EP1463888B1 - Device for pressure regulation of hydraulic pumps - Google Patents

Abstract

Device for pressure regulation of a hydraulic pump for pumping a hydraulic medium under pressure, comprising delivery-quantity regulation; a piston unit including first biasing element; a piston member; a first surface on the piston member to be biased by a first biasing force of the hydraulic medium in a first direction; a second surface on the piston member engaged by the first biasing element to be biased by a second biasing force in a second direction, opposite to the first direction; second biasing element to bias the piston member in addition to the hydraulic medium and the first biasing element, thus influencing the pressure of the hydraulic medium.

Description

Field of the invention:

The invention relates to devices for pressure control of hydraulic pumps, in particular for oil pumps with a flow control device for lubricating oil supply of internal combustion engines, with a control piston and a control spring for controlling the flow rate control device and with a control device for the control piston. Such control devices have the task of the delivery of the hydraulic pump, and in particular an oil pump, to changing needs, e.g. the lubrication system of an internal combustion engine in terms of oil pressure and oil quantity to adapt. As a result, unnecessarily high oil pressures are avoided, as well as kept low the drive power of the lubricating oil pump in view of a good efficiency of the internal combustion engine.

Background of the invention:

Known oil pumps with delivery rate control, in which the oil delivery rate adapts to the demand of the internal combustion engine to be supplied according to the oil pump design, have a lower oil pump drive power than oil pumps with short-circuit control. The flow rates are controlled essentially by the oil pressure, which take place in particular at higher engine speeds as well as at low operating temperatures appropriate Fördermengenabregelungen.

In simple oil pump versions with flow control, the oil pressure is determined directly by a control spring. However, this embodiment has the disadvantage that the spring design must be made according to the maximum oil pressure demand at the highest engine speed, which then unnecessarily high oil pressures with correspondingly high drive power in the lower speed range result. A flow control exclusively by a control spring, as proposed for example in DE 3028573 and DE 3528651, continues with increasing stroke of the control spring by their increasing spring force to an additional oil pressure increase, so that the desired drive power advantage is at least partially compensated by reducing the flow rate due to the unnecessary increase in oil pressure.

The external gear oil pump with axial gear shift proposed in DE 10043842 A1 largely avoids the undesirable increase in oil pressure at flow rates. However, during control operation, your oil pressure pulsates through a slight regulation-dependent constant variation of the axial engagement overlap of the two conveyor gears. The axial gear shift counteracting friction forces amplifies this effect. For further minimization of flow rate and oil pressure, in particular according to the lower oil pressure requirement at low engine speeds, this throttle control requires additional electrical control components.

In DE 19915737 A1 a method for controlling the lubrication of an internal combustion engine is described in which the control of the oil pump is controlled depending on the operating state of the internal combustion engine via a map, wherein the characteristic quantities are taken from the engine control unit. An unspecified actuator of the oil pump sets the electrical controls in changes in the flow rate of the oil pump.

DE-C-753580 describes an oil pump with a variable speed delivery, in which the governor of an injection pump via a mechanical coupling changes the flow rate of the oil pump. Other embodiments of controllable oil pumps can be found in DE-A-37 26 800 and US-A-4,828,462.

Summary of the invention:

Based on this prior art, it is an object of the invention to provide a control device for oil pumps with a flow control device, depending on predetermined operating values, for example, from the operating speed of an internal combustion engine, reliable oil pressure as well as the oil flow rate largely minimized according to the hydraulic supply needs and thus the Drive power of the oil pump lowers.

To solve this problem, a device for pressure control of hydraulic pumps with the features mentioned is proposed, which is characterized in that the control piston has an effective surface for constantly applied oil pressure and continues to be acted upon by the drive with an additional force. This causes the oil pressure to set at least in two control pressure levels. For this purpose, the control piston, which can be acted upon by a drive device with a variable force, effects the associated setting of the flow rate control device.

Brief description of the drawings:

Fig. 1

eine fördermengenregelbare Außenzahnradpumpe mit elektromagnetisch veränderlicher Kraftbeaufschlagung ihres Regelkolbens;

Fig. 2

eine fördermengenregelbare Außenzahnradpumpe mit veränderlicher Kraftbeaufschlagung ihres Regelkolbens durch einen Schrittmotor;

Fig. 3

eine fördermengenregelbare Außenzahnradpumpe mit veränderlicher, hydraulischer Kraftbeaufschlagung eines gestuften Regelkolbens durch einen fliehkraftbetätigten Schaltkolben;

Fig. 4

eine fördermengenregelbare Außenzahnradpumpe mit veränderlicher Kraftbeaufschlagung ihres Regelkolbens durch ein Elektroventil und/oder durch eine drehzahlabhängige Öldrucfcbeaufschlagung;

Fig. 5

ein weiteres Ausführungsbeispiel, als Variante zu Fig. 3;

Fig. 6

eine Alternative zu Fig. 2; und

Fig. 7

ein bevorzugtes Ausführungsbeispiel einer Regeleinheit.

