HUBMASCHINE

Description

technical field

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

[0002] On the one hand, lifting machines with a movable arm and a hydraulic actuator configured to move the arm in response to signals transmitted by a hydraulic actuator control system are known to operate this type of machine. In this type of machine, the operator activates a movement command until the hydraulic actuator reaches its end-stop. However, if the operator maintains the movement command after the hydraulic actuator has reached its end-stop, this results in excessive energy consumption, which is then wasted.

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

[0004] Document CN104649192A discloses a lifting machine according to the preamble of claim 1. Summary of the invention

[0005] The inventors also found that forcibly holding a hydraulic actuator stop at the end of its stroke causes several drawbacks, such as: a drop in engine speed, which can cause a low-power internal combustion engine to stall; limited autonomy, due in particular to excessive energy consumption when maintaining the hydraulic actuator stop; a loss of hydraulic performance; an increase in the noise of the lifting machine; and / or premature aging of components due to unnecessary pressure in the hydraulic circuit.

[0006] The inventors also noted that prior art machines including a control limitation system as indicated above do not allow for the performance of all desired manipulations, particularly when the action of stopping a hydraulic actuator at the end of its stroke is useful to obtain a result.

[0007] Such a situation exists, for example, for the tilting cylinder of a bucket carried by the arm, in order to: to help discharge a load present in the bucket by producing vibratory shocks resulting from successive stops; and to allow effective digging.

[0008] One idea behind the invention is to solve the aforementioned problems.

[0009] One idea underlying the invention is to create a lifting machine that does not present one or more of the aforementioned problems.

[0010] 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 supply 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 power 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 a stop position at the end of stroke of the hydraulic actuator according to the position signal and to control 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.

[0011] Thanks to these features, the machine offers the following advantages: a reduction in energy consumption if the operator maintains his control of the movement of the hydraulic actuator while the hydraulic actuator is at the end of its stroke, an extension of the life of the machine, a reduction in noise and vibration, 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.

[0012] Depending on the embodiment, such a lifting machine may include one or more of the following characteristics.

[0013] According to one embodiment, the control unit commands the hydraulic actuator to stop being supplied with pressure after a time delay has elapsed from the detection of the stop position at the end of the stroke, the time delay being less than or equal to 5 seconds.

[0014] The time delay creates a controlled delay between the moment the end-of-stroke position is detected (this detection may have a margin of error) and the interruption of the hydraulic actuator's power supply. This ensures that the hydraulic actuator reaches its end-of-stroke position before the hydraulic pressure supply is cut off, despite any potential margin of error in the end-of-stroke position detection.

[0015] According to one embodiment, the delay time is between 0.5 seconds and 5 seconds.

[0016] According to one embodiment, the timing period 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.

[0017] Depending on the embodiment, the position sensor may include a linear position sensor or an angular position sensor. Suitable position sensors include, for example, capacitive sensors, magnetic Hall effect sensors, optical sensors, or others.

[0018] According to one embodiment, the position sensor includes a Hall effect magnetic sensor positioned to measure the field of a magnet carried by a moving part of the hydraulic actuator.

[0019] According to one embodiment, the position signal is a quantitative signal and the control unit 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.

[0020] According to one embodiment, the position sensor is a limit switch 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.

[0021] Thus, the position signal transmitted by the limit switch sensor can be directly representative of the stop position at the end of the stroke and does not require further processing by the control unit.

[0022] In this case, the position signal representing the end-of-travel position can be in the form of a logic or Boolean signal. According to one embodiment, the end-travel sensor can be an electrical contact that closes or opens in the end-travel position.

[0023] According to one embodiment, the hydraulic actuator is a cylinder 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 a contact between a first stop piece integral with the cylinder and a second stop piece integral with the piston.

[0024] In one embodiment, the first and second stop pieces are located inside the internal chamber. In another embodiment, the first stop piece includes a rear flange located at a first end of the internal chamber. In another embodiment, the second stop piece includes a front flange located at a second end of the internal chamber.

