Design method of beating rocker arm tooling for suspension spring fatigue test

Abstract

A design method for a slapping rocker arm fixture for suspension spring fatigue testing includes: specifying a first feature point and a second feature point on a three-dimensional image model of the lower rubber pad of the suspension spring, wherein the first feature point and the second feature point are located on different planes along the height direction of the three-dimensional image model of the lower rubber pad; connecting the upper and lower swing points of the first feature point to create a first feature line segment; connecting the upper and lower swing points of the second feature point to create a second feature line segment; creating the perpendicular bisectors of the first and second feature line segments; and using the intersection of the perpendicular bisectors of the first and second feature line segments as the rotation axis of the slapping rocker arm fixture. The slapping rocker arm fixture designed in this invention simulates a spring motion trajectory that is closer to the actual motion trajectory of the suspension spring, thereby improving the accuracy of the test results of the suspension spring fatigue test.

Description

Technical Field

[0001] This invention relates to the field of automotive chassis technology, and in particular to the inspection technology of automotive rear suspension springs. Background Technology

[0002] Suspension coil springs are one of the key components of a car's chassis system. They are related to the safety of the car's driving, the comfort of the ride, and the vehicle's adaptability to complex road surfaces. Whether the suspension springs function well in the whole vehicle is a key factor in ensuring the car's driving performance. Figure 1 This diagram illustrates the assembly of suspension springs in a vehicle suspension system. Figure 1 As shown, the upper and lower ends of the suspension spring 90 are positioned on the upper rubber pad 91 and the lower rubber pad 92, respectively. The upper rubber pad 91 is connected to the vehicle body (not shown in the figure), and the lower rubber pad 92 is fixed to the lower control arm 93. One end of the lower control arm 93 is hinged to the vehicle frame (not shown in the figure), and the other end is connected to the wheel hub 94. Figure 1 The diagram shows the hinge rotation axis 931 of the lower control arm 93, and also the shock absorber 95. When the lower control arm 93 and the lower rubber pad 92 swing upward relative to the hinge rotation axis 931, they cause the suspension spring 90 (which is compressed at this time) to swing together. Since the hinge rotation axis 931 of the suspension spring 90 is a rubber bushing, its movement is complex and has many degrees of freedom.

[0003] Traditional suspension spring fatigue testing machines have a single degree of freedom. Specifically, direct-impact fatigue testing machines release only a single-axis translational degree of freedom, while tapping fatigue testing machines release only a single-axis rotational degree of freedom. To ensure that the load on the suspension spring during fatigue testing is consistent with the actual suspension system, the design of the tapping rocker arm fixture is the most crucial step. Existing design methods for tapping rocker arm fixtures typically fall into two categories: the projection method and the three-point method. Both of these methods have limited applicability and certain limitations, the main ones of which are described below.

[0004] Figure 2 A schematic diagram illustrating the principle of the projection method is shown. The main design idea of ​​the projection method is to project the upper and lower limit positions (i.e., the upper and lower stop positions of the lower rubber pad's swing) of the 3D image model of the lower rubber pad of the suspension spring onto the same plane. The rotation axis of the lower control arm when the rubber pad is at its upper limit position below the projection plane is the normal direction, the center of rotation is the rotation point of the lower control arm (the rotation point of the lower control arm is the midpoint of the rotation axis of the lower control arm), and the direction of the rotation axis is the normal direction of the projection plane. The projection method simplifies the translational motion of the spring during actual movement. For suspension structures with large translational displacements, the simplification of translational motion by the projection method leads to a large deviation from reality, and fatigue tests cannot accurately reflect the fatigue performance of the actual suspension spring.

