DE4113736A1 - STABILIZING DEVICE FOR VEHICLES - Google Patents

Description

The invention relates generally to stabilizing devices for Vehicles and in particular on a stabilization device with a liquid or gaseous pressure medium works, for example a hydraulic stabilization device.

An example of a conventional hydraulic stabilization system is shown in published Japanese utility model application 60-76 506 described. There are two double-acting hydraulic cylinders in this system with a piston rod between the vehicle body and the respective suspension arms arranged. The hydraulic cylinders are through cross lines connected in such a way that an upper cylinder chamber of one Hydraulic cylinder with one lower cylinder chamber in the other Connection is established. The cross lines are each with bottlenecks or throttling points provided and also point at positions between the top Cylinder chambers and the throttling points spring-loaded mechanical accumulators on, through the hydraulic fluid in the lines and cylinders is kept under pressure.

In the conventional stabilization system, they are used in the cross lines arranged throttling points to limit the flow of the hydraulic fluid both in the rolling movement and in the pitching movement of the vehicle body. Consequently, the stabilization system also demonstrates the pitching movement of the vehicle body has a damping effect, so that a stiff or rough driving feeling is created and the driving comfort of the vehicle is impaired.

The mechanical accumulators can be set manually beforehand to achieve a desired roll stiffness, but can be Settings not every time the cornering conditions change, d. H. when changing the lateral acceleration. Hence it is not always the case with the conventional stabilization system possible, the desired roll stiffness and thus the desired steering characteristics to achieve the vehicle.

The invention has for its object a stabilizing device for  To create vehicles with greater driving comfort and better adaptation to the respective driving conditions is possible.

This object is achieved with those specified in claim 1 Features resolved.

The stabilization device according to the invention is intended for vehicles, the two spaced apart on the side of the vehicle body Have suspension arms. The stabilizing device comprises in detail a stabilizer with two with double piston rods double acting cylinders, each between the vehicle body and the suspension arms are arranged and each have an upper and a lower Cylinder chamber have two first lines, the upper and lower Cylinder chamber of the first cylinder with the lower or upper chamber of the second cylinder connect two accumulators, two more Lines, the accumulators each with the associated first line connect, and two throttling points arranged in the second lines to limit the flow.

Furthermore, the stabilizing device has adjusting means for changing the fluid pressure in the stabilizer for controlling the actuating means in Dependency on the driving condition of the vehicle.

In this way, an active control of the rolling stiffness of the vehicle achieved without impairing driving comfort. Through the so made possible Stabilizing the vehicle body will also improve the driving safety of the vehicle elevated.

Preferred exemplary embodiments of the invention are described below of the drawings explained in more detail.

It shows

Figure 1 is a schematic sketch of a hydraulic stabilization device according to an embodiment of the invention.

FIG. 2 shows a flow diagram of the mode of operation of a control unit of the stabilization device according to FIG. 1; and

Fig. 3 is a schematic sketch of part of a hydraulic stabilization device according to a modified embodiment.

In Fig. 1, a vehicle 10 is shown having a vehicle body 16, the left and right wheels 12 L and 12 R and two axles 14, onto which the wheels 12 L and 12 R are rotatably mounted. Between the steering knuckles 14 and the vehicle body 16 , spring struts 18 are arranged, each of which contains an axially extendable and compressible shock absorber 18 A. Coil springs 20 of the struts are arranged between respective spring plates 18 B, which in turn are installed on the vehicle body 16 and on the steering knuckles 14 , ie between the sprung and sprung parts of the struts 18 . Furthermore, lower wishbones 22 are arranged between the steering knuckles 14 and the vehicle body 16 , and are pivoted up and down in accordance with the upward and downward movement of the steering knuckles 14 and 15 .

The vehicle 10 is equipped with a hydraulic stabilization device 24 .

The stabilization device 24 includes a hydraulic stabilizer 26 , which is inserted between the left and right steering knuckles 14 and the vehicle body 16 , and a control unit 28 for controlling the hydraulic pressure of the stabilizer 26 and thus for controlling the roll stiffness of the vehicle 10 when cornering.

