Radial piston devices (either pumps or motors) are often used in aerospace hydraulic applications and are characterized by a rotor rotatably engaged with a pintle. The rotor has a number of radially oriented cylinders disposed around the rotor and supports a number of pistons in the cylinders. A head of each piston contacts an outer thrust ring that is not axially aligned with the rotor. A stroke of each piston is determined by the eccentricity of the thrust ring with respect to the rotor. When the device is in a pump configuration, the rotor can be rotated by operation of a drive shaft associated with the rotor. The rotating rotor draws hydraulic fluid into the pintle, and forces the fluid outward into a first set of the cylinders so that the pistons are displaced outwardly within the first set of the cylinders. As the rotor further rotates around the pintle, the first set of the cylinders becomes in fluidic communication with the outlet of the device and the thrust ring pushes back the pistons inwardly within the first set of the cylinders. As a result, the fluid drawn into the first set of the cylinders is displaced into the outlet of the device through the pintle.
The fluid drawn into the cylinders exerts different degrees of pressure onto the pintle depending on the stroke of each piston. For example, the fluid entering the cylinders has a lower pressure on one side of the pintle than the fluid discharging from the cylinder has on the opposite side of the pintle. This resulting difference in pressure that the fluid exerts onto the pintle causes the pintle to deflect along the pintle axis. The curvature of the pintle results in misalignment with the rotor. This misalignment prevents the rotor from rotating about the pintle as designed. The problem of the pintle deflection is exacerbated when the radial piston device is used for high pressure flows or when the pintle is designed to have a small diameter to minimize the overall size of the device.
The present disclosure relates generally to a radial piston device. In one possible configuration and by non-limiting example, the radial piston device includes a housing, a pintle, a rotor, a plurality of pistons, and a drive shaft.
In one example, the housing has a hydraulic fluid inlet and a hydraulic fluid outlet. The pintle is attached to the housing and has a pintle shaft. The rotor is rotatably mounted on the pintle shaft and has a plurality of cylinders. The plurality of pistons is displaceable in the plurality of cylinders, respectively. The drive shaft is coupled to the rotor and rotatably supported within the housing. The pintle shaft defines a fluid communication between the hydraulic fluid inlet and the plurality of cylinders and a fluid communication between the plurality of cylinders and the hydraulic fluid outlet.
In another example, the housing includes a hydraulic fluid inlet and a hydraulic fluid outlet. The pintle may be attached to the housing and includes a pintle shaft which defines a pintle inlet and a pintle outlet. The pintle inlet is configured to be in fluid communication with the hydraulic fluid inlet, and the pintle outlet is configured to be in fluid communication with the hydraulic fluid outlet. The rotor may be mounted on the pintle shaft so as to rotate about the pintle shaft relative to the pintle. The rotor may define multiple cylinders that are radially oriented around the rotor. The rotor may also define multiple rotor fluid ports below the cylinders, respectively. The rotor fluid ports are in fluid communication with the corresponding cylinders. The pistons are displaceably accommodated within the cylinders, respectively. The radial piston device may further include a thrust ring. The thrust ring may be disposed about the rotor while being in contact with each of the pistons. A thrust ring axis of rotation is radially offset from a rotor axis of rotation. Accordingly, as the rotor rotates about the rotor axis of rotation, the pistons reciprocates radially within the cylinder, and the rotor fluid ports are alternatively in fluid communication with either the pintle inlet or the pintle outlet depending on the position of the rotor. The drive shaft may be coupled to the rotor and rotatably supported within the housing.
When the rotor is in a first position of rotation, a first rotor fluid port is in fluid communication with the pintle inlet so that hydraulic fluid is drawn from the hydraulic fluid inlet into the first rotor fluid port via the pintle inlet and then flows into a first cylinder or a first cylinder set associated with the first rotor fluid port, pushing the first cylinder or the first cylinder set radially outwardly. When the rotor is in a second position opposite to the first position, the first rotor fluid port is in fluid communication with the pintle outlet so that the drawn hydraulic fluid is discharged from the first cylinder or the first cylinder set and flows from the first rotor fluid port into the hydraulic fluid outlet via the pintle outlet.
