Lifting machine

Abstract

The invention relates to a lifting machine (1) comprising: a main body (2), a handling arm (3), a hydraulic actuator configured to move the handling arm, a hydraulic power supply device, and; a control system comprising: a control unit (7) configured to receive a movement request signal and to control the hydraulic power supply device in response to the movement request signal and a position sensor (13, 14, 15) configured to transmit a position signal representative of a position of the hydraulic actuator to the control unit, wherein the control unit is further configured to detect an end-of-travel stop position of the hydraulic actuator according to the position signal and to control the hydraulic power supply device so as to stop the supply of pressure to the hydraulic actuator in response to the detection of the end-of-travel stop position.

Description

Lifting machine

[0001] The invention relates to the field of lifting machines such as loaders or elevators, and more particularly to a control system for a hydraulic actuator installed in such a lifting machine. Technological background

[0002] On the one hand, lifting machines are known comprising a movable arm and a hydraulic actuator configured to move the arm in response to signals transmitted by a control system of the hydraulic actuator. In this type of machine, the operator activates a movement command until a limit stop of the hydraulic actuator is triggered. However, if the operator maintains his command to move the hydraulic actuator while the hydraulic actuator is at the limit stop, this results in excessive consumption of energy which is then lost.

[0003] On the other hand, EP3885586 describes an excavator, comprising a system for limiting the drive control of the hydraulic actuator in order to stop its movement before reaching an end of travel of the hydraulic cylinder in order to prevent an impact at the end of travel stop of the hydraulic cylinder.

[0004] The inventors have also found that forcibly maintaining a stop of a hydraulic actuator at the end of its travel causes several disadvantages such as: - a drop in engine speed, which can cause a low-power thermal engine to stall; - limited autonomy, due in particular to excessive energy consumption when maintaining the hydraulic actuator at the end of its travel; - a loss of hydraulic performance; - an increase in the noise of the lifting machine; and / or - premature aging of the components due to unnecessary pressure in the hydraulic circuit.

[0005] The inventors have also noted that machines of the prior art comprising a control limitation system as indicated above do not allow all of the desired manipulations to be carried out, in particular when the action of stopping a hydraulic actuator at the end of its travel is useful for obtaining a result.

[0006] Such a situation exists, for example, for the tilt cylinder of a bucket carried by the arm to:- help dump a load present in the bucket by creating vibratory shocks resulting from successive stops; and- allow efficient digging.

[0007] One idea behind the invention is to solve the above-mentioned problems.

[0008] One idea behind the invention is to provide a lifting machine that does not have one or more of the aforementioned problems.

[0009] According to one embodiment, the invention provides a lifting machine comprising: a main body, a handling arm mounted on said main body and movable relative to the main body, a hydraulic actuator configured to move the handling arm, a hydraulic power device connected to the hydraulic actuator and;a control system comprising:a control unit configured to receive a movement request signal from a human-machine interface and to control the hydraulic supply device in response to the movement request signal so as to cause movement of the handling arm according to the movement request signal,a position sensor configured to transmit a position signal representative of a position of the hydraulic actuator to the control unit,the control unit being further configured to detect an end-of-travel stop position of the hydraulic actuator according to the position signal and to control the hydraulic supply device so as to stop supplying pressure to the hydraulic actuator in response to the detection of the end-of-travel stop position.;

[0010] Thanks to these characteristics, the machine has the following advantages: - a reduction in energy consumption if the operator maintains his command to move the hydraulic actuator while the hydraulic actuator is at the end stop, - an extension of the machine's service life, - a reduction in noise and vibrations, - an improvement in the availability of hydraulic pressure in the case where the hydraulic supply device is also connected to another element of the lifting machine.

[0011] According to embodiments, such a lifting machine may comprise one or more of the following features.

[0012] According to one embodiment, the control unit commands to stop supplying the hydraulic actuator with pressure after the lapse of a delay time from the detection of the end-of-travel stop position, the delay time being less than or equal to 5 seconds.

[0013] The time delay creates a controlled delay between the instant at which the end-of-travel stop position is detected, this detection being able to have a margin of error, and the interruption of the power supply to the hydraulic actuator. This ensures that the hydraulic actuator is effectively stopped before stopping the supply of pressure to the hydraulic actuator, despite a possible margin of error in the detection of the end-of-travel stop position.

