JP2516336B2 - Power steering used in vehicles - Google Patents

Description

Description: FIELD OF THE INVENTION This invention relates to power steering used in vehicles, and more particularly to road friction sensitive power steering.

BACKGROUND ART In general, speed-sensitive power steering has been widely used in automobiles, but with this type of power steering, the road surface becomes slippery at a curved portion of a road, as when frozen. If the car rushed into the slippery road surface, there was too much steering.

Further, when such a speed-sensitive power steering is used in a truck or a bus, the steering force is changed according to the loaded weight, and the feeling of operation and the driving safety are different.

Further, JP-A-59-124462 and JP-A-60-5007.
Although the power steering was disclosed in the first publication,
The valve structure and the hydraulic circuit are complicated and the manufacturing cost is high. Moreover, in the power steering disclosed in Japanese Patent Laid-Open No. 59-118572, the sliding friction coefficient (μ) of the road surface is
Optimal steering force corresponding to is not obtained.

An object of the present invention is to detect the sliding friction coefficient (μ) of a road surface without being affected by changes in the load weight and obtain an optimum steering force corresponding to the sliding friction coefficient (μ) of the road surface. A power steering used in a vehicle that has so-called road friction sensitivity characteristics and load sensitivity characteristics, and can be easily controlled to simplify the entire apparatus and reduce manufacturing costs. Is provided.

SUMMARY OF THE INVENTION AND CONTENTS OF CLAIMED INVENTION ACCORDING TO THE PROBLEM In connection with the above-mentioned problems, a power steering used in a vehicle of the present invention includes a power cylinder having a pair of cylinder chambers, an oil pump, and a pair of cylinders. It is configured in a hydraulic circuit including a control valve with a reaction chamber and an oil reservoir, where a reaction force compensation passage connects the pair of reaction chambers of the control valve to each other,
An electromagnetic two-way control valve is arranged in the reaction force compensation passage, a pressure sensor is arranged in the supply side hydraulic pipe of the hydraulic circuit immediately upstream of the control valve, and the controller preliminarily controls steering resistance, vehicle speed, And the optimum value of the hydraulic pressure corresponding to the steering amount are input, and signals are input from the pressure sensor, the vehicle speed sensor, and the steering amount sensor for calculation, and the calculated value is compared to the optimum value for the hydraulic reaction force. Determines the output current obtained at the optimum value of hydraulic pressure, and causes the output current to flow through the solenoid coil of the electromagnetic two-way control valve to close the electromagnetic two-way control valve, and the sliding friction coefficient of the road surface. Corresponding to (μ), the pressure sensor senses the oil pressure corresponding to the steering load (steering resistance) determined by the product of the sliding friction coefficient (μ) and the load on the road surface. Converted hydraulic pressure to electric signal,
The electric signal is given to the controller, the controller opens and closes the electromagnetic two-way control valve, the reaction chambers are communicated with each other, and the reaction chambers are cut off from each other to obtain an optimum steering force.

Specific examples of the power steering used in the vehicle of the present invention will be described below with reference to the drawings.

The figure schematically shows a tenth embodiment of the power steering used in the vehicle of the invention applied to a truck.

This power steering 10 is a linkage type embodiment for steering the front wheels.
Arm (not shown), drag link (not shown),
Link lever (not shown), compensating
Rod (not shown), pitman arm (not shown), steering gear box (not shown), steering shaft (not shown), steering wheel (not shown), pair of cylinder chambers 34, Power cylinder 11 with 35, oil pump 12, pair of reaction chambers 4
Control valve 13 with 6,47, flow control valve 14, oil reservoir 15, reaction force compensating passage 16 for connecting a pair of reaction force chambers 46, 47 of the control valve 13 to each other, and its reaction force Comprising an electromagnetic two-way control valve 17 arranged in the compensation passage 16, a pressure sensor 18, a controller 19, a vehicle speed sensor 20, and a steering amount sensor 21, and corresponding to the sliding friction coefficient (μ) of the road surface, The pressure sensor 18 detects the hydraulic pressure corresponding to the steering load (steering resistance) determined by the product of the sliding friction coefficient (μ) and the load on the road surface, and the vehicle speed sensor 20 detects the vehicle speed. The steering amount is detected by the steering amount sensor 21, and an optimum steering force corresponding to the slip friction coefficient (μ) of the road surface, the vehicle speed, and the steering amount can be obtained. It has so-called road friction sensitivity characteristics, load sensitivity characteristics, and speed sensitivity characteristics.

