JPS5981260A - Four-wheel steering gear for vehicle - Google Patents

Abstract

PURPOSE:To prevent uncontinuous change in a steering angle at junction of change positions, by enlarging a steering ratio in dependent upon increase in an engine speed. CONSTITUTION:A steering direction of front wheels 1 is inputted as an output 4a from a front wheel steering angle sensor 4 to a controller 10, and whether a phase of rear wheels 2 is to be the same phase or reverse phase relative to the front wheels 1 is determined by the controller 10 in dependent upon a change position detected by a change position sensor 12a and in accordance with a predetermined pattern. A steering ratio is sequentially increased in response to sequential shift-up operation from a second speed position, and it is increased in response to an engine speed at each engine position. Therefore, it is possible to relieve uncontinuous change in a steering angle at junction of change positions in speed change operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for steering both the front wheels and the rear wheels of a four-wheel vehicle such as an automobile, that is, a four-wheel steering system that steers the rear wheels as well as the front wheels by steering the front wheels, which are steering wheels. It is related to the device.

Conventionally, the J3 steering system for four-wheeled vehicles steers only the front wheels, and the rear wheels do not have anything to do with front wheel steering, and although they do some toe-in or toe-out depending on the driving situation, they steer the rear wheels actively. It has not become. However, recently, a four-wheel steering device has been proposed in which both the front wheels and the rear wheels are steered, and research on this type of device is being carried out (for example, in Japanese Patent Application Laid-Open No. 55-91458).

The four-wheel steering system enables convenient maneuvering that was previously impossible, as well as driving with improved steering performance, depending on the various driving conditions of the vehicle. For example, when maneuvering a vehicle at extremely low speeds such as parallel parking or parking in a garage, the direction of the vehicle is drastically changed by steering the rear wheels in the opposite direction to the front wheels (this is called anti-phase). This makes it possible or easy to park in narrow spaces, which was previously impossible or extremely difficult. Further, in a U-turn, the minimum turning radius can be made small, which is advantageous. Furthermore, by steering the rear wheels in a phase opposite to that of the front wheels, the difference between the inner wheels can be made extremely small or eliminated, which is advantageous when turning a narrow corner. In addition, when steering a vehicle at such extremely low speeds, if the rear wheels are steered in the same direction as the front wheels (
This is called in-phase), which makes it possible to move the entire vehicle in parallel, which is often convenient when parking or putting it in a garage.

On the other hand, when changing lanes while driving at medium to high speeds,
By performing four-wheel steering in the same phase, lateral force is applied to the front and rear wheels at the same time, making it possible to change lanes smoothly without phase lag. At this time, yawing does not occur, so changing lanes at high speeds can be scary. It can be done without feeling. Furthermore, when cornering, the direction of the vehicle can be effectively changed by steering the rear wheels in opposite phases.

Furthermore, when driving straight ahead, if the rear wheels are steered in a direction that counteracts the effect of external disturbances such as crosswinds, stable driving can be maintained against external disturbances, and stable high speeds can be achieved. Go straight f1 to 1! □I can also do it.

Also, during a turn, even if the steering angle of the front wheels is kept constant and acceleration/deceleration is performed at lσ, the steering angle of the rear wheels will be changed according to the acceleration/deceleration. It is also possible to make a turn.

In other words, in conventional vehicles, the steering characteristics are adjusted to have a slight tendency to understeer in order to maintain straight-line stability, and when accelerating during a turn, there is a tendency for the vehicle to deviate outward from the base. By turning the steering wheel, it is possible to correct the deviation of the steering wheel, and it is possible to realize a stable turning.

In terms of comfort, it is possible to obtain a smaller minimum turning radius with the same wheel (゛, the wheelbase can be increased, and the actual steering angle of the front wheels can also be increased). It has many advantages, such as being able to write small items, making it possible to experiment with new designs.

As described above, four-wheel steering has many practical advantages and is extremely useful.

