WO2014189445A1

WO2014189445A1 - Method and system for controlling hydraulic device

Info

Publication number: WO2014189445A1
Application number: PCT/SE2014/050608
Authority: WO
Inventors: Björn HELLHOLM; Max THORÉN
Original assignee: BAE Systems Hägglunds Aktiebolag
Priority date: 2013-05-24
Filing date: 2014-05-19
Publication date: 2014-11-27
Also published as: SE1350633A1

Abstract

The invention relates to a system (I, II) for controlling a hydraulic device of a vehicle, the hydraulic device comprising a hydraulic reservoir (100), a hydraulic pump (90), a pump drive unit (110) for driving the hydraulic pump (90), a pressure and a return line (C1, C2), and at least one consumer. The hydraulic pump (90) is arranged to pump hydraulic medium from the hydraulic reservoir (100) to the pressure line in order to pressurize the pressure line to provide pressurized pressure medium to said at least one consumer. Said consumer is connected to the pressure line (C1 ) in order to receive said pressurized hydraulic medium and to said return line (C2) in order to return said hydraulic medium to the hydraulic reservoir (100). The hydraulic pump is a fixed displacement pump. The pump drive unit is an electric motor (110) arranged to drive said hydraulic pump (90). Said electric motor (110) is arranged to control the motor speed of the hydraulic pump (90) in order to control pressure in the pressure line (C1 ). The invention also relates to a method for controlling a hydraulic device of a vehicle. The invention also relates to a motor vehicle.

Description

METHOD AND SYSTEM FOR CONTROLLING HYDRAULIC DEVICE

TECHNICAL FIELD

The present invention relates to a system for controlling a hydraulic device of a vehicle according to the preamble of claim 1 . The present invention relates to a method for controlling a hydraulic device of a vehicle according to the preamble of claim 5. The present invention further relates to a vehicle.

BACKGROUND ART Traditionally, hydraulic pumps of hydraulic systems of vehicles are driven with the combustion engine of the vehicle, i.e. the same engine used for the propulsion of the vehicle. One problem with such a solution is that the combustion engine cannot be used optimally when adjusting for driving the hydraulic pump is required. Losses are generated in operation of the hydraulic pump.

Hence, there is a need to introduce improvements in controlling hydraulic devices of vehicles, such as in tracked vehicles.

OBJECT OF THE INVENTION An object of the present invention is to provide a method for controlling a hydraulic device of a vehicle which is energy-efficient.

A further object of the present invention is to provide a method for controlling the hydraulic device which enables decoupling of propulsion of the vehicle and driving the pump. A further object of the present invention is to provide a method for controlling the hydraulic device which enables energy-efficient driving of the pump.

An object of the present invention is to provide a system for controlling the hydraulic device of vehicles which enables which is energy-efficient. A further object of the present invention is to provide a system for controlling the hydraulic device which enables decoupling of propulsion of the vehicle and driving the pump.

A further object of the present invention is to provide a system for controlling the hydraulic device which enables energy-efficient driving of the pump.

SUMMARY OF THE INVENTION

These and other objects, which will become apparent by the following description, are provided by means of a system, a method and a vehicle of initially mentioned kind and which further exhibit the features mentioned in the characterizing part of the appended respective independent claims. Preferred embodiments of the system and the method are defined in the appended dependent claims.

According to the an aspect, the objects are obtained by a system for controlling a hydraulic device of a vehicle, the hydraulic device comprising a hydraulic reservoir, a hydraulic pump, a pump drive unit for driving the hydraulic pump, a pressure and a return line, and at least one consumer, said hydraulic pump being arranged to pump hydraulic medium from the hydraulic reservoir to the pressure line in order to pressurize the pressure line to provide pressurized pressure medium to said at least one consumer, said consumer being connected to the pressure line in order to receive said pressurized hydraulic medium and to said return line in order to return said hydraulic medium to the hydraulic reservoir, wherein said pump drive unit is an electric motor arranged to drive said hydraulic pump. This enables, as opposed to driving the hydraulic pump by means of a propulsion motor of the vehicle, such as a combustion engine, to only drive the hydraulic pump when hydraulic demand arise. When no consumer is used, the hydraulic pump will stand still accordingly and thus not use any energy at all. Hence, an energy- efficient operation is enabled by means of the hydraulic pump. Hence, optimizing the motor speed of the combustion engine only for the propulsion of the vehicle is enabled when driving the vehicle by means of a combustion engine, such as diesel engine.

According to an embodiment, the system comprises a plurality of consumers which are connected in parallel across said pressure and return lines. The system further comprises a control unit arranged to control the electric motor in order to control the motor speed of the hydraulic pump for controlling pressure in said pressure line. Further, the hydraulic device comprises a load sensing system for sensing current pressure demand of pressurized hydraulic medium of said plurality of consumers. The control unit is hereby arranged to, by controlling the electric motor, control the motor speed of the hydraulic pump based on signals indicating said current pressure demand so that the pressure in the pressure line at least corresponds to the pressure demand of the consumer having the highest pressure demand. Thereby, it can be ensured that the pressure in the pressure line never drops below the maximum pressure demand of the consumers and thus that each consumer can obtain necessary hydraulic pressure.

