Method for determining state between available tooth surfaces of gear pair and method for evaluating lubrication state between available tooth surfaces of gear pair

Abstract

To provide an accurate determination method for a state between available tooth surfaces in a gear pair.SOLUTION: In an evaluation method for evaluating a gearwheel pair GP including a first gearwheel side T1 having a first available flank side G1 and a second gearwheel side T1 having a second available flank side T2 in contact with the first available flank side G2 by using an electric circuit 10, a DC current is applied to the gearwheel pair GP in the electric circuit 10, and a voltage VR is measured by a voltage meter VM while rotating the first gearwheel side G1 and the second gearwheel side G2. If the measured voltage VP2 is greater than the critical value Vth, it is determined that the first available flank T1 and the second available flank T2 are in a separation state, and if the measured voltage VP2 is less than or equal to the critical value Vth, it is determined that the first available flank T1 and the second available flank T2 are in a contact state of at least partial contact.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a method for determining the condition of the usable tooth flanks of a gear pair and a method for evaluating the condition of lubrication between the usable tooth flanks of a gear pair. [Background technology]

[0002] A method is known in which a direct current is passed through a pair of metal members that slide against each other, the voltage is measured, and based on the measured voltage, the state of the metal members is determined to be in contact or separated. Patent Document 1 discloses a method for determining whether the inner ring and balls, and the outer ring and balls of a rolling bearing are in contact or separated. The determination method disclosed in Patent Document 1 determines based on the measured voltage whether the inner ring and balls, and the outer ring and balls are in contact with each other via a solid lubricant. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-311427 Summary of the Invention [Problem to be solved by the invention]

[0004] In a gear pair including a first gear having a first usable tooth flank and a second gear having a second usable tooth flank, the contact state between the first usable tooth flank and the second usable tooth flank changes from moment to moment as the gears rotate from the start of meshing to the end of meshing. For this reason, the determination method disclosed in Patent Document 1 cannot accurately determine the contact state between the usable tooth flanks of the gear pair. An object of the present disclosure is to provide a method for accurately determining the contact state between usable tooth flanks in a gear pair. [Means for solving the problem]

[0005] The present disclosure provides a method for determining a condition between usable tooth surfaces of a gear pair including a drive gear having a first usable tooth surface and a driven gear having a second usable tooth surface that contacts the first usable tooth surface, using a circuit including the gear pair, a DC power source, a voltmeter, a first resistor, a second resistor, and lubricating oil, wherein the circuit connects the drive gear, a first side of the first resistor, and a first side of the voltmeter, connects the driven gear, a second side of the first resistor, and a second side of the voltmeter, directly connects one of the positive and negative poles of the DC power source to one of the drive gear and the driven gear, and connects the other of the positive and negative poles to a first resistor of the second resistor. a first resistor connected to one side of the first gear and a second resistor connected to the other of the drive gear and the driven gear; the lubricating oil is interposed between the first usable tooth surface and the second usable tooth surface; a direct current is passed through the gear pair in the circuit; the voltage is measured with the voltmeter while the drive gear and the driven gear are rotated; if the measured voltage is greater than a threshold value, it is determined that the first usable tooth surface and the second usable tooth surface are in a separated state in which they are in contact via an oil film; and if the measured voltage is equal to or smaller than the threshold value, it is determined that the first usable tooth surface and the second usable tooth surface are in a contact state in which they are in contact at least partially without an oil film between them.

