GB2362192A

GB2362192A - Regulatable pump

Info

Publication number: GB2362192A
Application number: GB0111550A
Authority: GB
Inventors: Marko Gretzschel; Nico Jakel; Tilo Koch; Jorg Patzold
Original assignee: DaimlerChrysler AG
Current assignee: Daimler AG
Priority date: 2000-05-12
Filing date: 2001-05-11
Publication date: 2001-11-14
Anticipated expiration: 2021-05-11
Also published as: DE10023330C1; GB2362192B; GB0111550D0; FR2808847A1; FR2808847B1

Abstract

A regulatable pump 1 has a suction side provided with an inflow 2, a delivery side provided with an outflow 3 and a regulating device 14 by means of which the volume flow and / or pressure at the outflow can be adjusted. The regulating device 14 is controlled by a 3/2-way valve 10. The regulating element may have a regulating piston 13 which is supported in the pump casing by a spring 19 with a comparatively low spring constant. The boss 18 of a setting ring 15 may be arranged between the spring and the piston such that as the piston is depressed the eccentricity of the setting ring is altered regulating the outflow pressure / volume. The valve may be activated by a pressure derived electric signal.

Description

2362192 Regulatable piim m The invention relates to a regulatable pump for

the generation of pressure in an internal combustion engine with pressure circulation lubrication.

pump of this type is described in US Patent Specification 42 93 284.

hydraulic system for loading a hydraulic consumer is described in DE 43 34 167 AI. A further pump is known from DE 33 33 647 C2.

In such pumps, the volume flow or the pressure occurring at the outflow can be changed by adjusting the eccentricity of the so-called setting ring of a regulating device. For this purpose, for example, a regulating piston and a spring element counteracting the regulating piston and supporting the latter are provided. In this way, the volume flow, which, in the case of a non-adjustable pump, depends on the rotational speed of the internal combustion engine, can be limited at higher rotational speeds by very low eccentricity being set. In such pumps the lower the eccentricity of the setting ring is, the lower the volume flow also is, since, in this state, the chambers of the suction region and of the delivery region have approximately the same size and, due to the reduced or no longer occurring displacement, only a correspondingly reduced oil feed takes place.

Before such regulatable pumps were used, there was the problem, with nonregulatable pumps, that these had to be set to a maximum oil feed in the case of a minimum rotational speed of the internal combustion engine, in order to make it possible to supply the internal combustion engine with sufficient oil even in hot-idling states. At higher rotational speeds, however, such pumps, by being dependent on rotational speed, fed too great a volume flow, the result of which was that a large part of the oil which had already run through the pump was fed back into the suction region or into the oil sump again. Pumps of this type therefore had a very high energy requirement which also contributed to an increase in fuel consumption.

Pumps of this type, as described in DE 33 33 647 C2, thus make it possible to have a lower fuel consumption, as compared with the pumps previously used, since they necessitate a lower energy requirement.

However, setting when such a pump is started up and cut out or when the adjustment of the eccentricity of the setting ring begins and when it ends depends on the nature of the spring element which counteracts the pressure acting on the regulating piston. This leads to the pressure difference between the start-up and cut-off of such pumps often 2 being very high, since the spring has to execute a relatively long excursion from maximum to minimum eccentricity. For the designer of such a pump, this means, in practice, that, to achieve a desirably low volume flow at a specific pressure, he must reduce the volume flow even when the pressure is very much lower. If the designer sets this point too low, there is no guarantee of a sufficient oil supply at all the operating points, but if the point is selected too high, this may lead to an inadmissably high oil pressure, with the risk of failure of individual sealing elements.

The present invention, therefore, seeks to provide a regulatable pump which can comply with the oil requirement of the assembly supplied by it, in particular an internal combustion engine, and in which, at the same time, there is both a sufficient oil supply at each operating point and an effective limitation of the oil pressure.

According to the present invention, there is provided a regulatable pump for the generation of pressure in an internal combustion engine with pressure circulation lubrication, with an inflow, an outflow and a regulating device, by means of which the volume flow and/or the pressure at the outflow is adjustable, the regulating device having a pressurecontrolled valve and a regulating element assigned to the pump for controlling the feed capacity of the said regulating element, the pressure-controlled valve comprising a 3/2way valve which releases the outflow at a low feed pressure and releases a regulating line connected to the regulating element at a high feed pressure.

