JPS61108065A - Four-wheel steering device for car - Google Patents

Abstract

PURPOSE:To prevent the overload of a motor lock and a control means by making a rear wheel steering control means inoperative when a fluid pump that is the driving source of a fluid actuator that assists the rear wheel steering is set to the inoperative state. CONSTITUTION:A rear wheel steering mechanism 8 is provided with a stepping motor 14 that varies the steering state of rear wheels 7. The stepping motor 14 is controlled by a controller 31. The car speed and the front wheel steering angle or lateral acceleration G and the rear wheel angle coming from a characteristic switching means 32, the output coming from the characteristic switching means and such are output to the controller 31 to vary the rear wheel steering state according to the car speed, front wheel steering angle and such and always the optimum rear wheel steering state. In addition, when a fluid pump 23 is set to the inoperative state, the stepping motor 14 is provided with a set means 34 that prevents the motor 14 from being operated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a four-wheel steering system for a vehicle that steers the rear wheels in response to the steering of the front wheels. For more details,
The present invention relates to a four-wheel steering device in which a rear wheel steering mechanism is configured to steer rear wheels with assistance from an assist force of a fluid actuator such as a power steering device.

(Prior art) Conventionally, four-wheeled vehicles were typically steered by using a steering wheel to steer only the front wheels. However, steering only the front wheels may cause the rear wheels to skid depending on the driving conditions, or the turning radius may be affected. Problems have been pointed out in terms of maneuverability and steering, such as the limited ability to make small turns, and in light of this, a four-wheel steering system that steers the rear wheels as well as the front wheels has recently been proposed and researched. .

As one such four-wheel steering device,
There is one disclosed in Japanese Patent No. 8052. The four-wheel steering device disclosed in the publication is a four-wheel steering system for a vehicle that includes a steering device that steers front wheels, a rear wheel steering mechanism that steers rear wheels, and a controller that controls the rear wheel steering mechanism. The rear wheel steering mechanism includes a steering gear mechanism connected to a rear wheel tie rod, a power cylinder that provides a steering assist force to the rear wheel tie rod, and a power cylinder that applies steering assist force to the rear wheel tie rod. A control valve that controls the supply of pressure oil to the cylinder and a motor that drives the several inputs 111 of the steering gear A71 are used together, and the comma roller has at least a front wheel steering angle signal 9. The input signal is input and the motor is configured to be driven and controlled to steer the rear wheels in accordance with the front wheel steering angle.

However, in this way, one rear wheel steering mechanism is provided with a control means (in the above conventional example, a motor that drives the input shaft of the rear wheel steering mechanism) that changes the steering state of the rear wheels, and the control means is used to control the rear wheel steering mechanism. In a four-wheel steering system configured to steer the rear wheels with the assistance of the assist force of a fluid actuator (the steering assist force of a power cylinder in the above conventional example) when changing the steering state of the wheels, If you try to change the steering condition of the rear wheels, for example, the steering angle, by operating the control means such as the motor when the actuator is not operating, the steering assist force by the fluid actuator will not be increased by 1q, so the control As a result, the control means is overloaded and, in the case of a DC motor or a stepping motor, in which the control means is normally used, the rear wheel cannot be controlled due to motor lock (in the case of a DC motor). ) or erroneous VJ (in the case of a stepping motor) due to step-out.

(Object of the invention).

In view of the above circumstances, it is an object of the present invention to solve the above-mentioned problems such as motor lock and step-out caused by the control means operating when the fluid actuator is inoperative and attempting to change the steering state of the rear wheels. It is an object of the present invention to provide a four-wheel steering system that can prevent inconveniences caused by overloading control means such as the above.

(Structure of the Invention) In order to achieve the above object, the four-wheel steering device for a vehicle according to the present invention provides an operation detection means for detecting the operation of a fluid pump that is a driving source for a fluid actuator that assists rear wheel steering. and maintains the control means for changing the steering state of the rear wheels only when the fluid pump is in the operating state based on the output of the operation detecting means, and the fluid pump is in the inactive state. The present invention is characterized in that the control means is configured to prohibit operation of the control means at certain times.

