JPH023717A - Disc brake for high load - Google Patents

Abstract

PURPOSE:To obtain a disc brake having a large thermal absorbing capacity and the less abrasion quantity by constituting a stator by installing a carbonaceous stator lining onto a metal stator plate and constituting a rotor disc by installing a carbonaceous rotor lining onto a metal robot plate. CONSTITUTION:Since a stator lining 6a and a rotor lining 4a are made of the carbonaceous material having a high thermal conductivity, the increase allowable limit temperature of a frictional disc, in other words, the allowable load capacity in brake application is increased, and a rotor blade 4b which is made of metal and used as structure member is protected from the abnormal temperature rise in brake application, and also the actual using limit can be increased. In this case, if the carbonaceous material for rotor lining whose hardness is larger than that of the stator lining is used, the abrasion quantity of the material can be reduced drastically. Further, since inert gas is supplied between the both linings 4a and 6a by a gas feeding means 16, antioxidation performance is provided, and reliability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high-load disc brake suitable for braking large vehicles such as large automobiles, high-speed automobiles, and wheel-running high-speed railways.

(Prior art) As traffic and means of transportation become faster and larger, demands on brake systems are becoming increasingly strict to ensure safety. Stability, 2) Stability of brake distribution, 3) Heat resistance, 4
Disc brakes are increasingly being used because they are () lightweight, and (5) produce less noise such as judder and squeal.

Disc brakes have the ability to gradually increase the braking force and bring the vehicle to a stop, making them extremely suitable for transporting cargo that is easily broken or that is sensitive to mechanical shock. It is extremely significant to install disc brakes on large vehicles that often carry such cargo.

However, in order to use disc brakes to stop a large vehicle or a vehicle traveling at high speed, the vehicle's large kinetic energy must be converted into thermal energy and dissipated into the atmosphere in a short period of time. The rate of energy conversion is extremely high, and the rate of heat generation on the friction surface during brake operation reaches several hundred kilowatts of electric power.

Since such rapid generation of frictional heat occurs on the friction surface of the brake, friction materials for brakes must not only have excellent frictional wear properties but also properties that can withstand this rapid generation of heat. Furthermore, the thermal energy generated in this way is first stored inside the brake and then slowly dissipated outside the brake, but this is not the case for brakes that are operated frequently, such as land vehicle brakes. The issue is the ability of the atmosphere to dissipate heat.

Conventionally, disc brakes used in land vehicles are disc pad-shaped, but in this type of brake, metal materials such as cast iron and cast steel are used for the rotor disc, and organic materials are used for the lining material. Materials with excellent friction properties, such as semi-metallic friction materials or semi-metallic friction materials, are used.

In other words, in this high-load disc brake, thermal energy generated during brake operation is mainly absorbed by the rotor disc, and the lining material only needs to have excellent frictional properties.

However, as vehicles become faster and larger, the amount of thermal energy that brakes must absorb has increased significantly. It is extremely difficult to obtain one that satisfies all of the various requirements.

Brakes are used to convert the kinetic energy of a vehicle into thermal energy for a short period of time and release it to the outside. In the conventional disc brake described above, a rotor disc made of cast iron or the like is responsible for absorbing thermal energy. For this reason, as the load becomes higher, the thickness of the disk is increased, the weight is increased, and the heat capacity is increased.

By the way, the specific heat of metal materials is generally small, with c
al/kt”c. Since the required weight of the material per amount of heat absorption is inversely proportional to the specific heat of the material,
If an increase in brake load capacity is to be imposed on the metal rotor disk, the weight increase will naturally be very large. If the weight of the brake device increases, the fuel efficiency of automobiles will deteriorate. Moreover, from the perspective of energy conservation of the vehicle, the increase in the weight of the rotor disk not only increases the actual weight but also increases the inertial weight, resulting in a double burden.

Another problem with increasing the thickness of the rotor disc is the large thermal distortion that occurs during braking operation. As mentioned above, the rate of heat generation during brake operation is extremely high. In order to avoid an abnormal temperature rise on the friction surface by rapidly diffusing the heat generated at the friction surface into the disk, it is necessary to use a material with high thermal conductivity for the rotor disk. However, as the load capacity of the brake increases and the thickness of the disc increases, even if metal materials such as cast iron or cast steel are used, problems such as cracking and permanent deformation of the material due to thermal distortion become a problem. . Therefore, there is a limit to the thickness of the disc that can be used with this method, and therefore there is a limit to the amount of thermal energy that the brake can absorb.

