Method for controlling a hydrodynamic machine and hydrodynamic machine

Abstract

A method for controlling a hydrodynamic machine, including the steps of: providing a hydrodynamic machine which includes a bladed primary wheel and a bladed secondary wheel, which together form a working chamber, which can be filled with a working medium from a working medium supply contained in a working medium reservoir, to transfer drive power hydrodynamically from the bladed primary wheel to the bladed secondary wheel by forming a working medium circuit in the working chamber; applying a control pressure to the working medium supply in order to force the working medium from the working medium supply into the working chamber; detecting, at least indirectly, a pressure increase in the working medium reservoir, when the control pressure is applied to the working medium supply; and determining, as a function of the pressure increase that has been detected, a fill level of the working medium supply in the working medium reservoir.

Claims

1. A method for controlling a hydrodynamic machine, comprising the steps of: providing a hydrodynamic machine which includes a bladed primary wheel and a bladed secondary wheel, which together form a working chamber, which is configured for being filled with a working medium from a working medium supply contained in a working medium reservoir, in order to transfer a drive power hydrodynamically from the bladed primary wheel to the bladed secondary wheel by forming a working medium circuit in the working chamber; applying a control pressure to the working medium supply in order to force the working medium from the working medium supply into the working chamber; detecting, at least indirectly, a pressure increase in the working medium reservoir, when the control pressure is applied to the working medium supply; and determining, as a function of the pressure increase that has been detected, a fill level of the working medium supply in the working medium reservoir, wherein a pressure is (a) detected at least indirectly in the working medium reservoir at a predetermined time period after a start of an application of one of the control pressure and a changed control pressure and (b) compared with a limit value that is predetermined.

2. The method according to claim 1, wherein a fill level is determined to be too low if the pressure that has been detected is one of below the limit value and below a limit range that includes the limit value.

3. The method according to claim 2, wherein the hydrodynamic machine is configured for being activated by way of an activation command from one of a vehicle driver and a control device by filling the working chamber with the working medium and is configured for being deactivated by way of a corresponding deactivation command by emptying the working chamber; wherein the control pressure is applied to the working medium supply after the activation command has been detected in order to ensure a predetermined fill level of the working medium in the working chamber; wherein, to additionally determine the fill level in a deactivated state without detecting an activation command of the hydrodynamic machine, a predetermined control pressure is applied to the working medium supply.

4. The method according to claim 3, wherein a pressure sensor is provided in the working medium reservoir which detects the pressure in the working medium reservoir.

5. The method according to claim 4, wherein with the pressure sensor, the pressure in the working medium reservoir can then be detected also in an activated state of the hydrodynamic machine and used to regulate the fill level in working chamber.

6. The method according claim 5, wherein in order to determine the limit value in the working medium reservoir, a predetermined level of the working medium supply is set, and a predetermined control pressure is applied to the working medium supply for the predetermined time period, after an expiration of which the pressure in the working medium reservoir is detected, at least indirectly, and is specified as the limit value.

7. The method according to claim 6, wherein a reference pressure curve is specified over the predetermined time period, and a pressure curve in the working medium reservoir (a) is detected at least indirectly over the predetermined time period after the start of the application of one of the control pressure and the changed control pressure and (b) is compared with the reference pressure curve for a determination of the fill level.

8. The method according to claim 1, wherein the hydrodynamic machine is operated as a hydrodynamic retarder.

9. A hydrodynamic machine, comprising: a bladed primary wheel; a bladed secondary wheel, the bladed primary wheel and the bladed secondary wheel together forming a working chamber which is configured for being filled with a working medium in order to transfer a drive power hydrodynamically from the bladed primary wheel to the bladed secondary wheel by way of a working medium circuit in the working chamber; a working medium reservoir configured for containing a working medium supply therein to which a control pressure is applied in order to displace one of more and less of the working medium from the working medium supply into the working chamber in order to adjust a predetermined fill level; and a control device configured for carrying out a method including the steps of: detecting, at least indirectly, a pressure increase in the working medium reservoir, when the control pressure is applied to the working medium supply; and determining, as a function of the pressure increase that has been detected, a fill level of the working medium supply in the working medium reservoir, wherein a pressure is (a) detected at least indirectly in the working medium reservoir at a predetermined time period after a start of an application of one of the control pressure and a changed control pressure and (b) compared with a limit value that is predetermined.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 is a hydrodynamic machine according to the invention; and

(3) FIG. 2 is a comparison of a detected pressure value or pressure curve with a limit value or a reference pressure curve to determine the fill level therefrom.

(4) Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 is a schematic illustration of a hydrodynamic machine in the embodiment of a hydrodynamic retarder 10. Said retarder has a bladed primary wheel 1 driven by means of a drive shaft 7 and a bladed secondary wheel 2 located opposite primary wheel 1 viewed in the axial direction, which is designed here as a stator. By means of rotationally driving primary wheel 1, a working medium circuit 8 is generated in a working chamber 3 which is formed by primary wheel 1 and secondary wheel 2, by means of which torque or drive power is transmitted from primary wheel 1 to secondary wheel 2, whereby primary wheel 1 and thus drive shaft 7 are braked. Such a hydrodynamic retarder 10 is for example a component of a motor vehicle drive train.

