Hydraulic system

Abstract

A hydraulic device (1) comprising a rotor (3, 9, 10, 11, 16-18, 23) and a port member (5) including a high pressure port (6) and a low pressure port (7). An outer surface (21) of the rotor faces an outer surface (22) of the port member (5) and is rotatable in a rotational direction about a rotation axis (19) relative to the port member (5). The rotor comprises a plurality of cylinders (11) angularly spaced apart from one another about the rotation axis (19) and a plurality of cooperating pistons (10) movable within each cylinder (11). The cylinders (11) communicate with respective open ends (25) at the outer surface (21) of the rotor, each of the open ends (25) alternately communicating with the high pressure port (6) and the low pressure port (7) under operating conditions. Every two consecutive cylinders (11) of the plurality of cylinders (11) are interconnected via a fluid displacement member (26). The fluid displacement member has a first opening (27) communicating with one of the two consecutive cylinders (11), a second opening (28) communicating with the other of the two consecutive cylinders (11), and a closure element (29) freely movable between the first and second openings (27, 28) and configured to substantially block either the first opening (27) or the second opening (28) when, under operating conditions, the pressure in the cylinder (11) communicating with the second opening (28) is higher or lower, respectively, than the pressure in the cylinder (11) communicating with the first opening (27). A flow resistor (30) is provided in the rotor (3, 9, 10, 11, 16-18, 23) at a position away from each open end (25), and a first opening (27) and a second opening (28) of each of two fluid displacement members (26) communicating with one cylinder (11) are in fluid communication with that cylinder (11) on the opposite side of the flow resistor (30).

Description

Technical Field

[0001] The present invention relates to a hydraulic device comprising a rotor and a port member including a high-pressure port and a low-pressure port, where an outer surface of the rotor faces an outer surface of the port member and is rotatable relative to the port member in a rotational direction about a rotation axis, the rotor comprising a plurality of cylinders arranged at angular intervals from one another about the rotation axis and cooperating pistons movable within respective ones of the cylinders, the cylinders each communicating with a respective open end at the outer surface of the rotor, each of the open ends communicating alternately with the high-pressure port and the low-pressure port under operating conditions, each two consecutive cylinders of the plurality of cylinders being interconnected via a fluid displacement member, the fluid displacement member having a first opening communicating with one of the two consecutive cylinders, a second opening communicating with the other of the two consecutive cylinders, and a closure element movable freely between the first and second openings and configured to substantially close either the first opening or the second opening when, under operating conditions, the pressure in the cylinder communicating with the second opening is respectively higher or lower than the pressure in the cylinder communicating with the first opening. It relates to such a device.

Background Art

[0002] Such hydraulic apparatuses are known from NL 1016738. This known hydraulic apparatus has a rotor connected to a swash plate, and during the rotation of the rotor, pistons in each cylinder move between their respective bottom dead center and top dead center. Under operating conditions, a portion of the cylinders communicates with a high-pressure port, and another portion of the cylinders communicates with a low-pressure port. Each cylinder is connected to a continuous, adjacent, or neighboring cylinder via a fluid displacement member. The fluid displacement member includes a closing element that is freely movable between a first opening and a second opening of the member. Under operating conditions, if the pressure of the hydraulic fluid in the cylinder communicating with the second opening is higher than the pressure of the hydraulic fluid in the cylinder communicating with the first opening, the closing element can move to the first opening and substantially close it; and if the pressure in the cylinder communicating with the first opening is higher than the pressure in the cylinder communicating with the second opening, the closing element can move to the second opening and substantially close it. A limited volume of hydraulic fluid flows between the two consecutive cylinders while the closing element moves from the first opening to the second opening and vice versa.

[0003] Under operating conditions, when one of the open ends on the outer surface of the rotor moves between the high-pressure port and the low-pressure port, i.e., along the seal land of the port member, the position of the piston in the cylinder changes while the open end is closed by the seal land, causing a change in the pressure of the hydraulic fluid in the cylinder communicating with that open end. This pressure change, called commutation, can lead to increased noise and vibration if the pressure in the high-pressure port differs from the pressure in the cylinder when the corresponding open end begins to communicate with the high-pressure port, and / or if the pressure in the low-pressure port differs from the pressure in the cylinder when the corresponding open end begins to communicate with the low-pressure port. Known hydraulic systems suppress excessive pressure differences by using fluid displacement members, also called shuttles, which can transfer excess hydraulic fluid between successive cylinders.

[0004] For example, consider a case where one of the open ends moves from the low-pressure port to the high-pressure port, and its open end is closed by a seal land between the low-pressure port and the high-pressure port. As the piston in the cylinder communicating with the open end under consideration moves from bottom dead center to top dead center, the pressure in the cylinder communicating with the open end under consideration increases during the movement. The subsequent cylinder communicating with the low-pressure port remains at a lower pressure, and thereafter, the closing element of the fluid displacement member interconnecting these cylinders substantially blocks one of the first and second openings of that member, thereby preventing any or limited flow of hydraulic fluid into the subsequent cylinder. The other subsequent cylinder already communicating with the high-pressure port initially has a higher pressure than the cylinder communicating with the open end under consideration as its open end moves along the seal land, so the closing element of the fluid displacement member interconnecting these cylinders also substantially blocks one of the first and second openings of that member. As the open end under consideration moves along the seal land, if the pressure in the corresponding cylinder exceeds the pressure in the high-pressure port (which is equal to the pressure in the adjacent cylinder already communicating with the high-pressure port), the closing element of the fluid displacement member connecting these cylinders will move from one of the first and second openings to the other. During this movement, hydraulic fluid flows from the cylinder communicating with the open end under consideration to the fluid displacement member, displacing the closing element of that member. As a result, further pressure increases are avoided.