In disc pad type brakes, the rotor disc functions as a heat absorbing material as described above, but the rotor disc is mostly exposed to the atmosphere, and the thermal energy temporarily stored in the disc is absorbed by the rotor disc. It is designed so that it can be dissipated directly from the surface into the atmosphere. Therefore, the friction surface itself is used as a heat dissipation surface.
It has an excellent cooling structure.

However, as the load capacity increases, it is necessary to increase the cooling area accordingly. However, in this type of brake, it is extremely difficult to increase the cooling area by increasing the diameter and thickness of the rotor disk due to its structure. As a countermeasure to this problem, high-load brakes have been designed to increase the contact area with air by drilling holes in the rotor disc for ventilation, and to increase the amount of ventilation air by using the centrifugal force effect caused by the rotation of the rotor disc. There is a limit to the cooling area that can be increased by such methods. There are also 10 vehicles
Even if the vehicle runs at a speed of about 0 km/h, the centrifugal effect caused by the rotation of the wheels is not very large, and neither is satisfactory.

In addition, disc brakes are those in which a disc-shaped rotor with a lining is pressed against the surrounding stator (see page 188 of "Tires and Brakes" in Automotive Engineering Complete Book, Volume 12), or in a sealed box. Two clutch-type pressure plates are placed inside the box, and these are spread out on both sides to press against the inside of the box (Automobile Sensho, ``
There are also all-circumference pressurized type brakes (see page 25 of Sankaido).

This all-circumference pressure type is called a clutch-type desk brake, and because the contact area of the friction material is large, it is said to provide excellent braking force even during high-frequency braking.

However, due to its complicated structure and high cost, it has not been widely used. Furthermore, since the sliding parts are housed in a sealed box, there is a limit to the cooling capacity, although measures have been taken to increase the cooling effect, such as attaching fins to the outside of the box. Therefore, it cannot be said that the structure is suitable for high-load brakes.

Therefore, it may be possible to absorb thermal energy in such a disc brake by changing its material. Carbonaceous materials that have recently attracted attention as materials for disc brakes include carbonaceous materials.

This carbonaceous material has the highest heat resistance temperature among industrially usable materials, and its specific heat is among the highest among heat-resistant materials, so it is used under high loads that strongly require a large heat capacity. It has ideal properties as a brake material.

However, this material has only recently been used industrially, and has not yet reached the stage where it can be designed with sufficient reliability as a structural material.

Moreover, carbonaceous materials used as high-load brake materials still have various problems, such as resistance to oxidation and wear. Regarding oxidation resistance at high temperatures, carbonaceous materials are originally used as fuels, so it is natural for them to be oxidized and depleted when exposed to an oxygen atmosphere at high temperatures. On the other hand, disc butt type brakes have a structure that exposes the friction surface to the atmosphere, which is very disadvantageous for carbonaceous materials. For example, disc brakes whose discs and pads are both made of carbonaceous materials are used for competitive automobiles, but in this case, the temperature rise due to brake operation is large and the material deteriorates in a short period of time, so this type of brake is The reality is that they are consumable items and are replaced every race.

Various methods have been proposed to increase the oxidation resistance of this material, such as coating or impregnating it with a heat-resistant material. However, we have not yet reached the stage where we can expect sufficiently reliable effects. In fact, even in aircraft brakes that widely use this material, antioxidants are only applied to the inner and outer periphery of the disc, which is not related to friction, and it is considered that sufficient anti-oxidation measures have been taken. I can't say that.

The best way to protect carbonaceous materials from oxidative depletion is to use them in isolation from an oxygen atmosphere (see, for example, JP-A-62-165.037).

The method disclosed in JP-A-62-165,037 uses a carbon-carbon composite material for a wet clutch of an automobile, but the carbon-carbon composite material is impregnated with lubricating oil. However, it is now used in a closed system. However, it is naturally impossible to use this method for brakes, which generate a large amount of frictional heat unlike clutches.

