JPS6333590B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a differential drive mechanism. The invention particularly relates to an automotive transmission in which the differential drive mechanism has one input element and two output elements. However, the invention also relates to a differential drive mechanism with two input elements and one output element.

Differential gears, including both spur gear and planetary gear types, are well known. This mechanism requires that the differential gear mechanism is not equipped with an "anti-slip" device, in which case one of the two output elements (or one of the two input elements) can become dislodged. If there is, there is a disadvantage that driving force cannot be transmitted.

A clutch-type differential drive mechanism includes both a friction and one-way clutch and incorporates a dual-clutch device. In this case, for differential operation, 2
This is accomplished by providing a mechanical latch mechanism that is or is differentially differential to permit overrunning action on one or the other of the output elements. Clutch-type differential drive mechanisms do not exhibit the disadvantages of gear-type differential drives, but they are less practical. Prone to mechanical wear and “snapping”
or otherwise exhibit a tendency to "slip" and generally have unreliable or unsatisfactory performance.

According to the invention, there is provided a differential drive mechanism consisting of at least three members that rotate relative to each other, and the transmission of driving force between the members in the mechanism is achieved by a viscous fluid coupling mechanism. (viscous shear coupling device or sliding coupling device)
It is based on

Whereas viscous fluid coupling mechanisms can tolerate relatively small differences in rotational speed and also relatively small rates of change in rotational speed, conversely, viscous fluid coupling mechanisms can tolerate relatively large differences in rotational speed, and respond or react to relatively high rates of change of rotational speed. Therefore, although this viscous fluid coupling mechanism can smoothly perform a moderate differential operation, in other aspects, it is possible to independently perform a differential operation through one of the two output members or one of the two input members. It can transmit relatively high torque. Such a differential mechanism avoids the drawbacks of known or previously proposed mechanisms.

In a viscous fluid coupling mechanism, torque transmission and differential rotation occur simultaneously through viscous shear forces and "fluid slip," respectively. Our findings indicate that, at least in the case of automotive drive power transmission, the sustained transmission of useful drive torque can be achieved simultaneously with a viscous fluid coupling mechanism with a continuous but relatively small rotational speed difference across the coupling mechanism. It can be achieved.

The torque transmission capacity of a conventional viscous fluid coupling mechanism is directly expressed by the viscosity of the fluid and the area and distance between the elements of the coupling mechanism that are fluidly coupled together. However, the performance of such conventional coupling mechanisms is affected by temperature changes and/or fluid shear rates.

A preferred form of the viscous fluid coupling mechanism is
It is a device called a "control coupling" as shown in our British Patent Specification No. 1357106. One feature of the device is that the torque values transmitted or developed within the device are maintained with remarkable stability over a wide range of temperatures and fluid shear rates within the device. According to our findings, another feature of the above device is that rapidly increasing torque values are transmitted simultaneously with a rapid pressure increase within the device, or are stored within the device. be. This pressure increase is
This occurs due to thermal expansion of the viscous fluid, which continues to act on the device when it has occupied all available room within the device.

The driving force is required to be distributed on a "continuous" basis. In the differential drive mechanism according to the invention (i.e., where the differential drive mechanism is the only or primary drive transmission), the viscous fluid coupling mechanism preferably provides a It is preferable to design the "smooth speed" to be as small as possible so that the differential motion required for this can be at least minimized. Required to be distributed on driving force and "interruption" basis. In the differential drive mechanism according to the invention (i.e.
When the differential drive mechanism is secondary to the positive primary drive force in the automotive transmission), the viscous fluid coupling mechanism can be used at higher "slip speeds" to almost fully perform the differential operation. ”.

Further in accordance with the invention there is provided a motor vehicle drive transmission incorporating a differential drive mechanism as described above.

Here, the differential drive mechanism is arranged and connected to transmit driving force from the motor to one set of running wheels, and the other set of running wheels is driven by the differential gear from the motor. is desirable.

Further, in accordance with the invention, there is provided an automotive live shaft assembly comprising a viscous fluid coupling mechanism having mutually independent rotating members arranged and connected to transmit drive torque to side and opposite running wheels, respectively. It is equipped.

Next, embodiments of the present invention will be described based on the drawings.

