# Study on Temperature Characteristics of Lubrication Film of Valve Plate Pair in Axial Piston Pumps
## 5 Conclusions  
In this paper, the temperature distribution of the valve plate pair in the axial piston pump was studied theoretically and experimentally. The main conclusions are as follows:  
1. To improve the accuracy of the film temperature model, a test platform was built, in which three displacement sensors were installed in the low-pressure side of the valve  
Figure 16: Film temperature distribution along the inner side of the auxiliary support belt at different working conditions: (**a**) conditions 1 and 2; (**b**) conditions 3 and 4; (**c**) conditions 1 and 3; (**d**) conditions 2 and 4.  
plate and eleven thermocouples were laid in the high-pressure side of the back of the valve plate. Based on the collected data from the three-point film displacement sensors, a film shape model of the valve plate pair was established, considering the effects of the fluctuation factor (coaxiality factor) and constant factors (force, moment, and off-wear factors). Then, the film temperature model was established, considering the viscosity-temperature characteristics of hydraulic oil, the energy loss caused by viscous friction and leakage, and the heat conduction among the oil, cylinder block, and valve plate. The theoretical and experimental film temperature results agree well with each other.
2. Film thickness tests were conducted under the working pressures of 3 MPa and 7 MPa, swash plate tilt angles of 12\({}^{\circ}\) and 16\({}^{\circ}\), and a working speed of 1000 rpm. Under working condition 1 of 3 MPa and 12\({}^{\circ}\), the average value error of the film thickness test curve and the theoretical curve is less than 0.4 \(\times\) 10\({}^{-5}\) m. Under working condition 2 of 3 MPa and 16\({}^{\circ}\), their average value error is less than 0.5 \(\times\) 10\({}^{-5}\) m. Under working condition 3 of 7 MPa and 12\({}^{\circ}\), their average value error is less than 0.2 \(\times\) 10\({}^{-5}\) m. Under working condition 4 of 7 MPa and 16\({}^{\circ}\), their average value error is less than 0.7 \(\times\) 10\({}^{-5}\) m. The theoretical film thickness curves agree well with the experimental film thickness curves.
3. The film temperature increases with an increase in the working pressure and swash plate tilt angle. The absolute error between the test and theoretical results of the maximum oil film temperature in the valve plate pair is less than 3.5 \({}^{\circ}\)C. As the working pressure increases from 3 MPa to 7 MPa and the swash plate tilt angle increases from 12\({}^{\circ}\) to 16\({}^{\circ}\), the position of the highest-temperature point shifted from \(-15^{\circ}\) to 5\({}^{\circ}\) in the circumferential direction of the valve plate.
4. This manuscript also has some limitations. This manuscript does not take into account the effects of triangular grooving on the film of the valve plate pair and the effects of cavitation on the film forming of the valve plate pair. Theoretical modeling and testing were carried out under relatively low pressure, and no tests were carried out under relevant high-pressure and high-speed conditions.  
The authors declare no conflicts of interest.