JPH0342335A - Differential limiting device for four-wheel drive car - Google Patents

Abstract

PURPOSE:To reduce torque required for limiting differential by limiting differential between the respective input members of front and rear wheels for transmitting power from a drive source through a differential gear by controlling the engagement of an electromagnetic clutch through a boosting mechanism. CONSTITUTION:In a four-wheel drive car, the rotation of a mount case 5 integral with a ring gear 2 to which a power from an engine side is transmitted to right and left front wheel drive shafts 11, 10 through a front differential gear A and the rotation of a right side gear 14 is transmitted to a rear wheel input shaft 16. In this case, in mount cases 19a, 19b connected to the rear wheel input shaft 16, a differential limiting device C comprising a planetary gear mechanism D as a speed increasing gear, a boosting mechanism D and an electromagnetic clutch device F is disposed. In case the generation of slip is apt to arise on an icy road or the like, the engagement of the electromagnetic clutch device F is controlled to limit the differential between the respective input shafts 15, 16 of the front and rear wheels.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power transmission device that can be applied to, for example, a center differential differential limiting clutch or a two-wheel/four-wheel switching clutch in a four-wheel drive vehicle.

[Conventional technology]

Generally, when driving a car, front-wheel drive has better straight-line stability than rear-wheel drive, but when cornering,
Front-wheel drive vehicles tend to be harder to turn because you have to use the steering wheel to apply force to the tires that are trying to return. In this respect, rear-wheel drive vehicles are easier to turn, but if the driving force is too strong, they have the disadvantage of causing the vehicle to turn too much. Therefore, it is ideal for driving a car to drive the front wheels and the rear wheels in equal proportion.
In this respect, four-wheel drive vehicles are extremely superior.

By the way, the left and right wheels of a car have different turning radii when cornering, so in order to absorb this effect and perform smooth cornering, the difference in rotation speed between the left and right wheels is absorbed according to the difference in turning radius. mechanism, namely the differential mechanism (
It has a front differential and a rear differential. This difference in turning radius also occurs between the front wheels and rear wheels, so in four-wheel drive vehicles, there is a mechanism that absorbs the difference in rotation speed between the front and rear wheels according to the difference in turning radius, that is, a center differential. A device equipped with a mechanism has been proposed.

However, since this center differential mechanism has the function of distributing the torque between the front wheels and the rear wheels in an equal ratio, the driving force transmission limit is balanced to the value of the lower driving force of the front wheels or the rear wheels. For example, if one of the front wheels spins, the driving energy will escape there,
The driving force of the rear wheels becomes extremely small. For this reason,
A four-wheel drive vehicle with a center differential may have inferior transmitted driving force when the road surface friction coefficient is low, compared to a four-wheel drive vehicle without a center differential. For example, when a large driving force is generated, such as during acceleration, the driving force cannot be sufficiently transmitted to the road surface, and this appears as phenomena such as front or rear wheels slipping (spin).

In order to prevent such negative effects, conventionally a locking mechanism has been installed that directly connects the differential between the front and rear wheels without going through a center differential. When necessary, the center differential mechanism was locked, and during normal driving, when large driving force was not required, it was unlocked.

Figure 1+ is a diagram for explaining the driving force value l: speed mechanism of a full-time four-wheel drive vehicle with a setter differential in which the engine is mounted on the front side. In this driving force transmission mechanism, power from the engine is transmitted to a torque converter 81, a main transmission 82, and an auxiliary transmission a83 arranged in an automatic transmission 80, and the output is transmitted to a drive gear 84 and a center differential input shaft 85. is transmitted to the center differential mechanism 86 via. The center differential mechanism 86 transmits rotation to a rear wheel drive propeller shaft 88 via a hypoid gear 87 and to a front differential mechanism 90 via a front wheel input shaft 89. It absorbs the difference between Further, the front differential mechanism 90 absorbs the differential between the left and right front wheel drive shafts 91 and 92.

On the other hand, a center differential differential limiting clutch 93 is disposed between the center differential input shaft 85 and the front wheel input shaft 89, and when the clutch 93 is engaged, the center differential mechanism 86 rotates integrally. Limits the differential movement between the front and rear wheels. Then, the clutch 9 is
By controlling the coupling state of the center differential mechanism 86, the degree of restriction of the center differential mechanism 86 is controlled.

