JPH04372427A - Four-wheel drive unit and control thereof - Google Patents

Abstract

PURPOSE:To use a common transaxle to four-wheel and front-wheel drive cars so as to reduce a manufacturing cost of the transaxle by disposing a clutch for disconnecting a power transmission way to rear wheels on the opposite side to a case for a front-wheel differential gear mechanism exceeding a center part of the width of car body. CONSTITUTION:A transaxle 21 for a four-wheel drive car has a front-wheel differential gear mechanism of which gear case 6 is drive connected to an output shaft of an unillustrated gear type transmission, and a left side front axle 5 extending left from the differential gear mechanism. An output of the transaxle 21 is transmitted by a transfer 22 to a propeller shaft 23 for driving rear wheels vertically disposed at a center part of the width of a car body. In this case, an electromagnetic clutch 35 for disconnecting a power transmission line to the rear wheels is disposed on the opposite side of the case 6 of the front-wheel differential gear 4 exceeding the center part of the width of the car body, the electromagnetic clutch 35 connects a main clutch hub 42 with the case 6, and the main clutch drum 43 is connected with a ring gear 14.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a four-wheel drive system for a horizontally mounted front engine four-wheel drive vehicle and a control method thereof, and in particular to a four-wheel drive system for a transverse front engine four-wheel drive vehicle and a method for controlling the same. The present invention relates to a device that can reasonably make the lengths of the wheels the same, and a control method that can reduce the size and weight of the drive mechanism on the rear wheel side.

0002

2. Description of the Related Art Conventionally, this type of four-wheel drive device is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-80354.
There is a device as shown in a partially exploded sectional view in FIG. 5, and this drive device consists of an automatic transaxle 2 combined with an engine 1 placed horizontally at the front of a four-wheel drive vehicle (not shown), and the transaxle. 2 to a rear wheel drive propeller shaft (not shown) installed vertically in the center of the left-right direction of the vehicle. A differential gear mechanism 4 and a left front axle 5 extending leftward in the figure from the front wheel differential gear mechanism 4.
and a double piston type hydraulic clutch 7 which is disposed on the axis of the gear case 6 which is drive-coupled to the output shaft of the auxiliary transmission of the front wheel differential gear mechanism 4 and which connects and disconnects the power transmission path to the rear wheels. A clutch drum 8 serving as an input member of the hydraulic clutch 7 is directly connected to the gear case 6.

The transfer 3 is arranged on the right front axle 9 extending from the front wheel differential gear mechanism 4 to the right side in the figure beyond the center in the left-right direction of the vehicle body, and on the axis of the front axle 9. A cylindrical output shaft 11 is integrally formed with a clutch hub 10 as an output member of the hydraulic clutch 7 at one end thereof, and a direction change driven gear is installed vertically at the center in the left-right direction of the vehicle body and integrally formed therewith at the front end. Pinion 1 as
2, and a center drive shaft 13 having a rear end connected to the rear wheel propeller shaft;
The ring gear 14 is arranged around the output shaft 11 and is coupled to the output shaft 11, and also includes a ring gear 14 serving as a direction changing drive gear that meshes with the pinion 12.

In such a four-wheel drive system, power from the engine 1 is transmitted to the gear case 6 after being changed through the automatic transmission in the transaxle 2, and the power is transmitted from the front wheel differential gear mechanism 4 to the gear case 6. The power is transmitted to the left and right front wheels (not shown) through the left and right front axles 5 and 9 and the left and right front drive shafts (not shown) that are drive-coupled thereto, so that the left and right front wheels are driven as appropriate, and furthermore, when the front wheels slip, the power is transmitted to the gear case 6. Based on the operation of the hydraulic clutch 7, the generated power is transferred from the clutch drum 8 to the internal clutch disc and clutch hub 10.
is transmitted to the output shaft 11 via a ring gear 14 and a pinion 12, and then transmitted to a center drive shaft 13 via a ring gear 14 and a pinion 12.
The power transmitted to 3 is transmitted to the final reduction gear (not shown) via the rear wheel propeller shaft, and then from there to the left and right rear wheels (not shown) via the left and right rear drive shafts (not shown) that are drive-coupled to the final reduction gear. The left and right rear wheels are driven accordingly.