According to an embodiment, based on the signals indicating current pressure demand, the control unit is arranged to compare the pressure demand of the different consumers, determine the maximum pressure demand among the respective pressure demands of the consumers and control the pressure in the pressure line based on the maximum pressure demand so that it at least corresponds to the maximum pressure demand.

According to an embodiment, the system comprises at least one proportional valve for controlling the hydraulic flow from the pressure line to a consumer. Typically, the system comprises a plurality of proportional valves, each associated with a respective consumer. The proportional valves are configured to control the hydraulic pressure so that the pressure reaching the respective consumer substantially corresponds to the pressure demand of the consumer. According to an embodiment, this is achieved by the control unit controlling the proportional valves based on the signals indicating the current pressure demand of the respective consumer. Thereby, each consumer can be supplied with the hydraulic pressure that is required for the current load.

Thus, according to an embodiment, the system is configured so that a sole hydraulic pump supplies a plurality of consumers with pressurized hydraulic medium, which consumers are connected in parallel across a pressure line included in the system. The pressure in the pressure line is controlled to a pressure corresponding to or exceeding the maximum pressure demand of the plurality of consumers and the system comprises at least one, and typically a plurality of, proportional valve(s) controlled so that the consumers are supplied with a hydraulic pressure corresponding to respective pressure demand of the consumers. Thereby, a single hydraulic pump can supply a plurality of consumers in a reliable and energy-efficient way. According to an embodiment of the system, said electric motor thus is arranged to control the motor speed of the hydraulic pump in order to control pressure in the pressure line. This provides energy-efficient operation of the hydraulic pump in that the hydraulic pump is utilized for current demand.

According to an embodiment, said system thus comprises a control unit for controlling the electric motor for said motor speed control. This will facilitate the optimization of the control of the electric motor for the motor speed control, where the control unit may compare hydraulic pressure of consumers in order to determine which flow the hydraulic pump needs to provide and thus by which motor speed the hydraulic pump needs to be driven. According to an embodiment of the system, said hydraulic pump is a fixed displacement pump. Thus, by using a fixed displacement pump energy- efficient operation of the hydraulic pump is enabled in that the hydraulic pump will not consume any energy when no consumer is used. According to an embodiment of the system, said hydraulic device thus comprises a plurality of consumers connected in parallel across said pressure and return lines. This enables to easily connect further consumers to the same pressure and return lines or equivalent to remove/disconnect a connected consumer. Thus, a flexible system is obtained. This reduces the number of hydraulic lines which leads to reduced maintenance and reduced service costs, as well as reduced installation volume, reduced weight and reduced risk of leakage. Such a hydraulic device leads to further reduced maintenance. Such a hydraulic device requires less hydraulic oil.

According to an embodiment of the system, said hydraulic device thus includes a load sensing system for sensing a current pressure demand of pressurized hydraulic medium for said at least one consumer. This enables more optimized control of the hydraulic pump and hence a more energy- efficient operation of the hydraulic pump.

According to an embodiment, the system comprises a communication bus for transmitting signals indicating said sensing of current pressure demand to said control unit. This enables more optimized control of the hydraulic pump and hence a more energy-efficient operation of the hydraulic pump. Said communication bus is constituted by a variant of a CAN bus.

According to an embodiment of the system, the control unit is thus arranged to control the motor speed based on said signals indicating current pressure demand of pressurized hydraulic medium. This enables a more optimized control of the hydraulic pump and hence a more energy-efficient operation of the hydraulic pump. According to an aspect, the objects are obtained by a method for controlling a hydraulic device of a vehicle comprising the steps of: driving, by means of a pump drive unit, a hydraulic pump for pumping hydraulic medium, pumping, with said hydraulic pump, hydraulic medium from a hydraulic reservoir to a pressure line in order to pressurize said pressure line with hydraulic medium to provide pressurized pressure medium to at least one consumer, to at least one consumer of pressurized hydraulic medium, returning said hydraulic medium from said at least one consumer to said hydraulic reservoir, wherein said pump drive unit is an electric motor arranged to drive said hydraulic pump.

According to an embodiment, a plurality of consumers are connected in parallel across said pressure and return lines and the method is characterized by the steps of sensing, by means of a load sensing system of the hydraulic device, a current pressure demand of pressurized hydraulic medium for said plurality of consumers and controlling said electric motor, by means of a control unit, for controlling the motor speed of the hydraulic pump based on signals indicating said current pressure demand so that the pressure in the pressure line at least corresponds to the pressure demand of the consumer having the highest pressure demand. According to an embodiment, the method comprises the steps of, by means of said control unit and based on the signals indicating current pressure demand, comparing the pressure demand of the different consumers, determining the maximum pressure demand among the respective pressure demand of the consumers and controlling the pressure in the pressure line to a pressure which at least corresponds to said maximum pressure demand.

According to an embodiment, the method thus comprises the step of controlling the motor speed of the hydraulic pump in order to control pressure in the pressure line by means of said electric motor. According to an embodiment, the method thus comprises the step of controlling said electric motor by means of a control unit for said motor speed control.

According to an embodiment of the method, said hydraulic pump is a fixed displacement pump.

According to an embodiment of the method, said hydraulic device thus comprises a plurality of consumers connected in parallel across said pressure and return lines.

