at equal intervals in the circumferential direction. The measuring device 30 is fixed to the housing 2 by the bolts 103 inserted into the bolt holes 2b (details will be discussed later).

[0034] An O-ring groove 2d is formed over the entire circumference of the outer peripheral surface of the housing 2 at a portion closer to the electric motor 100 than the outer flange portion 2a. An O-ring 104 is mounted in the O-ring groove 2d. The O-ring 104 seals the housing 2 and the measuring device 30 (details will be described later).

[0035] A plurality of pin grooves 2c are formed along the axial direction on the inner peripheral surface of the housing 2. The pin grooves 2c are arranged at equal intervals in the circumferential direction. An internal gear pin 5 is inserted into each pin groove 2c. The internal gear pin 5 functions as an internal tooth that meshes with the swing external gears 15 and 16 of the speed reduction mechanism 4 to be described later.

[0036] Main bearings 6a and 6b (first main bearing 6a and second main bearing 6b) are provided on both axial sides of the inner peripheral surface of the housing 2. The gear carrier 3 is rotatably supported by the housing 2 via the main bearings 6a and 6b. The main bearings 6a and 6b are, for example, angular contact ball bearings.

[0037] The outer peripheral surface of the oil seal 105 is fitted to the end of the inner peripheral surface of the housing 2 located on the axially opposite side to the electric motor 100. The oil seal 105 is arranged to be located further axially outward relative to the first main bearing 6a of the two main bearings 6a and 6b that is arranged axially away from the electric motor 100. The oil seal 105 seals the space between the housing 2 and the gear carrier 3.

[0038] <Gear rack>

[0039] The gear carrier 3 includes a disc-shaped base plate portion 7 and an end plate portion 8 which are arranged to face each other in the axial direction, and three column portions 9 which are formed so as to protrude from the base plate portion 7 toward the end plate portion 8 .

[0040] The pillars 9 are arranged at equal intervals in the circumferential direction. The end plate 8 is arranged in contact with the top end 9a of the pillar 9. The end plate 8 is fixed to the pillar 9 by bolts 10. Thus, a space having a certain width in the axial direction is formed between the base plate 7 and the end plate 8.

[0041] A pin 11 is provided at a portion of the column 9 located radially inward of the bolt 10. The pin 11 positions the end plate 8 relative to the base plate 7. The pin 11 fits into a pin hole 12a provided in the base plate 7 and a pin hole 12b provided in the end plate 8.

[0042] The outer peripheral surface of the base plate portion 7 and the outer peripheral surface of the end plate portion 8 are rotatably supported by the housing 2 via the corresponding main bearings 6a and 6b, respectively. The inner peripheral surface of the oil seal 105 is fitted into a portion of the outer peripheral surface of the base plate portion 7 that is located on the side opposite to the electric motor 100 relative to the first main bearing 6a. Thus, the housing 2 and the gear carrier 3 are sealed by the oil seal 105 at a position axially outside the first main bearing 6a.

[0043] A shaft insertion hole 7a and a shaft insertion hole 8a are formed at the radial center of the base plate 7 and the radial center of the end plate 8, respectively. The two shaft insertion holes 7a and 8a are arranged coaxially. Of the two shaft insertion holes 7a and 8a, the shaft insertion hole 7a formed in the base plate 7 is closed by a sealing cap 20.

[0044] Three crankshaft insertion holes 7b and 8b are formed in the base plate portion 7 and the end plate portion 8, respectively. Each crankshaft insertion hole 7b and 8b is formed in a manner arranged between the column portions 9 adjacent in the circumferential direction. Moreover, each crankshaft insertion hole 7b and 8b is arranged on the same axis. Therefore, the central axis A2 of the crankshaft insertion holes 7b and 8b opposite to each other in the axial direction is parallel to the first rotation axis A1. A crankshaft bearing 18 is provided in each crankshaft insertion hole 7b and 8b. The crankshaft bearing 18 is, for example, a tapered roller bearing.