[0014] According to one embodiment, the delay time is between 0.5 seconds and 5 seconds.

[0015] According to one embodiment, the delay time is within an interval chosen from: between 0.5 seconds and 1 second; between 0.5 seconds and 2 seconds; between 0.5 seconds and 3 seconds; between 0.5 seconds and 4 seconds; between 1 second and 2 seconds; between 1 second and 3 seconds; between 1 second and 4 seconds; between 2 seconds and 3 seconds; between 2 seconds and 4 seconds; between 3 seconds and 4 seconds.

[0016] According to embodiments, the position sensor may comprise a linear position sensor or an angular position sensor. Suitable position sensors are, for example, capacitive sensors, magnetic Hall effect sensors, optical sensors, or the like.

[0017] According to one embodiment, the position sensor comprises a Hall effect magnetic sensor positioned to measure the field of a magnet carried by a moving part of the hydraulic actuator.

[0018] According to one embodiment, the position signal is a quantitative signal and the control unit is configured to detect the end-of-travel stop position of the hydraulic actuator as a function of the position signal by comparing a quantity represented by the position signal with a reference value stored in a memory.

[0019] According to one embodiment, the position sensor is an end-of-travel sensor configured to detect an end-of-travel stop position of the hydraulic actuator and transmit a position signal representative of the end-of-travel stop position of the hydraulic actuator to the control unit.

[0020] Thus, the position signal transmitted by the limit switch sensor can be directly representative of the end stop position and does not require further processing by the control unit.

[0021] In this case, the position signal representative of the end-of-travel stop position may be in the form of a logic or Boolean signal. According to one embodiment, the end-of-travel sensor may be an electrical contact that closes or opens in the end-of-travel position.

[0022] According to one embodiment, the hydraulic actuator is a jack comprising a cylinder defining an internal chamber and a piston sliding in said internal chamber, and in which the stop position at the end of the stroke of the hydraulic actuator corresponds to contact between a first stop part secured to the cylinder and a second stop part secured to the piston.

[0023] According to one embodiment, the first and second stop pieces are located within the inner chamber. According to one embodiment, the first stop piece comprises a rear flange located at a first end of the inner chamber. According to one embodiment, the second stop piece comprises a front flange located at a second end of the inner chamber.

[0024] According to one embodiment, the first and second stop pieces are located outside the internal chamber.

[0025] According to one embodiment, the piston has a stop portion located outside the internal chamber, the stop portion being inserted into a groove between the first and second stop pieces.

[0026] According to one embodiment, the lifting arm has a first end mounted on said main body and a second end opposite the first end, wherein the hydraulic actuator is a tilt cylinder disposed at the second end of the lifting arm and intended to tilt a tool relative to the lifting arm.

[0027] According to one embodiment, the tool is chosen from a bucket, a clamp, a fork, a jib, a nacelle or a load backrest.

[0028] According to one embodiment, the hydraulic supply device comprises at least one pump driven by a motor and at least one hydraulic distributor.

[0029] According to one embodiment, the hydraulic supply device is a proportional distributor, for example an electroproportional distributor.

[0030] According to one embodiment, the engine is a heat engine. According to one embodiment, the heat engine is low power.

[0031] The human-machine interface may take various forms and include one or more components, for example a voice recognition interface, a touch screen, joysticks, pedals, buttons or the like. According to one embodiment, the human-machine interface includes a manipulator intended to be manipulated by an operator to produce the movement request signal. According to one embodiment, the manipulator includes one or more joysticks.

[0032] According to one embodiment, the lifting machine is chosen from:- a telescopic arm forklift;- a loader;- a personnel lifting platform;- a warehousing machine;- a mast forklift.

[0033] According to one embodiment, the hydraulic actuator is a cylinder chosen from: a tilt cylinder, a telescoping cylinder and a lifting cylinder.

[0034] According to one embodiment, the handling arm is a telescopic arm.

[0035] According to one embodiment, the lifting machine comprises a pair of front wheels and a pair of rear wheels.

