Antioxidant replenishment system and method

Abstract

To provide an antioxidant refill system that maintains good quality of oil and reduces the frequency of oil replacement.SOLUTION: An antioxidant refill system 10 refills the oil that flows in an oil hydraulic circuit 1 of a work machine with an antioxidant. The system includes: a computing unit 30 that calculates a level of antioxidant consumption, which is a difference between a reference content of an antioxidant in new oil and a current content of an antioxidant in used oil, during the operation of the work machine; and a refill part 40 that refills the used oil with recovery oil that contains a new antioxidant corresponding to the level of antioxidant consumption.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antioxidant replenishment system and method for replenishing antioxidant to oil flowing in a hydraulic circuit of a work machine. [Background technology]

[0002] Lubricating oils used in construction machinery, vehicles, and other work machines deteriorate over time due to chemical changes, etc. When oil chemically changes, its lubricating properties are lost, and the equipment that makes up the hydraulic circuit may not operate smoothly and may be damaged.

[0003] The main cause of oil chemical deterioration is oxidation. Oil oxidation is accelerated by oxygen, humidity, water, metal ions, and light, but oxygen in the air has the greatest impact on oil oxidation. The oxygen in the air, which contains approximately 21%, reacts with oil to cause oxidation.

[0004] The oxidation reaction of oil occurs through a radical chain reaction (autoxidation). Specifically, peroxides are first produced in the oil. These peroxides are then oxidized to alcohols and ketones, which then become oxides of carboxylic acids, oxyacids, hydroxyacids, and other compounds. These secondary products increase in molecular weight through ester formation and condensation polymerization of oxyacids, turning them into insoluble substances that cause a deterioration in lubricity.

[0005] The oxidation rate of oil is calculated according to the Arrhenius equation as K = Aexp(E / RT) [K: oxidation rate constant, R: gas constant, T: absolute temperature, E: activation energy, A: frequency factor], where the oxidation rate constant K increases exponentially as 1 / T. It is generally said that the reaction rate doubles when the oil temperature rises by 10°C. Furthermore, machinery and equipment that use oil tend to be in high temperatures, creating an environment in which oil oxidation is more likely to progress.

[0006] Patent Document 1 discloses an oil deterioration diagnosis device that detects early signs of oil deterioration by detecting a decrease in an antioxidant that suppresses oxidation of oil flowing within the hydraulic circuit of a work machine while the work machine is in operation. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6869419 Summary of the Invention [Problem to be solved by the invention]

[0008] The device described in Patent Document 1 is capable of diagnosing oil deterioration caused by a decrease in antioxidants at an early stage, thereby enabling prediction of when the oil needs to be changed, but it has the problem of having to replace oil with new oil when the antioxidants have been consumed.

[0009] Therefore, there is a technical problem that needs to be solved in order to maintain good oil quality and reduce the frequency of oil changes, and an object of the present invention is to solve this problem. [Means for solving the problem]

[0010] In order to achieve the above object, the antioxidant replenishment system of the present invention is an antioxidant replenishment system that replenishes antioxidant to oil flowing within the hydraulic circuit of a work machine, and is equipped with: a calculation unit that calculates the amount of antioxidant consumption, which is the difference between the standard content of the antioxidant contained in new oil, which is new oil, and the current content of the antioxidant contained in used oil, which is deteriorated oil, while the work machine is in operation; and a replenishment unit that replenishes the used oil with recovery oil containing new antioxidant equivalent to the amount of antioxidant consumption.

[0011] Furthermore, in order to achieve the above-mentioned object, the antioxidant replenishment device according to the present invention is an antioxidant replenishment system that replenishes antioxidant to oil flowing in the hydraulic circuit of a work machine, and is equipped with a calculation unit that calculates the amount of antioxidant consumption, which is the difference between the reference content of the antioxidant contained in new oil, which is new oil, and the current content of the antioxidant contained in used oil, which is deteriorated oil, while the work machine is in operation.