Therefore, the present inventors believe that if high-load disc brakes are not improved based solely on the general design theory regarding the constriction mechanism described above (and the cooling structure itself is not improved), the current As vehicles become faster and larger, and the amount of energy absorbed by brakes increases, we believe that it is not possible to obtain the desired brakes, and as a result of intensive research, we have determined that the biggest problems with conventional disc brakes are: We believe that this lies in the fact that most of the role of absorbing this thermal energy is placed on the rotor disk.

Therefore, the basic design theory when designing a high-load disc brake is to make the rotor disc and stator lining work together to quickly absorb the large amount of heat energy generated by brake operation. This is a high-load brake system that takes advantage of the features of an all-circumference pressurized disc brake, which has various advantages in its function as a brake, and uses carbonaceous material to increase heat dissipation capacity after brake operation. We developed and proposed a disc brake.

In other words, this high-load disc brake is an all-circumference pressurized disc brake in which either the rotor disc or the stator lining is made of metal and the other is made of carbonaceous material. The carbonaceous material is a carbon-carbon composite material whose fibers are oriented in the thickness direction.

(Problem to be solved by the invention) However, since this high-load disc brake uses metal for either the rotor disc or the stator, the maximum allowable temperature on the friction surface depends on the metal material used. There is a possibility that it will be restricted by the heat resistance temperature of the device.

For example, when this high-load disc brake is used for a vehicle that absorbs a particularly large amount of heat per brake operation, or when it is used as a brake for a vehicle that requires sudden braking operation. In this case, the temperature rise on the friction surface becomes large, and there is a possibility that the metal material becomes unusable.

Therefore, as a result of further research, the present inventors were able to use carbon material, which has the highest temperature resistance among industrial materials, for both the friction material and the friction partner material without impairing the drag and wear properties. They have discovered a method that makes this possible, and have completed the present invention.

The object of the present invention is to solve the above-mentioned drawbacks and problems associated with the prior art, to have a high maximum allowable temperature on the friction surface, to be free from the possibility of being restricted by the heat-resistant temperature, to have a large heat absorption capacity, and to reduce the amount of wear. Our objective is to provide a high-load disc brake that is small, lightweight, and has high heat dissipation.

(Means for Solving the Problems) The present invention has been made to achieve the above objects, and
In a disc brake equipped with a disc-shaped rotor disc and a stator that approaches and separates over the entire circumference of at least one surface of the rotor disc, the stator has a carbonaceous stator lining on a metal stator plate, and The rotor disk is characterized in that it is constructed by attaching carbon rotor linings to metal rotor plates.

The carbonaceous material used in the present invention is characterized in that the hardness of the rotor lining is higher than that of the stator lining.

Further, the present invention achieves the above object by providing heat radiation fins on the stator plate 1.

Furthermore, the present invention achieves the above object by introducing an inert gas around the rotor disk and stator lining.

(Function) As described above, in the present invention, the linings of the stator and rotor are both made of carbonaceous material with high thermal conductivity, so that the permissible rise limit temperature of the friction surface, that is, the permissible load capacity during braking is increased. In addition, it is possible to protect the metal rotor plate used as a structural material from an abnormal temperature rise during brake operation, and it is also possible to increase the practical limit of use of this metal rotor plate.

In this case, if the hardness of the carbonaceous material for the rotor lining is higher than the hardness of the carbonaceous material for the stator lining, the amount of wear of the material can be greatly reduced compared to the case of using a carbonaceous material with the same characteristics. It can be held small.

In addition, this disc brake also uses an all-circumference pressurized disc brake in which the stator lining slides on the entire circumference of the disc-shaped rotor disc, and inert gas is guided to the outer periphery of the friction surface, so the friction area is reduced. A disc brake that is large, oxidation resistant, and has excellent braking performance that is sufficiently reliable as a disc brake for high-load vehicles that perform frequent braking can be obtained.

Furthermore, if the stator plate is provided with radiation fins, the ability to dissipate absorbed heat will also be improved.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a front view schematically showing an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG.

The disc brake 1 shown in FIG. 1.2 is of a so-called floating type, and has a rotor disc 4 connected via an axle 2 and a wheel disc 3 shown in FIG.

