JPH09128117A - Braking device in car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a brake device which can shorten the braking distance of an automobile and improve the safety by evading the spinning of the vehicle body if a sudden brake is applied during a fast travel by providing a clutch shaft, to which a transmission and the crank shaft of an engine are connected integrally, with a planetary gear means. SOLUTION: The planetary gear means 7 is provided between a clutch 6 and the transmission 3. Further, a disk 68 is coupled with the clutch 6 rotatably in one body with a clutch cover 63 and a braking means 8 which brakes the disk 68 is provided. When the disk 68 is locked by the braking means 68, each planetary gear 72 is unable to revolve around a sun gear 71 and only able to rotate on its axis, and then the planetary gear 72 rotates on its axis with the turning force of the sun gear 71 in the opposite direction from the rotating direction of the clutch shaft 60. Its rotation is transmitted to connected driving wheels through a ring gear 70 and the transmission 3 and the wheels rotate in the opposite direction from the rotating direction at travel time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake device for a motor vehicle, and more particularly, to a vehicle equipped with a manual transmission, in a case where the vehicle is stopped by applying a sudden brake, the driving wheels are rotated in reverse to shorten the braking distance. The present invention relates to a brake device that can be used.

[0002]

2. Description of the Related Art As shown in FIG. 11, in a drive system of a rear-wheel drive type automobile equipped with a conventional manual transmission, the driving force of an engine 1 is transmitted through a clutch 2, a transmission 3 and a drive shaft 4. ,
It is transmitted to the rear wheel 5 (drive wheel). Specifically, as shown in FIG. 12, the crankshaft 10 of the engine 1 drives the flywheel 21 of the clutch 2. When the flywheel 21 is driven, the clutch cover 22 and
The operation of the clutch shaft 23
Rotates / stops as an input shaft of the transmission 3, and the driving force of the engine 1 is transmitted to the transmission 3. The transmission 3 drives the vehicle by operating the shift lever 31 to set the transmission gear 32 to forward, neutral, and reverse.

In the above drive system, the rotation direction of the clutch shaft 23 coincides with that of the crankshaft 10 and the rotation of the clutch shaft 23 is transmitted directly to the transmission 3. ,
The rotation direction of the drive shaft 4 must be the clutch shaft 23
And the drive shaft 4 cannot rotate in the reverse direction. Therefore, in the conventional vehicle, the rear wheel 5 does not automatically rotate in the reverse direction while traveling forward or when the brake is applied.

[0004] In automobiles, the safety of the brake device is particularly emphasized. Brake devices used in automobiles include a drum brake device and a disc brake device. In these devices, by stepping on the brake pedal, the hydraulic pressure is averagely transmitted to the brake device of each wheel via the brake master cylinder and the wheel cylinder, and the brake shoe lining is applied to the brake drum,
Alternatively, the brake pad is brought into contact with the disc, and the rotation of the wheels is stopped by these frictions so that the purpose of braking can be achieved. On the other hand, the hand brake device
A parking or auxiliary brake that brakes wheels via a brake cable.

The braking efficiency of the brake device is determined by various factors, and the frictional force between the brake shoe lining and the drum and the frictional force between the brake pad and the disk are one of the fundamental factors.

[0006]

However, the above-mentioned conventional brake device can brake the wheels,
If a sudden brake is applied while the vehicle is running at a high speed, the wheels lock and slip forward due to the inertia of the vehicle, or spin out of balance and cause an accident. On the other hand, in recent years, antilock brake systems often mounted on automobiles can avoid skidding of the vehicle body, but have a problem that the effect of shortening the braking distance is not remarkable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional brake device, and when the vehicle is suddenly braked while driving at high speed, the braking distance can be reduced and the vehicle body can be spun. It is an object of the present invention to provide a brake device that can improve the stability by avoiding the operation.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is mounted on a transmission and a clutch shaft integrally connected to a crankshaft of an engine, and is synchronized with the clutch shaft when the transmission is driven. A clutch having a clutch cover that rotates while freely rotating around the outer periphery of the clutch shaft when not driven,
A disk connected to the clutch cover, braking means for braking the disk, and a ring gear provided between the disk and the transmission, integrally connected to an input shaft of the transmission and having internal teeth on its inner peripheral surface. A sun gear rotatably mounted at the center of the ring gear and integrally connected to the clutch shaft; and a pivot that meshes with the teeth of the sun gear and the teeth of the ring gear, respectively, and that projects from the center thereof to the disc. And a planetary gear means comprising a plurality of worn planetary gears.

