AUTOMOTIVE VEHICLE WITH BEARING OF PROPELLER SHAFT ASSEMBLY VARIABLE IN POSITION

Abstract: A system for reducing vibration and noise generated from a propeller shaft assembly (1,2) of an automotive vehicle comprises a center bearing which is variable in position relative to the vehicle body under the control of a controller (30). Operating conditions of the vehicle are sensed by sensors (31-33) whose output signals (P.G.TH) are fed to the controller (30). The position of the center bearing is varied by means (23,25) responsive to a control signal from the controller (30).

Description: The present invention relates to an automotive vehicle with a bearing of a propeller shaft assembly variable in position relative to the vehicle body, and more particularly to a system for reducing vibration and noise due to secondary couple generated with angles of cardan joints upon vehicle starting. There is shown, by way of example, a propeller shaft of the prior art in Fig. 7a, in which reference numerals 1 and 2 denote a first propeller shaft and a second propeller shaft of a propeller shaft assembly, respectively, and 3, 4,and 5 cardan joints (referred hereinafter to as first, second,and third cardan joints) which swingably connect a main shaft or a transmission output shaft 6 with the first propeller shaft 1, the propeller shaft 1 with the propeller shaft 2,and the propeller shaft 2 with a drive pinion of a differential 7. A center bearing 8 is fixed near the middle position of the shaft total length obtained by adding the length of the first propeller shaft 1 to that of the second propeller shaft 2. As seen from an enlarged detail show in Fig. 7b, the center bearing 8 is supported by an upper bracket 11 connected to a vehicle body through a cushion rubber layer 10. A lower bracket 12 is connected to the upper bracket 11 by means of a bolt. With this propeller shaft, when vibration is transmitted to the first and second propeller shafts 1, 2 from the main shaft 6 and the differential 7, the propeller shaft 1 moves up and down in a movable area defined by the center bearing 8 and the upper and lower brackets 11, 12, which is absorbed by an insulator 9 and the cushion rubber layer 10. A vehicle having this 3-joint type propeller shaft is pretty excellent in occurrence of noise at a high speed and critical engine speed performance as compared with a vehicle having a 2-joint type propeller shaft, so that the 3-joint type propeller shaft is frequently used on a small vehicle in recent years. The 3-joint type propeller shaft offers the above-mentioned advantages, but this propeller shaft is worse than the 2-joint type propeller shaft in respect to vibration and noise due to secondary couple generated with angles of cardan joints during vehicle starting when there occurs wind-up of the differential. That is, with the 2-joint type, the above-mentioned vibration and noise can be reduced by arranging the main shaft and the differential on the same straight line to provide a drive system in which variations in exciting force become small when there occurs wind-up of the differential. On the other hand, with the 3-joint type, the propeller shaft is fixed to the vehicle body by the center bearing so that a certain angle is inevitably formed between the main shaft and the differential. Specifically, during vehicle starting where there are great variations in torque of the propeller shaft, which are proportional to input torque, the insulator and the cushion rubber are not sufficient for preventing the above-mentioned vibration and resultant noise. What is desired is a system for reducing vibration and noise derived from a drive system of an automotive vehicle owing to a propeller shaft assembly US-A-2 939 540 discloses an automotive vehicle as set forth in the pre-characterising part of claim 1. According to one aspect of the present invention, as set forth in claim 1, the automotive vehicle is characterised by: sensor means for sensing operating conditions which the automotive vehicle is subject to and generating sensor output signals; and means for generating a control signal in response to the sensor output signals; the bracket structure including means responsive to the control signal for varying the position of the bearing relative to the vehicle body. According to another aspect of the present invention, as set forth in claim 10, there is provided a method of suppressing noise characterised by: sensing operating conditions which the automotive vehicle is subject to and generating corresponding output signals; generating a control signal in response to the output signals; and varying the position of the bearing relative to the vehicle body in response to the control signal. In the accompanying drawings: Fig. 1 is a diagrammatic view showing a portion of an automotive vehicle with a drive system including a propeller shaft assembly with a center bearing variable under the control of a controller; Figs. 2a and 2b are front and side elevations showing details of a bracket structure for the center bearing rotatably supporting a predetermined portion of the propeller shaft assembly shown in Fig. 1; Fig. 3 is a diagrammatic view showing a model for analyzing angles of cardan joints; Fig. 4 is a diagrammatic view showing an objective angular range to be obtained by the present embodiment; Fig. 5 is a flow chart showing a control program of the present embodiment; Fig. 6a and 6b are diagrammatic views respectively showing characteristics of contents of two kinds of table data stored in the controller, illustrating