JPH0218167A - Power steering device for vehicle - Google Patents

Abstract

PURPOSE:To allow steering resistance to be increased at the time of high speed running, and thereby prevent meandering operations by controlling a relief valve provided for a hydraulic circuit for power steering in such a way that relief pressure is lowered roughly in reverse proportion to engine revolutions when the high speed position of a running speed change mechanism is detected. CONSTITUTION:When a handle is rotationally actuated, the switch-over valve 57 of a controller 13 is switched from its neutral condition, and concurrently a gyrator 58 is rotated so as to let the specified quantity of working oil is supplied to a power cylinder 7 from a hydraulic pump 54 through the switch-over valve 57 and the gyrotor 58 so that front wheels are steered by the power. In this case, a relief valve 55 which can assume duty control while a controlling solenoid 59 is attached, is connected with the delivery side circuit of the hydraulic pump 54. And the solenoid 59 allows a solenoid drive circuit 99 to assume duty control in such a way that relief pressure is lowered roughly in reverse proportion to engine revolutions detected by a speed detector 98 when it is detected by a high speed position detector 88 that a main speed change mechanism is in a high speed position.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a power steering device for a vehicle.

(Prior Art) Some conventional tractors are equipped with a power steering device (for example, Japanese Utility Model Application No. 60-24671).
. In this case, there is an advantage that the steering handle can be operated easily.

(Problem to be solved by the invention) However, in the conventional case, the rotational resistance of the steering wheel is small and constant regardless of whether the vehicle speed is high or low, so when driving at high speed, the steering wheel is taken, resulting in meandering driving. , there was a problem that safe high-speed driving was no longer possible.

(Means for Solving the Problem) The technical means of the present invention for solving this technical problem is that an electromagnetic relief valve 55 capable of controlling the relief pressure is provided in the hydraulic circuit of the power steering, and the travel transmission mechanism 64 A high-speed position detector 88 that detects a high-speed position is provided, and an engine speed detector 98 that detects the rotational speed of the engine 2.
is provided, and when the high-speed position detector 88 detects the high-speed position,
The electromagnetic relief valve 5 is configured such that the relief pressure decreases in substantially inverse proportion to the rotational speed detected by the engine speed detector 98.
The point is that a control means for controlling 5 is provided.

(Function) When the traveling speed mechanism 64 is set to the high speed position, the relief pressure of the relief valve 55 decreases in substantially inverse proportion to the rotational speed of the engine 2. Therefore, when a vehicle such as a tractor is driven at high speed, the power steering hydraulic circuit is in a relief state, and therefore, for example, hydraulic oil from the hydraulic pump 54 shown in FIG. 2 is not supplied to the controller 13.
The gerotor 58 of the controller 13 functions as a hydraulic pump, and the rotational resistance of the steering handle 24 is quite large.

(Embodiment) The present invention will be described in detail below with reference to the illustrated embodiment.
The figure shows an agricultural tractor equipped with an independent cabin. In FIG. 4, 1 is a tractor body, which is composed of an engine 2, a transmission case 3, and the like. 4 is a front axle frame attached to the engine 2, and 5 is a front axle case, which is suspended on the front axle frame 4 via a center bin, and front wheels 6 are provided at both left and right ends of this front axle case 5. .

7 is a power cylinder for front wheel steering, which is attached to the rear of the front axle case 5. 11 is a radiator, 12
is the bonnet that covers the second engine. 13 is a fully hydraulic steering controller for controlling the cylinder 7, and is connected to the cylinder 7 via hoses 14 and 15.

16 is a rear wheel, and 17 is a rear wheel fender. 18 is an independent cabin, which has doors 19 on both the left and right sides.

The cabin 18 has a driver's seat 21 on the internal floor plate 20, and an instrument panel 23 and a steering wheel 2 on the front wall plate 22 side.
4, each of which is removably mounted on the vehicle body l from above via a mount rubber or the like. The handle 24 is supported by a handle post 26 via a handle shaft 25, and the handle post 26 is attached to a support frame 27 within the instrument panel 23 via a vibration isolator. The handle shaft 25 is operatively connected to an input shaft 33 of the controller 13 via a joint 28, a shaft 29, a joint 30, a shaft 31, and a joint 32, as shown in FIG.

A bulging wall 35 is formed on the rear surface of the front wall plate 22, and a support frame 27 having a gutter-shaped cross section is welded to the bulging wall 35, and covers the joint 28 and the shaft 29, and the shaft 29 has a spherical bearing 3.
6 and is supported by the bulging wall 3'5.

Further, as shown in FIG. 5, the shaft 29 is supported by ball bearings 41 at two locations in the axial direction to form an assembly, and the lower side of the support frame 27 is closed with a bottom plate 42, and the wall 27A
It is made by stacking upright plates 43 and attaching them with bolts 44,
Thereby, noise (engine sound, etc.) that enters the cabin 18 through the hole 22A of the front wall plate 22 and the hole 35A of the bulging wall 35 is shielded.

