Grease replacement timing prediction method

Abstract

To predict grease replacement timing.SOLUTION: A grease replacement timing prediction method in a speed reducer 4 having a casing 41 in which a gear is housed and a specified amount of grease is encapsulated predicts prediction time from an operation starting day to a day when a consumption rate of an additive of the grease in the casing 41 reaches a predetermined management reference value as grease replacement timing on the basis of an inclination of a linear line passing through a consumption rate of an additive of the grease in the casing 41 on the operation starting day of the speed reducer 4 and the consumption rate of the additive of the grease in the casing 41 on an optional day.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The technology disclosed herein relates to a method for predicting when to replace grease. [Background technology]

[0002] Grease for lubrication is sealed inside gear devices such as reducers installed in robots and machine tools, and the grease deteriorates depending on the operating conditions and must be replaced as appropriate. For example, in the replacement method disclosed in Patent Document 1, new grease is injected from a grease inlet of a gear case, and the old grease is pushed out from a grease drain outlet of the gear case. Then, when the color of the grease pushed out from the grease drain outlet changes to the color of the new grease, the injection of the new grease is stopped and the grease replacement is completed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-177914 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the grease replacement method of Patent Document 1 simply pushes out the old grease with new grease, which does not adequately replace the old grease inside the reducer, and therefore the grease replacement rate is insufficient.

[0005] The technology disclosed herein has been made in consideration of the above points, and its purpose is to improve the grease replacement rate and to make it possible to predict the time for grease replacement. [Means for solving the problem]

[0006] The technology disclosed herein is a grease replacement method for a gear device having a casing that houses gears and has a specified amount of grease sealed therein. This grease replacement method includes performing a replacement operation in which grease is discharged from the casing and new grease is injected into the casing until the amount of grease in the casing exceeds the specified amount, rotating the gears after the replacement operation, and performing an amount adjustment operation in which grease is discharged from the casing until the amount of grease in the casing reaches the specified amount after the rotation of the gears. The method for predicting the time to change grease is a method for predicting the time to change grease in a gear device having a casing in which gears are housed and a specified amount of grease is sealed, and predicts the time to change grease based on the slope of a straight line passing through the consumption rate of additives in the grease in the casing on the operation start date of the gear device and the consumption rate of additives in the grease in the casing on an arbitrary day, as the predicted time from the operation start date to the date on which the consumption rate of additives in the grease in the casing reaches a predetermined management standard value. The grease replacement time prediction method is a method for predicting the time to change grease in a gear device having a casing that houses gears and contains a specified amount of grease, and based on the slope of a straight line passing through the consumption rate of the additives in the grease in the casing for any two days, regards the day on which the consumption rate of the additives in the grease in the casing is a predetermined value P0 as the operation start date of the gear device, and predicts the time to change grease as the predicted time from the day regarded as the operation start date to the day on which the consumption rate of the additives in the grease in the casing will reach a predetermined management standard value. Effect of the Invention

[0007] According to the above-described grease replacement method, it is possible to improve the grease replacement rate. According to the above-described grease replacement timing prediction method, it is possible to predict the grease replacement timing. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a robot. [Diagram 2] FIG. 2 is a flowchart showing a grease replacement method. [Diagram 3] FIG. 3 is a schematic diagram showing one state of the reducer during grease replacement. [Figure 4] FIG. 4 is a schematic diagram showing one state of the reducer during grease replacement. [Diagram 5] FIG. 5 is a schematic diagram showing one state of the reducer during grease replacement. [Figure 6] FIG. 6 is a schematic diagram showing one state of the reducer during grease replacement. [Figure 7] FIG. 7 is a schematic diagram showing one state of the reducer during grease replacement. [Figure 8] FIG. 8 is a schematic diagram showing one state of the reducer during grease replacement. [Figure 9] FIG. 9 is a graph for explaining an example of prediction of the first grease change date. [Figure 10] FIG. 10 is a graph for explaining an example of prediction of the first grease change date. [Figure 11] FIG. 11 is a graph for explaining an example of prediction of the second and subsequent grease change dates. [Figure 12] FIG. 12 is a schematic diagram showing one state of the reducer during grease replacement. [Figure 13] FIG. 13 is a schematic diagram showing one state of the reducer during grease replacement. [Figure 14] FIG. 14 is a schematic diagram showing one state of the reducer during grease replacement. [Figure 15] FIG. 15 is a schematic diagram showing one state of the reducer during grease replacement. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Exemplary embodiments will now be described in detail with reference to the accompanying drawings, in which: Fig. 1 is a block diagram showing a schematic configuration of a robot.

[0010] The grease replacement method of the present embodiment is a method for replacing grease in a reducer 4 having a casing 41 that houses gears and in which a specified amount of grease is sealed. The reducer 4 is an example of a gear device. In this example, the reducer 4 is intended to be installed in an industrial robot 100.

