Cooling system for an internal combustion engine

Abstract

Cooling system (1) for an internal combustion engine (2), comprising a cooling circuit (5) with a first section (6) passing through a cylinder head (4), a second section (9) passing through an engine block (3) downstream, and a cooler section (12) arranged downstream of the second section (9) and upstream of the first section (6), characterized by a third section (10) connected to the first section (6) in parallel to the second section (9) and bypassing the engine block (3), which passes through an oil cooler, part of a heating and ventilation system, or other vehicle components that are to be heated or cooled and which are not part of the engine, i.e., external to the engine, before the second section (9) and the third section (10) are joined again at the inlet of the cooler section (12), and wherein a control unit (30) is configured toto determine a required relative temperature increase of the engine block (3) relative to the cylinder head (4) and to control a pump arrangement (7) for supplying coolant in the cooling circuit (5) in order to reduce a coolant flow in the first section (6) to achieve a relative temperature increase, wherein the control device (30) is configured to determine the required relative temperature increase at least partially based on an engine load and wherein the control unit (30) is configured to increase the coolant flow with a delay when the engine load is increased and to decrease it with a delay when the engine load is decreased.

Description

[0001] The invention relates to a cooling system for an internal combustion engine having the features of the preamble of claim 1.

[0002] The generic patent DE 102 19 481 A1 describes an internal combustion engine with a cylinder crankcase and a cylinder head, with a cooling water circuit comprising a first cooling water channel extending between an inlet opening and an outlet opening in the cylinder head, and with a second cooling water channel extending separately in the cylinder crankcase between an inlet opening and an outlet opening, and with a common cooling water pump arranged in the cooling water circuit, wherein a third cooling water channel connects the outlet opening of the first cooling water channel formed in the cylinder head with the inlet opening of the cooling water pump, and wherein a fourth cooling water channel connects the outlet opening of the cooling water pump with the inlet opening of the second cooling water channel formed in the cylinder crankcase for conveying the cooling water from the first to the second cooling water channel.

[0003] Internal combustion engines in motor vehicles are known to consist of an engine block and a cylinder head. These engine components typically each have a coolant jacket or water jacket through which a coolant, such as a water-glycol mixture, can be pumped. A common cooling circuit design involves arranging the coolant jackets of the engine block and the cylinder head parallel to each other with respect to the coolant flow. To achieve improved engine block warm-up during a cold start, for example, while simultaneously maintaining coolant flow to other systems (such as exhaust gas recirculation or the heating system), so-called split cooling systems have been developed. These systems allow for the interruption of coolant flow to the engine block while maintaining flow to the cylinder head or parts thereof.Under normal operating conditions, i.e., with a warm engine, the engine block and cylinder head are cooled equally, resulting in nearly identical temperatures. However, tests have shown that different temperatures in the engine block and cylinder head are optimal for optimal performance. High temperatures (especially above 85 °C) in the engine block lead to reduced friction, reduced heat loss, and thus lower fuel consumption. Conversely, low temperatures (especially below 85 °C) in the cylinder head reduce knocking and therefore lower fuel consumption.

[0004] One solution (also described as "Cross Reverse Serial Coolant Flow") involves first routing the coolant through the cylinder head's coolant jacket and then through the engine block's coolant jacket, with a portion of the coolant bypassing the engine block. US Patent 9,140,176 B2 describes such a system, where the coolant flow to the engine block can be temporarily interrupted by a shut-off valve. This allows for faster warm-up of the engine block during a cold start or for achieving a higher engine block temperature during normal operation. However, the temporary interruption of the coolant flow results in a highly uneven temperature distribution within the engine block.

[0005] Alternatively, different temperatures in the engine block and cylinder head could be achieved by using two separate cooling circuits, each with two pumps, two radiators or heat exchangers, and two thermostats. However, this would increase the complexity of the design, as well as the weight and cost.

[0006] DE 602 23 188 T2 discloses a cooling system for a water-cooled internal combustion engine, comprising a heat exchanger, a pump, a temperature sensor, and a control device that controls the pump based on a detected value of the coolant temperature. A fan is also provided to generate an airflow at the heat exchanger. The control device controls the pump in such a way that the combined drive power of the pump and the fan is minimized when the coolant temperature exceeds a predetermined target temperature, whereby the flow state of the coolant in the heat exchanger is designed to fall within a defined Reynolds number range of 1800 to 6000.

