Filling level sensing device for a liquid reservoir and liquid reservoir

Abstract

A filling level sensing device for a liquid reservoir and a liquid reservoir are disclosed. The present invention relates to a filling level sensing device (14) for a liquid reservoir (10), in particular for a compensating tank of a vehicle braking system, the filling level sensing device comprising: at least one float (16) designed to come into contact with the liquid in the liquid reservoir (10); at least one sensor element (26) connected to the at least one float (16); and at least two sensors (22, 24) for detecting the position of the at least one sensor element (26), wherein at least one of the sensors (22, 24) senses a change in the filling level of the liquid reservoir (10) based on the position of the at least one sensor element (26) relative to the at least two sensors (22, 24).

Description

Technical Field

[0001] The present invention relates to a filling level sensing device and to a liquid reservoir comprising such a filling level sensing device. Background Art

[0002] Filling level sensing devices are known from the prior art, for example, from the published patent DE 10 2004 061 357 A1. The published patent DE 10 2004 061 357 A1 discloses a compensating tank connected to a guide tube. A float is arranged on the guide tube in a displaceable manner. The float is equipped with an annular magnet. A tube support protruding from the base of the compensating tank and partially concentrically surrounding the guide tube is provided as a stop for the float. A carrier element equipped with a switch is arranged inside the guide tube. Summary of the Invention

[0003] An object of the present invention is to provide a filling level sensing device that can detect at least two different filling levels in a simple and reliable manner.

[0004] This object is achieved by the filling level sensing device.

[0005] A filling level sensing device for a liquid reservoir, in particular for a compensating tank of a vehicle braking system, according to the present invention comprises: at least one float designed to come into contact with the liquid in the liquid reservoir; at least one sensor element connected to the at least one float; and at least two sensors for detecting the position of the at least one sensor element. At least one of the sensors senses a change in the filling level of the liquid reservoir based on the position of the at least one sensor element relative to the at least two sensors.

[0006] At least two different filling levels can be detected by the filling level sensing device according to the invention. This is particularly advantageous for autonomous vehicles, since there is no driver as a superior entity for monitoring vehicle systems in an autonomous vehicle, such as the braking system. A signal representing at least two different filling levels can be generated by the filling level sensing device according to the invention based on a change in the position of at least one sensor element, which change is detected by at least one of the sensors. A change in the position of at least one sensor element, which change is detected by one of the sensors, can be used, for example, to generate a warning signal indicating a non-critical liquid loss present in the liquid reservoir. However, a change in the position of at least one sensor element, which change is detected by the other sensor accordingly, can be used to generate a warning signal indicating a critical filling level of the liquid reservoir and warning of a threat of failure of the braking system of the vehicle. A constant filling level or a negligible liquid loss can equally be indicated by at least one of the at least two sensors, where in this case a warning signal is not necessary.

[0007] The at least one sensor element is displaceable relative to the at least two sensors in a vertical direction. The at least two sensors can be mounted in fixed positions and detect a relative movement of the at least one sensor element in the vertical direction. When the filling level of the liquid reservoir changes and thus also the position of at least one float changes, the sensor element connected to the at least one float can change its vertical position.

[0008] At least one float can have at least one connecting element. The at least one sensor element can be arranged on the at least one connecting element. The sensor element can have a cylindrical or cubic design. The cross-section of the connecting element can equally have a cylindrical design or a rectangular design. The at least one sensor element can be received in the connecting element. As an alternative, the at least one sensor element can be arranged on the outer surface of the connecting element. This outer surface of the connecting element can face the at least two sensors.

[0009] At least two sensors can be integrated into at least one liquid reservoir. Thus, the at least two sensors can be part of the liquid reservoir. The at least two sensors can be accommodated in a sensor housing. The sensor housing can be arranged at a fixed position in or on the liquid reservoir. The sensor housing can have an elongated design and extend into the liquid reservoir in a horizontal direction. The sensor housing can be connected to the liquid reservoir in a fixed or releasable manner. The sensor housing can have a low structural height. The sensor housing together with the sensors can be inserted into the liquid reservoir. Fastening means interacting with corresponding means on the liquid reservoir can be provided on the sensor housing. Such means on the liquid reservoir can be, for example, guide rails that allow the sensor housing to be pushed in. The sensor housing can be completely or partially accommodated in the liquid reservoir. It is conceivable that sections of the sensor housing protrude from the liquid reservoir.

