DE102007047724A1 - Method and device for controlling a hydraulic unit - Google Patents

Abstract

The present invention provides a method of controlling a hydraulic power unit comprising an engine and a variable displacement pump driven by the engine. First, an engine map is given which describes an efficiency of the engine as a function of a torque and a speed of the engine. In further steps, a desired power of the variable displacement pump is determined and a characteristic curve determined from the engine map, which corresponds to the desired power. By determining a maximum of the characteristic curve, an optimized torque and an optimized rotational speed are determined. The variable displacement pump is set to the optimized torque, and the engine to the optimized speed. In another aspect, the invention provides a control device for controlling a hydraulic power unit having a motor and a variable displacement pump driven by the engine. The apparatus includes a memory storing an engine map describing an efficiency of the engine as a function of a torque and a speed of the engine. Also provided are a desired power determination unit which determines a nominal power of the variable displacement pump, a characteristic determiner which determines a characteristic curve corresponding to the desired power from the engine map, an optimization unit which determines an optimized torque and an optimized rotational speed by determining a maximum of the characteristic curve, a pump actuator which the variable pump on the optimized ...

Description

The The present invention relates to a method for driving a Hydraulic unit, a motor and a pump driven by the motor includes. Furthermore, the invention relates to a drive device for controlling a hydraulic unit and a hydraulic unit with such a drive device.

hydraulic Power units the type mentioned are in a variety of stationary and Mobile on vehicles mounted hydraulically operated devices such as B. used construction and agricultural machinery. A hydraulic unit Fulfills in such devices the function of hydraulic fluid on a needed Compressing pressure and a consumer of hydraulic energy such as B. a working cylinder or a hydraulic motor as a volume flow one needed To provide quantity. Here is the power requirement of the consumer generally time-varying.

at a type of conventional Hydraulic power units, the motor is constantly set to a speed, where the pump delivers a flow rate that is the highest needed at any time Volume flow corresponds. In excess compressed hydraulic fluid will be over, Pressure control valve relaxed and returned to the pump circuit. There a significant part of the energy used by the relaxation in the pressure control valve in heat is converted, the efficiency of such aggregates is low.

Around reduce the energy consumption of the engine, z. B. at a another type of conventional Hydraulic power units the engine is variably set to a speed, when the pump is currently a volume flow in the currently required amount supplies. A pump control unit depends on it from the to be provided by the hydraulic pump flow with the pump control unit via a Bus connection connected engine control unit a target speed before and changed this, if the volume flow required by the consumer changes. Of the Efficiency of hydraulic units of this type is in temporal Means, however, reduced by the fact that the efficiency of the engine over its Speed range is generally not constant and therefore at least while operated part of the operating time with an unfavorable efficiency becomes.

It is therefore an object of the present invention, the efficiency of To improve hydraulic power units with variable power.

According to the invention this Task by a method for controlling a hydraulic unit with the features of claim 1, and by a device for controlling a hydraulic unit with the features of claim 7 solved.

The The idea underlying the present invention is that a variable displacement pump with adjustable torque (i.e. displacement given the pressure difference to be overcome) to be driven by an adjustable speed motor, so that a required nominal power (ie a required one Volume flow at a given pressure difference) always by a variety different combinations of torque and speed achievable is. It is from the variety of combinations of torque and speed that needed the Provide target power, which determines the one with the highest efficiency. For this will be first an engine map specified, the efficiency of the engine as a function of a torque and a speed of the motor describes. From the engine map, a characteristic is determined along which the power delivered by the pump is constantly equal to the target power is. Then a point is determined on the characteristic curve at which the Efficiency assumes a maximum value. The variable pump is adjusted so that it requests the torque determined by the engine, and the engine is adjusted so that it detects the pump with the Speed drives.

In the dependent claims find advantageous embodiments and improvements of Invention.