[0012] Furthermore, in order to achieve the above-mentioned object, the antioxidant replenishment method according to the present invention is a method for replenishing antioxidant to oil flowing within a hydraulic circuit of a work machine, and includes the steps of: calculating, during operation of the work machine, the amount of consumed antioxidant, which is the difference between a standard content of the antioxidant contained in new oil, which is new oil, and the current content of the antioxidant contained in used oil, which is deteriorated oil; and replenishing the used oil with recovery oil containing new antioxidant equivalent to the amount of consumed antioxidant. [Effects of the Invention]

[0013] The present invention can maintain good oil quality and reduce the frequency of oil changes. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing the configuration of a work machine to which an antioxidant replenishment system according to an embodiment of the present invention is applied. [Figure 2] A schematic diagram showing the process of autoxidation of oil. [Figure 3] 1 is a graph showing an infrared absorption spectrum illustrating the change in wavenumber and absorbance over time for an oil containing an antioxidant. [Figure 4] Graph showing the evaluation results of the RBOT test on oil. [Figure 5] 2 is a graph showing the change over time in absorbance relative to acceleration time and the concentration of antioxidants contained in the oil. [Figure 6]FIG. 10 is a schematic diagram showing the configuration of a work machine to which an antioxidant replenishment system according to a first modified example of the present invention is applied. [Figure 7] FIG. 10 is a schematic diagram showing the configuration of a work machine to which an antioxidant replenishment system according to a second modified example of the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described below with reference to the drawings. When referring to the number, numerical value, amount, range, etc. of components, unless otherwise specified or when the number is clearly limited to a specific number in principle, the number is not limited to the specific number, and may be greater than or less than the specific number.

[0016] Furthermore, when referring to the shape or positional relationship of components, etc., it includes things that are substantially similar or approximate to those shapes, etc., unless otherwise specified or when it is clearly considered otherwise in principle.

[0017] In addition, the drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional proportions of the components may not be the same as in reality. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

[0018] FIG. 1 is a schematic diagram showing the configuration of a hydraulically driven construction machine to which an antioxidant replenishment system 10 according to one embodiment of the present invention is applied. The construction machine is equipped with a hydraulic circuit 1 as a power source. The hydraulic circuit 1 includes an oil tank 2, a hydraulic pump 3, a directional control valve 4, and an actuator 5. Oil stored in the oil tank 2 is pressurized by the hydraulic pump 3 and supplied to a predetermined actuator 5 via the directional control valve 4. The actuator 5 is connected to a power source (motor, cylinder, etc.) not shown. The oil returning from the actuator 5 returns to the oil tank 2 via the directional control valve 4. The operation of the various components of the hydraulic circuit 1 is controlled by a controller not shown. The oil is a concentrated oil obtained by adding an antioxidant to a base oil. The antioxidant contained in the oil is, for example, a phenolic antioxidant or zinc dialkyldithiophosphate.

[0019] The antioxidant replenishment system 10 includes a detection unit 20, a calculation unit 30, and a replenishment unit 40.

[0020] <Detection unit> The detection unit 20 diagnoses the deterioration state of the oil flowing in the hydraulic circuit 1. The detection unit 20 is an infrared sensor including a light projector 21, a light receiver 22 provided opposite the light projector 21 across the pipes 6 connecting the various devices of the hydraulic circuit 1, and a signal processing unit 23.

[0021] The projector 21 is equipped with a laser diode as a light source. The laser diode continuously or intermittently emits measurement light set to a predetermined wave number or wavelength. The laser diode irradiates the measurement light toward the oil flowing through the pipe 6 upstream of the oil tank 2. A portion of the pipe 6 is formed to be transparent so that the measurement light can pass through. The projector 21 may be arranged to irradiate the measurement light toward the oil in the oil tank 2. The projector 21 is not limited to a laser diode and may be, for example, an infrared light source.

[0022] The light receiver 22 includes a photodiode as a light receiving element and an amplifier that amplifies a signal output by the photodiode. The photodiode receives measurement light (transmitted light) that has passed through the pipe 6. The detection wavelength of the photodiode is set to correspond to the measurement light emitted by the laser diode. The light receiver 22 is not limited to a photodiode, and may be, for example, a pyroelectric sensor. Furthermore, the installation location of the light projector 21 and the light receiver 22 is not limited to the pipe 6 in the hydraulic circuit 1. For example, the installation location may be a dummy pipe that is provided separately from the pipe 6 and returns oil to the oil tank 2 after being sucked up from the oil tank 2.