[0045] <Reduction Mechanism>

[0046] The reduction mechanism 4 rotates the gear carrier 3 at a speed reduced by a certain ratio relative to the speed of the input shaft 101. The reduction mechanism 4 includes: three crankshafts 13; transmission spur gears 14, which are respectively provided at the axial ends of the crankshafts 13; and two swing external gears 15 and 16, which are provided between the base plate portion 7 and the end plate portion 8.

[0047] The three crankshafts 13 are inserted into the crankshaft insertion holes 7 b and 8 b , respectively, and are rotatably supported by the carrier 3 (the base plate portion 7 and the end plate portion 8 ) via the crankshaft bearings 18 .

[0048] External teeth 17 are formed on the outer periphery of the transmission spur gear 14. The external teeth 17 mesh with external teeth 102 formed on the input shaft 101. The external teeth 17 and 102 mesh with each other, so that the rotation of the input shaft 101 is transmitted to the transmission spur gear 14, and the transmission spur gear 14 rotates.

[0049] The crankshaft 13 includes a shaft body 13c that rotates about the central axis A2, and a first eccentric portion 13a and a second eccentric portion 13b formed at a portion of the shaft body 13c located in the axial center. The portions of the shaft body 13c located on both sides in the axial direction are rotatably supported by the gear frame 3 (the base plate portion 7 and the end plate portion 8) by means of crankshaft bearings 18.

[0050] A transmission spur gear 14 is provided at the axial end of the shaft body 13c. The shaft body 13c and the transmission spur gear 14 are coaxially arranged and integrated. Therefore, the crankshaft 13 and the transmission spur gear 14 rotate integrally around the central axis A2. Hereinafter, the central axis A2 is defined as the second rotation axis A2 of the crankshaft 13.

[0051] The first eccentric portion 13a and the second eccentric portion 13b are formed in an eccentric manner relative to the second rotation axis A2. The first eccentric portion 13a and the second eccentric portion 13b are arranged between the two crankshaft bearings 18, and are arranged adjacent to the two crankshaft bearings 18 in the axial direction. In other words, the first eccentric portion 13a and the second eccentric portion 13b are arranged adjacent to each other in the axial direction between the base plate portion 7 and the end plate portion 8. The first eccentric portion 13a and the second eccentric portion 13b are arranged in a manner that the phase angle is shifted by 180°.

[0052] The inner peripheral surface of the roller bearing 19 is fitted in each of the eccentric portions 13a and 13b. The roller bearing 19 is, for example, a cylindrical roller bearing. The first oscillating external gear 15 and the second oscillating external gear 16 are rotatably supported by the crankshafts 13 via the roller bearings 19.

[0053] The first swing external gear 15 and the second swing external gear 16 are arranged in the space between the base plate portion 7 and the end plate portion 8. Through holes 15a and 16a are formed in the first swing external gear 15 and the second swing external gear 16, respectively, into which the outer peripheral surface of the roller bearing 19 is fitted. Therefore, when the first eccentric portion 13a and the second eccentric portion 13b swing and rotate due to the rotation of the crankshaft 13, the first swing external gear 15 and the second swing external gear 16 swing and rotate with the help of the roller bearing 19.

[0054] The first swing external gear 15 and the second swing external gear 16 are respectively formed with openings 15b and 16b for avoiding interference with the column portion 9. Shaft insertion holes 15c and 16c are formed in radially central portions of the first swing external gear 15 and the second swing external gear 16. External teeth 15d and 16d are respectively formed in the outer peripheral portions of the first swing external gear 15 and the second swing external gear 16. The number of teeth of each external tooth 15d and 16d is less than the number of internal tooth pins 5 of the housing 2, for example, by one.

[0055] Based on such a structure, as the first swing external gear 15 and the second swing external gear 16 swing and rotate, a part of the external teeth 15d and 16d of each swing external gear 15 and 16 meshes with the internal tooth pin 5 of the housing 2. The number of teeth of each external tooth 15d and 16d is less than the number of internal tooth pins 5, for example, one. Therefore, the meshing parts of each external tooth 15d and 16d with respect to the internal tooth pin 5 (housing 2) are sequentially deviated in the circumferential direction, and each swing external gear 15 and 16 rotates. The rotation is reduced relative to the rotation of the crankshaft 13.