In the above-described brake device, when the transmission is not driven, the clutch cover and the disk connected to the clutch cover can freely rotate with respect to the clutch shaft. At this time, in the planetary gear means, while the sun gear rotates directly and synchronously by the clutch shaft, the planetary gear is pivotally mounted on a rotatable disk. Revolves around the outer periphery of the gear while rotating.

When the disc is braked by operating the braking means when the transmission is not driven, the rotational speed of the disc is instantaneously reduced, and the revolving speed of the planetary gear pivotally mounted on the disc is also reduced. At this time, since the rotation speed of the sun gear is the same as the rotation speed of the clutch shaft, the ring gear is synchronized with the sun gear by the rotation of the planetary gear due to the difference between the rotation speed of the sun gear and the revolution speed of the planetary gear. Rotate at a speed that does not.

Since the revolving speed of the planetary gear is remarkably reduced via the disk by the braking means, the rotational speed of the ring gear is also instantaneously reduced, and the rotational speed of the input shaft of the transmission and the rotational speed of the vehicle are reduced. The number of revolutions of the drive wheels also decreases instantaneously.

When the disk is locked by the braking means, each planetary gear cannot revolve around the sun gear, but can only rotate. At this time, since the sun gear receives the driving force of the clutch shaft and rotates in synchronization with the clutch shaft, the driving force causes the planetary gear to rotate in the direction opposite to the rotation direction of the sun gear and the clutch shaft. As a result, the ring gear meshed with the planetary gear also rotates in the direction opposite to the rotation direction of the clutch shaft, and the drive wheels connected via the transmission rotate in the direction opposite to the rotation direction during traveling.

As a result, a large frictional force is generated between the drive wheels and the road surface, and the frictional force reduces the inertia of the vehicle, thereby shortening the braking distance before the vehicle stops and causing the vehicle to spin. In order to avoid this, the driving wheels are reversely rotated while the non-driving wheels of the running vehicle are braked, and the vehicle is quickly stopped.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the drawings. The brake device of the present invention is formed by improving a conventional clutch mechanism.
As shown in FIG. 2, a planetary gear means 7 is provided between the clutch 6 and the transmission 3. A disk 68 is connected to the clutch 6 so as to be rotatable integrally with the clutch cover 63, and a braking means 8 for braking the disk 68 is provided. The operation of the means 7 causes the drive wheels to rotate in the reverse direction to quickly stop the vehicle. The vehicle of the present embodiment is of a rear-wheel drive type.

As shown in FIG. 1, the brake device of the present invention comprises a clutch 6, a planetary gear means 7, a braking means 8,
It comprises a transmission 3 similar to the conventional one and a flywheel 21 connected to the crankshaft 10 of the engine. In the present embodiment, the brake device is:
It is controlled by the control system 9 shown in FIG.

The clutch 6 includes a clutch shaft 60, a clutch operating fork 61, a disconnect bearing 62, a clutch cover 63, support rings 64, 64, a disc spring 65, a pressure plate 66, a clutch plate 67, , A disk 68. The mounting structure of each of these members is substantially the same as the conventional structure except for the disk 68. However, since the planetary gear means 7 is provided in a small space between the clutch 6 and the transmission 3, the arrangement direction is substantially the same as the conventional one. The opposite is true.

As shown in FIG. 2, the disk 68
It is integrally connected to the clutch cover 63 by bolts (not shown) to form a hollow shell structure, and is rotatably attached to the clutch shaft 60 in this state. The support rings 64, 64, the disk spring 65, the pressure plate 66, and the clutch plate 67 are passed through the hollow interior formed by the disk 68 and the clutch cover 63, and the clutch shaft 60 is passed through the center of each. It is arranged in the state.

