JPS5834674B2 - hydraulic axial piston pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides pistons that are inserted and built into a number of cylinders that are bored into a cylinder block that rotates in sliding contact with a valve gear. position,
That is, the present invention relates to a hydraulic axial piston pump in which a pressure reducing means is disposed in a fluid passage communicating the cylinder with a low pressure source during the period of movement of the cylinder to its previous position in communication with the suction port.

A conventional hydraulic pump will be explained with reference to FIGS. 1 to 4.

Figure 1a is an end view of a normally used valve system 1' of an axial piston pump in which a suction side port 1'a and a discharge side port 1'b are provided symmetrically with respect to the x-x axis and the y-y axis. ,
Figure b shows the cylinder pressure diagram.

Fig. 2 A shows the valve system shown in Fig. 1 by avoiding sudden changes in pressure (sudden rise, sudden drop) during the suction and discharge strokes of the piston.
As a method of reducing noise through gradual pressure fluctuations,
It uses pre-compression and pre-expansion.

That is, the suction and discharge side ports 2'a and 2' of the valve system 2'
b is asymmetric, and the piston performs confinement compression in the precompression angle θC section, and confinement expansion in the preexpansion angle θe section.

The opening diagram is an in-cylinder pressure diagram when the valve system 2' shown in Figure A is used.

Fig. 3 is a developed view showing the state of the piston 4' during rotation of the cylinder 3'75i in the hydraulic pump equipped with the valve device 2' of Fig. 2a (2'a is the suction side port, 2'b This type of hydraulic pump can reduce noise on the discharge and suction sides, but has the disadvantage that it can only be applied to Pd where the discharge pressure is constant.

Figure 4 shows the state of the cylinder pressure when the discharge pressure changes in a hydraulic pump using the valve system 2' shown in Figure 2. Figure 1 shows the state of the cylinder pressure when the discharge pressure is low, Figure 11 shows is high.

That is, as shown in Figure 2, the constant discharge pressure is Pd.
If the discharge pressure in Figure 1 is low, the in-cylinder pressure will drop to atmospheric pressure at a'ra in the middle of the pre-expansion section θe, and the section from point a to bZa will cause vacuum due to overexpansion, and the in-cylinder pressure will decrease. Leaves negative effects such as bubble generation.

In addition, when the discharge pressure is high as shown in Figure 11, the decrease in cylinder pressure is not completed at cia at the end of the pre-expansion period, so the cylinder pressure drops rapidly from point C to point d, and the effect of reducing noise is small. stomach.

As mentioned above, the hydraulic pumps shown in Figs. 2 and 3 are only effective at a certain discharge pressure, and it is difficult to ensure a sufficient pre-expansion section due to the danger of vacuum, etc. The pre-expansion angle θe could only be designed to be around 10° to 20°.

In the conventional hydraulic pump, the pressure can only be reduced after the piston passes the top dead center, and even if the pressure is reduced, there is a problem of cavitation at low pressure, and a wide pressure reduction section is provided. In order to improve the problem that was previously difficult and to start reducing the cylinder pressure while the piston is moving from bottom dead center to top dead center, the valve gear or swash plate is placed at a position just before the piston reaches top dead center. A pressure reduction orifice is provided to release the oil, and the pressure reduction orifice makes it possible to reduce the pressure from a position before the top dead center while the piston is moving forward, making the effective pressure reduction range considerably large, for example, a gradual pressure drop from 35° to 75° or more. It seeks to eliminate the drawbacks of conventional hydraulic axial piston pumps by providing the following advantages:

The present invention will be explained based on embodiment drawings.

First Embodiment (See Figures 5 to 9) Figure 5 is an exploded view of the piston state, where 1 is a cylinder block fixed to the main shaft (not shown), 2 is a cylinder block drilled in the cylinder block 1, and 2 is a cylinder block fixed to the main shaft (not shown). multiple cylinders, 3 is each cylinder 2
One end of the piston 3 is in sliding contact with a swash plate (not shown), and the piston 3 is caused to reciprocate between top dead center and bottom dead center in order to alternately perform a discharge stroke and a suction stroke. , completes its discharge stroke at top dead center.