The stabilizer 26 is formed by hydraulic cylinders 30 L and 30 R, throttling points 32 L and 32 R and spring-loaded mechanical accumulators 34 L and 34 R as well as first hydraulic lines 36 A and 36 B and second hydraulic lines 38 A and 38 B.

The hydraulic cylinders 30 L and 30 R are double-acting cylinders with a double piston rod, each of which has a cylinder tube 30 a, a slidably displaceable in the cylinder tube 30 a and its interior divided into upper and lower cylinder chambers U and L pistons 30 b and have a piston rod 30 c attached to the piston 30 b, which extends axially in opposite directions from the piston. The piston rods 30 c have upper and lower end portions which protrude from the cylinder tube 30 L and 30 R, and are connected at their lower ends to one of the lower control arms 22 . The upper ends of the piston rods 30 c are formed as free ends. The cylinder tubes 30 a are articulated with their upper ends on the vehicle body 16 . The hydraulic cylinders 30 L and 30 R are thus arranged essentially in an upright position between the sprung and unsprung parts of the vehicle 10 .

The upper cylinder chamber U of the left hydraulic cylinder 30 L is connected to the lower cylinder chamber L of the right hydraulic cylinder 30 R via the first hydraulic line 26 A, while the lower cylinder chamber L of the left hydraulic cylinder 30 L is connected to the upper cylinder chamber U via the first hydraulic line 30 B of the right hydraulic cylinder 30 R is connected. The first lines 26 A and 26 B are thus arranged crosswise. The second lines 28 A and 28 B are arranged between the first lines 26 A and 26 B and the spring-loaded mechanical batteries 34 L and 34 R, so that they connect the batteries to the first lines. Thus, the second hydraulic lines 28 A and 28 B are each connected at one end to the middle section of the associated first hydraulic line 26 A or 26 B and at the other end to the associated accumulator 34 L or 34 R. The throttling points 32 L and 32 R are located in the second lines and serve to limit the flow of the hydraulic fluid through these lines.

Each of the accumulators 34 L and 34 R has a cylinder tube 34 a, a slidable piston 34 B in the cylinder tube, which delimits a cylinder chamber D, and a spring 34 c with a predetermined spring constant, which in the cylinder tube 34 A on the Cylinder chamber D opposite side of the piston 34 b is arranged and acts on the piston. The cylinder chambers D are each connected to the second hydraulic line 28 A or 28 B.

The control unit 28 contains a control cylinder 36 , third hydraulic lines 38 A and 38 B, an electric motor 40 , a control unit 42 and a lateral acceleration sensor 44 . The control cylinder 36 is a double-acting cylinder with a double piston rod and has a cylinder tube 36 a, a sliding piston 36 b in the cylinder tube 36 a, which divides the inside of the cylinder into two cylinder chambers R 1 and R 2 , and a piston rod 36 c on, which is connected to the piston 36 b and extends axially in opposite directions from the piston. The cylinder chambers R 1 and R 2 are connected by hydraulic lines 38 A and 38 B to the first hydraulic lines 26 A and 26 B, respectively. The piston rod 36 c has axially opposite ends that protrude from the cylinder tube 36 a, and one end forms a free end, while the other end is provided with a rack 36 d, which meshes with a drive pinion 40 a of the electric motor 40 .

The control unit 42 has a microcomputer and a motor driver circuit and is set up to carry out the operations illustrated in the flowchart in FIG. 2 in accordance with a signal G received from the lateral acceleration sensor 44 and to control the electric motor 40 with a drive signal i. The lateral acceleration sensor 44 generates a lateral acceleration signal in the form of a voltage signal which becomes positive or negative depending on the direction of the inertial force acting when the vehicle is cornering. A rotation angle sensor, not shown, is arranged on the electric motor 40 and generates a signal that indicates the rotation angle of the motor 40 , ie the rotation angle of the drive pinion 40 a or the drive shaft of the motor connected to it, so that monitoring and control of the motor 40 is made possible .

