EP2014919B1 - Adjustment valve for adjusting the supply volume of a pressure pump - Google Patents

Description

The invention relates to an adjustment valve for the adjustment of the delivery volume of a positive displacement pump and a positive displacement pump with the adjustment valve, which is arranged for the adjustment of 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 adjustment valve as such, as far as it is provided for the adjustment of the delivery volume of a positive displacement pump.

The publication US Pat. No. 5,876,185 A , which is considered to be the closest prior art, discloses an adjustment valve having a valve piston which is moved against the force of a valve spring as the valve actuating pressure increases. This valve can be used to control an adjustable pump.

Positive displacement pumps deliver fluids at 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, in practice, can be regarded as constant, at least to a good approximation. The constancy per revolution or stroke and, accordingly, the proportionality to the pump speed is troublesome, for example, in applications in which the unit to be supplied by the respective pump has a fluid requirement which is lower in one or more speed range (s) of the pump than that from the Proportionality resulting volumetric flow. Accordingly, in the respective speed range, the pump delivers a volume flow above the demand, which is dissipated with loss. The problem is in the US 6 126 420 B already disclosed an internal gear pump with adjustable delivery volume to solve the problem.

The US Pat. No. 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 adjusting unit, which is formed as a double-acting piston. The adjusting unit is acted upon by a 4/3-way adjusting valve with the pumped fluid from the pump. The adjustment valve has a valve housing and a valve piston axially reciprocating valve piston which is acted upon at one axial end with the funded fluid and at the other axial end with a pressure of the fluid counteracting force of a valve spring. The position of the valve piston adjusts according to the balance of the force of the valve spring and the force generated by the fluid pressure. The Adjustment valve is designed so that the adjustment of the pump moves on reaching a predetermined by the valve spring fluid pressure from an axial position for maximum delivery volume towards an axial position for minimum delivery. The preload force of the valve spring is adjusted at the adjustment valve in advance.

From the WO 03/058071 A1 a positive displacement pump with an adjusting valve is known, the movable valve piston for adjusting the delivery volume of the pump in an axial direction with fluid of the high pressure side of the pump and the fluid counteracting acted upon by a spring force. In order to be able to lower the fluid pressure at which the pump is stopped, a control device is provided for the adjusting valve, which exerts an additional force on the valve piston. As examples of control means, an electric stepping motor for adjusting the biasing force of the valve spring and a magnetic coil for generating an additional magnetic force are called. The switched by means of the adjustment fluid flow acts on a displacement unit of the pump only in the direction of maximum delivery volume, while in the opposite direction always the pressure of the high pressure side acts.

From the DE 103 24 092 A1 5, a controllable lubricating oil pump with a flow regulator is known. The flow regulator comprises a valve with an axially movable control piston. 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 to extend the travel of the control piston or to adjust the spring force of the spring. The EP 1 555 436 A2 describes a gear pump with flow control with a valve whose passage opening can be changed by a control unit. The valve is a pulse width modeled solenoid valve which is operatively connected to flow control via a pressure transducer connected to the first pressure chamber of the pump with a controller coupled thereto. From the DE 102005 029 086 A1 An oil pump for an internal combustion engine with an adjustment valve is known. The valve is an electrically controllable valve and comprises a valve body axially movable in the valve body with sections of different diameters, during their displacement slot-shaped control openings of the valve are released or closed. 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 valve spool movably mounted in the valve. The JP 57 131890 A describes a controllable feed pump with an adjustable by pressurizing valve. Other relevant pumps are also in the US 7 726948 B2 . US Pat. No. 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 requirements of an aggregate to be supplied and to always ensure an adequate supply of the aggregate.

The invention is based on a positive displacement pump for the supply of an aggregate with fluid, which has a pump housing with a delivery chamber and a delivery member movable in the delivery member, which acts directly on the fluid to convey it through the delivery chamber. The delivery member may, upon execution of a conveying movement, the fluid alone or in cooperation with one or possibly several further delivery member (s) of an inlet of the delivery chamber while increasing the pressure through an outlet of the delivery chamber. The inlet becomes 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 in principle can also serve to convey the fluid in an open fluid circuit. When integrated in a closed fluid circuit, it draws 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 the or possibly several to be supplied with the fluid unit (s). Downstream of the unit (s), the fluid returns to the reservoir, closing the fluid circuit. The pump can be used, for example, to supply a hydraulic press with pressurized fluid. In preferred embodiments, it is installed in a motor vehicle or provided for installation in order to supply a motor vehicle driving the engine with lubricating fluid or an automatic transmission with hydraulic fluid. Preferably, the internal combustion engine drives the pump.

