technical knowledge
What is the impact of oil distribution accuracy on the efficiency of cycloid hydraulic motors? You'll know after reading it
I don't know if you have ever understood that the effect of oil distribution accuracy on the efficiency of a hydraulic motor can be compared to the effect of the ignition time of an internal combustion engine on its power. According to the working principle of the cycloid hydraulic motor, the oil distribution sleeve and the rotor rotate synchronously. The so-called oil distribution accuracy refers to the accuracy of the oil distribution link with the rotation of the rotor to enter, close, and discharge the oil. Next, I will give you a detailed introduction to the relevant knowledge of the influence of oil distribution accuracy on the efficiency of cycloid hydraulic motors.
When the rotor of the cycloid hydraulic motor rotates and a large closed cavity appears, the oil in this cavity has already done work, and the rotor rotates again to make the tooth cavity smaller
There are many factors that affect the accuracy of oil distribution, such as the asymmetry between the rotor spline and the cycloid tooth profile, the position accuracy of the stator sleeve pin tooth hole relative to its bolt hole, and the asymmetry of the pin hole on the output shaft relative to its internal spline The degree of division accuracy of the longitudinal oil groove on the oil distribution sleeve and the position accuracy of the relative wedge groove are linked to the asymmetry of the splines at both ends of the shaft. As long as these factors are controlled within the tolerance range, they will not have a great impact on the accuracy of oil distribution, because all machining errors will not be side-tracked. The most important factor that affects the oil distribution accuracy is the fitting clearance of the splines at both ends, followed by the position accuracy of the housing oil distribution hole relative to the screw hole, which is difficult to ensure in the process, for installing the stator, and when the stator is fixed on the housing, relative to the housing The position accuracy of the oil distribution hole. The cycloidal pin wheel meshing pair is used as the power element of the cycloidal hydraulic motor. The rotor is the active part, and the output shaft and the oil distribution sleeve connected with it are the passive parts. Due to the spline clearance, the output shaft and the oil distribution sleeve lag behind the rotor by an angle, so the oil distribution sleeve deviates from the correct position. The following discussion is divided into two situations. A situation: When the rotor of the cycloid hydraulic motor rotates and a large closed cavity appears, the oil in this cavity has completed its work, and the rotor rotates again, which will make the tooth cavity smaller. This cavity should match the oil distribution through the oil distribution hole of the housing. The oil drain grooves of the sleeve are connected. However, due to the large spline clearance and the oil distribution sleeve lags behind the rotor and the housing oil distribution hole by an angle, this cavity remains in communication with the oil inlet groove of the oil distribution sleeve, but not with the oil discharge groove. According to the rotation direction of the rotor in the figure, the left side of the oil distribution hole of the casing corresponding to the larger enclosed cavity is the oil inlet groove of the oil distribution sleeve, and the right side is the oil drain groove. The solid line is the correct position, and the dashed line is the actual position. From this point of view, this cavity is not low pressure oil, but high pressure oil. High pressure oil always increases the volume. Therefore, the high-pressure oil in this cavity hinders the rotation of the rotor and reduces the mechanical efficiency. At the same time, the volumetric efficiency will also decrease. This is because in the correct position, there is a closed cavity between the high-pressure cavity and the low-pressure cavity. The high-pressure oil should pass through the two radial gaps of the stator to leak to the low-pressure cavity. There is only a radial gap between the cavities, so leakage increases. Not only that, but what’s more serious is that since the radial seal band B between the rotor tooth root and the central hole of the partition is only 1.3 mm, the high pressure oil in this cavity will leak a lot from the inner cavity of the cycloid hydraulic motor from this end to increase the volumetric efficiency. decline. In the second case, when the rotor rotates and a small closed cavity appears, the cavity is drained and the high-pressure oil is waited for to perform work. When the rotor rotates again, the tooth cavity becomes larger, and the oil distribution hole of the shell communicating with this cavity should communicate with the oil inlet groove of the oil distribution sleeve. However, due to the large spline clearance, the oil distribution sleeve lags behind the rotor and the housing oil distribution hole by an angle, so that the smaller tooth cavity remains in communication with the oil drain groove on the oil distribution sleeve, but not the oil inlet groove. According to the rotation direction of the rotor in the figure, the left side of the oil distribution hole of the casing corresponding to the smaller enclosed cavity is the oil drain groove of the oil distribution sleeve, the right side is the oil inlet groove. The solid line is the correct position, and the dashed line is the actual position. Therefore, this cavity cannot do work before the high-pressure oil is connected, which reduces the mechanical efficiency of the cycloid hydraulic motor. Because this cavity is connected to the oil drain groove, the displacement is reduced and the volumetric efficiency is reduced. In the above two cases, both are in the state of high and low pressure commutation. The two sides of the enclosed cavity are three-chamber high-pressure and three-chamber low-pressure. This requires the oil distribution mechanism to accurately match the rotor to achieve commutation. Otherwise, it will affect the efficiency. improve. In other cases, three or four chambers on one side are always high pressure, and four or three chambers on the other side are low pressure. The oil distribution accuracy has little effect on efficiency.
