Hydraulic rotating machine

Abstract

A hydraulic rotating machine 1 according to one embodiment includes: a rotating shaft 2, which extends along a rotational axis 20; a housing 5 including cylinder bores 50, which are radially located around the rotational axis 20; and a drum 4, which moves pistons 61 in a reciprocating manner by rotating together with the rotating shaft 2, the pistons 61 being located within the respective cylinder bores 50. The hydraulic rotating machine 1 further includes: an eccentric amount adjuster 3, which changes an eccentric amount of the drum 4, the eccentric amount being a distance from the rotational axis 20 to a center of the drum 4; a rotary encoder 84, which detects a rotational angle of the rotating shaft 2; and at least one linear encoder that detects, on a straight line that perpendicularly intersects the rotational axis 20, a position of a particular circle that is concentric with the drum 4.

Description

[Technical Field]

[0001] The present disclosure relates to a hydraulic rotating machine of a radial piston type.[Background Art]

[0002] Conventionally, there has been a known hydraulic rotating machine of a radial piston type in which: cylinder bores are radially located around a rotational axis; and a drum whose center is located at a position different from the position of the rotational axis rotates, thereby moving pistons that are located in the respective cylinder bores in a reciprocating manner. Such a hydraulic rotating machine is, in some cases, a hydraulic pump, and in other cases, a hydraulic motor.

[0003] For example, Japanese Laid-Open Patent Application Publication No. 2021-63447 discloses a variable displacement hydraulic pump of a radial piston type. In this hydraulic pump, an eccentric amount of the drum, i.e., a distance from the rotational axis to the center of the drum, is changed by an eccentric amount adjuster, and thereby the displacement of the hydraulic pump is changed. In Japanese Laid-Open Patent Application Publication No. 2021-63447, the drum is referred to as an "eccentric cam" and the eccentric amount adjuster is referred to as an "eccentric amount changing mechanism".[Summary of Invention]

[0004] There is a desire to be able to control the displacement of a variable displacement hydraulic rotating machine with high precision. In order to do so, it is necessary to measure the eccentric amount of the drum.

[0005] In view of the above, an object of the present disclosure is to provide a hydraulic rotating machine of a radial piston type that is capable of measuring the eccentric amount of the drum.

[0006] The present disclosure provides a hydraulic rotating machine of a radial piston type, the hydraulic rotating machine including: a rotating shaft that extends along a rotational axis; a housing including cylinder bores that are radially located around the rotational axis; a drum that moves pistons in a reciprocating manner by rotating together with the rotating shaft, the pistons being located within the respective cylinder bores; an eccentric amount adjuster that changes an eccentric amount of the drum, the eccentric amount being a distance from the rotational axis to a center of the drum; a rotary encoder that detects a rotational angle of the rotating shaft; and at least one linear encoder that detects, on a straight line that perpendicularly intersects the rotational axis, a position of a particular circle that is concentric with the drum.

[0007] The present disclosure provides a hydraulic rotating machine of a radial piston type that is capable of measuring the eccentric amount of the drum.[Brief Description of Drawings]

[0008] FIG. 1 is a front view of a hydraulic rotating machine according to one embodiment. FIG. 2 is a sectional view taken along line II-II of FIG. 1. FIG. 3 is a sectional view taken along line III-III of FIG. 2. FIG. 4 is a sectional view taken along line IV-IV of FIG. 1. FIG. 5 is a perspective view of a drum and a drum plate. FIG. 6A is a perspective view of a carriage, and FIG. 6B is a perspective view of a guide. FIG. 7 shows a relationship among a radius Rd of a particular circle, a distance X, an eccentric angle θ, and an eccentric amount e. [Description of Embodiments]

[0009] FIG. 1 and FIG. 2 show a hydraulic rotating machine 1 of a radial piston type according to one embodiment. The hydraulic rotating machine 1 may be a hydraulic pump, or may be a hydraulic motor. Typically, a hydraulic liquid used in the hydraulic rotating machine 1 is oil.

[0010] The hydraulic rotating machine 1 includes: a rotating shaft 2, which extends along a rotational axis 20; a housing 5, which supports the rotating shaft 2 via bearings 11 and 12 such that the rotating shaft 2 is rotatable; and an annular drum 4 located within the housing 5. Hereinafter, for the sake of convenience of the description, the left side in FIG. 2, which is one side in the extending direction of the rotational axis 20, is referred to as "forward", and the opposite side, i.e., the right side in FIG. 2, is referred to as "backward".

[0011] As shown in FIG. 3, the housing 5 includes cylinder bores 50, which are radially located around the rotational axis 20. That is, the axial directions of the respective cylinder bores 50 are radial directions with respect to the rotational axis 20. In the present embodiment, the number of cylinder bores 50 is seven. Alternatively, the number of cylinder bores 50 may be five, six, eight, or more than eight.

[0012] In the present embodiment, the housing 5 includes: a housing body 5A, which is positioned around and backward of the drum 4; and cylinder covers 5B mounted to the housing body 5A such that the cylinder covers 5B cover the respective cylinder bores 50 from the outer side in the respective radial directions with respect to the rotational axis 20; a front cover 5C positioned forward of the drum 4 and the housing body 5A; a spacer 5D positioned backward of the housing body 5A; and a valve housing 5E positioned backward of the spacer 5D.

[0013] The front cover 5C, the housing body 5A, and the spacer 5D are penetrated by the rotating shaft 2. A valve spool 72 is located backward of the rotating shaft 2 coaxially with the rotating shaft 2, and the valve spool 72 is coupled to the rotating shaft 2 by a cross coupling 71. The valve spool 72 is accommodated in the valve housing 5E, and slides on the valve housing 5E.

