EP3960933A1 - Method for adjusting the temperature of a screed plate of a paving screed of a road finisher - Google Patents

Abstract

Method for adjusting a temperature of a screed plate of a screed (101) of a road finisher (100), characterized in that the screed has a heating element (113) which heats the screed plate (111) and a temperature sensor (114) which measures the temperature of the screed plate over a period of time, and the road finisher comprises a control unit (130) which sets a desired temperature of the heating element (113) as a function of a time profile of the temperature of the screed plate.

Description

The present invention relates to a method for adjusting a temperature of a screed plate of a screed of a road finisher according to the preamble of claim 1 and a method for adjusting a temperature of a screed plate of a screed of a road finisher according to the preamble of claim 5 and a road finisher for spreading material onto a substrate.

State of the art

Road finishers and corresponding methods, also for adjusting the temperatures of the paving screeds or screed plates that are usually provided, are sufficiently known from the prior art. Such methods are commonly used to ensure a screed plate temperature that will ensure reliable dispensing of the material to form the road while preventing the material from being overheated.

So is about from the DE 10 2018 127 353 A1 a system for controlling the heating of a smoothing plate is known, in which the temperature of the material is measured along its conveying path from the material container into the screed. This temperature, which corresponds to the actual temperature of the paving material, is used by the control unit to operate a heater in comparison with the temperature values measured by another temperature sensor for the screed plate in order to keep the screed plate temperature within a temperature fluctuation range with respect to an otherwise estimated paving material temperature.

By providing various sensors, it is possible with the method disclosed in this document to estimate the temperature of the paving material and thus to precisely regulate the control of the heating. On the other hand, so many sensors become necessary, which increases the possibility of malfunctions if one or more sensors fail. Since the sensors that measure the temperature of the paving material are independent of the sensors that measure the smoothing plate temperature, and both temperature measurements are necessary for operation, there is also no redundancy in these sensors, so that the failure of one of the corresponding sensor types already triggers the implementation of the procedure hindered.

In addition, the control unit must receive and process an abundance of inputs, so that the number of interfaces is high and the control unit is therefore complex.

task

Based on the known state of the art, the technical problem to be solved consists in specifying a method for heating a screed plate of a screed of a road finisher, which achieves a reduced susceptibility to errors while at the same time using fewer components.

solution

This object is achieved by the method according to claim 1, by the method according to claim 5 or by the road finisher according to claim 11. Advantageous developments of the invention are included in the dependent claims.

The method according to the invention for setting a temperature of a screed plate of a screed of a road finisher is characterized in that the screed comprises a heating element that heats the screed plate and a temperature sensor that measures the temperature of the screed plate over a period of time, and the road finisher includes a control unit includes that sets a target temperature of the heating element depending on a time profile of the temperature of the smoothing plate.

This method advantageously does not require a sensor for directly measuring the temperature of the material that is applied to the subsoil (road surface) by the screed of the road finisher. This means that a sensor specially designed to measure the temperature of the material does not have to be provided. The invention provides that due to a heat exchange between the smoothing plate and the material that is to be heated by this smoothing plate, the temperature profile of the smoothing plate is changed depending on the material temperature and this allows conclusions to be drawn about the material temperature when the temperature of the smoothing plate is otherwise known, with which a desired target temperature of the smoothing plate and thus the heating power can be set advantageously without an exact determination of the temperature of the material being necessary for this, which reduces the number of necessary components.

Provision can be made for the smoothing plate to be heated to a first temperature by the heating element and then for the heating element to be switched off and for the smoothing plate to be brought into contact with material that is applied to a substrate, with the temperature of the smoothing plate being shown as a function of time the switching off of the heating element by the Control unit, a material temperature is determined and depending on the material temperature, the target temperature is determined.

This embodiment makes use of the fact that the smoothing plate cools down when it comes into contact with the material if it has been brought to a high temperature. This cooling takes place in accordance with known physical laws and, if the temperature of the smoothing plate is known, allows conclusions to be drawn about the temperature of the material, which likewise does not have to be determined by means of a sensor or other means.

In addition, it can be provided that the heating element heats the smoothing plate to a heating temperature that is lower than a material temperature of the material that is applied to a substrate, and then the smoothing plate is brought into contact with the material while the heating element the smoothing plate is heated, the material temperature being determined by the control unit from the temperature profile of the smoothing plate over time while it is being heated by the heating element and being in contact with the material, and the target temperature is determined as a function of the material temperature will.

