Hydraulic drive system with gerotor-type motor having friction brake

Abstract

A hydraulic drive (100) in which a mechanical friction brake (124, 132, 134) is implemented in a gerotor hydraulic motor (113). The orbital motion of the gerotor star (118) is converted to the rotational motion of one set of brake pads (132) via the brake hub (124). The rotational motion of the gerotor outer ring (114) is transferred to another set of brake pads (134). The two sets of brake pads (132, 134) are axially pressed together to brake the gerotor motor (113). The braking force compressing the brake pads is applied via a spring force (138) and is removed by transferring the motor's operating pressure to a brake piston (136) via a release member (139, 201) that extends through the central shaft (130) and the brake hub (124).

Description

[Background technology]

[0001] In many vehicle applications of low-speed, high-torque gerotor motors, it is desirable for the motor to have some type of parking brake or parking lock that is intended to be engaged only after the vehicle has come to a stop. Such parking brake devices are not intended to be dynamic brakes that can be engaged to stop the vehicle while it is moving. In some cases, the parking brake can be incorporated into the motor output shaft, outside the motor. In other cases, the parking brake can be incorporated into the motor. For example, motors may have pin brakes, where a pin is inserted into the star at predetermined braking points (e.g., between adjacent splines or teeth of the star). However, such brakes can only be applied when the pin is aligned with one of the predetermined braking points, which can result in improper positioning of the vehicle driven by the motor. Furthermore, such braking systems can be difficult to release the pin brake on steep slopes, and a jolt can occur when the pin brake is released. Summary of the Invention [Means for solving the problem]

[0002] Some aspects of the present disclosure are directed to the attachment of a mechanical friction brake to a hydraulic drive system. This friction brake can function as a parking brake for a gerotor motor in low-speed, high-torque applications, such as driving large machines, vehicles, or construction equipment. When a machine operator activates the machine for movement, the hydraulic fluid driving the motor can be used to release the motor's friction brake. When the machine operator commands the machine to stop, a pressure change in the hydraulic fluid engages the motor's friction brake.

[0003] The friction brake can be engaged and then released at any point in the motor's rotation, allowing the vehicle or machine to be properly positioned even on steep slopes. Eliminating the need to align a pin with an opening (e.g., between adjacent splines or teeth) prevents shock when the friction brake is released and allows the brake to be released while the vehicle or machine is on a slope, which may increase vehicle starting safety.

[0004] According to some aspects of the present disclosure, a friction brake includes first and second friction brake pads that rotate at different speeds. The brake is applied by pressing the first and second brake pads together to prevent relative motion between them. The brake is applied via spring force and is released by the operating pressure of the motor. Thus, the brake is applied when the hydraulic drive is not being actuated by the user and is released when the user actuates the hydraulic drive.

[0005] A first friction brake pad is mounted on a brake hub that rotates relative to a gerotor hydraulic motor arrangement of a hydraulic drive. A second friction brake pad is mounted on a brake cover that rotates with an outer ring of the gerotor hydraulic motor arrangement. The brake hub is configured to rotate faster than the outer ring so that the first brake pad rotates relative to the second brake pad. Thus, pressing the first and second brake pads together stops relative motion between the brake hub and the outer ring.

[0006] The friction brake system can include a thrust plate, which limits the range of travel of the piston that drives the brake release, reducing axial load on the brake release. Shims between components of the friction brake system can help the friction brake function properly by accounting for variations in component dimensions due to manufacturing tolerances. In some instances, a split brake release rod can reduce mechanical wear. Phosphating certain components can eliminate additional bushings in the motor assembly.

[0007] The present invention provides a hydraulic drive with mechanical braking. The hydraulic drive includes a spindle, a drive housing, and a gerotor hydraulic motor arrangement including an outer motor ring coupled to the drive housing such that the outer motor ring and drive housing rotate together about a central axis. The hydraulic drive also includes a brake arrangement for braking (e.g., preventing motion of) the gerotor hydraulic motor arrangement and a brake release arrangement for selectively releasing the brake arrangement (e.g., allowing motion of the gerotor hydraulic motor arrangement).

[0008] In a particular example, the spindle has a first mounting flange. The spindle defines a central axis. The drive housing is attached to the spindle. The drive housing includes a second mounting flange. The bearing allows the drive housing to rotate relative to the spindle about the central axis. The central shaft is configured to allow the gerotor star to orbit about the central axis while preventing the gerotor star from rotating relative to the spindle about the star axis.

[0009] In a specific example, the outer motoring ring includes radially inward pockets spaced circumferentially about the central axis. The gerotor hydraulic motor arrangement also includes a gerotor star including a plurality of lobes positioned circumferentially about a star axis defined by the gerotor star. The gerotor star is positioned within the outer motoring ring with the star axis offset from the central axis such that the gerotor star is eccentric relative to the outer motoring ring. The gerotor star is mounted to orbit about the central axis, and as the outer motoring ring is hydraulically driven about the central axis, the lobes move in and out of the pockets of the outer motoring ring. One orbit of the gerotor star about the central axis corresponds to movement of the outer motoring ring one pocket position about the central axis relative to the gerotor star.

[0010] In a particular example, the brake arrangement includes a brake hub including a first portion concentric with the central axis and a second portion concentric with the gerotor star. The second portion of the brake hub is mechanically coupled to the gerotor star such that orbital motion of the gerotor star about the central axis drives rotation of the brake hub about the central axis. The brake hub rotates once about the central axis for each orbit of the gerotor star about the central axis. A first brake pad is mounted to rotate integrally with the brake hub about the central axis, and a second brake pad is mounted to rotate integrally with the drive housing and outer motor ring about the central axis. A brake piston is configured to axially press the first and second brake pads together to provide braking for the gerotor hydraulic motor arrangement. The brake piston is axially spring-biased toward the first and second brake pads by a brake spring.