[0023] The signal processing unit 23 calculates the absorbance or transmittance according to the wavelength or wavenumber specific to the antioxidant in the transmitted light received by the light receiver 22. The transmittance is the ratio of the measured light intensity to the transmitted light intensity, and the absorbance is calculated from the measured light intensity and the transmitted light intensity based on the Beer-Lambert law. Note that the detection unit 20 is not limited to the configuration described above.

[0024] Next, a procedure for the detection unit 20 to detect a decrease in the antioxidant will be described.

[0025] First, let us explain the oxidation reaction of oil. In Figure 2, the horizontal axis represents the duration of oil use, and the vertical axis represents the amount of products produced in the oil.

[0026] First, as shown in Figure 2, the amount of products in the oil changes over time depending on the degree of deterioration. Oil flowing through the hydraulic circuit 1 tends to reach high temperatures, making it susceptible to oxidation reactions. This oxidation reaction is caused by a radical chain reaction (autoxidation reaction), and first, peroxides in the oil increase exponentially (peroxide generation period). The peroxides are then oxidized to alcohols and ketones, and then to oxides such as carboxylic acids, oxyacids, and hydroxyacids (oxide generation period). These secondary products increase in molecular weight through ester formation and condensation polymerization of oxyacids, becoming insoluble substances, which increase the viscosity of the oil and reduce its lubricity (viscosity increase period).

[0027] New oil also contains antioxidants that react with free radicals to suppress radical chain reactions, but as the oxidation reaction progresses, the antioxidants are consumed and reduced, after which peroxides are produced (induction period). In the following, new oil will be referred to as "new oil," and oil that has undergone oxidation and deteriorated as the oxidation reaction progresses will be referred to as "used oil."

[0028] Next, Figure 3 is a graph showing the infrared absorption spectrum of a phenolic antioxidant, showing the change over time in absorbance at wavenumbers around 3650 to 3660 cm. In Figure 3, the solid line represents new oil in a state where no oxidation has occurred, the dashed line represents used oil in a state where oxidative degradation has progressed (middle stage of the induction period), and the dashed-dotted line represents used oil in a state where oxidative degradation has further progressed (final stage of the induction period).

[0029] As shown in Figure 3, the transmitted light through oil containing a phenolic antioxidant increases and the absorbance decreases as oxidation progresses in the vicinity of 3650 to 3660 cm-1. In other words, it is clear that the decrease in the phenolic antioxidant contained in the oil can be detected by detecting the decrease in absorbance in the wavenumber range of 3650 to 3660 cm-1.

[0030] The detection unit 20 detects the decrease in antioxidants due to oil oxidation in the following manner: First, while the construction machine is in operation, the projector 21 emits measurement light at predetermined intervals (for example, every few seconds), and the photoreceiver 22 receives the transmitted light that has passed through the oil flowing in the pipeline 6. The wavenumber of the measurement light is set to 3650 to 3660 cm-1, which indicates a decrease in absorbance or an increase in transmittance, which is characteristic infrared absorption due to the consumption of phenolic antioxidants.

[0031] Next, the signal processing unit 23 acquires the absorbance of the light received by the light receiver 22. The signal processing unit 23 also stores the acquired absorbance in chronological order to facilitate comparison along the oil usage time. The absorbance is calculated using the following equation 1.

[0032]

number

[0033] Next, the diagnostic unit 24 detects the decrease in the antioxidant in the oil based on the change in absorbance over time. Specifically, when the absorbance of the phenolic antioxidant at wavenumbers of 3650 to 3660 cm decreases, the diagnostic unit 24 determines that the oil is deteriorating and the antioxidant is being consumed and reduced.

[0034] In this way, the detection unit 20 can detect the degree of oil deterioration in real time while the construction machine is in operation, without collecting oil.

