JP2000248958A - Vibration reducing device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration reducing device for an engine, capable of improving cooling of a generator driving gear also ensuring flexibility of layout and suppressing a vertical vibration of the engine. SOLUTION: Balancer shafts 21L, 21R provided with unbalance masses 22L, 22R as a rotary shaft, in parallel to the rotational center axis of a crankshaft, are arranged through a power transmission mechanism 10 in the crankshaft 5 of an engine 1, a generator drive gear 12 is arranged in at least one of the shafts 21L, 21R, and a torque variation of the crankshaft is canceled by control torque, composed of brake torque and drive torque generated in the generator driving gear 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration reducing device for an engine having a crankshaft driven by a vertical movement of a piston.

[0002]

2. Description of the Related Art As a conventional engine vibration reducing device, for example, one described in Japanese Patent Application Laid-Open No. 61-61922 is known. In this conventional example, two types of rotation-side electromagnetic coils are disposed on a flywheel connected between the output side of a crankshaft of an engine, that is, a transmission, and fixed-side electromagnetic coils are disposed on a fixed side opposite to this. The electric drive device and the power generation device are configured by disposing, one of the rotation-side electromagnetic coils is used as an armature coil of a motor, and the other is used as a field coil of an alternator. The amount of torque fluctuation is estimated based on vehicle operation information such as speed, accelerator opening, engine rotation information, and the like, and driving or power generation is controlled in accordance with this to suppress engine torque fluctuation.

[0003]

However, in the above-mentioned conventional vibration reducing device for an engine, an electric drive device for suppressing a fluctuation in engine torque between an output side of a crankshaft, that is, between the engine and a transmission, and a power generator. Since the device is arranged, both the electric drive unit and the power generation unit generate heat, and in addition, it is difficult to cool because of being sandwiched between the engine and the transmission that are the heat source. There is an unsolved problem that the output of both the device and the power generator decreases.

Further, since the installation positions of the electric drive unit and the power generation unit are set on the output side of the crankshaft,
There is no degree of freedom in layout, and with torque fluctuation,
There is an unsolved problem that even if the vibration of the drive system and the roll vibration of the engine can be reduced, the vertical vibration of the engine cannot be reduced. Therefore, the present invention
The present invention has been made by paying attention to the unsolved problem of the conventional example, and it is possible to improve the cooling of the power generation driving device, secure the freedom of layout, and suppress the vertical vibration of the engine. It is intended to provide a reduction device.

[0005]

According to a first aspect of the present invention, there is provided an engine vibration reducing apparatus for reducing the vibration of an engine having a crankshaft driven by a vertical movement of a piston. An engine vibration reduction device, wherein a power generation driving means is provided on a rotating shaft connected to the crankshaft via a power transmission means so as to rotate at a predetermined rotation ratio, and the power generation driving means is provided with an engine torque. The present invention is characterized in that control is performed so as to generate a reverse-phase torque with respect to a fluctuation component.

In the invention according to the first aspect, the rotating shaft is connected to the crankshaft via the power transmission means,
Since the power generation driving means is disposed on the rotating shaft, by controlling the braking force and the driving force generated by the power generation driving means,
Engine torque fluctuation can be suppressed.
The degree of freedom in the layout of the power generation drive means is increased, so that it can be mounted not only on the rear side (clutch side) of the engine but also on the front side (crank pulley side).
Since the mounting surface of the generator driving means can be arranged so as to be in contact with only the engine, the cooling efficiency can be improved.

According to a second aspect of the present invention, there is provided an engine vibration reducing apparatus for reducing the vibration of an engine having a crankshaft driven by a vertical movement of a piston. Power generation driving means are individually disposed on a plurality of rotating shafts connected to rotate at a predetermined rotation ratio via a power transmission means, and the power generation driving means has an opposite phase with respect to a fluctuation component of engine torque. It is characterized in that it is controlled to generate torque.

According to the second aspect of the present invention, in addition to the function of the first aspect, since a plurality of rotating shafts are connected to the crankshaft and these are individually provided with power generation driving means, each power generation is provided. The output torque of the driving means can be reduced, and the size of the power generation driving means can be reduced. Further, the engine vibration reducing device according to claim 3 is characterized in that, in the invention according to claim 1 or 2, the rotating shaft is constituted by a balance shaft having an unbalance mass that suppresses engine vibration. .