According to one preferred development is still a step of modifying the engine map provided with a pump map, the one Efficiency of the variable displacement pump as a function of torque and describes the speed. In this way it is possible by the modified map the overall efficiency of the hydraulic unit, in which both the losses of the engine and the losses of the Pump are taken into account, to describe. The maximum due to the modified map determined characteristic along which the output from the pump Power is constantly equal to the target power, thus corresponds at the time of delivery of the required Target power maximum possible Overall efficiency of the hydraulic unit.

According to another preferred embodiment, a current efficiency of the engine is further determined and the function value of the engine map for the optimized torque and the optimized speed corrected in accordance with the determined efficiency. This has the advantage that the engine map reflects the real, current characteristics of the engine. That corrected The map takes into account both individual deviations of the engine used within the range of the series as well as aging-related changes in the engine that occur over its lifetime.

Preferably will be there first judges whether the engine is in a normal operating condition, d. H. the state in which it is predominantly during operation of the hydraulic power unit. This is z. B. a state in which the engine is at its steady operating temperature has achieved and no special features, such. B. in the case of Diesel engine regeneration of exhaust particulate filters or catalysts are active. The correction of the function value then takes place only when the engine is in the normal operating condition. This prevents short-term deviations of the Efficiency z. B. affect the map when the engine is cold. Further preferably, a maximum tolerated deviation of the corrected engine map from an originally specified engine map specified. The corrected engine map is then judged whether it's from the original given engine map by more than the maximum tolerated deviation differs. If the corrected engine map is from the original one Engine map deviates by more than the maximum tolerated deviation, a warning signal is output. This allows a user to do that Hydraulic unit with abnormal deterioration of efficiency subject without delay to an inspection and, if necessary, repair.

The The present invention will be described below with reference to preferred embodiments and attached Figures explained. In the figures show:

1 a schematic diagram of a hydraulic unit with a drive device according to an embodiment of the invention;

2 a map, the efficiency of the hydraulic unit from 1 as a function of torque and speed describes;

3 a characteristic that is out of the map 2 was determined and describes the efficiency at a given target power of the hydraulic unit; and

4 a flowchart of a method for controlling a hydraulic unit according to another embodiment of the invention.

In In the figures, the same reference numerals designate the same or the same function Components, unless stated otherwise.

An in 1 schematically illustrated hydraulic unit 100 includes a diesel engine 102 coming from a fuel tank 134 supplied with diesel fuel and a common shaft 103 rigid with a hydraulic pump 104 is coupled. A pump input 133 the hydraulic pump 104 is in connection with a reservoir 132 , which with hydraulic fluid at low pressure, z. B. atmospheric pressure is filled. A pump outlet 134 the hydraulic pump 104 is in connection with a consumer 136 hydraulic energy. The consumer 136 is z. B. designed as a working cylinder or hydraulic motor. It may be composed of several components such as working cylinders and hydraulic motors and also include valves, pressure accumulators, etc.

The hydraulic pump 104 is as a variable displacement pump 104 formed, in which the displacement volume, ie the volume of during a revolution of the drive shaft 103 from the pump inlet 133 to the pump outlet 134 subsidized hydraulic fluid is adjustable. Because of the pump 104 Calculated hydraulic work calculated as the product of the volume delivered and the pressure difference overcome is thus at a given pressure difference Δp between pump input 133 and pump outlet 134 during one revolution of the drive shaft 103 from the pump 104 performed hydraulic work adjustable. Because for reasons of energy conservation this work is done by the diesel engine 102 on the drive shaft 103 must be made, changes with that of the pump 104 per revolution of the drive shaft 103 Hydraulic work performed by the engine 102 per revolution of the drive shaft 103 to be performed mechanical work and thus that on the drive shaft 103 demanded and by the engine 102 applied torque.

The hydraulic unit 100 further comprises an engine control unit 106 , a pump control unit 108 and a dashboard 126 that have a common data bus 130 connected to each other. The engine control unit 106 has a motor plate 120 that makes it possible for the diesel engine 102 during operation to a predefinable setpoint speed of the drive shaft 103 adjust. Appropriately, the motor plate has 120 For this purpose, means for monitoring the actual speed of the drive shaft 103 and a regulator that controls the fuel supply from the tank 134 increases when the actual speed falls below the target speed, and decreases when the actual speed exceeds the target speed.

