Patent Abstract:
A hydraulic circuit for operating a tool is provided that is particularly useful in construction equipment such as an excavator, crane, wheel loader, drilling machine, or others. Furthermore, a control unit and a method for controlling the hydraulic circuit and construction equipment including such a hydraulic circuit is disclosed.

Full Description:
BACKGROUND AND SUMMARY 
     The invention relates to a hydraulic circuit for operating a tool especially of a construction equipment like e.g. an excavator, crane, wheel loader, drilling machine, grass cutter or others. Furthermore, the invention relates to a control unit and a method for controlling the hydraulic circuit and to a construction equipment comprising such a hydraulic circuit. 
     If a tool which is mounted at a construction equipment is exchanged by another tool, the operator of the construction equipment has to change and adjust accordingly the hydraulic parameter settings of the construction equipment like the pressure, the flow, the operation mode and other parameter settings which are specifically required for operating the new tool. This is usually very time consuming and implies the risk that inappropriate settings are selected by the operator. 
     It is desirable to provide a hydraulic circuit and a method for operating a hydraulic circuit by which this time consuming task is substantially reduced and the related risk is substantially reduced as well. 
     It is desirable to provide a hydraulic circuit which is simple in construction and enables to be controlled with an electronic control unit in a comparatively simple way. 
     According to an aspect of the invention, a hydraulic circuit is provided and, according to another aspect of the invention, a method for operating a hydraulic circuit is provided. One of the advantages of aspects of the invention is that an operator of the construction equipment is offered a high flexibility to realize settings for a plurality of different tools in an easy and quick manner. 
     More in detail, these solutions offer a flexible way to set and control the hydraulic circuit in a construction equipment. This is achieved especially by the fact that the settings and operating parameters of a nearly unlimited number of different tools can be programmed and stored, and then a certain tool which has been connected to the construction equipment can easily be selected by the operator, and the hydraulic parameter settings of the construction equipment for this tool can be adjusted in a quick and easy manner. 
     This is true for very different kinds of tools. For example, a toggle function can be realized on a related tool in an easy way. For example, a tool in the form of a hammer can be operated by the hydraulic circuit as long as a related button is pressed “on”. Furthermore, for operating a related proportional tool, e.g. a proportional and progressive roller switch or a proportional foot pedal can be used in order to generate an accordingly increasing hydraulic flow or hydraulic pilot pressure for actuating the tool. 
     Another advantage of aspects of the invention is that a proportional foot pedal valve for the tool control can be easily included in order to keep a maximum flow limitation in both directions of the pilot pressure, wherein a de-activation function of the hydraulic circuit is kept, i.e. even if the pedal is pressed in order to operate a tool, the hydraulic circuit can be de-activated, if necessary, by means of the first proportional valve by switching the same such that substantially no hydraulic pressure is applied at its output. 
     Furthermore, a progressive and proportional control of the output flow of the hydraulic circuit is provided, for which only one PWM (Pulse Width Modulation) output from the control unit or ECU (Electronic Control Unit) is necessary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details, features and advantages of the invention will become apparent from the following description of exemplary and preferred embodiments of the invention in connection with the drawings, in which shows: 
         FIG. 1  shows an exemplary and preferred embodiment of a hydraulic circuit for generating a hydraulic flow or pilot pressure according to the invention to control the main pressure of a hydraulic circuit for the actuation of a tool; 
         FIG. 2  is a schematic illustration of a hydraulic circuit for generating a hydraulic main pressure for the actuation of a tool; 
         FIG. 3  an first exemplary flowchart for settings in a display for X1 function for parameters of a first tool according to the invention; 
         FIG. 4  a second exemplary flowchart for settings in a display for X3 function for parameters of a second tool according to the invention; 
         FIG. 5  schematic displays for setting up a new X1 tool in the IECU; 
         FIG. 6  schematic displays for setting certain parameters; and 
         FIG. 7  schematic displays for selecting a certain tool from a saved list of tools. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an exemplary and preferred embodiment of a hydraulic circuit according to the invention for operating or actuating a tool. The circuit is provided for setting a hydraulic flow and for generating a hydraulic pilot pressure at one or both of its output lines C 1  and C 2  which lines C 1  and C 2  are continued in  FIG. 2  and are connected with a first and a second spool, respectively, of a main control valve  20  which actuates a tool  30  by means of a hydraulic main pressure in a known manner. The tool  30  operated by the hydraulic circuit according to  FIG. 1  can be a one-way tool like a hammer or a two-way tool like a shear. Furthermore, the tool  30  can be a proportional tool, and it can be a tool for high pressure, high power and/or high flow (like e.g. a hammer or a shear) or a tool for low pressure, low power and/or low flow (like e.g. a rotary tool or a grass clipper). 