[0036] According to one embodiment, the lifting machine comprises a plurality of hydraulic actuators configured to move the handling arm, and the hydraulic supply device is connected to the plurality of hydraulic actuators, the lifting machine comprising at least one position sensor per actuator, each position sensor being respectively configured to transmit a position signal representative of a position of a hydraulic actuator of the plurality of hydraulic actuators to the control unit, the control unit being configured to detect a stop position at the end of travel of each hydraulic actuator.

[0037] According to one embodiment, the plurality of hydraulic actuators comprises a digging cylinder, a telescoping cylinder and a lifting cylinder.

[0038] According to one embodiment, the lifting machine comprises a state selector configured to selectively activate and deactivate in a reversible manner the response of the control unit to the detection of the end-of-travel stop position.

[0039] According to one embodiment, the state selector has a first state in which the response of the control unit to the detection of the end stop position is deactivated, i.e. the control unit does not stop supplying pressure to the hydraulic actuator in response to the detection of the end stop position, and a second state in which the response of the control unit to the detection of the end stop position is activated, i.e. the control unit stops supplying pressure to the hydraulic actuator in response to the detection of the end stop position.

[0040] According to one embodiment, the state selector is a switch intended to be toggled into the first state or the second state by an operator. When the operator places the state selector in the first state, the response of the control unit to the detection of the end stop position is deactivated. When the operator places the state selector in the second state, the response of the control unit to the detection of the end stop position is activated. Brief description of the figures

[0041] The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the accompanying drawings.

[0042] The figure represents a schematic view of a lifting machine according to one embodiment.

[0043] This is a functional diagram representing a control system for a hydraulic actuator installed in the lifting machine shown in the.

[0044] Laest is a graph representing different parameters implemented in the control system of the during an actuation of the hydraulic actuator.

[0045] The figure represents a hydraulic actuator according to a first embodiment in abutment, in the retracted position.

[0046] It represents the hydraulic actuator of the stop, in the deployed position.

[0047] The figure represents a hydraulic actuator according to a second embodiment in abutment, in the retracted position.

[0048] It represents the hydraulic actuator of the stop, in the deployed position.

[0049] Illustrates a lifting machine 1, for example a telescopic arm forklift, comprising a main body comprising a chassis 2, an operator's cabin and two pairs of wheels. The lifting machine 1 comprises a handling arm 3 carried by the chassis 2 and provided with one or more hydraulic actuators and a hydraulic supply device 6 for supplying the hydraulic actuator(s). The hydraulic supply device 6 comprises a hydraulic pump driven by a motor 4, for example a thermal or electric motor.

[0050] The handling arm 3 is pivotally mounted about a transverse horizontal axis. The handling arm 3 can move from a low position to a high position and vice versa using a first hydraulic actuator 10 such as a lifting cylinder. The first hydraulic actuator 10 may comprise a single double-acting cylinder supplied with fluid by the hydraulic pump. A pair of parallel single-acting cylinders supplied with fluid in turn could have been used in an equivalent manner.

[0051] The handling arm 3 illustrated in is a telescopic arm of adjustable length in a retraction direction and in a deployment direction. The handling arm 3 is formed of a first section 16 coupled to the frame 2 and a second section 17 slidably mounted in the first section 16.

[0052] Alternatively, the handling arm 3 may not be telescopic.

[0053] The movement between the retracted position and the deployed position of the handling arm 3 is obtained via a second hydraulic actuator 12 present in the handling arm 3, such as a telescoping cylinder.

[0054] As similarly indicated above, one can use a double-acting cylinder or two parallel single-acting cylinders powered in turn.

[0055] The handling arm 3 is equipped with a tool holder 11, pivotally mounted at the distal end of the second section 17 of the handling arm 3. The tool holder 11 illustrated on the carries a bucket 5. Alternatively, the tool holder 11 is a universal tool holder, adapted to receive a plurality of tools. The operator can then select the desired tool and attach it to the tool holder 11.

[0056] The tool holder 11 is connected to the handling arm 3 via a third actuator 18. This third actuator 18 allows the tool holder 11 to be driven in a digging direction and in a dumping direction by pivoting the tool holder 11 about a transverse horizontal axis. The dumping position corresponds to the extreme position of pivoting towards the ground of the tool holder 11 and the associated tool. The digging position of the tool holder 11 corresponds to an upward pivoting position of the tool holder 11 and the associated tool.