In another example, the pintle may include a mounting flange that is attached to the housing. The mounting flange may be fixed to the housing via fasteners.
In some examples, the radial piston device may include a flexible coupling for coupling the drive shaft with the rotor. The flexible coupling may define an inlet in fluid communication with the hydraulic fluid inlet and the pintle inlet.
In other examples, the housing may include a drive shaft housing having a hydraulic fluid inlet and a rotor housing having a hydraulic fluid outlet. The pintle may be attached or fixed to the rotor housing so as to be accommodated within the rotor housing. The drive shaft may be supported within the drive shaft housing.
The radial piston device may be used either as a pump or as a motor.
The radial piston device according to the present disclosure may further include a mechanism for minimizing deflection or curvature of the pintle shaft, which may be caused by a resulting pressure applied to the pintle shaft. Hydraulic fluid entering the cylinders and hydraulic fluid exiting the cylinders exert different pressures on the pintle shaft at different sides, thereby creating a resulting pressure on the pintle shaft. Such a resulting pressure applied to the pintle shaft causes deflection or curvature of the pintle shaft along the pintle axis of rotation.
In one aspect, the rotor is at least partially supported by the housing with a bearing while being also supported by the pintle shaft with another bearing. In some examples, the rotor may be supported radially on the pintle shaft adjacent to the pintle outlet (or at an outlet end of the rotor) with a first bearing, and may be partially supported by the housing adjacent to the pintle inlet (or at an inlet end of the rotor) with a second bearing. The bearings may be a hydrodynamic journal bearing, which is also referred to as a fluid film bearing, or a hydrostatic bearing. In the examples in which the housing includes the drive shaft housing and the rotor housing, the rotor may be at least partially received within the drive shaft housing and rotatably supported by the drive shaft housing with a bearing.
In another aspect, the pintle has an inlet end and an outlet end, the outlet end opposite to the inlet end along the length of the pintle shaft, and the pintle shaft includes a tapered portion arranged around the pintle shaft at the inlet end of the pintle. The tapered portion of the pintle shaft is configured and arranged to compensate a deflection of the pintle shaft, thereby allowing the rotor to rotate around the deflected pintle shaft. In some examples, the tapered portion includes a first tapered portion and a second tapered portion. The first tapered portion may be arranged circumferentially around the pintle shaft adjacent the inlet end of the pintle, and the second tapered portion may be arranged circumferentially around the pintle shaft adjacent the outlet end of the pintle. The tapered portion may have a cone shape. In some examples, the cone shape may be arranged circumferentially around the pintle shaft adjacent the inlet end of the pintle and configured to have an apex of the cone shape biased in a direction opposite to the inlet end of the pintle.
In still other aspects, the rotor and the drive shaft may be integrally formed as one piece.
In still other aspects, the pintle shaft may be at least partially supported by the drive shaft, and the drive shaft may be engaged at least partially with the pintle shaft and rotatable with respect to the pintle shaft. In some examples, the drive shaft has a driving end and a power transfer end that is opposite to the driving end along a drive shaft axis of rotation. The drive shaft may have a receiving portion formed at the power transfer end for at least partially receiving the pintle shaft therein so that the pintle shaft may be partially supported in the receiving portion of the drive shaft at the power transfer end. The receiving portion of the drive shaft is rotatably engaged at least partially with the pintle shaft at the power transfer end of the drive shaft. The drive shaft and the rotor may be coupled with a flexible coupling therebetween.
In still other aspect, the drive shaft and the rotor may be coupled by spline coupling. In some examples, the drive shaft has a shaft head, a stem and a power transfer flange. The stem extends between the shaft head and the power transfer flange. The power transfer flange may be coupled to the rotor by spline coupling, in other examples, the power transfer flange has a coupling portion protruding therefrom. The coupling portion may have a number of splines located on an outer surface thereof, and the rotor may have a number of corresponding splines located on an inner surface of the bore of the rotor at the inlet end. The splines of the coupling portion are engaged with the corresponding splines of the rotor.