[0056] As the swing external gears 15 and 16 rotate, the crankshafts 13 also rotate about the second rotation axis A2 and revolve around the first rotation axis A1. Each crankshaft 13 is rotatably supported on the gear frame 3 (base plate 7, end plate 8). Therefore, the gear frame 3 rotates as the crankshafts 13 revolve.

[0057] As a result, the reduction gear device 1 reduces the speed of rotation of the input shaft 101 and outputs the rotation from the carrier 3. Assuming that the carrier 3 is fixed, the reduction gear device 1 can reduce the speed of rotation of the input shaft 101 and output the rotation from the case 2.

[0058] The housing 2 is filled with a lubricant (not shown) to reduce the friction resistance of the gear frame 3 and the speed reduction mechanism 4 or to suppress the temperature rise. The measuring device 30 detects the leakage of the lubricant from the inside of the housing 2. In addition, the measuring device 30 also detects whether the amount of the filled lubricant is appropriate.

[0059] <Measurement device>

[0060] The measuring device 30 includes a bottomed cylindrical housing 31 that covers the case 2 from the electric motor 100 side, a pressure sensor 32 and a temperature sensor 33 that are provided in the housing 31 , and a control unit 34 that receives output signals from the pressure sensor 32 and the temperature sensor 33 .

[0061] The housing 31 is arranged with the opening 31a facing the case 2. The opening 31a of the housing 31 fits with a portion of the outer peripheral surface of the case 2 located closer to the electric motor 100 than the outer flange 2a. An O-ring 104 is provided at this fitting portion.

[0062] The housing 2 and the outer shell 31 are sealed by an O-ring 104. In addition, a measurement chamber 40 is formed by the portion of the housing 2 that fits with the outer shell 31 and the outer shell 31, which is blocked from the outside air outside the housing 2. Unlike between the base plate portion 7 and the housing 2, no sealing member such as an oil seal is provided between the end plate portion 8 facing the measurement chamber 40 and the housing 2. In addition, no sealing cover is provided in the shaft insertion hole 8a of the end plate portion 8.

[0063] Therefore, the measurement chamber 40 communicates with the inside of the housing 2. In other words, the measurement chamber 40 communicates with the inside and outside of the housing 2, and is blocked from the outside air outside the housing 2.

[0064] A through hole 35 for inserting the input shaft 101 is formed in a radially central portion of the bottom wall 31b of the housing 31. A motor base 36 formed in a cylindrical shape is integrally formed on the bottom wall 31b of the housing 31 so as to surround the through hole 35. The motor base 36 protrudes from the bottom wall 31b toward the electric motor 100. An internal thread portion 36a is formed at the top end of the motor base 36 (the end on the electric motor 100 side).

[0065] Based on such a structure, the electric motor 100 is arranged on the motor base 36, and the bolts 106 are fastened to the internal thread portion 36a from the flange portion 100a of the electric motor 100. Thus, the electric motor 100 is fixed to the housing 31. The motor base 36 and the flange portion 100a of the motor are sealed by an O-ring (not shown).

[0066] The pressure sensor 32 is provided on the bottom wall 31b of the housing 31. The pressure sensor 32 detects the pressure of the measurement chamber 40, and outputs the detection result to the control unit 34 as a signal.

[0067] As the temperature sensor 33, for example, an RFID tag 37 having a built-in temperature sensor is used. The temperature sensor 33 includes an RFID tag 37 and an RFID reader 38. The RFID tag 37 is provided at the end of the shaft body 13c of the crankshaft 13 that is exposed to the measurement chamber 40. The RFID tag 37 transmits the detected temperature as a signal. The RFID reader 38 is provided at the bottom wall 31b of the housing 31. The RFID reader 38 receives the signal transmitted from the RFID tag 37, and further outputs the signal to the control unit 34.