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

As a delivery volume, the specific volume flow of the pump is understood as such in preferred embodiments, in the case of a rotary pump, the volume flow per revolution and in the case of a reciprocating pump, the flow rate per stroke. Although less preferred, the pump may also be a fixed displacement pump and the adjustment valve may be disposed on the high pressure side of the pump as a bypass valve to deliver excess fluid being conveyed bypassing the at least one unit into the reservoir. Such a bypass conveyance does not reduce the power consumption of the pump, but still ensures demand-based delivery. It is not in such embodiments, the delivery volume at the outlet of the delivery chamber, but that to the at least one aggregate funded delivery volume needs controlled or regulated. It is also possible to combine a pump adjustable in its delivery volume with such a bypass valve by adjusting the volume flow per revolution or stroke via an adjusting valve according to the invention or otherwise and downstream of the pump, but upstream of the unit to be supplied, part of the pump the pump funded flow is diverted and unused returned to a reservoir. In preferred embodiments, the delivery volume of the pump as such, as seen directly at the outlet of the delivery chamber, adjusted by means of the adjustment valve. In such embodiments, an actuator is arranged movably in the pump housing, which can be acted upon in the direction of its mobility with a dependent on the need of at least one unit actuating force. The actuator may be arranged in particular to an end face of the conveyor member or the conveyor member surrounding. The actuator and the delivery member are in first variants part of an in the pump housing as a whole back and forth movable adjustment, for example, a linearly movable or pivotable or otherwise movable transversely to a rotation axis of the preferably rotatable conveyor member adjustment. Examples of such adjusting units describe, for example, the US 6 28.3 735 B1 for outside-axle, the US 6 126 420 B and US Pat. No. 6,244, 8.39 B1 for internal-axis pumps In second variants, the actuator is adjustable relative to the conveyor member and the pump housing. The actuator of the second variant may in particular be a collar surrounding the conveyor member as known from vane pumps including vane pumps, rotary vane pumps and internal tame gear pumps to adjust the eccentricity to the conveyor member, for example by a linear lifting or pivotal movement of the actuator.

The actuating force is preferably generated fluidically by the actuator forming an actuating piston, which is acted upon by a pressurized 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 via the adjustment valve as a partial flow of the total volume flow delivered by the pump. The pressurized fluid, which is applied to the actuator, but in principle can also another fluid, such as a fluid provided from a pressure reservoir or from another pump.

In yet another variant, a partial flow of the fluid is conducted 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 described, for example, in US Pat US Pat. No. 6,935,851 B2 By the return and filling of the conveyor cells, the delivery volume is also adjusted at the same time, whereby this type of adjustment with one of the other types mentioned above can also be realized in combination.

According to the invention the Verstelleinriclttullg is formed so 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 assault otherwise in the sense of the invention encompasses the meaning of "either ......... or" and also the meaning of "and", as far as the respective context not necessarily surrounds a limited meaning. Accordingly, the adjustment means may be constructed to counteract or preferably counteract the force of the valve set pressure only in the same direction and the valve spring, and alternatively may be constructed to bias the valve piston both in and against the force of the valve set 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 by means of a correspondingly smaller force of the adjusting device against the force of the valve spring.

In a second preferred embodiment, the adjusting device for adjusting the valve piston is set up both in the direction of the valve set pressure and against the valve set pressure. If the adjustment device is a magnetic adjustment device with only a single magnetic coil, the magnetic coil can be repolished in such embodiments. Alternatively, for each of two directions of the mobility of the valve piston own solenoid with one each Anchor be provided and one of these anchors on the valve piston a force in the one and the other armature exert a force in the other direction of the mobility 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 force acting on the active surfaces Ventilstelldruck, and the delivery volume of the pump can be adjusted accordingly. The adjustment valve can thus adjust the delivery volume over a larger operating range of the unit to be supplied in a continuously or arbitrarily stepped manner and not only to a specific pressure at which the delivery volume is reduced.