[0025] According to one embodiment, the first and second stop pieces are located outside the inner chamber.

[0026] 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.

[0027] According to one embodiment, the lifting arm has a first end mounted on said main body and a second end opposite to the first end, in which the hydraulic actuator is a tilting cylinder disposed at the second end of the lifting arm and intended to tilt a tool relative to the lifting arm.

[0028] According to one embodiment, the tool is chosen from a bucket, a clamp, a fork, a jib, a platform or a load backrest.

[0029] According to one embodiment, the hydraulic supply device comprises at least one pump driven by a motor and at least one hydraulic distributor.

[0030] According to one embodiment, the hydraulic supply device is a proportional distributor, for example an electroproportional distributor.

[0031] In one embodiment, the engine is a heat engine. In another embodiment, the heat engine is low power.

[0032] The human-machine interface can take various forms and include one or more components, such as a voice recognition interface, a touchscreen, joysticks, pedals, buttons, or other elements. In one embodiment, the human-machine interface includes a manipulator intended to be used by an operator to generate the movement request signal. In another embodiment, the manipulator includes one or more joysticks.

[0033] According to one embodiment, the lifting machine is chosen from: a telescopic boom forklift; a loader; a personnel lift; a warehouse machine; a mast forklift.

[0034] According to one embodiment, the hydraulic actuator is a cylinder chosen from: a tilting cylinder, a telescoping cylinder and a lifting cylinder.

[0035] According to one embodiment, the handling arm is a telescopic arm.

[0036] According to one embodiment, the lifting machine includes a pair of front wheels and a pair of rear wheels.

[0037] According to one embodiment, the lifting machine comprises a plurality of hydraulic actuators configured to move the handling arm, and the hydraulic power 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 stroke of each hydraulic actuator.

[0038] According to one embodiment, the plurality of hydraulic actuators includes a digging cylinder, a telescoping cylinder and a lifting cylinder.

[0039] According to one embodiment, the lifting machine includes a state selector configured to selectively and reversibly activate and deactivate the control unit's response to the detection of the end-stop position.

[0040] 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-of-stroke stop position is deactivated, i.e. the control unit does not stop supplying the hydraulic actuator with pressure in response to the detection of the end-of-stroke stop position, and a second state in which the response of the control unit to the detection of the end-of-stroke stop position is activated, i.e. the control unit stops supplying the hydraulic actuator with pressure in response to the detection of the end-of-stroke stop position.

[0041] In one embodiment, the state selector is a switch intended to be toggled into the first or second state by an operator. When the operator places the state selector in the first state, the control unit's response to the detection of the end-of-stroke limit switch position is disabled. When the operator places the state selector in the second state, the control unit's response to the detection of the end-of-stroke limit switch position is enabled. Brief description of the figures

[0042] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings. There [ Fig.1 ] represents a schematic view of a lifting machine according to one embodiment. The [ Fig. 2 ] is a functional diagram representing a control system for a hydraulic actuator installed in the lifting machine shown on the [ Fig.1 ]. There [ Fig.3 ] is a graph representing different parameters implemented in the control system of the [ Fig. 2 ] during actuation of the hydraulic actuator. The [ Fig. 4 ] represents a hydraulic actuator in a first embodiment at the stop, in the retracted position. The [ Fig. 5 ] represents the hydraulic actuator of the [ Fig. 4 ] fully extended, in the deployed position. The [ Fig. 6 ] represents a hydraulic actuator according to a second embodiment at the stop, in the retracted position. The [ Fig. 7 ] represents the hydraulic actuator of the [ Fig. 6 ] fully extended, in the deployed position. Description of the implementation methods

[0043] There [ Fig.1Figure 1 illustrates a lifting machine, for example a telescopic handler, comprising a main body including a chassis 2, an operator's cab, and two pairs of wheels. The lifting machine 1 includes a handling arm 3 carried by the chassis 2 and equipped with one or more hydraulic actuators and a hydraulic power supply 6 for supplying the hydraulic actuator(s). The hydraulic power supply 6 includes a hydraulic pump driven by a motor 4, for example, a combustion or electric motor.