According to an embodiment, the method thus comprises the step of sensing a current pressure demand of pressurized hydraulic medium for said at least one consumer by means of a load sensing system of the hydraulic device.

According to an embodiment, the method comprises the step of transmitting, by means of a communication bus, signals indicating said sensing of current pressure demand to said control unit. According to an embodiment, the method thus comprises the step of controlling, by means of the control unit, the motor speed based on said signals indicating current pressure demand of pressurized hydraulic medium.

DESCRIPTION OF FIGURES The present invention will be better understood by reference to the following detailed description together with the accompanying drawings, where equal reference numerals refer to the same parts throughout the several views, and in which:

Fig. 1 schematically illustrates a perspective view of a tracked vehicle according to an embodiment of the invention; Fig. 2 schematically illustrates a perspective view of a rear vehicle unit of the tracked vehicle of Fig. 1 ;

Fig. 3a schematically illustrates a perspective view of a centre beam for connecting a resilient suspension device according to the present invention; Fig. 3b schematically illustrates a perspective view of the centre beam in Fig. 6a without housing;

Fig. 4 schematically illustrates a plan view of a vehicle according to an embodiment of the present invention;

Fig. 5 schematically illustrates a system for controlling a hydraulic device of a vehicle according to an embodiment of the present invention;

Fig. 6 schematically illustrates a system for controlling a hydraulic device of a vehicle according to an embodiment of the present invention; and

Fig. 7 schematically illustrates a block diagram of a method for controlling a hydraulic device of a vehicle according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Herein, the term "link" refers to a communication link which may be a physical line, such as an opto-electronic communication line, or a non- physical line, such as a wireless connection, for example a radio or microwave link.

Herein, the term "track support beam" refers to a structural element arranged to support ground engaging means, such as for example an endless track.

Herein, the term "track assembly" refers to a unit arranged to support and drive ground engaging means in the form of for example an endless track. The term "track assembly" thus refers to an example of a drive unit adapted to application for tracked vehicles.

Referring to Fig. 1 , a tracked vehicle 10 according to the present invention is shown, provided with a front vehicle unit 1 1 and a rear vehicle unit 12. Each of the front and rear vehicle units comprises a pair of track assemblies 20. Said pair of track assemblies 20 is constituted by or is comprised of a pair of drive units. Said pair of track assemblies 20 comprises two track assemblies 21 arranged on opposite sides of the vehicle. Respective track assembly 21 is constituted by or is comprised of a drive unit. Respective track assembly 21 is constituted by a driving track assembly and is arranged for propulsion of the vehicle. Respective pair of track assemblies 20 is interconnected by an intermediate centre beam 30, 32, such as a chassis beam.

Said centre beam 30, 32 of the respective vehicle unit 1 1 , 12 is arranged for supporting the vehicle structure, for example in the form of a vehicle cab, a power unit, load-carrying structure and a crane.

According to this configuration, the centre beam 30 of the front vehicle unit 1 1 of the vehicle 10 is arranged to support a vehicle cab 15 and a power unit 5, such as a combustion engine, where the combustion engine, according to a variant, is constituted by a diesel engine.

According to this configuration, the centre beam 30, 32 of the front and rear vehicle units 1 1 , 12 of the vehicle 10 is further arranged to support a load- carrying structure including a load-carrying frame 40, where, according to this variant, said load-carrying frame 40 is configured to support a U-beam configuration 42 or a load bank configuration 42 for supporting timber and a loading gate 43. According to this variant, the load-carrying frame is also arranged to support a crane 44 for loading/unloading timber. The load- carrying frame 40 is configured to distribute the load substantially centrally across the front and rear vehicle units 1 1 , 12. The vehicle 10 further comprises a hydraulic pump 90 for pumping hydraulic medium to supply consumers of the vehicle, such as crane, hydraulic suspension, steering cylinders, etc.

The vehicle 10 comprises a system, which is not shown in Fig. 1 , for controlling a hydraulic device of the vehicle. System I, II is shown in Figs. 5 and 6.

The exemplified vehicle 10 is a tracked forestry vehicle in the form of a forwarder adapted to transport timber from a felling site to a collection site. The vehicle 10 of the present invention may be constituted by any suitable tracked vehicle. According to a variant, the vehicle 10 is a harvester adapted to fell timber.

The exemplified vehicle 10 is a diesel-electrically driven vehicle. The vehicle 10 may in one variant have any suitable power supply for propulsion of the vehicle. According to a variant, the vehicle 10 is hybrid driven. According to a variant, the vehicle 10 is electrically driven where, according to a variant, power supply occurs by means of an energy storage device, such as a battery unit, a fuel cell or a capacitor device.

Referring to Fig. 2, a rear vehicle unit 12 comprising a pair of track assemblies 20 interconnected by an intermediate centre beam 32 is shown. In more detail, a rear vehicle unit 12 is shown by reference to Fig. 2 with a pair of track assemblies 20 and a centre beam connected to and configured for suspension of the centre beam 32.