[0035] <Arithmetic section> The calculation unit 30 calculates the amount of antioxidant consumed based on the absorbance calculated by the signal processing unit 23. Specifically, the calculation unit 30 calculates the amount of antioxidant consumed, which is the difference between the content of antioxidant contained in new oil (reference content) and the content of antioxidant contained in used oil (current content). The reference content of antioxidant is a value obtained by multiplying the oil weight by the concentration of antioxidant contained in the oil (e.g., 0.17 wt%). The amount of antioxidant consumed is calculated based on the decrease in absorbance, which is the difference between the absorbance of antioxidant in new oil (reference absorbance) and the absorbance of antioxidant in used oil (current absorbance), calculated using Equation 1.

[0036] Specifically, as shown in Figure 3, the absorbance of oil near wavenumbers 3650 to 3660 cm-1 is greatest in new oil and decreases as the oil deteriorates and the antioxidant is consumed. Furthermore, according to Equation 1, the absorbance of the antioxidant increases or decreases in proportion to the concentration of the antioxidant when the extinction coefficient and measurement distance are constant. Therefore, the calculation unit 30 calculates the reference absorbance E1 and the current absorbance E2 using Equation 1, and then calculates the amount of antioxidant consumption ΔV based on Equation 2, assuming that the antioxidant has been consumed in accordance with the decrease ΔE in the current absorbance E2 from the reference absorbance E1.

[0037]

number

[0038] Furthermore, the calculation unit 30 divides the consumption amount ΔV of the antioxidant by the specific gravity of the antioxidant to calculate the refill amount of new oil containing antioxidant (hereinafter referred to as "recovery oil") that is stored in a refill tank 41 and refilled into the used oil by a refill pump 42. The recovery oil is a stock solution of the antioxidant or a concentrated solution in which an antioxidant is added to a base oil of oil.

[0039] When the recovery oil is a concentrate of antioxidant, it is either liquid at room temperature or liquefied by heating an antioxidant that is solid at room temperature to above its melting point.On the other hand, when the recovery oil is a concentrated liquid, it is obtained by adding the liquid antioxidant concentrate to a base oil and diluting it to a predetermined concentration.

[0040] For example, to replenish the entire amount of antioxidant contained in new oil with the following physical property values ​​of oil and antioxidant with recovery oil, the weight of the concentrated antioxidant would be 696g and the volume (replenishment amount) would be 67.6cc, and the weight of the concentrated antioxidant (10% concentration) would be 6960g and the volume (replenishment amount) would be 8L. Total oil volume in hydraulic circuit 1: 400L Oil density: 0.87g / cc Antioxidant concentration: 0.2wt% Antioxidant specific gravity: 1.03g / cc

[0041] In the following, an example will be described in which an undiluted antioxidant is used as the recovery oil, but the recovery oil may also be a concentrated antioxidant. When the recovery oil is a undiluted antioxidant, the refill tank 41 that stores the recovery oil can be made smaller than when a concentrated antioxidant is used. Note that even when the antioxidant is undiluted, a mechanism for mixing the recovery oil and used oil is not essential because the used oil circulates within the hydraulic circuit 1 in a short time.

[0042] <Supplementary section> Returning to FIG. 1, the refilling unit 40 includes a refilling tank 41 and a refilling pump 42.

[0043] The replenishment tank 41 stores recovery oil. The amount of recovery oil stored in the replenishment tank 41 is preferably set to an amount that allows the recovery oil to be repeatedly replenished without the need for additional oil. The replenishment tank 41 is equipped with a heater 41a that keeps the recovery oil at a temperature above the melting point of the antioxidant (for example, 70°C) to prevent the antioxidant contained in the recovery oil from solidifying.

[0044] The replenishment pump 42 is, for example, a metering pump, and supplies the recovery oil stored in the replenishment tank 41 to the used oil in the oil tank 2. The amount of recovery oil discharged by the replenishment pump 42 is controlled by the pump control unit 43 so that it approximately matches the replenishment amount calculated by the calculation unit 30.

[0045] Next, we will explain an experiment to confirm the effectiveness of the antioxidant replenishment system 10. In this experiment, we compared the consumption of the antioxidant contained in the used oil and the amount of oxides produced in the used oil between a case where recovery oil was appropriately supplied to the used oil (experimental example) and a case where recovery oil was not supplied to the used oil (comparison example).

