JPH01106777A - Steering angle ratio control mechanism - Google Patents

Abstract

PURPOSE:To keep the safety of operation by providing a detecting means for a hydraulic defect of a hydraulic rear wheel steering mechanism and a means for setting a steering angle ratio to naught on a signal sent from the detecting means. CONSTITUTION:When hydraulic pressure detected to a hydraulic sensor 37 to detect a hydraulic defect of a hydraulic rear wheel steering mechanism 21 becomes lower than fixed value, a steering angle ratio is kept at its present value. When a front wheel steering angle detected by a steering angle sensor 32 becomes lower than fixed value, a step motor 44 of a steering angle ratio control mechanism 14 is driven to set the steering angle ratio to naught. Namely, a sliding pin 59 to connect an output link 51 to a control lever 57 is locked at a position where the pin 59 lies on a supporting shaft 53 of the control lever 57 or the steering angle ratio is naught. The rear wheel steering mechanism is thereby returned to a neutral position to change a four wheel steering state into a two wheel steering state formed by a front wheel steering mechanism. Thus the safety of operation can be kept.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a steering angle ratio 1tdlll1 mechanism for a four-wheel steering vehicle.

[Prior Art] For example, as disclosed in Japanese Unexamined Patent Publication No. 108065/1981, a four-wheel steering system in which the steering angle ratio (the ratio of the steering angle of the rear wheels to the steering angle of the first wheel) is controlled according to the vehicle speed. In a vehicle, when oil pressure fails in the hydraulic rear wheel steering mechanism, the steering angle ratio is maintained at the state immediately before the failure, so if oil pressure failure occurs while driving on an oil road at medium or high speed, the vehicle Straight driving is impaired, and turning ability is impaired at low speeds.

[Problems to be Solved by the Invention] In view of the above-mentioned problems, an object of the present invention is to provide a steering angle ratio II, I that ensures steering stability and small turning ability at low speeds even in the event of oil pressure failure.
The purpose is to provide an I till l structure.

[Means for Solving the Problem] In order to achieve the above object, the present invention includes means for detecting oil pressure failure of a hydraulic rear wheel steering mechanism, and a steering angle ratio determined by a signal from the detection means. and means for setting the value to 0.

[Function] When the rear wheel steering mechanism 21 fails in oil pressure, the output signal of the electronic control unit @28 that is detected by the oil pressure sensor 37 stops the operation of the steering angle ratio controller W414, and the current steering angle ratio is adjusted. maintain. The front wheel steering angle value detected by the steering angle sensor 32 is determined by the steering angle ratio control mechanism 1.
When the load of 4 enters a certain range where it is small, the steering angle ratio sensor 35
The steering angle ratio 11J W III mechanism 14 is operated so that the detected value becomes O. Thereby, four-wheel steering is switched to two-wheel steering without overload acting on the steering angle ratio control mechanism 14, and safe operation of the vehicle is maintained.

[Embodiments of the Invention] FIG. 1 is a plan view showing a schematic configuration of a four-wheel steered vehicle equipped with a steering angle ratio control mechanism according to the present invention. The four-wheel steering vehicle transmits the longitudinal movement of the input rod 13 linked to the front wheel steering [8] to the steering angle ratio control mechanism 14, and operates the rear wheel steering III mechanism 21 by the longitudinal movement of the output rod 15. . For example, when the handle 5 of the steering shaft 7 is turned to the right while driving at low speed, the drop arm 6 rotates together with the output shaft 9 of the front wheel steering mechanism 8, the drag link 12 moves forward, and the knuckle arm 3 moves forward. It rotates clockwise about the support shaft 3a, and the front wheel 2 is deflected to the right. The knuckle arms 3 of the left and right front wheels 2 are interlocked and connected by a tie rod 4.

At the same time, the input rod 13 connected to the middle portion of the drop arm 6 by the pin 1O moves forward, the amount of operation is reduced by the steering angle ratio i control mechanism 14, and the output rod 15 moves forward. The rod 19 of the rear wheel steering mechanism 21 moves forward, the rod 23 moves backward, the knuckle arm 25 rotates counterclockwise around the support shaft 25a, and the rear wheel 24 moves to the left (towards the front wheel). (opposite phase).

The hydraulic front wheel steering mechanism 8 is the rear wheel steering mechanism 21 in the illustrated example.
Although the model is different, the pressure oil from the hydraulic pump 30 is sent to one oil chamber of the actuator T-ri via a servo title valve, and the other oil chamber is returned to the oil tank 31 via a servo control valve. .

