JPS5831475B2 - axial piston pump - Google Patents

Description

[Detailed Description of the Invention] Most hydraulic pumps are of the positive displacement type, so when moving from the suction side to the discharge side, or from the discharge side to the suction side, the pressure in the confined volume is then released. Since it is different from the pressure inside the port, the pressure changes in steps between them.

At this time, the pressure waves generated become pulsating, which is a major cause of pump noise.

To avoid this, set the confinement angle so that the confinement pressure is the same as the discharge pressure that is used a lot, or use a notch, etc., so that the pressure changes in steps. It prevents you from doing so.

However, since these methods are all carried out for fixed dimensions, they are influenced by the pump rotation speed, the temperature, type, properties, etc. of the hydraulic oil.

Furthermore, there was also a device (Japanese Patent Publication No. 49-37209) in which an auxiliary circulation hole was provided between the suction port and the discharge port of the valve plate, and this auxiliary circulation hole was appropriately communicated with the above port via a check valve provided in the main body. However, in this case, excess pressure is always released to the discharge port, so when the cylinder port is switched, it is not possible to sufficiently eliminate pulsation due to the influence of high-pressure oil remaining in the auxiliary flow path. Ta.

The present invention provides a pair of oil chambers in the lid body of the main body that are located between the valve plate and the discharge port and open through a narrow passage toward the cylinder block side, so that the oil chambers can communicate with the cylinder hole of the cylinder block. An oil passage is provided on the opposite side of the cylinder block to the next opening suction port or discharge port formed on the lid of the main body on the side in the relative rotational direction of the cylinder block, and the suction port is provided on the cylinder block side of the oil chamber. By providing an oil passage that is opened and closed by a free piston that leads to This invention relates to an axial pump having a pulp mechanism that equalizes the internal pressure of the port, eliminates pulsation that occurs when hydraulic oil in a confined volume is opened to a port, and performs smooth switching.

Next, an embodiment in which the present invention is applied to a diagonal shaft type axial piston pump will be described with reference to the drawings.As shown in FIG. A cylinder block 5 that forms a fixed angle θ with respect to the shaft 3 and is rotatable around a pin 4 is built in. Bevel gears 6 and 7 provided on each mesh with each other, and the cylinder block 5 is moved from the drive shaft 3 to the cylinder block 5. The rotation is transmitted to the

A plurality of cylinder holes 8 are bored in the cylinder block 5 in the longitudinal direction, and a piston 9 is slidably inserted into each cylinder hole 8.

The spherical head 10 of the piston is accommodated in a recess 11 formed in the end of the drive shaft 3.

Further, a valve plate 12 is attached in contact with the cylinder block 5.
is positioned on the lid 13 of the main body 1 by a pin 14.

As shown in detail in FIG. 2, the valve plate 12 is provided with a fan-shaped suction port 15 and a discharge port 16, which communicate with a suction port 17 and a discharge port 18 formed in the lid 13 of the main body. .

Additionally, the lid body 13 has a pair of oil chambers 20 that communicate with a narrow oil passage 19 that opens toward the cylinder block between the suction port 15 and the discharge port 16 of the valve plate 12.
21 is bored, and a free piston 22゜2 is attached to this.
3 is inserted.

24 is a narrow oil passage 19 to prevent drastic changes in the amount of oil passing through.
It is a ■-shaped notch provided in the opening of the

A cylinder block 5 is installed in the oil chamber 20 formed in the middle part.
For the part that rotates from the suction port 17 to the discharge port 18, as shown in FIG. An oil passage 26 that is opened and closed by 22 and communicates with the suction port 17 is provided.

In addition, in the portion where the cylinder block 5 rotates from the discharge port 18 to the suction port 17, an oil passage 27 that faces the opposite side of the oil chamber 21 from the cylinder block 5 and leads to the suction port 11 and a free passage are connected to each other, as shown in FIG. An oil passage 28 that is opened and closed by the piston 23 and communicates with the suction port 17 is provided.

That is, although it is not necessary, a passage 29 is bored in the free piston 23, and the piston 23 is connected to the oil passage 28.
When the valve reaches the position where the valve is closed, the oil passage 30 is opened to equalize the pressure in the cylinder hole 8 and the suction port 17.

As shown in detail in FIG. 3, when the cylinder block 5 switches from the suction port 17 to the discharge port 18, the piston starts closing near the bottom dead center, and the discharge port 1
The pressure inside the cylinder hole 8 continues to rise at 1 which opens at 8.