<Examples> Hereinafter, the present invention will be described in detail with reference to examples shown in the drawings.

FIG. 1 is a schematic plan view showing one embodiment of the present invention. In this embodiment, there is no mechanical connection between the front wheel steering device and the rear wheel steering mechanism, and therefore the rear wheel steering mechanism is directly driven by a control means consisting of a motor. The steering device 2 that steers the right front wheel 1.1 has a steering wheel 3 and the rotational speed of this wheel 3! It consists of a rack and pinion mechanism 4 that converts l1JJ into linear reciprocating motion, left and right tie rods 5, 5, and knuckle arms 6°6 that transmit the operation of this mechanism 4 to the front wheels 1, 1 and steer them. There is.

On the other hand, the rear wheel steering mechanism 8 that steers the left and right rear wheels 7, 7,
A rear wheel operating rod 9 is held on the vehicle body so as to be slidable in the left and right direction, and a tie rod IO is installed at both left and right ends of this rod 9, respectively.
Left and right knuckle arms 11 connected via io,
11, and the rear wheels 7.7 are steered by the axial movement of the operating rod 9.

A rack 12 is formed on the operating rod 9, and a pinion 13 meshing with the rack 12 is driven by a stepping motor 14 to a pair of bevel gears 15, 16 and a pinion shaft 17.
, the rear wheels 7, 7 are steered in accordance with the amount of one rotation of the stepping motor 14 in the rotational direction.

Further, the rear wheel operating rod 9 passes through the power cylinder 18, and the left and right hydraulic chambers 18a,
A piston 19 partitioning into a piston 18b is fixed to the operating rod 9, and the hydraulic chambers 18a and 18b have hydraulic passages 21a and 2tb led from a control valve 20 installed around the pinion shaft 17, respectively. connected to the control valve 20 and the pump 2.
A hydraulic supply passage 24 and a return passage 25 are provided between the
is provided. Here, the control valve 20 operates according to the rotational force applied to the pinion shaft 11 when the stepping motor 14 rotates, and controls the hydraulic pressure supplied from the pump 23 through the hydraulic pressure supply passage 24 by the shuttle. Depending on the direction of the rotational force, it is introduced into either one of the hydraulic chambers 18a or +8b of the power cylinder 18, and the other h gas pressure is
The hydraulic oil in b or +8a is returned to the pump 23 via the return passage 25. Therefore, when the operating rod 9 is moved in the axial direction by the stepping motor 14 via the bevel gear 15, 16, the pinion shaft 17, the pinion 13, and the rack 12, the hydraulic pressure introduced into the power cylinder 18 is applied to the piston 19. The movement of the operating rod 9 is assisted through the .

That is, in the above embodiment, a stepping motor (control means) 14 is installed in the rear wheel steering mechanism 8 to vary the steering state of the rear wheels 7, and when steering the rear wheels, a stepping motor (control means) 14 is installed. A power cylinder (fluid acter Lff) operates by receiving oil (fluid) supplied from a pump (fluid pump) 23.
-T) It is configured to be assisted by the assist force of 1B.

The stepping motor 14 is driven by a controller 31 via a stepping motor drive circuit 30.

In order to always achieve the optimum rear wheel steering condition by changing the rear wheel steering condition according to the vehicle speed, heavy wheel steering angle, etc., the controller 31 has a characteristic switching means 32 that changes the rear wheel steering condition according to the vehicle speed, the front wheel steering angle, or the lateral direction. Acceleration G.

It is configured so that the rear wheel steering angle, the output from the characteristic changeover switch, etc. are input.

The present invention further includes an operation detecting means 33 for detecting the operation of the fluid pump 230, and a control means 14 that receives an output from the means 33 to maintain the control means 14 in an operable state only when the fluid pump 23 is in an operating state. Hit means 34 are provided which prevent the control means 14 from being activated when 23 is inactive.