[0007] US Patent 8,904,974 B2 discloses a cooling device for an engine in which an electric pump for circulating coolant is arranged upstream of the engine. After leaving the engine, the coolant passes through a thermostat and a radiator before returning to the pump. The thermostat allows coolant to be diverted around the radiator via a bypass line. A control unit is configured to adjust the pump speed based on various parameters such as engine speed, fuel consumption, and coolant temperature. The control unit also controls the thermostat. A similarly designed system is disclosed in US Patent 2017 / 0321596 A1, in which the thermostat is located downstream of the radiator and at the outlet of the bypass line.

[0008] A pump device installed in the cooling system of an internal combustion engine, according to US 2011 / 0 088 638 A1, comprises: a first housing element with a generally circular recessed section; a pump rotor arranged in the recessed section; and a second housing element attached to the first housing element to define a pump operating chamber corresponding to the recessed section. The first housing element includes a housing body section in which the recessed section is formed and an outlet-side cylindrical section formed integrally with the housing body section to define an outlet passage for the cooling water.The second housing element comprises a cover section that covers an opening end side of the recess section, and a suction-side cylindrical section that is formed integrally with the cover section to create an intake channel for the cooling water.

[0009] The aforementioned US patent 9,140,176 B2 discloses a method for temperature control in which coolant is pumped to an inlet side of a cylinder head coolant jacket, which is connected in series with an inlet side of an engine block coolant jacket. A first portion of coolant is routed from an outlet housing to the inlet side of the engine block coolant jacket and from there, via a block return line, to a control element, while a second portion of coolant is routed from the cylinder head coolant jacket, bypassing the engine block coolant jacket, to the outlet housing and the control element. Based on an engine temperature, the amount of the first portion of coolant is adjusted by opening and closing a block shut-off valve.

[0010] US Patent 9,611,781 B2 discloses a cooling system for an engine in which an engine block coolant jacket and two cylinder head coolant jackets are arranged parallel to each other in a single cooling circuit. Coolant exchange between the cylinder head coolant jackets is also provided. A downstream shut-off valve allows the flow of coolant through the engine block coolant jacket to be interrupted. The coolant flow is maintained by an electric pump whose speed is adjusted depending on the cylinder head temperature and the coolant temperature.

[0011] US Patent 9,416,720 B2 discloses another cooling system for an engine in which coolant is circulated by an electric pump through an engine cooling circuit. A thermostat allows the coolant to be directed either through a radiator or bypassed. The speed of the electric pump is adjusted based on the thermostat setting and various other parameters, such as coolant temperature, ambient temperature, and engine torque.

[0012] US Patent 4,434,749 A discloses a cooling system for an engine which, according to one embodiment, can have separate, parallel branches for the water jackets of an engine block on the one hand and a cylinder head on the other. Each branch has its own pump. If the engine temperature falls below a minimum value, the pump for the engine block's water jacket is switched off. The speed of the pump for the cylinder head's water jacket is also adjusted depending on the engine temperature.

[0013] DE 11 2016 003 821 T5 discloses a cooling device for an internal combustion engine of a vehicle, comprising an electric water pump, a first path which includes a coolant passage in a cylinder head and extends through a heating element for the vehicle's air heating system and a radiator, and a second path which bypasses the heating element and the radiator. A control device causes a path-division device to reduce the opening area of ​​the second path when the internal combustion engine is automatically stopped, compared to a state before stopping, wherein the second path extends through a heat exchanger for oil of the internal combustion engine and / or a heat exchanger for oil of a drivetrain for the internal combustion engine.When the combustion engine is automatically stopped, the control device reduces the opening area of ​​the second path such that the reduction in the opening area of ​​the second path is greater the lower the temperature of the oil.

[0014] DE 10 2007 042 866 A1 discloses a variable-speed coolant pump comprising a pump housing, a shaft mounted in a pump bearing on the pump housing and driven by a pulley, an impeller fixedly mounted on a free, flow-side end of this shaft, a pressure-actuated valve spool spring-loaded by a return spring, a backplate, and an outer cylinder variably covering the outlet area of ​​the impeller, as well as a shaft seal arranged in a seal receptacle in the pump housing between the impeller and the pump bearing. A working housing of a pressure intensifier is arranged on the pump housing, the working piston chamber of which is connected via a chamber bore to an annular channel located adjacent to the outer radius of the seal receptacle on the impeller side. A sleeve receptacle is arranged in the pump housing adjacent to the annular channel on the impeller side.

[0015] Given the current state of the art, ensuring suitable operating temperatures for both an engine block and a cylinder head still offers room for improvement.

[0016] The invention is based on the objective of enabling improved control of the operating temperatures of an engine block and a cylinder head of an internal combustion engine.

[0017] According to the invention, the problem is solved by a cooling system with the features of claim 1.

