JPH04260870A - Rear wheel steering device four-wheel steering vehicle - Google Patents

Abstract

PURPOSE:To enable rear wheel side steering link mechanism to act interlockingly with the steering action of front wheels and hold rear wheels into the neutral positions at the two-wheel steering or fail time to lock them into the non-steered state, thus securing safety. CONSTITUTION:A centering spring mechanism part 83 for resetting rear wheel side steering link mechanism 1 into its neutral position is provided parallel on the side of a rear wheel steering power cylinder 3. Dead lock point mechanism parts 82 formed of dead point surpassing bent links are provided between both side parts of the centering spring mechanism 83 and the piston rod 96 side of the power cylinder 3. There are also provided lock releasing cylinder mechanism parts 100 formed of plungers operated in such a way as to let the bent connecting points 82c of the mechanism parts 82 surpass the dead point with pressure oil fed to the left and right chambers 3a, 3b of the power cylinder 3. There is additionally provided a neutral position detecting means 16 for detecting the relative rectilinear movement position between both side parts of the centering spring mechanism part 83 so as to detect the rear wheel steering state.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is used to steer a rear wheel in the opposite direction in conjunction with the front wheels by steering operation, thereby achieving a small turning radius at low speeds. Concerning improvements to rudder devices.

0002

[Prior Art] In recent years, by steering the rear wheels in the opposite direction or the same direction according to the amount of steering (steering amount) of the front wheels, it has been possible to improve the ability to turn around at low speeds, and to improve the ability to turn around when driving at medium or high speeds. Four-wheel steering vehicles that can improve driving stability are attracting attention. For example, when driving at low speeds, the front wheels are steered with a large steering angle. At this time, by setting the steering directions of the front and rear wheels in opposite phases (reverse direction steering), the vehicle's turning radius is minimized and the turning (small turning) performance is improved. It is particularly suitable for application to long vehicles such as trucks. Rear wheel steering devices for this type of four-wheel steering vehicle are disclosed, for example, in Japanese Patent Laid-Open Nos. 59-128054 and 59-128054;
Publication No. 143769, Publication of Utility Model Application No. 61-53271,
Many devices having various structures have been proposed in the past, including the hydraulic device shown in Japanese Patent Application Laid-Open No. 61-67665. Hydraulic type rear wheel steering devices in particular selectively supply hydraulic pressure controlled to a predetermined pressure using a servo valve or the like to the left and right chambers of hydraulic cylinders for steering the rear wheels. , which allows the rear wheels to be steered in the desired direction, and has greater freedom in terms of movement and structure than mechanical devices in which the front and rear wheels are mechanically connected by a connecting shaft, etc. It had advantages such as a large value.

0003

[Problems to be Solved by the Invention] However, the above-mentioned conventional device still has advantages and disadvantages in terms of structure and operational performance, and there is still room for improvement in putting it into practical use. For example, this type of rear wheel steering device requires the minimum number of component parts, improves the workability and ease of assembly of each part, reduces manufacturing costs, and efficiently arranges hydraulic piping and electrical wiring. In addition to properly performing various drive controls, it also ensures straight-line driving performance at medium and high speeds and driving stability on low-friction roads such as snowy roads, and the rear wheel steering system can be activated only when necessary. It is desirable to maintain two-wheel steering at all times, and it is also desirable to have sufficient measures to ensure that the rear wheels are locked in a state where steering is not possible in the event of a failure in the hydraulic system, electrical system, etc. It is rare. In particular, what is needed in such a request,
While driving at low speeds, the rear wheels can be appropriately steered in conjunction with the steering operation of the front wheels associated with the steering operation, and it also improves operational reliability and safety during medium and high speed driving and in the event of a failure. In some cases, a rear wheel steering control system is configured in which the above-mentioned requirements are met, and it is desirable to take such points into consideration and take some measures that can satisfy the above-mentioned requirements. For example, in a hydraulic rear wheel steering system, when the driving force is lost due to a failure in the rear wheel steering drive system, or when a failure occurs in the command transmission system of the rear wheel steering control system, the rear wheels are brought into a non-steerable state. Sometimes you have to keep it. In the event of a failure such as oil pressure failure, the problem is to adopt a configuration that can reliably lock the rear wheels in a straight-ahead state (neutral position) and maintain that state. . In other words, according to the steering link mechanism that supports the rear wheels so that the rear wheels can be steered, the rear wheels can be freely steered. Some kind of mechanism for locking the vehicle at this neutral position is required in order to ensure safety during 2WS driving in which the rear wheels are not steered or in the event of the above-mentioned fail. For this reason,
Conventionally, in rear wheel steering systems, a method has been adopted in which a centering spring mechanism or the like acts on a biasing force that allows the rear wheels to always return to the neutral position, and the force that overcomes this is always applied to steer the wheels, but this method is not practical. There is a big problem in terms of In other words, while a large urging force is required to return the rear wheels to the neutral position, overcoming this force and steering the rear wheels requires unnecessary force, resulting in a loss in terms of energy efficiency. I end up. In addition, with the above-mentioned spring mechanism, the rear wheels suddenly return to the neutral position from the steered state when a hydraulic system failure occurs, which poses a problem in ensuring driving stability. There is a need to solve these problems.