[0057] The lifting machine 1 further comprises a control unit 7 configured to control the operation of the first, second and third hydraulic actuators 10, 12, 18, which makes it possible to control the movements of the handling arm 3 and the tool holder 11. For example, the control unit 7 receives a movement request signal from the joystick-type manipulator 9 manipulated by an operator. These movement request signals can be interpreted by the control unit 7 as movement instruction signals for the handling arm 3 and / or the tool holder 11.

[0058] The control unit 7 is an electronic and / or computer unit which comprises, for example, a microcontroller or a microprocessor associated with a memory.

[0059] Thus, when it is specified that the control unit is configured to perform a given operation, this means that the control unit comprises computer instructions and execution computer hardware that make it possible to perform said operation and / or corresponding electronic components. In other words, the functions and steps described below can be implemented in the form of a computer program and / or via hardware components. In particular, the functions and steps operated by the control unit 7 can be performed by instruction sets and computer modules implemented in a processor or controller and / or be performed by dedicated electronic components or FPGA or ASIC type components. It is also possible to combine computer parts and electronic parts.

[0060] The lifting machine 1 comprises position sensors 13, 14, 15. A first position sensor 13 associated with the first hydraulic actuator 10 to measure a parameter representative of the position of the first hydraulic actuator 10, for example an angular position of the handling arm 3. A second position sensor 14 is associated with the second hydraulic actuator 12 to measure a parameter representative of the position of the second hydraulic actuator 12, for example a length of the handling arm and a third position sensor 15 is associated with the third hydraulic actuator 18 to measure a parameter representative of the position of the third hydraulic actuator 18, for example the angular position of the tool.

[0061] The first, second and third position sensors 13, 14, 15 are further configured to transmit to the control unit 7 position signals representing the measured parameter each time.

[0062] These position signals are used by the control unit 7 to determine whether the corresponding hydraulic actuator has reached an end stop position.

[0063] According to one embodiment, the control unit 7 comprises a memory in order to process the received position signal. The memory is calibrated in order to store a first position value representative of the stop of the hydraulic actuator, in the retracted position and a second value representative of the stop of the hydraulic actuator in the deployed position. Thus, when the control unit 7 receives a position signal, the control unit 7 compares the position signal with the first and second values ​​stored in the memory, and if the position signal reaches or crosses the first value or the second value, the control unit 7 detects the corresponding end-of-travel stop position.In response to this detection, it interrupts the control signal and therefore causes the hydraulic supply to the hydraulic actuator to stop, possibly after a delay time has elapsed from the detection of the end-of-travel stop position.

[0064] In an alternative embodiment, the position sensor is an end-of-travel sensor configured on the one hand to detect an end-of-travel stop position of the hydraulic actuator and configured on the other hand to transmit to the control unit 7 a position signal representative of the end-of-travel stop position of the hydraulic actuator, i.e. an end-of-travel stop signal, in the retracted or extended position. Such an end-of-travel stop signal of the hydraulic actuator is, for example, triggered via an electrical contact that closes or opens in the stop position. Thus, further processing of the end-of-travel stop signal by the control unit 7 is not necessary because the stop position has already been detected by the end-of-travel sensor.

[0065] Several types of end stops for a hydraulic cylinder 19 are illustrated in Figures 4 to 7.

[0066] Such a hydraulic cylinder 19 comprises a cylinder 43, defining an internal chamber 46 and a piston 40 positioned in the internal chamber 46 and capable of sliding in a longitudinal direction of the internal chamber 46.

[0067] According to an embodiment shown in Figures 4 and 5, the end-of-travel positions of the piston 40 are delimited by a stop inside the internal chamber 46. Thus, the piston 40 is capable of sliding from a rear flange 41 located at a first end of the internal chamber 46 towards a front flange 45 located at a second end of the internal chamber 46, until said piston 40 of the hydraulic cylinder 10 stops against the front flange 45.

