JP7728231B2 - Oil change notification device and work machine - Google Patents

Description

The present invention relates to an oil change notification device and a work machine.

A known example of a work machine capable of estimating when to change oil is the work machine disclosed in Patent Document 1.

Patent No. 7009408

In the prior art, there was room for consideration in terms of appropriately determining when to change the oil.
An object of the present invention is to provide an oil change determination/notification device and a work machine that can appropriately determine when it is time to change oil and notify the user that it is time to change the oil.

An oil change determination and notification device according to one aspect of the present invention is an oil change determination and notification device that determines and notifies the user when it is time to change the oil that operates a hydraulic drive unit, and includes: an acquisition unit that acquires the dielectric constant and oil temperature of the oil; a recording unit that records relationship data between the oil temperature and the dielectric constant when the oil temperature of the oil drops within a predetermined temperature range; a coefficient calculation unit that performs linear regression on the relationship data between the oil temperature and the dielectric constant recorded in the recording unit to calculate a temperature-dependent coefficient; a calculation unit that uses the temperature-dependent coefficient to convert the dielectric constant acquired by the acquisition unit into a dielectric constant at a predetermined oil temperature; a determination unit that determines when the oil should be changed based on the dielectric constant calculated by the calculation unit; and a notification device that notifies the user that it is time to change the oil when the determination unit determines that it is time to change the oil.

The determination unit may estimate the amount of contamination in the oil based on the dielectric constant calculated by the calculation unit, and determine when the oil should be changed and the reason for changing the oil, and the alarm device may notify the user of the time when the oil should be changed and the reason for changing the oil.
When the dielectric constant calculated by the calculation unit exceeds a predetermined upper threshold, the determination unit determines that the amount of contaminants mixed into the oil exceeds a predetermined amount and determines that it is time to change the oil, and the alarm device may be configured to notify that the reason the oil should be changed is that the amount of contaminants mixed into the oil exceeds a predetermined amount and that it is time to change the oil.

The oil change determination notification device may include a judgment unit that determines whether the viscosity and density of the oil have increased relative to a reference value, and if the viscosity and density have increased relative to the reference value, the judgment unit may determine that the contaminants mixed in the oil are wear powder, and the notification device may issue a notification that the contaminants mixed in the oil are wear powder.
The oil change determination notification device may include a judgment unit that judges whether the viscosity and density of the oil have increased relative to a reference value, and if the viscosity and density have not increased relative to the reference value, the judgment unit may judge that the contaminant mixed in the oil is water, and the notification device may issue a notification that the contaminant mixed in the oil is water.

The device may be provided with a measurement sensor that measures the dielectric constant and oil temperature of the oil, the acquisition unit acquires the dielectric constant and oil temperature from the measurement sensor, and the calculation unit calculates the dielectric constant at the oil temperature obtained from the measurement sensor into a dielectric constant at the specified temperature.
In a work machine equipped with the oil change determination notification device and a gear-type transmission, the oil may also serve as a lubricating oil for the gear-type transmission.

The work machine may include a hydrostatic continuously variable transmission, a supply line that supplies the oil to a charge circuit of the hydrostatic continuously variable transmission, an oil filter provided in the supply line, and a measurement sensor that measures at least the dielectric constant or oil temperature of the oil acquired by the acquisition unit, and the measurement sensor may be configured to perform the measurement of the oil flowing upstream or downstream of the oil filter in the supply line.

The work machine includes a hydrostatic continuously variable transmission, a supply line that supplies the oil to a charge circuit of the hydrostatic continuously variable transmission, a return line through which oil returning from the supply line flows, an oil cooler provided in the return line, and a measurement sensor that measures at least the dielectric constant or oil temperature of the oil acquired by the acquisition unit, and the measurement sensor may be configured to measure the oil flowing upstream or downstream of the oil cooler in the return line.

The work machine may include steering wheels, a steering cylinder that steers the steering wheels, a hydraulic controller that receives the oil and operates the steering cylinder, and a measurement sensor that measures at least the dielectric constant or oil temperature of the oil acquired by the acquisition unit, and the measurement sensor may be configured to measure the oil supplied to the hydraulic controller or the oil returning from the hydraulic controller.

The work machine includes a vehicle body, a lift cylinder that raises and lowers an implement attached to the vehicle body, a lift control valve that receives the oil and controls the lift cylinder, and a measurement sensor that measures at least the dielectric constant or oil temperature of the oil acquired by the acquisition unit, and the measurement sensor may be configured to measure the oil discharged from the lift control valve, the oil supplied to the lift control valve, or the oil returning from the lift cylinder.

With the above configuration, the oil's dielectric constant is calculated to the dielectric constant at a specified oil temperature, and the time to change the oil is determined based on this calculated dielectric constant, making it possible to appropriately determine when the oil needs to be changed and to notify the driver that it is time to change the oil.

FIG. 1 is a side view of a tractor as a work machine. FIG. 2 is a circuit diagram showing a hydraulic system. FIG. 2 is a diagram illustrating the configuration of an oil change determination notification device. 4 is a flowchart showing the processing operation of the oil change determination notification device. 1 is a graph showing the relationship between dielectric constant and time. FIG. 2 is a circuit diagram showing the installation locations of measurement sensors. FIG. 2 is a circuit diagram showing the installation locations of measurement sensors. FIG. 2 is a circuit diagram showing the installation locations of measurement sensors.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate.
1 is a schematic side view showing the overall configuration of a work machine 1 according to this embodiment. In this embodiment, a tractor is shown as an example of the work machine 1.
As shown in Figure 1, the tractor 1 has a body 2, front wheels 4 arranged on the left and right of a front frame 3 that supports the front of the body 2, rear wheels 5 arranged on the left and right of the rear of the body 2, and a driver's section 8 arranged above the body 2 and equipped with a steering wheel 6, a driver's seat 7 in which an operator sits, etc.

