Method for controlling a hydraulic machine and hydraulic machine

Abstract

The invention relates to a method for controlling a hydraulic machine having a primary impeller with blades and a secondary impeller with blades, the primary impeller and the secondary impeller jointly forming a working chamber which can be filled with working medium from a working medium reservoir in a working medium storage container in order to hydraulically transmit drive power from the primary impeller to the secondary impeller by forming a working medium circulation in the working chamber, wherein a control pressure is applied to the working medium reservoir in order to displace working medium from the working medium reservoir into the working chamber. The method according to the invention is characterized in that when the control pressure is applied to the working medium reservoir, a pressure increase in the working medium reservoir is at least indirectly detected and the filling level of the working medium reservoir in the working medium reservoir is determined as a function of the detected pressure increase.

Description

Technical Field

[0001] The invention relates to a method for controlling a hydraulic machine, in particular a hydraulic brake, and to such a hydraulic machine, in particular a hydraulic brake. Background Art

[0002] In a hydraulic machine, the degree of filling of the working chamber with the working medium can be adjusted by different methods. According to one method, a shut-off valve is arranged at the inlet to the working chamber and a regulating valve is arranged at the outlet of the working chamber. The supply of the working medium to the working chamber can be interrupted by the shut-off valve. The flow cross section in the working medium outlet can be changed by the regulating valve, so that a greater or lesser pressure loss is formed in the working medium outlet and thereby the amount of working medium and the working medium pressure in the working chamber are adjusted. According to a second method related to the invention, a working medium storage container with a working medium reserve is provided, to which a preset variable control pressure can be applied in order to displace more or less working medium from the working medium reserve into the working chamber.

[0003] In both methods, as in the present invention, the working medium can also simultaneously serve as a lubricant for the hydrodynamic machine, for example for lubricating bearings.

[0004] If, in a hydraulic machine of the type according to the invention controlled according to the second method, the working medium reserve decreases during the operating time of the hydraulic machine due to unavoidable leakage, this can lead to an excessively low filling level of the working medium reserve in the working medium container. Such an excessively low filling level can also be the result of incorrect filling during commissioning or maintenance of the hydraulic machine. Such an excessively low filling level can lead to an undesired increase in the ejection of working medium during operation of the hydraulic machine and also to insufficient lubrication of the hydraulic machine. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for controlling a hydraulic machine and a corresponding hydraulic machine in which a too low filling level of a working medium reserve in a working medium container is detected. The present invention is characterized by low expenditure in terms of apparatus technology.

[0006] The object of the invention is achieved by a method for controlling a hydraulic machine and a hydraulic machine.

[0007] The hydrodynamic machine according to the invention is designed in particular as a hydrodynamic brake.

[0008] The method according to the invention is applied in a hydrodynamic machine having a bladed primary impeller and a bladed secondary impeller, which together form a working chamber which can be filled with working medium from a working medium reservoir in a working medium storage container, in order to transfer the driving power hydraulically from the primary impeller to the secondary impeller by forming a working medium circulation in the working chamber, wherein a control pressure is applied to the working medium reservoir in order to displace the working medium from the working medium reservoir into the working chamber. If the hydrodynamic machine is a hydrodynamic brake, in particular only the bladed primary impeller rotates, while the bladed secondary impeller is stationary, in order to hydrodynamically brake the primary impeller. However, brakes with a secondary impeller driven in the opposite direction to the primary impeller are also conceivable. In a hydrodynamic machine designed as a hydrodynamic coupling or a hydrodynamic converter, as one embodiment of the invention relates to, the primary impeller hydrodynamically drives the secondary impeller, whereby this drive is achieved by the interposition of at least one guide wheel or guide vane ring positioned in the working chamber.

[0009] According to the invention, when a control pressure is applied to the working medium reserve, the pressure rise in the working medium storage container is detected at least indirectly and the filling level of the working medium reserve in the working medium container is determined based on the detected pressure rise. If it is thus determined that the filling level of the working medium reserve in the working medium container is insufficient, a warning, in particular an acoustic warning and / or a visual warning, can be issued. Additionally or alternatively, further activation of the hydraulic machine can also be prevented until a sufficient filling level is established or detected again.

[0010] According to one embodiment of the invention, a single pressure value in the working medium storage container is detected and compared with a predefined reference value or a predefined reference range. According to another embodiment of the invention, a pressure curve is detected and compared with a predefined reference pressure curve.

