JPH08297084A - Friction testing machine for drum-brake friction material - Google Patents

Abstract

PURPOSE: To obtain a friction testing machine which is suitable for testing the friction of a drum-brake friction material by measuring the reaction force of a braking torque generated by the friction between a brake drum and a lining test piece. CONSTITUTION: In a state that a lining test piece 21 together with a vibration pickup 22 is mounted on a hole 23d on the side closest to a heel and that a piston-rod tip part 27a is mounted on a hole 23a so as to correspond to its mounting position, the test piece 21 is pressed to a brake drum 27 which is turned in the direction of C by a cylinder 24. A pressure force at this time is measured by a load cell 25, and the reaction force of a braking torque in this operating point is measured by the load cell 25. On the basis of the pressure force and the reaction force which have been measured in this manner, an apparent coefficient of friction in the operating point is obtained, and the change with the passage of time of a frictional force in the operating point is measured by the pickup 22. When the same test is made, measurements on other operating points can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction tester for drum brake friction materials.

[0002]

2. Description of the Related Art When a brake of an automobile is actuated, a brake squeal sometimes occurs. To clarify the brake squeal, it is necessary to conduct a friction test of a brake friction material.

Japanese Unexamined Patent Publication No. 61-11630 previously disclosed discloses a friction tester for a friction material for performing such a test. Hereinafter, the friction tester for the friction material will be described with reference to the drawings. 9 is a side view of the friction tester for friction materials, FIG. 10 is a view of the test piece holder shown in FIG. 9 as seen in the direction of arrow a, and FIG. 11 is a left side view of FIG.

As shown in FIG. 9, a support shaft 69 of a test piece holder 68 is supported on a machine base 61 by a bearing 70 so as to be movable in the axial direction. A bell crank is provided at an end of the support shaft 69. One end 73 of 72 is engaged. Bell crank 72
Is pivotally attached to a supporting portion 71 fixed to the machine base 61, and a weight 75 is hung at the other end 74 to push the spindle 6 leftward in FIG. A torque arm 67 is projected from the side surface of the test piece holder 68 and is brought into contact with the load cell 76.

A rotor 66 is rotatably provided so as to face the test piece holder 68 with its shaft 65 supported by radial bearings 63, 64 and thrust bearing 62.
Is driven via a belt 78 by a motor 77 installed inside the machine base 61.

The friction material test piece 79 is inserted into a recess formed in the test piece holder 68 as shown in FIGS. 10 and 11, and protrudes from the surface of the test piece holder 68. Next to the friction material test piece 79, a vibration force pickup 78 is fixed to the test piece holder 68 by abutting on the friction material test piece 79.

Therefore, according to the friction tester having the above structure, when the rotor 77 is rotated in the direction of arrow b in FIG. 10 by the motor 77 and the spindle 75 is pushed by the weight 75 to bring the test piece holder 68 close to the rotor 66. The friction material test piece 79 is pressed against the surface of the rotor 66 to generate vibration due to a frictional action, and this vibration is detected by the vibration force pickup 78. Further, the torque due to the frictional force between the friction material test piece 79 and the rotor 66 is measured by the load cell 76, and the frictional force can be known.

[0008]

However, the friction tester for the friction material according to the prior art described above has a flat contact type.
/ Flat, that is, the plane of the friction material test piece 79 and the rotor 66
The friction test is performed by contacting the flat surface of
It is suitable for studying squeal of disc brakes whose contact type is flat / flat (the flat surfaces of the brake disc and the lining are in contact with each other), but the curved surfaces contact each other and the contact pressure varies depending on the contact point position (operating point position). Is not suitable for squealing research.

That is, as shown in FIG. 12 (an example of a leading trailing type drum brake), the drum brake is installed inside the brake drum 86 that rotates integrally with the wheels in the direction of arrow C (when moving forward). The ends are rotatably supported by anchor pins 84 and 85, and the tips are connected to both ends 83a and 83b of the cylinder 83, and the linings 87a and 88, which are friction materials, are attached to the lining mounting parts 81a and 82a. The brake shoes 81 and 82 each have a stretched arcuate shape, and the brake shoes 81 and 82 are rotated about the anchor pins 84 and 85 by the operation of the cylinder 83, so that the lining 87,
By pressing 88 against the brake drum 86, the curved surfaces of the linings 87, 88 and the brake drum 86 are brought into contact with each other to stop the brake drum 86 (that is, the wheels).

