JP4134381B2 - Variable displacement piston pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a hydraulic piston pump that supplies pressure fluid to various actuators to operate these actuators. More specifically, the present invention relates to a variable displacement piston pump that adjusts a reciprocating stroke of a piston according to an inclination angle of a variable swash plate.
[0002]
[Prior art]
  Conventionally, variable displacement axial piston pumps have been used in construction machines such as excavators as disclosed in JP-A-9-280161. The pump includes, for example, three independent hydraulic supply systems that supply pressure oil to the right traveling system, left traveling system, and turning system of the excavator, respectively.
[0003]
  The configuration of this type of pump will be described below. As shown in FIG. 10 (a cross-sectional view showing the periphery of the pump cylinder block), the cylinder block (a) includes an inner cylinder row (b) positioned on the inner peripheral side and an outer cylinder row (c) positioned on the outer peripheral side. ) And are formed. Pistons (d, d) are accommodated in the cylinder chambers (b1, c1) of the cylinder rows (b, c) so as to be able to reciprocate. The port side end surface (e) of the cylinder block (a) is formed with three port groups (e1, e2, e3) formed at concentric circumferential positions having different diameters around the pump shaft (f). ing. Half of each cylinder chamber (b1, b1,...) Of the inner cylinder row (b) is in the first port group (e1) located on the outermost side among the three port groups (e1, e2, e3). Communicate. The other half of the cylinder chambers (b1, b1,...) Communicates with the second port group (e2) located inside the first port group (e1). Further, the cylinder chambers (c1, c1,...) Of the outer cylinder row (c) communicate with the third port group (e3) located further inside the second port group (e2).
[0004]
  As shown in FIG. 11, the discharge side of the valve plate (g) that is in sliding contact with the port side end face (e) of the cylinder block (a) can be individually communicated with the port groups (e1, e2, e3). In this way, three arc-shaped discharge side through holes (g1, g2, g3) are formed in the inner and outer peripheral directions. That is, the pressure oil is independently discharged through each of the discharge side through holes (g1, g2, g3). Note that (g4) in FIG. 11 is a suction side through hole for sucking oil into each cylinder chamber (b1, c1). (h, h,...) are notches formed in the through holes (g1, g2, g3, g4). This notch (h) gradually increases the communication area between each through hole (g1, g2, g3, g4) of the valve plate (g) and each cylinder chamber (b1, c1) as the cylinder block (a) rotates. To avoid sudden fluctuations in hydraulic pressure.
[0005]
  With this configuration, hydraulic pressure is independently supplied from one port group to the right traveling system, from the other port group to the left traveling system, and from the remaining one port group to the turning system. That is, three independent discharge flows can be supplied from one cylinder block (a).
[0006]
  Further, the tip surfaces of the pistons (d, d,...) Are slidably in contact with the variable swash plate (i). The variable swash plate (i) is inclined by a predetermined angle with respect to the reciprocating direction of the piston (d, d,...). The stroke of the reciprocating motion of the piston (d) is adjusted by the inclination angle of the variable swash plate (i). That is, the reciprocating stroke of the piston (d) is determined by the inclination angle of the variable swash plate (i).
[0007]
  As a mechanism for adjusting the inclination angle of the variable swash plate (i), a biasing force (P) of a spring (not shown) is applied to one end edge (the upper end edge in FIG. 10) of the variable swash plate (i). ) Acts on the side that increases the inclination angle (the side that increases the reciprocating stroke of the piston (d)). On the other hand, the variable swash plate (i) receives the pump discharge pressure (F1, F1) via each piston (d, d,...). The variable swash plate (i) has a rotation center (A) set slightly above the axis of the pump shaft (f) in the drawing. Due to the moment generated around the rotation center (A), the pump discharge pressure acts on the side where the inclination angle of the variable swash plate (i) is reduced (the side where the reciprocating stroke of the piston (d) is reduced). That is, the inclination angle of the variable swash plate (i) is determined to be a predetermined angle by the balance between the biasing force (P) of the spring and the reaction force (F2) generated by the pump discharge pressure.
[0008]
  With this configuration, when the pump discharge pressure (F1, F1) is relatively low, the inclination angle of the variable swash plate (i) is set large by the biasing force (P) of the spring, while the pump discharge pressure (F1, F1) ) Increases, the reaction force (F2) counteracts the urging force (P) of the spring to reduce the inclination angle of the variable swash plate (i). By reducing the inclination angle of the variable swash plate (i), so-called constant horsepower control is performed that suppresses the discharge flow rate, reduces the load applied to the drive source, and prevents the drive source from being overloaded. ing.
[0009]
[Problems to be solved by the invention]
  However, in the conventional variable displacement piston pump, a technique that specifically considers the opening position of the discharge side through holes (g1, g2, g3) of the valve plate (g), particularly the formation position of the notch (h) has been proposed. Not. In other words, the opening position of the discharge side through holes (g1, g2, g3) may be an area where the piston (d) is pushed down by the variable swash plate (i), and each notch (h) The formation position is set only considering that it is sufficient to provide a function for avoiding sudden fluctuations. In other words, no other functions have been proposed for the discharge-side through holes (g1, g2, g3) and the notches (h).
[0010]
  For this reason, the change state of the pressure applied to the variable swash plate (i) by the pump discharge pressure of each cylinder row (b, c) has always been fixed at a constant ratio. That is, the inclination angle of the variable swash plate (i) accompanying the change in pump discharge pressure is governed by the biasing force (P) of the spring, and the constant horsepower characteristics are determined by the biasing force (P) of the spring. The degree of freedom in changing the constant horsepower characteristics was extremely low.