A work implement lifting hydraulic system 9 and a power take-off shaft (PTO shaft) 10 are provided at the rear of the vehicle body 2. The work implement lifting hydraulic system 9 is a device that raises and lowers an implement that is attached to the rear of the vehicle body 2 via a connecting mechanism such as a three-point linkage so that it can be raised and lowered. The PTO shaft 10 is a shaft that takes off power from the tractor 1 to transmit power from the tractor 1 to the implement.

The vehicle body 2 has an engine (prime mover) 11 supported by the front frame 3, a housing case 12 connected to the rear of the engine 11, and a transmission case 13 connected to the rear of the housing case 12. The housing case 12 houses a flywheel 14 that stabilizes the rotation of the crankshaft of the engine 11, a main clutch 15 that transmits power from the flywheel 14 in an intermittent manner, and the like.

The transmission case 13 is composed of a first case 17 that houses a hydrostatic continuously variable transmission (HST) 16 and a second case 19 that houses a geared transmission 18. The HST 16 transmits power from the main clutch 15 to the geared transmission 18. The geared transmission 18 has a traction transmission and a PTO transmission. The traction transmission transmits the power output from the HST 16 to the rear wheel differential and to the rear wheels 5 (drive wheels) via the rear wheel differential. The PTO transmission transmits the power from the main clutch 15 to the PTO shaft 10 before it is shifted by the HST 16. In other words, the HST 16 transmits power to the traction transmission in the geared transmission 18, but does not transmit power to the PTO transmission.

The second case 19 stores transmission oil (oil), a lubricating oil that lubricates the gear transmission 18, rear wheel differential, and other components. In the tractor 1, this oil also serves as hydraulic oil to operate the hydraulic drive system equipped on the tractor 1. In other words, the tractor 1 is equipped with a hydraulic drive system that is driven by hydraulic pressure, and transmission oil is used as the hydraulic oil to operate this hydraulic drive system. The second case 19 is an oil tank (oil storage section) in which oil is stored.

FIG. 2 shows the hydraulic system (hydraulic circuit) of the tractor 1.
The hydraulic system includes hydraulic drive devices such as a power steering device 21, HST 16, work implement lifting hydraulic device 9, and clutch actuation device 22, which are driven by oil (hydraulic pressure) that also serves as transmission oil. The hydraulic system also includes a plurality of hydraulic pumps 23 that suck in and discharge oil stored in a second case 19. The plurality of hydraulic pumps 23 include a first pump 23A, a second pump 23B, and a third pump 23C. The first pump 23A, the second pump 23B, and the third pump 23C are configured as fixed displacement hydraulic pumps driven by the engine 11. It should be noted that at least one hydraulic pump is sufficient.

The power steering device 21 has a steering cylinder 24 that steers the left and right front wheels 4 (steerable wheels), and a hydraulic controller 25 that operates the steering cylinder 24. The hydraulic controller 25 has a steering valve 26 that is operated by the steering wheel 6 to switch the direction of oil, a metering pump 27 that measures and supplies an amount of oil to the steering cylinder 24 according to the degree of rotation of the steering wheel 6, a relief valve 28, and a check valve 29. The hydraulic controller 25 (steering valve 26) is supplied with oil discharged from the second pump 23B.

The HST 16 includes a swash plate-type variable displacement pump (HST pump) 31 and an HST motor 33. The HST motor 33 is connected to the HST pump 31 in a closed circuit via a pair of transmission oil passages 32a and 32b and is driven by oil discharged from the HST pump 31 to output power. The HST 16 also includes a servo cylinder 34 that controls the swash plate of the HST pump 31, a swash plate control valve 35 that controls the servo cylinder 34, and a charge circuit 36 that replenishes oil to the pair of transmission oil passages 32a and 32b. Oil discharged from the third pump 23C is supplied to the charge circuit 36 via a supply line 37. The supply line 37 is provided with an oil filter (HST filter) 38. The supply line 37 is also connected to a return line 39 through which oil flows from the supply line 37 back to the second case 19. The return line 39 is provided with a relief valve 40 and an oil cooler 41 located downstream of the relief valve 40.

On the other hand, the oil flowing through the supply line 37 after passing through the oil filter 38 is branched and supplied to the swash plate control valve 35 and the clutch actuator 22 via a pressure compensation valve 42 .
The work implement lifting hydraulic system 9 has a hydraulic case 43, lift cylinders 44 that raise and lower lift arms disposed on the left and right of the hydraulic case 43, a lift control valve 45 that controls the lift cylinders 44, a descent speed adjustment valve 68 that controls the descent speed of the implement connected to the connecting mechanism, and a safety valve 46 for the lift cylinders 44. The work implement lifting hydraulic system 9 (lift control valve 45) is supplied with oil discharged from the first pump 23A.

The lift arm is connected to the connecting mechanism (three-point linkage) via a lift rod. The lift cylinder 44 is a single-acting hydraulic cylinder that swings the lift arm upward when oil is supplied to it, and swings the lift arm downward when oil is discharged. The lift arm moves up and down, thereby raising and lowering the connecting mechanism and the implement. In other words, the lift cylinder 44 is a hydraulic cylinder that raises and lowers the implement attached to the vehicle body 2. The lift control valve 45 includes a main spool valve 69. The main spool valve 69 can be switched between a position that supplies oil supplied from the first pump 23A to the lift cylinder 44, a position that returns oil drained from the lift cylinder 44 to the second case 19 via the descent speed adjustment valve 68 and shutoff valve 70, and a position that returns oil supplied from the first pump 23A to the second case 19 but does not drain oil from the lift cylinder 44.