In general, four-wheel drive vehicles include part-time four-wheel drive vehicles in addition to the above-mentioned full-time four-wheel drive vehicles. This is a two-wheel drive system that does not have a center differential and usually drives either the front or rear wheels, and when driving power is required, such as on snowy roads, the remaining wheels are directly connected to the drive shaft via a clutch etc. The system switches intermittently between 4-wheel drive and 4-wheel drive.

In addition to the method of hydraulically controlling the center differential differential limiting clutch or the two-wheel/four-wheel switching clutch described above, a viscose coupling is arranged between the front wheel drive shaft and the rear wheel drive shaft. Another known method is to mainly drive the front wheels, and when a differential occurs between the front and rear wheels due to slip, the power is distributed to the rear wheels using the shearing force of the viscous oil in the viscose coupling.

[Problem to be solved by the invention]

By the way, the torque that rotates the wheels in the above-mentioned four-wheel drive vehicle is decelerated in many stages compared to the torque generated by the engine, and although the rotational speed is low, the torque is extremely high, so the differential is limited. It is characterized by the large amount of torque required.

On the other hand, the above-mentioned method of hydraulically controlling the center differential differential limiting clutch or the two-wheel/four-wheel switching clutch can actively control the engagement degree of the clutch, but the rise of the hydraulic pressure is slow. Therefore, even when there is no need for differential differential restriction, a slight differential restriction is applied, which worsens fuel efficiency. Furthermore, since the clutch engagement torque can only be controlled in several stages (depending on the number of on/off combinations of the solenoid valves), a limit torque higher than necessary is often applied. Furthermore, it is difficult to miniaturize the clutch device, and a hydraulic power source must be secured, such as by combining it with an autotransformer F7 system, which poses problems for use in manual transmissions.

Therefore, it is possible to combine an electromagnetic clutch with a manual transmission, but as mentioned above, the torque required to limit the differential is large, so there is a problem that the weight, size, and power consumption of the electromagnetic clutch will be large. ing.

In addition, in the above-mentioned system using a viscose coupling, the degree of engagement cannot be actively controlled as in the hydraulic system, and since torque is transmitted by the shearing force of viscous oil, the torque There are problems such as a small capacity, a time lag in response, and continuous differential restriction resulting in high temperatures and deterioration of performance.

An object of the present invention is to solve the above-mentioned problems, and to provide a differential limiting device for a four-wheel drive vehicle with an electrical system.
By making it possible to control the differential limiting torque in proportion to the current, we aim to improve starting performance, stability during turns, stability during braking, and fuel-efficient driving, and expand the potential of 4-wheel drive vehicles. It's about making the most of it.

Another object of the present invention is to make it possible to downsize the clutch device and to make it applicable to a manual transformer 3+7 system.

[Means to solve the problem]

For this purpose, the invention described in claim 1 provides a front wheel input member (15) and a rear wheel input member (16, 19a, 19b) that transmit power from a drive source via a differential device (B).
, first and second cam members (30, 32) on which a cam surface (37) is formed, a ball member (33) sandwiched between the cam surfaces, and the rear wheel input member (19b). Second
The electromagnetic solenoid (41) is arranged between the cam members (32) of the
), an electromagnetic clutch device (F) controlled by a planetary gear mechanism (
D), and the invention described in claim 2 is characterized in that the differential between the front wheel input member (15) and the rear wheel input member (16) is limited by controlling the electromagnetic solenoid. The planetary gear mechanism (D) is
A carrier (29) connected to the front wheel input member (15) and a ring gear (27) formed on the rear wheel input member (16).
) and a sun gear connected to the second cam member (32).
25) The invention described in claim 3 is characterized in that a spring (35) for pressing the ball member (33) is provided between the first and second cam members (30, 32). The invention described in claim 4 is characterized in that:
The electromagnetic clutch device (F) has a multi-disc clutch (39), and among the friction plates of the multi-disc clutch (39), several friction plates on the second cam member (32) side are connected to the rear wheel. Input member (19b
) side with spline fitting, and the outermost Pi!
The remaining friction plates are spline-fitted inside the friction plate (39a), and a disc spring (43) is interposed between the outermost friction plate (39a) and the rear wheel input member (19b). The invention described in claim 5 is characterized in that the planetary gear mechanism (D) has a common sun gear (51), a common ring gear (55), and two pinions (52, 53). Yes, the common sun gear (51) is connected to the first cam member (3
0), one pinion (53) is connected to the rear wheel input member (19a), and the carrier (29) supporting the other pinion (52) is connected to the front wheel input member (15). The invention described in claim 6 is characterized in that the front wheel input member (15) and the rear wheel input member (16, 19a) transmit power from the drive source via the differential device (B). , 19b), a second cam member (30, 32) on which a cam surface (37) is formed, a ball member (33) sandwiched between the cam surfaces, and the rear wheel input member. (19b) and the second cam member (32) and controlled by the electromagnetic solenoid (41), and the front wheel input member (15) and the rear wheel input member (19a). A multi-plate clutch (4
6), the first cam member (30) presses the multi-disc clutch (46) under the control of the 1ift solenoid, and the front wheel input member (15) and the rear wheel input member (16)
The invention described in claim 7 is characterized in that the differential between This is a control map that sets differential limiting torque T according to θ and vehicle speed V, and there are multiple control maps (fl(θ, ■),
rz (θ, V), fs (θ, V)) is stored in the storage means (107) and the signal detected by the detection means is processed based on the control map and the electromagnetic solenoid (
41), and the electronic control device outputs a signal to the plurality of control maps according to at least one switching condition of cornering force, front and rear wheel rotation speed difference, switching time, and each switching condition of the brake. The invention described in claim 8 is characterized in that the cornering force c
When r is small, the front and rear wheel rotational speed difference ΔN is small, the switching time t and the brake are on, the control map is switched to the high FJ friction coefficient road map side, the cornering force C1 is large, and the front and rear wheel rotational speed difference ΔN is large. Large, throttle opening change rate dθ/d
When t is large, the control map is switched to a low friction coefficient road surface map.The invention described in claim 9 calculates the number of slips within a predetermined time based on the front and rear wheel rotational speed difference ΔN. However, the switching time t is changed when the number of times exceeds a predetermined value.