According to the invention, a control or regulation device for the adjustment valve is set up so that by means of the adjustment valve the delivery volume can be adjusted adjusted over the entire operating range of the unit. On the other hand, ensure the valve spring and the valve spring constantly counteracting the force of the valve spring secure supply of the unit, although in case of failure of the adjusting device only as known from conventional positive displacement with a reduction of the delivery volume in response to the biasing force and spring constant of the valve spring. The invention combines an accurate and flexible Anpassbarlceit to the needs with a guaranteed even in case of failure of the adjustment supply security, it creates a so-called second-level control or regulation of the delivery volume.

The adjusting valve is preferably a proportional valve. It is preferably controlled electrically. The adjusting device preferably acts magnetically. It may comprise a proportional solenoid which is voltage or current controlled or regulated, that is to say by a variation of the applied voltage or of the electric current oriented on the requirement of the at least one aggregate. In other preferred embodiments, the adjustment valve is controlled or regulated by pulse modulation. When using a pulse-modulated adjustment 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 each other following pulses is adjusted to the needs. The period of the manipulated variable is preferably constant. Preferably, a pulse width modulated adjustment valve is used. The period of the manipulated variable for the adjustment valve is significantly smaller than the time constant of the positive displacement pump which determines the adjustment of the delivery volume. The pulse modulation uses the Tiefpasscharakters the pump. By varying the on-time of the pulse width modulation or the time interval in the case of a pulse frequency modulation adapted to the needs, the flow through the adjustment valve and consequently the displacement of the positive displacement pump can be quasi-continuously controlled or regulated according to the momentary demand of the unit.

The Veistellventil is preferably a multi-way valve with at least three ports, preferably with four ports. It is preferably switchable between at least two switch positions, preferably between three switch positions.

The adjustment valve is controlled or regulated in preferred embodiments in response to a desired value for the volume flow to be delivered by the positive displacement pump or a fluid supply pressure to be generated by the positive displacement pump. A setpoint specification specifies the setpoint value of a control or regulation device provided for the adjustment valve. The set point is preferably varied depending on the demand of the unit. Preferably, a characteristic field is specified for the setpoints dependent on the operating state of the unit. The at least one desired value or more preferably the plurality of desired values is or are predefined as a function of a physical variable characterizing the operating state, which is sensed during operation of the unit by means of a detection device. The at least one physical variable may in particular be a temperature, a rotational speed or a load state of the aggregate. Preferably, the desired value or the desired values for the volume flow or the fluid supply pressure are predefined as a function of at least two variables characterizing the operating state of the unit. If the positive displacement pump is used as a lubricating oil pump for an internal combustion engine, the temperature of the lubricating oil or of the cooling fluid in the region of the internal combustion engine or the speed or for the load state can detect or determine the accelerator pedal position or throttle position, and from this using the characteristic field of the corresponding Determined setpoint and the control or regulating device for the adjustment valve can be specified.

In a preferred first embodiment, the adjustment valve is only controlled as a function of the respective desired value. The detection of an actual value representative of the requirement of the physical quantity forming the desired value, namely of the volume flow or of the fluid supply pressure, is dispensed with, as well as elaborate processing for a control based on a desired / actual comparison.

In a likewise preferred second embodiment, the adjustment valve is regulated as a function of a desired / actual comparison of the respective setpoint value and an actual value of the volume flow or the fluid supply pressure measured continuously or at sufficiently small time intervals. A control is in such cases of Vorteig, in which the volumetric flow demand of the unit changes due to wear over the life of the unit.

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 control according to the second embodiment. In this case, it is preferred if the adjustment valve is initially controlled on the basis of the predefined volumetric flow and, with increasing leakage losses as a result of wear of the unit, is later converted to pressure regulation. In yet another embodiment, a conductive control device is provided, which detects increasing wear based on a sensory detection of the volume flow or fluid supply pressure and the setpoint or the setpoint characteristic adjusted at least once or in several stages, possibly continuously shifts during the life of the unit.

