JPH082470Y2 - Piston pump - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a piston pump, and more particularly to a piston pump designed to prevent an increase in discharge pulsation.

[Prior Art] As a conventional piston pump, an axial piston pump in which the direction of reciprocating motion of the piston is substantially parallel to the central axis of the cylinder block is generally known.
There is a diagonal type. For example, a fixed swash plate type axial piston pump has, as shown in FIG. 8, a drive shaft 2 fitted and supported in a housing 1, a cylinder block 3 rotatably provided with the drive shaft 2 and having a plurality of bores 31,
A swash plate 4 arranged so that the tilt angle can be adjusted with respect to the cylinder block 3; Is equipped with. Each piston 5 is generally formed with a cavity 51 that is open to the head side for weight reduction. The cavities 51 are formed to have the same size in consideration of the rotation balance of the cylinder block 3.

[Problems to be Solved by the Invention] By the way, if the cavities 51 of the pistons 5 are formed to have the same size as in the above-mentioned conventional case, fluids such as oil discharged by the pistons have the same volume, which causes Regular discharge pulsation occurs according to the number of cylinders. However, as shown in FIG. 9, at a specific rotational speed at which the discharge pulsation of the pump and the reflected wave from the pump circuit device match, the resonance may remarkably amplify the discharge pulsation. Is the vibration of the pump and pump circuit equipment.
The inconvenience of loud noise occurs.

The present invention has been devised in view of the above inconvenience,
The technical problem is to prevent amplification of discharge pulsation and reduce vibration and noise.

[Means for Solving the Problems] In order to solve the above problems, the piston pump of the present invention is
A plurality of bores arranged in the cylinder block, and a relative movement mechanism that reciprocates the pistons fitted in the bores based on the rotation of the drive shaft, It is composed of a piston.

[Operation] A fluid such as oil that is sucked into and discharged from the bore by the piston is slightly compressed. For this reason,
The smaller the cavity volume of the piston, the higher the compression rate of the fluid in the bore, the larger the discharge amount and the larger the discharge pulsation. Further, the timing at which the fluid is discharged from the bore becomes slightly earlier as the cavity volume becomes smaller. Therefore, the waveform of the discharge pulsation becomes irregular, and resonance with the reflected wave of the pump circuit device is unlikely to occur. The discharge pulsation increases as the discharge pressure increases, but the compression rate of the fluid also increases, so that resonance is less likely to occur.

[Embodiment] An embodiment in which the present invention is applied to a fixed swash plate type axial piston pump will be described below.

(First Embodiment) The piston pump of the present embodiment is the same as the conventional fixed swash plate type axial piston pump except for the piston group, and the other configurations are the same. Therefore, the description of the entire structure is omitted and only the main parts are omitted. Will be explained. The same reference numerals are used for common parts.

The piston group in this embodiment is composed of nine pistons corresponding to the cylinder block 3 of nine cylinders, and includes a piston group of six large hollow pistons 6 having a large cavity volume and three pistons having a small cavity volume. It is configured with a piston group including a small cavity piston 7. The large hollow piston 6 has a first
As shown in the figure, a substantially cylindrical cavity 61 that opens toward the head is formed along the cylindrical main body portion. The cavity 61 is formed as large as possible within a range where there is no problem in strength. Further, an oil supply hole 62 for sending out oil as a lubricant from the cavity 61 is formed in a spherical portion where the large cavity piston 6 is held by the shoe 41. And the small cavity piston 7 is, as shown in FIG.
A resin block 73 is embedded in the entire cavity 71 of the same as that of the large cavity piston 6. A communication passage 74 is formed in the resin block 73 so that the oil supply hole 72 communicates with the piston head side.

And, as shown in FIG. 3, these two piston groups are
The two large cavity pistons 6 are arranged in this order along the rotation direction of the cylinder block 3 so that one small cavity piston 7 follows, so that stable rotation balance is ensured.

