JP5050988B2 - Vehicle control device - Google Patents

Description

  The present invention relates to a vehicle control apparatus, and particularly to a vehicle that pulls a towed vehicle.

  As shown in FIG. 4, when a lane change is performed while the tractor 51 (towed vehicle) is traveling by pulling a trailer 52 (towed vehicle), the trailer 52 is swung left and right. A phenomenon called a snakeing phenomenon occurs in which vibration is difficult to attenuate. The vibration in the snake phenomenon becomes more severe as the vehicle speed increases. Further, in the snaked state, as can be seen from the change in the steering angle in FIG. 5A and the change in the yaw rate in FIG. 5B, the vehicle body is shaken and the steering is swung. FIGS. 5 (a) and 5 (b) are actual measurements with the steering in a free state after an impulse-like steering input at a vehicle speed of 100 km / h.

JP 2006-185376 A

  The above-mentioned snakeing phenomenon can be suppressed by steering the rear wheels with the rear wheel steering device provided on the towing vehicle, but there are limitations on the stroke amount of the rear wheel steering device, possible thrust, actuator responsiveness, tire characteristics, etc. Therefore, the amount that can be suppressed is physically determined. In particular, if the driver relies on suppression of the snakeing phenomenon by the rear wheel steering device and increases the vehicle speed, the limit amount that can be suppressed by the rear wheel steering device may be exceeded, or the response control will be delayed. In such a case, the vibration mode of the snakeing phenomenon may occur suddenly.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle control device that suppresses falling into a vibration mode of a snake phenomenon.

A vehicle control apparatus according to a first invention for solving the above-described problems is
Steering assist means for assisting the steering force of the steering wheel for steering the front wheels of the vehicle;
Rear wheel steering means for steering the rear wheels of the vehicle;
Traction detection means for detecting that the vehicle is towing a towed vehicle;
Vehicle speed measuring means for measuring the vehicle speed of the vehicle;
Control means for controlling the steering assist means and the rear wheel steering means based on information from the traction detection means and the vehicle speed measurement means,
The control means includes
When the traction detection means detects that the vehicle is towing the towed vehicle, the steering assist means suppresses the movement of the steering system,
When the vehicle speed measured by the vehicle speed measuring means is greater than a predetermined vehicle speed set in advance, the steering assist means further suppresses the movement of the steering system and reduces the steering amount by the rear wheel steering means. And

A vehicle control apparatus according to a second invention for solving the above-described problems is
In the vehicle control apparatus according to the first invention,
When the steering assist means is hydraulic power steering, the control means suppresses the movement of the steering system by adjusting the amount of oil supplied to and discharged from the hydraulic cylinder of the hydraulic power steering,
When the steering assist means is electric power steering, the control means suppresses the movement of the steering system by performing damping control in the electric power steering.

A vehicle control apparatus according to a third invention for solving the above-described problems is
In the vehicle control apparatus according to the first or second invention,
When the vehicle has four-wheel drive means that can change the distribution of driving force to the front and rear wheels,
The control means includes
When the vehicle speed measured by the vehicle speed measuring means is greater than the predetermined vehicle speed, the four-wheel driving means increases the distribution of driving force to the front wheels.

  According to the present invention, when there is a towed vehicle, and further, when the vehicle speed is high, by suppressing the movement of the steering system by the steering assist means, the driver can foresee that the vehicle is approaching the limit, Even if the snakeing phenomenon occurs, the vibration can be attenuated to prevent the vibration mode.

  Further, according to the present invention, when the vehicle has four-wheel drive means capable of changing the distribution of the driving force to the front wheels and the rear wheels, the limit of the rear wheels is improved by the movement of the driving force toward the front wheels. And safety can be improved.

  Hereinafter, a vehicle control apparatus according to the present invention will be described in detail with reference to the drawings.

  First, a vehicle control apparatus according to this embodiment will be described with reference to a schematic configuration diagram shown in FIG.