[0006] According to the present disclosure, it is possible to provide a determination method for accurately determining whether a first usable tooth surface and a second usable tooth surface of a gear pair are in a contact state or a separated state. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing an electrical circuit used in the method of determining the state of the gap between usable tooth flanks of a gear pair according to the present disclosure. [Figure 2] FIG. 2 is a diagram showing a voltage measured by an electric circuit, a voltage after processing by a median filter, and a voltage after processing by a moving average filter. [Figure 3] FIG. 3 is a flow diagram of a method of determining the condition of the usable tooth flanks of a gear pair and evaluating the lubrication condition of the usable tooth flanks of a gear pair according to the present disclosure. [Figure 4]FIG. 4 is an explanatory diagram of threshold values ​​used to determine the state of the gap between usable tooth surfaces of a gear pair. [Figure 5] FIG. 5 is a diagram showing a change in voltage accompanying the rotation of the first gear. [Figure 6] FIG. 6 is a diagram showing the lubrication state index used to evaluate the lubrication state of a gear pair, and an index obtained by dividing the average value of the measured voltage by the value of the applied voltage. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Details of the embodiment of the present disclosure> An embodiment of the present invention will be described below. Fig. 1 is a schematic diagram showing an electric circuit used in the method for determining the state between the usable tooth flanks T1 and T2 of a gear pair according to the present disclosure. Fig. 1 shows an electric circuit 10, which is an example of an electric circuit used in the method for determining the state between the usable tooth flanks T1 and T2 of a gear pair according to the present disclosure. As shown in Fig. 1, the electric circuit 10 includes a DC power supply B, a voltmeter VM, a first resistor R1, a second resistor R2, a first connection terminal P1, a second connection terminal P2, and electric wires 11 that electrically connect these components.

[0009] The electric circuit 10 further includes a gear pair GP to be determined. The gear pair GP includes a first gear G1 and a second gear G2. The first gear G1 is a drive gear having a first usable tooth surface T1 and is rotatably supported by a first shaft X1. The first shaft X1 is connected to a drive source such as a motor (not shown) and is driven by the drive source to rotate about its axis. The first shaft X1 is electrically connected to a first connection terminal P1 via a conductive member (not shown) (e.g., a rotary connector, a slip ring, a carbon brush, etc.). The first gear G1 is electrically connected to the first connection terminal P1 via the first shaft X1.

[0010] The second gear G2 is a driven gear having a second usable tooth surface T2 and is rotatably supported by a second shaft X2. The second gear G2 meshes with the first gear G1 and rotates about the second shaft X2 in accordance with the rotation of the first gear G1. The second shaft X2 is electrically connected to a second connection terminal P2 via a conductive member (not shown) (e.g., a rotary connector, a slip ring, a conductive brush, etc.). The second gear G2 is electrically connected to the second connection terminal P2 via the second shaft X2. The first usable tooth surface T1 of the first gear G1 meshes with the second usable tooth surface T2 of the second gear G2.

[0011] In the electric circuit 10 of this embodiment, the first gear G1 is connected to a first side of the first resistor R1 (point a in FIG. 1 ) and a first side of the voltmeter VM (point c in FIG. 1 ). The second gear G2 is connected to a second side of the first resistor R1 (point b in FIG. 1 ) and a second side of the voltmeter VM (point d in FIG. 1 ). The second gear G2 is directly connected to the negative electrode of the DC power supply B. The positive electrode of the DC power supply B is connected to a first side of the second resistor R2 (point e in FIG. 1 ). The second side of the second resistor R2 (point f in FIG. 1 ) is connected to the first gear G1. Note that the electric circuit 10 may be configured such that the first gear G1 is directly connected to the positive electrode of the DC power supply B, the negative electrode of the DC power supply B is connected to the first side of the second resistor R2 (point e), and the second side of the second resistor R2 (point f) is connected to the second gear G2. The electric circuit 10 may also be configured such that the first gear G1 is directly connected to the negative electrode of the DC power supply B, the positive electrode of the DC power supply B is connected to a first side (point e) of the second resistor R2, and the second side (point f) of the second resistor R2 is connected to the second gear G2. Furthermore, the electric circuit 10 may also be configured such that the second gear G2 is directly connected to the positive electrode of the DC power supply B, the negative electrode of the DC power supply B is connected to the first side (point e) of the second resistor R2, and the second side (point f) of the second resistor R2 is connected to the first gear G1.

[0012] (Method of measuring voltage using an electric circuit) The method of determining the state between the available tooth surfaces T1, T2 of the gear pair GP of the present disclosure is performed by measuring the voltage V between the gear pair GP using an electric circuit 10 shown in Fig. 1. In the method of determining the state between the available tooth surfaces T1, T2 of the gear pair GP of the present disclosure, the voltage V is measured by a voltmeter VM while a DC power source B is supplying a DC current to the gear pair GP, while the first gear G1 is being driven to rotate and the second gear G2 is being driven to rotate. In the following description, the raw data of the voltage V measured by the voltmeter VM is also referred to as the voltage VR.