By means of the pressure-controlled valve device designed according to the invention as a 3/2-way valve and located in the regulating line to the regulating element, it becomes possible for the regulating line to the regulating element to be released only when a specific defined pressure level is reached in a region downstream of the outflow. Thus, in the case of a specific pressure, this is immediately transferred via the regulating line to the regulating element which is capable of reducing the volume flow of the pump with the aid of the regulating device in a very short time and therefore also with a very small pressure difference. Advantageously, therefore, a much smaller pressure difference is obtained between start-up and cut-off than is the case with pumps known hitherto, and a greatly improved cut-off behaviour of the pump is brought about.

According to the invention, then, it is possible to use a very much softer spring, that is to say a spring with a lower spring constant, which is immediately compressed completely at the preselected pressure which occurs abruptly after the switching of the valve device. A spring with a lower spring constant may be used, thus bringing about a reduction in the maximum obtainable pressure and the power consumption in corresponding operating 3 states and also the avoidance of damage to sealing elements. This is possible, since, up to the switching of the valve device, the spring used in the regulating element of the pump has to absorb only forces within the pump and, by contrast, has to support the setting ring. The regulation of the pump is thereby uncoupled from the disturbing forces prevailing within the pump, and a considerably improved cut-off behaviour of the pump can be brought about.

Advantageous refinements and developments of the invention may be gathered from the subclairns and from the exemplary embodiment illustrated in principle below and described with reference to the drawing in whi& Figure I shows a circuit diagram of a regulatable pump according to the invention; Figure 2 shows a section through an embodiment of the regulatable pump; and Figure 3 shows a graph -in which the respective volume flow of two different pumps is plotted against the pressure.

The circuit diagram according to Figure I illustrates highly diagrammatically a Tegulatable pump I with an inflow 2 and with an outflow 3. The inflow 2 is located on a suction side 4 of the pump I and is connected to an oil tank 5. By contrast, the outflow 3 is arranged on a delivery side 6 of the pump I or is attached to the latter. Furthermore, a driveshaft 8 of the pump I and a regulating line 9 leading to the pump I are provided.

Arranged in the outflow line 7 and in the regulating line 9 is a valve device 10 (a 3/20way valve). The outflow fine 7 has branching off from it a further control fine I I which leads to the valve device 10 and which is capable of changing over the latter in a way known per se. It can also be seen that the regulating fine 9 leading to the pump 1 emanates from one outlet of the valve device 10. The outflow line 7 is continued from another outlet of the valve device 10 to a merely diagrammatically illustrated internal cornbustion engine 12 with pressure circulation lubrication.

With the valve device 10 in the present position, the regulating line 9 is shut off, that is to say there is no pressure at the pump-side end of the regulating line 9 and the pump I feeds the oil through the outflow he 7 to the internal combustion engine 12. When a specific freely selectable pressure level is reached in the outflow line 7, the valve device 10 is brought into its second position via the control line I L The oil leaving the delivery side 6 then not only flows through the outflow 3 to the internal combustion engine 12, but the corresponding pressure also occurs in the regulating line 9. Consequently, a closed control loop for regulating the pump I is obtained from the pump 1, the outflow 3, the control fine 11, the regulating line 9 and the valve device 10.

4 The regulating pressure in the regulating line 9 acts on a regulating element, illustrated in Figure 2, which comprises a bolt 13 and which is also designated as regulating piston 13 and is part of a below-described regulating device 14 of the pump 1, by means of which the volume flow and/or the pressure at the outflow 3 of the pump 1 can be adjusted.

As can be seen in Figure 2, in the present case, the pump 1 is a vanecell pump 1, but there may also be another form of a regulatable pump 1, for example an internally or externally geared pump, a positive displacement pump or else a centrifugal pump. In addition to the regulating piston 13, the regulating device 14 also has a setting ring 15, known per se, which is mounted on a casing 17 of the pump 1 via a bearing journal 16. On the side located opposite the bearing journal 16, the setting ling 15 has a boss 18, on which the regulating piston 13 acts from one side and a spring 19 supported on the casing 17 acts from the other side.

The driveshaft 8, a rotor body 20, in which are located a plurality of radially displaceable vanes 21 arranged so as to be distributed over the circumference, and a guide ring 22 for the radial inner support of the vanes 21 against the setting ring 15 are situated inside the setting ring 15 in a known way.