[0018] A cooling system for an internal combustion engine is shown, comprising a cooling circuit with a first section passing through a cylinder head, a second section passing through an engine block downstream of the second section, and a radiator section arranged downstream of the second section and upstream of the first section. According to the invention, a third section bypassing the engine block is connected to the first section in parallel with the second section, wherein the third section passes through an oil cooler, part of a heating and ventilation system, or other vehicle components that are to be heated or cooled and which are not part of the engine, i.e., external to the engine, before the second section and the third section are rejoined at the inlet of the radiator section, and wherein a control unit is provided for this purpose.to determine a required relative temperature increase of the engine block compared to the cylinder head and to control a pump arrangement for conveying coolant in the cooling circuit in order to reduce a coolant flow in the first section relative to the temperature increase, wherein the control device is configured to determine the required relative temperature increase at least partially on the basis of an engine load and wherein the control unit is configured to increase the coolant flow with a delay when the engine load is increased and to decrease it with a delay when the engine load is decreased.

[0019] The dependent claims relate to advantageous embodiments of the invention.

[0020] It should be noted that the features and measures listed individually in the following description can be combined in any technically feasible manner and demonstrate further embodiments of the invention. The description further characterizes and specifies the invention, particularly in conjunction with the figures.

[0021] The invention provides a cooling system for an internal combustion engine. The internal combustion engine can be, in particular, a gasoline engine or a diesel engine of a motor vehicle.

[0022] The cooling system comprises a cooling circuit with a first section running through the cylinder head, a second section running downstream through the engine block, and a radiator section located downstream of the second section and upstream of the first. The cooling circuit circulates a coolant (e.g., a water-glycol mixture) to cool the cylinder head and engine block. The first section of the cooling circuit runs through the cylinder head, typically within a water jacket or coolant jacket. As the coolant passes through this first section, it absorbs heat from the cylinder head, thus cooling it. Each of the sections of the cooling circuit mentioned here and below can have variously designed lines for conveying the coolant.Regarding the coolant flow direction during operation, a second section is arranged downstream of the first. Specifically, the second section can connect directly downstream of the first. This second section passes through the engine block of the internal combustion engine; that is, as the coolant flows through the second section, it absorbs heat from the engine block and thus cools it. It should be noted that by the time the coolant reaches the second section and the engine block, it has already absorbed heat from the cylinder head and has therefore warmed up. Consequently, the engine block tends to receive less cooling compared to the cylinder head. This is advantageous because different temperatures are optimal for the engine block than for the cylinder head.As explained above, higher temperatures (above 85 °C) in the cylinder block lead to reduced friction, reduced heat losses and thus reduced fuel consumption, while lower temperatures (below 85 °C) in the cylinder head lead to reduced knocking and thus reduced fuel consumption.

[0023] As mentioned above, a control unit is configured to detect a required relative temperature increase of the engine block compared to the cylinder head and to control a pump arrangement to circulate coolant in the cooling circuit in order to reduce the coolant flow in the first section relative to the temperature increase. The relative temperature increase refers to the temperature of the engine block in relation to the temperature of the cylinder head. A relative temperature increase means that the engine block heats up relative to the cylinder head, which can mean that the engine block heats up more (absolutely) than the cylinder head, that it cools down less (absolutely) than the cylinder head, or that it heats up while the cylinder head cools down.

[0024] The control unit is designed to detect a required relative temperature increase of the engine block compared to the cylinder head. This means the control unit can determine, at least qualitatively, whether a corresponding temperature increase is necessary. The decision regarding whether to increase the temperature can be based on various criteria and can be made by the control unit itself. Alternatively, the decision can be made externally, and the control unit can receive a simple external signal containing information about the change. In particular, the control unit can determine whether the relative temperature increase is necessary based on at least one parameter. This at least one parameter can also be referred to as the input variable, while the coolant flow rate can be considered the output variable. Specifically, this parameter can be a parameter of the internal combustion engine.In this context, parameters can be, for example, any quantity that describes the state of the internal combustion engine. These can include quantities such as engine speed or drive torque, which directly describe the operating state, or quantities such as the temperature of the internal combustion engine or a part thereof. The parameter can also be a parameter of the coolant or the cooling circuit, in particular a temperature or a temperature difference. The control unit can access the corresponding parameter, for example, through one or more sensors to which the control unit is connected.

[0025] The pump assembly is designed to circulate coolant within the cooling circuit. It preferably comprises a single pump, but multiple pumps are also possible. The pump assembly is preferably located in the first section, particularly upstream of the cylinder head or the coolant jacket of the cylinder head. The pump assembly is controlled by the control unit. The control unit could be integrated into the pump assembly or it could be an external control unit connected to the pump assembly via suitable control lines. The control unit can be implemented at least partially in software. Furthermore, the control unit can be partially implemented by a device that performs other functions in addition to controlling the pump assembly.In this context, the terms "upstream" and "downstream" are defined by the function of the arrangement when it is controlled by the control unit in the operating state.