0004

[Means for Solving the Problems] In order to meet such demands, a rear wheel steering device for a four-wheel steering vehicle according to the present invention is arranged side by side with a power cylinder for rear wheel steering. A centering spring mechanism section consisting of a centering spring that returns the link mechanism to a neutral position and body sections on both sides of the centering spring mechanism;
and a second link, one end of which is pivotally supported on both ends of the piston rod of the power cylinder, and a connecting pin that connects these and is configured to cross the dead center of the line segment connecting the pivot points of each link. For releasing the left and right locks, it has a left and right deadlock point mechanism and a plunger that is operated to move the connecting pin (connection point) beyond the dead point by pressurized oil supplied to the left and right cylinder chambers. The vehicle is configured to include a cylinder mechanism and a neutral position detecting means for detecting a rear wheel steering state based on the relative linear movement position between both body parts in a centering spring mechanism part.

[0005]

[Operation] According to the present invention, the power cylinder can normally steer the rear wheels in the required state in conjunction with the steering operation of the front wheels, and at the time of 2WS or fail, the rear wheels can be returned to the neutral position and The deadlock point mechanism maintains a secure locked state beyond the dead center, and the neutral position detecting means attached to the centering spring mechanism can reliably detect this state. Further, according to the present invention, a rear wheel steering request is sensed by supplying pressure oil to the rear wheel steering power cylinder, and the lock release cylinder mechanism is actuated thereby to unlock the deadlock point mechanism. , the rear wheels can be steered.

[0006]

[Embodiment] Figures 1 to 13 show an embodiment of a rear wheel steering device for a four-wheel steering vehicle according to the present invention.
As shown in , the steering link mechanisms for steering the front and rear wheels (only the rear wheel side is designated by reference numeral 1, and the front wheel side is not shown) are independently driven by hydraulic power cylinders 2 and 3, respectively. In addition, only the front wheel side steering displacement information is transmitted as a hydraulic signal to the rear wheel steering drive system, and the rear wheel side steering displacement (the amount of rod movement of the power cylinder 3) is transmitted to the control system (to be described later) using the feedback cable 4. Rudder control valve 1
1) A rear wheel steering device 10 having a configuration including a signal system 5 that feeds back feedback will be described. Here, 6
, 7 is an oil pump for supplying pressure oil to the front and rear power cylinders 2 and 3, 8 is an oil tank, and the pressure oil from the front wheel pump 6 is guided to the front power cylinder 2 through a hydraulic pipe 6a. A well-known front wheel side power steering device is configured in which the oil is returned to the oil tank 8 through the return pipe 6b. Further, 9 is an on-vehicle battery, and in FIG. 12, hydraulic piping is shown as a double line, and electrical wiring is shown as a single solid line. In addition,
Although the oil pumps 6 and 7 are dual pumps driven simultaneously by an automobile engine (not shown), the present invention is not limited to this, and the oil pumps 6 and 7 may be configured with independent hydraulic systems for the front and rear wheels.

Furthermore, this embodiment device 10 uses the required play in the rear wheel steering control valve mechanism 11 for controlling the steering of the rear wheels by using the steering displacement information on the front wheels accompanying the steering operation. As a displacement transmission control means for rear wheel steering that selectively transmits transmission with a dead zone (dead zone), rotation transmission is not performed while the steering wheel is being steered within a certain angle from the neutral position, and when the steering wheel is steered further than that, a predetermined A displacement transmission control mechanism 12 using a dead zone link mechanism or the like configured to transmit rotational displacement with characteristics is used. The displacement transmission control mechanism 12 includes steering detection switches SW1 and SW2 for detecting the steering direction and steering state of the steering wheel.
By turning on and off these switches SW1 and SW2, the steering direction display lamps 13a and 13b are turned on, so that the steering direction of the front and rear wheels can be displayed from the driver's seat or the like. Here, these steering detection switches SW1 and SW2 are configured to turn off when the steering angle is within about 300 degrees from the straight-ahead state (neutral position), and turn on when the steering wheel is steered beyond that point. Further, the rear wheel steering device 10 is connected to the battery 9 shown in FIG.
In the electric circuit leading up to the above, reference numeral 14 is an emergency switch for manually forcibly turning off the rear wheel steering device 10 and putting only the front wheels in the 2WS state when the driver senses an abnormality while driving, and 15 is described later. A detection switch 16 serves as a cable/return spring failure detection means, and 17 is a neutral position detection switch attached to the power cylinder 3 side constituting the steering link mechanism 1 for steering the rear wheels and detects the neutral position of the rear wheels as an off signal. is a normally closed type relay switch for controlling current flowing to a negative actuation type clutch mechanism, which will be described later. Further, reference numeral 18 denotes a normally open type bypass valve that opens and closes a bypass path between a hydraulic pipe 7a from the rear wheel steering oil pump 7 and a return pipe 7b from a control valve, which will be described later. 9 turns on the solenoid, which closes the bypass path, and the emergency switch 14, cable/return spring failure detection switch 15, etc. are turned off and are no longer energized, opening the bypass path. 2WS without wheel steering
It is configured to be in a state.