The clutch operating device 22 is a device that operates a clutch that interrupts the power transmission of the PTO system transmission mechanism, and has a clutch operating cylinder 20 that operates the clutch, and a clutch operating valve 30 that operates the clutch operating cylinder 20.
In work machines that use transmission oil as hydraulic fluid for hydraulic equipment, wear particles can get into the oil due to wear on drivetrain components, and water can get into the oil when used or stored in a humid environment. To prevent machine failures caused by wear particles or water getting into the oil, recommended oil change intervals are determined through market research and reproduction tests such as bench tests and actual vehicle tests. However, because the amount of wear particles and water mixed in varies depending on individual differences in the machine, the user's usage conditions, and the usage environment, it is difficult to determine the appropriate oil change interval based on the length of time the oil has been used.

Therefore, the tractor 1 of this embodiment is equipped with an oil change determination and notification device 47 (see Figure 3) that can determine the appropriate time to change the oil and notify the operator that it is time to change the oil.
As shown in FIG. 3, the oil change determination/notification device 47 includes a measurement sensor 48 , a determination device 49 , and a notification device 50 .
The measurement sensor 48 measures the dielectric constant, oil temperature, viscosity, and density of the oil. Specifically, the measurement sensor 48 is composed of a plurality of sensors, including a dielectric constant sensor 48A that measures the dielectric constant of the oil, a temperature sensor 48B that measures the oil temperature, a viscosity sensor 48C that measures the viscosity of the oil, and a density sensor 48D that measures the density of the oil.

In addition, the measurement sensor 48 may be a single sensor that measures the dielectric constant, oil temperature, viscosity, and density (a single sensor body that has the function of measuring the dielectric constant, oil temperature, viscosity, and density).
In order to ensure stable measurements and to constantly monitor the oil, it is desirable to install the measurement sensor 48 where there is a flow of oil circulating through the hydraulic system and where the oil pressure (oil pressure) is maintained within a range that does not cause problems for the sensor's operation. Also, it can be said that a suitable location for installing the measurement sensor 48 is somewhere in the pipeline connecting the hydraulic components.

Figure 2 shows an example of the installation location of the measurement sensor 48, indicated by the symbol A1. As shown in Figure 2, in this embodiment, the measurement sensors 48 (dielectric constant sensor 48A, temperature sensor 48B, viscosity sensor 48C, and density sensor 48D) are installed in the supply line 37, in the line 37a between the third pump 23C and the oil filter 38. Specifically, the measurement sensors 48 are installed upstream of and near the oil filter 38 and measure the dielectric constant, oil temperature, viscosity, and density of the oil flowing upstream of the oil filter 38. A relief valve 40 is often installed near the oil filter 38, making this an ideal location for installing the measurement sensors 48. Furthermore, installing the measurement sensors 48 upstream of the oil filter 38 has the advantage that if the measurement sensor 48 is damaged, debris will not flow through the hydraulic circuit and reach and damage the hydraulic equipment. Another advantage is that the measurement sensors 48 can be easily installed near the oil filter 38.

The determination device 49 is configured using, for example, a microcomputer equipped with a CPU, an EEPROM, etc. A dielectric constant sensor 48A, a temperature sensor 48B, a viscosity sensor 48C, and a density sensor 48D are connected to the determination device 49, and the dielectric constant measured by the dielectric constant sensor 48A, the oil temperature measured by the temperature sensor 48B, the viscosity measured by the viscosity sensor 48C, and the density measured by the density sensor 48D are input to the determination device 49.
The determination device 49 includes an acquisition unit 51 , a calculation unit 52 , a storage unit 53 , a determination unit 54 , a judgment unit 61 , an output unit 55 , a recording unit 56 , and a coefficient calculation unit 57 .

The acquisition unit 51 acquires the dielectric constant, oil temperature, viscosity, and density of the oil. Specifically, the acquisition unit 51 acquires the dielectric constant, oil temperature, viscosity, and density obtained from the measurement sensors 48 (dielectric constant sensor 48A, temperature sensor 48B, viscosity sensor 48C, and density sensor 48D).
The dielectric constant, oil temperature, viscosity, and density obtained from the measurement sensor 48 may be the measured value itself, or may be a rounded value (approximate value) obtained by rounding the measured value.
The calculation unit 52 converts the dielectric constant obtained by the acquisition unit 51 into a dielectric constant at a predetermined oil temperature. In other words, the calculation unit 52 converts the dielectric constant obtained by the dielectric constant sensor 48A at the oil temperature obtained by the temperature sensor 48B into a dielectric constant at a predetermined oil temperature (e.g., 100°C). Note that the predetermined temperature is not limited to 100°C.

The physical properties of oil, such as its dielectric constant, depend linearly (proportional) on temperature, but because these coefficients can vary depending on factors such as the oil lot, it is desirable to calculate them as needed. In this process, contamination (foreign matter) in the oil and differences in the equipment's operating conditions can become noise, but this can be eliminated by using data from when large temperature changes occur in a short period of time. In other words, to accurately estimate the oil's physical properties, the calculation unit 52 converts the dielectric constant obtained from the dielectric constant sensor 48A into the dielectric constant at a specified temperature using a temperature-dependent coefficient determined from data on the relationship between oil temperature and dielectric constant when the oil temperature drops within a predetermined temperature range.