[0011] In a particular example, the brake release arrangement includes a brake release portion extending through the central shaft and the brake hub, the brake release portion adapted to release the brakes on the gerotor hydraulic motor arrangement by axially urging the brake piston away from the first and second brake pads against the spring bias of the brake spring.

[0012] In the following description, various additional inventive aspects will be set forth. Inventive aspects may relate to individual features and combinations of features. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the broad inventive concepts on which the embodiments disclosed herein are based.

[0013] The accompanying drawings, which are incorporated in and constitute a part of this description, illustrate several aspects of the disclosure. A brief description of the drawings follows. [Brief explanation of the drawings]

[0014] [Figure 1]FIG. 1 is an isometric view of a hydraulic drive system constructed in accordance with the principles of the present disclosure. [Figure 2] 2 is an axial cross-sectional view of a first exemplary embodiment of the hydraulic drive device of FIG. 1. [Figure 3] 2 is a perspective view of the hydraulic drive of FIG. 1, with certain components of its brake arrangement and brake release arrangement externally exploded; [Figure 4] FIG. 2 is an elevational view of the hydraulic drive system of FIG. 1 with portions of the brake arrangement removed to better view the outer motoring, gerotor star, and brake hub constructed in accordance with the principles of the present disclosure. [Figure 5] FIG. 3 is an enlarged view of a portion of FIG. 2. [Figure 6] FIG. 4 is an exploded view of the first and second brake pads shown in FIG. 3. [Figure 7] FIG. 1 is a perspective view of a first exemplary brake hub constructed in accordance with the principles of the present disclosure. [Figure 8] FIG. 8 is a front view of the brake hub of FIG. 7. [Figure 9] FIG. 8 is a rear view of the brake hub of FIG. 7. [Figure 10] FIG. 3 is an enlarged view of another portion of FIG. 2. [Figure 11] FIG. 1 is a perspective view of a second exemplary brake hub constructed in accordance with the principles of the present disclosure and exploded outwardly from a gerotor star, with the components of the second brake hub exploded from one another; [Figure 12] FIG. 12 is a perspective view of the body of the second exemplary brake hub of FIG. 11. [Figure 13] FIG. 12 is a side view of the body of the second exemplary brake hub of FIG. 11. [Figure 14] FIG. 12 is a front view of the body of the second exemplary brake hub of FIG. 11. [Figure 15] FIG. 12 is a rear view of the body of the second exemplary brake hub of FIG. 11. [Figure 16] 12 illustrates the second exemplary brake hub and gerotor star of FIG. 11 mating with the outer motor ring of a gerotor hydrostatic drive. [Figure 17]FIG. 12 is a perspective view of a cross section of the second exemplary brake hub of FIG. 11. [Figure 18] FIG. 18 is an enlarged view of a portion of FIG. [Figure 19] 12 is an axial cross-sectional view of a second exemplary embodiment of the hydraulic drive system of FIG. 1 including the second exemplary brake hub of FIG. 11. [Figure 20] 20 shows the brake application piston and brake release of FIG. 19 disposed in an applied position and a brake release position to release the brake pads. [Figure 21] FIG. 21 is an enlarged view of a portion of FIG. 20. [Figure 22] FIG. 21 is an enlarged view of another portion of FIG. 20. [Figure 23] 20 shows the hydraulic drive of FIG. 19 with a bushing and washer disposed between the brake hub and surrounding components. [Figure 24] FIG. 10 is a perspective view of a third exemplary brake arrangement constructed in accordance with the principles of the present disclosure, with the components of the third brake hub separated from one another; [Figure 25] FIG. 25 is a rear perspective view of the brake hub of the third brake arrangement of FIG. 24. [Figure 26] 25 is an axial cross-sectional view of a second exemplary embodiment of the hydraulic drive of FIG. 1 including the third exemplary brake arrangement of FIG. 24. DETAILED DESCRIPTION OF THE INVENTION

[0015] Reference will now be made in detail to the exemplary aspects of the present disclosure, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0016] The present disclosure is directed to a mechanical friction brake on a hydraulic drive system that may be used to propel large equipment, vehicles, or machines. In certain embodiments, the mechanical friction brake is integrated into the hydraulic drive system so that it is located within the footprint of the hydraulic drive system. In certain embodiments, the mechanical friction brake can provide braking regardless of the position of the drive housing about the spindle. A hydraulic drive system constructed according to the principles of the present disclosure may also be used to drive a drill head, a drive wheel or disk, a chipping / grinding drum, or other rotatable structure.

[0017] 1-4 , in some examples, a hydraulic drive 100 includes a spindle 102 that defines a central axis 104 of the motor. The spindle 102 may have a first mounting flange 106 that can connect to a support housing or framework of an apparatus, vehicle, or machine. A drive housing 108 is attached to the spindle 102 and configured to rotate relative to the spindle 102 about the central axis 104. The drive housing 108 may include a second mounting flange 110 that connects to a driven member, such as a wheel, sprocket drum, or other rotatable structure. The hydraulic drive 100 converts hydraulic fluid flow within the drive housing 108 into rotational motion of the drive housing 108 relative to the spindle 102. Torque from the hydraulic drive housing 108 is transmitted to the driven member. In some examples, the hydraulic drive 100 may include bearings 112 to facilitate rotation of the drive housing 108 relative to the spindle 102 about the central axis 104.