The control cylinder 36 , the third hydraulic lines 38 A and 38 B and the electric motor 40 together form an actuating mechanism for changing the hydraulic pressure in the stabilizer 26 . The control unit 42 and the lateral acceleration sensor 44 form a control device for controlling the actuating mechanism as a function of the driving state of the vehicle.

The mode of operation of the system described above is explained below will.

The control functions of the control unit 42 will first be explained with reference to FIG. 2.

In step (1), a signal G of the lateral acceleration sensor 44 indicating the lateral acceleration is read. In step (2) it is decided whether the amount | G | is greater than a reference value or threshold G₀. If the result in step (2) is negative, it is decided that the vehicle experiences only a relatively small lateral acceleration when cornering. In this case, a control operation is performed in step (3) by which the piston 36 b of the control cylinder 36 is held in a neutral position in which it is equidistant from the opposite ends of the cylinder tube 36 a. The position of the piston 36 is adjusted by transmitting the motor drive signal i to the electric motor 40 so that it is driven until it is reported by the angle of rotation sensor that the piston 26 b has reached the neutral position. If, on the other hand, the query result in step (2) is positive, it is decided that the vehicle is exposed to a relatively large lateral acceleration when cornering. In this case, an engine drive signal i is generated in step (4), by which the piston rod 36 b of the control cylinder 36 is adjusted in the direction in which there is an increased hydraulic pressure in the cylinder chambers U and L, which is due to the curve inclination of the vehicle are compressed. The position control of the piston 36 b again takes place on the basis of the signal supplied by the angle of rotation sensor. It is then decided in step (5) whether the control has ended. If the control is not finished, the processes described above are repeated.

The mode of operation of the stabilizing device 24 will be explained below.

When the vehicle is traveling on a straight lane, the lateral acceleration sensor 44 supplies a signal G = 0. In the control processes illustrated in FIG. 2, the piston rod 36 b of the control cylinder 36 is therefore held in the neutral position, so that the cylinder chambers R 1 and R 2 have the same volume. As a result, the hydraulic pressure in the first and second hydraulic lines 26 A and 28 A, which are connected to the one pair of the upper and lower cylinder chambers U and L, is equal to the pressure in the other two first and second hydraulic lines 26 B and 28 B, belonging to the other pair of upper and lower cylinder chambers U and L. In this driving condition there is practically no compression and rebound of the wheels 12 L and 12 R, so that there is practically no change in length of the left and right hydraulic cylinders 30 L and 30 R and consequently hardly any fluid flow through the lines 26 A, 26 B , 28 A and 28 B occurs. As a result, no appreciable damping effect is produced, and a more desirable suspension characteristic can be maintained.

If the bumps 12 L and 12 R cause a certain deflection and rebound of the bumps while driving straight ahead, the lateral acceleration sensor 44 still delivers the signal G = 0. The control cylinder 36 thus does not cause a significant change in the hydraulic pressure in the lines 26 A, 26 B, 28 A and 28 B. If, under these circumstances, the vehicle drives with both wheels 12 L and 12 R over raised bumps on the road surface, so that both Spring wheels and the pistons 30 b of the hydraulic cylinders 30 L and 30 R are pushed upwards, the upper cylinder chambers U of both hydraulic cylinders are compressed and at the same time the lower cylinder chambers L are expanded, so that a negative pressure is generated there. This causes a flow of the hydraulic fluid from the upper cylinder chambers U through the first hydraulic lines 26 A and 26 B into the lower cylinder chambers L of the cylinder on the opposite side. However, since the volume changes of the upper and lower cylinder chambers U and L are the same, since the cylinders 30 L and 30 R are those with a double piston rod, there is no significant change in the hydraulic pressure in the lines 26 A, 26 B , 28 A and 28 B. The same applies in the event that the vehicle with both wheels 12 L and 12 R drives simultaneously over road depressions, so that the wheels rebound and the lower cylinder chambers L are compressed.

