JP2014054962A - Vehicle suspension system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform highly accurate compliance control.SOLUTION: A vehicle suspension system includes: first and second arms 11, 12 juxtaposed in a vehicle longitudinal direction viewed from the upper side of a vehicle; a load detection bush 21 that supports the first arm 11 and detects an input load to itself; a liquid seal bush 22 that supports the second arm 12 and has a liquid chamber enabling adjustment of its rigidity; a liquid amount adjustment part 32 for adjusting an input/output amount of liquid of the liquid chamber; and a control device 40 that controls the liquid amount adjustment part 32 on the basis of the input load to the load detection bush 21 and presence/absence of steering input in a steering device 50.

Description

  The present invention relates to a vehicle suspension device disposed between a vehicle body side and a wheel side in a vehicle.

  Conventionally, as a vehicle suspension device, a rubber bush that supports an arm and has a liquid chamber (so-called liquid seal bush) is known. For example, Patent Document 1 below discloses a vehicle suspension device having this type of liquid seal bush. This vehicle suspension system determines the traveling state of the vehicle based on the steering angle, the vehicle speed, the yaw rate, and the lateral acceleration, and changes the rigidity of the liquid seal bush according to the traveling state, thereby performing compliance control according to the traveling state. Do.

Japanese Patent Laid-Open No. 10-058934

  By the way, since the conventional vehicle suspension system changes the rigidity of the liquid seal bush based on the traveling state estimated from the steering angle or the like, the load input to the liquid sealed bush that would be estimated from the traveling state is input. And the actual load input to the liquid seal bush do not always match. Therefore, in the conventional vehicle suspension system, there is a possibility that a deviation occurs between the target rigidity of the liquid seal bush according to the traveling state and the target rigidity that is actually necessary, and the accuracy of compliance control may be reduced.

  Therefore, an object of the present invention is to provide a vehicle suspension apparatus that can improve the inconveniences of the conventional example and can perform highly accurate compliance control.

  To achieve the above object, the present invention provides two arms arranged in the vehicle front-rear direction when viewed from above the vehicle, and a load detection bush that supports one of the arms and detects an input load to itself. A liquid seal bushing having a liquid chamber that supports the other of the arms and capable of adjusting its own rigidity, a liquid amount adjusting unit that adjusts the amount of liquid in and out of the liquid chamber, and the load detection And a control device for controlling the liquid amount adjusting unit based on the input load to the bush and the presence or absence of the steering input in the steering device.

  Here, the control device is configured to adjust the liquid amount adjusting unit so as to increase the rigidity of the liquid seal bush when an input load in the vehicle longitudinal direction is detected by the load detection bush and the steering input is not detected. On the other hand, when an input load in the lateral direction of the vehicle is detected by the load detection bush and the steering input is detected, the liquid amount adjustment unit is controlled to reduce the rigidity of the liquid seal bush. Is desirable.

  The vehicle suspension device according to the present invention grasps the input load to the load detection bush by the load detection bush, and the liquid seal bush according to the input load and the presence or absence of the steering input in the steering device (that is, the presence or absence of the steering operation). Since the rigidity of the head is adjusted, highly accurate compliance control can be performed. For example, when an input load in the vehicle front-rear direction is detected and a steering input is not detected, the straight travel stability can be improved by increasing the rigidity of the liquid seal bush. Further, when an input load in the lateral direction of the vehicle is detected and a steering input is detected, steering stability can be improved by reducing the rigidity of the liquid seal bush. As described above, this vehicle suspension device can achieve both straight running stability and steering stability.

FIG. 1 is a diagram illustrating the configuration of a vehicle suspension device according to the present invention. FIG. 2 is a diagram showing characteristics of the liquid seal bush. FIG. 3 is a flowchart for explaining the control operation of the vehicle suspension system according to the present invention. FIG. 4 is a diagram illustrating the operation of the vehicle suspension device when the straight traveling stability is improved. FIG. 5 is a diagram illustrating the operation of the vehicle suspension device when the steering stability is improved.

  Embodiments of a vehicle suspension apparatus according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments.

[Example]
An embodiment of a vehicle suspension system according to the present invention will be described with reference to FIGS.