In the illustrated embodiment, since a hydraulic pump that generates oil pressure using engine rotation is used as the fluid pump 23, the fluid pump operation detection means 33 detects the engine rotation based on the ignition pulse '33a. The above-mentioned cut means 34 is composed of a bidirectional buffer placed on a line connecting the controller 31 and the stepping motor drive circuit 30, and the engine rotation When the number of revolutions is below a predetermined number of revolutions, the control means 14 is prevented from operating due to no or sufficient assist force of the fluid pump,
The fluid pump is determined to be in an operating state only when the rotational speed is above a predetermined number of revolutions -E, and the control means 14 is maintained in an operable state by a bidirectional buffer.

In short, the fluid pump operation detection means 33 may be of any type as long as it can detect whether or not the fluid pump is in a state where the necessary assist force is generated and the fluid pump is in a state of 1q. In the case where IE and fh are performed by the pump drive motor, the pump operation can be detected based on the pump discharge pressure. Further, the hit means 34 may also be of any type other than those in the embodiments, as long as it can receive the output of the pump operation detection means 33 and maintain the control means 14 in an operable state only when the pump is in operation. You may do so.

Next, the operation of the controller 31 in the above embodiment will be explained with reference to the main routine shown in FIG. First, start with step S1, then step S2
Initialize the system in step S3, and set the vehicle speed (
V) and the front wheel steering angle (θF) are read, and step S4
It is determined whether the vehicle speed is zero or not, and in your case, in step S5, the rear wheel actuator (stepping motor 14, which is a control means) is initially hit, and in step S6
Set the target position PT to PT←0 and set the rear wheel actuator position PM to PM←0. Here, PM means the actual position of the stepping motor, and in this embodiment, the position when the initial cell is pressed at vehicle speed V-0 is 0 (PM←0), and the other positive controllers are at this O position. It is expressed as the number of steps driven from. In addition, PT is the control target position l of the stepping motor that is the control target of the controller 31, and similarly, the target position when an initial hit is made when the vehicle speed V=O is 0 (PT'-0 ), and the target position of that arrow is expressed by the number of steps from this O position. From step S6, the process returns to step S3. If the vehicle speed V≠0 in step S4, the process proceeds to step S7, where the data table at data M (ADR) is set from the vehicle speed ■ and the front wheel steering angle θF, and the system register is reset in step S9. Return to step S3.

In this main routine, the stepping motor 1
In order to match the actual position PM of No. 4 to the target position PT set in step S8 described above, an interrupt process is performed by a motor drive section interrupt subroutine not shown in FIG. This interrupt processing is performed every j-1 seconds (f = nisterrabine (PPS) motor drive frequency). That is, when the interrupt process is started in the motor drive unit in step 310, it is determined in step 811 whether or not the target position PT of the stepping motor and the actual position PM match, and if Pr=PM. If there is, there is no need to drive the stepping motor, so step 816
The next interrupt generation timer is defined in step 3.
At step 17, the process returns to the main routine described above. If it is PT-f-PM, the engine rotation speed (N) is read in step 812, and N is larger than the set value (the predetermined rotation speed that is the criterion for determining whether the fluid pump mentioned in # is in an operating state). If N>set value, the fluid pump 23 is in operation, so in step S14 a drive signal is output in the direction of PT=PM to drive and control the stepping motor, and in step 815 the above-mentioned The stepping motor is rotated one step by the drive No. 4a (before or after the step), passes through the aforementioned step 31G, and returns to the main routine at step 517.If J3 is determined in the aforementioned step 313 and N≦the set value, the fluid is Since the pump 23 is inactive, the stepping motor is not controlled, and the process immediately proceeds to step 816, and then returns to the main routine in step 817.

The above-mentioned FIG. 4 J3 and FIG.
A flowchart in the case where 4 is a DC motor is shown in FIG. To explain this diagram, first, step 81
8 and initialize the system in step 819.
In step S20, the vehicle speed (V) and front wheel steering angle (
θF) is read, and in step S21 the target position (control target position of the DC motor) PT is calculated from the vehicle speed V and the front wheel steering angle θF. In step 322, the rear wheel steering angle sensor (included in the characteristic switching means 32) is Read the motor position (actual position f?Z>PM of the DC motor) from the motor position (actual position of the DC motor f? Since there is no one, the process returns to step S20.