For example, when the oil temperature drops suddenly (temperature changes), such as immediately after the engine 11 is stopped, data on the relationship between oil temperature and dielectric constant is recorded, and a linear regression is performed on this relationship data to calculate a temperature-dependent coefficient. Using this temperature-dependent coefficient, the dielectric constant obtained from the dielectric constant sensor 48A is converted to the dielectric constant at a predetermined temperature.
Furthermore, the oil temperature during operation varies within a temperature range of, for example, approximately 50° C. to approximately 80° C. Furthermore, since the dielectric constant of oil changes depending on the temperature, in order to use the dielectric constant at the same temperature to determine the timing and reason for changing the oil, the calculation unit 52 converts the dielectric constant at the oil temperature obtained from the measurement sensor 48 into, for example, the dielectric constant when the oil temperature is 100° C. (dielectric constant at 100° C.).

The memory unit 53 pre-stores an upper threshold value that serves as the basis for determining whether the amount of contaminants mixed into the oil exceeds a predetermined amount, and a reference value that serves as the basis for determining whether the contaminants mixed into the oil are wear particles or moisture. The dielectric constant threshold value (upper threshold value) is determined as a physical quantity, for example, from the results of a bench test prepared in advance. In other words, the dielectric constant threshold value is determined based on the 100°C dielectric constant data from the bench test. This dielectric constant threshold value (upper threshold value) may also be determined as the relative change from when the oil was new. The reference values for viscosity and density can be, for example, the viscosity and density values before the dielectric constant exceeded the upper threshold value.

Contamination refers to foreign matter such as wear particles (metal wear particles) and moisture mixed into the oil.
The determination unit 54 determines when to change the oil based on the dielectric constant (dielectric constant at 100°C) calculated by the calculation unit 52. More specifically, the determination unit 54 determines when to change the oil by estimating the amount of contaminants mixed into the oil based on the dielectric constant calculated by the calculation unit 52. Specifically, when the dielectric constant at 100°C exceeds an upper threshold, the determination unit 54 determines that the amount of contaminants mixed into the oil exceeds a predetermined amount, and determines that it is time to change the oil.

Furthermore, the determination unit 54 determines the reason for changing the oil based on the dielectric constant (dielectric constant at 100°C) calculated by the calculation unit 52. More specifically, the determination unit 54 determines the reason for changing the oil by estimating the amount of contaminants mixed into the oil based on the dielectric constant calculated by the calculation unit 52. Specifically, when the dielectric constant at 100°C exceeds the upper limit threshold, the determination unit 54 determines that the reason for changing the oil is that the amount of contaminants mixed into the oil exceeds a predetermined amount.
As described above, the determining unit 54 quantitatively evaluates the deterioration of the oil based on the dielectric constant calculated by the calculating unit 52, thereby determining when the oil should be changed and the reason why the oil should be changed.

The judgment unit 61 determines whether the viscosity and density of the oil have increased relative to their reference values. More specifically, if the 100°C dielectric constant (dielectric constant at a specified temperature) exceeds the upper threshold (if the amount of contaminants mixed into the oil exceeds a specified amount) and the viscosity and density have increased relative to their reference values, the judgment unit 61 determines that the contaminants are wear particles. Also, if the 100°C dielectric constant (dielectric constant at a specified temperature) exceeds the upper threshold (if the amount of contaminants mixed into the oil exceeds a specified amount) and the viscosity and density have not increased relative to their reference values, the judgment unit 61 determines that the contaminants are water.

Whether the viscosity and density of the oil have increased relative to the reference values can be determined, for example, by comparing the viscosity and density before the 100°C dielectric constant exceeds the upper threshold with the viscosity and density after the upper threshold has been exceeded when the 100°C dielectric constant exceeds the upper threshold. In other words, although not limited to this, the determination unit 61 determines whether the viscosity and density have increased relative to the reference values based on whether the viscosity and density after the 100°C dielectric constant exceeds the upper threshold have increased compared to before the 100°C dielectric constant exceeded the upper threshold.

When the determination unit 54 determines that it is time to change the oil, the output unit 55 outputs a signal (alert signal) to the alarm device 50 indicating that it is time to change the oil. The output unit 55 also outputs the reason for the oil change determined by the determination unit 54 to the alarm device 50. More specifically, the output unit 55 outputs a signal to the alarm device 50 indicating that the reason for determining that it is time to change the oil is that the amount of contaminants mixed in the oil exceeds a predetermined amount. When the amount of contaminants mixed in the oil exceeds a predetermined amount and the viscosity and density have increased relative to their reference values, the output unit 55 outputs a signal to the alarm device 50 indicating that the contaminants mixed in the oil are wear particles, and when the viscosity and density have not increased relative to their reference values, the output unit 55 outputs a signal to the alarm device 50 indicating that the contaminants mixed in the oil are water.

The recording unit 56 records data on the relationship between oil temperature and dielectric constant when the oil temperature drops within a predetermined temperature range (when the oil temperature drops suddenly).
The coefficient calculation unit 57 performs linear regression on the data on the relationship between oil temperature and dielectric constant recorded in the recording unit 56 to calculate a temperature-dependent coefficient.
The notification device 50 is a device that can notify the operator that it is time to change the oil, the reason for the oil change, and whether the contaminants in the oil are wear particles or water, and is configured, for example, as a display device having a display unit that can display text indicating that it is time to change the oil and the reason for the oil change. The notification device 50 may also be a voice generating device that can notify the operator that it is time to change the oil by voice. The display device may also be equipped with a voice generating device in addition to a display unit that can display text. The display device may also be equipped with an alarm generating device that can sound a buzzer or the like that notifies the operator that it is time to change the oil.