Regarding this four-wheel steering, various specific configurations have been proposed so far to effectively steer the rear wheels. For example, four-wheel steering is performed in opposite phases at low speeds and in the same phase at high speeds (Japanese Patent Laid-Open No. 55-91457).
, the steering angle of the rear wheels is the same as that of the front wheels when the steering angle of the front wheels is small, and the phase of the large wheels is opposite (Japanese Patent Application Laid-open No. 5270). Sea urchin will steer in proportion to 1. A system is known in which the steering angle of the rear wheels is kept constant regardless of the steering angle of the front wheels within a predetermined range or more (Japanese Patent Application Laid-open No. 163969/1983).

These four-wheel steering devices often require steering to change the direction of the vehicle significantly when the vehicle speed is low or when the front wheel steering angle is large, and when the vehicle speed is high or the front wheel steering angle is small. The system always steers the rear wheels in the desired direction based on the empirical rule that a slight lateral movement is often desired.

However, a system that simply controls the turning angle of the rear wheels according to the vehicle speed or the front wheel steering angle cannot adequately respond to the various driving conditions of the vehicle that is actually running, and may be inconvenient in some cases. There are many things.

For example, in four-wheel steering, which changes the steering direction of the rear wheels depending on the vehicle speed, in other words, the control is performed in opposite phases at low speeds and in the same phase at medium and high speeds, when the rear wheels are decelerated during a turn at medium and high speeds, the rear wheels reduces the steering angle regardless of the driver's will,
In particular, when the brakes are applied to reduce the speed to a low speed range, the rear wheels change from the same phase to the opposite phase, causing a so-called "squeezing" phenomenon, which is dangerous. Therefore, at low speeds, the steering ratio (rear wheel steering angle/front wheel steering angle) is set to zero,
In other words, the rear wheels are not steered! There have also been proposals to prevent accidents such as those described in F. (For example, JP-A-56-1.67F162) However, in this case, the steering angle of the rear wheels is set to zero at low speeds regardless of the steering angle of the front wheels. Even when the vehicle turns or changes its direction significantly, the steering angle of the rear wheels becomes zero, making it no different from a conventional vehicle in which only the front wheels are steered. 1 Therefore, even if the vehicle speed changes, if the driver has no intention of changing the rear wheel steering phase or steering ratio, 11 the phase or steering ratio should not change. In order to make it easier for the driver to parallel park or park at low speeds or when reversing, the controller's control mode is set to reverse phase mode (in other words, the rear wheel steering angle is changed in the opposite direction as the front wheel steering angle increases). When the change position of the transmission of a vehicle equipped with this four-wheel steering device is in first gear or reverse, control is performed using this reverse phase mode, and when the change position is in second gear or higher, control is provided. Even if the width speed decreases to a low speed range b
If the front wheel steering angle does not change, the rear wheel steering angle should not change to prevent the phenomenon of slumping during sudden braking as described above, and also to prevent the driver from intentionally changing the change position. When the vehicle is in first gear or reverse, it is possible to perform reverse phase mode control to make it easier to park the vehicle in a garage or parallel park. When the change position is at 2nd gear or higher, the same phase mode (a mode that controls the rear wheel steering angle to increase in accordance with the increase in the front wheel steering angle) is used with a phase lag during steering during medium-high speed driving. It is conceivable to reduce this and improve the responsiveness of lane changes.

At this time, if the steering ratio is sequentially increased in accordance with the change position in 2nd gear or above, responsiveness at high speeds will be improved, direction changes at medium speeds will be made easier, and even more A vehicle with excellent maneuverability, responsiveness, etc. that meets the driver's demands can be realized.

However, the change position is discontinuous from 2nd gear to I to knob, and if the steering ratio is controlled only by this change position, the steering ratio will change discontinuously, resulting in smooth rear wheel rotation. I can't steer. That is, when the change position is sequentially shifted up from second gear to top gear while the vehicle is running, there is a problem that the transition seam becomes discontinuous.

In view of this point, the present invention provides a device that performs desirable four-wheel steering by changing the steering ratio according to changes in the change position of the aircraft. It is an object of the present invention to provide a four-wheel steering device that eliminates repeated changes in the rear wheel steering angle and enables smooth rear wheel steering.

