JPH0419267A - Four-wheel steering device for power vehicle - Google Patents

Abstract

PURPOSE:To facilitate switching of a mode by providing a control means to sound an alarm when front wheel or rear wheel, locked to a straight forward state,are displaced in a given angle or more arc from a straight forward direction, in a power vehicle formed such that front and rear wheel can be respectively independently steered. CONSTITUTION:In a front wheel steering mode, rear wheels 3 and 3 are locked and in a rear wheel steering mode, front wheels 2 and 2 are locked. However, through operation of a mode change-over switch 46 by an operator, a corresponding hydraulic cylinder is locked. Subsequently, a detecting value from a steering angle sensor on the locked side is read. Further, a difference between a detecting value and the value of the steering angle sensor when a wheel on the locked side is pointed to the straight forward direction is calculated. It is then discriminated whether an absolute value is higher or lower than a specified value alpha(an allowable value at which it is decided that a wheel is pointed approximately to a straight forward direction). When the absolute value is higher than alpha, it is detected that an amount of working oil leaking from a hydraulic cylinder is excessive, and report is effected by means of lamps L5 and L6. The operator can detect it before a subsequent mode is set that synchronism of front and rear wheels with each other is out of order.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a four-wheel steering device for tractors, construction machines, etc.

[Prior art and its section M] There have been conventional devices in which the front wheels and the rear wheels can be steered, but these devices usually have four steering modes, and it is difficult to steer only the front wheels. a front wheel steering mode that enables rear wheel steering operations, a rear wheel steering mode that allows rear wheel steering operations, a front and rear wheel same phase steering mode where the front and rear wheels are steered in the same phase, and a front wheel steering mode that allows the front and rear wheels to be steered in opposite directions. It consists of a front and rear wheel reverse phase steering mode.

Normally, these steering modes are switched when both the front and rear wheels are facing straight ahead, but the hydraulic actuators that rotate the front and rear wheels gradually change over time. Hydraulic oil may leak, and as a result, even if the operator attempts to set the same number of steering wheels in the straight-ahead direction, each wheel will not follow the same number accurately, making it difficult to switch modes.

[Means for Solving the Problems] The present invention is proposed in view of the above problems, and takes the following technical measures.

That is, in a power vehicle 1 configured such that the front and rear wheels 2.3 can be independently steered, the front wheels 2.3 are fixed in a straight-ahead state.
Alternatively, the four-wheel steering system for a power vehicle is characterized in that it is provided with a control means 55 that issues an alarm when the rear wheels 3 deviate from the straight-ahead direction by more than a predetermined angle.

[Embodiments and their effects] The present invention will be described in detail below with reference to the drawings. First, to explain the structure, reference numeral 1 is a four-wheel drive type tractor, which is equipped with front wheels 2.2 and rear wheels 3.3 at the front and rear of the machine body, respectively. The rotational power of engine 5 is transmission case 6
The speed is appropriately reduced through a gear mechanism (not shown) inside the engine, and is transmitted to the front wheels 2.2 and rear wheels 3.3. In addition, this tractor 1 is configured to be able to steer not only the front wheels 2.2 but also the rear wheels 3.3, and is equipped with a front wheel steering system F and a rear wheel steering system R based on the schematic plan view of FIG. will be explained in detail.

7.8 is a pitman arm, which has a fulcrum pin 9 on the fuselage.
．． It is pivotably mounted around 10. Each pitman arm 7.8 is interlocked and connected to the steering knuckle arm 12.12 of the front wheel 2.2 and the knuckle arm 13.13 for the rear wheel via tie rods 15.15.16.16, respectively, and One end of a piston rod 20.21 of a hydraulic cylinder 18.19 is pivotally connected to arm portions 7a, 8a protruding from one side of the pitman arm 7.8.

The front wheel steering system F and the rear wheel steering system R each include a hydraulic cylinder 18.19, a piston rod 20.21, a pitman arm 7.8, and a knuckle arm 12.12.13.13.
Consisted of. Both of the hydraulic cylinders 18 and 19 are rotatably supported at their intermediate portions on the fuselage.

25 is an electromagnetic valve that controls the front wheel steering system F, with position 2 and 4.
It is composed of a boat-type valve, and under normal conditions, the hydraulic pump 3o side and the cylinder chamber (18a or 18b) of the hydraulic cylinder 18 are in communication, and when the solenoid C of the electromagnetic valve 25 is energized, the right side chamber is in communication. As a result, the hydraulic pump 30 and the hydraulic cylinder 18 side are cut off.

