EP2014919B2 - Adjustment valve for adjusting the supply volume of a pressure pump - Google Patents

Description

The invention relates to an adjustment valve for adjusting the delivery volume of a positive displacement pump and a displacement pump with the adjustment valve which is arranged for adjusting the delivery volume of a fluid to be delivered by the pump in a fluid circuit of the pump. The invention accordingly also relates to the adjusting valve as such, insofar as it is provided for adjusting the delivery volume of a positive displacement pump.

The publication US 5 876 185 A , which is considered to be the closest prior art, discloses a variable valve with a valve piston which is moved against the force of a valve spring when the valve control pressure increases. An adjustable pump can be controlled with this valve.

Positive displacement pumps deliver fluids with a volume flow proportional to the pump speed. The delivery volume per revolution or reciprocating stroke, the so-called specific volume flow, is constant or can be regarded as constant in practice, at least to a good approximation. The constancy per revolution or stroke and, accordingly, the proportionality to the pump speed is disruptive, for example, in applications in which the unit to be supplied by the respective pump has a fluid requirement that is lower in one or more speed range (s) of the pump than that resulting from the Volume flow resulting in proportionality. In the respective speed range, the pump accordingly conveys a volume flow that is higher than required and that is derived with loss. The problem is in the US 6,126,420 B described, which already discloses an internal gear pump with adjustable delivery volume to solve the problem.

The US 6 244 839 B1 also discloses an internal gear pump with adjustable delivery volume. For the adjustment, the inner gear is axially displaceable relative to the outer gear. The inner gear is part of an axially displaceable adjustment unit, which is formed as a piston acting on both sides. The adjustment unit is acted upon by a 4/3 adjustment valve with the fluid conveyed by the pump. The adjusting valve has a valve housing and a valve piston which can be moved axially back and forth in the valve housing and is acted upon at one axial end with the fluid conveyed and at the other axial end with a force of a valve spring counteracting the pressure of the fluid. The position of the valve piston is adjusted according to the balance of the force of the valve spring and the force generated by the fluid pressure. The adjustment valve is designed in such a way that the adjustment unit of the pump moves from an axial position for maximum delivery volume towards an axial position for minimum delivery volume when a fluid pressure predetermined by the valve spring is reached. The preload force of the valve spring is set in advance on the adjusting valve.

From the WO 03/058071 A1 a positive displacement pump with a variable valve is known, the movable valve piston of which acts to counteract the spring pressure of the pump and the fluid in an axial direction to adjust the delivery volume of the pump in an axial direction with a spring force. In order to be able to lower the fluid pressure when the pump is shut down, a control device is provided for the adjusting valve, which exerts an additional force on the valve piston. Examples of control devices include an electric stepper motor for adjusting the biasing force of the valve spring and a solenoid for generating an additional magnetic force. The fluid flow switched by means of the adjustment valve acts on a displacement unit of the pump only in the direction of the maximum delivery volume, while the pressure on the high pressure side always acts in the opposite direction.

From the DE 103 24 092 A1 5, a controllable lubricating oil pump with a flow regulator is known. The flow rate controller comprises a valve with a control piston that is axially movable. The control piston works against the force of a spring, which is supported on the side facing away from the control piston on a device which allows the spring travel of the control piston to be extended or the spring force to be adjusted. The EP 1 555 436 A2 describes a gear pump with flow control with a valve, the passage opening can be changed by a control unit. The valve is a pulse-width-modulated solenoid valve which is operatively connected to a control unit coupled to it for the purpose of regulating the delivery rate via a pressure converter connected to the first pressure chamber of the pump. From the DE 102005 029 086 A1 an oil pump for an internal combustion engine with a variable valve is known. The valve is an electrically controllable valve and comprises a valve body which is axially movable in the valve and has sections of different diameters, the displacement of which opens or closes elongated control openings in the valve. The DE 31 09 045 A1 describes a controllable hydraulic pump with a control valve. The valve is a 3/2-way valve, the switching of which is effected by the action of fluid pressure on the end face of a slide piston movably mounted in the valve. The JP 57 131890 A describes a controllable feed pump with an adjustable pressure valve. Other relevant pumps are also in the US 7 726948 B2 . US 6 244 839 B1 and FR 2 326 600 A known.

It is an object of the invention to adapt the delivery volume of a positive displacement pump flexibly and precisely to the needs of a unit to be supplied and to always ensure an adequate supply of the unit.

The invention is based on a positive displacement pump for supplying an aggregate with fluid, which has a pump housing with a delivery chamber and a delivery member movable in the delivery chamber, which acts directly on the fluid to deliver it through the delivery chamber. When a conveying movement is carried out, the conveying member can convey the fluid alone or in cooperation with one or possibly also a plurality of further conveying members from an inlet of the conveying chamber while increasing the pressure through an outlet of the conveying chamber. The inlet is assigned to a low pressure side and the outlet is assigned to a high pressure side of the pump. The pump is preferably arranged in a closed fluid circuit, but can in principle also be used to convey the fluid in an open fluid circuit. When integrated in a closed fluid circuit, it sucks the fluid on the low-pressure side from a reservoir through the inlet into the delivery chamber and conveys it on the high-pressure side to one or more units (s) to be supplied with the fluid. Downstream of the aggregate (s), the fluid returns to the reservoir, which closes the fluid circuit. The pump can, for example, be used to supply a hydraulic press with pressurized fluid. In preferred embodiments, it is installed in a motor vehicle or is intended for installation in order to supply an internal combustion engine driving the motor vehicle with lubricating fluid or an automatic transmission with hydraulic fluid. The internal combustion engine preferably drives the pump.

The positive displacement pump further comprises an adjusting valve, by means of which the delivery volume of the pump can be adjusted to the needs of the at least one unit to be supplied and the energy required to drive the pump can preferably be reduced accordingly. The adjustment valve comprises a valve housing, a valve piston movable in the valve housing, a valve spring and an adjustment device. The valve piston has an active surface for a fluidic valve control pressure. The valve spring is arranged in such a way that it counteracts the valve actuating pressure acting overall on the valve body on the valve piston.