[0005] Figure 3The diagram illustrates the principle of the three-point method. The main design concept of the three-point method is based on the rotation point P0 of the lower control arm, the upper stop point S1 of the swing of the characteristic point (e.g., the center of mass) of the lower rubber pad, and the lower stop point S2 of the swing of the characteristic point (e.g., the center of mass) of the lower rubber pad. The rotation center is the rotation point of the lower control arm, and the direction of the rotation axis is the normal direction of the plane formed by the three points. As can be seen from the diagram, this method cannot account for the degree of freedom of rotation around the lower control arm. For suspensions with a large rotation angle around the lower control arm, this method deviates significantly from reality. Fatigue tests conducted using the rocker arm fixture designed with this method cannot reflect the actual performance of the suspension spring. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a design method for a slapping rocker arm fixture for suspension spring fatigue testing. Compared with the prior art, the slapping rocker arm fixture simulates a spring motion trajectory that is closer to the actual motion trajectory of the suspension spring, thereby improving the accuracy of the test results of suspension spring fatigue testing.

[0007] A design method for a slapping rocker arm fixture for suspension spring fatigue testing according to an embodiment of the present invention includes:

[0008] On the three-dimensional image model of the lower rubber pad of the suspension spring, a first feature point and a second feature point are specified. The first feature point and the second feature point are located on different planes along the height direction of the three-dimensional image model of the lower rubber pad.

[0009] Connect the upper and lower oscillation points of the first feature point to create the first feature line segment; connect the upper and lower oscillation points of the second feature point to create the second feature line segment.

[0010] Construct the perpendicular bisectors of the first and second feature segments, and use the intersection of the first and second feature segments as the axis of rotation of the striking arm of the striking rocker arm fixture.

[0011] The present invention has at least the following advantages:

[0012] 1. Compared with the existing design method of the slapping rocker arm, the slapping rocker arm fixture designed according to the embodiment of the present invention can more accurately and efficiently simulate the motion trajectory of the suspension spring in the real working environment, making the fatigue test results of the suspension spring more accurate, thereby helping to improve the production quality of the suspension spring;

[0013] 2. The embodiments of the present invention realize single-axis rotation to simulate the actual suspension spring motion trajectory, without the need to modify the traditional fatigue testing equipment, and are easy to implement. Attached Figure Description

[0014] Figure 1A schematic diagram of the assembly of suspension springs in a car suspension system is shown.

[0015] Figure 2 A schematic diagram illustrating the principle of the projection method is shown.

[0016] Figure 3 A schematic diagram illustrating the principle of the three-point method is shown.

[0017] Figure 4 A schematic diagram illustrating the design principle of a slapping rocker arm fixture for suspension spring fatigue testing according to an embodiment of the invention is shown.

[0018] Figure 5 A schematic diagram of a slapping rocker arm fixture used for suspension spring fatigue testing is shown.

[0019] Figure 6 A schematic diagram of the working state of a suspension spring tack fatigue testing machine using a tack rocker arm fixture for suspension spring fatigue testing is shown. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] Please see Figure 4 The design method of the slapping rocker arm fixture for suspension spring fatigue testing according to an embodiment of the present invention includes the following steps:

[0022] Step S1: Specify a first feature point and a second feature point on the three-dimensional image model 2 of the lower rubber pad of the suspension spring. The first feature point and the second feature point are located on different planes along the height direction of the three-dimensional image model 2 of the lower rubber pad.

[0023] exist Figure 4 In the example, the first feature point is a point on the bottom surface of the lower rubber pad, and the second feature point is a point on the protruding post on the bottom surface of the lower rubber pad. In other embodiments, the second feature point can also be the centroid or the center point of the top surface of the lower rubber pad.

[0024] Step S2: Connect the upper stop point P1 and the lower stop point P3 of the first feature point to construct the first feature line segment P1P3 (i.e., ... Figure 4 In the L1), connect the upper stop point P2 and the lower stop point P4 of the second feature point, and construct the second feature line segment P2P4 (i.e., Figure 4 L2 in the middle.