In a further preferred embodiment, the adjustment valve is firstly controlled and additionally energized by means of a nominal value or a nominal value map for the fluid supply pressure or the volume flow. A particularly preferred embodiment is one based on one or more desired values or a setpoint characteristic map for the fluid supply pressure or the volume flow by means of Pulse width modulation controlled and additionally current controlled adjustment valve. With the current control advantageously associated with temperature changes are compensated for changes in the electrical resistance of a Magnetverstelleinrichtung. It detects the current consumption of the Magnetverstelleinrichtung and compensated for the changes in the size of the electric current due to changes in resistance by the duty cycle of the variation of the current consumption is regulated accordingly. Accordingly, however, not only for the preferred embodiment as pulse width modulated adjustment valve, but also be operated at differently controlled adjustment valves. By a current control in addition to the control of a setpoint or setpoint characteristic map for the flow or the fluid supply pressure can be dispensed with a flow or pressure control, although in the case of a current control additionally a flow or pressure control can be used.

The control or regulating device may be integrated part of the adjustment valve or installed separately from it. The setpoint specification can be embodied component of the control or regulation device or representational 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. The adjustment valve may advantageously be arranged in the integrated embodiment of 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. The connections of the adjusting valve can be shaped in such embodiments space and weight saving as holes or other shaped channels in the housing, in particular in said housing wall, the pump housing can therefore simultaneously also form the valve housing or even a 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 actuator piston with two axially opposite, preferably oppositely facing piston surfaces and by means of the adjustment either the one or the other piston surface can be acted upon with a pressurized fluid under pressure, optionally also both piston surfaces simultaneously.

If the actuator forms an actuating piston which can be pressurized with pressurized fluid, for example a piston which can be pressurized only on one side or preferably a double-acting piston, it is acted upon in preferred embodiments by a pump spring with a spring force, the pump spring acting in the direction of increasing the delivery volume of the pump. 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 significant extent by the adjustment valve. In principle, it is also possible to dispense with a pump spring in such embodiments. On the other hand, the use of a weak pump spring is advantageous, wherein such a pump spring is designed so that it only ensures that in low-speed displacement pump, the maximum pumping speed for this pump speed is promoted. Suffice a pump spring, which exerts on the actuator a spring force corresponding to a fluid pressure of at most 1 bar.

Preferably, the fluid controlled by means of the adjustment valve or regulated to the positive displacement pump for the purpose of adjustment or in the case of an only used as a bypass valve adjusting valve generates the branched off to a reservoir fluid at its flow through the adjusting valve the valve set pressure. In such embodiments, a separate Ansclaluss is needed for the generation of the valve actuating pressure. The same inlet, through which the fluid flow passing through the adjusting valve passes into the adjusting valve, also forms the connection for the fluid which generates the valve actuating pressure.

It is preferred if the valve actuating pressure is generated by means of a plurality of active surfaces, preferably by means of exactly two effective surfaces which differ in size, so that the valve actuating pressure exerts a differential force corresponding to the area difference of the active surfaces on the valve piston. Particularly preferably, the feature of the differential force is combined with the further feature, after which the fluid also simultaneously generates the valve set pressure during the flow through the adjustment valve.

In a further development, the biasing force of the valve spring can be adjusted, preferably fluidly while the positive displacement pump delivers the fluid. Thus, the adjustment valve may have a further piston which is preferably used only to adjust the biasing force and preferably is acted upon by the fluid, which also generates the valve actuating pressure. wherein for the piston for adjusting the biasing force provided a separate connection or preferably a force acting on this adjusting piston force 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.

Hereinafter, an embodiment of the invention will be explained with reference to figures. The features disclosed in the exemplary embodiment each individually and in each combination of marks form the subject matter of the claims and also the embodiments described above. Show it:

FIG. 1

a positive displacement pump in a cross section,

FIG. 2

the positive displacement pump in a longitudinal section,

FIG. 3

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

FIG. 4

the adjusting valve individually as a symbol and

FIG. 5

the adjusting valve in a longitudinal section.

FIG. 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. In the delivery chamber, a first delivery member 4 and a second delivery member 5 are movably arranged. The conveyor members 4 and 5 are in a conveying engagement with each other When the conveyor members 4 and 5 are driven, they perform a conveying movement in the conveying engagement through which a fluid, such as lubricating oil or a hydraulic fluid, sucked through the inlet 2 into the delivery chamber and higher pressure through the outlet 3 is displaced. The conveyor member 4 is driven and drives the conveyor member 5 in the conveying engagement.