Further, as is clear from FIG. 13, the rear wheel steering control valve mechanism 11 for controlling the steering of the rear wheels by the rotational displacement transmitted from the displacement transmission control means described above is configured to A rotary rear wheel steering control that performs switching control of a hydraulic passage from an oil pump 7, which is a rear wheel side hydraulic power source, in accordance with the amount of displacement obtained by the control mechanism 12, and operates the power steering 3 for rear wheel steering. valve 20
A feedback shaft 2 is disposed coaxially with the input and output shafts 21 and 22 of the rear wheel steering control valve 20.
A winding pulley 27 of the feedback cable 4, which constitutes the feedback signal system 5 that is pivotally supported on the rear wheel steering link mechanism 1, and the winding pulley 27 is attached in the winding direction of the cable 4. and a cable winding mechanism 28 consisting of a return spring 29 that biases the cable. Furthermore, within the body in which the control valve 20 and the cable winding mechanism 28 described above are incorporated, the control valve 20 side output shaft 22 and the feedback shaft 23 are interposed between these mechanical parts. a delay absorbing spring mechanism 25 for absorbing a steering delay on the rear wheel side in response to a steering operation by connecting the components in a relatively rotationally displaceable state, and this delay absorbing spring mechanism 25.
A negative actuation type clutch mechanism 26 is interposed between the control valve 20 and the control valve 20 and selectively connects the two. Note that the cable winding mechanism 2
8 includes a cable/return spring failure that is activated in conjunction with the movement of the cable winding mechanism 28 that occurs when either the return spring 29 or the cable 4 fails and sends a failure signal. A defect detection means 30 is attached. These rear wheel steering control valve 20, negative actuation type clutch mechanism 26, delay absorption spring mechanism 25, cable winding mechanism 28, and cable/return spring failure detection means 30 are connected to the input and output shafts of the control valve 20. 21, 22 and the feedback shaft 23 on the same axis to form a unit, the overall structure of the device is simplified, displacement transmission is ensured, and the mechanical unit is easy to assemble and integrate into a vehicle. It can also improve the

The schematic structure of the rear wheel steering control valve mechanism 11 unitized in this way will be briefly explained using FIG. 13 and the like.
The housing body 33 that constitutes the valve mechanism section 11 with the rotor 34 and sleeve 35 (on the output shaft 22 that constitute the valve 20 attached by screwing to the end on the housing body 31A side) integrally formed) is provided therein, and a pump port 36,
It is a valve body in which a hydraulic passage leading to the tank port 37 etc. is formed, and a part of the above-mentioned hydraulic passage is formed in the output port 38, 3 formed on the housing body 31A side.
9. In addition,
In the figure, P is the pump 7, T is the tank 8, C1, C2
are the left and right chambers of the power cylinder 3 on the rear wheel side. Further, 40 is a torsion bar that connects the input and output shafts 21 and 22 such that they can rotate relative to each other. Then, this control valve 20 is switched to a desired state by rotational displacement from the displacement transmission control mechanism 12 in response to a steering operation, so that the rear wheel steering control by the rear wheel steering power cylinder 3 is controlled to a desired state. It is configured so that it can be done.