[0010] There can be guides for at least one connecting element to guide the connecting element together with at least one sensor element in a vertical displacement. The guides for at least one connecting element can be formed or fastened, for example, on the liquid reservoir. For example, the cross-section of the guide can have a U-shaped design. The guide can further be formed on at least one sensor housing. An opening can be formed in the sensor housing into which the connecting element can be inserted and which can guide the relative movement of the connecting element with respect to the sensor housing.

[0011] At least one sensor element can be designed such that it generates a magnetic field. The at least one sensor element can be, for example, a permanent magnet. The sensor element designed as a permanent magnet can be accommodated in or arranged on the connecting element.

[0012] The at least two sensors can respond to the magnetic field generated by the at least one sensor element. If the magnetic field moves closer to or away from the sensors, this can be detected by at least one of the two sensors. The magnetic field detected by at least one of the sensors or the magnetic effect of the sensor element can change due to a change in the vertical position of the sensor element relative to the at least two sensors. The greater the distance between the at least one sensor element and the at least two sensors, the weaker the magnetic effect of the at least one sensor element on the at least two sensors.

[0013] The magnetic sensitivities of the at least two sensors can be different. One of the two sensors can have a higher sensitivity to the magnetic field than the other correspondingly. Thus, one of the sensors can detect changes in the magnetic field generated by the sensor element more easily than the other. In particular, the sensor that is more sensitive to changes in the magnetic field can detect the magnetic field at a greater distance than the less sensitive sensor. In other words, there is a state where the less sensitive sensor no longer detects the magnetic field while the more sensitive sensor does.

[0014] Each of the at least two sensors can be connected to a circuit. The two circuits can be connected to an electronic control unit. The electronic control unit can record, via the circuits, a change in state caused by the position of the sensor element (which position is detected by the sensor), and generate and output a signal based on these changes in state.

[0015] At least one of the at least two sensors can be a switch, which can change its switching state according to the magnetic field generated by the at least one sensor element. The two sensors can also both be switches. The sensors can cause the circuits connected to them to be interrupted or closed based on their switching states. The electronic control unit connected to the circuits can detect a change in the circuit state based on the change and output signals, which can indicate liquid loss in the liquid reservoir. The electronic control unit can output a warning signal based on a change in the switching state of a less sensitive sensor, which warning signal indicates liquid loss in the liquid reservoir. If a more sensitive sensor changes its switching position, the electronic control unit can output an alarm signal, which alarm signal warns of an impending failure of the braking system of the vehicle. Correspondingly, a change in the switching state of the more magnetically sensitive sensor can correspond to a relatively larger liquid loss, for example, due to a relatively large leak. In particular, the switch can be a so-called reed switch.

[0016] The at least two sensors can be arranged next to each other in the vertical direction. The at least two sensors can be arranged at the same height position in the vertical direction. Looking at the positions of the at least two sensors in a coordinate system having an x-axis, a y-axis, and a z-axis, where the z-axis corresponds to the vertical direction, the positions of the at least two sensors can have the same coordinate value in the direction of the z-axis. The at least two sensors can be arranged offset from each other in the direction of the x-axis (i.e., in the horizontal direction). At least one connecting element on which the sensor element is arranged can be arranged between the at least two sensors and can be displaced relative to the at least two sensors in the vertical direction.

[0017] The at least one connecting element may have at least one travel limiting element. The at least one travel limiting element may be a protrusion. The protrusion may extend away from the connecting element in a radial direction. The travel limiting element may be configured such that the travel limiting element may bear against at least one sensor housing so as to limit the relative movement of the connecting element relative to the sensor housing. Accordingly, the travel limiting element may define an upper end position of the float. When at least one float is in its upper end position (wherein the travel limiting element bears against the sensor housing), the float cannot rise further due to the travel limiting element despite the buoyancy of the float. In its upper end position, the float may be immersed in the liquid in the liquid reservoir. For example, this may be the case after an initial filling operation or during refilling as part of a service during vehicle maintenance when the liquid reservoir has been filled.