The engine control unit 106 also has a memory 110 on by a map 200. of the diesel engine 102 is stored. The map 200. describes an efficiency of the diesel engine 102 as a function of the speed of the drive shaft 103 as well as that of the pump 104 requested and from the engine 102 on the drive shaft 103 applied torque. The through the map 200. specified efficiency is defined as the ratio of the drive shaft 103 per unit of time mechanical work done on the chemical energy contained in the amount of fuel consumed per unit of time. In alternative embodiments, the map 200. also the ratio of per unit time on the drive shaft 103 indicate the amount of fuel consumed per unit of time, ie a reciprocal specific fuel consumption. The per unit time on the drive shaft 103 performed mechanical work, ie the mechanical output of the engine 102 is known to be equal to the product of a constant factor 2π, the speed of the drive shaft 103 and through the drive shaft 103 transmitted torque.

The memory 110 is a non-volatile, overwritable memory 110 educated. At the time of manufacture of the hydraulic unit 100 gives that in memory 110 stored map 200. Characteristics of the diesel engine 102 in a brand-new condition again, if necessary taking into account a reasonable break-in period. The stored values of the efficiency refer to a normal operating condition of the engine 102 in which the engine 102 has warmed to a steady operating temperature and no fuel consumption affecting measures such. B. the regeneration of particulate filters or catalysts are active.

The engine control unit 106 also has a characteristic map correction unit 124 on that the efficiency of the diesel engine 102 monitored in normal operating condition and that in the memory 110 stored map 200. corrected if the actual value of the efficiency determined by the monitoring of the through the map 200. specified value deviates.

The engine control unit 106 is designed to be automatic or at the request of the pump control unit 108 that in the store 110 saved map 200. over the common data bus 130 to the pump control unit 108 to convey. The pump control unit 108 has a memory 110 ' which is adapted to a copy of the engine control unit 106 received map 200. save. Furthermore, the pump controller 108 a map modification unit 122 on, in which a pump map 201 stored in non-volatile form. The pump map 201 describes analogous to the engine map 200. an efficiency of the variable displacement pump 104 for a given pressure difference Δp between pump input 133 and pump outlet 134 as a function of the speed of the drive shaft 103 and by the drive shaft 103 transmitted torque. The efficiency of the pump 104 is defined as the ratio of the pump 104 to the consumer 136 delivered hydraulic power, ie the product of the pump at the output 134 Exceeding flow rate and the pressure difference .DELTA.p, and that of the engine 102 to the pump 104 over the drive shaft 103 transmitted mechanical power, ie the product of the speed of the drive shaft 103 , that of the drive shaft 103 transmitted torque and a constant factor 2π.

In the map modification unit 122 can have multiple pump maps 201 for different values of the pressure difference Δp between pump input 133 and pump outlet 134 stored or appropriately defined mathematically, wherein the map modification unit 122 is suitably designed to continuously monitor the pressure difference Δp and each one of the current pressure difference .DELTA.p corresponding map 201 to activate.

The pump control unit 108 also has a desired power determination unit 112 on, which is a nominal power of the hydraulic unit 100 determined, z. B. from an electronic power request signal of the consumer 136 or by manual dialing. Furthermore contained in the pump control unit 108 are a characteristic investigator 114 that from the map 200. determines a characteristic along which the by the hydraulic unit 100 delivered hydraulic power equal to that of the target power determination unit 112 certain target performance is an optimization unit 116 along the determined characteristic curve a maximum of the efficiency of the hydraulic unit 100 determined, and a pump actuator 118 , which is the displacement volume of the variable displacement pump 104 such that the pump 104 on the drive shaft 103 requesting the torque corresponding to the determined maximum.

On the dashboard 126 is a warning light 128 attached by a signal of the map correction unit 124 in the engine control unit 106 is activatable if that is in memory 110 stored and by the map correction unit 124 continuously corrected map 200. and more than a predetermined tolerance threshold from the uncorrected, originally in memory 110 stored map 200. of the diesel engine 102 deviates in new condition.