If they do not match, the engine speed (N>) is read in step 824, and in step 825, similarly to step 313 described above, it is determined whether N is greater than the set value, and if N>the set value. PT-P in the next step 826
The DC motor is drive-controlled so that M is achieved, and when N≦set value, the motor drive control is not performed and step 8 is performed.
Return to 20.

Next, the front wheel steering device and the rear wheel steering mechanism are mechanically connected, and the steering ratio (
An embodiment in which the present invention is applied to a four-wheel steering system including a control means for changing the ratio of the rear wheel steering angle to the front wheel steering angle in accordance with at least the vehicle speed will be described.

FIG. 2 is a conceptual plan view showing the embodiment, and FIG. 3 is an enlarged plan view of the variable steering ratio mechanism portion in FIG. 2.

In FIG. 2, the same reference numerals as those in FIG. 1 are used to designate the same reference numerals, and the explanation thereof will be omitted, and only the parts that are different from the embodiment of FIG. 1 will be explained below.

Front wheel steering equipment fW2 rack and pinion machine ll1
A binion Abffi is engaged with the rack 4a of the iS4, which transmits the amount of movement of the rack 4a to the rear wheel steering mechanism 8. This pinion 4b is connected to a bevel gear 41 via a connecting rod 40, and the bevel gear 41 is connected to a rotation shaft 42a (third
(see figure) and meshes with a bevel gear 42 fixed in one direction. The rotating shaft 42a has a cylindrical portion 42b fitted into a swinging shaft 43a integrally fixed to the rocker 43 so as to be movable in the axial direction.
It has a radially protruding part and is rotatably supported by a bearing 42c.

The rear wheel drive rod 44 is 1m long! IIJ child 43's hole 4
3b, and one end 44a is connected to the control valve 20.
The drive rod 20a is pivotally supported by a ball joint, and the other end 441) is connected to the swing arm 4 for controlling the steering ratio.
Similarly, it is pivotally supported at the tip 45a of 5 by a free joint such as a ball joint. The drive rod 20a of the control valve 20 is movable in the axial direction, and the swing arm 45 is swingably supported by the support arm 47 integrally with the swing @46.

This support arm 47 is integrally fixed to a shaft 47a, and is rotatable together with this @47a. This shaft 47
a is a worm 48 rotated by the stepping motor 14;
The worm wheel 49 is rotated by the stepping motor 14 to change the steering ratio. A steering ratio sensor 50 is disposed on the worm wheel 49 to detect the rotation angle of the shaft 47a, that is, the support arm 47, and input a steering ratio signal to the controller 31.

In the configurations shown in FIGS. 2 and 3 above, the controller 31
When the stepping motor 14 is driven via the drive circuit 30 and the worm 48 is rotated, the worm wheel 49 is rotated, the shaft 47a is rotated, the support arm 47 is rotated, and the rotation axis of the swing shaft 46 is rotated. The swing locus (1♂ trend) of the swing arm 45 is changed by being tilted. on the other hand,
When the front wheels 1, 1 are steered and the front wheel rack 4a moves in the left-right direction, the binion 4b rotates, and the bevel gear 41 rotates via the connecting rod 40.

This causes the other bevel gear 42 to rotate and the rotation shaft 42 to rotate.
The affi rocker rib 43 is rocked. Then, one end 44a of the rear wheel drive rod 44 passing through this pivots. At this time, the other end 44b is
5, the one end 44a moves while being restrained by the swinging surface of the control valve 20.
Move 0a in the axial direction.

As a result, either the hydraulic chamber 18a or the +
Oil pressure is introduced to 8b, and the rear wheels are steered by the oil pressure.