[0013] (Lubrication condition between available tooth surfaces of gear pairs) As shown in FIG. 1, in an electric circuit 10, a lubricant J is interposed between a first usable tooth surface T1 and a second usable tooth surface T2. In this description, when the first usable tooth surface T1 and the second usable tooth surface T2 are completely separated by an oil film (lubricant J), the lubrication state between the first usable tooth surface T1 and the second usable tooth surface T2 is said to be in a "hydrodynamic lubrication" state. On the other hand, when the first usable tooth surface T1 and the second usable tooth surface T2 are not completely separated by the oil film (lubricant J) and a portion of the first usable tooth surface T1 and the second usable tooth surface T2 are in direct contact, the lubrication state between the first usable tooth surface T1 and the second usable tooth surface T2 is said to be in a "mixed lubrication" state. Note that in the "mixed lubrication" state, a portion of the first usable tooth surface T1 and the second usable tooth surface T2 is separated by an oil film (lubricant J). When the state between the usable tooth surfaces T1, T2 of the gear pair GP is determined to be a "contact state" as described below, the lubrication state between the usable tooth surfaces T1, T2 of the gear pair GP is evaluated to be "hydrodynamic lubrication," and when the state between the usable tooth surfaces T1, T2 of the gear pair GP is determined to be a "separated state" as described below, the lubrication state between the usable tooth surfaces T1, T2 of the gear pair GP is evaluated to be "mixed lubrication."

[0014] (Regarding processing equipment) 1, in electric circuit 10, voltmeter VM is connected to processing device 20. Processing device 20 is configured by a computer, and includes an arithmetic processing unit 21 configured by a CPU, a memory unit 22 that stores various data, and an output unit 23 (e.g., a display) that outputs the determination results by arithmetic processing unit 21.

[0015] The voltage VR measured by the voltmeter VM is input to the processing device 20. The calculation processing unit 21 calculates the voltage VR according to an installed program. The calculation processing unit 21 determines the state of the first usable tooth surface T1 and the second usable tooth surface T2 of the gear pair GP based on the result of calculating the voltage VR. The memory unit 22 stores the input voltage VR, a threshold value (threshold value Vth described later), etc.

[0016] The calculation processing unit 21 has a filter processing unit 24, a contact state determination unit 25, and a lubrication state index calculation unit 26 as functional units that perform each calculation process.

[0017] (About filter processing) 2 is a diagram showing a voltage measured by an electric circuit, a voltage after processing by a median filter, and a voltage after processing by a moving average filter. As shown in FIG. 2, the filter processing unit 24 of the processing device 20 filters the voltage VR input from the voltmeter VM. In this embodiment, the processing device 20 performs two-stage filtering.

[0018] (median filter) The filter processing unit 24 performs a first stage of filtering on the voltage VR using a median filter F1. The median filter F1 extracts multiple (e.g., five) adjacent voltage VR values ​​in time series and replaces the median value of the multiple voltage VR values ​​with the value of the multiple intermediate data VP1. The filtering by the median filter F1 is mainly intended to remove noise contained in the voltage VR. The filter processing unit 24 filters the voltage VR (see the upper diagram in FIG. 2) using the median filter F1 to generate intermediate data VP1 (middle diagram in FIG. 2). As shown in FIG. 2, the intermediate data VP1 is data obtained by removing noise from the voltage VR.

[0019] (moving average filter) The filter processing unit 24 performs second-stage filtering on the intermediate data VP1 using a moving average filter F2. The moving average filter F2 extracts values ​​of multiple (e.g., five) adjacent sets of intermediate data VP1 in time series and replaces the average value of the multiple sets of intermediate data VP1 with the value of the multiple sets of determination voltage data VP2. The filtering by the moving average filter F2 is primarily intended to smooth the waveform of the voltage VR. The filter processing unit 24 filters the intermediate data VP1 (see the middle diagram in Figure 2) using the moving average filter F2 to generate determination voltage data VP2 (see the bottom diagram in Figure 2). As shown in Figure 2, the determination voltage data VP2 is data obtained by smoothing the intermediate data VP1.