In this embodiment it is possible to determine the point in the course of the temperature of the smoothing plate over time at which there is no longer any additional heat transfer from the material to the smoothing plate because the temperature of the smoothing plate is above the temperature of the material. This allows conclusions to be drawn about the temperature of the material, which in turn allows the target temperature of the heating to be determined without exact knowledge of the material temperature.

In one embodiment it is provided that the control unit determines the target temperature from the material temperature by increasing the material temperature by a differential value. This ensures that the temperature of the smoothing plate is always above the determined material temperature. This is particularly important when the screed heating is either in cyclic operation and the screed plate is therefore not heated at times. When the desired temperature of the smoothing plate is reached, the control unit will switch off the heating element and supply the heating element with energy again after the smoothing plate has cooled down to the material temperature.

The differential value can be viewed as an "offset" and can thus be used, for example, to keep the temperature of the screed above or at least equal to the temperature of the material whenever possible. Undesirable adhesion of paving material is thus avoided.

An alternative method according to the invention for adjusting a temperature of a screed plate of a screed of a road finisher is characterized in that the screed a Heating element that heats the screed, comprises and the road finisher comprises a control unit, wherein the control unit determines the target temperature of the screed taking into account an operating parameter of the road finisher and / or the environment and / or the road surface.

The term "operating parameters" of the road finisher, the environment or the road surface is understood to mean values that are already determined during normal operation of the road finisher, such as the road surface temperature, the temperature of the material upon delivery or the like. For example, when scanning the road behind the road finisher, it is customary to record the surface temperature of the road with the material spread on it and thus in particular the temperature of the material spread on the ground. Corresponding means are usually provided independently of the sensors of the screed. The temperature determined for the spread material can then be used to determine a required temperature of the smoothing plate, for example by taking into account that the material temperature before spreading and while the material is in contact with the smoothing plate of the screed is slightly higher than that during temperature of the material already spread, measured during the scan. In particular, to simplify the calculation, it can be assumed here that the temperature of the discharged material (which is determined by the scan) is equal to the material temperature T _mat in the area of the screed, in particular when it comes into contact with the screed. The target temperature of the screed's screed can then be set as a value T _mat +ΔT, where ΔT>0K can be a temperature offset that is chosen to avoid sticking of the material to the screed.

By using appropriate operating parameters for determining the setpoint temperature, a system that is more compact in terms of hardware requirements can also be provided, since no additional sensors have to be provided.

The consideration of the operating parameters is to be understood in such a way that, contrary to the embodiments described above, it may be possible to dispense with further calculations, but to determine the material temperature directly from the values generally described as "operating parameters" and, based on this (e.g. by adding a temperature offset as described above) to determine the target temperature of the screed.

In one embodiment, the pavement operating parameter comprises a pavement surface temperature determined during a temperature scan. The surface temperature of the road surface can, in particular, be behind in the direction of travel of the vehicle be measured in the vehicle and thus characterizes the temperature of the material that has just been spread, as already described above, which means that the material temperature is known (within certain limits or with a certain degree of accuracy).

This implements a preferred variant of this embodiment and, assuming a temperature that remains constant between contact with the smoothing plate and measurement behind the vehicle, allows the material temperature to be determined directly and thus economically with regard to the necessary computing power.

Provision can also be made for the operating parameters of the road finisher to include information about the material temperature upon delivery, which is entered into the control unit.

If the material, such as asphalt, is delivered by truck, this material is usually already heated to a certain temperature, which is specified with the delivery and can be entered manually by an operator in the control unit or by scanning a delivery note from the Control unit can be supplied. This is also an "operating parameter" because it characterizes the condition of the material when it is delivered. If this temperature is known to the control unit, the heating power of the heating element can then advantageously be controlled in such a way that the temperature of the smoothing plate is approximately in a range around the temperature of the material, or knowing this temperature can be used to estimate what temperature the material is still at will possess when it arrives at the screed. As already explained above, an offset can then be added to this material temperature, i.e. a ΔT>0K, in order to reliably prevent the material from adhering to the smoothing plate.

Furthermore, it can be provided that the operating parameter of the environment includes an ambient temperature.