28 is an electromagnetic valve that controls the rear wheel steering system R, and is composed of a 3-position, 4-port type valve. Under normal conditions, it maintains a neutral position, and when solenoid B is energized, it switches to the right chamber.
Conversely, when solenoid A is energized, it switches to the left chamber. In the figure, reference numeral 35 indicates a fully hydraulic steering mechanism, and when the steering handle 38 is turned, the oil passage and oil amount are controlled at the same time. For example, in the same figure, when the steering wheel 38 is turned to the left, the hydraulic oil sent from the hydraulic pump 30 passes through the oil passage (A) to the electromagnetic valve 2.
8, and further passes through the left chamber of the electromagnetic valve 25 and flows into the cylinder chamber 8a of the hydraulic cylinder 18. Then, the piston rod 20 is pushed forward, causing the pitman arm 7 to rotate to the left around the fulcrum pin 9, and the front wheel 2.2 to rotate to the left. Conversely, when the steering wheel 38 is turned to the right, the hydraulic oil passes through the oil passage (b) and enters the left chamber of the electromagnetic valve 25, and further flows into the cylinder chamber 18b of the hydraulic cylinder 18, causing the hydraulic oil to flow into the left chamber of the electromagnetic valve 25. It passes through the neutral position and is collected into the tank 70.

In addition, 40 is a diverting valve built into this hydraulic steering mechanism 35, and a part of the hydraulic oil diverted by this diverting valve 40 raises and lowers a working machine (not shown) attached to the rear of the tractor 1. It is led to the main control valve 42. The main control valve 42 has a neutral position, a raised position, and a lowered position, and supplies and discharges hydraulic oil into the cylinder chambers of the left and right hydraulic cylinders 44 for raising and lowering the work equipment, thereby raising and lowering the work equipment. do.

The two electromagnetic valves 25 and 28 described above are for switching the oil passages, and the following four modes can be selected by electrically turning on and off the three solenoids A, B, and C. That is, as shown in Fig. 3, if all three solenoids A-B and C are off, the rear wheel 3.3
is fixed in a straight-ahead state, and is switched to a front wheel steering mode in which only the front wheels 2.2 can be steered.

On the other hand, when solenoids B and C are energized, the front wheels 2.2 are locked in a straight-ahead state and the vehicle is switched to a rear wheel steering mode in which only the rear wheels 3.3 can be steered.

Furthermore, when only the solenoid A of the electromagnetic valve 28 is energized, the mode is switched to the front and rear wheels same phase steering mode in which the front wheels 2.2 and the rear wheels 3.3 are steered in the same direction. Also, when the solenoid C of the solenoid valve 25 is off, the rear wheel side solenoid valve 28
When only the solenoid B is energized and switched to the right side chamber, the front wheel reverse phase steering mode is switched to the front wheel reverse phase steering mode in which the front wheels 2.2 and the rear wheels 3.3 are switched in opposite directions. These changes are made by a mode changeover switch 46 provided near the cockpit, and changeover between each mode is possible when the front wheels 2.2 and rear wheels 3.3 are in a straight-ahead state. It is configured so that

50.51 are steering angle sensors for detecting the steering angles of the front wheels 2, 2 and rear wheels 3.3, respectively, and the fulcrum pins 9.10
It is installed coaxially with.

Next, the control circuit shown in FIG. 4 will be briefly explained.

A steering angle sensor 50.51 that detects the steering angles of the front wheels 2.2 and rear wheels 3.3 is connected via an A/D converter 53 and an input interface 54 to a control unit 55 as a control means consisting of a microcomputer. There is.

A mode changeover switch 46 is connected to a microcomputer 55 via an input interface 54. When the mode selector switch 54 is set to ■, the mode switches to the front wheel steering mode, and when it is set to ■.

The mode becomes rear wheel steering mode, and if you switch to ■, the front and rear wheels will be in reverse phase steering mode, and if you switch to ■, it will switch to front and rear wheels same phase steering mode.

The lamp groups labeled Ll to L4 connected to the output interface 59 side display each mode, and the lamp of the selected mode lights up. Lamp L5. L6
lights up when a leak occurs in the hydraulic cylinders 18 and 19 and they deviate from their predetermined positions.

The program shown in FIG. 5 is stored in the memory of the control device 55 described above, and its contents will be explained below.

In the front wheel steering mode, the rear wheels 3.3 are locked, and in the rear wheel steering mode, the front wheels 2.2 are locked, but first, the corresponding hydraulic cylinder is fixed according to the operator's mode setting (step 81).