In operation of the hydraulic unit 100 transmits the engine control unit 106 that in the store 110 filed engine map 200. over the data bus 130 to the pump control unit 108 , The pumping Control Module 108 saves the received map 200. in memory 110 ' , The map modification unit 122 the pump control unit 108 modifies this in memory 110 stored engine map 200. by looking at the engine map 200. that the efficiency of the diesel engine 102 indicates with the pump map 201 that the efficiency of the variable displacement pump 104 indicates multiplied. Because both the engine map 200. as well as the pump map 201 a respective efficiency of the engine 102 or the pump 104 as a function of the transmitted torque and the speed of the drive shaft 103 indicated by the map modification unit 201 modified map 200. after modification, the product of the respective efficiencies of the engine 102 and the pump 104 , ie the overall efficiency of the hydraulic unit 100 also as a function of the transmitted torque and the rotational speed of the drive shaft 103 ,

The characteristic determiner 114 now determines from the modified map 200. a characteristic curve along which the output power of the pump 104 and thus the entire hydraulic unit 100 the constant value of the target power determination unit 112 having predetermined target power. The characteristic determiner 114 transfers the determined characteristic of the optimization unit 116 along the characteristic curve a maximum of the overall efficiency of the hydraulic unit 100 finds. Subsequently, the optimization unit hands over 116 the optimized value of the torque specified by the position of the maximum to the pump actuator 118 , taking into account the pressure difference Δp the variable displacement pump 104 so that adjusts to the drive shaft 103 inquires about the optimized value of the torque. The optimization unit 116 continues to send over the data bus 130 a signal containing the optimized value of the speed determined by the position of the maximum, to the motor controller 120 in the engine control unit 106 , The engine plate 120 puts the diesel engine 102 to set the optimized value of the speed by injecting diesel fuel from the tank 134 so regulates that the drive shaft 103 just turning at the optimized speed.

In continuous operation, the map correction unit monitors 124 the fuel consumption of the diesel engine 102 , correct that in memory 110 saved map 200. and transmits the corrected map 200. to the pump control unit 108 , Represents the map correction unit 124 notice that the map 200. from one for the diesel engine 101 The engine control unit transmits more strongly than is predefined by a predefined tolerance value in the relevant operating age 106 a signal over the data bus 130 to the dashboard 126 , Upon receipt of the signal, the dashboard will switch 126 the warning light 128 to prompt the user to inspect.

2 shows an exemplary map in a three-dimensional coordinate system 200. that has an overall efficiency 208 of the hydraulic unit 1 as a function of torque 202 and speed 204 indicates. The total efficiency plotted along the vertical axis 208 of the hydraulic unit is equal to the product of the efficiency of the engine alone, multiplied by the efficiency of the pump alone. Thus, the map shown corresponds 200. the in 1 as stored in the memory of the pump control device shown engine map after its modification, ie multiplication with the pump map.

On the surface of the map 200. are also exemplary three characteristics 206 . 206 ' . 206 '' drawn, each corresponding to different output power of the hydraulic unit. Each of the characteristics 206 . 206 ' . 206 '' is just set so that along its course the hydraulic output power delivered by the pump is constant. The in 1 shown characteristic investigator determined on the map 200. a characteristic along which by combinations of torque 202 and speed 204 defined operating points are at which the pump always outputs the previously determined desired power. Is z. B. in operation, the target power equal to that power that at all on the curve 206 is discharged, the characteristic determiner determines the characteristic curve 206 ,

3 shows an example of a characteristic 206 that out of the map 2 was determined and the overall efficiency 208 of the hydraulic unit at a given target power of the hydraulic unit describes. The characteristic 206 gives the efficiency 208 as a function of the speed 204 the drive shaft. The characteristic 206 has a maximum 304 on, where the efficiency 208 within the illustrated value range of the speed 204 a maximum value 305 accepts. This maximum 304 corresponds to an optimized operating point, consisting of an optimized speed 302 and an optimized torque of the drive shaft, in which the hydraulic unit provides the desired performance with the highest possible efficiency. Because the characteristic 206 the efficiency 208 as a function of the speed 204 indicating the drive shaft is the optimized speed 302 directly by the position of the maximum 304 certainly. The associated optimized torque results from the optimized speed 304 from the course of the characteristic 206 within the in 2 shown map.