Respective track assembly 21 is arranged for driving the vehicle unit 12. Respective track assembly 21 comprises a track support beam 22, which here is constituted by a ski beam. Respective track assembly further comprises a set of support wheels 23, at least one drive wheel 24, and an endless track 25. Said endless track 25 is arranged to run over said at least one drive wheel 24 and said set of support wheels 23. Said set of support wheels 23 and said at least one drive wheel 24 are arranged to be appropriately rotatably supported by said track support beam 22. Said set of support wheels 23 are arranged in a pair configuration, i.e. respective support wheels 23 in each pair configuration are arranged on opposite sides of said track support beam 22. The support wheel 23 arranged rearmost of the track support beam 22 also has a tensioning wheel function and is constituted by a tensioning wheel, where, according to a variant, the track tension is accomplished by means of a hydraulic track tensioning device which thus constitutes a consumer. Said track assemblies 21 further also comprise an electrical drive arrangement (not shown) drivably connected to said at least one drive wheel. According to a variant, respective track assembly comprises an electrical drive arrangement. According to a variant, said electric drive arrangement is arranged in said track support beam 22 of said track assembly 21 . In more detail, said centre beam 32 is arranged for attachment to and suspension of said two opposite track assemblies 21 , i.e. said pair of track assemblies 20, via a suspension device including a trailing arm configuration in the form of trailing arms 27 articulately connected at one end to the track support beam 22 and at the other end to the centre beam 32 and hydraulic cylinders 28 articulately connected at one end to the track support beam 22 and at the other end to the centre beam 32. The hydraulic cylinders are included in a gas hydraulic cylinder configuration, and thus constitute consumers of the vehicle. The two track assemblies 21 of the pair of track assemblies 20 are arranged on opposite sides of the centre beam 32 so that the centre beam 32 is arranged in between said track assemblies 21 of the pair of track assemblies 20 and so that the main extension direction of the centre beam 32 is substantially parallel to the main extension direction of respective track assembly 21 of the pair of track assemblies 20 shown Fig. 2. The same applies to the front vehicle unit 1 1 shown in Fig. 2. The front vehicle unit 1 1 and the rear vehicle unit 12 are in a basic configuration where the vehicle unit(s) includes a pair of track assemblies 20, a centre beam 30, 32 with vertical steering joint and a suspension configuration for suspension and resilient suspension of track assemblies formed and dimensioned substantially identical, reducing items with reduced costs for construction, spare parts inventory and maintenance.

According to the embodiment described above, the front vehicle unit 1 1 and the rear vehicle unit 12 have driving on the respective track assembly 21 . According to a variant, the driving of the respective track assembly is individual driving of the respective track assembly 21 . According to an alternative variant, the vehicle unit(s) 1 1 , 12 may be driven by driving the respective pair of track assemblies, i.e. a common driving by means of drive means for the respective pair of track assemblies.

Figs. 3a and 3b schematically illustrate a perspective view of a centre beam 30 with and without housing for the front vehicle unit 1 1 in Fig. 1 , and Fig. 4 is a plan view of a vehicle according to an embodiment of the present invention.

Consumers of the vehicle, such as front and rear hydraulic cylinders 28 shown in Fig. 2 and steering cylinders 54a, 54b of the front vehicle unit arranged at the centre beam 30 as shown in Figs. 3a-b, are configured to be supplied by means of a hydraulic medium from a hydraulic line configuration L arranged in said centre beam 30. The hydraulic line configuration comprises a pressure and a return line C1 , C2, illustrated by a dashed line in Fig. 4.

Said pressure and said return line C1 , C2 are arranged to run over substantially the entire vehicle for facilitating the connection to consumers of the vehicle. Said pressure and said return line C1 , C2 are arranged to run centrally in the vehicle in the longitudinal extension of the vehicle. Said pressure and said return line C1 , C2 are arranged to run in connection with said load-carrying frame 40 and in said centre beams 30, 32 via rotary bearings/connections 52, 72 so as to facilitate connection of different consumers of the vehicle. According to the present invention, said pressure and said return line form a hydraulic bus to which consumers of the vehicle may be connected. The vehicle comprises the hydraulic pump 90 connected to the pressure line C1 and the hydraulic reservoir 100 connected to the return line C2. The hydraulic pump 90 is arranged to pump hydraulic medium from the hydraulic reservoir 100 to the pressure line for hydraulic supply of consumers of the vehicle. The hydraulic pump 90 is arranged to be driven by an electric motor 1 10.

As seen in Fig. 4, the hydraulic reservoir 100 is placed in connection with the crane, where the crane attachment 44a is shown in Fig. 4. Further, electric motor 1 10 and hydraulic pump 90 are arranged in connection with the hydraulic reservoir 100. This results in short lines from hydraulic reservoir 100 to hydraulic pump 90. By arranging hydraulic pump 90 and electric motor 1 10 near the crane, a short line to the crane which requires the greatest hydraulic flow of hydraulic medium is accomplished.

According to a variant, the hydraulic reservoir 100 has a centrifugal function.

Consumers such as hydraulic cylinders for resilient suspension and steering cylinders are fluidly connected to pressure and return lines via a valve block 80 arranged in the centre beam 30. Equivalent there is a valve block arranged in the centre beam 32 of the rear vehicle unit.

Valves of said valve block 80 are arranged to control the hydraulic flow of the hydraulic medium to/from consumers. According to a variant, the hydraulic medium includes oil.