[0005]

[Problems to be Solved by the Invention] However, in the above conventional four-wheel drive system, since the hydraulic clutch 7 is disposed not on the transfer 3 side but on the transaxle 2 side, it is difficult to drive the transaxle 2 with the front wheels. There is a problem that the manufacturing cost of the transaxle 2 increases because it cannot be shared with the car, and the left front axle 5
Since the tip of the front drive shaft is quite far from the center in the left-right direction of the vehicle body, it is necessary to forcibly extend the right front axle 9 in order to make the left and right front drive shafts the same length in order to prevent torque steer (for example, in Figure 5 Y) shown in Figure 2), there is a problem in that the length of the front drive shaft becomes shorter as a result, and furthermore, there is no limit to the maximum transmission torque of the hydraulic clutch 7, so the rear wheel drive mechanism is There was a problem in that a material with high rigidity and weight equivalent to that required was required.

[0006]

[Means for Solving the Problems] An object of the present invention is to provide a four-wheel drive device and a control method thereof that advantageously solve the above-mentioned problems. A transaxle capable of transmitting power from an engine placed horizontally at the front of the vehicle body to two front axles via a front wheel differential gear mechanism after shifting, and a transaxle arranged on the axis of the case of the front wheel differential gear mechanism. a clutch that connects the input member to the case and connects the output member to the direction changing drive gear to connect and disconnect the power transmission path to the rear wheels; and a propeller for driving the rear wheels, which is vertically placed in the center of the vehicle body in the left-right direction. A four-wheel drive device comprising: a center drive shaft having a rear end coupled to the shaft; and a direction change driven gear coupled to a front end of the center drive shaft and meshing with the direction change drive gear, wherein the clutch is arranged on the side opposite to the case of the front wheel differential gear mechanism beyond the center portion in the left-right direction of the vehicle body.

Furthermore, the four-wheel drive control method of the present invention controls the transmission torque when the clutch is engaged so that its maximum value is substantially equal to the torque required for traveling on a road with a low friction coefficient. It is characterized by:

[0008]

[Operation] In such a four-wheel drive system, a clutch that connects and disconnects the power transmission path to the rear wheels is arranged beyond the center in the left-right direction of the vehicle body on the side opposite to the case of the differential gear mechanism for the front wheels. As a result, the transaxle can be used in common with front-wheel drive vehicles, reducing the manufacturing cost of the transaxle.Moreover, since the tip of the front axle on the transaxle side is close to the center in the left-right direction of the vehicle body, it can be used to prevent torque steer. Even if the lengths of the front drive shafts are made equal, there is no need to forcibly extend the front axle on the transfer side, and the front drive shafts can be made sufficiently long.

[0009] Furthermore, in this control method, the maximum transmission torque of the clutch is limited to be substantially equal to the torque required for traveling on a road with a low friction coefficient, so that the original function of the low coefficient of friction is reduced. without compromising on-road performance.
The drive mechanism for the rear wheels needs to be less rigid and lighter than that for the front wheels.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a skeleton diagram showing an embodiment of a four-wheel drive device and its control method according to the present invention, FIG. 2 is a partially developed cross-sectional view illustrating the specific configuration of the four-wheel drive device of the embodiment, and FIG. FIG. 3 is a cross-sectional view showing a further enlarged section A in FIG. 2, in which the same parts as in the conventional example are designated by the same reference numerals.