[0044] The handling arm 3 is mounted to pivot about a horizontal transverse axis. The handling arm 3 can move from a lowered position to a raised position and vice versa by means of 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 alternately with fluid, could have been used equivalently.

[0045] The handling arm 3 illustrated on the [ Fig.1 [ ] is a telescopic arm with adjustable length in both the retraction and extension directions. The handling arm 3 consists of a first section 16 coupled to the chassis 2 and a second section 17 slidably mounted within the first section 16.

[0046] Alternatively, the handling arm 3 may not be telescopic.

[0047] The movement between the retracted position and the deployed position of the handling arm 3 is achieved via a second hydraulic actuator 12 present in the handling arm 3, such as a telescoping cylinder.

[0048] As similarly indicated above, one can use a double-acting cylinder or two parallel single-acting cylinders fed alternately.

[0049] 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 in the [ Fig.1 ] carries a bucket 5. Alternatively, the tool holder 11 is a universal tool holder, suitable for receiving a plurality of tools. The operator can then choose the desired tool and attach it to the tool holder 11.

[0050] The tool holder 11 is connected to the handling arm 3 via a third actuator 18. This third actuator 18 enables the tool holder 11 to move in a digging direction and in a tipping direction by pivoting the tool holder 11 around a horizontal transverse axis. The tipping position corresponds to the extreme downward pivoting position of the tool holder 11 and its associated tool. The digging position of the tool holder 11 corresponds to an upward pivoting position of the tool holder 11 and its associated tool.

[0051] The lifting machine 1 also includes a control unit 7 configured to control the operation of the first, second, and third hydraulic actuators 10, 12, and 18, thereby controlling 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 operated 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.

[0052] The control unit 7 is an electronic and / or computer unit which includes, for example, a microcontroller or a microprocessor associated with a memory.

[0053] Thus, when it is specified that the control unit is configured to perform a given operation, this means that the control unit includes computer instructions and computer hardware to execute said operation and / or corresponding electronic components. In other words, the functions and steps described below can be implemented as a computer program and / or via hardware components. In particular, the functions and steps performed by the control unit 7 can be carried out by instruction sets and computer modules implemented in a processor or controller and / or by dedicated electronic components or FPGA or ASIC type components. It is also possible to combine computer and electronic components.

[0054] The lifting machine 1 includes position sensors 13, 14, 15. A first position sensor 13 is 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.

[0055] The first, second and third position sensors 13, 14, 15 are further configured to transmit to the control unit 7 position signals representing each time the measured parameter.

[0056] These position signals are used by the control unit 7 to determine whether the corresponding hydraulic actuator has reached a stop position at the end of its stroke.

[0057] In one embodiment, the control unit 7 includes a memory for processing the received position signal. The memory is calibrated to store a first position value representing the hydraulic actuator's end stop in the retracted position and a second value representing the hydraulic actuator's end stop in the extended position. Thus, when the control unit 7 receives a position signal, it compares the position signal with the first and second values ​​stored in the memory, and if the position signal reaches or exceeds either the first or second value, the control unit 7 detects the corresponding end 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 time delay has elapsed since the detection of the stop position at the end of the stroke.

[0058] In one embodiment, the position sensor is a limit switch configured to detect the end-of-stroke position of the hydraulic actuator and to transmit to the control unit 7 a position signal representing the end-of-stroke position of the hydraulic actuator, i.e., a limit switch signal in the retracted or extended position. Such a limit switch signal is triggered, for example, by an electrical contact that opens or closes in the limit switch position. Therefore, further processing of the limit switch signal by the control unit 7 is unnecessary because the limit switch position has already been detected by the limit switch.

[0059] Several types of end-of-stroke stops for a hydraulic cylinder 19 are illustrated on the figures 4 to 7 .

[0060] 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 able to slide in a longitudinal direction of the internal chamber 46.