[0011]
  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a constant horsepower characteristic of the pump without greatly changing the configuration of the swash plate type variable displacement piston pump. The purpose is to increase the degree of freedom of change.
[0012]
[Means for Solving the Problems]
  In order to achieve the above object, according to the present invention, a variable displacement piston pump having desired constant horsepower characteristics is obtained by improving the shape of the discharge port (discharge side through hole) of the valve plate.
[0013]
  Specifically, as shown in FIGS. 1 and 6, the first solving means includes a cylinder block (2) that rotates with a plurality of cylinders (24, 25) in which pistons (41, 42) are housed. A valve plate (3) having a suction port (31) and a plurality of arc-shaped discharge ports (32, 33, 34) in sliding contact with the cylinder block (2), and a piston (41, 42) and a variable swash plate (5) that changes the reciprocating stroke., Multiple discharge ports above (32,33,34) The above valve plate (3) Are arranged in the inner and outer circumferential directions on the discharge sideA variable displacement piston pump is assumed. With respect to the variable displacement piston pump, at least one (34) of the formation regions of the discharge ports (32, 33, 34) has a circumferential angle range other than the discharge ports (32 , 33) is different from the angular range in the circumferential direction.
[0014]
  Due to this specific matter, the piston (41, 42) reciprocates with a reciprocating stroke corresponding to the inclination angle of the variable swash plate (5) by the rotation of the cylinder block (2). By this reciprocation, a fluid is sucked into the cylinders (24, 25) from the suction port (31), and a pump operation is performed to discharge the fluid from the discharge ports (32, 33, 34).
[0015]
  The inclination angle of the variable swash plate (5) is adjusted by the pistons (41, 42) pressing the variable swash plate (5). And the angle range of the formation region of at least one (34) of each discharge port (32, 33, 34) in the valve plate (3) is different from the angle range of the other discharge ports (32, 33). Depending on these angular ranges, the region where the piston (41, 42) presses the variable swash plate (5) differs. As a result, by setting this angular range arbitrarily, a so-called self-returning moment of the variable swash plate (5) can be arbitrarily set, and a desired constant horsepower characteristic can be obtained.
[0016]
  The second solving means specifies means for making the angular ranges of the formation regions of the discharge ports (32, 33, 34) different from each other. That is, in the first solving means, notches (35, 36, 37) for suppressing pressure fluctuations in the cylinders (24, 25) are provided in the discharge ports (32, 33, 34) of the valve plate (3). ). Of these notches (35, 36, 37), the circumferential angular position of at least one notch (37) tip is made different from the circumferential angular position of the other notch (35, 36) tip.
[0017]
  With this specific matter, a desired constant horsepower characteristic can be obtained with a simple configuration in which the notches (35, 36, 37) provided in the discharge ports (32, 33, 34) are improved.
[0018]
  The third solving means is the above first solving means, wherein the pump discharge receiving the inclination angle of the variable swash plate (5) via the piston (41, 42) and the urging force in the direction opposite to the discharge pressure. Adjustment is made by a balance with the pressure of the generated biasing means (6).
[0019]
  Due to this specific matter, by improving each discharge port (32, 33, 34) of the valve plate (3), the pressure against the pressure of the biasing means (6) (the self-resetting moment of the so-called variable swash plate (5)) ) To change the constant horsepower characteristics.
[0020]
  According to a fourth solution means, in the first solution means, the cylinders (24, 25) of the cylinder block (2) are formed at concentric circumferential positions having different diameters around the rotation center axis (X). It consists of a cylinder (25) and an inner cylinder (24). First, second and third port groups (21, 2) formed at concentric circumferential positions with different diameters around the rotation center axis (X) on the valve plate side end surface (2a) of the cylinder block (2). 22,23). A part of the inner cylinder (24) communicates with the first port group (21) and the other communicates with the second port group (22). The outer cylinder (25) communicates with the third port group (23). Further, the discharge port (32, 33, 34) of the valve plate (3) communicates with the first discharge port (32) and the second port group (22) communicating with the first port group (21). It is composed of a second discharge port (33) and a third discharge port (34) communicating with the third port group (23).
[0021]
  Due to this specific matter, each piston (41, 42) reciprocates as the cylinder block (2) rotates, so that it is independent from the three discharge ports (32, 33, 34) formed in the valve plate (3). Pressure fluid is discharged. For this reason, it becomes possible to supply pressurized liquid as three independent discharge flows from one cylinder block (2) of one piston pump. In addition, since the reciprocating stroke of each piston (41, 42) is increased, decreased, changed or adjusted by one variable swash plate (5), the three discharge flows discharged from each of these cylinders (24, 25) For all, it is possible to adjust the increase / decrease / change of the discharge amount in accordance with the change of the discharge pressure.
[0022]
  The fifth solving means specifies the application form of the variable displacement piston pump according to the present invention. That is, this piston pump is applied to a hydraulic excavator. In other words, in the fourth solution means, the cylinder block (2) is rotated by receiving the output of the prime mover of the hydraulic excavator, and the first discharge port (32) is connected to one traveling system of the hydraulic excavator for the second discharge. The port (33) supplies hydraulic pressure to the other traveling system of the hydraulic excavator, and the third discharge port (34) supplies hydraulic pressure to the swinging system of the hydraulic excavator.
