GB2049526A - <A device for forming transition surfaces at the edges of holes in cylinders - Google Patents

Abstract

A device for the forming of transition surfaces (18) between oil passages (17) and a sliding surface (6) of a slide bearing, and more generally for forming surfaces blending smoothly with the sliding surface (6) of the bearing, comprises a mechanism for generating of the pressure force of a burnishing roll (5) and having at least two servos (2,3) acting on a mechanism 4 for transferring of the pressure force to the burnishing roll. The stroke lengths (51, 52) of the servos are limited by means of adjustable stops (12, 16). At least one servo preferably hydraulic servo (2) generates a variable force depending on the changes of the position of its piston (10). The servos are preferably connected in-series. <IMAGE>

Description

SPECIFICATION A device for forming transition surfaces at the edges of holes in cylinders The subject of the invention is a device for forming transition surfaces at the edges of holes in cylinders, such as transition surface between oil passages and the sliding surface of a sliding bearing, e.g. such transition surfaces which adjoin tangentially said sliding surface. Transition surfaces may be for example those between surfaces of oil holes, pockets or clearances and the sliding surface, as well as between a face of a bearing and its sliding surface. It is also possible to apply the device wherever a tangent, or in other words an edgeless course of transition surfaces e.g. transition surfaces which blend smoothly with adjoining surfaces, is of the substantial importance for optimisation of the flow of a fluid.

There are known devices for burnishing a sliding surface of a bearing by means of a roll or a ball which is pressed down pneumatically, by a spring or hydraulically to a rotating and shifting bearing (German Patent Specifications (DR-PS) 431048 cl.

67a 10, DR-PS 644268 cl. 67a 31/10). For burnishing cylinder holes there are also applied several balls or rollers (DE-PS 923953, cm. 67a 9, DE-PS 935476 cl. 67a 9). There is also known a device wherein rolls are pressed down to the surface being machined by means of a hydraulically supplied cylinder (DE-AS 1279499 cl. 67a - 9). In said device, for each roll two hydraulic cylinders are provided whose favourable configuration enables skew setting of rolls during burnishing. From the patent specification DE-PS 1139767 cl. 67a 10 there is also known a device wherein a single roll is pressed down by means of a hydraulic system.The roll is suspended flexibly on leaf springs which are initially stressed by means of a hydraulic pressing-down force due to which the roll is pressed down with a constant force. The movement of the roll is limited in both directions by stops. However, none of the known devices for burnishing of the sliding surface can be used for the simultaneous forming of transition surfaces between oil passages and the sliding surface of a bearing. This results from the fact that in the vicinity of the edge of the oil passage the roll decreases its contact area with the bearing, and as a result of the constant pressing down force of the roll its unitary pressure increases and the edge undergoes an undesirable deformation or even spalling.However, there is generally known the formation of transition surfaces, for example multi-edged surfaces, in order to provide a continuous, hydro-dynamically carrying, thin film of a lubricant. Due to this the cavitational erosion as well as an increased resistance of flow and friction is avoided, which has a substantial effect upon the durability of a slide bearing, especially a heavily loaded bearing. It is known that an oval transition surface between the sliding surface and the oil passage, which adjoins tangentially the sliding surface, as described in Polish Patent application No. P.212032, is especially advantageous. These transition surfaces have been hitherto formed only manually, for example by means of a scraper, which produced an uneven and rough surface thereby also causing interruptions in the supply of the lubricant.

An advantage of the invention is that it makes it possible to design a possibly simple device adapted for the mechanical and reproducible forming of transition surfaces by a cold work method with the possibility of simultaneously burnishing the sliding surface of the bearing, whereby the transition surface being formed extends tangentially to the burnished sliding surface of the bearing.

According to the invention the mechanism producing the pressing down force of the burnishing tool, which may for example, be in the form of a roll, comprises at least two independently actuable servos arranged to act on the same mechanism for transferring of a pressure force to the tool and to generate different and adjustable forces.

The stroke lengths of these servos may be limited by two adjustable stops, whereby at least one servo generates a variable force depending on the changes of the position of its piston rod. The pressure transfer mechanism may comprise a double-arm lever having a leverage which is preferably 1:1, and the pressure generation mechanism is preferably provided with one spring-type servo providing a substantially constant force through an operating cycle, and one hydraulic servo producing a force which decreases as its piston approaches its corresponding stop, wherein the servos are connected in-series and the values of strokes of the servos are set by means of the stops so that the stroke of the spring-type servo is that much larger than the stroke of the hydraulic servos as the force of the hydraulic servo is larger than that of the spring-type servo.

A device according to the invention can serve not only for burnishing of the sliding surface, but also for the optimum forming of a transition surface using the same burnishing tool. This possibility results from the fact that during burnishing of the sliding surface the pressure forces of the servos sum up, but at a decrease of the contact area between the tool and the sliding surface in the vicinity of its edge with the oil passage the pressure of the tool, which falls to a unit of the surface, remains constant because at this moment the pressure force generated by at least one servo decreases nearly proportionately to the changes of the contact area of the tool. The number of servos applied depends on the shape of oil passages and the material of which the sliding bearing is made.The invention also renders it possible not only to form transition surfaces between the sliding surface and the oil passages situated within this sliding surface, but also to form the edges of the face surface of a bearing, which also facilitates the flow of a lubricant in a required manner.