[0061] According to an embodiment shown in the figures 4 And 5 The end-of-stroke positions of the piston 40 are delimited by a stop inside the internal chamber 46. Thus, the piston 40 is able to slide from a rear flange 41 located at the level of a first end of the internal chamber 46 towards a front flange 45 located at the level of a second end of the internal chamber 46, until the piston 40 of the hydraulic cylinder 10 comes to a stop against the front flange 45.

[0062] Conversely, the piston 40 is able to slide 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 is brought against the rear flange 41.

[0063] According to another embodiment shown on the figures 6 and 7The end-stroke positions of the piston 40 are delimited by a stop outside the internal chamber 46. Thus, the hydraulic cylinder 19 further includes 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 integral with the cylinder 43. During the 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.

[0064] THE figures 2 And 3 illustrate the operation and consequences of the control system as presented on the [ Fig.1 ] during the actuation of the third hydraulic actuator 18 corresponding to a tilting cylinder.

[0065] When the operator wishes to move the bucket 5, the first step is to activate the manipulator 9 in order to transmit a movement request signal 20 to the control unit 7.

[0066] The second step is the acquisition of the movement request signal 20 and the processing of said signal by the control unit 7.

[0067] In a third step, the control unit 7 sends a control signal 22 to the hydraulic power device in order to set the third hydraulic actuator 18 in motion.

[0068] In a fourth step, the position sensor 15 detects a position of the third hydraulic actuator 18 corresponding to a limit switch as illustrated in the figures 4 to 7and transmits a position signal 23 representing the end 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 elapsed of a predetermined time delay, to stop the movement of the third hydraulic actuator 18.

[0069] Thus, even if the operator maintains the demand for movement in push towards the stop position of the third hydraulic actuator 18, the hydraulic push at the end of stroke stop is stopped.

[0070] The resumption of movement of the third hydraulic actuator 18 takes place during a reversal of the piloting direction, that is to say when the operator operates the manipulator 9 in order to transmit to the control unit 7 a signal requesting movement in the opposite direction.

[0071] The advantages of this control method are now explained with the graphs illustrated on the [ Fig.3 The x-axis is common to all graphs and represents the passage of time in seconds (s).

[0072] It is illustrated with six graphs, representing: 20: The movement request signal 20 produced by the manipulator 9 of the hydraulic actuator, with the y-axis representing the percentage of the transmitted request relative to a maximum request. In this example, the operator holds the manipulator 9 in a position to request movement of the bucket 5 from time 9s to time 19s. 22: The control signal 22 for initiating movement of the hydraulic actuator 18, produced by the control unit 7 and sent to an electroproportional valve, with the signal intensity in mA on the y-axis. 23: The position signal of the hydraulic actuator rod 18 in millimeters. 33: The fuel consumption of the internal combustion engine 4 in liters / hour. 34: The load factor of the internal combustion engine 4 as a percentage. 35: The engine speed of the internal combustion engine 4 in revolutions per minute.

[0073] Reference 36 schematically represents the moment of hydraulic stop of the hydraulic actuator 18, at approximately 17s.

[0074] It is visible on curves 20 and 23 that the operator maintains the demand for movement of the hydraulic actuator after a stop position at the end of the stroke of the hydraulic actuator has been reached, represented on the third graph, to the right of line 36, after 17 seconds.

[0075] Despite the continued demand for movement 20, the control unit 7 stops the control signal 22 from the hydraulic actuator 18 immediately after reference 36. After a delay of 0.5 seconds, the signal intensity rapidly decreases from 1500 mA to 0 mA. Consequently, the hydraulic power supply 6 no longer supplies power to the hydraulic actuator 18.

[0076] Thus, thanks to these characteristics, it is observed that the load rate 34 and the consumption 33 of the internal combustion engine 4 each exhibit a brief peak of increase which is quickly erased after the reference 36 and well before the end of the motion demand 20. In addition, the engine speed 35 only undergoes a brief decline.