[0011] For example, the robot 100 includes a base 1 and a robot arm 2 connected to the base 1. The robot arm 2 has a plurality of links rotatably connected to each other. A base end of the robot arm 2 is rotatably connected to the base 1. A hand (not shown) is rotatably connected to a tip end of the robot arm 2. The robot 100 further includes, for example, a motor 3 and a reducer 4 that drive the robot arm 2. The motor 3 is connected to the robot arm 2 via the reducer 4. In other words, the reducer 4 transmits the rotational power of the motor 3 to the robot arm 2.

[0012] Fig. 3 is a schematic diagram showing one state of the reducer 4 during grease replacement. As shown in Fig. 3, the reducer 4 has a sealed casing 41. The casing 41 houses gears, more specifically, a gear train 45. The gear train 45 is formed by a plurality of gears meshing with each other. The casing 41 is filled with a specified amount of grease (old grease Gо) for lubricating the gear train 45 and bearings (not shown). The grease is a semi-solid (so-called gel-like) lubricant with high viscosity.

[0013] The above-mentioned specified amount is an amount that can sufficiently ensure lubrication of the gear train 45 and the like while preventing an abnormal increase in pressure inside the casing 41 when the gear train 45 is operated (i.e., rotated) by the motor 3 in the sealed casing 41. For example, if the reduction gear 4 is operated with an amount of grease larger than the specified amount sealed in the casing 41, the pressure inside the casing 41 will abnormally increase, and various seal members provided in the casing 1 may be damaged by the abnormal pressure. In addition, if the reduction gear 4 is continued to be operated with an amount of grease smaller than the specified amount sealed in the casing 41, the abnormal increase in pressure inside the casing 41 can be prevented, but the lubrication of the gear train 45 and the like will be insufficient.

[0014] Two through holes (i.e., a first through hole 42 and a second through hole 43) for supplying and discharging grease are formed in the casing 41 of the reduction gear 4. Specifically, the first through hole 42 is formed in the lower part of the casing 41, and the second through hole 43 is formed in the upper part of the casing 41. More specifically, the first through hole 42 is formed in the lowermost part of the casing 41, and the second through hole 43 is formed in the uppermost part of the casing 41. Both the first through hole 42 and the second through hole 43 are through holes that can be opened and closed freely.

[0015] Furthermore, the casing 41 of the reduction gear 4 has a portion 44 from which it is difficult to drain the grease. The portion 44 is an area within the casing 41 where it is difficult to replace the grease due to the structure and arrangement of the gear train 45, etc., i.e., an area where it is difficult to drain the grease from the outside of the casing 41.

[0016] Fig. 2 is a flow chart showing a grease replacement method. Each of Figs. 4 to 8 is a schematic diagram showing one state during grease replacement in the reducer 4. The grease replacement method in the reducer 4 is performed based on the flow chart in Fig. 2. The grease replacement method of this example includes performing a replacement operation, rotating the gears, and performing an amount adjustment operation. Furthermore, the grease replacement method of this example includes performing an operation of checking the degree of grease replacement, and performing an operation of predicting the replacement time.

[0017] The replacement operation is performed by steps S1 to S3. In the replacement operation, first, a grease discharge operation is performed (step S1). This discharge operation is an operation for discharging old grease (hereinafter also referred to as old grease Go) from the casing 41. Specifically, as shown in FIG. 3, the reducer 4 before the discharge operation is performed is in a state in which a specified amount of grease (i.e., old grease Go) is sealed in the casing 41. More specifically, the specified amount of grease is sealed in the casing 41 by sealing the grease up to a specified height H. In this state, the first through hole 42 and the second through hole 43 are closed.

[0018] As shown in FIG. 4, in the grease discharge operation, the first through hole 42 and the second through hole 43 are opened. That is, the inside of the casing 41 is opened to the outside air. Then, the old grease Go in the casing 41 is discharged from the first through hole 42. In this example, although not shown, the old grease Go is discharged from the casing 41 by sucking it with a suction cylinder. Also, in this discharge operation, since the second through hole 43 is opened, as the old grease Go is discharged from the first through hole 42, the outside air is taken into the casing 41 from the second through hole 43. Therefore, it is possible to prevent the inside of the casing 41 from becoming a negative pressure state, and the old grease Go is smoothly discharged from the casing 41.

[0019] On the other hand, in this discharging operation, the old grease Go present in the difficult-to-discharge portion 44 in the casing 41 remains without being discharged. In other words, in this discharging operation, the old grease Go in the area other than the difficult-to-discharge portion 44 in the casing 41 is discharged from the casing 41.

