EP0797727A1 - Hydraulic system for a motor vehicle - Google Patents

Hydraulic system for a motor vehicle

Info

Publication number
EP0797727A1
EP0797727A1 EP95904468A EP95904468A EP0797727A1 EP 0797727 A1 EP0797727 A1 EP 0797727A1 EP 95904468 A EP95904468 A EP 95904468A EP 95904468 A EP95904468 A EP 95904468A EP 0797727 A1 EP0797727 A1 EP 0797727A1
Authority
EP
European Patent Office
Prior art keywords
valve
steering
pressure
hydraulic system
hydraulic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95904468A
Other languages
German (de)
French (fr)
Inventor
Egon Eisenbacher
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hilite Germany GmbH
Original Assignee
Mannesmann Rexroth AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mannesmann Rexroth AG filed Critical Mannesmann Rexroth AG
Priority claimed from PCT/EP1994/004144 external-priority patent/WO1996018809A1/en
Publication of EP0797727A1 publication Critical patent/EP0797727A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
    • B62D5/07—Supply of pressurised fluid for steering also supplying other consumers ; control thereof
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01P—COOLING OF MACHINES OR ENGINES IN GENERAL; COOLING OF INTERNAL-COMBUSTION ENGINES
    • F01P7/00—Controlling of coolant flow
    • F01P7/02—Controlling of coolant flow the coolant being cooling-air
    • F01P7/04—Controlling of coolant flow the coolant being cooling-air by varying pump speed, e.g. by changing pump-drive gear ratio
    • F01P7/044—Controlling of coolant flow the coolant being cooling-air by varying pump speed, e.g. by changing pump-drive gear ratio using hydraulic drives
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01P—COOLING OF MACHINES OR ENGINES IN GENERAL; COOLING OF INTERNAL-COMBUSTION ENGINES
    • F01P5/00—Pumping cooling-air or liquid coolants
    • F01P5/02—Pumping cooling-air; Arrangements of cooling-air pumps, e.g. fans or blowers
    • F01P5/04—Pump-driving arrangements
    • F01P5/043—Pump reversing arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/31—Directional control characterised by the positions of the valve element
    • F15B2211/3122—Special positions other than the pump port being connected to working ports or the working ports being connected to the return line
    • F15B2211/3127—Floating position connecting the working ports and the return line
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40515—Flow control characterised by the type of flow control means or valve with variable throttles or orifices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
    • F15B2211/41509—Flow control characterised by the connections of the flow control means in the circuit being connected to a pressure source and a directional control valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/45—Control of bleed-off flow, e.g. control of bypass flow to the return line
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/50—Pressure control
    • F15B2211/505—Pressure control characterised by the type of pressure control means
    • F15B2211/50509—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means
    • F15B2211/50518—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using pressure relief valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/50—Pressure control
    • F15B2211/515—Pressure control characterised by the connections of the pressure control means in the circuit
    • F15B2211/5151—Pressure control characterised by the connections of the pressure control means in the circuit being connected to a pressure source and a directional control valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/50—Pressure control
    • F15B2211/515—Pressure control characterised by the connections of the pressure control means in the circuit
    • F15B2211/5157—Pressure control characterised by the connections of the pressure control means in the circuit being connected to a pressure source and a return line
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/62—Cooling or heating means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/63—Electronic controllers
    • F15B2211/6303—Electronic controllers using input signals
    • F15B2211/632—Electronic controllers using input signals representing a flow rate
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/63—Electronic controllers
    • F15B2211/6303—Electronic controllers using input signals
    • F15B2211/634—Electronic controllers using input signals representing a state of a valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7053—Double-acting output members
    • F15B2211/7054—Having equal piston areas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7058—Rotary output members