The rear wheel steering gear 1121 is integrally equipped with a servo control valve 16 and a seven-wheel drive unit 41. The actuator 41 has a piston 18 fitted into a cylinder 17, and oil chambers are formed at both ends. The servo control valve 16 has one valve element formed in a rod 19 connected to the piston 18, and the other valve element formed in a portion connected to the output rod 15.

Pressure oil supplied from a hydraulic pump 43 driven by an engine or a battery to the servo control valve 16 enters one of the oil chambers of the actuator 41, and oil in the other oil chamber passes through the servo control valve 16 and returns to the oil tank 42. It will be done. In this way, the force acting on the piston 18 of the actuator 41 in response to the movement of the output rod 15 causes the rod 19 to follow the output rod 15 in the same direction. A rod 19 is connected to one end of a lever 22 rotatably supported on the vehicle body side by a support shaft 20,
The other end is connected to a knuckle arm 25 via a rod 23. The knuckle arms 25 of the left and right rear wheels 24 are interlocked and connected by tie rods 26.

A steering angle ratio controller 41414 that connects the input rod 13 and the output rod 15 is driven by a step motor 44,
It is configured to obtain a state with a steering angle ratio O and a state with an arbitrary steering angle ratio in the same phase or in an opposite phase.

The steering angle ratio controller 1114 includes a motor clutch actuator 38 that disconnects a step motor 44 and an output link, which will be described later, a lever clutch actuator 39 that disconnects a control lever from an input lever, and a control lever and a sliding pin. and an actuator 40 that locks the steering angle ratio to the zero position. These hydraulic (or electromagnetic)
The actuator is controlled by an electronic control unit 28.

The steering status by the electronic control unit 28 is displayed on a lamp of an indicator 29.

The electronic control device 2B includes, for example, a steering angle sensor 32 disposed facing the drop arm 9 of the front wheel steering mechanism 8, and an engine rotation speed sensor 33 disposed, for example, on the crankshaft of the engine.
For example, a vehicle speed sensor 34 disposed on the output shaft of a gear transmission
For example, piping that connects the steering angle ratio sensor 35 disposed on the shaft of the step motor 44, the voltage sensor 36 disposed on the power supply battery 27 of the electronic control@@2B, the hydraulic pump 43, and the servo control valve 16. The above-mentioned actuators are controlled based on the signals from the oil pressure sensor 37 disposed in the hydraulic pressure sensor 37 as input.

As shown in FIG. 2, the steering angle ratio ill all mechanism 14
are input levers 4711m levers 57 stacked on top of each other.
is rotatably supported on the vehicle body side by a support shaft 53, and the rear end of the input link 45 is connected to the input lever 47 by a pin 46. The front end of the input link 45 is connected to the input lot 13 by a pin 55. A sliding pin 59 that is slidably engaged along an arcuate @57a provided in the longitudinal direction of the w111 lever 57 is coupled to the fan-shaped output link 51. The end of the output link 51 is connected to the output lot 15 by a pin 52. A gear 54 connected to the shaft of the step motor 44 is meshed with a partial gear 58 provided on the peripheral edge of the output link 51 . The step sweater 44 is guided by a longitudinal guide groove 56 provided on the vehicle body side, and is slid so as to be released from the engagement between the partial teeth 1158 and the teeth 4154 by the actuator 39 (not shown orally in FIG. 2).

The groove 578 is formed so as to be able to pass above the support shaft 53,
When the sliding pin 59 is aligned coaxially with the support shaft 53, the input rod 13 causes the λ cover 4f and the IIdJtll lever 57
Even when the output lot 15 is rotated, the output link 51 does not transmit the force that moves the output lot 15 back and forth. Input lever 47 and l11
The tla lever 57 is releasably coupled to the clutch pin 50. Therefore, the support shaft 53 is attached to the tip of the control lever 57.
An arcuate groove 49 centered at is provided, and a notch 49a (FIG. 3) is provided in the middle of this groove. On the other hand, l1lt
The ll lever 57 is provided with an elongated length 48 in the longitudinal direction. The actuator 39 (second
When the lower end of the clutch pin 50, which is moved by a method (not shown in the figure), engages the notch 49a of the input lever 47, the input lever 47 and 1. An integral connection with the Ill lever 57 is achieved. However, when the clutch pin 50 moves from the notch 49a to the groove 49, the rotation of the input lever 47 is not transmitted to the control lever 57.

