The most popular way to change the output flow of

Ways to change the output flow of gear pump

1 introduction

various hydraulic pumps used in positive displacement hydraulic transmission mainly include gear pump, vane pump and plunger pump. Among them, gear pump is the simplest one, and it has small volume, few parts (especially the parts requiring high-precision processing), light weight, convenient manufacturing and maintenance, low price, and can work reliably even under poor working conditions, Therefore, it is widely used in hydraulic transmission and control technology, as well as in the field of fluid transmission in various hydraulic machinery and petrochemical industry. Up to now, vane pumps and plunger pumps can be made into various forms of variable displacement pumps according to relevant standards. Only gear pumps have no variable products yet. Exploring the variable mode of gear pump is of great practical significance for expanding the application field of gear pump. This paper describes several ways to solve the variable of gear pump, which can provide reference for the research and development of variable gear pump

2 ways to realize variable of gear pump

2.1 stepwise variable mode

(1) as we all know, the conventional two tooth gear pump adopts two involute gears with the same parameters (that is, the size and size of the two gears are exactly the same). If the number of teeth of the two gears (other parameters of the gears remain unchanged), the size of the two gears will be different (Figure 1), The gear pump thus formed can obtain two kinds of output displacement. When the speed of the prime mover is the same, if the pinion is used as the driving wheel, the output displacement and flow of the gear pump are small; If the big gear is used as the driving wheel, the gear pump can output a larger displacement. In this way, a gear pump can provide two displacement. According to the displacement calculation formula of the gear pump, the ratio of these two displacements is equal to the ratio of the number of teeth of the large and small gears (in direct proportion). This assumption has certain practical significance for hydraulic equipment requiring two flows, but the driving system of the gear pump is more complex than that of the conventional gear pump

Figure 1 gear pump composed of two different gears

(2) multi gear wheel type uses three or more gears to form a multi gear gear gear pump, and the driven gears are evenly distributed to guide the healthy development of the new material industry around the driving gear (Figure 2), which can make the sample size of this kind of gear: measure the width, thickness and thickness of the sample with a measuring tool with a small division value of no more than 0.02mm; Check the notch size with an optical projector, and the pump can get a variety of displacement. Each displacement can be shunted to drive different actuators respectively, or combined to output large displacement, so as to realize the rapid movement of the working mechanism. Several oil inlets and outlets are opened on the shell or front and rear end covers of the pump, which are respectively connected with the oil suction pipe and the oil discharge pipe. In addition to obtaining a variety of output displacements, this multi gear gear pump has another significant advantage: because the suction and discharge ports are symmetrically arranged, and the driven gears are evenly distributed, the hydraulic pressure and meshing force are balanced, thereby reducing the load on the pump shaft and bearings and improving the service life of the gear pump. However, the oil distribution device of this gear pump is more complex than the conventional two tooth gear pump, especially the design and processing of the internal gear in the gear pump with internal gear is more difficult, and these problems still need to be further studied

Fig. 2 multi gear gear gear pump

2.2 stepless variable mode

(1) the former Soviet Union once developed a gear pump with uniform variable, the driving gear 1 is meshed with the intermediate gear 2 (ring gear with internal ring gear), and the driven gear 3 is meshed with the internal ring gear of 2 (Fig. 3). The axle position of gear 3 is adjustable. By adjusting the axle position of gear 3 (the performance characteristics of the plane back door tail support pressure tester move), the output displacement of the pump can change evenly between qmin and Qmax (corresponding to the movement of the driven gear from the dotted line position to the solid line position, and the symbol Q represents the displacement of the pump). However, the intermediate gear 2 needs to process both external teeth and internal teeth, which is difficult to process, and radial through holes need to be opened at the root of the gear 2, which weakens the strength of the gear

Figure 3 uniform variable gear pump

(2) rotating shaft sleeve type

we know that on the inner surface of the pump housing of the conventional two toothed gear pump, the included angle of the transition seal area between the high and low pressure cavities is φ ≥ 360o/z (z is the number of teeth of a single gear). A new idea of changing the included angle of the sealing area is put forward in the relevant literature: using a rotatable shaft sleeve (with a shunt groove on it)/changing the included angle of the transition sealing area with the help of the rotation of the shaft sleeve (making φ