According to the third aspect of the present invention, since the rotating shaft is constituted by the balance shaft having an unbalance mass, the roll vibration of the engine due to the torque fluctuation of the crankshaft caused by the power generation driving means is suppressed, and Vertical vibration of the engine can be suppressed by the balance mass. Still further, according to a fourth aspect of the present invention, in the engine vibration reducing device according to the first to third aspects, the power transmission means is configured to increase a rotational speed of a crankshaft and transmit the rotational speed to the rotary shaft. It is characterized by being.

According to the fourth aspect of the present invention, the rotational speed of the crankshaft is increased and transmitted to the rotating shaft on which the power generation driving means is provided, so that the torque fluctuation generated in the power generation driving means is suppressed. The torque can be suppressed to a small value, and the size of the power generation driving means can be reduced. Still further, according to a fifth aspect of the present invention, in the engine vibration reducing device according to any one of the first to fourth aspects, a plurality of power generation driving units are disposed on the rotating shaft.

In the invention according to claim 5, since a plurality of power generation driving means are provided on one rotating shaft, the configuration of each power generation driving means can be reduced in size. According to a sixth aspect of the present invention, in the engine vibration reducing device according to any one of the first to fifth aspects, a clutch mechanism for interrupting power transmission is provided in a power transmission path between the crankshaft and the power generation driving means. It is characterized by.

In the invention according to claim 6, since the clutch mechanism is provided in the power transmission path between the crankshaft and the power generation driving means, the clutch mechanism is engaged in a low rotation region where the torque fluctuation of the engine and the roll vibration are large. In the high-speed region, the power-generating drive unit is prevented from becoming an engine load.

[0013]

According to the first aspect of the present invention, the rotary shaft is connected to the crankshaft via the power transmission means, and the power generation drive means is disposed on the rotary shaft. By controlling the power and the driving force, the torque fluctuation of the engine can be suppressed, and at this time, the power generation driving means can be arranged on an arbitrary rotating shaft separated from the rotating shaft of the crankshaft. The degree of freedom of the layout of the power generation drive means is increased, so that the power generation drive means can be mounted not only on the rear side (clutch side) but also on the front side (crank pulley side). Since it can be arranged so as to be in contact with only the engine, the effect that the cooling efficiency can be improved can be obtained.

According to the second aspect of the invention, in addition to the effect of the first aspect, a plurality of rotating shafts are connected to the crankshaft, and each of them is provided with a power generation driving means individually. Therefore, it is possible to reduce the output torque of each of the power generation driving means, to reduce the size of the power generation driving means, and to obtain the effect of further improving the layout flexibility.

Further, according to the third aspect of the present invention, since the rotating shaft is constituted by the balance shaft having an unbalanced mass, the roll vibration of the engine due to the torque fluctuation of the crankshaft by the power generation driving means can be suppressed and the unbalance can be reduced. The vertical vibration of the engine by the balance mass can be suppressed at the same time, and the effect of reliably reducing the vibration of the engine can be obtained.

According to the fourth aspect of the present invention, the rotational speed of the crankshaft is increased and transmitted to the rotating shaft provided with the power generation driving means, so that the torque fluctuation generated by the power generation driving means is reduced. The control torque to be suppressed can be suppressed to a small value, the size of the power generation drive unit can be reduced, and the effect of further improving the degree of freedom in layout can be obtained.

According to the fifth aspect of the present invention, a plurality of power generation driving means are provided on one rotating shaft.
It is possible to reduce the size of each of the power generation driving means, and it is possible to further improve the degree of freedom in layout. According to the invention of claim 6,
Since the clutch mechanism is provided in the power transmission path between the crankshaft and the power generation drive means, the clutch mechanism is set in the engaged state in the low rotation region where the torque fluctuation of the engine and the roll vibration are large, thereby reliably suppressing the engine vibration, and the high rotation region. In this case, the effect that the power generation drive means can be reliably prevented from becoming an engine load in the cutoff state can be obtained.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a first embodiment of the present invention, and FIG. 2 is a front view thereof. In the drawing, reference numeral 1 denotes an engine in which a plurality of, for example, four pistons 2 are disposed in a housing 2. The vertical movement of the piston 3 is transmitted to the crankshaft 5 via the connecting rod 4, and the crankshaft 5 is driven to rotate in a certain direction.