In still other aspect, the pintle may have has an inlet end and an outlet end that is opposite to the inlet end along a pintle shaft axis. The pintle may include a mounting flange located at the outlet end of the pintle and attached to the rotor housing, and the pintle shaft may include at least one undercut section around the pintle shaft adjacent the mounting flange.
Various examples will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various examples does not limit the scope of the disclosure and the aspects upon which the examples are based. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible ways in which the various aspects of the present disclosure may be put into practice.
In the present disclosure, radial piston devices are described generally. These devices may be used in both motor and pump applications, as required. Certain differences between motor and pump applications are described herein when appropriate, but additional differences and similarities would also be apparent to a person of skill in the art. The radial piston device disclosed herein exhibits high power density, is capable of high speed operation, and has high efficiency. Although the technology herein is described in the context of radial piston devices, the benefits of the technologies described may also be applicable to any device in which the pistons are oriented between an axial position and a radial position.
The housing 102 may be configured as a two-part housing that includes a drive shaft housing 104 and a rotor housing 106. The drive shaft housing 104 includes a hydraulic fluid inlet 108 through which hydraulic fluid is drawn into the drive shaft housing 104 when the device 100 operates as a pump. The rotor housing 106 includes a hydraulic fluid outlet 122 through which hydraulic fluid is discharged when the device 100 operates as a pump.
The pintle 110 has a first end 111 (also referred to herein as an outlet end) and a second end 113 (also referred to herein as an inlet end) that is opposite to the first end along a pintle axis AP (
The pintle 110 may further include an inlet port 115 and an outlet port 117. The inlet port 115 and the outlet port 117 are formed on the pintle shaft 112. In some examples, the inlet port 115 is arranged substantially opposite to the outlet port 117 on the pintle shaft 112. The inlet port 115 is configured to be in fluid communication with the pintle inlet 114, and the outlet port 117 is configured to be in fluid communication with the pintle outlet 116.
The rotor 130 defines a bore 131 that allows the rotor 130 to be mounted on the pintle shaft 112. The rotor 130 has an inlet end 133 and an outlet end 135 that is opposite to the inlet end 133 along a rotor axis AR. The rotor axis AR extends through the length of the pintle shaft 112 and is coaxial with the pintle axis AP. The rotor 130 is mounted on the pintle shaft 112 so that the outlet end 135 of the rotor 130 is arranged adjacent the first end 111 of the pintle 110 (which is adjacent the mounting flange 118). The inlet end 133 of the rotor 130 is coupled to the drive shaft 190 as explained below.
The rotor 130 is configured to rotate relative to the pintle 110 on the pintle shaft 112 about the rotor axis AR. The rotor 130 defines a number of radial cylinders 132, each of which receives a piston 150. In the depicted example, the cylinders 132 are in paired configurations such that two cylinders 132 are located adjacent each other along a linear axis parallel to the rotor axis AR. In the present application, such linearly-aligned cylinders 132 and pistons 150 are referred to as cylinder sets and piston sets, respectively.
The rotor 130 includes rotor fluid ports 134 and common fluid chambers 136 (
The pistons 150 are received in the radial cylinders 132 defined in the rotor 130 and displaceable in the radial cylinders 132, respectively. Each piston 150 is in contact with the thrust ring 170 at a head portion of the piston 150.
The thrust ring 170 is supported radially by the rotor housing 106 and rotatably mounted in the rotor housing 106. The thrust ring 170 may be supported with a hydrodynamic journal bearing 172.
The drive shaft 190 is at least partially located within the drive shaft housing 104. An oil seal assembly 192 surrounds the drive shaft 190 and prevents hydraulic fluid from inadvertently exiting the housing 102. The drive shaft 190 is supported with a plurality of alignment bushings 194 such that there is no radial load on the drive shaft 190.