[0023]
  With this specific matter, the application form of the variable displacement piston pump can be realized, and the constant horsepower characteristics of the hydraulic excavator can be arbitrarily changed by the action in the first solution.
[0024]
  As shown in FIG. 6, the sixth solution means is configured to set the angular position of the communication start point of the third discharge port (34) with respect to the third port group (23) as shown in FIG. The first and second discharge ports (32, 33) with respect to the two-port group (23) are positioned on the front side in the cylinder block rotation direction from the angular position of the communication start point.
[0025]
  As shown in FIG. 9, the seventh solution means is configured to set the angular position of the communication start point of the third discharge port (34) with respect to the third port group (23) as shown in FIG. The first and second discharge ports (32, 33) with respect to the two-port group (23) are positioned on the rear side in the cylinder block rotation direction from the angular position of the communication start point.
[0026]
  With these specific matters, the degree of influence of the turning system on the traveling system can be arbitrarily set. That is, in the sixth solution means, the area of the fluid supplied to the swing system of the hydraulic excavator presses the variable swash plate (5) is small, so the degree of influence is small. On the contrary, in the seventh solving means, since the area is increased, the influence degree is increased. In particular, in the sixth solution means, it is possible to adopt a configuration in which even if the turning system is driven during traveling of the hydraulic excavator, the traveling performance is hardly adversely affected.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, a case where the variable displacement piston pump according to the present invention is applied to a hydraulic pump of a hydraulic excavator will be described.
[0028]
  -Description of the overall configuration of the pump-
  FIG. 1 shows a variable displacement axial piston pump (hereinafter simply referred to as a pump) according to the present embodiment. In the figure, (1) is a pump shaft that is driven to rotate by a motor (engine) (not shown), (2) is a cylindrical cylinder block that rotates integrally with the pump shaft (1), and (3) is this cylinder block (2 ) To the port side end surface (2a) so as to be oil-tightly slidable and distribute the pressure oil discharged from the cylinder block (2). (4a) is a first cylinder row disposed on the inner peripheral portion of the cylinder block (2), (4b) is a second cylinder row disposed on the outer peripheral portion thereof, (41, 41, .., 42, 42,... Are pistons accommodated in the cylinder chambers (24, 24,..., 25, 25,...) As cylinders referred to in the present invention constituting these cylinder rows (4a, 4b). , (5) is a variable swash plate that adjusts the stroke of the reciprocating movement of these pistons (41, 41, ..., 42, 42, ...), and (6) is the variable swash plate (5) with an inclination angle. It is a spring mechanism as a biasing means for biasing in an increasing direction. Further, (7) is a balance piston mechanism that receives the discharge pressure from the second cylinder row (4b) and presses the front end surface (1a) of the pump shaft (1), and (8) is the cylinder block (2). A journal bearing constituted by a sliding bearing arranged on the outer peripheral surface of the cylinder body, (9) is a casing main body that accommodates the cylinder block (2), and (10) is an open end of the casing main body (9). It is an end cap which closes (the left end in a figure). The casing body (9) includes a cylindrical center body (9a) and a front cap (9b) attached to one end surface (the right end surface in FIG. 1) of the center body (9a). And the inside of the pump casing comprised by the said casing main body (9) and an end cap (10) is satisfy | filled with oil.
[0029]
  The pump shaft (1) is rotatably supported around the central axis (X) by a bearing (1b) on the base end side (right side in the figure). The front end side (left side in the figure) of the pump shaft (1) is inserted partway from the swash plate side (right side in the figure) to the center of the cylinder block (2) so as to be non-penetrating. The tip of the pump shaft (1) is coupled to the cylinder block (2) via a spline (1c). Thus, the cylinder block (2) and the pump shaft (1) are assembled so as to rotate together in a state where they can be relatively displaced in the direction of the central axis (X).
[0030]
  As shown in FIG. 2 (sectional view taken along line YY in FIG. 1) and FIG. 3 (showing the swash plate side end surface of the cylinder block (2)) inside the cylinder block (2). Ten cylinders which are formed in a row in the circumferential direction around the pump shaft (1) and accommodate the pistons (41, 41,...) So as to be slidable in the longitudinal direction of the pump shaft (1). Chambers (24, 24, ...) are formed. These cylinder chambers (24, 24,...) Constitute the first cylinder row (4a). Further, on the outer peripheral side of the first cylinder row (4a), there are five cylinder chambers (25) for accommodating the pistons (42, 42,...) So as to be slidable in the longitudinal direction of the pump shaft (1). , 25, ...) are formed. These cylinder chambers (25, 25,...) Constitute the second cylinder row (4b).
[0031]
  On the port side end surface (2a) (see FIG. 4) as the valve plate side end surface of the cylinder block (2), the port groups (21, 22) are arranged at three concentric circumferential positions around the pump shaft (1). , 23) is formed. Five ports (21a) constituting the first port group (21) are formed at equal intervals at the first circumferential position near the outer periphery. Each of these ports (21a) is connected to each of the five cylinder chambers (24a, 24a,...) Of the first group disposed every other in the first cylinder row (4a). The cylinder chambers (24a) are individually communicated with each other through communication passages extending in the direction of the pump shaft (1) from a substantially central position (see FIG. 5). In addition, at the second circumferential position on the inner side, the ports (22a) constituting the second port group (22) are alternately spaced with respect to the ports (21a) of the first port group (21). 5 are formed. Each port (22a) of the second port group (22) is connected to five cylinder chambers (24b, 24b,...) Of the second group other than the first group in the first cylinder row (4a). On the other hand, the cylinder chambers (24b) are individually communicated with each other through a communication path extending in the direction of the pump shaft (1) from a position near the pump shaft (1). Further, five ports (23a, 23a,...) Constituting the third port group (23) are formed at equal intervals at the third circumferential position closest to the inner periphery. These ports (23a) are connected to the second cylinder row by first communication passages (26, 26,...) That are radially formed so as to extend from the inner peripheral side to the outer peripheral side in the radial direction of the cylinder block (2). The cylinder chambers (25) of the third group constituting (4b) are individually communicated.