[0068] The control unit 34 has a table 39 for detecting leakage of lubricant from the inside of the housing 2 based on the signal input from the pressure sensor 32 and the signal input from the temperature sensor 33 (RFID reader 38). The control unit 34 and the pressure sensor 32 and the temperature sensor 33 (RFID reader 38) may be connected either by wire or by wireless.

[0069] Figure 2It is a diagram showing the table 39 of the control unit 34 .

[0070] like Figure 2 As shown, Table 39 is a graph showing the change of the pressure inside the reduction gear 1 when the vertical axis is the pressure inside the reduction gear 1 (reduction gear internal pressure) and the horizontal axis is the temperature rise value (reduction gear temperature rise) of the reduction gear 1. Table 39 shows the change of the pressure inside the reduction gear 1 according to the filling ratio of the lubricant inside the reduction gear 1 (hereinafter referred to as the filling ratio of the lubricant).

[0071] The horizontal axis of Table 39 is based on 20° C. That is, 0° C. on the horizontal axis means that the temperature rise relative to 20° C. is 0° C.

[0072] The pressure inside the reduction gear 1 refers to the pressure inside the housing 2. The inside of the housing 2 is connected to the measuring chamber 40, so the pressure inside the housing 2 is the same as the pressure in the measuring chamber 40. Therefore, detecting the pressure in the measuring chamber 40 using the pressure sensor 32 is synonymous with detecting the pressure inside the housing 2 using the pressure sensor 32.

[0073] The filling ratio of the lubricant refers to the ratio of the lubricant to the total volume obtained by adding the internal volume of the housing 2 and the internal volume of the measuring chamber 40 (hereinafter simply referred to as the total volume).

[0074] Here, a description will be given of a situation in which the lubricant leaks from the inside of the housing 2 and a change in the filling ratio of the lubricant depending on the state of the lubricant inside the housing 2 .

[0075] First, the characteristics of a case where the lubricant leaks from the inside of the housing 2 and a method of monitoring the state of the lubricant in the housing 2 by the control unit 34 will be described.

[0076] The measurement chamber 40 formed by the measurement device 30 is connected to the inside of the housing 2, so the lubricant leaks from the inside of the housing 2, specifically, the lubricant leaks from the inside of the housing 2 to the outside through the oil seal 105 and the sealing cover 20. In this case, the volume of the housing 2 increases by an amount corresponding to the leaked lubricant, so the pressure inside the housing 2 and the measurement chamber 40 decreases.

[0077] On the other hand, if the temperature of the lubricant increases, the lubricant expands. In this case, the volume inside the housing 2 decreases, so the pressure inside the housing 2 and the measuring chamber 40 increases. Therefore, the control unit 34 determines that the lubricant is leaking based on the signal input from the pressure sensor 32 and the signal input from the temperature sensor 33 (RFID reader 38), for example, when the temperature of the lubricant remains unchanged but the pressure of the measuring chamber 40 drops sharply.

[0078] Next, a description will be given of a change in the filling ratio of the lubricant together with a method of monitoring the state of the lubricant in the housing 2 by the control unit 34 .

[0079] The change in pressure inside the housing 2 and the measuring chamber 40 caused by the change in temperature also varies depending on the filling ratio of the lubricant. The filling ratio of the lubricant is preferably approximately in the range of 0.7 to 0.9. Therefore, in Table 39, the area Ar (refer to Figure 2 The hatched area in the figure is set as the appropriate range. Hereinafter, the area Ar is defined as the appropriate area Ar.

[0080] The control unit 34 compares the signal input from the pressure sensor 32 and the signal input from the temperature sensor 33 (RFID reader 38) with the table 39, and estimates the filling ratio of the lubricant. When the estimated filling ratio of the lubricant is included in the appropriate region Ar, it is determined that the filling amount of the lubricant is appropriate. On the other hand, when the estimated filling ratio of the lubricant is not included in the appropriate region Ar, it is determined that the filling amount of the lubricant is not appropriate.