The four-wheel steering system according to the present invention changes the -C steering according to changes in the change position of the transmission, and takes into account the engine speed at each change position, and adjusts the speed of the engine to 7 to 7 when the engine speed increases. The steering ratio is increased accordingly, thereby eliminating discontinuous changes in the steering angle at the transition between change positions. In other words, if the four-wheel steering system of the present invention has J:, when the change position of the transmission is at least second speed or higher, the second
By sequentially increasing the steering ratio as the speed changes from top speed to top speed, and increasing the steering ratio at each change position as the engine speed increases, steering at the transition between change positions is achieved. The difference in ratio can be reduced or eliminated, and discontinuous changes in the steering angle at the joint between change positions can be eliminated.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Figure 1 shows the front wheel steering angle θF in the four-wheel steering system of the present invention.
This shows an example of the rear wheel steering angle θR characteristics for
When E V ), the steering ratio is negative, that is, the phase is opposite;
Other change positions (2nd gear <2nd)
, 3rd speed (3rd) and top (TOP), the steering ratio is positive, that is, the same 8-phase, and the magnitude of the steering ratio is the smallest in 2nd and 3rd.
rd is larger than 2nd, and the king OP is the maximum. With the four-wheel steering having the characteristics of the rear wheel steering angle relative to the front wheel steering angle as in this embodiment, when the change position is low or RE V, the reverse phase steering makes it easy to perform movements with a small turning radius such as parking the vehicle. , at medium and low speeds such as 2nd and above, maneuverability is emphasized with an emphasis on bling performance at medium speeds and lane change performance at high speeds.

Figure 2 shows the front wheel steering angle (θ
This figure shows how the ratio of the rear wheel steering angle (θR) to F), that is, the steering ratio (θR/θF) changes in response to changes in engine speed at change positions of 2nd gear or higher. It is something.

When speeding up the car by changing change positions sequentially after starting, increase the engine speed from low to high at each change position and increase the vehicle speed.
Move to the next position.

At this time, the steering ratio at each change position is increased in accordance with the engine rotation, so it can be brought closer to the steering ratio at the next change position, and discontinuous changes in rear wheel steering angle at the joint between change positions can be avoided. This allows for relatively smooth rear wheel steering.

Next, with reference to FIG. 3 and FIG. M4, a specific configuration of a four-wheel steering system that implements the characteristics as in the above embodiment will be explained.

FIG. 3 shows an example using hydraulic pressure, and FIG. 4 shows an example using links.

In the configuration shown in FIG. 3, the front wheels 1, 1 and the rear wheels 2, 2 are mechanically separated, and the steering angle θH of the steering wheel 3 is
The output 4a of the front wheel steering angle sensor 4 that detects the front wheel steering angle is input to the controller 10 of the rear wheel steering device, and the rear wheels 2, 2 are steered by this input signal. As is well known, the front wheel steering device moves a rack 6 in the width direction of the vehicle (indicated by arrow A) using a pinion 5 fixed to a steering shaft 3A to which a steering wheel 3 is fixed.
The knuckle arms 8.8 of the left and right front wheels 1.1 are connected to their shafts 8 through tie rods 1 and 7 continuous to both ends of the rack 6.
a, 8a to steer the front wheels 1.1 left and right. That is, when the steering wheel 3 in the figure is rotated in the direction of the arrow, the steering shaft 3A is rotated in the direction of the arrow, the pinion 5 is also rotated in the L direction, and the rack 6 is moved in the L direction. As a result, the knuckle arms 8, 8 of the left and right front wheels 1, 1
rotates in the L direction via links 7, 7, and the front wheels 1, 1
is rotated in the L direction around the axes 8a, 8a of the knuckle arms 8, 8, and steered to the left. At this time, the steering angle sensor 4
The fact that the steering wheel 3 has rotated in the L direction by an angle θH is output as an output signal 4a, and this is input to the front wheel steering angle input 10A of the controller 10 of the rear wheel steering device.

The controller 10 is supplied with J stiff power to a power source 11, and the change lever 1 is connected to the front wheel steering angle input 10A.
Engine position input 10 [3 connected to engine position sensor 12a that detects engine position from a part of the second-class transmission and feedback input connected to rear wheel steering angle sensor 13): 110C and input 1 from the engine rotation sensor 14 that detects the engine rotation speed.
motor 21A of the hydraulic main pump 21 that controls the steering direction output 10D and the steering angle θR of the rear wheels, which is connected to the solenoid 20 that roughly controls the steering direction of the rear wheels.
The hydraulic main pump 21 is equipped with a pump 21B that discharges oil (hydraulic oil), and this pump 21B is connected to a steering direction switching valve 22. Is it connected to the hydraulic actuator 23? An orifice path 24F3 is provided between the valve 22 and the pump 21B, which short-circuits the oil outgoing path 24A and the oil outgoing path 24C, and has an orifice 24b in the middle, and an oil reservoir is provided in the middle of the oil outgoing path 24C. 25 are arranged.

