EP1036883B1 - Process for heating a screed of a road paver and corresponding road paver - Google Patents

Description

The invention relates to a method according to the preamble of claim 1 and a paver according to the preamble of the independent claim 7.

When it comes to ready-to-use pavers, it is known from practice that working components of the screed to be heated either electrically or with gas. This applies in particular to the so-called Tamper bars, the smoothing plates and any pressure bars provided. This Working components must be heated until the likewise hot installation material no longer tends to stick. The temperature of the paving material used by the screed installed, is e.g. about 170 ° C. The heating must be done during the Installation to be continued. With an electric screed heater For example, electrical heating rods in the screed, which are distributed over one of the Primary drive source, usually a diesel engine, driven three-phase generator Three-phase supply. It is common practice to use screed heating equipment to operate permanently and at full capacity. However, this will make the three-phase generator especially under unfavorable operating conditions, extremely stressed and / or considerable energy is wasted.

From DE-A-195 37 691 it is known for a paver to have every heating element an assigned thermostat when a maximum temperature is exceeded or Switching on or off individually when the temperature falls below a minimum temperature. To this The setpoint temperature of the working component heated by the respective heating element becomes of the screed.

From GB-A-21 28 374 it is for a room heater with several electric heating elements known to switch on and off at least some heating elements clocked. Dependent on The clocking for these heating elements is based on the detected room temperature varies individually until the respective heating element is either switched off completely or permanently remains switched on.

The invention has for its object a method of the type mentioned and to specify a road paver suitable for carrying out the method, with which an energy saving and long Service life of the three-phase generator can be achieved.

The task is with the features of claim 1 and the sibling Claim 7 solved.

If there is a risk of overloading or Overheating of the alternator, then the load on the alternator by alternating switching between at least two heating elements in the left and right screeds - halves reduced, see above that the three-phase generator can cool down or its critical operating temperature not reached. This also relates Extending screed parts on the left and right halves of the screed, and if necessary also widened parts that also have to be heated. During the cycle, the three-phase generator therefore only needs about 50% of the deliver maximum performance. The knowledge that the heated working components of the screed despite switching off their heating elements have a relatively long run-on time, during which there is no noticeable temperature drop occurs, and that even in the installation phase, the heated paving material provides enough heat so that there is no loss of installation quality due to clocking occurs and also an inappropriate contamination of the working components omitted. Additive is carried by the paving material Heat is taken into account in order to save energy through the clocking and still one ensure sufficient heating of the screed. The timing is only useful controlled during the paving operation of the screed, for the first time Heating of the screed is not delayed and that of the paving material to use the heat carried along profitably when the paver is paving and there is sufficient external heat available.

At the paver, the management section in the heating system monitors various operating parameters on the side of power generation and in the road to buy the declined Controlling performance to a permissible maximum, namely by modulated Switching between heating elements, whereby carried by the installation material Heat used profitably, energy saved and the three-phase generator, e.g. protected against overload under unfavorable operating conditions.

To ensure the safety of the three-phase generator, the clocking can then be activated in any case be when the operating temperature of the alternator by predetermined temperature value, e.g. 20 ° C, above the ideal operating temperature should be. As a rule, this is still far below the critical level Three-phase generator temperature threshold. By alternating clocking reduce the load on the three-phase generator so far that it is up to cools down to the ideal operating temperature.

The cycle times are expediently approximately 30 seconds. These are periods of time which have no noticeable influence on the quality of the installation or the tendency to become dirty the screed and make sure that none are clearly noticeable Temperature leaps occur in the screed.

The operating parameters "travel of the Paver, promotion of the paving material and nominal speed of the primary drive source ".

The operating temperature of the three-phase generator can be measured with high reliability using temperature-sensitive resistors in its winding. Multiple temperature sensitive resistors are useful to monitor different temperature thresholds to be able to.

If an additional heating, if applicable, is to be provided across the screed, this remains excluded from the switching cycle.