[0014] As shown in FIG. 3, the drum 4 has a center 40, which is located at a position different from the position of the rotational axis 20. Pistons 61 are located within the respective cylinder bores 50. The pistons 61 are container-shaped and are open inward in the respective radial directions with respect to the rotational axis 20. Inside each piston 61, a connection rod 62 is coupled to the piston 61. The drum 4 moves the pistons 61 in a reciprocating manner via the connection rods 62 by rotating together with the rotating shaft 2.

[0015] In the present embodiment, the connection rods 62 slide on the outer peripheral surface of the drum 4. Specifically, the connection rods 62 are kept in contact with the outer peripheral surface of the drum 4 by a ring 64. Each piston 61 includes a through-hole at the center thereof, and each connection rod 62 includes a lubricant path 63 extending along the center line thereof. The hydraulic liquid is fed, as a lubricant, to sliding surfaces between the connection rod 62 and the drum 4 through the through-hole and the lubricant path 63.

[0016] As shown in FIG. 2 and FIG. 3, the housing body 5A includes: an annular portion 51, which surrounds a rotation space 13, in which the drum 4 rotates; a bottom wall 53, which covers the rotation space 13 from the back side; and bosses 52, each of which protrudes outward from the annular portion 51 in a radial direction with respect to the rotational axis 20. Each boss 52 has a tubular shape, and the bosses 52 form the respective cylinder bores 50 together with the annular portion 51.

[0017] The front cover 5C covers the rotation space 13, in which the drum 4 rotates, from the front side. The bearing 11 is held by the front cover 5C, and the bearing 12 is held by the bottom wall 53 of the housing body 5A.

[0018] The valve housing 5E includes a first port 1a and a second port 1b, each of which extends from the outer side surface of the valve housing 5E to the inner side surface thereof. The inner side surface of the valve housing 5E is a surface on which the valve spool 72 slides. In a case where the hydraulic rotating machine 1 is a hydraulic pump, one of the first port 1a or the second port 1b serves as a suction port, and the other serves as a delivery port, whereas in a case where the hydraulic rotating machine 1 is a hydraulic motor, one of the first port 1a or the second port 1b serves as an inflow port, and the other serves as an outflow port.

[0019] The same number of passages 5a as the number of cylinder bores 50 are located in the valve housing 5E, the spacer 5D, and the housing body 5A, such that the passages 5a extend from the inner side surface of the valve housing 5E to the respective cylinder bores 50.

[0020] Further, the valve spool 72 includes: a passage 7a, which allows some of the passages 5a to communicate with the first port 1a in accordance with a rotational position of the valve spool 72; and a passage 7b, which allows some of the other passages 5a to communicate with the second port 1b in accordance with a rotational position of the valve spool 72.

[0021] The hydraulic rotating machine 1 further includes an eccentric amount adjuster 3, which changes an eccentric amount e of the drum 4. The eccentric amount e is a distance from the rotational axis 20 to the center 40 of the drum 4. In the present embodiment, as shown in FIG. 3, a portion of the rotating shaft 2, the portion being positioned inward of the drum 4, is substantially H-shaped for the arrangement of the eccentric amount adjuster 3.

[0022] To be more specific, the portion of the rotating shaft 2, the portion being positioned inward of the drum 4, includes a protrusion 22, which protrudes from a columnar body of the rotating shaft 2 in an eccentric direction of the drum 4, which is a direction from the rotational axis 20 toward the center 40 of the drum 4. The center of the columnar body of the rotating shaft 2 coincides with the rotational axis 20. The protrusion 22 includes a first recess 23, which is open in the eccentric direction of the drum 4. The portion of the rotating shaft 2, the portion being positioned inward of the drum 4, further includes a second recess 21, which is located on the opposite side to the first recess 23 and which is open in the opposite direction to the eccentric direction of the drum 4.

[0023] The eccentric amount adjuster 3 includes: a first eccentric piston 31 located in the first recess 23; a spring 32, which is located in a first pressure chamber 24 and which urges the first eccentric piston 31 in the eccentric direction of the drum 4, the first pressure chamber 24 being located between the first eccentric piston 31 and the bottom of the first recess 23; and a second eccentric piston 33 located in the second recess 21. A second pressure chamber 26 is located between the second eccentric piston 33 and the bottom of the second recess 21.

[0024] The spacer 5D includes a first eccentric switching port 1c and a second eccentric switching port 1d, each of which extends from the outer side surface of the spacer 5D to the inner side surface thereof. The rotating shaft 2 includes: a passage 25, which allows the first eccentric switching port 1c and the first pressure chamber 24 to communicate with each other; and a passage 27, which allows the second eccentric switching port 1d and the second pressure chamber 26 to communicate with each other. As a result of an eccentricity switching pressure led to the first pressure chamber 24 through the first eccentric switching port 1c and the passage 25 being changed, the position of the first eccentric piston 31 is changed, whereby the eccentric amount e of the drum 4 is adjusted and the displacement of the hydraulic rotating machine 1 is changed.

[0025] In the case of switching the displacement of the hydraulic rotating machine 1 from a large displacement to a small displacement, while keeping the eccentricity switching pressure being led to the first pressure chamber 24, the eccentricity switching pressure is led to the second pressure chamber 26 through the second eccentric switching port 1d and the passage 27. Since the area of the second pressure chamber 26 is set to be greater than the area of the first pressure chamber 24, even though the eccentricity switching pressure led to the first pressure chamber 24 and the eccentricity switching pressure led to the second pressure chamber 26 are equal to each other, the second eccentric piston 33 advances and the first eccentric piston 31 retracts as a result of the eccentricity switching pressure being led to the second pressure chamber 26.

[0026] In the present embodiment, the hydraulic rotating machine 1 further includes a rotary encoder 84 as shown in FIG. 2 and two linear encoders 9 as shown in FIG. 1.

[0027] As shown in FIG. 2, a drive shaft 83 is mounted to the valve spool 72 coaxially, and at the distal end of the drive shaft 83, the rotary encoder 84 detects the rotational angle of the rotating shaft 2. The rotary encoder 84 is accommodated in a rotary encoder casing 82, and the rotary encoder casing 82 is fixed to the valve housing 5E via a spacer 81.