On the other hand, as is clear from FIG. 13, one end of a cable 4 for feeding back the steering state of the rear wheels is connected to the feedback shaft 23 in the body 31B mentioned above. A winding pulley 2 constituting a cable winding mechanism 28 that enables winding.
7 is rotatably supported on the shaft, and a feedback transmission plate 41 connectable to the winding pulley 27 in the rotational direction is fixed on the feedback shaft 23 adjacent to the pulley 27. . The transmission plate 41 is then moved to the pulley 2 by the return spring 29.
7 is biased in the cable winding direction. The reference numeral 43 denotes a failure detection promoting spring for the cable 4 or the return spring 29, which is provided to extend between the winding pulley 27 and the transmission plate 41. On the other hand, on the side of the cable winding mechanism section 28 described above, there is a movable member 50 that is movable in the axial direction inside the pulley 27, and a movable member 50 that is connected to this and has the other end connected to the cable/return spring failure detection switch 15.
A contactor 51 that selectively comes into contact with is disposed, thereby configuring the cable/return spring failure detection means 30. A detailed explanation of the operation of the cable 4 winding mechanism 28 and the cable/return spring failure detection means 30 will be omitted. Further, in the control valve mechanism section 11 described above, a coil is provided between the feedback shaft 23 to which the feedback system is connected and the output shaft 22 on the control valve 20 side, which connects these members so that these members can be relatively rotationally displaced. Although a delay absorbing spring mechanism 25 using a spring 63 and a well-known negative actuation type clutch mechanism 26 for selectively transmitting rotation between both members are provided, a detailed explanation thereof will be omitted. Here, this negative actuation type clutch mechanism 26 eliminates changes over time such as elongation of the cable 4, and eliminates the deviation that occurs between the neutral position state of the control valve 20 and the neutral position state on the rear wheel side. This is for use when the steering wheel is in the neutral state or when the front wheel is only 2W.
At the time of S, the clutch mechanism 26 is energized and turned on to disengage the clutch, and at the time of 4WS, the clutch mechanism 26 is turned off to engage the clutch.

In the rear wheel steering device 10 having the above configuration, rear wheel steering control is performed as follows. That is, when the engine is started, pressure oil is supplied from the pumps 6 and 7 to the steering systems on the front and rear wheels, and during normal driving, the oil is supplied through the front wheel control valve, the rear wheel control valve 20, or the bypass valve 18. A circulation path returning to the tank 8 is constructed. In this state, the steering wheel is steered in either direction, and the steering link mechanism on the front wheel side sends pressurized oil to either cylinder chamber of the power cylinder 2 on the front wheel side using the flow path switching function by the control valve on the front wheel side. The front wheels are steered in the desired steering direction. On the other hand, when the steering angle on the front wheel side reaches a certain angle or more, either of the steering detection switches SW1 and SW2 is turned on, thereby turning on the bypass valve 18, and a flow path for rear wheel steering is configured.
In addition, the power supply to the negative actuation type clutch 26 is stopped within the control valve mechanism 11, and the clutch is in the clutch engagement state.
The WS becomes ready. In this state, the steering angle on the front wheel side becomes greater than that, and the rotational displacement from the displacement transmission control mechanism 12 for rear wheel steering causes the rear wheel side control valve 20 to move toward the relative position that occurs between its input and output shafts 21 and 22. By switching the flow paths between the rotor 34 and the sleeve 35 due to rotational displacement, pressure oil is supplied to either cylinder chamber of the rear wheel steering power cylinder 3 on the steering linkage mechanism 1 side on the rear wheel side. . At this time, in the cable winding mechanism 28, the cable 4 side or the return spring 29 side becomes a load, and this causes the input and output shafts 21 to
, 22 due to the torsion of the torsion bar 40. At the same time, the lock release cylinder mechanism is actuated by the supplied pressure oil to release the deadlock point mechanism parts 82, 82, which will be described later as a rear wheel neutral position lock mechanism, so that either one of them to release the locked state. After this lock is released, the power cylinder 3 operates to operate the rear wheel side steering link mechanism 1 to control steering of the rear wheels in a desired direction. This rear wheel steering state is fed back from the above-mentioned winding mechanism 28 to the control valve 20 side via the cable 4. On the other hand, when the steering wheel is returned to a predetermined angle from the above-mentioned steering state, this movement is transmitted to the control valve 20, and the rear wheel side The steering linkage device 1 is controlled to be steered in the return direction. When the rear wheels are in the neutral position, the deadlock point mechanisms 82, 82 lock the rear wheels, and the neutral position detection switch 16 is turned off. Furthermore, when the steering wheel is returned to the neutral position, the steering detection switch is turned off, power supply to the bypass valve 18 is stopped, and power is supplied to the negative actuation type clutch 26, resulting in a clutch disengaged state. The state will be as follows.

