FR3050902A1 - METHOD FOR ANTICIPATING THE CLOSURE OF A PNEUMATIC DISTRIBUTION CIRCUIT OF AN AGRICULTURAL MACHINE - Google Patents

Abstract

The invention relates to a method for anticipating closure of the pneumatic distribution circuit of an agricultural machine comprising the steps of: determining the mean speed (Vm) of a seed distribution flow in a conduit (14; 16a) of the distribution circuit (20); comparing the average speed with a lower tolerance threshold (102); triggering an unclogging pulse (Δω) by increasing the speed of rotation (co) of the wind tunnel when the average speed drops below the lower tolerance threshold, so that the average speed of the flow reaches or exceeds a predetermined uncapping threshold (105) greater than a normal setpoint (101).

Description

Description

The present invention relates to the general technical field of agricultural machinery. The invention relates in particular to agricultural machines with pneumatic distribution in rows of granular materials such as seeds or chemical fertilizer. The invention relates more specifically to a method of anticipating closures in the pneumatic circuit of such machines.

For the sake of simplicity, only seeds will be mentioned below, it being understood that these granular elements may be replaced, if necessary, by granules of fertilizers or other types of granular elements.

The pneumatic distribution circuit 10 of an agricultural machine 100 with pneumatic distribution is illustrated schematically in FIG. 1 without respecting the real proportions for a good readability. Such a machine 100 is generally coupled to a tractor directly or via an intermediate hitch element such as a seeding bar. The machine 100 is here a seed drill. The pneumatic circuit 10 has a hopper 11 containing seeds to be dispensed. A metering element 12 is disposed at the bottom of the hopper 11. The metering element 12 distributes the seeds in a main pipe 14. The main pipe 14 comprises in the illustrated example a horizontal portion 14a, a bend 14b and a vertical portion 14c . The vertical portion 14c opens into a dispensing head 15 also called spark gap. A plurality of outflow lines 16 are connected to the spark gap, each opening at ground level 5 to a seed release member 18 which in this case is called a sowing unit. A blower 13 conveys the seeds as soon as they are ejected by the metering element 12 from the main line 14 to the lower part 18a of the sowing units 18 where they are released.

The machine 100 also comprises a control circuit 17 having an exchange interface IE, a database BDD, a calculation unit UC. The IE exchange interface allows the user to read, select or enter parameters related to the current job site. The database BDD can store in memory the parameters related to certain types of seeds and granules. The calculation unit UC manages and exchanges data between the exchange interface IE, the database BDD and the metering element 12, and the data transmission to the wind tunnel 13. The parameters of Considerations taken into account before and during seed distribution include, for example: the nature of the material (type of seed and / or granules), the working width, the number of rows, the desired site rate (eg seed rate to be distributed per hectare or stand), speed of travel, airflow. Some of these parameters can or must be set before each sowing project. Others may have to evolve during the construction site such as the speed of advance, the dose of seeds or the flow of blower.

In the embodiment illustrated in FIG. 1, the blower 13 behaves as a passive element. With each new setting and calibration of the metering element 12 for a change of seed dose or a change of seeds, the rotational speed of the blower 13 must be readjusted. The blower 13 is then manually adjusted, for example in steps, by means of a control valve 19 or a variation of the oil flow from the tractor in the case of a hydraulic adjustment, or electrically. The transition from one step to another is done punctually and at the request of the user in accordance with the recommendations of the manufacturer.

In other machines, the CPU calculating unit controls whether the speed of rotation of the blower 13 remains in the dedicated range for a given seed dose. In case of problems, an alarm device alerts the operator.

Agricultural machines with pneumatic distribution 100 are heavy and consume a lot of energy. Among the components of these machines, the blower 13 is one of the components that consume the most. The energy consumption and the induced cost are all the more important as the working width is large.

A pneumatic dispensing machine described in document US 2013/0061789 is known. The machine is able to distribute seeds or fertilizer. A pressure sensor having a pierced plate is mounted on the main pipe upstream of the hopper to characterize the air flow. Alternatively, this pierced plate is replaced by a pitot probe or a hot wire sensor. In addition, two pressure sensors are connected at two successive points on the main pipe downstream of the hopper to characterize the mixed air-seed flow.

Another type of machine is known from US 6584920. This is a pneumatic seeder for which a table of values is determined empirically in the laboratory. A statistical formula is then derived from the values obtained. At a planting site, the speed of rotation of the blower is adjusted only according to the desired flow rate per unit area and the measured speed of machine advancement in real time.

