DE102007058575B4 - Motor vehicle with compressed air based cooling system - Google Patents

Abstract

Motor vehicle with an engine, the engine having a liquid cooling system (2) for cooling the engine and the cooling liquid of this liquid cooling system (2) during operation of the engine is under a predetermined pressure, and at least one sensor, which at least one Operating state of the engine detected and which outputs a characteristic of this operating condition signal, the motor vehicle having a compressed air system (10), and between the compressed air system (10) and the cooling system, a connecting line (12) is provided which the cooling system (2) at least temporarily supplied with compressed air, wherein a control device (30) is provided, which controls the supply of the cooling system (2) with compressed air in response to the signal output from the sensor (14), and wherein between the compressed air system (10) and the cooling system (2 ) a pressure reduction device (20) is provided by means of the of the Druckluftsyy Stem (10) to the cooling system (2) reaching pressure can be reduced so that a depending on the operating condition according to demand overpressure in the cooling system (2) is provided, characterized in that the pressure reducing means (20) comprises two pressure reducing valves (24, 25), where a controllable valve (22, 23) is connected upstream.

Description

The present invention relates to a motor vehicle and more particularly to a road vehicle which is at least powered by an internal combustion engine. Such engines typically include liquid cooling systems wherein a cooling fluid is circulated to cool the heating parts of the engine.

Such vehicle cooling systems require overpressure to prevent boiling and cavitation of the usually liquid coolant. This overpressure is generated by the heating of the coolant during operation of the vehicle. The size of a compensation volume and the coolant temperature determines the resulting overpressure. When starting the engine, the coolant is usually cold and therefore there is no overpressure, which may cause cavitation on the Wasserpumpensaugseite may occur. With increasing warming of the coolant, this expands, and generates in the system an overpressure, which shuts off the cavitation phenomenon at a certain level, as from this pressure no shortfall of the vapor pressure occurs.

This is the problem in the prior art that not always sufficient overpressure in the cooling system is available, but this is dependent on the coolant temperature.

If, after operation of the engine, this is switched off, locally hot parts can occur within the engine and, in turn, due to the now lacking flow, the coolant can boil up. The resulting vapor bubble displaces coolant into the expansion tank. If the equalization volume of the surge tank is too small, coolant loss can occur in this way. Another problem in the prior art is therefore to be seen in that it can come to a boiling of the coolant at engine standstill.

Furthermore, pressure relief valves are usually used in motor vehicles. These can lead to a drop in tightness due to dirt particles which, for example, due to ventilation when the opening pressure is exceeded. It is also possible that leaks occur as a result of aging of the seals, it being noted here that the seals are made of elastomers.

In the presence of such leaking pressure relief valves, it may happen that no or only too low excess pressure builds up, so that cavitation can take place permanently, which in turn leads to reduced water pump delivery and coolant loss. Also, it can permanently lead to loss of coolant when hot shut off as there is no sufficient pressure to increase the boiling temperature is available.

In the DE 10 2005 007 781 a method and an arrangement for rapid construction of the system pressure in the cooling system of an internal combustion engine is provided. The expansion tank of the cooling system is connected to a driven by the internal combustion engine pressure generator.

From the DE 37 16 555 is a liquid-cooling circuit for power and working machines, in particular internal combustion engines, with which the safety against pump cavitation is increased during operation at relatively high speeds.

The DE 29 31 821 describes a coolant circuit for an internal combustion engine, which comprises a compressed air generating device for increasing the boiling temperature of the coolant. The compressed air generating device has a diaphragm pump, which is connected to the suction side of an air processor.

In the DE 33 45 931 a cooling circuit for an internal combustion engine with a pressure and volume expansion tank is described. The compressed air source used here is the exhaust air pressure side of a vacuum air pump.

Next is from the DE 101 38 083 A1 a cooling water circulation system for an internal combustion engine, in which a pressure level is generated by a compressor of an exhaust gas turbocharger, which allows using a pressure control valve to set a constant pressure level in a surge tank of a cooling system. Above this pressure level, the pressure level on the suction side of the cooling water pump is raised, whereby the cavitation can be reduced. According to one embodiment, a valve may be provided in a pressure control line, which is controlled by an electronic control unit as a function of input variables. Such input variables may be the pressure level of the suction side of the cooling water pump, the temperature of the cooling water and the engine speed.

The present invention has for its object to provide a device available, on the one hand ensures sufficient overpressure in the cooling system regardless of the coolant temperature on the other hand, a sufficient or increased overpressure in a motor standstill provides to suppress boiling and finally a tracking a lost by a leak overpressure allows.

More specifically, an apparatus and a method for controlling the overpressure in cooling systems are to be provided, which is designed to avoid boiling and cavitation to such an extent that in the operating conditions occurring during vehicle operation, the respectively required overpressure is set.

This is achieved according to the invention by the subject matter of the independent claims. Advantageous embodiments and further developments are the subject of the dependent claims.