[0032]
  The port-side end face (2a) has a circular recess (2c) on the inner peripheral side of the third port group (23) around the central axis (X) of the pump shaft (1), and the third port. An annular first annular groove (2d) is provided at an intermediate position between the group (23) and the second port group (22), and an annular second annular ring is provided on the outer peripheral side of the first port group (21). The groove portions (2e) are formed concentrically. The circular recess (2c) and the first annular groove (2d) are communicated with each other in the casing body (9) through a communication passage (not shown) to form a drain passage. The second annular groove (2e) is communicated with the casing body (9) by five concave grooves (2f, 2f,...) Extending radially outward from the outer peripheral edge thereof to form a drain passage. Yes. Furthermore, between the circular recess (2c) and the first annular groove (2d) and between the first annular groove (2d) and the second annular groove (2e), respectively, the first, second or The seal portion surrounds the third port group (21, 22, 23).
[0033]
  Cylinder chambers (24, 24,...) Constituting the first cylinder row (4a) are opened on the inner peripheral side of the swash plate side end face (2b) (see FIG. 1) of the cylinder block (2). Further, cylinder chambers (25, 25,...) Constituting the second cylinder row (4b) are opened on the outer peripheral side. Further, the pistons (41, 42) inserted into the cylinder chambers (24, 25) are housed in the cylinder chambers (24, 25) at the base end sides, while the tip ends are variablely inclined from the openings. It protrudes toward the plate (5) and slidably contacts the variable swash plate (5) via slippers (43, 44) disposed at the tip thereof. Each piston (41, 42) revolves around the pump shaft (1) by the rotation of the cylinder block (2), and the variable swash plate (5) in the longitudinal direction of the pump shaft (1). It reciprocates according to the inclination angle. In FIG. 1, reference numeral (45) denotes a holding plate for connecting the pistons (41, 42) and the slippers (43, 44). (46) denotes a holding plate (45) which is connected to the pump shaft (1). It is the presser plate guide connected so that rotation is possible.
[0034]
  The valve plate (3) (see FIG. 6) is joined to the inner surface of the end cap (10), and slidably joined to the port side end surface (2a) of the cylinder block (2). Yes. The suction side range (left side range in the figure) that occupies approximately half of the circumference of the valve plate (3) around the pump shaft (1) is the suction side as a wide, substantially arc-shaped suction port. The through hole (31) is substantially half of each port (21a, ..., 22a, ..., 23a, ...) of the three port groups (21,22,23) disposed on the port side end face (2a). However, they are arranged so that they can communicate simultaneously. The suction side through hole (31) communicates a later-described suction side passage (10a) formed in the end cap (10) with the ports (21a, ..., 22a, ..., 23a, ...). Then, oil is supplied from an oil tank (not shown) into the cylinder chamber (24, 24, ..., 25, 25, ...).
[0035]
  Further, a discharge side range (a right side range in FIG. 6) occupying approximately half of the circumferential direction around the pump shaft (1) of the valve plate (3) is centered on the pump shaft (1). Discharge side through-hole rows (32, 33, 34) as three substantially arc-shaped discharge ports are formed at concentric circumferential positions. Each discharge side through-hole row (32, 33, 34) includes a plurality of concentric arc-shaped openings. The first discharge side through hole row (32) on the outermost peripheral side includes first to fourth four openings (32a, 32b, 32c, 32d), and ports constituting the first port group (21) ( 21a, 21a,...) Are arranged so that they can communicate simultaneously with approximately half of them. The second discharge side through-hole row (33) formed on the inner peripheral side of the first discharge side through-hole row (32) has first to third three openings (33a, 33b, 33c). Are arranged so as to be able to communicate simultaneously with substantially half of the ports (22a, 22a,...) Constituting the second port group (22). Further, the third discharge side through hole row (34) on the inner peripheral side includes first to third three openings (34a, 34b, 34c), and ports (23a) constituting the third port group (23). , 23a,. Here, the third discharge-side through-hole row (34) is formed on the innermost side of the three discharge-side through-hole rows (32, 33, 34), and the total opening area thereof is the other. It is smaller than the total opening area of the discharge side through-hole row (32, 33) (in the example shown, about half of the first discharge-side through-hole row (32)). Then, the reciprocating motion of the pistons (41, 41,..., 42, 42,...) Causes the pressure oil in the cylinder chambers (24a,..., 24b,..., 25,. Are discharged from the ports (21a, ..., 22a, ..., 23a, ...) and pass through the openings (32a to 34c) of the discharge side through-hole rows (32, 33, 34), respectively, independently of the end caps (10 ) Are distributed to a first discharge side passage (10b), a second discharge side passage (10c), or a three discharge side passage (10d), which will be described later. In addition, the arrow shown with a broken line in FIG. 6 has shown the rotation direction of the cylinder block (2) with respect to this valve plate (3).