It may happen that a distribution head outlet pipe is blocked in which case the corresponding row is no longer sown. Such clogging requires that the user stops the machine to intervene on the blocked pipe. Such an interruption of construction is not desirable. Interruption directly affects workflow and can cause delays. In addition, the intervention may be billed when third parties work on the site. In addition, an intervention may prevent completion of a site before the arrival of rain. The invention therefore aims to provide an effective solution to plugging problems. The invention thus proposes a method of anticipating closure of the pneumatic distribution circuit of an agricultural machine comprising the steps of: determining the average speed of a seed distribution flow (or other granular elements such as granules fertilizer or other) in a conduit of the distribution circuit; - comparison of the average speed with a lower tolerance threshold; triggering a blow-off pulse by increasing the speed of rotation of the wind tunnel when the average speed drops below the lower threshold, so that the average speed of the flow reaches or exceeds a predetermined unblocking threshold greater than a normal diet setpoint. The invention has the advantage of preventing the formation of plugs. The downtime for manual unclogging of the agricultural machine are thus reduced or even avoided and this results in a substantial saving of time in use and therefore a high worksite throughput.

The release threshold is preferably between 105% and 150% of the normal diet setpoint, preferably between 108% and 120%, more preferably between 110% and 115%. These values allow the machine to perform its anticipation function, while avoiding the ejection of seeds (or other granular elements such as granules of fertilizer, etc.) out of the furrow.

In a particularly advantageous embodiment, the unclogging threshold is chosen to be greater than the upper limit of a tolerance band in which the average speed fluctuates in the normal distribution mode.

Advantageously, the unblocking threshold is reached or exceeded for a period greater than 1 second, preferably greater than 2 seconds.

These values are chosen to extract all possible stagnant materials from the pipes. Then we find the normal diet without risk that residues remain and bring up the problem.

To avoid an untimely triggering of the unclogging system, the triggering step of the unclogging pulse advantageously occurs at the end of a latency period during which the average speed is less than a lower tolerance threshold. Preferably, but not exclusively, the latency period is between 1 and 4 seconds.

Advantageously, the average speed is calculated from a measurement in two pressure taps of the distribution circuit which can be provided downstream, upstream, or on both sides of a dispensing head of the machine.

In a very advantageous manner, the machine comprises at least one device for measuring a Venturi tube on which pressure taps are provided. The Venturi tube is preferably disposed on one of the outlet lines of the dispensing head but may also be disposed on the main pipe connecting the hopper to the dispensing head.

Advantageously, the computing unit is configured to adapt in real time the speed of rotation of the blower according to pressure measurements by the measuring device at the two pressure taps. Other features and advantages of the invention will become apparent from the description which follows with reference to the accompanying drawings which are given by way of non-limiting examples of the invention. In these drawings: FIG. 1 is a schematic representation of a known pneumatic seed dispensing machine; - Figure 2 is a schematic representation of a pneumatic seed dispensing machine preferred for implementing the method according to the invention; FIG. 3 is an example of a curve of the speed of the seed distribution flow as a function of time; FIG. 4 is an example of a curve of the desired speed of rotation of the blower as a function of time, in response to the speed of the measured flow as illustrated in the example of FIG. 3.

An agricultural machine 200 is illustrated in FIG. 2. The dispensing circuit 20 of the machine 200 takes up certain mechanical elements of the machine 100: the hopper 11, the metering element 12, the main pipe 14, the spark gap 15, certain pipes 16 of output of spark gap, the sowing elements 18.

The machine 200 further comprises a blower 13, here free of adjustment valve 19.

The machine 200 also comprises a closed-loop control circuit 27 comprising a database BDD, a calculation unit UC and an exchange interface IE.

The agricultural machine 200 comprises a measuring device 28 which, in the embodiment illustrated in FIG. 2, comprises two individual pressure sensors C1 and C2 and a Venturi tube 29.

The Venturi tube 29 is here mounted on one of the outlet ducts 16a of the dispensing head 15. A homogeneous distribution of the pressures between the different outlet ducts 16 and 16a has been observed. Since the abrupt change of direction (of the order of 90 °) of the mixed air-seed flow causes significant pressure losses and accompanied by a fluctuation of pressure, it is preferable to measure the pressure of the flow not in the main pipe 14 but in the outlet pipe 16a. The characterization of the flow between the dispensing head 15 and the seed release members 18 or sowing elements is thus particularly precise and makes it possible to adjust the speed of the blower 13 in a particularly fine manner.