[0028] As shown in FIG. 5, each of the two linear encoders 9 detects the position of a particular circle 14, which is concentric with the drum 4. As shown in FIG. 1, one of the linear encoders 9 detects the position of the particular circle 14 on a straight line 9a, which perpendicularly intersects the rotational axis 20, and the other linear encoder 9 detects the position of the particular circle 14 on a straight line 9b, which perpendicularly intersects the rotational axis 20. That is, the two linear encoders 9 are spaced apart from each other in a circumferential direction about the rotational axis 20.

[0029] Each of the two linear encoders 9 is mounted to the annular portion 51 between bosses 52 of the housing body 5A. In other words, in the extending direction of the rotational axis 20, the two linear encoders 9 are located within a region in which the bosses 52 are present. When seen in the circumferential direction about the rotational axis 20, the two linear encoders 9 overlap the bosses 52.

[0030] In the present embodiment, the angle between the straight lines 9a and 9b is 72 degrees. If the angle between the straight lines 9a and 9b is 72 degrees, then both in a case where the number of bosses 52 is seven as in the present embodiment and in a case where the number of bosses 52 is five as in another embodiment, each of the two linear encoders 9 can be mounted to the annular portion 51 between bosses 52. However, the angle between the straight lines 9a and 9b is not limited to 72 degrees, but is changeable as necessary.

[0031] As shown in FIG. 5, in the present embodiment, a drum plate 45 is mounted to the front surface of the drum 4 as an accessory to the drum 4, and the drum plate 45 includes an annular groove 46, which extends along the particular circle 14. That is, the center line of the annular groove 46 is the particular circle 14. As shown in FIG. 4, the drum plate 45 is fixed to the drum 4 by bolts 47.

[0032] As shown in FIG. 4, each linear encoder 9 includes a linear encoder cover 91, a linear encoder body 93, a rod 92, a carriage 94, a roller 95, and a guide 96. The annular portion 51 of the housing body 5A includes through-holes at positions where the respective linear encoders 9 are located, each through-hole penetrating the annular portion 51 in a radial direction with respect to the rotational axis 20.

[0033] The linear encoder body 93 is fixed in such a manner that the linear encoder body 93 is received in the aforementioned through-hole in the annular portion 51 of the housing body 5A. The rod 92 is supported by the linear encoder body 93 such that the rod 92 is slidable in the radial direction with respect to the rotational axis 20. The linear encoder cover 91 is container-shaped and accommodates a portion of the rod 92 therein, the portion protruding outward from the linear encoder body 93. The linear encoder cover 91 is fixed to the annular portion 51 of the housing body 5A.

[0034] The carriage 94 is mounted to the distal end of the rod 92, and the roller 95 is mounted to the carriage 94 via a shaft. As the roller 95 and the shaft, for example, a cam follower can be used. The roller 95 is fitted in the annular groove 46 of the drum plate 45.

[0035] To be more specific, there is a fitting hole in the distal end surface of the rod 92. On the other hand, as shown in FIG. 6A, the carriage 94 includes: an L-shaped body 94a, which extends in the axial direction of the rod 92 and also in a direction orthogonal to the axial direction; and a columnar portion 94b, which protrudes from the body 94a toward the rod 92 and which is fitted in the fitting hole. The body 94a includes a hole 94c, in which the aforementioned shaft is fitted. The aforementioned shaft supports the roller 95 in a rotatable manner.

[0036] The guide 96 guides movement of the carriage 94 in a radial direction with respect to the rotational axis 20. As shown in FIG. 4 and FIG. 6B, the guide 96 includes: a disc 96a, which is received in the aforementioned through-hole in the annular portion 51 of the housing body 5A together with the linear encoder body 93; and a pillar 96b, which protrudes from the disc 96a toward the rotational axis 20. The disc 96a includes, at the center thereof, a through-hole 96c, which receives the rod 92 therein. The pillar 96b includes a guide groove 96d, in which the carriage 94 is engaged. Movement of the carriage 94 is guided by the engagement of the carriage 94 in the guide groove 96d.

[0037] As described above, in the hydraulic rotating machine 1 of the present embodiment, as shown in FIG. 7, from the position of the particular circle 14 detected by each linear encoder 9, a distance X between the rotational axis 20 and the detected position of the particular circle 14 can be determined, and from the rotational angle of the rotating shaft 2 detected by the rotary encoder 84, an eccentric angle θ can be determined, which is an angle between the eccentric direction of the drum 4 and the straight line 9a or 9b, on which the linear encoder 9 detects the position of the particular circle. Then, by using a radius Rd of the particular circle in addition to the distance X and the eccentric angle θ, the eccentric amount e of the drum 4 can be calculated. Thus, the eccentric amount e of the drum 4 can be measured.

[0038] Regarding the calculation of the eccentric amount e of the drum 4, to be more specific, an equation 1 shown below is derived by applying the law of cosines to a triangle whose vertices are the position of the particular circle 14 on the straight line 9a or 9b, the rotational axis 20, and the center 40 of the drum 4. Rd 2 = e 2 + X 2 − 2 eXcosθ

[0039] By modifying the equation 1, an equation 2 shown below is obtained. e 2 − 2 eXcosθ + X 2 − Rd 2 = 0

[0040] By solving the equation 2 regarding e by using the quadratic formula, the eccentric amount e can be calculated. Since one of the two solutions will be a negative value or an unrealistic value, the other solution, which is not such a value, is to be selected as a proper solution.

[0041] Further, in the present embodiment, since each of the two linear encoders 9 is mounted to the annular portion 51 between bosses 52 of the housing body 5A, the spaces between the bosses 52 can be efficiently utilized as the arrangement spaces for the linear encoders 9.<Variations>

[0042] The present disclosure is not limited to the above-described embodiment. Various modifications can be made without departing from the scope of the present disclosure.

