JP2018193981A - Extremely-low speed/high-torque type piston pump/motor suppressed in friction loss and leakage of working fluid - Google Patents

Abstract

To provide a piston pump/motor which can be operated at a low speed and high torque.SOLUTION: In a piston, static pressure bearings having self-equilibrium characteristics are added to a shoe and the piston. A wave power generation device is thus expected. A plurality of static pressure bearing pads are installed at the piston of a hydraulic transmission pump, and an optimum piston motion is automatically performed due to mutual actions of the pads. The piston is stroked by a cam motion, and operates the pump. Since a clearance is formed of a vertical component of a cam at a cylinder part of a part of the piston, and the clearance becomes a leakage passage of high-pressure oil, a particular pressure distribution which is formed of an oil film is generated at a piston face. By using the particular distribution, a friction force generated at the piston face is offset. Then, a plurality of the static pressure bearings are installed at a slide face of the shoe, a variation of a bearing force occurs when oil film thicknesses are changed, and the moment in a direction in which the oil film thicknesses are restored to uniform thicknesses acts on the shoe, thus automatically restoring the piston and the shoe to equilibrium states.SELECTED DRAWING: Figure 4-1

Description

  The present invention relates to a swash plate type piston pump / motor of the “piston motion / rotation motion” conversion type by a combination of “piston / swash plate cam”, and at a remarkably low speed which is impossible with a conventional piston pump / motor. Aims to enable high torque operation. The final goal is to easily realize the large-scale wave power generator by using the hydraulic transmission employing this pump / motor.

  The conventional wave power generator is a relatively small device shown in FIG. 1, and the output is 150 kW class. In order to meet local power demand, it is necessary to realize an extremely large capacity wave power generation device at a moderate cost. However, there were very few engineers other than the present inventor who actively worked on wave power generation. The reason why the wave power generation device shown in FIG. 1 is a highly efficient method is that it is necessary to understand the physical phenomenon of wave interference, so it is thought that the engineers did not understand. As a countermeasure, it is considered necessary to accumulate results.

JP 2017-15068

WATANABE Junji Wave power generation toward practical use, Power Company, 2009

  First, technical issues in developing a single-unit 10 MW class pendulum wave power generator will be described. This power generation converts ocean wave energy into hydraulic energy and produces electricity. Ocean waves are born from the energy of the wind blowing over the ocean surface, and large-scale wave power generation targets waves that have sufficiently grown ocean waves (wave height, wavelength, period, and energy density are large).

  For example, in the 150 kW pendulum wave power generator shown in FIG. 1, the pendulum shaft torque = 0.72 MNm (directly connected to the pump), the pump average rotational speed: equivalent to about 3 rpm, the generator speed = 1,800 rpm (speed increase ratio = 600) ).

When considering a single-machine power output of 1,000 kw with reference to this, pendulum shaft torque = 0.72
MNm × (1000 kW / 150 kW) × 3 rpm / (1 to 1.5) rpm = (9.6 to 14.4) MNm. However, the pump average rotation speed = (1 to 1.5) rpm.

  From the above results, the 1000 kW wave power generator is a pump with extremely low speed and high torque conditions such as pendulum shaft torque = (9.6 to 14.4) MNm and pump average rotational speed = (1 to 1.5) rpm. Is no longer possible with the prior art. The present invention is intended to overcome this problem.

  The single machine power output 1-10 MW class pendulum type wave power generator targeted by the present invention will be described from the problems that prevent this appearance. The wave power generation apparatus of FIG. 1 opens an entrance toward a wave propagating from the offshore and introduces a wave into the water chamber. The wave is reflected and reversely reflected by the wall at the back of the water chamber and overlaps with the following wave, and changes into a standing wave. The standing wave at the 1/4 wavelength position from the wall always has a zero wave height, but doubles pure horizontal reciprocating motion. When the pendulum plate is suspended at this position, the reciprocating flow of waves vibrates the pendulum, creating a pendulum motion. This creates a pendulum movement via the hydraulic transmission. As a result, the pendulum motion is converted into the steady rotational motion of the hydraulic motor shaft via the hydraulic transmission, and electric power generated by the generator is generated.