Determined during operation of the hydraulic unit the optimization unit the maximum 304 the characteristic 206 , determined from the position of the maximum 304 the optimized speed, and from the course of the characteristic curve 206 within the in 2 the map shown the associated optimized torque. In alternative embodiments, the characteristic is 206 the efficiency 208 as a function of torque. In this case, the optimization unit determines the optimized torque directly from the position of the maximum 304 , and the associated optimized speed 302 about the optimized torque from the characteristic curve 206 within the in 2 shown map.

4 shows a flowchart of a method for controlling a hydraulic unit with a motor and a variable displacement pump driven by the engine. In a first step 400 is given a map that describes an efficiency of the engine as a function of a torque applied by the engine to its crankshaft and a speed of the crankshaft. The map refers to the efficiency of the warm engine and reflects the characteristics of the engine in a brand new condition. In a further step 418 is a maximum tolerated deviation of the actual efficiency of the engine from the data in step 400 predetermined map set. This deviation can be defined differently, for. B. as a maximum or over a range of different speeds averaged deviation of the efficiency of the values of in step 400 given engine map. The definition of the maximum tolerated deviation may include other criteria such. B. take into account the age of the engine or the atmospheric pressure.

In step 412 will that be in step 400 modified engine map by applying a pump map that describes an efficiency of the variable displacement pump as a function of torque and speed. The result is a new map that contains the product of the engine map efficiency value and the corresponding pump map function value for each torque and speed value combination as a new function value for each torque and speed combination. The modified map indicates an overall efficiency of the hydraulic unit.

In step 402 If a target power of the variable is determined, the z. B. is needed to operate a working cylinder. In step 404 a characteristic curve is determined from the modified characteristic map which includes those combinations of rotational speed and torque in which the output power of the variable displacement pump exactly corresponds to the nominal power. In step 406 an optimized torque and an optimized speed of the characteristic curve is determined for which the efficiency assumes a maximum value along the course of the characteristic curve. In step 408 the variable displacement pump is set to request exactly the optimized torque at the drive shaft. In step 410 the motor is adjusted to the optimized speed.

In the branch 424 It is judged whether the engine is in a normal, warmed-up operating condition without special measures influencing the efficiency. If this is not the case, z. B. if the engine has just been started and is still cold, the method in step 402 continued, where a new target power is determined, which may differ from that in the previous execution of the step, when z. B. the operated cylinder has come to a standstill. If the engine is in a normal operating condition, in step 414 measure the instantaneous efficiency of the engine. In step 416 the engine map is corrected to take into account the new measurement result.

In the branch 420 it is judged whether the corrected engine map from that in step 400 given engine map deviates by more than the maximum tolerated deviation. If not, the procedure goes to step 412 continued, in which the corrected engine map is in turn modified by application of the pump map. This results in a new map of the overall efficiency of the hydraulic unit, which is based on the corrected engine map and the pump map. If the corrected engine map is in the branch 420 by more than the maximum tolerated deviation from that in step 400 specified engine map deviates, in step 422 a warning light activates before the procedure in step 412 will continue.

Even though the present invention with reference to preferred embodiments has been described herein, it is not limited thereto, but on diverse Modifiable way. For example, the step of determining the characteristic and the step of determining the optimized torque and the optimized speed in one step or the optimized torque and the optimized speed directly be determined from the map. The drive energy can be on others Way as above a common shaft between the motor and pump are transmitted. The pump map or the map of the overall efficiency of the hydraulic unit can continuously on changes monitored. Instead of a diesel engine can, for. B. an electric motor can be used.