The notification device 50 is connected to the determination device 49 and receives a signal output from the output unit 55 (determination device 49). Upon receiving the signal output from the output unit 55, the notification device 50 notifies the user that it is time to change the oil, the reason for changing the oil, and whether the contaminants in the oil are wear particles or water.
The notification device 50 is provided, for example, in the driver's section 8, and preferably in the vicinity of the driver's seat 7. When the notification device 50 is configured as a display device, it is preferable that the notification device 50 be provided in a position that is easily visible to the operator seated in the driver's seat 7.

4 is a flowchart showing the processing operation of the oil change determination/notification device 47. The processing operation of the oil change determination/notification device 47 will be described using this flowchart.
The processing operation begins after the engine 11 is started, and is performed in real time or at predetermined timing while the engine 11 is running.
After starting the processing operation, the oil change determination/notification device 47 first measures the dielectric constant and the oil temperature using the dielectric constant sensor 48A and the temperature sensor 48B (step S1). In practice, the acquisition unit 51 acquires the dielectric constant and the oil temperature obtained from the dielectric constant sensor 48A and the temperature sensor 48B.

After the dielectric constant and oil temperature are measured, the process proceeds to step S2, where the temperature correction of the dielectric constant is performed by the calculation unit 52. Specifically, the dielectric constant acquired by the acquisition unit 51 (dielectric constant at the oil temperature at the time of measurement) is calculated to the dielectric constant at a predetermined temperature (dielectric constant at 100°C).
Next, the determining unit 54 determines whether or not the 100° C. dielectric constant exceeds the upper limit threshold (step S3).

If the 100°C dielectric constant exceeds the upper threshold (step S3: YES), the determination unit 54 determines that contamination has been mixed into the oil (the amount of contamination mixed into the oil exceeds a predetermined amount) (step S4), and the output unit 55 outputs to the alarm device 50 a message that the reason for the oil change is the presence of contamination (the amount of contamination exceeds a predetermined amount) and that it is time to change the oil. The alarm device 50 then issues a message that the reason for the oil change is the presence of contamination (the amount of contamination exceeds a predetermined amount) and that it is time to change the oil (step S5).

On the other hand, if the 100° C. dielectric constant does not exceed the upper limit threshold in step S3 (step S3: NO), the process returns to step S1, and the processing operations from step S1 onwards are executed.
5 is a graph showing the relationship between the dielectric constant and time, with the horizontal axis representing time and the vertical axis representing the dielectric constant, and showing how the dielectric constant changes when it exceeds the upper threshold value. Note that the graph in FIG. 5 is simplified, but in reality, the graph exhibits an oscillating waveform.

In FIG. 5, reference numeral 58 denotes the upper threshold value of the dielectric constant, which is, for example, 2.26.
In bench tests, the dielectric constant value tends to decrease over time. This is thought to be because wear particles (metal wear particles) mixed in the oil settle over time, reducing the amount of wear particles flowing toward the installation location A1 (sensor installation location) of the measurement sensor 48. Specifically, when the engine is started, some of the wear particles in the oil are stirred up and reach the sensor installation location A1, causing the dielectric constant to increase. However, over time, the wear particles in the oil settle, reducing the amount of wear particles flowing toward the sensor installation location A1.

In an actual vehicle, the amount of wear debris stirred up and the rate at which it settles are expected to vary depending on the driving conditions, and therefore the amount of wear debris in the oil and the dielectric constant value are also expected to vary. However, this variation is expected to fall within the range observed in the bench test, and therefore the upper threshold value for the dielectric constant can be determined based on the data from the bench test.
As shown in FIG. 5, when the dielectric constant exceeds the upper threshold (see reference numeral 60), it is determined that it is time to change the oil, and the reason for changing the oil is determined to be that the amount of contaminants (wear particles, moisture) mixed in exceeds a predetermined amount.

When making this determination, if the dielectric constant rises sharply, exceeds the upper threshold, and then immediately (in a short time) falls below the upper threshold, the determination unit 54 will not determine that the dielectric constant has exceeded the upper threshold. In other words, in Figure 5, the graph (dielectric constant value) may rise in a spike-like manner as indicated by reference numeral 59, but in such a case, it will not be determined that it is time to change the oil.
As shown by the reference numeral 60 in FIG. 5 , when the dielectric constant exceeds the upper threshold and remains above the upper threshold for a predetermined time, the determination unit 54 determines that the dielectric constant has exceeded the upper threshold, and determines that it is time to change the oil, and that the reason for changing the oil is that the amount of contaminants has exceeded a predetermined amount.

As shown in FIG. 4, after it has been determined that it is time to change the oil and that the reason for changing the oil is that the amount of contaminants exceeds a predetermined amount, the determination unit 61 determines whether the viscosity and density of the oil have increased relative to the reference values (step S6).
If the amount of contaminants exceeds a predetermined amount and the viscosity and density have increased relative to the reference values (step S6: YES), that is, if the viscosity and density after the dielectric constant has exceeded the upper threshold have increased compared to the viscosity and density values before the dielectric constant exceeded the upper threshold, the judgment unit 61 judges that the contaminants are wear powder (step S7).
If it is determined that the contaminants are wear powder, the output unit 55 outputs a signal to the notification device 50 indicating that the contaminants are wear powder, and the notification device 50 notifies the user that the contaminants are wear powder (step S8).