[0020] In the next step S2, a connecting operation of the auxiliary container 47 is performed. This connecting operation is an operation of connecting the auxiliary container 47, which can be opened to the outside air, to the second through hole 43, as shown in Fig. 5. The auxiliary container 47 is formed, for example, in a bottomed cylindrical shape with one end closed, and the end on the closed side is connected to the second through hole 43. The auxiliary container 47 and the second through hole 43 are connected, for example, by screwing. In this way, the inside of the casing 41 and the inside of the auxiliary container 47 communicate with each other via the second through hole 43. That is, the inside of the casing 41 is opened to the outside air via the second through hole 43 and the auxiliary container 47.

[0021] In the next step S3, a grease injection operation is performed. This injection operation is an operation in which new grease (hereinafter also referred to as new grease Gn) is injected into the casing 41 until the amount of grease in the casing 41 becomes greater than the specified amount described above. Specifically, as shown in FIG. 6, the new grease Gn is injected into the casing 41 from the first through hole 42. At this time, the new grease Gn is injected into the casing 41 until the grease in the casing 41 (in this example, the new grease Gn) exceeds the specified height H. Therefore, the amount of new grease Gn injected into the casing 41 increases compared to, for example, the case in which new grease Gn is injected until the grease in the casing 41 reaches the specified height H.

[0022] More specifically, new grease Gn is injected until the grease in the casing 41 enters the auxiliary container 47 through the second through hole 43. Therefore, the grease in the casing 41 can be easily filled without the new grease Gn spilling from the casing 41 onto the floor or the like. In other words, it can be determined that the grease in the casing 41 is full when the new grease Gn enters the auxiliary container 47 from the second through hole 43. In this way, by injecting new grease Gn until the grease in the casing 41 is full, the amount of new grease Gn injected into the casing 41 is maximized.

[0023] In addition, in this injection operation, since the inside of the casing 41 is open to the outside air through the second through-hole 43 and the auxiliary container 47, as the new grease Gn is injected from the first through-hole 42, the air inside the casing 41 is discharged from the auxiliary container 47. Therefore, the new grease Gn can be smoothly injected into the casing 41.

[0024] In this way, the replacement operation is an operation of discharging the old grease Go from the casing 41 and injecting new grease Gn into the casing 41 until the amount of grease in the casing 41 becomes greater than a specified amount, which is essentially an operation of replacing the old grease Go with new grease Gn. More specifically, in the replacement operation, after discharging the old grease Go from the casing 41, new grease Gn is injected into the casing 41 from the first through hole 42. Then, in the replacement operation, when injecting the new grease Gn from the first through hole 42, an auxiliary container 47 that can be opened to the outside air is connected to the second through hole 43.

[0025] In the next step S4, the gears are rotated. The gears are rotated by operating the gear train 45 after the replacement operation, that is, by rotating each gear of the gear train 45. Specifically, the gear train 45 is operated by the motor 3. The operation of the gear train 45 stirs up the grease in the casing 41. As a result, as shown in FIG. 7, the new grease Gn and the old grease Go present in the difficult-to-discharge portion 44 are mixed in the casing 41. The grease thus mixed with the new grease Gn and the old grease Go is hereinafter also referred to as mixed grease Gm.

[0026] During the rotation of the gears, the casing 41 is opened to the outside air. That is, the gear train 45 is operated with the inside of the casing 41 open to the outside air. Specifically, the inside of the casing 41 is opened to the outside air via the second through hole 43 and the auxiliary container 47. In this example, the first through hole 42 is closed. In this way, since the gear train 45 is operated with the inside of the casing 41 open to the outside air, an abnormal increase in pressure inside the casing 41 is prevented.

[0027] In the next step S5, a grease amount adjustment operation is performed. This amount adjustment operation is an operation in which, after the gears have been rotated, grease is discharged from the casing 41 until the amount of grease in the casing 41 reaches a specified amount.

[0028] Specifically, the amount adjustment operation in this example is performed with the auxiliary container 47 still connected to the casing 41. Immediately after the gears rotate, the inside of the casing 41 is filled with the mixed grease Gm (see FIG. 7). In other words, the amount of mixed grease Gm in the casing 41 is greater than the specified amount. In addition, since the second through-hole 43 is open via the auxiliary container 47, the inside of the casing 41 is open to the outside air.

[0029] In this amount adjustment operation, as shown in FIG. 8, the mixed grease Gm in the casing 41 and the auxiliary container 47 is discharged from the first through hole 42. At this time, the mixed grease Gm is discharged from the casing 41 until the mixed grease Gm in the casing 41 reaches the specified height H. In this example, although not shown, the mixed grease Gm is discharged from the casing 41 by sucking the mixed grease Gm with a suction cylinder. In addition, as the mixed grease Gm is discharged from the first through hole 42, outside air is taken into the casing 41 from the second through hole 43, so that the mixed grease Gm is smoothly discharged from the casing 41. When the mixed grease Gm in the casing 41 reaches the specified height H, the amount adjustment operation ends, and then the auxiliary container 47 is removed from the casing 41. At this time, since there is no grease (i.e., the mixed grease Gm) in the auxiliary container 47, the auxiliary container 47 can be removed without spilling the grease.

