JP3797789B2 - Electromagnetic friction clutch - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic friction clutch.
[0002]
[Prior art]
As one type of friction clutch, as disclosed in JP-A-7-71563, an inner clutch plate and an outer clutch plate are provided, and the clutch plates are frictionally engaged by the action of magnetic force. There is an electromagnetic friction clutch. The electromagnetic friction clutch is configured as a pilot clutch mechanism that operates a main clutch that transmits torque between the inner and outer rotating members, and is incorporated in the driving force transmission device. Further, in each clutch plate, the friction engagement surface is formed in a concavo-convex shape with a predetermined surface roughness, and the pilot clutch mechanism is operated by the friction engagement of the convex portion. In this case, oil for lubricating and cooling the electromagnetic friction clutch is held in the concave portion of the friction engagement surface.
[0003]
[Problems to be solved by the invention]
By the way, in a friction clutch, the uneven | corrugated shape of the friction engagement surface of each clutch plate lose | disappears by long-term use, and a friction engagement surface becomes a mirror surface. When the concave and convex shapes remain on the frictional engagement surface, oil is retained in the concave portion. However, when the frictional engagement surface is mirrored, an oil film of oil is easily formed between the frictional engagement surfaces. When the relative rotation between the plates is small, a phenomenon is observed in which the oil film force of the oil existing between the two clutch plates is larger than the friction engagement force, and the transmission torque with respect to the relative rotation of the two clutch plates gradually decreases.
[0004]
Graphs a and c shown in FIG. 3 show the relative rotational speed between the clutch plates and the transmission torque before and after a new driving force transmission device including the electromagnetic friction clutch as a constituent mechanism and a durability test after long-term use. Shows the relationship. In the graph in the figure, graph c shows that when both clutch plates are new (before the durability test) and have a predetermined surface roughness, graph a shows that both clutch plates have been used for a long time and their surfaces have worn. This is the case when it is mirror-finished (after the durability test). As shown in graph a, when the friction clutch surfaces are worn and mirrored due to long-term use of the friction clutch, the transmission torque is greatly reduced when the relative rotation between the clutch plates is small. Is recognized.
[0005]
In addition, a gap due to the uneven shape of the friction engagement surface exists between both clutch plates. In an electromagnetic friction clutch in which the friction clutch is frictionally engaged by the action of a magnetic force, this gap decreases the friction engagement force of the friction clutch by reducing the acting magnetic force. It is not constant due to variations in (surface roughness), and this is a variation in torque transmission characteristics for each product in an electromagnetic friction clutch.
[0006]
Accordingly, an object of the present invention is to address these problems and improve the torque transmission characteristics of an electromagnetic friction clutch.
[0007]
[Means for Solving the Problems]
To achieve the above object, the present invention is, each other initiative Relative rotatably same both rotated by frictional engagement positioned between the outer side rotating member and the inner side rotating member which is supported coaxially member a main clutch mechanism for torque transmission between a solenoid type pilot clutch mechanism example Bei the inner clutch plate and the outer clutch plates frictionally engaged by the action of the electromagnetic force, the main clutch a frictional engagement force of the pilot clutch mechanism A cam mechanism that frictionally engages the main clutch mechanism by transmitting to the mechanism, and adjusts the friction engagement force of the pilot clutch mechanism to control the driving force distribution ratio transmitted to the outer rotating member and the inner rotating member. in the driving force transmission apparatus, iron both clutch plates constituting the pilot clutch mechanism to form the unevenness of each predetermined rough surface of its frictional engagement surface It is a friction plate, and a nitrogen compound layer is formed to a thickness of 20-40 μm on the friction engagement surface of one of these friction plates via a nitrogen diffusion layer, and an oxide film is formed on the surface of the nitrogen compound layer. there is provided a driving force transmission device, characterized in that there.
[0008]
In the electromagnetic friction clutch according to the present invention, the multilayer clutch plate is formed by subjecting a plate made of an iron base material to gas nitriding-oxidizing-rapid cooling.
[0009]
[Operation and effect of the invention]
In the electromagnetic friction clutch according to the present invention, the multi-layered clutch plate employed has an oxide film, a nitrogen compound layer, and a nitrogen diffusion layer from the surface side, and is resistant to corrosion, abrasion, and resistance. Fatigue is exhibited synergistically, and mirroring at the friction engagement surface is prevented. For this reason, the fall of the transmission torque between both clutch plates resulting from mirror-finishing of a friction engagement surface is suppressed, and the torque transmission characteristic in an electromagnetic friction clutch can be improved.