Furthermore, if the amount of contaminants exceeds a predetermined amount and the viscosity and density have not increased relative to the reference values (step S6: NO), that is, if the viscosity and density after the dielectric constant has exceeded the upper threshold have not increased compared to the viscosity and density values before the dielectric constant exceeded the upper threshold, the judgment unit 61 judges that the contaminants are moisture (step S9).
If it is determined that the contaminant is moisture, the output unit 55 outputs a message to the notification device 50 indicating that the contaminant is moisture, and the notification device 50 notifies the user that the contaminant is moisture (step S10).

The notification device 50 notifies the user that it is time to change the oil, or that the reason for changing the oil is that the amount of contaminants exceeds a predetermined amount, for example, while the engine 11 is running. The notification may also be made when the engine 11 is started or when the engine 11 is turned off.
As described above, in this embodiment, the oil change timing, which varies depending on individual differences between machines and the user's operating conditions and environment, can be appropriately determined, and the user (operator) can be notified of the oil change timing.

The present invention is not limited to the above-described embodiments.
For example, the acquisition unit 51 may acquire the oil dielectric constant and oil temperature from a source other than the measurement sensor 48. In other words, the measurement sensor 48 may be a sensor that measures at least either the oil dielectric constant or the oil temperature when the acquisition unit 51 acquires the oil dielectric constant and oil temperature.
Furthermore, after determining the reason why the oil should be changed and whether the contaminants mixed in the oil are wear powder or water, the oil change determination notification device 47 may be configured not to immediately output the reason why the oil should be changed and whether the contaminants mixed in the oil are wear powder or water, but to store the reason why the oil should be changed and whether the contaminants mixed in the oil are wear powder or water as data, and to output to the notification device 50 the reason why the oil should be changed and whether the contaminants mixed in the oil are wear powder or water when some operation is performed.
The installation location of the measurement sensor 48 is not limited to the above-mentioned installation location A1. Other examples of installation locations of the measurement sensor 48 are shown in Figures 6 to 8.

The measurement sensor 48 may be installed in the supply line 37, in line 37b downstream of the oil filter 38, as shown by reference symbol A2 in FIG. 6. That is, the measurement sensor 48 may be installed in the supply line 37 downstream of and near the oil filter 38, to measure the dielectric constant, oil temperature, viscosity, and density of the oil flowing downstream of the oil filter 38. The measurement sensor 48 may also be installed in the return line 39, through which oil flows from the supply line 37 to the second case 19, in line 39a downstream of the oil cooler 41, as shown by reference symbol A3 in FIG. 6, or in line 39b upstream of the oil cooler 41, as shown by reference symbol A4 in FIG. 6. That is, the measurement sensor 48 may be installed in the return line 39, upstream or downstream of the oil cooler 41, to measure the dielectric constant, oil temperature, viscosity, and density of the oil flowing upstream or downstream of the oil cooler 41. The installation location may also be set in the pipeline 65 downstream of the suction filter (oil filter) 64, as shown by reference symbol A5 in Figure 6. In other words, the measurement sensor 48 may be installed downstream of the suction filter 64 to measure the dielectric constant, oil temperature, viscosity, and density of the oil flowing downstream of the suction filter 64.

The measurement sensor 48 may be installed in the conduit (oil supply line) 66 that supplies oil to the hydraulic controller 25, as shown by reference symbol A6 in FIG. 7, or in the conduit (oil return line) 67 that returns oil from the hydraulic controller 25 to the second case 19, as shown by reference symbol A7 in FIG. 7. In other words, the measurement sensor 48 may be installed in the oil supply line 66 or the oil return line 67 and measure the dielectric constant, oil temperature, viscosity, and density of the oil supplied to the hydraulic controller 25 or the oil returned from the hydraulic controller 25.

When the steering wheel 6 is not operated, the oil return line 67 has a steering inflow pressure of, for example, 2.5 to 3 MPa, and when the steering wheel 6 is operated, the pressure becomes negative. This is a suitable pressure for installing a sensor. Although not limited to this, in a tractor 1 that does not have an HST 16, the measurement sensor 48 can be installed in the return line (oil return line 67) from this hydraulic controller 25.

The measurement sensor 48 may be installed in the pipeline 71 (first oil drain pipeline 71A, second oil drain pipeline 71B, third oil drain pipeline 71C) that drains oil from the lift control valve 45, as shown by symbols A8 to A10 in Figure 8, or in the pipeline (oil supply pipeline) 72 that supplies oil to the lift control valve 45, as shown by symbol A11 in Figure 8, or in the pipeline (oil return pipeline) 73 that returns oil from the lift cylinder 44 to the second case 19 via the safety valve 46 for the lift cylinder 44, as shown by symbol A12 in Figure 8. In other words, the measurement sensor 48 may be installed in the first oil drain line 71A, the second oil drain line 71B, the third oil drain line 71C, the oil supply line 72, or the oil return line 73, and may measure the dielectric constant, oil temperature, viscosity, and density of the oil discharged from the lift control valve 45, the oil supplied to the lift control valve 45, or the oil returning from the lift cylinder 44.

The measurement sensor 48 installed in the oil supply passage 72 is located between the first pump 23A and a connection 75a of a relief circuit 75 having a relief valve 74 that sets the discharge pressure of the first pump 23A.
The measurement sensor 48 installed in the oil return path 73 is set downstream of the safety valve 46 for the lift cylinder 44 .
The installation locations of the measurement sensors 48 are not limited to the locations shown in Figures 6 to 8. Furthermore, at the installation locations, the measurement sensors 48 are installed that measure at least the dielectric constant or oil temperature, viscosity, and density of the oil acquired by the acquisition unit 51.

