Patent Description:
An internal combustion engine can have a fluid circuit, for example an oil circuit or a fuel circuit. A working fluid, for example oil or fuel, circulates in the fluid circuit. Depending on the operational conditions of the engine, it can be necessary to cool or to heat the working fluid. This can be done by means of a heat exchanger or heater. Furthermore, a bypass for bypassing the heat exchanger or heater can be provided. To guide the working fluid either to the heat exchanger or heater or to bypass the heat exchanger or heater, a thermostat system can be provided. The thermostat system can comprise a wax motor or a solenoid valve. <CIT> discloses a thermostat system, according to the preamble of claim <NUM>.

Against this background, it is one object of the present invention to provide an improved electrohydraulic thermostat system.

Accordingly, an electrohydraulic thermostat system for a filter device is provided. The electrohydraulic thermostat system comprises a main valve and a pilot valve, wherein the main valve comprises a valve body which is arranged in a receiving section of a housing, wherein the valve body subdivides the receiving section into a fluid distribution chamber, which receives a pressurized fluid through a pressure line and is configured to distribute a working fluid to an inflow line of a component for changing a temperature of the working fluid and/or to a bypass line for bypassing the component, and a control chamber, wherein the pilot valve is configured to cause a pressure difference between the fluid distribution chamber and the control chamber as a function of the temperature of the working fluid so that the working fluid moves the valve body in the receiving section due to the pressure difference for opening and closing the inflow line and/or the bypass line.

Due to the valve body being moved by the working fluid itself, the pilot valve can be downsized compared to known solenoid valves. Thus, the electrohydraulic thermostat system is cheaper and consumes less energy compared to a solenoid valve. Furthermore, the electrohydraulic thermostat system reacts faster and can operate in a wider temperature range than a wax motor. The quick reaction of the electrohydraulic thermostat system allows to keep the working fluid in a working temperature range that helps to fulfill the viscosity requirements of the working fluid in the best possible way. This contributes to fuel savings of an engine with such an electrohydraulic thermostat system.

The filter device can be an oil filter or fuel filter, for example. The electrohydraulic thermostat system can be part of the filter device. "Pilot" in this context means that the pilot valve pilots or controls the main valve. In other words, the function of the main valve is dependent on the pilot valve. "Electrohydraulic" in this context means that the electrohydraulic thermostat system has both, an electric and a hydraulic functionality. The electric functionality is assigned to the pilot valve that is preferably an electromagnetic valve. In particular, the pilot valve has a movable piston and a coil or magnet for actuating the piston. The hydraulic functionality is assigned to the main valve, the valve body thereof being moved by means of the pressurized working fluid.

The receiving section preferably is a bore that is provided in the housing. The housing can be part of the electrohydraulic thermostat system or of the filter device. The valve body can be moved inside the receiving section in a linear way. The bypass line and the inflow line have openings that discharge into the receiving section, in particular into the fluid distribution chamber. The valve body covers the bypass line to close it. In the same way, the valve body covers the inflow line to close it.

"Subdividing" the receiving section into the fluid distribution chamber and the control chamber in this context means that the valve body is at least partly sandwiched between the fluid distribution chamber and the control chamber. However, this does not exclude that the fluid distribution chamber and the control chamber are fluidly connected to each other. "Distributing" the working fluid can mean that either all the working fluid is guided into the bypass line, all the working fluid is guided into the inflow line or that the working fluid is split and guided into the bypass line as well as into the inflow line.

The component for changing the temperature of the working fluid can be a heater or a heat exchanger, for example. The component is configured to extract heat from the working fluid and/or to apply heat to the working fluid. The temperature of the working fluid is controlled by guiding at least a part of the working flow through the component. The electrohydraulic thermostat system is thus suitable for controlling the temperature of the working fluid.

The electrohydraulic thermostat system can be brought from a switch off mode, in which the pressure in the fluid distribution chamber and the control chamber is equal, into a bypass mode, in which the bypass line is completely open and the inflow line is completely closed, a control mode, in which the bypass line and the inflow line are at least partly open, and a working mode in which the bypass line is completely closed and the inflow line is completely open. In the control mode, the position of the valve body changes depending on the pressure difference and thus as a function of the temperature of the working fluid.