In FIG. 1, an input member or crown wheel 10 and an associated drive input member or pinion gear 11 cooperate to form a final reduction gear mechanism within a motor vehicle live shaft assembly in a conventional manner. Apart from this, the assembly is constructed such that the drive torque transmitted by the output members or half-shafts 12 and 13 to the respective running wheels (not shown) is incorporated into a differential drive mechanism indicated by the number 14. This differs from conventional systems in that it is transmitted only through a viscous fluid coupling mechanism. The half-shafts 12 and 13 are constituted by two relatively rotating members of a differential drive mechanism, the third rotating member being of hollow cylindrical shape and having a flange to which the crown wheel 10 is bolted. 1
6. The housing 15 includes a housing 15. The shaft assembly includes a main casing 17 that supports a housing 15 in rotation by tapered roller bearings 18 and 19. The above roller bearing is for shaft 1
2 and 13, and the shafts 12 and 13
annular seals 20A and 21 that protrude while rotating.
It engages the short tubular lands 20 and 21 incorporating A from the outside. The right end wall of the housing 15 is constructed separately from the rest of the housing and includes a sealing ring 22 and is held in place by a circlip 23. The threaded plug 24 allows the viscous fluid to enter the housing 15.
be introduced inside. The housing is airtight when screwed down and does not leak fluid. The differential drive mechanism also incorporates three sets of annular plates within the housing 15. One set of these is
It consists of a plate 25 (see FIG. 2) which engages splines formed in the inner wall of the housing 15. The other two sets of annular plates are number 2
6 and are associated with shafts 12 and 13, respectively. Plate 26 engages the grooved inner ends of shafts 12 and 13 as shown in FIG. Plate 25 is “outside”
plate, and plate 26 is referred to as the "inner" plate. The inner plates each include a plurality of circular through holes 27, and the inner plates each include a plurality of open-ended grooves 28.
It is equipped with The holes 27 and grooves 28 give different shapes to the surface of the annular plate. It is conceivable that the individual annular plates of any of the three sets of plates have surfaces with mutually different surface shapes. In addition to the annular plate, the housing 15
includes a viscous fluid, preferably a silicone fluid, and preferably a dimethyl silicone fluid. This viscous fluid is introduced into the housing 15 through a hole that tightens the threaded plug 24.

General technical information regarding the structure and operation of viscous fluid coupling mechanisms is contained in our British Patent Specification No. 1357106. The purpose is to integrate the shaft assembly into the drive transmission of a medium-sized passenger car. In this case, the following information provides a general indication of the quantities and dimensions in question: That is, the viscosity of the fluid is considered to be on the order of 200,000 centiStokes. The nominal diameter of housing 15 is approximately 4 inches (approximately 10 cm). The annular plates provide an approximately 80/90 working face, and the average interplate spacing is approximately 0.01 inch.
0.25mm). Housing 1 at approximately 25°C
The volume of viscous fluid within 5 will be between 10 and 14% of the total volume of space available for fluid to occupy within the housing.
The annular plate is described in our British patent specification.
As shown in No. 1357106, it can be moved freely in the axial direction or alternatively it can be positioned in the axial direction by a spacer.

The shaft assembly described in connection with FIG.
As illustrated in the figure, it is contemplated that it could be used in an automotive drive transmission. In the transmission shown in FIG.
A propulsion shaft 32 coupled to the front wheels is provided by a conventional reduction gear mechanism or differential drive 34 incorporating positive differential gears.
The driving force to the front wheels 30 is the "primary" reliable transmission force. Gearbox 31 also transmits drive power to rear propulsion shaft 35 via universal joint 36 to drive pinion gear 11. In FIG. 7, the shaft assembly of FIG. 1 is illustrated diagrammatically as drive running wheels 12A and 13A. Components of the differential drive mechanism corresponding to those in FIG. 1 are given the numbers used in FIG. The propulsion shaft 32, universal joints 33, 36, and propulsion shaft 35 constitute a drive transmission device.