[0005] If the open end under consideration begins to communicate with the high-pressure port before the closing element of the fluid displacement member interconnecting the consecutive cylinders substantially blocks the other of the first and second openings (in which case both consecutive cylinders communicate with the high-pressure port), the pressure in the cylinder communicating with the open end under consideration will balance with the pressure at the high-pressure port, thus avoiding a large pressure difference. If the closing element has already substantially blocked the other of the first and second openings before the open end under consideration begins to communicate with the high-pressure port, the pressure in the cylinder communicating with the open end under consideration will rise even higher than the pressure at the high-pressure port. Since the pressure in the cylinder will reach the pressure at the high-pressure port more quickly as the pressure at the high-pressure port decreases, the distance between the first and second openings should be such that the distance the closing element travels is sufficient to avoid an undesirable pressure difference at the relatively low pressure of the high-pressure port.

[0006] The same effect as described above occurs when the open end moves from the high-voltage port to the low-voltage port. [Overview of the project]

[0007] The object of the present invention is to provide an improved hydraulic system.

[0008] This objective is achieved by the hydraulic device according to the present invention, which is characterized in that a fluid resistance is provided in the rotor at a position away from each open end, and the first and second openings of each of two fluid displacement members communicating with a cylinder are in fluid communication with the cylinder on the opposite side of the fluid resistance.

[0009] An advantage of the present invention is that the closing element of the fluid displacement member is biased to a predetermined position before the open end of the rotor reaches the seal land between the low-pressure port and the high-pressure port. Under operating conditions, a continuous cylinder communicating with the low-pressure port generates a hydraulic fluid flow that causes a pressure drop across its respective fluid resistance in the direction from the corresponding open end to the cylinder, while a continuous cylinder communicating with the high-pressure port generates a hydraulic fluid flow that causes a pressure drop across its respective fluid resistance in the direction from the corresponding cylinder to the open end. Since the first and second openings of each fluid displacement member communicate with two continuous or adjacent cylinders on the opposite side of the corresponding fluid resistance, the closing elements of the fluid displacement member interconnecting two continuous cylinders communicating with either the low-pressure port or the high-pressure port will be biased in the same direction. As a result, when an open end communicating with a cylinder arrives at the seal land, the closing element of the fluid displacement member interconnecting that cylinder with a subsequent cylinder arriving at the seal land will always substantially close either the first opening or the second opening of the member. This provides an opportunity for compression or expansion to begin at the seal land in the fixed reference state of the fluid displacement member. This prevents the closing element from being positioned, for example, by centrifugal force.

[0010] It should be noted that when the closing element of the fluid displacement member substantially blocks the first or second opening, the fluid flow through the first or second opening is minimized, respectively. This means that either the first or second opening is completely closed, or a very small amount of fluid still flows through the first or second opening. In the latter case, the fluid flow will typically be much smaller than the fluid flow through the first and second openings when the closing element moves between them.

[0011] In a practical embodiment, each of the cylinders communicates with the corresponding open end through a passage provided with the fluid resistance. The cross-sectional area of ​​the passage may be smaller than the cross-sectional area of ​​each cylinder. The passage and the fluid displacement member may be formed as a rigid unit.

[0012] The above-mentioned flow resistance may be formed by localized narrowing of the passage.

[0013] In one embodiment, the first opening of each fluid displacement member communicates with the corresponding cylinder via a first aperture in the passage, and the second opening of each fluid displacement member communicates with the corresponding cylinder via a second aperture in the passage. In a more specific embodiment, considering one of the fluid displacement members, the first opening of that member is in fluid communication with a first aperture in the passage corresponding to the first of the cylinders, and the second opening of that member is in fluid communication with a second aperture in the passage corresponding to a successive cylinder following the first of the cylinders under operating conditions.

[0014] Preferably, the first aperture is located at a greater distance from the open end than the second aperture. In this embodiment, the flow resistance can be formed by the length of the passage between the first aperture and the second aperture. This provides a simple flow resistance that avoids localized narrowing of the passage.

[0015] Each of the fluid displacement members has a linear channel between the first aperture of one of the two consecutive passages and the second aperture of the other of the two consecutive passages, and the channel may have a cylindrical portion between the first and second openings. As a result, the closing element moves within its cylindrical portion.

[0016] In a practical embodiment, the closing element is a ball, and the first and second openings are surrounded by respective sheets cooperating with the ball, so that when the ball is pressed against the sheet at the first opening, the fluid flow through the first opening is substantially obstructed, and when the ball is pressed against the sheet at the second opening, the fluid flow through the second opening is substantially obstructed. This is a simple but effective configuration of the fluid displacement member. The ball may be made of ceramic. Furthermore, the ball of the fluid displacement member may be smaller than the diameter of the cylindrical portion between the first and second openings, insofar as the ball substantially closes the first or second opening when pressed against the corresponding sheet. Nevertheless, alternative shapes for the closing element and / or the sheets include, for example, a small piston. In an alternative embodiment, the closing element fits snugly into the cylindrical portion between the first and second openings. In this case, the corresponding sheets in the first and second openings as described herein may be omitted. This is because, when a tightly fitting closure element is located at each opposite end within the cylindrical portion, the closure element automatically substantially closes the first and second openings. As described herein, when the closure element substantially closes the first or second opening, it may allow minimal leakage through the first or second opening.

