Method for controlling pump of construction machine

Abstract

Method of controlling a construction machine pump together with a control system, a construction machine and a computer program implementing this control method, the method comprising the following steps: controlling (82) the pump to a first pumping speed (V1) according to a setpoint desired by the user, determining (83) the product output flow rate of the construction machine, progressively reducing (84) the pumping speed of the pump as long as the product output flow rate remains stable, until reaching a second pumping speed (V2) from which the product output flow rate begins to decrease, stabilizing (87) the pumping speed.

Description

Technical Field

[0001] This disclosure relates to a method for controlling a construction machine pump as well as a control system, a construction machine and a computer program implementing this control method.

[0002] Such a control method can be used for any type of pump and any type of construction machine used in the building and construction sector, and in particular machines for pumping and / or mixing pasty or viscous products such as mortars, concretes and fluid screeds. Prior art

[0003] Document US 2015 / 204322 discloses a method for controlling a construction machine pump known in the prior art, said pump being configured to pump products such as concrete. In particular, this document discloses a method in which a controller operating in a closed loop adjusts the flow rate of the pump according to the desired flow rate indicated by an operator and the direct or indirect measurement of the actual flow rate, in which the flow rate is adjusted by adjusting the speed of the driving source.

[0004] Known machines for pumping and / or mixing pasty or viscous products in the building and construction sector suffer from relatively low efficiency and rapid wear.

[0005] Indeed, most of the pumps used by these machines include components made of deformable materials, such as elastomers, which deteriorate rapidly due to the viscosity and abrasiveness of the products being pumped. This is particularly the case for peristaltic pumps and progressive cavity pumps (PCP). Thus, these pumps, whose initial efficiency is already quite low, see their efficiency decrease rapidly as these components wear out, until they can no longer perform their function.

[0006] A second reflux phenomenon further aggravates the situation. In fact, the viscosity of the pumped products causes a significant increase in pressure at the pump outlet, an increase that is all the more significant since the transport pipes connected to the pump outlet are generally of small diameter (most often 50 mm), very long (frequently more than 20 m), with high friction coefficients, and therefore cause significant pressure losses.

[0007] The pressure thus obtained at the pump outlet can then significantly exceed the resistance characteristics of the pump materials, causing backflows which hinder the progression of the product and, given the abrasiveness of the latter, quickly damage the moving parts of the pump as well as its sealing segments.

[0008] There is therefore a real need for a method for controlling a construction machine pump as well as a control system, a construction machine and a computer program, making it possible to reduce the disadvantages inherent in the aforementioned known configurations. Statement of the invention

[0009] The present disclosure relates to a method for controlling a construction machine pump, said pump being configured to pump fluid, pasty and / or viscous products such as mortars, concretes or fluid screeds, comprising the following steps: control of the pump at a first pumping speed according to a setpoint desired by the user, determination of the product output flow rate of the construction machine, progressive reduction of the pump pumping speed as long as the product output flow rate remains stable, until reaching a second pumping speed from which the product output flow rate begins to decrease, and stabilization of the pumping speed.

[0010] For the reasons explained above, the outlet pressures of such construction machine pumps are very high, typically exceeding 10 bar, and therefore cause these pumps to operate beyond their theoretical operating range. The inventors then noted that, in such pressure ranges, beyond a certain rotation speed, the product outlet flow rate no longer increases linearly as a function of the rotation speed: in fact, in this operating range, the effort required is increasingly greater to increase the product outlet flow rate. Consequently, the efficiency of the pump decreases more and more as one seeks to achieve a high output flow rate.

[0011] However, probably due to the viscosity of the pumped product, the inventors found that if a significant effort had to be made to establish a given output flow rate, it was then possible, once this flow rate had been established, to maintain it by exerting a less significant effort. In other words, the inventors discovered that the relationship linking the output flow rate of the pump to its rotation speed of the pump presented, in such an operating range, a hysteresis phenomenon.

[0012] Thus, thanks to the control method according to the present disclosure, it is possible to take advantage of this hysteresis phenomenon to achieve, once an output flow rate has been established, a reduction in the rotation speed of the pump while maintaining the output flow rate thus established. This increases the efficiency of the pump.

