JPH0128898B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apparatus for measuring the speed dependence of the friction coefficient of friction materials for automobiles, railways, and industrial applications.

(Prior Art) There are various frictional characteristics of friction materials, but the most difficult to measure is the frictional vibration (self-excited vibration) characteristic.

Frictional vibrations caused by friction materials include brake squeal in automobiles and trains, clutch jerking that occurs when automobiles start, and chatter in industrial machinery, which have become industrial problems.

According to vibration theory, it is known that frictional vibration occurs when the differential value of the friction coefficient with respect to velocity becomes negative. Figure 1 is a graph showing the relationship between the friction coefficient and speed of a certain friction material.In the relationship between the friction coefficient and speed in Figure 1, the area surrounded by the dashed ellipse is where frictional vibrations are likely to occur. Become.

Based on this idea, conventional efforts have been made to determine the velocity dependence of the friction coefficient and thereby to understand the frictional vibration characteristics of friction materials. However, the correlation between the results of measuring the speed dependence of the friction coefficient using a conventional testing device and the frictional vibrations that occur during actual use was not good.

As a conventional device for measuring the speed dependence of the friction coefficient: (1) A rotating body is rotated at a certain rotation speed, for example, 500 rpm, a friction material is pressed against it, the friction coefficient at 500 rpm is determined, and then the pressing is performed. Release the rotation, rotate the rotating body at the next rotation speed, for example, 400 r.pm, press the friction material against it, and find the friction coefficient at 400 r. pm. Step by step, find the friction coefficient at each speed. The speed dependence of the friction coefficient was determined by linking them together.

(2) In order to continuously determine the speed dependence of the friction coefficient, the inertial body is rotated at a constant speed in advance and the friction material is pressed against it. A so-called inertia type dynamo (inertia type bench friction tester) was created.
In the case of the inertia type, (a) testing is carried out by keeping the hydraulic pressure that enters the cylinder and piston that presses the friction material constant, and (b) controlling the hydraulic pressure so that the frictional force is constant. There is an exam.

(Problems to be Solved by the Invention) However, when measuring the speed dependence of the friction coefficient, which governs the frictional vibration characteristics of friction materials, with a conventional device for measuring the speed dependence of the friction coefficient, there is a problem with the actual phenomenon. No consensus could be obtained.

In other words, the friction characteristics of the friction material are controlled by temperature, pressing time, and history. Therefore, when testing the friction material each time by changing the rotation speed in stages as in (1), the surface condition of the friction material and the mating material differs depending on the number of stages and the pressing time. The correlation with actual characteristics such as brake squeal, clutch facing noise, and industrial machinery chatter is extremely poor. Particularly in the case of resin-based friction materials that use organic materials, the condition of the friction surface can easily change under a few conditions. Therefore, it does not match the speed dependence of the friction coefficient, which is obtained step by step from a phenomenon that occurs instantaneously over a short period of time.

In addition, in the case of an inertia type in which the pressing force is constant as in (2) (a), the deceleration rate varies depending on the characteristics of the friction material, so it is not possible to make the measurement conditions constant for each sample. In other words, in the case of a friction material that has a small coefficient of friction at high speeds and a large coefficient of friction at low speeds,
The rotation time of the inertial body is long in the high speed region, but the rotation time is short in the low speed region. On the other hand, if a sample with the opposite characteristics has a large friction coefficient at high speeds and a small friction coefficient at low speeds, the inertial body will rotate for a short time in the high speed range and long in the low speed range. As the friction conditions vary depending on the characteristics of the sample, it is not possible to test under the same conditions.

Furthermore, in the case of the inertia type, which controls the hydraulic pressure so that the frictional force is constant, as in (2) (b), the frictional conditions differ depending on the sample, so the speed dependence of the friction coefficient under the same conditions. cannot be measured. That is, in the case of a sample with a low coefficient of friction, the oil pressure becomes high and the pressing force becomes large, but in the case of a sample with a high coefficient of friction, the oil pressure becomes low and the pressing force becomes small. Furthermore, the frictional force changes due to the speed dependence of the friction coefficient, but if the hydraulic pressure is changed to make the frictional force constant, the pressing force will fluctuate, so it is not possible to evaluate each material under the same measurement conditions.

Therefore, in order to measure the speed dependence of the friction coefficient of a friction material that governs phenomena such as brake squeal, clutch jerk, and chatter in industrial machinery, it is necessary to keep the pressing force constant within a short period of time when the phenomenon occurs. , it is necessary to change the speed, but as mentioned above, this has not been possible with conventional devices.