[0017] The cylindrical portion described above lies in a plane extending tangentially to the axis of rotation at the rotational position in which the cylindrical portion is located, or has a centerline that is inclined at an angle less than 45°, preferably less than 25°, with respect to that plane. This minimizes the effect of centrifugal force on the closing element (which may act against the displacement of the closing element due to the pressure difference across the flow resistance).

[0018] In a preferred embodiment, the virtual extension of the channel in the direction from the rotor to the port member passes through the open end of the passage where the second aperture is located. This is because it provides an opportunity to drill the channel through the open end. As a result, drilling another hole that would later need to be partially closed and sealed can be omitted.

[0019] In a particular embodiment, The above-mentioned outer surfaces (multiple) are located within a common plane. The above axis of rotation extends perpendicularly to the above outer surface (multiple), The centerlines of the above cylinders extend parallel to the axis of rotation. The high-pressure port and the low-pressure port are arc-shaped around the axis of rotation.

[0020] In a more specific embodiment, The above rotation axis is the first rotation axis, The rotor has a shaft that is rotatable around a second axis of rotation and a flange that extends perpendicularly to the second axis of rotation. The above-mentioned multiple pistons are fixed to the flange at equiangled distances around the second rotation axis, The above-mentioned multiple cylinders are separate sleeves mounted on a barrel plate provided with the above-mentioned passages. The second rotation axis intersects the first rotation axis at an acute angle, so that when the shaft is rotated, each of the pistons reciprocates within the cooperative cylinder. Such a configuration is called a floating cup hydraulic system because the position of the cylinder on the barrel plate is determined by the actual position of the cooperating piston. In this embodiment, the channel may have a virtual extension in the direction from the port member toward the cylinder, and this extension passes through the entrance of the passage opposite the open end of the member. This is because it provides an opportunity to drill the channel through the entrance.

[0021] In one embodiment, the outer surface of the port member has a first seal land between the low-pressure port and the high-pressure port where the cooperating piston of the passing open end reaches bottom dead center, and a second seal land between the low-pressure port and the high-pressure port where the cooperating piston of the passing open end reaches top dead center, hmm and the length of each of the first and second seal lands, measured in the rotational direction, is greater than the length of each of the open ends. The distance between the edge of the first seal land adjacent to the low-pressure port and the position where the piston reaches bottom dead center on the first seal land, measured in the rotational direction, may be half the length of each open end, and / or the distance between the edge of the second seal land adjacent to the high-pressure port and the position where the piston reaches top dead center on the second seal land, measured in the rotational direction, may be half the length of each open end. This means that bottom dead center and top dead center are reached when the first and second seal lands begin to close the corresponding passing open ends.

[0022] <0000​​​​​​​​​​​​​​​​​ [Figure 1] This is a cross-sectional view showing one embodiment of the hydraulic device according to the present invention. [Figure 2] Figure 1 is a front view of the port plate of the hydraulic system. [Figure 3] This is an enlarged perspective view of the barrel plate in the embodiment shown in Figure 1. [Figure 4] This figure is similar to Figure 3, but shows a magnified portion of it. [Figure 5] This is a cross-sectional view showing an enlarged portion of Figure 4. [Figure 6] This is a schematic diagram illustrating the function of the embodiment shown in Figure 1. [Figure 7] This figure is similar to Figure 6 and is used to illustrate the functions of other embodiments. [Figure 8] This figure is similar to Figure 6 and illustrates the function of yet another embodiment. [Modes for carrying out the invention]

[0026] Figure 1 shows internal components of a hydraulic device 1, such as a pump or hydromotor, which are mounted to a housing 2 in a known manner. The hydraulic device 1 includes a shaft 3 rotatably supported in the housing 2. An opening is provided on one side of the housing 2, through which a toothed shaft end 4 of the shaft 3 protrudes from the housing 2. If the hydraulic device 1 is a pump, a motor may be connected to the toothed shaft end 4; if the hydraulic device 1 is a motor, a driven tool may be connected.

[0027] The hydraulic system 1 includes port members in the form of port plates 5 mounted spaced apart from each other within a housing 2. Figure 2 shows one of the port plates 5 in more detail. Each port plate 5 includes an arc-shaped high-pressure port 6 and an arc-shaped low-pressure port 7. Between the high-pressure port 6 and the low-pressure port 7 are a first seal land 8a and a second seal land 8b. The port plates 5 have a fixed position relative to the housing 2 in their rotational direction, but in alternative embodiments (not shown), the port plates 5 may be rotatable relative to the housing 2. The shaft 3 extends through the central through-hole of each port plate 5.

[0028] A flange 9 is provided on the shaft 3. Multiple pistons 10 are fixed to each side of the flange 9 by press-fitting; in this case, 14 pistons 10 are fixed to each side. The pistons 10 shown in Figure 1 are made of separate parts, but they may be a single unit. Each piston 10 works in cooperation with a separate cylinder 11 to form a volume-variable compression chamber 12. The hydraulic system 1 shown in Figure 1 has 28 compression chambers 12. Each cylinder 11 comprises a cylinder bottom 13 and a cylinder jacket 14 extending from the cylinder bottom 13.