[0043] For example, the connection rods 62 need not slide on the outer peripheral surface of the drum 4. Alternatively, similar to the hydraulic pump of Japanese Laid-Open Patent Application Publication No. 2021-63447, bearings may be located between the drum 4 and the connection rods 62.

[0044] In the above-described embodiment, the number of linear encoders 9 is two. Alternatively, the number of linear encoders may be one. However, if the number of linear encoders 9 is one, there is a case where both the solutions of the quadratic equation 2 are improper values depending on the eccentric angle θ of the drum 4. On the other hand, if the number of linear encoders 9 is two as in the above-described embodiment, one of the four solutions will be a proper value whatever value the eccentric angle θ of the drum 4 is. Therefore, the eccentric amount e of the drum can be calculated properly.

[0045] Each linear encoder 9 need not include the guide 96. However, if each linear encoder 9 includes the guide 96 as in the above-described embodiment, the eccentric amount e of the drum can be measured with high precision.

[0046] The drum plate 45 may be eliminated, and the drum 4 may include the annular groove 46 in the front surface thereof. Alternatively, the roller 95 of each linear encoder 9 may be pressed onto the outer peripheral surface of the drum 4 by a spring, and may roll on the outer peripheral surface of the drum 4. In this case, the particular circle 14 is defined by the outer peripheral surface of the drum 4.<Summary>

[0047] The present disclosure provides, as a first mode, a hydraulic rotating machine of a radial piston type, the hydraulic rotating machine including: a rotating shaft that extends along a rotational axis; a housing including cylinder bores that are radially located around the rotational axis; a drum that moves pistons in a reciprocating manner by rotating together with the rotating shaft, the pistons being located within the respective cylinder bores; an eccentric amount adjuster that changes an eccentric amount of the drum, the eccentric amount being a distance from the rotational axis to a center of the drum; a rotary encoder that detects a rotational angle of the rotating shaft; and at least one linear encoder that detects, on a straight line that perpendicularly intersects the rotational axis, a position of a particular circle that is concentric with the drum.

[0048] According to the above configuration, from the position of the particular circle detected by the linear encoder, a distance X between the rotational axis and the detected position of the particular circle can be determined, and from the rotational angle of the rotating shaft detected by the rotary encoder, an eccentric angle θ can be determined, which is an angle between the eccentric direction of the drum and the straight line, on which the linear encoder detects the position of the particular circle. Then, by using a radius Rd of the particular circle in addition to the distance X and the eccentric angle θ, an eccentric amount e of the drum can be calculated. Thus, the eccentric amount e of the drum 4 can be measured.

[0049] As a second mode, in the first mode, the at least one linear encoder may include two linear encoders that are spaced apart from each other in a circumferential direction about the rotational axis. According to this configuration, the eccentric amount e of the drum can be calculated properly whatever value the eccentric angle θ of the drum is.

[0050] As a third mode, in the first or second mode, the housing may include: an annular portion that surrounds a rotation space in which the drum rotates; and bosses, each of which protrudes from the annular portion in a radial direction with respect to the rotational axis, the bosses forming the respective cylinder bores together with the annular portion, and the at least one linear encoder may be mounted to the annular portion between the bosses. According to this configuration, the space between the bosses can be efficiently utilized as the arrangement space for the linear encoder.

[0051] As a fourth mode, in any of the first to third modes, for example, the at least one linear encoder may include: a linear encoder body fixed to the housing; a rod supported by the linear encoder body such that the rod is slidable in a radial direction with respect to the rotational axis; a carriage mounted to a distal end of the rod; and a roller mounted to the carriage. The roller may be fitted in an annular groove or rolls on an outer peripheral surface of the drum, the annular groove being included in the drum or in an accessory to the drum and extending along the particular circle.

[0052] As a fifth mode, in the fourth mode, the at least one linear encoder may include a guide that guides movement of the carriage in the radial direction with respect to the rotational axis. According to this configuration, the eccentric amount e of the drum can be measured with high precision.

[0053] As a sixth mode, in any one of the first to fifth modes, for example, the hydraulic rotating machine may further include connection rods that are coupled to the respective pistons and that slide on an outer peripheral surface of the drum.

Examples

Embodiment Construction

[0009]FIG. 1 and FIG. 2 show a hydraulic rotating machine 1 of a radial piston type according to one embodiment. The hydraulic rotating machine 1 may be a hydraulic pump, or may be a hydraulic motor. Typically, a hydraulic liquid used in the hydraulic rotating machine 1 is oil.

[0010]The hydraulic rotating machine 1 includes: a rotating shaft 2, which extends along a rotational axis 20; a housing 5, which supports the rotating shaft 2 via bearings 11 and 12 such that the rotating shaft 2 is rotatable; and an annular drum 4 located within the housing 5. Hereinafter, for the sake of convenience of the description, the left side in FIG. 2, which is one side in the extending direction of the rotational axis 20, is referred to as "forward", and the opposite side, i.e., the right side in FIG. 2, is referred to as "backward".

[0011]As shown in FIG. 3, the housing 5 includes cylinder bores 50, which are radially located around the rotational axis 20. That is, the axial directions of the respe...

[Technical Field]

[0001] The present disclosure relates to a hydraulic rotating machine of a radial piston type.[Background Art]

[0002] Conventionally, there has been a known hydraulic rotating machine of a radial piston type in which: cylinder bores are radially located around a rotational axis; and a drum whose center is located at a position different from the position of the rotational axis rotates, thereby moving pistons that are located in the respective cylinder bores in a reciprocating manner. Such a hydraulic rotating machine is, in some cases, a hydraulic pump, and in other cases, a hydraulic motor.