[0026] By controlling the pump assembly, the coolant flow in the first section (or through the first section) can be adjusted. This means the coolant flow rate (e.g., measured as volume per unit of time) can be modified. The control unit makes the appropriate adjustment to reduce the coolant flow rate relative to the temperature increase. In other words, if the control unit determines that a relative temperature increase is desired (i.e., the engine block should heat up relative to the cylinder head), it reduces the coolant flow rate.

[0027] Due to the arrangement of the cylinder head and engine block within the first section, the coolant has already experienced a (possibly only slight) temperature increase by the time it reaches the engine block. This results in less effective cooling of the engine block and thus a higher engine block temperature. A high coolant flow rate ensures that the coolant experiences a comparatively small temperature increase as it passes through the cylinder head and engine block, while a low coolant flow rate results in a greater temperature increase. Furthermore, the cooling of the cylinder head is more effective with a high coolant flow rate than with a low one, so the cylinder head temperature is also lower. These principles also apply to the temperature within the engine block, although the coolant has generally already passed through the cylinder head by the time it reaches the engine block.Therefore, the engine block is generally cooled less effectively than the cylinder head, which can lead to higher temperatures there. In general, the cooling, and thus the temperature, of the cylinder head is less dependent on the coolant flow than the cooling and temperature of the engine block. Consequently, reducing the coolant flow can result in a relative warming of the engine block compared to the cylinder head.

[0028] Overall, the cooling system according to the invention aims for and generally achieves a low temperature level in the cylinder head and a high temperature level in the engine block. Two mechanisms are used to accomplish this. First, the coolant is preheated in the cylinder head before flowing into the engine block. Second, the coolant temperature at the exit from the cylinder head and within the engine block depends on the coolant flow rate; specifically, it increases when the coolant flow rate is reduced. Consequently, the metal temperature in the engine block also rises. Furthermore, reducing the coolant flow rate in the first section also reduces the coolant flow rate in the second section, thus impairing the heat transfer (i.e., the heat transfer coefficient) from the engine block to the coolant. This also contributes to an increased temperature level in the engine block.

[0029] The mechanisms described above are used according to the invention to change the temperature difference between the (usually warmer) engine block and the (usually cooler) cylinder head by means of the coolant flow. The coolant flow is reduced to achieve a relative temperature increase of the engine block.

[0030] The advantages of a higher or lower coolant flow rate can be utilized depending on the situation. Reducing the coolant flow rate can be used to counteract an increase in the temperature of engine components, particularly the engine block, thereby reducing friction and heat loss through the walls. Conversely, increasing the coolant flow rate can be used to improve the durability and knock resistance of engine components by reducing their temperature.

[0031] As mentioned above, the control unit is designed to determine the required relative temperature increase, at least partially, based on engine load. Engine load can be characterized by engine speed and / or drive torque. The corresponding parameter(s) can be determined by the control unit using suitable sensors. Engine load has a significant influence on heat generation within the engine, which affects the temperature in both the cylinder head and the engine block. Furthermore, the engine load can determine which operating characteristics of the engine are particularly important, and these operating characteristics (such as friction or knock resistance) can themselves be temperature-dependent. Specifically, the heat input to the cylinder head and the engine block can depend on the engine load in different ways.This, in turn, can lead to a temperature in the engine block that is too low relative to the cylinder head, especially under low engine load. To counteract this, the coolant flow can be reduced.

[0032] It is generally preferred that the control unit be configured to increase the coolant flow rate when the engine load increases, thus accommodating the overall increased cooling requirements. In the most general case, this means that the control unit increases the coolant flow rate at least within a specific load range when the engine load increases. This includes the possibility that the coolant flow rate remains constant in at least one other load range when the engine load increases. It would even be conceivable that the coolant flow rate is reduced in certain ranges as a function of the engine load. However, the coolant flow rate typically increases either continuously or, if necessary, in stages as a function of the engine load. Conversely, the coolant flow rate can be reduced when the engine load decreases.It is not necessarily the case that a single value of the coolant flow is assigned to a single engine load, but rather a kind of hysteresis could be provided, e.g. such that the coolant flow is increased with a delay when the engine load is increased, while it is decreased with a delay when the engine load is reduced.