At this time, the amount of steering is determined by the inclination of the swing shaft 46, the rotation angle of the worm wheel 49, and the amount of steering of the front wheels. The steering ratio will be determined.

d3, a drive circuit 30 for the control means (in this embodiment, a stepping motor that changes the steering ratio) that changes the rear wheel steering state; Control [1-ra 31. Characteristic switching means 32. Fluid pump operation detection means 33. The hit means 34 is similar to the embodiment of FIG. Further, in the figure, the steering ratio sensor 50 is shown separately from the characteristic switching means 32, and its output is inputted to the controller 31, but this is because the control means 14 of this embodiment changes the steering ratio. This steering ratio sensor 50 is included in the characteristic switching means 32.

In the case of this embodiment as well, except when the swing arm 45 is in the horizontal plane, when the stepping motor 14 is driven to rotate the support arm 47 around @47a in order to change the steering ratio, the rear wheel The position of one end 44a of the drive rod changes, resulting in a state in which the rear wheels are steered. Therefore, if the stepping motor 14 is driven when the fluid actuator 18 is not operating, the motor 14 will be overloaded.
It is something that can be done.

The flow of the control 31 in this embodiment is almost the same as in FIGS. 4 and 5 described above, however, in this embodiment, the front wheel steering angle is controlled by the rear wheel steering mechanism via a mechanical connecting rod 40. Since there is no need to refer to the front wheel steering angle θF when setting the target position Pr of the stepping motor 14 that changes the steering ratio, step S3 in FIG. )READ
j, and step S7 simply becomes [data table address meter ADR=f(V)J].

Furthermore, in this embodiment, a DC motor is used instead of a stepping motor as described above, and the flow in the case of a DC motor is almost the same as the flow shown in FIG. 6 described above. Yes, the difference is based on the same reason as above, step S20 is [vehicle speed (V) REΔD],
Step 321 simply becomes [Pv=f(V) Meiki].

In addition, as in this embodiment, the four-wheel steering system is a type in which the front wheel steering device 2 and the rear wheel steering mechanism 8 are connected by six separate connecting rods 40! In the AM, if a fluid actuator is provided to assist front wheel steering, part of its steering assist force also assists rear wheel steering via the connecting rod 40. Therefore, in the case of this type of four-wheel steering device, the fluid actuator for assisting rear wheel steering according to the present invention may be a front wheel steering fluid actuator in addition to the rear wheel steering fluid actuator.

(Effects of the Invention) As described above, the four-wheel steering device according to the present invention includes an operation detection means for detecting the operation of a fluid pump that is a drive source of a fluid actuator that assists rear wheel steering. A control means for changing the steering state of the rear wheels based on the output is maintained in an operable state only when the fluid pump is in an operating state, and the control means is not operated when the fluid pump is in an inactive state. This structure prevents inconveniences caused by the control means operating when the fluid actuator is inactive and attempting to change the steering state of the rear wheels, such as motor lock or tax adjustment. This has the effect of being able to prevent inconveniences caused by the application of a load.

[Brief explanation of the drawing]

Fig. 1 is a conceptual plan view and top view showing an embodiment of the 4A arrangement according to the present invention, Fig. 4 is a flowchart showing the main routine of the controller in Fig. 1, and Fig. 5 is a motor drive unit interrupt processing subroutine. FIG. 6 is a flowchart showing the main routine of the controller when the control means of the embodiment shown in FIG. 1 is a DC motor. 1...Front wheel 7...Rear wheel 8...
・Rear wheel steering mechanism 14...Control means 18...Rear wheel actuator 23...Fluid pump 33...Fluid pump operation check (means 34...Hit means □A Fig. 6

Claims (1)

[Claims] 4 of a vehicle configured to steer rear wheels in accordance with steering of front wheels.
The wheel steering device is configured such that a rear wheel steering mechanism that steers the rear wheels is assisted by an assist force of a fluid actuator that operates in response to fluid supplied from a fluid pump to steer the rear wheels. and the rear wheel steering concave groove is provided with a control means for varying the steering state of the rear wheels, further comprising an operation detection means for detecting the operation of the fluid pump, and an output of the operation detection means. and a hit means for maintaining the control means in an operable state only when the fluid pump is in an operating state.
Wheel steering device.