Preferably, the pressure difference is a pressure drop. That means that the pilot valve is suitable of reducing the pressure in the control chamber. For example, this can be done by opening a drain line to a low-pressure region, in particular to a reservoir. The revervoir can be under atmospheric or close to atmospheric pressure. The pressure difference is a function of the temperature of the working fluid. This means that an increase of the temperature of the working fluid leads to an increase of the pressure difference. Preferably, a decrease of the temperature of the working fluid leads to a decrease of the pressure difference. The higher the temperature of the working fluid, the more working fluid is fed into the inflow line. The lower the temperature of the working fluid, the more working fluid is fed into the bypass line. This is valid for the case that the component is a heat exchanger for cooling the working fluid. When the pressure in the control chamber is released by means of the pilot valve, the pressurized working fluid in the fluid distribution chamber moves the valve body.

In embodiments, in a bypass mode of the electrohydraulic thermostat system, the valve body completely closes the inflow line and opens the bypass line to guide the working fluid into the bypass line. In the bypass mode, the component is bypassed so that no heat is extracted from or applied to the working fluid. The bypass mode can be used when an engine comprising such an electrohydraulic thermostat system is running under normal conditions.

In embodiments, in a working mode of the electrohydraulic thermostat system, the valve body completely closes the bypass line and opens the inflow line to guide the working fluid into the inflow line. The working mode can be called cooling mode or cooler mode. In the working mode, all the working fluid is guided to the component to extract heat therefrom or to apply heat to the working fluid.

In embodiments, in a control mode of the electrohydraulic thermostat system, the valve body opens the inflow line and the bypass line to guide the working fluid into the inflow line and the bypass line. The volume flow of working fluid to the inflow line and to the bypass line is controlled on basis of the temperature of the working fluid to keep the temperature in a preset temperature range.

In embodiments, the pilot valve is configured to open and to close a drain line to a reservoir as a function of the temperature of the working fluid to generate the pressure difference between the fluid distribution chamber and the control chamber. The reservoir is a low-pressure area. That means that the working fluid is not pressurized in the reservoir. The reservoir can be a tank or the like.

In embodiments, the pilot valve comprises a piston for opening and closing the drain line, wherein the piston closes the drain line in an initial state of the pilot valve, and wherein the piston opens the drain line in an energized state of the pilot valve. The piston has a coil or magnet for moving the piston. The piston can be moved binary. In other words, the drain line can be either closed completely or opened completely. Also, an adjustment to intermediate pressure levels is possible. Intermediate switching positions can be set. Alternatively or additionally, a pulsed actuation of the piston is possible.

According to the invention, the valve body comprises a divider plate which subdivides the receiving section into the fluid distribution chamber and the control chamber. In a preferred embodiment the divider plate comprises a controlled leakage gap for pressure equalization between the fluid distribution chamber and the control chamber. The controlled leakage gap allows pressure equalization when the drain line is closed by means of the piston of the pilot valve.

According to the invention, the divider plate has a predetermined radial clearance against the receiving section, wherein the predetermined radial clearance creates a controlled leakage gap for pressure equalization between the fluid distribution chamber and the control chamber.

In another embodiment the inflow line and the bypass line are fluidically connected with the fluid distribution chamber at axially spaced positions. This enables the inflow line and the bypass line to be efficiently selectively closed and/or opened by the axial movement of the valve body.

In another embodiment the valve body can comprise a fail safe opening that allows an auxilary flow of the working fluid to the inflow line in an axial position of the valve body that corresponds to the inflow line being actually closed. This allows to provide at least a small volume flow to the component for changing a temperature of the working fluid (e.g. a heater or cooler) in case of a malfuction of the pilot valve, especially when the pilot valve in stuck in its closed position. The failsafe opening can be arranged axially neighbouring the divider plate and can be provided as a radial opening of the valve body.

In embodiments, the valve body is at least partially hollow and comprises at least one radial outlet. Preferably the valve body comprises a first outlet opening, which is assigned to the inflow line, and a radial second outlet opening which is assigned to the bypass line. Preferably, the valve body has the shape of a hollow cylinder. The outlet openings break through a wall of this cylinder shape. One front face of the valve body is open and the other front face is closed by means of the divider plate. The working fluid discharges into the open front face.

In a preferred embodiment the valve body comprises two axially spaced cylinder shells, wherein the at least one radial outlet opening is arranged between the two axially spaced cylinder shells. The axially spaced cylinder shells can be connected by suitable force transmitting means, e.g. a plurality of axial struts. This is especially advategeous in combination with the embodiment that has the the inflow line and the bypass line being fluidically connected with the fluid distribution chamber at axially spaced positions as an axial movement of the valve body then selectively allows to close the inflow line and/or the bypass line when aligned with one of the cylinder shells or to open the inflow line and/or the bypass line when aligned with the at least one radial outlet opening.