[0030] In this way, in the amount adjustment operation, the mixed grease Gm, which is a mixture of the old grease Go and the new grease Gn in the difficult-to-discharge portion 44, is discharged until it reaches a specified amount. Therefore, the ratio of the new grease Gn contained in the specified amount of grease in the casing 41 increases. In other words, by discharging the mixed grease Gm, a part of the old grease Go in the difficult-to-discharge portion 44 is discharged, so the ratio of the old grease Go contained in the specified amount of grease decreases, and the ratio of the new grease Gn increases accordingly. Therefore, the grease replacement rate R described later is improved. If the gear rotation operation is not performed, the old grease Go and the new grease Gn in the difficult-to-discharge portion 44 are not mixed, so the grease discharged by the amount adjustment operation is essentially only the new grease Gn. Therefore, the ratio of the new grease Gn contained in the specified amount of grease does not increase.

[0031] In the next step S6, a confirmation operation of the degree of grease replacement is performed. This confirmation operation is an operation to confirm the degree of grease replacement by obtaining a grease replacement rate R based on the additive consumption rate P1 of the old grease Go in the casing 41 before the replacement operation and the additive consumption rate P2 of the mixed grease Gm in the casing 41 after the amount adjustment operation.

[0032] The degree of grease replacement is the ratio of the amount of new grease Gn replaced to a specified amount of old grease Go. The grease replacement rate R is an index that specifically represents the degree of grease replacement. In other words, by calculating this grease replacement rate R, the effectiveness of the grease replacement performed in steps S1 to S5 can be confirmed. In other words, the higher the grease replacement rate R, the greater the amount of new grease Gn that has been replaced, and therefore the more effective the grease replacement is. Specifically, the grease replacement rate R is calculated using the following formula 1. In this example, the unit of the grease replacement rate R is %. Formula 1: R=((P1-P2) / P1)×100

[0033] Grease contains a certain amount of additives. In this example, phosphorus compounds and compounds containing phosphorus-sulfur double bond groups are contained as additives (specifically, extreme pressure additives and friction modifiers). Grease additives that are often used in the reducer 4 of the robot 100 include, for example, ZnDTP (zinc dialkyldithiophosphate) and MoDTP (molybdenum dialkyldithiophosphate). This is also true for greases used in the reducers of machine tools. There are various analytical methods and analytical instruments, and one example of a quantitative analysis method for phosphorus-sulfur double bond groups is spectroscopic analysis using Fourier transform infrared spectroscopy (FT-IR).

[0034] The additives in the grease are gradually oxidized and consumed as the reducer 4 operates. The additive consumption rate mentioned above is the ratio of the amount of additive consumed to the amount of additive contained in the grease at the time of shipment of the reducer 4 (robot 100). The higher the additive consumption rate, the more the performance of the grease is degraded, i.e., the more deteriorated the grease is. The additive consumption rate P1 is measured by sampling a portion of the old grease Go of the reducer 4 in the state shown in FIG. 3, for example, before the replacement operation is performed. The additive consumption rate P2 is measured by sampling a portion of the mixed grease Gm of the reducer 4 in the state shown in FIG. 8 after the amount adjustment operation. Naturally, the consumption rate P1 is higher than the consumption rate P2.

[0035] In this way, the additive consumption rate is a value according to the deterioration of the grease, so it can be said to be a parameter that appropriately reflects the difference between the old grease Go and the new grease Gn. Therefore, the grease replacement rate R calculated based on the additive consumption rate is an index that appropriately reflects the degree of grease replacement.

[0036] In the next step S7, a prediction operation for the grease change time is performed. In this prediction operation, an operation for predicting the first grease change time (hereinafter also referred to as the grease change date) from the operation start date (i.e., the delivery date) of the reduction gear 4, and an operation for predicting the second and subsequent grease change times are performed. Hereinafter, the operation start date of the reduction gear 4 will also be simply referred to as the "operation start date."

[0037] The operation of predicting the first grease change time will be described. Figures 9 and 10 are graphs for explaining an example of predicting the first grease change date. In this example, it is determined that it is time to change the grease when the consumption rate of the additive in the grease in the casing 41 reaches a predetermined management reference value.

[0038] First, when the operation start date of the reducer 4 is known, the first grease change date is predicted as follows. As shown in Fig. 9, a predicted time t1 from the operation start date to the date when the additive consumption rate reaches the control reference value (shown as consumption rate P1 in Fig. 9) is predicted based on the slope of a line passing through the additive consumption rate P0 (generally 0%) on the operation start date and the additive consumption rate P01 on an arbitrary day. In this example, correction is required if the additive consumption rate P0 on the operation start date is not zero, but a description of this correction will be omitted.