An embodiment of the invention wil now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a cross-section of a device for burnishing the bushings of a sliding bearing including a mechanism for generation of a pressure force and a mechanism for transferring this force to a tool, and Figure 2 is a diagrammatic representation of a simplified distribution of the pressure force along the path of the burnishing tool, as well as the force of the spring-type servo.

The mechanism 1 for the generation of the pressure force comprises a hydraulic servo 2 and a spring-type servo 3. The servos act upon a lever 4 whose end is provided with a burnishing roll 5. The ratio of the lengths of the arms of the lever 4 is 1:1.

The roll 5 is pressed down to the sliding surface 6 of a bearing mounted on a support 7. In order to generate pressure, a hydraulic fluid is pressed through a nozzle 8 to a space 9 of a cylinder. Said hydraulic fluid acts on a hydraulic piston 10 which acts on a lever 4 through intermediary of a push rod 1 1. The stroke of the piston 10 is limited by an adjustable stop 12. The push rod 11 is provided with a stopper ring 13 on which a spring 14 acts. Said spring rests on an adjusting ring 15. The length of stroke S2 of the spring-type servo 3, so also of the push rod 11, is adjusted by means of a second adjustable stop 16. The hydraulic servo 2 operating with a bigger pressure force has a smaller stroke S1 than a stroke S2 of the spring-type servo 3 operating with a smaller pressure force F2.Moreover, settings of the stops 12 and 16 are selected so that strokes S1 and S2 of the servos are inversely proportional to the forces generated by these servos. Forces generated by the servos sum up thus giving the pressure force F1 with which the roll 5 is pressed down. After selecting of a pressing-down force F1 of the roll, required for a given bearing, it is introduced to the interior of the bearing and the device is actuated. At burnishing of the sliding surface 6 of the bearing the piston 10 and the push rod 11 do not change their positions because the contact area of the roll and its pressing-down force are constant.At the edge of an oil passage 17 the contact area of the roll with the sliding surface 6 decreases, thus the unitary press ure of the roll increases and the cold-work depth of a transition surface 18 begins to increase. The roll together with the lever 4 start to move in a radial direction, due to which the push rod 11 moves under the action of the servos, and the strokes S1 and S2 of said servos begin to decrease. An expansion of a spring 14 practically does not change its force F2 very much, whereas the force generated by the hydraulic servo begins to decrease. The total press ure force of the roll begins to decrease correspond tingly to the decreasing of the stroke S1 of the hydraulic servo, as well as to the changes of the contact area of the roll.Since the stroke S1 of the hydraulic servo is smallerthan the stroke S2 of the spring-type servo, the piston 10 comes to rest on its stop 12 before the stopper ring 13 contacts the stop 16 of the spring-type servo. As a result, when the cold-work depth ofthetransition surface 18 exceeds the value of the stoke S1 of the hydraulic servo, the pressure force F1 of the roll begins to decrease to the value of the force F2 of the spring-type servo, which acts on the roll until the stopper ring 13 rests on the stop 16 of the spring-type servo. A further move ment of the roll in the oil passage 17 is interrupted.

An analogous process of forming and burnishing occurs at the change of the advance direction of the support 7, when the roll enters the sliding surface of the bearing. First of all, only the force of the spring 14 acts until the moment when the push rod touches the piston 10 and its pressure force sums up with the force F2 of the spring 14. After the machining process is completed, the roll is moved away from the sliding surface of the bearing by means of a circular cam 19 and guided outwards from the bearing.

Claims (7)

1. A device for forming transition surfaces at the edges of holes or other recesses in, cylinders which device is provided with a burnishing tool, a mechanism for generating a pressure force on the tool, and a mechanism for transferring said force to the tool, wherein said mechanism for generating the pressure force includes at least two independently actuable servos arranged to act independently on the same mechanism for transferring the pressure force and having different and adjustable forces, the stroke lengths of the servos being limited by means of adjustable stops, and at least one servo being adapted to generate in use a variable force depending on the change of the position of a piston rod thereof.

2. A device according to claim 1, wherein said mechanism for transferring said pressure force comprises a double-arm lever, and said mechanism for generating a pressure force comprises a springtype servo and a hydraulic servo for generating a force which decreases as a piston thereof reaches the stop thereof, the servos being arranged to act in series for providing a combined pressure force to said mechanism for transferring said force to the tool.

3. A device according to claim 3 wherein said spring-type servo generates a force which is substantially constant during an operating cycle of the device to form a transition surface.

4. A device according to claim 2 or claim 3, wherein each of said servos is provided with stop means to limit the stroke of the corresponding servo, said stop means are arranged so that the respective strokes of the servos are such that the stroke of the spring-type servo is that much greater than the stroke of the hydraulic servo in accordance with the amount that the required force of hydraulic servo is greater than the required force of the spring-type servo.

5. A device according to any of claims 2 to 4 wherein the double-arm lever has a leverage ratio of 1:1.

6. A device according to any preceding claim wherein the burnishing tool is in the form of a roll.

7. A device for forming transition surfaces at the edges of, or at the edges of holes or other recesses in, cylinders, the device being substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.