[0018] In certain embodiments, the hydraulic drive system 100 includes a gerotor hydraulic motor arrangement 113 including an outer motor ring 114 coupled to the drive housing 108 such that the outer motor ring 114 and the drive housing 108 rotate together about the central axis 104. A motor cover 142 is attached to the outer motor ring 114 such that the motor cover rotates together with the outer motor ring 114. In certain embodiments, a valve plate 115 is attached between the drive housing 108 and the outer motor ring 114 and supplies hydraulic fluid to the outer motor ring 114.

[0019] 4 , the outer motor ring 114 may include a plurality of radially inward pockets 116 spaced circumferentially about the central axis 104. In a particular example, the gerotor hydraulic motor arrangement 113 may also include a gerotor star 118 having a plurality of lobes 120 positioned circumferentially about a star axis 122 defined by the gerotor star 118. The gerotor star 118 is positioned within the outer motor ring 114 with the star axis 122 offset from the central axis 104 such that the gerotor star 118 is eccentric with respect to the outer motor ring 114. The gerotor star 118 may be mounted to orbit about the central axis 104 to move the lobes 120 in and out of the pockets 116 of the outer motor ring 114 as the outer motor ring 114 is hydraulically driven about the central axis 104. In certain examples, one revolution of the gerotor star 118 about the central axis 104 corresponds to the outer motoring ring 114 moving one pocket position about the central axis 104 relative to the gerotor star 118. The number of lobes 120 on the gerotor star 118 is one less than the number of pockets 116. For example, if the outer motoring ring 114 has seven pockets 116, the associated gerotor star 118 has six lobes 120. In certain examples, the pockets 116 may be separated by rollers 146 (see, e.g., FIGS. 4 and 16 ). For example, the gerotor hydraulic motor arrangement 113 may be a Geroler® gerotor motor offered by Eaton Corporation. In some examples, the number of pockets 116 is equal to the number of rollers 146.

[0020] Returning to FIG. 2 , a central shaft 130 extends between the gerotor star 118 and the spindle 102. A first end of the central shaft 130 is splined or otherwise mechanically coupled to the spindle 102. A second end of the central shaft 130 is splined or otherwise mechanically coupled to the gerotor star 118. The engagement between the first end of the central shaft 130 and the spindle 102 constrains rotation of the central shaft 130, which in turn constrains rotation of the gerotor star 118 relative to the spindle 102. Rather, the second end of the central shaft 130 moves relative to the first end in the orbit of the gerotor star 118. Additional details regarding the function of the gerotor hydraulic motor arrangement 113 can be found in U.S. Pat. Nos. 6,132,194 and 8,157,552, the disclosures of which are incorporated herein by reference in their entireties.

[0021] 5-9, the hydraulic drive system 100 includes a brake arrangement 123, 209 configured to stop rotation of the drive housing 108 relative to the spindle 102. In certain embodiments, the brake arrangement 123, 209 functions as a parking brake that inhibits rotation of the drive housing 108 when hydraulic fluid is not supplied or is drained from the gerotor hydraulic motor arrangement 113. The brake arrangement 123, 209 is released when hydraulic fluid is supplied to the gerotor hydraulic motor arrangement 113. A first exemplary brake arrangement 123 is shown in FIGS. 2-10, and a second exemplary brake arrangement 209 is shown in FIGS. 11-22.

[0022] In certain embodiments, the brake arrangement 123, 209 is integrated within the footprint of the hydraulic drive 100. In certain examples, the brake arrangement 123, 209 is disposed within the drive housing 108. In certain examples, the brake cover 156 can be attached to the outside of the motor cover 142 (see, for example, FIG. 1). In such examples, the brake cover 156 rotates integrally with the motor cover 142, the outer motor ring 114, and the drive housing 108. In certain examples, a brake chamber 158 is defined between the motor cover 142 and the brake cover 156 (see, for example, FIG. 5).

[0023] In certain embodiments, the brake arrangement 123, 209 includes first and second brake pads 132, 134 disposed within the brake chamber 158 (see, e.g., FIG. 5 ). In certain examples, the first and second brake pads 132, 134 are mounted concentrically about the central axis 104 of the hydraulic drive 100. The first brake pad 132 rotates relative to the second brake pad 134 as the brake pads 132, 134 are axially spaced apart from one another (e.g., along the central axis 104). When pressed axially together, friction causes the first brake pad 132 to slow and then stop motion relative to the second brake pad 134. In some examples, the first and second brake pads 132 are single friction brake pads. In other examples, the first and / or second brake pads 132 form part of a set of multiple friction brake pads. In a particular example, the sets of first and second brake pads 132, 134 are interleaved (see, for example, FIG. 5).

[0024] The second brake pad 134 is carried by a brake cover 156 that is attached to the motor cover 142 (e.g., by axial bolts 160) so as to rotate therewith. Thus, the second brake pad 134 rotates integrally with the drive housing 108 and outer motor ring 114. In certain embodiments, the second brake pad 134 includes a petal 242 (see, e.g., FIG. 6 ) or other protrusion that mates with a recess defined by the brake cover 156 to secure the second brake pad 134 to the brake cover 156. Other mounting configurations are possible.

[0025] The first brake pad 132 is mounted on the brake hub 124, which is configured to rotate relative to the motor cover 142. Thus, the first brake pad 132 is carried by the brake hub 124 and rotates relative to the brake cover 156 and the second brake pad 134. In some examples, the inner periphery of the first brake pad 132 defines one or more flat surfaces that engage flat surfaces 237 on the brake hub 124 (see, e.g., FIGS. 7 and 8). In other examples, the first brake pad 132 includes teeth 232 (see, e.g., FIG. 6) that align with splines 234 on the brake hub 124 (see, e.g., FIG. 12). Other mounting configurations are possible. The engagement between the first brake pad 132 and the brake hub 124 allows the first brake pad 132 to rotate integrally with the brake hub 124.

