JPH0419414A - Method for judging degree of pollution of hydraulic circuit - Google Patents

Abstract

PURPOSE:To understand concentration of pollution of oil accurately so as to take appropriate action by providing filters having different grain size of filtration in circuit and displaying changes of pressure difference at outlet per unit time by judgment items of a plural number of steps. CONSTITUTION:A branch pipe 10, a flow control valve 11, and a flow dividing valve 12 are mounted on the upstream side of a filter 2 in a return pipe passage 1 and connected with a tank 3 through pipe passages 13, 15 via filters 14, 16. The inlet and outlet of the filters 14, 16 are connected with a control unit 22 and a display unit 23 via differential pressure sensors 20, 21. The grain size of filtration of the filter 14 is larger than that of the filter 16. Differential pressure is time differentiated by the control unit 22 and displayed in the display unit 23. Consequently, it is possible to understand degree of pollution of oil accurately and take appropriate action in accordance with display to prevent accident in advance.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for determining the degree of contamination of hydraulic oil in a hydraulic circuit, and particularly relates to a method for determining the degree of contamination of hydraulic oil in a hydraulic circuit for industrial vehicles, construction vehicles such as hydraulic power shovels, etc. Concerning a method for determining the degree of contamination.

[Conventional technology]

A conventional method for determining the degree of contamination of hydraulic oil is shown in FIG.

Return oil from actuators, hydraulic motors, etc. (not shown) flows from a return pipe 51 through a filter 52 to an oil tank 53.
Returning to , a bypass valve 54 is arranged in parallel with the filter 52 . Further, a pressure sensor 55 is provided to detect the pressure difference between the inlet and outlet of the filter 52, and is connected to a display device 56.

When the amount of contaminants in the oil increases and the filter 52 becomes increasingly clogged, and the resistance to oil flow increases, the oil pressure on the filter inlet side increases, the bypass valve 54 opens, and the oil bypasses the oil tank 53. flows to That is, the amount of contaminants in the oil increases and the pressure difference between the inlet and outlet of the filter increases. By detecting the magnitude of the pressure difference, it is possible to know whether the filter 52 is clogged. The pressure sensor 55 is activated when the pressure difference between the filter inlet and outlet exceeds a predetermined value, and sends a signal to the display device 56 to indicate that the filter 5 is activated.
2 indicates that a blockage has occurred. Then, replace the filter, clean it, or replace the contaminated oil, etc.
The system is used to prevent malfunctions in hydraulic systems, detect hydraulic system failures early, and prevent major accidents from occurring.

[Problem to be solved by the invention]

However, the conventional method described above has the following problems. In general, such hydraulic circuits have contaminant particles whose sizes range from those close to O to several hundred micrometers, and even a small amount of relatively large particles can easily cause problems in hydraulic equipment.

Normally, a single filter is used that has the ability to capture particles larger than 20-30 μm, so the filter captures all particles from 20-30 μm to several hundred μm, and the amount increases. Since the display is designed to display when the pressure difference between the inlet and outlet of the filter reaches a predetermined value, it is not possible to determine the size of the particles. Additionally, even if relatively large particles are generated, if the number of particles is small, the pressure difference between the inlet and outlet of the filter is small, causing the display device to not operate, which can eventually lead to damage to hydraulic equipment. .

In order to solve this problem, the present inventor proposed a hydraulic circuit contamination level display device in Japanese Patent Application No. 1-46988, and a method for determining the degree of hydraulic circuit contamination in Japanese Patent Application No. 1-44089.

According to the above proposal, multiple filters with different filtration particle sizes are provided, and the clogging state of each filter is detected.
Since a warning is displayed when clogging exceeds a certain amount, it is possible to understand the clogging status of the filter by particle size. However, in this method, the determination is made when the filter is clogged to a certain level, so over a long period of time, even if the concentration of contaminants is low, it will accumulate and eventually be determined to be clogged, and the concentration of contaminants will increase. There is a problem in that the display is displayed even when the hydraulic equipment is low and does not cause any malfunction to the hydraulic equipment, causing unnecessary maintenance to be performed.

The present invention has been made with attention to the above-mentioned problems, and an object of the present invention is to provide a method for determining the degree of contamination of a hydraulic circuit, which displays an instruction to take measures only when the amount of contaminants is likely to cause malfunctions in hydraulic equipment. It is an object.

[Means to solve the problem]

In order to achieve the above object, the method for determining the degree of contamination of a hydraulic circuit according to the present invention determines the degree of contamination of hydraulic fluid by detecting the presence or absence of clogging of a filter provided in the circuit of hydraulic fluid. In the pollution level determination method, multiple filters with different filtration particle sizes are installed in a circuit, and the presence or absence of clogging in each filter is determined based on the change in pressure difference between the inlet and outlet of the filter per unit time. It is characterized by displaying the following judgment items.