  The tractor 1 (vehicle) is capable of towing a trailer (towed vehicle) using a hitch ball (towing tool). The tractor 1 is provided with a handle 11 for steering the front wheel 14 of the tractor 1, and this handle 11 is connected to a power steering 13 (steering assisting means) via a steering shaft 11a. Therefore, the steering force applied to the handle 11 is assisted by the power steering 13 and transmitted to the front wheels 14.

  In the tractor 1, the steering shaft 11 a is provided with a steering angle sensor 12 that detects the steering angle of the handle 11. The front wheel 14 is provided with a wheel speed sensor 15 (vehicle speed measuring means) for detecting a wheel speed proportional to the vehicle speed. A yaw rate sensor 20 that detects the yaw rate of the tractor 1 is provided at the center of the tractor 1. In the hitch ball, the trailer is connected to the brake harness, and the trailer towing is detected based on the presence or absence (towing detection means). The power steering 13 is controlled by an ECU (Electronics Control Unit; control means) (not shown) based on the detection values obtained by the steering angle sensor 12, the wheel speed sensor 15, the yaw rate sensor 20, the traction detection means, and the like. . As the traction detection means, for example, the traction of the trailer may be detected by the ECU based on the weight gradient before and after the shift up in the transmission of the tractor 1, the resistance deviation, and the like.

  In the tractor 1, the front wheel 14 and the rear wheel 18 are connected via a propeller shaft 16 and an electric control coupling 17 to form a so-called 4WD (4 Wheels Drive). There is also provided an actuator 19 (rear wheel steering means) that performs the above steering, and has a so-called 4WS (4 Wheels Steering) configuration. These are also controlled by the ECU.

  The configuration of the tractor 1 shown in FIG. 1 shows an example of the present invention, but the configuration of 4WD is not necessarily required.

  In the vehicle control apparatus according to the present embodiment, hydraulic power steering, electric power steering (hereinafter referred to as EPS), or the like can be applied as power steering. First, hydraulic power steering used in the vehicle control apparatus according to the present embodiment will be described with reference to FIG. 1 and the schematic diagram of FIG.

<Hydraulic power steering>
The hydraulic power steering 13 is provided in the tractor 1 that can pull the trailer. The hydraulic power steering 13 includes a reserve tank 25 that stores oil recovered via a pipe T, an oil pump 26 that pressurizes and supplies oil stored in the reserve tank 25 via a pipe P, and a handle. 11, a rotary valve 27 (control valve) for supplying and discharging oil supplied from the oil pump 26 to and from the power cylinder 23 in accordance with the direction and magnitude of the steering force applied to the cylinder 11, and cylinder chambers 23b on both sides of the piston 23a. , 23c, and a double-acting power cylinder 23. Further, the flow rate of oil passing through at least one of the pipes L, R connecting the power cylinder 23 and the rotary valve 27 is controlled. A flow rate variable valve 24 (flow rate control means) is provided. In addition, as the flow variable valve 24, for example, a solenoid valve including a solenoid, a spring, a movable iron core, or the like is applicable.

  The rotary valve 27 is a rotary control valve that utilizes the rotation of the steering shaft 11 a that transmits the operation of the handle 11. Specifically, the rotary valve 27 is divided into an input shaft (not shown) connected to the steering shaft 11a side and an output shaft 29 connected to the rack shaft 21 side, and is coaxially connected via a torsion bar 28. This is a structure in which an input shaft (inner valve) 27b integrally formed with the other connecting end is fitted inside a cylindrical outer valve 27a engaged with one connecting end so as to be relatively rotatable.

  Further, the output shaft 29 is provided with a pinion gear 22, arranged so as to intersect with the rack shaft 21 connected to the piston 23 a, and configured so that the pinion gear 22 and the rack gear 21 a of the rack shaft 21 mesh with each other. Has been. Therefore, when the handle 11 is steered, the steering force is transmitted to the output shaft 29 and the pinion gear 22 via the torsion bar 28, and the rack shaft 21 is moved in the axial direction as the pinion gear 22 rotates. At the same time, the steering force is assisted by the power cylinder 23, and the front wheel 14 is steered via the tie rod 30 provided at the end of the rack shaft 21.