The shaft 29 is rotatably supported by a ball bearing 41 via a pair of ball bearings 45, and the outer ring of the ball bearing 45 is entirely covered with a cushioning material 46 made of rubber or the like as shown in FIG. A buffer material 46 is inserted between the ball bearing 45 and the ball bearing 41 to prevent the vibrations of the engine 2 from being transmitted to the handle 24 side. In addition, in FIG. 6, 47 is a retaining ring fitted inside the ball bearing 41.

FIG. 1 shows a simplified plan view of a fully hydraulic power steering system installed in the tractor, and FIG. 2 shows a hydraulic circuit thereof. In the figure, reference numeral 51 denotes a steering arm for the front wheels 6, which is interlocked and connected to an operating arm 53 via a tie rod 52, and when the operating arm 53 is rotated by the power cylinder 7, both front axles 6 are rotated. It is designed to be steered.

54 is a hydraulic pump, which is rotationally driven by the engine 2. The hydraulic oil from the hydraulic pump 54 is supplied to the electromagnetic relief valve 55.
, are supplied to the power cylinder 7 via the steering controller 13.

The controller 13 controls the power cylinder 7 by operating the handle 24, and includes a check valve 56 and a 6-bottom 3.
It consists of a position switching valve 57 and a gerotor 58.

Then, when the handle 24 is rotated, the controller 1
The switching valve 57 of No. 3 is switched from the neutral position shown in FIG. 1, and the gerotor 58 is rotated.
A desired amount of hydraulic fluid from the hydraulic pump 54 is supplied to the power cylinder 7 via the switching valve 57 and the gerotor 58 of the controller 13, the power cylinder 7 is operated, and the front wheels are steered by a desired angle by a light operation of the handle 24. It is designed to be operated in the opposite direction.

The front wheel electromagnetic relief valve 55 is an electromagnetic proportional relief valve having a control solenoid 59, and is configured so that the relief pressure decreases in inverse proportion to the value of the current flowing through the control solenoid 59.

60 is an oil tank, and 61 is a magnetic filter.

FIG. 7 shows the transmission system of the tractor, and in the same figure,
62 is a main clutch, the power of the engine 2 is transmitted to the propulsion shaft 63 via this clutch 62, and the power of this propulsion shaft 63 is transmitted to the rear wheels via a main transmission mechanism 64, a super reduction mechanism 65, and an auxiliary transmission mechanism 66. It is transmitted to the differential pinion shaft 67.

The drive system for the rear wheels 16 is connected to a rear axle 80 via a rear wheel differential W68 and a final reduction mechanism 69 from a rear wheel differential pinion shaft 67.
A rear wheel brake device 71 is arranged on the left and right output shafts 70 of the rear wheel differential device 68.

The drive system for the front wheels 6 transmits power from a rear wheel differential pinion shaft 67 to a power take-off shaft 75 outside the transmission case 3 through gears 72, 73, 7 (t-), and a front wheel differential pinion shaft directly connected to this power take-off shaft 75. 76 to the front axle 81 via the left and right differential output shaft 78 of the front wheel differential device 77 and the final reduction mechanism 79.
It is intended to be transmitted to

The main transmission mechanism 64 includes a main transmission lever 84 shown in FIG.
It can be switched to four forward speeds and one reverse speed.

That is, as shown in FIG. 8, the main shift lever 84 is connected to the main shift lever 84 via a shift rod 86 held movably back and forth by a shift cover 85 mounted on the transmission case 3, and a shift fork 87 that accompanies this shift rod 86. The gears of the main transmission mechanism 64 are operated by this, and thereby the speed can be changed between forward travel from the first speed to the fourth speed and back travel. A high-speed position detector 88 is provided so as to correspond to a shift fork 87 for switching the main transmission mechanism 64 to the fourth speed, and when the main transmission mechanism 64 fails to switch to the fourth speed, which is the highest speed. The high speed position detector 88 is pressed by the shift fork 87 to detect that the main transmission mechanism 64 is at the high speed position.

FIG. 9 shows the accelerator operation system of the tractor. In the figure, 91 is a fuel injection pump attached to the engine 2, and is provided with a speed adjustment lever 92 and an engine stop lever (not shown). The speed adjustment lever 92 is connected to a relay link 94 via an accelerator rod 93, and an accelerator pedal rod 95 is connected to the relay link 94, and a rod that transmits the movement of the hand accelerator lever (not shown) is also linked. These are connected together to form an accelerator operation system. A foot accelerator pedal 96 is connected to an accelerator pedal rod 95, and is supported by a step 97 of the tractor.

Reference numeral 98 denotes an engine speed detector constituted by a potentiometer or the like, which is attached to the rotating shaft portion of the speed adjustment lever 92 and configured to detect the opening degree of the slot of the speed adjustment lever 92 as a voltage signal.