[0003] For example, Japanese Laid-Open Patent Application Publication No. 2021-63447 discloses a variable displacement hydraulic pump of a radial piston type. In this hydraulic pump, an eccentric amount of the drum, i.e., a distance from the rotational axis to the center of the drum, is changed by an eccentric amount adjuster, and thereby the displacement of the hydraulic pump is changed. In Japanese Laid-Open Patent Application Publication No. 2021-63447, the drum is referred to as an "eccentric cam" and the eccentric amount adjuster is referred to as an "eccentric amount changing mechanism".[Summary of Invention]

[0004] There is a desire to be able to control the displacement of a variable displacement hydraulic rotating machine with high precision. In order to do so, it is necessary to measure the eccentric amount of the drum.

[0005] In view of the above, an object of the present disclosure is to provide a hydraulic rotating machine of a radial piston type that is capable of measuring the eccentric amount of the drum.

[0006] The present disclosure provides a hydraulic rotating machine of a radial piston type, the hydraulic rotating machine including: a rotating shaft that extends along a rotational axis; a housing including cylinder bores that are radially located around the rotational axis; a drum that moves pistons in a reciprocating manner by rotating together with the rotating shaft, the pistons being located within the respective cylinder bores; an eccentric amount adjuster that changes an eccentric amount of the drum, the eccentric amount being a distance from the rotational axis to a center of the drum; a rotary encoder that detects a rotational angle of the rotating shaft; and at least one linear encoder that detects, on a straight line that perpendicularly intersects the rotational axis, a position of a particular circle that is concentric with the drum.

[0007] The present disclosure provides a hydraulic rotating machine of a radial piston type that is capable of measuring the eccentric amount of the drum.[Brief Description of Drawings]

[0008] FIG. 1 is a front view of a hydraulic rotating machine according to one embodiment. FIG. 2 is a sectional view taken along line II-II of FIG. 1. FIG. 3 is a sectional view taken along line III-III of FIG. 2. FIG. 4 is a sectional view taken along line IV-IV of FIG. 1. FIG. 5 is a perspective view of a drum and a drum plate. FIG. 6A is a perspective view of a carriage, and FIG. 6B is a perspective view of a guide. FIG. 7 shows a relationship among a radius Rd of a particular circle, a distance X, an eccentric angle θ, and an eccentric amount e. [Description of Embodiments]

[0009] FIG. 1 and FIG. 2 show a hydraulic rotating machine 1 of a radial piston type according to one embodiment. The hydraulic rotating machine 1 may be a hydraulic pump, or may be a hydraulic motor. Typically, a hydraulic liquid used in the hydraulic rotating machine 1 is oil.

[0010] The hydraulic rotating machine 1 includes: a rotating shaft 2, which extends along a rotational axis 20; a housing 5, which supports the rotating shaft 2 via bearings 11 and 12 such that the rotating shaft 2 is rotatable; and an annular drum 4 located within the housing 5. Hereinafter, for the sake of convenience of the description, the left side in FIG. 2, which is one side in the extending direction of the rotational axis 20, is referred to as "forward", and the opposite side, i.e., the right side in FIG. 2, is referred to as "backward".

[0011] As shown in FIG. 3, the housing 5 includes cylinder bores 50, which are radially located around the rotational axis 20. That is, the axial directions of the respective cylinder bores 50 are radial directions with respect to the rotational axis 20. In the present embodiment, the number of cylinder bores 50 is seven. Alternatively, the number of cylinder bores 50 may be five, six, eight, or more than eight.

[0012] In the present embodiment, the housing 5 includes: a housing body 5A, which is positioned around and backward of the drum 4; and cylinder covers 5B mounted to the housing body 5A such that the cylinder covers 5B cover the respective cylinder bores 50 from the outer side in the respective radial directions with respect to the rotational axis 20; a front cover 5C positioned forward of the drum 4 and the housing body 5A; a spacer 5D positioned backward of the housing body 5A; and a valve housing 5E positioned backward of the spacer 5D.

[0013] The front cover 5C, the housing body 5A, and the spacer 5D are penetrated by the rotating shaft 2. A valve spool 72 is located backward of the rotating shaft 2 coaxially with the rotating shaft 2, and the valve spool 72 is coupled to the rotating shaft 2 by a cross coupling 71. The valve spool 72 is accommodated in the valve housing 5E, and slides on the valve housing 5E.

[0014] As shown in FIG. 3, the drum 4 has a center 40, which is located at a position different from the position of the rotational axis 20. Pistons 61 are located within the respective cylinder bores 50. The pistons 61 are container-shaped and are open inward in the respective radial directions with respect to the rotational axis 20. Inside each piston 61, a connection rod 62 is coupled to the piston 61. The drum 4 moves the pistons 61 in a reciprocating manner via the connection rods 62 by rotating together with the rotating shaft 2.

[0015] In the present embodiment, the connection rods 62 slide on the outer peripheral surface of the drum 4. Specifically, the connection rods 62 are kept in contact with the outer peripheral surface of the drum 4 by a ring 64. Each piston 61 includes a through-hole at the center thereof, and each connection rod 62 includes a lubricant path 63 extending along the center line thereof. The hydraulic liquid is fed, as a lubricant, to sliding surfaces between the connection rod 62 and the drum 4 through the through-hole and the lubricant path 63.

[0016] As shown in FIG. 2 and FIG. 3, the housing body 5A includes: an annular portion 51, which surrounds a rotation space 13, in which the drum 4 rotates; a bottom wall 53, which covers the rotation space 13 from the back side; and bosses 52, each of which protrudes outward from the annular portion 51 in a radial direction with respect to the rotational axis 20. Each boss 52 has a tubular shape, and the bosses 52 form the respective cylinder bores 50 together with the annular portion 51.

[0017] The front cover 5C covers the rotation space 13, in which the drum 4 rotates, from the front side. The bearing 11 is held by the front cover 5C, and the bearing 12 is held by the bottom wall 53 of the housing body 5A.