In a preferred embodiment the fail safe opening can be arranged axially between one of the cylinder shells and the divider plate. In embodiments, the electrohydraulic thermostat further comprises an elastic element which biases the valve body against a pressure of the working fluid. The elastic element can be a spring, in particular a pressure spring. When the pilot valve closes the drain line, pressure equalizes in the fluid distribution chamber and in the control chamber so that the elastic element moves the valve body back into the switch off mode.

In embodiments, the elastic element is arranged inside the control chamber. Thus, the elastic element is bathed in the working fluid. Alternatively, the elastic element can be placed outside the control chamber.

In embodiments, the electrohydraulic thermostat system further comprises a temperature sensor and/or a control unit for operating the pilot valve. The pilot valve is controlled in a closed loop. The control unit can be an electronic control unit (ECU) that operates the pilot valve as a function of a signal received from the temperature sensor to achieve a certain axial position of the valve body in the receiving section. The correlation between a given temperature, the desired axial position of the valve body and the corresponding operational state of the pilot valve can be stored in data maps within the ECU. The pilot valve can be operated in a binary manner (open or closed) and optionally cyclically with varying frequency.

In an equally preferred embodiment the electrohydraulic thermostat system comprises at least one sensor being adapted for determining a position of the valve body in the receiving section. Any sensors that allow for the determination of an axial position of the valve body can be used, e.g. hall sensor, magneto resistive sensor (MGR), pressure sensor, mechanically coupled linear displacement sensor (linear sensor), optical sensor and/or ultrasonic sensor.

Preferably and depending on the sensor concept the sensor comprises a first sensor part arranged on the valve body and a second sensor part arranged on the housing, i.e. the sensor being a "divided sensor".

The first sensor part being arranged on the valve body can be a magnet and the second sensor part arranged on the housing can be a hall or MGR sensor. The first sensor part can be preferably arranged at the divider plate of the valve body and the second sensor part can be preferably arranged on an opposing part of the housing.

Alternatively a linear sensor directly attached to the valve body detecting the relative movement of the valve to the the housing, an optical sensor or a ultrasonic sensor detecting the relative movement of the vavle body in comparison to an opposing part of the housing can be used as non-divided sensors.

The sensor can be coupled to the control unit so as to give back a value of the current axial position of the valve body and allow for a closed control loop, what increases the positioning accuracy of the valve body and allows for an easy detection of malfunctions.

Furthermore, a filter device is provided. The filter device comprises an electrohydraulic thermostat system as explained before, a component for changing a temperature of a working fluid, wherein the component is arranged downstream of the electrohydraulic thermostat system, a filter for filtering the working fluid, wherein the filter is arranged downstream of the component, an inflow line which connects the component to the electrohydraulic thermostat system, and a bypass line which bypasses the component.

As explained before, the component can be a heater, a heat exchanger or the like. The filter device can be an oil filter device or a fuel filter device, for example.

Moreover, a method for controlling a temperature of a working fluid by means of an electrohydraulic thermostat system is provided, wherein the electrohydraulic thermostat system comprises a main valve and a pilot valve, wherein the main valve comprises a valve body which is arranged in a receiving section of a housing, and wherein the valve body subdivides the receiving section into a fluid distribution chamber, which is configured to distribute a working fluid to an inflow line of a component for changing a temperature of the working fluid and/or to a bypass line for bypassing the component, and a control chamber, the method comprising the following steps: a) generating a pressure difference between the fluid distribution chamber and the control chamber as a function of the temperature of the working fluid by means of the pilot valve, b) moving the valve body in the receiving section due to the pressure difference for opening and closing the inflow line and/or the bypass line by means of the working fluid, and c) controlling the temperature of the working fluid by means of the component.

Preferably, in step a) a pressure drop is generated. This means that the pressure in the control chamber is lower than in the fluid distribution chamber. Due to the lower pressure in the control chamber, the working fluid can move the valve body to either open the inflow line and close the bypass line, to close the inflow line and open the bypass line or to open both, the bypass line and the inflow line. When the bypass line and the inflow line are both open, the distribution of the working fluid to the inflow line and the bypass line is done as a function of the temperature to keep the temperature of the working fluid in a preset temperature range.

In Embodiments, in step b) the working fluid moves the valve body against a spring force of an elastic element. An equilibrium is established between the pressure of the working fluid and a spring force of the elastic element.