By controlling the operating amount of the step motor 44 that drives the sliding pin 59 of the steering angle north side tlEltlli 14 in relation to the vehicle speed, the sliding pin 59 moves to the left side of the support shaft 53 along the groove 57a at high speeds, While the input rod 13 moves forward, the output rod 15 moves tangentially, and the rear wheel 24 is deflected to the right (in the same phase as the front wheel). In other words, as shown in Figure 6, the steering angle ratio changes depending on the vehicle speed! l1ll
lllll be.

The electronic control unit t28 consisting of a microcomputer is
When a failure in the hydraulic system of the rear wheel steering mechanism 21 is detected by the oil pressure sensor 37, the steering angle ratio υI@ by the steering angle ratio control unit M414 is stopped, and the current steering angle ratio is maintained. Thereafter, the front wheel (or rear wheel) steering angle sensor 32 detects the steering angle, and when the value falls within a certain range where the load is small, the steering angle ratio is set to zero. As a result, the steering angle ratio is 11 riJ11
To safely and smoothly switch from four-wheel steering to two-wheel steering while preventing overload from acting on the mechanism 14.

A mechanism is configured in which a sliding pin 59 is engaged with the support shaft 53 to cancel rear wheel steering. In other words, 15% of the support shaft 53
In addition to engaging the sliding pin 59 with the actuator 4
When the support shaft 53 is rotated by 0, the sliding pin 59 is locked, and the rotational movement of the control lever 57 is no longer transmitted to the output rod 15 via the output link 51.

As shown in FIG. 4, the support shaft 53 is supported rotatably but immovably in the axial direction with respect to a base frame 65, input lever 47, and control lever 57 that are fixed to the vehicle body. Therefore, a large diameter portion is formed at the upper end of the support shaft 53, and a nut 60 is screwed into the small diameter portion at the lower end. A split groove 53a provided at the upper end of the support shaft 53 can communicate with an arcuate groove 57a of the control lever 57. A lever 63 is coupled to the lower end of the support shaft 53,
One end is connected to the actuator 40, while the other end has a rotation range regulated by a stopper 64 that projects downward from the base frame 65.

As shown in FIG.
2 and a rod 6 protruding from the piston 69 fitted thereto.
It consists of 7. A rod 67 is connected to an elongated hole of a lever 63 by a pin 66, and a cylinder 62 is supported by a pin 70 on the vehicle body side. The stopper 64 includes end walls 64a and 64b that project into the rotation path of the lever 63.

The rod 67 is projected by the force of the spring 68, and the lever 63
In the normal state in which the support shaft 53 abuts against the end wall 64b, the split groove 53a of the support shaft 53 comes off from the bulge 57a of the control lever 57.

Electronically controlled Xl device according to the invention m! 28 moves as follows when oil pressure fails. When the oil pressure p of the rear wheel steering mechanism 21 detected by the oil pressure sensor 37 becomes smaller than a predetermined value ps,
Maintain the current steering angle ratio k. When the front wheel steering angle θ detected by the steering angle sensor 32 becomes smaller than a predetermined value θS, the step motor 44 of the steering angle ratio control mechanism 14 is driven to set the steering angle ratio k to zero. That is, the sliding pin 59 connecting the output link 51 and the control lever 57 is locked at a position overlapping the support shaft 53 of the control lever 57. As a result, the steering angle ratio is maintained at 0, and abnormal operation of the rear wheel 2I4 due to oil pressure failure is avoided.

If the front wheel steering angle θ becomes larger than the predetermined value θS again while the step motor 44 is in operation, the step motor 44 is immediately stopped.

FIG. 7 is a flowchart of the above-mentioned control program.

In the figure, p11 to p30 represent each step of the program. This program starts with pll and p1
At step 2, the oil pressure p of the rear wheel steering mechanism 21 is detected by the oil pressure sensor 37. At p13, it is determined whether the oil pressure p is smaller than a predetermined value of 11 ps. If the oil pressure p is larger than the predetermined 1aps, turn off the motor stop plug at p14,
Step motor 44 is stopped. Vehicle speed sensor 3 with p15
4 to detect the vehicle speed ■. At p16, the steering angle ratio k corresponding to the vehicle speed V is determined from the control map. At p17, the steering angle ratio k is set to the target steering angle ratio k.