That is, in the figure, 1 is an engine placed horizontally in the front part of the vehicle (not shown) of a four-wheel drive vehicle, 21 is a manual transaxle combined with the engine 1,
22, the output of the transaxle 21 is transferred to a propeller shaft 23 for driving the rear wheels, which is vertically placed in the center of the vehicle body in the left-right direction.
24, 25 are left and right front drive shafts, 26, 27 are left and right front wheels drive-coupled to these front drive shafts via constant velocity joints (not shown), 28, 29 are left and right rear drive shafts, 30, 31 32 is a constant velocity joint that transmits the power transmitted to the propeller shaft 23 for driving the rear wheels to the left and right rear drive shafts 28 and 29, respectively. As shown in FIGS. 2 and 3, the transaxle 21 here includes a normal clutch and gear transmission (not shown), as well as a gear case on the output shaft of the gear transmission. The front wheel differential gear mechanism 4 has a front wheel differential gear mechanism 4 that is drive-coupled with the front wheel differential gear mechanism 6, and a left front axle 5 that extends from the front wheel differential gear mechanism 4 to the left in the figure. It does not have a clutch for contact.

Further, as shown in FIGS. 2 and 3, the transfer 3 here extends from the front wheel differential gear mechanism 4 of the transaxle 21 to the right side of the front axle 9 extending beyond the center in the left-right direction of the vehicle body. a cylindrical intermediate shaft 34 disposed on the axis of the front axle 9 and having one end splined to the gear case 6; cylindrical output shaft 1
1, and a pinion 12, which is vertically placed in the center of the vehicle body in the left-right direction, and is integrated with the front end as a direction change driven gear.
a center drive shaft 13 having a rear end formed therein and connected to the rear wheel propeller shaft; and a center drive shaft 13 disposed around the output shaft 11 and having the pinion 12
Ring gear 1 as a direction change drive gear meshing with
4, and an electromagnetic clutch 35 serving as a clutch for connecting and disconnecting the power transmission path to the rear wheels is arranged on the right side in the figure opposite to the case 6 of the front wheel differential gear 4 beyond the center part in the left-right direction of the vehicle body. It is equipped with
The left and right front axles 5 and 6 are constant velocity joints 36
The drive shafts are coupled to left and right front drive shafts 24 and 25, respectively, through the drive shafts.

The electromagnetic clutch 35 includes an electromagnet 41 fixed to the case 40 of the transfer 3, and a main clutch hub 42 as an input member integrally formed on the other end of the intermediate shaft 34. and a main clutch drum 43 as an output member disposed around the main clutch hub 42, and the main clutch drums 43 are arranged so that those engaging with the main clutch hub 42 and those engaging with the main clutch drum 43 are alternately positioned. A large number of main clutch plates 44 are arranged between the clutch drum and the main clutch hub, and a main clutch hub 42 is used to press the main clutch plates 44.
A main pressure disc 45 is arranged around the front axle 9 to support the main clutch plate 44 from the opposite side. A clutch portion 47 is provided.

Further, the electromagnetic clutch 35 includes a sub-clutch hub 48 rotatably disposed around the main clutch hub 42, and a sub-clutch hub 48 disposed around the sub-clutch hub 48 whose ends are engaged with the main clutch drum 43. A main clutch is arranged between the sub-clutch drum and the sub-clutch hub such that the sub-clutch drum 49 that engages with the sub-clutch hub 48 and the sub-clutch drum 49 are arranged alternately. A sub-clutch plate 50 whose number is smaller than the plate 44 and a sub-clutch plate 5
A sub-pressure disk 51 is arranged around the sub-clutch hub 48 so as to be movable forward and backward in order to press 0.
is rotatably arranged around the intermediate shaft 34 to support the sub-clutch plate 50 from the opposite side, and the central hub part is spline-coupled to one end of the output shaft 11, and the outer peripheral edge is connected to the sub-clutch drum. 49 and drive-coupled to the main clutch drum 43 via the sub-clutch drum 49, and trapezoidal recesses formed in the sub-clutch hub 48 and the main pressure disc 45 and facing each other. The clutch includes an auxiliary clutch portion 54 having balls 53 disposed in the clutch.

