JPH0381575A - Radial piston pump - Google Patents

Abstract

PURPOSE:To minimize the amount of air entrained in a cylinder and obtain stable flow rate characteristics by equipping a piston with a delivery port for a hydraulic fluid, and providing a member for reducing an initial cylinder volume at such a position in the cylinder as free from interference with the piston. CONSTITUTION:An intake port 13 is formed at the center of the bottom of a piston 6, and the opposite end of the piston 6 is made open to the inside of a cylinder 5. A volume reduction member 11 projected to the inside of the cylinder 5 is so retained between a spring 8 and a cap 7 as not to interfere with the piston 6, and a delivery port 16 normally continuous to the annular groove 15 of the cylinder 5 is formed on the piston 6. Each piston 6 is driven with a cam 3 and repeats reciprocal motion with the predetermined phase difference. Also, each cylinder 5 repeatedly sucks and delivers a hydraulic fluid. As the delivery port 16 is provided on the piston 6 and the volume reduction member 11 is added, the cylinder 5 has no dead space and the amount of the whole entrained air in the cylinder 5 is reduced correspondingly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in fixed cylinder radial piston pumps.

(Prior Art) The present applicant has proposed a method for reducing noise and improving durability by preventing the occurrence of cavitation and wear of the contact portion between the cam and the piston in a fixed sill type radial piston pump. Patent application No. 63-164355
No. is proposed.

As shown in FIG. 2, a ring 10 having an outer circumference 10A with a polygonal cross section equal to the number of pistons 6 is freely rotatable on the outside of a circular cam 3 fixed to a rotating shaft 2 at an eccentric position. The proximal end of the piston 6, which is fitted into the cylinder 5 and slidably housed in the cylinder 5, is connected to the outer circumference 10 of the ring 10 by the spring 8.
A1: Sliding and holding, the outer peripheral part 1 of the ring 10.
A notch 14 is formed in the OA to communicate a hydraulic oil suction port 13 formed in the piston 6 with the cam chamber 4 according to the rotational position of the cam 3.

When the cam 3 is rotationally driven via the rotating shaft 2, the ring 10 moves in a parallel circle corresponding to the eccentricity of the 0 cam 3, and the outer circumference 1
While sliding 0A in the transverse direction with respect to the piston 6, it also moves in the axial direction of the piston 6, thereby expanding and contracting the volume of the shilling 5. In the expansion stroke, hydraulic oil is sucked from the cam chamber 4 into the sill 5 through the suction port 13 communicating with the notch 14, and in the contraction stroke, the suction port 13 is closed, the hydraulic oil in the sill 5 is pressurized, and the check is performed. It is discharged through a valve 9 into a discharge passage (not shown).

(Problem to be solved by the invention) By the way, in this pump, when the cylinder 5 moves from the contraction stroke to the expansion stroke, the air mixed in the hydraulic oil in the cylinder 5 expands due to the pressure drop, causing the cylinder to expand as shown in Figure P143. At the beginning of the stroke, hydraulic oil could flow out from the cylinder 5 into the cam chamber 4 due to this expanded air. Note that the higher the discharge pressure, the more the air mixed in the hydraulic oil is compressed, and the expansion when the shilling 5 shifts to the expansion stroke also increases accordingly. Therefore, this backflow phenomenon 3
- occurs more easily as the discharge pressure is higher, and this reduces the suction amount accordingly.As a result, under high discharge pressure, the problem arises that the discharge flow rate decreases as the rotation speed increases, as shown in Figure 4. there were.

In order to solve the above problems, the present invention aims to obtain stable flow characteristics by minimizing the amount of mixing chambers in the sill.