[0033] The control unit can also be configured to adjust the coolant flow rate based on the coolant outlet temperature downstream of the engine block. This means the control unit can measure the outlet temperature using a suitable temperature sensor and adjust the coolant flow rate accordingly. Therefore, the coolant flow rate is not adjusted, or not exclusively adjusted, based on at least one parameter of the internal combustion engine (e.g., engine load), but rather the outlet temperature is used as an alternative or additional criterion. For example, if the outlet temperature exceeds a predefined maximum value, this can be considered an indication of overheating of the engine block and / or cylinder head, which would correspond to ineffective cooling.Preferably, the control device is configured to determine the required relative temperature increase, at least in part, based on the coolant outlet temperature downstream of the engine block. If the outlet temperature falls below a predetermined minimum value, this may indicate that the engine block (and possibly the cylinder head) is undercooled. In this case, reducing the coolant flow rate can warm the engine block relative to the cylinder head. Alternatively, it may also indicate that a very high coolant flow rate results in only a slight temperature increase of the coolant as it passes through the engine block and cylinder head. This, too, can be considered ineffective cooling, as an excessively high coolant flow rate is maintained and the pump assembly operates at unnecessarily high power.

[0034] Other parameters can also be used as an alternative or additional measure to adjusting the coolant flow, for example, a cylinder head outlet temperature downstream of the cylinder head but upstream of the engine block. Maximum and minimum values ​​could also be defined for these parameters, or the control unit could attempt to regulate the cylinder head outlet temperature to a setpoint. For instance, a thermostat or similar device could predefine a coolant temperature upstream of the cylinder head, and the control unit could be configured to maintain the cylinder head outlet temperature at a setpoint by adjusting the coolant flow. Furthermore, the control unit can determine the required relative temperature increase based on both the cylinder head outlet temperature and the outlet temperature. For example...By comparing the cylinder head outlet temperature with the exhaust temperature, the current temperature of the engine block, or how effectively it is currently being cooled, can be estimated. If the coolant inlet temperature upstream of the first section is also known, this can likewise be included to estimate the cylinder head temperature, or the effectiveness of its cooling, by comparing it with the cylinder head outlet temperature.

[0035] Preferably, the control device is configured to increase the coolant flow rate to reduce the outlet temperature. For example, an upper limit may be defined for the outlet temperature. If this upper limit is exceeded, it could indicate overheating of the cylinder head and / or engine block. In this case, the control device increases the coolant flow rate. The coolant then flows through the cylinder head and engine block at a higher velocity and heats up to a lesser extent. Since there is a greater temperature difference between the coolant and the internal combustion engine components, the heat flow to the coolant increases, resulting in more effective cooling.

[0036] As mentioned above, the cooling system has a third section connected to the first section in parallel with the second section, bypassing the engine block. In other words, downstream of the first section, there is a branch to the second section on the one hand and to the third section on the other. The second and third sections are parallel to each other with respect to the coolant flow; one could say they are connected in parallel and in series with the first section. Due to the presence of the third section, a portion of the coolant flow can bypass the engine block after passing through the first section without cooling it.While the first section is traversed by the entire coolant flow, thus providing comparatively strong cooling of the cylinder head, the second section is only traversed by a partial flow, while a secondary flow bypasses it and does not contribute to cooling. This means that, by design, the cooling of the engine block is already of a lower quality, which supports the generally desired effect of maintaining a higher temperature in the cylinder head than in the engine block. Furthermore, the third section is advantageously designed for heat transfer with at least one external component. That is, the coolant in the third section can absorb heat from or transfer heat to this external component. For example...The third section can pass through an oil cooler, part of a heating and ventilation system, or other vehicle components that need to be heated or cooled and are not part of the engine, i.e., external to the engine. Preferably, the second and third sections not only branch off from the first section together, but also connect together to the radiator section. This means that the cooling of the coolant that has passed through the third section occurs simultaneously with the cooling of the coolant that has passed through the second section.

[0037] Preferably, the pump arrangement includes an electric pump with controllable power. This allows the coolant flow to be easily varied by changing the pump's power, typically by varying its speed. Another advantage is that, with sufficient power (e.g., from a vehicle battery), the electric pump is constantly ready to maintain the coolant flow, regardless of the combustion engine's operating state. Furthermore, reducing the coolant flow allows the pump's drive power to be reduced, thus saving fuel. The electric pump can be positioned upstream or downstream of the cylinder head.

[0038] Alternatively, the pump arrangement can also include a mechanical pump coupled to the internal combustion engine and a controllable valve arranged in series with it. The mechanical pump is connected to the internal combustion engine via suitable power transmission elements and, if necessary, reduction or gearing. This means that when the internal combustion engine is switched off, the mechanical pump is also out of operation. However, this is a relatively minor limitation with regard to the cooling of the engine block and cylinder head, as cooling is unnecessary when the internal combustion engine is switched off anyway. The mechanical pump can be arranged upstream or downstream of the cylinder head. The controllable valve is preferably electrically controlled.Since the mechanical pump, due to its connection to the combustion engine, does not allow for a targeted change in the coolant flow, the coolant flow in this embodiment is controlled by a valve arranged in series with the mechanical pump with respect to the coolant flow. In the simplest case, the valve could have two states: open and closed. In this case, the coolant flow could be varied by opening and closing the valve at intervals. Preferably, however, the valve allows for a continuous or discontinuous change in the flow rate.