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

In order to adapt the volume of the pump to the needs of a to be supplied with the fluid aggregate along the axes of rotation is R ₄ and R ₅ measured axial length of the conveying engagement of the conveying members 4 and 5, the engagement length, adjustable. For the adjustment, the conveying member 5 is movable relative to the conveying member 4 and the pump housing 1 axially between a position of maximum engagement length and corresponding maximum delivery volume and a position of minimum engagement length and correspondingly minimal delivery volume.

FIG. 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 comprises an actuator with two adjusting pistons 6 and 7 via the conveying member 5 addition. This adjusting unit 5-7 is as a whole in the pump housing 1 axially movable back and forth to adjust the engagement length can. The conveying member 5 is arranged axially between the adjusting pistons 6 and 7. The actuator 6, 7 supports the conveyor member ₅ rotatable about the axis of rotation R ₅ . The adjusting unit 5-7 is accommodated in a cylindrical cavity of the pump housing 1. The cavity forms an axial track for the movements of the adjustment, 5-7. Furthermore, it forms on one axial side of the adjusting 5-7 a pressure chamber 8 and on the other side a further pressure chamber 9. The control pistons 6 and 7 separate the two pressure chambers 8 and 9 of unavoidable leakage fluidly apart from each other and also from the delivery chamber. The Pressure chambers 8 and 9 are each printable with a pressurized fluid, in the embodiment with the funded by the positive displacement pump fluid. In the pressure chamber 9, a pump spring 10 is arranged, the spring force acts on the adjusting unit, 5-7, namely on the actuating piston 7, in the direction of maximum engagement length.

FIG. 3 The fluid circuit includes a reservoir 11 from which the pump draws the fluid on the low pressure side through the inlet 2 and with higher pressure on the high pressure side through the outlet 3, a connected Supply line 12 and a cooling and cleaning device 13 with a radiator and a filter to the supplied with the fluid unit 14, for example, a Biennkraftmaschine for driving a motor vehicle, promotes. Downstream of the unit 14, the fluid is passed through a conduit 15 back into the reservoir 11.

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

FIG. 4 shows the adjustment valve 20 as in FIG. 3 as a switching symbol, only in enlarged cooking position. Entered are the four ports of the adjusting valve 20, of which the inlet for the recirculated partial flow 16 with I, the outlet to the reservoir 11 with O, the connection for the pressure chamber 8 with A and the connection for the pressure chamber 9 with B are designated.

The adjustment valve 20 is a proportional valve with a constantly acting fluidic valve set pressure P20, namely the pressure of the fluid recirculated in the partial flow 16, and a valve spring 25, which is arranged counter to the valve set pressure P ₂₀ . However, the fluidic valve actuating pressure P ₂₀ and the force of the valve spring 25 alone do not determine its switching position when the adjustment valve ₂₀ functions properly. The adjustment valve 20 comprises as a proportional valve an adjusting device, which adjusts the adjustment valve 20 adapted to the fluid requirement of the unit 14 from one of the switching positions to another. 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 adjusting device is a magnetic adjustment device, which is connected 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 having a constant upper and a constant lower signal level, for example voltage level, and a specific period t. According to the pulse width modulation, the time duration of the upper signal level, the so-called on-time, and subsequently in the sequence The duration of the lower signal level, the switch-off time, can be varied. The magnetic force of the adjusting device changes according to the duty cycle of the actuating signal, ie the ratio of the switch-on time to the period t. The switching position of the adjusting valve 20 results from the force equilibrium of the force of the valve spring 25 and the two counteracting forces, namely the fluidic force generated by the valve actuating pressure P ₂₀ and the Magnetlcraft. The larger the valve actuating pressure P ₂₀ , the smaller is the Balance of forces corresponding magnetic force. If the sum of fluidic force and 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 positive displacement pump is stopped. If the force of the valve spring 25 predominates, the valve piston 22 moves to the second switching position, and the displacement unit 5-7 moves accordingly in the direction of maximum delivery volume.