     The hydraulic circuit according to  FIG. 1  comprises a first proportional valve  11 , a first and a second on/off valve  12 ,  13 , each in the form of a switch-over valve, a first and a second shuttle valve  14 ,  15  and a pedal unit  10  ( FIG. 1(A)  shows an enlarged view of it) comprising a pedal  101  for actuating a second and a third proportional valve  102 ,  103 , wherein these valves  102 ,  103  could alternatively be actuated by a joystick, a two-way switch or other means as well. 
     The first proportional valve  11  comprises a first, a second and a third port  1 ,  2 ,  3 , wherein the first port  1  is proportionally switched by means of an electrical solenoid in a known manner between the second and the third port  2 ,  3 , so that the flowing-through between the first and the second port  1 ,  2  continuously decreases while the flowing-through between the first and the third port  1 ,  3  continuously increases and vice versa. 
     This first proportional valve  11  is actuated by a control unit  40  in dependence on a set of stored parameters for a certain tool  30  (see  FIG. 2 ) which has been mounted at the construction equipment and which has been selected by an operator of the construction equipment e.g. on a touch screen or a display  41  of the control unit  40 , in such a way that a certain (admissible) maximum value of a hydraulic flow or hydraulic pilot pressure is applied (and will not be exceeded) at the first port  1  of the proportional valve  11 , by accordingly connecting the port  3  of the valve  11  with the port  1  of the valve  11 . 
     The first and the second on/off valve  12 ,  13  each comprises a first, a second and a third port  1 ,  2 ,  3 , wherein the first port  1  is connected by means of an electrical solenoid in an known manner either with the second port  2  or with the third port  3 . 
     The first and the second on/off valve  12 ,  13  can be switched by an operator of the construction equipment by means of a related first and second switch  42 ,  43 , respectively, at the control unit  40 . In order to operate a one-way tool  30  with one operating direction (like e.g. a hammer), one of the two valves  12 ,  13  is switched. In order to operate a two-way tool  30  (like e.g. a shear), one of the valves  12 ;  13  is switched for the operation of the tool  30  in a first direction and the other of the valves  13 ;  12  is switched for the operation of the tool  30  in a second direction. 
     The first and the second shuttle valve  14 ,  15  each comprises a first and a second input  1 ,  2  and one output  3 , wherein the one input ( 1  or  2 ), at which the higher hydraulic pressure is applied in comparison to the other input, is connected with the output  3 , and the other input ( 2  or  1 ) at which the lower pressure is applied is blocked. If at both inputs  1 ,  2  the same pressure is applied, this pressure is as well applied at the output  3 . 
     In the second and the third proportional valve  102 ,  103  of the pedal unit  10 , each valve has a first port which is proportionally switched between a second and a third port, as described above with reference to the first proportional valve  11 . However, the second and the third proportional valve  102 ,  103  are alternatively actuated by means of the pedal  101  in a known manner, i.e. the second valve  102  is actuated by pressing the pedal  101  down in the forward direction (counterclockwise in  FIG. 1 ) while the third valve  103  is not actuated during this operation, and the third valve  103  is actuated by pressing the pedal  101  down in the backward direction (clockwise in  FIG. 1 ) while the second valve  102  is not actuated during this operation. In case the pedal  101  is in the neutral position as shown in  FIG. 1  both valves  102 ,  102  are in a non-actuated position as well. 
     The pedal unit  10  comprising the second and the third proportional valve  102 ,  103  comprises a first port  1 , to which the first port of the second proportional valve  102  is connected, a second port  2 , to which the first port of the third proportional valve  103  is connected, a third port  3 , to which the second port of the second and of the third proportional valve  102 ,  103  is, connected, and a fourth port  4 , to which the third port of the second and of the third proportional valve  102 ,  103  is connected. 
     The second and the third proportional valve  102 ,  103  are alternatively operated by an operator of the related construction equipment by means of the pedal  101  (or another means as mentioned above) in order to proportionally operate a related tool  30  (see  FIG. 2 ) mounted at the construction equipment. 