A crank pulley 6 for winding a belt connected to an alternator, a power steering pump, an air conditioner compressor, and the like is disposed at a front end of the crank shaft 5 projecting forward from the housing 2. An automatic transmission 8 is connected via a torque converter 7 to a rear end projecting rearward from the rear end 2.

A power transmission mechanism 1 is provided on the front end side of the crankshaft 5 in the housing 2 as a power transmission means, for example, a pair of gears having the same number of teeth meshing with each other.
The rotation shaft 11 is rotatably disposed so as to be horizontally separated from the rotation center of the crankshaft 5 by a predetermined distance and parallel to the rotation center of the crankshaft 5.
A power generation drive device 12 as a power generation drive means is disposed at a front end protruding forward of the power generation device.

The generator drive 12 has an electric motor having a rotor 12r attached to the front end of a rotating shaft 11 and a stator 12s fixedly supported on the front end face of the housing 2 on the outer peripheral side of the rotor 12r. The electric motor operates as a generator to generate a braking torque by regenerative braking, and operates as an electric motor to generate a driving torque.

As shown in FIG. 3, the power generation drive unit 12 includes a vehicle speed sensor, an accelerator opening sensor, an engine speed sensor, and the like for detecting vehicle driving information such as a running speed, an accelerator opening, and engine rotation information. The control device 16 estimates the amount of torque fluctuation based on the vehicle operation information input from the vehicle operation information detection device 15 including the vehicle operation information, and the braking torque or the driving torque generated by the power generation drive device 12 so as to cancel the estimated amount of torque fluctuation. , The regenerative electric power when the braking torque is generated is stored in the power storage device 17 including a battery and a capacitor, and the supply power when the driving torque is generated is supplied from the power storage device 17 to the power generation drive device 12.

Next, the operation of the above embodiment will be described. First, assuming that the vehicle is stopped, the ignition switch is in the off state and the engine 1 is stopped, in this state, the ignition switch is in the off state. Even execution has been stopped.

When the ignition switch is turned on from this state, the engine 1 is started in response to this, and the torque fluctuation suppression control by the control device 16 is started. Therefore, the vertical movement of the piston 3 is transmitted to the crankshaft 5 through the connecting rod 4, and the crankshaft 5 starts rotating in a predetermined direction. The vehicle driving information at this time is detected by the vehicle driving information detecting device 15, and the control device 16 estimates the torque fluctuation amount of the engine 1 based on the vehicle driving information.

Therefore, when the torque of the engine 1 increases in the predetermined direction of rotation, the control device 16 causes the power generation drive device 12 to function as a generator to generate regenerative braking torque, which is transmitted to the rotating shaft 11 and the power transmission. By transmitting the power to the crankshaft 5 via the mechanism 10, the amount of increase in the torque of the engine 1 is offset, and the regenerative power is supplied to the power storage device 17 to store the power.

Conversely, when the torque of the engine 1 decreases in the predetermined rotation direction, the control device 16 controls the power storage device 17.
Supplies electric power to the generator drive device 12 to make it function as an electric motor to generate a rotational drive torque, which is transmitted to the crankshaft 5 via the rotary shaft 11 and the power transmission mechanism 10 in the same manner as described above. By the engine 1
Offset the amount of torque reduction.

In this way, the control device 16 causes the generator drive device 12 to generate a braking torque as a generator so as to decrease the engine torque when the engine torque increases, and to increase the braking torque when the engine torque decreases. By generating driving torque as an electric motor, torque fluctuations of the engine 1 can be reliably suppressed, and roll vibrations of the engine 1 and rotation fluctuations of the drive shaft are reduced. Reduction can be achieved.