The oil change determination and notification device 47 of this embodiment determines and notifies the user when it is time to change the oil that operates the hydraulic drive system, and includes an acquisition unit 51 that acquires the oil's dielectric constant and oil temperature, a calculation unit 52 that converts the dielectric constant acquired by the acquisition unit 51 into the dielectric constant at a predetermined oil temperature, a determination unit 54 that determines when the oil should be changed based on the dielectric constant calculated by the calculation unit 52, and a notification device 50 that notifies the user that it is time to change the oil when the determination unit 54 determines that it is time to change the oil.

According to this configuration, the dielectric constant of the oil is calculated to the dielectric constant at a specified oil temperature, and the time to change the oil is determined based on this calculated dielectric constant, so that the time to change the oil can be appropriately determined and an alert can be given that it is time to change the oil.
In addition, the judgment unit 54 estimates the amount of contamination in the oil based on the dielectric constant calculated by the calculation unit 52, and determines when the oil should be changed and the reason for changing the oil, and the alarm device 50 notifies the user of the time when the oil should be changed and the reason for changing the oil.

This configuration not only notifies the driver when it is time to change the oil, but also the reason why the oil should be changed.
Furthermore, when the dielectric constant calculated by the calculation unit 52 exceeds a preset upper threshold value 58, the judgment unit 54 determines that the amount of contaminants mixed into the oil exceeds a predetermined amount and determines that it is time to change the oil, and the alarm device 50 notifies the user that the reason for the oil change is that the amount of contaminants mixed into the oil exceeds a predetermined amount and that it is time to change the oil.

According to this configuration, it is possible to notify not only the time when the oil should be changed, but also the reason for changing the oil, which is that the amount of contaminants mixed into the oil exceeds a predetermined amount.
The oil change determination/notification device 47 also includes a determination unit 61 that determines whether the viscosity and density of the oil have increased relative to their reference values. If the viscosity and density have increased relative to their reference values, the determination unit 61 determines that the contaminants mixed in the oil are wear particles, and notifies the notification device 5.
0 indicates that the contaminants mixed in the oil are wear particles.

According to this configuration, it is possible to notify not only the time when the oil should be changed, but also that the reason for changing the oil is that the contaminants mixed in the oil are wear particles.
In addition, the oil change determination notification device 47 is equipped with a judgment unit 61 that judges whether the viscosity and density of the oil have increased relative to the reference values. If the viscosity and density have not increased relative to the reference values, the judgment unit 61 judges that the contaminant mixed in the oil is water, and the notification device 50 notifies that the contaminant mixed in the oil is water.

According to this configuration, it is possible to notify not only the time when the oil should be changed, but also that the reason for changing the oil is that the contaminant mixed in the oil is water.
The oil change determination notification device 47 also includes a recording unit 56 that records data on the relationship between oil temperature and dielectric constant when the oil temperature drops within a predetermined temperature range, and a coefficient calculation unit 57 that calculates a temperature-dependent coefficient by performing linear regression on the data on the relationship between oil temperature and dielectric constant recorded in the recording unit 56, and the calculation unit 52 uses the temperature-dependent coefficient to calculate the dielectric constant at a predetermined temperature from the dielectric constant acquired by the acquisition unit 51.

According to this configuration, the dielectric constant of the oil at a predetermined temperature can be calculated with high accuracy.
In addition, the oil change determination notification device 47 is equipped with a measurement sensor 48 that measures the dielectric constant and oil temperature of the oil, an acquisition unit 51 acquires the dielectric constant and oil temperature from the measurement sensor 48, and a calculation unit 52 calculates the dielectric constant at the oil temperature obtained from the measurement sensor 48 into a dielectric constant at a predetermined temperature.

According to this configuration, it is possible to more appropriately determine when the oil needs to be changed and to notify the driver that the oil needs to be changed.
The work machine 1 of this embodiment is a work machine 1 equipped with an oil change determination notification device 47 and a gear-type transmission 18 , and the oil also serves as lubricating oil for the gear-type transmission 18 .

According to this configuration, it is possible to appropriately determine and notify when the oil needs to be changed in a work machine 1 in which the lubricating oil for the gear-type transmission 18 is also used as the oil for operating the hydraulic drive unit.
The work machine 1 also includes a hydrostatic continuously variable transmission 16, a supply line 37 that supplies oil to a charge circuit 36 of the hydrostatic continuously variable transmission 16, an oil filter provided in the supply line 37, and a measurement sensor 48 that measures at least the dielectric constant or oil temperature of the oil acquired by the acquisition unit 51, and the measurement sensor 48 measures the oil flowing upstream or downstream of the oil filter in the supply line 37.

This configuration allows for stable oil measurement and allows for constant monitoring of the oil.
The work machine 1 also includes a hydrostatic continuously variable transmission 16, a supply line 37 that supplies oil to a charge circuit 36 of the hydrostatic continuously variable transmission 16, a return line 39 through which oil returning from the supply line 37 flows, an oil cooler provided in the return line 39, and a measurement sensor 48 that measures at least the dielectric constant or oil temperature of the oil acquired by the acquisition unit 51, and the measurement sensor 48 measures the oil flowing upstream or downstream of the oil cooler in the return line 39.

This configuration also allows for stable oil measurement and constant monitoring of the oil.
The work machine 1 also includes steerable wheels (front wheels 4), a steering cylinder 24 that steers the steerable wheels 4, a hydraulic controller 25 that receives oil and operates the steering cylinder 24, and a measurement sensor 48 that measures at least the dielectric constant or oil temperature of the oil acquired by the acquisition unit 51, and the measurement sensor 48 may be configured to measure the oil supplied to the hydraulic controller 25 or the oil returning from the hydraulic controller 25.