The invention will be explained in more detail with reference to the following drawings in terms of function and design options. Show it:

Fig. 1

a variable delivery outside gear pump with electromagnetically variable force application of their control piston;

Fig. 2

a variable delivery outside gear pump with variable force application of their control piston by a stepper motor;

Fig. 3

a variable delivery outside gear pump with variable, hydraulic application of force to a stepped control piston by a centrifugally operated switching piston;

Fig. 4

a variable delivery outside gear pump with variable force application of their control piston by an electric valve and / or by a speed-dependent Ölldrucfcbeaufschlagung;

Fig. 5

a further embodiment, as a variant of Fig. 3;

Fig. 6

an alternative to Fig. 2; and

Fig. 7

a preferred embodiment of a control unit.

Detailed description of the drawings

Fig. 1 shows a first embodiment of the pressure control device according to the invention for an external gear oil pump with flow control. In this case, this oil pump consists of an oil pump housing 1, in which a fixed on a drive shaft 2 drive gear 3 is arranged. The drive shaft 2 is mounted in a cover piston 4 associated with a cover piston 5. In a flow control is in a known manner relative to the drive gear 3 in meshing engagement with him sliding shift gear 6 is axially displaced, so that then by the changed meshing width, the oil flow rate is changed accordingly.

The sliding gear 6 is mounted on a non-rotating bolt 7, the right side a shift piston 8 and the left side carries a spring piston 9. This formed composite is referred to as a displacement unit 10. The shifting unit 10 is at its Displacement piston 8 constantly subjected to oil pressure, while counteracting the spring piston 9, a piston spring 11 as well as acting in the spring chamber 12, controllable control pressure make the flow control.

The control of the control pressure acting in spring chamber 12 is made via a control bore 13 of a control piston 14, which is acted upon at its active surface 15 via a connection 16 constantly with oil pressure. In the illustrated control position of the control piston 14 is its control pin 18 directly opposite to the control bore 13. The control pin 18 is bounded on the left side by a pressure groove 19 and the right side of a relief groove 20.

Since the control pin 18 is slightly narrower than the diameter of the control bore 13, a control pressure is adjusted in the control position shown in the spring chamber 12, which between the over another connection 21 in the pressure groove 19 applied oil pressure and one can be fed via the discharge groove 20, complete Pressure relief can be. Via a diagonal bore 22 in control piston 14, the relief groove 20 is in communication with the environment.

As soon as the oil pressure applied to the effective surface 15 exceeds the level of the maximum required operating oil pressure of, for example, 5 bar of the associated internal combustion engine, a displacement of the control piston 14 takes place against the force of the control spring 17 in order to reduce the control pressure in the spring chamber 12. This produces the displacement unit 10 shifted so far to the left for the purpose of a flow reduction until the oil pressure reaches the target value of, for example, 5 bar. A shortfall of the target oil pressure of 5 bar, in turn, by the control spring 17 to a shift of control piston 14 to the right, which triggers by increasing the control pressure in the spring chamber 12, a corresponding increase in flow with a resulting increase in oil pressure.

The required for lowering the oil pressure according to the invention control means of the control piston 14 consists of a magnetic coil 23 which exerts a magnetic additional force to the control piston 14 via a corresponding control by a control unit of the engine via its armature 24. A change in the additional magnetic force can be made either continuously or stepwise demand-oriented by the control unit, which has a corresponding effect on the control of oil pressure and flow rate of the oil pump.

The only after the oil filter 25 branching hydraulic connections 16, 21 and 26 to the displacement piston 8 and the control piston 14 have two advantages. On the one hand, the oil pressure behind the oil filter 25 is adjusted to the desired pressure level by the pressure control of the oil pump, so that regardless of pollution caused by variable pressure losses of the oil filter 25 a reliable oil pressure is ensured for the lubrication of the engine. On the other hand, all parts of the control device as well as all bearings of the oil pump, for example, the storage of the drive shaft 2 in cover piston 5 via an oil hole 27 from the displacement chamber 28, supplied with filtered oil, so that the reliability and the life of the oil pump can be increased.