The ambient temperature, ie the temperature of the air, for example, can advantageously be used to determine the target temperature of the smoothing plate and does not require any additional components, since this temperature is already usually determined by road finishers.

In one embodiment, the control unit determines a material temperature of the material when it reaches the smoothing plate from the material temperature upon delivery and from the ambient temperature, and the control unit sets the target temperature as a function of the determined material temperature.

This advantageously combines the embodiments already described.

It can also be considered that the control unit uses information stored in a memory assigned to the control unit to determine the target temperature.

This information can relate, for example, to temperatures required for a specific material and can differ from material to material, so that the control unit can be supplied with the necessary information.

The road finisher according to the invention for spreading material onto a substrate comprises a material container, a screed and a conveyor system for conveying material from the material container to the screed, the screed being designed to spread material onto the substrate and the screed having a smoothing plate and a heating element for heating of the screed, wherein the road finisher comprises a temperature sensor for measuring a temperature of the screed and a control unit that is designed to control the temperature of the heating element, wherein the road finisher is designed to carry out a method according to one of the preceding embodiments.

This road finisher can implement the advantageous properties of the methods described in the previous embodiments.

Short description of the figures

1

schematic representation of a paver according to an embodiment

2

Flow diagram of a method according to one embodiment

3

Flow diagram of a method according to another embodiment

4

Flow chart according to another embodiment

Detailed description

1 12 shows a paver 100 according to an embodiment of the invention. In this embodiment, the road finisher is essentially configured as a vehicle part (also called a tractor unit) 102 and a screed 101 .

In the embodiment shown here, the vehicle part 102 includes, among other things, a driver's platform 124 on which, for example, the driver of the road finisher 100 can sit. Operating elements can also be provided there, for example, in order to enable the driver to operate the road finisher.

The road finisher 100 also has a material goods container 122 in the vehicle part 102, also known as a goods bunker. The material 123 to be spread onto the road, such as asphalt, is stored in this in order to be kept available for further transport or use.

A conveyor system, which is arranged in the vehicle part 102 and supplies the material from the material goods container 122 (or goods bunker) to the screed 101, is not shown in detail here.

The screed 101 is connected to the vehicle part 102 via connections (usually towing bars) 125 that are well known from the prior art (these can be fastened to both sides of the vehicle part 102) and can be connected, for example, via one or more leveling cylinders (not shown here) in a specific Alignment relative to the ground 103 on which the road finisher is driving, be stored.

The vehicle part 102 usually also includes a drive unit 121, which can be embodied in the form of a chain drive, for example, in order to enable the road finisher 100 to move on the subsurface 103.

In front of the screed 101, the road finisher 100 usually includes, on the one hand, an auger 112 with which the material is applied to the subsoil 103. This auger is part of the vehicle part 102, so structurally it does not belong to the downstream screed. On the other hand, the screed comprises one or more smoothing plates 111, the screed smoothing or compacting the material applied to the subsoil 103 by its own weight.

All the parts of the road finisher 100 described so far can be present in this form or in a modified form, and are therefore to be understood merely as examples of the invention. According to the invention, the road finisher 100 comprises at least one screed with a smoothing plate and a control unit.

In order to prevent the material from sticking to the smoothing plate and thus preventing the discharge result from being adversely affected, it is provided according to the invention that a heating element 113 is assigned to the smoothing plate. This heating element is arranged and designed in such a way that it can heat the smoothing plate, in particular can heat it to a specific temperature in a targeted manner by supplying heat.

In addition, the smoothing plate 111 is assigned a temperature sensor 114 which can measure the temperature of the smoothing plate.

Since the heating element usually supplies the screed plate with heat, the temperature of the screed plate is not yet known simply because of the possibly known amount of heat, since this also depends on the further heat transfer from the screed plate to the material applied to the substrate 103, for example. If this material has already cooled down considerably, for example through contact with the subsurface 103 or with the ambient air, or at least has a lower temperature than the temperature of the smoothing plate, then when a certain amount of heat is supplied, different temperatures can be reached for the smoothing plate, depending on the temperature of the material and the associated heat transfer from the smoothing plate to the material or vice versa. However, in order to effectively prevent the material from sticking to the screed, the temperature of the screed should always be higher than or at least equal to the temperature of the material.

