JPH0555732B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a friction multi-plate differential limiting device (Limited Slip Differential, hereinafter abbreviated as "LSD"), and in particular, the present invention relates to a friction multi-disc differential limiting device (hereinafter abbreviated as "LSD"), and in particular, the friction performance of the friction plates is significantly improved. Regarding friction multi-plate LSD. [Prior Art] LSD is a device for distributing and transmitting driving force to the driving axle of a vehicle. For example, when turning or driving on a rough road, LSD is a device that distributes and transmits driving force to the driving axle of a vehicle. It distributes and transmits power to the left and right drive wheels. Figure 1 shows a cross-sectional view of a friction multi-plate LSD. In FIG. 1, 1 is a differential case (differential case), which rotates integrally with the final reduction gear. A pinion shaft 2 is fixedly installed in the differential case 1 so as to be orthogonal to the rotation axis of the differential case 1. Reference numerals 3 and 4 designate a pair of opposing pinion gears, which are housed within the differential case 1 and rotatably supported by the pinion shaft 2. 5 and 6 are a pair of opposing side gears, which have the same rotation axis as the rotation axis of the differential case 1;
It meshes with pinion gears 3 and 4 and is connected to left and right drive axles 7 and 8 that are connected to left and right drive wheels, respectively. Between the differential case 1 and the side gears 5 and 6, there is a friction plate provided on the differential case side, that is, a thrust washer 10, and a clutch plate 9 which is sandwiched between these and rotatably supported by the side gears 5 and 6.
is provided. By sliding these thrust washers (friction plates) 10 and clutch plates 9, the difference in rotational speed between the differential case 1 and the side gears 5 and 6 is controlled. Note that mineral oil is contained inside the differential case 1 as a lubricant. In such a friction multi-plate LSD, the material for the friction plates 10 has conventionally been that the iron friction sliding surface is mechanically processed such as polishing, then treated with hydrochloric acid to make the surface porous, and then treated with manganese-based phosphoric acid. There are types with a coating formed on them, types with a self-lubricating material applied to the contact surface, and types with a conformable surface treatment. [Problems to be Solved by the Invention] However, the LSD equipped with a friction plate made of the conventional friction plate material described above has the following drawbacks. Because the friction coefficient of the friction plate is low, it is not possible to obtain the friction torque suitable for recent high-output, high-performance vehicles, and sufficient LSD performance cannot be obtained. In order to obtain the torque that corresponds to the required characteristics, it is necessary to increase the number of friction plates, and in this case,
The LSD differential case becomes large, making it unsuitable for downsizing the engine mechanism. When the friction plate and the mating clutch plate slide, the stick slip phenomenon causes abnormal noise when turning at low speeds. Since the friction plate does not have sufficient wear resistance, it will wear out after long-term use. For this reason, LSD does not have sufficient durability. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and provide a friction multi-plate LSD equipped with friction plates that have excellent friction performance and excellent wear resistance. [Means and effects for solving the problems] The friction multi-plate LSD of the present invention uses molybdenum disulfide (hereinafter abbreviated as "Mos ₂ ") and tetrafluoroethylene resin (hereinafter "PTFE") as solid lubricants.
It is abbreviated as ) and 5 to 15% by weight of carbon fiber as a friction modifier, with the remainder being substantially epoxy resin and/or amino resin. It is characterized by The present invention will be explained in detail below with reference to the drawings. FIG. 2 is a front view showing one embodiment of the friction plate of the friction multi-plate LSD of the present invention. The LSD of the present invention has the same structure as the general friction multi-plate LSD shown in FIG. 1, except that a dry film of a specific composition is formed on the friction plates. The friction plate 10 according to this embodiment has lattice-shaped oil grooves 1
A dry film 11 having the composition shown below is formed on the surface of the friction plate main body of a steel plate on which Oa is formed, with a base layer of manganese phosphate or the like interposed therebetween if necessary. Dry film composition Solid lubricant: Mos ₂ and PTFE = 40 to 55% by weight Friction modifier: Carbon fiber = 5 to 15% by weight Binder: Epoxy resin and/or amino resin = balance In the present invention, Mos ₂ and PTFE If the solid lubricant is less than 40% by weight, good friction performance that can prevent the stick slip phenomenon cannot be obtained, and wear resistance is also insufficient. On the other hand, even if the solid lubricant exceeds 55% by weight, the friction performance decreases and the wear resistance significantly decreases. Although there is no particular restriction on the ratio of Mos ₂ and PTFE in the solid lubricant, it is usually preferable to use about 50 to 150 parts by weight of PTFE per 100 parts by weight of Mos ₂ . On the other hand, if the carbon fiber content is less than 5% by weight, a sufficiently high coefficient of friction cannot be obtained, and if it exceeds 15% by weight, the wear resistance decreases. In order to obtain sufficient wear resistance, the proportion of carbon fiber is preferably 5 to 10% by weight. Further, if the fiber diameter of the carbon fiber used is smaller than 5 μm, the role as a friction modifier cannot be fully exhibited, and it may not be effective in improving the friction coefficient and wear resistance. On the other hand, if the fiber diameter is larger than 30 μm, sufficient bonding with the binder cannot be obtained and the fibers will fall off due to sliding, resulting in poor wear resistance. Therefore, the fiber diameter of carbon fiber is 5~
The thickness is preferably 30 μm, particularly preferably 10 to 20 μm. Regarding the length of carbon fibers, carbon fibers having an aspect ratio of about 10, that is, fiber lengths of 50 to 300 μm, particularly 100 to 200 μm, are suitable for production. The blending ratio of the epoxy resin and/or amino resin used as the binder can be arbitrarily selected. The thickness of the dry film made of such a component composition is preferably 15 μm or more in order to ensure wear resistance sufficient to withstand long-term use. When the thickness of this dry film exceeds 35 μm, thermal conductivity deteriorates and wear resistance decreases. In addition, the film becomes easy to peel off, the strength of the film decreases, and the cost becomes high. Therefore, the thickness of the dry film to be formed is preferably 15 to 35 μm. In addition, if the surface roughness of the dry film is smaller than 5 μm, the level of the friction coefficient will be low (for example, the dynamic friction coefficient μd = 0.05 to 0.08), and conversely, if the surface roughness is rougher than 30 μm, the initial μd will be high, but the change over time (μd decreases). ) is large and a stable friction coefficient cannot be obtained. Therefore, the surface roughness of the dry film is preferably 5 to 30 μm,
In particular, it is preferably 10 to 20 μm. Such a dry film can be formed using a binder, for example.
A solid lubricant is added to 100 parts by weight dissolved in 100 to 200 parts by weight of a solvent (such as xylene), and the mixture is ground in a ball mill for 3 hours. The sample was then sprayed with air spray, etc. onto a steel plate (with oil grooves) that had been treated with manganese phosphate as a base treatment.
It can then be easily formed by heating and curing at about 200°C for about 30 minutes. In addition, in the present invention, if the surface roughness of the clutch plate, which is the mating material of the friction plate, is rougher than 0.8 μm, the wear of the friction plate will increase and the durability and stability of the coefficient of friction will be impaired. The roughness is
It is preferably 0.8 μm or less, particularly 0.5 μm or less. [Example] The present invention will be described in more detail below with reference to Examples, Comparative Examples, and Reference Examples. Examples 1 to 3 Friction plates according to the present invention shown in FIG. 2 were manufactured. That is, first, the surface of a steel plate on which a grid-like oil groove was formed was subjected to manganese phosphate treatment as a base treatment. Separately, resin compositions were prepared at the blending ratios shown in Table 1. Specifically, 100 parts by weight of the binder was dissolved in 100 to 200 parts by weight of a solvent (M・E・K, xylene), a solid lubricant was added, the mixture was ground in a ball mill for 3 hours, and then To this, a predetermined amount of friction modifier is added and stirred. The resin composition thus obtained was air-sprayed onto the surface of a steel plate, and then heated and cured at 200° C. for 30 minutes to form a dry film with a thickness of about 25 μm. A friction test and an abrasion test were conducted on the obtained friction plate according to the following method. The results are shown in Table 1. Friction test Friction plate A with the above-mentioned dry film formed, and friction plate B (outer diameter 120 mm, A friction test was conducted using a thrust tester using a combination of 100mm inner diameter and 1.8mm thickness. In the test, friction plate A was pressed against friction plate B with a load of 400 kgf in LSD oil, and friction plate B was rotated at approximately 5 rpm, and the friction coefficient (static friction coefficient (hereinafter referred to as static friction coefficient) was calculated from the friction torque generated at that time. ) and the coefficient of kinetic friction (hereinafter referred to as "μd").
It is abbreviated as )) was investigated. Similar to the wear test, friction plate A was loaded with a load of 500 kg against friction plate B, which was rotating at approximately 50 rpm in LSD oil.
The amount of wear (wear depth) after 200 hours of pressing at f was examined. Comparative Examples 1 to 6 Friction plates A were manufactured in the same manner as in Example 1, except that the coating was formed using the raw material composition shown in Table 1, and a performance test thereof was conducted. The results are shown in Figure 3.