Fig. 2 shows another embodiment of the invention with continuously variable oil pressure control. For the oil pressure reduction according to the invention, a stepping motor 29 with an adjustable spring system 30 for the control spring 17 of the now shown uncut control piston 14 is used instead of the solenoid 23 of Figure 1 here. Due to the basic position of the spring system 30 of control spring 17, which adjusts automatically without electrical control of the stepping motor 29, the maximum required operating oil pressure of, for example, 5 bar is ensured by the corresponding bias of the control spring 17. By an appropriately programmed control unit of the internal combustion engine, the oil pressure can be lowered as needed or even further increased in special applications.

Fig. 3 shows a preferred embodiment of the oil pressure and flow control according to the invention using the example of an external gear oil pump, in which the control device of the control piston takes place exclusively centrifugally dependent in two speed-related control pressure stages. The now formed as a stepped piston 51 control piston is derived from the control piston 14 of FIG. 1 and 2 respectively. On the left side, it has a control spring 52 and on the right side a first active surface 53, which is constantly subjected to oil pressure. A right-side second active surface 54 of stepped piston 51 is also acted upon at low operating speeds of the engine with oil pressure, so that an oil pressure control at, for example, 2.5 bar of the first control pressure stage takes place by an oil pressure effect on the two active surfaces 53 and 54 and the appropriately designed control spring 52. The engine at high speeds required oil pressure increase to an oil pressure level of, for example, 5 bar of the second control pressure level requires for the corresponding control function of the stepped piston 51 a complete pressure relief of the second active surface 54th Die Ansteuereinrichtung für den Umschaltung between the two control pressure levels by Öldruckbeaufschlagung or pressure relief of the second effective surface 54 of the stepped piston 51 is in this embodiment consists of a drive gear 55 arranged in speed-dependent centrifugal force valve.

The Fig. 4 belonging to Fig. 4 shows the compact centrifugal valve enlarged. It consists of a switching piston 56 and a switching piston spring 57. The switching piston 56 is aligned for spatial reasons obliquely to the radial centrifugal force direction, but could also be radially aligned in certain cases, i. its orientation must have at least one radial component. The stepped receiving bore of the switching piston 56 and the switching piston spring 57 can partially protrude even for reasons of space in a tooth of the drive gear 55. The position shown of the control piston 56 with a relaxed control piston spring 57 corresponds to low operating speeds with low centrifugal force. A control pin 59 located on the control piston 56 ensures the radial guidance of the control piston spring 57 and prevents its centrifugal force-induced deflections.

The pressure applied via the oil bore 27 and the associated peripheral bevel of the cover piston 5 on the control piston 56 oil pressure acts through its central bore 60 also constantly in the chamber of the switching piston spring 57. At low operating speeds, the oil pressure due to the position shown in Fig. 4 of the switching piston 56 via a Oblique bore 61 of drive gear 55 and passed through a connecting hole 62 of the oil pump housing 63 to the second effective surface 54 of stepped piston 51, thereby activating the first control pressure stage with, for example, 2.5 bar, oil pressure.

After exceeding the switching speed to activate the second control pressure level, for example, at 2500 / min, the switching piston 56 shifts centrifugal force against the switching piston spring 57 in its outer end position. As a result, the oil pressure increase to the second control pressure level of 5 bar of the stepped piston 51 relieved of pressure on its second effective surface 54 by a connection to the central bore 65 of the open-end drive shaft 58 is made via the oblique bore 61 and a circumferential groove 64 of the control piston 56 and other cross-sections ,

Referring to FIG. 3, FIG. 5 shows an exemplary embodiment in which the stepped piston 51 can be acted upon with oil pressure at its second active surface 54 by two further independent control devices shown in FIG. 5. The two control devices can, as shown in Fig. 5, both in combination with each other in function, but also each work for themselves in elimination of the other drive means.

The first drive means has on the drive shaft 74 a spiral groove 73 which is bounded on both sides by the circumferential grooves 75 and 76. It has a relatively small groove depth and generated upon rotation of the drive shaft 74 by occurring Ölscherkräfte over its length a speed-dependent pressure gradient. The left-side circumferential groove 75 is acted upon by the oil bore 27 with oil pressure. The pitch direction of the spiral groove 73 is now selected so that upon rotation of the drive shaft 74, the pressure gradient acting in the spiral groove 73 causes a pressure reduction in the right-side circumferential groove 76. The variable-speed pressure in the circumferential groove 76 is guided via a longitudinal bore of the drive shaft 74 and a connection bore 79 located in the housing 78 on the second effective surface 54 of stepped piston 51.