Definitions

  • the invention relates to a hydraulic system for a motor vehicle, which has the features from the preamble of claim 1.
  • Various concepts are known for driving a hydraulic fan motor and a hydraulic steering motor.
  • One concept is based on the provision of two completely separate pressure medium circuits, ie two pumps, for driving a fan and for a hydraulic steering device.
  • the two pumps can be largely integrated into one another and are then referred to collectively as a tandem pump.
  • a tandem pump is more expensive than a simple hydraulic pump, such as is used in motor vehicles e.g. only one hydraulic power steering device is used for the pressure medium supply.
  • DE-OS 28 50 481 for driving a hydraulic steering motor and a hydraulic fan motor
  • a single hydraulic pump is used.
  • the hydraulic pump is followed by a priority valve, which ensures that up to a limit value, the entire quantity of pressure medium delivered by the hydraulic pump flows to the steering device. Only the excess amount can be fed to the fan motor.
  • a pump with a large stroke volume is necessary since, in addition to the delivery volume flowing constantly to the steering device, an excess amount has to be generated for the fan motor.
  • a priority valve is required, so that a hydraulic system according to DE-OS 28 50 481 is also complex and costly.
  • Cooling power requirement is changeable. If the cooling capacity requirement increases, the bypass valve is adjusted so that the pressure medium flow through the bypass line is reduced. Conversely, the pressure medium flow through the bypass line increases when the cooling power requirement decreases. Basically, a two-point control is also possible in such a way that the bypass valve either closes the bypass line completely or completely.
  • the hydraulic pump should be able to cover the added pressure requirement of the hydraulic steering device and the fan motor, regardless of the respective height, and must be designed accordingly.
  • a pressure limiting valve which is set to the pump pressure mentioned, has its input with the output of the hydraulic pump, which is also the input of the fan motor, and its output with the output of the Fan motor connected.
  • the invention has for its object to provide a hydraulic system with the features from the preamble of claim 1 so that it can be manufactured at low cost.
  • bypass valve is adjustable in the sense of an increase in the flow of pressure medium through the bypass line during actuation of the steering valve.
  • no further valve is necessary in order to be able to control the fan in such a way that on the one hand the temperature of a coolant is within a certain temperature range and on the other hand the pressure requirement of the steering device can be covered by the hydraulic pump without the pump in terms of delivery volume and must be dimensioned larger than necessary for the steering device. It is sufficient to limit the maximum system pressure to the maximum pressure required by the steering device.
  • the invention can be used in a particularly advantageous manner if the hydraulic steering device is part of a so-called power steering system, with which a high percentage of all road vehicles are equipped today.
  • the power requirement of the fan motor of such a road vehicle is approximately equal to or less than the power requirement of an auxiliary power steering device of the power steering system, so that the power steering pump of such a power steering system can also be used as a pressure medium source for the fan motor in a hydraulic system according to the invention, since Even when the hydraulic steering device is activated due to the possible retraction of the fan motor, the pressure in the system does not rise above a pressure that can be built up and handled by the hydraulic pump.
  • the output of the fan motor in the middle position of a steering valve, is connected to a pressure medium reservoir via the steering valve. There is therefore no need for an additional valve which connects the output of the fan motor to the pressure medium reservoir when the steering device is not required and to the pressure medium reservoir when the steering device is required.
  • the bypass valve is adjustable during actuation of the steering valve depending on the pressure building up on the steering motor. It seems favorable if according to claim 6 in the adjustment of the bypass valve during actuation of the steering valve, the presetting of the bypass valve is also taken into account. For example, it is only possible to open the bypass line when the added pressure requirement of the steering device and the fan motor reaches the maximum system pressure.
  • the bypass valve can remain in its position beforehand.
  • the control of the bypass valve becomes particularly simple if, according to claim 7, it can be adjusted to a specific position while the steering valve is actuated, independently of the pressure building up on the steering motor.
  • the position of the steering valve could be adjusted with a sensor, e.g. with an electrical switch, and an electromagnet, by which the bypass valve can be adjusted, is supplied with a certain current.
  • the specific position of the bypass valve is preferably an end position in which the opening cross section of the bypass line is at a maximum.
  • two adjusting devices can also be provided for adjusting the bypass valve, namely a first adjusting device, by which the bypass valve can be adjusted as a function of the cooling power requirement, and a second adjusting device, by which the bypass valve is actuated the steering valve is adjustable.
  • the bypass valve can have three working connections and can be arranged upstream of the fan motor. One working connection is then connected to the hydraulic pump, the second working connection to the fan motor and the third working connection to the bypass line.
  • the bypass valve is simpler and only needs exactly two work connections if it is arranged in the bypass line according to claim 13. Then the pressure drop at the fan motor is not increased by a pressure drop at the bypass valve.
  • the bypass valve is preferably continuously adjustable.
  • it is a flow valve, the opening cross section of which is more or less large depending on the desired distribution of the pressure medium flow.
  • a particularly simple embodiment consists in using, as a bypass valve, a continuously adjustable pressure relief valve which can be acted upon in the opening direction by a force derived from the pressure upstream of the fan motor and in the closing direction by a force determined by an actuating device and dependent on the cooling capacity requirement .
  • Figure 1 shows a first embodiment in which in the
  • FIG. 2 shows a second exemplary embodiment, in which a throttle valve in the bypass line of the fan motor can only be adjusted by an electromagnet in the closing direction
  • FIG. 3 shows a third embodiment which has a pressure relief valve in the bypass line of the fan motor, which has a pressure spring in the closing direction is applied, the pretension of which can be changed by an expansion element
  • FIG. 4 shows an embodiment similar to that of FIG. 3, in which but the force in the closing direction can be changed by an electromagnet.
  • 10 denotes a hydraulic pump, which sucks in pressure medium from a tank 11 and delivers it into a pressure line 12.
  • the hydraulic pump 10 is driven by the internal combustion engine 13 of a motor vehicle at different speeds.
  • the hydraulic pump 10 is a constant pump, a largely constant flow flows in the pressure line 12, because in the pressure line 12 a fixed orifice, not shown, is arranged in a conventional manner and a pressure control valve, also not shown, which detects the pressure drop across the orifice keeps constant by returning excess amount of pressure medium from the pressure side to the suction side of the pump.
  • Measuring orifice and pressure control valve can be referred to as a flow rate regulator, which is provided with the reference number 14 in its entirety in the figures.
  • the maxiamle system pressure is set by a pressure limiting valve 15 connected to the pressure line 12, which is usually integrated in the hydraulic pump 10.
  • the pressure line 12 leads to the input 16 of a hydraulic fan motor 17 with which a fan wheel 18 can be driven.
  • the output 19 of the fan motor 17 is connected to the pressure connection 20 of a hydraulic power steering device 21.
  • the hydraulic power steering device 21 comprises a power steering valve 25 and a power steering motor in the form of a synchronous cylinder 26.
  • the power steering valve 25 has four working connections, one of which with the pressure input 20 of the power steering device, a second with a tank connection 27 of the power steering device 21 and above with the tank 11, a third with the annular chamber 28 on one side of the piston 29 and the fourth with the annular chamber 30 on the other side of the piston 29 of the synchronous cylinder 26.
  • all four connections of the power steering valve are connected to one another.
  • the annular chamber 28 of the synchronous cylinder 26 is connected to the pressure connection 20 and the annular chamber 30 of the synchronous cylinder 26 is connected to the tank connection 27 of the power steering device 21.
  • the steering aid valve 25 is deflected into the other working position, the connections are changed.
  • the hydraulic pump 10 including the flow control 14 and the
  • Pressure relief valve 15 and the steering device 21 are conventional structural units which are already installed in large numbers in motor vehicles.
  • the fan motor 17 is bypassed by a bypass line 31, in which a continuously adjustable throttle valve 32 is arranged in the embodiments according to FIGS. 1 and 2 and a pressure-limiting valve 33 in the embodiments according to FIGS. 3 and 4.
  • the throttle valve 32 is acted upon by a compression spring 34 in the closing direction.
  • Two actuating devices 40 and 41 can act on the throttle valve 32 in the opening direction.
  • the first actuating device 40 is a proportional electromagnet, which is controlled by control electronics not shown in FIG. 1.
  • the second actuating device 41 is a hydraulic actuating device which is acted upon by the pressure present at the input 20 of the auxiliary power steering device 21 via a line 42 connected to the outlet 19 of the fan motor 17.
  • the temperature of the coolant of the internal combustion engine is reported to the control electronics, which controls the electromagnet 40 so that, depending on the cooling power requirement, the opening cross section of the throttle valve 32 and thus the bypass line 31 is more or less large.
  • the smaller the opening cross section the more pressure medium quantity flows through the fan motor 17 and the higher the pressure at the inlet 16 of the fan motor, since the torque to be applied increases with the speed of the fan wheel 18.
  • the hydraulic actuator 41 is designed to operate at a pressure of e.g. 10 bar at the input 20 of the auxiliary power steering device 21, the throttle valve 32 can open completely. As soon as the load pressure in the cylinder 26 reaches the threshold value of 10 bar, the throttle valve 32 is in any case completely open. The fan motor 17 is therefore at a standstill. Since the force exerted by the adjusting device 41 on the throttle valve 32 is added to that of the electromagnet 40, the throttle valve 32 can be completely open even at a steering pressure which is less than 10 bar. In any case, however, the speed of the fan motor 17 is reduced even when the steering pressure is less than 10 bar. Since the steering of a motor vehicle and in particular the power steering are only activated for a short time, the temperature of the coolant cannot reach an impermissibly high value during this time. A slight increase in temperature can be compensated for by increased cooling after the steering process.
  • the embodiment according to FIG. 2 differs in three respects from that according to FIG. 1.
  • the throttle valve 32 there is only a single actuating device in the form of the electromagnet 40 in addition to the compression spring 34.
  • the compression spring 34 does not act in the closing direction but in the opening direction and the electromagnet 40 does not act in the opening direction but in the closing direction of the throttle valve 32.
  • a so-called fail-safe function of the throttle valve 32 for the steering elements get direction 21. If the electromagnet 40 fails, the throttle valve 32 is completely open, so that the quantity of pressure medium delivered by the hydraulic pump 10 can flow unhindered to the steering device and this reacts quickly when actuated.
  • the fan motor 17 stops in this case or rotates at a minimum speed.
  • an electric switch 43 is assigned to the power steering valve 25, which then gives a signal to the control electronics 44 when the power steering valve 25 has been moved out of its central position.
  • the control electronics 44 is also supplied with a signal which is a measure of the temperature of the coolant.
  • the control electronics 44 control the electromagnet 40 as a function of this signal and of the position of the electrical switch 43. If the switch 43 is open, ie the steering device 21 is not activated, the higher the coolant temperature, the higher the current flowing through the electromagnet 40. With the switch 43 closed, that is to say with the steering device 21 activated, different control modes are conceivable.
  • a first possibility is that the control electronics 44 always switch off the electromagnet 40 when the electrical switch 43 is closed. That is, when the steering device 21 is activated, the throttle valve 32 opens completely, so that the fan motor 17 stops or rotates at a minimum speed.
  • Another possibility is to control the electromagnet 40 in such a way that the maximum system pressure is established upstream of the fan motor 17. In this case, it would be necessary to detect the pressure upstream of the fan motor 17 with a pressure sensor, which sends a signal corresponding to the pressure to the control electronics 44, as indicated by a dashed line leading to the control electronics 44 is interpreted.
  • the pressure limiting valve 33 of the embodiment according to FIG. 3 located in the bypass line 31 is acted upon in the opening direction by the pressure upstream of the fan motor 17 and in the closing direction by a compression spring 45, the pretension of which depends on the expansion of an expansion element 46, which cools ⁇ exposed to medium temperature, and which is located in a spring chamber, which is relieved via a leak oil line to the tank 11, so that the pressure downstream of the fan motor 17 can not affect the valve 33.
  • a different pressure is set at the input 16 of the fan motor 17, so that the fan motor 17 rotates at different speeds depending on the expansion of the expansion element 46 .
  • the prestressing of the compression spring 45 is possible up to a certain value, which thus determines the maximum pressure drop across the fan motor 17.
  • the hydraulic pump 10 conveys pressure medium into the pressure line 12, which flows to the tank 11 via the fan motor 17 and the bypass line 31 and via the power steering valve 25 located in its central position.
  • the pressure drop across the fan motor 17 is e.g. 40 bar.
  • the maximum system pressure is 60 bar.
  • the steering device 21 is now activated and a pressure of e.g. 10 bar required.
  • a consequent increase in pressure at the inlet 16 of the fan motor 17 causes the pressure limiting valve 33 to open further and the pressure at the inlet 16 of the fan motor 17 initially remains limited to 40 bar.
  • the pressure drop across the fan motor 17 has therefore decreased to 30 bar and the current cooling capacity is below the required cooling capacity.
  • the steering device 21 has a Druckbe r may of 30 bar.
  • the pressure remains at inlet 16 the fan motor 17 initially at 40 bar.
  • the pressure drop across the fan motor 17 is now only 10 bar.
  • the steering device 21 is actuated for a longer time, the coolant temperature rises.
  • the expansion element 46 becomes larger and prestresses the spring 45 more.
  • the maximum system pressure of 60 bar will be set at the input 16 of the fan motor 17, so that the pressure drop across the fan motor 17 is 30 bar and the cooling capacity is too low to keep the coolant temperature at the previous value within the permitted temperature range . After deactivation of the steering device 21, this will be compensated for by increased cooling.
  • the pressure limiting valve 33 is opened completely.
  • the fan motor 17 rotates at minimum speed or stands still. Even if the
  • valve 33 in the opening direction apart from the pressure upstream of the fan motor 17 by a further actuating device, e.g. is acted upon by an electromagnet. Then, when the steering device is activated, the valve 33 e.g. be completely opened.
  • the embodiment according to FIG. 4 differs from that according to FIG. 3 on the one hand in that the pressure limiting valve 33 can be acted upon directly by a force-controlled proportional electromagnet 40 in the closing direction. Depending on the temperature of the coolant, a different current is applied to the electromagnet and exerts a force of different magnitude on a valve body of the valve 33.
  • the mode of operation of the system according to FIG. 4 can be the same as that of the system according to FIG. 3.
  • the use of an electromagnet also offers the possibility of completely switching off the electromagnet 40 when the steering device 21 is activated and thus reducing the pressure drop across the fan motor 17 to a minimum value each time the steering device 21 is activated, regardless of its pressure requirement.
  • the respective time period in which the steering device 21 is activated is generally so short and the total duration of the activation, expressed as a percentage of the total operating time of the motor vehicle, is generally so short that the temperature of the coolant during the steering is the permissible one Range does not exceed and can be reduced again during the time in which the steering device 21 is not activated.
  • the valve body of the pressure relief valve 33 of the system according to FIG. 4 is acted upon in the opening direction apart from the pressure upstream of the fan motor 17 by a weak compression spring 47 which, when the electromagnet 40 is switched off or has failed, ensures a defined rest position of the pressure relief valve 33 . In this position the valve 33 is open.
  • one side of the pressure relief valve 33 is connected to the tank 11 by a leak oil line.
  • the invention has created a hydraulic system for a motor vehicle which is inexpensive and in which a hydraulic steering device and a hydraulic motor for driving a fan wheel are combined with one another in such a way that the steering part fulfills its function in the usual manner and the cooling capacity also meets the requirements.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Transportation (AREA)
  • Power Steering Mechanism (AREA)

Abstract

The invention starts from a hydraulic system for a motor vehicle and comprises the following elements: a hydraulic pump (10) which has a hydraulic steering device (21) comprising a steering motor (26) and a steering valve (25) which can move from an intermediate position in opposing directions and by which hydraulic fluid lines to and from the steering motor (26) can be controlled; a ventilator motor (17) which is circumvented by a bypass line and fitted in series with the steering device (21) between the latter and the hydraulic pump (10); and a bypass valve (32, 33) with which the distribution of fluid flow through the ventilator motor (17) and the bypass line (31) can be adjusted in accordance with the cooling power required. The aim is to achieve a particularly inexpensive design for a hydraulic system of this type. This is achieved by the feature according to which the bypass valve (32, 33) can be adjusted to allow more hydraulic fluid to flow through the bypass line (31) during actuation of the steering valve (25). This makes it possible to keep the system pressure low and thus to use a simple and inexpensive hydraulic pump (10). No additional valves are required.