Therefore, the contact pressure differs depending on the operating point position ψ between the linings 87 and 88 and the brake drum 86, and the apparent friction coefficient μ ₀ also differs as shown in FIG. The difference in the friction coefficient μ ₀ between the leading side and the trailing side is that the brake shoes 81, 8 when the drum 86 is rotating in the direction of arrow C in FIG.
Since the rotation fulcrum (anchor pin 84, 85) of 2 is on the right side in FIG. 12, the leading side lining 87 is sucked by the drum 86, and the trailing side lining 88 is repelled by the drum 86. This is because it becomes a form.

The brake squeal of the drum brake is
The angle Θ (see FIG. 12) formed by a straight line connecting a fulcrum (anchor pin) receiving the reaction force of the braking torque generated by the friction between the brake drum and the lining and the operating point, and the operation It is considered that this occurs due to the relationship with the friction coefficient at the point.

Therefore, in order to clarify the brake squeal of the drum brake, it is necessary to measure the frictional force of the friction material (lining, brake drum) at each operating point in consideration of the structure of the drum brake as described above. There was a need for a testing machine for that purpose.

Therefore, in view of the above-mentioned prior art, it is an object of the present invention to provide a friction tester suitable for performing a friction test of a drum brake friction material.

[0014]

A first structure of the present invention that achieves the above object is to provide rotatably supported first and second shafts respectively provided on both sides in an axial direction, and the first shaft. Rotational drive means for rotating a brake drum, which has the same shape as the actual machine, attached to the end portion of the shaft together with the first shaft, and an anchor pin fixed along the inner peripheral surface of the brake drum and on the first shaft side. Brake shoe of the same shape as the actual machine, which is rotatably supported on the lining and the lining test piece is sequentially removably mounted at each position in the circumferential direction of the lining mounting part, and one end side corresponds to the mounting position of the lining test piece. The brake shoe is detachably attached to the inner side of the brake shoe, and the other end side is coupled to the second shaft side, and the lining test piece is attached to the inner peripheral surface of the brake drum. A pressing means for pressing, a pressing force measuring means for measuring the pressing force of the pressing means, and a reaction force of the braking torque which is provided on the second shaft side and is generated by friction between the brake drum and the lining test piece. And a reaction force measuring means for measuring.

The second structure is different from the first structure in that it is attached to each position in the circumferential direction of the lining mounting portion, supports the lining test piece so as to be movable along the circumferential direction of the lining mounting portion, and It is characterized by having a vibration force pickup for measuring the vibration force generated in the lining test piece.

A third structure is the first or second structure, wherein the pressing means is a cylinder and the pressing force measuring means is interposed so as to detect the pressing force of the cylinder.
And the reaction force measuring means includes an arm projectingly provided on the second shaft side and a second load cell that abuts on the tip of the arm.

[0017]

According to the present invention having the above-described structure, the lining test piece is mounted at an arbitrary position of the lining mounting portion of the brake shoe, and one end side of the pressing means (cylinder or the like) corresponds to the mounting position of the lining test piece. When the lining test piece is pressed against the brake drum by the pressing means after mounting the inside of the brake shoe, the pressing force at this time is measured by the pressing force detecting means (such as the first load cell) and the operating point The reaction force of the braking torque generated by the frictional force between the lining test piece and the brake drum in the brake shoe, the anchor pin, and the second
It is measured by a reaction force detecting means (such as one having an arm and a second load cell) via the shaft of. Similarly, the pressing force and the reaction force are measured at other operating points.

Further, by providing a vibration pickup, the vibration force pickup measures the change with time (vibration characteristic) of the frictional force between the lining test piece and the drum when the lining test piece is pressed against the drum.

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a side view showing a friction tester for a friction material of a drum brake according to an embodiment of the present invention, with a part thereof being cut away.
3 is a front view showing details of the brake part shown in FIG. 1 (the mounting positions of the lining test pieces and the like are different between FIG. 2 and FIG. 3), and FIG. 4 is a sectional view taken along the line BB of FIG. FIG. 5 is FIG.
6 is an enlarged sectional view of the vibration pickup shown in FIG. 1, and FIG. 7 is a sectional view taken along the line CC of FIG.

As shown in FIG. 1, on the left side of the machine base 2,
A shaft 5 is rotatably supported by a supporting portion 4 fixed to the machine base 2, and a brake drum 7 of an actual machine is attached to the right end of the shaft 5. The left end of the shaft 5 is connected to the motor 1 in the machine base 2 via the flywheel 3.
6. Therefore, when the motor 16 operates, the brake drum 7 is rotated together with the shaft 5.