[0026] 5, 7, and 8, the brake hub 124 has a first portion 126 attached to the motor cover 142. The first portion 126 is concentric with the central axis 104 such that the brake hub 124 rotates relative to the motor cover 142 about the central axis 104. The brake hub 124 has a second portion 128 concentric with the gerotor star 118 (see, for example, FIG. 4). As discussed in further detail herein, the second portion 128 mechanically interfaces with the gerotor star 118 such that the orbital motion of the gerotor star 118 about the central axis 104 drives the rotation of the brake hub 124 about the central axis 104. In certain embodiments, the orbital motion of the gerotor star 118 causes the brake hub 124 to rotate faster than the outer motor ring 114. In a particular example, the brake hub 124 rotates once about the central axis 104 each time the gerotor star 118 orbits about the central axis 104 (i.e., each time the outer motor ring 114 indexes to one pocket position).

[0027] In certain examples, the number of revolutions of the brake hub 124 is equal to the number of pockets 116 defined by the gerotor hydraulic motor arrangement 113. For example, if there are seven pockets 116, the brake hub 124 rotates seven times for every rotation of the outer motor ring 114. In this way, by converting the orbital motion of the gerotor star 118 into rotational motion of the outer motor ring 114 and the brake hub 124, the brake arrangement 123, 209 can be designed with less torque. For example, in a system in which the brake hub 124 rotates seven times for every rotation of the outer motor ring 114, the brake arrangement 123, 209 can be designed with approximately seven times less torque. In some examples, this can result in the brake arrangement 123, 209 being less expensive and using less material.

[0028] In certain embodiments, a brake hub bushing 164 is positioned between the brake hub 124 and the motor cover 142. In certain examples, the brake hub bushing 164 helps maintain the brake hub 124 in its proper position for reliable motor performance. In some examples, a star bushing 166 is positioned in the central opening 144 of the gerotor star 118. In other examples, the outer surface of the second portion 128 of the brake hub 124 is phosphate treated to protect it from mechanical wear and damage.

[0029] In certain embodiments, the brake arrangement 123, 209 includes a brake piston 136 configured to selectively axially (e.g., along the central axis 104) press the first brake pad 132 and the second brake pad 134 together to provide braking for the gerotor hydraulic motor arrangement 113 (see, for example, FIG. 5 ). The brake piston 136 may be spring biased axially toward the first brake pad 132 and the second brake pad 134 by a brake spring 138. Thus, the brake piston 136 activates the brake arrangement 123, 209 in the absence of a release force that overcomes the bias of the brake spring 138. In certain examples, the brake piston 136 and the brake spring 138 are disposed in a brake chamber 158. In the illustrated example, the brake spring 138 is a disc spring. Other types of springs (e.g., a coil spring) may also be used.

[0030] Pressing the first and second brake pads 132, 134 axially together stops relative motion between the brake hub 124 and the outer motor ring 114. Because the rotation of the brake hub 124 is coupled to the orbital motion of the gerotor star 118, stopping relative motion between the brake hub 124 and the outer motor ring 114 also stops relative motion between the gerotor star 118 and the outer motor ring 114. Stopping the orbital motion of the star 118 stops the rotation of the outer motor ring 114. Because the brake hub 124 and star 118 are always engaged (rather than engaging at indexed positions along the gear), braking force can be applied at any desired time.

[0031] In certain embodiments, the hydraulic drive system 100 includes a brake release arrangement 139, 201 configured to selectively release the brake arrangement 123, 209. The brake release arrangement 139, 201 applies a force to the brake piston 136 sufficient to overcome the bias of the brake spring 138 and move the brake piston 136 away from the first and second brake pads 132, 134, thereby allowing axial separation of the first and second brake pads 132, 134. In certain examples, the brake release arrangement 139, 201 is automatically activated when hydraulic fluid is applied to the gerotor hydraulic motor arrangement 113, as described in more detail herein. A first exemplary embodiment of the brake release arrangement 139 is shown in FIGS. 2-10, and a second exemplary embodiment of the brake release arrangement 201 is shown in FIGS. 11-22.

[0032] In certain embodiments, the brake release arrangement 139, 201 is integrated within the footprint of the hydraulic drive system 100. In certain examples, a portion of the brake release arrangement 139, 201 is disposed within a release chamber 162 formed between the end cover 154 and a thrust plate 150, 216 attached to the spindle 102 (see, for example, FIGS. 10 and 22 ). In such examples, the end cover 154 remains stationary relative to the spindle 102. The end cover 154 defines hydraulic inlet and outlet ports for hydraulic lines extending through the hydraulic drive system 100 to the gerotor hydraulic motor arrangement 113.

[0033] The brake release arrangement 139, 201 includes a brake release portion 140, 203 that extends through the central shaft 130 and through the brake hub 124 (see, e.g., FIGS. 2 and 19). The brake release portion 140, 203 is configured to slide relative to the central shaft 130 and relative to the brake hub 124 between a braking position (see, e.g., FIGS. 2 and 19) and a release position (see, e.g., FIG. 20). The brake release portion 140, 203 is operably coupled to the brake piston 136 such that, when moved to the release position, the brake release portion 140, 203 releases the brake on the gerotor hydraulic motor arrangement 113 by urging the brake piston 136 axially (e.g., along the central axis 104) away from the first brake pad 132 and the second brake pad 134 against the spring bias of the brake spring 138. However, when the brake release portions 140, 203 are disposed in the braking position, the brake release portions 140, 203 allow the brake spring 138 to bias the first and second brake pads 132, 134 together via the brake piston 136.