Description

Beschreibungdescription
Hydraulikanlage für ein KraftfahrzeugHydraulic system for a motor vehicle
Die Erfindung betrifft eine Hydraulikanlage für ein Kraftfahr¬ zeug, die die Merkmale aus dem Oberbegriff des Anspruches 1 auf- weist.The invention relates to a hydraulic system for a motor vehicle, which has the features from the preamble of claim 1.
Für den Antrieb eines hydraulischen Lüftermotors und eines hydraulischen Lenkmotors sind verschiedene Konzepte bekannt. Ein Konzept beruht darauf, für den Antrieb eines Lüfters und für eine hydraulische Lenkeinrichtung zwei völlig getrennte Druck- mittelkreise, also auch zwei Pumpen vorzusehen. Die beiden Pum¬ pen können weitgehend ineinander integriert sein und werden dann gemeinsam als Tandempumpe bezeichnet. Trotz der weitgehenden In¬ tegration ist eine solche Tandempumpe teurer als eine einfache Hydropumpe, wie sie in Kraftfahrzeugen z.B. für die Druckmittel- Versorgung nur einer hydraulischen Hilfskraftlenkeinrichtung eingesetzt wird.Various concepts are known for driving a hydraulic fan motor and a hydraulic steering motor. One concept is based on the provision of two completely separate pressure medium circuits, ie two pumps, for driving a fan and for a hydraulic steering device. The two pumps can be largely integrated into one another and are then referred to collectively as a tandem pump. Despite the extensive integration, such a tandem pump is more expensive than a simple hydraulic pump, such as is used in motor vehicles e.g. only one hydraulic power steering device is used for the pressure medium supply.
Bei einem anderen aus der DE-OS 28 50 481 bekannten Konzept zum Antrieb eines hydraulischen Lenkmotors und eines hydraulischen Lüftermotors wird nur eine einzige Hydropumpe verwendet. Der Hy- dropumpe ist ein Prioritätsventil nachgeschaltet, das sicher¬ stellt, daß bis zu einem Grenzwert die gesamte von der Hydro¬ pumpe geförderte Druckmittelmenge zur Lenkeinrichtung fließt. Nur die überschüssige Menge kann dem Lüftermotor zugeführt wer¬ den. Bei einer solchen Ausführung einer Hydraulikanlage ist eine Pumpe mit einem großen Hubvolumen notwendig, da zusätzlich zu der ständig zur Lenkeinrichtung fließenden Fördermenge eine Überschußmenge für den Lüftermotor erzeugt werden muß. Außerdem wird ein Prioritätsventil benötigt, so daß auch eine Hydrau¬ likanlage gemäß der DE-OS 28 50 481 aufwendig und kostenträchtig ist.In another concept known from DE-OS 28 50 481 for driving a hydraulic steering motor and a hydraulic fan motor, only a single hydraulic pump is used. The hydraulic pump is followed by a priority valve, which ensures that up to a limit value, the entire quantity of pressure medium delivered by the hydraulic pump flows to the steering device. Only the excess amount can be fed to the fan motor. In such a design of a hydraulic system, a pump with a large stroke volume is necessary since, in addition to the delivery volume flowing constantly to the steering device, an excess amount has to be generated for the fan motor. In addition, a priority valve is required, so that a hydraulic system according to DE-OS 28 50 481 is also complex and costly.
Schließlich ist aus der US-A 36 64 129 eine Hydraulikanlage be¬ kannt, bei der der Lüftermotor in Serie zur Lenkeinrichtung zwi- sehen dieser und einer Hydropumpe angeordnet ist. Wie bei den anderen skizzierten Ausführungen ist auch bei derjenigen nach der US-Patentschrift ein Bypassventil vorhanden, mit dem die Aufteilung des Fluidflusses durch den Lüftermotor und durch eine den Lüftermotor umgehende Bypassleitung in Abhängigkeit vomFinally, a hydraulic system is known from US Pat. No. 3,664,129, in which the fan motor is connected in series to the steering device. see this and a hydraulic pump is arranged. As with the other outlined embodiments, there is also a bypass valve in the one according to the US patent, with which the division of the fluid flow through the fan motor and through a bypass line that bypasses the fan motor as a function of
Kühlleistungsbedarf veränderbar ist. Steigt der Kühlleistungbe¬ darf, so wird das Bypassventil so verstellt, daß sich der Druck¬ mitteldurchfluß durch die Bypassleitung verringert. Umgekehrt erhöht sich der Druckmitteldurchfluß durch die Bypassleitung, wenn sich der Kühlleistungsbedarf verringert. Grundsätzlich ist dabei auch eine 2-Punktregelung derart möglich, daß das By¬ passventil die Bypassleitung entweder ganz zu oder ganz auf macht. Bei der Hydraulikanlage nach der US-A 36 64 129 soll die Hydropumpe unabhängig von der jeweiligen Höhe den addierten Druckbedarf der hydraulischen Lenkeinrichtung und des Lüftermo¬ tors decken können und ist entsprechend auszubilden. Lediglich zur Begrenzung von parasitären Leistungsverlusten der die Hydro¬ pumpe antreibenden Brennkraftmaschine ist vorgesehen, daß ab ei¬ nem bestimmten Pumpendruck der Druckabfall über den Lüftermotor reduziert wird, so daß der Pumpendruck erst wieder ansteigen würde, wenn über den Lüftermotor kein Druck mehr abfällt und der Lüftermotor still steht. Zur Reduzierung des Druckabfalls über den Lüftermotor ab einem bestimmten Pumpendruck ist ein Druckbe¬ grenzungsventil, das auf den erwähnten Pumpendruck eingestellt ist, mit seinem Eingang mit dem Ausgang der Hydropumpe, der gleichzeitig der Eingang des Lüftermotors ist, und mit seinem Ausgang mit dem Ausgang des Lüftermotors verbunden.Cooling power requirement is changeable. If the cooling capacity requirement increases, the bypass valve is adjusted so that the pressure medium flow through the bypass line is reduced. Conversely, the pressure medium flow through the bypass line increases when the cooling power requirement decreases. Basically, a two-point control is also possible in such a way that the bypass valve either closes the bypass line completely or completely. In the hydraulic system according to US Pat. No. 3,664,129, the hydraulic pump should be able to cover the added pressure requirement of the hydraulic steering device and the fan motor, regardless of the respective height, and must be designed accordingly. Merely to limit parasitic power losses of the internal combustion engine driving the hydraulic pump, it is provided that from a certain pump pressure the pressure drop across the fan motor is reduced, so that the pump pressure would only rise again when no more pressure dropped via the fan motor and the Fan motor stands still. To reduce the pressure drop across the fan motor from a certain pump pressure, a pressure limiting valve, which is set to the pump pressure mentioned, has its input with the output of the hydraulic pump, which is also the input of the fan motor, and its output with the output of the Fan motor connected.
Der Erfindung liegt die Aufgabe zugrunde, eine Hydraulikanlage mit den Merkmalen aus dem Oberbegriff des Anspruches 1 so auszu- bilden, daß sie mit geringen Kosten hergestellt werden kann.The invention has for its object to provide a hydraulic system with the features from the preamble of claim 1 so that it can be manufactured at low cost.
Diese Aufgabe wird für eine Hydraulikanlage mit den Merkmalen aus dem Oberbegriff des Anspruches 1 dadurch gelöst, daß während einer Betätigung des Lenkventils das Bypassventil im Sinne einer Vergrößerung des Durchflusses von Druckmittel durch die By- passleitung verstellbar ist. Somit ist außer dem Bypassventil kein weiteres Ventil notwendig, um den Lüfter so steuern zu kön¬ nen, daß einerseits die Temperatur eines Kühlmittels innerhalb eines bestimmten Temperaturbereichs liegt und andererseits der Druckbedarf der Lenkeinrichtung von der Hydropumpe gedeckt wer- den kann, ohne daß die Pumpe in Bezug auf Fördervolumen und auf Druck größer als für die Lenkeinrichtung ohnehin nötig dimensio¬ niert sein muß. Es genügt, den maximalen Systemdruck auf den ma¬ ximal von der Lenkeinrichtung benötigten Druck zu begrenzen.This object is achieved for a hydraulic system with the features from the preamble of claim 1 in that the bypass valve is adjustable in the sense of an increase in the flow of pressure medium through the bypass line during actuation of the steering valve. Thus, besides the bypass valve no further valve is necessary in order to be able to control the fan in such a way that on the one hand the temperature of a coolant is within a certain temperature range and on the other hand the pressure requirement of the steering device can be covered by the hydraulic pump without the pump in terms of delivery volume and must be dimensioned larger than necessary for the steering device. It is sufficient to limit the maximum system pressure to the maximum pressure required by the steering device.
Vorteilhafte Ausgestaltungen einer erfindungsgemäßen Hydrau¬ likanlage kann man den Unteransprüchen entnehmen.Advantageous embodiments of a hydraulic system according to the invention can be found in the subclaims.
