QC/T 299.2-2014Automotive hydraulic power steering pumps - Part 2: Test methods (English PDF)

5.1 Performance test

5.1.1 Maximum pressure

Start the steering pump under no-load pressure. Increase the speed to 1500 r/min.

Quickly close the output oil circuit, to make the output flow zero. Keep it for 2 s ~ 3 s.

At this time, the stable pressure value is the opening pressure of the safety valve, that is, the maximum pressure.

5.1.2 Run-in

Start the steering pump under the no-load pressure. Increase the speed to the highest speed nmax and keep it for 10 s. Then adjust the speed to 1500 r/min. Start from the no-load pressure and increase the pressure step by step to 0.5Pmax, 0.85Pmax working pressure, which is kept for 30 s, respectively.

5.1.3 Control flow

5.1.3.1 No-load control flow

Start the steering pump under no-load pressure. Measure the output flow, at different speeds, from the lowest speed nmin to the highest speed nmax. The detection interval is not more than 10 r/min. Draw the control flow characteristic curve. According to the overall trend of the flow characteristic curve, find out the inflection point of the flow curve, before and after the opening of the flow control valve. The speed and flow corresponding to this inflection point are taken as the no-load opening speed n1k and the no-load opening flow Q1k.

5.1.3.2 Load control flow

Start the steering pump under no-load pressure. Adjust the pressure to 0.6Pmax working pressure, when the speed rises to the minimum speed nmin. Measure the output flow, at different speeds from the minimum speed nmin to 0.65nmax speed. The detection interval is not more than 10 r/min. Draw the control flow characteristic curve. According to the overall trend of the flow characteristic curve, find the inflection point of the flow curve, before and after the flow control valve is opened. The speed and flow corresponding to When the pressure drop method is used for detection: Cut off the gas feeding circuit; measure the drop value of the inner chamber air pressure of the steering pump, within 10 s.

5.1.8 Noise

The noise is measured at a rotational speed of 1000 r/min and a specified working pressure. The background noise shall not exceed 55 dB(A). The sound level meter probe shall be on the axis of the steering pump under test, which is 150 mm away from the rear end face of the steering pump.

5.1.9 Cleanliness

5.1.9.1 Extraction of impurities.

Inject a certain amount (accounting for 2/3 of the volume of the inner cavity) of the cleaning test liquid, into the inner cavity of the steering pump. Seal the oil inlet, the oil outlet, the oil return port. Use the method of vibration, to wash the internal impurities into the test liquid. Then pour all the test fluid from the inner chamber of the steering pump into the measuring cylinder. Repeat this for not less than 3 times. Read the total liquid sample volume. The selection of cleaning test solution is as shown in Table 1.

Note: For special cleaning oil, clean gasoline or No.120 solvent oil is recommended, except for special product requirements.

5.1.9.2 Weighing method

Carry out vacuum filtration and filter membrane drying for the collected liquid samples.

The method shall be carried out, according to GB/T 20082. Then use the balance to weigh the mass of impurities

5.1.9.3 Microscopy

Carry out vacuum filtration and filter membrane drying for the collected liquid samples.

Use an optical microscope, to count the number of particles, which have a particle size greater than or equal to 5 µm and greater than or equal to 15 µm. Calculate the total number of particles, according to formula (3). The method is in accordance with GB/T 20082.

The total number of particles in GB/T 20082 is expressed by the number of particles, which are greater than or equal to the selected size per 100 mL of liquid sample.

Where:

N - The number of particles greater than or equal to the selected size per 100 mL of liquid sample;

A - The effective filtration area of the filter membrane, mm2; n - The number of particles greater than or equal to the selected size;

105 - The factor used in the normative unit; f - Number of cells counted; L - The length of the counting unit, mm; W - The width of the counting unit, mm; V - Liquid sample volume, mL.

In order to be consistent with the expression of solid particle pollution levels in GB/T 14039, the number of particles greater than or equal to the selected size per 100 mL of liquid sample is converted to the number of particles greater than or equal to the selected size per milliliter of wet volume of the steering pump, according to formula (4).

Where:

N' - The number of particles, which are greater than or equal to the selected size per milliliter of wet volume of the steering pump;

N - The number of particles, which are greater than or equal to the selected size per 100 mL of liquid sample;

V - Liquid sample volume, mL; v - Wet volume of the inner cavity of the steering pump (take the theoretical displacement q of the steering pump), mL.

5.1.9.4 Automatic particle counting method

The collected liquid sample is fully precipitated. The solution on the liquid surface is sucked up by a pipette, until the volume of the remaining liquid sample is equal to the wet volume of the inner cavity of the steering pump, to obtain the contaminated liquid of impurities inside the steering pump. According to GB/T 14039, use the shading principle, to automatically count the number of particles in the polluted liquid, which have a size greater than or equal to 4 µm (c), greater than or equal to 6 µm (c), greater than or equal to 14 µm (c). Then convert it into a pollution level.

5.1.10 Pressure switch characteristics

5.1.10.1 Make-on pressure, cut-off pressure, pressure hysteresis

Start the steering pump, which has pressure switch, under the no-load pressure. Adjust the speed to 600 r/min. Increase the pressure, from the no-load pressure until the pressure switch is turned on. The pressure, which is corresponding to the moment the pressure switch is turned on during the boosting process, is the make-on pressure P2.

Then reduce the pressure, until the pressure switch is disconnected. The pressure, which is corresponding to the moment the pressure switch is disconnected during the depressurization process, is the cut-off pressure P1. Calculate the pressure hysteresis deltaP, according to formula (5). The curve of pressure switch resistance and working pressure is as shown in Figure 3. […]