The Venturi tube 29 comprises for example two wide sections 29a and 29e of constant diameter and substantially identical to the diameter of the pipe 16a. The tube

Venturi also has a narrow section 29c of constant diameter and smaller than the sections 29a and 29e and the diameter of the pipe 16a. The Venturi tube further comprises two frustoconical sections: a section of decreasing diameter 29b and a section of increasing diameter 29d. The decreasing section 29b extends between sections 29a and 29c and makes them communicate. The increasing section 29d extends between sections 29c and 29e and makes them communicate. The diameter of the decreasing section 29b decreases substantially linearly from the diameter of the wide section 29a to the diameter of the narrow section 29c. Conversely, the diameter of the increasing section 29d increases substantially linearly from the diameter of the narrow section 29c to the diameter of the wide section 29e.

The respective wall of the frustoconical sections 29b and 29d is inclined at an angle less than 10 degrees, preferably less than 8 degrees with respect to the longitudinal axis of the Venturi tube 29, for example 5 or 7 degrees. This value range is particularly advantageous for limiting the maximum pressure drop in the case of a mixed air-seed flow. Indeed, in this range, there is no separation of the boundary layers and the pressure gradient remains constant.

Two pressure taps PI and P2 are provided on the Venturi tube 29 respectively in the wide sections 29a and 29c narrow (Figure 2). The sensors C1 and C2 here make it possible to measure a respective pressure p1 and p2 at each pressure tap P1 and P2. The calculation unit UC can then calculate the speed of the air in a driving section by means of the Bernoulli theorem (A) and the law of conservation of the mass flow (C).

For a current line passing through the pressure taps PI and P2, that is to say for measurements of the air velocity in two distinct sections, Bernoulli's theorem is expressed as follows: \ pvl + pgz1 + p1 = \ pvl + pgz2 + p2 (A), where p is the density of air in kg / m3, g the acceleration of gravity in N / kg or m / s2, zi and z2 altitude in m, pi and p2 the pressure measurements at the points PI and P2 in N / m2, va and Vb the flow rates in PI and P2 in m / s, that is to say respectively the speed of the flow in the pipe 16a such as before or after the venturi tube 29, and the speed of the flow in the constriction 29c. In equation (A), the pressure drop between the two sections is neglected because it is not significant.

Considering the altitudes zi and Z2 equal, equation (A) becomes:

The law of conservation of the mass flow is thus expressed in the Venturi tube 29:

in which Fi and F2 are the respective sections in m2 of the pipe 16a in PI and P2. Substituting Vb in (B), we obtain the generic equation for calculating the speed

Goes :

in which Ap is the difference of the static pressures between two sections in pascals, that is to say:

taking di and d2 as diameter circular sections 29a and 29c in m. The value Va represents an average speed in the section (va = Vm). Therefore :

Depending on the input parameters (relative to the seed, the working width of the machine 200, the number of rows, etc.), a desired value is prescribed and the calculation unit UC adjusts in real time the setpoint of speed of rotation ω of the blower 13 as a function of the pressures measured at P1 and P2 (FIG. 4). The correspondence between the average speed of the flow Vm and the rotational speed ω of the blower 13 is for example derived from a correspondence function stored in the database BDD. The calculation unit UC calculates the average speed of the flow Vm as a function of the pressure measurements pi and p2 and calculates the speed of rotation ω of the fan 13 as a function of the speed of the flow Vm. The calculation unit UC therefore adapts the speed of rotation ω of the blower 13 as a function of the pressure measurements pi and p2.

The machine 200 described above has many advantages over the existing one.

Indeed, the measurement of pressures in a Venturi tube 29 makes it possible to place the sensors out of the flow. Thus, the pressure measurements pi and p2 are not affected by the intermittent presence of seeds or their impacts as would be other pressure sensors such as pitot probes. All the more reason, the profile of the flow velocities in the pipes differs from the parabolic form observed for purely gaseous flows because of the presence of the seeds, especially near the rate of stagnation of the seeds. This is called a deformed velocity profile. Placing the sensors out of the flow makes it possible to measure stable static pressures and thus to obtain reliable measurements.

In addition, the detection of variations in physical parameters of the mixture such as pressure is instantaneous, which is a particular advantage over seed-related measuring systems, such as optical sensors or impact-sensitive piezoelectric sensors which depend on the inertia of the seeds and with which the instant of detection of the variations is delayed.

In addition, the use of a Venturi tube as a measuring tool makes it possible to limit as much as possible the pressure losses of the flow related to the measurement and therefore the alteration of the information.