In preferred embodiments, the delivery volume is understood to mean the specific volume flow of the pump as such, in the case of a rotary pump the volume flow per revolution and in the case of a reciprocating piston pump the volume flow per stroke. Although less preferred, the pump can also be a constant pump and the adjustment valve can be arranged on the high-pressure side of the pump as a bypass valve in order to convey excess fluid into the reservoir bypassing the at least one unit. Such bypass conveyance does not reduce the energy consumption of the pump, but it still ensures that it is conveyed as required. In such designs, it is not the delivery volume at the outlet of the delivery chamber, but the delivery volume delivered to the at least one unit that is controlled or regulated as required. It is also possible to combine a pump adjustable in its delivery volume with such a bypass valve, in that the volume flow per revolution or stroke is adjusted via an adjusting valve according to the invention or in some other way and downstream of the pump, but upstream of the unit to be supplied, part of the the pumped volume flow is branched off and returned unused to a reservoir. In preferred embodiments, the delivery volume of the pump as such, viewed directly at the outlet of the delivery chamber, is adjusted by means of the adjustment valve. In such designs, an actuator is movably arranged in the pump housing, which can be acted upon in the direction of its movability with an actuating force which is dependent on the requirement of the at least one unit. The actuator can in particular be arranged on an end face of the conveying member or surrounding the conveying member. In a first variant, the actuator and the conveying element are part of an adjusting unit that can be moved back and forth in the pump housing as a whole, for example a linearly movable or pivotable or otherwise adjustable adjusting unit that is movable transversely to an axis of rotation of the preferably rotatable conveying element. Examples of such adjustment units describe, for example, the US 6 28.3 735 B1 for off-axis who US 6,126,420 B. and US 6 244 8.39 B1 for internal-axis pumps In the second variant, the actuator can be adjusted relative to the delivery element and the pump housing. The actuator of the second variant can in particular be an adjusting ring surrounding the delivery element, as is known from vane pumps including vane pumps, Pcndelschieberpumpen and also from internal gear pumps to adjust the eccentricity to the delivery member, for example by a linear stroke or a pivoting movement of the actuator.

The actuating force is preferably generated fluidically by the actuator forming an actuating piston which is acted upon by a pressure fluid. This pressure fluid can be branched off, in particular, on the high-pressure side of the pump and can be returned to the actuator as a partial flow of the volume flow conveyed by the pump as a whole via the adjustment valve. In principle, however, the pressure fluid with which the actuator is acted on can also be another fluid, for example a fluid that is provided from a pressure reservoir or from another pump.

In yet another variant, a partial flow of the fluid is fed via the adjustment valve into the delivery chamber back to the low-pressure side in order to increase the degree of filling of delivery cells there, as is the case, for example, in US 6 9.35 851 B2 Through the return and filling of the delivery cells, the delivery volume is also adjusted at the same time, this type of adjustment being able to be implemented in combination with one of the other types already mentioned.

According to the invention, the adjusting device is formed in such a way that it can adjust the valve piston in the direction of the force exerted by the valve actuating pressure on the valve body or against the valve actuating pressure. It preferably acts electromagnetically The word "or" here as well as attack includes the meaning of "either ......... or" and also the meaning of "and" as far as is clear from the respective context does not necessarily encompass a restricted meaning. The adjusting device can accordingly be constructed in such a way that it only counteracts the force of the valve control pressure or preferably only in the same direction and counteracts the valve spring, and alternatively it can also be constructed in such a way that it counteracts the valve piston both in and against the force of the valve control pressure can adjust.

In a preferred first embodiment, the valve actuating pressure and a force exerted by the adjusting device on the valve piston act together against the force of the valve spring. If the valve actuating pressure increases, the valve piston can be adjusted against the force of the valve spring by means of a correspondingly smaller force of the adjusting device.

In a second preferred embodiment, the adjusting device is set up for adjusting the valve piston both in the direction of the valve actuating pressure and against the valve actuating pressure. If the adjusting device is a magnetic adjusting device with only a single magnetic coil, the magnetic coil can be reversed in such embodiments. Alternatively, a separate solenoid coil with one armature each can be provided for each of two directions of movement of the valve piston, and one of these armatures exerts a force on the valve piston in one direction and the other armature exerts a force in the other direction on the movement of the valve piston to move the valve piston back and forth.

The position of the valve piston can thus be adjusted relative to the valve housing, at least in the second embodiment, but preferably also in the first embodiment, independently of the valve actuating pressure acting on the active surfaces, and the delivery volume of the pump can be adjusted accordingly. The adjusting valve can thus adjust the delivery volume over a larger operating range of the unit to be supplied, continuously or in any step, and not only to a certain pressure, when the delivery volume is regulated.

According to the invention, a control or regulating device for the adjusting valve is set up in such a way that the delivery volume can be adjusted over the entire operating range of the unit by means of the adjusting valve. On the other hand, the valve spring and the valve actuating pressure, which constantly counteracts the force of the valve spring, ensure a reliable supply to the unit, even if the adjusting device fails only as known from conventional positive displacement pumps with a reduction of the delivery volume depending on the preload force and spring constants of the valve spring. The invention combines an exact and flexible adaptability to the demand with a security of supply guaranteed even in the event of a failure of the adjusting device, it creates a so-called second-level control or regulation for the delivery volume.

The adjustment valve is preferably a proportional valve. It is preferably controlled electrically. The adjusting device preferably acts magnetically. It can have a proportional magnetic coil that is voltage or current controlled or regulated, that is to say by a variation of the applied voltage or of the electrical current that is oriented towards the requirement of the at least one unit. In other preferred embodiments, the variable valve is controlled or regulated in a pulse-modulated manner. When using a pulse-modulated variable valve, the duration of the individual pulses or the time interval between two successive pulses of the manipulated variable can be varied, which also includes the case that both the pulse duration and the Time between successive pulses is varied according to the need. The period of the manipulated variable is preferably constant. A pulse width modulated adjustment valve is preferably used. The period of the manipulated variable for the variable valve is significantly smaller than the time constant of the displacement pump that determines the displacement of the delivery volume. The pulse modulation uses the low-pass character of the pump. By varying the switch-on time of the pulse width modulation or the time interval in the case of pulse frequency modulation to suit the demand, the flow through the adjustment valve and consequently the delivery volume of the displacement pump can be controlled or regulated quasi continuously according to the current demand of the unit.