[0077] The same steps can be applied independently for other hydraulic actuators.

[0078] According to an alternative embodiment illustrated with the [ Fig. 2 ], the lifting machine control system includes a state selector 24, for example a switch, configured to selectively and reversibly activate and deactivate the response of the control unit 7 to the detection of the end-stop position.

[0079] When the operator places the state selector 24 in its first state, the state selector 24 transmits an interrupt signal 25 to the control unit 7, and the control unit 7's response to the end-of-stroke position detection is deactivated. This action is reversible; that is, when the operator places the state selector 24 in its second state, the interrupt signal 25 is not transmitted, and the control unit 7's response to the end-of-stroke position detection is activated.

[0080] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them 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.

[0081] The use of the verb "comporter", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0082] In claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

1. A lifting machine (1) comprising: a main body (2), a manipulator arm (3) that is mounted on said main body (2) and is movable with respect to the main body (2), a hydraulic actuator (10, 12, 18) that is configured to move the manipulator arm, a hydraulic supply device (6) that is connected to the hydraulic actuator (10); and a control system comprising: a control unit (7) that is configured to receive a movement request signal from a human-machine interface and to command the hydraulic supply device in response to the movement request signal so as to cause the manipulator arm to move on the basis of the movement request signal, a position sensor (13, 14, 15) that is configured to transmit a position signal (23) representative of a position of the hydraulic actuator (10, 12, 18) to the control unit (7), characterized in that the control unit (7) is also configured to detect an end-of-travel stop position of the hydraulic actuator on the basis of the position signal and to command (21) the hydraulic 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.

2. The lifting machine as claimed in claim 1, wherein the control unit commands (21) the stopping of the supply of pressure to the hydraulic actuator after a delay time has elapsed starting from the detection of the end-of-travel stop position, the delay time being less than or equal to 5 seconds.

3. The lifting machine as claimed in claim 2, wherein the delay time is between 0.5 second and 5 seconds.

4. The lifting machine as claimed in one of claims 1 to 3, wherein the position sensor comprises a linear position sensor.

5. The lifting machine as claimed in one of claims 1 to 4, wherein the position sensor comprises an angular position sensor.

6. The lifting machine as claimed in one of claims 1 to 5, wherein the position sensor is an end-of-travel sensor that is configured to detect an end-of-travel stop position of the hydraulic actuator and to transmit a position signal representative of the end-of-travel stop position of the hydraulic actuator to the control unit (7).

7. The lifting machine as claimed in 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-of-travel stop position of the hydraulic actuator on the basis of the position signal by comparing a quantity represented by the position signal with a reference value stored in a memory.

8. The lifting machine as claimed in one of claims 1 to 5, wherein the hydraulic actuator (10, 12, 18) is a cylinder comprising a cylindrical part (43) defining an internal chamber (46) and a piston (40) sliding in said internal chamber, and wherein the end-of-travel stop position of the hydraulic actuator corresponds to contact between a first stop piece secured to the cylinder and a second stop piece secured to the piston.

9. The lifting machine as claimed in claim 8, wherein the first and second stop pieces (40, 41, 45) are situated inside the internal chamber (46).

10. The lifting machine as claimed in claim 8, wherein the first and second stop pieces (47, 48) are situated outside the internal chamber (46).

11. The lifting machine as claimed in one of claims 1 to 10, wherein the lift 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 tilt cylinder that is disposed at the second end of the lift arm and intended to tilt a tool with respect to the lift arm (3).

12. The lifting machine as claimed in 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.

13. The lifting machine as claimed in one of claims 1 to 12, wherein the human-machine interface comprises a manipulator (9) that is intended to be manipulated by an operator in order to produce the movement request signal.

14. The lifting machine as claimed in one of claims 1 to 13, comprising a state selector that is 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.

15. The lifting machine as claimed in one of claims 1 to 14, wherein the lifting machine is chosen from: - a telescopic arm lift truck; - a loader; - an aerial personnel lift; - a warehousing machine; - a mast lift truck.