[0018] The invention further relates to a liquid reservoir comprising a filling level sensing device of the type described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Exemplary embodiments of the invention will be described hereinafter with reference to the schematic drawings, in which:

[0020] Figure 1 and Figure 2 a view of a liquid reservoir including a filling level sensing device is shown;

[0021] Figures 3 to 5 a view of a liquid reservoir having different filling levels detected by the filling level sensing device is shown;

[0022] Figure 6 and Figure 7 a view of a guide of a filling level sensing device according to an exemplary embodiment is shown; and

[0023] Figure 8 and Figure 9 a view of a guide of a filling level sensing device according to another exemplary embodiment is shown. DETAILED DESCRIPTION

[0024] Figure 1 A plan view of a liquid reservoir 10 having a filling opening 12 is shown. The liquid reservoir 10 is a compensating tank of a vehicle braking system. Accordingly, the liquid reservoir 10 houses a brake fluid that can be supplied to the brake circuit of the vehicle's braking system.

[0025] Figure 2A side view of the liquid reservoir 10 is shown, in which a filling level sensing device 14 is shown. A filling opening 12 can be seen on the top side of the liquid reservoir 10. The filling level sensing device 14 has a float 16 (shown using a dashed line). The float 16 is in contact with the liquid contained in the liquid reservoir 10. The float 16 can be submerged in the liquid or float on the surface of the liquid, depending on the filling level of the liquid in the liquid reservoir 10.

[0026] The float 16 has a connecting element 18, which is also shown using a dashed line in Figure 2 The connecting element 18 is guided in the liquid reservoir 10 such that the connecting element can be displaced in the vertical direction relative to the sensor housing 20. Two sensors 22 and 24 are arranged in the sensor housing 20, and these two sensors detect the position of a sensor element 26 arranged on the connecting element 18. If the position of the float 16 changes, then the position of the connecting element 18 connected to the float 16 and thus also the position of the sensor element 26 relative to the sensors 22 and 24 also change.

[0027] The liquid reservoir 10 has two outlet nozzles 28 and 30 provided on the bottom side of the liquid reservoir 10. The outlet nozzles 28 and 30 have a tubular design and each have an annular protrusion at their ends.

[0028] Figure 3 A side view of the liquid reservoir 10 and the filling level sensing device 14 assembled to the liquid reservoir is shown. For the purpose of showing the design of the filling level sensing device 14, even if at least one section of at least the float 16, the connecting element 18, and the sensor housing 20 is arranged within the liquid reservoir 10, in Figure 3 the elements and components of the filling level sensing device 14 are shown using solid lines. Figure 3 also includes a coordinate system having an x-axis, a y-axis, and a z-axis, with reference to which the liquid reservoir 10 and the filling level sensing device 14 are described. The z-axis extends vertically, while the x-axis extends horizontally.

[0029] Sensors 22 and 24 are arranged in a common sensor housing 20. The sensor housing 20 can be assembled to the liquid reservoir 10. The sensor housing 20 has an elongated design and extends in the x-direction in the liquid reservoir 10. The sensor housing 20 has a relatively low structural height in the z-direction. The connecting element 18 extends in the X-direction between the two sensors 22 and 24. Accordingly, the sensor element 26 arranged on the connecting element 18 is also arranged between the two sensors 22 and 24, as seen in the x-direction. The connecting element 18 is guided on the sensor housing 20 in a vertically displaceable manner. The guide for the connecting element 18 is formed on the sensor housing 20 between the two sensors 22 and 24. Due to the guide on the sensor housing 20, the float 16 and the connecting element 18 are oriented in the vertical direction in the liquid reservoir 10. The float 16 together with the connecting element 18 can be displaced relative to the sensor housing 20 in the z-direction, that is, in the vertical direction.

[0030] Guide rails 32 can be provided on the liquid reservoir 10, for example, on the inner wall of the liquid reservoir 10. The guide rails 32 can be engaged with corresponding devices on the sensor housing 20 and thus allow the sensor housing 20 to be pushed into the liquid reservoir 10. The guide rails 32 can hold the sensor housing 20 and thus the connecting element 18 and the float 16 in a predetermined position and orientation.