At this time, since the power generation driving device 12 is mounted on the rotating shaft 11 arranged in parallel with the rotation center of the crankshaft 5 and connected to the crankshaft 5 via the power transmission mechanism 10, The degree of freedom in layout can be increased without specifying the installation position of the rotating shaft 11. Further, since the power generation drive device 12 is disposed in contact with only the housing 2 of the engine 1 and is separated from the torque converter 7 and the automatic transmission 8, the torque converter 7 and the automatic transmission 8 are separated from each other. 8 can be reliably prevented from being transmitted to the power generation drive device 12, and the cooling efficiency of the power generation drive device 12 can be improved.

In the first embodiment, a case has been described in which the power generation drive device 12 is disposed on the front side of the rotary shaft 11 in the housing 2 of the engine 1.
The present invention is not limited to this. As shown in FIG. 4, a rotating shaft 11 is rotatably connected to a rear end side of the crankshaft 5 via a power transmission mechanism 10, and The power generation drive device 12 may be provided at the rear end protruding from the power generation drive device.

In the first embodiment, the case where the rotating shaft 11 is disposed at a position horizontally separated from the rotation center axis of the crankshaft 5 by a predetermined distance has been described. However, the present invention is not limited to this. Instead, as shown in FIG. 5, the crankshaft 5 can be disposed in parallel with the rotation center axis of the crankshaft 5 in a direction perpendicular to the rotation center axis.
Can be arranged at any position around the center of rotation.

Further, in the above embodiment, the case where the rotating shaft 11 is provided in parallel with the rotation center axis of the crankshaft 5 has been described. However, the present invention is not limited to this. You may make it extend in the direction which intersects with the rotation center axis of the shaft 5. Next, a second embodiment of the present invention will be described with reference to FIGS.

In the second embodiment, a power transmission mechanism 10
The control torque generated in the power generation drive device 12 is reduced by changing the power transmission ratio in the power transmission. That is, in the second embodiment, as shown in FIGS.
In the configuration of FIG. 1 of the first embodiment described above, the gear ratio of the pair of gears 10a and 10b constituting the power transmission mechanism 10 is set to 2: 1, that is, the rotation speed ratio is set to 1: 2, and the rotation shaft is set. When the control device 16 is configured to function as an electric motor by the reduction gear mechanism when viewed from the side 11, the rotation speed is set to 2 times the rotation speed in the first embodiment.
FIG. 1 except that the rotation speed is controlled at a double speed.
The same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

According to the second embodiment, the rotary shaft 11 on which the crankshaft 5 and the power generation drive device 12 are mounted is provided.
And the power transmission mechanism 10 is configured such that the rotation speed on the rotating shaft 11 side is twice the rotation speed on the crankshaft side, and is configured as a reduction gear mechanism when viewed from the rotating shaft 11 side. The braking torque and the driving torque required to suppress the torque fluctuation generated in the engine 1 by the power generation driving device 12 are only half of the braking torque and the driving torque in the first embodiment described above. It is possible to apply the power generation drive device 12 having a small output torque. As a result, since the outer diameter of the rotor 12r serving as a torque generation source of the power generation drive device 12 may be small, the power generation drive device 12 can be downsized, and the degree of freedom in layout can be further improved.

In the second embodiment, similarly to the first embodiment, the power generation drive device 12 can be disposed at the rear end of the housing 2 and the location of the rotary shaft 11 can be set. May be disposed at any position around the rotation center axis of the crankshaft 5, and may extend in a direction intersecting the rotation center axis of the crankshaft 5.

Next, a third embodiment of the present invention will be described with reference to FIGS. In the third embodiment, vertical vibration is also suppressed in addition to suppressing roll vibration of the engine. That is, in the third embodiment, as shown in FIGS. 8 and 9, in the configuration of FIGS.
The balancer shafts 21L and 21R as two rotation shafts are connected via the power transmission mechanism 10 of the first embodiment, and one balancer shaft 21R is parallel to the rotation center axis of the crankshaft 5 and is separated from the crankshaft 5 by a predetermined distance in the horizontal direction. The other balancer shaft 21L is connected to the crankshaft 5 via the power transmission mechanism 10 so as to rotate in a direction opposite to that of the crankshaft 5. The idler gear 10c is spaced apart and rotates in the same direction as the crankshaft 5.
And unbalance masses 22L and 22R for suppressing vertical vibration of the engine 1 are disposed on both balancer shafts 21L and 21R, and protrude forward of the housing 2 of one of the balancer shafts 21R. 6 and 7 except that the power generation drive device 12 is disposed at the front end of the vehicle, and the same reference numerals are given to the portions corresponding to FIGS. Detailed description is omitted.