According to claim 1, a motor vehicle on an engine, wherein the engine has a liquid cooling system for cooling the engine and the cooling liquid of this liquid cooling system is during operation of the engine under a predetermined pressure. In addition, the motor vehicle and preferably the motor has at least one sensor which detects at least one operating state of the motor and which outputs a signal characteristic of this operating state.

Furthermore, the motor vehicle has a compressed air system and between this compressed air system and the cooling system, a connecting line is provided which supplies the cooling system at least temporarily with compressed air. Furthermore, a control device is provided, which controls the supply of the cooling system with compressed air as a function of the signal output by the sensor.

This is achieved by supplying compressed air into the cooling system that the period of insufficient excess pressure in the cooling system is shortened or eliminated and in this way the period is shortened, in which cavitation can occur on the water pump suction side. More specifically, this supply of compressed air in the cooling system is set to a tolerable for a normal engine operation pressure.

The use of the sensor ensures that the compressed air is supplied only in certain operating conditions of the vehicle, for example at a certain temperature of the coolant, a certain pressure thereof or after shutdown.

The cooling systems commonly used today are designed so that the overpressure in the cooling systems is limited to 0.6-1.1 bar by means of a pressure relief valve. With the mentioned additional dynamic pressure generated by the water pump, overpressures occur locally in the cooling system, to which the respective components such as the water cooler, the heating heat exchanger and the hoses are designed in terms of strength.

The load capacity of these components simultaneously limits the usable cooling water overpressure.

When hot shutdown of an engine usually eliminates the coolant circulation. This eliminates the dynamic overpressure by the water pump so that only a cooling system overpressure, which is between 0.6 and 1.1 bar is available, so that, as mentioned above, boiling occurs in hot spots. To safely suppress this boiling, high overpressure - considerably more than 1 bar - is required or a correspondingly large compensating volume in which the amount of coolant displaced by the vapor bubble is absorbed. This can also be achieved by the present invention that this compensating volume is reduced or an existing compensating volume is operated in the cooling system with higher coolant temperatures.

Further, a pressure reducing device is provided between the compressed air system and the cooling system, by means of which the reaching of the compressed air system to the cooling system pressure can be reduced so that depending on the operating condition needs adequate pressure in the cooling system is provided.

Since the pressure level of this compressed air system is usually above 8 bar, it is too high for the coolant circuit, so that the pressure is lowered by the pressure reducing device.

According to the invention, the pressure reducing device on two pressure reducing valves, which is preceded by a controllable valve. More specifically, it is possible to connect these two pressure reducing valves a solenoid valve, these pressure reducing valves can be switched depending on the operating condition with this one solenoid valve. Preferably, these two pressure reducing valves have different working pressures. Thus, the one pressure reducing valve can have a working pressure between 0.6 and 1, 1 bar and the second pressure reducing valve a working pressure between 1 and 2 bar. Thus, the first mentioned pressure reducing valve is used in normal vehicle operation and the second pressure reducing valve, for example, after stopping the engine to prevent boiling.

In a further advantageous embodiment, the liquid cooling system has an auxiliary container and the connection line opens into this expansion tank. Of the Expansion tank is particularly suitable for reducing excess pressure, since, as mentioned above, it has a compensation volume, in which directly the overpressure can be fed.

The controllable valve may be a pressure regulating valve, which is regulated depending on the operating state.

The controller may control the supply of the cooling system with compressed air in response to an operating condition of the engine. These operating states can be, for example, an on or off state, ie the decision as to whether the engine is running or not. Also, in an operating state may be a cooling water temperature or a time interval after stopping the engine. Furthermore comes as operating condition and a pressure of the coolant in the cooling system into consideration.

The pressure reduction device preferably has a pressure regulating valve which regulates the pressure as a function of an operating state of the engine. Thus, the two different pressure levels required in the operating state can be achieved in different ways.

Advantageously, the motor vehicle has a large number of sensors which detect operating states of the engine, wherein the sensors are designed such that they forward signals characteristic of the operating states to the control device. As mentioned above, these conditions may be operating temperatures, times and the like.

Furthermore, the control device particularly preferably has a process device which logically combines the characteristic signals. It is thus possible to switch a specific valve only if, on the one hand, no more than 15 minutes have passed after the engine has been switched off and, on the other hand, the coolant temperature is above 100 °. Also, corresponding logical OR operations would be conceivable.

The present invention is further directed to a method of operating an automotive engine, and more particularly an internal combustion engine.

In particular, the compressed air system is the compressed air system which is used for the brake system of the vehicle. The existing in this compressed air system pressure usually continues even after the engine is switched off and can therefore be used to supply the cooling system with compressed air. It should be noted that instead of compressed air, other gaseous media can be used.

The resulting advantages have already been presented in detail before.