For this reason, the temperature sensor 114 is provided, which measures the temperature of the screed. This can be, for example, an electrically operating sensor or any suitable temperature sensor.

According to the invention, a control unit 130 is also provided, which is arranged in vehicle part 102 here merely for the purpose of illustration and is connected both to sensor 114 and to the heating element for the purpose of data exchange (for example with the aid of cables and/or by means of wireless communication means). is.

According to the invention, in some embodiments it is provided that the temperature sensor 114 measures the temperature of the smoothing plate over a certain period of time (either while the heating element 113 is switched on or while it is switched off) and, depending on the measured temperature profile of the smoothing plate over time, the control unit 130 then (in particular after determining the temperature of the material 131), controls the heating element 113 in such a way that the smoothing plate is heated to a desired target temperature, in particular is kept at the target temperature (for example, taking into account a permitted temperature window, for example in the case of intermittent operation the heating).

Alternatively, it can also be provided that the control unit takes into account one or more (further) operating parameters that are taken into account when determining the desired temperature of the smoothing plate, such as the ambient temperature, the temperature of the material 123 upon delivery or the surface temperature of the road surface.

Embodiments are particularly preferred in which previous road finishers do not have to be modified with regard to the sensors used in order to carry out the method according to the invention in accordance with one of the embodiments yet to be described. In particular, it is provided that road finishers without sensors for measuring the temperature of the material themselves can be converted by providing suitable control programs for the control unit 130 in order to implement the method according to the invention.

Preferred embodiments of the method are in the Figures 2 to 4 shown as a flow chart and will be explained in more detail below.

In the 2 an embodiment is shown in which the material temperature is deduced from the cooling behavior of the smoothing plate.

The process begins by activating the heating element to heat the screed. This preferably takes place before any material is applied to the subsurface or comes into contact with the smoothing plate. In step 202, the smoothing plate is first heated to a temperature T ₁ which is above the temperature of the material to be applied to the subsurface. However, the temperature of the material T _mat is not yet known in step 202 . The smoothing plate can therefore be heated to a temperature T ₁ which is at least above the maximum mix temperature (material temperature) of around 180°C, ie around T ₁ =200°C. This then ensures that, regardless of the actual material temperature, the smoothing plate temperature T ₁ in step 202 is greater than the material temperature T _mat .

If the temperature T ₁ is reached, the heating element is switched off in step 203, so that the heating element no longer supplies heat to the smoothing plate and the smoothing plate begins to cool down.

At this time, however, material is already being fed to the screed 101, so that the material also comes into contact with the screed plate, and the screed plate gives off heat to the material. The smoothing plate will then cool down.

Under the simplified assumption that the material temperature T _mat remains constant (that is, the material can be viewed as a heat reservoir with constant temperature), the following applies to the change in heat Q transferred to the material over time t $$\frac{\mathit{dQ}}{\mathit{German}}=-c\frac{\mathit{dT}}{\mathit{German}}$$

ist, wobei T ₁ und T ₂ die Temperatur der am Wärmeaustausch beteiligten Gegenstände sind.However, this is true for heat flow at any time $\frac{\mathit{dQ}}{\mathit{German}}=a\left(T_1-{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="imgf0003.png"\; state="\{\{state\}\}">T</figure-callout>}}_2\right)$

where T ₁ and T ₂ are the temperature of the objects involved in the heat exchange.

Ultimately, this means that the temperature of the smoothing plate is a function of time $$T\left(t\right)=\left(T_0-T_{\mathit{mat}}\right)e^{-\mathit{Bt}}+T_{\mathit{mat}}$$

The constant B is insignificant but depends on the material properties of the smoothing plate (in particular its size or contact surface with the mixed material) and the material or mixed material.

From this, the temperature of the material T _mat can be determined at least approximately.

To do this, the temperature of the smoothing plate is measured over a specific time Δt. The material temperature T _mat , which is then calculated in step 205 , can then be deduced from the course of the curve.

If this temperature is known, then in a next step 206 the desired setpoint temperature T setpoint of the smoothing plate can _be determined. This target temperature will be used to control the heating element in step 207 below.