[0011] The pressure value or the pressure trend can be detected by a pressure sensor arranged in the medium storage container. However, in principle, such a pressure sensor can also be arranged at another location, for example in a connecting line for the working medium, which leads to the working medium storage container at one end and to the working chamber at the other end at least indirectly. It is usually also possible to indirectly detect the pressure increase in the working medium storage container by detecting other variables and to determine the pressure increase based on these variables. When the hydraulic machine is no longer available, the vehicle driver is particularly preferably notified by a corresponding display. This can be realized, for example, via a vehicle display.

[0012] According to a particularly advantageous embodiment of the invention, as shown in the figure, the pressure rise is detected based on (at least) one single or discrete pressure value. For example, the pressure in the medium storage container is detected at least indirectly within a preset time period after the start of the application of the control pressure or after the application of the changed control pressure and compared with a preset limit value. The filling level is then determined from the result of the comparison. In particular, if the detected pressure is below a preset limit value or a limit value range containing the limit value, it can be concluded that the filling level is too low.

[0013] Advantageously, no additional sensors which are not present in the first place are required to carry out the method according to the invention. For example, the hydraulic machine can be activated by filling the working chamber with working medium by means of an opening command from the vehicle driver or a control device, and can be deactivated by emptying the working chamber by means of a corresponding closing command, wherein after the opening command is detected, a control pressure is applied to the working medium reservoir in order to bring the working chamber to a predetermined filling degree. In order to determine the filling level of the working medium reservoir in the working medium storage container, a predetermined control pressure can additionally be applied to the working medium reservoir in the deactivated state, i.e., when no opening command is detected or if no opening command is present, in order to determine the filling level.

[0014] Then, via the same pressure sensor or via a plurality of identical pressure sensors, the pressure in the storage container can be detected in the activated state of the hydraulic machine and used to control or regulate the filling degree of the working chamber, while at the same time the pressure in the storage container can be detected in the deactivated state of the hydraulic machine when determining the filling level of the working medium reserve in the working medium storage container.

[0015] In particular, the operating medium storage container has no float for detecting the fill level of the operating medium reserve.

[0016] According to one embodiment of the invention, in order to determine the limit value in the working medium storage container, a predetermined filling level of the working medium reservoir is set and a predetermined control pressure is applied to the working medium reservoir for a predetermined period of time. After the predetermined period of time has elapsed, the pressure in the working medium reservoir is at least indirectly detected and preset as a limit value. A calibration is thus performed.

[0017] According to one embodiment of the invention, a reference pressure profile over a period of time is predefined, and after the start of applying a control pressure or a changed control pressure, the pressure profile in the working medium storage container over a predefined period of time is at least indirectly detected and compared with the reference pressure profile in order to determine the fill level.

[0018] The hydraulic machine according to the invention has a control device which is designed to carry out the method according to the invention so that a pressure increase in a working medium storage container can be detected at least indirectly by applying a control pressure to the working medium reserve and the fill level of the working medium reserve in the working medium storage container can be determined based on the detected pressure increase. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be described below by way of example based on an embodiment and the accompanying drawings. In the accompanying drawings:

[0020] Figure 1 A hydraulic machine according to the invention is shown;

[0021] Figure 2 A comparison of the detected pressure value or pressure curve with a limit value or a reference pressure curve is shown in order to determine the fill level therefrom. DETAILED DESCRIPTION

[0022] exist Figure 1 Schematically shows a hydraulic machine in the form of a hydraulic brake 10. The hydraulic machine has a bladed primary impeller 1 driven by a drive shaft 7 and a bladed secondary impeller 2 arranged opposite the primary impeller 1 in the axial direction, which is designed as a stator. By driving the primary impeller 1 in rotation, a working medium circulation 8 is generated in the working chamber 3 formed by the primary impeller 1 and the secondary impeller 2, by means of which a rotational torque or driving power is transmitted from the primary impeller 1 to the secondary impeller 2, thereby braking the primary impeller 1 and thus the drive shaft 7. Such a hydraulic brake 10 is, for example, a component of a motor vehicle drive train.

[0023] A hydraulic machine, here a hydraulic brake 10, usually has an external working medium circuit 9 with a working medium storage container 5 for accommodating a working medium reservoir 4. A cooler 11 is also provided in the exemplary external working medium circuit 9 shown. Further devices not shown here may be provided.