In Embodiments, in step c) the component applies heat to the working fluid or extracts heat from the working fluid to control the temperature of the working fluid. "Control" in this context means that the temperature of the working fluid is kept in the preset temperature range.

In the figures, identical or functionally identical elements have been given the same reference signs unless otherwise indicated.

<FIG> shows an embodiment of a filter device <NUM>. The filter device <NUM> is configured to supply a working fluid <NUM> to a system <NUM>. The system <NUM> can be an internal combustion engine. The working fluid <NUM> can be motor oil. However, the working fluid <NUM> can be any other liquid like water, fuel or the like. The filter device <NUM> is designed to filter the working fluid <NUM> before supplying it to the system <NUM>. In the case that the working fluid <NUM> is motor oil, the filter device <NUM> is an oil filter system or can be named oil filter system.

The filter device <NUM> comprises a reservoir <NUM> that is at least partly filled with the working fluid <NUM>. The reservoir <NUM> can be a tank, an oil sump or the like. In the reservoir <NUM>, the working fluid <NUM> is under low pressure, preferably under ambient pressure. A pump <NUM> is provided for taking in the working fluid <NUM> by means of an intake line <NUM>. The pump <NUM> pressurizes the working fluid <NUM> and supplies it to a pressure line <NUM>.

By means of the pressure line <NUM>, the working fluid is supplied to an electrohydraulic thermostat system <NUM>. The electrohydraulic thermostat system <NUM> comprises a pilot valve <NUM> and a main valve <NUM>. The pilot valve <NUM> is an electromagnetic valve. A temperature sensor <NUM> is assigned to the pilot valve <NUM>. The temperature sensor <NUM> is configured to measure a temperature of the working fluid <NUM>. Furtermore, a control unit <NUM> can be provided. The control unit <NUM> is configured to control the pilot valve <NUM> based on temperature signals from the temperature sensor <NUM>.

The pressure line <NUM> supplies the working fluid <NUM> to the main valve <NUM>. The main valve <NUM> will be explained later. The pilot valve <NUM> is interposed in a drain line <NUM> that is guided from the main valve <NUM> to the reservoir <NUM>. By means of the drain line <NUM>, the working fluid <NUM> can be discharged into the reservoir <NUM>.

The filter device <NUM> has a component <NUM> for influencing or changing a temperature of the working fluid <NUM>. The component <NUM> can be a heat exchanger or a heater, for example. In the following, the component is named heat exchanger <NUM>. The heat exchanger <NUM> is suitable for exchanging heat between the working fluid <NUM> and a cooling fluid. The cooling fluid can be water, any other liquid or air. An inflow line <NUM> connects the main valve <NUM> to the heat exchanger <NUM>. A discharge line <NUM> connects the heat exchanger <NUM> to a filter <NUM>. The filter <NUM> can be an oil filter or a fuel filter. The filter <NUM> can be bypassed by a bypass line <NUM>. The bypass line <NUM> has a check valve <NUM>. The system <NUM> is connected to the reservoir <NUM> by means of a discharge line <NUM>. A further bypass line <NUM> is provided that bypasses the heat exchanger <NUM>. The bypass line <NUM> starts at the main valve <NUM> and discharges into the discharge line <NUM>.

<FIG> shows a schematic view of one embodiment of the electrohydraulic thermostat system <NUM>. The electrohydraulic thermostat system <NUM> has a housing <NUM>. The housing <NUM> can be part of an oil filter module (not shown), for example. The lines <NUM>, <NUM>, <NUM> and <NUM> end or start at the housing <NUM>.

The main valve <NUM> has a valve body <NUM> that is received in the housing <NUM>. The valve body <NUM> is shaped in the form of a hollow cylinder. A front side of the valve body <NUM> facing the pressure line <NUM> is open so that the working fluid <NUM> coming from the pump <NUM> can enter the valve body <NUM>. The valve body <NUM> is provided with a first outlet opening <NUM>, which can be connected to the inflow line <NUM> of the heat exchanger <NUM>, and a second outlet opening <NUM> that can be connected to the bypass line <NUM>.

A front side of the valve body <NUM> facing away from the pressure line <NUM> is closed by means of a divider plate <NUM>. The divider plate <NUM> is provided with a controlled leakage gap <NUM>. The controlled leakage gap <NUM> can be a bore. Next to the divider plate <NUM>, a fail safe opening <NUM> is provided in the valve body <NUM>.