[0020] (Method for determining the condition of the available tooth surface gap of a gear pair) FIG. 3 is a flow diagram of a method of determining the condition between the usable tooth surfaces T1 and T2 of a gear pair and evaluating the lubrication state between the usable tooth surfaces T1 and T2 according to the present disclosure. FIG. 4 is an explanatory diagram of thresholds used to determine the condition between the usable tooth surfaces T1 and T2 of a gear pair. FIG. 5 is a diagram showing changes in voltage accompanying the rotation of the first gear. Here, a method of determining the condition between the usable tooth surfaces T1 and T2 of a gear pair GP and evaluating the lubrication state between the usable tooth surfaces T1 and T2 using an electric circuit 10 (see FIG. 1) will be described. As shown in FIG. 3, when determining the condition between the usable tooth surfaces T1 and T2 of the gear pair GP and evaluating the lubrication state between the usable tooth surfaces T1 and T2 using the electric circuit 10 (see FIG. 1), a user first performs the following preparation step (S0).

[0021] In the preparation step (S0), the user first measures the voltage V for a certain period of time using the electric circuit 10 in a state in which no lubricant J is interposed between the first usable tooth surface T1 and the second usable tooth surface T2. In the preparation step (S0), the calculation processing unit 21 of the processing device 20 calculates the mean value Vmean, normal distribution, and standard deviation σ (see FIG. 4) of the voltage V measured at this time. The calculation processing unit 21 further calculates the threshold value Vth based on the calculated mean value Vmean and standard deviation σ (see FIG. 4).

[0022] In this embodiment, the calculation processing unit 21 adopts the value of the average value Vmean+3σ as the threshold value Vth (see FIG. 4). In the evaluation method for a gear pair GP of the present disclosure, after performing the preparation step (S0), the user further performs the following steps (S1) to (S5).

[0023] As shown in FIG. 3 , in the method of determining the condition between the available tooth surfaces T1 and T2 of a gear pair GP and evaluating the lubrication state between the available tooth surfaces T1 and T2 of the gear pair GP of the present disclosure, a user executes a first step (S1). In the first step (S1), the user uses an electric circuit 10 to measure the voltage VR of the gear pair GP to be evaluated. The measurement of the voltage VR is performed for a sampling time ST. A preferred sampling time ST is the time required for the second gear G2, which is the driven gear, to make one rotation. At this time, the processing device 20 acquires the voltage VR. The processing device 20 stores the acquired voltage VR in the memory unit 22. In the method of evaluating the gear pair GP of the present disclosure, the processing device 20 acquires the voltage VR for each rotation speed of the first gear G1. Note that a more preferred method of evaluating the gear pair GP of the present disclosure is a method in which the voltage VR is acquired for each condition of the driving torque of the first gear G1, the temperature, and the kinematic viscosity of the lubricating oil J. The kinematic viscosity is expressed as the kinematic viscosity at two temperatures, for example, "100 mm2 / s@40°C 20 mm2 / s@100°C."

[0024] In the evaluation method for a gear pair GP of the present disclosure, the processing device 20 then executes a second step (S2). In the second step (S2), the filtering unit 24 performs filtering on the acquired voltage VR using the median filter F1 to generate intermediate data VP1.

[0025] In the method for determining the condition between the available tooth surfaces T1, T2 of a gear pair GP and evaluating the lubrication state between the available tooth surfaces T1, T2 of the gear pair GP disclosed herein, the processing device 20 then executes a third step (S3). In the third step (S3), the filter processing unit 24 performs filtering on the generated intermediate data VP1 using a moving average filter F2 to generate determination voltage data VP2. Note that in the method for evaluating a gear pair GP disclosed herein, the filter processing unit 24 performs filtering on the voltage VR acquired by the electric circuit 10 using a filter different from the median filter F1 and the moving average filter F2.

[0026] In the method of determining the state between the usable tooth surfaces T1, T2 of a gear pair GP and evaluating the lubrication state between the usable tooth surfaces T1, T2 according to the present disclosure, the processing device 20 then executes a fourth step (S4). In the fourth step (S4), the contact state determination unit 25 of the calculation processing unit 21 determines the state between the usable tooth surfaces T1, T2 using the threshold value Vth for the generated determination voltage data VP2.