[0036]
  The feature of this embodiment is located on the discharge start side (counterclockwise direction side in FIG. 6 of each discharge side through hole row (32, 33, 34)) in each discharge side through hole row (32, 33, 34). It is in the shape of notches (35, 36, 37) formed in the first openings (32a, 33a, 34a). This notch (35, 36, 37) gradually increases the communication area between the discharge side through hole row (32, 33, 34) and each cylinder chamber (24a, 24b, 25) as the cylinder block (2) rotates. To avoid sudden fluctuations in hydraulic pressure at the start of hydraulic fluid discharge. A similar notch (38) is also formed in the suction side through hole (31).
[0037]
  The tip positions of the notches (35, 36) formed in the first openings (32a, 33a) of the first discharge side through hole row (32) and the second discharge side through hole row (33) are the valve plate (3 ) At the same phase position in the circumferential direction (position on the same straight line extending in the radial direction). On the other hand, the tip position of the notch (37) formed in the first opening (34a) of the third discharge side through hole row (34) is the first discharge side through hole row (32) and the second discharge side. It is set at a position slightly shifted in the clockwise direction in the figure from the tip position of the notches (35, 36) of the side through hole row (33). In FIG. 6, the region surrounded by the alternate long and short dash line is a high pressure region. This high pressure region is a region where the discharge pressure from each port (21a to 23a) of the cylinder block (2) acts, and is a portion that generates a pressing force against the variable swash plate (5). Therefore, as described above, by reducing the length of the notch 37 of the third discharge side through hole row 34, the discharge of the first opening 34a of the third discharge side through hole row 34 is performed. The starting point is shortened in the clockwise direction in the figure. In other words, the third discharge-side through-hole row with respect to the angle range (region surrounded by the one-dot chain line) of the formation region of the first discharge-side through-hole row (32) and the second discharge-side through-hole row (33). The angle range of the formation region of (34) is slightly smaller. For this reason, in the formation region of the third discharge side through hole row (34), the region for applying the pressing force is set small.
[0038]
  The variable swash plate (5) has a donut-shaped main body (51) having a sliding surface (51a) on its upper surface (left side in FIG. 1), and a spring mechanism with respect to the center position of the main body (51). (6) The rotation shaft (52) formed to protrude outward from the outer peripheral surface of the main body (51) so as to pass the rotation center position (A) offset to the side, and the main body (51) It is comprised by the protrusion part (53) which protrudes outward from an outer peripheral surface by the one end side (upper end side of FIG. 1) of the direction orthogonal to the rotating shaft (52). The variable swash plate (5) is inclined by the reaction force of the pistons (41, 41,..., 42, 42,...) That discharge the pressure oil due to the offset arrangement of the rotating shaft (52). A self-returning moment is generated in a decreasing direction (counterclockwise in FIG. 1). The variable swash plate (5) is in a state in which the protrusion (53) is in contact with the bottom wall (the right wall in FIG. 1) of the casing body (9) and is prevented from further rotation. While the inclination angle reaches the maximum (for example, 17 degrees), the main body (51) contacts the bottom wall of the casing main body (9) by rotating to the opposite side and further rotates. In the blocked state, the tilt angle is set to a neutral state of zero degrees. The piston (41, 41, slidably contacting the sliding surface (51a) via the slippers (43, 43, ..., 44, 44, ...) according to the inclination angle of the variable swash plate (5). ..., 42, 42, ...), the stroke of the reciprocating movement is adjusted to increase / decrease / change.
[0039]
  The spring mechanism (6) includes two coil springs (61, 62) arranged coaxially with each other. These coil springs (61, 62) include a support member (63) that is slidably mounted on the end cap (10), and a contact member that is in contact with the protruding portion (53) of the variable swash plate (5). (64). As a result, the coil spring (61, 62) causes the variable swash plate (5) to move to the maximum inclination side (clockwise in FIG. 1) by the pressing biasing force of both coil springs (61, 62) that is substantially proportional to the inclination angle. Is energized.
[0040]
  The balance piston mechanism (7) (see FIG. 1, FIG. 2 and FIG. 7) is the innermost circumferential side centered on the central axis (X) of the pump shaft (1) on the port side in the cylinder block (2). The circular cross-sections are arranged at equal intervals in the circumferential direction and open to face the front end surface (1a) of the pump shaft (1), respectively, while extending in the direction of the central axis (X). The five balance cylinder chambers (71, 71,...) And the balance cylinder chambers (71) have a base end side that is liquid-tight and relatively slidable with respect to each balance cylinder chamber (71). On the other hand, it is configured by a substantially cylindrical balance piston (72, 72,...) Disposed so that the tip side is in contact with the tip surface (1a) of the pump shaft (1). Each balance cylinder chamber (71) is individually communicated with the first communication passage (26, 26,...) By the second communication passage (27, 27,...) And discharged from the second cylinder row (4b). The cylinder block (2) is configured so that the balance piston (72, 72,...) Receiving the discharge pressure presses the front end surface (1a) of the pump shaft (1). A pressing force is applied to the valve plate (3) side.
[0041]
  The journal bearing (8) is disposed between the outer peripheral surface of the cylinder block (2) and the inner peripheral surface of the casing body (9), and an oil film is formed between the outer peripheral surface of the cylinder block (2). The cylinder block (2) is supported in the radial direction by this oil film.