Both with simultaneous deflection and with simultaneous rebound of the wheels 12 L and 12 R there is thus no significant change in the hydraulic pressure in the lines 28 A and 28 B, so that there is hardly any flow of hydraulic fluid through the throttle points 32 L and 32 R and thus no appreciable damping effect occurs. When driving the vehicle straight ahead, almost the entire damping effect is generated by the shock absorbers 18 A. In this case, the stabilization device 24 hardly contributes to the damping effect. In the case of the stabilization system according to the prior art described at the outset, on the other hand, an additional damping effect is produced by the hydraulic stabilizer when the wheels are deflected and rebounded while driving straight ahead, so that driving comfort is impaired.

When the vehicle takes a curve, for example a right-hand curve, a rolling movement symbolized by the arrow A in FIG. 1 occurs, and the left wheel 12 L, seen from behind, is pressed more downwards against the ground, while for the wheel 12 R occurs the right side has a tendency to lift the wheel. When cornering in this manner, the sensor 44 determines a lateral acceleration of the vehicle, and a signal G corresponding to this lateral acceleration is generated. The signal G is either positive or negative depending on the direction of the curve movement. The controller 42 performs the control operations illustrated in FIG. 2 and drives the electric motor 40 depending on the cornering state of the vehicle in the direction in which the roll motion is suppressed or damped (ie, clockwise in FIG. 1). The piston rod 36 c is moved a certain distance to the right in the direction "a" in FIG. 1.

As a result, the cylinder chamber R 1 of the control cylinder 36 is compressed so that hydraulic fluid flows from the cylinder chamber R 1 through the third line 38 A into the first hydraulic line 26 A. At the same time, the other cylinder chamber R 2 is expanded so that the pressure there decreases. Consequently, the pressure in the first hydraulic line 26 A and thus the pressure in the upper cylinder chamber U of the left hydraulic cylinder 30 L and the pressure in the lower cylinder chamber L of the right hydraulic cylinder 30 R. At the same time, the pressure in the cylinder chamber D of the accumulator 34 L decreases gradually to. On the other hand, hydraulic fluid flows from the cylinder chamber D of the accumulator 34 R gradually into the first and second hydraulic lines 26 B and 28 B and into the lower cylinder chamber L of the left hydraulic cylinder 30 L and into the upper cylinder chamber U of the right hydraulic cylinder 30 R. By the action of Throttling points 32 L and 32 R thus achieve an additional damping effect in addition to the damping effect of the shock absorbers 18 A, which counteracts the immersion of the vehicle body 16 on the left hydraulic cylinder 30 L and the lifting of the vehicle body 16 on the right hydraulic cylinder 30 R, so that the Rolling motion of the vehicle body is effectively damped or suppressed in response to changes in the lateral acceleration. When the vehicle exits the curve, the control cylinder 36 is returned to the neutral position.

When the vehicle 10 is turning to the left, the stabilization device 24 generates a damping device similar to that in the process described above, only the left and right sides being interchanged.

By the rotation angle of the electric motor 40 and thus the deviation of the piston 36 b of the control cylinder is controlled by its neutral position 36, can thus the hydraulic pressure in the stabilizer 26 is changed so that the roll stiffness can be varied in response to changes in the lateral acceleration.

With the help of the system described, active control of the roll stiffness can be achieved be carried out without affecting the driving comfort of the vehicle becomes.

The stabilization system is also suitable for active control of the Steering behavior by controlling the load-dependent movement in the transverse direction of the vehicle body.

If the hydraulic cylinders 30 L and 30 R are subjected to a violent impact or a strong deflection as a result of road surface elevations or potholes, these violent impacts or deflections can be effectively absorbed by the accumulators 34 L and 34 R and the throttling points 32 L and 32 R.

The stabilizing device 24 described thus achieves an effective improvement in driving safety despite its relatively simple construction.

The accumulators 34 L and 34 R do not necessarily have to be spring-loaded mechanical accumulators. Hydropneumatic accumulators 46 L and 46 R can also be provided, as shown in FIG. 3. The working fluid used in the stabilization device 24 does not necessarily have to be hydraulic fluid, but another incompressible fluid can also be used.