[0018] The valve housing 5E includes a first port 1a and a second port 1b, each of which extends from the outer side surface of the valve housing 5E to the inner side surface thereof. The inner side surface of the valve housing 5E is a surface on which the valve spool 72 slides. In a case where the hydraulic rotating machine 1 is a hydraulic pump, one of the first port 1a or the second port 1b serves as a suction port, and the other serves as a delivery port, whereas in a case where the hydraulic rotating machine 1 is a hydraulic motor, one of the first port 1a or the second port 1b serves as an inflow port, and the other serves as an outflow port.

[0019] The same number of passages 5a as the number of cylinder bores 50 are located in the valve housing 5E, the spacer 5D, and the housing body 5A, such that the passages 5a extend from the inner side surface of the valve housing 5E to the respective cylinder bores 50.

[0020] Further, the valve spool 72 includes: a passage 7a, which allows some of the passages 5a to communicate with the first port 1a in accordance with a rotational position of the valve spool 72; and a passage 7b, which allows some of the other passages 5a to communicate with the second port 1b in accordance with a rotational position of the valve spool 72.

[0021] The hydraulic rotating machine 1 further includes an eccentric amount adjuster 3, which changes an eccentric amount e of the drum 4. The eccentric amount e is a distance from the rotational axis 20 to the center 40 of the drum 4. In the present embodiment, as shown in FIG. 3, a portion of the rotating shaft 2, the portion being positioned inward of the drum 4, is substantially H-shaped for the arrangement of the eccentric amount adjuster 3.

[0022] To be more specific, the portion of the rotating shaft 2, the portion being positioned inward of the drum 4, includes a protrusion 22, which protrudes from a columnar body of the rotating shaft 2 in an eccentric direction of the drum 4, which is a direction from the rotational axis 20 toward the center 40 of the drum 4. The center of the columnar body of the rotating shaft 2 coincides with the rotational axis 20. The protrusion 22 includes a first recess 23, which is open in the eccentric direction of the drum 4. The portion of the rotating shaft 2, the portion being positioned inward of the drum 4, further includes a second recess 21, which is located on the opposite side to the first recess 23 and which is open in the opposite direction to the eccentric direction of the drum 4.

[0023] The eccentric amount adjuster 3 includes: a first eccentric piston 31 located in the first recess 23; a spring 32, which is located in a first pressure chamber 24 and which urges the first eccentric piston 31 in the eccentric direction of the drum 4, the first pressure chamber 24 being located between the first eccentric piston 31 and the bottom of the first recess 23; and a second eccentric piston 33 located in the second recess 21. A second pressure chamber 26 is located between the second eccentric piston 33 and the bottom of the second recess 21.

[0024] The spacer 5D includes a first eccentric switching port 1c and a second eccentric switching port 1d, each of which extends from the outer side surface of the spacer 5D to the inner side surface thereof. The rotating shaft 2 includes: a passage 25, which allows the first eccentric switching port 1c and the first pressure chamber 24 to communicate with each other; and a passage 27, which allows the second eccentric switching port 1d and the second pressure chamber 26 to communicate with each other. As a result of an eccentricity switching pressure led to the first pressure chamber 24 through the first eccentric switching port 1c and the passage 25 being changed, the position of the first eccentric piston 31 is changed, whereby the eccentric amount e of the drum 4 is adjusted and the displacement of the hydraulic rotating machine 1 is changed.

[0025] In the case of switching the displacement of the hydraulic rotating machine 1 from a large displacement to a small displacement, while keeping the eccentricity switching pressure being led to the first pressure chamber 24, the eccentricity switching pressure is led to the second pressure chamber 26 through the second eccentric switching port 1d and the passage 27. Since the area of the second pressure chamber 26 is set to be greater than the area of the first pressure chamber 24, even though the eccentricity switching pressure led to the first pressure chamber 24 and the eccentricity switching pressure led to the second pressure chamber 26 are equal to each other, the second eccentric piston 33 advances and the first eccentric piston 31 retracts as a result of the eccentricity switching pressure being led to the second pressure chamber 26.

[0026] In the present embodiment, the hydraulic rotating machine 1 further includes a rotary encoder 84 as shown in FIG. 2 and two linear encoders 9 as shown in FIG. 1.

[0027] As shown in FIG. 2, a drive shaft 83 is mounted to the valve spool 72 coaxially, and at the distal end of the drive shaft 83, the rotary encoder 84 detects the rotational angle of the rotating shaft 2. The rotary encoder 84 is accommodated in a rotary encoder casing 82, and the rotary encoder casing 82 is fixed to the valve housing 5E via a spacer 81.

[0028] As shown in FIG. 5, each of the two linear encoders 9 detects the position of a particular circle 14, which is concentric with the drum 4. As shown in FIG. 1, one of the linear encoders 9 detects the position of the particular circle 14 on a straight line 9a, which perpendicularly intersects the rotational axis 20, and the other linear encoder 9 detects the position of the particular circle 14 on a straight line 9b, which perpendicularly intersects the rotational axis 20. That is, the two linear encoders 9 are spaced apart from each other in a circumferential direction about the rotational axis 20.

[0029] Each of the two linear encoders 9 is mounted to the annular portion 51 between bosses 52 of the housing body 5A. In other words, in the extending direction of the rotational axis 20, the two linear encoders 9 are located within a region in which the bosses 52 are present. When seen in the circumferential direction about the rotational axis 20, the two linear encoders 9 overlap the bosses 52.

[0030] In the present embodiment, the angle between the straight lines 9a and 9b is 72 degrees. If the angle between the straight lines 9a and 9b is 72 degrees, then both in a case where the number of bosses 52 is seven as in the present embodiment and in a case where the number of bosses 52 is five as in another embodiment, each of the two linear encoders 9 can be mounted to the annular portion 51 between bosses 52. However, the angle between the straight lines 9a and 9b is not limited to 72 degrees, but is changeable as necessary.