In operation of the vehicle transmission of FIG. 7 incorporating the shaft assembly of FIG. The various conduction ratios, including the crown wheel and pinion ratios, as well as the diameter of the nominal running wheels, are such that during straight forward motion of the vehicle, the rotational speed of the housing 15 is greater than that of the half shafts 12 and 13.
selected to match the rotational speed of the Therefore, the rear differential drive does not require any differential operation. Differential gearing in the reduction drive gear 34 provides differential action to the front wheels 30 to successfully negotiate curves and corners in the road. rear wheel 1
The differential action between 2A and 13A is provided by sliding between the interleaved plates in the housing 15. The normal differential operation between the vehicle running wheels, expressed as a rotational speed difference, is relatively low, and furthermore, the rate at which said rotational speed is established is also relatively low. The viscous fluid coupling mechanism of the differential drive handles the rotational speed differences associated with normal differential operation, and the forces absorbed by the viscous fluid are not significant. If the running wheel 30 attempts to rotate under the drive, a direct acceleration is exerted on both the propulsion shafts 32 and 35 and thus also on the crown wheel 10. This acceleration is sensed by the viscous fluid coupling mechanism and torque is immediately transmitted to the half shafts 12 and 13. As a result, the vehicle transmission is instantaneously converted from normal two-wheel drive to excessive four-wheel drive. It has been found that due to the damping properties of the viscous fluid mechanism, the transient nature of the transmission's operation is preserved and the driving characteristics of the vehicle remain intact. Similarly,
In the case of front running wheels 30 that exhibit a tendency to lock up during braking on slippery road surfaces,
The rapid deceleration force of the propulsion shafts 32 and 35 causes
Provided, of course, that the braking of the running wheels 12A and 13A is always free from instantaneous effects, which is counteracted by the excessive transmission of torque from the half-shafts 12 and 13 through the differential drive mechanism.

As can be seen from the differential drive mechanism of FIG. 1, the gear ratio of the crown wheel and pinion produces deceleration. To this end, the viscous fluid coupling mechanism
Despite the need to transmit a high drive torque compared to the average propulsion shaft torque, the design transmission ratio is due to over or under tire pressure, use of incorrect tire dimensions, or uneven tire tread wear. undergoes a small “slip” value attributable to the departure from

In the transmission of FIG. 7, the viscous fluid coupling mechanism typically requires a more "stiff" setting than when using a viscous coupling in conjunction with a positive differential gear. Nevertheless, such a "rigid" viscous fluid coupling mechanism allows for practical differential operation. It is important to recognize that this is distinct from the mathematical parameters for the differential operation associated with the onset of lock.

It is also contemplated that the shaft assembly of FIG. 1 could be used in an automotive transmission such as that shown in FIG. In this case, as in FIG. 7, the same reference numerals are used for parts corresponding to those shown in FIG. The transmission shown in Fig. 6 is a transmission that drives only two wheels, and the driving force is one set of running wheels 12A.
and is transmitted only to 13A. In this case, it is necessary to design the viscous fluid coupling mechanism to a large "stiffness" value compared to the "stiffness" required for the mechanism of FIG. Nevertheless,
It would be easy to match the "stiffness" of the coupling mechanism with the available drive capacity at the running wheels, and at the same time provide sufficient continuous slippage to accommodate normal differential movements. Such automotive transmissions provide considerably simpler parts manufacturing, smooth operation, and an inexpensive transmission mechanism.

The differential drive mechanism of FIG. 1 is illustrated diagrammatically in FIG. 4, and illustration in a similar manner is used in FIG. In FIG. 5, parts corresponding to those in FIG. 4 are given the same reference numerals as were sailed in FIG.

In FIG. 5, the differential drive mechanism is
Line viscous fluid coupling mechanism 15B and 15C
Drive shaft mechanisms 12 and 13 incorporating
It can be thought of as consisting of. During driving, these drive shaft mechanisms are connected to another drive shaft 10A that supports the crown wheel 10.
It is connected to a common rotating member consisting of. Respective viscous fluid coupling mechanisms 15B and 15C
is constructed using the same principles employed in the mechanism of Figure 1 and is identical in construction to that described in our British Patent Specification No. 1357106.
The differential drive mechanism of FIG. 5 operates similarly to the mechanism of FIG. 4, except that the differential drive mechanism of FIG. This provides the possibility of working with dynamic drive mechanisms.

The differential drive mechanism according to the invention can be used in cases other than automotive drive transmission drives. For example, two primary data sources can be combined on a common output shaft. Furthermore, 2
It is easy to combine one or more primary motors into an arrangement in which each of the plurality of input drive shaft mechanisms incorporates an in-line viscous fluid coupling mechanism.