The hydraulic circuit diagram of FIG. 2 is a hydraulic circuit diagram in which wave energy in a water chamber that reciprocates horizontally is provided for the purpose of “maximizing power generation efficiency”. For this purpose, the following measures are taken.
(1) The pendulum is basically “pendulum and stationary wave are vibrated under resonance” by the reciprocating flow of the standing wave. (Resonant operation)
(2) The pendulum shaft and the pump shaft are shared. If the magnitude of the load torque acting on the pump shaft matches the wave-making damping of the pendulum, the power generation efficiency is maximized, so the pump dimensions are determined accordingly. (Impedance matching)
(3) The time average pump hydraulic pressure is proportional to the generator load. (From the relationship of generator driving torque = hydraulic motor torque) Since wave energy is proportional to the square of the wave height, the hydraulic motor torque is increased or decreased along with the incident wave power following the change in the wave height (motor displacement: Dm is adjusted) Then, the amount of generated power is equivalent to the maximum limit.
(4) This method is easy to put into practical use. An example is shown below. (Example of optimization method for power generation efficiency)
Generator used: Three-phase induction generator The generator speed is constrained to the synchronous speed. If the generator is driven with a torque proportional to the square of the input wave height, the generated output is proportional to the total amount of input wave energy. If the proportionality constant in this case is appropriate, the amount of power generation is maximized. If the displacement of the hydraulic motor: Dm is increased or decreased in proportion to the motor circuit hydraulic pressure: p, the generator drive power by the motor = input wave power. One of the methods for maximizing generated power. FIG. 2 shows this state. One generator is driven by two variable displacement hydraulic motors. (By the accumulator connected to the motor circuit, the motor circuit oil pressure becomes a value proportional to the hydraulic oil volume accumulated in the circuit.)

  Under this condition, since the pendulum strokes in proportion to the wave height, the amount (volume) of oil discharged from the pump is proportional to the wave height. As a result, the motor circuit hydraulic pressure is proportional to the magnitude of the wave height (if the hydraulic pressure p and the displacement volume Dm are controlled to be proportional to the wave height), the motor torque changes in proportion to the square of the wave height. Therefore, the power generation output maintains a value corresponding to the level according to the change in the wave height, and the power generation efficiency optimization operation is realized.

  Even if the pendulum device and the hydraulic transmission are increased in size according to the above, there is a situation in which the power generation output does not increase. This is because the lubrication environment for the moving parts of the pendulum and the pump becomes very severe, and it is difficult to cope with the current technology. For example, in the hydraulic transmission (rotary vane pump) of FIG. 1, deformation of the main body due to an excessive increase in internal pressure increases friction loss and leakage loss of high-pressure oil.

The present invention solves the above problems by the following means.
(1) Since the generator is driven by a pendulum, Japanese Patent Application Laid-Open No. 2017-015068, wind power / wave power generation machine / hydraulic compound transmission is employed, and in this case, the piston pump shoe of the piston pump The problem of enlargement is solved by improving the characteristics of the transmission at low speed / high torque operation, resulting from the improvement of the invention.
(2) An axial piston pump incorporating the piston shoe of the present invention is shown in FIG. (Characteristics relating to this pump are posted in Japanese Patent Application Laid-Open No. 2017-015068) In this pump structure. Since the rotation of the shaft 29 is extremely low, the pump is driven after increasing the speed. This is accompanied by the effect of power distribution.

  In FIG. 3, the piston pump 27 is driven at a speed obtained by increasing the reciprocating rotation of the pendulum shaft 29 via the gear 22 and the pinion 23. The swash plate cam 24 rotates, and the pistons 26 inserted into a number of cylinders 28 reciprocate. The piston 26 sucks hydraulic oil from the suction pipe 30 and sends high-pressure hydraulic oil to the discharge pipe 31. The shoe 25 is connected by a ball joint at the right end of the piston 26, and the hydrostatic bearing unique to the present invention is provided on the sliding surface. As a result, the swash plate cam 24 slides smoothly on the sliding surface despite the ultra-low speed / high torque operation.

The details of the shoe 25 and the details of the piston 26 will be described in more detail with reference to FIGS. FIGS. 4-1 and 4-2 are spherical joints 42 of the piston 26, and the joint center: O ₁ point is coupled to rotate freely on the X, Y, Z, and three axes. It shows the state. Here, the structure of the piston 26 and the structure of the shoe 25 are characteristic.
(1) The piston 26 is tilted and pressed against the cylinder 28 by the action of the Y direction (vertical) component: Fy of the force Fr acting on the O ₁ point. Further, the X (horizontal) direction component of Fr: Fx pushes the piston 26 in the left direction, and the force generates the pump pressure: p. At the right end of the piston, there is a crowning portion 40 having a very gentle curved surface, followed by a gap portion 41 on the left side. (The piston 26 can incline in the gap range of the gap portion 41.) The gap of the crowning portion 40 is small, and the hydraulic pressure p at this portion minimizes the leakage of hydraulic oil to the atmosphere side.
(2) Since the piston 26 inclines in the gap 41, the upper gap is large in FIG. 4-1, and the lower gap = 0. As a result, the pump pressure flows into the gap oil film, the pressure changes, the upper pressure decreases, and the lower pressure increases. Accordingly, an upward force acts on the piston 26 due to the difference in vertical pressure. If this force can cancel the force Fy acting on the O ₁ point, the frictional force acting on the piston 26 becomes extremely small.
(3) If the shape of the piston 26 is determined, the force Fy is almost determined, and the adjustment thereof is also possible. A plurality of circular pockets 41-2 are arranged at equal intervals on the boundary between the gap portion 41, which is a tapered portion of the piston 26, and the crowning portion 40. On the surface of the cylindrical portion of the piston 26, there is a flow of leaked oil toward the atmosphere side. The surface gap has a minimum at one point on the circumference, and the 180 ° opposite side has a maximum value. The pocket hydraulic pressure along the path is maximized. Since the size of the pocket and its arrangement change the size of the hydraulic pressure acting on the piston cylindrical portion, this can be used to improve the low speed performance of the large hydraulic transmission.
4-1 and 4-2 show the piston and shoe of the present invention.