[0010]
In this case, the inner clutch plate and the outer clutch plates, since Write hardness difference increases the transmission torque, the clutch plate hardness is greater multilayer structure to one of the inner clutch plates or A SONG clutch plate It is advantageous to adopt.
[0011]
In addition, the clutch plate having a multi-layer structure has a lower magnetic permeability due to its structure and slightly lowers the strength of the magnetic force, but the lowering of the magnetic force reduces the influence of variations in the flatness (surface roughness) of the clutch plate. The variation in the torque transmission characteristics of each product of the driving force transmission device when it is new is reduced.
Furthermore, the present invention provides the above-described three-layer clutch plate, thereby improving the torque transmission characteristics after a long-term use of the driving force transmission device compared to the conventional one, and even after a long-term use. Torque transmission characteristics when new can be maintained.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 shows a driving force transmission device employing an electromagnetic friction clutch according to the present invention. As shown in FIG. 2, the driving force transmission device 10 is mounted on a driving force transmission path to the rear wheel side in a four-wheel drive vehicle.
[0013]
In the four-wheel drive vehicle, the transaxle 21 is integrally provided with a transmission, a transfer, and a front differential, and the driving force of the engine 22 is output to both axle shafts 23a via the transaxle 21 and left and right. The front wheel 23b is driven and output to the propeller shaft 24 side. The propeller shaft 24 is coupled to the rear differential 25 via the driving force transmission device 10. When the propeller shaft 24 and the rear differential 25 are coupled so as to be able to transmit torque, the driving force is transmitted to the rear differential 25. The differential 25 is output to both axle shafts 26a to drive the left and right rear wheels 26b.
[0014]
The driving force transmission device 10 is housed in a differential carrier 27 together with the rear differential 25 and is supported by the carrier 27, and is supported by the vehicle body via the carrier 27. As shown in FIG. An outer case 10a that is a rotating member, an inner shaft 10b that is an inner rotating member, a main clutch mechanism 10c, a pilot clutch mechanism 10d, and a cam mechanism 10e are provided. The electromagnetic friction clutch according to the present invention is configured as a pilot clutch mechanism 10d.
[0015]
The outer case 10a includes a bottomed cylindrical front housing 11a and a rear housing 11b that is screwed into a rear end opening of the front housing 11a to cover the opening. The front housing 11a is made of a nonmagnetic material. The rear housing 11b is made of iron which is a magnetic material. A stainless steel cylinder 11b1, which is a nonmagnetic material, is embedded in the radial intermediate portion of the rear housing 11b, and the cylinder 11b1 forms an annular nonmagnetic part.
[0016]
A nut member 11c is screwed to a screw portion formed on the rear end outer peripheral portion of the rear housing 11b so as to be able to advance and retreat. The nut member 11c fastens the front housing 11a from the rear end side, presses the screw portion of the front housing 11a against the screw portion of the rear housing 11b, and eliminates backlash between these two screw portions.
[0017]
The outer case 10a is rotatably supported by the differential carrier 27 on the outer periphery of the front end portion of the front housing 11a, and is rotatably supported by the differential carrier 27 on the outer periphery of the rear end portion of the rear housing 11b. The rear end portion of the propeller shaft 24 is connected to the front end portion of the front housing 11a so that torque can be transmitted.
[0018]
The inner shaft 10b penetrates the central portion of the rear housing 11b in a liquid-tight manner and is inserted into the front housing 11a. The inner shaft 10b is rotatable to the front housing 11a and the rear housing 11b in a state where movement in the axial direction is restricted. It is supported. A distal end portion of the drive pinion shaft 28 is inserted into the inner shaft 10b so as to be able to transmit torque.
[0019]
The main clutch mechanism 10c is a wet multi-plate friction clutch, and includes a large number of clutch plates (an inner clutch plate 12a and an outer clutch plate 12b), and is disposed on the back wall side of the front housing 11a. Each of the inner clutch plates 12a constituting the friction clutch is spline fitted to the outer periphery of the inner shaft 10b so as to be movable in the axial direction, and each of the outer clutch plates 12b is splined to the inner periphery of the front housing 11a. It is assembled so that it can be fitted and moved in the axial direction. The inner clutch plates 12a and the outer clutch plates 12b are alternately positioned so as to contact each other and frictionally engage with each other, and are separated from each other to be in a free state.
