JP5208009B2 - Plunger pump bearing - Google Patents

Description

  The present invention relates to a bearing used for driving a plunger of a plunger pump such as an automobile ABS.

  Instead of a conventional pump that drives a plunger by a combination of an electric motor and cam, a plunger pump having a motion conversion mechanism using a bearing is adopted so as to enable more stable pump driving. It has become like this. In this plunger pump, an eccentric shaft is connected to the motor output shaft, a general-purpose ball bearing is attached to the eccentric shaft, the outer peripheral surface of the outer ring of this ball bearing is brought into contact with the plunger, and the plunger is reciprocated by the rotation of the eccentric shaft. It is something to be made.

  By the way, with the recent high performance and high performance of ABS and the like, the load capacity required for the ball bearing tends to increase more and more, but the outer ring that collides with the plunger has a concentrated load on the outer peripheral surface. There are special circumstances that act. This one-point concentrated load generates a tensile stress in the inner diameter of the outer ring, and the tensile stress may cause breakage in the outer ring.

  In order to obtain a high-load type ball bearing so that such breakage does not occur, the outer ring thickness may be increased. However, simply increasing the outer ring wall thickness results in an increase in radial size, weight, and cost.

  Therefore, as shown in FIG. 5, a bearing is proposed in which an eccentric shaft 32 is connected to an output shaft 31 of a motor, and general-purpose ball bearings 33 are mounted on the eccentric shaft 32 in a double row (see, for example, Patent Document 1). . In this bearing, the outer rings 33a and 33a of the ball bearings are connected by a sleeve 34, and the outer peripheral surface of the sleeve 34 is directly brought into contact with the plunger 35 of the pump. If the double-row ball bearings are used in this way, the load can be distributed, so that the load capacity can be increased without increasing the size of the bearing in the radial direction.

JP 2001-187915 A

  However, when the ball bearings 33 are used in a double row, the bearing size in the axial direction increases. The present invention has been made in view of the above circumstances, and an object thereof is to improve the cracking resistance of the outer ring without changing the bearing main dimensions of the single row ball bearing.

According to the present invention, the inner ring of a ball bearing formed by interposing a plurality of balls between inner and outer rings is fitted to an eccentric shaft, and the outer peripheral surface of the outer ring is abutted against a plunger of a pump to rotate the eccentric shaft. A plunger pump bearing for reciprocating a plunger, characterized in that the thickness of the thinnest portion in the radial direction of the outer ring is 50% or more and 60% or less of the ball diameter without changing the main dimensions of the bearing. It is related to.

The present invention is based on the fact that the thickness of the thinnest portion of the outer ring in the radial direction is 50% or more and 60% or less of the ball diameter, and the material of the outer ring is SUJ2, and at least the outer ring is subjected to nitriding treatment, So-called “TM treatment” in which at least the outer ring is made of carburized steel, and at least the outer ring is heated to a temperature higher than usual and then slowly cooled around the Ms point (starting temperature of martensitic transformation). By applying nitriding treatment and TM treatment to at least the outer ring, the crack strength can be further improved. The “TM treatment” is a term commonly used by the applicant, and this TM treatment has an advantage that the life of foreign matters is improved because residual austenite increases.
Further, by setting the curvature radius r of the groove on the outer peripheral surface of the inner ring, which is the raceway surface of the ball, to D <2r <1.02D where D is the ball diameter, the surface pressure is reduced as the ball diameter is reduced. be able to.

  According to the plunger pump bearing of the first to seventh aspects of the present invention, the ratio of the wall thickness / ball diameter is 50% or more and 60% or less, so that the crack strength of the bearing is improved without changing the bearing main dimensions. An excellent effect of being able to be made can be achieved.

Sectional drawing of the bearing for plunger pumps concerning the Example of this invention. The figure which shows the specification of the execution example and the comparison example The side view of the testing apparatus of a durability test. The figure which shows the durability test result of an Example and a comparative example. Sectional drawing of the conventional plunger pump bearing.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a plunger pump bearing 1 used in the present invention. The bearing 1 is a single-row general-purpose ball bearing, and includes an inner ring 2, an outer ring 3, and a plurality of balls 4 interposed between the inner and outer rings. On the outer peripheral surface of the inner ring 2 and the inner peripheral surface of the outer ring 3, circumferential grooves 2a and 3a for guiding the circulation of the ball 4 are formed. The plurality of balls 4 are rotatably held by a cage 5 in order to maintain a circumferential interval between the balls 4. Seal plates 6 and 6 are mounted on both sides of the bearing 1. The seal plates 6 and 6 hold grease between the inner and outer rings and prevent foreign matters from entering from the outside.