The present invention has been made in view of the above drawbacks, and is an apparatus for measuring the speed dependence of the friction coefficient, which has a good correlation with the frictional vibrations (brake squeal, clutch jerking, etc.) that occur during actual use. The purpose is to provide the following.

(Means for Solving the Problems) The structure of the present invention for achieving the above object will be explained using FIGS. 2 to 4 corresponding to the embodiments. 2, an actuator 9 that presses the friction material 6 against the rotating body 2 via the mounting jig 7 in response to an electric signal, and a sensor 8 that measures the pressing force of the actuator 9.
, a sensor 17 that detects the friction force generated on the pressed friction material 6, and a sensor 17 that detects the friction force generated on the pressed friction material 6, and a sensor 17 that detects the friction force generated on the pressed friction material 6, and a
an electric motor 4 capable of uniformly decelerating the deceleration of the rotating body 2;
Alternatively, a temperature sensor 3 that informs that the friction material 6 has reached a set temperature, a control means that controls the pressing force of the actuator 9 based on an electric signal from the sensor 3, and a motor 4 that uses the electric signal from the sensor 3. The technology includes a control means for controlling the deceleration of the vehicle at a set deceleration rate.

(Example) An example of the present invention will be described below based on FIGS. 3 and 4.

2 is a disk rotatably attached to the chuck 1 of the rotating lathe. Reference numeral 7 denotes a jig for mounting a measurement sample, which is disposed facing the surface of the disk 2, and is connected and fixed to a shaft 18 coaxial with the rotation axis of the disk 2. The mounting jig 7 for the friction material 6 has a structure that allows it to rotate around the rotation axis of the disk 2 and to move along the rotation axis. An actuator 9 is fixed to the other end of the shaft 18, and the shaft 18 is pressed by a piston of the actuator 9. In the middle of the shaft 18 is an actuator 9.
A load cell 8 that measures the pressing force is fixed. Further, a ball bearing 10 is interposed between the shaft 18 and the piston of the actuator 9 so that the mounting jig 7 can rotate even when pressed. Reference numeral 15 denotes an arm fixed to the shaft 18, the tip of which is held in the middle of the coil spring 16, and a load cell for measuring the vertical vibration of the coil spring 16 is fixed to the upper part of the coil spring 16. has been done. The coil spring 16 brakes the rotation of the mounting jig 7 by the sliding friction between the friction materials 6, 6 attached to the mounting jig 7 and the surface of the disk 2.

3 is a temperature sensor that measures the surface temperature of the disk 2. 4 is a motor that rotates the disk 2 and decelerates the rotation of the disk 2 at a constant deceleration until it stops. The motor 4 is composed of a three-phase AC motor, a rotational drive source consisting of an eddy current coupling, and a motor control section 5 using a closed loop control system.

The temperature sensor 3 is connected to the controller main body 11 via an amplifier 22', a pen recorder 23, and an A-D converter 13.
It is connected to the. The controller main body 11 is connected to the actuator 9 via the peripheral interface 12 and to the control unit 5 of the motor 4 via the DA converter 14 . moreover,
Load cell 17 and load cell 8 are each amplifier 2
2. It is connected to the controller main body 11 via the pen recorder 23 and the A-D converter.

As the rotatable disk 2 in the measuring device of the present invention, it is preferable to use the same disk used in an actual brake, or to use a disk made of the same material. It is desirable that the rotational speed of the second disk be uniformly decelerated from the maximum disk rotational speed in the actual vehicle to a standstill.

The friction material 6 used in the test is full size (20 cm ² ~
200 cm ² ), but 1 cm ² to 20 cm ² may be used to reduce the required horsepower of the test machine. Basically, a pair of friction materials 6 are arranged so that the center of the friction materials 6 is symmetrical with respect to the diameter of the disk 2, but no force that would cause the disk 2 to tilt is applied. Several pairs of friction materials 6 may be arranged symmetrically on the same diameter as shown in FIG.

The mounting jig 7 for the friction material 6 is movable coaxially with the rotation axis of the disk 2, and if it is structured so that it can move smoothly along the axis, measurements can be made regardless of wear of the friction material 6. . Further, the attachment jig 7 and the friction material 6 are attached using screws or adhesive so that there is no looseness. As a method of braking the rotation of the mounting jig 7 via a spring, the spring may be directly attached to the jig, or an arm may be protruded from the rotating surface of the jig 7 and fixed via a spring. It's okay. Suitable springs include torsion springs, leaf springs, coil springs, and spiral springs. If the amount of deformation of the spring is larger than the total amount of deformation of the friction material 6, the mounting jig 7, the arm, etc. when friction torque is applied, it will be easier to measure the vibration.
It is most preferable to set the frequency of the friction vibration to be about 1 Hz to 100 Hz.