[0046] In this experiment, the RBOT test was used as an accelerated oil degradation test. In a typical RBOT test, oil, water, and a copper catalyst are placed in a cylinder-type test vessel, which is then sealed. After the vessel is pressurized with oxygen at 620 kPa and rotated in an oil bath at 150°C, the vessel is evaluated by measuring the time it takes for the pressure to drop from the maximum pressure to 175 kPa. However, in this experiment, to confirm oxidation stability under actual operating conditions, no water was added, and instead of conducting an accelerated test in which the oxygen pressure drops from the maximum pressure to 175 kPa, the oil was removed at predetermined intervals and evaluated.

[0047] <Experimental procedure for the experiment example> New oil and a copper catalyst were placed in a test vessel, which was then sealed. Oxygen was pumped into the vessel at 620 kPa, and the vessel was rotated in a 150°C oil bath for three hours. The oil was then sampled and measured using a spectrophotometer (FTIR) for absorbance at a wavenumber of 3650 cm-1, where a peak decrease in absorbance occurs for phenolic antioxidants, and absorbance at a wavenumber of 1740 cm-1, which increases in proportion to the amount of oxides produced in the used oil. The amount of antioxidant consumed was then calculated based on the decrease in absorbance, and regenerated oil containing an antioxidant equivalent to the amount of antioxidant consumed was added to the used oil.

[0048] The test vessel was then resealed, oxygen was pumped into the vessel at 620 kPa, and the vessel was rotated in an oil bath at 150°C for 2 hours. As described above, the absorbance at 3650 cm-1 and 1740 cm-1 was measured, and the restored oil was added to the used oil according to the amount of antioxidant consumed. This procedure was repeated until the accelerated deterioration time reached 11 hours.

[0049] <Experimental Procedure for Comparative Example> Fresh oil and a copper catalyst were placed in a test vessel, which was then sealed. After that, oxygen was pumped into the vessel at 620 kPa and the vessel was rotated in an oil bath at 150°C for 3 hours. The oil was then sampled and its absorbance at a wavenumber of 3650 cm-1 and 1740 cm-1 was measured by FTIR.

[0050] The test vessel was then resealed, oxygen was pressurized to 620 kPa, and the vessel was rotated in an oil bath at 150°C for 2 hours. The absorbance at a wavenumber of 3650 cm-1 and at a wavenumber of 1740 cm-1 was then measured as described above. This procedure was repeated until the accelerated degradation time reached 11 hours.

[0051] 4 is a graph showing the deterioration of the oil used in the experimental examples and comparative examples, with the horizontal axis representing acceleration time [hr], the first vertical axis representing the absorbance of the oil used at a wavenumber of 3650 cm-1, and the second vertical axis representing the absorbance of the oil used at a wavenumber of 1740 cm-1. It is known that when the antioxidant contained in the oil used is consumed and the amount of oxides in the oil used increases, the absorbance at a wavenumber of 1740 cm-1 increases.

[0052] 4, it can be seen that in the comparative example, the antioxidant was consumed after 7 hours of acceleration and then the amount of oxides increased rapidly, whereas in the experimental example, the antioxidant was not consumed until 11 hours of acceleration and the amount of oxides generated was low. Specifically, the amount of oxides generated in the experimental example was significantly lower than that of the comparative example, about 1 / 3.4 times faster after 9 hours of acceleration and about 1 / 5 times faster after 11 hours of acceleration, prolonging the life of the oil.

[0053] Figure 5 is a graph showing the change over time in the antioxidant in the experimental example of Figure 4. The horizontal axis is acceleration time [hr], and the vertical axis is the absorbance of the oil used at a wave number of 3650 cm-1.

[0054] Figure 5 shows that after 3 and 5 hours of acceleration, the absorbance decreased by approximately 0.005; however, the supply of equivalent recovery oil to the used oil temporarily increased the absorbance. After 7 hours of acceleration, the absorbance decreased by approximately 0.015; however, the supply of equivalent recovery oil to the used oil temporarily increased the absorbance. After 9 hours of acceleration, the absorbance decreased by approximately 0.02; however, the supply of equivalent recovery oil to the used oil temporarily increased the absorbance. Furthermore, after 11 hours of acceleration, the absorbance decreased by approximately 0.015.