[Effect]

According to the above method, since the clogging of multiple filters with different filtration particle sizes is judged, it is possible to judge by particle size, and the judgment can be made based on the increase or decrease per unit time of the pressure difference between the filter inlet and outlet. Since this is done based on the amount, the concentration can be detected according to the size of the pollutant particles.

〔Example〕

Examples of the method for determining the degree of contamination of a hydraulic circuit according to the present invention will be described in detail below. FIG. 1 shows an overall configuration diagram of the contamination level determination method of the present invention. Return oil from an actuator and a hydraulic motor (not shown) passes through a return pipe 1, passes through a filter 2, and reaches an oil tank 3.

A bypass valve 5 is provided in the bypass line 4 . A branch pipe 10, a flow rate control valve 11, and a diversion valve 12 are provided in the return pipe l upstream of the filter 2, and the oil divided into three equal parts by the diversion valve 12 is divided into three parts through a pipe 13, and then passes through a filter 14. The other reaches the oil tank 3, and the other passes through the pipe 15 to the filter 1.
6 and reaches the oil tank 3. The inlet and outlet of the filter j4 are connected to a differential pressure sensor 20, and the inlet and outlet of the filter 16 are connected to a differential pressure sensor 21. Filter 14
and the filtration particle size of the filter 16 are Kl, respectively.

K2, and Kl>K2. The differential pressure sensor 20° 21 and the control device 22 are connected, and the control device 22 and the display device 23 are connected.

Next, a method for determining the degree of contamination in the above configuration will be explained.

To determine the filter clogging status per unit time,
The time differential value of the differential pressure ΔP between the inlet and outlet of the filter is used. Now, in order to eliminate the confusion of symbols, ΔP is written as PΔ. The time differential of the differential pressure is dPΔ/dt=PΔ, −PΔ1/ j 2 L, + where PΔ2: difference at time L2 Pressure PΔ,: time t1
The differential pressure at If the equipment in the hydraulic circuit breaks down and the amount of contaminants increases, the value of clPΔ/dt will also increase, so the above differential value is detected and compared with a predetermined reference value of dPΔ/dt to check for clogging. Make a judgment.

In the configuration of the determination method shown in FIG.
It is possible to calculate Δ/dt.

As mentioned above, the filtration particle size of filter 14.16 is 1, 2
The relationship is Kl>K2.

Now, Ml near (pollutant M2 captured by filter 14: pollutant captured by filter 16, particle size of Ml≧Kl, particle size of M2≧2, and since Kl>K2, the pollutant The particle size distribution of M2 includes the particle size distribution of contaminant M1.

Now, A1 is (dPΔ/d t) + A2 is (dP
If the criterion value is Δ/dt)2, then 70- in Fig. 2
In step 35 of the chart, calculate the time differential value of the differential pressure, and in step 36, compare (clPΔ/dL)2 and A2. If dPΔ/dt)z<A2, the contaminant has a particle size of 2 or less. Since this indicates that only fine particles are present in the oil, the display device is caused to display a normal display in step 38.

(If clPΔ/dtL≧A2, compare (dPΔ/dt)+ and Al in step 37.
), <Al, there are no large particles, but this indicates that particles larger than K2 are present, so step 39
to display a warning.

If (dPΔ/dL)l≧Al in step 37, this indicates that large particles are captured by the coarse filter 14, so an abnormality is displayed in step 40.

The above is summarized in a table in Figure 3.

〔Effect of the invention〕

As detailed above, the present invention calculates the time differential value of the differential pressure between the inlet and outlet of a plurality of filters with different filtration particle sizes,
Since the display device has multiple levels of display, it is possible to accurately grasp the concentration of oil contamination, and if you take measures according to the display, there is no risk of unnecessary maintenance, and you can perform appropriate maintenance without waste. As a result, it is possible to prevent malfunctions in hydraulic equipment and prevent small failures from developing into major accidents.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of the hydraulic circuit contamination level determination method of the present invention. FIG. 2 is a 70-diameter diagram of the contamination level determination method of the present invention. FIG. 3 is an explanatory diagram of the relationship between contamination level determination criteria and display. Figure 11 shows the overall configuration of a conventional hydraulic circuit contamination level determination method... ・Flow rate control valve 12... Diversion valve, filter, differential pressure sensor, control device, display device

Claims (1)

[Claims] In a method for determining the degree of contamination of hydraulic oil by detecting the presence or absence of clogging of a filter installed in the hydraulic oil circuit, a plurality of filters with different filtration particle sizes are arranged in the circuit. A method for determining the degree of contamination of a hydraulic circuit, characterized in that the presence or absence of clogging in each filter is determined based on a change per unit time in the pressure difference between the inlet and outlet of the filter, and the result is displayed in multiple stages of determination items.