[Table] As is clear from Figure 3, the friction coefficients of Examples 1 to 3 and Comparative Examples 3 to 6, in which carbon fibers were blended, were significantly higher than those of Comparative Examples 1 and 2, and as the amount of carbon fibers increased. Therefore, it tends to increase, reaching a peak at about 20% by weight and becoming saturated. In addition, in Comparative Example 1 (conventional material), μs is higher than the average μd, and exhibits a characteristic that abnormal noise is likely to occur due to the stick slip phenomenon, whereas Examples 1 to 3 and Comparative Examples 3 to 6 always μs≦μd, and has good characteristics that prevent abnormal noise from occurring. On the other hand, regarding wear, when the carbon fiber content is 5 to 15% by weight (Examples 1 to 3), a low amount of wear is shown within the thickness of the dry film, but when the content is 20% by weight or more,
As in Comparative Examples 1 and 2, the underlying manganese phosphate treatment layer becomes exposed, and the abrasion resistance tends to deteriorate. This is because when the amount of carbon fiber increases, the amount of binder (epoxy resin, etc.) necessary for bonding becomes insufficient, and the bonding force between carbon fiber and solid lubricant and binder decreases, resulting in poor wear resistance. It is thought that this is because From the above results, the amount of carbon fiber is 5
~15% by weight is good, especially when considering wear resistance 5
It is clear that ~10% by weight is preferred. Examples 4 to 7, Comparative Examples 7 and 8 Example 1 except that the amount of carbon fiber was fixed at 7% by weight and the amount of solid lubricant (Mos ₂ + PTFE) was varied as shown in Table 2. Friction plate A was manufactured in the same manner as above, and its performance tests were conducted. The results are shown in Table 2.