[0042]
  The end cap (10) is formed with a suction side passage (10a) (see FIG. 7) and first, second, and third discharge side passages (10b, 10c, 10d), each of which is a valve. Individually with the cylinder chamber (24a, ..., 24b, ..., 25, ...) via each discharge side through hole row (32, 33, 34) and suction side through hole (31) formed in the plate (3) Communicating with The first discharge side passage (10b) is an unillustrated left side travel system of the shovel, the second discharge side passage (10c) is the right side travel system of the shovel, and the third discharge side passage (10d) is The excavator swivel system is independently connected to each other by hydraulic piping. The suction side passage (10a) is connected to an oil tank (not shown) disposed in the excavator by a hydraulic pipe. Further, the suction side passage (10a) communicates with the inside of the casing body (9) by the drain passage (10e), and the port side end face (2a) and the valve plate (3) on the discharge side of the cylinder block (2). The pressure oil leaking into the casing main body (9) from the gap between the casing main body (9) and the suction side passage is recirculated from the casing main body (9).
[0043]
  In FIG. 1, (11) is a trochoid pump that is rotationally driven by a pump shaft (1). The trochoid pump (11) sucks oil in the casing body (9) and supplies pressure oil to a pilot operation circuit (not shown) of the shovel through a passage (11b) formed in the casing body (9). It has become.
[0044]
  -Explanation of pump operation-
  Next, the operation of the pump according to the present embodiment and the operation and effect thereof will be described.
[0045]
  First, when the pump shaft (1) is rotated by the operation of the prime mover, the piston (41, 41, ..., 42, 42, ...) reciprocates the maximum reciprocating stroke along the variable swash plate (5) with the maximum inclination state. By moving, the maximum amount of oil is sucked and the maximum amount of pressurized oil is discharged. At this time, the pressure oil in the cylinder chambers (24a, 24a,...) Of the first group passes through the first port group (21) and the openings (32a to 32d) of the first discharge side through hole row (32). In the first discharge side passage (10b), the pressure oil in the second group of cylinder chambers (24b, 24b,...) Is opened to the second port group (22) and the second discharge side through hole row (33) ( 33a to 33c) to the second discharge side passage (10c), and the pressure oil in the third group of cylinder chambers (25, 25,...) Passes through the third port group (23) and the third discharge. It passes through the openings (34a to 34c) of the side through hole row (34) and flows independently to the third discharge side passage (10d), and is independently supplied to each hydraulic system of the shovel via the hydraulic piping. . Here, the first discharge flow discharged from the first group of cylinder chambers (24a, 24a,...) And the second discharge flow discharged from the second group of cylinder chambers (24b, 24b,...) Both are the same amount of discharge flow discharged from the equal volume cylinder chamber (24) constituting the first cylinder row (4a), and both discharge flows are independently supplied to the left and right traveling systems of the shovel. As a result, the straight traveling performance of the excavator can be improved. Further, by supplying the third discharge flow discharged from the third group of cylinder chambers (25, 25,...) To the swing system of the shovel, this swing system is not affected by the operation of the left and right traveling systems. And the operability can be improved. That is, pressure oil can be independently supplied from one cylinder block (2) to the three hydraulic systems of the excavator, and the pump as a whole can be made compact.
[0046]
  The variable swash plate (5) receives the discharge pressure of the pump acting via the piston (41, 42) on the discharge side, and the inclination angle decreases against the pressing force of the spring mechanism (6). Therefore, the angle of the variable swash plate (5) is maintained in a state where the oil pressure on the discharge side and the pressing force of the spring mechanism (6) are balanced. As a result, each of the first discharge flow, the second discharge flow, and the third discharge flow can be reduced as their discharge pressure increases, so that the prime mover is overloaded as the hydraulic pressure of the traveling system and the turning system increases. Power loss can be reduced by preventing the operation and reducing the frequency of opening the relief valve. That is, further effective utilization of the output of the prime mover can be achieved by performing comprehensive total horsepower control based on the total load as the flow rate / pressure control of the pump.
[0047]
  -Effect of the embodiment-
  As described above, in the present embodiment, the tip position of the notch (37) formed in the first opening (34a) of the third discharge side through hole row (34) of the valve plate (3) is the other discharge position. It is located in the clockwise direction of FIG. 6 from the tip position of the notch (35, 36) of the side through hole row (32, 33). For this reason, in the area | region of the inner peripheral side part (circumferential area | region of the part in which the 3rd discharge side through-hole row | line | column (34) is formed) in a valve plate (3), a high pressure area is reduced compared with the conventional one. (A region surrounded by an alternate long and short dash line in FIG. 6). That is, the pressure region for rotating the variable swash plate (5) in the counterclockwise direction in FIG. 1 is small. As a result, the variable swash plate (5) does not rotate counterclockwise until the pump discharge pressure reaches a relatively high predetermined value, and when the pump discharge pressure reaches a relatively high predetermined value, The variable swash plate (5) rotates counterclockwise and is set to a position where it is balanced with the coil springs (61, 62) of the spring mechanism (6).
[0048]
  This will be described with reference to the graph of FIG. This graph shows the relationship between the discharge pressure and the discharge flow rate in the pump. (Α) is the case where the conventional valve plate shown in FIG. 11 is employed. That is, the variable swash plate (5) does not rotate until the discharge pressure reaches the predetermined value (I), and when the predetermined pressure (I) is reached, the variable swash plate (5) is variable against the biasing force of the spring mechanism (6). The swash plate (5) rotates and shifts to constant horsepower control.
[0049]
  (Β) in FIG. 8 shows this embodiment. That is, the variable swash plate (5) does not rotate until the discharge pressure reaches a relatively high predetermined value (II), and resists the biasing force of the spring mechanism (6) when the discharge pressure reaches this predetermined value (II). Then, the variable swash plate (5) rotates and shifts to constant horsepower control.