At maximum speed of the voltage applied in the circumferential groove 75 oil pressure, for example, 5 bar, reduced by a generated by the spiral groove 73, relatively high pressure drop to almost 0 bar in the circumferential groove 76, so that the second effective surface 54 of stepped piston 51 for the desired pressure control the oil pressure at 5 bar is effectively depressurized. With decreasing speed, the pressure drop across the spiral groove 73 is reduced continuously, so that pressure at the second effective surface 54 of the stepped piston 51 increases accordingly and an oil pressure control takes place at a speed-dependent variable pressure level.

The second, alone or together with the first installable, drive means for the stepped piston 51 consists of an electric valve 71 which switches the oil pressure on the second effective surface 54 when electrically activated to the oil pressure reduction of the oil pump. Thus, both active surfaces 53 and 54 are oil pressure loaded, so that the stepped piston 51 already exerts its control function, for example, at 2.5 bar oil pressure of the first control pressure stage against the force of the control spring 52 and provides the appropriate control pressure for flow control.

When the solenoid valve 71 is not actuated, the oil pressure supply is interrupted and a pressure relief or load of the second effective surface 54 is produced via a discharge port 72 on the solenoid valve 71. The now only on the first effective surface 53 of stepped piston 51 applied oil pressure shifts the start of control then to a higher value, for example, 5 bar, the second control pressure level. The second control pressure stage is at a defect-related interruption of the electrical connections of the solenoid valve 71st guaranteed as safety oil pressure for all operating conditions of the internal combustion engine.

In the example shown combination function of the two control devices shown in Fig. 5, a continuously variable speed oil pressure control can be performed at operating warm combustion engine through the spiral groove 73, but the solenoid valve 71 must then keep its connection to the stepped piston 51 by an additional function. When cold operation and then because of viscous oil effectively unusable effect of the spiral groove 73 then enters the solenoid valve 71 in operation. Its two-stage oil pressure control by pressurization or pressure relief of the second effective surface 54 of the stepped piston 51 is then carried out in a known manner.

In principle, the control of the oil pressure with the stepped piston 51 can also be carried out in several stages with a correspondingly designed graduated piston. In this case, its part-active surfaces, for example, would have to be subjected to a rotational speed offset by a multi-stage control device with oil pressure.

When using electrical components for the oil pressure control of an internal combustion engine, an arrangement of the electrical parts outside of the oil pump receiving crankcase is advantageous. While the load on temperature and / or oil-sensitive electrical parts is thereby reduced on the one hand, on the other hand, the electrical connections to the crankcase are also eliminated, whereby the accessibility to the electrical parts, for example for repair purposes, is improved. The solenoid valve 71 shown in Fig. 5, for example, be mounted externally on the crankcase. The electrically switchable Öldruckbeaufschlagung the second effective surface 54 of the stepped piston 51 can then be done via oil holes through the flange surface of the oil pump attachment to the crankcase. In the electrically generated effect of an additional force on the control piston 14 according to FIGS. 1 or 2, however, an external arrangement of the crank coil 23 or stepping motor 29 also requires a co-displacement of the control piston 14.

As an alternative to FIG. 2, the exemplary embodiment in FIG. 6 shows an arrangement in which the stepping motor 29 is combined with the control piston 80 in a common housing 81 to form a control unit 82. The externally mounted on the crankcase 84 control unit 82 ensures a trouble-free electrical connection 83 and a flange 85 penetrating the control bore 87 to the spring chamber 12 of the oil pump 86 a reliable oil pump pressure control.

To further increase the reliability of the control unit 82 is fed from an adjacent crankcase main oil hole 88 with purified oil filter 89 in pressurized oil. This pressure oil is constantly relevant to regulation via corresponding connection cross sections of the control unit 82 end face on the effective surface 90 of the control piston 80 as well as a line 91 in the displacement chamber 28 of the oil pump 86. The necessary pressure relief of the spring side of the control piston 80 as well as the discharge of oil from the spring chamber 12 at a flow rate control via corresponding connection cross-sections of the control unit 82 in the open to the interior of the crankcase 84 discharge channel 92nd

In Fig. 7, a working in two control stages, electrically controlled control unit 100 is shown with an arrangement on the crankcase. It consists of the already described with reference to FIG. 5 step piston 51, an associated housing 101 and an electric valve 102. As in the embodiment of Fig. 6, the oil pump 103 is pressure-controlled only via the connecting control bore 87 in this two-stage pressure control. As a result, as well as by a Ölpumpeninteme pressurization of the displacement chamber 28 with the delivery oil pressure (elimination of the line 91 of FIG. 6), an advantageous simplification of the oil pump is also possible with a two-stage pressure control. Without electrical control of the solenoid valve 102, the second active surface 54 of the stepped piston 51 is relieved of pressure via the left relief channel 92 in FIG. 7 so that the stepped piston 51 acted upon by the oil pressure only via the first effective surface 53 then executes the oil pump pressure control at a higher pressure control level with its control spring 52 , In contrast, with the electrical control of the solenoid valve 102 in addition, the second effective surface 54 of the stepped piston 51 is acted upon by the oil pressure, so that then the pressure control of the oil pump 103 is carried out at lowered pressure control level.