In the above-mentioned rear wheel steering device 10, the above-mentioned control valve 20 at the side of the steering linkage mechanism 1 for rear wheel steering extends from the left and right chambers 3a and 3b of the power cylinder 3 for rear wheel steering. Hydraulic passage 80a consisting of hydraulic piping, etc.
, 80b, as is clear from FIGS. 1 and 12, there is a hydraulic failure check valve mechanism 81 for performing hydraulic control to restore the rear wheels only to the neutral position in the event of oil pressure failure. is provided. To explain this oil pressure failure check valve mechanism 81 with reference to FIG. 1, FIG. 6, FIG. 7, etc., the cylinder chamber 3a is
, 3b side, and a pair of left and right check valves 90, 91 arranged to prevent the flow of pressure oil from the sides, and the balls 90a, 91a of these check valves 90, 91 at all times.
Left and right plungers 92 are biased by springs 92a and 93a to maintain a disengaged state, and forcefully open each check valve 90 and 91 when their engaging ends 92b and 93b are engaged. , 93, and a chamber 92c formed on the opposite end side of each of these plungers 92, 93.
, 93c, hydraulic passages 80b, 80 on opposite sides to each other.
Left and right pilot passages 94b and 94a that lead the pressure in a
and left and right bypass passages 95a and 95b that are branched from the middle of each hydraulic passage 80a and 80b, bypass the respective check valves 90 and 91, and open and connect to the end portions of the power cylinder left and right chambers 3a and 3b. The opening ends of these bypass passages 95a and 95b to the respective cylinder chambers 3a and 3b can be closed when the oil pressure fails.
It consists of left and right valve plates 97 and 98 that are slidably provided on a piston rod 96. In addition, 99
a, 99b are arranged on both sides of the piston 96a provided on the piston rod 96, and left and right valve plates 97,
Springs 96b and 96c urge valve plates 97 and 98 in both directions in the axial direction.
This is a locking ring that locks the movement of the cylinder 3 in a neutral state by contacting the end portion of the cylinder 3. Further, in this embodiment, the hydraulic passages 80a, 80b having the check valves 90, 91 are also provided to open at the end portion of the cylinder 3, and in this case, these passages 80a, 80
A communication hole is bored in the valve plates 97 and 98 so that the openings of the valve plates 97 and 98 are not blocked by the valve plates 97 and 98. moreover,
As is clear from FIGS. 2 and 3, the bypass passages 95a and 95b described above are a part of the body 110 that constitutes the rear wheel steering link mechanism 1 having the power cylinder 3, and are a shaft hole that holds the piston rod 96. The cylinder chambers 3a, 3 are connected to each other by a passage hole 111 formed separately along the axial direction.
It opens at the end portion of b, and is formed so that it can be closed by valve plates 97 and 98. Also, Figures 1 and 6
120 is a block body constituting the oil pressure failure check valve mechanism 81, and 121 and 122 are control valves 2.
Plugs 123 and 124 are plugs connected to 0 through hydraulic passages 80a and 80b, and plugs 123 and 124 are plugs for connecting the hydraulic passages to the power cylinder left and right chambers 3a and 3b, and left and right bypass passages 95a and 95b are , plugs (not shown) provided perpendicularly to the plane of the drawing are connected to the left and right chamber sides of the cylinder.