The adjusting valve is preferably a multi-way valve with at least three connections, preferably with four connections. It is preferably switchable between at least two switching positions, preferably between three switching positions.

In preferred embodiments, the adjustment valve is controlled or regulated as a function of a setpoint for the volume flow to be delivered by the displacement pump or a fluid supply pressure to be generated by the displacement pump. A setpoint specification specifies the setpoint of a control or regulating device provided for the adjusting valve. The setpoint is preferably varied depending on the needs of the unit. A characteristic diagram is preferably specified for the setpoints which are dependent on the operating state of the unit. The at least one setpoint or, more preferably, the plurality of setpoints is or are predefined as a function of a physical variable which is characteristic of the operating state and which is during operation of the unit is sensed by means of a detection device. The at least one physical variable can in particular be a temperature, a speed or a load state of the unit. The setpoint or the setpoints for the volume flow or the fluid supply pressure are preferably predetermined as a function of at least two variables which characterize the operating state of the unit. If the displacement pump is used as a lubricating oil pump for an internal combustion engine, the temperature of the lubricating oil or the coolant in the area of the internal combustion engine or the speed or, for the load condition, the accelerator pedal or throttle valve position can be sensed and the associated setpoint can be determined and determined based on the map the control or regulating device for the variable valve can be specified.

In a preferred first embodiment, the adjustment valve is only controlled as a function of the respective setpoint. The acquisition of an actual value representative of the requirement of the physical quantity forming the target value, namely the volume flow or the fluid supply pressure, is dispensed with, as is complex processing for regulation on the basis of a target / actual comparison.

In a likewise preferred second embodiment, the adjusting valve is regulated as a function of a target / actual comparison of the respective target value and an actual value of the volume flow or the fluid supply pressure measured continuously or at sufficiently small time intervals. Regulation is advantageous in cases where the volume flow requirement of the unit changes due to wear over the course of the unit's service life.

In an optional combination of the two embodiments, a control device is provided which can switch from a controller according to the first embodiment to a regulation according to the second embodiment. It is preferred if the adjusting valve is initially controlled on the basis of the predetermined volume flow and, if the leakage losses increase as a result of wear on the unit, the pressure control is changed over later. In yet another embodiment, a conductive control device is provided which determines increasing wear on the basis of a sensory detection of the volume flow or fluid supply pressure and adjusts the setpoint or the setpoint map at least once or in several stages, possibly continuously during the service life of the unit.

In another preferred embodiment, the adjustment valve is controlled on the one hand on the basis of a setpoint or a setpoint map for the fluid supply pressure or the volume flow and is additionally flow-controlled. A particularly preferred embodiment is one on the basis of a setpoint or several setpoints or a setpoint map for the fluid supply pressure or the volume flow controlled by pulse width modulation and additionally flow-controlled adjustment valve. The current control advantageously compensates for changes in the electrical resistance of a magnet adjustment device that are associated with temperature changes. The current consumption of the magnet adjustment device is recorded and the changes in the size of the electrical current due to changes in resistance are compensated for by regulating the pulse duty factor according to the variation in the current consumption. Correspondingly, however, not only for the preferred embodiment as a pulse-width-modulated adjusting valve, but also with differently controlled adjusting valves. A flow control in addition to the control based on a setpoint or setpoint map for the volume flow or the fluid supply pressure means that a volume flow or pressure control can be dispensed with, although in the case of a flow control an additional volume flow or pressure control can also be used.

The control or regulating device can be an integral part of the adjustment valve or installed separately from it. The setpoint specification can be realized as a part of the control or regulating device or separately from the other parts of the control or regulating device. The adjustment valve is preferably an integral part of the positive displacement pump, for example mounted on the pump housing. In the integrated version, the adjustment valve can advantageously also be arranged in the housing of the positive displacement pump, for example in a receiving bore or a differently shaped receiving space in a wall of the pump housing. In such designs, the connections of the adjusting valve can be shaped as bores or other-shaped channels in the housing, in particular in said housing wall, in a space- and weight-saving manner. The pump housing can accordingly also simultaneously form the valve housing or only part of the valve housing.

In the embodiments in which the delivery volume is adjusted directly to the pump, it is advantageous if the actuator is formed as a double-acting adjusting piston with two axially facing, preferably facing opposite piston surfaces and by means of the adjusting valve either one or the other piston surface with one pressurized pressurized fluid can be applied, possibly also both piston surfaces simultaneously.

If the actuator forms an actuating piston that can be pressurized with pressure fluid, for example a piston that can only be pressurized with pressure fluid on one side or preferably a double-acting piston, in a preferred embodiment a pump spring acts on it with a spring force, the pump spring acting in the direction of an increase in the delivery volume of the Pump works. If the actuator forms a double-acting piston, it is preferred if the pump spring is so weak that the adjustment dynamics of the pump are not significantly influenced by the pump spring, but exclusively or at least to a large extent by the adjustment valve. In principle, a pump spring of this type can also be dispensed with. On the other hand, the use of a weak pump spring is advantageous, such a pump spring being designed in such a way that it only ensures that the maximum delivery volume for this pump speed is delivered when the displacement pump is running at low speed. A pump spring is sufficient, which exerts a spring force on the actuator corresponding to a fluid pressure of at most 1 bar.

Preferably, the fluid, which is guided or regulated to the displacement pump by means of the adjustment valve, or in the case of an adjustment valve used only as a bypass valve, the fluid branched off to a reservoir generates the valve control pressure when it flows through the adjustment valve. In such designs, no separate connection is required to generate the valve control pressure. The same inlet through which the fluid flow flowing through the adjustment valve reaches the adjustment valve also forms the connection for the fluid generating the valve actuating pressure.