[0027] Figure 5 shows the change in voltage V (determination voltage data VP2) accompanying the rotation of the first gear G1. As shown in Figure 5, when the value of the determination voltage data VP2 is greater than the threshold value Vth, the contact state determination unit 25 determines that the state between the first usable tooth surface T1 and the second usable tooth surface T2 is a "separated state," and when the value of the determination voltage data VP2 is equal to or less than the threshold value Vth, the contact state determination unit 25 determines that the state between the first usable tooth surface T1 and the second usable tooth surface T2 is a "contact state."

[0028] The method of determining the state between the available tooth surfaces T1, T2 of the gear pair GP according to the present disclosure can suppress the influence of noise and accurately determine the state between the available tooth surfaces of the gear pair GP based on the smoothed determination voltage data VP2 and the threshold value Vth.

[0029] As shown in FIG. 5 , the method for determining the state between the available tooth surfaces T1 and T2 of the gear pair GP of the present disclosure can confirm how the voltage VR changes with the rotation of the first gear G1 from the start of meshing between the first available tooth surface T1 and the second available tooth surface T2 to the end of meshing. In other words, the method for determining the state between the available tooth surfaces T1 and T2 of the gear pair GP expresses the changes in the "contact state" and "separation state" that accompany the rotation of the first gear G1. The method for determining the state between the available tooth surfaces T1 and T2 of the gear pair GP of the present disclosure can more accurately determine the state between the first available tooth surface T1 and the second available tooth surface T2 of the gear pair GP than conventional methods. Furthermore, when this determination method determines the state between the available tooth surfaces T1 and T2 of the gear pair GP as "contact state," the lubrication state between the available tooth surfaces T1 and T2 of the gear pair GP is evaluated as "hydrodynamic lubrication." When this determination method determines that the state between the usable tooth surfaces T1 and T2 of the gear pair GP is in a "separated state," the lubrication state between the usable tooth surfaces T1 and T2 of the gear pair GP is evaluated as "mixed lubrication."

[0030] In the method for determining the condition between usable tooth surfaces T1, T2 of a gear pair GP and the method for evaluating the lubrication condition of the present disclosure, the processing device 20 then executes a fifth step (S5). In the fifth step (S5), the lubrication condition index calculation unit 26 of the arithmetic processing unit 21 calculates a lubrication condition index (LCI) based on the determination result of the determination voltage data VP2 relative to the threshold value Vth.

[0031] The lubrication condition index calculation unit 26 calculates the lubrication condition index LCI using the following formula (1): Note that the value "N" in formula (1) is the number of samples of the voltage VR during the sampling time ST (the total number of measurement data of the voltage V), and the value "Ns" is the number of measurement data determined to be in a "separated state" out of the total number of measurement data during the sampling time ST. If the sampling period of the voltage VR is f, the number of samples of the voltage VR is calculated by multiplying the sampling period ST by the sampling period f.

[0032] (Number 1) LCI=Ns / N (1)

[0033] (Lubrication condition index) The ideal lubrication state between the first usable tooth flank T1 and the second usable tooth flank T2 of the gear pair GP is a state in which "hydrodynamic lubrication" is always achieved. In other words, the preferable lubrication state between the first usable tooth flank T1 and the second usable tooth flank T2 of the gear pair GP is a state in which "mixed lubrication" is rarely achieved. A gear pair GP in an ideal state has a lubrication condition index LCI of "1." In other words, the lubrication condition index LCI is an index that indicates the quality of the lubrication state between the first usable tooth flank T1 and the second usable tooth flank T2 of the gear pair GP. The closer the lubrication condition index LCI of the gear pair GP is to "1," the better the lubrication state between the first usable tooth flank T1 and the second usable tooth flank T2 is judged to be. Furthermore, when comparing two gear pairs GP, the lubrication condition between the first usable tooth flank T1 and the second usable tooth flank T2 of the gear pair GP with the larger lubrication condition index LCI is judged to be better than the lubrication condition between the first usable tooth flank T1 and the second usable tooth flank T2 of the other gear pair GP. Furthermore, if the lubrication condition indices LCI of two gear pairs GP are equal, the lubrication conditions between the first usable tooth flank T1 and the second usable tooth flank T2 of the two gear pairs GP are judged to be equivalent.