In the piston pump configured as described above, the discharge pulsation of the oil delivered by each piston is as shown in FIG. That is, the discharge pulsation of the small-cavity piston 7 becomes larger than the discharge pulsation of the large-cavity piston 6 by Δp, and is displaced toward the Δt earlier side.
Becomes irregular due to the discharge pulsation of. Therefore, the discharge pulsation is less likely to resonate with the reflected wave from the pump circuit device, so that vibration and noise of the pump and the pump circuit device can be reduced.

(Second Embodiment) A piston group in this embodiment includes a piston group including three large cavity pistons 6 having a large cavity volume, a piston group including three small cavity pistons 7 having a small cavity volume, and a cavity. It is composed of a piston group including three medium hollow pistons 8 having a medium volume. The large cavity piston 6 and the small cavity piston 7 are the same as those of the first embodiment. As shown in FIG. 5, the medium hollow piston 8 has a resin block 83 of approximately half the volume of the hollow 81 on the oil supply hole 82 side in the hollow 81 as compared with the large hollow piston 6. It is buried. A communication passage 84 is formed in the resin block 83 similarly to the resin block 73 of the small cavity piston 7.

As shown in FIG. 6, these three piston groups are arranged in the order of the large cavity piston 6, the medium cavity piston 8, and the small cavity piston 7 along the rotation direction of the cylinder block 3.

The discharge pulsation of the piston pump configured as described above is as shown in FIG. That is, the discharge pulsation of the medium-cavity piston 8 becomes a little larger than the discharge pulsation of the large-cavity piston 6, and is slightly earlier than the discharge pulsation of the large-cavity piston 6.
The discharge pulsation of is slightly larger than the discharge pulsation of the hollow piston 8 and is slightly shifted to the earlier side. Therefore, the discharge pulsation as a whole becomes irregular, and vibration and noise of the pump and pump circuit equipment can be reduced as in the case of the first embodiment. In this embodiment, since the pistons are composed of three types of piston groups, the discharge pulsation as a whole becomes more irregular than that of the first embodiment, and the discharge pulsation resonates more with the reflected wave from the pump circuit device. It becomes difficult.

In the first and second embodiments, the weight difference between the piston groups is reduced by using a lightweight resin block for the same piston in order to make the cavity volumes different, but the piston is divided by the weight of the embedded resin block. It is even better to reduce the weight to make the weight of each piston group uniform.

Further, although the first and second embodiments have described the fixed swash plate type axial piston pump, the present invention is not limited to this, and is also applied to a rotary swash plate type or a swash shaft type axial piston pump or a radial piston pump. can do.

[Advantages of the Invention] In the pump according to the present invention, since the piston group is composed of a plurality of types of pistons having different cavity volumes, the discharge pulsation becomes irregular and it is difficult to resonate with the reflected wave. It is possible to reduce the generated vibration and noise.

[Brief description of drawings]

1 to 4 relate to a first embodiment of the present invention. FIG. 1 is a sectional view of a large cavity piston, FIG. 2 is a sectional view of a small cavity piston, and FIG. 3 is an arrangement state of piston groups. FIG. 4 is a sectional view of the cylinder block shown, and FIG. 4 is a graph showing discharge pulsation. 5 to 7 relate to the second embodiment, FIG. 5 is a cross-sectional view of a hollow piston, FIG. 6 is a cross-sectional view of a cylinder block showing an arrangement state of piston groups, and FIG. 7 is a discharge pulsation. It is a graph shown. 8 and 9 relate to a conventional example, and FIG. 8 is a sectional view of a fixed swash plate type axial piston pump,
FIG. 9 is a graph showing an increase in discharge pulsation. 1 ... Housing, 2 ... Drive shaft 3 ... Cylinder block, 4 ... Swash plate 5 ... Piston, 6 ... Large cavity piston 7 ... Small cavity piston, 8 ... Medium cavity piston 61, 71, 81 ... Cavity 73, 83 ... Resin block

Claims (1)

[Scope of utility model registration request] 1. A cavity having a plurality of bores arranged in a cylinder block and a relative movement mechanism for reciprocating a piston inserted in each bore based on the rotation of a drive shaft. A piston pump comprising a plurality of types of pistons having different volumes.