[0013] Furthermore, by reducing the rotation speed of the pump for a given output flow rate, it is possible to avoid unnecessarily over-stressing the internal components of the pump: it is thus possible to limit the impact of this overpressure regime on the internal components of the pump, in particular its deformable components, which increases the service life of the pump. Indeed, it is understood that, without the speed reduction step proposed by this process, the energy differential associated with this speed differential, which is not productive since it occurs at a constant output flow rate, contributes to damaging the internal components of the pump. Therefore, a reduction in backflow phenomena is also obtained.

[0014] In particular, the pumped products may have a viscosity greater than 500 Pa.s, preferably between 500 and 5000 Pa.s.

[0015] In some embodiments, the pump is a positive displacement pump. Indeed, these positive displacement pumps often include deformable members and are therefore particularly sensitive to overpressures and reflux phenomena.

[0016] In some embodiments, the pump includes at least one deformable element capable of causing backflow in the pump.

[0017] In some embodiments, the pump is a progressive cavity pump or a peristaltic pump. Both types of pumps include deformable components. In particular, progressive cavity pumps are frequently used in construction machinery intended to pump and / or mix pasty or viscous products.

[0018] In some embodiments, the pump is hydraulically driven.

[0019] In some embodiments, the pump is driven by a variable flow hydraulic motor.

[0020] In some embodiments, the speed of the pump is determined by measuring the hydraulic flow rate of the hydraulic pump.

[0021] In some embodiments, the speed of the pump is determined by measuring the rotational speed of its shaft.

[0022] In some embodiments, the pump is used in a pressure range beyond its nominal pressure range. This nominal pressure range is the pressure range indicated by the pump manufacturer. As a result, the pump is used outside its optimal efficiency range. The proposed method then makes it possible to limit the drop in efficiency necessarily observed outside this optimal range.

[0023] In some embodiments, the construction machine includes a product outlet pipe connected to the pump outlet. This outlet pipe, due to its long length and small diameter, contributes significantly to the pressure losses generated by the pumped product and therefore to the increase in pressure at the pump outlet.

[0024] In some embodiments, the product outlet pipe has a diameter less than or equal to 100 mm, preferably less than or equal to 50 mm.

[0025] In some embodiments, the product outlet pipe has a length greater than or equal to 10 m, preferably greater than or equal to 20 m.

[0026] In some embodiments, the product outlet pipe is flexible. It may in particular be made of elastomer. This further contributes to increasing the pressure losses generated by the pumped product.

[0027] In some embodiments, the output flow rate of the construction machine is determined by direct measurement at the output of the construction machine using a flow meter. If the construction machine is equipped with an output pipe, this output flow measurement may be performed at the output of the output pipe. For example, this flow meter may be an electromagnetic flow meter.

[0028] In some embodiments, the output flow rate of the construction machine is determined by calculation from the measurement of the pressure at the pump outlet. In particular, a pressure sensor, for example a membrane sensor, may be provided at the pump outlet. Such a calculation may be based on Poiseuille's law, along the outlet pipe, this law being expressed as follows: Q = π . Δ P . r 4 / 8 . η . I Or Q is the volume flow rate, i.e. the outlet flow rate, ΔP is the differential pressure between the pressure at the pump outlet and atmospheric pressure, r is the inner radius of the outlet pipe, η is the dynamic viscosity of the pumped product, and l is the length of the outlet pipe.

[0029] In some embodiments, the construction machine comprises a human-machine interface for entering at least one parameter of the outlet pipe and / or the pumped product. In particular, it is possible to enter the values ​​of r, η and / or l. It is also possible to choose the name of the product from a list or to choose a pre-recorded configuration.

[0030] In some embodiments, a new second pumping speed is determined each time a new setpoint is set by the user. Thus, each time the user changes the flow rate setpoint, either directly or by manually changing the rotational speed of the pump, the control method automatically adapts the rotational speed of the pump to obtain the same output flow rate, corresponding to the user's setpoint, with a lower rotational speed. The efficiency of the pump is thus optimized at all times.

[0031] In some embodiments, the step of progressively reducing the pumping speed is carried out in increments, i.e. discontinuously. The value of these increments may be fixed and predetermined or variable depending on the rotation speed of the pump. For example, this reduction is carried out in increments of 2% of the set speed with continuous scanning of the effects of this reduction. This control loop is repeated at regular intervals, for example every 10s.

[0032] In some embodiments, the step of gradually reducing the pumping speed is carried out continuously, preferably linearly.