[0031] As shown in FIG. 5, in the present embodiment, a drum plate 45 is mounted to the front surface of the drum 4 as an accessory to the drum 4, and the drum plate 45 includes an annular groove 46, which extends along the particular circle 14. That is, the center line of the annular groove 46 is the particular circle 14. As shown in FIG. 4, the drum plate 45 is fixed to the drum 4 by bolts 47.

[0032] As shown in FIG. 4, each linear encoder 9 includes a linear encoder cover 91, a linear encoder body 93, a rod 92, a carriage 94, a roller 95, and a guide 96. The annular portion 51 of the housing body 5A includes through-holes at positions where the respective linear encoders 9 are located, each through-hole penetrating the annular portion 51 in a radial direction with respect to the rotational axis 20.

[0033] The linear encoder body 93 is fixed in such a manner that the linear encoder body 93 is received in the aforementioned through-hole in the annular portion 51 of the housing body 5A. The rod 92 is supported by the linear encoder body 93 such that the rod 92 is slidable in the radial direction with respect to the rotational axis 20. The linear encoder cover 91 is container-shaped and accommodates a portion of the rod 92 therein, the portion protruding outward from the linear encoder body 93. The linear encoder cover 91 is fixed to the annular portion 51 of the housing body 5A.

[0034] The carriage 94 is mounted to the distal end of the rod 92, and the roller 95 is mounted to the carriage 94 via a shaft. As the roller 95 and the shaft, for example, a cam follower can be used. The roller 95 is fitted in the annular groove 46 of the drum plate 45.

[0035] To be more specific, there is a fitting hole in the distal end surface of the rod 92. On the other hand, as shown in FIG. 6A, the carriage 94 includes: an L-shaped body 94a, which extends in the axial direction of the rod 92 and also in a direction orthogonal to the axial direction; and a columnar portion 94b, which protrudes from the body 94a toward the rod 92 and which is fitted in the fitting hole. The body 94a includes a hole 94c, in which the aforementioned shaft is fitted. The aforementioned shaft supports the roller 95 in a rotatable manner.

[0036] The guide 96 guides movement of the carriage 94 in a radial direction with respect to the rotational axis 20. As shown in FIG. 4 and FIG. 6B, the guide 96 includes: a disc 96a, which is received in the aforementioned through-hole in the annular portion 51 of the housing body 5A together with the linear encoder body 93; and a pillar 96b, which protrudes from the disc 96a toward the rotational axis 20. The disc 96a includes, at the center thereof, a through-hole 96c, which receives the rod 92 therein. The pillar 96b includes a guide groove 96d, in which the carriage 94 is engaged. Movement of the carriage 94 is guided by the engagement of the carriage 94 in the guide groove 96d.

[0037] As described above, in the hydraulic rotating machine 1 of the present embodiment, as shown in FIG. 7, from the position of the particular circle 14 detected by each linear encoder 9, a distance X between the rotational axis 20 and the detected position of the particular circle 14 can be determined, and from the rotational angle of the rotating shaft 2 detected by the rotary encoder 84, an eccentric angle θ can be determined, which is an angle between the eccentric direction of the drum 4 and the straight line 9a or 9b, on which the linear encoder 9 detects the position of the particular circle. Then, by using a radius Rd of the particular circle in addition to the distance X and the eccentric angle θ, the eccentric amount e of the drum 4 can be calculated. Thus, the eccentric amount e of the drum 4 can be measured.

[0038] Regarding the calculation of the eccentric amount e of the drum 4, to be more specific, an equation 1 shown below is derived by applying the law of cosines to a triangle whose vertices are the position of the particular circle 14 on the straight line 9a or 9b, the rotational axis 20, and the center 40 of the drum 4. Rd 2 = e 2 + X 2 − 2 eXcosθ

[0039] By modifying the equation 1, an equation 2 shown below is obtained. e 2 − 2 eXcosθ + X 2 − Rd 2 = 0

[0040] By solving the equation 2 regarding e by using the quadratic formula, the eccentric amount e can be calculated. Since one of the two solutions will be a negative value or an unrealistic value, the other solution, which is not such a value, is to be selected as a proper solution.

[0041] Further, in the present embodiment, since each of the two linear encoders 9 is mounted to the annular portion 51 between bosses 52 of the housing body 5A, the spaces between the bosses 52 can be efficiently utilized as the arrangement spaces for the linear encoders 9.<Variations>

[0042] The present disclosure is not limited to the above-described embodiment. Various modifications can be made without departing from the scope of the present disclosure.

[0043] For example, the connection rods 62 need not slide on the outer peripheral surface of the drum 4. Alternatively, similar to the hydraulic pump of Japanese Laid-Open Patent Application Publication No. 2021-63447, bearings may be located between the drum 4 and the connection rods 62.

[0044] In the above-described embodiment, the number of linear encoders 9 is two. Alternatively, the number of linear encoders may be one. However, if the number of linear encoders 9 is one, there is a case where both the solutions of the quadratic equation 2 are improper values depending on the eccentric angle θ of the drum 4. On the other hand, if the number of linear encoders 9 is two as in the above-described embodiment, one of the four solutions will be a proper value whatever value the eccentric angle θ of the drum 4 is. Therefore, the eccentric amount e of the drum can be calculated properly.

[0045] Each linear encoder 9 need not include the guide 96. However, if each linear encoder 9 includes the guide 96 as in the above-described embodiment, the eccentric amount e of the drum can be measured with high precision.