[0039] Furthermore, if the operation start date of the reducer 4 is not known, the first grease change date is estimated as follows: As shown in Fig. 10, based on the slope of a straight line passing through the additive consumption rates P01 and P02 for any two days, the day when the additive consumption rate is zero (shown as consumption rate P0 in Fig. 10) is regarded as the operation start date, and a predicted time t1 from the day regarded as the operation start date to the day when the additive consumption rate reaches the control reference value (shown as consumption rate P1 in Fig. 10) is predicted. In this way, the first grease change date can be predicted.

[0040] Next, the operation of predicting the second and subsequent grease change times will be described. Fig. 11 is a graph for explaining an example of predicting the second and subsequent grease change dates. In this prediction method, it is also determined that it is time to change the grease when the consumption rate of the additive in the grease in the casing 41 reaches a predetermined management reference value.

[0041] In the operation of predicting the timing of the second and subsequent grease changes, the N+1th grease change time, when the N+1th degree of grease change is confirmed from the operation start date, is predicted based on the elapsed time from the operation start date of the reducer 4 to the first grease change time, when the degree of the first grease change is confirmed, and the grease change rate R obtained when confirming the Nth degree of grease change from the operation start date. Note that N is a natural number.

[0042] Specifically, the second and subsequent grease change dates are predicted by predicting the time (hereinafter referred to as predicted time t) from the Nth (i.e., current) grease change date to the N+1th (i.e., next) grease change date, as shown in Fig. 11. Note that in Fig. 11, the "first grease change date", the "second grease change date", etc. are referred to as the "first change date", the "second change date", etc., respectively. The predicted time t is calculated using the following formula 2. Formula 2: Predicted time t = elapsed time t1 x grease replacement rate R / 100 Here, the elapsed time t1 is the time from the start of operation to the first grease change date. The grease change rate R is the grease change rate obtained when checking the degree of the Nth grease change, i.e., the grease change rate obtained when the Nth grease change was performed.

[0043] For example, when predicting the second grease change date (i.e., when N=1), the predicted time t2, which is the time from the first grease change date to the second grease change date, is calculated by the above formula 2. In this case, the grease change rate R is the grease change rate R1 calculated when the first grease change is performed. That is, the grease change rate R1 is calculated from the additive consumption rate P1 before the grease change and the additive consumption rate P2 after the grease change. The value obtained by multiplying this grease change rate R1 and the elapsed time t1 is derived as the predicted time t2. In addition, when predicting the third grease change date (i.e., when N=2), the predicted time t3, which is the time from the second grease change date to the third grease change date, is similarly calculated by the above formula 2. In this case, the grease change rate R is the grease change rate R2 calculated when the second grease change is performed. That is, the grease change rate R2 is calculated from the additive consumption rate P1(1) before the grease change and the additive consumption rate P2(1) after the grease change. The value obtained by multiplying this grease change rate R2 by the elapsed time t1 is derived as the predicted time t3. Note that the consumption rates P1(1) and P2(1) are synonymous with the consumption rates P1 and P2, respectively, and the grease change rates R1 and R2 are synonymous with the grease change rate R. In this manner, the second and subsequent grease change dates are predicted.

[0044] Furthermore, when predicting the third or subsequent grease change date (that is, when N≧2), the predicted time t can also be calculated by the following formula 3. Equation 3: Predicted time t = elapsed time t / (first grease replacement rate R / 100) × (second grease replacement rate R / 100) Here, the elapsed time t is the time from the N-1th grease change date to the Nth grease change date. The first grease change rate R is the grease change rate obtained when the N-1th grease change is performed. The second grease change rate R is the grease change rate obtained when the Nth grease change is performed. For example, when predicting the third grease change date (i.e., when N=2), the elapsed time t is the elapsed time t2 from the first grease change date to the second grease change date. The first grease change rate R is the grease change rate R1 obtained when the first grease change is performed, and the second grease change rate R is the grease change rate R2 obtained when the second grease change is performed. Furthermore, when predicting the fourth grease change date (i.e., when N=3), the elapsed time t is the elapsed time t3 from the second grease change date to the third grease change date. The grease change rate R2 obtained when the second grease change is performed is used as the first grease change rate R, and the grease change rate obtained when the third grease change is performed (not shown) is used as the second grease change rate R. This method also makes it possible to predict the third and subsequent grease change dates.

[0045] As described above, the grease replacement method of the embodiment is a grease replacement method in a reducer 4 (gear device) having a casing 41 that houses gears and in which a specified amount of grease is sealed. The grease replacement method includes performing a replacement operation in which old grease Go is discharged from the casing 41 and new grease Gn is injected into the casing 41 until the amount of grease in the casing 41 becomes greater than the specified amount, rotating the gears after the replacement operation, and performing an amount adjustment operation in which mixed grease Gm is discharged from the casing 41 until the amount of grease in the casing 41 becomes the specified amount after the gear rotation operation.