  Reference numeral 1 in FIG. 1 indicates the vehicle suspension device of the present embodiment. FIG. 1 is a view of the vehicle suspension device 1 as viewed from above the vehicle. Although FIG. 1 shows only the vehicle suspension device 1 on the right side of the vehicle, the vehicle left side has the same configuration as the vehicle suspension device 1 described below. However, in this example, the control device 40 described later is shared by the left and right vehicle suspension devices 1 and 1. Moreover, this vehicle suspension apparatus 1 may be arrange | positioned at the vehicle front side, and may be arrange | positioned at the vehicle rear side. In FIG. 1, a vehicle suspension device 1 for the rear wheel on the right side of the vehicle is shown.

  The vehicle suspension device 1 has two arms arranged in the vehicle front-rear direction as viewed from above the vehicle. Here, the arm disposed on the front side of the vehicle is referred to as a first arm 11, and the arm disposed on the rear side of the vehicle is referred to as a second arm 12. The first and second arms 11 and 12 have one end connected to the wheel W side and the other end connected to the vehicle body side via a suspension bush. The illustrated first and second arms 11 and 12 are integrated at one end thereof and connected to the wheel W side, but are individually connected to the wheel W side. Also good.

  Here, in order to improve the straight running stability with the vehicle suspension device 1, it is only necessary to suppress a change in steering (change in toe angle) due to road surface input, so that the front and rear force compliance steer is reduced in each suspension bush. It may be configured to be highly rigid. On the other hand, in order to improve the steering stability in the vehicle suspension device 1, it is generally sufficient that the suspension characteristics exhibit an understeer tendency, so that one suspension bush is increased so that the lateral force compliance understeer increases. It is necessary to make it rigid and to lower the rigidity of the other suspension bush. That is, the improvement in straight running stability and the improvement in steering stability are in a trade-off relationship with each other.

  Therefore, one of the suspension bushes on the vehicle body side of the first and second arms 11 and 12 has a high rigidity capable of improving the straight running stability, and the other is improved in the straight running stability and the steering stability. It is configured such that the rigidity can be adjusted so as to achieve both improvement.

  In this vehicle suspension device 1, the load detection bush 21 is used as a high-rigidity material capable of improving the straight running stability, and the liquid seal bushing 22 is used as a device capable of adjusting the rigidity. In this example, a load detection bush 21 is provided as a suspension bush that supports the other end of the first arm 11, while a liquid seal bush 22 is provided as a suspension bush that supports the other end of the second arm 12.

  The load detection bush 21 has not only a function as a suspension bush in the rubber part, but also a function for detecting an input load to itself (in other words, an input load to the first and second arms 11 and 12). Have. The load detection bush 21 is configured so that the deflection of the rubber portion due to an input load corresponding to a road surface input or the like can be output as an electrical signal. For example, the load detecting bush 21 of this example is configured such that the rubber portion is made of a variable resistance rubber (conductive rubber mixed with a conductive material), so that the deflection of the rubber portion due to an input load is output as an electric resistance. be able to. The electric resistance value of the rubber part is measured by the electric resistance measuring device 31 and transmitted to the control device (ECU) 40. For example, in this load detection bush 21, the load input directions (at least the vehicle front-rear direction and the vehicle lateral direction) to the rubber portion can be detected by outputting electric resistance values at a plurality of locations in the rubber portion. When the load calculation unit of the control device 40 receives an electrical resistance value from the electrical resistance measuring device 31, the load calculation unit calculates an input load to the rubber unit and an input direction of the input load based on the change in the electrical resistance value. .

  By the way, the load detection bush 21 may have a load detection unit such as a piezoelectric element that converts the deflection of the rubber part into an electric signal. A plurality of load detectors are arranged so that the load input direction (at least the vehicle longitudinal direction and the vehicle lateral direction) to the rubber portion can be detected. In this case, when an electric signal is received from the load detection unit, the load calculation unit of the control device 40 calculates an input load to the rubber unit and an input direction of the input load based on the electric signal.

  As described above, the load detecting bush 21 determines the hardness of the rubber portion so as to have a high rigidity capable of improving the straight running stability. The rigidity of the load detection bush 21 may be determined based on the results of experiments and simulations.