It is preferred if the valve control pressure is generated by means of a plurality of active surfaces, preferably by means of exactly two active surfaces, which differ in size, so that the valve control pressure on the valve piston exerts a differential force corresponding to the area difference of the active surfaces. The characteristic of the differential force is particularly preferably combined with the further characteristic, according to which the fluid also generates the valve actuating pressure when it flows through the adjusting valve.

In one development, the biasing force of the valve spring can be adjusted, preferably fluidly, while the displacement pump conveys the fluid. The adjusting valve can thus have a further piston, which is preferably only used to adjust the pretensioning force and is preferably acted upon by the fluid, which also generates the valve actuating pressure. wherein a separate connection is provided for the piston for adjusting the prestressing force, or preferably a force acting on this adjusting piston can also be generated by the fluid flowing through.

Advantageous features are also described in the subclaims and their combinations.

Figur 1

eine Verdrängerpumpe in einem Querschnitt,

Figur 2

die Verdrängerpumpe in einem Längsschnitt,

Figur 3

die Verdrängerpumpe mit einem Verstellventil für die Verstellung des Fördervolumens der Pumpe,

Figur 4

das Verstellventil einzeln als Schaltzeichen und

Figur 5

das Verstellventils in einem Längsschnitt.

An exemplary embodiment of the invention is explained below with reference to figures. Features that become apparent from the exemplary embodiment, each individually and in each combination of features, advantageously form the subject matter of the claims and also the embodiments described above. Show it:

Figure 1

a positive displacement pump in a cross section,

Figure 2

the positive displacement pump in a longitudinal section,

Figure 3

the positive displacement pump with an adjustment valve for adjusting the delivery volume of the pump,

Figure 4

the variable valve individually as a circuit symbol and

Figure 5

the adjustment valve in a longitudinal section.

Figure 1 shows a positive displacement pump in a cross section, in a pump housing 1, a delivery chamber is formed with an inlet 2 on a low pressure side and an outlet 3 on a high pressure side. A first conveying member 4 and a second conveying member 5 are movably arranged in the conveying chamber. The conveying members 4 and 5 are in a conveying engagement with one another. If the conveying members 4 and 5 are driven, they carry out a conveying movement in the conveying engagement, through which a fluid, for example lubricating oil or a hydraulic fluid, is drawn into the conveying chamber through the inlet 2 and carried out at a higher pressure the outlet 3 is displaced. The conveying member 4 is driven and drives the conveying member 5 in the conveying engagement.

The positive displacement pump of the exemplary embodiment is an external gear pump. Accordingly, the conveying members 4 and 5 are externally toothed conveying rotors and the conveying engagement is a tooth engagement. The conveyor members 4 and 5 are rotatably mounted about an axis of rotation R ₄ and R ₅ . In the case of a rotary drive, the sucked-in fluid is transported from the inlet 2 into the conveying cells formed by the tooth gaps in each of the conveying members 4 and 5 through the region of the so-called wrap 1a and expelled through the outlet 3.

In order to be able to adapt the delivery volume of the pump to the requirement of an assembly to be supplied with the fluid, the axial length of the delivery engagement of the delivery members 4 and 5, the engagement length, measured along the axes of rotation R ₄ and R _{5 is} adjustable. For the adjustment, the conveying member 5 can be moved axially relative to the conveying member 4 and the pump housing 1 between a position of maximum engagement length and correspondingly maximum delivery volume and a position of minimum engagement length and accordingly minimum delivery volume.

Figure 2 shows the positive displacement pump in a longitudinal section. The conveyor member 4 is secured against rotation on a drive shaft which protrudes from the pump housing 1 and carries a drive wheel for driving the pump. The conveying member 5 is part of an adjusting unit which, in addition to the conveying member 5, comprises an actuator with two actuating pistons 6 and 7. This adjusting unit 5-7 can be moved axially back and forth as a whole in the pump housing 1 in order to be able to adjust the engagement length. The conveying member 5 is arranged axially between the actuating pistons 6 and 7. The actuator 6, 7 supports the conveying member 5 so as to be rotatable about the axis of rotation R ₅ . The adjustment unit 5-7 is in a cylindrical Cavity of the pump housing 1 added. The cavity forms an axial track for the movements of the adjustment unit, 5-7. Furthermore, it forms a pressure chamber 8 on one axial side of the adjusting unit 5-7 and a further pressure chamber 9 on the other side. The actuating pistons 6 and 7 fluidically separate the two pressure chambers 8 and 9 from one another and also from the delivery chamber, apart from unavoidable leakage losses. The pressure chambers 8 and 9 can each be printed with a pressurized fluid, in the exemplary embodiment with the fluid delivered by the displacement pump. A pump spring 10 is arranged in the pressure chamber 9, the spring force of which acts on the adjusting unit 5-7, namely on the actuating piston 7, in the direction of the maximum engagement length.

Figure 3 shows the positive displacement pump integrated in a closed fluid circuit, for example a lubricating oil of a motor vehicle, the fluid circuit contains a reservoir 11 from which the pump sucks the fluid on the low pressure side through the inlet 2 and with a higher pressure on the high pressure side through the outlet 3, a connected one Supports supply line 12 and via a cooling and cleaning device 13 with a cooler and a filter to the unit 14 to be supplied with the fluid, for example a bee engine for driving a motor vehicle. Downstream of the unit 14, the fluid is fed back into the reservoir 11 through a line 15.

Downstream from the cooling and cleaning device 13, in particular downstream from the cleaning part of the cooling and cleaning device 1.3, but still upstream from the unit 14, a partial flow 16 of the fluid is branched off and returned to the pump via an adjustment valve 20. The adjustment valve 20 has an inlet for the partial flow 16, an outlet short-circuited with the reservoir 11 and two further connections, one of which is connected to the pressure chamber 8 via a line 18 and the other is connected to the pressure chamber 9 via a line 19. The adjusting valve 20 is a multi-way switching valve. In a first switching position, it leads the partial flow 16 into the pressure chamber 8 and connects the pressure chamber 9 to the reservoir II, thus switching the pressure chamber 9 to ambient pressure. In a second switch position, which the adjustment valve in Figure 3 occupies, it reverses these conditions by leading the partial flow 16 into the pressure chamber 9 and short-circuiting the pressure chamber 8 with the reservoir 11. The adjustment valve 20 of the exemplary embodiment can assume three switch positions, namely the two switch positions mentioned and also a middle position in which it separates the pressure chambers 8 and 9 from one another and also from the reservoir 11 and the partial flow 16, so that the respective pressure in the pressure chambers 8 and 9 is retained, one ignores leaks and the associated leakage losses. In the exemplary embodiment, a 4/3-way valve was selected for the adjusting valve 20.