[0033] In some embodiments, the step of gradually reducing the pumping speed is carried out according to a slope between 100 rpm -2< and 200 rpm -2< .

[0034] In some embodiments, during the pumping speed stabilization step, the pumping speed is stabilized at the value of the second pumping speed.

[0035] In some embodiments, during the pumping speed stabilization step, the pumping speed is stabilized at a value between the second pumping speed and the first pumping speed. In other words, during the pumping speed stabilization step, the pumping speed is raised above the second pumping speed. This is useful, for example, if the output flow rate has decreased too significantly before the stabilization step.

[0036] Control method, in which, during the pumping speed stabilization step, the pumping speed is stabilized at a value V3 established according to the following equation: V3 = V2 + e, where V2 is the second pumping speed, and e is a strictly positive value less than 10% of V2. This value e can be fixed and predetermined or variable and a function of the value of V2.

[0037] In some embodiments, the value e is between 1 rpm and 30 rpm.

[0038] In some embodiments, the product output flow rate is continuously monitored and the pumping speed is continuously adjusted to find the lowest speed that achieves the desired product output flow rate. In such a case, the stabilization step is performed dynamically, thereby optimizing the pump's efficiency at all times.

[0039] The present disclosure also relates to a control system for a construction machine comprising a pump configured to pump fluid, pasty and / or viscous products such as mortars, concretes or fluid screeds, comprising a sensor, configured to measure the product output flow rate of the machine or a parameter representative of this product output flow rate, a control unit, configured to control the pump and impose a pumping speed on it, in which the control unit is configured to, in a first step, control the pump at a first pumping speed, in which the control unit is configured to, in a second step, gradually reduce the pumping speed of the pump as long as the product output flow rate remains stable, until reaching a second pumping speed at which the product output flow rate begins to decrease, and in which the control unit is configured to, in a third step, stabilize the pumping speed.

[0040] All or part of the additional characteristics presented above regarding the control method can be transposed to this control system, and vice versa. In particular, this control system benefits from all the advantages of the control method presented above.

[0041] This disclosure also relates to a construction machine, comprising a pump, configured to pump fluid, pasty and / or viscous products such as mortars, concretes or fluid screeds, and a system according to any of the preceding embodiments.

[0042] The present disclosure also relates to a computer program, comprising instructions for carrying out the steps of the control method of any of the preceding embodiments.

[0043] The above-mentioned and other features and advantages will become apparent from the following detailed description of embodiments of the proposed control method, control system and construction machine. This detailed description refers to the attached drawings. Brief description of the drawings

[0044] The attached drawings are schematic and are intended primarily to illustrate the principles of the presentation.

[0045] In these drawings, from one figure to another, identical elements (or parts of elements) are identified by the same reference signs. [ Fig. 1 ] There figure 1 is a perspective view of an example of a construction machine according to the disclosure. Fig. 2 ] There figure 2 is a diagram of the control system of this construction machine. Fig. 3 ] There figure 3 schematically illustrates the control process implemented by this control system. Description of the embodiments

[0046] In order to make the disclosure more concrete, an example of a control method and control system equipping a construction machine is described in detail below, with reference to the attached drawings. It is recalled that the invention is not limited to this example.

[0047] There figure 1 illustrates an example of a construction machine 1 according to the disclosure. This construction machine 1 takes the form of a trailer equipped with wheels 2 and a coupling system 3. It comprises a chassis 10, a pump 20 and a distribution module 30.

[0048] The construction machine 1 comprises a hopper 11, mounted in the chassis 10. This hopper 11 is intended to receive a fluid product to be distributed on a construction site, for example a screed. Thus, typically, the hopper will be supplied with fluid product using a mixer truck. A grid 12, acting as a screen or sieve, is provided at the top of the hopper 11 in order to retain any unwanted large particles such as pebbles.

[0049] The pump 20 is here a progressive cavity pump. It comprises a stator made of elastomeric material, enclosed in a metal casing 21 and forming a succession of axial cavities, and a rotor engaged in the cavities of the stator.