The clutch shaft 60 has a flange-like front end 603 integrally connected to the flywheel 21 so as to be driven by the crankshaft 10 and has a required space from the rear end 602. A spline shaft 601 is provided at the clutch plate mounting position. The clutch shaft 60 has the spline shaft portion 6.
01 at the rear end side of the disc mounting position.
Disk receiver 681 for rotatably supporting the disk
Is fixed.

The clutch operating fork 61 has one end pivotally connected to the shut-off bearing 62 and the other end connected to a clutch pedal 91 of the control system 9 described later.
Can be pressed against and separated from the disk 68.

The shut-off bearing 62 is mounted movably in the axial direction with respect to the clutch shaft 60, and its rear end 621 projects slightly forward of the disk spring 65 and is formed like a lead. So as to be rotatably in contact with the front central portion.

The disk spring 65 has a locking groove 661 whose outer peripheral edge is recessed in the inner peripheral edge of the pressure plate 66.
Has been fitted. The disk spring 65 is held by a rivet 651 and support rings 64 and 64 together with the pressure plate 66 in a concentric position inside the clutch cover 63 so as to be relatively movable in the axial direction of the clutch shaft 60. The disc spring 65 presses the pressure plate 66 against the clutch plate 67 by the elastic force of the spring, and the clutch plate 67
Is pressed.

The clutch plate 67 is sandwiched between the pressure plate 66 and the disk 68, and a spline 671 for mutual connection with the spline shaft portion 601 of the clutch shaft 60 is provided on the inner peripheral surface of the central fitting hole 672. ing. When the clutch plate 67 is not pressed against the disk 68 by the pressure plate 66,
While rotating in synchronization with the clutch shaft 60, the clutch shaft 60 can slide along the spline shaft portion 601 in the axial direction.

When the clutch pedal 91 is operated, the clutch operation fork 61 of the clutch 6 operates to move the cut-off shaft portion 62 in the front-rear direction along the axial direction of the clutch shaft 60. For example, when the clutch spring 91 is depressed and the disc spring 65 is pressed rearward by the shut-off shaft portion 62 as shown in FIG. 5, the outer peripheral edge of the disc spring 65 warps forward. As a result, the pressure plate 66 moves forward, and the pressing action on the clutch plate 67 is released, so that the pressure plate 66, the clutch plate 67, and the disk 68
Completely separate.

As shown in FIG. 1, the planetary gear means 7 includes a ring gear 70, a sun gear 71, and two planetary gears 72. Note that the number of the planetary gears 72 is not limited to two.

The ring gear 70 has a circular bottom wall 70.
5, with an outer wall 706 protruding cylindrically from the outer peripheral edge,
On the inner peripheral surface of the outer wall 706, the teeth 72 of the planetary gear 72 are provided.
2 are provided. The bottom wall 7
A boss 70 projecting toward the rear side
The input shaft 30 of the transmission 3 is spline-connected to the bearing hole 702 of the boss 703. Further, a bearing 704 that rotatably supports the rear end 602 of the clutch shaft 60 is provided on the front side of the bottom wall 705 so as to be coaxial with the boss 703.

As shown in FIGS. 1 and 2, the sun gear 71 has a diameter smaller than that of the ring gear 70, and the clutch shaft 60
Is stuck to. In this state, the rear end 602 of the clutch shaft 60 is mounted on the bearing 704 of the ring gear 70 so that the sun gear 71 can rotate in synchronization with the clutch shaft 60 at the center of the ring gear 70.

The planetary gear 72 has a diameter that can be attached between the sun gear 71 and the ring gear 70, and has a pivot 721 protruding from the center thereof via a bearing 720.
These planetary gears 72 are provided with outer teeth 722 and sun gears 7.
710 and the ring gear teeth 701, respectively, and the pivot 721 is attached to the mounting hole 6 of the disk 68.
It is pivotally attached to 82 so that it can revolve around the pivot 721 as a rotation axis, and can revolve around the outer periphery of the sun gear 71 by rotation of the disk 68.

As shown in FIG. 2, the braking means 8 is provided at the periphery of the disk 68. In the present embodiment, the same disk brake device as in the related art is used, and the disk 68 is braked by hydraulic pressure.