[0034] 10 and 22, the brake releases 140, 203 are hydraulically actuated. The brake releases 140, 203 are operatively coupled to a brake application piston 152 located on the spindle side of the hydraulic system 100. The brake application piston 152 is configured to be hydraulically actuated to move along the central axis 104 toward and away from the gerotor hydraulic motor arrangement 113 between a start position and an actuated position. Moving the brake application piston 152 from the start position to the actuated position moves the brake releases 140, 203 from the braking position to the release position.

[0035] 2 and 19, when an operator selects the neutral or park function, motor inlet hydraulic fluid is reduced (to near zero pressure in some instances) and no force is exerted against the brake apply piston 152. The spring force of the brake spring 138 can then exert a force against the brake release portions 140, 203 and against the first brake pad 132 and the second brake pad 134. Friction generated between the first brake pad 132 and the second brake pad 134 can slow or prevent rotation of the brake hub 124 relative to the brake cover 156 (and thus the outer motor ring 114, motor cover 142, and drive housing 108, which are connected to the brake cover 156), thus potentially engaging the brake.

[0036] In certain examples, when an operator selects the travel or drive function, motor inlet hydraulic fluid may pressurize the brake application piston 152, moving it from the start position to the apply position, as shown in Figure 20. This axial force is transmitted to the brake piston 136 through the brake release members 140, 203, compressing the brake spring 138, thereby relieving the pressure of the brake piston 136 against the first brake pad 132 and the second brake pad 134, thus releasing the brake. In certain examples, the axial force may also be transmitted through the spacer 224 and shimming 228 before being transmitted to the brake release members 140, 203, as discussed in more detail with respect to Figures 19-22.

[0037] In certain embodiments, the inlet hydraulic fluid pressure exerted on the brake application piston 152 may exceed the force required to counter the bias of the brake spring 138. In certain instances, the inlet hydraulic fluid pressure may be high enough to bottom out the brake spring 138, which may lead to deformation of the brake spring 138 or otherwise damage components of the brake arrangement 123, 209 or brake release arrangement 139, 201. To mitigate the forces exerted on these components, certain embodiments of the brake release arrangement 139, 201 include a thrust plate 150, 216 that limits the axial range of travel of the brake piston 152, thereby limiting the extent to which the brake piston 152 can push against the brake release portion 140, 203. The thrust plate 150, 216 faces the brake application piston 152 and may be bolted between the spindle 102 and the end cover 154. In the examples shown in FIGS. 10 and 22 , the brake application piston 152 is mounted within a pocket in the thrust plate 150, 216. The thrust plate 150, 216 is positioned to engage the brake application piston 152 when the brake application piston 152 is moved to an applied position corresponding to the released position of the brake release portion 140, 203. Therefore, the brake application piston 152 cannot push the brake release portion 140, 203 beyond the released position. In this manner, the thrust plate 150, 216 may help transfer this high axial thrust load to the spindle 102 and maintain a low axial thrust load on the brake release portion 140, 203 and brake piston 136. In some examples, this reduction in applied force can increase the operational life and reliability of the brake arrangement 123, 209 and brake release arrangement 139, 201 and reduce the likelihood of damage to affected components. Additionally, the stroke of the brake actuation piston 152 may be limited to less than the range of motion of the brake spring 138, which may allow the friction brake system to be designed with only a single brake spring 138. However, in other examples, multiple brake springs 138 may be used.

[0038] 7-9, a first example of a brake arrangement 123 includes a single-piece brake hub 124. As shown in FIG. 8, a first portion 126 of the brake hub 124 is substantially circular to facilitate rotational attachment to the motor cover 142. A second portion 128 of the brake hub 124 is also substantially circular but is larger than the first portion 126. The brake hub 124 defines a passageway 127 through which the brake release portion 140 extends. In this particular example, the passageway 127 is centrally disposed relative to the first portion 126 of the brake hub 124 about a longitudinal axis C1. Because the first portion 126 is attached to the motor cover 142, the brake hub 124 rotates about the longitudinal axis C1, which extends coaxially with the central axis 104.

[0039] The second portion 128 of the brake hub 124 has a longitudinal axis C2 that is offset from the longitudinal axis C1. The second portion 128 is sized to fit concentrically within the central opening 144 of the gerotor star 118. In certain examples, the longitudinal axis C2 is aligned with the central longitudinal axis 122 of the gerotor star 118. As the gerotor star 118 orbits, the gerotor star 118 entrains the second portion 128 of the brake hub 124, which acts as a crank arm to rotate the first portion 126. Thus, the brake hub 124 rotates once for each orbit of the gerotor star 118.

[0040] 2 and 10 , a first exemplary brake release arrangement 139 includes a single-piece brake release portion 140 extending between the brake piston 136 and the brake application piston 152. In a particular example, the single-piece brake release portion 140 directly contacts both the brake piston 136 and the brake application piston 152. The brake release portion 140 extends through a passage 127 defined through the brake hub 124 to the brake piston 136. The brake release portion 140 also extends through the central shaft 130 to the brake application piston 152. Thus, hydraulically supplied axial thrust force applied to the brake application piston 152 is transmitted to the brake release portion 140, which transmits the axial thrust force to the brake piston 136 to compress the brake spring 138.

[0041] 11-18, a second exemplary brake arrangement 209 includes a multi-piece brake hub 124 including a body 210 and an outer collar 212. The outer collar 212 interfaces with the gerotor star 118 so as to orbit with the star about a star axis 122 (see, for example, FIG. 16). Interaction between the outer collar 212 and the body 210 converts the orbital motion of the star 118 and outer collar 212 into rotational motion of the body 210 and collar 212. This rotational motion is imparted to the first brake pad 132 via the body 210. This second exemplary brake arrangement 209 can be used with any of the brake release arrangements 139, 201 disclosed herein.