[Action and effect of the invention]

In the present invention, as shown in FIGS. 1 and 2, for example, when a large driving force is required on an icy road, a sandy road, a bumpy road, etc., or when there is a risk of wheel slipping or bumping, In this case, the current value of the electromagnetic solenoid (41) is controlled to proportionally control the degree of engagement of the multi-disc clutch (39). Depending on the degree of engagement of the multi-disc clutch (39), the second cam member (32) is pressed toward the first cam member (30), and due to the relative rotation between the two, the ball member (33) is moved to the position shown in FIG. Cam surface shown (3
7), the second cam member (32) compresses the spring (35) to apply a reaction force to the multi-disc clutch (39), thereby providing a predetermined engagement force to the multi-disc clutch (39).

At this time, the differential rotational speed is increased by the speed increasing mechanism, and the torque required for limiting the differential is reduced accordingly, so that the torque capacity of the electromagnetic clutch device F can be reduced.

In addition, in case of an emergency such as when the wheels come off, the electromagnetic solenoid (41)
When the current value is set to the maximum value, the multi-disc clutch (39)
Since the ball member (33) further moves on the cam surface (37) while being pressed with a pressing force F1 proportional to the first flow, the second cam member (32) further compresses the spring (35) and causes a multiplier. Press the plate clutch (39) and connect the multi-plate clutch (3
9) against the mount case (19b), the reaction force Fz is doubled and the multi-disc clutch (39) can be completely engaged.

Furthermore, in the control method of the present invention, as shown in FIG. 12, for example, depending on the level of the friction coefficient of the road surface, the low μ road map r + (θ, V) IIL and the medium μ road map rt (θ,
V) 112 and high μ road map rz (θ, V) 11
3, and depending on the throttle opening θ and vehicle speed V,
The differential limiting torque Tc is set so that the differential limiting torque T becomes higher as it goes toward the low μ road side. Cornering force CF is small, front and rear wheel rotation speed difference ΔN
is small, and when the predetermined switching time t and the brakes are on, the map is switched to the high μ road map side to improve fuel efficiency and braking stability.On the other hand, the cornering force C4 is large, the front and rear wheel rotational speed difference ΔN is large, and the throttle When the opening degree change rate dθ/dt is large, the map is switched to the low μ road map side to improve turning stability and acceleration.

Therefore, according to the present invention, the following effects are achieved.

(a) Since differential limiting is performed via a booster mechanism, the torque required for differential limiting is reduced by that amount, making it possible to install a small, small-capacity clutch device.

(b) Since the clutch capacity can be proportionally controlled simply by controlling current without using oil pressure, extremely fine control can be performed to improve fuel efficiency, braking stability, turning stability, and acceleration.