[0068] Conversely, the piston 40 is capable of sliding from the front flange 45 of the second end of the internal chamber 46 towards the first end of the internal chamber 46 until the piston 40 of the cylinder 10 stops against the rear flange 41.

[0069] According to another embodiment shown in Figures 6 and 7, the end-of-stroke positions of the piston 40 are delimited by a stop outside the internal chamber 46. Thus, the hydraulic cylinder 19 further comprises a stop element 47 projecting from the rod 44 of the piston 40. The stop element 47 is located outside the internal chamber 46 and inserted into a sliding groove 49 formed in a first stop piece 48 secured to the cylinder 43. During actuation of the cylinder 19, the stop element 47 slides in the longitudinal direction of the sliding groove 49 between two stop positions defined by the two ends of the sliding groove 49.

[0070] Figures 2 and 3 illustrate the operation and consequences of the control system as presented on the during actuation of the third hydraulic actuator 18 corresponding to a tilt cylinder.

[0071] When the operator wishes to carry out a movement of the bucket 5, the first step consists of actuating the manipulator 9 in order to transmit to the control unit 7 a movement request signal 20.

[0072] The second step is the acquisition of the movement request signal 20 and the processing of said signal by the control unit 7.

[0073] In a third step, the control unit 7 sends a control signal 22 to the hydraulic supply device in order to set the third hydraulic actuator 18 in motion.

[0074] In a fourth step, the position sensor 15 detects a position of the third hydraulic actuator 18 corresponding to an end-of-travel stop as illustrated in FIGS. 4 to 7 and transmits a position signal 23 representative of the end-of-travel stop of the third hydraulic actuator 18 to the control unit 7. The control unit 7 then interrupts the control signal 22, as indicated by the arrow 21, possibly after the lapse of a predetermined time delay, to stop the movement of the third hydraulic actuator 18.

[0075] Thus, even if the operator maintains the request for movement in thrust towards the stop position of the third hydraulic actuator 18, the hydraulic thrust at the end stop is stopped.

[0076] The resumption of movement of the third hydraulic actuator 18 occurs during a reversal of the control direction, that is to say when the operator actuates the manipulator 9 in order to transmit to the control unit 7 a signal requesting movement in the opposite direction.

[0077] The advantages of this control method are now explained with the graphs illustrated on the. The abscissa is common to all the graphs and represents the flow of time in seconds (s).

[0078] Six graphs are illustrated, representing:

[0079] 20: the movement request signal 20 produced by the manipulator 9 of the hydraulic actuator, with on the ordinate a percentage of the transmitted request compared to a maximum request. In this example, the operator holds the manipulator 9 in a position to request a movement of the bucket 5 from time 9s until time 19s.

[0080] 22: the control signal 22 for setting the hydraulic actuator 18 in motion, produced by the control unit 7 for an electroproportional distributor, with the intensity of the signal in mA on the ordinate.

[0081] 23: the position signal of the hydraulic actuator rod 18 in millimeters.

[0082] 33: the consumption of the thermal engine 4 in Liters of diesel / hour.

[0083] 34: the load rate of the thermal engine 4 in percentage

[0084] 35: the engine speed of the thermal engine 4 in revolutions / minute.

[0085] Reference 36 schematically represents the instant of hydraulic stop of the hydraulic actuator 18, at approximately 17s.

[0086] It is visible from curves 20 and 23 that the operator maintains the movement request of the hydraulic actuator after a stop position at the end of the hydraulic actuator stroke has been reached, shown in the third graph, to the right of line 36, after 17 seconds.

[0087] Despite maintaining the movement request 20, the control unit 7 stops the control signal 22 of the hydraulic actuator 18 just after the reference 36. After a delay of 0.5s has elapsed, the signal intensity decreases rapidly from 1500mA to 0mA. Thus, the hydraulic supply device 6 no longer supplies the hydraulic actuator 18.

[0088] Thus, thanks to these characteristics, it is observed that the load rate 34 and the consumption 33 of the thermal engine 4 each present a brief peak of increase which is quickly erased after the reference 36 and well before the end of the movement request 20. In addition, the engine speed 35 only undergoes a brief descent.

[0089] The same steps can be applied independently for other hydraulic actuators.