[0034] Fig. 6 shows the lubrication condition index (LCI) used to evaluate the lubrication condition between the usable tooth flanks of a gear pair, and an index obtained by dividing the average value of the measured voltage by the value of the applied voltage. Fig. 6 shows the lubrication condition index (LCI) and an index X (X = Vmean / Vin) obtained by dividing the average value Vmean of the voltage VR by the applied voltage Vin. The index X is a normalized value obtained by dividing the average value Vmean of the voltage VR used in the conventional method for evaluating the lubrication condition between the usable tooth flanks of a gear pair by the applied voltage Vin.

[0035] As shown in Figure 6, the index X is a value that appears in the range of approximately 0 to 0.6. On the other hand, the lubrication condition index LCI is a value that appears in the range of approximately 0 to 0.85, which is a wider range of values ​​than the index X. The method of evaluating the lubrication condition between usable tooth flanks using the lubrication condition index LCI provides more precise indices than the method of evaluating the lubrication condition between usable tooth flanks using the index X, so the lubrication condition between the first usable tooth flank T1 and the second usable tooth flank T2 of the gear pair GP can be evaluated with greater sensitivity than conventional methods.

[0036] In contrast, the conventional method for evaluating the lubrication state between usable tooth flanks using the index X uses the average value of the voltage VR over a certain period of time. Therefore, the conventional method for evaluating the lubrication state between usable tooth flanks using the index X is not a method for accurately evaluating the lubrication state of an object whose contact state changes from moment to moment, such as the usable tooth flanks of a gear. On the other hand, the method for evaluating the lubrication state between usable tooth flanks using the lubrication state index LCI evaluates the lubrication state that changes between the first usable tooth flank T1 and the second usable tooth flank T2 from the start to the end of meshing. Therefore, the method for evaluating the lubrication state between the usable tooth flanks of a gear pair GP disclosed herein can evaluate the lubrication state between the first usable tooth flank T1 and the second usable tooth flank T2 of the gear pair GP more accurately than the conventional method for evaluating the lubrication state between usable tooth flanks.

[0037] As described above, the method of determining the state between the usable tooth surfaces of the gear pair GP of the present disclosure is a determination method in which a DC current is passed through the gear pair GP in the electric circuit 10, and the voltage VR is measured with the voltmeter VM while the first gear G1 and the second gear G2 are rotating. If the measured voltage VP2 is greater than the threshold value Vth (VP2>Vth), it is determined that the first usable tooth surface T1 and the second usable tooth surface T2 are in a "separated state." If the measured voltage VR (VP2) is equal to or smaller than the threshold value Vth (VP2≦Vth), it is determined that the first usable tooth surface T1 and the second usable tooth surface T2 are in a "contact state" in which at least a portion of the first usable tooth surface T1 and the second usable tooth surface T2 are in contact.

[0038] Furthermore, the method for evaluating the lubrication state between the usable tooth surfaces of the gear pair GP of the present disclosure is an evaluation method in which a direct current is passed through the gear pair GP in an electric circuit 10, and the voltage VR is measured with a voltmeter VM while the first gear G1 and the second gear G2 are rotated. If the measured voltage VP2 is greater than a threshold value Vth (VP2>Vth), the first usable tooth surface T1 and the second usable tooth surface T2 are evaluated as being in "fluid lubrication," in which they are in contact with each other via an oil film. If the measured voltage VR (VP2) is equal to or smaller than the threshold value Vth (VP2≦Vth), the first usable tooth surface T1 and the second usable tooth surface T2 are evaluated as being in "mixed lubrication," in which they are in contact with each other at least partially without an oil film.