(c) When increasing the differential rotation speed using a speed increasing mechanism,
Since the torque required for limiting the differential is reduced accordingly, it becomes possible to install a small and small capacity clutch device.

(d) By adopting an electromagnetic clutch, no hydraulic power source is required, so it can be applied regardless of automatic or manual transmission.

(e) Since the power consumption is small, there is little impact on the power capacity of the vehicle.

Note that the numbers added to the above configurations are for comparison with the drawings, and the configurations of the present invention are not limited thereby.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 is a sectional view showing an embodiment of the differential limiting device of the present invention applied to a four-wheel drive vehicle with a center differential, Fig. 2 is an enlarged sectional view of the differential limiting device, and Fig. 3 is a sectional view of the cam member. A plan view, a sectional view, and FIG. 4 are diagrams for explaining the operation of the differential limiting device.

In FIG. 1, a front differential device A and a center differential device B fix a ring gear 2 that meshes with an output gear (not shown) of a transmission mechanism, and fix a transaxle case 3.
It is arranged in a mount case 5 that is supported by conical roller bearings 4 at a and 3b.

The front differential device A has a front differential carrier 6 rotatably supported within the mount case 5.

A pinion shaft 7a supporting a pinion 7 extends vertically and is rotatably supported on the differential carrier 6, and left and right side gears 8.9 are rotatably supported. A front wheel drive shaft 10.11 is coupled for power transmission.

Further, a center differential device B is disposed directly adjacent to the front differential, and the center differential device B has a pinion shaft 12a rotatably supported by the mount case 5, and is attached to the pinion shaft 7a. The differential gears 12 mesh with left and right side gears 13 and 14, respectively. A front wheel input shaft 15 and a front wheel drive shaft 11 integrally formed with the differential carrier 6 are connected to the inside of these side gears 13 and 14.
The left side gear 13 is spline-coupled to the differential carrier 6, and the right side gear 14 is spline-coupled to the rear wheel input shaft 16.

Furthermore, a transfer case 17 is assembled to the transaxle case 3b, and inside the transfer case 17 there are left and right mount cases 19a, 19.
b is rotatably supported via a pair of conical roller bearings 21. One mount case 19a fixes a hypoid gear 20 for driving the rear wheels, and is spline-coupled to the rear wheel input shaft 16. A hypoid gear 24 of a drive pinion shaft 23 meshes with the hypoid gear 20 for driving the rear wheels, and the drive pinion shaft 23 is connected to the rear axle via a known propeller shaft and rear differential device so as to be capable of transmitting power. ing.

A differential limiting device C according to the present invention is disposed within the mount cases 19a and 19b. The differential limiting device C includes a speed increase mechanism D, a booster mechanism E, and an electromagnetic clutch device F.

As shown in detail in Figure 2, the field difference mechanism is the sun gear 2
5, pinion 26, ring gear 27 and carrier 29
The sun gear 25 is formed integrally with a first cam member 30 described later, the ring gear 27 is formed on the inner peripheral surface of one mount case 19a, and the carrier 29 is It is spline-coupled to the front wheel input shaft 15 and rotatably supported on the inner peripheral surface of the mount case 19a via a hair ring 31.

The boosting mechanism E consists of first and second cam members 30.32 and six ball members 33 sandwiched between both cam members 31.32, and is formed on the first cam member 30. A second cam member 32 is fitted into the flange 30a, and a spring 35 is disposed between the flange 30a and the back surface of the second cam member 32. In addition, the first cam member 30
is rotatably supported by the mount case 19a via a bearing 34, and a clutch hub 36 is integrally formed on the back side of the second cam member 32. Both cam members 3
1.32 has six cam surfaces 37 formed on the inner surface as shown in FIGS. 3(A) and 3(B).

The electromagnetic clutch device F engages the mount case 19b and a clutch hub 36 formed on the second cam member 32,
Multi-disc clutch 39 for half-clutching and releasing state
, a cylindrical magnetic body 4 disposed on the outer periphery of the front wheel drive shaft 11
0, has a 7R, Ta solenoid 41 and a piston 42 disposed within the magnetic body 40, and attracts the piston 42 by magnetic lines of force generated by energization of the electromagnetic solenoid 41;
By pressing the multi-disc clutch 39, it is possible to cause the second cam member 32 to generate a differential limiting torque.

Next, the operation of the differential limiting device of the present invention having the above configuration will be explained.