  In the bearing 1 according to the embodiment of the present invention, as shown in FIG. 2, the thickness t (1.4 mm) of the thinnest portion in the radial direction of the outer ring 3 is 50% of the diameter D (2.8 mm) of the ball 4. Alternatively, it is set to 50% or more and 60% or less. The wall thickness t may be just 50% of the diameter D of the ball 4 or may be larger than 50% (D ≦ t), but should not exceed 60%. The reason for setting the wall thickness t in this way is as follows.

  That is, in order to improve the cracking resistance of the outer ring 3, it is necessary to increase the thickness of the outer ring, but in order to increase the thickness of the outer ring 3 without increasing the radial size of the bearing 1, the ball diameter is increased. There is no choice but to change the thickness of the inner ring 2 without changing it. Therefore, how to set the relationship between the outer ring wall thickness and the ball diameter becomes a problem. However, if the ball diameter is too small, the surface pressure of the circumferential groove 2a of the inner ring becomes excessive, and the durability of the inner ring may become a problem.

  In order to find the optimum relationship between the outer ring wall thickness and the ball diameter, the present inventors set the crack strength at two ratios as shown in FIG. 2 (50% in the example and 35% in the comparative example). The test was conducted.

  FIG. 3 is a schematic view of a test apparatus for testing the durability (cracking strength) of the bearing. In the figure, 10 is a pad, 11 is a drive roll, 12 is a fueling nozzle, 13 is a guide roll, 14 is a bearing outer ring as a test object, and 15 is a load roll. The bearing outer ring 14 is sandwiched between the drive roll 11 and the load roll 15, and a test is performed by applying a load while rotating the outer ring 14.

As shown in FIG. 4, the bearings according to the first to fourth embodiments, that is, the material of the outer ring, the first is made of carburized steel (L ₁₀ ), and the second is TM. Treated (L ₅₀ ), third treated with nitriding (L ₅₀ ), fourth treated with both TM treatment and nitriding (L ₅₀ ), and the above four bearings were tested for rotational cracking fatigue strength. Went. The comparative examples were all bearings having the same specifications as the examples except that the material was SUJ2.

  As a result of the test, as shown in FIG. 2, the crack strength was 4690N when the thickness / ball diameter ratio was 50%, and 2640N when the ratio was 35%. Further, when the thickness t of the thinnest part was 60% of the ball diameter, the surface pressure of the outer ring 3 reached 4200 MPa. This value was found to be approximately equal to the allowable surface pressure of the bearing outer ring.

  On the other hand, the test results of the rotational cracking fatigue strength are as shown in FIG. 4. In the case of carburized steel, the durability time is about 4 times longer. As a result, durability of about 53 times was obtained.

  Since the 50% bearing has a crack strength of 4690N, the safety factor for a load of 1000N is about 4.7 times.

  The plunger pump bearing 1 may be subjected to a maximum load of about 1000 N, but it is generally said that the fatigue strength is about 1/4 of the static strength. Therefore, it can be said that a crack strength of at least 4000 N is sufficient.

  From the above, it was found that a bearing having sufficient fatigue strength can be obtained by setting the thickness / steel ball diameter to 50% or more and 60% or less in consideration of variations in use conditions.

  In the bearing of the present invention, the outer ring strength is improved by about 80% compared to the conventional one (2640N → 4690N), which contributes to improved durability of the bearing and improved reliability of the plunger pump.

  The bearing for the plunger pump of the present invention can be applied to other than the plunger pump of the automobile ABS.

1 Bearing for plunger pump 2 Inner ring 3 Outer ring 4 Ball

Claims (7)

The inner ring of a ball bearing formed by interposing a plurality of balls between inner and outer rings is fitted to an eccentric shaft, and the outer peripheral surface of the outer ring is abutted against a plunger of a pump, and the plunger is reciprocated by rotation of the eccentric shaft. In the plunger pump bearing, the thickness of the radially thinnest portion of the outer ring is 50% or more and 60% or less of the ball diameter without changing the main dimensions of the bearing.   The plunger pump bearing according to claim 1, wherein the material of the outer ring is SUJ2.   2. The plunger pump bearing according to claim 1, wherein at least the outer ring is subjected to nitriding treatment.   The plunger pump bearing according to claim 1, wherein at least the material of the outer ring is carburized steel.   2. The plunger pump bearing according to claim 1, wherein at least the outer ring is quenched at a temperature higher than usual and then slowly cooled in the vicinity of the Ms point. 3.   2. The plunger pump bearing according to claim 1, wherein at least the outer ring is subjected to nitriding treatment and quenching to slowly cool the vicinity of the Ms point after heating to a temperature higher than normal.   The plunger pump bearing according to any one of claims 1 to 6, wherein a radius of curvature r of the groove on the outer peripheral surface of the inner ring serving as the raceway surface of the ball is D <2r <1.02D when the ball diameter is D. .

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