4 is a valve system, 5 is a piston chamber, and 6 is a discharge port (discharge passage).While the piston 3 is in the discharge stroke, the cylinder 2
It is for discharging fluid from inside, and is provided in the radial direction of the cylinder block 1 to communicate the discharge groove 7 provided around the cylinder block 1 with the piston chamber 5.

8 is installed in the discharge-only port (discharge passage) 6, and during the discharge stroke of the piston 3, the fluid pressure inside the cylinder 2 (
9 is a spring, and 10 is a suction side port provided in the valve system 4. The check valve opens when the cylinder pressure (in-cylinder pressure) becomes larger than the discharge pressure of the pump, and allows the fluid inside the cylinder 2 to flow.

FIG. 6A is an end view of the valve system 4, and shows the suction side port 1.
0 has a semicircular arc shape and is provided on one side.

3 is the above-mentioned piston, G is for pressure reduction provided in the valve system 4 (
This orifice (for oil relief) (pressure reducing means) is arranged in the fluid passage described later, and this orifice G is located just before the top dead center of the piston, as shown in Figures 5 and 6A. It is provided at a position below the rotation angle θ=1800, and extends to a position slightly beyond top dead center.

To explain the operation, when the piston 3 starts moving forward from the bottom dead center and the fluid pressure in the cylinder becomes greater than the discharge pressure of the pump, the check valve 8 opens and discharge begins, entering the discharge stroke.

Then, the piston 3 further advances to point D and communicates with the orifice G for pressure reduction.

At this time, if the amount of oil escaping from the orifice G is greater than the amount of oil discharged due to the forward movement of the piston 3, the cylinder pressure will drop below the discharge pressure, so the check valve 8 will immediately close, and the cylinder pressure will begin to decrease.

That is, when the piston 3 reaches point D, pressure reduction starts, and the piston 3 continues to move forward until it reaches the top dead center, and the pressure decreases slowly to compensate for the amount of oil escaping from the orifice G. ``Furthermore, the pressure is reduced until it reaches point F (a point slightly past top dead center), and at the point when point F is reached, the piston chamber 5 communicates with the suction side port 10 of the valve system 4.

During the period in which the piston 3 moves from the position before reaching the top dead center to the position past the top dead center (the position before the cylinder 2 communicates with the suction port 10), the passage connecting the cylinder 2 to the low pressure source is It is a passageway.

In conventional hydraulic pumps, as shown in Figure 3, all pistons on the discharge side communicate with each other until they reach top dead center, and no means are taken to reduce the pressure in only one piston. Therefore, it was not possible to reduce the pressure at a position before top dead center.

Note that even in conventional hydraulic pumps, there is a means for temporarily closing the discharge port 2'a at a position before the piston top dead center (indicated by K/) as shown in FIG. In this case, it became trapped, and compression pressure was generated separately from the discharge pressure, causing problems.

However, according to the present invention, the pressure reducing means, that is, the pressure reducing orifice G
The fluid passage in which the piston 3 is provided extends from a considerably large angle, for example 35 degrees, before the piston 3 reaches the top dead center to before the piston 3 passes the top dead center and the cylinder 2 communicates with the low pressure source. 2, and during this period, the effective decompression angle range is approximately 75 degrees, that is, as shown in Figure 6, D
The pressure reduction angle θd from point to point F can be secured, and the fluid pressure in the cylinder can be gradually reduced within this large angle range.

This large effective pressure reduction angle range can only be obtained by the discharge passage 6 that communicates with the cylinder 2 during the discharge stroke, the check valve 8 and the pressure reduction means G installed therein.

Without the above three factors, a problem would occur that would cause confinement compression before the top dead center.

The cylinder pressure state in the conventional case without any pressure reducing means (curve y
Compared to FIG. 8, which shows the pressure (indicated by ), a gentle pressure drop as shown by P in FIG. 6B is possible, which contributes to a reduction in noise.

Further, the hydraulic pump which employs a pressure reduction method using a pressure reduction orifice G as in the present invention is effective even when the discharge pressure changes as shown in FIG.