The rotation of the engine is appropriately changed in speed via a transmission mechanism (not shown) and transmitted to the mount case 5 via the ring gear 2. During normal driving mainly focused on low fuel consumption, the 1ift solenoid 41 is off and the multi-plate clutch 39 is in a released state, as shown in FIG. 2, and in this state, the rotation of the mount case 5 is as follows. From the differential binion 12 of the center differential mechanism B to the left and right side gears 13.1
4. The rotation of the left side gear 13 is transmitted to the differential carrier 6 of the front differential mechanism A, and further transmitted from the differential pinion 7 to the left and right side gears 8.9, and then to the left and right front wheel drive shafts 1O111, respectively. On the other hand, the rotation of the right side gear 14 of the center differential mechanism B is transmitted to the rear wheel input shaft 16 connected to the gear, and further,
Mount case 19aS hypoid gear 2 for rear wheel drive
0 and 24 to the drive pinion shaft 23. The center differential mechanism B provides a differential between the front wheels and the rear wheels.

At this time, as shown in FIG. 2, in the speed increasing mechanism, the rotation of the ring gear 27 by the rear wheel input shaft 16 and the rotation and revolution of the pinion 26 by the front wheel input shaft 15 cause the rotation of the ring gear 27, which is integral with the sun gear 25. The first cam member 30 and the second cam member 32, which is pressed by a spring 35 via the first cam member 30 and the ball member 33, are freely rotating.

In addition, when a large driving force is required on frozen roads, sandy roads, uneven roads, etc., or when there is a risk that the wheels may slip, the current value of the IUI solenoid 41 is controlled to engage the multi-disc clutch 39. Proportional control of degree. Now, multi-plate clutch 3
9 is fully engaged, the rotation of the mount case 5 is transmitted to the left and right side gears 13 and 14 of the center differential mechanism B in FIG.
Since the sun gear 25 is fixed by the engagement of 9, the front wheel input shaft 15 and the rear wheel input shaft 16 rotate together, so the left and right side gears 13 and 14 rotate integrally without differential movement. . As a result, rotation at the same speed as that of the mount case 5 is transmitted to the front wheels and the rear wheels. When the degree of engagement of the multi-disc clutch 39 is controlled proportionally, the differential motion between the left and right side gears 13, 14 is limited depending on the degree of engagement.

FIG. 4(A) shows a state in which the degree of engagement of the multi-disc clutch 39 is controlled proportionally. As described above, in the speed increasing mechanism, the sun gear 25 rotates at an increased speed due to the rotation of the ring gear 27 by the rear wheel input shaft 16 and the rotation and revolution of the pinion 26 by the front wheel input shaft 15. The cam members 30, 32 of are rotating at an increased speed. The speed increasing ratio in this embodiment is given by the following equation, where ZI is the number of teeth of the sun gear 25 and Z2 is the number of teeth of the ring gear 27.

Speed increase ratio = Sun gear rotation speed / Power shaft rotation speed = 1 + (
Zt /Z,) When the current of the electromagnetic solenoid 41 is controlled in this state, the piston 42 is attracted and presses the multi-disc clutch 39 with a pressing force F proportional to the current. Then, the second cam member 32 engages the first cam member 3 according to the degree of engagement of the multi-disc clutch 39.
As the ball member 33 moves on the cam surface 37 shown in FIG. 3 due to the relative rotation between the two when pressed in the zero direction, the second cam member 32 compresses the spring 35 and applies a reaction force to the multi-disc clutch 39. , applies a predetermined engagement force to the multi-plate clutch 39.

At this time, the differential rotation speed is increased by a speed increasing mechanism, and in order to reduce the torque required to limit the differential by that amount, an electromagnetic flanch is installed. The torque capacity of the IF can be reduced.

Figure 4 (B) shows the multi-disc clutch 3 in case of an emergency such as when the wheels come off.
9 is fully engaged.

When the current value to the electromagnetic solenoid 41 is maximized, the multi-plate clutch 39 is pressed with a pressing force F proportional to the current, and the ball member 33 further moves on the cam surface 37, so that the second cam member 32 further compresses the spring 35 and presses the multi-disc clutch 39, and as a result presses the multi-disc clutch 39 against the mount case 19b, the reaction force F2 is doubled and the multi-disc clutch 39 can be completely engaged. .

