DE102013013452A1 - Method for activating e.g. hydrodynamic retarder for heating internal combustion engine of vehicle to maintain engine operating temperature, involves activating retarder if torque is requested and temperature falls below minimum temperature - Google Patents

Abstract

The method involves determining a current temperature of engine oil or cooling fluid of an internal combustion engine (30) by a fluid temperature sensor (45). Determination is made whether a braking torque is currently requested by a brake input unit (50) by a brake input unit-sensor (55). A retarder (20) of a vehicle (10) is automatically activated by a control unit (60) if the torque is requested and the temperature falls below a preset minimum temperature. An engine brake is activated by the control unit when an amount of the requested torque is not completely provided by the retarder. The brake input unit is an accelerator. An independent claim is also included for a device for activating a retarder of a vehicle.

Description

Temperature-dependent activation of a retarder

The invention relates to a method for activating a retarder of a vehicle, a corresponding device and a corresponding vehicle.

Operating phases of an internal combustion engine in which the cooling water temperature or the engine temperature are low, are disadvantageous, since the wear of the internal combustion engine increases, any exhaust aftertreatment is less efficient and the effect of an engine-dependent heating is limited. Such operating phases occur, for example, in the warm-up phase after a start of the internal combustion engine or during its operation at low temperatures and low power output.

In the DE 10 2006 012 847 A1 For example, a method and apparatus for heating a refrigeration cycle with a retarder are described. In this case, the retarder is automatically switched on in a warm-up phase of the internal combustion engine and emits heating power as a function of operating parameters. The retarder is thereby switched on, if there are still power reserves of the internal combustion engine in the warm-up phase, so that deliberately unnecessary for the driving operation, excess power of the internal combustion engine is converted by mechanical work of the retarder into heat.

The object of the invention is to provide alternative methods and devices with which a retarder of an internal combustion engine contributes to the heating of the internal combustion engine or to the maintenance of a favorable operating temperature.

The invention results from the features of the independent claims. Advantageous developments and refinements are the subject of the dependent claims.

The object is achieved in a first aspect by a method for activating a retarder of a vehicle, wherein the retarder comprises a working fluid, which can be brought into thermal contact with the engine oil and / or the cooling liquid of an internal combustion engine of the vehicle, wherein at least one fluid temperature sensor current temperature T _{akt of} the engine oil or the cooling liquid of the internal combustion engine determined, a Bremsingabemittel sensor determines whether a braking torque is currently requested via a brake input means, and in the event that a braking torque is requested and the temperature T _act undershoot a predetermined minimum temperature T _min , is automatically activated by a control unit of the retarder. If no more braking torque is requested, the retarder is deactivated again.

Retarders are well known to those skilled in the art and are used in vehicles in particular as a so-called continuous brakes, which allow a substantially wear-free brakes, which can be carried out without significantly decreasing braking power over a longer period. Examples of retarders are hydrodynamic retarders in which the working fluid is a liquid, in particular an oil, which generates a braking torque by braking a driveline-related rotor interacting with a fixed stator. Further examples are electrodynamic retarders, in which the working medium is usually a gas and the braking torque is generated via induced magnetic fields. The retarders are directly or indirectly connected to the drive train of the internal combustion engine and brake it on activation with the development of heat, which is dissipated via the working fluid. According to the invention, it is provided that the working medium can be brought into thermal contact with the engine oil and / or the cooling liquid of the internal combustion engine and in thermal contact with the engine oil and / or the cooling liquid in thermal contact, so that a transfer of heat from the working medium is possible. If, for example, a hydrodynamic retarder is flooded on activation with the working medium, this may either already constitute the engine oil or the cooling liquid of the internal combustion engine and thus already be in thermal contact with these two fluids, or the working medium is via a heat exchanger with the engine oil or Coolant can be brought into thermal contact.

The predeterminable minimum temperature T _min is readily determinable by the person skilled in the art depending on the respective internal combustion engine and, according to a development, lies at the lower end, but still within an optimum temperature range specified for the respective internal combustion engine. A suitable minimum temperature T _min , for example, can be preset in the corresponding vehicle as a default value at the factory. If the temperature T _{akt of} the engine oil or of the cooling liquid approaches from above the minimum temperature T _min , it can be counteracted in good time by means of the method according to the invention to a further decrease in temperature before the temperature T _akt leaves the optimum temperature range. Brake after falling below the minimum temperature T _min of the driver of a vehicle from this now by a brake inputting means, that any device which is suitable to initiate a braking operation actuated and thus requests a braking torque, so by the method kinetic energy of the corresponding vehicle to be degraded by means of the braking torque, converted via the retarder into thermal energy and advantageously contributes to that the minimum temperature T _{min of} the engine oil or the cooling liquid of the internal combustion engine is exceeded again.