The housing <NUM> has a receiving section <NUM> in form of a bore that receives the valve body <NUM>. By means of the divider plate <NUM>, the receiving section <NUM> is divided into a fluid distribution chamber <NUM> and a control chamber <NUM>. An elastic element <NUM>, in particular a compression spring, is received in the control chamber <NUM>. The elastic element <NUM> rests on one side on the divider plate <NUM> and on its other side on a shoulder <NUM> of the housing <NUM>. The elastic element <NUM> is configured to press the valve body <NUM> against a shoulder <NUM> of the housing. The shoulders <NUM>, <NUM> face each other.

The pilot valve <NUM> is at least partly received in the housing <NUM>. However, the pilot valve <NUM> can be arranged at any arbitrary position along the drain line <NUM>. The pilot valve <NUM> has a piston <NUM> that is axially displaceable to open and to close the drain line <NUM>. The drain line <NUM> is connected to the control chamber <NUM> by means of a bore <NUM>. To close the drain line <NUM>, the bore <NUM> is covered by the piston <NUM>. To open the drain line <NUM>, the bore <NUM> is uncovered.

In the following, the functionality of the of the electrohydraulic thermostat system <NUM> is explained with reference to <FIG>. <FIG> shows the electrohydraulic thermostat system <NUM> in a switch off mode M1. In the switch off mode M1, the system <NUM>, for example an internal combustion machine, is stopped. The working fluid <NUM> is not pressurized. The pilot valve <NUM> is not energized so that the piston <NUM> is in an initial position. In the initial position of the piston <NUM>, the piston <NUM> covers the bore <NUM> completely so that the drain line <NUM> is closed.

Due to the controlled leakage gap <NUM>, the pressure in the fluid distribution chamber <NUM> and in the control chamber <NUM> is the same. Thus, the elastic element <NUM> presses the valve body <NUM> against the shoulder <NUM> of the housing <NUM>. The second outlet opening <NUM> of the valve body <NUM> overlaps the bypass line <NUM> so that the bypass line <NUM> is completely open. The pressure line <NUM> is thus fluidly connected to the bypass line <NUM>. The first outlet opening <NUM> of the valve body <NUM> is completely covered by the housing <NUM> so that the first outlet opening <NUM> is closed.

The inflow line <NUM> of the heat exchanger <NUM> is covered by the valve body <NUM> so that the inflow line <NUM> is at least partly closed. The fail safe opening <NUM> of the valve body <NUM> overlaps the inflow line <NUM> so that the inflow line <NUM> is also fluidly connected to the pressure line <NUM>. The fail safe opening <NUM> provides a flow of working fluid <NUM> to the heat exchanger <NUM> in the case that the pilot valve <NUM> does not work, i.e. stays in its closed state.

<FIG> shows the electrohydraulic thermostat system <NUM> in a bypass mode M2. The system <NUM> is running under normal condition and the working fluid <NUM> is pressurized. The pilot valve <NUM> is energized to open the bore <NUM> at least partly to discharge part of the working fluid <NUM> into the reservoir <NUM>. The power consumption of the pilot valve <NUM> does not exceed <NUM> W. Opening the bore <NUM> results in a pressure release in the control chamber <NUM>. Thus, the pressure in the fluid distribution chamber <NUM> is higher than in the control chamber <NUM>. The pressurized working fluid <NUM> moves the valve body <NUM> to the right and thus compresses the elastic element <NUM>. The valve body <NUM> makes an axial movement of around <NUM>.

The valve body <NUM> covers the inflow line <NUM> completely so that there is no flow of working fluid <NUM> to the heat exchanger <NUM>. The second outlet opening <NUM> overlaps the bypass line <NUM> so that the working fluid <NUM> is directly guided to the filter <NUM>. Except for a leakage flow of working fluid <NUM> trough the drain line <NUM>, in the bypass mode M2 there is <NUM> % flow of working fluid <NUM> to the bypass line <NUM> and <NUM> % flow of working fluid <NUM> to the inflow line <NUM>.

<FIG> shows the electrohydraulic thermostat system <NUM> in a control mode M3. In the control mode M3, the system <NUM> is running under hot conditions. The pilot valve <NUM> is controlled in a closed loop by means of the control unit <NUM>. The control mode M3 allows to divide the flow of working fluid <NUM> between the bypass line <NUM> and the inflow line <NUM> of the heat exchanger <NUM> depending on the demand of the system <NUM>. In other words, the first outlet opening <NUM> overlaps the inflow line <NUM> so that the inflow line <NUM> is fluidly connected to the pressure line <NUM> and the second outlet opening <NUM> overlaps the bypass line <NUM> so that the bypass line <NUM> is also fluidly connected to the pressure line <NUM>. The pilot valve <NUM> can allow a binary adjustment. However, the pilot valve <NUM> can also allow and adjustment of intermediate pressure levels, for example by setting intermediate switching positions and/or a pulsed actuation thereof.