That is, when the discharge pressure in Figure A is low, the amount of escape from the orifice G is small, so the pressure reduction effect is small, and the rate of decrease in the cylinder pressure is slow, as shown by the curve P1.

When the discharge pressure is high, the rate of descent is fast, as shown by curve P2 in diagram B.

In any case, it is gentler than the curve P' shown in FIG. 8, which shows the conventional case without pressure reducing means.

In addition, problems such as cavitation at low pressure due to normal confinement expansion and sudden drop in pressure at high pressure are greatly alleviated.

2nd Embodiment (See Figures 10 and 11) In the first embodiment, there was one orifice for pressure reduction, but in this embodiment, as shown in Figure 10, there are two orifices for pressure reduction in the valve type 4. Orifice G
, and 02 are provided at positions corresponding to points D and F in FIG. 5, respectively.

Note that the number of orifices for depressurization is not limited to two, but a plurality of orifices can be provided at appropriate positions, and these may be designed and set in the depressurization waveform.

When one pressure reducing orifice G is provided as in the first embodiment, the effect is limited to I in FIG. 11a, but as in the second embodiment, the effect is 01. When two G2 are provided, the effect shown by ■ is added as shown in Fig. 6.

Third Embodiment (See Figure 12) In each of the above embodiments, a pressure reducing orifice is provided in the valve shape, but this orifice does not necessarily need to be provided in the valve shape, and as in this third embodiment, the orifice is provided in the front surface of the piston. side swash plate 2
A decompression orifice G3 may be installed at 0.

In this case, as in the previous embodiment, it is essential that the pump be an axial piston pump of the type that has a discharge valve (a check valve provided on the discharge side).

In FIG. 12, S indicates the main shaft, 1 indicates the cylinder block, 3 indicates the piston, and 4 indicates the valve type.

As described above, when the swash plate 20 is provided with the pressure reducing orifice G3, the valve type 4 is provided with the orifice G1 or G1. This is more effective than installing G2.

That is, when an orifice is installed in a valve type, the oil jetted out from the orifice generates bubbles, and if the oil enters the suction side, this results in unfavorable noise.

On the other hand, if an orifice is installed in the swash plate, the oil jetted out from the orifice is drained through the pump casing, which does not affect the suction conditions, which is preferable in terms of noise reduction.

In short, the present invention consists of a valve mold 4, a cylinder block 1 that rotates in sliding contact with the valve gear, and a number of cylinders 2 that are inserted into the cylinder block, respectively, as explained in detail in each of the above embodiments. A built-in piston 3 is made to reciprocate between top dead center and bottom dead center in order to perform the discharge stroke and suction stroke alternately, and completes the discharge stroke at the top dead center, and one end of each piston is The swash plate that comes into sliding contact with the piston is built into the discharge passage 6 that discharges fluid from the cylinder while the piston is in the discharge stroke, and the piston begins to move forward from the bottom dead center and the fluid pressure in the cylinder becomes the pump discharge pressure. In a type of hydraulic axial piston pump that has a check valve that opens when the piston reaches the top dead center, the piston moves forward and the piston reaches the top dead center. This hydraulic axial piston pump is characterized in that during the period of movement of the cylinder past the point to the position before communicating with the suction port, a pressure reducing means G is installed in the fluid passage that communicates the cylinder with a low pressure source.

That is, in the present invention, as described above, when the fluid pressure in the cylinder becomes greater than the discharge pressure of the pump during the discharge stroke of the piston, the check valve is opened to allow the fluid in the cylinder to flow; When the piston moves forward and the cylinder communicates with the pressure reducing means, and at this time, the amount of oil escaping from the pressure reducing means is greater than the amount of oil discharged due to the forward movement of the piston, the pressure inside the cylinder becomes less than the discharge pressure, so the check valve closes. The cylinder pressure begins to decrease.