According to one embodiment, the amount of the requested braking torque continues to be determined via the brake input sensor when a braking torque is determined, and in the event that the amount of the requested braking torque is completely provided by the retarder, only the retarder is activated to provide the braking torque. The amount of the requested braking torque can be determined, for example, via the degree of deflection of the brake input means, for example a brake pedal, wherein a specific deflection is assigned a specific requested braking torque. In this embodiment, all of the braking torque is provided by the retarder, so that it can advantageously emit a maximum amount of heat energy to the engine oil and / or the cooling liquid via the thermal contact, while at the same time the desired braking effect is provided.

In an alternative embodiment, the amount of the requested braking torque continues to be determined via the brake input sensor when a brake torque is requested, and in the event that the amount of the requested braking torque can not be completely provided by the retarder, the control unit activates an engine brake present in the vehicle , Thus, it is advantageously ensured that a heat energy which can be supplied by the retarder is still used to a maximum for heating the engine oil and / or the cooling fluid, wherein the requested braking torque which can not be provided by the retarder is supplemented by a braking torque provided by the engine brake, preferably in full , requested scope is supplemented.

According to a further development, a difference amount or at least the difference between the requested amount of the braking torque and a sum of the amounts of the braking torques that can be provided by the retarder and by the engine brake is automatically provided by a service brake. Thus, in turn, it is ensured that, as before, a heat energy which can be supplied by the retarder is advantageously used maximally for heating the engine oil and / or the cooling fluid, the requested braking torque is provided as far as possible by wear-resistant retarders, namely the retarder and an engine brake, but also a requested braking torque, which goes beyond the brake torque that can be supplied together by the retarder and the engine brake, is reliably provided.

According to one embodiment, the brake input means is an accelerator pedal, a cruise control, a dashboard or steering wheel input means, and / or a brake pedal. In the case of the execution of the brake input as an accelerator pedal can thus already be the reduction or shutdown of the fuel supply or combustion air supply for the internal combustion engine, in particular the reduction to a value required for an idle speed value as a request for a braking torque, which then as far as in the context of the inventive method is provided via the retarder provided that the temperature T _act below the predetermined minimum temperature T _min . If the brake input means is designed as a cruise control, a desired setpoint speed is entered via this. If the instantaneous actual speed of the vehicle is above the desired setpoint speed, then the retarder is activated to reduce the actual speed to the setpoint speed when it is included in the method according to the invention, provided that the temperature T _akt falls below the predefinable minimum temperature T _min . As a further option, it is provided that the brake input means is a dashboard or steering wheel input means, for example a lever or switch with two or more shift positions. In one switching position, a continuous braking function is deactivated, activated in the other, wherein optional intermediate shift positions set different strengths of the retarding function. As yet another option, the brake input means is configured as a brake pedal, or analogously as a hand-operated brake lever. According to a development, the actuation of one of the abovementioned brake input means first of all activates the retarder, and only upon request of a braking torque which is greater than the braking torque which can be provided by the retarder, and / or on actuation beyond a certain position or beyond a resistance an activation of the service brake. According to another embodiment, it is provided that the brake input means can activate both a retarder and an engine brake, but whose actuation primarily activates the retarder before the engine brake, provided that the temperature T _act falls below the predeterminable minimum temperature T _min . Only when a braking torque is requested which exceeds the brake torque that can be provided by the engine brake, the engine brake and, if appropriate, the service brake is activated. Examples of engine brakes are pure engine brakes, which in turn are activated by reducing or shutting off the fuel or combustion air supply, or more powerful engine brakes, For example, engine dust brakes with flap closable exhaust pipes and / or devices for reducing the cylinder pressure after the compression stroke. According to a particular embodiment, the brake input means is designed as a brake pedal or analog as a manually operated brake lever. In this case, corresponds to a region of low deflection, so small depression of the brake pedal, a low requested braking torque, which is provided as part of the process of the invention primarily from the retarder or the retarder with the addition by the engine brake if the temperature T _akt falls below the predetermined minimum temperature T _min. At greater deflection, optionally after overcoming a resistance, an additional braking torque is then provided by the service brake of the vehicle.