[0055] Furthermore, Figure 5 shows that the amount of antioxidant consumed per unit time tends to increase as the acceleration time becomes longer. In other words, Figure 5 shows that the amount of antioxidant consumed after five hours of acceleration is particularly large compared to before that time, and after nine hours of acceleration, the amount of antioxidant consumed is greater than after seven hours of acceleration, and the antioxidant is almost completely consumed. Therefore, rather than replenishing antioxidant periodically at predetermined intervals, it is preferable to calculate the amount of antioxidant consumed constantly or intermittently at very short intervals and maintain the antioxidant content in used oil at the same level as that of new oil.

[0056] In this way, the antioxidant replenishment system 10 according to this embodiment is an antioxidant replenishment system 10 that replenishes antioxidant to oil flowing within the hydraulic circuit 1 of a work machine, and is configured to include a calculation unit 30 that calculates the amount of antioxidant consumption, which is the difference between the reference content of antioxidant contained in new oil and the current content of antioxidant contained in used oil, while the work machine is in operation, and a replenishment unit 40 that replenishes the used oil with recovery oil containing new antioxidant equivalent to the amount of antioxidant consumption.

[0057] With this configuration, by adding new recovery oil containing antioxidant to the used oil according to the amount of antioxidant consumed while the work machine is in operation, the antioxidant content in the used oil can be maintained at approximately the same level as the standard antioxidant content in the new oil, allowing the hydraulic circuit 1 to continue operating smoothly and reducing the frequency of oil changes in the hydraulic circuit 1.

[0058] Furthermore, the antioxidant replenishment system 10 according to this embodiment is configured such that the calculation unit 30 calculates the amount of antioxidant consumed based on the decrease in absorbance, which is the difference between the reference absorbance measured from the transmitted light that has passed through new oil and the current absorbance measured from the transmitted light that has passed through used oil.

[0059] With this configuration, the amount of antioxidant consumed can be calculated in real time with high accuracy based on the absorbance of the oil used measured while the work machine is in operation.

[0060] In addition, the antioxidant replenishment system 10 of this embodiment is configured so that the calculation unit 30 calculates the replenishment amount of recovery oil equivalent to the amount of antioxidant consumed, and the replenishment unit 40 includes a replenishment pump 42 that can supply the recovery oil stored in the replenishment tank 41 to the used oil, and a pump control unit 43 that controls the supply amount of recovery oil that the replenishment pump 42 supplies to the used oil depending on the replenishment amount of recovery oil.

[0061] With this configuration, the calculation unit 30 calculates the amount of recovery oil to be replenished according to the amount of antioxidant consumed, and the pump control unit 43 controls the amount of recovery oil supplied by the replenishment pump 42 according to the amount of recovery oil to be replenished, so that the antioxidant content in the used oil can be maintained at approximately the same level as the standard antioxidant content in the new oil.

[0062] <Variation 1> Next, an antioxidant replenishment system 50 according to a first modified example of the above-described embodiment will be described with reference to Fig. 6. The antioxidant replenishment system 50 according to this modified example differs from the antioxidant replenishment system 10 according to the above-described embodiment only in the configuration described below, and the other configurations are the same. Therefore, the common configurations are assigned the same reference numerals, and redundant explanations will be omitted.

[0063] The calculation unit 30 calculates the amount of antioxidant consumption, which is the difference between the reference content of antioxidant contained in new oil and the current content of antioxidant contained in used oil, based on the absorbance calculated by the signal processing unit 23 and Equation 1 and Equation 2. The calculation unit 30 also determines whether the calculated amount of antioxidant consumption has reached a predetermined threshold.

[0064] The replenishing unit 40 includes a replenishing pump 44, a replenishing container 45, and a pump control unit 46. The replenishing pump 44 is an air cylinder or the like that pushes out the entire amount of recovery oil in the replenishing containers 45, each containing a predetermined amount of concentrate of antioxidant. The operation of the replenishing pump 44 is controlled by the pump control unit 46.