  In the rotary valve 27, a plurality of axially extending grooves are provided in the circumferential direction on the inner peripheral side of the outer valve 27a and the outer peripheral side of the inner valve 27b, and the plurality of grooves of the outer valve 27a are provided in the circumferential direction. The cylinder chamber 23b or the cylinder chamber 23c is alternately communicated, and the plurality of grooves of the inner valve 27b are alternately communicated with the pipe P or the pipe T in the circumferential direction. That is, in the outer valve 27a, grooves (hereinafter referred to as LH grooves) communicating with the cylinder chamber 23b and grooves (hereinafter referred to as RH grooves) communicating with the cylinder chamber 23c are alternately arranged in the circumferential direction. In the inner valve 27b, grooves communicating with the pipe P (hereinafter referred to as supply grooves) and grooves communicating with the pipe T (hereinafter referred to as recovery grooves) are alternately arranged in the circumferential direction.

  Then, in the rotary valve 27, when a steering force is applied to the steering shaft 11a, it communicates with any one groove of the outer valve 27a from the groove of the adjacent inner valve 27b in accordance with the direction of the steering force. One groove to be selected is selected, oil is supplied to one of the cylinder chamber 23b and the cylinder chamber 23c, and the oil is recovered from either one. When a steering force is applied to the steering shaft 11a, a relative angular displacement is generated between the outer valve 27a and the inner valve 27b as the torsion bar 28 is twisted, and communication is performed according to the relative angular displacement. In the throttle portion between the groove of the outer valve 27a and the groove of the inner valve 27b, the throttle area is changed, and the flow rate of the passing oil is controlled.

  For example, in a neutral state in which no steering force is applied to the handle 11 and the torsion bar 28 is not twisted, the grooves of the adjacent inner valve 27b are simultaneously formed with respect to any one groove of the outer valve 27a. Communicate. For this reason, the oil supplied to the rotary valve 27 is supplied to the supply groove of the inner valve 27b and then flows into the recovery groove of the inner valve 27b through the groove of the outer valve 27a communicating with the oil. It passes through and is collected in the reserve tank 25. As a result, no pressure difference is generated between the cylinder chamber 23b and the cylinder chamber 23c communicating with each groove of the outer valve 27a, and the power cylinder 23 does not generate any force.

  On the other hand, when a steering force is applied to the handle 11, a relative angular displacement occurs between the outer valve 27a and the inner valve 27b as the torsion bar 28 is twisted, so that any one groove of the outer valve 27a is displaced. Thus, one groove communicating from the grooves of the adjacent inner valve 27b is selected, and the throttle area of the throttle portion between the groove of the outer valve 27a communicating with the groove of the inner valve 27b changes.

  For example, in FIG. 2, the supply groove of the inner valve 27b is selected for the LH groove of the outer valve 27a, and the recovery groove of the inner valve 27b is selected for the RH groove of the outer valve 27a. At this time, the oil supplied to the rotary valve 27 is supplied to the supply groove of the inner valve 27b, and then introduced to the LH groove of the outer valve 27a through the throttle portion on the side where the throttle area has been increased. It passes through the variable flow valve 24 and is supplied to the cylinder chamber 23b. On the other hand, the recovery groove of the inner valve 27b that communicates with the pipe T communicates with the RH groove of the outer valve 27a that communicates with the pipe R, so that the oil in the cylinder chamber 23c flows into the RH groove of the pipe R and the outer valve 27a. The recovery groove 25 of the inner valve 27b and the pipe T are sequentially passed back to the reserve tank 25. As a result, a pressure difference is generated between the cylinder chamber 23b and the cylinder chamber 23c, and this pressure difference is applied to the rack shaft 21 connected to the piston 23a to assist the steering force.