[0020]
The pilot clutch mechanism 10 d is an electromagnetic friction clutch according to an example of the present invention, and includes an electromagnet 13, a friction clutch 14, and an armature 15. The electromagnet 13 has an annular shape, and is fitted in the annular recess of the rear housing 11b while being fitted to the yoke 16. The yoke 16 is supported by the differential carrier 27 and is rotatably supported on the outer periphery of the rear end portion of the rear housing 11b.
[0021]
The friction clutch 14 is a wet multi-plate friction clutch including a plurality of clutch plates (an inner clutch plate 14a and an outer clutch plate 14b), and each inner clutch plate 14a is a first cam member constituting a cam mechanism 10e described later. The outer clutch plate 14b is assembled to the outer periphery of the front housing 11a so as to be movable in the axial direction. The outer clutch plate 14b is assembled to the inner periphery of the front housing 11a so as to be movable in the axial direction. Yes. The inner clutch plates 14a and the outer clutch plates 14b are alternately positioned so as to contact each other and frictionally engage with each other, and are separated from each other to be in a free state.
[0022]
The friction engagement surfaces of both clutch plates 14a and 14b are formed in an uneven shape with a predetermined surface roughness, and the pilot clutch mechanism 10d is operated when the protrusions are frictionally engaged. . In this case, oil for lubricating and cooling the pilot clutch mechanism 10d is held in the recess of the friction engagement surface.
[0023]
The armature 15 has an annular shape, and is assembled to the inner periphery of the front housing 11a by spline fitting so as to be movable in the axial direction.
[0024]
In the above configuration of the pilot clutch mechanism 10d, the magnetic path between the yoke 16, the rear housing 11b, the friction clutch 14, the armature 15, the friction clutch 14, the rear housing 11b, and the yoke 16 is energized by energizing the electromagnetic coil of the electromagnet 13. Is formed. Note that the energization of the electromagnetic coil of the electromagnet 13 is intermittently performed by switching a switch, and three drive modes described later can be selected. The switch is arranged in the vicinity of the driver's seat in the passenger compartment so that the driver can easily operate it. This switch need not be configured only in the second drive mode described later.
[0025]
The cam mechanism 10 e includes a first cam member 17, a second cam member 18, and a cam follower 19. The first cam member 17 and the second cam member 18 are formed with a plurality of cam grooves facing each other on the opposing surfaces while maintaining a predetermined interval in the circumferential direction. The first cam member 17 is rotatably fitted to the outer periphery of the inner shaft 10b and is rotatably supported by the rear housing 11b. The inner clutch plates 14a of the friction clutch 14 are spline-fitted to the outer periphery thereof. ing.
[0026]
The second cam member 18 is spline-fitted to the outer periphery of the inner shaft 10b and assembled so as to be integrally rotatable, and is positioned facing the inner clutch plate 12a of the main clutch mechanism 10c. A ball-shaped cam follower 19 is interposed in the cam grooves of the second cam member 18 and the first cam member 17 facing each other.
[0027]
In addition, in the lead wire 13 a for energizing the electromagnetic coil of the electromagnet 13, the tip portion on the electromagnetic coil side is embedded in the synthetic resin support member 16 a, and the support member 16 a is fitted to the yoke 16. Yes. As a result, contact between the lead wire 13a and the outer case 10a, which is a rotating member, is prevented, and occurrence of disconnection due to these contacts is prevented.
[0028]
In the driving force transmission device 10 having such a configuration, when the electromagnetic coil of the electromagnet 13 constituting the pilot clutch mechanism 10d is not energized, no magnetic path is formed, and the friction clutch 14 is in an unengaged state. . Therefore, the pilot clutch mechanism 10d is in an inoperative state, and the first cam member 17 constituting the cam mechanism 10e can rotate integrally with the second cam member 18 via the cam follower 19, and the main clutch mechanism 10c is in an inactive state. For this reason, the vehicle constitutes a first drive mode of two-wheel drive.