So ist die Erfindung in besonders vorteilhafter Weise anwendbar, wenn die hydraulische Lenkeinrichtung Teil einer sogenannten Servolenkung ist, mit der heutzutage ein hoher Prozentsatz aller Straßenfahrzeuge ausgerüstet ist. Der Leistungsbedarf des Lüf¬ termotors eines solchen Straßenfahrzeugs ist in etwa gleich dem oder kleiner als der Leistungsbedarf einer Hilfskraftlenkein¬ richtung der Servolenkung, so daß die Lenkhilfspumpe einer sol¬ chen Servolenkung in einer erfindungsgemäßen Hydraulikanlage auch als Druckmittelquelle für den Lüftermotor verwendet werden kann, da auch bei einer Aktivierung der hydraulischen Lenkein¬ richtung durch das mögliche Zurückfahren des Lüftermotors der Druck im System nicht über einen von der Hydropumpe aufbaubaren und verkraftbaren Druck ansteigt.Thus, the invention can be used in a particularly advantageous manner if the hydraulic steering device is part of a so-called power steering system, with which a high percentage of all road vehicles are equipped today. The power requirement of the fan motor of such a road vehicle is approximately equal to or less than the power requirement of an auxiliary power steering device of the power steering system, so that the power steering pump of such a power steering system can also be used as a pressure medium source for the fan motor in a hydraulic system according to the invention, since Even when the hydraulic steering device is activated due to the possible retraction of the fan motor, the pressure in the system does not rise above a pressure that can be built up and handled by the hydraulic pump.
Gemäß Anspruch 4 ist in der Mittelstellung eines Lenkventils der Ausgang des Lüftermotors über das Lenkventil mit einem Druckmit¬ telvorratsbehälter verbunden. Es wird deshalb kein zusätzliches Ventil benötigt, das bei nicht benötigter Lenkeinrichtung den Ausgang des Lüftermotors mit dem Druckmittelvorratsbehälter und bei benötigter Lenkeinrichtung mit dieser verbindet.According to claim 4, in the middle position of a steering valve, the output of the fan motor is connected to a pressure medium reservoir via the steering valve. There is therefore no need for an additional valve which connects the output of the fan motor to the pressure medium reservoir when the steering device is not required and to the pressure medium reservoir when the steering device is required.
In der bevorzugten Ausführung gemäß Anspruch 5 ist das By¬ passventil während einer Betätigung des Lenkventils in Abhängig¬ keit vom sich am Lenkmotor aufbauenden Druck verstellbar. Dabei erscheint es günstig, wenn gemäß Anspruch 6 bei der Verstellung des Bypassventils während einer Betätigung des Lenkventils zu¬ sätzlich auch die Voreinstellung des Bypassventils berücksich¬ tigt wird. So ist es z.B. möglich, die Bypassleitung erst dann weiter zu öffnen, wenn der addierte Druckbedarf der Lenkeinrich- tung und des Lüftermotors den maximalen Systemdruck erreicht. Vorher kann das Bypassventil in seiner Stellung verbleiben.In the preferred embodiment according to claim 5, the bypass valve is adjustable during actuation of the steering valve depending on the pressure building up on the steering motor. It seems favorable if according to claim 6 in the adjustment of the bypass valve during actuation of the steering valve, the presetting of the bypass valve is also taken into account. For example, it is only possible to open the bypass line when the added pressure requirement of the steering device and the fan motor reaches the maximum system pressure. The bypass valve can remain in its position beforehand.
Die Steuerung des Bypassventils wird besonders einfach, wenn es gemäß Anspruch 7 während einer Betätigung des Lenkventils unab¬ hängig von dem sich am Lenkmotor aufbauenden Druck in eine be- stimmte Stellung verstellbar ist. Dazu könnte die Position des Lenkventils mit einem Sensor, z.B. mit einem elektrischen Schal¬ ter, erfaßt und ein Elektromagnet, von dem das Bypassventil ver¬ stellt werden kann, mit einem bestimmten Strom beaufschlagt wer¬ den. Die bestimmte Stellung des Bypassventils ist bevorzugt eine Endstellung, in der der Öffnungsquerschnitt der Bypassleitung maximal ist.The control of the bypass valve becomes particularly simple if, according to claim 7, it can be adjusted to a specific position while the steering valve is actuated, independently of the pressure building up on the steering motor. To do this, the position of the steering valve could be adjusted with a sensor, e.g. with an electrical switch, and an electromagnet, by which the bypass valve can be adjusted, is supplied with a certain current. The specific position of the bypass valve is preferably an end position in which the opening cross section of the bypass line is at a maximum.
Für die Verstellung des Bypassventils können jedoch gemäß An¬ spruch 11 auch zwei Stelleinrichtungen vorgesehen sein, nämlich eine erste Stelleinrichtung, von der das Bypassventil in Abhän- gigkeit vom Kühlleistungsbedarf verstellbar ist, und eine zweite Stelleinrichtung, von der das Bypassventil während einer Betäti¬ gung des Lenkventils verstellbar ist.However, according to claim 11, two adjusting devices can also be provided for adjusting the bypass valve, namely a first adjusting device, by which the bypass valve can be adjusted as a function of the cooling power requirement, and a second adjusting device, by which the bypass valve is actuated the steering valve is adjustable.
Grundsätzlich kann das Bypassventil, wie in der DE-OS 28 50 481 gezeigt, drei Arbeitsanschlüsse besitzen und stromauf des Lüf- termotors angeordnet sein. Ein Arbeitsanschluß ist dann mit der Hydropumpe, der zweite Arbeitsanschluß mit dem Lüftermotor und der dritte Arbeitsanschluß mit der Bypassleitung verbunden. Das Bypassventil ist einfacher und braucht nur genau zwei Arbeitsan¬ schlüsse, wenn es gemäß Anspruch 13 in der Bypassleitung ange- ordnet ist. Auch wird dann der Druckabfall am Lüftermotor nicht um einen Druckabfall am Bypassventil erhöht.In principle, as shown in DE-OS 28 50 481, the bypass valve can have three working connections and can be arranged upstream of the fan motor. One working connection is then connected to the hydraulic pump, the second working connection to the fan motor and the third working connection to the bypass line. The bypass valve is simpler and only needs exactly two work connections if it is arranged in the bypass line according to claim 13. Then the pressure drop at the fan motor is not increased by a pressure drop at the bypass valve.
Wie schon erwähnt, ist es möglich, für den Lüftermotor eine 2- Punktregelung vorzusehen. Für das Bypassventil sind dann genau zwei Schaltstellungen nötig, wobei in der einen Schaltstellung die Bypassleitung geschlossen und in der anderen Schaltstellung die Bypassleitung ganz offen ist. Vorzugsweise ist das By¬ passventil jedoch stetig verstellbar. In einer ersten bevorzug¬ ten Ausbildung gemäß Anspruch 14 ist es ein Stromventil, dessen Öffnungsquerschnitt je nach der gewünschten Aufteilung des Druckmittelflusses mehr oder weniger groß ist. Eine besonders einfache Ausführung besteht jedoch darin, gemäß Anspruch 15 als Bypassventil ein stetig verstellbares Druckbegrenzungsventil zu verwenden, das in Öffnungsrichtung von einer vom Druck stromauf des Lüftermotors abgeleiteten Kraft und in Schließrichtung von einer von einer Stelleinrichtung bestimmten, vom Kühlleistungs¬ bedarf abhängigen Kraft beaufschlagbar ist. Mit einem solchen Druckbegrenzungsventil als Bypassventil wird ohne weitere Ma߬ nahmen bei der Aktivierung der Lenkeinrichtung der Druckabfall über den Lüftermotor reduziert und sichergestellt, daß die Lenk¬ einrichtung mit dem maximalen Systemdruck beaufschlagt werden kann.As already mentioned, it is possible to provide a 2-point control for the fan motor. Exactly two switching positions are then necessary for the bypass valve, one in the switching position the bypass line is closed and in the other switching position the bypass line is completely open. However, the bypass valve is preferably continuously adjustable. In a first preferred embodiment according to claim 14, it is a flow valve, the opening cross section of which is more or less large depending on the desired distribution of the pressure medium flow. A particularly simple embodiment, however, consists in using, as a bypass valve, a continuously adjustable pressure relief valve which can be acted upon in the opening direction by a force derived from the pressure upstream of the fan motor and in the closing direction by a force determined by an actuating device and dependent on the cooling capacity requirement . With such a pressure relief valve as a bypass valve, the pressure drop across the fan motor is reduced without further measures when the steering device is activated, and it is ensured that the maximum system pressure can be applied to the steering device.
Mehrere Ausführungsbeispiele einer erfindungsgemäßen Hydrau¬ likanlage sind in den Zeichnungen dargestellt. Anhand der Figu- ren dieser Zeichnungen wird die Erfindung nun näher erläutert.Several exemplary embodiments of a hydraulic system according to the invention are shown in the drawings. The invention will now be explained in more detail with reference to the figures of these drawings.
Es zeigenShow it
Figur 1 ein erstes Ausführungsbeispiel, bei dem in derFigure 1 shows a first embodiment in which in the
Bypassleitung des Lüftermotors ein von zwei Stell¬ einrichtungen in Öffnungsrichtung verstellbares Drosselventil angeordnet ist,Bypass line of the fan motor, a throttle valve which is adjustable in the opening direction by two adjusting devices is arranged,