Claims (10)

Method for controlling a hydraulic unit ( 100 ), which is a motor ( 102 ) and one of the engine ( 102 ) driven variable displacement pump ( 104 ), comprising the steps: 400 ) of an engine map ( 200. ), which has an efficiency ( 208 ) of the motor ( 102 ) as a function of a torque ( 202 ) and a speed ( 204 ) of the motor ( 102 ) describes; - Determine ( 402 ) a desired power of the variable displacement pump ( 104 ); - Determine ( 404 ) of a characteristic ( 206 ) from the engine map ( 200. ), which corresponds to the target power; - Determine ( 406 ) of an optimized torque ( 300 ) and an optimized speed ( 302 ) by determining a maximum ( 304 ) of the characteristic ( 206 ); - To adjust ( 408 ) of the variable displacement pump ( 104 ) to the optimized torque ( 300 ); and - setting ( 410 ) of the motor ( 102 ) to the optimized speed ( 302 ). Method according to claim 1, characterized in that further comprises a step of modifying ( 412 ) of the engine map ( 200. ) with a pump map ( 201 ) is provided, wherein the pump map ( 201 ) an efficiency of the variable displacement pump ( 104 ) as a function of the torque ( 202 ) and the speed ( 204 ) describes. Method according to one of the preceding claims, characterized in that the further steps are provided: - determining ( 414 ) of an actual efficiency of the engine ( 102 ); and - correct ( 416 ) of the function value ( 208 ) of the engine map ( 200. ) for the optimized torque ( 300 ) and the optimized speed ( 302 ) according to the determined efficiency. A method according to claim 3, characterized by further comprising a step of judging ( 424 ) is provided, whether the engine ( 102 ) is in a normal operating state, wherein the correcting ( 416 ) of the function value ( 208 ) takes place only when the engine ( 102 ) is in the normal operating state. A method according to claim 3 or 4, characterized in that the further steps are provided: - predetermine ( 418 ) a maximum tolerated deviation of the corrected engine map ( 200. ) from an originally given engine map; - Judge ( 420 ), whether the corrected engine map ( 200. ) deviates from the originally specified engine map by more than the maximum tolerated deviation; and - spend ( 422 ) of a warning signal ( 128 ), if the corrected engine map deviates the corrected engine map from the originally specified engine map by more than the maximum tolerated deviation. Computer program product with program instructions stored on a machine-readable carrier for carrying out the method according to one of the preceding claims, when the program instructions are stored on a computer or on a control unit ( 106 . 108 ). Control device ( 106 . 108 ) for controlling a hydraulic power unit ( 100 ), which is a motor ( 102 ) and one of the engine ( 102 ) driven variable displacement pump ( 104 ), comprising: - a memory ( 110 . 111 ), which a motor map ( 200. ) stores an efficiency ( 208 ) of the motor ( 102 ) as a function of a torque ( 202 ) and a speed ( 204 ) of the motor ( 102 ) describes; A target power determination unit ( 112 ), which is a nominal power of the variable displacement pump ( 104 ) certainly; A characteristic determiner ( 114 ), which has a characteristic curve ( 206 ) from the engine map ( 200. ), which corresponds to the target power; An optimization unit ( 116 ) determined by determining a maximum ( 304 ) of the characteristic ( 206 ) an optimized torque ( 202 ) and an optimized speed ( 204 ) determined; - a pump plate ( 118 ), which the variable displacement pump ( 104 ) to the optimized torque ( 202 ); and - a motor plate ( 120 ), the engine ( 102 ) to the optimized speed ( 204 ). Control device ( 106 . 108 ) according to claim 7, characterized in that further comprises a map modification unit ( 122 ) is provided, which the engine map ( 200. ) with a pump map ( 201 ), which has an efficiency of the variable displacement pump ( 104 ) as a function of the torque ( 202 ) and the speed ( 204 ) describes. Hydraulic unit ( 100 ) with a motor ( 102 ), a variable displacement pump driven by the engine ( 104 ) and a control device ( 106 . 108 ) according to claim 7 or 8. Hydraulic unit ( 100 ) according to claim 9, characterized in that the engine ( 102 ) as internal combustion engine ( 102 ), in particular as a diesel internal combustion engine ( 102 ) is trained.