(Means for Achieving the Object) The present invention includes a circular cam fixed eccentrically to a rotating shaft, rotatably housed in a cam chamber formed in a pump body, and radially extending from the cam chamber to the pump body. Each piston is slidably housed in the formed sill ring, and a ring having an outer circumference with a polygonal cross section equal to the number of pistons is fitted to the outside of the cam, and the base end of the piston is fitted into this ring. A suction port for hydraulic oil that communicates with the inside of the cylinder is formed in the piston, and a notch is formed on the outer periphery of the ring to communicate the suction port to the cam chamber according to changes in the relative position between the ring and the piston. In the lanoal piston pump formed in the section, the piston is provided with a discharge port for discharging the hydraulic oil pressurized within the syring, and a member for reducing the initial volume of the shilling is provided inside the syring at a position where it does not interfere with the piston. There is.

(Function) Since the discharge port is provided in the piston and the member for reducing the initial volume of the shilling is provided at a position that does not interfere with the invading piston, the initial volume of the shilling can be reduced without reducing the effective discharge amount. Therefore, the amount of empty space present in the sill is reduced, and the backflow of hydraulic oil due to the expansion of air when the sill is expanded is less likely to occur.

(Embodiment) FIG. 1 shows an embodiment of the present invention. In this figure, 1 is a pump body, 2 is a rotating shaft, and 3 is a cam with a circular cross section fixed to the rotating shaft 2 at an eccentric position.

The cam 3 is housed inside a cam chamber 4 formed in the pump body 1, and on the pump body 1 outside the cam chamber 4, six sills 5 are formed radially around the rotating shaft 2. A piston 6 formed in a cylindrical shape with a bottom in the sill 5
is housed in a state where it can freely slide with its bottom protruding toward the cam chamber 4.

A suction port 13 opens in the center of the bottom of the piston 6, and the opposite end of the piston 6 opens into the sill 5. The cap 7 screwed onto the pump body 1 of the sill 5 is hermetically sealed via a socket 12.

A ring 10 having an outer periphery 10A with a regular hexagonal cross section equal in number to the number of pistons 6 is fitted onto the outside of the cam 3 so as to be freely rotatable. The piston 6 is biased by a spring 8 as sliding contact holding means supported by the cap 7, and its bottom portion slides against the outer peripheral portion 10A of the ring 10. Outer periphery 1 of ring 10
A notch 14 is provided near each top of 0A to communicate the suction port 13 with the cam chamber 4 depending on the sliding position with the bottom of the piston 6.
is formed.

Further, in order to reduce the initial volume of the syringe 5, a rod-shaped volume reducing member 11 is held between the spring 8 and the cap 7 and projects inside the syringe 5 to such an extent that it does not interfere with the invading piston '6.

An annular groove 15 is formed in the cylinder 5 facing the side surface of the sliding piston 6, and a discharge port 16 is formed in the piston 6, which is in constant communication with the annular groove 15. Note that the annular groove 15
communicates with a discharge passage (not shown) via a check valve 9.

Next, the action will be explained.

When the rotating shaft 2 rotates, the cam 3 rotates together, and the ring 10, which is rotatably fitted to the outside of the cam 3, does not rotate itself but is guided by the rotating cam 3 and changes the eccentric distance of the cam 3. Displaced along a circular orbit with radius.

In other words, when the cam 3 rotates once, the outer circumference 1 of the ring 10
0A is a notch 14 for the suction port 13 at the bottom of the piston 6.
The piston 6 is driven in the axial direction by performing one reciprocating movement left and right while changing the position of the piston 6, and at the same time performing one reciprocating movement up and down.

To explain specifically, for example, the piston 6 shown in (,) in the figure is at the top dead center position where it has penetrated the deepest into the cylinder 5,
When the cam 3 rotates in the direction of the arrow from this position, the ring 10 is displaced (parallel movement) downward to the right.
The piston 6, biased by the spring 8, slides its bottom portion along the outer circumference 10A of the displacing ring 10, communicates the suction port 13 with the notch 14, and projects into the cam chamber 4, so that the cam 3 When rotated by °, it will be in the same state as (1) in the figure.