Figur 2 eine zweites Ausführungsbeispiel, bei dem ein Dros¬ selventil in der Bypassleitung des Lüftermotors in Schließrichtung nur von einem Elektromagneten ver¬ stellbar ist, Figur 3 eine dritte Ausführung, die in der Bypassleitung des Lüftermotors ein Druckbegrenzungsventil aufweist, das in Schließrichtung von einer Druckfeder beaufschlagt ist, deren Vorspannung von einem Dehnstoffelement veränderbar ist, und Figur 4 eine Ausführung ähnlich der aus Figur 3, bei der je- doch die Kraft in Schließrichtung von einem Elektro¬ magneten veränderbar ist.2 shows a second exemplary embodiment, in which a throttle valve in the bypass line of the fan motor can only be adjusted by an electromagnet in the closing direction, FIG. 3 shows a third embodiment which has a pressure relief valve in the bypass line of the fan motor, which has a pressure spring in the closing direction is applied, the pretension of which can be changed by an expansion element, and FIG. 4 shows an embodiment similar to that of FIG. 3, in which but the force in the closing direction can be changed by an electromagnet.
In den Figuren ist mit 10 eine Hydropumpe bezeichnet, die aus einem Tank 11 Druckmittel ansaugt und in eine Druckleitung 12 abgibt. Die Hydropumpe 10 wird von der Brennkraftmaschine 13 ei¬ nes Kraftfahrzeugs mit unterschiedlichen Drehzahlen angetrieben. Obwohl die Hydropumpe 10 eine Konstantpumpe ist, fließt in der Druckleitung 12 ein weitgehend konstanter Förderstrom, weil in der Druckleitung 12 in an sich üblicher Weise eine nicht näher dargestellte feste Meßblende angeordnet ist und ein ebenfalls nicht näher dargestelltes Druckregelventil, das den Druckabfall über die Meßblende konstant hält, indem es überschüssige Druck¬ mittelmenge von der Druckseite zur Saugseite der Pumpe zurück¬ führt. Meßblende und Druckregelventil kann man als Förderstrom- regier bezeichnen, der in den Figuren in seiner Gesamtheit mit der Bezugszahl 14 versehen ist. Durch ein an die Druckleitung 12 angeschlossenes Druckbegrenzungsventil 15, das üblicherweise in die Hydropumpe 10 integriert ist, wird der maxiamle Systemdruck eingestellt.In the figures, 10 denotes a hydraulic pump, which sucks in pressure medium from a tank 11 and delivers it into a pressure line 12. The hydraulic pump 10 is driven by the internal combustion engine 13 of a motor vehicle at different speeds. Although the hydraulic pump 10 is a constant pump, a largely constant flow flows in the pressure line 12, because in the pressure line 12 a fixed orifice, not shown, is arranged in a conventional manner and a pressure control valve, also not shown, which detects the pressure drop across the orifice keeps constant by returning excess amount of pressure medium from the pressure side to the suction side of the pump. Measuring orifice and pressure control valve can be referred to as a flow rate regulator, which is provided with the reference number 14 in its entirety in the figures. The maxiamle system pressure is set by a pressure limiting valve 15 connected to the pressure line 12, which is usually integrated in the hydraulic pump 10.
Die Druckleitung 12 führt zum Eingang 16 eines hydraulischen Lüftermotors 17, mit dem ein Lüfterrad 18 antreibbar ist. Der Ausgang 19 des Lüftermotors 17 ist mit dem Druckanschluß 20 ei¬ ner hydraulischen Hilfskraftlenkeinrichtung 21 verbunden.The pressure line 12 leads to the input 16 of a hydraulic fan motor 17 with which a fan wheel 18 can be driven. The output 19 of the fan motor 17 is connected to the pressure connection 20 of a hydraulic power steering device 21.
Die hydraulische Hilfskraftlenkeinrichtung 21 umfaßt ein Lenk- hilfeventil 25 und einen Lenkhilfemotor in Form eines Gleich¬ gangzylinders 26. Das Lenkhilfeventil 25 besitzt vier Arbeitsan¬ schlüsse, von denen einer mit dem Druckeingang 20 der Hilfs- kraftlenkeinrichtung, ein zweiter mit einem Tankanschluß 27 der Hilfskraftlenkeinrichtung 21 und darüber mit dem Tank 11, ein dritter mit der Ringkammer 28 auf der einen Seite des Kolbens 29 und der vierte mit der Ringkammer 30 auf der anderen Seite des Kolbens 29 des Gleichgangzylinders 26 verbunden ist. In der fe¬ derzentrierten Mittelstellung des Lenkhilfeventils 25 sind alle vier Anschlüsse des Lenkhilfeventils miteinander verbunden. Durch eine Drehung am Lenkrad eines Kraftfahrzeugs kann das Lenkhilfeventil 25 aus seiner Mittelstellung je nach Drehrich¬ tung in eine erste oder in eine zweite seitliche ArbeitsStellung gebracht werden. In der einen Arbeitsstellung ist die Ringkammer 28 des Gleichgangzylinders 26 mit dem Druckanschluß 20 und die Ringkammer 30 des Gleichgangzylinders 26 mit dem Tankanschluß 27 der Hilfskraftlenkeinrichtung 21 verbunden. Bei einer Auslenkung des Lenkhilfeventils 25 in die andere Arbeitsstellung sind die Verbindungen gewechselt.The hydraulic power steering device 21 comprises a power steering valve 25 and a power steering motor in the form of a synchronous cylinder 26. The power steering valve 25 has four working connections, one of which with the pressure input 20 of the power steering device, a second with a tank connection 27 of the power steering device 21 and above with the tank 11, a third with the annular chamber 28 on one side of the piston 29 and the fourth with the annular chamber 30 on the other side of the piston 29 of the synchronous cylinder 26. In the spring-centered central position of the power steering valve 25, all four connections of the power steering valve are connected to one another. By turning the steering wheel of a motor vehicle, the steering aid valve 25 can be brought from its central position into a first or a second lateral working position, depending on the direction of rotation. In one working position, the annular chamber 28 of the synchronous cylinder 26 is connected to the pressure connection 20 and the annular chamber 30 of the synchronous cylinder 26 is connected to the tank connection 27 of the power steering device 21. When the steering aid valve 25 is deflected into the other working position, the connections are changed.
Die Hydropumpe 10 inklusive des Förderstromregiers 14 und desThe hydraulic pump 10 including the flow control 14 and the
Druckbegrenzungsventils 15 sowie die Lenkeinrichtung 21 sind üb¬ liche Baueinheiten, die heute schon in großer Anzahl in Kraft¬ fahrzeuge eingebaut werden.Pressure relief valve 15 and the steering device 21 are conventional structural units which are already installed in large numbers in motor vehicles.
Der Lüftermotor 17 wird bei allen vier Ausführungsbeispielen von einer Bypassleitung 31 umgangen, in der bei den Ausführungen nach den Figuren 1 und 2 ein stetig verstellbares Drosselventil 32 und bei den Ausführungen nach den Figuren 3 und 4 ein Druck¬ begrenzungsventil 33 angeordnet ist.In all four exemplary embodiments, the fan motor 17 is bypassed by a bypass line 31, in which a continuously adjustable throttle valve 32 is arranged in the embodiments according to FIGS. 1 and 2 and a pressure-limiting valve 33 in the embodiments according to FIGS. 3 and 4.
Bei der Ausführung nach Figur 1 wird das Drosselventil 32 in Schließrichtung von einer Druckfeder 34 beaufschlagt. In Öff¬ nungsrichtung können auf das Drosselventil 32 zwei Stelleinrich¬ tungen 40 bzw. 41 wirken. Die erste Stelleinrichtung 40 ist ein Proportional-Elektromagnet, der von einer in Figur 1 nicht näher dargestellten Regelelektronik angesteuert wird. Die zweite Stel- leinrichtung 41 ist eine hydraulische Stelleinrichtung, die über eine mit dem Ausgang 19 des Lüftermotors 17 verbundene Leitung 42 mit dem am Eingang 20 der Hilfskraftlenkeinrichtung 21 anste¬ henden Druck beaufschlagt wird.In the embodiment according to FIG. 1, the throttle valve 32 is acted upon by a compression spring 34 in the closing direction. Two actuating devices 40 and 41 can act on the throttle valve 32 in the opening direction. The first actuating device 40 is a proportional electromagnet, which is controlled by control electronics not shown in FIG. 1. The second actuating device 41 is a hydraulic actuating device which is acted upon by the pressure present at the input 20 of the auxiliary power steering device 21 via a line 42 connected to the outlet 19 of the fan motor 17.
Im Betrieb eines Kraftfahrzeugs wird die Temperatur des Kühlmit- tels der Brennkraftmaschine der Regelelektronik gemeldet, die den Elektromagneten 40 so ansteuert, daß je nach dem Kühllei¬ stungsbedarf der Öffnungsquerschnitt des Drosselventils 32 und damit der Bypassleitung 31 mehr oder weniger groß ist. Je klei¬ ner der Öffnungsquerschnitt ist, desto mehr Druckmittelmenge fließt durch den Lüftermotor 17 und um so höher ist der Druck am Eingang 16 des Lüftermotors, da das aufzubringende Drehmoment mit der Drehzahl des Lüfterrads 18 steigt.In the operation of a motor vehicle, the temperature of the coolant of the internal combustion engine is reported to the control electronics, which controls the electromagnet 40 so that, depending on the cooling power requirement, the opening cross section of the throttle valve 32 and thus the bypass line 31 is more or less large. The smaller the opening cross section, the more pressure medium quantity flows through the fan motor 17 and the higher the pressure at the inlet 16 of the fan motor, since the torque to be applied increases with the speed of the fan wheel 18.