[0039] According to one embodiment, the radiator section has a first branch with a radiator and a second branch parallel to it for bypassing the radiator. A temperature controller is provided to adjust the distribution of the coolant flow between the first and second branches in order to regulate the coolant inlet temperature upstream of the first section. The first and second branches are parallel to each other with respect to the coolant flow, with the first branch serving for the actual cooling of the coolant, while no (significant) cooling normally occurs in the second branch. The second branch can also be referred to as a bypass or bypass line. The radiator is typically an air-cooled heat exchanger located at the front of the vehicle.At the outlet of the cooler section, where the first and second branches rejoin, the coolant temperature depends primarily on its distribution between the two branches. This distribution is controlled by the temperature controller, which thereby regulates the coolant inlet temperature or at least aims to regulate it. A temperature range, limited at least on one side, can be specified for the inlet temperature. The temperature controller can measure the inlet temperature using a suitable sensor. Depending on the arrangement and design of the temperature controller, the sensor can be located adjacent to it or even integrated within it. Physically, the temperature controller can be a single component or comprise multiple parts. At least parts of the temperature controller can be integrated into the control unit, or vice versa.In one embodiment, the temperature controller has a thermostat (or is designed as such) into which the first and second branches open. In another embodiment, the temperature controller has an electrically controlled valve connected to both the first and second branches. By electrically controlling the valve, the distribution of the coolant flow between the first and second branches can be adjusted. Such an electrically controlled valve can, for example, be controlled by the control unit, which in this case integrates functions or elements of the temperature controller. The valve can be arranged either upstream or downstream of the first and second branches.

[0040] Several options exist for regulating the inlet temperature. For example, the temperature controller can be configured to limit the inlet temperature both upwards and downwards. This means that a lower limit and / or an upper limit can be defined. A setpoint for the inlet temperature can also be defined, which the temperature controller attempts to maintain, with the actual inlet temperature typically fluctuating around this setpoint. Preferably, the temperature controller is configured to keep the inlet temperature below 85 °C. This can mean that an upper limit is defined below 85 °C, or that a setpoint is defined below 85 °C. By limiting the inlet temperature to below 85 °C, it is ensured that cooling the cylinder head to a temperature below 85 °C is (still) possible.For effective cooling, a significantly lower value is usually chosen. The corresponding upper limit or setpoint can, for example, be between 50 °C and 70 °C.

[0041] Further advantageous details and effects of the invention are explained in more detail below with reference to exemplary embodiments illustrated in the figures. These show: Fig. 1 a first embodiment of a cooling system according to the invention; Fig. 2 a part of a second embodiment of a cooling system according to the invention; Fig. 3 a third embodiment of a cooling system according to the invention; as well as Fig. 4 a fourth embodiment of a cooling system according to the invention.

[0042] In the different figures, identical parts are always provided with the same reference symbols, which is why they are usually only described once.

[0043] Fig. Figure 1 shows a schematic representation of a cooling system 1 for an internal combustion engine 2, e.g., a diesel engine of a motor vehicle. The internal combustion engine 2 has an engine block 3 and a cylinder head 4 connected to it. For cooling, the cylinder head 4 is traversed by a first section 6 of a cooling circuit 5, whereby an electric pump 8 is connected upstream of the cylinder head 4 (more precisely, a coolant jacket thereof) by which the coolant, e.g., a water-glycol mixture, is circulated. Downstream of the first section 6, the cooling circuit 5 branches off, and a second section 9, which runs through the engine block 3, and a third section 10 running parallel to it, are connected. The third section 10 can, for example, pass through an oil cooler 11 to extract heat from it. Alternatively, other components, not shown here, can also be cooled or, if necessary, heated by the third section 10.The second section 9 and the third section 10 are joined again at the inlet of a radiator section 12. The radiator section 12 has a first branch 13 with a radiator 14, which can be located, for example, at the front of the vehicle. The first branch 13 leads to a thermostat 17, which acts as a temperature regulator 16, as does a second branch 15 of the radiator section 12, which bypasses the radiator 14. From the thermostat 17, the cooling circuit runs back to the first section 6 with the pump 8.