In step 206, the target temperature T set of the smoothing plate can _be determined in such a way that the smoothing plate has at least a slightly higher temperature than the material, so that T set >T _mat can _be selected. For example, it can be provided that the temperature of the smoothing plate is about 10K above the actual material temperature. When determining or ascertaining the target temperature of the smoothing plate in step 206, it can also be provided that a temperature range is defined as the “target temperature”. For example, it can be provided that the temperature of the smoothing plate is not set to a specific temperature value, but rather to a temperature range between a (maximum) target temperature T set and the actual material temperature T _mat , so that the temperature of the smoothing plate _is always within to move in this area.

In step 207, the control unit will then control the heating element (e.g. by supplying more or less power or by switching it on and/or off) in such a way that the temperature of the smoothing plate corresponds to the target temperature or in the intended range of the temperature for the smoothing plate lies. This prevents the mixture from sticking to the smoothing plate.

This preferably takes place as part of a control cycle that is fundamentally known from the prior art, with the control unit controlling heating element 113 based on a measured temperature value of the smoothing plate (temperature sensor 114 can be used for this purpose, for example) and the temperature then being measured again with temperature sensor 114 and the heating element is controlled again, and so on.

In this way, the temperature of the smoothing plate can be controlled reliably, particularly given the boundary condition of keeping the temperature within a specific temperature window between a maximum target temperature and the material temperature.

In 2 an embodiment was described in which the initial temperature of the screed is above the temperature of the material.

However, embodiments are also conceivable in which the initial temperature (at which the measurement of the temperature of the screed over a certain time interval is started) is lower than the temperature of the material.

Such an embodiment will now be 3 described.

in the in 3 In the embodiment shown, the heating element is first activated in step 301, analogously to step 201.

However, this warming-up phase of the smoothing plate is only carried out up to a temperature T ₂ <T _mat and the measurement of the temperature T _G of the smoothing plate is then started in step 303 over a certain time interval Δt.

In this context, the material can then be regarded as a heat reservoir with a higher temperature and the heating element as a heat reservoir for the screed with a second constant temperature, with the temperature of the heating element or the heat provided by it being greater than the temperature of the material, in particular the heating element, should have a higher temperature than the material.

ein Vorzeichenwechsel erfolgt, sobald T₁ von einer Temperatur, die kleiner als T₂ ist, auf eine Temperatur größer als T₂ wechselt. Für die hier beschriebene Ausführungsform gilt für die Änderung der Wärme über die Zeit $\frac{\mathit{dQ}}{\mathit{dt}}=a\left(T_G-T_{\mathit{mat}}\right)+b\left(T_G-T_H\right){\mathrm{T}}_{\mathrm{mat}}$

gibt hier die Materialtemperatur an und T_H gibt die Temperatur des Heizelements an, wobei T die Temperatur des Glättblechs in Abhängigkeit von der Zeit ist. Die Größen a und b sind Konstanten. Die Temperaturen T_mat und T_H können hier als zeitlich konstant angesehen werden.Analogous to the calculation above, the corresponding steps for adding the heat transfer, which is carried out both by the material and by the heating element, lead to a time dependence of the temperature. However, in this case, preferential use can be made of that in the relationship $\frac{\mathit{dQ}}{\mathit{German}}=a\left(T_1-T_2\right)$

a sign change occurs as soon as T ₁ changes from a temperature that is lower than T ₂ to a temperature that is higher than T ₂ . For the embodiment described here applies to the change in heat over time $\frac{\mathit{dQ}}{\mathit{German}}=a\left(T_G-T_{\mathit{mat}}\right)+b\left(T_G-T_H\right){\mathrm{T}}_{\mathrm{mat}}$

here indicates the material temperature and T _H indicates the temperature of the heating element, where T is the temperature of the screed as a function of time. The quantities a and b are constants. The temperatures T _mat and T _H can be regarded as constant over time.

Since T _mat <T _H , there will be a kink in the time course of the heat quantity (in particular its dissipation) as soon as the temperature T _G of the screed plate exceeds the temperature T _mat of the material, since from this point on the material no longer generates heat the screed gives off, but rather the screed begins to give off heat to the material.

The material temperature T _mat can now be determined from this equation by measuring the temperature of the smoothing plate over a certain period of time when the jump in the derivation is found, so that this can again form the output variable in order to determine the target temperature T target in steps 304 _to 306 of the screed plate and to control the heating element accordingly by the control unit.

The procedure in steps 304 to 306 corresponds to the procedure of steps 205 to 207, where instead of to 2 given equations then according to the 3 equation to be solved is used.