[0046] According to this configuration, in the replacement operation, new grease Gn is injected into the casing 41 until the amount of grease in the casing 41 becomes greater than the specified amount. Therefore, the amount of new grease Gn injected into the casing 41 can be increased, compared to the case where new grease Gn is injected until the amount of grease in the casing 41 becomes the specified amount. In addition, by rotating the gears, the old grease Go that is difficult to discharge remaining in the casing 41 can be mixed with the injected new grease Gn. The mixed grease Gm thus mixed is discharged until it reaches the specified amount, so the ratio of new grease Gn contained in the specified amount of grease in the casing 41 increases. In other words, by discharging the mixed grease Gm, a part of the old grease Go that is difficult to discharge in the casing 41 is discharged, so the ratio of old grease Go contained in the specified amount of grease decreases, and the ratio of new grease Gn increases accordingly. Therefore, according to this grease replacement method, the grease replacement rate R can be improved.

[0047] In the grease replacement method of the above embodiment, the casing 41 is exposed to the outside air during the rotation of the gears.

[0048] According to this configuration, since the inside of the casing 41 is open to the outside air, it is possible to prevent an abnormal increase in pressure caused by the rotation of the gears inside the casing 41. Therefore, it is possible to prevent damage to the sealing members caused by an abnormal increase in pressure inside the casing 41.

[0049] In addition, in the grease replacement method of the above embodiment, in the replacement operation, after the old grease Go is discharged from the casing 41, new grease Gn is injected into the casing 41 through the first through hole 42 formed in the lower part of the casing 41, and when the new grease Gn is injected into the casing 41 through the first through hole 42, an auxiliary container 47 that can be opened to the outside air is connected to the second through hole 43 formed in the upper part of the casing 41.

[0050] According to this configuration, new grease Gn can be injected until the new grease Gn in the casing 41 enters the auxiliary container 47 through the second through hole 43. Therefore, the grease in the casing 41 can be easily filled without spilling the new grease Gn from the casing 41 onto the floor or the like. In this way, by injecting new grease Gn until the grease in the casing 41 is filled up, the amount of new grease Gn injected into the casing 41 can be maximized. Therefore, the grease replacement rate R can be further improved.

[0051] In addition, the grease replacement method of the above embodiment further includes determining a grease replacement rate R based on the additive consumption rate P1 of the old grease Go in the casing 41 before the replacement operation and the additive consumption rate P2 of the mixed grease Gm in the casing 41 after the quantity adjustment operation, to confirm the degree of grease replacement.

[0052] According to this configuration, the grease replacement rate R is calculated based on the additive consumption rate, which is a parameter that appropriately reflects the difference between the old grease Go and the new grease Gn, and can therefore be said to be an index that appropriately reflects the degree of grease replacement. Therefore, by calculating such a grease replacement rate R, the degree of grease replacement can be reliably confirmed. And, by checking the degree of grease replacement, the effectiveness of the grease replacement can be confirmed and evaluated.

[0053] In the grease replacement method of the embodiment, the grease replacement rate R is calculated by the above-mentioned formula 1.

[0054] According to this configuration, the grease replacement rate R can be realized.

[0055] In the grease replacement method of the above embodiment, the additive is a phosphorus compound or a compound containing a phosphorus-sulfur double bond group.

[0056] According to this configuration, since the phosphorus compound or the compound containing a phosphorus-sulfur double bond group is a major component as an additive to the grease, a more appropriate grease replacement rate R can be calculated by determining the grease replacement rate R based on the consumption rate of these additives.

[0057] In addition, the grease replacement method of the above embodiment further includes predicting the N+1th grease replacement time to confirm the N+1th degree of grease replacement from the operation start date, based on the elapsed time t1 from the operation start date of the reducer 4 (gear device) to the first grease replacement time to confirm the degree of the first grease replacement, and the grease replacement rate R obtained when confirming the Nth (N is a natural number)th degree of grease replacement from the operation start date.

[0058] According to this configuration, the N+1th (i.e., next) grease change time can be predicted with high accuracy. The N+1th grease change time depends on the Nth (i.e., current) grease change rate R. In other words, the higher the current grease change rate R, the longer the time until the next grease change time. The next grease change time predicted based on the grease change rate R and the elapsed time t1 from the operation start date to the first grease change time can be predicted with high accuracy.

[0059] The grease replacement method of the embodiment includes a method for checking the degree of grease replacement. This method for checking the degree of grease replacement solves a problem different from the problem of improving the grease replacement rate R, that is, grasping the degree of grease replacement.

[0060] Specifically, the method for checking the degree of grease replacement is a method for checking the degree of grease replacement when grease replacement is performed in a reducer 4 (gear device) having a casing 41 that houses gears and in which grease is sealed, by discharging old grease Go from the casing 41 and injecting new grease Gn into the casing 41. The method for checking the degree of grease replacement includes determining a grease replacement rate R based on a consumption rate P1 of additives of the old grease Go in the casing 41 before the grease replacement is performed (i.e., before the old grease Go is discharged) and a consumption rate P2 of additives of the grease in the casing 41 after the grease replacement is performed (i.e., after the new grease Gn is injected) to check the degree of grease replacement.