By using the above-mentioned oil pressure failure check valve mechanism 81, the rear wheels can be steered in the required state by the steering operation of the front wheels at all times, and in the event of oil pressure failure, the oil pressure loss can be avoided. By the action of the check valve mechanism 81, of the left and right cylinder chambers 3a and 3b, the hydraulic passage 80a or 80b to the chamber on the steering direction side is closed, and only the hydraulic passage to the chamber toward the neutral position is closed to the low pressure side. By opening to It is possible to perform recovery steering to return to the neutral position, and to lock the rear wheels at the neutral position. That is, this oil pressure failure check valve mechanism 81
functions as a check valve in the normal state, and when the piston rod 96 attempts to move to the left in FIG. 8 due to a cutting operation on the front wheel side, for example, the chuck valve 91 on the right side to which the high-pressure oil pressure, that is, the pump P side is connected, is opened. As a result, high pressure is supplied into the cylinder right chamber 3b, and the power cylinder 3 is operated to the left in the figure. On the other hand, the check valve 90 connected to the tank T side has the above-mentioned pressure on the high pressure side connected to the plunger 92.
The cylinder is forcibly opened by the plunger engaging end 92b, which is operated by being guided to the chamber 92c on the opposite engaging end side, thereby allowing a flow from the cylinder left chamber 3a to the tank side, and refluxing to the tank side. It has become so. In addition, in the cylinder right chamber 3b, the valve plate 98 moves to the left side together with the piston rod 96, and the bypass passage 95b is also opened and high-pressure oil pressure is introduced into the cylinder. Also,
When the steering wheel is returned in the above-mentioned state and the hydraulic circuit is reversely switched by the control valve 20, as shown in FIG. 9, the cylinder left chamber 3a is moved to the pump P side and the right chamber 3b is connected to the tank T side, and can apply the required steering force to the piston rod 96. In this case, it will be easily understood that the left check valve 90 is opened by high pressure hydraulic pressure, and the right check valve 91 is opened by the plunger 93. Of course, when steering in the opposite direction, the power cylinder 3 is operated with a completely opposite hydraulic pressure supply state. on the other hand,
When a hydraulic failure occurs in the hydraulic circuit for steering the rear wheels when the rear wheels are in a steered state and the piston rod 96 of the power cylinder 3 is moving to the left in the figure, as shown in FIG. 10, for example. When self-alignment torque, centering force by the centering spring mechanism 83, or kickback force from the rear wheel side is applied in the direction of returning to the neutral position, the hydraulic fluid in the cylinder right chamber 3b bypasses the check valve 91. The water is returned to the tank T side through the bypass passage 95b, and the cylinder left chamber 3a has
Hydraulic oil from the tank T side is supplied by opening the check valve 90 and passing it through. As a result, the piston rod 96 and the rear wheel gradually return to the neutral position. On the other hand, when a load such as a kickback is applied in the steering direction of the rear wheels, that is, in the direction of increasing steering during oil pressure failure in the above-mentioned rear wheel steering state, the left cylinder chamber 3a is blocked as shown in FIG. By keeping the valve in this state and sealing in the hydraulic oil, movement in the direction of increasing cutting can be restrained. That is, when the piston 96a tries to move to the left in FIG.
7 comes into contact with the end portion of the cylinder left chamber 3a, closes the bypass passage 95a, and closes the check valve 9.
0 is also occluded, which causes this cylinder's left ventricle 3a
Since the hydraulic oil is sealed inside, the rod 96 will not move, and the rear wheel will not be cut further. Of course,
It will be easily understood that if a force is applied in the neutral direction from this state, the state shown in FIG. 10 described above will occur. According to such a configuration, the oil pressure failure check valve mechanism 81 can be unitized and configured compactly, and the degree of freedom such as installation space and mounting location is increased. 98 and plunger 92,
Since the check valves 93, 90, 91, etc. are all operated by hydraulic pressure, the operational reliability thereof can be greatly improved.

Now, according to the present invention, in the above-mentioned rear wheel steering device 10, a centering spring is provided in parallel to the side of the rear wheel steering power cylinder 3 and returns the rear wheel side steering link mechanism 1 to the neutral position. 102 and its both side body parts 83a, 83b, first links 82a, 82a whose ends are pivoted to the both side body parts 83a, 83b, and the piston rod 96 (steering wheel) of the power cylinder 3. The second links 82b, 82b, one end of which is pivotally supported on both ends of the link mechanism (which also serves as a tie rod), are connected to each other, and the line segment h connecting the pivot points of each link is configured to cross the dead center. Left and right deadlock point mechanism parts 82, 82 consisting of connecting pins 82c, 82c, and the connecting pins 82c,
left and right lock release cylinder mechanisms 100, 100 having plungers 100a, 100a that are operated to move 82c (connection point) beyond the dead center by pressure oil supplied to the left and right cylinder chambers 3a, 3b; The centering spring mechanism part 83 is characterized by a structure in which a neutral position detection switch 16 is provided as a neutral position detection means for detecting the rear wheel steering state based on the relative linear movement position between the body parts 83a and 83b on both sides. have. Here, in the left and right deadlock point mechanisms 82, 82, the connecting pin 82c connecting the first and second links 82a, 82b is a line connecting the pivot points of each link, as is clear from FIG. By moving the minute h outward, the piston rod 96 forming the steering link is allowed to move and the rear wheels can be steered, and the connecting pin 82c is normally caused to move inward beyond the dead center as shown in the figure. It is designed to maintain the locked state at the neutral position at all times, maintain the rear wheels in an unsteered state during 2WS driving, and function as a neutral position locking mechanism. Further, in order to release the deadlock state of the left and right deadlock point mechanisms 82 and 82, lock release cylinder mechanisms 100 and 100, which are operated by pressure oil in the hydraulic passages 80a and 80b, are connected to the piston rod 96. Engagement pins 101 are disposed orthogonally to each other, and have their base ends facing the middle of the hydraulic passages 80a, 80b, and their tips provided on a portion of the first links 82a, 82a.
101 and forcibly rotate the links 82a, 82a, allowing the connecting pins 82c, 82c to move beyond their dead centers. Furthermore, the centering spring mechanism section 83 has a left side where the first links 82a, 82a are pivotally supported;
It is provided between the right body parts 83a and 83b and is configured to be expandable and retractable in the axial direction, and when the piston rod 96 moves in the left-right direction by the centering spring 102, it returns to the initial position, that is, the neutral position, so that the rear wheel It is designed to always return to the neutral position state, and there are some parts where the relative position of the members on both sides is shifted,
In other words, a neutral position detection switch 16 for detecting whether or not the rear wheel is in the neutral position is provided in the rod part 105 extending from one side and the fitting hole 106 into which the rod part 105 is slidably fitted. is attached. In addition, 103,10
4 are cylindrical parts on both the left and right sides that are fitted into each other, 107
is a bellows-like boot that covers the centering spring 102. Note that the centering spring 10 described above
2 is set so that the spring force near the neutral position is maximum, as is clear from the characteristic diagram shown in FIG. According to such a configuration, the power cylinder 3 can normally steer the rear wheels in a desired state in accordance with the steering operation of the front wheels, and at the time of 2WS or fail, the rear wheels can be returned to the neutral position. At the same time, a deadlock point mechanism section 82 which is a mechanical locking means locks the state.
, 82 beyond the dead center, and this state can be reliably detected by the neutral position detection switch 16 attached to the centering spring mechanism section 83. Further, by supplying pressure oil to the rear wheel steering power cylinder 3, a rear wheel steering request is sensed, and one of the lock release cylinder mechanisms 100, 100 is actuated thereby, and rear wheel steering is required. By unlocking the deadlock point mechanism section 82 on the side, the rear wheels can be steered in the desired state. In particular, with such a configuration, the rear wheel side steering link mechanism 1 can be reliably maintained in a non-steered state by a mechanical lock, and the lock can be easily locked by supplying pressure oil to the power cylinder 3 side. Moreover, it can be automatically removed and the required rear wheel steering can be performed. In addition, the centering spring mechanism 83 not only achieves the required function by minimizing the spring force, but also allows the neutral position detection switch 16 to sense the relative movement of the members on both sides. Therefore, the switch 16 is superior in terms of reliability, and also has the advantage that the switch 16 can be easily installed and configured compactly.