Using such a measuring device, attach a full-size disk pad or a sample cut out to reduce the friction area, and measure the disk rotation speed at a surface pressure in the range of 0.1 Kg/cm ² to 50 Kg/cm ² to the maximum rotation speed of the actual vehicle (100 rpm). If the vibration is measured by slowly changing the rotation speed from ~2000 rpm) to rest, or from rest to the maximum rotation speed, frictional vibration will occur within a certain rotation speed range. Disc pads that tend to squeal generate large vibrations over a wide range of rotational speeds, but pads that do not squeal have a narrower range of frictional vibrations or smaller vibrations.

The magnitude level at which this frictional vibration occurs can be selected within a range that is easy to measure by appropriately selecting the spring constant and the damping due to the viscosity and friction of the part that contacts the mounting jig 7. can. It is also possible to measure frictional vibrations over a wide range by installing a damper such as an oil damper in parallel with the spring to saturate the frictional vibrations that tend to diverge to an appropriate level.

The disk 2 may be heated by frictional heat or may be controlled by heating with something such as an electric heater. Furthermore, since the occurrence of frictional vibrations is often influenced by the thermal history of the friction material, more accurate results can be obtained by appropriately determining test codes for heating and cooling.

As the temperature detection sensor 3, a thermocouple may be embedded in the rotating body or a friction material, or an infrared thermometer capable of non-contact measurement may be used to measure the temperature on the surface of the rotating body.

The actuator 9 that presses the friction material 6 against the rotating body using an electric signal may use pneumatic pressure or hydraulic pressure, and the friction is controlled by turning air and oil to the air cylinder and oil cylinder on and off using electromagnetic valves. The material 6 may be pressed or released.

Among electric motors that can control the speed of a rotating body using electrical signals, a closed-loop control type electric motor can control deceleration with the most precision. FIG. 3 shows a closed-loop control type electric motor that can control the speed of a rotating body using electrical signals, and electrical signals that control the speed to constant deceleration. In a closed loop system, a rotation detector is required to feed back the rotation results, and a regulator or amplifier is provided to compare the electrical signal with the command value and issue a command to the control equipment.

Although it is common to use a direct current (DC) motor as the rotational drive source, it is also possible to use an AC motor to control the excitation current of the eddy current joint (for example, Hitachi HC Motor). .

An electric signal from a temperature sensor notifies that the rotating body or friction material has reached the set temperature.
A sequence controller may be used as a controller that provides an electric signal to an actuator to press the friction material against a rotating body, or a controller that provides an electric signal to an electric motor to decelerate a rotating body at a set deceleration rate. A type controller is suitable.

It is preferable to use a microcomputer consisting of a storage section, an arithmetic section, and an input/output section as a program store type controller.

In a microcomputer, an analog electrical signal from a temperature sensor is converted into a digital signal by an A-D converter, and then input into a storage section and a calculation section. Further, signals from the storage section and the calculation section to the actuator are taken out through the peripheral interface. Further, digital signals from the storage section and calculation section that control the rotational speed of the motor are converted into analog signals and taken out by a DA converter.

(Function) FIG. 2 shows a basic operation flowchart of the friction testing device of the present invention. Rotate disk 2 at a constant speed,
Set the test temperature and deceleration. The rotation speed, test temperature, and deceleration of the disk 2 may be changed each time the flowchart is passed, or may be set the same each time. The temperature sensor 3 constantly monitors whether the temperature of the disk 2 exceeds the set temperature, and presses the friction material 6 against the disk 2 when the temperature exceeds the set temperature. Then, almost at the same time when the friction material 6 is pressed against the disk 2, the disk 2 is forcibly decelerated at a set deceleration rate and stopped. At this time, the deceleration of the disk 2 is determined not by the frictional force of the friction material 6, but by the controlled rotation of the electric motor 4, which is the power source. The most common deceleration is a uniform deceleration. When the disk 2 stops, the friction material 6 is released from being pressed against the disk 2. This ends the basic operation, but depending on the purpose, the flowchart may be repeated in a loop, or the setting conditions may be changed for each loop.