[0042] The body 210 defines the first portion 126 of the brake hub 124. The body 210 and the outer collar 212 cooperate to define the second portion 128 of the brake hub 124. The body 210 has a brake pad mounting section 233, a hub mounting section 235, and an inner portion 148 (see, e.g., FIG. 13 ). The hub mounting section 235 is configured to be rotatably mounted within an opening in the motor cover 142 (see, e.g., FIG. 19 ). The brake pad mounting section 233 is configured to support and key with the first brake pad 132 so that the first brake pad 132 rotates unitarily with the body 210. For example, the brake pad mounting section 233 may include teeth or splines 234 (see, e.g., FIGS. 12 and 14 ) that key with the inwardly facing teeth 232 of the first brake pad 132 (see, e.g., FIG. 6 ).

[0043] The inner portion 148 of the body 210 mates with the outer collar 212. The inner portion 148 has a rectangular shape (see, e.g., FIG. 15) with opposed flat edges 238. The inner portion 148 is offset relative to the hub mounting section 235 (see, e.g., FIG. 13) such that the longitudinal axis C2 of the inner portion 148 is offset from the longitudinal axis C1 of the hub mounting section 235 (see, e.g., FIG. 15). This offset allows the inner portion 148 to function as a crank to rotate the hub mounting section 235 of the body 210.

[0044] The outer collar 212 is attached to the inner portion 148 of the brake hub 124 (see, for example, FIGS. 11 and 16 ). The outer collar 212 defines an aperture 215 that receives the inner portion 148 of the body 210. In particular examples, the aperture 215 is keyed to an outer surface of the inner portion 148 such that the outer collar 212 is rotationally fixed relative to the inner portion 148. In the illustrated example, the inner surface 218 of the outer collar 212 includes a collar flat edge 236 that mates with a hub flat edge 238 of the inner portion 148 of the body 210. The engagement between the collar flat edge 236 and the hub flat edge 238 causes the body 210 to rotate as a unit with the outer collar 212.

[0045] The outer surface 214 of the outer collar 212 is positioned concentrically with the central opening 144 of the gerotor star 118 (see, for example, FIG. 12 ). In certain embodiments, the outer surface 214 of the outer collar 212 is phosphate treated. The phosphate treatment helps protect the outer surface 214 from frictional wear, thereby eliminating the need for a star bushing 166 in the central opening 144 of the gerotor star 118. The star 118 imparts orbital motion to the outer collar 212. Because the body 210 is retained in the motor cover 142 at the brake hub mounting section 235, the body 210 cannot orbit with the outer collar 212. Instead, the orbital force exerted by the star 118 on the outer collar 212 is converted into a rotational force of the outer collar 212 relative to the star 118. The engagement of the flat edges 236, 238 between the outer collar 212 and the body 210 transmits the rotational motion of the outer collar 212 to the body 210.

[0046] In some examples, the outer collar 212 includes tabs 244 that prevent the outer collar 212 from tilting and keep the outer collar 212 properly aligned for reliable motor performance. In certain embodiments, the engagement of the outer collar 212 with the body 210 forms a gap 246 between the outer collar 212 and the body 210. In certain examples, the gap 246 is more pronounced between uneven edges. The gap 246 can provide clearance to accommodate variations in manufacturing tolerances of the brake hub 124.

[0047] 17 and 18 , in certain embodiments, the outer surface 214 of the inner portion 148 of the brake hub 124 and the inner surface 218 of the outer collar 212 face each other along the axial thickness T of the outer collar 212. In some embodiments, the facing portions of the outer surface 214 and the inner surface 218 are flat. In other embodiments, the facing portions have curvatures 220 and 222, respectively. In certain examples, the curvatures 220, 222 are configured to reduce edge loading between the collar 212 and the inner portion 148, which may reduce stress at the fillet 240 between the inner portion 148 and the hub mounting section 235. For example, the curvatures 220, 222 may have peaks that are offset from the edges of the outer collar 212 such that the initial point of contact between the outer collar 212 and the inner portion 148 is located at an intermediate position 223 along the axial thickness T. In certain instances, the inclusion of such curvatures 220, 222 may help to evenly distribute torque loads through the part interface, thereby avoiding edge loading and reducing high bending stresses at the fillet 240. The resulting reduction in high bending stresses may help to extend the fatigue life of the brake hub 124.

[0048] 19-22, another exemplary brake release arrangement 201 includes a multi-piece release member 203. This brake release arrangement 201 can be used with any of the brake arrangements 123, 209 disclosed herein. In certain embodiments, the multi-piece release member 203 includes a first rod 202 extending through the central shaft 130 and a separate second rod 204 extending through the brake hub 124. Separating the brake release portion 203 into separate rods 202, 204 reduces wear on the brake piston 136 by allowing the first rod 202 to move with the orbital movement of the gerotor star 118 without imparting orbital movement to the second rod 204. Thus, the second rod 204 does not slide on the surface of the brake piston 136. Additionally, the second rod 204 may contact the brake piston 136 via a generally flat end surface 205 (see, for example, FIG. 21) instead of a contoured or angled surface as shown in FIG.