This rotor disk 4 is finished into a single disk by attaching rotor linings 4a made of carbonaceous material to metal rotor plates 4b, respectively. are connected by bolts 5.

A stator 6 is provided on each side of the rotor disk 4.
This stator 6 has an annular carbonaceous stator lining 6a that is in sliding contact with both surfaces and the entire circumference of the rotor disk 4 and is housed in a metal stator plate 6b by pressure welding or fitting. It is something that

This stator 6 is held in a caliper 9, and a pin 10 (see FIG. 1) is provided at the end of the caliper 9, and the caliper 9 is movably supported by this pin 10. ing. A pair of pressurizing means 12 is provided on one side of the caliper 9 via a metal boot 11. This pressurizing means 12 moves a piston 13 provided in the caliper 9 forward and backward within the caliper 9 by hydraulic pressure supplied via a plug 14, and
The tip of the stator plate 6b is adapted to pressurize one side of the stator plate 6b.

Since this disc brake 1 is of a floating type, the reaction force of the pressurizing force applied when the piston 13 operates is transmitted to the other stator plate 8 via the caliper 9, and the pair of stator linings 7 They cooperate to pinch both sides of the metal rotor disk 4.

However, if it is necessary to further increase this clamping force, the number of pressure means 12 installed may be increased.

In this embodiment, the stator lining 6a and the rotor lining 4a are made of carbonaceous material, which has (1) excellent wear resistance under high temperatures, and (2)
It has the following characteristics: there is almost no decrease in the coefficient of friction even at high temperatures, the coefficient of friction is stable, (3) it has high thermal conductivity, and (4) it has a large heat absorption capacity.

Therefore, when a large amount of kinetic energy is converted into heat energy in a short time when the vehicle is braked, it is the best material to quickly absorb this heat energy.

Moreover, especially in this embodiment, this rotor lining 4
The hardness of the carbonaceous material constituting the stator lining 6a is made higher than that of the carbonaceous material of the stator lining 6a.

Generally, in a multi-disc clutch system or multi-disc system using carbon-carbon composite material, the same material is used for both the stator and rotor.

However, if you use a combination of low-hardness materials and high-hardness materials, the amount of wear of not only the low-hardness materials but also the wear of the high-hardness materials will be much greater than when the same materials are used in combination. It turns out that it can be held down low.

For example, as a result of appropriately combining samples A, B, and C, which had different hardnesses by changing the heat treatment temperature, and examining the amount of wear per 100 cycles, the measured values shown in FIG. 3 were obtained. According to this, it can be seen that the amount of wear is much smaller when a low hardness material and a high hardness material are used in combination than when the same materials are used in combination.

Therefore, if a high-hardness material is used as the rotor lining, the life of the rotor lining can be greatly extended compared to the case of using a carbonaceous material with the same characteristics. It becomes possible to configure a type of disc brake.

Therefore, in this embodiment, the hardness of the carbonaceous material constituting the rotor lining 4a is made higher than the hardness of the carbonaceous material forming the stator lining 6a, thereby reducing the amount of wear on both linings.

In order to form a carbonaceous material having such a difference in hardness, the degree of graphitization of the carbonaceous material may be adjusted.

In general, it is known that the degree of graphitization of carbon materials changes depending on the heat treatment temperature, and its physical properties can be adjusted over a wide range.As the degree of graphitization increases, the hardness decreases and at the same time the thermal conductivity increases. .

Therefore, a material with a low degree of graphitization, that is, high hardness and low thermal conductivity, is used for the rotor lining 4a, and a material whose hardness is lower than that of the rotor lining 4a is used for the stator lining 6a.

In this way, even under conditions where the temperature rise of the friction surface exceeds the allowable temperature limit of the metal material, it is possible to avoid an abnormal temperature rise of the rotor plate 4b, which is a metal material.

This means that the abnormal temperature rise due to brake operation occurs on the friction surface, and the temperature on the opposite side, that is, the rotor plate 4b or stator plate 6b side, increases gradually from the initial temperature of the brake operation. This is evident from the fact that the average temperature of the material is reached and there are no temperature peaks during this time (see Figure 4). In FIG. 4, the graph on the friction side shows a peak when the brake is operated, but the graph on the cooling side shows a gentle curve.