That is, a pressure reducing means for releasing oil is provided in the valve gear or the swash plate at a position just before the piston reaches the top dead center, and the fluid passage in which the pressure reducing means is provided is considerably large before the piston reaches the top dead center. The piston communicates with the cylinder over an angle of, for example, 35 degrees until it passes the top dead center and the cylinder communicates with the low pressure source, and during this period, that is, the effective decompression angle range is approximately 75 degrees, as shown in Figure 6. As shown, the pressure reduction angle θd from point D to point F can be secured, and the fluid pressure in the cylinder can be gradually reduced in this large angle range.

In other words, the above-mentioned large effective pressure reduction angle range can only be obtained by the above-mentioned pressure reduction means, a discharge passage that communicates the cylinders during the discharge stroke, and a check valve interposed therein, and these are essential. However, in the present invention, by using a combination of the above-mentioned pressure reducing means, discharge passage, and check valve, the occurrence of trapped compression before top dead center does not occur. Furthermore, the occurrence of cavitation at low pressures can be eliminated, and a low-noise hydraulic axial piston pump can be provided.

[Brief explanation of drawings]

Figure 1 a is an end view of a normally used axial piston pump valve system, b is a cylinder pressure diagram of a pump using the valve system shown in a, and figure 2 A is the valve shown in Figure 1. An end view of a conventional valve system that attempts to reduce noise due to pressure fluctuations.
The mouth is shown in Figure 3 of the cylinder pressure diagram of the pump using the valve gear shown in A.
The figure is a developed view showing the state of the piston during one rotation of the cylinder in the hydraulic pump shown in Fig. 2, and Fig. 4 is a developed view showing the state of the piston in the hydraulic pump shown in Figs. 2 and 3 when the discharge pressure changes. Indicates the pressure state; 1 indicates low discharge pressure;
1 is a curve diagram when the height is high, FIGS. 5 to 9 are related to the first embodiment of the present invention, FIG. 5 is a developed view showing the state of the piston during one revolution of the cylinder, and FIG. is an end view of the valve system, B is a curve diagram showing the state of the cylinder pressure during pre-expansion, and Fig. 7 is a diagram showing one rotation of the cylinder of a conventional hydraulic pump with the discharge port closed at a position before the piston top dead center. FIG. 8 is a curve diagram showing the cylinder pressure state of a conventional pump without any pressure reducing means, and FIG. 9 is a diagram showing changes in the discharge pressure of the hydraulic pump according to the present invention shown in FIGS. 5 and 6. shows the cylinder pressure state when the discharge pressure is low, A is a curve diagram when the discharge pressure is low, B is a curve diagram when the discharge pressure is low
10 and 11 relate to the second embodiment of the present invention, FIG. 10 is a developed view of the piston state during one rotation of the cylinder, and FIG. 11 is a curve diagram of the first embodiment. , second
FIG. 12 is a partial longitudinal sectional schematic diagram of the third embodiment of the present invention. 4...Valve equipment, 1...Cylinder block, 2...Cylinder, 3...Piston,
20... Swash plate, 8...° Check valve, G, G
1. G2... pressure reducing orifice provided in valve system 4,
G3... Decompression orifice provided in the swash plate 20, 6
・・・・・・Discharge-only port, discharge passage, 10...
...Suction port, D...The point at which the piston 3 reaches the valve arrangement due to its forward movement, F...The point slightly past the top dead center.

Claims (1)

[Claims] 1. A valve system, a cylinder block that rotates in sliding contact with the valve system, and a number of cylinders that are inserted and built into the cylinder block and that are inserted into the cylinder block to perform the discharge stroke and suction stroke alternately. It is forced to reciprocate between bottom dead center and
A piston that completes its discharge stroke at the top dead center, a swash plate on which one end of each piston comes into sliding contact, and a swash plate that is built in a discharge passage that discharges liquid from the cylinder while the piston is in the discharge stroke; In a hydraulic axial piston pump, the piston has a check valve that opens when the piston begins to move forward from the bottom dead center and the fluid pressure in the cylinder becomes greater than the discharge pressure of the pump, allowing the fluid in the cylinder to flow. During the period in which the piston advances and moves from a position before reaching top dead center to a position past the top dead center and before the cylinder communicates with the suction port, a pressure reducing means is provided in the fluid passage that communicates the cylinder with the low pressure source. Hydraulic axial piston pump characterized by the installation.