[0049] The first rod 202 is angled relative to the central axis 104 so that a first engagement end 206 of the first rod 202 can orbit with the star 118, while the opposite end of the first rod 202 remains stationary on the spindle 102. The first rod 202 does not rotate relative to the central shaft 130. In certain examples, the second rod 204 extends coaxially or parallel to the central axis 104 through the brake hub 124. In certain examples, the second rod 204 is configured to rotate with the brake hub 124. For example, the key 207 may engage a pocket defined in the brake hub 124 with a pocket defined in the second rod 204, causing the brake hub 124 and the second rod 204 to rotate as a unit. Other key configurations are possible.

[0050] In certain embodiments, the first engagement end 206 of the first rod 202 engages the second engagement end 208 of the second rod 204 (see, for example, FIG. 21 ). In certain examples, as the drive housing 108 and the brake hub 124 rotate, the first engagement end 206 and the second engagement end 208 contact each other in a rolling-type motion. This rolling-type motion may result in less mechanical wear on the first rod 202 and the second rod 204. In certain examples, the first rod 202 may be positioned at an angle to the central axis 104, and the second rod 204 may be positioned on the central axis 104, so that the first engagement end 206 maintains end contact with the second engagement end 208. Furthermore, the second engagement end 208 rotates with the brake hub 124, while the first engagement end 206 orbits with the star 118. These relative motions reduce the pressure-velocity ratio between them.

[0051] In certain embodiments, the brake release member 203 (e.g., the first rod 202) does not directly contact the brake application piston 152. Rather, a spacer 224 (e.g., a dowel pin) can space the brake release member 230 from the brake application piston 152. The spacer 224 serves a similar function to the second rod 204 in that the brake application piston 152 can engage an associated flat surface instead of an angled surface on the first rod 202. For similar reasons, a drive spacer 226 is provided between the central shaft 130 and the thrust plate 216.

[0052] 22, the spacer 224 extends through a portion of the thrust plate 216 and reaches the brake application piston 152. In some examples, the spacer 224 directly contacts the brake application piston 152. In other examples, one or more shims 228 (e.g., metal disks) are disposed between the spacer 224 and the brake application piston 152. The shims 228 may help accommodate variations in the stroke length of the brake application piston 152 (which may result from variations in manufacturing tolerances of the motor components). The shims 228 may also help control variations in the release stroke, allowing for the use of a single brake spring 138.

[0053] In some examples, the motor components comprising the brake arrangement 123, 209 and / or the brake release arrangement 139, 201 may be installed on a newly manufactured motor. In some examples, the motor components comprising the brake arrangement 123, 209 and / or the brake release arrangement 139, 201 may be installed on a refurbished motor or placed on a motor undergoing maintenance. In other examples, the motor components comprising the brake arrangement 123, 209 and / or the brake release arrangement 139, 201 may be configured as a kit that can be used to retrofit a motor that originally had a different type of brake system.

[0054] 23 shows a second exemplary embodiment of the hydraulic drive system of FIG. 19 including the second exemplary brake hub 124 of FIG. 11, except that bushings 260, 262 are shown around the body 210 and outer collar 212, respectively. The bushings 260, 262 prevent friction between the brake hub 124, the motor cover 142, and the gerotor star 118. A washer 264 may also be placed between the outer collar 212 and the central shaft 130 to prevent friction.

[0055] 24-26 illustrate an alternative brake arrangement 250 suitable for use with any of the brake release arrangements 139, 201 disclosed herein. The brake arrangement 250 combines features of the brake arrangements 123, 209. The exemplary brake arrangement 250 includes a single-piece brake hub 252 substantially similar to the brake hub 124 of FIG. 7, except that a first portion 254 of the hub 252 defines a splined brake pad mounting section 258 of the hub 124 of FIG. 12. The splines 258 are configured to engage the internal teeth 232 of the first brake pad 132 such that the first brake pad 132 rotates with the brake hub 252.

[0056] A bushing 258 is disposed on the body 254 and interfaces directly with the motor cover 142. Similar to the brake hub 124, the second portion 256 of the brake hub 252 is larger than the gerotor star 118 and is sized to fit over the gerotor star 118, orbiting with the gerotor star 118 about the star axis 122. Another bushing 260 is disposed on the outer collar 256 and interfaces directly with the gerotor star 118. Finally, a washer 264 is disposed between the second portion 256 of the brake hub 250 and the central shaft 130.

[0057] Also similar to the brake hub 124 of FIG. 7, the hub 252 defines a passageway 255 centered about a first portion 254 of the brake hub 252. A first portion 255a of the passageway 255 is generally cylindrical through the first portion 254 of the brake hub 252, while a second portion 255b of the passageway 255 defines an elliptical shape through the second portion 256 of the brake hub 252. The elliptical shape facilitates initial insertion of the second release rod 204 into the hub 252. In certain examples, the second portion of the passageway through any of the brake hubs 124 disclosed herein may be elliptical. In certain embodiments, a key 207 (FIG. 12) may engage a pocket 253 (FIG. 24) defined in the first portion 255a of the passageway 255 and a pocket defined in the second release rod 204 such that the brake hub 252 and the second rod 204 rotate as a unit.

[0058] While preferred aspects and embodiments of the present disclosure have been described, modifications and equivalents of the disclosed concepts may readily occur to those skilled in the art, and such modifications and equivalents are however intended to be included within the scope of the claims appended hereto.