Said hydraulic line configuration L comprises a hydraulic line La, Lb, Lc, Ld, connected to respective front and rear hydraulic cylinder 62, 64 via said valve block 80, for controlling hydraulic medium in respective front and rear hydraulic cylinder. Said hydraulic line configuration L also comprises hydraulic lines Le, Lf connected via the valve block 80 to steering cylinders 54a, 54b for controlling the tracked vehicle 10.

Fig. 5 schematically illustrates a system I for controlling a hydraulic device of a vehicle according to an embodiment of the present invention.

The system I comprises said hydraulic device for distribution of hydraulic medium. According to a preferred variant, said hydraulic medium is constituted by oil.

The system I comprises a hydraulic line configuration for supplying a set of consumer configurations 60, 61 , 62, 63, 64, 65, 66, 67, 68 of the vehicle with hydraulic medium. Respective consumer configuration comprises a consumer arranged to be supplied with said hydraulic medium.

The consumer of respective consumer configuration 60-68 may be constituted by any suitable consumer arranged to be supplied with hydraulic medium.

According to a variant, said consumer configurations 60-68 for the vehicle according to Fig. 1 include a crane configuration 60 including the crane 44, where the crane consumer configuration comprises hydraulic cylinders, valve means for controlling hydraulic flow and pressure sensor means for determining load of the crane.

According to a variant, said consumer configurations 60-68 for the vehicle according to Fig. 1 include a gas hydraulic suspension configuration 61 , 62 of front and rear vehicle units 1 1 , 12 including said front and rear hydraulic cylinders 28, where the gas hydraulic suspension configuration further comprises valve means for controlling hydraulic flow and pressure sensor means for determining load of the hydraulic cylinders.

According to a variant, said consumer configurations 60-68 for the vehicle according to Fig. 1 include a steering configuration 63, 64 for the front and rear vehicle units 1 1 , 12 including said front steering cylinders for the front vehicle unit 1 1 and rear steering cylinders for the rear vehicle unit, where the steering configuration further comprises valve means for controlling hydraulic flow and pressure sensor means for determining load of the steering cylinders.

According to a variant, said consumer configurations 60-68 for the vehicle according to Fig. 1 include a rolling steering configuration 65 for controlling the pivoting of the front and rear vehicle units 1 1 , 12 around a rolling link including rolling steering cylinders, where the rolling steering configuration further comprises valve means for controlling hydraulic flow and pressure sensor means for determining load of the rolling steering cylinders.

According to a variant, said consumer configurations 60-68 for the vehicle according to Fig. 1 include a cab configuration 66 including the cab 15, where the cab configuration comprises hydraulic cylinders for raising/lowering, rotating and/or tilting the cab, valve means for controlling hydraulic flow and pressure sensor means for determining load of the cab.

According to a variant, said consumer configurations 60-68 for the vehicle according to Fig. 1 include a load-carrier configuration 67 including load- carrier hydraulics for load-carrying structure, such as gate, timber supports, where the load-carrier configuration comprises hydraulic cylinders, and valve means for controlling hydraulic flow.

According to a variant, said consumer configurations 60-68 for the vehicle according to Fig. 1 include a brake configuration 68 including front and rear brakes, where the braking configuration comprises hydraulic cylinders, valve means for controlling hydraulic flow and pressure sensor means for determining load of the braking configuration.

According to a variant, said valve means are included in valve block(s), see for example Fig. 6. According to a variant, valve means for different consumer configurations are comprised in a common valve block. According to the variant shown in Fig. 3b, a valve block is arranged in the centre beam 30, 32 of the respective vehicle unit, wherein consumers of the front vehicle unit are connected to the valve block of the front vehicle unit and consumers of the rear vehicle unit are connected to the valve block of the rear vehicle unit. Further, according to variants, consumers may have their own separate valve means.

Further, according to a variant, a consumer configuration in the form of a track tensioning configuration includes hydraulics for tensioning of the tracks 25 of the track assemblies 21 of the front and rear vehicle units 1 1 , 12. The hydraulic line configuration comprises a pressure line C1 to which pressurized hydraulic medium is arranged to be supplied for supply to respective consumer configuration. The pressure line C1 is thus arranged to supply pressurized hydraulic medium to the respective consumer of the vehicle. The hydraulic line configuration further comprises a return line C2 configured to receive hydraulic medium from respective consumer configuration. The return line C2 is thus arranged to receive pressurized hydraulic medium from respective consumer of the vehicle.

Said pressure line C1 and said return line C2 are configured to distribute all hydraulic medium for the consumers of the consumer configurations 60-68.

Respective consumer configuration 60-68 is connected in parallel across said pressure and return lines C1 , C2 via a supply line, connected to the pressure line, for supplying pressurized hydraulic medium to the consumer and a reverse line, connected to the return line, for returning pressurized hydraulic medium to the return line.

The system further comprises a hydraulic distribution unit H including a hydraulic reservoir for housing hydraulic medium connected to and configured to receive hydraulic medium from the return line and a hydraulic pump for pumping hydraulic medium connected to the pressure line. Said hydraulic pump is a fixed displacement pump.