[0081] However, when the pressure inside the reduction gear 1 is lower than the pressure in the appropriate area Ar, it can be determined that the lubricant is leaking. In contrast, the case where the pressure inside the reduction gear 1 is higher than the pressure in the appropriate area Ar is considered. In such a case, it is highly likely that the initial filling ratio of the lubricant during the initial assembly of the reduction gear 1 is not appropriate.

[0082] The measuring device 30 monitors the state of the lubricant to determine whether there is leakage of the lubricant or whether the filling amount of the lubricant is appropriate.

[0083] On the assumption that the initial filling of the lubricant is properly performed, when the pressure inside the reduction gear 1 is higher than the pressure in the proper area Ar after the reduction gear 1 is driven, it is conceivable that the cause is not leakage of the lubricant but abnormal pressure inside the reduction gear 1 or abnormality of each sensor 32, 33 itself. Even in such a case, the control unit 34 can make a judgment.

[0084] Next, a method for obtaining the lines of each filling ratio of the lubricant forming Table 39 will be described.

[0085] First, each value is defined as follows.

[0086] Total volume: V1

[0087] Lubricant volume: V2

[0088] The volume of the interior of the housing 2 and the measuring chamber 40 occupied by air (gas): V3

[0089] Lubricant filling ratio: A

[0090] Temperature change: Δt

[0091] · Lubricant volume expansion rate: N[×10 -3 / ℃]

[0092] The linear expansion coefficient of the housing 2 and the shell 31 (for example, cast iron): M[×10 -6 / ℃]

[0093] Atmospheric pressure: B (0.101325 [Mpa])

[0094] At this time, the volume V3 satisfies

[0095] V3=V1(1-A)···Formula (1).

[0096] The total volume V1' obtained due to the temperature change Δt satisfies

[0097] V1′=V1(1+3×M×Δt)···Formula (2).

[0098] The volume V2' of the lubricant obtained due to the temperature change Δt satisfies

[0099] V2'=V1×A(1+N×Δt)···Formula (3).

[0100] According to the above formulas (2) and (3), the volume V3' satisfies

[0101] V3'=V1'-V2'=V1{(1+3×M×Δt)-A(1+N×Δt)}···Equation (4).

[0102] When the temperature change Δt is a positive value, the air is pressurized and the volume is reduced due to the expansion of the lubricant. When the temperature change Δt is a negative value, the air is decompressed and the volume is expanded due to the shrinkage of the lubricant. When considering the air (gas) in such a closed space, Boyle's Charles law can be applied. That is, when the pressure is set to P, the volume is set to V, and the absolute temperature is set to T, these pressure P, volume V, and absolute temperature T satisfy

[0103] P×V / T=constant···Formula (5).

[0104] When the equation (5) is applied to the time of assembly of the reduction gear 1 (normal temperature T, atmospheric pressure B) and the time of temperature rise (Δt) during driving of the reduction gear 1, the following equation (6) is obtained.

[0105] {B×V1×(1-A)} / T=[P×V1{(1+3×M×Δt)-A(1+N×Δt)}] / (T+Δt)···Equation (6)

[0106] When the above-mentioned formula (6) is rearranged with respect to the pressure P, the following formula (7) is obtained, and the pressure P inside the reduction device 1 can be obtained.

[0107] P={B×V1×(1-A)×(T+Δt)} / [T{(1+3×M×Δt)-A(1+N×Δt)}]···Equation (7)

[0108] In this way, the filling amount of the lubricant can be estimated with high accuracy using the correlation between the temperature change Δt and the pressure P inside the reduction gear device 1 .

[0109] However, for example, the lubricant may be judged to be leaking from the inside of the housing 2 based only on the detection result of the pressure sensor 32. That is, when the pressure inside the measurement chamber 40 drops suddenly, it can be judged that the lubricant is leaking from the inside of the housing 2.