Further advantages and embodiments will become apparent from the attached drawing:
In the single figure, the reference numeral refers 2 on a partially illustrated liquid Kühlystem. More precisely, here is a surge tank 4 for this cooling system 2 shown. In this expansion tank 4 there is coolant 5 , which reaches here to a level N level. If, as mentioned above, form vapor bubbles within the cooling circuit, the space lying above the level N level can 7 be used to accommodate this expansion. However, if the level rises further than the room 7 allows, coolant is via an outlet 8th leak out and get lost in this way for the cooling circuit. The reference number 6 refers to a pipe that opens into the cooling circuit.

The reference number 10 refers generally to a compressed air system of the vehicle. In this case, the reference numeral 11 a compressed air tank for the vehicle. About a connecting line according to the invention 12 stands this compressed air system 10 with the liquid cooling system 2 in connection with, as mentioned above, this connection line 12 preferably in the expansion tank 4 the cooling system and more preferably in the area 7 of the expansion tank 4 that is, the area above the liquid level N opens.

That way the pressure in the room can be reduced 7 and thus the pressure on the coolant 5 be increased if necessary so that, for example, the occurrence of vapor bubbles can be at least partially compensated.

The reference number 20 refers to a pressure control, which in the reservoir 4 reaching pressure of the compressed air controls. More specifically, this is a pressure reducer 20 , which from the compressed air system 10 lowers escaping pressure.

At the in 1 embodiment shown, this pressure reducing device 20 two solenoid valves 22 and 23 on and these solenoid valves 22 . 23 downstream pressure reducing valves 24 and 25 , The two solenoid valves 22 and 23 be via a control device 30 controlled and in response to the signals from various sensors 14 ,

The pressure reducing valve 24 reduces the pressure of the compressed air system 10 originating pressure to a pressure in the range of 0.6-1.1 bar. The pressure reducing valve 25 reduces this pressure to a pressure between 1 and 2 bar.

Depending on the sensors 14 Measured signals can either be access to the pressure reducing valve 24 or access to the pressure reducing valve 25 released or both accesses are blocked or opened.

For example, if it is detected by the sensors that the engine is running, it is possible to use the solenoid valve 22 to open and thus a pressure between 0.6 and 1.1 bar on the expansion tank 4 and thus allow the cooling circuit. If the engine is in another operating state and the temperature of the cooling water is above a certain value, for example above 100 °, the first solenoid valve 22 closed, the solenoid valve 23 opened and over the pressure reducing valve 25 a pressure of 1,1-2 bar allowed on the cooling circuit.

Furthermore, it is possible to determine the time after which the engine has been switched off and, for example, to allow a pressure between 1.1 and 2 bar over a period of 15 minutes, by the solenoid valve 23 opened and the solenoid valve 22 is closed.

LIST OF REFERENCE NUMBERS

2

Vehicle Cooling System

4

surge tank

5

coolant

6

management

7

room

8th

exit

10

Compressed air system

11

Air receiver

12

connecting line

14

sensors

20

pressure control

22, 23

magnetic valve

24, 25

Pressure Reducing Valves

26

Pressure control valve

30

control device

N

filling level

Claims (5)

Motor vehicle with an engine, the engine having a liquid cooling system ( 2 ) for cooling the engine and the cooling liquid of this liquid cooling system ( 2 ) is under a predetermined overpressure during operation of the engine, and with at least one sensor which detects at least one operating state of the engine and which outputs a signal characteristic of this operating state, wherein the motor vehicle is a compressed air system ( 10 ), and between the compressed air system ( 10 ) and the cooling system a connecting line ( 12 ) is provided, which the cooling system ( 2 ) at least temporarily supplied with compressed air, wherein a control device ( 30 ) is provided which the supply of the cooling system ( 2 ) with compressed air as a function of that of the sensor ( 14 ) and wherein between the compressed air system ( 10 ) and the cooling system ( 2 ) a pressure reducing device ( 20 ) is provided by means of that of the compressed air system ( 10 ) to the cooling system ( 2 ) pressure is so reducible that a depending on the operating condition needs-based overpressure in the cooling system ( 2 ), characterized in that the pressure reducing device ( 20 ) two pressure reducing valves ( 24 . 25 ), to which a controllable valve ( 22 . 23 ) is connected upstream. Motor vehicle according to claim 1, characterized in that the liquid cooling system ( 2 ) a surge tank ( 4 ) and the connecting line ( 12 ) opens into this expansion tank. Motor vehicle according to claim 1 or 2, characterized in that the motor vehicle a plurality of sensors ( 14 ), which detect operating states of the engine, wherein the sensors ( 14 ) are designed in such a way that they send signals which are characteristic of the operating states to the control device ( 30 ) hand off. Motor vehicle according to claim 3, characterized in that the control device ( 30 ) a processor device ( 32 ), which logically combines the characteristic signals. Method for operating a motor vehicle according to one of Claims 1 to 4, characterized in that one of the pressure-reducing valves ( 24 ) is used to apply compressed air when the engine is in operation, and that one of the pressure reducing valves ( 25 ) is used to apply compressed air when the engine is stopped.

Images