  The liquid seal bush 22 has a rubber part and a liquid chamber, and changes the rigidity by adjusting the amount of liquid in and out of the liquid chamber. By changing the rigidity of the liquid seal bushing 22, the amount of bending of the rubber portion (hereinafter referred to as “bushing amount of bending”) changes, whereby the amount of displacement of the second arm 12 is changed. For example, the liquid sealing bush 22 has a reduced rigidity when the steering stability is improved as compared with the rigidity when the straight running stability is improved. Therefore, as shown in FIG. 2, the liquid seal bush 22 improves the handling stability as compared with the case where it is necessary to improve the straight running stability even when the input load is the same (when the straight running stability is important). The bush deflection increases when necessary (when steering stability is important). The liquid seal bushing 22 gradually increases the amount of bending of the bush with a predetermined proportional coefficient as the input load increases.

  Here, the liquid seal bushing 22 of this example uses the rigidity under a predetermined condition as the reference rigidity. The predetermined condition is, for example, when the vehicle travels straight when the load detection bush 21 does not detect input loads in the vehicle longitudinal direction and vehicle lateral direction (that is, when straight travel stability and steering stability are ensured). That is. In this case, the liquid seal bush 22 increases the rigidity from the reference rigidity when it is necessary to improve the straight running stability, and decreases the rigidity from the reference rigidity when it is necessary to improve the steering stability. The amount of increase or decrease in the rigidity (that is, the rigidity that improves the straight running stability or the rigidity that improves the steering stability) may be determined based on the results of experiments and simulations.

  The vehicle suspension device 1 is provided with a liquid amount adjustment unit 32 that adjusts the amount of liquid in and out of the liquid chamber in the liquid seal bush 22. The liquid amount adjusting unit 32 increases the rigidity of the liquid sealing bush 22 by increasing the amount of liquid flowing into the liquid chamber, and decreases the rigidity of the liquid sealing bush 22 by increasing the amount of liquid flowing out of the liquid chamber. As the liquid amount adjusting unit 32, for example, a liquid pressure adjusting valve or the like may be used. The operation of the liquid amount adjusting unit 32 is controlled by the compliance control unit of the control device 40.

  The compliance control unit emphasizes the improvement of straight-line stability over steering stability (when straight-line stability is important), and the compliance control unit places importance on improvement of steering stability over straight-line stability (steering stability) And compliance control at the time of emphasis). When the straight-running stability is important, the load detection bush 21 detects the input load in the vehicle front-rear direction and is during straight-running travel. On the other hand, when steering stability is important, the load detection bush 21 detects a vehicle lateral input load during turning. Therefore, the compliance control unit controls the liquid amount adjustment unit 32 based on the input load to the load detection bush 21 and the presence / absence of the steering operation (presence / absence of the steering input in the steering device 50), and the straight running stability or the steering stability. To improve.

  The compliance control for improving the straight running stability or the steering stability will be described with reference to the flowchart of FIG. The compliance control may be performed simultaneously on all the front and rear wheels W having the vehicle suspension device 1 of the present embodiment. The front wheel W or the rear wheel W having the vehicle suspension device 1 may be used. It may be implemented in one of the above.

  For example, the control device 40 determines whether or not an input load is detected by the load detection bush 21 at a predetermined calculation cycle during traveling. The calculation cycle is, for example, the calculation cycle of the control device 40 or the detection cycle of the input load in the load detection bush 21 (measurement cycle of the electrical resistance measuring device 31). This determination is made, for example, depending on whether or not the load calculation unit has performed an input load calculation in the current calculation cycle or in the previous calculation cycle. In this case, if the calculation is performed, it is determined that the input load is detected. If the calculation is not performed, it is determined that the input load is not detected. When the input load is not detected, the control device 40 holds the liquid seal bush 22 with the current reference rigidity.

  When the input load is detected (step ST1), the compliance control unit of the control device 40 determines whether the load input direction of the input load is the vehicle front-rear direction or the vehicle lateral direction (step ST2).

  When the compliance control unit detects an input load in the vehicle front-rear direction, it determines whether there is no steering input (step ST3). This determination is made based on the detection result of the steering angle detection unit in the steering device 50, for example. The steering angle detector is a steering angle sensor or the like that detects the steering angle of the steering wheel, and outputs a positive or negative electrical signal (steering angle to either the left or right) if a steering operation is performed. In step ST3, if a positive or negative electrical signal is received from the steering angle detection unit, it is determined that there is a steering input, and if such an electrical signal is not received, it is determined that there is no steering input.