  In this embodiment, the flow rate variable valve 24 is provided in at least one of the pipes L, R connecting the power cylinder 23 and the rotary valve 27 (pipe L in FIG. 2). When it is detected that the trailer is being pulled and the vehicle speed is high, a control signal is applied from the ECU to the flow variable valve 24, and the valve opening degree of the flow variable valve 24 is electrically controlled to control the flow variable valve 24. The flow rate of the oil passing through is adjusted. Thus, the damping is increased by the hydraulic power steering 13, the movement of the power cylinder 23 (steering system) is suppressed, and the operating resistance of the rack shaft 21 is increased. On the other hand, when the ECU does not detect the traction of the trailer, the flow rate variable valve 24 is not operated, or the valve opening degree is made larger than when the tractor is being pulled to allow the oil to pass therethrough.

  As described above, in the hydraulic power steering 13, when the flow rate variable valve 24 is provided in at least one of the pipes L, R between the power cylinder 23 and the rotary valve 27 and the trailer is pulled, the vehicle speed is high. Since the flow rate of the oil passing through the flow rate variable valve 24 is adjusted, damping is increased by the hydraulic power steering 13 and the movement of the power cylinder 23 (steering system) is suppressed when the trailer is towed. For this reason, it becomes difficult for the driver to steer suddenly, so that it does not fall into the snake phenomenon, and even if the snake phenomenon occurs beyond the control limit by the rear wheel steering device, the vibration is attenuated, The change in the behavior can be made as gentle as possible. As a result, the driving stability can be improved and the sense of security of steering can be improved. On the other hand, when the trailer is not towed, the flow rate of the oil passing through the flow rate variable valve 24 is not restricted. Therefore, when the trailer is not towed, the stability can be improved without giving a sense of incongruity to steering.

  Next, EPS used in the vehicle control apparatus according to the present embodiment will be described.

<Electric power steering (EPS)>
In the vehicle control apparatus according to the present embodiment, EPS may be used instead of the hydraulic power steering. This EPS uses an electric force generation source including a DC motor, an electromagnetic clutch, a worm shaft, a worm wheel shaft, and the like, instead of a hydraulic pressure generation source such as a power cylinder in hydraulic power steering, to obtain a steering force applied to a handle. It is to assist.

  Since EPS does not have oil damping characteristics such as hydraulic power steering, it is equipped with a damping control function that adds damping characteristics by reducing an appropriate amount when applying a force to assist steering force. Yes. That is, in a vehicle equipped with EPS, the movement of the steering system can be suppressed by changing the generated force from the electric power generation source in consideration of the damping characteristics. Therefore, as with hydraulic power steering, when the trailer is towed and the vehicle speed is high, the control amount of damping is increased by EPS to suppress the movement of the steering system and increase the operating resistance of the rack shaft 21. What should I do? As a result, the amount by which the handle 11 is swung is reduced, and the driver's sense of security is improved. For example, when the trailer is being pulled and the vehicle speed is high, the ECU may be switched to a map that increases the amount of damping control.

  Here, the vehicle control apparatus according to the present embodiment will be described with reference to FIGS. 1 and 2 and the flowchart shown in FIG.

  First, it is determined whether or not the trailer is pulled by the tractor 1 (step S1). If there is no traction, the process proceeds to step S2, and the traveling stability of the tractor 1 is improved by normal rear wheel steering. If there is traction, the process proceeds to step S3, and the steering system is operated by hydraulic power steering or EPS. Is controlled to suppress the movement of the steering system (steps S2, S3).

  Next, the vehicle speed of the tractor 1 is determined (step S4). When the vehicle speed is low, the process proceeds to step S5, where the driving stability of the tractor 1 is improved by normal rear wheel steering. When the vehicle speed is high, the process proceeds to step S6, and the steering system is operated by hydraulic power steering or EPS. Is further controlled to further suppress the steering system movement (steps S5 and S6). This makes it difficult for the driver to steer suddenly, so that it does not fall into the snake phenomenon, and even if the snake phenomenon occurs, the vibration is attenuated and the behavior change is made as gentle as possible. Can do.