Then, when the cam 3 further rotates by 60 degrees, the piston 6
is in the same state as shown in (c) of the figure, and when the cam 3 further rotates 60 degrees, the piston 6 reaches the bottom dead center position where it is most protruded into the cam chamber 4, as shown in (d). . During this time, the cylinder 5 continues to expand, and the hydraulic oil in the cam chamber 4 flows into the cylinder 5 through the suction port 13 communicating with the notch 14.
be sucked into. In addition, when reaching the bottom dead center position, the suction port 13
will be closed.

Now, when the cam 3 further rotates, the piston 6 changes its operating direction and enters the cylinder 5, while the notch 14 moves away from the suction port 13, and the cylinder 5 is cut off from the cam chamber 4. As a result, as shown in FIGS. 8(e) and 5(f), the pressurized hydraulic oil in the shrinking cylinder 8-5 flows through the annular groove 15 through the discharge port 16.
The liquid is then discharged through the check valve 9 into a discharge passage (not shown). In this way, when the cam 3 makes one revolution, the piston 6 returns to the top dead center position again.

In this way, each piston 6 is driven by the rotating cam 3 and repeats reciprocating motion with a predetermined phase difference, and each cylinder 5 repeatedly sucks and discharges hydraulic oil, but the discharge port 16 is directly connected to the cylinder f5. Since it is provided in the piston 6 instead of being provided, and the volume reducing member 7 is also provided, there is less dead space within the cylinder 5, and therefore, the amount of air mixed in the cylinder 5 as a whole is also reduced accordingly. Therefore, when changing from the contraction stroke to the expansion stroke at the top dead center, it is possible to suppress as much as possible the phenomenon in which the expanded air causes hydraulic oil to flow out from the cylinder 5 to the cam chamber 4, and after the rotation speed exceeds a predetermined number. , a constant discharge amount can be obtained regardless of the rotation speed.

Note that even if the volume reducing member 7 is provided, the effective volume change amount of the cylinder 5 corresponding to the displacement of the piston 6 does not decrease, so there is no change in the basic discharge amount.

(Effects of the Invention) As described above, the present invention provides a piston with a discharge port for discharging pressurized hydraulic oil in a cylinder, and a member for reducing the initial volume of the cylinder in a position that does not interfere with the piston inside the cylinder. The initial volume of the cylinder is kept small relative to the discharge amount, and it is possible to suppress the phenomenon in which the hydraulic oil flows back from the cylinder to the cam chamber due to the expansion of the air compressed in the cylinder. This has the effect of preventing insufficient suction due to backflow of hydraulic oil and stabilizing flow characteristics.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a radial piston pump showing an embodiment of the present invention, Fig. 2 is a sectional view of a radial piston pump showing a conventional example, Fig. 3 is a graph explaining the backflow phenomenon, and Fig. #4 is the same. It is a graph showing the relationship between the rotation speed of the pump and the discharge flow rate. . 1... Pump body, 2... Rotating shaft, 3... Cam, 4... Cam chamber, 5... Cylinder, 6... Piston, 8... Spring, 9... Check Valve, 10・
... Ring, 11 ... Volume reducing member, 1 3 ... Suction port, 4 ... Notch, 5 ... Annular groove, 6 ... Discharge port.

Claims (1)

[Claims] A circular cam fixed eccentrically to the rotating shaft is rotatably housed in a cam chamber formed in the pump body, and pistons are housed freely and slidably in cylinders formed radially in the pump body around the cam chamber. a ring having an outer periphery having a polygonal cross section equal to the number of pistons is rotatably fitted to the outside of the cam, and includes means for slidingly holding the base end of the piston to the ring, communicating with the inside of the cylinder. A radial piston pump in which a hydraulic oil suction port is formed in the piston, and a notch is formed in the outer periphery of the ring to communicate this suction port to a cam chamber according to changes in the relative position between the ring and the piston.
A radial piston pump characterized in that the piston is provided with a discharge port for discharging hydraulic oil pressurized within the cylinder, and a member for reducing the initial volume of the cylinder is provided inside the cylinder at a position that does not interfere with the piston.