In a modification, the switch-on time and the switch-off time are assigned to the first and the second switch position of the adjustment valve 20. With proper function of the adjustment device, the position of the valve piston 22 and, associated therewith, the switching position of the adjustment valve _{20 are} decoupled from the valve set pressure P ₂₀ . By way of example, let it be assumed that the adjustment valve 20 assumes the first switching position during each switch-on time, in which the fluid of the partial flow 16 is returned to the pressure chamber 8, and during each switch-off time assumes the second switch position, in which the fluid is returned to the pressure chamber 9 ,

By varying the switch-on time and corresponding to the switch-off time, the flow through the adjustment valve 20 to the respective pressure chamber 8 or 9 can be varied practically continuously in both embodiments because of the significantly shorter period duration t of the actuating signal compared to the relevant time constant of the pump. Accordingly, the pressure in the pressure 8 and the pressure in the pressure chamber 9 can be changed continuously.

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

For the needs-based supply of the unit 14 is stored in a control of the unit 14, in the embodiment of a motor controller, a map in an electronic or optical memory. The map contains for the relevant with regard to the fluid requirements operating conditions of the unit 14 each have a predetermined setpoint for the Fluid supply pressure P ₁₄ or the flow rate V ₁₄ , which requires the unit 14 in each operating condition. These volume flow or pressure setpoints are stored in the map in dependence on physical quantities that characterize the operating conditions to be distinguished with regard to the fluid requirement. Examples of the physical variables are the temperature T, the speed D and the load L called. The unit 14 has a detection device for detecting one or more, the different operating conditions characteristic physical variable (s) on the temperature T, for example, at a critical point of the unit 14, in a cooling of the unit 14 serving cooling fluid or in that of the pump 3 funded fluid can be measured. The speed D can be detected very easily by means of a tachometer and the load L on the accelerator pedal or a throttle position. Depending on the detected variables selects a setpoint input based on the map of the associated pressure or flow setpoint and outputs it to the control device for the adjustment valve 20. The control device forms the actuating signal, namely the ratio of the switch-on time to the period t, in accordance with the current setpoint value. A feedback by means of a control variable, in this case a measured actual value of the fluid supply pressure P ₁₄ or the volume flow V ₁₄ , is not required as long as the actual eluid demand of the unit 14 corresponds to the desired value.

The control on the basis of the desired value 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 adjustment device, as they can take place especially in temperature changes. In this case, the current consumption of the adjusting device is detected by a detection device and kept at a specific current value. If, by means of the detection device, a change in the current consumption and accordingly of the electrical resistance of the adjusting device is detected, the duty cycle is changed in such a way that the current consumption again corresponds 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 desired values of the characteristic field, for example due to a wear taking place in the course of the service life of the unit 14, an adjustment valve 20 is also used Control device provided. The control device forms the control signal for the adjustment valve 20 as a function of a desired-actual comparison on the basis of a required for the unit 14 fluid supply pressure P ₁₄ or flow V ₁₄ . The control device has access to a memory in which other setpoint values of the pressure P ₁₄ or volumetric flow V ₁₄ are stored in the form of a characteristic map comparable to the characteristic 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 may be part of the pressure or volume flow control device or the control device and switches from the controller to a control, if it is determined that the demand of the unit has changed so much that the map of the setpoints does not adequately describe actual demand because demand has increased, for example due to wear. For the desired-actual pressure comparison, the actual prevailing fluid supply pressure P ₁₄ can be detected, for example, at the most downstream point of consumption of the unit 14 or in the example of the internal combustion engine at the motor gallery and compared with the relevant for the respective operating pressure target value, for example by subtraction of target and actual value.

The example described as non-feedback pressure or flow control can be further developed to a pressure or flow control with a target / actual comparison of the respective pressure or flow rate setpoint 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 demand for different times in the life cycle of the unit 14, for example, a map for the first n kilometers of a motor vehicle or n operating hours of the unit 14, the next m mileage of the vehicle or m operating hours of the unit etc. On the basis of, for example, the mileage of the vehicle or a Betriebsdatiererfassung can be converted in such embodiments of the first used map to the next, etc. Finally, the controller may also detract from the ability to change the setpoint values of the map in accordance with the state of the engine 14 to better match the adjustment valve 20 with the engine based on the altered map be able to control the respective state of the unit 14 adapted. The change of the setpoint values of the characteristic map or the selection of one of several predetermined Guynfeldelm 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 predetermined in the form of a characteristic pressure setpoint (en Although such a target / actual comparison could be used for a pressure control of the adjustment 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 flow rate setpoints of a single predetermined map is used for control.