the relation between a base amount of displacement of supporting position of the center bearing and an amount of compression of a rear suspension, and the relation between a correction amount of displacement of the supporting position of the center bearing and a throttle opening degree TH; and Figs. 7a and 7b are diagrammatic views respectively showing a propeller shaft of the prior art and details of its center bearing portion. Referring first to Fig. 1, there is shown a drive system of an automotive vehicle with a vehicle body 200. The drive system includes an engine 202 with a throttle 204 which opens by degrees, a transmission 206 operatively coupled with the engine 202, a propeller shaft assembly including a first and a second propeller shafts 1 and 2, a differential 208, and a pair of driving wheels, only one being shown in phantom and designated by 210. A rear suspension system 212 is operatively connected between the driving wheels 210 and the vehicle body 200 to support the weight of the vehicle body 200. A hydraulic pump 20 provides a hydraulic pressure to a servo valve 23 through an unloading pressure control valve 21 and an accumulator 22. A reservoir 24 is interposed between the unloading pressure control valve 21 and the servo valve 23, and an actuator 25 is used for controlling a center bearing supporting position, which is connected to the unloading pressure control valve 21. A controller 30 is connected to a position sensor 31 for sensing an amount of compression of a rear suspension, which is a potentiometer in this embodiment, a gear position sensor 32 for sensing a gear position,and a throttle opening sensor 33 for sensing a throttle opening degree of an engine throttle valve, to which controller a position signal P, a gear position signal G, and a throttle opening signal TH are provided respectively. The controller 30 is also connected to a servo amplifier 34 which provides a control signal to the servo valve 23 in response to a control signal provided from the controller 30. The servo valve 23 hydraulically actuates a movable rod 25a of the actuator 25 in response to the control signal. Next, a propeller shaft portion is described. Referring to Figs. 2a and 2b, a spring 25b for returning the movable rod 25a is mounted on the actuator 25. An upper end portion of the movable rod 25a is associated with a lifting bracket 27 connected to an upper bracket 26 supporting a center bearing 8. Further, a mounting flange of a bracket 28 connected to the side of the actuator 25 is fixed on a vehicle body 29. The operation is described. As shown in Fig. 3, forces applied to the first, second,and third cardan joints (referred to as exciting forces) designated F₁, F₂,and F₃ respectively, the exciting forces F₁, F₂,and F₃ can be expressed by the following formulae: F₁ = T 2 { 1 A (ϑ₁ + ϑ₂) + B A.L 2 (ϑ₁ + ϑ₂)} sin 2β F₂ = T 2 { 1 A (ϑ₁ + ϑ₂) + L 1 A.L 2 (ϑ₁ + ϑ₂)} sin 2β F₃ = - T 2 { 1 L 2 (ϑ₂ + ϑ₃) )} sin 2β wherein ϑ1 (theta one) is an angle between the main shaft and the first propeller shaft, ϑ2 (theta two) an angle between the first propeller shaft and the second propeller shaft, ϑ3 (theta three) an angle between the second propeller shaft and the differential, A a distance between the first cardan joint and the center bearing, B a distance between the second cardan joint and the center bearing,L₁ a length of the first propeller shaft, L₂ a length of the second propeller shaft, T a torque of the drive shaft, β (beta) an angle of rotation of the drive shaft (when a yoke surface on the drive side is perpendicular to a surface formed by a drive shaft and a driven shaft, the angle β (beta) is assumed to be 0). With this embodiment, an admissible angular range for the exciting forces F₁, F₂,and F₃ is set, as shown in Fig. 4, to limit the exciting forces F₁, F₂,and F₃ to predetermined values. There are two terms (ϑ₁ + ϑ₂) and (ϑ₂ + ϑ₃) as parameters of the above-mentioned formulae (1) to (3). Designating the terms (ϑ₁ + ϑ₂) and (ϑ₂ + ϑ₃) by angles ₁ (phi one) and ₂ (phi two) respectively, the angles ₁ (phi one) and ₂ (phi two) are expressed by the following formulae: ₁ = ϑ₁ + ϑ₂ = Φ E - Φ₂ ₂ = ϑ₂ + ϑ₃ = Φ₁ - Φ D wherein Φ E (phi E), Φ D (phi D), Φ₁ (phi one), and Φ₂ (phi two) are inclinations between the surface formed by the drive shaft and the driven shaft, and the engine, the differential, the first propeller shaft, and the second propeller shaft respectively. When a rigid axle (axle suspension) type rear suspension vehicle such as a four-link or five-link vehicle is loaded, the inclination Φ₂ (phi two) is decreased and also the inclination Φ₁ (phi one) is slightly decreased, so that angular condition varies in the direction of arrow A in Fig. 4. In this embodiment, a positional margin is made in the direction of the wind-up by raising a supporting position of the center bearing in accordance with a live load. Then, when the differential is wound up by transmission of the driving torque, the inclination Φ D (phi D) is increased and the inclination Φ₂ (phi two) is slightly decreased, so that angular condition varies in the direction of arrow B. On the other hand, when the supporting position of the center bearing is raised, the inclination Φ₂ (phi two) is increased and the inclination Φ₁ (phi one) is decreased, so that angular condition varies in the direction of arrow C. As described above, an objective angular range is set on the exciting forces F₁ F₂,and F₃, so that, when the exciting force F₁ acts in a manner to exceed the objective angular range by wind-up during