[0029] The cylinder bottom 13 of each cylinder 11 is supported by two barrel plates 16. These barrel plates 16 are fitted around the shaft 3 by their respective ball hinges 17 and coupled to the shaft 3 by keys 18. As a result, the barrel plates 16 rotate with the shaft 3 under operating conditions. Figure 3 shows one of the barrel plates 16 in more detail. It should be noted that although the cylinder bottom 13 rests on each barrel plate 16, these cylinder bottoms 13 do not have a fixed position relative to each barrel plate 16.

[0030] Figure 1 shows that the barrel plate 16 rotates around each of the first rotation axes 19, which are at an angle to the second rotation axis 20. The shaft 3 is rotatable around the second rotation axis 20, and the flange 9 extends perpendicular to the second rotation axis 20. The pistons 10 are arranged at equiangled distances around the second rotation axis 20. The pistons 10 have a centerline that extends parallel to the second rotation axis 20. The arc-shaped low-pressure port 7 and arc-shaped high-pressure port 6 of each port plate 5 extend around the corresponding first rotation axis 19. The angle between the second rotation axis 20 and each of the first rotation axes 19 is actually about 9 degrees, but may be smaller or larger.

[0031] As the shaft 3 is rotated, the barrel plate 16 and the cylinder 11 rotate around their respective first axis of rotation 19. Each cylinder 11 performs a combination of translational and orbital motion around its cooperating piston 10. Each piston 10 moves relative to its cooperating cylinder 11 between bottom dead center BDC and top dead center TDC. As a result, the volume of the corresponding compression chamber 12 changes.

[0032] Each barrel plate 16 is oriented away from the flange 9 and has an outer surface 21 facing the outer surface 22 of the cooperating port plate 5 (see Figures 1-3). The barrel plates 16 are pressed against each port plate 5 by springs 23 attached to holes in the shaft 3. The outer surfaces 21 and 22 extend perpendicular to their respective first pivot axes 19. Because the outer surface 22 of the port plate 5 is inclined with respect to the flange 9, the barrel plates 16 pivot around the ball hinge 17 while rotating with the shaft 3.

[0033] Considering one of the barrel plates 16, the cylinders 11 mounted on the barrel plate 16 communicate with cooperating passages 24 in the barrel plate 16 through a central through-hole in the bottom 13 of each cylinder. The passages 24 have open ends 25 on the outer surface 21 of the barrel plate 16, as shown in Figures 3 and 4. In this case, each barrel plate 16 has 14 consecutive open ends 25, which communicate with 14 consecutive cylinders 11. Under operating conditions, the open ends 25 alternately communicate with high-pressure and low-pressure lines (not shown) located within the housing 2, via high-pressure port 6 and low-pressure port 7, respectively.

[0034] In fact, in the embodiment shown in Figure 1, the shaft 3, barrel plate 16, piston 10, cylinder 11, ball hinge 17, key 18, and spring 23 can be considered as rotor components having outer surfaces 21 facing the outer surfaces 22 of the respective port plates 5.

[0035] Figures 3 to 5 show that each pair of continuous passages 24 is interconnected via fluid displacement members 26. This means that each pair of continuous cylinders 11 is also interconnected via fluid displacement members 26. Therefore, each barrel plate 16 is also provided with 14 continuous fluid displacement members 26. Each fluid displacement member 26 includes a channel between each pair of continuous passages 24 and has a first opening 27 and a second opening 28 spaced apart from each other. The channel has a cylindrical portion between the first and second openings 27, 28. A closing element in the form of a ball 29 is freely movable between the first and second openings 27, 28. Although two balls are shown in one fluid displacement member 26 for illustrative purposes in Figures 3 to 5, in reality, each fluid displacement member 26 has a single ball 29.

[0036] Referring to Figure 4, the first opening 27 communicates with the right-hand passage 24 of a pair of continuous passages 24, and the second opening 28 communicates with the left-hand passage 24 of a pair of continuous passages 24. The first and second openings 27, 28 and the ball 29 are configured such that, under operating conditions, if the pressure in the passage 24 communicating with the second opening 28, i.e., the left-hand passage 24 in Figure 4, is higher than the pressure in the passage 24 communicating with the first opening 27, i.e., the right-hand passage 24 in Figure 4, the ball 29 substantially blocks the first opening 27, while under operating conditions, if the pressure in the passage 24 communicating with the first opening 27, i.e., the right-hand passage 24 in Figure 4, is higher than the pressure in the passage 24 communicating with the second opening 28, i.e., the left-hand passage 24 in Figure 4, the ball 29 substantially blocks the second opening 28.

[0037] When the ball 29 moves from the first opening 27 to the second opening 28, it displaces fluid toward the passage 24 communicating with the second opening 28, and when the ball 29 moves from the second opening 28 to the first opening 27, it displaces fluid toward the passage 24 communicating with the first opening 27. Therefore, the greater the distance between the first and second openings 27 and 28, the greater the volume of fluid displaced between each pair of continuous passages 24.