According to the third embodiment, in a low rotation region where the roll vibration is the main engine vibration, the power generation drive unit 12 suppresses the fluctuation of the engine torque by the power generation drive device 12 as in the above-described second embodiment. In the high rotation region where the vertical vibration is mainly exerted, the unbalance mass 2 of the balancer shafts 21L and 21R is exhibited.
The vertical vibration reduction effect by the 2L and 22R is exhibited, and the engine vibration reduction effect can be obtained in the entire region of the engine rotation.

Next, a fourth embodiment of the present invention will be described with reference to FIGS. The fourth embodiment is different from the third embodiment in that the power generation drive device 12 can be further reduced in size. That is, in the fourth embodiment, as shown in FIGS. 10 and 11, FIGS. 8 and 9 in the third embodiment described above.
8 and 9 have the same configuration as that of FIGS. 8 and 9 except that the power generation drive device 12 'is also mounted on the other balance shaft 21L. And a detailed description thereof will be omitted.

According to the fourth embodiment, the effect of suppressing the roll vibration and the vertical vibration of the engine can be exerted in the same manner as in the above-described third embodiment. And 12 ′ are connected to each other, so that the control torque required to suppress the torque fluctuation of the crankshaft 5 can be controlled by the two power generation driving devices 1.
2 and 12 ′, and the control torque shared by the individual power generation drives 12 and 12 ′ is only half the control torque of the power generation drive 12 in the third embodiment. The outer diameter of the rotor 12r of 12 'can be made smaller and more compact, and the degree of freedom in layout can be further improved.

Next, a fifth embodiment of the present invention will be described with reference to FIG. In the fifth embodiment, the power generation drive device 12 is prevented from becoming an engine load in a high-speed region of the engine. That is,
In the fifth embodiment, as shown in FIG.
In the configuration of FIG. 8 according to the embodiment, the electromagnetic clutch 25 as a clutch mechanism is provided on the balancer shaft 21R on the front side of the power generation drive device 12 outside the housing 2.
While the electromagnetic clutch 25 is controlled by the control device 16 while the engine speed sensor detects that the crankshaft 5 is rotating in the low rotation range, the clutch is controlled to the engaged state. It has the same configuration as that of FIG. 8 except that it is controlled to be in the cut-off state when it is detected that the high rotation region has been reached, and the parts corresponding to FIG. Omit this.

According to the fifth embodiment, the engine 1
When the crankshaft 5 is rotating in the low rotation region, the electromagnetic clutch 25 is controlled to the engaged state by the control device 16, and thus the control torque for suppressing the torque fluctuation of the crankshaft 5 generated in the power generation drive device 12 is reduced. By transmitting the torque to the crankshaft 5 via the clutch mechanism 25, the rotating shaft 11, and the power transmission mechanism 10, torque fluctuations of the engine 1 can be suppressed. From this state, when the crankshaft 5 reaches the high rotation region. When the electromagnetic clutch 25 is controlled to be in the disconnected state by the control device 16, the power generation drive device 12
And the generator drive 12 can be reliably prevented from becoming an engine load. In this state, the balance shaft 21 is attached to the crankshaft 5.
Since only L and 21R are connected, vertical vibration can be suppressed by these balancer shafts 21L and 21R.

In the fifth embodiment, the case where the electromagnetic clutch is used as the clutch mechanism has been described. However, the present invention is not limited to this, and a mechanical clutch may be used. In the fifth embodiment, the case where the clutch mechanism is provided at a position close to the power generation drive device 12 of the balancer shaft 21R has been described. However, the present invention is not limited to this, and the power transmission mechanism 10 and the power generation drive It may be provided in any of the power transmission paths to and from the device 12.