[0050]
  In FIG. 8, (δ) is a constant horsepower line when the excavator's turning system is in an unloaded state. Thus, in this embodiment, the constant horsepower line can be brought close to the ideal constant horsepower line even when refueling the excavator's turning system, and the engine horsepower can be used efficiently.
[0051]
  In addition, when the swing system is driven from the state at the (D) point of the constant horsepower line (δ) while the excavator's swing system is running in a no-load state, the conventional system shifts to the (E) point. To do. That is, the discharge flow rate of the hydraulic oil is extremely reduced, and there is a possibility that the running stability of the excavator may be hindered. On the other hand, in the present embodiment, when the turning system is driven, the point moves to the point (F). That is, it is possible to suppress a decrease in the discharge flow rate of the hydraulic oil and maintain the excavator traveling stability well. In other words, the degree of influence of the turning system on the other traveling systems among the three hydraulic supply systems can be reduced.
[0052]
  As described above, in this embodiment, the constant horsepower characteristic can be changed only by slightly reducing the length of the notch (37) of the third discharge side through hole row (34).
[0053]
  In addition, by changing the tip position of each notch (35, 36, 37) in this way, the period of the boosting curve in each cylinder chamber (24, 25) can be made different. That is, the time when the cylinder internal pressure reaches the maximum pressure can be shifted, and the operation noise of the pump can be reduced.
[0054]
  <Other embodiments>
  In the embodiment described above, the tip position of the notch (37) formed in the first opening (34a) of the third discharge side through-hole row (34) is defined as the first discharge side through-hole row (32) and the second discharge side through-hole row (34). It was located in the clockwise direction of FIG. 6 from the tip position of the notches (35, 36) of the discharge side through hole row (33). The present invention is not limited to this, and as shown in FIG. 9, the tip position of the notch (37) formed in the first opening (34 a) of the third discharge side through hole row (34) The side through-hole row (32) and the second discharge-side through-hole row (33) may be positioned on the counterclockwise direction in the figure with respect to the tip positions of the notches (35, 36). The constant horsepower line in this case is as shown in (γ) of FIG. That is, when the discharge pressure reaches a relatively low predetermined value (III), the variable swash plate (5) rotates against the urging force of the spring mechanism (6) and shifts to constant horsepower control.
[0055]
  Thus, by changing the tip position of the notch (37) formed in the first opening (34a) of the third discharge side through hole row (34), it is possible to obtain an arbitrary constant horsepower characteristic.
[0056]
  Further, the present invention is not limited to changing the tip position of the notch (37) of the third discharge side through hole row (34), that is, the first discharge side through hole row (32) or the second discharge side through hole. An arbitrary constant horsepower characteristic can be obtained by changing the tip position of the notches (35, 36) of the hole row (33).
[0057]
  Note that the present invention is not limited to the above-described embodiments, but includes other various embodiments. That is, in the said embodiment, although applied to a hydraulic piston pump as a variable displacement piston pump, you may apply not only to this but to the hydraulic pump using liquids other than oil.
[0058]
  In the above embodiment, as a mechanism for adjusting the inclination angle of the variable swash plate (5), the rotational center of the variable swash plate (5) is offset to the spring mechanism (6) side, but this is not limiting. Various mechanisms are applicable.
[0059]
  In the above embodiment, the first cylinder row (4a) is constituted by 10 cylinder chambers, and the second cylinder row (4b) is constituted by 5 cylinder chambers. The first cylinder row may be composed of cylinder chambers other than ten, and the second cylinder row may be composed of cylinder chambers other than five.
[0060]
  In the above embodiment, the journal bearing is disposed on the outer peripheral surface of the cylinder block (2). However, the present invention is not limited to this, and other bearings such as a roller bearing may be disposed.
[0061]
【The invention's effect】
  As described above, according to the present invention, the following effects are exhibited. According to the first aspect of the present invention, a desired constant horsepower can be obtained by varying the angle range of the discharge port (32, 33, 34) of the valve plate (3) with respect to the swash plate type variable displacement piston pump. A variable displacement piston pump having characteristics was obtained. For this reason, it is possible to increase the degree of freedom in changing the constant horsepower characteristics of the pump with a simple configuration such as improving the formation region of the discharge port (32, 33, 34) of the valve plate (3). Further, by varying the angle range of the region where the discharge ports (32, 33, 34) are formed, the period of the boosting curve in each cylinder (24, 25) can be varied. For this reason, the time when the cylinder internal pressure reaches the maximum pressure can be shifted, and the operation noise of the pump can be reduced.
[0062]
  In the invention according to claim 2, the circumferential direction around the rotation center axis (X) at the tip of the notch (35, 36, 37) provided in each discharge port (32, 33, 34) of the valve plate (3) By varying the angular position, the angular range of the formation region of the discharge port (32, 33, 34) is varied. For this reason, desired constant horsepower characteristics can be obtained with a relatively simple configuration, and the practicality of the invention can be improved.
[0063]
  In the invention described in claim 3, the inclination angle is adjusted by the balance between the pump discharge acting on the variable swash plate (5) and the pressure of the urging means (6). For this reason, the angle adjusting mechanism of the variable swash plate (5) is embodied, and this can also improve the practicality of the invention.