[0050] The construction machine 1 also comprises a drive device 13 mounted in the chassis 10 (schematically visible in the figure 2 ), combining a thermal engine, for example of the diesel type, with a hydraulic machine. The output shaft of this drive device 13 is coupled to a transmission shaft extending through the hopper 11 and carrying transport members, for example an Archimedes screw, making it possible to drive the fluid product towards an outlet orifice of the hopper 11 communicating with the pump 20. The transport shaft is itself coupled with the rotor of the pump 20. Thus, the drive device 13 is capable of imposing the rotation speed V of the pump 20, that is to say its pumping speed. In this regard, a speed sensor 14 is mounted on one of these shafts in order to measure in real time the rotation speed V of the pump 20.

[0051] The distribution module 30 takes the form of a cone comprising an upstream end plate 31, connected to the outlet of the pump 20, and a downstream end plate 32, making it possible to connect an outlet pipe. The distribution module 30 further comprises a pressure sensor 33, of the membrane type, making it possible to measure the pressure of the fluid product at the outlet of the pump 20.

[0052] The construction machine 1 also comprises a computer 40 receiving, in particular, the measurements of the pressure at the outlet of the pump 20, transmitted by the pressure sensor 33, and the measurements of the rotation speed of the pump 20, transmitted by the speed sensor 14, and capable of controlling the drive device 13 so as to control the speed of the pump 20.

[0053] The computer 40 is also equipped with a human-machine interface 41 comprising at least one screen and several buttons. Among other possible functions, this human-machine interface 41 makes it possible, on the one hand, to enter the parameters of the configuration in which the machine 1 is intended to operate. In particular, the human-machine interface 41 makes it possible to enter the diameter and length of the outlet pipe currently connected to the outlet of the machine 1. It also makes it possible to enter the nature of the fluid product currently present in the machine 1: the computer 40 then extracts from its memory the value of the viscosity of this product.

[0054] On the other hand, the human-machine interface 41 allows the user to set a speed setpoint or, depending on the embodiment of the machine 1, a flow setpoint. In the present example, the human-machine interface 41 thus comprises a “+” button for accelerating the pump 20, and therefore increasing the output flow rate, and a “-” button for slowing down the pump 20, and therefore reducing the output flow rate.

[0055] The construction machine 1 thus comprises a control system 50, shown schematically in the figure 2 , implementing the computer 40, the speed sensor 14, the pressure sensor 33 and the human-machine interface 41, and capable of controlling the drive device 13 and therefore the pump 20.

[0056] The control method used by the control system 50 will now be described with reference to the figure 3 .

[0057] This control method begins with a step 81 in which the computer 40 checks whether the user has modified the setpoint via the human-machine interface 41. When this is the case, in particular when starting up the machine 1, the computer progresses to step 82 and controls the drive device 13 so as to satisfy the user's setpoint. The rotation speed V thus reached, and measured by the speed sensor 14, is recorded by the computer as the first speed V1.

[0058] The computer 40 then determines, during step 83, the output flow rate Q of the machine 1. In the present example, this output flow rate Q is calculated by the computer 40 on the basis of the measurement of the pressure P at the output of the pump 20, transmitted by the pressure sensor 33, using Poiseuille's law, the dynamic viscosity η of the product transported as well as the radius r and the length l of the output pipe having been entered using the human-machine interface 41. The computer 40 then records this output flow rate as the reference flow rate Qref associated with the first speed V1.

[0059] Then, during step 84, the computer 40 reduces the rotation speed V of the pump 20 by a certain increment and then, during step 85, checks whether the output flow rate Q has decreased relative to the reference flow rate Qref. If this decrease ΔQ is negligible, i.e. less than a predetermined threshold value ε, the computer repeats steps 84 and 85 in a loop until the output flow rate Q has a deviation ΔQ relative to the reference output flow rate Qref greater than the threshold value ε. This threshold value is preferably between 2 and 3% of the reference flow rate Qref.

[0060] When this condition is met, the computer determines, during step 86, the rotation speed V of the pump 20 and records it as the second speed V2.

[0061] Finally, during step 87, the computer 40 stabilizes the rotation speed V of the pump 20. In the present example, this stabilization consists of raising the rotation speed to a third speed V3 slightly higher than V2. More precisely, in this example, the stabilization aims to find the reference flow rate Qref to within ε.

[0062] Once the rotation speed V has stabilized, the computer restarts the process from the beginning and waits until the user requests a speed change again.