Figure 5 shows the relationship between differential limiting torque and multi-disc clutch pressing force when a planetary gear mechanism with a speed increasing ratio of 3.48 is adopted. The degree of engagement of the multi-disc clutch is controlled proportionally, the multi-disc clutch is fully engaged in the Y range, and the differential limiting torque is increased by the booster mechanism E.

Next, another embodiment of the differential limiting device according to the present invention will be described with reference to FIGS. 6 and 7. In addition, regarding the description of other embodiments below, the same components as those of the above embodiments will be given the same numbers and the explanation will be omitted.

In this embodiment, I'j of the multi-plate clutch 39: I
Of the N1 sensing plates, the friction plate N2 on the second cam member 32 side
The remaining friction plates N+-Nz are spline-fitted to the mount case 19b side, and the remaining friction plates N+-Nz are spline-fitted to the inner side of the friction plate 39a closest to the piston 42. A disc spring 43 is interposed between the friction plate 39a and the mount case 19b.

The effect will be explained. When the piston 42 is attracted by controlling the current of the electromagnetic solenoid 41, the multi-disc clutch 39 is pressed with a pressing force proportional to the current. Then, the second cam member 32 is pressed in the direction of the first cam member 30 according to the degree of engagement of the multi-disc clutch 39, and the relative rotation between the two causes the ball member 33 to move on the cam surface 37 shown in FIG. Therefore, the second cam member 32 presses the friction plate 39a while compressing the disc spring 35, and Nt friction plates on the second cam member 32 side receive a reaction force by the disc spring 43, and the disc spring 43 applies a reaction force to the friction plates Nt on the second cam member 32 side. engaged. In an emergency such as when the wheels come off, when the current value to the electromagnetic solenoid 41 is set to the maximum value, the multi-disc clutch 39 is further pressed and the ball member 33 further moves on the cam surface 37, so that the second cam member 32 As a result of further compressing the springs 35 and 43 and pressing the friction plate 39a and pressing the multi-plate clutch 39 against the mount case 19b, the reaction force is doubled and the multi-plate clutch 39 can be completely engaged. In this embodiment, as shown in FIG. 7, the differential limiting torque is linearly controlled over the entire region with respect to the multi-disc clutch pressing force, and the differential limiting torque can be increased when the clutch is locked.

Next, another embodiment of the differential limiting device according to the present invention will be described with reference to FIGS. 8 and 9.

In this embodiment, the speed increasing mechanism provided in each of the above embodiments is eliminated, and a clutch hub 45 is spline-coupled to the front wheel input shaft 15, and a multi-disc clutch 46 is connected between the clutch hub 45 and the mount case 19a. has been set up.

Further, a weak disc spring 47 is disposed between the first and second cam members 30 and 32, and the second cam member 32 is rotatably supported on the inner peripheral surface of the mount case 19b via a bearing 49. ing.

The effect will be explained. When the piston 42 is attracted by controlling the current of the electromagnetic solenoid 41, the multi-disc clutch 39 is pressed with a pressing force proportional to the current. Then, the second cam member 32 rotates according to the degree of engagement of the multi-disc clutch 39, and the ball member 33 moves on the cam surface 37 shown in FIG. , the clutch hub 45 connected to the front wheel input shaft 15 and the mount case 19a connected to the rear wheel input shaft 16 are engaged with a predetermined degree of engagement, and the differential movement between the two is limited. In the example, as shown in FIG. 9, the differential limiting torque is linearly controlled over the entire range with respect to the multi-disc clutch pressing force.

Next, another embodiment of the differential limiting device according to the present invention will be described with reference to FIG.

The difference between this embodiment and the embodiment shown in FIG. 2 is as follows.
The difference is that a two-stage planetary gear mechanism is used as the speed increasing mechanism. For this purpose, the speed increasing mechanism has a common sun gear 51.
It is a planetary gear mechanism consisting of two pinions 52, 53, a common ring gear 55, and a carrier 29. The sun gear 51 is integrally formed with the first cam member 30, and one pinion 53 is formed on the inner periphery of the mount case 19a. The other pinion 52 is connected to a partition wall 56 formed on the surface.
A carrier 29 supporting the front wheel input shaft 15 is spline-coupled to the front wheel input shaft 15. Since the operation is the same as that of the embodiment shown in FIG.
5, and the torque required for differential restriction is reduced by that much, so the torque capacity of the electromagnetic clutch device F can be reduced.

Next, a control system of the present invention employing the differential limiting device described above will be explained with reference to FIGS. 11 to 13.

