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EP-4219941-B1 - HYDRAULIC PUMP

EP4219941B1EP 4219941 B1EP4219941 B1EP 4219941B1EP-4219941-B1

Inventors

  • YOSHIDA, TAKESHI
  • MIURA, HIDETOSHI
  • HIRANO, Yasunori
  • MAKINO, YUTA
  • HYODO, Yuya

Dates

Publication Date
20260513
Application Date
20210928

Claims (7)

  1. A hydraulic pump comprising: a valve plate (6) including a suction port (61) and a delivery port (62); a valve cover (7) to which the valve plate is mounted, the valve cover including a suction passage (71) that communicates with the suction port and a delivery passage (72) that communicates with the delivery port; and a cylinder block (2) that slides on the valve plate, the cylinder block including cylinder bores (21) that receive therein respective pistons (3), wherein the valve cover includes a recess (75) in which a bearing (13) is fitted, the bearing rotatably supporting a rotational shaft (11) that penetrates the cylinder block; characterised in that the valve cover includes: a first chamber (8) that communicates with the delivery passage through a communication passage (81) and functions as a Helmholtz resonator; and a second chamber (9) that communicates with the delivery passage, or with the first chamber, through an introduction passage (91), in the valve cover and the valve plate, a supply passage (93) extends from the second chamber to a bottom dead center-side sealing surface (64) of the valve plate, the bottom dead center-side sealing surface being a surface located between the suction port and the delivery port; the first chamber and the second chamber are located between the suction passage and the delivery passage; and at least a part of the first chamber and at least a part of the second chamber are positioned within a region that is surrounded by the recess, the suction passage, and the delivery passage.
  2. The hydraulic pump according to claim 1, wherein at least a part of the introduction passage (91) functions as a restrictor.
  3. The hydraulic pump according to claim 1 or 2, wherein at least a part of the supply passage (93) functions as a restrictor.
  4. The hydraulic pump according to any one of claims 1 to 3, wherein the first chamber (8) and the second chamber (9) are located side by side in an axial direction of a rotational shaft (11) that penetrates the cylinder block (2).
  5. The hydraulic pump according to claim 4, wherein the second chamber (9) is positioned between the valve plate (6) and the first chamber (8).
  6. The hydraulic pump according to any one of claims 1 to 5, wherein when seen in an axial direction of the rotational shaft (11), the second chamber (9) extends in a manner to straddle the bottom dead center-side sealing surface (64) and a top dead center-side sealing surface (63) of the valve plate (6), the top dead center-side sealing surface being a surface located between the suction port (61) and the delivery port (62).
  7. The hydraulic pump according to any one of claims 1 to 6, wherein a volume of the second chamber (9) is less than a volume of the first chamber (8).

Description

Technical Field The present disclosure relates to a hydraulic pump that is an axial piston pump. Background Art Conventionally, there is a known hydraulic pump that is an axial piston pump. The hydraulic pump includes a valve plate and a cylinder block. The valve plate includes a suction port and a delivery port. The cylinder block slides on the valve plate. The cylinder block includes cylinder bores. The cylinder bores receive therein respective pistons. In each cylinder bore, in a state where the cylinder bore is in communication with the suction port, the piston shifts in a direction away from the valve plate, and thereby suction is performed, whereas in a state where the cylinder bore is in communication with the delivery port, the piston shifts in a direction toward the valve plate, and thereby delivery is performed. A bottom dead center is the position of the piston in which the piston is farthest from the valve plate, whereas a top dead center is the position of the piston in which the piston is closest to the valve plate. In a state where the cylinder bore is in communication with the suction port, the pressure of the cylinder bore is low. On the other hand, when the cylinder bore is brought into communication with the delivery port, the pressure of the cylinder bore becomes high. Accordingly, immediately after the cylinder bore is brought into communication with the delivery port (i.e., when the cylinder bore starts communicating with the delivery port), pulsation of delivery pressure occurs. One method of reducing the pulsation of delivery pressure, which occurs when the cylinder bore starts communicating with the delivery port, is to introduce delivery pressure into the cylinder bore near the bottom dead center. For example, Patent Literature 1 discloses a hydraulic pump in which a valve cover (referred to as a "case" in Patent Literature 1) to which a valve plate is mounted includes a suction passage and a delivery passage. The suction passage communicates with a suction port, and the delivery passage communicates with a delivery port. The delivery passage is connected to a chamber by a first communication passage. A second communication passage extends from the chamber to a bottom dead center-side sealing surface (referred to as a "sliding surface" in Patent Literature 1) of the valve plate between the suction port and the delivery port. An on-off valve is located on the first communication passage. The on-off valve opens/closes with, or more frequently than, a fundamental frequency R [Hz] (R = S × N / 60, where S is the number of pistons and N is a pump rotation speed [rpm]). According to this configuration, after the cylinder bore ends communicating with the suction port and before the cylinder bore starts communicating with the delivery port, delivery pressure is introduced into the cylinder bore. JPS 63202774 U discloses a hydraulic pump according to the pre-characterising portion of claim 1. WO 2006085547 A1 discloses a valve casing comprising: a valve plate having suction ports and discharge ports respectively communicating with a suction passage and a discharge passage of a pump case; a cylinder block slidably in contact with the valve plate and rotating; and a piston that slides in each of the cylinder bores and performs a stroke movement according to a rotation angle of each of the cylinder bores, wherein the suction port and the discharge port in the valve plate include a through hole for guiding the chamber pressure in the cylinder bore, a first oil passage for guiding the pressure oil of the chamber pressure to the through hole force, and a system pressure, a second oil passage that guides the pressure oil of the first oil passage from the discharge port, and a balance piston having a second end face receiving the pressure oil from the second oil passage. JP 2000097147 A discloses an axial piston pump that is composed so that, when pressure in a certain piston chamber reaches the pressure in discharge port T, openings of other piston chambers start to lie on top of the other openings L2, and when pressure in a certain piston chamber reaches the pressure in a suction port S, openings of other piston chambers start to lie on top of the other openings L1. US 6024541 A discloses a hydraulic axial pump or motor comprising a plurality of revolving as well as reciprocating pistons, operatively associated with a stationary port plate. The plate comprises at least a first, elongated, arcuate suction port and at least a second elongated, arcuate discharge port, divided by a bridging portion extending between the downstream side of the suction port and the upstream side of the discharge port. A tortuous passage of a non-uniform cross-section is formed in the bridging portion, allowing the by-passing of the fluid first in a direction towards the downstream side of the suction port and then towards and into the upstream side of the discharge port. Citation List Patent Literature PTL 1: Japanese