[0044] The thermostat 17 forms a temperature controller 16 and is configured to set an inlet temperature T1 at the inlet of the first section 6 to a setpoint below 85 °C, e.g., 60 °C. For this purpose, cooled coolant from the first branch 13 in the radiator 14 is mixed appropriately with uncooled coolant from the second branch 15. The coolant flow, tempered in this way, is pumped 8 through the first section 6, cooling the cylinder head 4. The coolant flow then splits between the second section 9 and the third section 10. The engine block 3 within the second section 9 thus receives less cooling than the cylinder head 4. This is because the coolant flow has already passed through the cylinder head 4 and has therefore warmed up.Secondly, part of the coolant flow is routed through the third section 10 and thus does not contribute to cooling the engine block 3. Therefore, in the cooling system according to the invention, a higher temperature can occur in the engine block 3 than in the cylinder head 4. Preferably, the temperature in the cylinder head 4 can be below 85 °C, while the temperature in the engine block 3 is above 85 °C. Although the coolant flow through the engine block 3 is lower than that through the cylinder head 4, it is nevertheless sufficient to establish an approximately homogeneous temperature distribution in the engine block 3.

[0045] The coolant flow can be influenced by the power output of the electric pump 8. The pump 8 is connected to a control unit 30. The latter receives an engine speed n and a drive torque M to determine the engine load. The control unit 30 then controls the pump 8 depending on the determined engine load. Specifically, the control unit 30 is configured to detect whether the temperature of the engine block 3 should be increased relative to the temperature of the cylinder head 4, for example, if both temperatures are below 85°C. This would mean that the engine block 3 would be undercooled, while the temperature of the cylinder head 4 would be in the optimal range. If it is detected that the engine block 3 should be heated relatively, the control unit controls the pump 8 so that the coolant flow in the first section 6 is reduced. At low engine loads, there is only a comparatively small heat input into the engine block 3.Therefore, pump 8 operates at low power, resulting in a lower coolant flow rate. This leads to a comparatively large temperature increase of the coolant as it passes through cylinder head 4. This, in turn, results in a relative temperature increase of the engine block 3 compared to cylinder head 4, since the coolant preheated in cylinder head 4 only cools engine block 3 to a limited extent. Under high engine load, pump 8 operates at high power, resulting in a larger coolant flow rate. This results in a comparatively small temperature increase of the coolant as it passes through cylinder head 4 and engine block 3, and a comparatively low temperature in cylinder head 4, as it is cooled effectively. The increased coolant flow protects engine block 3 from overheating.

[0046] For example, to detect potential overheating of the engine block 3, the control unit 30 monitors the coolant outlet temperature T2 in the second section 9 downstream of the engine block 3 using a first temperature sensor 18. A lower limit and an upper limit for the outlet temperature T2 can be defined. If the lower limit is undershot, this can be considered an indication of an excessively low temperature in the engine block 3. To achieve a relative temperature increase in the engine block 3, the control unit 30 reduces the coolant flow via the electric pump 8. This also prevents the pump 8 from operating at unnecessarily high power. If the upper limit is exceeded, the control unit 30 increases the coolant flow via the electric pump 8. This, for example, prevents overheating of the engine block 3.Instead of monitoring both the engine load and the outlet temperature T2, it would also be conceivable for the control unit 30 to monitor only one of these parameters and adjust the coolant flow accordingly. Other parameters could also be used to adjust the coolant flow, for example, the cylinder head outlet temperature downstream of the cylinder head 4 but upstream of the engine block 3. Limit values ​​could also be defined for this, or the control unit 30 could attempt to regulate the cylinder head outlet temperature to a target value. The control unit 30 could also determine the required relative temperature increase based on both the cylinder head outlet temperature and the outlet temperature T2. For example, it could compare the cylinder head outlet temperature with the outlet temperature T2 and estimate the current temperature of the engine block 3, or how effectively it is currently being cooled.If the coolant inlet temperature upstream of the first section is also known, it can also be included to estimate the cylinder head temperature or the effectiveness of its cooling by comparing it with the head outlet temperature.

[0047] Fig. Figure 2 shows a part of a second embodiment of a cooling system 1 according to the invention, which is largely similar to the one described in Figure 2. Fig. The pump arrangement 7 shown in Figure 1 is identical. However, the pump arrangement 7 here includes a mechanical pump 19, which is located upstream of the cylinder head 4 in the first section 6, and an electrically controlled valve 20, which is located downstream of the cylinder head 4, but could alternatively be located, for example, upstream between the pump 19 and the cylinder head 4. While the pump 19 is mechanically fixed to the internal combustion engine 2, meaning its output cannot be controlled independently, the valve 20 is controlled by the control unit 30 to adjust the coolant flow. In the simplest case, the valve 20 could be designed as a shut-off valve, in which case the control unit 30 can open and close the valve 20 at intervals to achieve a suitable average coolant flow rate.Preferably, the flow rate can be adjusted in steps or continuously via valve 20, so that the coolant flow can be adjusted via this.

