JPH0457548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a steering control device for various vehicles such as agricultural tractors.

<Prior art> A steering device for a vehicle such as an agricultural tractor includes a steering cylinder controlled by a control valve linked to a steering handle, and the steering cylinder operates a steering wheel, for example, a front wheel. There is a power steering device that looks like this.

However, this has the disadvantage that the control valve has a complicated structure, which increases manufacturing costs.

Therefore, it has been considered that a solenoid valve is used, the amount of operation of the handle is converted into an electric signal, and the electric signal is used to drive the solenoid valve.

<Problems to be Solved by the Invention> When a control circuit for a steering cylinder is configured using such a solenoid valve, the operating speed of the steering cylinder is always constant because the solenoid valve normally opens and closes at a constant flow rate. It becomes constant. Therefore, when the front wheels operate up to a predetermined turning angle and the solenoid valve closes, the front wheels abruptly stop steering operation, resulting in a large shock. There have been cases of overruns.

In order to prevent such shocks when the steering operation stops, it is possible to limit the flow rate of the solenoid valve, but in that case, the operation speed of the steering cylinder becomes slower, so the overall steering operation is reduced. When the running speed is high, the turning radius becomes extremely large, making it impractical.

<Means for Solving the Problems> In view of these conventional problems, the present invention provides a method for quickly and smoothly performing steering operations while preventing the occurrence of shocks when steering operations are stopped. It is characterized by the fact that it generates a command signal for steering in a vehicle steering control device that operates steering wheels by a steering cylinder controlled by a solenoid valve. A command means for detecting the turning angle of the steering wheel; A direction determining means for determining the steering direction from a command signal of the command means and a detection signal of the detection means; A command signal of the command means and a detection signal of the detection means The deviation from the steering target is determined from the deviation signal, and depending on the magnitude of the deviation signal, the opening degree of the electromagnetic valve on the steering direction side determined by the direction determining means changes approximately in proportion to the magnitude of the deviation signal. The present invention also includes a driving means for driving the electromagnetic valve.

<Function> When the handle 14 is operated during steering, the handle potentiometer 16 operates and generates a predetermined command signal. On the other hand, potentiometers 17 and 18 detect the current turning angle of the steering wheel and generate detection signals thereof. Therefore, the deviation from the steering target is determined from the command signal and the detection signal together with the reference signal, and depending on the magnitude of the deviation signal, the solenoid valves 19 and 22 are driven so that the opening changes approximately proportionally thereto. The steering cylinders 7 and 11 are operated. Therefore, the steering cylinders 7 and 11 operate quickly when the difference between the command signal and the detection signal is large, and as the steering wheel approaches the target, the operating speed slows down, causing a shock when the steering operation stops. Quick and smooth steering is performed without any friction.

<Embodiments> The present invention will be described in detail below with reference to the illustrated embodiments. In FIG. 2, reference numeral 1 denotes a two-axle, four-wheel type tractor, which has a pair of left and right front wheels 2 and rear wheels 3. The front wheels 2 are rotatably supported at both left and right ends of a center-suspended front axle 4 around a king pin 5, and the pair of left and right front wheels 2 are interlocked and connected to a front wheel steering cylinder 7 via a knuckle arm 6 at the upper end of the king pin 5. Therefore, the front wheels 2 can be steered around the king pin 5 by the front wheel side steering 7. rear wheel 3
are rotatably supported around the king pin 9 at the outer ends of the rear axle 8 on both sides of the rear of the tractor 1, and similarly to the front wheels 2, are rotated around the king pin 9 by the rear wheel side steering cylinder 11 via the knuckle arm 10. Steering operation is possible. The main bodies of the steering cylinders 7 and 11 are supported by the vehicle body of the tractor 1 so as not to be laterally movable, and both left and right ends of the piston rods are connected to the respective knuckle arms 6 and 10. Also front wheel 2
The tractor 1 is driven in the forward and reverse directions through a power transmission system such as the front axle 4, and the rear wheels 3 are driven in the forward and reverse directions through a power transmission system such as the rear axle 8. It is possible to move forward and backward. A clutch is interposed in each power transmission system, and either two-wheel drive or four-wheel drive can be selected by engaging and disengaging the clutches.