[Table] From Table 2, when the amount of solid lubricant (Mos ₂ + PTFE) is 35% by weight (Comparative Example 7), the friction coefficient is high, but the relationship between μs and μd causes the stick slip phenomenon. Moreover, the amount of wear is larger than that of Examples 4 to 7. On the other hand, it can be seen that when the amount of solid lubricant is 60% by weight (Comparative Example 8), the μd level is slightly lower, and the wear resistance is significantly lowered. Therefore, the amount of solid lubricant is preferably 40 to 55% by weight. In addition, in Table 2, Mos ₂ and
The blending ratio of the PTFE solid lubricant is 100 parts by weight of PTFE to 100 parts by weight of Mos ₂ .
Similar results can be obtained by adding 50 to 150 parts by weight of PTFE. Further, in Examples 1 to 7 above, a mixed system of an epoxy resin and an amino resin is used as the binder, but similar results can be obtained even when these are used alone. Reference Example 1 A wear test was conducted in the same manner as in Example 1, using the friction plate of Example 2 as friction plate A and changing the surface roughness of friction plate B as shown in Table 3. The results are shown in Table 3 and Figure 4. As is clear from Table 3 and Figure 4, when the surface roughness (Rz) of the mating clutch plate becomes rougher than 0.8 μm, wear on the dry film side tends to increase due to abrasive action, and durability and μd,
0.8μm or less, as it greatly affects the stability of μs.
Preferably, the thickness is 0.5 μm or less.

【table】

[Table] [Effects of the invention] As detailed above, the friction multi-plate LSD of the present invention
According to the invention, the friction performance and wear resistance of the friction plate are significantly improved, resulting in the following effects. The friction plate has an extremely high coefficient of friction, approximately twice that of conventional friction plates, which results in high friction torque and greatly improves LSD performance. Since the number of friction plates can be reduced, the entire LSD can be made smaller and lighter. Friction plates always show a tendency for μd to be higher than μs, so there is no abnormal noise caused by the stick slip phenomenon. The wear resistance of the friction plate is much superior to that of conventional friction plates, so it can be used stably for a long period of time. This greatly improves the durability and reliability of LSD.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a friction multi-plate LSD, Fig. 2 is a front view showing a friction plate according to the LSD of the present invention, and Fig. 3 is a cross-sectional view of a friction multi-plate LSD.
The figure is a graph showing the results of Examples 1 to 3 and Comparative Examples 1 to 6, and FIG. 4 is a graph showing the results of Reference Example 1. 1... Differential case, 5, 6... Side gear, 9
...Clutch plate, 10...Friction plate.

Claims (1)

[Claims] 1 Contains 40 to 55% by weight of molybdenum disulfide and tetrafluoroethylene resin as a solid lubricant, and 5 to 15% by weight of carbon fiber as a friction modifier,
1. A friction multi-plate differential limiting device comprising a friction plate on which a dry film is formed, the remainder of which is substantially made of epoxy resin and/or amino resin.