An objective of the present inventi

An objective of the present invention is to provide a large-flow plunger pump to solve the problems in the prior art and to improve the performance and the service life of large-flow plunger pumps.To make the objectives, features and advantages of the present invention more obvious and comprehensible, the present invention will be further described below in detail by specific implementations with reference to the accompanying drawings.Embodiment 1As shown in Figs. 1, 2, 3 and 5, the structure and principle of a large-flow plunger pump of the present invention will be described in this embodiment.This embodiment provides a large-flow plunger pump, comprising a box 16, a crank-link mechanism 7, a crosshead 17, a plurality of plungers 2-7, a suction valve and a discharge valve. The crank-link mechanism 7 drives the plurality of plunger 2-7 to do reciprocating motion. A crosshead 17 guide hole comprises a detachable upper crosshead guide 1 and a lower crosshead guide 1-3 located on an inner surface of the box. The detachable upper crosshead guide 1 is connected to the lower crosshead guide 1-3 via positioning pins 1-1 and fixing bolts 1-2. On each of the plurality of plungers 2-7, a plunger packing lubrication system 2 is provided, which supplies lubrication oil to each of the plurality of plungers by a multi-point lubrication oil pump via a check valve 2-10 and a pressure sensor 2-11, and a high-pressure lubrication oil pump of the multi-point lubrication oil pump supplies lubrication oil to a plurality of plunger packing sets separately via a plurality of lubrication oil pipes. Both the suction valve and the discharge valve are damping valves 3, each of the damping valves 3 comprises a damping ring 3-3 which is provided between a valve plate 3-1 integrally vulcanized with the damping ring 3-3 and a valve seat 3-2, and a volume cavity Q which is connected to a valve chamber via pores K on the valve plate 3-1 is formed within the damping ring 3-3. The damping ring 3-3 has a reinforcing plate T on its bottom. On the top of the detachable upper crosshead guide 1, an upper cover plate 14 is provided; and a pull rod assembly 5 is provided between the detachable upper crosshead guide 1 and the upper cover plate 14.As shown in Fig. 1 and Fig. 3, as a large-flow plunger pump, a multi-cylinder (for example, five cylinders, seven cylinders, nine cylinders, etc.,) plunger pump is usually used. The detachable upper crosshead guide 1 forms, together with the lower guide located on the box 16, an integral guide hole via the positioning pins 1-1 and the fixing bolts 1-2. The interface between the upper guide and the lower guide is at a horizontal centerline of a cross-sectional circle. When it is necessary to maintain or replace parts such as crosshead pins, crosshead pin bushings, crossheads 17 and links, the upper cover plate 14 is opened, the pull rod assembly 5 is removed, the positioning pins 1-1 are pulled out, and the fixed bolts 1-2 are released. In this way, the detachable upper crosshead guide 1 can be taken out from the space on the top of the box 16. Thus, it is convenient for maintenance and replacement. Parts such as the crankshaft 7 are not needed to be first detached as the case in the conventional large-flow plunger pumps. It is therefore both effort and workload saving, safe and reliable.Since the detachable upper crosshead guide 1 is separated from the box 16, the guide has a substantially hollow upper half part, without sufficient support, and thus may be deformed during the operation of the large-flow plunger pump. As shown in Fig. 1, proving the pull rod assembly 5 in the upper part of a chassis (on the left side of the detachable upper crosshead guide 1) increases the compressive strength of the upper half part of the guide.Due to the large flow of large-flow plunger pumps, valves are designed in large size. Accordingly, a large contact area between the valve plates and the valve seats is caused, and the large contact area results in great impact on the valve seats from the valve plates. As a result, high noise is produced, which pollutes the environment and does harm to the physical and psychological health of operators. In the damping valve as shown in Fig. 5, the damping ring 3-3 is integrally vulcanized with the valve plate 3-1, and a volume cavity Q which is communicated with a valve chamber via pores K is formed within the damping ring. During the placement of the valve into the valve seat, the damping ring 3-3 comes into contact with the valve seat 3-2 first. The damping ring and the valve plate are made of rubber (for example, polyurethane) and thus somewhat elastic. The valve plate is integrally formed with the damping ring. The damping ring plays a role of caching and sealing, and absorbs most of impact so that the noise of the valve is reduced. Meanwhile, the volume cavity Q within the damping ring is filled with high-pressure medium via the pores K, so that the damping ring 3-