[0038] Considering one of the passages 24, it communicates with a first opening 27 and a second opening 28 of two consecutive fluid displacement members 26 located on opposite sides of the passage 24. The first opening 27 of one of the two consecutive fluid displacement members 26 is in fluid communication with the passage 24 via a first aperture 31 of the passage 24, and the second opening 28 of the other of the two consecutive fluid displacement members 26 is in fluid communication with the passage 24 via a second aperture 32 of the passage 24. The first aperture 31 is at a greater distance from the open end 25 of the passage 24 under consideration than the second aperture 32 (see Figures 4 and 5). The distance between the first aperture 31 and the second aperture 32 in the passage 24 creates a fluid resistance 30 between the first aperture 31 and the second aperture 32 under operating conditions (its effect will be described below). In another embodiment (not shown), each of the passages 24 is provided with flow resistance in the form of a restriction, which locally narrows the cross-sectional area of ​​the passage 24.

[0039] Figure 4 shows, indicated by arrows, how the fluid displacement member 26 is manufactured by inserting a drill through the open end 25 and drilling a hole in the direction of the arrow, thereby creating a channel in the form of an elongated stepped hole between each of the two consecutive passages 24. The advantage of this manufacturing method is that since the fluid displacement member 26 is located entirely within the barrel plate 16, no seals between different parts are required.

[0040] Figure 5 shows that the first opening 27 is close to the first aperture 31. The first opening 27 is surrounded by a sheet that cooperates with the ball 29, so when the ball 29 is pressed against the sheet in the first opening 27, the fluid flow through the first opening 27 is obstructed. Similarly, the second opening 28 is surrounded by a sheet that cooperates with the ball 29, so when the ball 29 is pressed against the sheet in the second opening 28, the fluid flow through the second opening 28 is obstructed. The sheet in the second opening 28 includes a through hole into which the ball 29 is screwed after being introduced into the cylindrical portion of the stepped hole. Socket screwIt is formed by the tapered end. Other structural designs are also possible, for example, a sheet fixed in a perforated hole by pressing, clamping, or adhesive.

[0041] Each of the elongated stepped holes has a centerline that is slightly inclined with respect to a plane extending tangentially to the first rotation axis 19 at the rotational position where the cylindrical portion of the fluid displacement member 26 is located. This means that the effect of centrifugal force on the ball 29 is limited. Therefore, the rotational speed of the shaft 3 has a limited effect on the function of the fluid displacement member 26. It should be noted that in embodiments such as those shown in Figures 1 to 5, the elongated stepped holes can be drilled from the barrel plate 16 side opposite to that shown by the arrows in Figure 4, preferably from a position away from the open end 25, i.e., from the entrance of each passage 24 located on the side on which the cylinder bottom 13 of the barrel plate 16 rests.

[0042] The ball 29 does not need to be tightly fitted within the cylindrical portion of the fluid displacement member 26, as long as the ball 29 is in contact with the seat of the first opening 27 or the second opening 28 and substantially obstructs the fluid flow, minimizing leakage.

[0043] The function of the hydraulic system 1 is shown in Figure 6, in which, for ease of explanation, the port plate 5 including the high-pressure port 6 and the low-pressure port 7 is shown linearly. Furthermore, only the 11 pistons 10, cylinders 11, passages 24, fluid resistance 30, open ends 25 and fluid displacement members 26 are shown. The passages 24 including the fluid resistance 30 and open ends 25, the cylinders 11 and fluid displacement members 26 are represented as parts of a unit that moves along the linear port plate 5. The direction of movement of this unit relative to the port plate 5 is indicated by arrow X in Figure 6. Each of the pistons 10 passes through bottom dead center BDC and top dead center TDC while the corresponding open end 25 moves along the first seal land 8a between the low-pressure port 7 and the high-pressure port 6 and the second seal land 8b between the high-pressure port 6 and the low-pressure port 7. The length of each open end 25 in the direction of movement X is smaller than the respective lengths of the first and second seal lands 8a and 8b in that direction, which means that while passing through the first and second seal lands 8a and 8b, the open end 25 will not move through the first and second seal lands 8a and 8b within a certain period of time. a,8b This means that it is closed by one of the two.

[0044] Preferably, the distance between the edge of the first seal land 8a adjacent to the low-pressure port 7 and the position in the first seal land 8a where the piston 10 reaches bottom dead center BDC is about half the length of the open end 25 in the direction of movement X. This is because compression in each of the cylinders 11 being passed through substantially begins at the bottom dead center BDC of the corresponding piston 10. Similarly, the distance between the edge of the second seal land 8b adjacent to the high-pressure port 6 and the position in the second seal land 8b where the piston 10 reaches top dead center TDC is preferably about half the length of the open end 25 in the direction of movement X. This is because expansion in each of the cylinders 11 being passed through substantially begins at the top dead center TDC of the corresponding piston 10. Figure 2 shows the above half length by angle α. The above half length is measured in the direction of rotation around the first rotation axis 19.

[0045] Furthermore, the distance between the position of the piston 10 at the first seal land 8a where it reaches bottom dead center BDC and the edge of the first seal land 8a adjacent to the high-pressure port 6 is greater than the distance between the position of the piston 10 at the second seal land 8b where it reaches top dead center TDC and the edge of the second seal land 8b adjacent to the low-pressure port 7. These distances are measured in the rotational direction and are shown as angles β1 and β2, respectively, in Figure 2. The reason β1 is greater than β2 is that after leaving top dead center TDC, only the dead volume in the cylinder 11 must expand, whereas after passing bottom dead center BDC, both the dead volume and the stroke volume to be displaced by the piston 10 must be compressed.