[0110] The reduction gear device 1 of this embodiment includes: a measuring chamber 40, which is connected to the inside and outside of the housing 2 and is blocked from the external air outside the housing 2; a pressure sensor 32, which detects the pressure inside the measuring chamber 40; and a control unit 34, which determines the leakage of lubricant from the inside of the housing 2 based on the detection result of the pressure sensor 32.

[0111] Therefore, the reduction gear 1 can monitor the state of the lubricant inside the housing 2 quickly and with high accuracy. For example, it is possible to determine the leakage of the lubricant. The state of the filling amount of the lubricant, etc. can be properly maintained based on the monitoring result. Since a large-scale measuring device is not required outside the reduction gear 1, the size of the reduction gear 1 can be suppressed.

[0112] When forming the measurement chamber 40, the reduction gear 1 includes the housing 31 independent of the case 2. Therefore, when installing the measurement device 30, for example, there is no need to process the case 2. The measurement chamber 40 and the pressure sensor 32 can be additionally provided to the existing reduction gear 1.

[0113] The measurement chamber 40 blocked from the outside air outside the case 2 is formed by the part of the case 2 fitted with the housing 31 and the housing 31. Therefore, the structure of the housing 31 can be simplified, and the size of the reduction gear 1 can be further suppressed.

[0114] The measuring device 30 is provided with a temperature sensor 33 in addition to the pressure sensor 32. The control unit 34 determines the leakage of the lubricant from the inside of the housing 2 based on the signal input from the pressure sensor 32 and the signal input from the temperature sensor 33. In this way, by detecting the temperature of the part exposed to the measuring chamber 40 using the temperature sensor 33, the leakage of the lubricant can be determined taking into account the thermal expansion of the lubricant. Therefore, the leakage of the lubricant can be determined with higher accuracy.

[0115] The control unit 34 has a table 39 that associates the temperature rise value of the temperature of the part exposed to the measuring chamber 40 with the reference temperature and the pressure inside the measuring chamber 40. The control unit 34 compares the signal input from the pressure sensor 32 and the signal input from the temperature sensor 33 with the table 39 to estimate the filling ratio of the lubricant. When it is determined based on the estimation result that the filling amount of the lubricant is not appropriate, for example, the state of the filling amount of the lubricant can be appropriately maintained. As a result, it is possible to prevent a bad situation from occurring in the reduction gear 1.

[0116] The leakage of lubricant can also be quickly determined using Table 39. The amount of lubricant leakage can be easily estimated using Table 39 to determine whether the reduction device 1 needs to be newly filled with lubricant. In addition, it is also possible to determine whether the amount of lubricant filled when the reduction device 1 is assembled is appropriate. Therefore, the reduction device 1 can be appropriately handled using the amount of lubricant leakage and the amount of filling.

[0117] Furthermore, the RFID tag 37 in the temperature sensor 33 is provided at the end of the shaft body 13c of the crankshaft 13 that is exposed to the measuring chamber 40. By measuring the temperature of a part of the reduction mechanism 4 that is in direct contact with the lubricant and is exposed to the measuring chamber 40, the correlation between the temperature change Δt in the table 39 and the pressure P inside the reduction mechanism 1 can be determined with high accuracy. Therefore, the leakage of the lubricant can be further accurately determined.

[0118] [Modifications]

[0119] In the above-mentioned embodiment, the following case is described: when forming the measurement chamber 40, the reduction gear 1 is provided with the housing 31 independent of the housing 2. However, this is not limited to this, and even if the housing 31 is not provided, it is sufficient to form the measurement chamber 40 that communicates with the inside and outside of the housing 2 and is blocked from the outside air outside the housing 2. The following is a specific description.

[0120] Figure 3 It is a cross-sectional view showing an enlarged portion of the reduction gear device 1 in a modified example.