The rest of the procedure is analogous here. In particular, it can also be provided here that the temperature of the smoothing plate is brought to a target temperature by appropriate control of the heating element, which is above the material temperature T _mat or at least moves in a range between a maximum target temperature and the material temperature, so that material is prevented from adhering to the smoothing plate.

A corresponding control circuit can also be used here, which causes the temperature to be regulated by controlling the heating element in such a way that the temperature is in the desired range.

The embodiments of figures 2 and 3 can also be used in competition. If the material temperature is unknown, the smoothing plate can first be heated to a temperature T ₀ . If the temperature then drops when the heating element is switched off, it can be determined that the temperature T ₀ is >T _mat and the method follows figure 2 can be done. If it turns out that the smoothing plate continues to heat up when the heating element is switched off, then T ₀ <T _mat and the procedure according to 3 can be done.

In a further embodiment according to the alternative to the previous method 4 the material temperature in the region of the smoothing plate is determined on the basis of at least one operating parameter and/or an operating parameter characterizing the environment and/or an operating parameter characterizing the road surface, in order to control the heating element.

For this shows 4 First, two methods that are alternative to one another or that can be used in parallel, with the first method scanning the road surface being carried out in step 401 after the material has been applied. Corresponding methods are already known and include, among other things, the measurement of the subsurface temperature, so that in step 403 the road surface temperature T _S can be determined from the scanning of the road surface 401 behind the road finisher. This pavement temperature is ultimately the temperature of the material being spread.

Alternatively or additionally, the control unit can access temperature sensors that are usually provided for measuring the ambient temperature and can thus measure the ambient temperature at a specific point in time or obtain a value indicative of it.

The pavement temperature T _S and the ambient temperature or one of both may then be combined along with a value of the material temperature T _mat obtained in step 404 upon delivery of the material to the paver, although this is not necessary and only the material temperature T _mat upon delivery Delivery can be considered for further proceedings. Alternatively, the pavement temperature T _S can also be used as a guide for the material temperature T _mat by assuming that the pavement temperature as measured in step 401 is considered equal to the material temperature T _mat .

The material temperature upon delivery can be entered in a delivery note, for example, and then made available to the control unit by an operator, for example using a suitable input device such as a keyboard. Alternatively or additionally, it can also be provided that a barcode scanner or a QR code scanner, which can detect a corresponding code on the delivery note in which the temperature is encoded, read the corresponding temperature (without errors) and make it available to the control unit.

The temperature of the material in the area of the smoothing plate can then be extrapolated from this material temperature, which the material has when it is delivered (to the goods bunker of the road finisher). will. If the road surface temperature T _S from step 403 and/or the ambient temperature from step 402 is available, this extrapolation can be determined with high accuracy since the cooling behavior of the material can be determined relatively accurately. Alternatively, the delivery temperature can also be assumed to correspond in principle to the temperature of the material when it passes through the smoothing plate. This means that the material temperature is known and it is sufficient to set the target temperature to be either the same as or slightly higher than the material temperature.

If the material temperature is not known upon delivery, i.e. step 404 cannot be carried out either because the information is not available or has not been considered, a "standard value" can be used for the material temperature upon delivery, where then, taking into account the ambient temperature from step 402 and/or the road surface temperature T _S from step 403, the material temperature in the area of the smoothing plate can still be approximately inferred.

With this material temperature T _mat , which can be determined in step 405 according to the explanations just described, in step 406 the setpoint temperature T set for the smoothing plate _is determined. The target temperature may be set analogously to the above embodiments, such as being above the estimated material temperature (e.g., 10K, 15K, or 20K) and/or the screed temperature ranging between a maximum target temperature and the estimated material temperature .

Based on this setpoint temperature or the corresponding range for the temperature of the smoothing plate, the heating element is then controlled in step 407 by the control unit in accordance with the control circuit already described.

Provision can be made for all of the above-mentioned embodiments that further information is taken into account in order to determine the desired temperature of the heating element. For example, when determining the target temperature, it is possible to take into account which material layer is applied to the substrate, such as a binder layer or a top layer, and set a target temperature depending on this, since different materials can have different requirements in terms of the maximum heat supplied to them , or should not be heated above a limit temperature. Therefore, in order to avoid the material sticking to the smoothing plate on the one hand and excessive heating of the material on the other hand, the temperature in this embodiment is preferably set such that it is only slightly higher than the estimated material temperature. Such information may be available to the control unit via a memory that may be associated with the control unit be asked. They can be stored in this, for example, in the form of one or more data structures, such as tables, and can be called up by the control unit if the setpoint temperature is to be determined.