[0046] When the open end 25 passes through the first or second seal lands 8a, 8b and is thereby closed, the pressure inside the cylinder 11 communicating with the open end 25 changes because the piston 10 is still moving during such a period. When the open end 25 reaches the high-pressure port 6 or the low-pressure port 7, it is desirable that the pressure inside the cylinder 11 and the pressure at the high-pressure port 6 or the low-pressure port 7 be the same or close to each other in order to avoid excessive pressure differences that would cause noise generation. This is achieved by fluid displacement members 26 between each pair of continuous passages 24, which are described below. The arrows on the piston 10 in Figure 6 indicate the direction of movement of the piston 10 and the direction of flow of the hydraulic fluid through the passage 24 when the open end 25 communicates with the high-pressure port 6 or the low-pressure port 7.

[0047] In Figure 6, one of the pistons 10, its cooperating cylinder 11, passage 24, and open end 25 are indicated by reference numerals 10', 11', 24', and 25', respectively. In the situation shown in Figure 6, piston 10' is approaching bottom dead center BDC, and cylinder 11' is still in communication with the low-pressure port 7 via passage 24' and open end 25'. The fluid displacement member 26 and its ball 29 on the left side of passage 24' are indicated by reference numerals 26' and 29', respectively, while the subsequent fluid displacement member 26 and its ball 29 on the right side are indicated by reference numerals 26'' and 29'', respectively. The passage 24 following the passage 24' cooperating with the fluid displacement member 26' is indicated by reference numeral 24'', and the passage 24 following the passage 24' cooperating with the fluid displacement member 26'' is indicated by reference numeral 24''''. A further subsequent passage 24 of passage 24''' is indicated by 24''''.

[0048] In the state shown in Figure 6, the fluid displacement member 26' obstructs the flow from passage 24' to passage 24'' by closing its first opening 27, while the fluid displacement member 26'' obstructs the flow from passage 24'''' to passage 24' by closing its first opening 27. The ball 29'' of the fluid displacement member 26'' is held in place due to the increased pressure at the high-pressure port 6 communicating with passage 24''''. The ball 29' of the fluid displacement member 26' is held in place due to the presence of fluid resistance 30, according to the present invention. The fluid resistance 30 in passage 24' is indicated by 30', and the fluid resistance 30 in passage 24'' is indicated by 30''.

[0049] The open end 25, which communicates with the low-pressure port 7, also communicates with the cylinder 11, where the piston 10 moves from top dead center (TDC) to bottom dead center (BDC). Therefore, under operating conditions, hydraulic fluid flows from the low-pressure port 7 to each cylinder 11 through the cooperating passages 24. This generates a lower pressure downstream of each fluid resistance 30, i.e., on the side where the corresponding cylinder 11 is located, than upstream, i.e., on the side where the open end 25 is located. As a result, as shown in Figure 6, the arrangement of the fluid displacement members 26 connecting the open ends 25 that communicate with the low-pressure port 7 biases each ball 29 of the fluid displacement member 26 upward relative to its respective first opening 27. In other words, the balls 29' of the fluid displacement member 26' are always already in a predetermined position before the open end 25' reaches the first seal land 8a.

[0050] It should be noted that even if the distance between the first and second apertures 31 and 32 along the passage 24 is increased without locally narrowing the passage 24, it may only cause a slight pressure drop, but because the weight of the ball 29 is small, it may be sufficient to displace the ball 29 of the fluid displacement member 26. For example, the diameter of the ball 29 is 4 mm and its weight is 0.1 g.

[0051] Referring again to Figure 6, if the open end 25' moves further in the direction of movement X, it is completely closed by the first seal land 8a when the piston 10' in the corresponding cylinder 11' reaches bottom dead center BDC. The pressure in cylinder 11' will rise after passing bottom dead center BDC as long as the open end 25' is closed. Due to the rising pressure, the first opening 27 of the fluid displacement member 26' remains blocked, but when the pressure in cylinder 11' exceeds the pressure at the high-pressure port 6, the ball 29'' of the fluid displacement member 26'' moves in the direction from passage 24' to the continuous passage 24'''', and the pressure in cylinder 11' no longer rises, or rises only slightly. As a result, when the open end 25' begins to communicate with the high-pressure port 6, the pressure in cylinder 11' becomes substantially equal to the pressure at the high-pressure port 6. The distance the ball 29'' of the fluid displacement member 26'' moves depends on the pressure level at the high-pressure port 6. If the pressure at the high-pressure port 6 is relatively low, the cylinder 11 will have already reached the low-pressure level while the open end 25' is moving along the first seal land 8a, thus requiring a relatively long travel distance.

[0052] As the open end 25' moves along the high-pressure port 6 after passing the first seal land 8a, the ball 29'' is moved to the position required for that ball 29'' before the piston 10' reaches the second seal land 8b, where it passes top dead center TDC, or it automatically remains in the position of that ball 29''. On the downstream side of each flow resistance 30, i.e., the side where the open end 25 is located, the pressure is lower than on the upstream side, i.e., the side where the cylinder 11 is located. This biases the ball 29''' to a lower position, as shown in Figure 6. Thereby, the ball 29''' obstructs the flow from its passage 24''' to the contiguous passage 24'''' by blocking the second opening 28.