Further, in the fifth embodiment,
Although the case where the clutch mechanism is added to the third embodiment has been described, the invention is not limited to this, and the clutch mechanism may be added to the first or second embodiment. If the crankshaft 5
A clutch mechanism may be provided in any of the power transmission paths between the power generation drive device 12 and the power generation drive device 12.

Further, in the first to fifth embodiments, the rotating shaft 11 or the balance shafts 21L, 21L
Although the case where the power generation drive device 12 or 12 'is disposed at one end of the 1R has been described, the present invention is not limited to this. By arranging two or more power generation drive devices for one rotation shaft, By sharing the control torque among the plurality of power generation driving devices, the power generation driving device can be further reduced in size and the degree of freedom in layout can be further improved.

Further, in the second to fifth embodiments, the case where the rotation speed ratio of the power transmission mechanism is set to 1: 2 has been described. Speed ratio can be set. In the first to fifth embodiments, the case where the gear mechanism is applied as the power transmission mechanism has been described.
It is needless to say that other power transmission mechanisms such as a chain and a sprocket, a V-belt, a toothed belt and a pulley can be applied.

Further, in the first to fifth embodiments, the case has been described in which the generator drive device 12 is used only as an actuator for suppressing engine torque fluctuation. However, the present invention is not limited to this. Or as an alternator.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing a first embodiment of the present invention.

FIG. 2 is a schematic front view of FIG.

FIG. 3 is a block diagram illustrating a control system according to the first embodiment.

FIG. 4 is a schematic plan view showing a modification of the first embodiment.

FIG. 5 is a schematic side view showing a modification of the first embodiment.

FIG. 6 is a schematic plan view showing a second embodiment of the present invention.

FIG. 7 is a schematic front view of FIG.

FIG. 8 is a schematic plan view showing a third embodiment of the present invention.

FIG. 9 is a schematic front view of FIG. 6;

FIG. 10 is a schematic plan view showing a fourth embodiment of the present invention.

FIG. 11 is a schematic front view of FIG.

FIG. 12 is a schematic plan view showing a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Housing 5 Crankshaft 7 Torque converter 8 Automatic transmission 10 Power transmission mechanism 11 Rotary shaft 12, 12 'Power generation drive device 15 Vehicle driving information detection device 16 Control device 17 Power storage device 21L, 21R Balancer shaft 22L, 22R Unbalance Shaft 25 Electromagnetic clutch

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuichi Sakuma, Nissan Motor Co., Ltd., 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture (72) Inventor Shigeki Sato 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa, Nissan Motor Co., Ltd. 72) Inventor Yoshiharu Nakaji 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside Nissan Motor Co., Ltd.

Claims (6)

[Claims] 1. An engine vibration reduction device configured to reduce vibration of an engine having a crankshaft driven by a vertical movement of a piston, wherein the vibration is reduced at a predetermined rotation ratio via a power transmission means to the crankshaft. A power generation driving means is provided on a rotating shaft connected to rotate, and the power generation driving means is controlled so as to generate a torque having an opposite phase to a fluctuation component of the engine torque. Engine vibration reduction device. 2. An engine vibration reducing device for reducing the vibration of an engine having a crankshaft driven by the vertical movement of a piston, wherein the vibration is reduced at a predetermined rotation ratio via a power transmission means to the crankshaft. Power generation drive means are individually arranged on a plurality of rotating shafts that are connected so as to rotate, and the power generation drive means is controlled so as to generate torque in opposite phase with respect to a fluctuation component of engine torque. An engine vibration reduction device characterized by the above-mentioned. 3. The engine vibration reduction device according to claim 1, wherein the rotation shaft is formed of a balance shaft having an unbalance mass for suppressing vibration of the engine. 4. The engine according to claim 1, wherein the power transmission means is configured to increase a rotation speed of a crankshaft and transmit the rotation speed to the rotation shaft. Vibration reduction device. 5. The engine vibration reduction device according to claim 1, wherein a plurality of power generation driving means are provided on the rotating shaft. 6. The engine vibration reduction device according to claim 1, wherein a clutch mechanism for interrupting power transmission is provided in a power transmission path between the crankshaft and the power generation driving means.