[0031] The connecting element 18 has a travel limiting element 34 at its end opposite the float 16. The travel limiting element 34 is designed in the form of an annular protrusion that extends radially away from the connecting element 18. The travel limiting element 34 can bear against the sensor housing 20 in order to limit the displacement of the float 16 and the connecting element 18 relative to the sensor housing 20 in the z-direction (more precisely, in the vertical direction). In this way, the travel limiting element 34 can define the upper end position of the float 16. In other words, when the surface of the liquid in the liquid reservoir 10 is above the float 16 in the z-direction, although the float 16 has buoyancy in the liquid in the z-direction, due to the travel limiting element 34, the float together with the connecting element 18 cannot move further upward in the z-direction. The float 16 can also be immersed in the liquid in the liquid reservoir 10.

[0032] In Figure 3 the surface of the liquid in the liquid reservoir 10 is at the fill level mark A, that is, above the float 16. For example, after an initial filling operation or after refilling as part of a service during vehicle maintenance, the liquid in the liquid reservoir 10 is at this fill level. The float 16 is accordingly immersed in the liquid in the liquid reservoir 10 because the travel limiting element 34 defines the upper end position of the float 16 and prevents further ascent of the float 16 by bearing against the sensor housing 20.

[0033] The sensors 22 and 24 are arranged together in the sensor housing 20. The connecting element 18 equipped with the sensor element 26 extends between the two sensors 22 and 24. Due to the guiding of the connecting element 18 on the sensor housing 20, when the vertical positions of the float 16 and the connecting element 18 change due to the change in the filling level of the liquid in the liquid reservoir 10, the sensor element 26 can change its position relative to the sensors 22 and 24 in the vertical direction. The sensors 22 and 24 are arranged at the same height in the direction of the z-axis or in the vertical direction, that is to say, the positions of the two sensors 22 and 24 have the same coordinate value on the z-axis. However, the two sensors 22 and 24 are offset relative to each other in the direction of the x-axis (that is, in the horizontal direction), and thus the connecting element 18 with the sensor element 26 can extend between them.

[0034] The sensors 22 and 24 can detect the vertical position (z-direction) of the sensor element 26. The sensor element 26 can generate a magnetic field. The sensor element 26 can be, for example, a permanent magnet. When the position of at least one sensor element 26 changes due to the change in the filling level of the liquid reservoir 10, the sensors 22 and 24 can detect it based on the magnetic field generated by the sensor element 26. These changes in the magnetic field (which are detected by the sensors 22, 24) can be caused by the change in the position of the sensor element 26, and thus by the change in the position of the float 16 and due to the connecting element 18 in the liquid reservoir 10. Each of the sensors 22 and 24 has a different sensitivity to the magnetic field. In other words, one of the sensors 22, 24 can respond to the magnetic field generated by the sensor element 26 earlier or faster than the corresponding other sensor 22, 24. Due to the different sensitivities of the sensors 22 and 24, multiple different filling levels can be detected by the sensors 22 and 24, even if the sensors 22 and 24 are located at the same position in the z-direction (that is, the z-coordinate values of the two sensors 22 and 24 are the same). In the exemplary embodiment described herein, the sensor 22 may respond less sensitively to the magnetic field generated by the sensor element 26 compared to the sensor 24.

[0035] According to this exemplary embodiment, sensors 22 and 24 are implemented as switches and each is connected to a circuit. Switches 22 and 24 can change their switching positions according to the magnetic field generated by sensor element 26. Depending on the magnetic field generated by sensor element 26, each of sensors 22 and 24 can cause the circuit associated therewith to be interrupted or closed respectively. Since switches 22, 24 respond to changes in the magnetic field generated by sensor element 26 with different sensitivities, different filling levels of the liquid in liquid reservoir 10 can be detected by the switches. Switches 22, 24 can respond to a magnetic field approaching or moving away and, in response, change their switching positions or their switching states. In particular, sensors 22 and 24 can be reed switches.