[0063] However, in this interval, the computer can also continue, permanently or at regular intervals, to scan the rotation speed V of the pump 20 and the output flow rate Q of the machine 1 in order to adjust the rotation speed V to the minimum speed making it possible to ensure the reference output flow rate Qref. This makes it possible to continue, without any intervention by the user, to optimize the speed, and therefore the efficiency, of the pump 20 even in the event of instability or transient disturbance in the operation of the pump 20.

[0064] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0065] It is also obvious that all the characteristics described with reference to a method are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a method.

Claims

1. A pump control method for controlling a pump of a construction machine, the said pump (20) being configured so as to pump fluid, pasty and / or viscous products such as mortars, concretes or fluid screeds, the method comprising the following steps: control (82) of the pump (20) at a first pumping speed (V1) according to a setpoint desired by the user; determination (83) of the product output flow rate (Q) of the construction machine and recording of this flow rate as a reference flow rate (Qref); - progressive reduction (84) of the pumping speed (V) of the pump (20) as long as the product output flow rate (Q) remains stable, that is to say as long as the decline (ΔQ) in the product output flow rate (Q) relative to the reference flow rate (Qref) remains below a predetermined threshold value (ε), until reaching a second pumping speed (V2) from which point the product output flow rate (Q) begins to decrease, that is to say from which point the said decrease (ΔQ) in the product output flow rate (Q) relative to the reference flow rate (Qref) exceeds the said predetermined threshold value (ε); stabilisation (87) of the pumping speed (V).

2. A control method according to claim 1, wherein the pump (20) is a progressive cavity pump or a peristaltic pump.

3. A control method according to claims 1 or 2, wherein the pump (20) is used within a pressure range that goes beyond its nominal pressure range.

4. A control method according to any one of claims 1 to 3, wherein the construction machine (1) comprises a product outlet pipeline connected to the outlet of the pump (20).

5. A control method according to any one of claims 1 to 4, wherein the product outlet flow rate (Q) of the construction machine (1) is determined by direct measurement at the outlet of the construction machine (1) making use of a flow meter.

6. A control method according to any one of claims 1 to 4, wherein the product output flow rate (Q) of the construction machine (1) is determined by calculation based on measurement of the pressure (P) at the outlet of the pump (20).

7. A control method according to any one of claims 1 to 6, wherein the speed reduction step (84) of progressively reducing the pumping speed (V) is performed incrementally or on a continuous basis, preferably in a linear manner.

8. A control method according to any one of claims 1 to 7, wherein, during the stabilisation step (87) of stabilising the pumping speed (V), the pumping speed (V) is stabilised at a value V3 = V2 + e, where V2 is the second control speed, and e is a strictly positive value equal to less than 10% of V2.

9. A control method according to any one of claims 1 to 8, wherein the product output flow rate (Q) is continuously monitored and the pumping speed (V) is continuously adjusted in a quest for the lowest speed at which it is possible to obtain the desired product output flow rate (Qref).

10. A machine control system for controlling a construction machine comprising a pump configured so as to pump fluid, pasty and / or viscous products such as mortars, concretes or fluid screeds, the system comprising: a sensor (33), configured so as to measure the machine's product output flow rate or a parameter (P) representative of this product output flow rate (Q); a control unit (40), configured so as to drive and impose on the pump (20) a particular pumping speed (V), wherein the control unit (40) is configured so as to, in a first stage (82), control and command the pump (20) to a first pumping speed (V1), determine the product output flow rate (Q) and record the same as a reference flow rate (Qref); wherein the control unit (40) is configured so as to, in a second stage (84), progressively reduce the pumping speed (V) of the pump (20) as long as the product output flow rate (Q) remains stable, that is to say as long as the decline (ΔQ) in the product output flow rate (Q) relative to the reference flow rate (Qref) remains below a predetermined threshold value (ε), until reaching a second pumping speed (V2) at which point the product output flow rate (Q) begins to decrease, that is to say from which point the said decrease (ΔQ) in the product output flow rate (Q) relative to the reference flow rate (Qref) exceeds the said predetermined threshold value (ε); and wherein the control unit (40) is configured so as to, in a third stage (87), stabilise the pumping speed (V).

11. A construction machine, comprising a pump (20) configured so as to pump fluid, pasty and / or viscous products such as mortars, concretes or fluid screeds; and a system (50) according to claim 10.

12. A computer programme, comprising the instructions bringing the control system according to claim 10 to execute the steps of the control method of any one of claims 1 to 9 when the said programme is run on a computer.

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