When the rotor of the cycloid hydraulic motor rotates and a large closed cavity appears, the oil in this cavity has already done work, and the rotor rotates again to make the tooth cavity smaller
There are many factors that affect the accuracy of oil distribution, such as the asymmetry between the rotor spline and the cycloid tooth profile, the position accuracy of the stator sleeve pin tooth hole relative to its bolt hole, and the asymmetry of the pin hole on the output shaft relative to its internal spline The degree of division accuracy of the longitudinal oil groove on the oil distribution sleeve and the position accuracy of the relative wedge groove are linked to the asymmetry of the splines at both ends of the shaft. As long as these factors are controlled within the tolerance range, they will not have a great impact on the accuracy of oil distribution, because all machining errors will not be side-tracked. The most important factor that affects the oil distribution accuracy is the fitting clearance of the splines at both ends, followed by the position accuracy of the housing oil distribution hole relative to the screw hole, which is difficult to ensure in the process, for installing the stator, and when the stator is fixed on the housing, relative to the housing The position accuracy of the oil distribution hole. The cycloidal pin wheel meshing pair is used as the power element of the cycloidal hydraulic motor. The rotor is the active part, and the output shaft and the oil distribution sleeve connected with it are the passive parts. Due to the spline clearance, the output shaft and the oil distribution sleeve lag behind the rotor by an angle, so the oil distribution sleeve deviates from the correct position. The following discussion is divided into two situations. A situation: When the rotor of the cycloid hydraulic motor rotates and a large closed cavity appears, the oil in this cavity has completed its work, and the rotor rotates again, which will make the tooth cavity smaller. This cavity should match the oil distribution through the oil distribution hole of the housing. The oil drain grooves of the sleeve are connected. However, due to the large spline clearance and the oil distribution sleeve lags behind the rotor and the housing oil distribution hole by an angle, this cavity remains in communication with the oil inlet groove of the oil distribution sleeve, but not with the oil discharge groove. According to the rotation direction of the rotor in the figure, the left side of the oil distribution hole of the casing corresponding to the larger enclosed cavity is the oil inlet groove of the oil distribution sleeve, and the right side is the oil drain groove. The solid line is the correct position, and the dashed line is the actual position. From this point of view, this cavity is not low pressure oil, but high pressure oil. High pressure oil always increases the volume. Therefore, the high-pressure oil in this cavity hinders the rotation of the rotor and reduces the mechanical efficiency. At the same time, the volumetric efficiency will also decrease. This is because in the correct position, there is a closed cavity between the high-pressure cavity and the low-pressure cavity. The high-pressure oil should pass through the two radial gaps of the stator to leak to the low-pressure cavity. There is only a radial gap between the cavities, so leakage increases. Not only that, but what’s more serious is that since the radial seal band B between the rotor tooth root and the central hole of the partition is only 1.3 mm, the high pressure oil in this cavity will leak a lot from the inner cavity of the cycloid hydraulic motor from this end to increase the volumetric efficiency. decline. In the second case, when the rotor rotates and a small closed cavity appears, the cavity is drained and the high-pressure oil is waited for to perform work. When the rotor rotates again, the tooth cavity becomes larger, and the oil distribution hole of the shell communicating with this cavity should communicate with the oil inlet groove of the oil distribution sleeve. However, due to the large spline clearance, the oil distribution sleeve lags behind the rotor and the housing oil distribution hole by an angle, so that the smaller tooth cavity remains in communication with the oil drain groove on the oil distribution sleeve, but not the oil inlet groove. According to the rotation direction of the rotor in the figure, the left side of the oil distribution hole of the casing corresponding to the smaller enclosed cavity is the oil drain groove of the oil distribution sleeve, the right side is the oil inlet groove. The solid line is the correct position, and the dashed line is the actual position. Therefore, this cavity cannot do work before the high-pressure oil is connected, which reduces the mechanical efficiency of the cycloid hydraulic motor. Because this cavity is connected to the oil drain groove, the displacement is reduced and the volumetric efficiency is reduced. In the above two cases, both are in the state of high and low pressure commutation. The two sides of the enclosed cavity are three-chamber high-pressure and three-chamber low-pressure. This requires the oil distribution mechanism to accurately match the rotor to achieve commutation. Otherwise, it will affect the efficiency. improve. In other cases, three or four chambers on one side are always high pressure, and four or three chambers on the other side are low pressure. The oil distribution accuracy has little effect on efficiency.