FIG. 11 shows the configuration of an electronic control device 101 for controlling the electromagnetic solenoid 41, and input signals include a throttle opening sensor 102, a front wheel rotation speed sensor 103, a rear wheel rotation speed sensor 104, a lateral G sensor 105, an anti- There is a skid brake (ABS) activation signal 106, and there is also a shift position sensor.

The electronic control unit 101 includes a CPU (processing unit) that includes a built-in memory such as RAM and ROM for storing calculations and control programs, and reads signals from each of the sensors to determine the running state of the vehicle.

That is, the throttle opening change rate dθ/dt is calculated from the throttle opening sensor 102 to determine the acceleration state of the vehicle, and the front and rear wheel rotational speed difference ΔN is calculated from the front wheel rotational speed sensor 103 and the rear wheel rotational speed sensor 104. The slip state of the vehicle is determined, and the lateral G sensor 105 determines the cornering force CF when the vehicle turns. Then, while referring to the control map 107 stored in the memory prior to the above-mentioned determination, the degree of engagement of the electromagnetic clutch device is set and the electromagnetic solenoid 41 is activated in order to perform differential restriction that is optimal for the current driving condition. Control.

FIG. 12 shows a principle diagram of the control system according to the present invention. The control map 107 has a low μ road map r+(θ, VNll, a medium μ road map rz(θ, V) 112, and a high μ road map r
s(θ, V) 113, and the differential limiting torque T is set so as to increase depending on the throttle opening θ and the vehicle speed V, and as you move towards the low μ road side. ing. Then, when the cornering force C7 is small, the front and rear wheel rotational speed difference ΔN is small, the predetermined switching time t and the brakes are on, the map is switched to the high μ road map side to improve fuel efficiency and braking stability. C
2 is large, the front and rear wheel rotational speed difference ΔN is large, and the throttle opening change rate dθ/dt is large, the map is switched to the low μ road map side to improve turning stability and acceleration.

The above control method will be specifically explained with reference to FIG. The figure shows how the control map is switched at point P, with the switching time t being 1 second.

First, at the time of starting, the differential limiting torque T is controlled according to the low μ road map r+(θ, V). After that, the throttle opening change rate dθ/dt, the front and rear wheel rotation speed difference ΔN per second
, if the value of cornering force CF is within a predetermined range, the control map is changed to the medium μ road map rz(θ, V
) 112, high μ road map ticθ, and VH13 in this order to lower the differential limiting torque Tc. If the above multi-value falls outside the predetermined range within one second, the map is switched to a map that increases the differential limiting torque T, and at the same time one second is counted again.

Also, the number of times the front and rear wheel rotational speed difference ΔN exceeds a predetermined range within a predetermined time is counted, that is, it is determined how many times the vehicle has slipped within a predetermined time, and the switching time t is set to 1 second, for example, by a certain number of times. to 5 seconds and perform learning control. This improves driving stability on roads where the friction coefficient of the road surface changes rapidly.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made.

For example, in the above embodiment, the clutch is applied to a center differential differential limiting clutch in a four-wheel drive vehicle, but it may also be applied to a two-wheel/four-wheel switching clutch, or to limit other rotational differences. It may be applied to a clutch for a power transmission device.

Further, in the above embodiment, the center differential differential limiting clutch is disposed between the front wheel input shaft 15 and the rear wheel input shaft 16, but as shown in FIG. It may be arranged between the rear wheel drive shafts 95, or the first
As shown in FIG. 5, it may be arranged between the center differential input shaft 85 and the front wheel input shaft 89.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the differential limiting device of the present invention applied to a four-wheel drive vehicle with a center differential, Fig. 2 is an enlarged sectional view of the differential limiting device, and Fig. 3 is a sectional view of a cam member. A plan view and a sectional view, FIG. 4 is a diagram for explaining the action of the differential limiting device, FIG. 5 is a diagram showing the relationship between clutch pressing force and differential limiting torque, FIGS. 6, 8, and FIG. 10 is an enlarged sectional view of a differential limiting device according to another embodiment of the present invention, FIGS. 7 and 9 are diagrams showing the relationship between clutch pressing force and differential limiting torque, and FIG. 11 is a diagram showing the relationship between clutch pressing force and differential limiting torque. A configuration diagram of an electronic control device related to the control method of the present invention, FIG. 12 is a principle diagram for explaining the control method according to the present invention, FIG. 13 is a diagram for explaining the processing of the control method related to the present invention, FIG. 14 is a diagram showing another arrangement example of the center differential limiting mechanism, and FIG. 15 is a diagram for explaining the driving force transmission mechanism of a conventional full-time four-wheel drive vehicle with a center differential. B... Differential device, D... Planetary gear mechanism, F... Electromagnetic clutch device, 15... Front wheel input member, 16.19
a. 19b... Rear wheel input member, 25... Sun gear, 27
...Ring gear, 29...Carrier, 30,32.
...Cam member, 33...Ball member, 35...Spring, 37...Cam surface, 39...Multi-plate clutch,
39a...Friction resistance, 41...Electromagnetic solenoid, 4
3... disc spring, 46... multi-plate clutch, 51...
Common sun gear, 55... Common ring gear, 52.
53...Pinion. Fig. 2 Ryo 3 Fig. (A) Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. Clutch n pressure Fig. 8 Fig. 9 Fig. 10 Fig. 5 Fig. 11 Figure 14