The caliper of the braking means 8 is a disc 6
Cylinders 81, 81 are provided so as to face both sides of 8, and a brake pad 83 is provided at the front end of a piston 82 in each cylinder 81. When the hydraulic oil flows from the pipe 80 by operating the emergency brake pedal 94 of the control system 9 described later, each of the pistons 82 advances toward the disk 68, and the brake pads 83 move the disk 68 from both sides. Braking in between.

As shown in FIG. 3, the control system 9 controls the clutch 6 via the clutch operating fork 61 by the clutch pedal 91 and the brake pedal 9.
2 controls a brake device attached to each wheel of the vehicle in the same manner as before, and
The carburetor / throttle 931 is controlled to change the vehicle speed. Further, the control system 9 of the present embodiment is provided with an emergency brake pedal 94 having an independent second brake system which does not interfere with a conventional brake device controlled by the brake pedal 92, on the right side of the accelerator pedal 93. I have.

When the emergency brake pedal 94 is depressed, the hydraulic oil is split into three paths through the branching device 90, and the hydraulic oil flows from the first path 901 to the braking means 8 to brake the disk 68. Further, the opening degree of the carburetor / throttle 931 is controlled so that hydraulic oil flows from the second path 902 to the carburetor / throttle 931 so that the engine does not stop. Further, the hydraulic oil flows from the third path 903 to the non-drive wheels, for example, flows to the brake system 100 of the front wheel 5a in the present embodiment, and
00 is controlled.

In the present embodiment, the brake system 100 is provided independently so as not to interfere with the conventional brake system controlled by the brake pedal 92. However, as shown in FIG. In addition, a guide valve 110 having a piston 101 may be further provided in the flow path of the hydraulic oil controlled by the above, and the flow path to the front wheel 5a which is a non-drive wheel may be shared.

In this case, when normal braking is performed by depressing the brake pedal 92, the hydraulic oil is partially transmitted to the brake of the rear wheel 5 which is a driving wheel, while the other is partially transmitted to the inlet 111 of the guide valve 110. Through the outlet 112 and to the brake of the front wheel 5a, which is a non-drive wheel, and the rear wheel 5 and the front wheel 5
Braking a and at the same time. On the other hand, when the emergency brake 94 is depressed, the hydraulic oil controlled by the brake system 100 flows from the inlet 113 of the guide valve 110 and moves the piston 101 as shown by a dashed line in FIG. The hydraulic oil input from the inlet 113 is closed and transmitted to only the brake of the front wheel 5a via the outlet 112. In order to improve the braking effect of the front wheel 5a, an anti-lock brake system having a known configuration may be used together.

In the clutch mechanism having the emergency brake device, when shifting the gear by changing the position of the shift lever 31, the clutch spring 91 is depressed and the disk spring 65 is bent backward as shown in FIG. Let As a result, the pressure of the clutch plate 67 against the disk 68 by the pressure plate 66 is released, and the clutch cover 63 and the disk 68 connected to the clutch cover 63 can freely rotate on the outer periphery of the clutch shaft 60.

At this time, the sun gear 71 connected to the clutch shaft 60 of the planetary gear means 7 rotates as shown in FIG. 6, but the pivot 721 of each planetary gear 72 receives any driving force or braking force. Each planetary gear 72 revolves around the sun gear 71 while rotating around the sun gear 71 because it is pivotally mounted on the disc 68. Therefore, the ring gear 70 can freely rotate without receiving any action. In addition, since the ring gear 70 generates a resistance force by connecting the input shaft 30 of the transmission 3 to the boss portion 703, the ring gear 70 normally shows a stationary state,
The transmission 3 is in a non-driving state. Therefore, the driver can smoothly change the position of the shift lever 31 to change the combination of the transmission gears.

When the gear of the transmission 3 is changed by the shift lever 31, the driving force of the crankshaft 10 is transmitted to the transmission 3 via the clutch 6 by relaxing the force on the clutch pedal 91.

Specifically, when the force on the clutch pedal 91 is reduced, the shut-off bearing 62 moves forward via the clutch operation fork 61, and the pressure plate 66 returns to the current state. Thereby, the pressure plate 66 presses the clutch plate 67,
The clutch plate 67 presses the disk 68, and the disk 68 rotates in synchronization with the clutch shaft 60.