The steering direction switching valve 22 has two inlets connected to an oil outgoing path 24A and an oil outgoing path 24G, and two inlets communicating therewith.
The valve part consisting of two outlets, forward 22A1 reverse 2B,
Three stop valves 22C are switchably provided in parallel, and by operating the solenoid 20, these three valve parts 2
Any one of 2A, 22B, and 22C is connected to the oil outgoing path 24A and the outgoing oil path 24C. The two outlets of this valve 22 are connected to the right oil passage 23R and left oil passage 23L of the hydraulic actuator 23, respectively, and these right oil passage 23R and left oil passage 23L are connected to the outgoing path 24A through this valve 22. 12- is connected to the long route 24G.

The hydraulic actuator 23 has right and left oil passages 23R.
Due to the pressure difference applied to 123←, the rod 26, which is the power axis, is moved in the width direction of the vehicle (indicated by arrow B), and the knuckle arms 28, 28 of the rear wheels 2.2 are moved through the tie rods 27.27. It rotates around the shafts 28a, 28a, thereby steering the rear wheels 2, 2 left and right.

'In the illustrated example &1', when the front wheels 1.1 are steered to the left and the rear wheels 2, 2 are steered in the same phase as the front wheels 1, 1, the steering direction switching valve 22 is set to the positive 22A. The oil flows from the outward path 2'4 A to the outward path 2/Ic via the orifice path 24B, and returns to the pump 21B through the reservoir 25.
In other words, the pressure on the outgoing path 24A side is too high, and the ``orifice 2''
- 4b, that is, the pressure on the far path 24C side becomes low, and the right oil passage 2 passes through the positive 22A portion of the valve 22.
The pressure in 3R becomes higher than the pressure in the left oil passage 23m, and the operating rod 26 of the hydraulic actuator 23 is driven in the L direction. The driving force at this time is determined by the current 2 input to the main pump motor 21A. As a result, the rear wheels 2, 2 are steered to the left via the tie rods 27.degree. 27, and the rear wheels 2, 2 are steered in the same phase as the front wheels 1.1.

Steer the front wheels 1 and 1 to the right, and turn the rear wheels 2 and 2 to the front wheels 1°1.
When steering in the same phase as the steering direction switching valve 22
is set to the reverse position 22B, the pressure relationship between the right oil passage 23R and the left oil passage 23L is reversed to that described above, and the actuating rod 26 is driven rightward.

In addition, when steering the rear wheels 2.2 in the opposite phase to the front wheels 1.1, the steering direction and the steering direction switching valve 22 are
The correspondence of 2A1 inverse 22B is opposite to the case of same phase as above,
In other words, when steering the front wheels 1.1 to the left, reverse 22
B, when steering the front wheels 1, 1 to the right, use the positive 22A.
Set to .

When the steering angle θR of the rear wheels 2, 2 is set to zero, the valve 22
Connect the stop 22C part of the pump 2 to the aisle passage.
The communication between the IC and the hydraulic actuator 23 is cut off, the pressure difference between the left and right oil passages 23L, 23R of the hydraulic actuator 23 is eliminated, and the actuating rod 26 is set at a neutral position. At this point, in order to ensure that the actuating rod 26 is set in the neutral position, it is recommended to put a set cart on the actuating rod 26 and mechanically force it to the middle position. desirable.

The steering direction of the front wheels 1, 1 is determined by the output 4 of the front wheel steering angle sensor 4.
a] is input to the controller 10, and the rear wheels 2,
The change position sensor 12a determines whether 2 is set in the same phase or in opposite phase for the front wheels 1 and 1.
The controller 10 determines the 'f-engine position according to a preset pattern in accordance with the detected 'f-engine position.