By the way, in the rear wheel steering device 10 in the embodiment described above, the rear wheel side steering link mechanism includes the power cylinder 3, the above-mentioned centering spring mechanism section 83, left and right deadlock point mechanism sections 82, 82, etc. 1 is assembled by neutral positioning of each part in the state shown in schematic FIG. 1. Here, it is important to note that the neutral position of the centering spring mechanism 83, the left and right deadlock point mechanisms 82, 82, etc. mentioned above is not the same as the neutral position of the power cylinder 3 and the piston rod 96 which becomes the tie rod. The purpose is to perform positioning adjustments reliably. Therefore, in the device of this embodiment, each part is positioned at the neutral position in the assembled state described above, and at the end portions on both ends of the piston rod 96,
A spacer ring 130 and its tightening nut 131 provide an adjustable latch portion, which allows the second link 82b to be fixed to the member 132 that is pivotally supported so that the assembly position in the axial direction can be adjusted. It is configured to obtain. According to such a configuration, the neutral position between the deadlock point mechanism section 82 side and the piston rod 96 side can be easily and reliably positioned.
Further, fine adjustment can be easily performed, which is advantageous in terms of ease of assembly. On the other hand, in the above-mentioned deadlock point mechanism section 82, the rotating parts exposed to the outside, such as the shaft support of each link 82a, 82b and the shaft support part of the connecting pin 82c, have their operational reliability ensured. Therefore, it is necessary to take waterproof measures. For this reason, the device of this embodiment employs a structure as shown in FIG. To explain this simply, 14 in the figure
0 is a rotating shaft with a flange at one end, 141 is a locking pin that locks the other end, 142 is a locking ring, and 143 is a metal bush fitted to the rotating shaft 140, with O-rings on both ends. 144, 144 are arranged, and the metal bush 143 has a nipple part 1 for sealing grease.
43a is formed to protect the rotating shaft portion and ensure waterproofness. In addition, 145 in the figure is a rotation stopper between the bearing member 146 and the rotating shaft 140.

It should be noted that the present invention is not limited to the structure of the above-described embodiment, and the shape, structure, etc. of each part of the rear wheel steering device 10 may be modified or changed as appropriate, and various modifications may be considered. For example, in the above-mentioned embodiment, although the specific disclosure is omitted as the displacement transmission control mechanism 12 for rear wheel steering, etc., it is possible to obtain a steering signal to the rear wheels in conjunction with the steering operation of the front wheels. Any configuration is acceptable, and various modifications may be considered. Furthermore, various modifications may be made to the control valve mechanism section 11 including the control valve 20 for steering the rear wheels.