In a further embodiment, an outside temperature sensor measures the temperature T _outside the outside air surrounding the internal combustion engine, wherein the predeterminable minimum temperature T _{min is} specified _{externally as a} function of the measured temperature T. In this embodiment, the outside temperature conditions of the environment through which the vehicle moves can be taken into consideration. For example, if the vehicle is moving at low outside temperatures, such as in winter or in the Nordic countries, it is more likely that the temperature of the engine oil and / or the coolant will drop than an excessive increase in temperature. In this case, a predetermined default factory minimum temperature T _min depending on correspondingly low temperatures T can be _externally set up. This has the consequence that when requirements of braking torques, in particular those that can be accomplished by continuous braking, the retarder of the vehicle is often active and thus current temperature T _{act of} the engine oil or the cooling liquid is increased or their drop below an actual critical temperature value prevented or delayed. Conversely, if the vehicle moves, for example, at high outside temperatures, such as in summer or in southern countries, less threatens the risk of lowering the temperature of the engine oil and / or the cooling liquid below a critical value, but rather the risk of overheating of the engine oil and / or the cooling liquid. Accordingly, the default minimum temperature T _min can be set depending on high temperatures T _outside down. The current temperature T _akt will consequently not fall below the minimum temperature T _min or less, which is why the retarder does not or seldom becomes active and does not introduce undesired heat energy into the engine oil and / or the cooling liquid.

The method described above is particularly suitable for operating a device for activating a retarder of a vehicle.

In a second aspect, the object is thus achieved by a device for activating a retarder of a vehicle, wherein the retarder has a working medium which can be brought into thermal contact with the engine oil and / or the cooling liquid of an internal combustion engine of the vehicle, and in a method as described above. In this case, the device comprises at least one fluid temperature sensor, with which a current temperature T _{act of} the engine oil or the cooling liquid of the internal combustion engine is determined, furthermore a brake input sensor, which is used to determine whether a braking input is currently being requested via a brake input means, and furthermore a control unit which is designed and arranged such that in the case in which a braking torque is requested and the temperature T _{act undershoot} a predetermined minimum temperature T _min , the retarder is automatically activated.

Advantageously, this provides a device with which a retarder can be activated as a function of a current temperature T _{akt of} the engine oil or of the cooling fluid and, in addition to a braking torque, in particular a brake torque suitable for sustained braking, further provides a thermal energy which further lowers the minimum temperature T _min of engine oil or coolant slows, stops or reverses. In the context of the above disclosure of the method according to the invention, explicit or implicit disclosures have also been made with regard to the device referred to with regard to the device. Likewise, the following further disclosure of the device optionally contains explicit or implicit disclosures regarding the method according to the invention, to which reference is again made with regard to the method.

According to one embodiment, the working medium of the retarder is the engine oil of the internal combustion engine. According to a particular embodiment, however, the working medium of the retarder is an oil which can be brought into thermal contact with the engine oil of the internal combustion engine via a heat exchanger. In both aforementioned cases, the thermal energy generated by the retarder can be introduced into the engine oil of the internal combustion engine. Preferably, however, the heat generated in the retarder is introduced into the cooling liquid of the internal combustion engine. This is done either directly, if the working medium of the retarder simultaneously represents the cooling liquid of the internal combustion engine, or indirectly, if the working medium of the retarder is a separate liquid from the cooling liquid of the internal combustion engine, for example an aqueous liquid, such as in turn cooling liquid, or in particular an oil, wherein the transmission of the heat energy takes place via a heat exchanger.

In a further aspect, the invention relates to a vehicle which comprises a device according to the invention as described above or in which a method according to the invention is carried out as described above.

Further advantages, features and details will become apparent from the following description in which - where appropriate, with reference to the drawings - at least one embodiment is described in detail. The same, similar and / or functionally identical parts are provided with the same reference numerals. Show it:

1 a schematic flow diagram of a method according to the invention

2 a schematic plan view of a vehicle with a device according to the invention shown.

1 shows a schematic flow diagram of a method according to the invention. In a first process step 100 is via a fluid temperature sensor, a current temperature T _{act of} the engine oil or the cooling liquid of the internal combustion engine 30 determined. In a first process step 200 is via a brake input sensor 55 determines whether via a brake input means 50 currently a braking torque is requested. In the event that a braking torque is requested and the temperature T _akt falls below a predeterminable minimum temperature T _min , in a third method step 300 from a control unit 60 the retarder 20 automatically activated.

2 shows a schematic plan view of a vehicle 10 with a device according to the invention. An internal combustion engine 30 is through a coolant 40 cooled between the internal combustion engine 30 and a radiator not indicated by a reference numeral in the area of the front of the vehicle 10 circulates, which is symbolized by two solid arrows. A fluid temperature sensor 45 determines the temperature of the coolant 40 and transmits them via a symbolized as a dashed arrow data connection to a control unit 60 , By means of a brake input sensor 55 is determined whether and, if appropriate, to what extent a braking torque via a brake input means 50 , which is exemplified as a brake pedal, is requested. The corresponding data are likewise transmitted to the control unit via a data connection (symbolized by a dashed arrow) 60 transmitted. Below that of the fluid temperature sensor 45 determined current temperature T _{act of} the cooling liquid 40 a predefinable and the control unit 60 known minimum temperature T _min and is simultaneously on the brake input means 50 requested a braking torque, then activates the control unit 60 via a data line (symbolized by an arrow with dotted line) a retarder 20 , for example by introducing a working medium 25 in the case of a hydrodynamic retarder or by generating required magnetic fields in an electrodynamic retarder. The activated retarder 20 is in connection with a not separately shown drive train of the internal combustion engine 30 and provides a braking torque over which the vehicle 10 is braked during a continuous braking.