The controller 10 receives an input θH(
This is proportional to the steering angle θF of the front wheels 1.1), and according to the input from the change position sensor 12a, a control signal is output according to the characteristics shown in FIG. Turn the 2.

According to the four-wheel steering device using the hydraulic actuator as described above, the rear wheels can be smoothly steered without applying a special load to the steering wheel for four-wheel steering, which is advantageous in practice.

However, hydraulic systems require heavy and costly parts such as motors, pumps, hydraulic actuators, and roll valves, which increase the weight of the vehicle and reduce manufacturing costs. It is not suitable for relatively small vehicles because it complicates assembly and causes high costs. Therefore, a four-wheel steering system using a simple link mechanism may be advantageous in practice.

An example of this type of link type mechanism will be explained below with reference to FIG. In the configuration of FIG. 4, the same members as those in the configuration of FIG. 3 are denoted by the same reference numerals, and the explanation thereof will be omitted.

In the link type configuration shown in FIG. 4, a slot 6A for sliding engagement is provided in a part of the rack 6 that is moved in the width direction of the vehicle by the steering wheel 3, and the steering wheels 2, 2 are steered from this slot 6A. A link mechanism connects the rod 41 up to the sliding engagement slot 41A,
The rear wheels 2, 2 are steered in a desired direction by a desirable magnitude of the steered angle θR in accordance with the steered angle θF of the front wheels 1.1.

This link mechanism includes a first L-shaped lever 31 having one end 31A slidably engaged with a sliding engagement slot 6A on the front wheel side and pivotally supported by a fixed shaft 31a; A connecting lever 32 has one end 32A rotatably connected to the other end 31B of the connecting lever 31, one end 33A is connected to the other end 32B of this connecting lever 32, and the other end 33F1 is pivotally supported on a fixed shaft 33a. A lever 33, a control lever 34 whose one end 34A is rotatably connected to a connecting shaft between the front end 33A of the swinging lever 33 and the other end 32B of the intermediate lever 32;
slidably engages near the free end of the roll lever 34,
The sleeve 35 is a receiver that is supported with a rotating shaft 35A on the feed sleeve 36 screwed onto the screw rod 37.
The motor 38.1 that rotates this screw rod 37
The shaft support 3 provided at an intermediate position of the control lever 34
a connecting lever 39 pivotally supported by 10iii39Δ on 4A;
and a second L-shaped lever 40 whose one end 40Δ is connected to the other end 39B of this connecting lever 39, and whose other end 40B is actively engaged with the sliding engagement gear 41A on the rear wheel side. It consists of

The motor 38 is connected to a controller 50 and driven by the output of the controller 50.

This controller 50 is supplied with power from a power source 51,
The output of a change position sensor 52a that detects a change position from a part of the transmission such as the change lever 52 and the output of an engine rotation sensor 53 that detects the engine rotation speed are input. In addition, screw rod 37
A potentiometer 54 is disposed near the screw rod 37 to feed back the position of the feed sleeve 36 screwed onto the screw rod 37 to the input of the motor 38, so as to control the position of the feed sleeve 36.

According to the four-wheel steering device equipped with the link mechanism as described above, when the steering wheel 3 is rotated to the left (in the direction of the arrow), the pinion 5, the rack 6, the tie rod 7.7, the knuckle arms 8, 8, and the front wheel 1 , 1 all rotate or move in the direction of the arrow, and at the same time steer the front wheels 1.1 to the left, the first L-shaped lever 31 is rotated around the fixed shaft 31a.
The swinging lever 33 rotates in the direction and rotates through the intermediate lever 32
around the fixed shaft 33a in the L direction, and
The lever 34 is swung in the L direction around the sleeve 35, and the connecting lever 39 is moved in the L direction, which simultaneously rotates the second L-shaped lever 40 in the L direction to rotate the rear wheel 2. 2 steering rod 41 in the L direction,
As a result, the rear wheels 2, 2 are steered to the left in the same phase.

The motor 38 is driven by the controller 50, and the feed sleeve 36 in the figure is moved downward (to the left of the vehicle) 111.
When the feed sleeve 36 reaches the position of one end 39A of the connecting lever 39, the control lever 34
Even if the connecting lever 39 swings around the rotation axis 35A of 5.
does not move forward or backward (in the left-right direction in the figure), so the rear wheels 2, 2
is not steered.