The system further comprises a pump drive unit 1 10 for driving said hydraulic pump 90 to pump said hydraulic medium. According to the present invention, said pump drive unit 1 10 is an electric motor arranged to drive said hydraulic pump. Said electric motor is arranged to control the motor speed of the hydraulic pump for controlling pressure in the pressure line C1 .

The system further comprises a control unit 230 for controlling the electric motor for said motor speed control. Respective consumer configuration 60-68 is signal connected to said control unit 230 via links. The control unit is arranged to receive, via the links, signals representing load data for the current load/current pressure of respective consumer. The control unit 230 is arranged to compare the load data so as to determine to which flow and thus to which motor speed the electric motor is to be controlled. The control unit 230 is thus arranged to control the motor speed of the electric motor for controlling the motor speed of the hydraulic pump based on said signals indicating the current load and thus the current pressure demand of pressurized hydraulic medium.

Fig. 6 schematically illustrates a system I for controlling a hydraulic device of a vehicle according to an embodiment of the present invention.

System II comprises said hydraulic device.

System II comprises a hydraulic line configuration for supplying at least one consumer configuration with hydraulic medium.

The hydraulic line configuration comprises a pressure line C1 to which pressurized hydraulic medium is arranged to be supplied for supplying to said consumer configuration. The hydraulic line configuration further comprises a return line C2 configured to receive hydraulic medium from the consumer configuration.

The system further comprises a hydraulic reservoir 100 arranged to accommodate hydraulic medium for said hydraulic line configuration. Said hydraulic reservoir 100 is arranged to receive hydraulic medium from said return line C2.

The system further comprises a hydraulic pump 90 for pumping hydraulic medium from said hydraulic reservoir 100 to said pressure line C1 . Said hydraulic pump 90 is arranged to pressurize said hydraulic medium. Said hydraulic pump 90 is constituted by a fixed displacement pump.

The hydraulic pump 90 and the hydraulic reservoir 100 constitute a hydraulic distribution unit H connected in parallel with the pressure and return lines C1 , C2.

The system further comprises a pump drive unit 1 10 for driving said hydraulic pump 90 for pumping said hydraulic medium. Said pump drive unit 1 10 is an electric motor arranged to drive said hydraulic pump. Said electric motor is arranged to control the motor speed of the hydraulic pump for controlling pressure in the pressure line C1 .

Said hydraulic pump 90 is arranged to pump hydraulic medium from the reservoir 100 via a line C3. Said hydraulic pump 90 is arranged to pump hydraulic medium to the pressure line C1 via a line C4.

Said hydraulic line configuration comprises a reservoir return line C5, fluidly connected to the return line C2, arranged to return the hydraulic medium to said hydraulic reservoir 100. Said hydraulic line configuration comprises a supply line arrangement C6, fluidly connected to the pressure line C1 , for supplying pressurized hydraulic medium to said consumer configuration. Said hydraulic line configuration comprises a reverse line arrangement C7, fluidly connected to the return line C2, for returning pressurized hydraulic medium from said consumer configuration to the return line C2.

Said consumer configuration comprises a valve block 80. Several consumer configurations may comprise the same valve block. Said valve block 80 is in hydraulic fluid connection with said supply line arrangement C6. Said valve block 80 is further in hydraulic fluid connection with said reverse line arrangement C7 for returning fluid medium via said valve block 80.

Said consumer configuration comprises a consumer. The consumer may be constituted by any suitable consumer, such as any of the consumers by reference to Fig. 3.

Said hydraulic line configuration comprises a first line arrangement C8, fluidly connected to the consumer, and a second line arrangement C9, fluidly connected to the consumer, where said first and second line arrangements C8, C9 are configured for fluid communication between the consumer and the valve block 80 for controlling pressure and hydraulic flow in the consumer.

The system comprises a so-called load sensing system. The load sensing system includes pressure sensor means 120 including one or more pressure sensors for determining the current pressure demand of the consumer where the current pressure corresponds to current load.

The system comprises an accumulator 130 connected to the line C4 after the hydraulic pump, i.e. downstream of the hydraulic pump 90. The accumulator 130 is configured to maintain a standby pressure in the pressure line C1 when no consumer is used. The hydraulic pump 90 can hereby stand still until the pressure has dropped. The hydraulic pump is hereby arranged to be rotated until said predetermined standby pressure is achieved in the pressure line C1 . The standby pressure may be any suitable pressure. According to a variant, the standby pressure is in the order of magnitude of 20 bar. System II further comprises a pressure sensor 140 for determining the pressure in the pressure line C1 .

The system comprises an electronic control unit 200 for controlling the load sensing system including controlling the electric motor 1 10 and the valve block 80.

Said electronic control unit 200 is signal connected to the electric motor 1 10 via a link L1 . Said electronic control unit is arranged to receive, via the link L1 , a signal from the electric motor 1 10 representing pump operating data including current motor speed for controlling pressure in the pressure line C1 . Said electronic control unit is arranged to transmit, via the link L1 , a signal to the electric motor 1 10 representing pump operation data for driving the pump.

The electronic control unit 200 is signal connected to the valve block via a link L2. The electronic control unit 200 is arranged to receive, via the link L2, a signal from the valve block 80 representing load data for current load.