Die hydraulische Stelleinrichtung 41 ist so konzipiert, daß sie bei einem Druck von z.B. 10 bar am Eingang 20 der Hilfskraft¬ lenkeinrichtung 21 das Drosselventil 32 vollständig öffnen kann. Sobald der Lastdruck im Zylinder 26 den Schwellenwert von 10 bar erreicht, ist das Drosselventil 32 auf jeden Fall ganz offen. Der Lüftermotor 17 steht deshalb still. Da sich die von der Stelleinrichtung 41 auf das Drosselventil 32 ausgeübte Kraft zu derjenigen des Elektromagneten 40 addiert, kann das Drosselven¬ til 32 auch schon bei einem Lenkdruck, der kleiner als 10 bar ist, ganz offen sein. In jedem Fall wird jedoch auch bei einem Lenkdruck kleiner als 10 bar die Drehzahl des Lüftermotors 17 reduziert. Da die Lenkung eines Kraftfahrzeugs und insbesondere die Hilfskraftlenkung jeweils nur kurzzeitig aktiviert sind, kann in dieser Zeit die Temperatur des Kühlmittels nicht einen unzulässig hohen Wert erreichen. Ein geringer Anstieg der Tempe¬ ratur kann durch eine verstärkte Kühlung nach dem Lenkvorgang wieder ausgeglichen werden.The hydraulic actuator 41 is designed to operate at a pressure of e.g. 10 bar at the input 20 of the auxiliary power steering device 21, the throttle valve 32 can open completely. As soon as the load pressure in the cylinder 26 reaches the threshold value of 10 bar, the throttle valve 32 is in any case completely open. The fan motor 17 is therefore at a standstill. Since the force exerted by the adjusting device 41 on the throttle valve 32 is added to that of the electromagnet 40, the throttle valve 32 can be completely open even at a steering pressure which is less than 10 bar. In any case, however, the speed of the fan motor 17 is reduced even when the steering pressure is less than 10 bar. Since the steering of a motor vehicle and in particular the power steering are only activated for a short time, the temperature of the coolant cannot reach an impermissibly high value during this time. A slight increase in temperature can be compensated for by increased cooling after the steering process.
Die Ausführung nach Figur 2 unterscheidet sich in dreierlei Hin¬ sicht von derjenigen nach Figur 1. Zum einen ist für das Dros¬ selventil 32 außer der Druckfeder 34 nur eine einzige Stellein¬ richtung in Form des Elektromagneten 40 vorhanden. Zum zweiten wirkt die Druckfeder 34 nicht in Schließ-, sondern in Öffnungs¬ richtung und der Elektromagnet 40 nicht in Öffnungs-, sondern in Schließrichtung des Drosselventils 32. Dadurch wird eine soge¬ nannte fail-safe-Funktion des Drosselventils 32 für die Lenkein¬ richtung 21 erhalten. Bei Ausfall des Elektromagneten 40 ist das Drosselventil 32 ganz offen, so daß die von der Hydropumpe 10 geförderte Druckmittelmenge ungehindert zur Lenkeinrichtung fließen kann und diese bei einer Betätigung schnell reagiert. Der Lüftermotor 17 bleibt in diesem Fall stehen oder dreht sich mit einer minimalen Drehzahl. Zum dritten ist dem Lenkhilfeven- til 25 ein elektrischer Schalter 43 zugeordnet, der jeweils dann ein Signal an die Regelelektronik 44 gibt, wenn das Lenkhilfe¬ ventil 25 aus seiner Mittelstellung heraus bewegt worden ist. Der Regelelektronik 44 wird außerdem ein Signal zugeführt, das ein Maß für die Temperatur des Kühlmittels ist. In Abhängigkeit von diesem Signal und von der Stellung des elektrischen Schal¬ ters 43 steuert die Regelelektronik 44 den Elektromagneten 40 an. Ist der Schalter 43 offen, die Lenkeinrichtung 21 also nicht aktiviert, so ist der durch den Elektromagneten 40 fließende Strom umso höher, je höher die Kühlmitteltemperatur ist. Bei ge- schlossenem Schalter 43, also bei aktivierter Lenkeinrichtung 21 sind verschiedene Ansteuerungsweisen denkbar. Eine erste Mög¬ lichkeit besteht darin, daß die Regelelektronik 44 den Elektro¬ magneten 40 immer dann ausschaltet, wenn der elektrische Schal¬ ter 43 geschlossen ist. D.h., daß bei einer Aktivierung der Lenkeinrichtung 21 das Drosselventil 32 ganz aufmacht, so daß der Lüftermotor 17 stehenbleibt oder sich mit einer minimalen Drehzahl dreht. Eine weitere Möglichkeit besteht darin, den Elektromagneten 40 so anzusteuern, daß sich stromauf des Lüfter¬ motors 17 gerade der maximale Systemdruck einstellt. In diesem Fall wäre es notwendig, den Druck stromauf des Lüftermotors 17 mit einem Drucksensor zu erfassen, der ein dem Druck entspre¬ chendes Signal an die Regelelektronik 44 gibt, wie dies mit ei¬ ner gestrichelten, zur Rege-lelektronik 44 führenden Leitung an¬ gedeutet ist. Schließlich ist es auch denkbar, bei geschlossenem Schalter 43 den Elektromagneten 40 in Abhängigkeit vom Druck am Eingang 20 der Lenkeinrichtung 21 zu steuern. Dann müßte dieser Druck mit einem Drucksensor erfaßt werden.The embodiment according to FIG. 2 differs in three respects from that according to FIG. 1. On the one hand, for the throttle valve 32 there is only a single actuating device in the form of the electromagnet 40 in addition to the compression spring 34. Secondly, the compression spring 34 does not act in the closing direction but in the opening direction and the electromagnet 40 does not act in the opening direction but in the closing direction of the throttle valve 32. As a result, a so-called fail-safe function of the throttle valve 32 for the steering elements get direction 21. If the electromagnet 40 fails, the throttle valve 32 is completely open, so that the quantity of pressure medium delivered by the hydraulic pump 10 can flow unhindered to the steering device and this reacts quickly when actuated. The fan motor 17 stops in this case or rotates at a minimum speed. Thirdly, an electric switch 43 is assigned to the power steering valve 25, which then gives a signal to the control electronics 44 when the power steering valve 25 has been moved out of its central position. The control electronics 44 is also supplied with a signal which is a measure of the temperature of the coolant. The control electronics 44 control the electromagnet 40 as a function of this signal and of the position of the electrical switch 43. If the switch 43 is open, ie the steering device 21 is not activated, the higher the coolant temperature, the higher the current flowing through the electromagnet 40. With the switch 43 closed, that is to say with the steering device 21 activated, different control modes are conceivable. A first possibility is that the control electronics 44 always switch off the electromagnet 40 when the electrical switch 43 is closed. That is, when the steering device 21 is activated, the throttle valve 32 opens completely, so that the fan motor 17 stops or rotates at a minimum speed. Another possibility is to control the electromagnet 40 in such a way that the maximum system pressure is established upstream of the fan motor 17. In this case, it would be necessary to detect the pressure upstream of the fan motor 17 with a pressure sensor, which sends a signal corresponding to the pressure to the control electronics 44, as indicated by a dashed line leading to the control electronics 44 is interpreted. Finally, it is also conceivable to control the electromagnet 40 as a function of the pressure at the input 20 of the steering device 21 when the switch 43 is closed. Then this pressure would have to be detected with a pressure sensor.
Das sich in der Bypassleitung 31 befindliche Druckbegrenzungs- ventil 33 der Ausführung nach Figur 3 wird in Öffnungsrichtung von dem Druck stromauf des Lüftermotors 17 und in Schließrich¬ tung von einer Druckfeder 45 beaufschlagt, deren Vorspannung von der Ausdehnung eines Dehnstoffelements 46 abhängt, das der Kühl¬ mitteltemperatur ausgesetzt ist, und die sich in einem Federraum befindet, der über eine Leckölleitung zum Tank 11 entlastet ist, so daß der Druck stromab des Lüftermotors 17 das Ventil 33 nicht beeinflussen kann. Je nach der Ausdehnung des Dehnstoffelements 46 und der davon abhängigen, von der Druckfeder 45 ausgeübten Kraft stellt sich am Eingang 16 des Lüftermotors 17 ein anderer Druck ein, so daß der Lüftermotor 17 in Abhängigkeit von der Ausdehnung des Dehn- stoffelements 46 mit verschiedenen Drehzahlen dreht. Je höher die Temperatur des Kühlmittels ist, desto größer ist das Dehn¬ stoffelement 46, desto stärker ist die Feder 45 vorgespannt, um so größer ist der Druck am Eingang des Lüftermotors 17 und um so höher ist die Drehzahl des Lüftermotors. Die Vorspannung der Druckfeder 45 ist bis zu einem bestimmten Wert möglich, der so¬ mit den maximalen Druckabfall über den Lüftermotor 17 bestimmt.The pressure limiting valve 33 of the embodiment according to FIG. 3 located in the bypass line 31 is acted upon in the opening direction by the pressure upstream of the fan motor 17 and in the closing direction by a compression spring 45, the pretension of which depends on the expansion of an expansion element 46, which cools ¬ exposed to medium temperature, and which is located in a spring chamber, which is relieved via a leak oil line to the tank 11, so that the pressure downstream of the fan motor 17 can not affect the valve 33. Depending on the expansion of the expansion element 46 and the dependent force exerted by the compression spring 45, a different pressure is set at the input 16 of the fan motor 17, so that the fan motor 17 rotates at different speeds depending on the expansion of the expansion element 46 . The higher the temperature of the coolant, the greater the expansion element 46, the stronger the spring 45 is preloaded, the greater the pressure at the inlet of the fan motor 17 and the higher the speed of the fan motor. The prestressing of the compression spring 45 is possible up to a certain value, which thus determines the maximum pressure drop across the fan motor 17.
