What is the process of research, development, and use of the Nippon Seiki hydraulic pumps?

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Among Niigata’s hydraulic pump products, the IPH and PVS series are widely used in the excavator industry, and they are also used in close cooperation with well-known domestic excavator manufacturers such as Sany. Let’s take a brief look at some aspects of the excavator hydraulic pump industry. The technologies related to excavators are not yet perfect; there are still many areas that need to be improved step by step. For example, hydraulic piston pumps have ten technical defects that cannot be overcome with current technology, and these issues will need to be resolved through future advances in science and technology. One of the ten technical shortcomings is that modern hydraulic piston pumps operate at low pressures; scientists consider an ideal \"pump\" or \"motor\" to operate at a pressure of 60 Mpa. When the rotation speed reaches over 6,000 revolutions per minute, and if such a condition can be achieved, the excavator designed by scientists consists of an engine that drives a generator; the generator in turn drives a DC servo variable-frequency motor, which then drives a small \"fixed-displacement piston pump\". When rapid movement is required from the excavator, the servo variable-frequency motor reaches its maximum speed, and the oil discharge volume of the fixed-displacement pump is also at its highest. When slower movement is needed, the servo variable-frequency motor operates at a lower speed, and the oil discharge volume of the fixed-displacement pump decreases. In this way, the variable part of the pump is eliminated, resulting in a significant reduction in the pump’s size as well as a decrease in the number of potential failure points. The greatest advantage of increased hydraulic pressure in a excavator is that the digging force of the same excavator increases, the bucket also becomes larger, allowing for more powerful digging. Any construction machinery in the world pales in comparison to an excavator. If one can understand all the technical aspects of excavators, repairing any construction machinery will be a piece of cake. Those construction machines are just copies of excavator technology. No construction machinery can function without power, and the power source for such machinery is the Nippon Kiko hydraulic pump. Within the hydraulic systems of excavators, the component with the highest level of technological sophistication is the \"hydraulic piston pump\". Personally, I believe that in order to repair an excavator, it is necessary first to understand the principles of pumps and be able to repair piston pumps; once one masters pump technology, the rest of the hydraulic technologies related to excavators will become much easier to understand. Among the piston pumps of European, American, and Japanese designs used in excavators, I personally appreciate the most those used in Komatsu’s Model 7 machines. The component I admire the most is the pressure reducing valve (which is a combination of a sequence valve, a pressure reducing valve, and an overflow valve). The more I study it, the more convinced I am of the design principles behind this valve. Currently, there are only two types of hydraulic piston pumps used in various excavators: one is the inclined shaft pump (such as PVS or Nippon Sharyo gear pumps), and the other is the straight shaft swash plate pump, with the PVS series of pumps being a typical example. At present, the variable principle used in hydraulic pumps for excavators is basically the same: the high-pressure oil from the pump itself (hydraulic power) is used to drive the variable mechanism. The variable mechanism of the pump includes a “servo valve, spool valve, and variable piston”. The variable piston is a small hydraulic cylinder. Hydraulic cylinders are divided into a rod-side chamber and a rodless side chamber, while the variable piston has a larger diameter and a smaller diameter. When oil flows into the larger diameter of the variable piston (when the pressure in the larger diameter is higher than that in the smaller diameter), the hydraulic force pushes the variable piston in the direction of the smaller diameter. The pin on the variable piston rod drives the swash plate in the pump to move; as the angle of the swash plate increases, the stroke of the plunger lengthens, resulting in an increased discharge volume from the pump and faster movement of the excavator. Oil enters through the small bore; when the pressure in the small bore is higher than that in the large bore, the hydrodynamic force pushes the variable piston back, causing the angle of the swash plate to decrease. As a result, the stroke of the plunger within the cylinder decreases, the pump’s displacement drops, but the pressure rises more gradually. In the hydraulic piston pumps of various excavators today, the small-diameter end of the variable piston is connected to the P port of the pump; thus, the pressure at that end is equal to the pressure within the pump. The oil passage at the larger diameter end of the variable piston is connected to the three oil ports on the regulator. One of these three oil ports is a T-port (an oil release port), which is referred to as a G-hole in Nippon Seiki oil pumps. One oil port is for the supply of fluid to the proportional valve; it is also known as port E. One oil port is for the supply of oil to the servo valve; it is also called hole D. The regulator determines the pressure of the control oil entering the larger-diameter end based on the feedback servo pressure and the pressure from the proportional valve; when the pressure entering that end is twice that at the smaller-diameter end, the variable piston remains in a neutral position. The variable theory behind this pump is quite advanced. Preparations before repairing the pump: Before starting repairs, it is necessary to identify the specific part of the pump that needs to be fixed, as well as to determine what issues the pump has. (1) What is the total service life of the Niigata hydraulic pump? Pumps cannot be used indefinitely; if they have been in use for over a decade, such pumps basically lose any value in terms of repair. Because steel also has a certain degree of periodicity, separation layers can form in the steel base, as well as deformation of the pump casing. (2) Find out how much time has passed since the last pump repair until now What were the parts replaced when the pump was repaired last time? What was the skill level of the person who repaired the pump last time? (3) What is the maximum operating pressure of the current pump in bars? Adjust the sensitivity of the pump’s variable mechanism, (response) feedback speed? What is the operating temperature of the pump? (4) Does the excavator have a hydraulic hammer attached? How long does an excavator use a hydraulic hammer? (5) What kind of noise does the pump make? Determine whether the noise is caused by mechanical factors or hydraulic noise? (6) What type of hydraulic oil is used? What is the current quality of the oil? Drain all the hydraulic fluid from the hydraulic tank of the excavator, and then check the quality of the fluid Check how much debris is on the bottom of the fuel tank? What kind of impurities are they? If the quality of the hydraulic oil deteriorates, the machine owner must have it replaced. Someone came to ask for help with repairing a pump. I asked what was wrong with the pump, and he said that the excavator wasn’t powerful enough – it could only dig one bucket of soil after a long time. I asked whether the excavator could fill a bucket with soil, and he replied that it could, but it did so slowly. I then asked if the bucket moved slowly while digging or if it stopped moving at times; he said that the bucket kept moving during digging, without stopping, though its movement was very slow. When lifting the arm, it rose slowly, and when the arm lowered to the middle position, it would stop for a few seconds. Answer: This phenomenon is caused by a low discharge volume of the pump. Upon arriving at the site, use the arm of an excavator to lift one of the tracks, pull the travel control lever to its full extent, and run the engine at its highest speed so that the track rotates idly. The time it takes for the track to complete three rotations was 43 seconds. By adjusting the regulator of the K3V pump, the dynamic performance improves; increasing the pump’s discharge volume reduces this time – it now takes only 18 seconds for the track to complete three rotations. This indicates that there is no problem with the pump’s variable mechanism. Testing the pump’s discharge volume is the best way to determine its performance. The displacement detection method for the K3V pump is the same as that for the A8V. If the time it takes for the tracks on both sides to complete three revolutions at the same engine speed is equal, it indicates that the displacement of pump P1 and pump P2 is equal. Adjusting the displacement of the hydraulic pump on the test bench cannot bring the pump’s displacement to its maximum value; it must be matched to the engine’s power. The operation should also be as fast as possible, without overloading the engine.