At this time, in the planetary gear means 7, since the sun gear 71 rotates in synchronization with the clutch shaft 60 as shown in FIGS. 2 and 7, the sun gear 71 and the disk 68 are synchronized. Then, the speed and the direction are matched to rotate.
Since each planetary gear 72 is pivotally mounted on the disk 68 receiving the driving force, the pivot 721 of the planetary gear 72 rotates in synchronization with the sun gear 71 and the clutch shaft 60.

As described above, the pivot 721 of each planetary gear 72 is
Rotates in synchronization with the sun gear 71, the planetary gear 72
Of the sun gear 71 and the teeth 701 of the ring gear 70, the planetary gear 71 cannot rotate on its own, but can only revolve around the clutch shaft 60. Thus, the ring gear 70 is directly connected to the sun gear 71 via the planetary gear 72, and the ring gear 70 rotates in synchronization with the clutch shaft 60 connected to the sun gear 71. Ring gear 70
Is rotated in synchronization with the clutch shaft 60, the driving force of the crankshaft 10 is applied to the boss 703 of the ring gear 70.
To the transmission 3 and the transmission 3 is driven.

When the vehicle is to be stopped normally while the vehicle is running, the brake pedal 92 is applied, and as described above, the brake system of each wheel is operated by the brake system similar to the conventional one to perform braking.

On the other hand, an automobile is driven at high speed (for example, 60 k / h).
(m / h or more), the emergency brake pedal 94 and the clutch pedal 91 are simultaneously depressed to stop the clutch 6 and the brake 6 as shown in FIG. Activate the means 8 to brake.

At this time, when the clutch pedal 91 is depressed, the transmission 3 is brought into a non-driving state, as described above, and the disk 68 becomes freely rotatable with respect to the clutch shaft 60. Also, the emergency brake pedal 9
By stepping on 4 simultaneously, as shown in FIG. 3, the hydraulic oil controls the opening of the carburetor / throttle 931 from the branching device 90 through the second path 902 (see FIG. 9). In addition, the brake system 100 of the front wheel 5a is controlled via the third path 903 to control the front wheel 5a.
a through the first path 901 and the braking means 8
Is controlled to brake the disk 68.

By the operation of the braking means 8, the number of rotations of the disk 68, which is rotatable about the clutch shaft 60, is instantaneously reduced from the high-speed rotation to the stop, and the disk 68 is pivotally attached to the disk 68. The revolving speed of the planetary gear 72 is also instantaneously reduced.

At this time, since the rotation speed of the sun gear 71 is the same as the rotation speed of the clutch shaft 60, the sun gear 71
The rotation of the planetary gear 72 due to the difference between the rotation speed of the planetary gear 72 and the revolution speed of the planetary gear 72 causes the ring gear 70 to rotate.
It rotates at a speed not synchronized with 1. Moreover, the planetary gear 7
2 is remarkably reduced, the rotation speed of the ring gear 70 is also instantaneously reduced, and the rotation speed of the input shaft 30 of the transmission 3, and
The rotation speed of the rear wheel 5 also decreases instantaneously.

As described above, the rear wheel 5 whose rotational speed is reduced
Since the rotation speed is lower than the rotation speed before the sudden braking is applied, a large frictional force is generated between the rear wheel 5 and the road surface, and the running speed of the vehicle itself can be instantaneously reduced to a low speed.

The rotational speed of the ring gear 70 connected to the rear wheel 5 via the transmission 3 is reduced from low speed to substantially zero immediately before the disk 68 is locked by the braking means 8.

When the disk 68 is locked by the braking means 8, as shown in FIG. 10, each planetary gear 72 cannot revolve around the sun gear 71 and can only rotate. At this time, the sun gear 71 is
As a result, the planetary gear 72 rotates in a direction opposite to the rotation direction of the sun gear 71 and the clutch shaft 60. The driving force of the planetary gear 72 is transmitted to the ring gear 70, and reverses the rotation direction of the ring gear 70. As a result, the rear wheel 5 connected to the ring gear 70 via the transmission 3 rotates in the direction opposite to the rotation direction during traveling.