[0061] According to this configuration, the grease replacement rate R is calculated based on the additive consumption rate, which is a parameter that appropriately reflects the difference between the old grease Go and the new grease Gn, and can therefore be said to be an index that appropriately reflects the degree of grease replacement. Therefore, by checking the degree of grease replacement used to calculate the grease replacement rate R, the degree of grease replacement can be reliably understood. And by understanding the degree of grease replacement, for example, the next time for grease replacement can be appropriately predicted.

[0062] In addition, in the method for checking the degree of grease replacement, the grease replacement rate R is calculated by the above-mentioned formula 1.

[0063] According to this configuration, the grease replacement rate R can be realized.

[0064] In the method for checking the degree of grease replacement, the additive is a phosphorus compound or a compound containing a phosphorus-sulfur double bond group.

[0065] According to this configuration, since the phosphorus compound or the compound containing a phosphorus-sulfur double bond group is a major component as an additive of the grease, a more appropriate grease replacement rate R can be calculated by determining the grease replacement rate R based on the consumption rate of such additives. Therefore, the degree of grease replacement can be more accurately grasped.

[0066] In addition, the method for confirming the degree of grease change further includes predicting the N+1th grease change time to confirm the N+1th degree of grease change from the operation start date, based on the elapsed time t1 from the operation start date of the reducer 4 (gear device) to the first grease change time when the first grease change degree is confirmed, and the grease change rate R obtained when confirming the Nth (N is a natural number)th grease change degree from the operation start date.

[0067] According to this configuration, the N+1th (i.e., next) grease change time can be predicted with high accuracy. The N+1th grease change time depends on the Nth (i.e., current) grease change rate R. In other words, the higher the current grease change rate R, the longer the time until the next grease change time. The next grease change time predicted based on the grease change rate R and the elapsed time t1 from the operation start date to the first grease change time can be predicted with high accuracy.

[0068] Other Embodiments As described above, the above embodiment has been described as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this, and can be applied to embodiments in which modifications, replacements, additions, omissions, etc. are appropriately performed. In addition, it is also possible to combine the components described in the above embodiment to form a new embodiment. In addition, among the components described in the attached drawings and detailed description, not only components essential for solving the problem but also components that are not essential for solving the problem in order to exemplify the technology may be included. Therefore, the fact that these non-essential components are described in the attached drawings and detailed description should not immediately be taken to mean that these non-essential components are essential.

[0069] For example, in the replacement operation of steps S1 to S3 in the above embodiment, the old grease Go is discharged from the casing 41 and then the new grease Gn is injected into the casing 41, but the old grease Go may be discharged from the casing 41 while the new grease Gn is being injected into the casing 41. In that case, the connection operation of the auxiliary container 47 (step S2) is omitted.

[0070] 12 to 14 are schematic diagrams showing one state during grease replacement of the reducer 4. Specifically, in the replacement operation according to this modified example, in the reducer 4 in which a specified amount of old grease Go is enclosed, new grease Gn is injected into the casing 41 from the first through hole 42 (see FIG. 12). At this time, the second through hole 43 is open. In this replacement operation, as shown in FIG. 13, as the new grease Gn is injected into the casing 41, the old grease Go in the casing 41 is discharged from the second through hole 43.

[0071] Then, as shown in FIG. 14, when the new grease Gn reaches the second through hole 43, the injection operation of the new grease Gn ends. Since the old grease Go and the new grease Gn are different in color, it is understood that the old grease Go has been discharged from the casing 41 and the new grease Gn has reached the second through hole 43 when the color of the grease discharged from the second through hole 43 changes to the color of the new grease Gn. When the injection operation of the new grease Gn ends in this way, the replacement operation ends. After the replacement operation ends, the operations from step S4 shown in FIG. 2 onwards are performed sequentially, as in the above embodiment. That is, the old grease Go and the new grease Gn in the difficult-to-discharge portion 44 are mixed by the rotation operation of the gears (step S4), and the mixed mixed grease is discharged from the casing 41 until a specified amount is reached by the amount adjustment operation (step S5).

[0072] In this manner, even in the replacement operation of this modified example, the operation of injecting new grease Gn into the casing 41 is performed until the amount of grease in the casing 41 becomes greater than the specified amount, more specifically, until the grease in the casing 41 is full. In this manner, by injecting new grease Gn until the grease in the casing 41 is full, the amount of new grease Gn injected into the casing 41 can be increased, as in the above embodiment. Therefore, the grease replacement rate R is improved.

[0073] In addition, in the above embodiment, the gear device is a reducer 4 provided in the robot 100, but the technology disclosed herein is not limited to this and may be, for example, a reducer provided in a machine tool.