[0029]
On the other hand, when the electromagnetic coil of the electromagnet 13 is energized, a magnetic path is formed in the pilot clutch mechanism 10 d and the electromagnet 13 attracts the armature 15. For this reason, the armature 15 presses and frictionally engages the friction clutch 14, connects the first cam member 17 of the cam mechanism 10 e to the front housing 11 a side, and causes relative rotation with the second cam member 18. Let As a result, in the cam mechanism 10e, the cam follower 19 presses both the cam members 17 and 18 away from each other.
[0030]
As a result, the second cam member 18 is pressed toward the main clutch mechanism 10c, and the main clutch mechanism 10c is frictionally engaged according to the friction engagement force of the friction clutch 14, thereby transmitting torque between the outer case 10a and the inner shaft 10b. I do. For this reason, the vehicle constitutes a second drive mode of four-wheel drive that is continuously variable with the propeller shaft 24 and the drive pinion shaft 28 being uncoupled. In this drive mode, the driving force distribution ratio between the front and rear wheels can be controlled from 100: 0 (two-wheel drive state) to 50:50 (directly connected four-wheel drive state) according to the running state.
[0031]
Further, when the current applied to the electromagnetic coil of the electromagnet 13 is increased to a predetermined value, the attractive force of the electromagnet 13 with respect to the armature 15 is increased, and the armature 15 is strongly attracted to increase the frictional engagement force of the friction clutch 14. The relative rotation between the cam members 17 and 18 is increased. As a result, the cam follower 19 increases the pressing force against the second cam member 18 to bring the main clutch mechanism 10c into the coupled state. For this reason, the vehicle constitutes a third drive mode of four-wheel drive in which the propeller shaft 24 and the drive pinion shaft 28 are directly connected.
[0032]
Thus, in the driving force transmission device 10, the friction clutch 14 of the pilot clutch mechanism 10d is formed in a multi-layer structure having an iron base as a basic structure, and the outer clutch plate 14b is a single base made of an iron base. The frictional engagement surfaces of both clutch plates 14a and 14b are formed to have a predetermined surface roughness.
[0033]
The inner clutch plate 14a having a multilayer structure has a multilayer structure having a nitrogen diffusion layer on the surface side of an iron base, a nitrogen compound layer on the surface side of the nitrogen diffusion layer, and an oxide film on the surface side of the nitrogen compound layer. Is the body. Such a composite structure is formed by gas nitriding-oxidation-quenching treatment.
[0034]
The gas nitridation-oxidation-quenching treatment has been developed in recent years as a composite surface treatment method, and this composite treatment method is known as the Nitrotech method (registered trademark of UK RUKAL).
[0035]
The inner clutch plate 14a is the same base material as the outer clutch plate 14b, which is subjected to a nitrotech treatment. For example, gas soft nitriding is performed by heating an iron base material at 500 to 600 ° C. for 1 to 2 hours in a nitrogen atmosphere. And then oxidized for a short time at high temperature in an oxygen atmosphere and finally quenched by quenching in a water-oil emulsion. In this Nitrotech treatment, a nitrogen compound layer and a nitrogen diffusion layer are formed to a thickness of about 20 to 40 μm by gas soft nitriding treatment, and an oxide film is formed to a thickness of about 0.5 to 1.5 μm by oxidation treatment. It becomes strong by rapid cooling.
[0036]
In the friction clutch 14 constituting the pilot clutch mechanism 10d constructed as described above, the adopted multilayer clutch plate 14a has a multilayer structure having an oxide film, a nitrogen compound layer, and a nitrogen diffusion layer from the surface side. Thus, the corrosion resistance, the wear resistance, and the fatigue resistance are synergistically exhibited and the mirror engagement on the friction engagement surface is prevented.
[0037]
A graph b shown in FIG. 3 shows both of the two after the endurance test, assuming the long-term use when the surface roughness of the friction engagement surfaces of both clutch plates 14a and 14b is equal to that of the conventional one. The relationship between the relative rotational speed between the clutch plates 14a and 14b and the transmission torque is shown. In this case, as shown in the graph b of the same figure, transmission between the clutch plates 14a and 14b due to the oil film force of the oil formed between the two friction engagement surfaces by mirroring the friction engagement surface. The torque reduction is suppressed, and the torque transmission characteristic in the driving force transmission device 10 can be improved as compared with the conventional one shown in the graph a of FIG.
[0038]
In this case, since there is a difference in hardness between the inner clutch plate 14a and the outer clutch plate 14b, the transmission torque is advantageously increased.