Figure 4 shows the adjustment valve 20 as in Figure 3 as a circuit symbol, only in an enlarged cooking position. The four connections of the adjustment valve 20 are entered, of which the inlet for the recirculated partial flow 16 is identified by I, the outlet to the reservoir 11 by O, the connection for the pressure chamber 8 by A and the connection for the pressure chamber 9 by B.

The adjustment valve 20 is a proportional valve with a constantly acting fluidic valve actuating pressure P20, namely the pressure of the fluid returned in the partial flow 16, and a valve spring 25 which is arranged to counteract the valve actuating pressure P ₂₀ . However, the fluidic valve actuating pressure P ₂₀ and the force of the valve spring 25 alone do not determine the switching position when the adjusting valve 20 is functioning properly. The adjusting valve 20 comprises, as a proportional valve, an adjusting device which reverses the adjusting valve 20 from one of the switching positions into another, adapted to the fluid requirement of the unit 14. The valve actuating pressure P ₂₀ and the valve spring 25 give the adjusting valve 20 a fail-safe property in the event of failure of the proportional adjusting device.

The adjustment device is a magnetic adjustment device that is switched with a pulse-width-modulated electrical control signal. The control signal is generated by a control device in the form of a square-wave signal with a constant upper and a constant lower signal level, for example voltage level, and a specific period duration. According to the pulse width modulation, the duration of the upper signal level, the so-called switch-on time, and subsequently the time period of the lower signal level, the switch-off time, can be varied. The magnetic force of the adjusting device changes in accordance with the duty cycle of the control signal, ie the ratio of the switch-on time to the period t. The switching position of the adjusting valve 20 results from the balance of forces between the force of the valve spring 25 and the two opposing forces, namely the fluidic force generated by the valve actuating pressure P ₂₀ and the magnetcraft. The greater the valve control pressure P ₂₀ , the smaller the magnetic force corresponding to the balance of forces. If the sum of the fluidic force and the magnetic force exceeds the spring force, the valve piston 22 moves in the direction of the first switching position, and the delivery volume of the displacement pump is reduced. If the force of the valve spring 25 predominates, the valve piston 22 moves into the second switching position, and the displacement unit 5-7 accordingly moves in the direction of the maximum delivery volume.

In a modification, the switch-on time and the switch-off time are assigned to the first and the second switching position of the adjusting valve 20. When the adjusting device is functioning properly, the position of the valve piston 22 and the associated switching position of the adjusting valve _{20 are} decoupled from the valve actuating pressure P ₂₀ . As an example, it is assumed that the adjusting valve 20, assumes the first switching position, in which the fluid of the partial flow, during each switch-on time 16 is returned to the pressure chamber 8, and during each switch-off time assumes the second switching position in which the fluid is returned to the pressure chamber 9.

By varying the switch-on time and the switch-off time, the flow through the adjusting valve 20 to the respective pressure chamber 8 or 9 can be varied practically continuously in both versions because of the significantly shorter period t of the control signal compared to the relevant time constant of the pump. The pressure in the pressure chamber 8 and the pressure in the pressure chamber 9 can also be changed correspondingly continuously.

As a result, the adjustment unit 5-7 can be moved along its axial adjustment path into any axial position and can also be held there. The delivery volume is thus flexible between the maximum and the minimum delivery volume and can be continuously and precisely adapted to the fluid requirement of the unit 14.

A map is stored in an electronic or optical memory in a controller for the unit 14, in the exemplary embodiment of a motor controller, for the supply of the unit 14 in accordance with requirements. For the operating states of the unit 14 which are relevant with regard to the fluid requirement, the characteristic diagram contains in each case a predetermined target value for the fluid supply pressure P ₁₄ or the volume flow V ₁₄ which the unit 14 requires in the respective operating state. These volume flow or pressure setpoints are stored in the map as a function of physical variables that characterize the operating states that are to be differentiated with regard to the fluid requirement. The temperature T, the speed D and the load L may be mentioned as examples of the physical quantities. The unit 14 has a detection device for detecting one or more physical quantity (s) that characterize the different operating states. The temperature T can be, for example, at a critical point of the unit 14, in a cooling fluid that serves to cool the unit 14, or in that of the pump 3 pumped fluid can be measured. The speed D can be detected very easily by means of a tachometer and the load L via the accelerator pedal or a throttle valve position. Depending on the detected quantities, a setpoint specification selects the assigned pressure or volume flow setpoint on the basis of the characteristic diagram and gives it to the control device for the adjusting valve 20. The control device forms the control signal, namely the ratio of the switch-on time to the period t, in accordance with the current setpoint. A feedback by means of a controlled variable, in the present case a measured actual value of the fluid supply pressure P ₁₄ or the volume flow V ₁₄ , is not necessary as long as the actual eluid requirement of the unit 14 corresponds to the target value.

The control based on the setpoint can in particular be supplemented by a current control. The current control is used, in particular, to compensate for changes in resistance of the magnetic adjusting device, as can occur especially when there are changes in temperature. The current consumption of the adjustment device is detected by a detection device and kept at a specific current value. If a change in the current consumption and accordingly the electrical resistance of the adjusting device is determined by means of the detection device, the pulse duty factor is changed in such a way that the current consumption corresponds again to the current value before the resistance change.