[0053] It is important that each of the balls 29 of each fluid displacement member 26 has a predetermined position before the open ends 25 reach the respective first and second seal lands 8a and 8b. For example, if ball 29' in Figure 6 is in an intermediate position somewhere between the first and second openings 27 and 28 before reaching the first seal land 8a, then ball 29' will first be moved to the correct upward position when closing the open end 25'. This delays the start of compression in cylinder 11', resulting in an indeterminate start state of compression in cylinder 11' after the corresponding piston 10' has passed bottom dead center BDC.

[0054] The same effect described herein as when the open end 25 passes the first seal land 8a also occurs when the open end 25 passes the second seal land 8b and the piston 10 of the cylinder 11 communicating with the open end 25 passes the top dead center TDC. When the open end 25 is closed by the second seal land 8b and the piston 10 moves from top dead center TDC towards bottom dead center BDC, the pressure inside the cylinder 11 decreases, thereby causing the ball 29 of the fluid displacement member 26 that interconnects the cylinder 11 and the subsequent cylinder 11 under operating conditions to remain in the same position, i.e., close the second opening 28. Meanwhile, the ball 29 of the other subsequent fluid displacement member 26 may be displaced toward the first opening 27 as soon as the pressure inside the cylinder 11 becomes lower than the pressure at the low-pressure port 7. The ball 29 will either move to the first opening 27, i.e., the upper position in Figure 6, or automatically remain in that upper position before reaching the first seal land 8a.

[0055] Figure 7 shows an alternative embodiment that functions similarly to the embodiment shown in Figure 6, but with a different arrangement of the fluid displacement member 26. In this case, the open end 25 communicating with the low-pressure port 7 biases the ball 29 of the corresponding fluid displacement member 26 upward. Figure 7 shows that when the open end 25' reaches the first seal land 8a, the ball 29' of the fluid displacement member 26' closes the first opening 27. Since the open end 25'' is already communicating with the high-pressure port 6, the ball 29'' of the fluid displacement member 26'' is biased downward, closing the second opening 28 of that member. As soon as the open end 25' is closed by the first seal land 8a, the piston 10' will begin moving from bottom dead center BDC, and the pressure inside the cylinder 11 will begin to rise. As a result, the ball 29' immediately moves downward, obstructing the flow from passage 24' to passage 24''. Next, when the pressure inside cylinder 11' exceeds the pressure at high-pressure port 6, the ball 29'' of the fluid displacement member 26'' moves in the direction from passage 24' towards the contiguous passage 24'''', i.e., upward. However, as soon as the open end 25' communicates with high-pressure port 6, the ball 29'' is biased downward due to the arrangement of the fluid displacement member 26.

[0056] The opposite effect is obtained with the second seal land 8b. Referring to Figure 7, the ball 29''' remains in the downward position until the piston 10''' reaches top dead center TDC, while the open end 25''' is closed by the second seal land 8b. After passing top dead center TDC, the ball 29''' immediately moves upward.

[0057] Since the balls 29 of the fluid displacement member 26 must immediately displace between the first and second openings 27, 28 after passing the top dead center TDC or bottom dead center BDC, respectively, so that they begin to expand or compress, the first and second seal lands 8a, 8b of the fluid displacement member 26 arrangement shown in Figure 7 will be larger when measured in the direction of movement X than those of the fluid displacement member 26 arrangement shown in Figure 6.

[0058] Figure 8 shows another alternative embodiment in which the hydraulic system 1 is applied as a motor. The passage(s) 24, including the fluid resistance(s) 30 and open ends(s) 25, the cylinder(s) 11, and the fluid displacement members(s) 26 are represented as components(s) of a unit that moves along the linear port plate 5 in the direction of movement Y, opposite to the direction of movement X in the embodiments shown in Figures 7 and 8. The function of the fluid displacement members 26 is equivalent to that in the embodiments shown in Figures 6 and 7.

[0059] The present invention is not limited to the embodiments shown in the drawings and described herein, but can be modified in different ways within the scope of the claims and their technical equivalents. For example, the hydraulic system may be a slipper-type axial flow pump or motor having a cylinder in a block, or the hydraulic system may be a transformer.

Claims

1. A hydraulic device (1) comprising rotors (3, 9, 10, 11, 16-18, 23) and port members (5) including high-pressure ports (6) and low-pressure ports (7), The outer surface (21) of the rotor faces the outer surface (22) of the port member (5), and is rotatable relative to the port member (5) in the rotational direction around the rotation axis (19). The rotor comprises a plurality of cylinders (11) arranged at angular intervals from each other around the rotation axis (19), and a plurality of cooperating pistons (10) that are movable within each of the cylinders (11). The cylinder (11) communicates with the open ends (25) on the outer surface (21) of the rotor, and each of the open ends (25) alternately communicates with the high-pressure port (6) and the low-pressure port (7) under operating conditions. Each of the two consecutive cylinders (11) of the above-mentioned plurality of cylinders (11) is interconnected via a fluid displacement member (26). The above fluid displacement member is, A first opening (27) that communicates with one of the two consecutive cylinders (11) mentioned above, A second opening (28) that communicates with the other of the two consecutive cylinders (11) mentioned above, A hydraulic system having a closing element (29) that is freely movable between the first and second openings (27, 28) and configured to substantially close either the first opening (27) or the second opening (28) when, under operating conditions, the pressure inside the cylinder (11) communicating with the second opening (28) is higher or lower than the pressure inside the cylinder (11) communicating with the first opening (27), Within the rotors (3, 9, 10, 11, 16-18, 23) described above, flow resistances (30) are provided at positions away from each open end (25). The first opening (27) and the second opening (28) of each of the two fluid displacement members (26) communicating with one cylinder (11) are in fluid communication with the cylinder (11) on the opposite side of the fluid resistance (30). A hydraulic device characterized by the following features.