Here, for example, when the gear ratio between the sun gear 71 and the ring gear 70 is set to 1: 4 to 1: 5 like the gear ratio of the back gear of the transmission 3, the disk 68 is locked as described above. In the case, the ring gear 70
Rotates reversely at the normal reverse speed, and the rear wheel 5 also rotates at the reverse rotational speed. When traveling forward at a high speed, the gear ratio of the transmission 3 is approximately 1: 1 to 1:
0.75.

As described above, when the driving wheels are rotated in the reverse direction, a large frictional force is generated between the driving wheels and the road surface. This frictional force instantaneously reduces the inertia of the vehicle and shortens the braking distance. be able to. When the drive wheels are rotated in the reverse direction, the vehicle may slightly retreat. In this case, the emergency brake pedal 94 is released and the brake pedal 92 is applied to stop.

According to the brake device of the present invention, when the transmission 3 is driven, the drive wheels of the automobile rotate in the direction in which the vehicle is to travel when the disk 68 is not locked, while the drive wheels are rotated when the transmission 3 is locked. Rotate in the opposite direction. That is, since the drive wheels are locked and do not enter the stopped state, the non-drive wheels (the front wheels 5a) can be braked so that the spin of the vehicle body can be stopped and the vehicle can be stopped quickly.

[0051]

As is clear from the above description, in the brake device of the present invention, the clutch mechanism for driving the automobile is improved, and when the emergency braking is suddenly applied, the braking means and the planetary gear means are used. Since the number of rotations of the crankshaft of the engine is transmitted to the transmission in a reduced manner, and the rotation of the drive wheels can be instantaneously reduced, the braking distance of the vehicle can be shortened. When the disc is locked by the braking means, the rotation of the engine crankshaft is transmitted to the transmission by the planetary gear means in the opposite rotation direction,
Since the driving wheels can be reversely rotated at a low speed, a large frictional force is generated between the driving wheels and the road surface, so that the vehicle can be stopped quickly. Furthermore, according to the above-mentioned brake device, since the driving wheels are not always rotated in any direction and locked, the non-driving wheels can be braked to easily prevent the automobile from spinning. , Safety can be improved.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a brake device of the present invention.

FIG. 2 is a sectional view of a brake device.

FIG. 3 is a schematic diagram showing a control system of the brake device.

FIG. 4 is a schematic diagram showing a flow of hydraulic oil according to a modified example of the control system.

FIG. 5 is a sectional view showing a state where the transmission is not driven.

FIG. 6 is a front view for explaining the operation of the planetary gear unit when the transmission is not driven.

FIG. 7 is a front view for explaining the operation of the planetary gear unit in a state where the transmission is driven.

FIG. 8 is a cross-sectional view showing a state where a clutch pedal and an emergency brake pedal are simultaneously depressed.

9 is a schematic diagram for explaining the operation of a carburetor / throttle in the control system shown in FIG.

FIG. 10 is a front view for explaining the operation of the planetary gear unit in a state where the disk is locked by the braking unit.

FIG. 11 is a schematic diagram showing a drive system of a rear-wheel drive type automobile equipped with a conventional manual transmission.

FIG. 12 is a schematic cross-sectional view of a clutch and a transmission in a rear-wheel-drive vehicle equipped with a conventional manual transmission.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Crankshaft 3 Transmission 30 Input shaft 6 Clutch 60 Clutch shaft 63 Clutch cover 68 Disc 7 Planetary gear means 70 Ring gear 71 Sun gear 72 Planetary gear 721 Axis 8 Braking means 10 Crankshaft

Claims (1)

[Claims] 1. A transmission, which is attached to a clutch shaft integrally connected to a crankshaft of an engine, and rotates in synchronization with the clutch shaft when the transmission is driven, and freely rotates around the outer periphery of the clutch shaft when not driven. A clutch having a clutch cover, a disk connected to the clutch cover, braking means for braking the disk, provided between the disk and a transmission,
A ring gear integrally connected to the input shaft of the transmission and having internal teeth on its inner peripheral surface;
A sun gear rotatably mounted at the center of the ring gear and integrally connected to the clutch shaft, and a pivot shaft meshing with the teeth of the sun gear and the teeth of the ring gear and projecting from the center thereof are pivotally mounted on the disc. A brake device for an automobile, comprising: a planetary gear unit including a plurality of planetary gears.