First, when the temperature of the rotating disk 2 reaches the set temperature, an electric signal from the temperature sensor 3 is sent to the amplifier 2.
A-2' is amplified and recorded on the pen recorder 23.
The controller main body 1 consists of an arithmetic unit and a memory that converts analog signals into digital signals by a D conversion unit 13.
1 is input. The signal input to the controller main body 11 is then taken out by the peripheral interface 12 and sent to the actuator 9 via the shaft 10 to the mounting jig 7.
The friction material 6 provided on the disk 2 is pressed against the disk 2. On the other hand, the signal input to the controller body 11 is converted from a digital signal into an analog signal by the D-A converter 14 and sent to the motor controller 5, which controls the motor 4 to decelerate at a constant speed and the disk 2 to a constant speed. bring it to a halt.

At this time, the pressing force signal from the load cell 8,
The friction force signal from the load cell 17 is sent to the amplifier 22.
The signal is amplified by the pen recorder 23 and inputted as a friction coefficient signal, and at that point the pressing force and the friction force are recorded.

Figure 5 shows the relationship between the friction coefficient of the disc parts and the rotational speed measured using a conventional device that measures the rotation by changing the rotation in stages, using disc parts that made noise and disc parts that did not make noise in actual vehicle tests as friction materials. , and FIG. 6 shows the relationship between the friction coefficient of the disk pad material and the rotational speed measured by the friction testing apparatus of the present invention.

The steady friction coefficient in FIG. 5 is obtained by measuring the friction coefficient while changing the rotational speed stepwise and plotting it. It can be seen that the curve with squeal is almost flat, and the curve without squeal is sloping upward to the left, which does not match the theory.

On the other hand, the friction coefficient shown in Figure 6 was measured using the device of the present invention while decelerating the disk rotation at a uniform deceleration to a stop in 5.6 seconds. The curve is upward-left, which agrees well with the frictional vibration theory, and the presence or absence of squeal can be easily determined using this device. In addition, Figure 5 shows the measurement at 100℃, and Figure 6 shows the set temperature at 100℃, 200℃, 300℃, 400℃, 100℃ again, and 100℃ again.
Shows the measurement results at 150℃ and 200℃.

(Results of the Invention) As described above, when the friction testing apparatus of the present invention is used, brake squeal, clutch jerk characteristics, and chatter of industrial machinery are controlled. It is possible to measure the speed dependence of the true friction coefficient, which governs the frictional vibration characteristics of friction materials.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the friction coefficient and speed of a certain friction material. FIG. 2 is a flowchart of a friction test using the friction test apparatus of the present invention. Third
The figure is an explanatory diagram showing an electric motor whose rotational speed can be controlled by an electric signal and an electric signal which controls the deceleration to be constant. FIG. 4 is a block diagram of a friction testing apparatus according to an embodiment of the present invention. FIG. 5 is a graph showing the relationship between the friction coefficient of disc pad material and the rotational speed measured using a conventional device. FIG. 6 is a graph showing the relationship between the friction coefficient of the disk pad material and the rotation speed measured by the friction testing apparatus of the present invention. Explanation of symbols, 1...chuck, 2...disk, 3...temperature sensor, 4...motor, 5...
...Motor control section, 6...Friction material, 7...Mounting jig, 8...Load cell, 9...Actuator, 10...Ball bearing, 11...Control unit body, 12...Peripheral interface Ace, 13...A-D conversion section, 14...D-A conversion section, 15...Arm, 16...Coil spring, 17
...Load cell, 18...Shaft, 22, 22
...Amplifier, 23...Pen recorder.

Claims (1)

[Claims] 1 A rotary body 2 that is rotationally driven, an actuator 9 that presses the friction material 6 against the rotary body 2 via a mounting jig 7 in response to an electric signal, and a sensor 8 that measures the pressing force of the actuator 9. , a sensor 17 that detects the frictional force generated on the pressed friction material 6, an electric motor 4 that can uniformly control the deceleration of the rotating body 2 by electric signals, and a sensor 17 that detects the frictional force generated on the pressed friction material 6, an electric motor 4 that can uniformly control the deceleration of the rotating body 2, and a sensor 17 that detects whether the rotating body 2 or the friction material 6 has reached a set temperature. a temperature sensor 3 that notifies the temperature; a control means that controls the pressing force of the actuator 9 based on the electrical signal from the sensor 3;
A device for measuring the speed dependence of a friction coefficient, comprising a control means for controlling deceleration at a set deceleration.