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)
• Transportation (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Power Steering Mechanism (AREA)

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• 1994
  • 1994-12-14 JP JP8518095A patent/JPH10510231A/ja active Pending
  • 1994-12-14 EP EP95904468A patent/EP0797727A1/de not_active Withdrawn
  • 1994-12-14 US US08/860,848 patent/US5975233A/en not_active Expired - Fee Related

Non-Patent Citations (1)

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