[0048] Fig. 3 and Fig. Figure 4 shows further embodiments of cooling systems 1 according to the invention, each largely based on the one described in Figure 4. Fig. The embodiment shown in Figure 1 corresponds to the embodiment shown and therefore does not need to be explained again. However, the temperature controller 16 here has an electrically controlled valve 21 and a second temperature sensor 22 instead of the thermostat 17. The second temperature sensor 22 detects the inlet temperature T1. Both the valve 21 and the second temperature sensor 22 are connected to the control unit 30. This unit registers the inlet temperature T1 and controls the valve 21 to regulate the inlet temperature T1 to a setpoint. Alternatively, the valve 21 and the second temperature sensor 22 could also form a closed control loop without involving the control unit 30. In the embodiment shown in Figure 1, the temperature controller 16 has an electrically controlled valve 21 and a second temperature sensor 22, which detects the inlet temperature T1. Fig. In the embodiment shown in Figure 3, the valve 21 is arranged on the outlet side of the first branch 13 and the second branch 15. Alternatively, the valve 20 can also be arranged on the inlet side of the first branch 13 and the second branch 15, as shown in Figure 3. Fig.Figure 4 illustrates this. If the aforementioned cylinder head outlet temperature is also known, it can likewise be included to estimate the temperature of the cylinder head 4, or the effectiveness of its cooling, by comparing it with the inlet temperature T1. This can then be compared to an (estimated) temperature of the engine block 3 to determine whether a relative temperature increase of the engine block 3 compared to the cylinder head 4 is necessary. List of reference symbols 1 Cooling system 2 Internal combustion engine 3 Engine block 4 cylinder head 5 Cooling circuit 6 first section 7 Pump arrangement 8 electric pump 9 second section 10 third section 11 Oil coolers 12 Cooling section 13 first branch 14 coolers 15 second branch 16 temperature controllers 17 Thermostat 18, 22 Temperature sensor 19 mechanical pump 20, 21 valve 30 control unit T1 Inlet temperature T2 Outlet temperature n engine speed M Drive torque

Claims

[1] Cooling system (1) for an internal combustion engine (2), comprising a cooling circuit (5) with a first section (6) passing through a cylinder head (4), a downstream second section (9) passing through an engine block (3) and a cooler section (12) arranged downstream of the second section (9) and upstream of the first section (6), characterized bya third section (10) connected to the first section (6) in parallel with the second section (9), bypassing the engine block (3), which third section passes through an oil cooler, a part of a heating and ventilation system, or other vehicle components that are to be heated or cooled and which are not associated with the engine, i.e., are external to the engine, before the second section (9) and the third section (10) are reunited at the inlet of the cooler section (12), and wherein a control unit (30) is configured to determine a relative temperature increase of the engine block (3) relative to the cylinder head (4) to be carried out and to control a pump arrangement (7) for conveying coolant in the cooling circuit (5) in order to reduce a coolant flow in the first section (6) for the relative temperature increase, wherein the control device (30) is configured todetermining the relative temperature increase to be carried out at least partially based on an engine load, and wherein the control unit (30) is configured to increase the coolant flow with a delay when the engine load increases and to decrease it with a delay when the engine load decreases. [2] Cooling system according to claim 1, characterized by that the control device (30) is designed to determine the relative temperature increase to be carried out at least partially on the basis of an outlet temperature (T2) of the coolant downstream of the engine block (3). [3] Cooling system according to one of the preceding claims, characterized by that the control device (30) is designed to increase the coolant flow to reduce the outlet temperature (T2). [4] Cooling system according to one of the preceding claims, characterized by that the pump arrangement (7) has an electric pump (8) with controllable power. [5] Cooling system according to one of claims 1 to 3, characterized by that the pump arrangement (7) has a mechanical pump (19) coupled to the internal combustion engine (2) and a controllable valve (20) arranged in series therewith. [6] Cooling system according to one of the preceding claims, characterized by in that the cooler section (12) has a first branch (13) with a cooler (14) and a second branch (15) parallel thereto for bypassing the cooler (14), wherein a temperature controller (16) is designed to adjust a division of the coolant flow between the first (13) and second branch (15) in order to regulate an inlet temperature (T1) of the coolant upstream of the first section (6). [7] Cooling system according to claim 6, characterized by that the temperature controller (16) is designed to keep the inlet temperature (T1) below 85° C.

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