Schuko and / or CEE sockets on the Asphalt pavers and / or the screed allow additional auxiliary equipment connect, e.g. Lighting devices for maintenance and / or night work.

The current current value is measured by means of a current transformer and on the basis the power value is calculated and reported to the section.

Expediently, further sockets are provided on the screed, on which Have heating elements of widening parts of the screed connected. This Heating elements of the widening parts can take part in the change cycle.

Fig. 1

ist ein Blockschaltbild einer Ausführungsform einer elektrischen Heizeinrichtung einer Einbaubohle eines Straßenfertigers.

The method according to the invention and a paver with an embodiment of an electric heating device are explained on the basis of the drawing:

Fig. 1

is a block diagram of an embodiment of an electric heater of a screed of a paver.

The essential components of an electrical heating device of a screed towed by a road paver, not shown B are in the block diagram shown schematically in Fig. 1.

A primary drive source Q, usually a diesel engine, of the road paver, not shown drives a three-phase generator G, from the supply lines 1, 2 to two screed halves 3, 4 of the screed B or heating elements E integrated therein to lead. The heating elements E are used to heat working components of the screed. These working components are, for example, tamper bars N, smoothing plates R and optionally provided pressure bars L, which are approximately at the temperature of the paving material must be heated so that the paving material does not adheres.

The heating device H has a control device C in which a microprocessor management section M is provided in which various operating parameters of the Paver and / or the screed is monitored and used to control the heating device be taken into account. At the control device C is a heating pre-selection switch W connected, adjustable between positions "zero, automatic, manual" is. In the "zero" position, the heating device is switched off. In the "automatic" position the heating device H is controlled automatically, with an alternating cycle to protect the three-phase generator G and to save energy and to optimally regulate the maximum permissible heating output. In the "hand" position the heating device H operated permanently and with full heating power. The protective measures for the generator can also be activated in the "hand" position.

So that the microprocessor management section M different operating parameters can take into account, it receives information and measurements and confirmations from various connected facilities. In the winding, not shown of the three-phase generator G, temperature-sensitive resistors are distributed, which differ Monitor operating temperature thresholds and by type of sensors T submit the respective measured values. The output of the three-phase generator G is one Current monitoring D is provided for power control, which is also connected to the control device C is connected. The current monitor D is a current transformer, which is the current value of one of the three phases of the alternator Section M reports. It is due to a symmetrical power rating of the load possible to get by with the measurement of only one phase and based on this measurement to calculate the power per phase. The speed of the primary drive source Q is detected by a device Qn and reported to the control device C. Further an insulation monitoring device J is provided which is connected to the screed B is connected, is controlled by section M and a good or bad signal transmitted. Using a voltage regulator that is not highlighted, the Generator voltage kept constant at 230 V per phase towards zero. The insulation monitoring device J measures the resistance between the live and the Neutral against earth. Therefore, the heating elements must have a PE conductor be grounded. If an insulation fault occurs, the insulation monitoring device J triggers and reports the error. Section M then carries out troubleshooting and gives only fault-free circuits free.

From the microprocessor management section M several contactors S1 to S5 driven. Contactors S1 and S2 are included in supply lines 1, 2 and are controlled depending on the operating situation. It expediently acts are four-pole contactors. Another contactor S5 is for the power supply a possibly additional plank heating 7 provided, which either is operated permanently or, depending on the operating situation, is switched off.

Additional contactors S3, S4 are provided for sockets F, expediently Schuko and / or CEE sockets. The CEE sockets and their leads are hedged. Due to the high temperatures in the screed B, the hedge must be used be made on the paver, expediently by a Motor protection switch. The motor protection switch serves as line protection. fused are all other supply lines too. Because of the temperature compensation the motor protection switch can be set to the maximum permissible nominal current of the screed be interpreted. The CEE sockets can be used for frequency-independent Devices, e.g. Lighting equipment. On the Schuko sockets, however, are likely only 50 Hz devices can be connected. Give the two shooters S3, S4 approval for CEE and Schuko sockets F depending on the operating state and alternative.