The delivery side 6 and the suction side 4 of the vane-cell pump 1, which are both of kidney-shaped design, can also be seen in Figure 2. The inflow 2 to the suction side 4 can be seen, in contrast to the outflow 3, concealed in the illustration, of the delivery side 6. In the state illustrated, the regulating device 14 of the vane-cell pump 1 has maximum eccentricity, that is to say the spring 19 is deflected completely, but the regulating piston 13 not at all. I then, a specific pressure occurs in the regulating line 9, which in Figure 2 terminates directly above the regulating piston 13, the regulating piston 13 is deflected in the axial direction and moves the boss 18 downwards, with the result that the spring 19 is compressed. Since the spring 19 has a relatively low spring constant, it is compressed in a very short time and the regulating device 14 assumes the position of minimum eccentricity.

As a result of the eccentricity of the setting ring 15 being low in this position, the pump 1 can feed only a very small oil quantity, even when the drive shaft 8 rotates at a very high rotational speed. When the pump 1 is operating normally, the low spring constant of the spring 19 gives rise to lower maximum pressures, without the risk of an insufficient oil supply due to a premature start of regulation. This may arise, according to the prior art, when internal (disturbing) forces and the pressure force of the regulating piston 13 act simultaneously, in the regulating device 14 of the pump 1, on a spring 19 which is used without the valve device 10 described, acting as a pilot control valve. Furthermore, the spring 19 ensures that the setting ring 15 is in the position of maximum eccentricity at the points in time when the regulating line 9 is pressureless. As already described above, the pressure in the regulating fine 9 depends on the state of the valve device 10 which, in the circuit according to Figure 1, switches at a specific pressure in the outflow line 7 and thus, in turn, gives rise to a pressure on the regulating line 9.

Figure 3 shows a graph in which the volume flow Q is plotted against the pressure p. This graph illustrates three different regulating curves which are to be considered as examples of the pressures indicated and which are discussed in more detail below. In the case of the curve III, the valve device 10 described above is used, in contrast to curves I and II.

Curves 1 and H show the regulating behaviour of pumps according to the prior art.

A start of regulation at a higher pressure is selected in curve I in order to maintain a minimum necessary pressure level when the pump 1 is in operation. The inadmissably high maximum pressures described may therefore arise.

By contrast, in a spring design according to curve II, a permissible level of the maximum pressure is ensured. In this case, due to the early start of regulation, there is no guarantee of a sufficient delivery of the pump 1 at all the operating points.

Curve M shows the regulating behaviour when the valve device 10 described is used. Both a permissible maximum pressure level and a delivery of the pump 1 at least necessary at all the operating points are ensured. By the valve device 10 described being used, the pressure difference between the start of regulation and the end of regulation of the pump 1 is reduced to a n-fininium value.

Alternatively to the described use of the pressure in the outflow line 7 and of the return of the latter via the control fine 11 to the valve device 10 as a regulating variable for the regulating element or the regulating piston 13, the oil pressure generated or brought about by the pump 1 may also be measured at any desired location in the internal combustion engine 12 or, in general, of the consumer and be transmitted electronically to the valve device 10. Then, when a predetermined pressure level is reached, the valve device 10, actuable in such a case by means of an electrical signal, can release the regulating line 9 to the relating piston 13 and cause an adjustment of the regulating device 14. The valve device 10 would then not necessarily have to be arranged in the outflow line 7, but only in the regulating line 9.

6

Claims

1. A regulatable pump for the generation of pressure in an internal combustion engine with pressure circulation lubrication, with an inflow, an outflow and a regulating device, by means of which the volume flow and/or the pressure at the outflow is adjustable, the regulating device having a pressure-controlled valve and a regulating element assigned to the pump for controlling the feed capacity of the said regulating element, the pressure-controlled valve comprising a 3/2-way valve which releases the outflow at a low feed pressure and releases a regulating line connected to the regulating element at a high feed pressure.

2. A pump according to Claim 1, wherein the 3/2-way valve is arranged in the outflow and releases the regulating element when a settable pressure is reached.

3. A pump according to Claim 1, wherein the 3/2-way valve releases the regulating line by means of an electrical signal derived from a specific pressure within the internal combustion engine.

4. A pump according to any one of Claims I to 3, wherein the regulating element has a regulating piston which is supported on a casing of the pump by means of a spring having a comparatively low spring constant.

5. A pump according to Claim 4, wherein a boss, which is part of a setting ring located within the casing, is arranged between the regulating piston and the spring.

6. A regulatable pump for the generation of pressure in an internal combustion engine with pressure circulation lubrication, substantially as described herein with reference to and as illustrated in, the accompanying drawings.