In the event that the actual fluid requirement of the unit 14 changes and deviates from the setpoint values of the map, for example due to wear occurring in the course of the service life of the unit 14, a regulating device is also provided for the adjusting valve 20. The control device forms the control signal for the adjusting valve 20 as a function of a target / actual comparison based on a fluid supply pressure P ₁₄ or volume flow V ₁₄ required for the unit ₁₄ . The control device has access to a memory in which other setpoints of the pressure P ₁₄ or volume flow V ₁₄ are stored in the form of a map comparable to the map previously used for the control. The maps of the pressure setpoints or volume flow setpoints can be stored in physically different memories or in the same memory in different areas. Furthermore, a higher-level control device is provided, which can be a component of the pressure or volume flow control device or the control device and changes from the control to a control if it is determined that the demand of the unit has changed to such an extent that the characteristic diagram of the setpoints no longer adequately describes the actual demand because the demand has increased due to wear, for example. For the target-actual pressure comparison, the actually prevailing fluid supply pressure P _{14 can be recorded,} for example, at the most downstream consumption point of the unit 14 or, in the example of the internal combustion engine, at the engine gallery and compared with the pressure target value relevant for the respective operating state, for example by forming the difference between the target - and actual value.

The pressure or volume flow control described by way of example as not being feedback can be further developed to a pressure or volume flow control with a target / actual comparison of the respective pressure or volume flow target value with an actual value to be measured for the comparison. Several maps for the volume flow V ₁₄ or fluid supply pressure P ₁₄ can be stored in advance, which describe the need for different times in the life cycle of the unit 14, for example one map for the first n kilometers of a motor vehicle or n operating hours of the unit 14, the next m kilometers of the vehicle or m hours of operation of the unit etc. Based on, for example, the mileage of the vehicle or an operating date recording can be switched from the map used first to the next etc. in such embodiments. Finally, the control device can also delay the ability to change the setpoint values of the map according to the state of the unit 14, in order to be able to control the adjusting valve 20 in a better adapted manner to the respective state of the unit 14 on the basis of the changed map. The change in the setpoint values of the map or the selection of one of a number of predefined guy fields is advantageously carried out automatically, for example on the basis of the already mentioned mileage or the operating time or a detection of the fluid supply pressure P ₁₄ and comparison with or in the form of a map setpoint pressure setpoint (s) ), such a target / actual comparison could be used for pressure control of the adjusting valve 20, but preferably only for the selection of the pressure or volume flow map to be used or the change in the pressure or volume flow setpoints of a single predetermined map is used for control.

In the Figures 3 and 4 For the generation of the valve control pressure P _20, a partial stream 17 is branched off again from the returned partial flow 16 in front of the adjusting valve 20 and thus a valve piston of the adjusting valve 20 acts against the valve spring 25

Figure 5 shows in a longitudinal section a modified with respect to the generation of the valve actuating pressure P ₂₀ valve 20. The valve actuating pressure P ₂₀ is different from that of the adjusting valve Figure 4 not by means of an additional partial flow into which Figures 3 and 4 the partial flow 17, but by means of the flow of the partial flow 16 to be controlled or regulated. Apart from this modification, the same applies to the adjusting valve 20 in FIG Figures 3 and 4 made versions also for the modified adjusting valve 20 and the statements made for this also for the adjusting valve 20 of the Figures 3 and 4 ,

The adjusting valve 20 has a valve housing 21 and a valve piston 22, which can move axially back and forth in the valve housing 21 along a central valve axis S. A magnetic coil 27 and an armature 28 made of soft iron are shown by the adjusting device. The electrical connections of the solenoid 27 are also indicated. The solenoid 27 is fixedly connected to the valve housing 21 and surrounds the armature 28. The armature 28 is connected to the valve piston 22 so that it cannot move axially, so that the valve piston 22 and the armature 28 have axial movements such as execute a unit.

The valve piston 22 has a first active surface 2.3 and a second active surface 24 for the valve control pressure P ₂₀ . The active surfaces 2, 3 and 24 axially jointly delimit a fluid space 26 and face each other axially. The active surface 23, on which the valve actuating pressure P _{20 of} the valve spring 25 counteracts, is larger than the active surface 24, wherein in Figure 5 the conditions are exaggerated. The difference in size is actually only slight, but is defined in such a way that the valve actuating pressure P ₂₀ on the valve piston 22 always exerts a differential force corresponding to the difference in size of the active surfaces 23 and 24, which counteracts the force of the valve spring 25. Since the valve piston 22 can be manufactured very precisely to the size difference of the active surfaces 23 and 24, the differential force can also be correspondingly small and the valve spring 25 advantageously softer than in the exemplary embodiment in FIG Figure 4 his. The adjusting device 27, 28 requires correspondingly low forces. The adjusting valve 20 becomes more sensitive overall, and the switching times of the adjusting valve 20 can be shortened.

The inlet I for the fluid to be controlled or regulated opens into the fluid space 26 in all switching positions of the adjusting valve 20. In the switching position shown, that of the switching position of the adjusting valve 4 in FIG Figures 3 and 4 corresponds, the port B opens into the fluid chamber 26, and the valve piston 22 separates the fluid chamber 26 and thus the inlet I from the other port A. Accordingly, the fluid of the partial flow 16 is returned to the pressure chamber 9, while the pressure chamber 8 via the port A is connected to the reservoir 11 and is therefore depressurized. In this switching position, the connection A is connected to the outlet O via a space of the valve housing 21, in which the valve spring 25 is arranged, and to the outlet 11 via this. If the control signal changes its signal level, in the exemplary embodiment from the lower to the upper signal level, the solenoid 27 is energized and moves the armature 28 against the force of the valve spring 25 in the axial direction initially into the middle switching position and, with a correspondingly long switch-on time, into the other extreme switching position , the first switch position. In the middle switching position, the valve piston 22 separates both ports A and B from the fluid chamber 26, into which the inlet I continues to open. In the first switching position, the valve piston 2.2 assumes an axial position such that the fluid chamber 26 is in axial overlap with both the inlet I and the port A, while the valve piston 22 in the relevant axial position is the port B of the fluid chamber 26 separates fluidically. In the first switching position, the fluid of the partial flow 16 is conducted through the fluid chamber 26 and the connection A into the pressure chamber 8, while the pressure chamber 9 is connected to the outlet O and finally to the reservoir 11 via the connection B and a passage C of the valve piston 22 is.