The step motor 4 is adjusted so that the target steering angle ratio kt is reached in p18.
4 and return to p12.

If the oil pressure p is smaller than the predetermined 1aps in p13, p
At step 19, the front wheel steering angle θ is detected by the steering angle sensor 32. p
At step 20, it is determined whether the absolute value of the front wheel steering angle θ is smaller than a predetermined value θS. If the absolute value of the front wheel steering angle θ is larger than the predetermined value θS, the actual steering angle ratio ks is detected by the steering angle ratio sensor 35 at p21. At p22, the actual steering angle ratio ks is set to the target steering angle ratio k[, and the process proceeds to p26.

If the absolute value of the front wheel steering angle θ is smaller than the predetermined value θS at p20, the target steering angle ratio k[ is set to O at p23.

At p24, the step motor 44 is driven so that the target steering angle ratio kt becomes O. At p25, the actual steering angle ratio ks is detected by the steering angle ratio sensor 35. At p26, it is determined whether the target steering angle ratio kt is equal to the actual steering angle ratio ks. If the target steering angle ratio kt is not equal to the actual steering angle ratio ks, the process returns to D12. If the target steering angle ratio k[ is equal to the actual steering angle ratio ks, the step motor 44 is stopped at p27, and it is determined whether the actual steering angle ratio ks is O or not at p2B. If the large steering angle ratio ks is not 0, p12
If the actual steering angle ratio ks is O, the rear wheel steering mechanism 21 is returned to the neutral position at 029, and the rear wheels 24 are set to the straight-ahead position. At this time, the 7-cut unit 40 moves and the drive pin 5
9 is locked in a position coaxial with the support shaft 53.

[Effects of the Invention] As described above, the present invention includes means for detecting oil pressure failure in the hydraulic rear wheel steering mechanism, and means for setting the steering angle ratio to 0 based on a signal from the detection means. Therefore, when the rear wheel steering mechanism fails in oil pressure, the step motor is driven by the output signal of the electronic control device based on the detected value of the oil pressure sensor.
1i111Il The sliding pin that connects the output link to the lever overlaps the control lever spindle! (Position where steering angle ratio is 0)
is locked. Therefore, the rear wheel steering mechanism is returned to the neutral position (straight traveling state) by a known return spring, and the four-wheel steering state is switched to the two-wheel steering state by the front wheel steering mechanism.
Operational safety is maintained.

The steering angle ratio control mechanism determines the load from the front wheel (or rear wheel) steering angle and is operated to the position of the steering angle ratio O when the load is smaller, so the operation is easy. In the event of oil pressure failure while traveling on an oil road, four-wheel steering is temporarily maintained, ensuring tight turning performance.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing a schematic configuration of a four-wheel steering vehicle equipped with a rudder angle suppression tan-side according to the present invention, Fig. 2 is a plan view of the rudder angle north side control structure, and Fig. 3 is a plan view of the same rudder angle control mechanism. A plan view of the input lever of the corner north control 11 mechanism, FIG. 4 is a front cross-sectional view of the mechanism that locks the sliding pin to the support shaft, FIG.
The figure is a characteristic diagram of the steering angle north side "afJ mechanism, and Figure 7 is a flowchart of the control program of the electronic control device that controls the steering angle ratio LSI m mechanism. 8: Front wheel steering mechanism 14: Steering angle ratio Control mechanism 21: Rear wheel steering mechanism 30: Hydraulic pump 32: Steering angle sensor 35
: Steering angle ratio sensor 37: Oil pressure sensor 44 Step motor 47: Input lever 51: Output link 53: Support shaft 57: Control lever 59: Sliding pin patent applicant Isuza Jidosha Co., Ltd.

Claims (3)

[Claims] (1) A steering wheel for a four-wheel steering vehicle characterized by having means for detecting a hydraulic failure in a hydraulic rear wheel steering mechanism, and means for setting a steering angle ratio to 0 based on a signal from the detecting means. Angular ratio control mechanism. (2) The scope of claim (1) in which the sliding pin that connects the output link of the steering angle ratio control mechanism and the control lever is moved onto the support shaft of the control lever when the hydraulic pressure of the rear wheel steering mechanism fails. ).The steering angle ratio control mechanism described in ). (3) The steering angle ratio control mechanism according to claim (2), comprising means for locking the sliding pin to the support shaft.