[0121] like Figure 3As shown, a through hole 41 communicating with the inside and outside may be formed in the housing 2, and the through hole 41 may be used as the measurement chamber 40. The pressure sensor 32 and the temperature sensor 33 may be arranged in the through hole 41. Alternatively, the through hole 41 may be blocked by the pressure sensor 32 and the temperature sensor 33 to block the through hole 41 from the outside air. Alternatively, the through hole 41 may be blocked by a sealing cover (not shown) or the like to block the through hole 41 from the outside air.

[0122] In addition, the present invention is not limited to the above-described embodiment, and includes embodiments in which various modifications are added to the above-described embodiment within a scope that does not depart from the gist of the present invention.

[0123] For example, in the above-mentioned embodiment, the reduction gear 1 is described as an example of a gear device. The case where the reduction gear 1 is a so-called eccentric oscillating type reduction gear is described. The reduction gear mechanism 4 is described as an example of a transmission mechanism.

[0124] However, the present invention is not limited thereto, and the transmission mechanism may include a plurality of gears that rotate by receiving power from outside the housing 2. The above-described measurement chamber 40, pressure sensor 32, and temperature sensor 33 can be employed in various gear devices having such a transmission mechanism.

[0125] In the above-mentioned embodiment, the case where the reduction gear 1 includes three crankshafts 13 has been described. The case where the oscillating external gears 15 and 16 are oscillatingly rotated by the three crankshafts 13 has been described.

[0126] However, the present invention is not limited thereto, and the reduction gear 1 only needs to include at least one crankshaft 13. For example, the reduction gear 1 may be a so-called center crankshaft type reduction gear including one crankshaft 13. In this case, one crankshaft 13 is coaxially arranged with the first rotation axis A1, and each oscillating external gear 15, 16 is oscillatingly rotated by the one crankshaft 13.

[0127] In the above-mentioned embodiment, the case where the column portion 9 of the carrier 3 is formed so as to protrude from the base plate portion 7 in the reduction gear device 1 has been described.

[0128] However, the present invention is not limited thereto, and the column portion 9 may not be formed integrally with the base plate portion 7. In this case, the column portion 9 is fixed to the base plate portion 7 using, for example, bolts, similarly to the end plate portion 8. The column portion 9 may have any shape, and a space having a certain width in the axial direction may be formed between the base plate portion 7 and the end plate portion 8 by using the column portion 9.

[0129] In the above-described embodiment, the case where the filling ratio of the lubricant refers to the ratio of the lubricant to the total volume obtained by adding the internal volume of the housing 2 and the internal volume of the measuring chamber 40 has been described.

[0130] However, the present invention is not limited to this, and the ratio may be set to only the ratio of the lubricant to the volume of the inside of the housing 2. In this case, the numerical value of the filling ratio in Table 39 is also changed.

[0131] In the above embodiment, the case where the measurement chamber 40 is formed by the cooperation of the housing 2 and the casing 31 is described. In the above modification, the case where the through hole 41 is formed in the housing 2 and the through hole 41 serves as the measurement chamber 40 is described.

[0132] However, the present invention is not limited thereto, and the measurement chamber 40 may be formed only in the housing 31. For example, the housing 31 may be formed in a box shape with the measurement chamber 40 formed therein, and a part of the housing 31 may communicate with the interior of the casing 2.

[0133] In the above embodiment, the case where the temperature sensor 33 includes the RFID tag 37 and the RFID reader 38 is described. The case where the RFID tag 37 is provided at the end portion of the shaft body 13c of the crankshaft 13 exposed to the measurement chamber 40 is described.

[0134] However, the present invention is not limited thereto, and the temperature sensor 33 can detect the temperature of the part exposed to the measuring chamber 40. That is, for example, in addition to directly installing the RFID tag 37 on the reduction gear 1, it can also be installed on the inner side of the housing 31. The temperature sensor does not need to be in contact with the outside air. The temperature sensor 33 can be either contact type or non-contact type. It can also be configured in a manner that the temperature sensor is inserted into the measuring chamber 40.