Claims

1. A hydraulic drive with mechanical braking, a spindle having a first mounting flange, said spindle defining a central axis; a drive housing attached to the spindle, the drive housing including a second mounting flange; a bearing that allows the drive housing to rotate relative to the spindle about the central axis; a gerotor hydraulic motor arrangement including an outer motor ring coupled to the drive housing such that the outer motor ring and the drive housing rotate together about the central axis, the outer motor ring including a plurality of radially inwardly directed pockets spaced circumferentially about the central axis, the gerotor hydraulic motor arrangement also including a gerotor star including a plurality of lobes positioned circumferentially about a star axis defined by the gerotor star, the gerotor star being positioned within the outer motor ring with the star axis offset from the central axis such that the gerotor star is eccentric relative to the outer motor ring, the gerotor star being mounted to orbit about the central axis to move the lobes into and out of the pockets of the outer motor ring when the outer motor ring is hydraulically driven about the central axis, one orbit of the gerotor star about the central axis corresponding to movement of the outer motor ring one pocket position about the central axis relative to the gerotor star; a brake hub including a first portion concentric with the central axis and a second portion concentric with the gerotor star, the second portion of the brake hub mechanically mating with the gerotor star such that orbital motion of the gerotor star about the central axis drives rotation of the brake hub about the central axis, and the brake hub rotates once about the central axis for each orbit of the gerotor star about the central axis; a central shaft configured to allow the gerotor star to orbit about the central axis while preventing the gerotor star from rotating about the star axis relative to the spindle; a first brake pad attached to the brake hub so as to rotate integrally with the brake hub about the central axis; a second brake pad mounted for rotation about the central axis in unison with the drive housing and the outer motor ring; a brake piston for axially urging the first and second brake pads together to provide braking of the gerotor hydraulic motor arrangement, the brake piston being spring biased axially toward the first and second brake pads by a brake spring; a brake release portion extending through the central shaft and the brake hub, the brake release portion adapted to release braking of the gerotor hydraulic motor arrangement by axially urging the brake piston away from the first and second brake pads against the bias of the brake spring; A hydraulic drive unit comprising:

2. 2. The hydraulic drive system of claim 1, wherein the second portion of the brake hub rotates within the gerotor star as the gerotor star orbits about the central axis and functions as a crank that rotates the brake hub about the central axis as the gerotor star orbits about the central axis.

3. 3. The hydraulic drive system of claim 2, wherein the first portion of the brake hub is rotatably mounted within an opening defined by a motor cover that rotates integrally with the outer motor ring and the drive housing.

4. The hydraulic drive system of claim 3 , wherein the second portion of the brake hub is concentrically mounted within a central opening of the gerotor star.

5. The hydraulic drive system of claim 4 , wherein the first and second portions of the brake hub are defined as a single piece.

6. The hydraulic drive system of claim 4 , wherein the brake hub comprises a multi-piece construction.

7. 7. The hydraulic drive system of claim 6, wherein the brake hub includes a body defining the first portion of the brake hub and an inner portion of the second portion of the brake hub, the second portion of the brake hub also including an outer collar attached to the inner portion of the second portion of the brake hub and including an outer surface concentric with the central opening of the gerotor star, the outer collar configured to rotate with the body about the central axis, and wherein relative rotation about the star axis occurs between the outer collar and the gerotor star as the brake hub rotates about the central axis and the gerotor star orbits about the central axis.

8. 8. The hydraulic drive system of claim 7, wherein an inner surface of the outer collar includes a collar flat edge, the inner portion of the second portion of the brake hub includes a hub flat edge, and the collar flat edge and the hub flat edge are aligned.

9. The hydraulic drive system of claim 7 , wherein the outer surface of the outer collar is phosphate treated.

10. 8. The hydraulic drive system of claim 7, wherein an outer surface of the inner portion of the brake hub second portion and an inner surface of the outer collar face each other along an axial thickness, and wherein the outer surface of the inner portion of the brake hub second portion and the inner surface of the outer collar have an eccentric radius curvature configured to reduce edge loads and concentrate loads in a central region of the axial thickness.

11. 4. The hydraulic drive system of claim 3, wherein a brake cover is attached to an exterior of the motor cover and configured to rotate integrally with the motor cover, the outer motor ring, and the drive housing; a brake chamber is defined between the motor cover and the brake cover; the brake hub includes a pad mounting extension extending into the brake chamber; a plurality of the first brake pads are attached to the pad mounting extension within the brake chamber and configured to rotate with the brake hub; a plurality of the second brake pads are coupled to the brake cover and configured to rotate integrally with the brake cover; and the first and second brake pads are interleaved.

12. The hydraulic drive system of claim 11 , wherein the brake cover, the motor cover, and the outer motor ring are secured to the drive housing by axial bolts.

13. The hydraulic drive system of claim 1 , wherein the brake release portion includes a single rod extending through the central shaft and the brake hub.

14. The hydraulic drive system of claim 1 , wherein the pockets are separated by rollers.

15. 2. The hydraulic drive system of claim 1, wherein the brake release portion includes a first rod extending through the central shaft and a second rod extending through the brake hub, the first and second rods engaging each other at engagement ends, the second rod being concentric with the central axis, and the engagement end of the first rod being eccentric with respect to the central axis and aligned with the gerotor star.

16. 16. The hydraulic drive system of claim 15, wherein the brake release portion is hydraulically actuated, a thrust plate is attached to the spindle, a brake application piston is mounted within the thrust plate, and during braking, hydraulic pressure is applied to the brake application piston such that the brake application piston drives the brake release portion toward the brake piston and moves the brake piston away from the first and second brake pads against the spring bias of the brake spring.

17. 17. The hydraulic drive system of claim 16, wherein the thrust plate defines a stop that limits the axial range of movement of the brake release portion and stops movement of the brake release piston at a predetermined position to prevent the brake spring from bottoming out.

18. The hydraulic drive system of claim 16 , further comprising a spacer between the brake release portion and the brake application piston.

19. The hydraulic drive system of claim 18 , further comprising a shim between the spacer and the brake application piston.

20. A hydraulic drive system according to any preceding claim, wherein the first brake pad includes teeth that align with splines on the brake hub.

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