vehicle starting, the exciting force F₁ can be kept within the objective angular range by raising the supporting position of the center bearing. Next, a control program stored in the controller is described with respect to a flow chart in Fig. 5. First, at step 101, it is judged whether an engine key is ON or not. If the engine key is ON, control proceeds to step 102 at which a gear position is checked. If the gear position falls in the neutral, control proceeds step 103. At step 103, it is judged whether the throttle opening degree TH is zero or not. When the throttle opening degree is 0, it is judged that a vehicle is at a standstill. Then, control of steps 104 to 106 is performed (control up to step 106 is achieved from turning-on of the engine key to idling). That is, at step 104, an amount of compression of the rear suspension is read by the position sensor 31 (potentiometer) and, at step 105, a table look-up of a table as shown in Fig. 6a is performed to determine a base amount of displacement of a supporting position of the center bearing corresponding to the amount of compression. The table as shown in Fig. 6a is stored in a ROM of the controller 30 and shows the characteristics that the greater is the amount of compression, the greater will be an amount of displacement of the supporting position. At next step 106, a control signal is provided from the controller 30 to the servo valve 23 through the servo amplifier 34 to lift or raise the supporting position of the center bearing by the displacement determined at the step 105. As a result, the servo valve 23 is ON and the movable rod 25a of the actuator 25 is hydraulically actuated to lift or raise the supporting position of the center bearing. Supporting position control of the center bearing of the above steps 101 to 106 is particularly effective when a 3-joint type propeller shaft is mounted on a rigid axle type rear suspension vehicle. In other words, in such vehicle, as soon as a vehicle position is changed by loading, an angle of the joint of the propeller shaft is also changed thereby to induce a secondary couple, causing vibration and noise during vehicle starting. Such vibration and noise can be reduced by the supporting position control: A positional margin is made in the direction of the wind-up (arrow B) by raising the supporting position of the center bearing (arrow C) as shown in Fig. 4, even if there is increase in loadage (arrow A). At above step 102, if it is judged that a gear position is at the first gear position, control proceeds to step 107 at which the throttle opening degree TH is compared with a predetermined value TH₀. When the throttle opening degree TH is equal to or greater than the predetermined value TH₀, correction during vehicle starting of the supporting position of the center bearing is carried out at steps 108 and 109. Specifically, at step 108, in order to determine a correction amount of displacement of a supporting position of the center bearing corresponding to the throttle opening degree TH, a table look-up of a table as shown in Fig. 6b is performed. As shown in the table of Fig. 6b, the greater is the throttle opening degree TH, the greater will be correction amount of displacement of the supporting position. At next step 109, the supporting position of the center bearing is lifted or raised in a similar manner to the above step 106. With supporting position control of the center bearing of the above steps 101, 102,and 107 to 109, if a very large torque is provided upon vehicle starting with the first gear position and the throttle opening degree more than a predetermined value, there occurs a further lift or raise of the supporting position in addition to the above-mentioned lift or rise when the vehicle is at a standstill, resulting in decrease in vibration and noise due to secondary couple generated with angles of cardan joints when there occurs wind-up of the differential. If the gear position is other than the neutral or the first gear position at step 102 or if the throttle opening degree TH is not zero at step 103 or if the throttle opening degree TH is less than the predetermined value TH₀, the supporting position control of the center bearing is cancelled at step 110, since such control is not necessary when the vehicle is running after the starting operation or when the vehicle is at a standstill with the accelerator depressed. As a result, the servo valve 23 is OFF and the movable rod 25a of the actuator 25 returns to its initial position due to force of the spring 25b. At the above step 101, if it is judged that the engine key is OFF, the supporting position control of the center bearing is cancelled at step 111 and a power supply of the controller 30 is OFF at step 112. Having described an embodiment of the present invention, it is to be understood that the embodiment is illustrative and not restrictive and that various modifications and variations are possible in light of the above teachings. For example, if an independent type rear suspension is used, a propeller shaft assembly is not subject to effect of increase in loadage, so that the position sensor 31 (potentiometer) and supporting position control of steps 103 to 106 may be omitted. Further, the throttle opening degree TH used for judgement of step 103 may be replaced by a throttle operating speed V TH . Furthermore, a vehicle speed V provided from a vehicle speed sensor or an engine rotation signal N E provided from an engine rotation sensor may be used for judgement whether the vehicle is at a standstill or not.