[0135] In the above-mentioned embodiment, the case where the measuring device 30 is provided with the temperature sensor 33 in addition to the pressure sensor 32 is described. The case where the control unit 34 determines the leakage of the lubricant from the inside of the housing 2 based on the signal input from the pressure sensor 32 and the signal input from the temperature sensor 33 is described. The case where the control unit 34 has the table 39 in which the temperature rise value of the temperature of the part exposed to the measuring chamber 40 relative to the reference temperature and the pressure inside the measuring chamber 40 are associated.

[0136] However, the invention is not limited thereto, and at least the pressure sensor 32 is provided, and the leakage of the lubricant from the inside of the housing 2 can be determined based on the detection result of the pressure sensor 32. The control unit 34 may not have the table 39. Even in the case of such a configuration, the reduction gear 1 can quickly and accurately determine the leakage of the lubricant. Since a large-scale measuring device is not required outside the reduction gear 1, the size of the reduction gear 1 can be suppressed.

[0137] In the above-described embodiment, the electric motor 100 is described as an example of power from outside the housing 2 .

[0138] However, the present invention is not limited to this, and any structure may be used to impart power to the speed reduction mechanism 4. For example, a hydraulic motor, an engine, etc. may be used instead of the electric motor 100.

[0139] In the above-described embodiment, the case where the temperature rise value of the reduction gear device 1 on the horizontal axis in Table 39 is based on 20° C. has been described.

[0140] However, the reference value is not limited to this, and the reference value can be set arbitrarily. For example, 30°C can be used as the reference. In this case, 0°C on the horizontal axis means that the temperature rise relative to 30°C is 0°C. When the reference value is changed, the lines of each filling ratio of the lubricant change relative to the case of 20°C as the reference.

[0141] In the above embodiment, the region Ar surrounded by the lubricant filling ratio of 0.7 to 0.9 in Table 39 is described as the appropriate region Ar. The lubricant leakage may be determined even when the pressure inside the reduction gear 1 is lower than the pressure in the appropriate region Ar.

[0142] However, this is not limited to this, and there may be a case where lubricant leakage may not necessarily occur even in the appropriate area Ar. For example, it may be caused by contaminants, damage to the speed reduction mechanism 4, etc. Therefore, in the control unit 34, the lubricant ratio is estimated using the table 39, and whether the lubricant filling amount is appropriate is determined based on the estimated result.

[0143] In the embodiments disclosed in this specification, a component composed of multiple objects may be integrated into one, or a component composed of one object may be divided into multiple objects. Regardless of whether the components are integrated or not, they may be configured in a manner that can achieve the purpose of the invention.

Claims

1. A gear device, wherein: The gear unit has: case; a transmission mechanism, which is accommodated inside the housing together with a lubricant and has a plurality of gears that rotate by receiving power from outside the housing; a measuring chamber, which is in communication with the inside and outside of the housing and is blocked from external air outside the housing; a pressure sensor that detects the pressure inside the measurement chamber; as well as A control unit monitors a state of the lubricant inside the housing based on a detection result of the pressure sensor.

2. The gear device according to claim 1, wherein: The gear device includes a housing that is provided independently of the casing and forms the measurement chamber that communicates with the interior of the casing.

3. The gear device according to claim 2, wherein: The measuring chamber is formed by a part of the housing and the outer shell.

4. The gear device according to claim 3, wherein: The gear device includes a temperature sensor, which is disposed in the measurement chamber and detects the temperature of a portion exposed to the measurement chamber. The control unit determines leakage of the lubricant from the interior of the housing based on a detection result of the temperature sensor and a detection result of the pressure sensor.

5. The gear device according to claim 4, wherein: The control unit includes a table in which a temperature increase value of a temperature of a portion exposed to the measurement chamber relative to a reference temperature is associated with a pressure inside the measurement chamber. The control unit compares the detection results of the temperature sensor and the detection results of the pressure sensor with the table, estimates the ratio of the total volume of the lubricant relative to the internal volume of the shell and the volume of the measuring chamber, and determines whether the filling amount of the lubricant is appropriate based on the estimated result.

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