Es sei nun eine bestimmte Temperatur des Kühlmittels und damit eine bestimmte Größe des Dehnstoffelements 46 angenommen. Die Hydropumpe 10 fördert Druckmittel in die Druckleitung 12, das über den Lüftermotor 17 und die Bypassleitung 31 und über das sich in seiner Mittelstellung befindliche Lenkhilfeventil 25 zum Tank 11 abfließt. Der Druckabfall über den Lüftermotor 17 be¬ trage z.B. 40 bar. Der maximale Systemdruck sei 60 bar. Es werde nun die Lenkeinrichtung 21 aktiviert und von dieser ein Druck von z.B. 10 bar benötigt. Ein daraus folgender Druckanstieg am Eingang 16 des Lüftermotors 17 führt dazu, daß das Druckbegren¬ zungsventil 33 weiter aufmacht und dadurch der Druck am Eingang 16 des Lüftermotors 17 zunächst auf 40 bar begrenzt bleibt. Der Druckabfall über den Lüftermotor 17 hat sich deshalb auf 30 bar verringert und die gegenwärtige Kühlleistung liegt unterhalb der benötigten Kühlleistung. Ist die Lenkeinrichtung 21 nur eine kurze Zeit betätigt, so hat dies keine wesentliche Auswirkung auf die Temperatur des Kühlmittels und auf die Größe des Dehn¬ stoffelements 46. Bei einer längeren Aktivierung der Lenkein- richtung 21 steigt jedoch die Kühlmitteltemperatur an und das Dehnstoffelement 46 wird größer. Letztendlich wird sich am Ein¬ gang des Lüftermotors 17 ein Druck von 40 bar plus 10 bar, also ein Druck von 50 bar einstellen.A certain temperature of the coolant and thus a certain size of the expansion element 46 is now assumed. The hydraulic pump 10 conveys pressure medium into the pressure line 12, which flows to the tank 11 via the fan motor 17 and the bypass line 31 and via the power steering valve 25 located in its central position. The pressure drop across the fan motor 17 is e.g. 40 bar. The maximum system pressure is 60 bar. The steering device 21 is now activated and a pressure of e.g. 10 bar required. A consequent increase in pressure at the inlet 16 of the fan motor 17 causes the pressure limiting valve 33 to open further and the pressure at the inlet 16 of the fan motor 17 initially remains limited to 40 bar. The pressure drop across the fan motor 17 has therefore decreased to 30 bar and the current cooling capacity is below the required cooling capacity. If the steering device 21 is actuated only for a short time, this has no significant effect on the temperature of the coolant and on the size of the expansion element 46. However, when the steering device 21 is activated for a longer time, the coolant temperature rises and the expansion element 46 becomes greater. Ultimately, a pressure of 40 bar plus 10 bar, that is to say a pressure of 50 bar, will occur at the inlet of the fan motor 17.
Es sei nun angenommen, daß die Lenkeinrichtung 21 ein Druckber darf von 30 bar hat. Auch hier verbleibt der Druck am Eingang 16 des Lüftermotors 17 zunächst bei 40 bar. Der Druckabfall über den Lüftermotor 17 beträgt nun nur noch 10 bar. Bei einer länge¬ ren Betätigung der Lenkeinrichtung 21 steigt die Kühlmitteltem¬ peratur an. Das Dehnstoffelement 46 wird größer und spannt die Feder 45 stärker vor. Letztendlich wird sich am Eingang 16 des Lüftermotors 17 der maximale Systemdruck von 60 bar einstellen, so daß der Druckabfall über den Lüftermotor 17 30 bar beträgt und die Kühlleistung zu gering ist, um die Kühlmitteltemperatur auf dem vorherigen Wert innerhalb des erlaubten Temperaturbe- reichs zu halten. Dies wird nach einer Deaktivierung der Lenk¬ einrichtung 21 durch eine verstärkte Kühlung wieder ausgeglichen werden.It is now assumed that the steering device 21 has a Druckbe r may of 30 bar. Here, too, the pressure remains at inlet 16 the fan motor 17 initially at 40 bar. The pressure drop across the fan motor 17 is now only 10 bar. When the steering device 21 is actuated for a longer time, the coolant temperature rises. The expansion element 46 becomes larger and prestresses the spring 45 more. Ultimately, the maximum system pressure of 60 bar will be set at the input 16 of the fan motor 17, so that the pressure drop across the fan motor 17 is 30 bar and the cooling capacity is too low to keep the coolant temperature at the previous value within the permitted temperature range . After deactivation of the steering device 21, this will be compensated for by increased cooling.
Ist der Druckbedarf der Lenkeinrichtung 60 bar, so wird das Druckbegrenzungsventil 33 ganz geöffnet. Der Lüftermotor 17 dreht mit minimaler Drehzahl oder steht still. Auch wenn dieIf the pressure requirement of the steering device is 60 bar, the pressure limiting valve 33 is opened completely. The fan motor 17 rotates at minimum speed or stands still. Even if the
Temperatur des Kühlmittels ansteigt und das Dehnstoffelement 46 größer wird, ändert dies nichts am Zustand des Druckbegrenzungs- ventils 33, da dieses z.B. durch einen Anschlag für das Dehn¬ stoffelement 46 auf einen maximalen Druck von 60 bar am Eingang 16 des Lüftermotors 17 ausgelegt ist.The temperature of the coolant rises and the expansion element 46 becomes larger, this does not change the state of the pressure relief valve 33, since this e.g. is designed for a maximum pressure of 60 bar at the inlet 16 of the fan motor 17 by a stop for the expansion element 46.
Eine Variation der Ausführung nach Figur 3 besteht darin, daß das Ventil 33 in Öffnungsrichtung außer vom Druck stromauf des Lüftermotors 17 von einer weiteren Stelleinrichtung z.B. von ei¬ nem Elektromagneten beaufschlagt wird. Dannn kann bei einer Ak- tivierung der Lenkeinrichtung das Ventil 33 z.B. ganz aufgemacht werden.A variation of the embodiment according to Figure 3 is that the valve 33 in the opening direction apart from the pressure upstream of the fan motor 17 by a further actuating device, e.g. is acted upon by an electromagnet. Then, when the steering device is activated, the valve 33 e.g. be completely opened.
Die Ausführung nach Figur 4 unterscheidet sich von derjenigen nach Figur 3 zum einen darin, daß das Druckbegrenzungsventil 33 in Schließrichtung unmittelbar von einem kraftgeregelten Propor- tional-Elektromagneten 40 beaufschlagbar ist. Je nach der Tempe¬ ratur des Kühlmittels wird der Elektromagnet mit einem anderen Strom beaufschlagt und übt eine verschieden große Kraft auf einen Ventilkörper des Ventils 33 aus. Die Funktionsweise der Anlage nach Figur 4 kann genauso sein wie diejenige der Anlage nach Figur 3. Die Verwendung eines Elektromagneten bietet jedoch auch die Möglichkeit, bei einer Aktivierung der Lenkeinrichtung 21 den Elektromagneten 40 ganz abzuschalten und damit den Druckabfall über den Lüftermotor 17 bei jeder Aktivierung der Lenkeinrichtung 21 unabhängig von deren Druckbedarf auf einen minimalen Wert zu reduzieren. Die jeweilige Zeitdauer, in der die Lenkeinrichtung 21 aktiviert ist, ist nämlich im allgemeinen so kurz und die Gesamtdauer der Aktivierung ausgedrückt als Prozentsatz von der gesamten Betriebzeit des Kraftfahrzeugs ist im allgemeinen so klein, daß die Temperatur des Kühlmittels wäh¬ rend des Lenkens den zulässigen Bereich nicht überschreitet und während der Zeit, in der die Lenkeinrichtung 21 nicht aktiviert ist, wieder reduziert werden kann. Zum anderen ist der Ventil¬ körper des Druckbegrenzungsventils 33 der Anlage nach Figur 4 in Öffnungsrichtung außer vom Druck stromauf des Lüftermotors 17 von einer schwachen Druckfeder 47 beaufschlagt, die bei abge¬ schaltetem oder ausgefallenen Elektromagnet 40 für eine defi¬ nierte Ruhestellung des Druckbegrenzungsventils 33 sorgt. In dieser Stellung ist das Ventil 33 offen. Auch bei der Ausführung nach Figur 4 ist die eine Seite des Druckbegrenzungsventils 33 durch eine Leckölleitung mit dem Tank 11 verbunden.The embodiment according to FIG. 4 differs from that according to FIG. 3 on the one hand in that the pressure limiting valve 33 can be acted upon directly by a force-controlled proportional electromagnet 40 in the closing direction. Depending on the temperature of the coolant, a different current is applied to the electromagnet and exerts a force of different magnitude on a valve body of the valve 33. The mode of operation of the system according to FIG. 4 can be the same as that of the system according to FIG. 3. However, the use of an electromagnet also offers the possibility of completely switching off the electromagnet 40 when the steering device 21 is activated and thus reducing the pressure drop across the fan motor 17 to a minimum value each time the steering device 21 is activated, regardless of its pressure requirement. The respective time period in which the steering device 21 is activated is generally so short and the total duration of the activation, expressed as a percentage of the total operating time of the motor vehicle, is generally so short that the temperature of the coolant during the steering is the permissible one Range does not exceed and can be reduced again during the time in which the steering device 21 is not activated. On the other hand, the valve body of the pressure relief valve 33 of the system according to FIG. 4 is acted upon in the opening direction apart from the pressure upstream of the fan motor 17 by a weak compression spring 47 which, when the electromagnet 40 is switched off or has failed, ensures a defined rest position of the pressure relief valve 33 . In this position the valve 33 is open. In the embodiment according to FIG. 4, too, one side of the pressure relief valve 33 is connected to the tank 11 by a leak oil line.
Man erkennt, daß durch die Erfindung eine Hydraulikanlage für ein Kraftfahrzeug geschaffen worden ist, die kostengünstig ist und in der eine hydraulische Lenkeinxichtung und ein Hydromotor zum Antrieb eines Lüfterrads derart miteinander kombiniert sind, daß der Lenkungsteil seine Funktion in der üblichen Weise er¬ füllt und auch die Kühlleistung den gestellten Forderungen ge¬ nügt. It can be seen that the invention has created a hydraulic system for a motor vehicle which is inexpensive and in which a hydraulic steering device and a hydraulic motor for driving a fan wheel are combined with one another in such a way that the steering part fulfills its function in the usual manner and the cooling capacity also meets the requirements.