Furthermore, temperature sensors provided on the working components in the screed A connected to the microprocessor management section M.

Sockets 8 attached to the screed B can be used for the heating elements of any extension parts 5, 6 attached to the power supply.

The release of the heating device depends on the section M Fulfills several conditions. These conditions for heating release are for example: heating pre-selection "manual or automatic"; depends on the Design of the three-phase generator G (heating only at nominal speed of the primary drive source, or enable heating at idling and at nominal speed) Confirmation the presence of idle speed or full throttle speed; Insulation monitoring device J not addressed; and second alternator temperature threshold not reached.

If the second three-phase generator temperature threshold is reached, then the heating device not released. The release takes place only after the Three-phase generator has cooled down and the heating pre-selector switch W is adjusted acknowledged to "zero".

An insulation monitoring acknowledgment switch, the microprocessor management section M and the insulation monitoring device J are in a control box on the paver (not shown).

The screed is connected via several wiring harnesses and CEE plugs (e.g. five wiring harnesses) connected to the control box.

If, after activating the heating preselection switch W, the aforementioned conditions for heating release are fulfilled, the heating process begins, controlled by the Section M. After starting the heating process, the different heating combinations controlled and the power requirement calculated per combination. The combinations are then ranked according to their performance. Then every combination checked for validity. The combination with the greatest valid performance is Approved.

Due to the linear characteristic of the temperature-dependent resistors, which in the Windings of the three-phase generator G are accommodated, several Thresholds are set. If due to extreme conditions the generator Reached 20 ° C above its ideal operating temperature (warning threshold), the Regulation in section M, also in the "manual" switch position, for a clock cycle. This means that, for example, the heating elements E in the left half of the screed have a predetermined period of time, e.g. 30 seconds, be turned off, and only the heating elements stay switched on in the right half of the plank. After this elapse The heating elements in the right half of the screed are switched off and those of the left half of the planks switched on again. This is repeated continuously. This allows the three-phase generator to cool down again, provided it there is no fault that leads to further heating. Another so-called The shutdown temperature threshold is set just below the critical temperature the generator winding. If this switch-off threshold is reached, there is an immediate one Complete shutdown of the heating device. Only some, all or only can be clocked a heating element can be switched on and off.

To check the validity of the power release, press the heating preselector W the performance of the various heating combinations with the Characteristic of the generator temperature correlated and released accordingly.

If the heating selector switch W is set to "Automatic" (normal operation), then the microprocessor management section M conducts the validity check of the release provided that the aforementioned conditions for heating release are met. Subsequently the section modulates the removed power to a maximum, so that the generator temperature always remains within the permissible range.

The screed or the heating elements E must be heated until the Working components N, R, L are heated so far that the installation material on them and not stuck to the screed. After the time required for heating has elapsed can be started with the installation. The temperature of the paving material is about 170 ° C. To in the installation phase due to the supplied by the installation material The temperature and the temperature storage capacity of the screed Temperature in the working components, e.g. Smoothing plates, vibrators, tamper bars and pressing bars, to keep approximately constant, is actually no longer the full performance needed. Therefore, the switching cycle is controlled so that the right and left sides of the planks can be switched on alternately over approx. 30 seconds. The Three-phase generator G then only needs 50% of the total screed output deliver is less burdened. It also saves a lot of energy.

At an operating temperature of the generator below the warning threshold, the Alternating clocking only activated when the screed is hot Paving material, i.e. during the installation phase. This happens after the paver's main switch is set to the "forward drive" position and the material conveying device is switched on and the diesel engine as the primary drive source runs at full throttle.

In the heating phase, the power is modulated in the "Automatic" position so that it remains at an allowable maximum, e.g. proportional to the generator temperature. In the "manual" position, the power is not modulated in the heating phase, but rather possibly clocked from a critical generator temperature. In the "automatic" position there are therefore two possibilities of influence, which are used alternatively or additively can be.

The "hand" position has, for example, at low ambient temperatures and / or cold installation material your justification.