Furthermore, the carbon material for the rotor lining 4b is a carbonaceous material with higher hardness than the carbonaceous material for the stator lining (high hardness means a relatively low degree of graphitization and a relatively low thermal conductivity). ), the sudden and abnormally large temperature rise that occurs on the friction surface will be shared by the carbonaceous material, and the metal rotor plate will be able to absorb the sudden and abnormally large temperature rise that occurs on the friction surface. 4
b and the stator plate 6b, and also increases the actual operating temperature limit of the metal material.

This means that metal materials commonly used as structural materials can be used safely enough as the rotor plate 4b of the high-load brake. Therefore, with this structure, the temperature rise limit of the rotor plate 4b can be kept low, and the strength necessary for the rotor plate to perform its original role of transmitting brake torque to the axle can be easily ensured. It is also possible to construct this using ordinary metal materials commonly used as structural forest materials.

Furthermore, in this embodiment, the basic design theory of the disc brake is based on the point that both the rotor disc 4 and the stator 6 cooperate to absorb frictional heat during brake operation. , the frictional heat is distributed to both the rotor disk 4 and the stator lining 7, so that the temperature rise on the friction surface can be suppressed to a low level, and even if the load capacity becomes large, it can be used satisfactorily. .

The heat generated during brake operation is transmitted to both the rotor lining 4a and the stator lining 6a, which are made of highly thermally conductive materials, and both absorb the heat.

In particular, carbonaceous materials have several times the heat absorption capacity per given weight of metal materials, and their heat-resistant temperature is also very high. Therefore, the usable temperature of the entire brake system, that is, the heat absorption capacity, should be further increased. becomes possible.

In this way, when the rotor lining 4a and the stator lining 6a are used as heat absorbing materials, the specific heat and usable temperature of the materials are important issues, but even more important than these is the thermal conductivity. The carbonaceous material also has better thermal conductivity than the -m metal material.

Since it is virtually impossible to accurately measure the sudden and unsteady temperature distribution that occurs inside the material during brake operation, it is possible to clarify this through simulation.
It will look like Figure 4.5.

FIG. 4 shows the result of simulating the temperature distribution that occurs in the thickness direction of the rotor disk 4 of a disk pad type brake during brake operation, and it can be seen that an extremely large temperature distribution occurs over time. Furthermore, FIG. 5 shows the influence of the thermal conductivity and thickness of the material on the maximum temperature reached on the friction surface of the rotor disk during the same brake operation.

If the outer diameter of the disk is constant, the load capacity, that is, the material thickness D
It can be seen that as the temperature increases, the maximum temperature of the friction surface increases rapidly.

As is clear from these figures, the temperature distribution generated inside the material during brake operation varies greatly depending on the thermal conductivity and thickness of the material.

Therefore, if the rotor disk 4a and the stator lining 6a are made of carbonaceous material, which is a material with high thermal conductivity, the temperature gradient generated in the brake material during brake operation can be reduced, and furthermore, the temperature gradient generated in the brake material during brake operation can be reduced. This means that heat can be effectively dissipated from the outer surface (opposite the friction surface) into the atmosphere.

On the other hand, regarding the stator lining 6a and the like, it has been found that the amount of wear of the friction material is largely controlled by the load per unit area (energy loading), and increases rapidly when the load exceeds a certain value. With all-circumference pressurized brakes, the energy loading is naturally smaller than with conventional pad-type brakes, so it is very advantageous in terms of material wear.

In addition, it is relatively easy to provide an allowance for the thickness of the stator lining 6a, etc., so even if the amount of wear of the stator lining is slightly larger than that of conventional organic or semi-metallic materials. However, maintenance frequency is low.

If the material has high heat absorption capacity and excellent thermal conductivity, the stator lining 6a can be replaced with the rotor lining 4.
It is also possible to use an all-circumference pressurizing type disc brake that abuts the entire circumference.

However, the biggest problem when using carbonaceous materials as heat absorbers for brakes is their oxidation resistance. When using a certain material as a friction material, it is virtually impossible to expect zero wear from that material, and even if a method to improve the oxidation resistance of carbonaceous materials in a static state could be developed, When actually using it as a brake, it is impossible to avoid exposing the carbon part of the material to the surface.