     The hydraulic circuit is supplied with hydraulic pilot pressure by means of a first pilot pressure source, e.g. a pump P 1  for feeding pressurized hydraulic fluid (typically with a pressure of about 35 to 40 bar) from a first tank T 1  to the second port  2  of the first proportional valve  11 . A first back or return flow line A into the first tank T 1  is connected with the third port  3  of the first proportional valve  11 . This line A is as usual substantially “pressure-less” in that its pressure is about equal to the atmospheric pressure of the surroundings. 
     The first port  1  of the first proportional valve  11  is connected with the third port  3  of the first on/off valve  12 , with the third port  3  of the second on/off valve  13  and with the third port  3  of the pedal unit  10 . 
     The fourth port  4  of the pedal unit  10  is connected via a second back or return flow line B with the first tank T 1 . This line B is as usual substantially “pressureless” in that its pressure is about equal to the atmospheric pressure of the surroundings. 
     The second port  2  of the first on/off valve  12  and the second port  2  of the second on/off valve  13  are connected with a third back or return flow line C which is leading into the first tank T 1 . This line C is as usual substantially “pressureless” in that its pressure is about equal to the atmospheric pressure of the surroundings. 
     The first port  1  of the first on/off valve  12  is connected with a first input  1  of the first shuttle valve  14  and the first port  1  of the second on/off valve  13  is connected with a first input  1  of the second shuttle valve  15 . 
     The second input  2  of the first shuttle valve  14  is connected with the second port  2  of the pedal unit  10 , whereas the second input  2  of the second shuttle valve  15  is connected with the first port  1  of the pedal unit  10 . 
     The output  3  of the first shuttle valve  14  is connected with the first output line C 1  and the output  3  of the second shuttle valve  15  is connected with the second output line C 2  of the hydraulic circuit. 
     The hydraulic flows or hydraulic (pilot) pressures generated at these two output lines C 1 , C 2  are fed according to  FIG. 2  to the spool of a main control valve  20  in order to convert the flow or pressure values in a known manner to a certain flow of hydraulic fluid or main pressure by which the tool  30  is actuated. 
     More in detail, the first output line C 1  is connected via a first input terminal Sa of the main control valve  20  with the first spool, and the second output line C 2  is connected via a second input terminal Sb of the main control valve  20  with the second, opposite spool. 
     For generating the main pressure for actuating the tool  30 , a second pressure source, e.g. a pump P 2  is provided for feeding a hydraulic fluid from a second tank T 2  (wherein the first and the second tank Tï, T 2  is usually one common tank) via a third input terminal P to the main control valve  20 . This second pump P 2  is controlled according to the operation of the spools via a fourth terminal LS, and a back or return flow line into the second tank T 2  is provided via a fifth terminal T of the main control valve  20 . This back or return flow line is as usual substantially “pressure-less” in that its pressure is about equal to the atmospheric pressure of the surroundings. 
     The operation of a main control valve  20  according to  FIG. 2  by feeding the right and the left side of the spool with the hydraulic flow or hydraulic pressure via the output lines C 1  and C 2 , respectively, in order to supply the required hydraulic main pressure via a first and a second output terminal TA, TB for actuating the tool  30  is generally known so that it need not to be described here. 
     In the following, the generation of the hydraulic flow or hydraulic pilot pressure which is supplied to the spool via the first and the second output line C 1 , C 2  shall be described with reference to  FIG. 1  and the displays shown in  FIGS. 5 to 7 . 
     After mounting a certain work tool  30  at the construction equipment, the operator starts a first setup sequence for this tool  30  by selecting on the display (or a touch screen)  41  a tool setup menu. By this, a list of stored tools appears on the display  41 . From this list the operator selects the tool  30  which is mounted at the construction equipment. Then, another list with the stored parameter settings for this selected tool, like the flow value, the pressure value, the kind of tool (one-way or two-way tool) and the kind of control of the tool (like on/off, push, toggle or proportional operation) is indicated on the display  41 . Then, the control unit  40  (or a VECU (Vehicle Electronic Control Unit) to which these parameter settings are submitted) adjusts the first proportional valve  11  such that a maximum admissible hydraulic flow or pilot pressure which corresponds to the stored parameter settings for the mounted tool  30  is applied (and will not be exceeded) at the first port  1  of the first proportional valve  11  by accordingly actuating this valve  11  by means of its solenoid. 