For example, the recipes of the individual mixture can also be specified as corresponding information, or it can be specified in which temperature range the temperature of the mixture in the area of the smoothing plate may vary at most, in order to determine the target temperature of the smoothing plate from this.

While the previous embodiments of Figures 2 to 4 are essentially described as alternatives to one another, it can also be provided that at least the embodiments of 2 and 3 with the embodiment of 4 be combined.

The embodiment of 4 ultimately, even without measuring the temperature of the screed, allows a target temperature to be set for the screed and then control the heating element to achieve the appropriate temperature.

If the temperature sensor for measuring the temperature of the screed according to the embodiments of FIG 2 and 3 out, it can be provided that the in 4 the method described is used without a control circuit, for example by using information stored in a memory about the amount of heat required to heat the smoothing plate to a specific temperature without a downstream control circuit, which allows a check to be made as to whether this temperature is actually reached, by the control unit, around the heating element 113 (see 1 ) to control accordingly. The heating element can then be controlled so that it outputs about an amount of heat which is usually sufficient to set the temperature of the screed to, for example, 155°C (again, any other desired value can be used). Thus, in the event that the temperature sensor fails, at least roughly, i.e. less precisely than with the embodiments of FIG 2 and 3 , the target temperature of the screed plate can be controlled in order to prevent the material from sticking to the screed plate. With this combination of embodiments, the functionality of the road finisher can thus be maintained even if a temperature sensor that may be provided fails.

Claims (11)

Method for adjusting a temperature of a screed plate of a screed of a road finisher, characterized in that the screed comprises a heating element that heats the screed plate and a temperature sensor that measures the temperature of the screed plate over a period of time, and the road finisher comprises a control unit, which sets a target temperature of the heating element as a function of a time profile of the temperature of the smoothing plate. The method of claim 1, wherein the screed is heated by the heating element to a first temperature and then the heating element is turned off and the screed is brought into contact with material that is applied to a substrate, wherein from the time history of the temperature of the screed after a material temperature is determined by the control unit after the heating element is switched off, and the target temperature is determined as a function of the material temperature. The method of claim 1, wherein the heating element heats the screed to a heat-up temperature less than a material temperature of material being applied to a substrate, and then contacts the screed with the material while the heating element the smoothing plate is heated, the material temperature being determined by the control unit from the temperature profile of the smoothing plate over time while it is being heated by the heating element and being in contact with the material, and the target temperature is determined as a function of the material temperature will. Method according to one of Claims 2 or 3, in which the control unit determines the target temperature from the material temperature by increasing the material temperature by a differential value. Method for adjusting a temperature of a screed plate of a screed of a road finisher, characterized in that the screed comprises a heating element that heats the screed plate, and the road finisher comprises a control unit, wherein the control unit determines the target temperature taking into account an operating parameter of the road finisher and/or the environment and/or the road surface is determined. 6. The method of claim 5, wherein the subsurface operating parameter comprises a pavement surface temperature determined during a temperature scan. Method according to Claim 5 or 6, in which the operating parameter of the paver comprises an indication of the temperature of the material entered into the control unit as it is delivered. A method according to any one of claims 5 to 7, wherein the operational parameter of the environment comprises an ambient temperature. Method according to claim 7 and 8, wherein the control unit determines a material temperature of the material when it reaches the smoothing plate from the material temperature upon delivery and from the ambient temperature and the control unit sets the target temperature depending on the determined material temperature. Method according to one of Claims 1 to 9, in which the control unit uses information stored in a memory assigned to the control unit to determine the setpoint temperature. Road finisher for spreading material onto a subsoil, comprising a material container, a screed and a conveyor system for conveying material from the material container to the screed, the screed being designed to spread material onto the subsoil and the screed having a smoothing plate and a heating element for heating the screed plate, wherein the road finisher comprises a temperature sensor for measuring a temperature of the screed plate and a control unit that is designed to control the temperature of the heating element, wherein the road finisher is designed to carry out a method according to any one of claims 1 to 10.

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