The valve piston 22 is hollow. The passage C is formed in a cylindrical jacket region of the valve piston 22, which adjoins the active surface 24 in the direction of the armature 28 and forms a narrow sealing gap with the surrounding jacket of the valve housing 21, which fluidically separates the adjusting device 27, 28 from the fluid chamber 26 , To the active surfaces 23 adjoins radially on the outside and from the adjusting device 27, 28 also a cylindrical jacket region of the valve piston 22, which forms a further narrow sealing gap with the valve housing 21, as long as the adjusting valve 20 does not assume the first switching position in which the valve piston 22 has the axial position occupies in which the fluid space 26 is in an axial overlap with the port A.

The adjusting device 27, 28 with the associated control device switches the adjusting valve 20 over the entire operating range of the unit 14 and controls or regulates the axial position of the adjusting unit 5-7 and consequently the delivery volume of the displacement pump over the entire volume flow range, which is necessary for the adapted supply of the unit 14 is required. The fluidic valve actuating pressure P ₂₀ and the valve spring 25 serve as backup in the event that the adjusting device 27, 28 or the associated control device fails due to a defect, for example due to a cable break or a loose electrical plug connection. The adjusting valve 20 is designed such that, in the event of a failure, the delivery volume of the pump from maximum to minimum is only adjusted when a fluid supply pressure P ₁₄ is reached that is greater than a maximum fluid supply pressure P ₁₄ , which is set when the adjusting valve 20 functions properly , For this purpose, the valve spring 25 is installed with a pretensioning force which is greater than a force exerted on the valve piston 22 by a greatest valve actuating pressure P ₂₀ , which can occur when the valve is functioning properly.

Reference numerals:

1

pump housing

1a

wrap

2

inlet

3

outlet

4

conveying member

5

conveying member

6

actuating piston

7

actuating piston

8th

pressure chamber

9

pressure chamber

10

pump spring

11

reservoir

12

management

13

Cooling and cleaning device

14

aggregate

15

management

16

partial flow

17

partial flow

18

management

19

management

20

adjusting valve

21

valve housing

22

plunger

2.3

effective area

24

effective area

25

valve spring

26

fluid space

27

solenoid

28

anchor

A

connection

B

connection

I

inlet

O

outlet

S

valve axis

t

period

D

rotational speed

L

load

T

temperature

P ₁₄

Fluid supply pressure

V ₁₄

flow

Claims (21)

1. An adjusting valve for adjusting the delivery volume of a displacement pump, said adjusting valve comprising:

   (a) a valve casing (21);

   (b) a valve piston (22) which is mounted such that it can be moved within the valve casing (21), comprising an active surface (23) for a valve-actuating pressure (P₂₀) of a fluid;

   (c) a valve spring (25) which counteracts a force exerted by the valve-actuating pressure (P₂₀) on the valve piston (22);

   (d) and an adjusting device (27, 28), by means of which the valve piston (22) can be adjusted in the direction of the force exerted by the valve-actuating pressure (P₂₀),

   (e) wherein the valve spring (25) is biased and exerts a spring force on the valve piston (22) which is greater than a force exerted on the valve piston (22) by a maximum valve-actuating pressure (P₂₀) when the adjusting device (27, 28) is functioning properly,

   (f) wherein the valve spring (25) is installed with a biasing force which is greater than the force which is exerted on the valve piston (22) by the maximum valve-actuating pressure (P₂₀) which can be set during proper functioning.
2. The adjusting valve according to the preceding claim and at least one of the following features:

   - the adjusting device (27, 28) can be operated electrically;

   - the adjusting device (27, 28) is formed as a magnetic adjusting device;

   - the adjusting device (27, 28) counteracts the force of the valve spring (25).
3. The adjusting valve according to any one of the preceding claims and at least one of the following features:

   - the adjusting valve (20) is a proportional valve;

   - the adjusting valve (20) is controlled or regulated by modulated pulses, preferably by width-modulated pulses;

   - the adjusting valve (20) is current-controlled or current-regulated;

   - the adjusting valve (20) is voltage-controlled or voltage-regulated;

   - the adjusting valve (20) comprises at least three ports (I, O, A, B), preferably four ports, for the fluid;

   - the adjusting valve (20) can be switched between at least two switching positions, preferably three switching positions;

   - the adjusting valve (20) is a port valve.
4. The adjusting valve according to any one of the preceding claims, comprising:

   - a control device or regulating device for controlling or regulating a fluid supply pressure (P₁₄) to be generated or a volume flow (V₁₄) to be delivered by the displacement pump;

   - and a nominal value preset for predetermining at least one pressure nominal value or volume flow nominal value, preferably a nominal value which is variable in a predetermined way;

   - wherein the control device or regulating device controls or regulates the adjusting device (27, 28) in accordance with the nominal value.
5. The adjusting valve according to any one of the preceding claims, comprising:

   - a regulating device for regulating a fluid supply pressure (P₁₄) to be generated by the displacement pump;

   - a nominal value preset for predetermining a nominal value for the fluid supply pressure (P₁₄), preferably a nominal value which is variable in a predetermined way;

   - and a sensor for ascertaining an actual value of the fluid supply pressure (P₁₄),