Claims: 1. An automotive vehicle including: a propeller shaft assembly (1,2) including a first propeller shaft (1) having one end coupled with driving power generating means (206) via a joint (3), a second propeller shaft (2) having one end coupled with the opposite end of the first propeller shaft (1) via a joint (4), the opposite end of the second propeller shaft (2) being coupled with a differential (208) via a joint (5); driving wheels (210) operatively coupled with the differential (208); a bearing (8) rotatably supporting the middle part of the propeller shaft assembly (1,2); and a bracket structure (26-28) fixedly connected to the vehicle body and supporting the bearing (8) so that its position is variable relative to the vehicle body; characterised by sensor means (31-33) for sensing operating conditions which the automotive vehicle is subject to and generating sensor output signals (P,G,TH); and means (30,34) for generating a control signal in response to the sensor output signals; the bracket structure (26,28) including means (23,25) responsive to the control signal for varying the position of the bearing (8) relative to the vehicle body. 2. An automotive vehicle as claimed in claim 1, wherein the driving power generating means includes an engine (202) with a throttle (204) which opens by degrees, characterised in that the sensor means includes a throttle sensor means (33) for sensing the opening degree of the throttle and generating a throttle opening degree indicative signal (TH). 3. An automotive vehicle as claimed in claim 1 or 2, including a suspension system (212) operatively connected between the driving wheels and the vehicle body for supporting the vehicle body, characterised in that the sensor means includes a position sensor means (31) for sensing a position of a predetermined portion of the suspension system (212) relative to the vehicle body and generating a positive indicative signal (P). 4. An automotive vehicle as claimed in any preceding claim, including a transmission (206), characterised in that the sensor means includes a gear position sensor means (32) for sensing which of various different positions the transmission is conditioned in and generating a transmission condition indicative signal (G). 5. An automotive vehicle as claimed in claim 2, wherein the controlling means (30,34) includes a controller (30) storing a data table (Fig. 6b) containing different amounts of displacement (Y) of the position of the bearing (8) versus different values of the throttle opening degree indicative signal (TH). 6. An automotive vehicle as claimed in claims 4 and 5 together wherein the controller (30) performs a table look-up operation of the data table (Fig. 6b) based on the throttle opening degree indicative signal (TH) to determine an appropriate amount of displacement (Y) of the position of the bearing (8) against the throttle opening degree indicative signal (TH) when the throttle opening degree indicative signal (TH) is greater than a predetermined value (THo) and the transmission condition indicative signal (G) indicates that the transmission (206) is in a condition suitable for the vehicle to start from standstill. 7. An automotive vehicle as claimed in claim 3 together with claim 5 or 6, wherein the controller (30) stores a second data table (Fig. 6a) containing different amounts of displacement (X) of the position of the bearing (8) versus different values (x) of the positive indicative signal (P). 8. An automotive vehicle as claimed in claim 7, wherein the controller (30) performs a table look-up operation of the second data table (Fig. 6a) based on the position indicative signal (P) to determine an appropriate amount of displacement (X) of the position of the bearing (8) against the position indicative signal (P) when the throttle indicative signal (TH) is substantially zero and the gear position indicative signal (G) indicates that the transmission (206) is in neutral. 9. An automotive vehicle as claimed in any preceding claim, wherein the bracket structure comprises a stationary bracket (28) fixedly connected to the vehicle body, a movable bracket (26) mounted on the stationary bracket (28) and fixedly supporting the bearing (8), and the varying means comprises a hydraulic actuator (25) mounted on the stationary bracket (28), the actuator (25) including a piston with a piston rod integral with a stay (27) fixedly connected to the movable bracket (26). 10. A method of suppressing noise derived from a drive system of an automotive vehicle, the drive system comprising: a propeller shaft assembly (1,2) including a first propeller shaft (1) having one end coupled with driving power generating means (206) via a joint (3), a second propeller shaft (2) having one end coupled with the opposite end of the first propeller shaft (1) via a joint (4), the opposite end of the second propeller shaft (2) being coupled with a differential (208) via a joint (5); driving wheels (210) operatively coupled with the differential (208); a bearing (8) rotatably supporting the middle part of the propeller shaft assembly (1,2); and a bracket structure (26-28) fixedly connected to the vehicle body and supporting the bearing (8) so that its position is variable relative to the vehicle body, the method being characterised by the steps of: sensing operating conditions which the automotive vehicle is subject to and generating corresponding output signals; generating a control signal in response to the output signals; and varying the position of the bearing (8) relative to the vehicle body in response to the control signal.

Inventors: HIRANO, YOSHINORI
Applicants: NISSAN MOTOR CO., LTD.
Application year: 1989
Main classification: B60K17
IPC codes: B60K17