[0074] Furthermore, the gear device is not limited to the reducer 4, but may be, for example, a device that houses a gear train that transmits power without reducing the speed.

[0075] Furthermore, the additives relating to the additive consumption rates P1 and P2 may be components other than phosphorus compounds and compounds containing a phosphorus-sulfur double bond group.

[0076] Further, the auxiliary container 47 may be connected to the second through-hole 43 via a tube or the like, rather than directly.

[0077] Also, the auxiliary container 47 may be omitted, and the grease from the second through hole 43 may be guided by a tube or the like to a container (e.g., a bucket) placed at a position lower than the casing 41, such as the floor. In this case, the inside of the casing 41 is opened to the outside air by directly opening one end of the tube on the container side to the outside air, or by opening one end of the tube on the container side to the outside air via the grease in the container. This container and tube are installed even during the rotation operation of the gear (step S4), similar to the auxiliary container 47 in the above embodiment. Also, this container and tube may be applied to the modified example described based on Figs. 12 to 14.

[0078] In the grease replacement method of the embodiment, the operation of connecting the auxiliary container 47 (step S2) may be omitted. In this case, in the grease injection operation (step S3), new grease Gn is injected into the casing 41 from the first through hole 42 with the second through hole 43 open, as shown in Fig. 15, for example. The new grease Gn is injected into the casing 41 until the grease in the casing 41 exceeds the specified height H, more specifically, until the grease in the casing 41 is full. In addition, the gear rotation operation (step S4) and the grease amount adjustment operation (step S5) are performed, for example, with the second through hole 43 open.

[0079] Furthermore, in the case where the auxiliary container 47 is omitted, for example, during the rotational operation of the gear (step S4), the second through hole 43 may be closed while the gear is rotated slowly so that the pressure does not rise above a certain level.

[0080] Furthermore, in the case where the auxiliary container 47 is omitted, for example, when the gears are rotated (step S4) with the second through-hole 43 open, the gears may be rotated knowing that the grease will spill if the amount of grease spilling from the second through-hole 43 is within an allowable range. In order to prevent the grease from spilling from the second through-hole 43, the rotation speed of the gears may be restricted, or the gears may be rotated with the amount of grease in the casing 41 being equal to or greater than a specified amount but not full.

[0081] In addition, the grease injection operation (step S3) and the gear rotation operation (step S4) are performed separately, but they may be performed in parallel. In other words, the gear may be rotated while the new grease Gn is injected into the casing 41.

[0082] In addition, in the grease discharge operation (step S1), instead of the configuration in which the old grease Go is sucked from the first through hole 42 by the suction cylinder, for example, a configuration in which pressurized air is supplied from the second through hole 43 into the casing 41 to discharge the old grease Go from the first through hole 42 may be adopted. When the auxiliary container 47 is connected to the second through hole 43, a lid having an opening may be attached to the auxiliary container 47 as appropriate, and pressurized air may be supplied from the opening of the lid into the casing 41. In such cases, in order to prevent the grease from scattering from the first through hole 42, a tube or the like may be connected to the first through hole 42, and the old grease Go may be discharged through the tube into a bucket or the like for disposing of grease. This configuration may also be adopted in the modified example in which the auxiliary container 47 is omitted.

[0083] In the above embodiment, the operation of predicting the replacement time in step S7 may be omitted, and in addition to step S7, the operation of checking the degree of grease replacement in step S6 may be omitted. [Explanation of symbols]

[0084] 4. Gearbox (gear device) 41 Casing 42 First through hole 43 Second Through Hole 47 Auxiliary container Go Old Grease (Grease) Gn New Grease (New Grease) Gm mixed grease (grease) P1 Additive consumption rate P2 Additive consumption rate R Grease replacement rate t1 Elapsed time

Claims

1. A method for predicting a time to replace grease in a gear device having a casing in which a gear is housed and a specified amount of grease is sealed, comprising: A grease replacement time prediction method for predicting the time to replace grease based on the slope of a straight line passing through the consumption rate of the grease additive in the casing on the operation start date of the gear device and the consumption rate of the grease additive in the casing on any given day, as a predicted time from the operation start date to the date on which the consumption rate of the grease additive in the casing reaches a predetermined management standard value.

2. A method for predicting a time to replace grease in a gear device having a casing in which a gear is housed and a specified amount of grease is sealed, comprising: A grease replacement time prediction method which, based on the slope of a straight line passing through the consumption rate of the additive in the grease in the casing for any two days, regards the day on which the consumption rate of the additive in the grease in the casing reaches a predetermined value P0 as the operation start date of the gear device, and predicts, as the grease replacement time, the predicted time from the day regarded as the operation start date to the day on which the consumption rate of the additive in the grease in the casing reaches a predetermined management standard value.

3. 3. The grease replacement time prediction method according to claim 1, The method for predicting when to replace grease, wherein the additive is a phosphorus compound or a compound containing a phosphorus-sulfur double bond group.

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