12 is a bonnet that covers the engine, etc.; 13 is a driver's seat; and 14 is a steering handle, which is supported by a handle shaft 15 at the rear of the bonnet 12. Reference numeral 16 denotes a handle potentiometer constituting a steering command means, which is attached to the fixed side so as to be interlocked with the handle shaft 15, and generates a command signal for steering according to the amount of operation of the handle 14. ing. 17 is a front wheel potentiometer constituting a detection means for detecting the turning angle of the front wheel 3;
A rear wheel potentiometer 18 constitutes a detection means for detecting the turning angle of the rear wheel 3, and these are both attached to the upper end sides of the king pins 5 and 9.

FIG. 3 shows the hydraulic circuit for the steering cylinders 7 and 11. Reference numeral 19 is an open/close type front wheel side solenoid valve that controls the front wheel steering cylinder 7, and a left solenoid 2 for left steering.
0 and a right solenoid 21 for right steering. 2
Reference numeral 2 designates an opening/closing type rear wheel solenoid valve that controls the rear wheel steering cylinder 11, and has a left solenoid 23 and a right solenoid 24 like the front wheel solenoid valve 19. 2
5 is an engine, and 26 is a hydraulic pump driven by the engine 25. 27 is a priority valve that preferentially supplies a constant flow rate of hydraulic oil from the hydraulic pump 26 to the electromagnetic valves 19 and 22 side, and supplies the surplus flow rate to a hydraulic device 28 provided at the front and rear of the tractor 1 for lifting and lowering the working machine. It is configured to send to. 29,
30 is a relief valve.

FIG. 1 shows the control circuit of the solenoid valves 19 and 22,
It has two systems: a front wheel control system and a rear wheel control system. 3
Reference numeral 1 denotes a steering mode selection means, which includes a forward/reverse selector switch 32 for selecting forward or reverse, a steering/straight selector switch 33 for selecting between steering and straight ahead, and two-wheel steering and four-wheel steering. A two-wheel/four-wheel selector switch 34 selects between parallel steering and V-shaped steering, a parallel/V-shaped selector switch 35 selects between automatic steering and manual steering, and automatic/manual selector switch 35 selects between automatic steering and manual steering. Changeover switch 3
It has 6. 37 is a first multiplexer, 38 is a second multiplexer, and 39 is a third multiplexer, all of which are for analog use. The first multiplexer 37 controls the steering wheel potentiometer 1 when steering (off) is selected with the changeover switch 33.
A command signal is output from 6, and when straight travel (on) is selected, a reference signal (1/2V) is output from the N terminal. Second multiplexer 38
outputs the signal from the first multiplexer 37 when the parallel steering (off) is selected with the changeover switch 35, and outputs the signal from the first multiplexer 37 when the parallel steering (on) is selected with the changeover switch 35;
It is designed to output a signal starting from 0. Third
The multiplexer 39 outputs a reference signal (1/2V) from the N terminal when two-wheel steering (off) is selected with the changeover switch 34, and outputs a reference signal (1/2V) from the N terminal when four-wheel steering is selected.
The signal from the multiplexer 38 is output.

The inverter 40 inverts the command signal or reference signal (1/2V) from the first multiplexer 37 in proportion to the reference signal (1/2V) at the N terminal.

Reference numeral 41 denotes an addition/comparison section on the front wheel side, which adds the signal from the inverting section 40 or the third multiplexer 39 and the detection signal from the front wheel potentiometer 17 on the input side, and compares the added signal with the reference signal at the N terminal. Then, the deviation of the front wheels 2 from the steering target is determined. 42 is an addition comparison section on the rear wheel side, and an inversion section 40
Alternatively, the signal from the third multiplexer 39 and the detection signal from the rear wheel potentiometer 18 are added on the input side, and the added signal is compared with the reference signal at the N terminal to determine the deviation from the steering target of the rear wheel 3. People are starting to look for it.