On the other hand, on the right side of the machine base 16, the shaft 1
2 is rotatably supported by supporting portions 11 and 13 fixed to the machine base 2, and a brake portion 8 (described in detail later) is provided at the left end portion of the shaft 12. Further, as shown in FIG. 5, an arm 9 is provided so as to project on the outer peripheral portion of the shaft 12, and a load cell 33 fixed to the machine base 2 side is in contact with the tip portion of the arm 9.

As shown in FIGS. 2 to 4, the above-mentioned brake unit 8 includes the air cylinder 24 and the brake shoe 2 of the actual machine.
3 and 30 are provided. Brake shoe 2
Reference numerals 3 and 30 are arc-shaped along the inner peripheral surface of the brake drum 7, and are rotatably supported by anchor pins 28 and 29 fixed to the shaft 12 side. And
The lining mounting portions 23c of these brake shoes 23, 30 are provided with holes 23d (four at one location) for mounting lining test pieces at respective circumferential positions (the brake shoe 30 side is not shown), and Cylinder mounting holes 2 are provided at respective circumferential positions of the rim 23b corresponding to these holes 23d.
3a is formed.

The air cylinder 24, as shown in FIG.
The front end portion 27a of the piston rod 27 is inserted into the hole 23a by a bolt 31 and a nut 32.
3 is connected to the rim 23b and the base end portion on the main body side is connected to the shaft 12 via the shaft 17, and the lining test piece 21 is extended by extending the piston rod 27 and pressing the brake shoe 23. Is pressed against the brake drum 7. A load cell 25 is provided in the middle of the piston rod 27, and the load cell 25 detects the pressing force F _i of the air cylinder 24.

The lining test piece 21 is attached to the lining attachment portion 23c of the brake shoe 23 together with the vibration force pickup 22 as shown in FIG.

The vibration force pickup 22 is shown in FIG. 6 and FIG.
It is configured as shown in. That is, the needle 45 is
And a lining test piece 21 installed on the pedestal 44, which is movable in the circumferential direction (left and right direction in the drawing) of the brake shoe 23, and is interposed between the pedestal 44 and the support frame 41. And a load cell 42 provided in the central portion of the support frame 41, and these are bolts 43 screwed to one end of the support frame 41.
And the inner surface of the support frame 41. The support frame 41 is provided with a lining mounting portion 2 by means of bolts 46 and nuts 47 which are inserted into the holes 41a formed at the four corners and the holes 23d formed in the lining mounting portion 23c.
It is fixed to 3c.

Therefore, according to the friction tester having the above-described structure, for example, as shown in FIG. 2, the lining test piece 21 is mounted together with the vibration pickup 22 in the hole 23d on the most heel side, and the lining test piece 21 is mounted at the mounting position. Correspondingly, when the piston rod tip portion 27a of the air cylinder 24 is attached to the most heel side hole 23a, the cylinder 24 presses the lining test piece 21 against the brake drum 27 rotating in the direction of arrow C. The pressing force F _{i at} this time is measured by the load cell 25, and the reaction force F _{o of} the braking torque generated by the friction between the lining test piece 21 and the brake drum 7 at the operating point.
Is measured by the load cell 33 via the brake shoe 23, the anchor pin 28, the shaft 12 and the arm 9.

The pressing force F _i and the reaction force F _o measured in this way
By substituting and into the equation shown in the following [Equation 1], the apparent friction coefficient μ ₀ at the operating point can be obtained.

[0029]

[Equation 1]

At the same time, the change over time (vibration characteristics) of the frictional force at the operating point is measured by the vibration force pickup 22. That is, the measurement signal waveform 50 as shown in FIG. 8 is obtained by the load cell 41 of the vibration force pickup 22, and the vibration of the D portion represents the change over time (vibration characteristic) of the frictional force.

Thus, the apparent friction coefficient μ _{0 at the} operating point and the change with time of the frictional force (vibration characteristic) are measured. Then, as shown in FIG. 3, the lining test piece 2
1 and the mounting position of the piston rod tip portion 27a of the air cylinder 24 are sequentially changed while corresponding to each other, and the same test as above is carried out to obtain an apparent friction coefficient μ _{0 at} other operating points. It is also possible to measure changes in frictional force with time (vibration characteristics). The test is performed a plurality of times by changing various conditions (rotational speed of the brake drum 7, pressing force F _i , ambient temperature) that affect the frictional force for each operating point. A friction test similar to the above is also performed on the other brake shoe 30 side.

Thus, the apparent friction coefficient μ _{0 at} each operating point and the change over time (vibration characteristics) of the frictional force can be measured. Therefore, the angle Θ (see FIG. 12) when the brake squeal occurs and the friction It is possible to measure the relationship with the force (apparent friction coefficient μ ₀ ) and the temporal change of the friction force (vibration characteristics). Then, based on these measurement data, it is possible to study the brake squeal of the drum brake in consideration of the contact state between the lining and the brake drum.