[0090] According to an alternative embodiment illustrated with the, the control system of the lifting machine comprises a state selector 24, for example a switch, configured to selectively activate and deactivate in a reversible manner the response of the control unit 7 to the detection of the end-of-travel stop position.

[0091] When the operator places the state selector 24 in a first state, the state selector 24 transmits an interrupt signal 25 for detecting the end stop position to the control unit 7 and the response of the control unit 7 to the detection of the end stop position is deactivated. Such an action is reversible, i.e., when the operator places the state selector 24 in a second state, the interrupt signal 25 is not transmitted and the response of the control unit 7 to the detection of the end stop position is activated.

[0092] Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

[0093] The use of the verb "comprise", "comprise" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those set out in a claim.

[0094] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

Lifting machine (1) comprising: a main body (2), a handling arm (3) mounted on said main body (2) and movable relative to the main body (2), a hydraulic actuator (10, 12, 18) configured to move the handling arm, a hydraulic power supply device (6) connected to the hydraulic actuator (10) and;a control system comprising: a control unit (7) configured to receive a movement request signal from a human-machine interface and to control the hydraulic power supply device in response to the movement request signal so as to cause a movement of the handling arm according to the movement request signal; a position sensor (13, 14, 15) configured to transmit a position signal (23) representative of a position of the hydraulic actuator (10, 12, 18) to the control unit (7); the control unit (7) being further configured to detect a stop position at the end of stroke of the hydraulic actuator according to the position signal and to control (21) the hydraulic power supply device so as to stop supplying the hydraulic actuator with pressure in response to the detection of the stop position at the end of stroke. Lifting machine according to claim 1, wherein the control unit commands (21) to stop supplying the hydraulic actuator with pressure after the elapsed time delay from the detection of the stop position at the end of the stroke, the time delay being less than or equal to 5 seconds. Lifting machine according to claim 2, wherein the time delay is between 0.5 seconds and 5 seconds. Lifting machine according to any one of claims 1 to 3, wherein the position sensor comprises a linear position sensor. Lifting machine according to any one of claims 1 to 4, wherein the position sensor comprises an angular position sensor. Lifting machine according to any one of claims 1 to 5, wherein the position sensor is a limit switch sensor configured to detect a stop position at the end of the stroke of the hydraulic actuator and transmit a position signal representative of the stop position at the end of the stroke of the hydraulic actuator to the control unit (7). Lifting machine according to any one of claims 1 to 5, wherein the position signal is a quantitative signal and the control unit (7) is configured to detect the end-stop position of the hydraulic actuator as a function of the position signal by comparing a quantity represented by the position signal with a reference value stored in a memory. Lifting machine according to any one of claims 1 to 5, wherein the hydraulic actuator (10, 12, 18) is a cylinder comprising a cylinder 43 defining an internal chamber (46) and a piston (40) sliding in said internal chamber, and wherein the stop position at the end of the stroke of the hydraulic actuator corresponds to a contact between a first stop piece integral with the cylinder and a second stop piece integral with the piston. Lifting machine according to claim 8, in which the first and second stop pieces (40, 41, 45) are located inside the internal chamber (46). Lifting machine according to claim 8, in which the first and second stop pieces (47, 48) are located outside the internal chamber (46). Lifting machine according to any one of claims 1 to 10, wherein the lifting arm (3) has a first end mounted on said main body (2) and a second end opposite to the first end, wherein the hydraulic actuator (18) is a tilting cylinder disposed at the second end of the lifting arm and intended to tilt a tool relative to the lifting arm (3). Lifting machine according to any one of claims 1 to 11, wherein the hydraulic supply device (6) comprises at least one pump driven by a motor (4) and at least one hydraulic distributor. Lifting machine according to any one of claims 1 to 12, wherein the human-machine interface comprises a manipulator (9) intended to be manipulated by an operator to produce the movement request signal. Lifting machine according to any one of claims 1 to 13, comprising a state selector configured to selectively and reversibly activate and deactivate the response of the control unit (7) to the detection of the end-of-stroke stop position. Lifting machine according to any one of claims 1 to 14, wherein the lifting machine is selected from: - a telescopic boom forklift; - a loader; - a personnel lift; - a warehouse machine; - a mast forklift.

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