The electronic control unit 200 is signal connected to the valve block 80 via a link L3. The electronic control unit is arranged to send a signal to the valve block 80 representing control data for controlling for opening/closing of valves of the valve block 80 based on inter alia said load data and data from actuators, tilt sensors and the corresponding for controlling said consumer.

According to a variant, the electronic control unit 200 comprises a node 210 for said signal representing load data from said pressure sensor means 120 of the valve block 80 via the link L2. The node 210 is signal connected to a control unit 230 of the electronic control unit 200 via a link L4. The electronic control unit 200, and hereby the control unit 230, is signal connected to the pressure sensor 140 via a link. The electronic control unit 200, and hereby the control unit 230 is arranged to receive a signal from the pressure sensor 140 representing pressure data for current pressure in the pressure line C1 .

The control unit 230 is correspondingly arranged to receive signals via links from further consumer configurations comprising further consumers, which signals correspondingly represents load data from the pressure sensor means of valve block(s) of said further consumer configurations for current load/current pressure of respective further consumer and thus the consumption of respective consumer. Thus, said load data via the link L2 corresponds to current pressure demand of the consumer 60. According to a variant, the link L4 is constituted by a communication bus which, according to a variant, is constituted by a CAN bus (Control unit Area Network) for transmitting signals indicating sensing of current pressure demand to said control unit 230 .

The control unit 230 is arranged to process load data from different consumers, connected in parallel with the pressure and return lines C1 , C2, and the pressure sensor 140, and compares hereby the pressures at the respective consumer and also the pressure in the pressure line so as to determine which flow the hydraulic pump 90 needs to provide and thus to which motor speed the electric motor is to be controlled. Thus, the control unit 230 is arranged to control the motor speed based on said signals indicating current pressure demand of pressurized hydraulic medium. According to a variant, the electronic control unit 230 is arranged to control the motor speed based on signals indicating current pressure demand so that the pressure in the pressure line C1 is kept at a specific pressure which is higher than the pressure of the consumer having the highest pressure, where said higher specific pressure, according to a variant, corresponds to said standby pressure.

The control unit 230 is thus arranged to control the motor speed of the hydraulic pump 90 based on signals indicating the current pressure demand of each of the plurality of consumers, wherein the control is made such that the pressure in the pressure line C1 never drops below a pressure corresponding to the pressure demand exhibited by the consumer having highest pressure demand. This means that the control unit is arranged to control the motor speed of the hydraulic pump 90 based on the pressure demand of the consumer which for the time has the highest pressure demand, and thus that the control unit is arranged for what can be called maximum demand based motor speed control of the hydraulic pump. The pressure demand of the consumer having the highest pressure demand will henceforth be called the maximum pressure demand and the control unit 230 is thus arranged to maintain the pressure in the pressure line C1 , by means of motor speed control of the hydraulic pump 90, so that this never drops below the maximum pressure demand.

The control unit 230 is thus arranged to compare, based on signals indicating the current pressure demand, the pressure demands of the different consumers, determine the maximum pressure demand among the respective pressure demands of the consumers, and control the pressure in the pressure line C1 based on the maximum pressure demand so that the pressure in the pressure line C1 at least corresponds to that maximum pressure demand. Further, the control unit 230 is preferably arranged to, in the event that the maximum pressure drops below the aforementioned standby pressure, maintain the pressure in the pressure line C1 so that this never drops below said standby pressure. Cosequently, this means that the control unit is arranged to control the pressure in the pressure line C1 based on the pressure demand of the consumer having the highest pressure demand as long as this pressure demand exceeds the standby pressure, and otherwise control the pressure based on the pre-set standby pressure in order to guarantee a certain minimum pressure in the pressure line C1 . By keeping the pressure in the pressure line C1 at or above the maximum pressure demand, and by the use of proportional valves controlled based on respective pressure demand of the consumers, each consumer can meet its pressure demand.

The system for controlling the hydraulic device thus comprises valve means in the form of proportional valves for controlling the hydraulic flow from the pressure line C1 to the respective consumer. According to an embodiment, each consumer configuration 60-68 comprises at least a valve means in the form of a proportional valve. The proportional valve is configured to control the hydraulic pressure so that the pressure reaching the respective consumer essentially corresponds to the pressure demand of the consumer, which in practice means that the proportional valves of all consumer configurations, except the one whose consumer exhibits the maximum pressure demand, have the function of lowering the hydraulic pressure so that the consumer in question is reached by a pressure corresponding to the pressure demand of the consumer and not the higher maximum demand based pressure in the pressure line C1 . The proportional valve of the respective consumer configuration is controlled based on the current load of the consumer, which indicates the current pressure demand of the consumer and is measured by a pressure sensor means of the consumer configuration.

The electronic control unit 200 further comprises a node 220 for controlling the valve block 80 and is thus signal connected via the link L3. According to a variant, the link L3 is constituted by an electrical conductor arranged to supply power to a coil of valve means of the valve block 80. According to a variant, the link L3 is constituted by a communication bus which, according to a variant, is constituted by a CAN bus for controlling a directional valve of the valve block.