[0024] In order to feed more or less working medium from the working medium storage container 5 or the working medium reservoir 4 into the working chamber 3, a correspondingly predetermined control pressure is applied to the working medium fill level of the working medium reservoir 4 in the working medium storage container 5. To generate the control pressure, a control valve, here in the form of a proportional valve 12, is provided, which is positioned in a control air line 13 between a compressed air source 14 and the air chamber in the working medium storage container 5. The proportional valve 12 is controlled by a control device 15 so that it adjusts the desired control pressure depending on the required braking torque.

[0025] Thus, the hydrodynamic brake 10 is activated in that, after detecting an opening command from the vehicle driver or a vehicle control device, a transmission control device of a vehicle transmission (not shown further here) of a motor vehicle powertrain (of which the brake 10 is a component), or a brake control device, the control device 15 actuates the proportional valve 12 and thereby fills the working chamber 3 of the hydrodynamic brake 10, which was previously substantially emptied in the deactivated state, with working medium from the working medium reservoir 4. When the brake 10 is deactivated, the working chamber 3 is accordingly emptied again and the working medium is fed back into the working medium reservoir 4. The control device 15 can be a component of the vehicle control device, the transmission control device or the brake control device.

[0026] In order to adjust the control pressure, a pressure sensor 6 is provided in the air chamber of the working medium storage container 5, which detects the pressure in the working medium storage container 5. The detected pressure is processed in a control device 15, for example.

[0027] The filling level of the working medium reservoir 4 in the working medium reservoir container 5 can vary. Thus, if working medium is lost in the hydraulic brake 10 during operation due to leakage, the filling level decreases. As a result, a lower filling level can be formed in the working medium reservoir container 5. This is indicated by the dashed line of the working medium level. However, in order to ensure the proper function and lubrication of the hydraulic brake 10, a minimum filling level must be maintained in the working medium reservoir container 5.

[0028] In order to determine the current filling level of the working medium reservoir 4 in the working medium storage container 5, preferably when the hydraulic brake 10 is deactivated (usually for a deactivated hydraulic machine), a predetermined control pressure is transmitted to the working medium storage container 5 by the proportional valve 12 in cooperation with the compressed air source 14, and the actual pressure that is built up after a predetermined time period is detected by the pressure sensor 6. In addition or as an alternative, the pressure trend that is built up can be detected by the pressure sensor 6 during this preset period. The detected pressure or the detected pressure trend is compared with a limit value or a reference pressure trend of the pressure and the filling level is determined from this. This is possible because at a lower filling level there is a larger air volume in the working medium storage container 5, which is sealed in a pressure-tight manner relative to the ambient pressure, wherein the air volume is compressible. Therefore, if the filling level is low, it takes a longer time for this pressure to build up in the working medium storage container 5. Therefore, the current filling level of the working medium reservoir 4 in the working medium storage container 5 is also obtained from the pressure detected after the predetermined time period has passed or from this pressure trend.

[0029] exist Figure 2In the diagram, on the one hand, the control pressure p generated or provided by the proportional valve 12 is shown over time in the method according to the invention. Y At time a, the proportional valve 12 opens (see Figure 1 ) and applies a control pressure p to the working medium storage container 5 Y At time b, the proportional valve 12 is closed again, thereby controlling the pressure p Y The time period between the two moments a and b is called the preset time period Δt.

[0030] The pressure or pressure profile in the working medium storage container 5 detected by the pressure sensor 6 is denoted by p ist At a relatively high filling level, a relatively high detected pressure p is formed after a period of time Δt. ist Or a relatively high detected pressure trend p is formed over a period of time Δt ist At relatively low fill levels, a correspondingly lower detected pressure or pressure profile p' is established. ist , which is shown here by a dashed line. The detected pressure or pressure trend can be compared to the limit value p lim Or reference pressure trend p ref If the detected pressure or pressure trend p ist Above the limit value p lim Or reference pressure trend p ref , then the filling level of the working medium reserve 4 in the working medium storage container 5 is sufficient. On the other hand, if the detected pressure or pressure trend p ist Below the limit value p lim Or reference pressure trend p ref (See the end point at the end of the time period Δt or the direction p' ist ), the fill level is too low.

