FR2705403A1 - Pressure limiting device in an engine lubrication circuit. - Google Patents

Abstract

Device for limiting the pressure of the oil in a pressurized lubrication circuit of an internal combustion engine, comprising a relief valve (1) adapted to close a return line connecting the pump delivery duct to the duct suction thereof or to a reservoir, this valve comprising a body (2) enclosing a shutter member (3) urged to close by a return spring (7), characterized in that a second return spring (8) acts on the shutter member in the direction opposite to said first return spring (7).

Description

PRESSURE LIMITATION DEVICE

  IN AN ENGINE LUBRICATION CIRCUIT

  The present invention relates to a device for limiting the pressure in a lubrication circuit of an internal combustion engine, so as to limit the pressure of the oil discharged into the circuit by a pump driven in

rotation by the motor.

  It is known, in particular by the publication Fr 89/09434, to use at the outlet of the oil pump a relief valve capable of closing a return pipe putting the pump discharge pipe and the oil reserve into communication. again the suction pipe of the pump. The valve opens when the pressure of the pumped oil reaches a predetermined threshold. This pressure limitation makes it possible to avoid excessive consumption of energy due to the driving of the pump, as well as rapid wear of the latter or premature deterioration of other elements of the circuit. Relief valves generally include a hollow body disposed at the inlet of the return pipe which contains a movable shutter member (such as a piston, a ball or even a valve) which is permanently biased by a spring against a stop. or a seat at one of the open ends of the body, against the hydraulic pressure exerted

on the active side of the organ.

  Thus the pressure of the oil exerted on the active face of the shutter can push the latter against the return spring, and the oil can then flow into the return line which is then unmasked. . As soon as the pressure stops, the spring pushes back the shutter

  then closing the inlet of the return line.

  Such an assembly has a certain number of drawbacks and in particular a space requirement and a

relatively significant noise.

  Indeed, the action of the return spring tends to cause the shock of the shutter member on its seat or on its stop when it is closed, and this shock is all the more violent as the stiffness of the spring is strong. As a result, to avoid noise from the valve, it is necessary to use a spring of fairly low stiffness, which then requires having a spring of great

  length to keep the same threshold value.

  The present invention therefore relates to a simple embodiment of such a device for limiting the pressure in a lubrication circuit, making it possible to remedy the drawbacks of the prior art, while ensuring both a reduced bulk and the elimination

from any noise.

  The device for limiting the pressure of the oil in a pressurized lubrication circuit of an internal combustion engine according to the invention comprises a relief valve suitable for closing a return line connecting the discharge line of the pump to the suction pipe thereof or to a reservoir, this valve comprising a body containing a shutter member urged to close by a spring

reminder.

  According to the invention, the pressure limiting device is characterized in that a second return spring acts on the shutter member in the opposite direction to said first

spring.

  According to another characteristic of the pressure limiting device according to the invention, the shutter member rests in the closed position against the second spring, the second spring then constituting an elastic stop for

the shutter member.

  According to one embodiment of the pressure limiting device according to the invention, the shutter member is formed by a piston mounted to slide in a corresponding cylindrical bore, this piston being subjected to the antagonistic action of two helical springs of pressure s extending between the ends of

the bore and the piston.

  According to another characteristic of the pressure limiting device according to the invention, the first helical spring recalling the piston in its closed position has a stiffness much greater than that of the second spring, which makes it possible to obtain a device

extremely compact.

  The objects, aspects and advantages of the present invention will be better understood from the

  description given below of a mode of

  embodiment of the invention, this embodiment given by way of nonlimiting example, with reference to the appended drawing, in which: FIG. 1 is a view in axial section of the device for limiting the pressure according to

the invention.

  In accordance with FIG. 1, only the constituent elements of the limitation device have been represented, necessary for the understanding of

the invention.

  Referring to FIG. 1, there is seen a device for limiting the pressure in a lubrication circuit which essentially comprises a discharge valve 1. This valve 1 comprises a hollow body 2 containing a shutter member such as a piston 3 mounted sliding in a corresponding cylindrical bore 4. The bore is provided with an inlet orifice 10 communicating with the discharge pipe of the oil pump not shown, and with an outlet orifice 9 communicating with a return pipe to the oil tank or at the

pump suction line.

  The inlet 10 opens at one end of the bore 4 and the thrust of the pumped oil is exerted on one of the transverse faces

  of the piston 3 delimiting a pressure chamber 6.

  The outlet 9 opens into the side wall of the bore and can be masked by the piston 3 when the latter occupies its position of

closing in the bore 4.

  Between the piston 3 and the two axial ends of the bore 4 are interposed two helical pressure springs. A first helical spring 7 of high stiffness acts on the face of the piston opposite to the pressure chamber 6, to return the piston 3 to its closed position. A second spring 8 of low stiffness is arranged in the pressure chamber 6 and constitutes an elastic stop for the piston 3

subject to spring thrust 7.

  The operating mode of the oil pressure limiting device is as follows. When the engine is running at low speed, the oil pressure in the pressure chamber 6 corresponding to the pump discharge pressure is low and therefore exerts only a slight push on the piston 3, the latter is so

  held by the spring 7 in the closed position.

  When the speed of rotation of the motor increases, the discharge pressure rises in the pressure chamber 6 until the piston 3 moves, against the spring 7, and thus put in communication the chamber 6 and the orifice outlet 9. This communication causes the return of part of the oil discharged to the oil tank or the suction line of the pump, and therefore generates the stabilization of the discharge pressure. Thanks to the use of the spring 8 as a stop for the piston 3, the active face of the piston 3 subjected to the hydraulic pressure action always has the same surface, in fact the spring 8 is permanently in contact with the piston 3, and this unlike the devices according to the prior art o the shutter members come to bear against 1s of the fixed seats. This arrangement therefore eliminates the sudden variations in thrust due to the separation of the obturator member from its seat, causing untimely beating of the spring 7

and piston 3.

  When the hydraulic thrust decreases, the action of the spring 7 again becomes preponderant and causes the return of the piston 3 to the closed position of the outlet orifice 9. The presence of the spring 8 then makes it possible to dampen the return of the piston 3 and avoids thus any impact of the latter against the valve body. This arrangement makes it possible to use a spring 7 of high stiffness and

therefore compact.

  Of course, the invention is in no way limited to the embodiment described and illustrated

  which was only given as an example.

  On the contrary, the invention includes all the technical equivalents of the means described as well as their combinations if these are carried out

following his spirit.

Claims (1)

  [11] Device for limiting the pressure of the oil in a pressurized lubrication circuit of an internal combustion engine, comprising a discharge valve (1) suitable for closing a return line connecting the discharge line of the pump to the suction pipe thereof or to a reservoir, this valve comprising a body (2) containing a shutter member (3) urged to close by a return spring (7), characterized in that a second return spring (8) acts on the shutter member in the opposite direction to said first return spring (7).   [2] Pressure limiting device according to claim 1, characterized in that the shutter member (3) rests in the closed position against said second spring (8), said second spring (8) constituting an elastic stop for said shutter member.   [3] Pressure limiting device   according to any one of claims 1 to 2,   characterized in that said obturating member is formed by a piston (3) slidably mounted in a corresponding cylindrical bore (4), said piston (3) being subjected to the antagonistic action of two helical pressure springs (7,8) s extending between the ends of the bore (4) and the piston (3). [4] Pressure limiting device according to claim 3, characterized in that the first helical spring (7) recalling the piston in its closed position has a very stiffness   greater than that of the second spring (8).