Although the invention has been further illustrated and explained in detail by way of preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention. It is therefore clear that a multitude of possible variations exists. It is also to be understood that exemplified embodiments are really only examples that are not to be construed in any way as limiting the scope, applicability, or configuration of the invention. Rather, the foregoing description and description of the figures enable one skilled in the art to practice the exemplary embodiments, and those skilled in the art, having the benefit of the disclosed inventive concept, can make various changes, for example, to the function or arrangement of individual elements recited in an exemplary embodiment, without Protected area, which is defined by the claims and their legal equivalents, such as further explanation in the description.

LIST OF REFERENCE NUMBERS

10

vehicle

20

retarder

25

Working medium of the retarder

30

internal combustion engine

40

Coolant of the internal combustion engine

45

Fluid temperature sensor

50

Brake input means

55

Brake input means sensor

60

control unit

70

heat exchangers

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006012847 A [0003]

Claims (10)

Method for activating a retarder ( 20 ) of a vehicle ( 10 ), whereby the retarder ( 20 ) a working medium ( 25 ), which with the engine oil and / or the cooling liquid of an internal combustion engine ( 30 ) of the vehicle ( 10 ) is brought into thermal contact, wherein - at least one fluid temperature sensor ( 45 ) an actual temperature T _{act of} the engine oil or the cooling liquid of the internal combustion engine ( 30 ), - a brake input sensor ( 55 ) determines whether via a brake input means ( 50 ) is currently a braking torque is requested, and - in the event that a braking torque is requested and the temperature T _{act undershoot} a predetermined minimum temperature T _min , from a control unit ( 60 ) the retarder ( 20 ) is activated automatically. Method according to claim 1, characterized in that via the brake input sensor ( 55 ) is determined at the request of a braking torque further the amount of the requested braking torque, and in the event that the amount of the requested braking torque completely from the retarder ( 20 ) can be provided to provide the braking torque excluding the retarder ( 20 ) is activated. Method according to claim 1, characterized in that via the brake input sensor ( 55 ) is determined at the request of a braking torque further the amount of the requested braking torque, and in the event that the amount of the requested braking torque is not completely from the retarder ( 20 ) is provided by the control unit ( 60 ) one in the vehicle ( 10 ) existing engine brake is activated. A method according to claim 3, characterized in that a difference between the requested amount of the braking torque and a sum of the amounts of the braking torque from the retarder ( 20 ) and provided by the engine brake is automatically provided by a service brake. Method according to one of the preceding claims, characterized in that the brake input means ( 50 ) is an accelerator pedal, a cruise control, a dashboard or steering wheel input means, and / or a brake pedal. Method according to one of the preceding claims, characterized in that an outside temperature sensor the temperature T _outside of the internal combustion engine ( 30 ) ambient ambient air and the predetermined minimum temperature T _{min is determined} depending on the measured temperature T _outside . Device for activating a retarder ( 20 ) of a vehicle ( 10 ), whereby the retarder ( 20 ) has a working medium, which with the engine oil and / or the cooling liquid ( 40 ) of an internal combustion engine ( 30 ) of the vehicle ( 10 ) is brought into thermal contact, and in which a method according to one of claims 1 to 6 is carried out, comprising - at least one fluid temperature sensor ( 45 ), with which a current temperature T _{act of} the engine oil or the coolant ( 40 ) of the internal combustion engine ( 30 ), - a brake input sensor ( 55 ), with which it is determined whether via a brake input means ( 50 ) currently a braking torque is requested, and - a control unit ( 60 ), which is designed and arranged in such a way that in the case in which a braking torque is requested and the temperature T _{act undershoot} a predetermined minimum temperature T _min , the retarder ( 20 ) is activated automatically. Apparatus according to claim 7, characterized in that the working medium ( 25 ) of the retarder ( 20 ) via a heat exchanger ( 70 ) in thermal contact with the cooling liquid ( 40 ) of the internal combustion engine ( 30 ) is oil that can be brought. Apparatus according to claim 7, characterized in that the working medium ( 25 ) of the retarder ( 20 ) the cooling liquid ( 40 ) of the internal combustion engine ( 30 ). Vehicle ( 10 ) comprising a device according to any one of claims 7 to 9.

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