[0039] (Regarding sampling time) As shown in FIG. 5 , the disclosed method for determining the condition between the usable tooth flanks of a gear pair GP and the method for evaluating the lubrication state between the usable tooth flanks can individually determine the condition between the first usable tooth flank T1 and the second usable tooth flank T2, assuming that the time from the start of meshing between a first usable tooth flank T1 and a second usable tooth flank T2 to the end of meshing is the sampling time ST. As a result, the disclosed method for determining the condition between the usable tooth flanks of a gear pair GP and the method for evaluating the lubrication state between the usable tooth flanks can identify combinations of the first usable tooth flank T1 and the second usable tooth flank T2 that have poor lubrication conditions among all combinations of the first usable tooth flank T1 and the second usable tooth flank T2 in the gear pair GP. By modifying the shapes of the first usable tooth flank T1 and the second usable tooth flank T2 identified as having poor lubrication conditions, the lubrication state between the first usable tooth flank T1 and the second usable tooth flank T2 can be improved.

[0040] Furthermore, the method for determining the condition of the usable tooth flanks of the gear pair GP and the method for evaluating the lubrication condition of the usable tooth flanks of the gear pair GP disclosed herein can easily determine the lubrication condition of the entire gear pair GP (first gear G1 and second gear G2) when the time it takes for the second gear G2 to make one rotation is used as the sampling time ST. Furthermore, the method for determining the condition of the usable tooth flanks of the gear pair GP and the method for evaluating the lubrication condition of the usable tooth flanks of the gear pair GP disclosed herein can use a sampling time ST that is longer than the time it takes for the second gear G2 to make one rotation (for example, the time it takes for the second gear G2 to make two or more rotations). In this case, the cumulative lubrication condition of the entire gear pair GP (first gear G1 and second gear G2) can be evaluated. [Explanation of symbols]

[0041] 10: Electrical Circuits (Circuits) GP: Gear Pair G1: First gear G2: Second gear T1: First usable tooth surface T2: Second usable tooth surface X1: First axis X2: Second axis R1: First Resistance R2: Second Resistance VM: Voltmeter B: DC power supply VR: (raw data) voltage VP2: (filtered) voltage Vth: Threshold voltage

Claims

1. A method for determining a condition between usable tooth flanks of a gear pair including a drive gear having a first usable tooth flank and a driven gear having a second usable tooth flank that contacts the first usable tooth flank, using a circuit including the gear pair, a DC power supply, a voltmeter, a first resistor, a second resistor, and lubricating oil, comprising: the circuit connects the drive gear, a first side of the first resistor, and a first side of the voltmeter, connects the driven gear, a second side of the first resistor, and a second side of the voltmeter, directly connects one of the positive and negative poles of the DC power source to one of the drive gear and the driven gear, connects the other of the positive and negative poles to the first side of the second resistor, connects the second side of the second resistor to the other of the drive gear and the driven gear, and interposes the lubricating oil between the first usable tooth surface and the second usable tooth surface; A direct current is applied to the gear pair in the circuit, and the voltage is measured with the voltmeter while rotating the drive gear and the driven gear. If the measured voltage is greater than a threshold value, it is determined that the first usable tooth surface and the second usable tooth surface are in a separated state in which they are in contact with each other via an oil film; If the measured voltage is equal to or smaller than the threshold value, it is determined that the first usable tooth surface and the second usable tooth surface are in contact with each other at least partially without an oil film therebetween. A method for determining the condition of the available tooth flanks of a gear pair.

2. Regarding the voltage measured by the voltmeter, The average value when the drive gear is rotated for a certain period of time is Calculation is performed for each condition of the rotational speed and torque of the drive gear, the temperature and kinematic viscosity of the lubricating oil.

2. The method for determining the condition of the available tooth flank gap of a gear pair according to claim 1.

3. When the state between the first usable tooth flank and the second usable tooth flank is determined to be a "contact state" by the method for determining the state between usable tooth flanks of a gear pair according to claim 1 or 2, the lubrication state between the usable tooth flanks of the gear pair is evaluated to be a "hydrodynamic lubrication", a method for evaluating the lubrication state between the usable tooth flanks of a gear pair, wherein when the state between the first usable tooth flank and the second usable tooth flank is determined to be a "separated state", the lubrication state between the usable tooth flanks of the gear pair is evaluated to be "mixed lubrication".

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