Claims

Patentansprüche claims
1. Hydraulikanlage für ein Kraftfahrzeug mit einer Hydro¬ pumpe (10), mit einer hydraulischen Lenkeinrichtung (21), die einen Lenkmotor (26) und ein aus einer Mittelstellung heraus in entgegengesetzte Richtungen verstellbares Lenkventil (25) um¬ faßt, mit dem die Druckmittelwege zum und vom Lenkmotor (26) steuerbar sind, mit einem Lüftermotor (17), der von einer By¬ passleitung (31) umgangen und in Serie zur Lenkeinrichtung (21) zwischen dieser und der Hydropumpe (10) angeordnet ist und mit einem Bypassventil (32, 33), mit dem die Aufteilung des Fluid- flusses durch den Lüftermotor (17) und durch die Bypassleitung (31) in Abhängigkeit vom Kühlleistungsbedarf veränderbar ist, dadurch gekennzeichnet, daß während einer Betätigung des Lenk¬ ventils (25) das Bypassventil (32, 33) im Sinne einer Vergröße- rung des Durchflusses von Druckmittel durch die Bypassleitung (31) verstellbar ist.1. Hydraulic system for a motor vehicle with a hydraulic pump (10), with a hydraulic steering device (21), which comprises a steering motor (26) and a steering valve (25) adjustable from a central position in opposite directions, with which the Pressure medium paths to and from the steering motor (26) can be controlled, with a fan motor (17) which is bypassed by a bypass line (31) and is arranged in series with the steering device (21) between the latter and the hydraulic pump (10) and with a bypass valve (32, 33), with which the distribution of the fluid flow through the fan motor (17) and through the bypass line (31) can be changed as a function of the cooling power requirement, characterized in that the bypass valve is actuated when the steering valve (25) is actuated (32, 33) in the sense of increasing the flow of pressure medium through the bypass line (31) is adjustable.
2. Hydraulikanlage nach Anspruch 1, dadurch gekennzeichne , daß die hydraulische Lenkeinrichtung (21) eine Hilfskraftlenk¬ einrichtung ist.2. Hydraulic system according to claim 1, characterized in that the hydraulic steering device (21) is an auxiliary power steering device.
3. Hydraulikanlage nach Anspruch 2, dadurch gekennzeichnet, daß die Hydropumpe (10) eine auf den Druck- und Fördermengenbe¬ darf der Hilfskraftlenkeinrichtung (21) abgestimmte Lenk¬ hilfspumpe ist.3. Hydraulic system according to claim 2, characterized in that the hydraulic pump (10) is a to the pressure and Fördermengebe¬ the auxiliary power steering device (21) coordinated Lenk¬ auxiliary pump.
4. Hydraulikanlage nach Anspruch 1, 2 oder 3, dadurch ge- kennzeichnet, daß in der Mittelstellung des Lenkventils (25) der4. Hydraulic system according to claim 1, 2 or 3, characterized in that in the central position of the steering valve (25)
Ausgang des Lüftermotors (17) über das Lenkventil (25) mit einem Druckmittelvorratsbehälter (11) verbunden ist.Output of the fan motor (17) via the steering valve (25) is connected to a pressure medium reservoir (11).
5. Hydraulikanlage nach Anspruch 1, 2, 3 oder 4, dadurch gekennzeichnet, daß das Bypassventil (32, 33) während einer Be- tätigung des Lenkventils (25) in Abhängigkeit vom sich am Lenk¬ motor (26) aufbauenden Druck verstellbar ist. 5. Hydraulic system according to claim 1, 2, 3 or 4, characterized in that the bypass valve (32, 33) is adjustable during an actuation of the steering valve (25) depending on the pressure building up on the steering motor (26).
6. Hydraulikanlage nach Anspruch 5, dadurch gekennzeichnet, daß das Bypassventil (32, 33) während einer Betätigung des Lenk¬ ventils (25) in Abhängigkeit von seiner Voreinstellung und in Abhängigkeit von dem sich am Lenkmotor (26) aufbauenden Druck verstellbar ist.6. Hydraulic system according to claim 5, characterized in that the bypass valve (32, 33) is adjustable during an actuation of the Lenk¬ valve (25) depending on its preset and depending on the pressure build-up on the steering motor (26).
7. Hydraulikanlage nach Anspruch 1, 2, 3 oder 4, dadurch gekennzeichnet, daß das Bypassventil (32, 33) während einer Be¬ tätigung des Lenkventils (25) unabhängig von dem sich am Lenkmo¬ tor (26) aufbauenden Druck in eine bestimmte Stellung verstell- bar ist.7. Hydraulic system according to claim 1, 2, 3 or 4, characterized in that the bypass valve (32, 33) during a Be¬ actuation of the steering valve (25) regardless of the build-up on the Lenkmo¬ gate (26) pressure in a certain Position is adjustable.
8. Hydraulikanlage nach einem der Ansprüche 5 bis 7, da¬ durch gekennzeichnet, daß das Bypassventil (32, 33) während ei¬ ner Betätigung des Lenkventils (25) in eine Endstellung ver¬ stellbar ist, in der der Öffnungsquerschnitt der Bypassleitung (31) maximal ist.8. Hydraulic system according to one of claims 5 to 7, da¬ characterized in that the bypass valve (32, 33) during ei¬ ner actuation of the steering valve (25) is adjustable in an end position in which the opening cross section of the bypass line (31 ) is maximum.
9. Hydraulikanlage nach einem vorhergehenden Anspruch, da¬ durch gekennzeichnet, daß das Bypassventil (32, 33) von einer Stelleinrichtung (40) in Abhängigkeit vom Kühlleistungsbedarf verstellbar ist und daß diese Stelleinrichtung (40) auch während einer Betätigung des Lenkventils (25) ansteuerbar ist.9. Hydraulic system according to one of the preceding claims, characterized by the fact that the bypass valve (32, 33) can be adjusted by an actuating device (40) as a function of the cooling power requirement, and that this actuating device (40) can also be actuated during actuation of the steering valve (25) is.
10. Hydraulikanlage nach Anspruch 9, dadurch gekennzeichnet, daß die Stelleinrichtung ein Elektromagnet (40) ist.10. Hydraulic system according to claim 9, characterized in that the actuating device is an electromagnet (40).
11. Hydraulikanlage nach einem der Ansprüche 1 bis 8, da¬ durch gekennzeichnet, daß das Bypassventil (32) von einer ersten Stelleinrichtung (40) in Abhängigkeit vom Kühlleistungbedarf und von einer zweiten Stelleinrichtung (41) während einer Betätigung des Lenkventils (25) verstellbar ist.11. Hydraulic system according to one of claims 1 to 8, da¬ characterized in that the bypass valve (32) of a first actuating device (40) in dependence on the cooling power requirement and of a second actuating device (41) adjustable during actuation of the steering valve (25) is.
12. Hydraulikanlage nach Anspruch 11, dadurch gekennzeich¬ net, daß die zweite Stelleinrichtung eine hydraulische Stellein- richtung (41) ist, die mit dem Druck am Ausgang des Lüftermotors (17) beaufschlagt ist. 12. Hydraulic system according to claim 11, characterized gekennzeich¬ net that the second actuating device is a hydraulic actuating device (41) which is acted upon by the pressure at the outlet of the fan motor (17).
13. Hydraulikanlage nach einem vorhergehenden Anspruch, da¬ durch gekennzeichnet, daß das Bypassventil (32, 33) zwei Ar¬ beitsanschlüsse besitzt und in der Bypassleitung (31) angeordnet ist.13. Hydraulic system according to one of the preceding claims, characterized in that the bypass valve (32, 33) has two working connections and is arranged in the bypass line (31).
14. Hydraulikanlage nach Anspruch 13, dadurch gekennzeich¬ net, daß das Bypassventil ein stetig verstellbares Stromventil (32) ist.14. Hydraulic system according to claim 13, characterized gekennzeich¬ net that the bypass valve is a continuously adjustable flow valve (32).
15. Hydraulikanlage nach Anspruch 13, dadurch gekennzeich¬ net, daß das Bypassventil ein stetig verstellbares Druckbegren- zungsventil (33) ist, das in Öffnungsrichtung von einer vom15. Hydraulic system according to claim 13, characterized gekennzeich¬ net that the bypass valve is a continuously adjustable pressure relief valve (33) which in the opening direction of one of the
Druck stromauf des Lüftermotors (17) abgeleiteten Kraft und in Schließrichtung von einer von einer Stelleinrichtung (40, 46) bestimmten, vom Kühlleistungsbedarf abhängigen Kraft beauf¬ schlagbar ist.Pressure upstream of the fan motor (17) and in the closing direction can be acted upon by a force determined by an actuating device (40, 46) and dependent on the cooling power requirement.
16. Hydraulikanlage nach Anspruch 15, dadurch gekennzeich¬ net, daß die Stelleinrichtung ein Dehnstoffelement (46) ist. 16. Hydraulic system according to claim 15, characterized gekennzeich¬ net that the adjusting device is an expansion element (46).
EP95904468A 1994-12-14 1994-12-14 Hydraulic system for a motor vehicle Withdrawn EP0797727A1 (en)

Applications Claiming Priority (1)

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PCT/EP1994/004144 WO1996018809A1 (en) 1993-12-01 1994-12-14 Hydraulic system for a motor vehicle

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EP0797727A1 true EP0797727A1 (en) 1997-10-01

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JP (1) JPH10510231A (en)

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US5975233A (en) 1999-11-02

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