The drive shaft 190 has a driving end 187 and a power transfer end 189, which is opposite to the driving end 187 along a drive shaft axis of rotation AS. In some examples, the drive shaft 190 includes a shaft head 191, a stem 193 and a power transfer flange 195. The shaft head 191 is configured to be engaged with a driving mechanism (not shown) at the driving end 187 of the drive shaft 190 so that torque is input to the drive shaft 190 to rotate the rotor 130 when the radial piston device 100 operates as a pump. A power transfer flange 195 is configured to be engaged with the rotor 130. The stem 193 extends between the shaft head 191 and the power transfer flange 195. In sonic examples, the drive shaft 190 is located within the drive shaft housing 104 such that hydraulic fluid entering the drive shaft housing 104 via the hydraulic fluid inlet 108 flows around the stem 193 of the drive shaft 190 and into the pintle inlet 114 of the pintle shaft 112.
The drive shaft 190 is configured to be connected to the rotor 130 at the power transfer end 189 of the drive shaft 190. In some examples, the drive shaft 190 is connected to the inlet end of the rotor 130 at a flexible coupling 200. For example, the power transfer flange 195 of the drive shaft 190 may be connected to the inlet end of the rotor 130 with the flexible coupling 200 therebetween.
The radial piston device 100 may further include an apparatus for monitoring temperature and/or pressure within the housing 102. Such a monitoring apparatus may be arranged at a number of different locations including a sensor port 124. The radial piston device 100 may include a case drain 126 that is connected to any number of interior chambers of the housing 102.
The drive shaft 190 includes a number of drive splines 196 at the shaft head 191 of the drive shaft 190. In some examples, the drive splines 196 are formed within the shaft head 191. In other examples, the splines may be arranged on an outer surface of the shaft head 191. As explained above, the drive shaft 190 includes the power transfer flange 195 at an end of the drive shaft 190 opposite to the shaft head 191 having the drive splines 196. The power transfer flange 195 includes a number of shaft teeth 198 to engage the flexible coupling 200. In this example, two shaft teeth 198 engage the flexible coupling 200 at an angle of about 90 degrees from two rotor teeth 138 that also engage the flexible coupling 200. The power transfer flange 195 at the power transfer end of the drive shaft 190 that supports the shaft teeth 198 defines one or more flow passages 202 that allow hydraulic suction flow to pass into the center of the flexible coupling 200. The drive shaft flow passage 202 may include a tapered or funneled inner surface 204 that reduces pressure losses as the hydraulic fluid is drawn into the pintle inlet 114.
The flexible coupling 200 defines a number of receivers 206 for receiving the shaft teeth 198 and the rotor teeth 138. The flexible coupling 200 defines a flow passage 208 to collect the hydraulic suction flow into the pintle inlet 114 (not shown in
In this example, each cylinder set 220A is offset from an adjacent cylinder set 220B, such that four rows 222a, 222b, 222c and 222d are present on the rotor 130 (See
A minimum of two rows 222 are necessary to balance the thrust loads on the thrust ring. In other examples, other numbers of rows and shafts may be utilized. In this example, four piston rows 222a, 222b, 222c and 222d are utilized. As noted above with regard to
The interface between the pistons 150 and the inner race of the thrust ring 170 is defined by a spherical piston geometry and a toroidal ring geometry. This promotes rolling of the pistons 150 on the thrust ring 170 in order to prevent sliding. An even number of cylinder sets are used in order to balance the thrust loads acting on the thrust ring 170. In the depicted example, eight cylinder sets are utilized. Special materials or coatings (such as ceramics or nanocoatings) can be used to decrease the friction and increase the longevity of the piston/ring interface.
As shown in
The radial piston device 100 may include several mechanisms for reducing such deflection of the pintle shaft 112 along the pintle axis AP due to hydraulic fluid pressure on the pintle shaft 112, and/or for minimizing the consequences of the pintle shaft deflection, such as misalignment between the pintle shaft 112 and the rotor 130. The mechanisms are hereinafter explained in detail. In some examples, each of the mechanisms may be separately implemented in a radial piston device 100. In other examples, any combination of the mechanisms may be used for the radial piston device.