Subsequently, the detected value of the steering angle sensor on the fixed side is read (step S2). Furthermore, the difference between this detected value and the value of the steering angle sensor when the wheel on the fixed side faces in the straight traveling direction is calculated (step S3). Then, it is determined whether the absolute value is larger or smaller than a specified value α (tolerable value for determining that the vehicle is heading in an approximately straight direction), and if it is smaller than α, the control continues as it is, and the absolute value is If it is larger than α, it means that the amount of hydraulic oil leaking from the hydraulic cylinder is excessive, and the lamp L5. Notification is made at L6 (step S5).

As described above, when the fixed side wheel deviates from the straight-ahead direction by more than a specified value in the front wheel steering mode or the rear wheel steering mode, the lamps L5 and L6 light up to notify the operator. It becomes possible to know before setting the next mode that the front and rear wheels are out of synchronization, and the risk of erroneous operation can be avoided.

Note that the flowchart shown in FIG. 6 allows the steering mode to be forcibly set by depressing the clutch pedal even when the steering sensors 50, 51 of the front and rear wheels become abnormal.

In this case, first turn the front and rear wheels 2.3 in a substantially straight direction, depress the clutch pedal (not shown), and then turn the solenoid A, B, and manually to switch to the desired mode.

The four-wheel steering system explained in this embodiment is controlled by a microcomputer so that the mode can be switched when the front wheels 2.2 and rear wheels 3.3 are facing in the straight-ahead direction. In other words, the flowchart in FIG. 7 explains means for improving the accuracy of mode switching when each wheel has detected its midpoint position.

That is, the detection range of each steering angle sensor 50, 51 is expressed in voltage from 0 to 5■, and the straight-ahead position is set at 2°5. 6 The range of the midpoint position is variable in proportion to the operating speed. When the operating speed of the steering handle 38 is high, the range of the midpoint position is wide < (2,3V
~2゜7■), and when the operating speed of the steering wheel 38 is slow, the range is narrow < (2,45~2゜55).
(2) Automatically changes the detection range of the midpoint so that the timing of mode switching is accurate. The operating speed is determined, and the midpoint range can be changed into three levels based on the magnitude relationship between the speed V and the set values α and β.

Next, the relationship between the steering wheel 38 and the steering angle display device will be explained based on FIG.

In this figure, a liquid crystal display section 62 is provided in a meter panel 61, and the steering state of the front and rear wheels 2, 2, 3, 3 is displayed on the liquid crystal. Each steering angle sensor 50.51
By inputting the value to the control unit 55 and displaying it on a dot matrix liquid crystal display, the operator can visually recognize the situation, and work adaptability can be greatly improved.

Note that the liquid crystal display section may be provided not in the meter panel 61 but in the center of the steering post 38. In this case, if a fixed part that does not rotate is provided at the center of the steering wheel 38, and a liquid crystal display board is provided on this fixed part to display the steering status of the front and rear wheels, the wheels can be moved without any trouble while operating the steering handle 38. The cutting angle can be accurately determined.

FIG. 9 shows a more simplified configuration in which the steering mode is displayed in the center of the steering handle 38. When the mode changeover switch 46 is operated to set a mode, one of the LEDs 65 corresponding to each mode lights up.

[Effects of the Invention] As described above, in the power vehicle 1 configured such that the front and rear wheels 2 and 3 can be independently steered, the front wheels 2 or the rear wheels 3, which are fixed in a straight-ahead state, are rotated at a predetermined angle from the straight-ahead direction. Since the controller 55 is provided with a control means 55 that issues an alarm when the steering wheel deviates from the above range, the operator can know before setting the next mode that there has been a leak of hydraulic fluid from the hydraulic actuator that moves the steering wheels. As a result, the operator can take immediate action, improving safety.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, in which Figure 1 is a side view of the tractor, Figure 2 is a plan view illustrating the principle of operation, and Figure 3 is a side view of the tractor.
The figure is a table showing the excitation relationship between each mode and the solenoid, Figure 4 is a block diagram, Figure 5 is a flowchart, Figures 6 and 7.
The figure is a control flowchart of the improved device, and FIGS. 8 and 9 are front views of the handle portion. 2, 2 3, 3 18, 19 25, 28 A, B, C Code explanation Tractor front wheel rear wheel hydraulic cylinder Solenoid valve mode changeover switch Control means solenoid

Claims (1)

[Claims] 1) In a power vehicle 1 configured so that the front and rear wheels 2 and 3 can be independently steered, a control means that issues an alarm when the front wheels 2 or the rear wheels 3, which are fixed in a straight-ahead state, deviate from the straight-ahead direction by more than a predetermined angle. 55. A four-wheel steering device for a power vehicle, characterized in that a four-wheel steering device is provided with the following.