[0046] The drum plate 45 may be eliminated, and the drum 4 may include the annular groove 46 in the front surface thereof. Alternatively, the roller 95 of each linear encoder 9 may be pressed onto the outer peripheral surface of the drum 4 by a spring, and may roll on the outer peripheral surface of the drum 4. In this case, the particular circle 14 is defined by the outer peripheral surface of the drum 4.<Summary>

[0047] The present disclosure provides, as a first mode, a hydraulic rotating machine of a radial piston type, the hydraulic rotating machine including: a rotating shaft that extends along a rotational axis; a housing including cylinder bores that are radially located around the rotational axis; a drum that moves pistons in a reciprocating manner by rotating together with the rotating shaft, the pistons being located within the respective cylinder bores; an eccentric amount adjuster that changes an eccentric amount of the drum, the eccentric amount being a distance from the rotational axis to a center of the drum; a rotary encoder that detects a rotational angle of the rotating shaft; and at least one linear encoder that detects, on a straight line that perpendicularly intersects the rotational axis, a position of a particular circle that is concentric with the drum.

[0048] According to the above configuration, from the position of the particular circle detected by the linear encoder, a distance X between the rotational axis and the detected position of the particular circle can be determined, and from the rotational angle of the rotating shaft detected by the rotary encoder, an eccentric angle θ can be determined, which is an angle between the eccentric direction of the drum and the straight line, on which the linear encoder detects the position of the particular circle. Then, by using a radius Rd of the particular circle in addition to the distance X and the eccentric angle θ, an eccentric amount e of the drum can be calculated. Thus, the eccentric amount e of the drum 4 can be measured.

[0049] As a second mode, in the first mode, the at least one linear encoder may include two linear encoders that are spaced apart from each other in a circumferential direction about the rotational axis. According to this configuration, the eccentric amount e of the drum can be calculated properly whatever value the eccentric angle θ of the drum is.

[0050] As a third mode, in the first or second mode, the housing may include: an annular portion that surrounds a rotation space in which the drum rotates; and bosses, each of which protrudes from the annular portion in a radial direction with respect to the rotational axis, the bosses forming the respective cylinder bores together with the annular portion, and the at least one linear encoder may be mounted to the annular portion between the bosses. According to this configuration, the space between the bosses can be efficiently utilized as the arrangement space for the linear encoder.

[0051] As a fourth mode, in any of the first to third modes, for example, the at least one linear encoder may include: a linear encoder body fixed to the housing; a rod supported by the linear encoder body such that the rod is slidable in a radial direction with respect to the rotational axis; a carriage mounted to a distal end of the rod; and a roller mounted to the carriage. The roller may be fitted in an annular groove or rolls on an outer peripheral surface of the drum, the annular groove being included in the drum or in an accessory to the drum and extending along the particular circle.

[0052] As a fifth mode, in the fourth mode, the at least one linear encoder may include a guide that guides movement of the carriage in the radial direction with respect to the rotational axis. According to this configuration, the eccentric amount e of the drum can be measured with high precision.

[0053] As a sixth mode, in any one of the first to fifth modes, for example, the hydraulic rotating machine may further include connection rods that are coupled to the respective pistons and that slide on an outer peripheral surface of the drum.

Examples

Embodiment Construction

[0009]FIG. 1 and FIG. 2 show a hydraulic rotating machine 1 of a radial piston type according to one embodiment. The hydraulic rotating machine 1 may be a hydraulic pump, or may be a hydraulic motor. Typically, a hydraulic liquid used in the hydraulic rotating machine 1 is oil.

[0010]The hydraulic rotating machine 1 includes: a rotating shaft 2, which extends along a rotational axis 20; a housing 5, which supports the rotating shaft 2 via bearings 11 and 12 such that the rotating shaft 2 is rotatable; and an annular drum 4 located within the housing 5. Hereinafter, for the sake of convenience of the description, the left side in FIG. 2, which is one side in the extending direction of the rotational axis 20, is referred to as "forward", and the opposite side, i.e., the right side in FIG. 2, is referred to as "backward".

[0011]As shown in FIG. 3, the housing 5 includes cylinder bores 50, which are radially located around the rotational axis 20. That is, the axial directions of the respe...

Claims

1. A hydraulic rotating machine of a radial piston type, the hydraulic rotating machine comprising: a rotating shaft that extends along a rotational axis; a housing including cylinder bores that are radially located around the rotational axis; a drum that moves pistons in a reciprocating manner by rotating together with the rotating shaft, the pistons being located within the respective cylinder bores; an eccentric amount adjuster that changes an eccentric amount of the drum, the eccentric amount being a distance from the rotational axis to a center of the drum; a rotary encoder that detects a rotational angle of the rotating shaft; and at least one linear encoder that detects, on a straight line that perpendicularly intersects the rotational axis, a position of a particular circle that is concentric with the drum.

2. The hydraulic rotating machine according to claim 1, wherein the at least one linear encoder includes two linear encoders that are spaced apart from each other in a circumferential direction about the rotational axis.

3. The hydraulic rotating machine according to claim 1 or 2, wherein the housing includes: an annular portion that surrounds a rotation space in which the drum rotates; and bosses, each of which protrudes from the annular portion in a radial direction with respect to the rotational axis, the bosses forming the respective cylinder bores together with the annular portion, and the at least one linear encoder is mounted to the annular portion between the bosses.

4. The hydraulic rotating machine according to any one of claims 1 to 3, wherein the at least one linear encoder includes: a linear encoder body fixed to the housing; a rod supported by the linear encoder body such that the rod is slidable in a radial direction with respect to the rotational axis; a carriage mounted to a distal end of the rod; and a roller mounted to the carriage, and the roller is fitted in an annular groove or rolls on an outer peripheral surface of the drum, the annular groove being included in the drum or in an accessory to the drum and extending along the particular circle.

5. The hydraulic rotating machine according to claim 4, wherein the at least one linear encoder includes a guide that guides movement of the carriage in the radial direction with respect to the rotational axis.

6. The hydraulic rotating machine according to any one of claims 1 to 5, further comprising connection rods that are coupled to the respective pistons and that slide on an outer peripheral surface of the drum.

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