Turning again to
When the rotor 130 is partially supported by the drive shaft housing 104 at the inlet end 133 of the rotor 130 with a journal bearing, the rotor 130 need not be additionally supported by the pintle shaft 112 at multiple locations on the length of the pintle shaft 112. Instead, in some examples, the pintle shaft 112 may only support the rotor 130 adjacent to the fixed/base end of the pintle shaft 112. This is significant because the base/fixed end of the pintle shaft 112 does not experience much or any deflection in use of the device. By supporting the rotor 130 at a location along the shaft 130 that does not experience substantial deflection, rotation of the rotor 130 on the pintle shaft 112 is not negatively affected by the pintle shaft deflection. In certain examples, a larger radial clearance (or spacing or gap) can be provided between the pintle shaft 112 and the rotor 130 at the region of the pintle shaft 112 that experiences the most deflection in use of the device so as to avoid unwanted contact between the pintle shaft 112 and the rotor 130 as the pintle shaft 112 deflects due to unbalanced pressure applied to the inlet and outlet sides 125 and 127. In certain examples, a bearing is provided between the pintle shaft 112 and the rotor 130 at a position that is spaced no more than ¼ of the length of the shaft from the base end of the pintle shaft 112, and no bearings are provided between the rotor 130 and the shaft 112 for the remaining ¾ of the length of the pintle shaft 112. In other examples, a bearing is provided between the pintle shaft 112 and the rotor 130 at a position that is spaced no more than ⅓ of the length of the pintle shaft 112 from the base end of the shaft, and no bearings are provided between the rotor 130 and the pintle shaft 112 for the remaining ⅔ of the length of the pintle shaft 112. In other examples, a bearing is provided between the pintle shaft 112 and the rotor 130 at a position that is spaced no more than ½ of the length of the shaft from the base end of the pintle shaft 112, and no bearings are provided between the rotor 130 and the pintle shaft 112 for the remaining ½ of the length of the pintle shaft 112.
As shown in
The tapered portions 300 may be configured as a truncated conical shape. In some examples, the first tapered portion 302 has a minor diameter 306 of the conical shape closest to the inlet end (i.e., the free end) of the pintle shaft 112 and a major diameter 307 farthest from the inlet end (i.e., the inlet end) of the pintle shaft 112. Thus, a cross section of the first tapered portion 302 has a diameter gradually decreasing as it goes along the length of the pintle shaft 112 in a direction toward the inlet end of the pintle shaft 112. In contrast, the second tapered portion 304 has a minor diameter 308 of the conical shape closest to the outlet end (i.e., the base or fixed end) of the pintle shaft 112 and a major diameter 309 furthest from the outlet end (i.e. the base or fixed end) of the pintle shaft 112. Thus, the second tapered portion 304 may have a cross section with a diameter gradually decreasing as it goes along the length of the pintle shaft 112 in a direction toward the outlet end of the pintle shaft 112. These faces of the first and second tapered portions 302 and 304 will engage in parallel with the inner surface of the rotor 130 when the pintle shaft 112 deflects along the pintle axis AP.
Although
In other examples, the tapered portion 300 is arranged circumferentially around the pintle shaft 112 only at the inlet end of the pintle 110. In still other examples, while the tapered portion 300 is formed around the pintle shaft 112 adjacent to the inlet end of the pintle 110, it is arranged partially on a surface of the pintle shaft 112 adjacent the inlet port 115 of the pintle shaft 112. This is because, when the radial piston device is used as a pump, fluid has a higher pressure on a surface of the pintle shaft 112 adjacent to the outlet port 117 than on a surface of the pintle shaft 112 adjacent to the inlet port 115, which is substantially opposite to the outlet port 117 of the pintle shaft 112.