43 to 46 are the first to fourth analog switches,
When forward is selected with the changeover switch 32, the first analog switch 43 sends the signal from the inverter 40 to the addition/comparison section 41, and the third analog switch 45 sends the signal from the third multiplexer 39 to the addition/comparison section 42. When reverse movement is selected with the switch 32, the second analog switch 44 adds the signal from the third multiplexer 39 to the comparator 41, and the fourth analog switch 46 adds the signal from the inverter 40 to the comparator 42.
It is now being sent to each of them.

Reference numeral 47 denotes direction determining means on the front wheel side, and comparison section 48,
49, AND circuits 50, 51 and comparison units 48, 4
The comparator 48 determines right steering when the deviation signal from the addition and comparison section 41 is larger than the upper reference value, and is smaller than the lower reference value. At this time, the comparator 49 determines left steering, and when the changeover switch 36 is automatic (off), respective signals are output from the AND circuits 50 and 51. Reference numeral 53 denotes direction determining means for the rear wheel, which includes comparison units 54 and 55 and AND circuits 56 and 5.
7, a variable resistor 58, etc., and an addition/comparison section 42
Similar to the direction determining means 47 on the front wheel side, the direction determining means 47 performs a direction determining operation based on the deviation signal from the front wheel.

Reference numeral 59 denotes a drive means, which includes a triangular wave signal transmitter 60 that generates a triangular wave signal, a front wheel drive section 61, and a rear wheel drive section 62. The front wheel side drive section 61 is for driving the solenoids 20 and 21 of the front wheel side solenoid valve 19, and is composed of switching elements 63 and 64, comparing sections 65 and 66, analog switches 67 and 68, and a reversing section 69. The comparison section 66 compares the triangular wave signal from the triangular wave signal transmitting section 60 with the deviation signal from the addition comparison section 41, outputs an output signal when the triangular wave signal is smaller than the deviation signal, and outputs an output signal via the analog switch 68 to the switching element. 64. Therefore, since the deviation signal changes sequentially during the steering operation, the switching element 64 repeats on/off operations with a pulse width corresponding to the change, causing a constant value of excitation current to flow through the right solenoid 21. The analog switch 68 is configured to send the signal from the comparator 66 to the switching element 64 when a right steering signal is received from the AND circuit 50. The inverter 69 compares and inverts the deviation signal from the addition/comparison unit 41 based on the reference signal at the N terminal. comparison section 65,
Analog switch 67, switching element 63
is constructed in the same manner as the comparison section 66, analog switch 68, and switching element 64.

The rear wheel side drive section 62 is for driving the solenoids 23 and 24 of the rear wheel side solenoid valve 22, and similarly to the front wheel side drive section 61, the switching elements 70 and 7
1. Comparing sections 72, 73, analog switch 74,
75, and an inversion section 76.

77 is a manual control means, which is a front wheel steering switch 7;
8, a non-travel steering switch 79, a V-shaped steering switch 80, a rear wheel steering switch 81, and left/right changeover switches 82 to 85 connected in series to these.

Each solenoid 20, 21, 23, 24 is provided with a resistor so that current flows through each solenoid 20, 21, 23, 24 due to the back electromotive force generated when the switching elements 63, 64, 70, 71 are turned off. Diodes are connected in parallel.

Next, the operation of the above configuration will be explained. As shown in FIG. 4, the steering modes include a straight-ahead mode, a front two-wheel steering mode, a parallel steering mode, a V-shaped steering mode, and a rear two-wheel mode. That is, the straight-ahead mode is a state in which the front and rear wheels 2 and 3 are both traveling straight, the front two-wheel steering mode is a state in which only the front wheel 2 is steered left and right, and the parallel steering mode is a state in which both the front and rear wheels 2 and 3 are both steered. A state in which the driver can steer in the same direction and drive diagonally forward. In the V-shaped steering mode, the front and rear wheels 2 and 3 are steered in opposite directions. In the rear two-wheel steering mode, only the rear wheel 3 is left and right. These are the states in which the vehicle is steered. These modes are selected by operating the respective changeover switches 32 to 36 of the steering mode selection means 31 in accordance with the procedure shown in FIG.