(6) In general, the hydrodynamic machine—in this case hydrodynamic retarder 10—has an external working medium circuit 9, including a working medium reservoir 5 which accommodates a working medium supply 4. In the illustrated exemplary external working medium circuit 9 a radiator 11 is moreover provided. Additional units which are not illustrated here can be provided.

(7) In order to move more or less working medium out of working medium reservoir 5 or respectively working medium supply 4 into working chamber 3, a correspondingly predetermined control pressure is applied to the working medium level of the working medium supply 4 in working medium reservoir 5. To generate the control pressure a control valve in the embodiment 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 space in working medium reservoir 5. Proportional valve 12 is actuated by a control device 15 so that it sets the desired control pressure according to the required braking torque.

(8) Thus, hydrodynamic retarder 10 is activated in that, after detection of an activation command by a vehicle driver or a vehicle control device, transmission control device of a vehicle transmission of a motor vehicle drive train, which is not shown here in more detail and of which retarder 10 is a component, or retarder control device control device 15 actuates proportional valve 12 and as a result, working chamber 3 of hydrodynamic retarder 10, which was previously largely emptied in the deactivated state, is filled with working medium from working medium supply 4. When retarder 10 is deactivated, working chamber 3 is again emptied accordingly and the working medium is moved back into working medium supply 4. Control device 15 can be an integral part of the aforementioned vehicle control device, transmission control device or retarder control device.

(9) To regulate the control pressure a pressure sensor 6 is provided in the air space of working medium reservoir 5 which detects the pressure in working medium reservoir 5. The detected pressure is processed for example in control unit 15.

(10) The fill level of working medium supply 4 in working medium reservoir 5 can vary. The fill level decreases if during operation working medium in hydrodynamic retarder 10 is lost due to leaks. This can result in a lower fill level setting in working medium reservoir 5. This is illustrated by the broken line of the working medium level. In order to ensure proper functioning and proper lubrication of hydrodynamic retarder 10 a minimum fill level must be maintained in working medium reservoir 5.

(11) In order to determine the current fill level of working medium supply 4 in working medium reservoir 5—preferably with the hydrodynamic retarder 10 deactivated (generally with the hydrodynamic machine deactivated)—a predetermined control pressure is introduced into working medium reservoir 5 by means of proportional valve 12 in conjunction with compressed air source 14, and pressure sensor 6 detects which actual pressure is established after a predetermined period of time. The recorded pressure or respectively the recorded pressure curve is compared with a limit value of the pressure, or respectively a reference pressure curve and the fill level is determined from this. This is possible because at a lower fill level, there is a larger volume of air in working medium reservoir 5, the latter being sealed in a pressure-tight manner against the environment, whereby the air volume is compressible. At a lower fill level it takes therefore comparatively longer for the pressure to build up in working medium reservoir 5. Thus the current level of working medium supply 4 in working medium reservoir 5 is also determined from the recorded pressure after expiration of a predetermined period of time or from the pressure curve.

(12) On the one hand, the diagram of FIG. 2 illustrates control pressure pγ generated or provided by proportional valve 12 over time for a method according to the invention. At one point in time a, proportional valve 12 (see FIG. 1) opens and supplies working medium reservoir 5 with control pressure pγ. At a point in time b, proportional valve 12 closes again, so that control pressure pγ drops back to zero. The time period between the two points in time a and b is referred to as a predetermined time period Δt.

(13) The pressure or pressure curve detected with pressure sensor 6 in working medium reservoir 5 is identified with p.sub.ist. At a comparatively high fill level, a comparatively high recorded pressure p.sub.ist occurs after expiration of time period Δt or a comparatively high recorded pressure curve p.sub.ist occurs over time period Δt. Accordingly, at a comparatively low fill level, a comparatively low recorded pressure or pressure curve p′.sub.ist occurs which is shown in a dashed line. The detected pressure or pressure curve can be compared with a limit value p.sub.lim or reference pressure curve p.sub.ref, which is illustrated in a dash-dot line. If the recorded pressure or pressure curve p.sub.ist is above limit value p.sub.lim or reference pressure curve p.sub.ref, a sufficient fill level of working medium supply 4 is present in working medium reservoir 5. In contrast, if it is below (refer to termination point at end of time span Δt or respectively curve p′.sub.ist), it means that the fill level is too low.

COMPONENT IDENTIFICATION LIST

(14) 1 primary wheel 2 secondary wheel 3 working chamber 4 working medium supply 5 working medium reservoir 6 pressure sensor 7 drive shaft 8 working medium circuit 9 external working medium circuit 10 hydrodynamic retarder 11 radiator 12 proportional valve 13 control air line 14 compressed air source 15 control device Δt time period a, b point in time p.sub.lim limit value p.sub.ref reference pressure curve p.sub.ist, p′.sub.ist detected pressure/pressure curve

(15) While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.