The work machine 1 also includes a vehicle body 2, a lifting cylinder 44 that lifts and lowers an implement attached to the vehicle body 2, a lifting control valve 45 that receives oil and controls the lifting cylinder 44, and a measurement sensor 48 that measures at least the dielectric constant or oil temperature of the oil acquired by the acquisition unit 51. The measurement sensor 48 detects oil discharged from the lifting control valve 45 or the temperature of the lifting control valve 45.
5 or the oil returning from the lift cylinder 44 may be measured.

Although one embodiment of the present invention has been described above, the embodiment disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

1 Work machine 2 Vehicle body 4 Steering wheels (front wheels)
16 Hydrostatic continuously variable transmission 18 Gear type transmission 24 Steering cylinder 25 Hydraulic controller 36 Charge circuit 37 Supply line 38 Oil filter 39 Return line 41 Oil cooler 44 Lift cylinder 45 Lift control valve 47 Oil change determination notification device 48 Measurement sensor 50 Notification device 51 Acquisition unit 52 Calculation unit 54 Determination unit 56 Recording unit 57 Coefficient calculation unit 58 Upper limit threshold 61 Determination unit

Claims (11)

An oil change determination and notification device that determines and notifies the timing of changing oil that operates a hydraulic drive device,
an acquisition unit for acquiring the dielectric constant and oil temperature of the oil;
a recording unit that records data on the relationship between oil temperature and dielectric constant when the oil temperature of the oil drops within a predetermined temperature range;
a coefficient calculation unit that calculates a temperature dependency coefficient by performing linear regression on the relationship data between oil temperature and dielectric constant recorded in the recording unit;
a calculation unit that calculates the dielectric constant acquired by the acquisition unit into a dielectric constant at a predetermined oil temperature using the temperature dependent coefficient;
a determination unit that determines when the oil should be changed based on the dielectric constant calculated by the calculation unit;
an alarm device that notifies the driver that it is time to change the oil when the determination unit determines that it is time to change the oil;
An oil change determination notification device comprising: the determining unit estimates the amount of contaminants mixed into the oil based on the dielectric constant calculated by the calculating unit, and determines when the oil should be changed and the reason for changing the oil;
2. The oil change notification device according to claim 1, wherein the notification device notifies the user of the timing for changing the oil and the reason for changing the oil. the determination unit determines that the amount of contaminants mixed into the oil exceeds a predetermined amount when the dielectric constant calculated by the calculation unit exceeds a predetermined upper threshold value, and determines that it is time to change the oil;
3. The oil change notification device according to claim 2, wherein the notification device notifies the driver that the reason for changing the oil is that the amount of contaminants mixed in the oil exceeds a predetermined amount, and that it is time to change the oil. a determination unit that determines whether the viscosity and density of the oil have increased relative to reference values;
the determination unit determines that the contaminants mixed in the oil are wear particles when the viscosity and the density have increased relative to their reference values;
4. The oil change determination and notification device according to claim 3, wherein the notification device notifies the user that the contaminants mixed in the oil are wear particles. a determination unit that determines whether the viscosity and density of the oil have increased relative to reference values;
the determination unit determines that the contaminant mixed in the oil is water when the viscosity and the density have not increased relative to their reference values;
4. The oil change determination and notification device according to claim 3, wherein the notification device notifies the user that the contaminant mixed in the oil is water. a measurement sensor for measuring the dielectric constant and oil temperature of the oil;
the acquisition unit acquires a dielectric constant and an oil temperature from the measurement sensor,
2. The oil change notification device according to claim 1, wherein the calculation unit calculates the dielectric constant at the oil temperature obtained from the measurement sensor into the dielectric constant at the predetermined temperature. A work machine equipped with the oil change determination notification device and a gear-type transmission according to claim 1,
The oil also serves as a lubricating oil for the gear-type transmission. A hydrostatic continuously variable transmission;
a supply line for supplying the oil to a charge circuit of the hydrostatic continuously variable transmission;
an oil filter provided in the supply line;
a measurement sensor that measures at least one of the dielectric constant and the oil temperature of the oil acquired by the acquisition unit;
Equipped with
The work machine according to claim 7 , wherein the measurement sensor measures the oil flowing in the supply pipe line upstream or downstream of the oil filter. A hydrostatic continuously variable transmission;
a supply line for supplying the oil to a charge circuit of the hydrostatic continuously variable transmission;
a return line through which the oil returning from the supply line flows;
an oil cooler provided in the return pipe;
a measurement sensor that measures at least one of the dielectric constant and the oil temperature of the oil acquired by the acquisition unit;
Equipped with
The work machine according to claim 7 , wherein the measurement sensor measures the oil flowing in the return pipe line upstream or downstream of the oil cooler. A steering wheel and
a steering cylinder for steering the steered wheels;
a hydraulic controller that receives the oil and operates the steering cylinder;
a measurement sensor that measures at least one of the dielectric constant and the oil temperature of the oil acquired by the acquisition unit;
Equipped with
The work machine according to claim 7 , wherein the measurement sensor measures oil supplied to the hydraulic controller or oil returned from the hydraulic controller. The car body and
a lifting cylinder for lifting and lowering an implement attached to the vehicle body;
a lift control valve to which the oil is supplied and which controls the lift cylinder;
a measurement sensor that measures at least one of the dielectric constant and the oil temperature of the oil acquired by the acquisition unit;
Equipped with
The work machine according to claim 7 , wherein the measurement sensor measures oil discharged from the lift control valve, oil supplied to the lift control valve, or oil returning from the lift cylinder.