Finally, adjusting the blower continuously makes it possible to further refine the adjustment of the blower 13. It is indeed possible to adjust the speed of rotation ω of the blower 13 as tight as possible and to further increase the energy efficiency of the blower 13. -this.

The general accuracy of the pressure measurement is thus improved both by the use of a Venturi tube 29 and by the measurement of pressures after the dispensing head 15.

In variant not shown, several Venturi tube measuring devices 29 as described above can be provided on as many ducts 16a respectively. At the extreme, each pipe 16a has a measuring device 28.

In a further variant not shown, the pressure taps PI and P2 are arranged differently, one and / or the other of the pressure taps PI and P2 being located (s) on the wide section 29e. A measurement upstream of the dispensing head 15, however, requires to provide a safety margin in the adjustment of the blower 13 due to pressure losses in the dispensing head 15.

Alternatively, in the measuring device 28, the two sensors C1 and C2 can be replaced by a single differential pressure sensor C3. The two pressure taps PI and P2 are then connected in fluid communication with the single differential pressure sensor C3. This differential pressure sensor is for example of the type comprising a chamber divided by a membrane in two volumes each in fluid communication with a respective pressure tap. The deformation of the membrane allows to know the pressure differential and calculate the velocity from the Bernoulli theorem.

The curve of FIG. 3 represents an example of an evolution of the mean speed Vm of the airflow as a function of time. The curve of FIG. 4 represents an example of an evolution of the rotational speed reference ω of the blower 13 as a function of time corresponding to a response to the evolution of the average speed Va illustrated in FIG. 3. For reasons of simplicity and readability, the curves of Figures 3 and 4 are shown without particular scale.

An air speed instruction 101 (FIG. 3), for example in m / s, is determined beforehand as a function of the physical parameters of the system: wind tunnel model 13, seed type, characteristics of the ducts 14 and 16, of the dispensing head 15, etc. The speed instruction 101 results from the operation of the blower 13 at a standard rotational speed 201 (FIG. 4). The instruction 101 may for example be set at 14.5 m / s for sowing wheat.

A tolerance band BT is defined between two lower tolerance thresholds 102 and greater 103. The tolerance band BT is a range of speeds in which it is assumed that the mean speed Vm of the flow in the conduit 16a evolves into a normal distribution regime. above and below the speed reference 101, without the need for corrective action. The thresholds 102 and 103 are for example respectively less than and greater than 5% of the setpoint 101.

A correction band BC is defined below the tolerance band BT, between a lower limit threshold 104 and an upper limit threshold 102 'which is the lower tolerance threshold 102 of the tolerance band BT in the illustrated embodiment. in Figure 3. When the average speed Vm crosses the lower threshold 102 downward, it is possible that a plug is being formed.

However, a latency period dmax, or dynamic tolerance, can be defined. The tolerance dmax is a maximum duration during which it is permissible for the average speed Vm to remain outside the tolerance band BT, without triggering any particular corrective action. Preferably dmax is less than 5 seconds. More preferably, dmax is between 1 and 4 seconds, for example 2 or 3 seconds.

In the example illustrated in FIG. 3: a first crossing of the lower threshold 102 for a duration dto does not cause a change of the speed of the wind tunnel since dto remains below the tolerance d max. The machine then remains in normal mode; - A second downward crossing of the threshold 102 for a duration dti greater than the tolerance dmax is problematic and triggers corrective action by UC calculation unit. It is said that an unblocking mode is engaged. This mode of unblocking has priority over the normal distribution regime.

In this second case, the holding out of the tolerance band BT for a duration greater than dmax triggers a correction signal from the CPU calculation unit. More particularly, the calculation unit UC orders a discharge pulse from the blower, that is to say a momentary increase in the speed of rotation ω of the blower 13 (see Figure 4). The rotational speed ω is increased to change from the standard speed 201 to an unclogging speed 202. The difference Δω between the rotational speeds 201 and 202 is for example chosen so that the speed Vm during the pulse reaches or exceeds a threshold of 105. More precisely, during the pulse, the speed successively exceeds the lower tolerance threshold 102, the speed reference 101, the upper tolerance threshold 103 and reaches or exceeds the release threshold 105.

The unblocking threshold 105 is greater than the high limit 103 of the tolerance band BT. The threshold 105 equals 105 to 150% of the speed reference 101. Preferably, the threshold 105 is between 108 and 120% and more preferably between 110 and 115% of the setpoint 101.

According to the parameters of the machine 200 and the type of seed, the threshold 105 is advantageously chosen high enough to allow a quick and efficient opening of the ducts 16 and 16a, and low enough to limit or prevent the ejection of seeds out of the groove.

