Patent Publication Number: US-2010107866-A1

Title: Three speed floating cup hydraulic motor

Description:
TECHNICAL FIELD 
     This patent disclosure relates generally to hydraulic motors and, more particularly to floating cup hydraulic motors. 
     BACKGROUND 
     Hydraulic motors can be used to propel a variety of machines, e.g., loaders, excavators, dozers and the like. To provide two different operating speeds, the piston pumps in conventional hydraulic motors may use a simple toggle to switch a swashplate angle between maximum and minimum displacement settings. The maximum displacement setting may provide relatively low speed and high torque, while the minimum displacement setting may provide relatively high speed and low torque. 
     Conventional hydraulic motors utilize piston pumps with five, seven or nine pistons. As a result, starting torque of the motor can be quite low. Hydraulic motors utilizing a so-called floating cup type pump can provide higher initial starting torque than conventional hydraulic motors. A hydraulic motor based on a floating cup type pump is disclosed in International Patent Publication No. WO 2006/094990-A1 in the name of Achten, having a publication date of Sep. 14, 2006. The disclosed floating cup type pump generally utilizes a plurality of piston elements projecting away from either side of a rotor. 
     The pumps described in this reference include a centrally disposed rotor having a plurality of pistons projecting away from both sides of the rotor. A pair of cooperating drum plates disposed outboard from the rotor support an arrangement of cup elements or drum sleeves adapted to house distal portions of the pistons. The rotor supporting the pistons rotates around a first axis of rotation. The drum plates rotate in angled relation to the first axis. The rotor supporting the pistons is rotated in tandem with the drum plates during operation. Due to the angle between the rotor and the drum plates, the cups are caused to stroke along the length of the corresponding piston elements such that the volume occupied by the piston elements is alternately increased and decreased during the rotational cycle. Thus, fluid introduced into a cup element when the complementary piston is in a substantially withdrawn position may be pressurized and expelled as the cup is pushed inwardly during the rotational cycle. The reference discloses infinitely varying the displacement of the pump by varying the angle of a swashplate that is disposed axially outward of the drum plate between a zero angle and a maximum angle. However, the reference does not disclose providing the pump with a discrete set of displacement settings. 
     SUMMARY  
     The disclosure describes, in one aspect, a hydraulic motor. The hydraulic motor includes a rotor supporting a plurality of piston elements projecting away from opposing faces of the rotor. The rotor is adapted to rotate about a first axis. The hydraulic motor further includes a pair of drum plates each supporting a plurality of cup elements. The plurality of cup elements are adapted to engage the piston elements. Each drum plate is arranged on an opposing side of the rotor and is adapted to rotate about a second axis in angled relation to the first axis. Each of a pair of swashplates is in operative engagement with a respective one of the drum plates. Each swashplate is adapted to pivot relative to the rotor with the respective drum plate between a maximum displacement position and a minimum displacement position to thereby change the angled relation between the first axis and the second axis. The pair of swashplates are independently pivotable between a first setting in which both swashplates are in their maximum displacement position, a second setting in which both swashplates in their minimum displacement position and a third setting in which one swashplate is in its maximum displacement setting and the other swashplate is in its minimum displacement setting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cutaway schematic perspective view illustrating the components of an exemplary floating cup hydraulic motor. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure relates to a hydraulic motor. To allow for greater torque at start-up of the motor, the disclosed hydraulic motor is based on a floating cup pump. The hydraulic motor may be powered by any source of pressurized fluid such as, for example, a hydraulic pump. In different applications, it may be advantageous that the hydraulic motor be able to operate at different speeds. 
       FIG. 1  illustrates a motor  10  that is mounted within a motor housing  12 . In this exemplary construction, an output shaft  14  extends along and is adapted for rotation about a first axis  16 . The output shaft  14  is adapted for rotation around the first axis  16 . The output shaft  14  engages a rotor  18  in the form of a disk or plate structure. Thus, rotation of the rotor  18  is translated to the output shaft  14  such that the rotor  18  rotates around the same axis as the output shaft  14 , namely the first axis  16 . 
     In the exemplary construction illustrated in  FIG. 1 , the rotor  18  supports an arrangement of piston elements  20  projecting away from opposing faces of the rotor  18  so as to define, in this case, left and right sides of the motor. As shown, the piston elements  20  may have a generally frusto-conical configuration such that the piston elements  20  taper outwardly as the distance increases away from rotor  18 . However, other suitable constructions may likewise be utilized as desired. 
     In the illustrated construction of  FIG. 1 , the motor  10  includes a pair of drum plates  22  disposed on either side of the rotor  18  in each side of the motor  10 . As shown, the drum plates  22  support an arrangement of cup elements  24  having open ends that project towards the rotor  18 . The cup elements  24  are arranged to house distal portions of the complementary piston elements  20 . With this configuration, the cup elements  24  circumferentially surround distal portions of the corresponding piston elements  20  such that the piston elements  20  cooperate with interior boundary walls of the cup elements  24  to define a plurality of variable volume piston chambers  25 . 
     The drum plates  22  are arranged in circumferential relation to the output shaft  14  and are oriented at an angle relative to the rotor  18 . Thus, the drum plates  22  and the cup elements  24  supported thereon are rotatable around axis lines disposed in angled relation to the first axis  16  of the output shaft  14  and rotor  18 . According to the exemplary construction, the drum plates  22  are supported in this angled orientation by curved surface support elements  26  which are arranged around the output shaft  14  outboard from the rotor  18 . The curved surface support elements  26  include a convex exterior support surface adapted to engage a portion of the drum plates  22 . In the illustrated motor  10 , a pair of swashplates  28  are provided with each being arranged outboard of and in operative engagement with a corresponding drum plate  22 . In this case, each swashplate  28  is in contacting relation with its respective drum plate  22 . 
     Although the motor  10  may be adapted for any number of uses, according to one contemplated practice, a high pressure fluid flows into the motor  10  through an intake port  30 . Inside the motor  10 , the power of the pressurized fluid is converted into mechanical energy in the form of rotation of the output shaft  14 . The fluid then exits the motor through a discharge port  32  at a lower pressure. More specifically, as each piston element  20  and corresponding cup element  24  assembly passes over the intake port  30 , the high pressure fluid enters the piston chamber  25  and causes the piston element  20  to extend outward relative to the corresponding cup element  24 . The angle of the drum plate  22  relative to the piston element  20  displacement causes the rotor  18  and thereby the output shaft  14  to rotate. As a result of this rotation, each piston element  20  and cup element  24  assembly periodically passes over the intake and discharge ports  30 ,  32 . Thus, the piston elements  20  undergo an oscillatory displacement in and out relative to their corresponding cup element  24  receiving high pressure fluid from the intake port  30  and discharging relatively lower pressure fluid through the discharge port  32 . 
     During each rotation of the rotor  18 , each piston element  20  displaces a certain distance in its corresponding cup element  24 . The angle of the drum plate  22  relative to the rotor  18  and output shaft  14  determines the magnitude of the displacement of each piston element  20 . In order to allow the displacement of the piston elements  20  to be varied, each swashplate  28 , and with its corresponding drum plate  22 , may be pivotable relative to the rotor  18  and output shaft  14  such that the angle of the swashplate  28  and drum plate  22  relative to the rotor  18  and output shaft  14 , i.e. the first axis  16 , can be changed. Varying the displacement of the piston elements  20  enables the speed and torque produced at the output shaft  14  of the motor  10  to be varied. 
     In this case, each swashplate  28  may be pivotable between a maximum displacement position in which the displacement of the piston elements  20  is maximized and a minimum displacement position in which the displacement of the piston elements  20  is minimized. Each of the swashplates  28  is shown in its maximum displacement position in  FIG. 1 . To reach the minimum displacement position, with reference to  FIG. 1 , the left swashplate  28  pivots clockwise and the right swashplate  28  pivots counter clockwise. The minimum displacement position can be any swashplate angle greater than a zero angle. 
     Each of the swashplates  28  may be independently pivotable with respect to the other swashplate. Accordingly, the disclosed motor  10  may operate at three different speed settings: A first low speed, high torque setting in which both swashplates  28  are in their maximum displacement position; a second high speed, low torque setting in which both swashplates  28  are in their minimum displacement position; and a third medium setting in which one swashplate  28  is in its minimum displacement position and one swashplate  28  is in its maximum displacement position. Providing three simple, discrete settings allows for greater flexibility for speed control than hydraulic motors that have only a single pivotable swashplate and are thus only capable of two operating speeds. 
     For pivoting the swashplates  28 , the motor  10  may be equipped with an actuating system  34  that is adapted to independently pivot the swashplates  28  between their maximum and minimum displacement positions. In the illustrated motor  10 , the actuating assembly  34  includes one or more actuators associated with each swashplate  28  that are operable in response to a control signal. In this case, a pair of actuators may be provided for each swashplate  28 . In particular, a first actuator  36  acts on the inside face of the swashplate  28  near its lower edge and a second actuator  38  acts on the opposing outside face of the swashplate  28  near its upper edge. The actuating system  34  further includes a spring  40  that extends between the two swashplates  28  and operatively engages the upper edge of the inside face of each. The spring  40  acts to push the two swashplates  28  into their maximum displacement positions. Each of the first and second actuators  36 ,  38  may comprise a hydraulically actuated piston  42  and cup  44  assembly with the cups  44  disposed on the swashplates  28  and the pistons  42  disposed on the motor housing  12 . 
     With the illustrated arrangement, the swashplates  28  may be pivoted into their respective minimum displacement positions by introducing a high pressure fluid into the cups  44  of each of the first and second actuators  36 ,  38 . For each actuator  36 ,  38 , the high pressure fluid pushes the cup  44  outward relative to the piston  42 . Because the pistons  42  are fixed relative to the motor housing  12 , this generates a forces at the lower edge of the inside face and the upper edge of the outside face of each swashplate  28  that together pivots the respective swashplate  28  against the force of the spring  40  to the minimum displacement position. Of course, actuators other than hydraulic actuators could be used including, for example, electrically actuated actuators. Additionally, the actuating system  34  could be configured such that the actuators  36 ,  38  pivot the swashplates  28  to the maximum displacement position and the spring  40  biases the swashplates  28  to the minimum displacement position. An actuating system that utilizes only a single actuator for each swashplate could also be used. Moreover, the actuators could comprise rotary devices configured to pivot the swashplates. 
     For independently actuating the actuators  36 ,  38  associated with each of the swashplates, the actuating system  34  may further include a control signal generator  46  that is operably coupled to the actuators  36 ,  38 . The control signal generator  46  may be capable of providing separate control signals to the actuators  36 ,  38  associated with each of the swashplates  28 . Upon receipt of the control signal, the respective actuators  36 ,  38  operate to pivot the swashplate  28  to the desired position. For example, with the illustrated motor  10 , the control signal may be a supply of pressurized fluid that is supplied to the piston  42  and cup  44  assemblies of the corresponding actuators  36 ,  38 . The pressurized fluid may be introduced to the motor  10  through separate first and second actuating ports  48 ,  50  that are provided in the motor housing  12 . As shown in  FIG. 1 , in the illustrated motor, the first actuating port  48  is in fluid communication with the first and second actuators  36 ,  38  associated with the left swashplate while the second actuating port  50  is in fluid communication with the first and second actuators  36 ,  38  associated with the right swashplate  28 . Because each swashplate is changing between only two discrete positions, the control signal generator can be relatively simple in that it only has to provide two signal types (i.e., an on/off type control) to each swashplate. 
     While the illustrated embodiment includes a single control signal generator  46 , two separate control signal generators may be provided with each being associated with a respective one of the swashplates  28 . Of course, if another type of actuator is used, such as electrical actuators, a corresponding control signal generator may be used such as a control signal generator that produces an electrical signal. Moreover, the control signal generator could be combined with a controller for the motor or integrated into the motor controller. 
     INDUSTRIAL APPLICABILITY 
     The present disclosure is applicable to any type of machine that may utilize a hydraulic motor. For example, the present disclosure may be applicable to a track loader. On such a machine, a first hydraulic motor may be used to drive a right-side track and a second hydraulic motor may be used to drive a left-side track. As compared to conventional two-speed hydraulic motors, the disclosed hydraulic motor may offer an operator of the machine with additional flexibility with respect to speed control in that it may operate in three different speed settings. Additionally, the use of a floating cup arrangement may provide a higher initial starting torque than conventional piston pumps. 
     It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. 
     Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. 
     Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.