   - wherein the regulating device compares the actual value with the nominal value and controls the adjusting device (27, 28) in accordance with the result of the comparison.
6. The adjusting valve according to a combination of the preceding two claims, comprising a checking device, by means of which the adjusting valve (20) can be changed from controlling the fluid supply pressure (P₁₄) or volume flow (V₁₄) to regulating the fluid supply pressure (P₁₄) or volume flow (V₁₄).
7. The adjusting valve according to any one of the preceding claims, wherein the valve piston (22) comprises another active surface (24) for the valve-actuating pressure (P₂₀), and the active surfaces (23, 24) are arranged to counteract each other and are of different sizes in order to generate a differential force which acts on the valve piston (22) counter to the valve spring (25) and corresponds to the difference in the size of the active surfaces (23, 24).
8. The adjusting valve according to the preceding claim, wherein the active surfaces (23, 24) limit the same fluid space (26) and face each other in the direction of the mobility of the valve piston (22).
9. The adjusting valve according to the preceding claim, wherein: the valve piston (22) can be moved back and forth between a first position and a second position; in the first position of the valve piston (22), an inlet (I) and a port (A) for a pressure fluid which generates the valve-actuating pressure (P₂₀) feed into the fluid space (26); and in the second position, the valve piston (22) separates the port (A) from the inlet (I) which still feeds into the fluid space (26).
10. The adjusting valve according to any one of the preceding claims, wherein: the valve casing (21) comprises an inlet (I), a first port (A) and a second port (B) for a pressure fluid; the valve piston (22) can be moved back and forth between a first position and a second position; and when the valve piston (22) is situated in the first position, the inlet (I) is connected to the first port (A) and separated from the second port (B), and when the valve piston (22) is situated in the second position, the inlet (I) is connected to the second port (B) and separated from the first port (A), in order to selectively channel the pressure fluid to the pump either via the first port (A) or via the second port (B).
11. A displacement pump exhibiting an adjustable delivery volume, and comprising:

    (a) a pump casing (1);

    (b) a delivery chamber which is formed in the pump casing (1) and comprises an inlet (2) for a fluid on a low-pressure side of the pump and an outlet (3) for the fluid on a high-pressure side of the pump;

    (c) a delivery member (5), which can be moved within the delivery chamber, for delivering the fluid;

    (d) and an adjusting valve (20) according to any one of the preceding claims for adjusting the delivery volume, arranged in a flow of the fluid delivered by the delivery member (5).
12. The displacement pump according to the preceding claim, wherein:

    - an actuating member (6, 7) is movably arranged facing a front face of the delivery member (5) or surrounding the delivery member, for adjusting the delivery volume in the pump casing (1);

    - the actuating member (6, 7) can be charged in the direction of its mobility with an actuating force which is dependent on the requirement of an assembly (14) to be supplied with the fluid;

    - wherein the actuating member (6, 7) and the delivery member (5) are part of an adjusting unit (5, 6, 7) which can be moved back and forth within the pump casing (1) as a complete unit, or one of the actuating member and the delivery member can be adjusted relative to the other and relative to the pump casing.
13. The displacement pump according to the preceding claim and at least one of the following features:

    - the pump is a rotational pump, and the delivery member (5) is a delivery rotor arranged in the delivery chamber such that it can rotate about a rotational axis (Rs);

    - a pump spring (10) is arranged to counteract the actuating force.
14. The displacement pump according to any one of the preceding two claims, wherein the actuating member (6, 7) can be charged with the fluid of the high-pressure side of the pump, in order to generate the actuating force.
15. The displacement pump according to the preceding claim, wherein: the actuating member (6, 7) forms a double-action actuating piston comprising a first piston surface and a second piston surface which faces away from the first piston surface; the first piston surface can be charged with a pressure fluid, preferably the fluid of the high-pressure side of the pump, via a first port (A) of the adjusting valve (20), and the second piston surface can be charged with a pressure fluid, preferably the fluid of the high-pressure side of the pump, via a second port (B) of the adjusting valve (20); and the valve piston (22) can be moved back and forth between a first position and a second position, wherein in the first position of the valve piston (22), the adjusting valve (20) only channels the pressure fluid to the first piston surface, and in the second position of the valve piston (22), the adjusting valve (20) only channels the pressure fluid to the second piston surface.
16. The displacement pump according to any one of the preceding four claims and at least one of the following features:

    - the actuating member (6, 7) can be moved together with the delivery member (5) or relative to the delivery member (5), axially or transversely in relation to the rotational axis (R₅);

    - the delivery member (5) is in a delivery engagement with another delivery member (4) of the displacement pump, in order to deliver the fluid;

    - the pump is an external gear pump or an internal gear pump;

    - the actuating member (6, 7) comprises a first actuating piston (6) and a second actuating piston (7), and the delivery member (5) is axially arranged between the actuating pistons (6, 7) can be axially moved back and forth together with the actuating pistons (6, 7) as an adjusting unit (5, 6, 7) in the delivery engagement, relative to the other delivery member (4);

    - the pump is a vane pump, a pendulum slider pump or an internal gear pump, and the actuating member is an actuating ring which surrounds the delivery member and can be moved transverse to the rotational axis of the delivery member.
17. The displacement pump according to any one of the preceding claims, wherein the fluid delivered by the displacement pump is branched off on the high-pressure side of the pump, preferably downstream of a cleaning device (13), and fed back to the pump via the adjusting valve (20), in order to generate the actuating force there.
18. The displacement pump according to the preceding claim, wherein the fluid being fed back generates the valve-actuating pressure (P₂₀), preferably while flowing through the adjusting valve (20).
19. The displacement pump according to any one of the preceding claims, comprising:

    - a detection device for detecting at least one physical variable (T, D, L) which characterises the fluid requirement of an assembly (14) to be supplied by the pump;

    - a nominal value preset which forms a nominal value for a volume flow (V₁₄) to be delivered or fluid supply pressure (P₁₄) to be generated by the displacement pump, in accordance with the at least one detected physical variable (T, D, L);

    - and a control device or regulating device which controls or regulates the adjusting device (27, 28) of the adjusting valve (20) in accordance with the nominal value.
20. The displacement pump according to the preceding claim, comprising: a sensor for ascertaining an actual value of the volume flow (V₁₄) or fluid supply pressure (P₁₄), wherein the regulating device forms an actuating variable for the adjusting device (27, 28) of the adjusting valve (20) in accordance with a comparison between the nominal value and the actual value.
21. The displacement pump according to any one of the preceding claims and at least one of the following features:

    - the pump is used as a lubricating oil pump in a vehicle for supplying an internal combustion engine (14) with lubricating oil or supplying an automatic transmission with hydraulic fluid;

    - the pump is driven by the internal combustion engine (14).

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