When the sleeve 35 is moved roughly downward by the drive of the motor 38 and exceeds the position of the one end 39A of the connection lever 39, the -1 control lever 34 swings in the same direction as above (L direction). Move the connecting lever 39 forward (in the opposite direction)! Ru. This is because the control lever 34 swings around the pivot shaft 35A of the push sleeve 35. Therefore, in this case, the L-shaped lever 40 rotates in the direction of the arrow R, and the rear wheel , 2 moves in the direction of arrow R, the rear wheels 2, 2 are steered to the right, and four-wheel steering with opposite phases is performed.

In this way, the output of the controller 50 causes the
By driving and controlling the feed sleeve 36
The receiver moves the sleeve 35 via the lever, thereby changing the position of the pivot axis of the control lever 34, changing the direction of the moving force 19 of the respective coupling lever 39, and causing the rotation of the rear wheel 2.2. You can change the direction of the rudder. Furthermore, the receiver controls the distance of movement of the sleeve 35, and determines whether the rear wheels are in the same phase or in opposite phases. , 2 can also be changed, and therefore, the direction and degree of steering of the rear wheels 2, 2 in response to the steering of the front wheels 11, 1 can be arbitrarily changed by the output of the controller 50. It becomes possible to control the

In this way, even with the link type configuration shown in Figure 4,
It is possible to easily realize the rear wheel turning angle characteristics with respect to the front wheel turning angle as in the above-described embodiments. In particular, this link type mechanism is less heavy than the hydraulic type, has a simple structure, is easy to assemble, and can be manufactured at low cost, making it suitable for small vehicles. There is.

As explained above in detail, in the four-wheel steering system of the present invention, when the change position of the transmission is 2nd gear or higher, the shift door is opened sequentially starting from 2nd gear. The steering ratio increases gradually as the steering angle increases, and at each change position,
Since the steering ratio increases greatly depending on the rotational speed, it is possible to eliminate or alleviate the discontinuous shift in the cabin, resulting in smooth acceleration and deceleration. Practical four-wheel steering with high performance is realized.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the front wheel steering angle and the rear wheel steering angle in the four-wheel steering system of the present invention, and is a graph showing an example of a characteristic curve, and Figure 2 shows the steering ratio and engine speed at each change position. A graph showing the relationship between numbers; FIG. 3 is a schematic diagram showing an example of the four-wheel steering device of the present invention using hydraulic pressure;
The figure is a schematic diagram showing an example of the four-wheel steering device of the present invention using a link mechanism. 1...Front wheel 2...Rear wheel 3...Steering wheel 4...Steering angle sensor 5...Pinion 6...
...Ra Tsuri 1.21...Tie rod 8.
28...Knuckle arm io, so...Controller 12.52...-Change lever 12a, 52a...Change position sensor 14.
53... Engine rotation sensor 20... Solenoid 21... Main pump 22..., Rear wheel steering direction switching valve 23... Hydraulic actuator 25... Reservoir 26... Rear wheel steering rod 31 ...First L-shaped arm 32 ... Intermediate lever 33 ... Swinging lever 34 ... Control lever 34A ... Shaft support part 35 ... The receiver is sleeve 35A ... Rotating shaft 36 ...Feed sleeve 37...Screw rod 38...Drive motor 39...Connection lever 40...Second L-shaped lever 41...Rear wheel steering rod 23- Fig. 1 Fig. 2

Claims (1)

[Claims] The steering device that steers the front wheels, the rear wheel steering device that steers the rear wheels, the change position sensor that detects the change position of the transmission, and the output of the engine rotation sensor and change position sensor are received when the change position of the transmission is at least When in 2nd gear or higher, the rear wheel steering angle is increased in the same direction as the front wheel steering angle increases, and the rear wheels are steered relative to the front wheel steering angle in response to upshifts at shift positions of 2nd gear or higher. As the ratio of the angle gradually increases, the output of the engine rotation sensor is used to steer the rear wheels based on the characteristic of the rear wheel steering angle relative to the front wheel steering angle such that the above ratio at each change position increases as the engine rotation speed increases. A four-wheel steering device for a vehicle, comprising a controller that controls the device.