Therefore, when steering, a predetermined steering mode is selected from each of the changeover switches 32 to 36 of the steering mode selection means 31, and then the steering wheel 14 is operated in a predetermined direction.

Now, we will explain the operation when operating the steering wheel 14 to the right from a state where the front wheels are in the front two-wheel steering mode during forward travel and the front wheels are facing left. Since the front wheel 2 is facing leftward, the front wheel potentiometer 17 detects its turning angle and outputs a detection signal smaller than 1/2V as shown in FIG. 6A. Therefore, when the handle 14 is operated to the right by a predetermined angle, the handle potentiometer 16 is operated to 1/2 as shown in FIG. 6B.
Outputs a command signal greater than 2V. This command signal is sent to the inverter 4 via the first multiplexer 37.
0 and the reference signal (1/2V) of its N terminal
After being inverted as shown in FIG.
sent to. Then, the detection signal indicating the current turning angle of the front wheel 2 and the inverted command signal are added on the input side of the addition and comparison section 41, and the added signal is compared with the reference signal of the N terminal in the addition and comparison section 41. The steering wheel is then reversed as shown in FIG. 6D, and a deviation signal from the steering target, which is the comparison result, is output. Then, the deviation signal is input to the direction determining means 47, and the comparing section 48,
At 49, the direction is determined. In this case, since the handle 14 is being operated to the right, the comparing section 48
A signal is output from the drive means 59 and sent to the analog switch 68 on the right side of the driving means 59 via the AND circuit 50.

On the other hand, the triangular wave transmitter 60 transmits a triangular wave signal E as shown in FIG. Since these signals are compared by the comparator 66, when the triangular wave signal is smaller than the deviation signal, a signal is output from the comparator 66, the switching element 64 is turned on via the analog switch 68, and the right solenoid is turned on. 21
is excited, and the front wheel side solenoid valve 19 is switched to the right. Therefore, the front wheel steering cylinder 11 operates in the right steering direction, and the front wheels 2 start steering operation in the right direction. Then, the detection signal of the front wheel potentiometer 17 gradually increases in conjunction with the steering operation of the front wheels 2, so that the deviation signal F from the addition/comparison section 41 increases with the steering operation as shown in FIG. It gradually becomes smaller. Therefore, the comparison section 66 outputs the deviation signal F.
and the triangular wave signal E, the width of the output signal gradually becomes smaller, and the period during which the switching element 64 is turned on by pulse width modulation, that is, the pulse width of the excitation current that drives the right solenoid 21 is determined as shown in FIG. It becomes smaller like G in In other words, the larger the difference between the command signal of the handle potentiometer 16 and the detection signal of the front wheel potentiometer 17, the larger the deviation signal, the wider the pulse width, and the longer the time period during which the excitation current of the right solenoid 21 flows. Therefore, the opening degree of the front wheel side electromagnetic valve 19 is large, the front wheel side steering cylinder 7 operates quickly, and the cutting speed of the front wheel 2 becomes faster. Then, as the front wheel 2 approaches the target value, the pulse width becomes smaller, and the right solenoid 21
As the time during which the excitation current flows becomes smaller,
The opening degree of the front wheel side solenoid valve 19 gradually decreases, and the steering operation of the front wheel 2 stops when the front wheel 2 reaches the target position. Therefore, it is possible to prevent a shock from occurring when the steering operation is stopped, and also to quickly and smoothly steer the vehicle to a predetermined turning angle without overrun. During steering operation, the switching element 64
Even during the off period, current continues to flow due to the back electromotive force of the solenoid 21, so current always flows through the right solenoid 21, which is also effective in terms of power consumption.

In parallel steering mode, the front wheel system operates as described above, so handle potentiometer 1
The command signal from 6 is sent to the first to
A detection signal from the rear wheel potentiometer 18 that detects the turning angle of the rear wheel 3 is sent to the addition comparison section 42 via the third multiplexer 37, 38, 39, and the detection signal is sent to the addition comparison section 42. 42,
The direction determining means 53 and the driving means 59 operate in the same manner, and the rear wheel steering cylinder 11 steers the rear wheels 3 in the same direction as the front wheels 2.