[0017]

As explained above, according to the rear wheel steering device for a four-wheel steered vehicle according to the present invention, the rear wheel steering link mechanism, which is arranged in parallel to the side of the power cylinder for rear wheel steering, can be moved to the neutral position. a centering spring mechanism consisting of a centering spring and body parts on both sides thereof, a first link having one end pivoted to the body parts on both sides, and a second link having one end pivoted to both ends of the piston rod of the power cylinder.
The left and right deadlock point mechanisms consist of links and connecting pins that connect these links and are configured to cross the dead center of the line segment connecting the pivot points of each link, and the connecting pins (connecting points). The left and right lock release cylinder mechanisms have plungers that are operated by pressure oil supplied to the left and right cylinders to move the cylinders past their dead points, and the centering spring mechanism allows the relative straight line between the body parts on both sides. The structure is equipped with a neutral position detection means that detects the rear wheel steering state based on the movement position, so despite the simple structure, the power cylinder is always used to steer the rear wheels to the required position when the front wheels are steered. In addition to being able to steer in the state of
In the event of a WS or fail, the rear wheels return to the neutral position, and a mechanical deadlock point mechanism maintains a secure locked state beyond the dead center, and this state is maintained at the neutral position attached to the centering spring mechanism. Not only can it be reliably detected by the detection means, but it also detects a rear wheel steering request by supplying pressure oil to the rear wheel steering power cylinder, which activates the lock release cylinder mechanism and locks the deadlock point mechanism. The lock can be easily and automatically released and the rear wheels can be steered, ensuring reliability in the operation of each part, and also improving safety since the lock can be reliably locked in the neutral position. There are various excellent effects such as:

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of the entire rear wheel steering power cylinder mechanism, which is featured in a rear wheel steering device for a four-wheel steered vehicle according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of a power cylinder portion in FIG. 1;

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a characteristic diagram showing spring characteristics in a centering spring mechanism section.

FIG. 5 is a sectional view of a main part of a mechanical deadlock point mechanism.

FIG. 6 is an enlarged sectional view of a main part of the oil pressure failure check valve portion in FIG. 1;

FIG. 7 is a diagram for explaining the schematic configuration of a hydraulic failure check valve and a rear wheel steering power cylinder.

FIG. 8 is an explanatory diagram of the oil pressure failure check valve and the rear wheel steering power cylinder during normal operation.

FIG. 9 is an explanatory diagram of the operation of the oil pressure failure check valve and the rear wheel steering power cylinder during normal operation.

FIG. 10 is an explanatory diagram of the operation of the hydraulic pressure failure check valve and the rear wheel steering power cylinder when the oil pressure failure occurs.

FIG. 11 is an explanatory diagram of the operation of the hydraulic pressure failure check valve and the rear wheel steering power cylinder when the oil pressure failure occurs.

FIG. 12 is a diagram showing a schematic configuration of the entire rear wheel steering device.

FIG. 13 is a schematic cross-sectional view of a rear wheel steering control valve mechanism in the rear wheel steering device.

[Explanation of symbols]

1 Rear wheel steering link mechanism 3 Rear wheel steering power cylinder 4 Feedback cable 7 Rear wheel oil pump 8 Oil tank 10 Rear wheel steering device 11 Rear wheel steering control valve mechanism section 16
Neutral position detection switch 18 Bypass valve 20 Rear wheel steering control valve 80a Hydraulic passage 80b Hydraulic passage 81 Hydraulic failure check valve mechanism 82
Left and right deadlock point mechanism (neutral position locking mechanism) 82a First link 82b Second link 82c Connection pin 83 Centering spring mechanism 83a
Body part 83b Body part 90 Check valve 91 Check valve 96 Piston rod 100 Lock release cylinder mechanism part 100a
Plunger 102 Centering spring 105
Rod part 106 fitting hole

Claims (1)

[Claims] Claim 1: A rear wheel steering link mechanism is controlled by pressurized oil selectively supplied from a rear wheel hydraulic source through a rear wheel steering control valve that is operated in conjunction with a front wheel steering operation. A centering spring consisting of a rear wheel steering power cylinder that performs steering control, a centering spring that is installed in parallel to the side of the rear wheel steering power cylinder and returns the rear wheel side steering link mechanism to a neutral position, and body parts on both sides of the centering spring. a first link having one end pivoted to both body parts of the centering spring mechanism; and a first link having one end pivoted to both ends of a piston rod of a power cylinder constituting the steering link mechanism. The left and right deadlock point mechanisms consist of two links and a connecting pin that connects these two links and is configured to cross the dead center of the line segment connecting the pivot points of each link, and this deadlock point. a left having a plunger that is operated to cause a connection point by a connection pin in the mechanism portion to cross the dead center by pressurized oil supplied to the left and right chambers of the power cylinder;
and a right pair of lock release cylinder mechanisms, and the centering spring mechanism section is provided with neutral position detection means for detecting movement in the power cylinder based on the relative linear movement position between both body sections. A rear wheel steering device for a four-wheel steering vehicle, characterized by: