Abstract:
A user input device is provided for a hydraulic system that has a source of pressurized fluid and a tank. The user input device includes a body with a supply passage for receiving the pressurized fluid, a tank passage for connection to the tank, and a first chamber. A handle is pivotally attached to the body and operates one or more valves within the body. In a preferred embodiment, the handle can be pivoted independently about two orthogonal axis with separate pairs of valves operated by movement about each axis. In response to the position of the handle, each valve connects a separate chamber alternately to either the supply passage or the tank passage and different pressure sensor produces an electrical signal indicating a level of pressure in the chamber of each valve. Thus an electrical signal is produced from each valve to indicate motion of the handle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The present invention relates to a manual control device, such as joystick, which operate a valve to control the flow of hydraulic fluid to an actuator on a machine; and in particular to such control devices that provide electrical signals which are used to operate solenoid valves. 
         [0005]    2. Description of the Related Art 
         [0006]    Construction and agricultural equipment have working members which are driven by hydraulic actuators, such as cylinder and piston assemblies, for example. Each cylinder is divided into two internal chambers by the piston and selective application of hydraulic fluid under pressure to one or the other chamber produces movement of the piston in corresponding opposite directions. 
         [0007]    Application of hydraulic fluid to and from the cylinder chambers often is controlled by a spool valve, such as the one described in U.S. Pat. No. 5,579,642. This type of hydraulic valve has an internal spool controls the fluid flow in response to being moved by a mechanical connection to an operator lever. Movement of the spool into various positions controls flow of fluid through two separate paths in the valve. The direction and amount of spool movement determines the direction and speed that the associated hydraulic actuator moves. 
         [0008]    To reduce the number of valve control levers that a machine operator must manipulate, joysticks have been provided. A typical joystick can be pivoted about two orthogonal axes to designate operation of two separate hydraulic actuators of the machine. For example, movement about one axis may swing an excavator boom left and right, while movement about the other axis raises and lowers the boom. The original joysticks incorporated small valves, two valves associated with each axis. The joystick was normally biased into a centered position at which the output ports of all the valves opened to the tank line of the hydraulic system and actuator movement did not occur. Pivoting the joystick handle along one axis caused one valve in the associated pair to connect a hydraulic supply line to its outlet port, while the other valve of that pair remained opened to the tank line. That pair of joystick valves pilot-operated a main spool valve that metered fluid to and from the hydraulic actuator being controlled. Another pair of valves responded in an identical manner to pivoting the joystick about the other axis and pilot operated a different spool valve for another hydraulic actuator. 
         [0009]    The load on the hydraulic actuator to being driven exerted a corresponding amount of fluid pressure back onto the main spool valve. Because the main spool valve was pilot-operated by the joystick valve, a dampened indication of the spool valve pressure was fedback to the joystick valve which exerted force on the joystick handle. Therefore, the machine operator received some feedback indicating the response of the hydraulic actuator to being driven by the fluid. 
         [0010]    There is a present trend toward electrical control systems that use solenoid operated valves. This type of control simplifies the hydraulic plumbing as the main valves do not have to be located near an operator station, but can be located adjacent the actuator being controlled. This technological change also facilitates computerized control of the machine functions. For electrical control, the joystick that incorporated hydraulic valves is replaced with an electrical joystick which produces electrical signals indicating the amount of handle motion along each axis. For example, a separate potentiometer is driven by motion along each joystick axis. Those electrical signals are used to derive electric currents for driving solenoids that operated the main valves to control the fluid flow to the hydraulic actuators. 
         [0011]    Machine operators objected to the different feel of the electrical joystick which did not provide the dampened feedback to which the operators were accustomed. In addition, electrical joysticks did not hold up well in the harsh operating conditions encountered by construction and other types of machinery. The electrical joysticks had a relatively short life, as compared with their hydraulic counterparts. 
         [0012]    Therefore, it is desirable to provide a joystick that produces electrical control signals, but has the feel and reliability of a hydraulic joystick. 
       SUMMARY OF THE INVENTION 
       [0013]    A joystick for a hydraulic system includes a body with a first chamber, a supply passage that receives the pressurized fluid from a source, a tank passage that is connected to the fluid reservoir of the hydraulic system. A handle is pivotally mounted on the body. A first valve in the body is operable by the handle to connect the first chamber selectively to the supply passage and the tank passage. A first pressure sensor produces an electrical signal indicating a level of pressure in the first chamber. 
         [0014]    In the preferred embodiment, the handle pivots about two orthogonal axes with respect to the body. In this case, the first valve and a second valve respond to motion of the handle about one axis, and a third valve and a fourth valve respond to motion of the handle about the other axis. Each of the first, second, third, and fourth valves selectively connect first, second, third, and fourth chambers in the body to the supply passage and the tank passage depending on a direction of movement of the handle about the two orthogonal axes. First, second, third, and fourth pressure sensors produce electrical signals indicating pressure levels in the first, second, third, and fourth chambers, respectively, thereby providing a set of four electrical signals indicating the direction and degree of handle movement. 
         [0015]    An aspect of the present invention is that for each valve there is a valve bore in the body and connected to one of the chambers and into which the supply passage and the tank passage open. Every valve also includes valve element that slides within the respective valve bore in response to the handle pivoting. Each valve element has a first position in which the tank passage is connected to the associated chamber and a second position in which the supply passage is connected to the associated chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a side elevational view of a joystick according to the present invention; 
           [0017]      FIG. 2  is a vertical cross sectional view through the joystick in  FIG. 1  with a handle grip removed; and 
           [0018]      FIG. 3  is schematic diagram of the hydraulic and electrical circuits of the joystick; and 
           [0019]      FIG. 4  is a vertical cross sectional view through another embodiment of a joystick similar to  FIG. 2  with electromagnetic tactile feedback. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    With initial reference to  FIG. 1 , a hybrid hydro-electrical joystick  10  is provided as an input device by which a human operator is able to control a hydraulic system on a machine. The joystick  10  comprises a valve assembly  12  to which an electronics module  13  is attached by machine screws or other suitable means. An operator handle  14  is pivotally mounted on the body  11  of the valve assembly  12  in a manner that allows the handle to be independently pivoted about two orthogonal axes  15  and  17  with respect to the valve assembly. Any of several well known couplings, such as gimbals or a ball and socket combination, can be employed to provide that dual axis, pivotable connection. The handle  14  includes a grip  16  is threaded into a coupling  19  that also attaches an inverted cup-like valve actuator  18  which has a flange  20 . 
         [0021]    With additional reference to  FIG. 2 , the flange  20  of the valve actuator  18  operate four valves  21 ,  22 ,  23 , and  24  within the valve assembly  12 . The first and second valves  21  and  22  are arranged in the valve assembly  12  along one orthogonal axis  15 , while the third and fourth valves  23  and  24  are arranged along the other orthogonal axis  17  (as schematically depicted in  FIG. 3 ).  FIG. 2  shows the details and relationship of the first and second valves  21  and  22  with the understanding that the third and fourth hydraulic valves  23  and  24  have identical construction but are oriented orthogonally to the cross section plane of the drawings. The joystick&#39;s first valve  21  has a first actuator shaft  26  with an end that projects out of the valve assembly  12  and abuts the actuator flange  20 . The first actuator shaft  26  extends through a first valve bore  30  in the valve assembly  12  and has an opposite end abutting a retainer  33  of a first spring assembly  32 . The first spring assembly  32  comprises a first spring  34  held between the retainer  33  and the body  11  of the valve assembly  12 , thereby biasing the first actuator shaft  26  outward from the valve assembly body. The spring assembly  32  also includes a second spring  36  located coaxially within the first spring  34  that abuts the retainer  33  and biases a first valve element  38  away from the first actuator shaft  26  within the first valve bore  30 . 
         [0022]    The first valve element  38  selectively controls the flow of fluid between a first chamber  44  and either a supply passage  40  or a tank passage  42  in the body  11 . Thus the first chamber  44  forms an outlet of the first valve  21  and opens only into the first valve bore  30 . The supply passage  40  is connected to a source of pressurized fluid, such as the outlet of a pump  45  of a machine to which the joystick  10  is mounted (see  FIG. 3 ). The tank passage  42  is connected to the tank  47  of the machine&#39;s hydraulic system. The first valve element  38  has a passage  46  that extends from an end that faces the first chamber  44  at one end of the first valve bore  30  to openings  48  in the sides of the valve element. In the normal state of the first valve  21 , when the joystick handle  14  is in the centered position illustrated in  FIG. 2 , the flow passage side openings  48  communicate with the tank passage  42 . As a consequence in the normal state, the first chamber  44  is connected to the tank  47  of the hydraulic system. The first chamber  44  and similar chamber for the other valves  22 ,  23 , and  24  may be an end section of the associated valve bore or may be spaced from that valve bore and connected thereto by a fluid passageway. Those chambers form an outlet of the respective valves  22 ,  23 , and  24 . 
         [0023]    The second valve  22  has an identical construction to that just described with respect to the first valve  21  and is located within the valve assembly  12  along the same first axis  15  on the opposite side of the handle  14 . It should be understood that although the first and second valves  21  and  22  are located along the first axis  15 , they respond to the handle  14  being pivoted about the second axis  17  that extends into and out of the plane of the drawing. Likewise the third and fourth valves  23  and  24 , located along the second axis  17 , respond to the handle  14  being pivoted about the first axis  15 . 
         [0024]    When the machine operator pivots the handle  14  to the left about the second axis  17  in  FIGS. 1 and 2 , the flange  20  of the valve actuator  18  pushes the first actuator shaft  26  of the first valve  21  into the valve assembly  12 . In turn the first actuator shaft  26  pushes the first valve element  38  through the valve bore  30  toward the first chamber  44 . This motion causes the openings  48  in the sides of the first valve element  38  to communicate with the supply passage  40 , thereby providing a path for pressurized fluid to flow into the first chamber  44  increasing the pressure therein. That leftward pivoting motion also moves the opposite right side of the actuator flange  20  upward. In response, the force of the second spring assembly  50  for the second valve  22  causes a second actuator shaft  27  to follow partially the right side of the actuator flange  20  upward causing the second valve element  52  also to move upward until the retainer  53  abuts the bore plug  55 . During that motion of the second valve element  52 , the side openings  54  of the internal passage  56  continuously open into the tank passage  42  so that the pressure in the second chamber  58  remains at the relatively low level of the tank  47  of the hydraulic system. 
         [0025]    Therefore, pivoting the handle  14  leftward applies a greater pressure from the supply passage  40  to the first chamber  44 . As a consequence, the pressure in the first chamber  44  increases while the pressure in the second chamber  58  remains at a low level. As will be described, the pressures in each of these chambers  44  and  58  are measured by separate first and second pressure sensors  61  and  62 , respectively. The first and second pressure sensors  61  and  62  are mounted on a plate  66  that extends across the bottom surface of the valve assembly  12  through which the first and second chambers  44  and  58  open. The combination of that plate  66  and the pressure sensors  61  and  62  close off the first and second chambers  44  and  58  and annular seals prevent fluid leakage there between. Therefore the only openings into the first and second chambers  44  and  58  are through the respective first and second valves  21  and  22 . The plate  66  is held in place by the attachment of the electronics module  13  onto the valve assembly  12 . 
         [0026]    Should the machine operator pivot the handle  14  to the right in  FIGS. 1 and 2 , the actions of the first and second valves  21  and  22  are reversed. Specifically the actuator flange  20  pushes the second actuator shaft  27  and associated second valve element  52  downward in the valve assembly  12 , so that valve element provides a fluid path between the supply passage  40  and the second chamber  58 . This opposite pivoting action also causes the first actuator shaft  26  and the first valve element  38  of the first valve  21  to move upward, however the first chamber  44  remains connected by the first valve element to the tank passage  42 . As a consequence, the pressure within the second chamber  58  increases due to coupling to the supply passage  40  and the pressure within the first chamber  44  is maintained at a relatively low level. These pressure levels a detected by the first and second pressure sensors  61  and  62 . 
         [0027]    Pivoting the handle  14  into or out of the plane of the  FIG. 2 , i.e. about the first axis  15 , operates the third and fourth valves  23  and  24  in identical manners to that described with respect to the first and second valves  21  and  22 . The pressures produced in the output chambers for the third and fourth valves  23  and  24  are measured by third and fourth pressure sensors  63  and  64  (see  FIG. 3 ). 
         [0028]    With reference to  FIG. 3 , the first and second pressure sensors  61  and  62  and another pair of third and fourth pressure sensors  63  and  64  associated with the third and fourth valves  23  and  24 , respectively, are part of an electrical circuit  70  in the electronics module  13  of the joystick  10 . That circuitry is mounted on a printed circuit board  72  to which wires from each of the four pressure sensors  61 - 64  connect. The four pressure sensors  61 - 64  are connected to inputs of a set of sensor signal conditioners  74 . In particular, a separate signal conditioning circuit amplifies and converts each sensor output signal into a signal that is compatible with a communication circuit  76  within the joystick  10 . The resultant four conditioned sensor signals are applied to a four-to-one multiplexer  78  which selectively applies one of those signals to an input of the communication circuit  76 . The communication circuit  76  interfaces the joystick  10  with a communication network  80  for the machine. For example, construction vehicles employ a Controller Area Network (CAN) that utilizes a protocol defined by the ISO 11898 standard promulgated by the International Organization for Standardization in Geneva, Switzerland. 
         [0029]    The joystick communication circuit  76  sends control signals to the multiplexer  78  which responds by sequentially applying each of the four conditioned pressure signals to the input of the communications circuit. Each of those pressure signals is digitized by the communication circuit  76  and transmitted serially over the communication network  80 . As illustrated in  FIG. 2 , the conductors of the communication network  80  are part of a cable  82  extending out of the electronics module  13  of the joystick  10 . That cable  82  also conducts electrical power to the circuitry of the joystick. 
         [0030]    Because the handle  14  of the joystick  10  operates a set of hydraulic valves  21 - 24  that control the application of pressurized fluid, the joystick provides dampened feedback to the operator in a manner similar to previous hydraulic joysticks. Therefore, the present joystick has a feel to the operator that corresponds closely to conventional hydraulic controls to which machine operators are accustomed. 
         [0031]    With reference to  FIG. 4 , a second joystick  90  is similar to the joystick  10  previously described, with identical components being assigned the same reference numerals. The second joystick  90  has elongated first and second actuator shafts  26  and  27 . A separate electromagnet coil  92  and  94  is placed around each of the first and second actuator shafts  26  and  27 , respectively. Another pair of electromagnet coils (not shown) are placed around the actuator shafts for the other two valve in the second joystick  90 . The electromagnet coils  92  and  94  are connected to the electrical circuit  70  that is mounted on a printed circuit board  72  and are activated by that circuit in response to load pressures sensed at the actuators being controllers by the joystick. The sensed pressure signals are sent to the electrical circuit  70  via the communication network  80 . Activation of the electromagnet coil  92  and  94  creates magnetic fields that exert forces on the actuator shafts  26  and  27  in proportion to the actuator load and which provide resistance to joystick motion the also corresponds to the magnitude of the actuator load. This provides tactile feedback to the operator much like conventional totally hydraulic joysticks. 
         [0032]    The foregoing description was primarily directed to a preferred embodiment of the invention. Although some attention was given to various alternatives within the scope of the invention, it is anticipated that one skilled in the art will likely realize additional alternatives that are now apparent from disclosure of embodiments of the invention. Accordingly, the scope of the invention should be determined from the following claims and not limited by the above disclosure.