FIG. 3 shows a block diagram of a control means for controlling the relief valve 55. In the figure, 101 is a solenoid drive circuit which inputs detection signals from the high speed position detector 88 and the engine speed detector 98. , when the high-speed position detector 88 is not detecting a high-speed position, no current is supplied to the solenoid 59 or a low current is supplied to maintain the relief pressure of the relief valve 55 at a constant high pressure, and the high-speed position detector 88 When 88 detects a high speed position, engine speed detector 9
A current proportional to the rotational speed of the engine 2 detected by 8 is applied to the solenoid 59, thereby reducing the relief pressure in approximately inverse proportion to the rotational speed of the relief valve 5.
5 is controlled.

In the embodiment described above, a potentiometer for detecting the slot opening of the speed adjustment lever 92 is used as the engine speed detector 98 for detecting the rotational speed of the engine 2, but instead of this, a potentiometer is used as shown by the chain line in FIG. The engine speed detector 98 is constituted by an engine rotation sensor that detects the rotation speed of the output shaft of the engine, and the high-speed position detector 8
8, the relief valve 55 may be controlled so that the relief pressure decreases in substantially inverse proportion to the rotational speed detected by the engine speed detector 98.

FIG. 10 shows another embodiment in which the relief valve 55 is constructed of an electromagnetic type whose duty can be controlled.
Due to the duty control, the relief pressure of the power steering hydraulic circuit is reduced in approximately inverse proportion to the rotational speed detected by the engine speed detector 98 when the high-speed position detector 88 detects the high-speed position. That is, when the high-speed position detector 88 does not detect a high-speed position, the power steering hydraulic circuit will not be relieved unless the duty ratio t/T of the relief valve 55 is held constant and the relief pressure becomes a constant high pressure. do not have. When the high-speed position detector 88 detects a high-speed position, the solenoid drive circuit 101 controls on/off the current flowing through the solenoid 59 to adjust the duty ratio t/T of the relief valve 55 to the rotational speed detected by the engine speed detector 98. , and the relief pressure of the relief valve 55 is lowered. In this case, the engine speed detector 98 is
A variable resistor or the like may be used to detect the opening degree of the slot of the speed adjustment lever 92 as shown in the figure, or a variable resistor or the like may be used to detect the rotation speed of the output shaft of the engine as shown by the chain line in Fig. 7. It may be configured by a sensor.

Further, in the above embodiment, a fully hydraulic type power steering is used, but instead of this, an integral type or a booster type power steering may be used.

Further, in the above embodiment, the high speed position detector 88 detects the high speed position of the main transmission mechanism 64, but instead of this, the high speed position of the illuminance speed mechanism 65 or the auxiliary transmission mechanism 66 is detected. Good too.

Further, in the embodiment, the relief valve 55 is the solenoid 5.
Instead of this, the relief pressure of the relief valve 55 decreases in inverse proportion to the current to the solenoid 59 or the duty ratio of the current flowing through the solenoid 59. In this case, the solenoid 59 may be configured to increase the relief pressure in inverse proportion to the rotational speed of the engine.
What is necessary is to lower the current to or the duty ratio.

(Effects of the Invention) According to the present invention, when the traveling transmission mechanism 64 is set to the high speed position, the relief pressure of the power steering hydraulic circuit can be lowered in approximately inverse proportion to the rotational speed of the engine 2. When the speed of the vehicle becomes high, the hydraulic circuit of the power steering is easily relieved, and the resistance of the steering handle 24 becomes large. This prevents the steering wheel from being taken off during high-speed driving, resulting in meandering driving, resulting in safer driving. The effect is significant.

[Brief explanation of the drawing]

1 to 9 show embodiments of the present invention, FIG. 1 is a simplified plan view of the power steering device, FIG. 2 is a hydraulic circuit diagram thereof, FIG. 3 is a block diagram of the control system, and FIG. 4 is a partially sectional side view of a tractor with a cabin, FIG. 5 is a side sectional view showing the shaft support structure, FIG. 6 is a side sectional view of the bearing part,
FIG. 7 is a diagram of the transmission system of the tractor, FIG. 8 is a sectional view of a portion of the main gear shift lever, and FIG. 9 is a perspective view of the accelerator operation system of the tractor. FIG. 1θ is a hydraulic circuit diagram of a power steering device showing another embodiment. 2.-engine, 55--electromagnetic relief valve, 64-
・-Main transmission mechanism, 88-・High speed position detector, 98-・Engine speed detector.

Claims (1)

[Claims] (1) The power steering hydraulic circuit is provided with an electromagnetic relief valve 55 that can control the relief pressure, and a high-speed position detector 88 that detects the high-speed position of the traveling transmission mechanism 64 and detects the rotational speed of the engine 2. An engine speed detector 98 is provided to control the electromagnetic relief valve 55 so that when the high-speed position detector 88 detects a high-speed position, the relief pressure decreases in approximately inverse proportion to the rotational speed detected by the engine speed detector 98. A power steering device for a vehicle, characterized in that it is provided with a control means.