Claims (13)

1. Method for heating the electric heating assembly (H) equipped paving screed (B) of a road finisher, the heating assembly (H) including electric heating elements (E) at least in left and right paving screed halves (3, 4), the electric heating elements being supplied with current by a rotary current generator (G), the heating elements being switched on and switched off by a control device (C) during the paving operation phase of the road finisher, characterised in that heating elements (E) in the left and right paving screed halves (3, 4) are interchangeably clocked in dependence from the operation temperature of the generator (G) or from the operation temperature of the generator (G) and of paving screed components which are in contact with paving material by periodically alternatingly switching on and switching off the heating elements (E), and that during clocking a switched off heating element is switched on immediately when an earlier switched on heating element is switched off.
2. Method as in claim 1, characterised in that for clocking at least two of the heating elements (E) of the paving screed (B) are periodically alternatingly switched on and off.
3. Method as in claim 2, characterised in that the heating elements are clocked as soon as a generator temperature threshold is exceeded as defined by a predetermined temperature value above an ideal generator operation temperature.
4. Method as in claim 1, characterised in that the clock intervals amount to between 15 seconds and 5 minutes, preferably last approximately 30 seconds.
5. Method as in claim 1, characterised in that the heating elements are clocked first when a main drive switch of the road finisher is set to "paving travel forwards", when a conveying device for paving material is set to "feed", and when a primary drive source (Q) is set to "rated speed".
6. Method as in claim 2, characterised in that the operation temperature of the rotary current generator (G) is detected by a plurality of temperature sensitive resistors (T) which are inserted into the generator winding, preferably at several temperature thresholds.
7. Road finisher comprising a paving screed (B) in which an electric heating assembly (H) is installed which has heating elements (E) associated to operating components (N, R, L) provided in left and right paving screed halves (3, 4), the heating elements being connected each alone or in groups via a control device (C) including a microprocessor to a rotary current generator (G), characterised in that the control device (C) comprises a management section (M) which is connected to sensors (T, A, D, J) for detecting the operation temperatures of the rotary current generator (G) and of the operating components (N, R, L) of the paving screed (B), for monitoring the current power control state, and for surveying the electric insulation state within the paving screed, and, furthermore, is connected to a heating operation pre-selector switch (W) and a speed detecting assembly (Qn) of a primary drive source (Q), and that the control device (C) contains a programming for the control of a periodic alternating clocking of at least two heating elements (E) in the left and right paving screed halves (3, 4) in dependence at least from the operation temperature of the rotary current generator (G).
8. Road finisher as in claim 7, characterised in that the sensors (T) for sensing the operation temperature of the rotary current generator (G) are temperature sensitive resistors provided in the winding of the rotary current generator for surveying a first temperature threshold and a switch off temperature threshold.
9. Road finisher as in claim 7, characterised in that the paving screed (B) has an auxiliary heating assembly (7) extending over the entire paving screed extension and including at least one further heating element (E), the auxiliary heating assembly being excluded from the periodic alternating clocking control.
10. Road finisher as in claim 7, characterised in that at least contactors (S3, S4) for outlets (F) provided at the road finisher and/or at the paving screed (B) for plugging-in 50 Hz devices and/or frequency independent devices are connected to the management section (M).
11. Road finisher as in claim 7, characterised in that at least one current monitoring system (D) is connected to the management section (M), the system (D) including a current converter for measuring the actual current, the system (D) being provided in supply lines (1, 2), preferably located between the rotary current generator (G) and the contactors (S1, S2) which are controlled by the management section (M).
12. Road finisher as in claim 7, characterised in that the rotary current generator (G) has a layout design for powering the heating assembly (H) for operation either at the rated speed of the primary drive source (Q) or within a speed range between the idling speed and the rated speed, respectively.
13. Road finisher as in claim 10, characterised in that further outlets (8) are provided at the paving screed (B) for connecting further heating elements of paving screed broadening parts (5, 6), the further outlets being controlled by the management section (M).

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