Advantageously, the threshold 105 is reached or exceeded for a period tmin greater than one second, for example a second and a half, two or advantageously more than two seconds.

In the general case, the average speed of the flow Vm will be restored to the setpoint 101 at the end of the unblocking pulse. Alternatively, a setpoint 101 '(not shown) other than 101 may be set at least temporarily for an accelerated lowering of the speed Vm. The setpoint 101 'is for example between the lower tolerance threshold 102 and the initial setpoint 101.

In total, between the triggering of the pulse and the return to a reference speed 101 or 101 ', there elapses a period W less than 5 seconds.

The setpoints 101, 101 ', the thresholds 102 to 105, and therefore the extent of the bands BT and BC may, without limitation, be stored in the database BDD by the manufacturer or else be entered on the exchange interface IE by the user according to the manufacturer's instructions or according to the user's calculations.

A method of anticipating closure of the conduits 16a may comprise the following steps: determination of the average speed Vm of the seed distribution flow in a conduit 14 or 16a of the distribution circuit 20; comparing the average speed Vm with a lower tolerance threshold 102; - triggering of a corrective action, that is to say of an unclogging pulse Δω, by increasing the speed of rotation ω of the wind tunnel when the average speed Vm drops below the lower threshold 102, so the average velocity Vm of the flow reaches or exceeds a predetermined decoupling threshold 105 greater than a normal operating setpoint 101.

Preferably, the method of anticipating clogging described above will advantageously be implemented in the machine 200 described above and comprising the measuring device 28 described with reference to FIG.

However, the method of anticipating closures can be implemented in other machines. In an implementation not shown, other types of measuring devices that the Venturi tube device 29 can supplement or substitute for it in the measurement of pressures. Devices for measuring pressure and / or flow velocity can thus be provided in the main pipe 14. Venturi tube-free measuring devices can still be implemented. In addition, at least one sensor of a type different from the sensors C1, C2 and C3 described above may supplement or substitute them, for example an optical sensor, a piezoelectric sensor, etc.

The control circuit 27 may also include an alarm (not shown) so that when the average speed of the flow Vm decreases to the point of crossing the lower limit threshold 104 downwards, or remains in the correction band BC for too long, the blower 13 stops and / or a warning signal, light and / or sound, is triggered in the cabin and / or on the machine 200 directly. This mode of distress then has priority over the normal distribution regime and the unblocking mode.

Claims (10)

claims A method for anticipating closure of the pneumatic distribution circuit of an agricultural machine comprising the steps of: determining the mean speed (Vm) of a seed distribution flow in a conduit (14; 16a) of the circuit dispensing (20); comparing the average speed (Vm) with a lower tolerance threshold (102); triggering an unclogging pulse (Δω) by increasing the speed of rotation (co) of the fan when the average speed (Vm) drops the lower tolerance threshold (102) so that the mean velocity (Vm) of the flow reaches or exceeds a predetermined unblocking threshold (105) greater than a normal duty setpoint (101). 2. The method of claim 1, wherein the release threshold (105) is between 105 and 150% of the setpoint (101) of normal regime, preferably between 108% and 120%, preferably between 110% and 115%. %. 3. Method according to one of the preceding claims, wherein the unclogging threshold (105) is reached or exceeded for a period (tmin) greater than 1 second, preferably greater than 2 seconds. 4. Method according to one of the preceding claims, wherein the step of triggering the unblocking pulse (Δω) occurs at the end of a latency period (dmax) during which the average speed (Vm) is less than a lower tolerance threshold (102). 5. Method according to the preceding claim, the latency period (dmax) being between 1 and 4 seconds. 6. Method according to one of the preceding claims, wherein the average speed (Vm) is calculated from a pressure measurement in two pressure taps (PI, P2) of the distribution circuit (20). 7. Method according to the preceding claim, wherein the two pressure taps (PI, P2) are downstream of a dispensing head (15) of the agricultural machine (200). 8. Method according to one of the preceding claims, the machine (200) comprising at least one measuring device (28) comprising a venturi tube (29). 9. Method according to one of the preceding claims, wherein the Venturi tube is disposed on one of the outlet ducts (16a) and the pressure taps (PI, P2) are provided at two distinct points of the Venturi tube (29). ). 10. Method according to one of the preceding claims, wherein the calculation unit (UC) is configured to adapt in real time the rotational speed (ω) of the blower (13) according to pressure measurements (pi, p2) by the measuring device (28) at the two pressure taps (PI, P2).