     If the parameter settings of the tool  30  which is mounted at the construction equipment are not stored in the control unit  40  so that the operator cannot find the tool  30  in the list of stored tools, he has the opportunity to store the required parameter settings of the new tool by starting a related second sequence. In such a second sequence, the operator selects on the display (or a touch screen)  41  a related setup menu for a new tool, in which he inputs a name for the new tool and the required settings for this tool like the flow value, the pressure value, the kind of tool (one-way or two-way tool) and the kind of control of the tool (like on/off, push, toggle or proportional operation). Thereafter, he can store these settings under the name of the new tool, so that the new tool is available in the list of stored tools when the first setup sequence is started the next time. 
     In both cases, the X1 function indicates a high pressure, high power, high flow tool like e.g. a shear or a hammer, and the X3 function indicates a low pressure, low power, low flow tool like e.g. a rotary tool. A flowchart for settings in a display for the X1 function is shown in  FIG. 3 , a flowchart for settings in a display for the X3 function is indicated in  FIG. 4 . 
       FIG. 5  exemplarily shows four displays during a setup of a new X1 tool in the control unit  40 .  FIG. 6  exemplarily shows four displays for setting the parameters: flow, pressure, operation mode, type of attachment, respectively, furthermore one display for the saving of all of these settings and another display with an overview of the selected parameters for the tool which is now ready for use. Finally,  FIG. 7  exemplarily shows how an operator can select a tool from a list of tools and the related parameters as stored, respectively, and another display in the form of an information screen regarding the selected tool if the operator switches on the X1 operation. 
     After the first proportional valve  11  has been adjusted by the control unit  40  to the tool as mentioned above such that at its first port  1  the maximum admissible flow or pilot pressure for the tool mounted at the construction equipment is applied (and will not be exceeded), the operator can start operating the tool without running the risk to expose the tool to operational modes and hydraulic pressures outside the normal mode of operation and outside to admissible pressure range which would damage the tool. 
     If a one-way tool  30  is mounted at the construction equipment, this tool is operated by actuating the first or the second on/off valve  12 ,  13  by means of the related first or second switch  42 ,  43  in dependence, on which output line C 1  or C 2  the hydraulic pilot pressure is needed for operating the one-way tool. 
     If for example the hydraulic pilot pressure for operating the tool is needed on the first output line C 1 , the first on/off valve  12  is switched from its off position shown in  FIG. 1  into its on position, so that the hydraulic pilot pressure at the first output  1  of the first proportional valve  11  is supplied through the first on/off valve  12  and the first shuttle valve  14  to the first output line C 1 . If e.g. the one-way tool  30  connected with the main control valve  20  is a hammer, the hammer is on when pressing down or pushing the first switch  42 , and the hammer is off when the first switch  42  is released (“one-way push tool”). 
     In case of a two-way push tool, both switches  42 ,  43  and accordingly both the first and the second on/off valves  12 ,  13  are accordingly used for actuating the tool in a first and a second direction, respectively. 
     More in detail, if the tool  30  mounted at the construction equipment is a two way tool like a shear the operator (i) actuates the first on/off valve  12  (by switching it from its off position shown in  FIG. 1  into its on position) by pressing the first switch  42  for operating the shear in one direction (e.g. opening the shear) while the second on/off valve  13  is in its off position during this time, and (ii) actuates the second on/off valve  13  (by switching it from its off position shown in  FIG. 1  into its on position) by pressing the second switch  43  for operating the shear in the opposite direction (e.g. closing the shear) while the first valve  12  is in its off position during this time. In other words, the actuation of the first and the second on/off valve  12 ,  13  controls the exertion of pressure onto the left and the right side of the spool, respectively, of the main control valve  20 . 
     Other tools (“toggle tools”) start running when one switch  42  (or  43 ) is pressed a first time, and stop running when the switch  42  (or  43 ) is pressed a second time. 
     If the tool  30  mounted at the construction equipment is a tool which is to be proportionally controlled by a proportional flow or pilot pressure, the related maximum (admissible) hydraulic pilot pressure or flow which is applied according to the parameter setup of the tool as explained above at the first port  1  of the first proportional valve  11  is proportionally reduced by means of at least one of the second and third proportional valve  102 ,  103  of the pedal unit  10 . In case of operating such a tool, the first and the second on/off valve  12 ,  13  remain in their closed position as shown in  FIG. 1 , in which each first port  1  is connected with the third back or return flow line C leading into the first tank Tï, so that a substantially zero (i.e. atmospheric) pressure is applied at the first ports  1  of the first and the second on/off valve  12 ,  13 . 