In the electromagnetic clutch 35, when the electromagnet 41 is energized, the electromagnet 41 pulls the auxiliary pressure disk 51, thereby connecting the auxiliary pressure disk 51 with the auxiliary backup disk 52 to form the auxiliary clutch. By sandwiching the plate 50, the auxiliary backup disks 52 are frictionally coupled to each other, whereby the auxiliary clutch drum 49 and the auxiliary clutch hub 48 are frictionally coupled, and the auxiliary clutch hub 48 rotates integrally with the output shaft 11. At this time, the main pressure disc 45 engaged with the main clutch hub 42 is rotating integrally with the intermediate shaft 34, so if there is a speed difference between the output shaft 11 and the intermediate shaft 34, the auxiliary clutch hub 48 and the main pressure disk 45 press the balls 53 in mutually opposite circumferential directions with the inclined side walls of the trapezoidal recess, and are urged away from each other by the action of the slopes of those side walls. , this biasing force causes the main clutch plate 44 to be sandwiched between the main pressure disk 45 and the main backup disk 46, thereby frictionally coupling the main clutch plates 44 to each other,
As a result, the main clutch drum 43 and the main clutch hub 42
are frictionally coupled, and torque is transmitted between the intermediate shaft 34 and the output shaft 11.

Note that, as is clear from the above points, the transmission torque of the electromagnetic clutch 35 is transmitted between the output shaft 11 and the intermediate shaft 3.
It increases or decreases depending on the speed difference between 4 and 4, and its maximum value is
As shown in FIG. 4, it increases or decreases depending on the increase or decrease in the engagement force of the sub-clutch section 54 as the operating current supplied to the electromagnet 41 increases or decreases. Here, as shown in FIG. 1, the above operating current C is
For example, a control unit 55 including a normal microcomputer receives a signal N1 indicating the front wheel rotation speed and a signal N2 indicating the rear wheel rotation speed from a rotation sensor (not shown), and a control device for an anti-skid braking system (ABS) (not shown). The ABS signal A indicating the operation of the system is controlled as appropriate based on the ABS signal A indicating the operation of the system.

In the above-mentioned four-wheel drive system, the power from the engine 1 is transmitted to the gear case 6 after being changed through the gear transmission in the transaxle 21, and the power is transmitted to the front wheel differential gear. The power is transmitted from the mechanism 4 to the left and right front wheels 26, 27 via the left and right front axles 5, 9 and the left and right front drive shafts 24, 25 drive-coupled thereto, and the left and right front wheels 26, 27 are appropriately driven. In the case of simultaneous slips or only one slip, the control unit 55 detects these slips from the above-mentioned signals and operates the electromagnetic clutch 35, whereby the power transmitted to the gear case 6 is controlled based on the above-mentioned operation of the electromagnetic clutch 35. After being appropriately transmitted from the intermediate shaft 34 to the output shaft 11, the power is transmitted from there to the center drive shaft 13 via the ring gear 14 and pinion 12, and the power transmitted to the center drive shaft 13 is transmitted via the rear wheel propeller shaft 23. After being transmitted to the final reduction gear 32, the signal is transmitted from there to the left and right rear wheels 30, 31 via the left and right rear drive shafts 28, 29.
31 is driven as appropriate.

[0018] Here, the control unit 55
controls the operating current supplied to the electromagnet 41 so that the maximum transmission torque of the electromagnetic clutch 35 becomes equal to the maximum rear wheel drive force Tcmax required for driving on a low friction coefficient road such as a snowy road or muddy road. limited to. Furthermore, the maximum rear wheel drive force Tcm
ax is roughly given by the following formula, where Wr is the rear wheel load, R is the rear wheel dynamic load radius, and μ is the road friction coefficient (0 on snowy roads).
．． 4). Tcmax≒Wr×R×μ