In the V-shaped steering mode, in the rear wheel system, the command signal inverted by the inverter 40 is sent to the addition/comparison unit 42 via the second and third multiplexers 38 and 39, so it is different from the parallel steering mode. In contrast, the rear wheel steering cylinder 11 operates, so that the front wheels 2 are steered to the right and the rear wheels 3 are steered to the left.

In the straight running mode, the command signal from the handlebar potentiometer 6 is cut off by the first multiplexer 37, and a neutral reference signal is input from the N terminal, so that all parts are controlled until the front and rear wheels 2 and 3 are facing straight. It operates and the front and rear wheels 2 and 3 are directed straight.

If the automatic control system fails, etc., by operating each switch of the manual control means 77, the solenoid valves 19,
22 is switched, and a predetermined steering can be performed.

In the embodiment, simple open/close type solenoid valves 19 and 22 are illustrated, but the addition and comparison section 4
A comparison operation type solenoid valve may be driven by the deviation signals of 1 and 42.

Further, although the embodiment uses an analog control method, a digital control method can be used as well.

Further, the steering type may be only one of a front two-wheel steering mode, a parallel steering mode, a V-shaped steering mode, and a rear two-wheel steering mode,
The mode is not limited to one that can be switched to each mode as in the embodiment.

Potentiometers 16, 17, and 18 are the simplest command means and detection means, but other means can be used as long as they can convert mechanical movements into electrical signals.

Furthermore, when only one of the front and rear wheels 2 and 3 is being steered, the deviation may be determined by simply comparing the command signal and the detection signal.

The potentiometer 16 may be directly operated by hand by the operator, and does not necessarily need to be linked to the handle 14.

<Effects of the Invention> According to the present invention, the deviation of the steering target is determined from the command signal and the detection signal, and the opening degree of the solenoid valve is set approximately proportional to the magnitude of the deviation signal. Since the steering operation is controlled by the steering wheel, it is possible to perform the steering operation quickly and smoothly while preventing the shock that conventionally occurs when the steering operation is stopped, and there is no overrun, so its practical value is extremely high. It's large.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is an electric circuit diagram, FIG. 2 is a plan view of the tractor, FIG. 3 is a hydraulic circuit diagram, FIG. 4 is an explanatory diagram of the steering mode, and FIG. 5 6 is a flowchart of steering mode selection, FIG. 6 is an operation explanatory diagram, and FIG. 7 is a signal waveform diagram. 1...Tractor, 2...Front wheel, 3...Rear wheel, 7
...Front wheel steering cylinder, 11...Rear wheel steering cylinder, 16...Handle potentiometer (command means), 17...Front wheel potentiometer (detection means), 18...Rear wheel potentiometer (detection means), 19, 22... solenoid valve, 41, 42... addition comparison section, 47, 53... direction determination means, 59...
...driving means, 60... triangular wave transmitter.

Claims (1)

[Scope of Claims] 1. In a vehicle steering control device in which a steering wheel is actuated by a steering cylinder controlled by a solenoid valve, a command means for generating a command signal for steering; Detection means for detecting the turning angle of the wheel; Direction determination means for determining the steering direction from the command signal of the command means and the detection signal of the detection means; The steering target is determined from the command signal of the command means and the detection signal of the detection means. the solenoid valve is adjusted so that the opening degree of the solenoid valve on the steering direction side determined by the direction determining means changes approximately in proportion to the magnitude of the deviation signal. A steering control device for a vehicle, comprising a driving means for driving the vehicle. 2. The vehicle steering control device according to claim 1, wherein the solenoid valve is an open/close type that operates when a predetermined value of excitation current is passed through a solenoid. 3. A patent claim characterized in that the driving means includes a triangular wave signal transmitting section that transmits a triangular wave signal, a comparing section that compares the deviation signal and the triangular wave signal, and a switching element that is driven by the comparison signal from the comparing section. A steering control device for a vehicle according to item 1 or 2. 4. The vehicle steering control device according to claim 1, wherein the command means is a potentiometer. 5. The vehicle steering control device according to claim 1, wherein the detection means is a potentiometer.