[0064]
  According to the fourth aspect of the present invention, a plurality of systems of fluid can be supplied from one cylinder block (2). For this reason, it becomes possible to supply pressurized liquid as a plurality of independent discharge flows from one cylinder block (2) of one piston pump.
[0065]
  The invention according to claim 5 applies the piston pump according to the present invention to a hydraulic excavator. Therefore, the application form of the piston pump can be realized, and the effect according to the invention of claim 1 can be obtained for each drive system of the hydraulic excavator, and the constant horsepower of the swing system and the traveling system of the hydraulic excavator can be obtained. It becomes possible to obtain characteristics arbitrarily.
[0066]
  In the inventions according to claims 6 and 7, it is possible to arbitrarily set the degree of influence of the turning system on the traveling system of the excavator by changing the angular position of the communication start point of the discharge port with respect to the port group. Become. In particular, according to the sixth aspect of the present invention, even if the turning system is driven during traveling of the hydraulic excavator, the traveling performance can be hardly affected, and traveling stability can be ensured.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a variable displacement piston pump according to an embodiment of the present invention.
2 is a cross-sectional view taken along line YY in FIG.
FIG. 3 is a view showing a swash plate side end face of a cylinder block.
FIG. 4 is a view showing a port side end face of a cylinder block.
FIG. 5 is a schematic diagram showing a communication state between the first and second cylinder rows and the port group.
FIG. 6 is a plan view showing a valve plate.
7 is a partial cross-sectional view taken along line ZZ in FIG.
FIG. 8 is a diagram showing constant horsepower lines when the notch length of the discharge-side through hole is changed.
FIG. 9 is a view corresponding to FIG. 6 in a modified example.
FIG. 10 is a diagram for explaining the principle of adjusting the tilt angle of the variable swash plate.
FIG. 11 is a view corresponding to FIG. 6 showing a conventional valve plate.
[Explanation of symbols]
(2) Cylinder block
(2a) Port side end face of cylinder block
(21-23) Port group
(24,25) Cylinder chamber (cylinder)
(3) Valve plate
(31) Suction side through hole (suction port)
(32 to 34) Discharge side through hole array (discharge port)
(4a, 4b) Cylinder row
(41,42) Piston
(5) Variable swash plate

Claims (7)

A cylinder block (2) rotating with a plurality of cylinders (24, 25) in which pistons (41, 42) are housed, and a sliding contact with the cylinder block (2), a suction port (31) and a plurality of arcuate shapes A valve plate (3) having a discharge port (32, 33, 34) and a variable swash plate (5) for changing the reciprocating stroke of the piston (41, 42) by adjusting the inclination angle ,
In the variable displacement piston pump, the plurality of discharge ports (32, 33, 34) are arranged in the inner and outer peripheral directions on the discharge side of the valve plate (3) .
Of the formation regions of the respective discharge ports (32, 33, 34), the formation region of at least one (34) has a circumferential angle range in the circumferential direction in the formation region of the other discharge ports (32, 33). The variable displacement piston pump is characterized in that it is different from the angle range. The variable displacement piston pump according to claim 1, wherein
Each discharge port (32, 33, 34) of the valve plate (3) has a notch (35, 36, 37) for suppressing pressure fluctuation in the cylinder (24, 25). At least one notch (37) tip of 35, 36, 37) is characterized in that the circumferential angular position is different from the circumferential angular position of the other notch (35, 36) tip. Variable displacement piston pump. The variable displacement piston pump according to claim 1, wherein
The tilt angle of the variable swash plate (5) is adjusted by the balance between the pump discharge pressure received through the piston (41, 42) and the pressure of the biasing means (6) that generates a biasing force against the discharge pressure. A variable displacement piston pump. The variable displacement piston pump according to claim 1, wherein
The cylinders (24, 25) of the cylinder block (2) are an outer cylinder (25) and an inner cylinder (24) formed at concentric circumferential positions with different diameters around the rotation center axis (X),
The valve plate side end face (2a) of the cylinder block (2) has first, second and third port groups (concentric circumferential positions having different diameters centered on the rotation center axis (X)) ( 21,22,23) is formed,
A part of the inner cylinder (24) communicates with the first port group (21) and the other communicates with the second port group (22), while the outer cylinder (25) communicates with the third port group (23). And
The discharge port (32, 33, 34) of the valve plate (3) has a first discharge port (32) communicating with the first port group (21) and a second discharge communicating with the second port group (22). A variable displacement piston pump comprising a third discharge port (34) communicating with the port (33) and the third port group (23). The variable displacement piston pump according to claim 4,
The cylinder block (2) rotates in response to the output of the excavator prime mover, while the first discharge port (32) is connected to one traveling system of the hydraulic excavator and the second discharge port (33) is connected to the other of the hydraulic excavator. A variable displacement piston pump characterized in that the third discharge port (34) supplies hydraulic pressure to the swing system of the excavator, respectively, in the traveling system. The variable displacement piston pump according to claim 4,
The angular position of the communication start point of the third discharge port (34) with respect to the third port group (23) is the start of communication of the first and second discharge ports (32, 33) with respect to the first and second port groups (23). A variable displacement piston pump characterized by being positioned in front of a cylinder block rotation direction with respect to an angular position of a point. The variable displacement piston pump according to claim 4,
The angular position of the communication start point of the third discharge port (34) with respect to the third port group (23) is the start of communication of the first and second discharge ports (32, 33) with respect to the first and second port groups (23). A variable displacement piston pump characterized in that it is located on the rear side of the cylinder block rotation direction with respect to the angular position of the point.

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