In the third example, bearings that are arranged around the drive shaft 190 to support the drive shaft 190 also operate to support the rotor 130. Thus, a larger clearance can be provided between the pintle shaft 112 and the rotor 130 adjacent the free end of the pintle shaft 112 to allow for the pintle shaft deflection. Alternatively, the integral piece of the drive shaft 190 and the rotor 130 functions as support for the free end of the pintle shaft 112, thereby preventing the pintle shaft 112 from deflecting due to unbalance fluid pressure and maintaining co-axial alignment between the pintle shaft 112 and the rotor 130. In some examples, a bearing can be provided between the pintle shaft 112 and the rotor 130 adjacent the free end of the pintle shaft 112 for the integral piece of the drive shaft 190 and the rotor 130 to support the free end of the pintle shaft 112.
In some examples, the drive shaft 190 has a bore or receiving portion 310 formed within the stem 193 along the drive shaft axis AS. The receiving portion 310 opens at the power transfer end of the drive shaft 190 and is configured to receive at least partially the pintle shaft 112 therein. To be received within the receiving portion 310 of the drive shaft 190, the pintle shaft 112 further extends at the inlet end or second end thereof along the pintle axis AP, than the pintle shaft 112 of
As in
Similarly to the third example, in the fourth example, bearings that are arranged around the drive shaft 190 to support the drive shaft 190 also operate to support the rotor 130. Thus, a larger clearance can be provided between the pintle shaft 112 and the rotor 130 adjacent the free end of the pintle shaft 112 to allow for the pintle shaft deflection. Alternatively, the rotor 130 functions to support the free end of the pintle shaft 112, thereby preventing the pintle shaft 112 from deflecting due to unbalance fluid pressure and maintaining co-axial alignment between the pintle shaft 112 and the rotor 130. In some examples, a bearing can be provided between the pintle shaft 112 and the rotor 130 adjacent the free end of the pintle shaft 112 for the rotor 130 to support the free end of the pintle shaft 112.
In some examples, the drive shaft 190 includes a drive shaft side coupling portion 322 at the power flange end. For example, the drive shaft side coupling portion 322 is configured to protrude from the power transfer flange 195 along the drive shaft axis AS. The drive shaft side coupling portion 322 has a number of splines located on an outer surface thereof. The rotor 130 can include a rotor side coupling portion 324 at the inlet end thereof. For example, the rotor side coupling portion 324 is configured to extend from the inlet end of the rotor 130 toward the power transfer flange 195 of the drive shaft 190. The rotor side coupling portion 324 has a number of splines, which are configured to correspond to the splines formed in the drive shaft side coupling portion 322. The number of splines of the rotor side coupling portion 324 is located on an inner surface of the bore of the rotor 130 at the inlet end. The splines of the drive shaft side coupling portion 322 are engaged with the corresponding splines of the rotor side coupling portion 324 to provide a torque transferring interface.
In some examples, the undercut section 330 is arranged around the pintle shaft 112 adjacent the mounting flange 118. The undercut section 330 may be configured as an annular groove formed circumferentially around the pintle shaft 112 adjacent the mounting flange 118. The undercut section 330 causes the pintle shaft 112 to have a smaller diameter at the undercut section 330 than at other portions of the pintle shaft 112. This structure reduces the curvature of the pintle shaft 112 along the pintle axis AP, which results from the difference in pressure on different sides of the pintle shaft 112, and allows the pintle shaft 112 to maintain more linear or straight shape along the pintle axis A. Such a straight shape of the pintle shaft 112, rather than a deflected shape, helps the rotor 130 to smoothly engage with the pintle shaft 112 when the rotor 130 rotates around the pintle shaft 112. In other examples, the undercut sections 330 may be formed discontinuously around the pintle shaft 112 adjacent the mounting flange 118.
The present disclosure has been described in detail in the foregoing specification, and it is believed that various alterations and modifications of the many aspects of the present disclosure will become apparent to those ordinary skilled in the art from a reading and understanding of the specification.
This application is being filed on Dec. 30, 2014, as a PCT International Patent application and claims priority to U.S. Patent Application Ser. No. 61/922,400 filed on Dec. 31, 2013, the disclosure of which is incorporated herein by reference in its entirety.
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/US14/72766 | 12/30/2014 | WO | 00 |
Number | Date | Country | |
---|---|---|---|
61922400 | Dec 2013 | US |