[0025] Step S3: Construct the perpendicular bisector α of the first feature line segment P1P3 and the perpendicular bisector β of the second feature line segment P2P4. Use the intersection line L3 of the perpendicular bisector α of the first feature line segment P1P3 and the perpendicular bisector β of the second feature line segment P2P4 as the rotation axis of the striking arm of the striking rocker arm fixture.

[0026] In this embodiment, the three-dimensional image model 2 of the lower rubber pad, the upper and lower swing points P1 and P3 of the first feature point, and the upper and lower swing points P2 and P4 of the second feature point are all predetermined by the upstream vehicle manufacturer. Steps S1 to S3 described above can be implemented using three-dimensional modeling software, such as UG, which is not limited in this application. After determining the rotation axis of the striking arm, a three-dimensional image model of the striking arm fixture can be further obtained in the same coordinate system as the three-dimensional image model 2 of the lower rubber pad.

[0027] Figure 5 A schematic diagram of a slapping rocker arm fixture used for suspension spring fatigue testing is shown. The figure shows the slapping rocker arm 4 and its rotation shaft 42.

[0028] Figure 6 A schematic diagram of the working state of a suspension spring tack fatigue testing machine using a tack rocker arm fixture for suspension spring fatigue testing is shown. Figure 6 In this suspension spring fatigue testing machine, there are two striking rocker arm fixtures, and the striking rocker arms 4 of the two fixtures share the same rotating shaft 42. The power cylinder 5 reciprocates, causing the striking rocker arms 4 to swing back and forth around the rotating shaft 42 to perform fatigue tests on the automotive suspension spring 90 to be tested.

[0029] In an automotive suspension system, the hinge rotation axis 931 of the suspension spring 93 is a rubber bushing, and the rotation axis is elastically connected. When the lower control arm 93 and the lower rubber pad 92 rotate around the hinge rotation axis, the rubber bushing deforms under stress, resulting in multiple degrees of freedom in the actual rotation. Existing tapping rocker arm fixture design methods (projection method and three-point method) all borrow the model of the hinge rotation axis 931 in their design, simplifying the motion to rotation around the hinge rotation axis 931 (motion in only one degree of freedom), without considering the motion in other degrees of freedom caused by the deformation of the rubber bushing, thus causing deviations from the actual motion. The tapping rocker arm fixture design method of this invention does not use the model of the hinge rotation axis 931, but redesigns the rotation axis of the tapping rocker arm fixture. The spring motion trajectory simulated by the tapping rocker arm fixture designed in this invention is closer to the actual motion trajectory of the suspension spring, thereby improving the accuracy of the test results of the suspension spring fatigue test.

[0030] The above description is a further illustration of the present invention in conjunction with specific embodiments and accompanying drawings. However, the present invention can obviously be implemented in many other ways different from those described herein, and those skilled in the art can extend and deduce it according to actual use without departing from the content of the present invention. Therefore, the content of the above specific embodiments should not limit the scope of protection defined by the present invention.

Claims

1. A design method for a slapping rocker arm fixture for suspension spring fatigue testing, characterized in that, include: On the three-dimensional image model of the lower rubber pad of the suspension spring, a first feature point and a second feature point are specified. The first feature point and the second feature point are located on different planes along the height direction of the three-dimensional image model of the lower rubber pad. The first feature point is the centroid of the lower rubber pad, and the second feature point is the center point of the bottom surface or the center point of the top surface of the lower rubber pad. Connect the upper and lower oscillation points of the first feature point to create the first feature line segment; connect the upper and lower oscillation points of the second feature point to create the second feature line segment. Construct the perpendicular bisectors of the first and second feature segments, and use the intersection of the first and second feature segments as the axis of rotation of the striking arm of the striking rocker arm fixture.

2. The design method of the slapping rocker arm fixture for suspension spring fatigue testing according to claim 1, characterized in that, The three-dimensional image model of the lower rubber pad, the upper and lower swing points of the first feature point, and the upper and lower swing points of the second feature point are all predetermined.

Images