Finally, the control unit 28 can also be designed such that it does not respond, or not only to the lateral acceleration, but also to other factors or parameters that are representative of the driving state of the vehicle, such as the steering angle, the rotational speed of the steering wheel and the like.

Claims (10)

1. Stabilizing device for a vehicle ( 10 ) with a vehicle body ( 16 ) and two wheel suspensions ( 14 ) arranged at a distance from one another in the transverse direction of the vehicle, with a stabilizer ( 26 ), the two between the vehicle body ( 16 ) and the wheel suspensions ( 14 ) arranged cylinders ( 30 L, 30 R) each with an upper (U) and a lower cylinder chamber (L), two first fluid lines ( 26 A, 26 B), which the upper and lower cylinder chambers (L and U) of the two cylinders ( 30 L and 30 R) crosswise, as well as two pressure accumulators ( 34 L, 34 R) and two throttle devices ( 32 L, 32 R) for limiting the flow of the working fluid, characterized in that the pressure accumulators ( 34 L, 34 R) each via a second fluid line ( 28 R, 28 B), which contains one of the throttle devices ( 32 L, 32 R), with one of the first fluid lines ( 26 A, 26 B), and that the fluid pressure in the Stabilizer ( 26 ) over e an actuating device ( 36, 40 ) and a control device ( 42, 44 ) controlling it can be controlled as a function of the driving state of the vehicle. 2. Stabilizing device according to claim 1, characterized in that the adjusting device has a double-acting cylinder ( 36 ) with a double piston rod, the two cylinder chambers (R 1 , R 2 ) each via a third fluid line ( 38 A, 38 B) with one of the first fluid lines ( 26 A, 26 B) are connected, and the piston rod ( 36 c) of which can be axially adjusted by drive means ( 40 ) as a function of changes in the driving state of the vehicle. 3. Stabilizing device according to claim 2, characterized in that the drive means are formed by an electric motor ( 40 ) which is in drive connection with the piston rod ( 36 c). 4. Stabilizing device according to claim 3, characterized in that the electric motor ( 40 ) has a drive pinion ( 40 a) and that the piston rod ( 36 c) of the actuating device is provided with a rack ( 36 d) which with the drive pinion ( 40 a ) is engaged. 5. Stabilization device according to claim 3 or 4, characterized in that the control device has a lateral acceleration sensor ( 44 ) for sensing the lateral acceleration of the vehicle and for generating a corresponding signal (G) and a control device ( 42 ) receiving the signal of the lateral acceleration sensor, which a Signal (i) for controlling the electric motor ( 40 ) generated. 6. Stabilizing device according to claim 5, characterized in that the control device ( 42 ) contains an evaluation device which decides whether the lateral acceleration signal is below a predetermined threshold value and that the control device in the piston ( 36 b) of the cylinder ( 36 ) of the actuating device in maintains a neutral position in which the cylinder chambers (R 1 , R 2 ) have the same volume when the lateral acceleration is below the threshold value and moves the piston out of the neutral position when the lateral acceleration is above the threshold value. 7. Stabilizing device according to one of the preceding claims, characterized in that the cylinders ( 30 L, 30 R) of the stabilizer ( 26 ) with the upper ends of their cylinder tubes ( 30 a) are articulated on the vehicle body ( 16 ) and that the piston rods ( 30 c) this cylinder is articulated with its lower ends to the wheel suspensions ( 14 ). 8. Stabilizing device according to claim 7, characterized in that the upper ends of the piston rods ( 30 c) protrude freely from the respective cylinder. 9. Stabilizing device according to one of the preceding claims, characterized in that the suspension arms between the vehicle body ( 16 ) and the steering knuckles ( 14 ) for the wheels ( 12 L, 12 R) of the vehicle are installed and an upward and downward movement of the wheels relative allow to build the vehicle. 10. Stabilizing device according to claim 7, characterized in that the vehicle has spring struts ( 18 ) which are arranged between the steering knuckles ( 14 ) and the vehicle body ( 16 ).