     In the non-actuated position of the pedal  101  as shown in  FIG. 1 , the first and the second port  1 ,  2  of the pedal unit  10  are connected with the fourth port  4 . The fourth port  4  is connected by means of the second back or return flow line B with the first tank Tï so that a substantially zero (i.e. atmospheric) hydraulic pressure is applied at the first and the second port  1 ,  2  of the pedal unit  10  and accordingly at both output lines C 1 , C 2 . 
     If for example the second proportional valve  102  of the pedal unit  10  is actuated by tilting the pedal  101  forwardly (in  FIG. 1 : tilting it counterclockwise, whereby the third proportional valve  103  is not actuated), the first port  1  of the pedal unit  10  is proportionally connected with the third port  3  of the pedal unit  10 . By this, the maximum (admissible) hydraulic pilot pressure which is supplied from the first port  1  of the first proportional valve  11  to the third port  3  of the pedal unit  10 , is proportionally reduced and supplied from the first port  1  of the pedal unit  10  to the second output line C 2 . 
     If the third proportional valve  103  of the pedal unit  10  is actuated by tilting the pedal  101  backwardly (in  FIG. 1 : tilting it clockwise, whereby the second proportional valve  102  is not actuated), the second port  2  of the pedal unit  10  is proportionally connected with the third port  3  of the pedal unit  10 , so that an accordingly reduced maximum (admissible) hydraulic pilot pressure is supplied from the first port  1  of the first proportional valve  11  via the third and the second port  3 ,  2  of the pedal unit  10  to of the first output line C 1 . 
     By these proportionally reduced pilot pressures at the first and the second output line C 1 , C 2 , the tool  30  is proportionally actuated in a first and a second direction, respectively. 
     If a proportional tool  30  (like e.g. a rotary tool) is operated by the operator by means a roller switch  44  instead of by means of the pedal unit  10 , then the first proportional valve  11  is proportionally actuated by the control unit  40  such that it as well generates a respective proportional hydraulic flow or pilot pressure (up to the maximum admissible flow or pressure value for that tool) according to the actuation, especially the stroke, of the roller switch  44 , instead of the actuation of the (pressure reducing) proportional valves  102 ,  103  of the pedal unit  10 . Furthermore, in dependence on the direction in which the roller switch  44  is rolled, either the first or the second on/off valve  12 ,  13  is opened by the control unit  40 . 
     Summarizing the above, the first proportional valve  11  is used for the following three functions: 
     1. Disengaging the hydraulic flow or pressure to the output lines C 1 , C 2  by reducing the pilot pressure to a value which is zero or at least below the cracking point of the spool of the main control valve  20 ; 
     2. Limiting the maximum pilot pressure or flow to an admissible value which is set by the control unit  40  or the operator when operating a certain tool  30 ; 
     3. Controlling the pilot pressure or flow in a dynamic way for proportionally controlling a related proportional tool  30 . 
     For disabling the hydraulic circuit, the first proportional valve  11  is actuated into the position as shown in  FIG. 1 , in which the first port  1  is fully connected with the third port  3  which is connected via the first back or return flow line A with the first tank Tï so that a substantially zero pressure (or, more precise, atmospheric pressure) is applied at the first port  1  of the first proportional valve  11 . 
     Finally, it shall be mentioned, that for one or more of the tools  30  each more than one set of parameter settings or operation modes (like proportional control, push or toggle modes) can be stored in the control unit  40 , which parameter settings or modes can accordingly be selected by an operator of the construction equipment in dependence on e.g. a certain task or work which has to be done by means of the tool. 
     In total, the hydraulic circuit according to the invention as indicated in  FIG. 1  is provided in an advantageous way for three different functions, namely to deactivate the hydraulic circuit if necessary, to control the maximum hydraulic flow or hydraulic pilot pressure which can be supplied to a certain mounted tool and to control the tool, especially a proportional tool, in a dynamic way. 
     The control unit  40  may be in the form of a computer and comprise a computer program code adapted to perform a method or for use in a method for controlling the hydraulic circuit, where the method includes a first step of receiving an input, made by a user, indicating a selected tool, and a second step of generating an output signal for actuating the first proportional valve in dependence on stored settings for the selected tool. The computer program may be downloaded to the control unit or one of its components when it is connected to the internet. A computer program product stored on a non-transitory computer readable medium can be provided comprising a program code for use in such a method.

Technology Classification (CPC): 5