[0031] List of Reference Numerals

[0032] 1Primary impeller

[0033] 2nd impeller

[0034] 3 working chambers

[0035] 4Working medium reserve

[0036] 5Working medium storage container

[0037] 6. Pressure Sensor

[0038] 7 Drive shaft

[0039] 8 Working medium circulation

[0040] 9 External working medium circulation

[0041] 10Hydraulic brake

[0042] 11 Cooler

[0043] 12 Proportional valve

[0044] 13 Control air line

[0045] 14 Compressed air source

[0046] 15. Control Equipment

[0047] Δt time period

[0048] a, b moment

[0049] p lim Limit value

[0050] p ref Reference pressure trend

[0051] p ist , p' ist Detected pressure / pressure trend

Claims

1. A method for controlling a hydraulic machine, the hydraulic machine having a primary impeller (1) with blades and a secondary impeller (2) with blades, the primary impeller and the secondary impeller jointly forming a working chamber (3) which can be filled with working medium from a working medium reserve (4) in a working medium storage container (5) in order to transfer drive power from the primary impeller (1) to the secondary impeller (2) hydraulically by forming a working medium circulation (8) in the working chamber (3); wherein: A control pressure (p Y ) in order to expel the working medium from the working medium reservoir (4) into the working chamber (3); It is characterized in that, when the control pressure (p Y ) is applied to the working medium reservoir (4), at least indirectly detecting a pressure increase in the working medium storage container (5) and determining the filling level of the working medium reservoir (4) in the working medium reservoir (5) based on the detected pressure increase, wherein at the beginning of the application of the control pressure (p ist ) or change the control pressure (p Y ) after a preset time period (Δt), at least indirectly detecting the pressure (p ist ) and compare it with the preset limit value (p lim )Compare.

2. The method according to claim 1, characterized in that If the detected pressure (p ist ) is lower than the preset limit value (p ref ) or including the preset limit value (p ref ), it is concluded that the fill level is too low.

3. The method according to claim 1, characterized in that The hydraulic machine can be activated by an opening command from the vehicle driver or a control device by filling a working chamber (3) with a working medium, and can be deactivated by a corresponding closing command by emptying the working chamber (3), wherein after the opening command is detected, the control pressure (p Y ) is applied to the working medium reservoir (4) in order to achieve a predetermined filling degree of the working chamber (3) with working medium and, in order to determine the filling level, in addition in the deactivated state when no opening command of the hydraulic machine is detected, a predetermined control pressure (p Y ) is applied to the working medium reservoir (4).

4. The method according to claim 1, characterized in that A pressure sensor (6) is provided in the working medium storage container (5), and the pressure sensor (6) detects the pressure (p ist ).

5. The method according to claim 4, characterized in that The pressure (p) in the working medium storage container (5) is detected by the pressure sensor (6) even in the activated state of the hydraulic machine. ist ) and the pressure (p ist ) is used to adjust the filling degree of the working chamber (3).

6. The method according to claim 1, characterized in that In order to determine the limit value (p lim ), adjusts a predetermined filling level in the working medium reservoir (4) and increases a predetermined control pressure (p Y ) is applied to the working medium reservoir (4), and after the predetermined period of time (Δt) has elapsed, the pressure (p) in the working medium storage container (5) is at least indirectly detected. ist ) and preset it as the limit value (p lim ).

7. The method according to claim 2, characterized in that Preset reference pressure trend (p ref ), when starting to apply control pressure (p Y ) or change the control pressure (p Y ) at least indirectly detects the pressure trend (p) in the working medium storage container (5) after a predetermined time period (Δt) ist ) and compare it with the reference pressure trend (p ref ) to determine the fill level.

8. The method according to claim 1, characterized in that The hydrodynamic machine operates as a hydrodynamic brake (10).

9. A hydraulic machine comprising a primary impeller (1) with blades and a secondary impeller (2) with blades, the primary impeller and the secondary impeller jointly forming a working chamber (3) which can be filled with a working medium, so that the drive power can be transmitted hydraulically from the primary impeller (1) to the secondary impeller (2) by means of a working medium circulation (8) in the working chamber (3), and the hydraulic machine also comprises a working medium reserve (4) in a working medium storage container (5), the working medium reserve (4) being acted upon by a control pressure (p Y ) in order to displace more or less working medium from the working medium reservoir (4) into the working chamber (3) in order to adjust a predetermined filling degree; It is characterized in that A control device (15) is provided which is designed to carry out a method according to one of claims 1 to 8.

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