[0036] In Figure 3 , the two sensors 22, 24 or the two switches have the same switching state. According to Figure 3 , the two switches 22, 24 are closed and thus the circuits connected to them are likewise closed. The circuits of switches 22, 24 can be connected to a control unit (not shown), which can optionally output a warning signal according to the filling level detected by switches 22, 24. Since Figure 3 the travel limiting element 34 abuts against the sensor housing 20 in Figure 3 , the liquid reservoir 10 is at a high filling level. The float 16 is immersed in the liquid in liquid reservoir 10. In this filling state, switches 22 and 24 do not detect a change in the vertical position of sensor element 26. In Figure 3 , switches 22 and 24 are closed because sensor element 26 is adjacent to switches 22, 24 or is located between the switches in the x direction. Due to the switching states of switches 22, 24, the circuits connected to switches 22, 24 are also closed. Due to the position of at least one sensor element 26 detected by the switches, switches 22, 24 indicate that there is sufficient liquid in liquid reservoir 10. In this state, the control unit connected to the circuit does not need to output a warning signal.

[0037] In Figure 4 , the filling level of the liquid in liquid reservoir 10 has dropped to filling level mark B. The float 16 floats on the surface of the liquid in liquid reservoir 10 and has moved downward relative to the sensor housing 20 in the vertical direction (z-axis) together with the connecting element 18 and the sensor element 26 mounted thereon, the position of the sensor housing being fixed and including two sensors 22 and 24. The travel limiting element 34 no longer abuts against the sensor housing 20 but is at a certain distance from the sensor housing 20 in the z direction. In Figure 4In [description], the sensor 22, which is less sensitive to the magnetic field of the sensor element 26, has changed its switching state based on the change in the vertical position of the sensor element 26. The switch 22 opens and thus interrupts the circuit connected to this switch. The interruption of the circuit connected to the switch 22 can be detected by the electronic control unit. The electronic control unit can output a warning signal based on the detected change in the switching state of the switch 22, and this warning signal indicates liquid loss in the liquid reservoir 10. Compared with the less sensitive sensor 22, the sensor 24, which is more sensitive to the magnetic field of the sensor element 26, remains closed.

[0038] In Figure 5 [description], the filling level in the liquid reservoir 10 has dropped to the filling level mark C. Due to the drop in the filling level, the float 16 also drops again in the vertical direction, and the connecting element 18 and the sensor element 26 also drop accordingly. Attributed to the change in the position of the float 16, the sensor element 26, which is connected to the float 16 by means of the connecting element 18, moves further away from the sensors 22 and 24. Due to this greater distance in the z direction, the more magnetically sensitive sensor 24 has now also changed its switching state and interrupted the circuit connected to this sensor. Thus, in Figure 5 [description], both switches 22 and 24 are open. The change in the switching state of the switch 24, which is more sensitive to the magnetic field of the sensor element 26, and the interruption of the circuit connected to the switch 24 are detected by the electronic control unit. Due to this additional change in the switching state of the switch 24, the electronic control unit (not shown) can output a warning signal, which indicates critical liquid loss in the braking system of the vehicle and warns of a threat of failure of the braking system.

[0039] Figure 6 A partial cross-sectional view of the filling level sensing device 14 is shown, in which a cross-section of the sensor housing 20 is shown. The sensors 22 and 24 are arranged in the sensor housing 20. The connecting element 18 is arranged between the sensors 22 and 24 in the x direction, and this connecting element can be displaced in the vertical direction relative to the two position-fixed sensors 22 and 24. The connecting element 18 is guided in a displaceable manner on the sensor housing 20 and has a substantially cylindrical design. The connecting element 18 is connected to the float 16 and has the sensor element 26. Each of the sensors 22 and 24 is connected to a circuit. Additionally, a travel limiting element 34 is present at the end of the connecting element 18 opposite to the float 16.

[0040] The sensors 22 and 24 can be inserted into the liquid reservoir 10 together with the sensor housing 20 and can be connected to the liquid reservoir 10. For example, the sensor housing 20 can be pushed into the liquid reservoir 10. Similarly, it is conceivable that the fill level sensing device 14 can be inserted into the liquid reservoir 10 as a unit (i.e., the sensor housing 20 with the sensors 22 and 24, the float 16, and the connecting element 18).

[0041] Figure 7 A plan view of the sensor housing 20 is shown. The sensors 22, 24 are shown using dashed lines in Figure 7 . An opening 36 forming a guide for the connecting element 18 can be seen on the sensor housing 20 between the sensors 22 and 24 in the x-direction. The connecting element 18 can be inserted into the opening 36.