The control of the oil pressure according to the invention is largely independent of the temperature-dependent viscosity of the feed oil. This can be achieved by the proposed pressure control for oil pumps of motor vehicle internal combustion engines not only with warm engine, but especially in daily cold operation with low after an engine even low oil temperatures effectively reduced fuel consumption by not inconsiderably lowered oil pump drive services.

Numerous modifications are conceivable within the scope of the invention, for example individual features from various embodiments described above can be combined with one another and / or with the state of the art. It is also possible that approximately the drive means comprises a plurality of the above-mentioned components.

Claims (9)

1. A device for regulating the pressure of hydraulic pumps, in particular for oil pumps for supplying lubricating oil to internal-combustion engines, having means for regulating the quantity delivered and a piston unit (8, 9) acted upon by oil pressure and - counteracting the oil pressure - by a piston spring (11) as well as by a control pressure supporting said piston spring (11) for controlling the means for regulating the quantity delivered, characterized in that the control pressure is generated by a regulating piston (14, 51, 80), which has a working surface (15, 53, 90) to which oil pressure is constantly applied, a regulating spring (17, 52) for counteracting the oil pressure, as well as actuating means (23, 29, 56, 71, 73, 102) with an additional force acting on the regulating piston (14, 51, 80) for influencing the control pressure.
2. A device for regulating the pressure of hydraulic pumps according to Claim 1, characterized in that, as regards the structure of the actuating means, at least one of the following features is provided:

   a) the actuating means of the regulating piston (14, 80) is formed with a magnet coil (23) with armature (24) acting on the regulating piston (14, 80);

   b) the actuating means of the regulating piston (14, 80) is formed with a stepping motor (29) for adjusting the spring mechanism (30) of the regulating spring (17);

   c) the actuating means is formed with a speed-dependent centrifugal valve with a control piston (56) and a control-piston spring (57);

   d) the actuating means is formed with an electrically operated valve (71, 102);

   e) the actuating means (23, 29, 71, 102) is formed in such a way that, in the event of an electrical failure of the system, it automatically raises the oil pressure to the maximum control-pressure stage;

   f) the actuating means is formed with a helical groove (73).
3. A device for regulating the pressure of hydraulic pumps according to one of the preceding claims, characterized in that, as regards the structure of the regulating piston (14, 80), at least one of the following features is provided:

   a) the regulating piston takes the form of a step piston (51) with a second working surface (54), which can be subjected to oil pressure or relieved of pressure by the actuating means (56, 71, 73, 102);

   b) a stepped regulating piston is formed so as to be multistage and can be charged with oil pressure by a correspondingly multistage actuating means.
4. A device for regulating the pressure of hydraulic pumps according to one of the preceding claims, characterized in that the axis of the control piston (56) is disposed at an angle relative to the radial direction of the centrifugal force.
5. A device for regulating the pressure of hydraulic pumps according to one of the preceding claims, characterized in that the control piston (56) and also the control-piston spring (57) are disposed inside a delivery gearwheel (55) with partial insertion into a delivery cog.
6. A device for regulating the pressure of hydraulic pumps according to one of the preceding claims, characterized in that the control piston (56) has a guiding pin (59) for the radial guidance of the control-piston spring (57).
7. A device for regulating the pressure of hydraulic pumps according to one of the preceding claims, characterized in that the oil pressure for pressurizing the working surfaces (15, 53, 54, 90) of the regulating piston (14, 51, 80) is tapped downstream of an oil filter (25, 89).
8. A device for regulating the pressure of hydraulic pumps according to one of the preceding claims, characterized in that electric components of the oil pump control means (23, 29, 71, 82, 102) are disposed outside oil chambers and communicate with the oil pump (78, 86, 103) via hydraulic lines (87, 91).
9. A device for regulating the pressure of hydraulic pumps according to one of the preceding claims, characterized in that the regulating piston (14, 80) together with the stepping motor (29), or with the magnet coil (23) and/or the electrically operated valve (102), are put together in a common housing (81, 101) to form a regulating unit (82, 100).

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