Further, since the vibration characteristics of the friction material can be measured only by using the test piece (lining test piece 21), the test can be performed more simply than the bench test and the actual vehicle test in the actual brake assembly. You can In addition, a more accurate result can be obtained by using the test by this test machine and the actual vehicle test together.

It should be noted that the apparent friction coefficient μ ₀ at each operating point of the brake drum is the true coefficient of friction (Fl for contact type).
Friction coefficient in the case of at / Flat) μ and angle Θ (Fig. 1
2)) and the theoretical formula shown in the following [Equation 2].

[0035]

[Equation 2]

However, due to the influence of various factors, the theoretical value obtained by the above theoretical formula and the actually measured value do not always match. In particular, the change with time of the frictional force (vibration characteristic) cannot be obtained by the above theoretical formula. Therefore, as described above, it is necessary to perform actual measurement using a test machine.

[0037]

As described above in detail with reference to the embodiments, according to the present invention, the friction test is performed by sequentially changing the mounting positions of the lining test piece and the pressing means while making them correspond to each other. The apparent coefficient of friction at a point can be obtained. Further, by providing the vibration force pickup, it is possible to measure the change with time (vibration characteristic) of the frictional force at each of the operating points. The brake squeal of the drum brake can be clarified based on these measurement data. Moreover, the test can be performed more easily than the bench test and the actual vehicle test in the actual brake assembly.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view showing a friction tester for a drum brake friction material according to an embodiment of the present invention.

FIG. 2 is a front view showing details of a brake unit shown in FIG.

FIG. 3 is a front view showing details of a brake unit shown in FIG.

FIG. 4 is a sectional view taken along the line BB of FIG.

5 is a cross-sectional view taken along the line AA of FIG.

6 is an enlarged plan view showing the vibration force pickup shown in FIG. 1. FIG.

7 is a cross-sectional view taken along the line CC of FIG.

FIG. 8 is an explanatory diagram showing a measurement signal waveform of the vibration force pickup.

FIG. 9 is a side view of a friction tester for a friction material according to a conventional technique.

FIG. 10 is a view of the test holder shown in FIG.

FIG. 11 is a left side view of FIG. 10 showing a part thereof in a cutaway manner.

FIG. 12 is an explanatory diagram showing an example of a drum brake.

FIG. 13 is a graph showing a relationship between an operating point position and an apparent friction coefficient.

[Explanation of symbols]

 2 machine stand 3 flywheel 4,11,13 support part 5,12 shaft 7 brake drum 8 brake part 9 arm 16 motor 17 axis 21 lining test piece 22 vibration force pickup 23,30 brake shoe 23a hole 23b, 30b rim 23c, 30c Lining attachment part 23d hole 24 Air cylinder 25,33,42 Load cell 27 Piston rod 27a Piston rod tip part 28,29 Anchor pin 31,46 Bolt 32,47 Nut 41 Support frame 41a Hole 43 Bolt 44 units 45 Needle

Claims (3)

[Claims] 1. A first and a second shaft rotatably supported and provided on both sides in the axial direction, and a brake drum attached to an end of the first shaft and having the same shape as that of an actual machine. Rotation driving means for rotating together with the shaft of No. 1 and rotatably supported by anchor pins fixed to the first shaft side along the inner peripheral surface of the brake drum and at respective circumferential positions of the lining mounting portion. The lining test pieces are removably attached to the brake shoe in the same shape as the actual machine, one end side is removably attached to the inside of the brake shoe so as to correspond to the mounting position of the lining test piece, and the other end side is Pressing means for connecting the lining test piece to the inner peripheral surface of the brake drum, and the pressing force of the pressing means. And a reaction force measuring unit that is provided on the second shaft side and that measures a reaction force of a braking torque generated by friction between the brake drum and the lining test piece. Brake drum friction material friction tester 2. The friction tester for a friction material of a drum brake according to claim 1, wherein the lining test piece is attached to each position in the circumferential direction of the lining mounting portion and is supported so as to be movable along the circumferential direction of the lining mounting portion. In addition, a friction tester for a drum brake friction material, which has a vibration force pickup for measuring a vibration force generated in the lining test piece. 3. The friction tester for a drum brake friction material according to claim 1, wherein the pressing means is a cylinder, and the pressing force measuring means is provided so as to detect the pressing force of the cylinder. And a second load cell in which the reaction force measuring means is provided with an arm protruding from the second shaft side and a second load cell that abuts on the tip of this arm. Friction testing machine for friction materials.