Therefore, in this embodiment, the carbonaceous material is substantially shielded from the oxygen atmosphere. In other words, caliper 9
A gas supply means 16 for supplying an inert gas between the stator lining 6a and the rotor lining 4a is provided at the top of the stator plate 4b.
It has a structure that envelops the two, preventing air from entering the friction surfaces between the two, while introducing inert gas from the outside.

Examples of this inert gas include nitrogen and carbon dioxide gas, but engine exhaust gas can also be used.

In this way, the friction surfaces of the stator lining 6a and the like will not come into contact with the atmosphere during brake operation, and oxidation of the stator lining 6a and the like will be prevented.

After the brake is operated, the stator lining 6a is released from the rotor lining 4a and a gap is created between the two to block the atmosphere by covering the inner and outer peripheries of the lining material with a heat-resistant fiber material or a metal band. The effect of introducing the inert gas can be further enhanced. Also,
Since the gap at this time is very small, a sufficient effect can be obtained with only a small amount of gas. Only by protecting the carbonaceous material from the oxidizing atmosphere in this way can the properties of the carbonaceous material as a heat absorbing material be effectively utilized.

Experiments have shown that the friction and wear characteristics of carbon-carbon composite materials are completely different when tested in an oxidizing atmosphere and in a non-oxidizing atmosphere, with the latter exhibiting less wear. It has been found that the coefficient of friction is also very stable.

Therefore, shielding the material from an oxidizing atmosphere is
This not only suppresses the oxidative wear and tear of the material, but also significantly improves its friction and wear characteristics.

FIG. 6 shows another embodiment of the present invention, in which radiation fins 17 are provided on the outer peripheral surface of the stator plate 6b. In this way, most of the thermal energy generated by the brake operation can be efficiently dissipated into the atmosphere from the outer surface of the stator plate 6b, which not only improves heat dissipation but also increases the load capacity. It is also extremely easy to increase the cooling surface area.

(Effects of the Invention) As described above, according to the present invention, the carbonaceous stator lining is attached to the metal stator plate, and the carbonaceous rotor lining is attached to the metal rotor plate 1-. The rotor disk and stator lining can quickly absorb thermal energy during brake operation, and are lightweight, heat-resistant, heat-resistant disks with large heat absorption capacity and low wear. It can be a brake.

In addition, if heat dissipation fins are provided on the stator plate, it will have excellent heat dissipation.Furthermore, if inert gas is introduced around the rotor disk and stator lining, the stator lining can be protected from oxidizing atmosphere. It can also be used as a brake for land vehicles.

[Brief explanation of the drawing]

FIG. 1 is a front view showing one embodiment of the present invention, and FIG. 2 is a front view showing an embodiment of the present invention.
1 is a sectional view taken along the line ■-■, FIG. 3 is a table showing the friction test results, FIG. 4.5 is an explanatory diagram showing the temperature characteristics during brake operation, and FIG. 6 is a diagram showing the present invention. FIG. 2 is a cross-sectional view of main parts showing an embodiment of a pond. 1... Disc brake, 4... Rotor disk, 4a... Rotor lining, 4b... Rotor plate, 6... Stator, 6a... Stator lining, 6b... Stator plate, 9. ... Caliper, 12... Pressurizing means, 16... Gas supply means, 17... Fin.

Claims (1)

[Scope of Claims] 1) A disc brake comprising a disk-shaped rotor disk and a stator that moves toward and away from the entire circumference of at least one surface of the rotor disk, the stator comprising:
A high-load disc brake, characterized in that a carbonaceous stator lining is attached to a metal stator plate, and the rotor disk has a carbonaceous rotor lining attached to a metal rotor plate. 2) The high-load disc brake according to claim 1, wherein the hardness of the carbonaceous rotor lining is higher than the hardness of the carbonaceous stator lining. 3) The high-load disc brake according to claim 1 or 2, wherein the stator plate is provided with heat radiation fins. 4) Claim 1 characterized in that an inert gas is introduced around the rotor disk and stator lining.
The high-load disc brake according to items 3 to 3.