Further, the piston 26 and the shoe 25 will be described with reference to FIGS. 4A and 4B, AA and BB. (The BB diagram shows the sliding surface of the shoe 25)
The hydraulic pressure p of the piston 26 is sent to the hydraulic chamber 43 located at the center. Three pressure pockets 44 that are sealed with the hydraulic chamber 43 by a seal land 48 are arranged on the outer periphery, and the outer periphery of the pocket 44 is further separated from the atmosphere side by a seal land 49. The pressure in the pressure pocket 44: p ₁ is such that the pressure in the hydraulic chamber 43: p ₀ leaks from the seal land 48 and enters the pocket 44, and goes from the pocket 44 through the seal land 49 to the atmosphere side. It goes up and down due to the difference in flow rate from the outflow. The leakage of the seal land greatly affects the change in the oil film thickness between the inclined plate and the shoe due to the inclination of the shoe. As a result, if one of the three pockets undergoes a “change in the oil film phenomenon” due to the inclination, the “oil film in the target pocket increases”. As a result, the respective pocket hydraulic pressures change, and a restoring moment is generated in the shoe 25 in the direction of tilt = 0. Thus, when the inclination of the shoe 25 disappears, the restoring moment = 0.

  The hydraulic pump / motor of the present invention has a plurality of hydrostatic bearings on the piston and piston of the piston pump, which is a basic sliding component, even when it is difficult to maintain an appropriate oil film on the sliding surface such as low speed / high pressure operation. By providing, each can maintain a balanced posture. As a result, each sliding surface can reliably hold an oil film, and can be expected to be put into practical use in a new field. For example, even the wave power generation that the present inventor has been pursuing practical research can develop megawatt-class natural energy, and can be expected to reduce carbon dioxide.

  Structure diagram of pendulum wave power generator   Hydraulic circuit diagram of pendulum wave power generator   Pump structure driven by pendulum   Piston and shoe structure   4-1 is a structural diagram of the piston and shoe with the inclined plate inverted 180 degrees

  An embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 3, the pump / motor drive source of the present invention is a pendulum shaft 29 of a pendulum wave power generator. Since the pendulum shaft can only swing very slowly, there is no effective means other than engaging the pinion 23 with the gear 22 having a large number of teeth and rotating it at a higher speed. However, even in this speed increasing operation, there is a problem in terms of cost because the rotational speed is lower than that of a general pump / motor.

  In the present invention, in order to enhance the durability of the piston pump / motor driven at low speed, the shoe and piston for driving the piston are provided with a plurality of pockets each bearing a plurality of hydrostatic bearings, and the oil film is securely held on the sliding surface. The structure is possible.

  FIG. 4A shows eight pockets 41-2 serving as a hydrostatic bearing in the piston 26 cross section in the AA diagram.

  In FIG. 4B, the back surface of the shoe 25 that slides on the inclined plate 24 is shown by the BB diagram. 3 shows a structure in which three arc-shaped groove-type pockets 44 are provided at positions sandwiched between an outer seal land 49 and an inner seal land 48 to form a static pressure bearing.

24 Swash plate cam 25 Shoe 26 Piston 27 Piston pump / motor 28 Cylinder 40 Crowning portion 41 Tapered portion 41-2 Circular pocket 42 Ball joint 44 Arc-shaped pocket 48 Seal land 49 Seal land

Claims (2)

  0.72 MNm (directly connected to the pump) on the sliding surface of the shoe sliding on the swash plate cam surface, pump average rotation speed: equivalent to about 3 rpm, generator speed = 1800 rpm, arc-shaped pockets carrying multiple hydrostatic bearings at equiangular intervals When installed, the pressing load acting on each pocket balances with the individual pocket oil pressure, so that a restoring moment is generated in the shoe and all the hydrostatic bearing sliding surface oil film thicknesses are automatically adjusted to be almost constant. Hydraulic piston pump / motor having a shoe to be operated.   The piston has a crowned portion at the end of the ball joint that receives the piston driving force, and has a tapered shape whose diameter continuously decreases slightly toward the tip of the piston. By installing a plurality of circular pockets at equiangular intervals in the working part and providing hydrostatic bearings that generate hydraulic pressure proportional to the pressing load acting on the side of the piston, the piston and cylinder solid on the piston sliding surface Piston pump / motor with a piston shape that automatically prevents contact and does not reduce efficiency during low-speed / high-torque operation, which is a negative effect of low-speed / high-torque operation

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