[0065] When the consumed amount of antioxidant reaches a predetermined threshold, the pump control unit 46 pushes out recovery oil from the replenishment container 45 to replenish a predetermined amount of antioxidant to the oil tank 2. The capacity (replenishment amount) of recovery oil in the replenishment container 45 is set to contain an amount of antioxidant equivalent to the consumed amount of antioxidant corresponding to the predetermined threshold. For example, if the total amount of antioxidant contained in new oil is 696 g and the threshold for the consumed amount of antioxidant is set to 10% (69.6 g), the capacity of the replenishment container 45 that holds the concentrated solution of antioxidant is set to 69.6 g.

[0066] The refill container 45 shown in FIG. 6 is provided with a heater 45a that heats the antioxidant concentrate before the refill pump 44 is activated. That is, when the consumed amount of antioxidant calculated by the calculation unit 30 reaches a predetermined threshold, the heater 45a starts heating the refill container 45, and after the antioxidant concentrate is liquefied, the refill pump 44 supplies the liquid antioxidant to the used oil in the oil tank 2. This makes the refill pump 44 less expensive than a metering pump and easier to handle because the capacity of the heater 45a can be reduced. Note that the refill container 45 may be configured to be refilled after the supply of antioxidant is completed, or multiple refill containers 45 may be provided and one that has finished supplying antioxidant may be replaced with one containing antioxidant.

[0067] In this way, the antioxidant replenishment system 50 of this modified example is configured such that the calculation unit 30 determines whether the amount of antioxidant consumed has reached a predetermined threshold, and the replenishment unit 40 includes a replenishment pump 44 that can supply a predetermined amount of recovery oil contained in each replenishment container 45 corresponding to the threshold to the used oil, and a pump control unit 46 that controls the replenishment pump 44 to supply the recovery oil in the replenishment container 45 to the used oil when the amount of antioxidant consumed reaches the threshold.

[0068] With this configuration, the calculation unit 30 determines whether the amount of antioxidant consumed has reached a predetermined threshold, and the replenishment pump 42 supplies recovery oil in the replenishment container 45 to the used oil, so that the antioxidant content in the used oil can be maintained at approximately the same level as the standard antioxidant content in new oil.

[0069] <Variation 2> Next, an antioxidant replenishment system 60 according to a second modified example of the above-described embodiment will be described with reference to Fig. 7. The antioxidant replenishment system 60 according to this modified example differs from the antioxidant replenishment system 50 according to the above-described first modified example only in the configuration described below, and the other configurations are the same. Therefore, the common configurations are assigned the same reference numerals, and redundant description will be omitted.

[0070] The calculation unit 30 calculates the amount of antioxidant consumption, which is the difference between the reference content of antioxidant contained in new oil and the current content of antioxidant contained in used oil, based on the absorbance calculated by the signal processing unit 23 and Equation 1 and Equation 2. The calculation unit 30 also determines whether the calculated amount of antioxidant consumption has reached a predetermined threshold.

[0071] When the amount of antioxidant consumed reaches a predetermined threshold, the notification unit 70 notifies the operator to replenish the oil tank 2 with recovery oil, and the operator manually replenishes the entire amount of recovery oil contained in the refill container 80 into the oil tank 2. The amount of recovery oil contained in the refill container 80 (refill amount) is set to contain an amount of antioxidant equivalent to the amount of antioxidant consumed corresponding to the predetermined threshold. For example, if the total amount of antioxidant contained in the new oil is 696 g and the threshold for the antioxidant consumption is set to 10% (69.6 g), the capacity of the refill container 80 containing the concentrated antioxidant solution is set to 69.6 g. Furthermore, if the concentration of the antioxidant is 20 wt%, the capacity of the recovery solution contained in the refill container 80 containing the concentrated antioxidant solution is set to 348 g.

[0072] In this way, the antioxidant replenishment system 60 of this modified example is configured to include a calculation unit 30 that determines whether the amount of antioxidant consumed has reached a predetermined threshold, and an alarm unit 70 that issues an alarm to supply recovery oil in the replenishment container 80 to the used oil when the amount of antioxidant consumed reaches the predetermined threshold.