According to the four-wheel drive device of this embodiment,
Since the electromagnetic clutch 35, which connects and disconnects the power transmission path to the rear wheels, is located beyond the center in the left-right direction of the vehicle body on the side opposite to the case 6 of the front-wheel differential gear, the transaxle 21 can be used in common with front-wheel drive vehicles. Therefore, the manufacturing cost of the transaxle 21 can be reduced. Moreover, since the tip of the front axle 5 on the transaxle 21 side is close to the center in the left-right direction of the vehicle body, the left and right front drive shafts 24
, 25 are equal lengths, the transfer 22
It is not necessary to forcibly extend the side front axle 9 as in the conventional case, and the front drive shafts 24, 25 can also be made sufficiently long.

Further, according to the control method of this embodiment,
Since the maximum transmission torque of the electromagnetic clutch 35 is limited to the torque required for driving on a low friction coefficient road, the transfer 22 and the The drive mechanism for the rear wheels such as the final reduction gear 32 is replaced by the transaxle 2 which is the drive mechanism for the front wheels.
It can be made to have lower rigidity and be lighter than 1.

Although the above description has been made based on the illustrated example, the present invention is not limited to the above example. For example, the electromagnetic clutch 35 may be replaced with the clutch that connects and disconnects the power transmission path to the rear wheels. , a hydraulic clutch, a normal clutch with a torque limiter, or even a viscous coupling such as a viscous coupling (trade name) may be used, and in such cases, the same effects as in the above example can be obtained.

[0022]

Thus, according to the four-wheel drive system of the present invention, the transaxle can be used in common with a front wheel drive vehicle, and the manufacturing cost of the transaxle can be reduced. Moreover, even when the lengths of the left and right front drive shafts are made equal in order to prevent torque steer, the front axle on the transfer side does not have to be forcibly extended as in the conventional case, and the front drive shaft is also made sufficiently long. be able to.

Furthermore, according to the four-wheel drive control method of the present invention, the drive mechanism for the rear wheels can be made more rigid than the front wheels without impairing its original function of running performance on roads with a low friction coefficient. It is possible to reduce the cost of parts and reduce the weight of a four-wheel drive vehicle.

[Brief explanation of the drawing]

FIG. 1 is a skeleton diagram showing an embodiment of a four-wheel drive device and a control method thereof according to the present invention.

FIG. 2 is a partially developed sectional view illustrating a specific configuration of the four-wheel drive device of the above embodiment.

3 is a further enlarged cross-sectional view of section A in FIG. 2; FIG.

FIG. 4 is a characteristic diagram showing the operating characteristics of the electromagnetic clutch used in the above embodiment.

FIG. 5 is a partially exploded sectional view showing a conventional four-wheel drive device.

[Explanation of symbols]

1 Engine 4 Front wheel differential gear mechanism 5 Front axle 6 Case 9 Front axle 12 Pinion 13 Center drive shaft 14 Ring gear 21 Transaxle 22 Transfer 23 Rear wheel drive propeller shaft 35 Electromagnetic clutch 42 Main clutch hub 43 Main clutch drum 55 Control unit

Claims (2)

[Claims] 1. A transaxle capable of transmitting power from an engine horizontally placed at the front of a vehicle body to two front axles via a front wheel differential gear mechanism after shifting, and a case of the front wheel differential gear mechanism. a clutch disposed on the axis, having an input member coupled to the case and an output member coupled to the direction change drive gear to connect/disconnect a power transmission path to the rear wheels; A four-wheel drive comprising: a center drive shaft whose rear end is coupled to a rear wheel drive propeller shaft; and a direction change driven gear which is coupled to the front end of the center drive shaft and meshes with the direction change drive gear. A four-wheel drive device, characterized in that the clutch is disposed on a side opposite to a case of the front wheel differential gear mechanism beyond a central portion in the left-right direction of the vehicle body. 2. The transmission torque when the clutch is engaged is controlled so that its maximum value is substantially equal to the torque required for traveling on a road with a low friction coefficient,
A method for controlling a four-wheel drive device according to claim 1.