In this case, the pressure inside the cylinder hole 8 is
2, but the pressure on the other discharge side is applied to the upper end 31 of the passage 2.
5 and acts on the lower end 32 of the free piston.

However, if the pressure inside the cylinder hole 8 is lower than the pressure on the discharge side, the free piston 22
It is pushed to the side, cutting off communication between the thin oil passage 19 and the oil passage 26.

As a result, the pressure within the cylinder hole 8 increases.

As this stroke progresses and the pressure inside the cylinder hole 8 becomes higher than the pressure on the discharge side, the upper end 31 of the free piston 22
Pressure oil in the cylinder hole 8 acts on the free piston 22 so that the thin oil passage 19 and the oil passage 26 communicate with each other.

Then, the pressure oil escapes to the suction port 17 through the oil passage 26, and the pressure inside the cylinder hole 8 becomes low.

In this way, the cylinder hole 8 is connected to the discharge ports 16, 18.
When it leads to , the pressure in both is equal.

Furthermore, when the cylinder block 5 switches from the discharge port 18 to the suction port 17, if the pressure in the cylinder hole 8 is higher than the pressure in the suction port 17, as shown in detail in FIG. The oil acts to lower the free piston 23 and open the oil passage 28.

As a result, the pressure oil passes through the oil passage 19.28 to the suction port 17.
The pressure in the cylinder hole 8 is reduced.

Furthermore, when the pressure in the cylinder hole 8 becomes lower than that on the suction side after the top dead center, the lower end 34 of the free piston 230 is pushed and moves to the valve plate side, and the pressure in the cylinder hole 8 becomes the pressure in the suction port 17. Make equal.

When the free piston 23 moves to the valve plate side, the oil passage 28 is blocked.

Since the internal volume of the cylinder is smaller in the discharge → suction section than between suction → discharge, even if the confinement range is small, the effect is small and the free piston 23 may reach the valve plate side end due to a slight machining error. Even if the cylinder hole 8 does not open to the suction port N5, 17, the pressure inside the cylinder hole 8 may become lower than the suction side pressure, and cavitation may occur.

In order to avoid this, if the free piston 23 is provided with a passage 29 as in the embodiment, the cylinder hole 8 will be connected to the passage 29,
It communicates with the suction port via the oil passage 30, and the pressure can be made equal to that of the suction port 17 to prevent negative pressure.

FIG. 5 shows the pressure change inside the cylinder hole 8 as the cylinder block rotates 50 times.

Section A-B is a confinement section when moving from the suction port to the discharge port, and section CD is a confinement section when moving from the discharge port to the suction port.

By the operation of the free piston 32, the negative pressure (sections α2 and β1) in the confinement section shown by the solid line in FIG.

In the above embodiments, a diagonal shaft type button is shown, but it goes without saying that a swash plate type or rotating swash plate type button can also be used.

As described above, this invention provides a free piston in the middle between the low pressure side and the high pressure side, equalizes the pressure in the confined volume and the pressure in the next port to be opened, and sucks in excess pressure. Since the high-pressure oil is released to the side, the high-pressure oil does not have an adverse effect on the cylinder hole, and the pulsation can be reduced close to the ideal level. pressure change.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a front view of a valve plate, FIG. 3 is a sectional view of the main part of the invention taken along the line FIG. 5 is a cross-sectional view of the same main part taken along the line IV--IV in FIG. 5, and is an explanatory diagram showing changes in discharge pressure according to the present invention. 5... Cylinder block, 8... Cylinder hole, 12... Valve plate, 15...
...Suction port, 16...Discharge port, 17
...Suction port, 18...Discharge port, 19...Narrow oil passage, 20,21...
Oil chamber, 22, 23...Free piston, 252
7...Oil passage that always runs in the direction of rotation, 26°2
8... Oil passage opened and closed by free piston.

Claims (1)

[Claims] 1 A thin oil passage 1 is installed on the cylinder block side between the suction port 15 and the discharge port 16 of the valve plate 12.
A pair of oil chambers 20 and 21 that open through 9 are connected to the lid 1 of the main body.
3 to be able to communicate with the cylinder hole 8 of the cylinder block 5, and a next opening suction port formed in the cover body 13 of the main body on the side in the relative rotation direction of the cylinder block 5 on the side opposite to the cylinder block of the oil chamber. 17 or discharge port 18
The axial piston pump 0 is equipped with oil passages 25 and 27 that are always in communication with the oil chambers 20 and 21, and oil M26 and 2B that communicate with the suction port 17 and are opened and closed by free pistons 22 and 23 on the cylinder block side of the oil chambers 20 and 21.