  If the tractor 1 is 4WD and the distribution of the driving force can be changed between the front and rear wheels, the distribution of the driving force is changed so as to increase the load of the driving force on the front wheels (step S7). This increases the straight traveling performance of the vehicle (understeer direction), reduces the load on the rear wheels, and further improves running stability. In addition, the tire lateral force limit on the rear wheel side is also improved.

  When the vehicle speed increases, the overshoot due to the rear wheel steering amount controlled by the rear wheel steering device increases. To prevent this, the rear wheel steering amount is reduced (step S8). Even if the rear wheel steering amount is reduced, in step S6, the damping of the steering system is further increased by hydraulic power steering or EPS, and the movement of the steering system is further suppressed, so that the snakeing phenomenon can be sufficiently suppressed. This also means that there is a margin in the rear wheel steering amount.

  The control by the rear wheel steering device has a great effect on improving the running stability when towing the trailer. However, there is a limit to the control, and naturally, if the limit is exceeded, the effect cannot be expected. Therefore, in the vehicle control device according to the present invention, when there is a towed vehicle, and further when the vehicle speed is high, the damping of the steering system is increased by hydraulic power steering or EPS to suppress the movement of the steering system. Thus, the driver can foresee that the vehicle is approaching the limit, and even if the snakeing phenomenon occurs, the vibration can be attenuated and the vibration mode can be suppressed. Further, when the vehicle is 4WD and the distribution of the driving force can be changed between the front and rear wheels, the limit of the rear wheel is improved and the safety is improved by the movement of the driving force toward the front wheels. be able to.

  The vehicle control device according to the present invention is suitable for towing a towed vehicle such as a trailer.

It is a schematic block diagram which shows an example of the control apparatus of the vehicle which concerns on this invention. It is a schematic diagram which shows an example of the hydraulic power steering used with the control apparatus of the vehicle which concerns on this invention. It is a flowchart explaining the control apparatus of the vehicle which concerns on this invention. It is a figure explaining a snakeing phenomenon. (A) is a graph of the actual measurement value of the steering angle in the snaked state, and (b) is a graph of the actual value of the yaw rate in the snaked state.

Explanation of symbols

11 Handle 13 Power steering 14 Front wheel 15 Wheel speed sensor 18 Rear wheel 19 Actuator

Claims (3)

Steering assist means for assisting the steering force of the steering wheel for steering the front wheels of the vehicle;
Rear wheel steering means for steering the rear wheels of the vehicle;
Traction detection means for detecting that the vehicle is towing a towed vehicle;
Vehicle speed measuring means for measuring the vehicle speed of the vehicle;
Control means for controlling the steering assist means and the rear wheel steering means based on information from the traction detection means and the vehicle speed measurement means,
The control means includes
When the traction detection means detects that the vehicle is towing the towed vehicle, the steering assist means suppresses the movement of the steering system,
When the vehicle speed measured by the vehicle speed measuring means is greater than a predetermined vehicle speed set in advance, the steering assist means further suppresses the movement of the steering system and reduces the steering amount by the rear wheel steering means. A vehicle control device. The vehicle control device according to claim 1,
When the steering assist means is hydraulic power steering, the control means suppresses the movement of the steering system by adjusting the amount of oil supplied to and discharged from the hydraulic cylinder of the hydraulic power steering,
When the steering assist means is electric power steering, the control means suppresses the movement of the steering system by performing damping control in the electric power steering. In the vehicle control device according to claim 1 or 2,
When the vehicle has four-wheel drive means that can change the distribution of driving force to the front and rear wheels,
The control means includes
When the vehicle speed measured by the vehicle speed measuring means is greater than the predetermined vehicle speed, the four-wheel drive means increases the distribution of the driving force to the front wheels.

Images