[0039]
Further, the inner clutch plate 14a having a multi-layer structure lowers the magnetic permeability from the structure and slightly reduces the strength of the magnetic force. However, the decrease in the magnetic force has an effect of variations in the flatness (surface roughness) of the clutch plate. Acts to reduce, and reduces variation in torque transmission characteristics for each product in the electromagnetic friction clutch.
[0040]
FIG. 4 is a graph showing the relationship between the magnetic flux density generated in each pilot clutch mechanism 10d and the magnetic field strength when a clutch plate having a multi-layer structure and a single-layer structure is employed as the inner clutch plate 14a. FIG. 5 is a graph showing the relationship between the flatness (surface roughness) of the clutch plate and the attractive force of the armature 15 in each of the pilot clutch mechanisms 10d.
[0041]
In the graphs of FIGS. 4 and 5, graph a is a result when the inner clutch plate 14a having a multilayer structure is employed, and graph b is a result when the inner clutch plate 14a having a single layer structure is employed. As is clear from these results, when the inner clutch plate 14a having a multi-layer structure is employed, the magnetic field strength is small and the attractive force with respect to the armature 15 is greater than when the inner clutch plate 14a having a single-layer structure is employed. In addition, the change in suction force with respect to the change in flatness (surface roughness) on the friction engagement surface of the clutch plate is small. This means that the variation in torque transmission characteristics for each product in the pilot clutch mechanism 10d is reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view of a driving force transmission device incorporating a pilot clutch mechanism that is an electromagnetic friction clutch according to an example of the present invention.
FIG. 2 is a schematic configuration diagram of a four-wheel drive vehicle equipped with the driving force transmission device.
FIG. 3 is a graph showing the relationship between relative rotational speed and transmission torque in a conventional pilot clutch mechanism with various surface roughnesses of friction engagement surfaces in a clutch plate.
FIG. 4 is a graph showing a relationship between magnetic flux density and magnetic field strength generated in each pilot clutch mechanism when a clutch plate having a multi-layer structure and a single-layer structure is employed.
FIG. 5 is a graph showing the relationship between the flatness of the clutch plate and the attractive force of the armature in these pilot clutch mechanisms.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Driving force transmission apparatus, 10a ... Outer case, 10b ... Inner shaft, 10c ... Main clutch mechanism, 10d ... Pilot clutch mechanism, 10e ... Cam mechanism, 11a ... Front housing, 11b ... Rear housing, 11b1 ... Cylindrical body, 11c ... nut member, 12a ... inner clutch plate, 12b ... outer clutch plate, 13 ... electromagnet, 13a ... lead wire, 14 ... friction clutch, 14a ... inner clutch plate, 14b ... outer clutch plate, 15 ... armature, 16 ... yoke, 16a ... support member, 17 ... first cam member, 18 ... second cam member, 19 ... cam follower, 21 ... transaxle, 22 ... engine, 23a ... axle shaft, 23b ... front wheel, 24 ... propeller shaft, 25 ... rear Differential, 26a ... Axle shaft, 26b ... rear wheel, 27 ... differential carrier, 28 ... drive pinion shaft.

Claims (2)

A main clutch mechanism for transmitting torque between the two rotary members by frictional engagement positioned between each other initiatives Relative rotatably outer side rotating member which is supported coaxially with the inner side rotation member, the electromagnetic a frictional engagement to the inner clutch plate and the example Bei the outer clutch plates solenoid type pilot clutch mechanism by the action of the force, frictional engagement of the frictional engagement force of the main clutch the main clutch mechanism is transmitted to a mechanism of the pilot clutch mechanism A driving force transmission device including a cam mechanism to be combined, and adjusting a friction engagement force of the pilot clutch mechanism to control a driving force distribution ratio transmitted to the outer rotating member and the inner rotating member;
A steel friction plates both clutches plates were formed irregularities of respective predetermined rough surface of its frictional engagement surface constituting the pilot clutch mechanism, the one of the frictional engaging surface of any of these friction plates A driving force transmission device, wherein a nitrogen compound layer is formed to a thickness of 20-40 μm through a nitrogen diffusion layer, and an oxide film is formed on the surface of the nitrogen compound layer . Claims, characterized in that it is formed by quenching treatment - said nitrogen diffusion layer, the nitrogen compound layer and the oxide coating, gas iron plates formed on the surface irregularities of the predetermined rough surface of nitride - oxide power transmission device drive described in 1.

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