The electric motor 1 10 is arranged to be energy supplied by means of an energy supply unit 500 which may be constituted by any suitable device for energy supplying for driving the electric motor 1 10. According to a variant, said energy supply unit 500 is constituted by a generator driven by means of a combustion engine. According to an alternative variant, the energy supply unit is constituted by a battery unit. According to an alternative variant, the energy supply unit is constituted by a capacitor unit. According to an alternative variant, the energy supply unit is constituted by a fuel cell.

According to an embodiment, the method for controlling the hydraulic device of a vehicle comprises a first step S1 . In this step, a hydraulic pump for pumping hydraulic medium is driven by means of an electric motor. According to an embodiment, the method for controlling the hydraulic device of a vehicle comprises a second step S2. In this step, hydraulic medium is pumped with said hydraulic pump from a hydraulic reservoir to a pressure line for pressurizing said pressure line with hydraulic medium to provide pressurized pressure medium to at least one consumer. According to an embodiment, the method for controlling the hydraulic device of a vehicle comprises a third step S3. In this step, said hydraulic medium is returned from said at least one consumer to said hydraulic reservoir.

According to the invention, the motor speed of the hydraulic pump, which is a fixed displacement pump, is controlled in order to control pressure in the pressure line by means of said electric motor.

The previous description of the preferred embodiments of the present invention has been provided for illustrative and descriptive purposes. It is not intended to be exhaustive or to limit the invention to the described variants. Obviously, many modifications and variants will be apparent to the skilled person. The embodiments were chosen and described to best explain the principles of the invention and its practical applications, thereby allowing the skilled person to understand the invention for various embodiments and with the various modifications suitable for the intended use.

Claims

1 . A system (I, II) for controlling a hydraulic device of a vehicle, the hydraulic device comprising a hydraulic reservoir (100), a hydraulic pump (90), a pump drive unit (1 10) for driving the hydraulic pump (90), a pressure and a return line (C1 , C2), and a plurality of consumers connected in parallel across said pressure and return lines (C1 , C2), said hydraulic pump (90) being arranged to pump hydraulic medium from the hydraulic reservoir (100) to the pressure line in order to pressurize the pressure line to provide pressurized pressure medium to said plurality of consumers, said consumer being connected to the pressure line (C1 ) in order to receive said pressurized hydraulic medium and to said return line (C2) in order to return said hydraulic medium to the hydraulic reservoir (100),wherein said pump drive unit is an electric motor (1 10) arranged to drive said hydraulic pump (90) and to control the motor speed of the hydraulic pump (90) in order to control pressure in the pressure line (C1 ), wherein said system (I, II) further comprises a control unit (230) for controlling the electric motor (1 10) for said motor speed control, characterized in that said hydraulic device includes a load sensing system for sensing a current pressure demand of pressurized hydraulic medium for said plurality of consumers, wherein the control unit (230) is arranged to control the motor speed of the hydraulic pump (90) based on signals indicating said current pressure demand so that the pressure in the pressure line (C1 ) at least corresponds to the pressure demand of the consumer having the highest pressure demand.

2. The system according to claim 1 , wherein the control unit (230) is arranged to compare, based on the signals indicating current pressure demand, the pressure demand of the different consumers, determine the maximum pressure demand among the respective pressure demand of the consumers, and control the pressure in the pressure line (C1 ) to a pressure which at least corresponds to said maximum pressure demand.

3. The system according to claim 1 or 2, wherein said hydraulic pump (90) is a fixed displacement pump.

4. The system according to any preceding claim, comprising a communication bus (L4) for transmitting said signals indicating current pressure demand to said control unit.

5. A method for controlling a hydraulic device of a vehicle (10), comprising the steps of: driving (S1 ), by means of a pump drive unit (1 10), a hydraulic pump (90) for pumping hydraulic medium; pumping (S2), with said hydraulic pump, hydraulic medium from a hydraulic reservoir (100) to a pressure line (C1 ) in order to pressurize said pressure line with hydraulic medium to provide pressurized pressure medium to a plurality of consumers connected in parallel across said pressure and return lines (C1 , C2); returning (S3) said hydraulic medium from said plurality of consumers to said hydraulic reservoir (100), wherein said pump drive unit is an electric motor (1 10) arranged to drive said hydraulic pump (90) and to control the motor speed of the hydraulic pump (90) in order to control pressure in the pressure line (C1 ), characterized by the steps of sensing, by means of a load sensing system of the hydraulic device, a current pressure demand of pressurized hydraulic medium for said plurality of consumers, and controlling said electric motor (1 10), by means of a control unit (230), for controlling the motor speed of the hydraulic pump (90) based on signals indicating said current pressure demand so that the pressure in the pressure line (C1 ) at least corresponds to the pressure demand of the consumer having the highest pressure demand.

6. The method according to claim 5, further comprising the steps of, by means of said control unit (230), based on the signals indicating current pressure demand, comparing the pressure demand of the different consumers, determining the maximum pressure demand among the respective pressure demand of the consumers, and controlling the pressure in the pressure line (C1 ) to a pressure which at least corresponds to said maximum pressure demand.

7. The method according to claim 5 or 6, wherein said hydraulic pump (90) is a fixed displacement pump.

8. The method according to any of the claims 5-7, comprising the step of transmitting, by means of a communication bus (L4), said signals indicating current pressure demand to said control unit (230).

9. A vehicle comprising a system according to any of the claims 1 -4.