  When the compliance control unit determines that there is no steering input, the compliance control unit instructs the liquid amount adjustment unit 32 to increase the amount of liquid flowing into the liquid chamber, and raises the rigidity of the liquid seal bush 22 above the current reference rigidity ( Step ST4). Thereby, in this vehicle suspension apparatus 1, since the rigidity of each of the load detection bush 21 and the liquid seal bush 22 is high, the amount of displacement of the second arm 12 supported by the liquid seal bush 22 is higher than that at the reference rigidity. (Fig. 4). Therefore, the vehicle suspension device 1 can improve the straight running stability because the longitudinal force compliance steer is reduced and the roll steer is also reduced. In addition, when the rigidity of the liquid seal bush 22 is lower than the reference rigidity, the vehicle suspension device 1 increases the rigidity of the liquid seal bush 22 at least in this step ST4 from the low rigidity when the steering stability is important, The straight running stability can be improved.

  On the other hand, when it is determined that the steering input is present, the compliance control unit holds the liquid seal bush 22 with the current reference rigidity (step ST5).

  On the other hand, the compliance control unit determines whether or not there is a steering input when detecting an input load in the vehicle lateral direction (step ST6).

  When the compliance control unit determines that the steering input is present, the compliance control unit instructs the liquid amount adjustment unit 32 to increase the amount of liquid flowing into the liquid chamber, and lowers the rigidity of the liquid seal bush 22 below the current reference rigidity ( Step ST7). Thereby, in this vehicle suspension apparatus 1, the rigidity of the liquid seal bush 22 is lower than the rigidity of the load detection bush 21, so the displacement amount of the second arm 12 supported by the liquid seal bush 22 is the reference. It becomes larger than when it is rigid (FIG. 5). Therefore, the vehicle suspension device 1 can improve the steering stability during turning because the lateral force compliance understeer increases and the roll understeer also increases. FIG. 5 shows the time of left turn traveling. In addition, when the rigidity of the liquid seal bush 22 is higher than the reference rigidity, the vehicle suspension device 1 lowers the rigidity of the liquid seal bush 22 at least in this step ST7 from the high rigidity when the straight running stability is emphasized. Steering stability can be improved.

  On the other hand, when it is determined that there is no steering input, the compliance control unit proceeds to step ST5 and holds the liquid seal bush 22 with the current reference rigidity.

  As described above, the vehicle suspension device 1 is liquid-sealed if the improvement in straight running stability is more important than the steering stability based on the input load to the load detection bush 21 and the presence or absence of a steering operation. If the rigidity of the bush 22 is increased above the reference rigidity, and the improvement of the steering stability is more important than the straight running stability, the rigidity of the liquid seal bush 22 is decreased below the reference rigidity. Therefore, the vehicle suspension device 1 can improve the straight running stability when the straight running stability is important, and can improve the steering stability when the steering stability is important. This is a contradiction and makes it possible to achieve both straight running stability and steering stability, which were difficult to achieve.

DESCRIPTION OF SYMBOLS 1 Vehicle suspension apparatus 11 1st arm 12 2nd arm 21 Load detection bush 22 Liquid seal bush 31 Electrical resistance measuring device 32 Fluid quantity adjustment part 40 Control apparatus 50 Steering apparatus W Wheel

Claims (2)

Two arms lined up in the vehicle longitudinal direction as seen from above the vehicle,
A load detection bush that supports one of the arms and detects an input load to itself;
A liquid seal bushing having a liquid chamber supporting the other of the arms and capable of adjusting its own rigidity;
A liquid amount adjusting unit for adjusting the amount of liquid flowing in and out of the liquid chamber;
A control device that controls the liquid amount adjusting unit based on an input load to the load detection bush and the presence or absence of a steering input in the steering device;
A vehicle suspension device comprising:   The control device controls the liquid amount adjusting unit to increase the rigidity of the liquid seal bush when an input load in the vehicle front-rear direction is detected by the load detection bush and the steering input is not detected. On the other hand, when an input load in a vehicle lateral direction is detected by the load detection bush and the steering input is detected, the liquid amount adjusting unit is controlled to reduce the rigidity of the liquid seal bush. The vehicle suspension apparatus according to claim 1.

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