2. In the hydraulic device (1) according to claim 1, Each of the cylinders (11) is in communication with the corresponding open end (25) through a passage (24) provided with the flow resistance (30). A hydraulic device characterized by the following features.

3. In the hydraulic device (1) according to claim 2, The above flow resistance (30) is formed by the local narrowing of the passage (24). A hydraulic device characterized by the following features.

4. In the hydraulic device (1) according to claim 2 or 3, The first opening (27) of each fluid displacement member (26) communicates with the corresponding cylinder (11) via the first aperture (31) in the passage (24), and the second opening (28) of each fluid displacement member (26) communicates with the corresponding cylinder (11) via the second aperture (32) in the passage (24). A hydraulic device characterized by the following features.

5. In the hydraulic device (1) according to claim 4, The first aperture (31) is located at a greater distance from the open end (25) than the second aperture (32). A hydraulic device characterized by the following features.

6. In the hydraulic device (1) according to claim 5, Each of the fluid displacement members (26) has a linear channel between the first aperture (31) of one of the two continuous passages (24) and the second aperture (32) of the other of the two continuous passages (24), and the channel has a cylindrical portion between the first and second openings (27, 28). A hydraulic device characterized by the following features.

7. In the hydraulic device (1) according to claim 6, The closing element is a ball (29), and the first and second openings (27, 28) are surrounded by respective sheets cooperating with the ball (29), so that when the ball (29) is pressed against the sheet at the first opening (27), the fluid flow through the first opening (27) is substantially obstructed, and when the ball (29) is pressed against the sheet at the second opening (28), the fluid flow through the second opening (28) is substantially obstructed. A hydraulic device characterized by the following features.

8. In the hydraulic device (1) according to claim 6, The cylindrical portion is located in a plane that extends tangentially to the axis of rotation (19) at the rotational position in which the cylindrical portion is located, or has a center line that is inclined at an angle of less than 45° with respect to that plane. A hydraulic device characterized by the following features.

9. In the hydraulic device (1) according to claim 6, The virtual extension of the channel in the direction from the rotor toward the port member (5) passes through the open end (25) of the passage (24) where the second aperture (32) is located. A hydraulic device characterized by the following features.

10. In the hydraulic device (1) according to claim 2 or 3, The above outer surfaces (21, 22) are in a common plane, The rotation axis (19) extends perpendicularly to the outer surfaces (21, 22), The center line of the cylinder (11) extends parallel to the axis of rotation (19), The high-pressure port (6) and the low-pressure port (7) are arc-shaped around the rotation axis (19). A hydraulic device characterized by the following features.

11. In the hydraulic device (1) according to claim 10, The above rotation axis is the first rotation axis (19), The rotor has a shaft (3) that is rotatable around a second rotation axis (20) and a flange (9) that extends perpendicularly to the second rotation axis (20). The multiple pistons (10) described above are fixed to the flange (9) at equal angular distances around the second rotation axis (20), The above-mentioned multiple cylinders are separate sleeves (11) that rest on the barrel plate (16) provided with the passage (24), The second rotating shaft (20) intersects the first rotating shaft (19) at an acute angle, so that when the shaft (3) is rotated, each of the pistons (10) reciprocates within the cooperating cylinder (11). A hydraulic device characterized by the following features.

12. In the hydraulic device (1) according to claim 1, 2, or 3, The outer surface (22) of the port member (5) has a first seal land (8a) between the low-pressure port (7) and the high-pressure port (6) through which the cooperating piston (10) of the open end (25) passes reaches bottom dead center (BDC), and a second seal land (8b) between the low-pressure port (7) and the high-pressure port (6) through which the cooperating piston (10) of the open end (25) passes reaches top dead center (TDC). The lengths of the first and second seal lands (8a, 8b) are measured in the direction of rotation and are greater than the lengths of the open ends (25). A hydraulic device characterized by the following features.

13. In the hydraulic device (1) according to claim 12, The distance between the edge of the first seal land (8a) adjacent to the low-pressure port (7) and the position in the first seal land (8a) where the piston reaches bottom dead center (BDC) is measured in the rotational direction and is half the length of each open end (25), and / or the distance between the edge of the second seal land (8b) adjacent to the high-pressure port (6) and the position in the second seal land (8b) where the piston (10) reaches top dead center (TDC) is measured in the rotational direction and is half the length of each open end (25). A hydraulic device characterized by the following features.

14. In the hydraulic device (1) according to claim 12, The length of the first seal land (8a) is measured in the direction of rotation and is greater than the length of the second seal land (8b). A hydraulic device characterized by the following features.

15. In the hydraulic device (1) according to claim 1, 2, or 3, The above hydraulic device is a pump, motor, or transformer. A hydraulic device characterized by the following features.

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