In the Figures 3 and 4 is for the generation of the valve actuating pressure P ₂₀ of the recirculated partial flow 16 again diverted a partial flow 17 before the adjustment valve 20 and thus a valve piston of the adjusting valve 20 of the valve spring 25 counteracted

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

The adjusting valve 20 has a valve housing 21 and a valve piston 22 which can be moved axially back and forth in the valve housing 21 along a central valve axis S. The adjusting device shows a magnet coil 27 and an armature 28 made of soft iron. The solenoid coil 27 is fixedly connected to the valve housing 21 and surrounds the armature 28. The armature 28 is connected to the valve piston 22 axially immovable, so that the valve piston 22 and the armature 28 axial movements such as to execute a unit.

The valve piston 22 has a first active surface 2.3 and a second active surface 24 for the valve actuating pressure P ₂₀ . The active surfaces 2, 3 and 24 together axially bound a fluid space 26 and face each other axially. The active surface 23, against which the valve actuating pressure P _{20 of} the valve spring 25 counteracts, is greater than the effective area 24, wherein in FIG. 5 the circumstances are exaggerated. In fact, the difference in size is only slightly, but defined so that the valve actuating pressure P ₂₀ always exerts on the valve piston 22 a differential force corresponding to the size difference of the active surfaces 23 and 24, which counteracts the force of the valve spring 25. Since the valve piston 22 can be made very accurate to the size difference of the active surfaces 23 and 24, and the differential force correspondingly small and the valve spring 25 advantageously softer than in the embodiment of FIG. 4 be. Correspondingly low forces required the adjusting device 27, 28. The adjustment valve 20 is more sensitive overall, and it can be the switching times of the adjustment valve 20 is shortened.

The inlet I for the fluid to be controlled or opens in all switching positions of the adjusting valve 20 in the fluid chamber 26. In the illustrated switching position, the switching position of the adjusting valve 4 in the 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 of the other terminal 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 connected to the reservoir 11 and thus connected without pressure. 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 reservoir 11 via this. If the control signal changes its signal level, in the exemplary embodiment from the lower to the upper signal level, the magnetic coil 27 is energized and shifts the armature 28 against the force of the valve spring 25 in the axial direction first in the middle switching position and with a correspondingly long switch-on until 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 still opens. In the first switching position, the valve piston 2.2 assumes such an axial position that the fluid space 26 is in axial overlap with both the inlet I and the port A, while the valve piston 22 in the respective axial position the port B of the Fluid space 26 fluidly separates. In the first switching position, the fluid of the partial flow 16 is passed through the fluid space 26 and the port A in the pressure chamber 8, while the pressure chamber 9 via the port B and a passage C of the valve piston 22 to the outlet O and finally connected to the reservoir 11 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 displaces the adjusting device 27, 28 from the fluid space 26 separates. A cylindrical jacket region of the valve piston 22, which forms a further narrow sealing gap with the valve housing 21, radially adjoins the active surfaces 23 and away from the adjusting device 27, 28, as long as the adjusting valve 20 does not assume the first switching position in which the valve piston 22 occupies the axial position in which the fluid space 26 is in axial overlap with the port A.

The adjusting device 27, 28 with the associated control device switches the adjustment valve 20 over the entire operating range of the unit 14 and controls or regulates the axial position of the adjustment 5-7 and consequently the delivery volume of the positive displacement pump over the entire volume flow range, for the adapted supply of the unit 14 is required. The fluidic valve actuating pressure P ₂₀ and the valve spring 25 serve as a backup application 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 connector. The Verstellverztil 20 is designed so that in the event of failure, the delivery volume of the pump from maximum towards minimum is adjusted only when reaching a fluid supply pressure P ₁₄ , which is greater than a maximum fluid supply pressure P ₁₄ , which is established with proper operation of the adjustment valve 20 , For this purpose, the valve spring 25 is installed with a biasing force which is greater than a force which exerts a maximum Ventilstelldruck P ₂₀ , which can be set with proper function, on the valve piston 22.

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

rotation 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,

   characterised in that

   f) the valve spring (25) 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.
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 (R₅);

    - 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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