[0073] With this configuration, the calculation unit 30 determines whether the amount of antioxidant consumed has reached a predetermined threshold, and when the amount of antioxidant consumed reaches the predetermined threshold, the notification unit 70 notifies the operator to supply recovery oil in the refill container 80 to the used oil, and the operator then supplies the recovery oil in the refill container 80 to the used oil, so that the antioxidant content in the used oil can be maintained at approximately the same level as the standard antioxidant content in new oil.

[0074] The present invention is not limited to the above-described embodiments and modifications, and various modifications can be made without departing from the spirit of the present invention. It goes without saying that the present invention also covers such modifications. Furthermore, the above-described embodiments and modifications can be combined.

[0075] Since the wave number and the wavelength are reciprocals of each other, they can be converted and interpreted accordingly. Furthermore, since transmittance and absorbance are correlated, the transmittance and absorbance in the above-described embodiments can be converted and interpreted accordingly.

[0076] It should be noted that the hydraulically driven working machine to which the present invention is applied is not limited to the construction machine described above, but may also be, for example, an automobile, a ship, an aircraft, etc. The antioxidant replenishment system according to the present invention can also be applied to the automatic replenishment of automobile engine oil, etc. [Explanation of symbols]

[0077] 1: Hydraulic circuit 2: Oil tank 3: Hydraulic pump 4: Directional control valve 5: Actuator 6: Conduit 10, 50, 60: Antioxidant Replenishment System 20:Detection unit 21: Floodlight 22:Receiver 23: Signal processing section 24: Diagnostic Department 30: Arithmetic section 40: Replenishment Department 41: Refill tank 41a, 45a: heater 42, 44: Refill pump 43, 46: Pump control section 45: Refill container 70: Information Department 80: Refill container

Claims

1. An antioxidant replenishment system that replenishes antioxidant to oil flowing in a hydraulic circuit of a work machine, a calculation unit that calculates a consumption amount of the antioxidant, which is the difference between a standard content of the antioxidant contained in new oil, which is new oil, and a current content of the antioxidant contained in used oil, which is deteriorated oil, during operation of the work machine, and determines whether the consumption amount of the antioxidant has reached a predetermined threshold value; a replenishing unit that replenishes the used oil with recovery oil containing new antioxidants in an amount corresponding to the amount of consumed antioxidant; Equipped with The replenishing section a refill pump capable of supplying a predetermined amount of the recovery oil contained in a refill container corresponding to the threshold value to the used oil; a pump control unit that controls the replenishment pump so as to supply the recovery oil in the replenishment container to the used oil when the consumed amount of the antioxidant reaches the threshold value; An antioxidant replenishment system comprising:

2. 2. The antioxidant replenishment system according to claim 1, wherein the calculation unit calculates the amount of consumption of the antioxidant based on the amount of decrease in absorbance, which is the difference between a reference absorbance measured from the transmitted light that has passed through the new oil and a current absorbance measured from the transmitted light that has passed through the used oil.

3. The refill container is provided in plurality, 2. The antioxidant replenishment system according to claim 1, wherein the recovery oil is contained in each of the plurality of replenishment containers.

4. 2. The antioxidant replenishment system according to claim 1, wherein the replenishment unit includes a heater for heating the recovery oil.

5. 1. A method for replenishing an antioxidant to oil flowing in a hydraulic circuit of a work machine, comprising: a step of calculating, during operation of the work machine, a consumption amount of the antioxidant, which is the difference between a standard content of the antioxidant contained in new oil, which is new oil, and a current content of the antioxidant contained in used oil, which is deteriorated oil, and determining whether the consumption amount of the antioxidant has reached a predetermined threshold value; a step of replenishing the used oil with recovery oil containing new antioxidants in an amount corresponding to the amount of antioxidant consumed; Including, In the step of replenishing the used oil with the recovery oil, when the consumed amount of the antioxidant reaches the threshold, a predetermined amount of the recovery oil contained in a replenishing container corresponding to the threshold is supplied to the used oil.

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