[0042] Figure 8 A view of the fill level sensing device 14 according to another exemplary embodiment is shown. The main difference from the fill level sensing device 10 described above with respect to Figure 6 and Figure 7 is the design or arrangement of the sensor element 26. The difference between the two embodiments is particularly clear from Figure 9 .

[0043] In Figure 9 , the sensor housing 20 in which the sensors 22 and 24 are arranged can be seen. The connecting element 18 together with the sensor element 26 is arranged or guided outside the sensor housing 20. The connecting element 18 is guided in a guide 38 which has a U-shaped cross-section. The guide 38 can be formed by a cutout in the liquid reservoir 10. The sensor element 26 is assembled to the outside of the connecting element 18 on the surface of the connecting element facing the sensor housing 20, which has a rectangular cross-section. Thus, the sensor element 26 is also arranged offset in the y-direction with respect to the sensors 22 and 24. The sensor element 26 is located substantially between the two sensors 22 and 24 in the x-direction.

[0044] Due to the different magnetic susceptibilities between the two sensors 22 and 24, the sensors 22 and 24 can be arranged in the same vertical position (z-axis) and can be accommodated in a common sensor housing 20 having a low structural height but still detecting at least two different fill levels, and this sensor housing can be pushed into the liquid reservoir.

Claims

1. A filling level sensing device (14) for a liquid reservoir (10), the filling level sensing device comprising: At least one float (16), the at least one float being designed to come into contact with the liquid in the liquid reservoir (10), At least one sensor element (26), the at least one sensor element being connected to the at least one float (16), the at least one sensor element (26) generating a magnetic field, and At least two sensors (22, 24), the at least two sensors being adapted to detect the position of the at least one sensor element (26) arranged between the at least two sensors (22, 24), the at least two sensors (22, 24) reacting to the magnetic field generated by the at least one sensor element (26), one of the at least two sensors (22, 24) having a higher magnetic sensitivity than the other corresponding sensor (24), wherein the at least two sensors (22, 24) are arranged at the same height in the vertical direction, and at least one of the at least two sensors senses a change in the filling level of the liquid reservoir (10) based on the position of the at least one sensor element (26) relative to the at least two sensors (22, 24).

2. The filling level sensing device according to claim 1, wherein, The liquid reservoir (10) is a compensation tank for a vehicle braking system.

3. The filling level sensing device according to claim 1, wherein, The at least one sensor element (26) is displaceable relative to the at least two sensors (22, 24) in the vertical direction.

4. The filling level sensing device according to claim 1 or 2, wherein, The at least one float (16) has at least one connecting element (18), the at least one sensor element (26) being arranged on the at least one connecting element.

5. The filling level sensing device according to claim 4, wherein, There are guides (36, 38) for the at least one connecting element (18), the guides guiding the displacement of the connecting element (18) in the vertical direction.

6. The filling level sensing device according to claim 1, wherein, Each of the at least two sensors (22, 24) is connected to a circuit.

7. The filling level sensing device according to claim 1, wherein, At least one of the at least two sensors (22, 24) is a switch, the switch changing its switching state based on the magnetic field generated by the at least one sensor element (26).

8. The filling level sensing device according to claim 4, wherein, The at least two sensors (22, 24) are arranged in a sensor housing (20) that can be connected to the liquid reservoir (10).

9. The filling level sensing device according to claim 8, wherein, The sensor housing (20) has a guide (36) for the at least one connecting element (18) in order to guide the at least one connecting element (18) in a vertical movement relative to the sensor housing (20).

10. The filling level sensing device according to claim 4, wherein, The at least one connecting element (18) has at least one travel limiting element (34).

11. The filling level sensing device according to claim 1, wherein, The at least two sensors (22, 24) can be connected to a control unit.

12. A liquid reservoir (10) comprising the filling level sensing device (14) according to any one of claims 1 to 11, wherein, The at least one float (16) has at least one connecting element (18).

13. The liquid reservoir according to claim 12, wherein, The guide for the at least one connecting element (18) is assembled or formed on the liquid reservoir (10).

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