Claims (9)

[Claims] (1) A front wheel input member and a rear wheel input member that transmit power from a drive source via a differential device, first and second cam members on which cam surfaces are formed, and a first and second cam member that is sandwiched between the cam surfaces. an electromagnetic clutch device disposed between the rear wheel input member and the second cam member and controlled by an electromagnetic solenoid; and an electromagnetic clutch device disposed between the front wheel input member, the rear wheel input member and the first cam member. A differential limiting device for a four-wheel drive vehicle, comprising a planetary gear mechanism provided therein, and limiting differential motion between the front wheel input member and the rear wheel input member by controlling the electromagnetic solenoid. (2) The planetary gear mechanism includes a carrier connected to the front wheel input member, a ring gear formed on the rear wheel input member,
The differential limiting device for a four-wheel drive vehicle according to claim 1, further comprising a sun gear connected to the second cam member. (3) A spring for pressing a ball member is provided between the first and second cam members.
Or a differential limiting device for a four-wheel drive vehicle according to claim 2. (4) The electromagnetic clutch device has a multi-disc clutch, and among the friction plates of the multi-disc clutch, several friction plates on the second cam member side are spline-fitted to the rear wheel input member side; The remaining friction plates are spline-fitted inside the outermost friction plate, and a disc spring is interposed between the outermost friction plate and the rear wheel input member. A differential limiting device for a four-wheel drive vehicle according to any one of Item 3. (5) The planetary gear mechanism is a planetary gear mechanism having a common sun gear, a common ring gear, and two pinions, and the common sun gear is integrally formed with the first cam member, and one pinion is used for rear wheel input. The differential limiting device for a four-wheel drive vehicle according to any one of claims 1 to 4, wherein the carrier connected to the member and supporting the other pinion is connected to the front wheel input member. (6) A front wheel input member and a rear wheel input member that transmit power from a drive source via a differential device, first and second cam members on which a cam surface is formed, and a first and second cam member that is sandwiched between the cam surfaces. an electromagnetic clutch device disposed between the rear wheel input member and the second cam member and controlled by an electromagnetic solenoid; and a multi-plate disposed between the front wheel input member and the rear wheel input member. a clutch, wherein the first cam member presses the multi-disc clutch under control of the electromagnetic solenoid to limit differential movement between the front wheel input member and the rear wheel input member. Differential limiter. (7) Detection means for detecting throttle opening, front wheel rotation speed, rear wheel rotation speed, and cornering force, and a control map that sets differential limiting torque according to throttle opening and vehicle speed. and an electronic control device that performs arithmetic processing on the signal detected by the detection means based on the control map and outputs a signal to the electromagnetic solenoid. 2. The electronic control device switches the plurality of control maps according to at least one switching condition of cornering force, front and rear wheel rotational speed difference, switching time, and braking switching conditions. A differential limiting device for a four-wheel drive vehicle according to any one of Item 6. (8) When the cornering force is small, the difference in rotational speed between the front and rear wheels is small, the switching time is on, and the brake is on, the control map is switched to the map for high friction coefficient road surfaces, and the cornering force is large and the difference in rotational speed between the front and rear wheels is large. 8. The differential limiting device for a four-wheel drive vehicle according to claim 7, wherein when the throttle opening degree change rate is large, the control map is switched to a low friction coefficient road surface map side. (9) The number of slips within a predetermined time is calculated based on the difference in rotational speed of the front and rear wheels, and when the number of slips exceeds a predetermined value, the switching time is changed. differential limiting device for four-wheel drive vehicles.