The bore <NUM> is opened by retracting the piston <NUM>. The movement of the piston <NUM> allows a specific pressure decrease in the control chamber <NUM>. The valve body <NUM> is moved by the pressure difference between the fluid distribution chamber <NUM> and the control chamber <NUM>. The more the piston <NUM> is retracted from the bore <NUM>, the further the valve body <NUM> moves to the right thus closing the bypass line <NUM> and opening the inflow line <NUM> of the heat exchanger <NUM>.

The valve body <NUM> makes an axial movement of around <NUM> to <NUM>. Depending on the temperature of the working fluid <NUM>, there is either guided more working fluid <NUM> to the bypass line <NUM> or to the inflow line <NUM>. Higher temperatures result in a higher volume flow of working fluid <NUM> to the heat exchanger <NUM> to cool the working fluid <NUM> down. Lower temperatures result in a higher volume flow of working fluid <NUM> to the bypass line <NUM> to bypass the heat exchanger <NUM>.

<FIG> shows the electrohydraulic thermostat system <NUM> in a working mode M4. The working mode M4 can be named cooler mode. In the working mode M4, the system <NUM> is running under hot conditions. The pilot valve <NUM> keeps being energized to open the bore <NUM> completely. The power consumption of the pilot valve <NUM> does not exceed <NUM> W. By opening the bore <NUM> completely,the pressure drop between the fluid distribution chamber <NUM> and the controll chamber <NUM> increases so that the pressure of the working fluid <NUM> being supplied by the pressure line <NUM> moves the valve body <NUM> further to the right. The valve body <NUM> makes a linear movement of <NUM>. In the working mode M4, the bypass line <NUM> is completely closed and the inflow line <NUM> of the heat exchanger <NUM> is completely open so that the heat exchanger <NUM> gets <NUM> % of the working fluid <NUM> and the bypass line <NUM> gets <NUM> % of the working fluid <NUM>.

<FIG> shows a schematic block diagram of one embodiment of a method for controlling the temperature of the working fluid <NUM>. In a step S1 the pressure difference between the fluid distribution chamber <NUM> and the control chamber <NUM> is generated as a function of the temperature of the working fluid <NUM> by means of the pilot valve <NUM>. In other words, when the temperature increases, the pilot valve <NUM> moves its piston <NUM> to open the drain line <NUM>. This leads to a pressure drop in the control chamber <NUM>.

Claim 1:
Electrohydraulic thermostat system (<NUM>) for a filter device (<NUM>), comprising a main valve (<NUM>) and a pilot valve (<NUM>), wherein the main valve (<NUM>) comprises a valve body (<NUM>) which is arranged in a receiving section (<NUM>) of a housing (<NUM>), wherein the valve body (<NUM>) subdivides the receiving section (<NUM>) into a fluid distribution chamber (<NUM>), which receives a pressurized working fluid (<NUM>) through a pressure line (<NUM>) and is configured to distribute the working fluid (<NUM>) to an inflow line (<NUM>) of a component (<NUM>) for changing a temperature of the working fluid (<NUM>) and/or to a bypass line (<NUM>) for bypassing the component (<NUM>), and a control chamber (<NUM>), wherein the pilot valve (<NUM>) is configured to cause a pressure difference between the fluid distribution chamber (<NUM>) and the control chamber (<NUM>) as a function of the temperature of the working fluid (<NUM>) so that the valve body (<NUM>) in the receiving section (<NUM>) is movable due to the pressure difference of the working fluid (<NUM>), wherein a movement of the valve body (<NUM>) causes the inflow line (<NUM>) and/or the bypass line (<NUM>) to selectively at least partially open and/or close,
wherein the valve body (<NUM>) comprises a divider plate (<NUM>) which subdivides the receiving section (<NUM>) into the fluid distribution chamber (<NUM>) and the control chamber (<NUM>), and characterized in that
the divider plate (<NUM>) has a predetermined radial clearance against the receiving section (<NUM>), wherein the predetermined radial clearance creates a controlled leakage gap for pressure equalization between the fluid distribution chamber (<NUM>) and the control chamber (<NUM>).