In FIG. 8, the differential drive mechanism is the same as that of FIG. 1, except that a lockout mechanism is incorporated. In FIG. 8, parts that are the same as those shown in FIG. 1 are given the same reference numerals as used in FIG. In FIG. 8, shaft casing 17 has been modified to define a chamber 37 that includes a lockout mechanism, indicated generally by reference numeral 38. The tubular land 21 is provided with an extension 39 extending outwardly into the chamber 37 . Adjacent to the extension part 39,
The half-shaft 13 is equipped with a filler step 40. The inwardly added collar 41 is a clutch ring that engages both the outer spline and the extension 39 and the step 40, thereby connecting the shaft 13 to the casing 1 of the differential drive.
Lock to 5. The collar 41 can be moved axially by a pneumatic actuator 42 through an actuator fork 43 that embraces the collar 41 in an annular groove 44 . The collar 41 is attached and removed at the 8th position.
Indicated by the dashed line in the figure.

The purpose of the lockout mechanism described above is to provide a direct driving force between the drive pinion 11 and the half-shaft 13 in case of emergency. It will be appreciated that an additional lockout mechanism as described above could be mounted on the opposite side of the shaft casing to provide direct emergency driving power to both half-shafts 12 and 13.

It is contemplated that a variety of alternative drive transmission designs incorporating the present invention are possible. For example, the reduction gear 34 shown in FIG. 7, which is incorporated with a differential gear, can be located at the rear of the vehicle with the differential drive mechanism 14 at the front. It is also possible, for example, in heavy motor vehicles, to incorporate a differential gear on one of the shafts in a "dandem" arrangement, and on the second shaft a differential drive mechanism according to the invention.

Also, the running wheel diameter and/or the various drive transmission ratios can be selected such that during normal driving, a preset speed difference exists between the inner and outer plates of the viscous fluid coupling mechanism. is also accepted. Therefore, even if neither wheel rotation nor wheel lock occurs in the vehicle transmission during normal driving, a certain amount of drive torque can be transmitted to the running wheels attached to the differential drive mechanism. can.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional plan view of an automotive live shaft assembly incorporating a differential drive mechanism according to the present invention. 2 and 3 are enlarged elevational views of the annular plate incorporated into the differential drive mechanism shown in FIG. 1. FIG. FIG. 4 is an explanatory diagram of the differential drive mechanism of FIG. 1. FIG. 5 is an explanatory diagram of another embodiment of the arrangement shown in FIG. 4. FIG. 6 is an explanatory diagram of an automobile transmission incorporating a differential drive mechanism according to the present invention. FIG. 7 is an explanatory diagram of another vehicle drive transmission incorporating a differential drive mechanism according to the present invention. Figure 8 shows
FIG. 2 is the same plan view as FIG. 1, but with the locking mechanism incorporated, in partial cross-section.

Claims (1)

[Claims] 1. A first drive input member having a drive input member and left and right wheels, respectively.
and a second drive shaft, first and second differential drive devices each disposed on the drive shaft so as to transmit drive force between the drive input member and the wheels, and a drive force simultaneously applied to each drive input member. In vehicle drive transmissions with a distributively arranged drive transmission, a first differential drive on one of the drive shafts transmits the drive power without slipping and a first differential drive on one of the drive shafts transmits the drive power to the other drive shaft. the second differential drive provided transmits driving force only when a speed difference exists;
A drive transmission for a vehicle, characterized in that it consists of a sliding coupling device. 2. The vehicle drive transmission according to claim 1, wherein the drive transmission device distributes driving force to each drive input member having a fixed speed relationship. 3. The vehicle drive transmission according to claim 1 or 2, wherein the first differential drive is a gear differential. 4. A drive transmission for a vehicle according to any one of claims 1 to 3, wherein the sliding coupling device is a viscous shear coupling device. 5. The viscous shear coupling device is characterized in that it has in a single housing an input member that connects to a drive input member of a drive shaft and two rotatable output members that are respectively coupled to left and right wheels of the drive shaft. A vehicle drive transmission according to claim 4. 6. The viscous shear coupling device includes a first viscous shear coupling device having an input member connected to the drive input member of the drive shaft, an output member coupled to the left wheel of the drive shaft, and an input connected to the drive input member of the drive shaft. 5. A vehicle drive transmission as claimed in claim 4, comprising a second viscous shear coupling device having a member and an output member coupled to the right wheel of the drive shaft. 7. The vehicle drive transmission according to any one of claims 1 to 6, wherein the first and second drive shafts are each one of a front drive shaft and a rear drive shaft. 8. The housing has a hollow cylindrical shape, and within the housing, the viscous fluid contacts interdigitated annular plates, the annular plates consist of three sets, one of which is in driving engagement with the housing, and the other 6. A vehicle drive transmission according to claim 5, wherein the two sets are relatively rotatable and are each drivingly connected to the output member.