As described above, the power steering 10 is composed of a portion configured in the link mechanism and a portion configured in the hydraulic circuit. The portion configured in the hydraulic circuit will be described in detail below.・ The cylinder 11 incorporates the valve body 38 of its control valve 13, and the power cylinder port of its control valve 13.
Power cylinder body with cylinder bore 31 communicating with oil ports 36,37 connected to 43,44,45
30 and a pair of cylinder chambers 34, 35 fitted in the cylinder bore 31 so as to be able to slide back and forth and connected corresponding to the oil ports 36, 37 in the cylinder bore 31. Power piston 32 and one end fixed to the power piston 32, the power cylinder body 30
It is composed of a piston rod 33 that extends so that the other end side can be put in and taken out from the outside of the power cylinder body 30 at its link lever and its piston rod.
33 are rotatably connected to a chassis frame (not shown).

In addition, the power cylinder 11 has a cylinder chamber 34
Oil passage 36 connecting the oil port 36 of the control valve 13 with the power cylinder port 44 of the control valve 13, and the oil port 37 of the cylinder chamber 35 and the power cylinder ports 43, 45 of the control valve 13 It is provided with connecting paths 63 and 64 for connecting with.

With its power cylinder 11 so configured,
The movement of the power cylinder body 30 is the link
It is transmitted to the front wheels via a lever, a drag link and a knuckle arm, so that its power cylinder 11 steers it.

The oil pump 12 is driven by an internal combustion engine (not shown) mounted on the truck,
To supply pressure oil to the cylinder 11, the supply side hydraulic surface of its hydraulic circuit where the oil reservoir 15 is connected to the pump port 41 of its control valve 13 is arranged in the pipe 60, and the oil The oil in the reservoir 15 is sucked up and pressurized to obtain a discharge amount of the pressure oil that is almost proportional to the rotation speed of the internal combustion engine. Of course, the oil pump 12 is manufactured in the same structure as the oil pump used for the existing power steering, and the description thereof will be omitted.

The control valve 13 is configured as a hydraulic reaction force type spool valve and is incorporated in the power cylinder body 30 of the power cylinder 11, and connects the spool shaft 70 to the compensating rod. , And that Pitman arm, steering
The steering wheel is valved through the gearbox and the steering shaft, and in its hydraulic circuit the power cylinder 11
The oil pump 12 and the oil reservoir 15 are connected to the pipes, that is, the supply-side hydraulic pipe 60, the return-side hydraulic pipe 61, and the communication passages 62, 63, 64, and from the oil pump 12. The discharged pressure oil is direction-controlled and supplied to the power cylinder 11, and the power
Directionally control the pressure oil that has been used in the cylinder 11
The pressure oil is returned to the oil reservoir 15 on the suction side of the pump 12.

The control valve 13 has a valve body 38.
And a control valve spool 40 that is reciprocally slidably arranged in the spool bore 39 of the valve body 38.
Including its control valve spool 40 with its spool shaft 70, compensating rod, Bitman arm, steering gear box, and its steering through the steering shaft, its spool with wheels. Sliding back and forth in the bore 39, the pair of cylinder chambers 34, 3 of the power cylinder 11
Switch the pressure oil flowing to 5, and along with the switching operation,
The pressure oil returned from the cylinder chambers 34, 35 to the oil reservoir 15 is directionally controlled.

The valve body 38 has a spool bore 39 formed therein having a predetermined inner diameter and a predetermined length, and the spool bore 39 is spaced on one side (upper side in the figure) at a predetermined distance. Three power cylinders that form a pump port 44 and a tank port 42 connected to each other and are separated from each other on the other side (lower side in the figure) at substantially equal intervals and are connected to their spool bores 39. -Forms ports 43, 44 and 45.

The pump port 41 is connected to the discharge side of the oil pump 12 via a supply side hydraulic pipe 60, and
The tank port 42 is connected to the oil reservoir 15 via the return side pressure pipe 61, and further, the power cylinder ports 44, 43, 45 are connected to the communication passages 62, 6
Cylinder chamber of its power cylinder 11 through 3,64 34,35
It is connected to the.

Furthermore, the valve body 38 has its spool bore
In 39, its control valve spool 40
Forming a pair of reaction force ports 48, 49 which are used to connect the reaction force chambers 46, 47 respectively formed on both sides thereof with each other.

The control valve spool 40 is provided reciprocally slidably in the spool bore 39 with bores 50, 51 opened at both end faces, and as such,
When fitted in the bore 39, the bores 50, 51 are
In the spool bore 39, the control
A pair of reaction chambers 4 formed on both sides of the valve spool 40.
Increase the volume of 6,47.

Further, when the control valve spool 40 slides back and forth in the spool bore 39, it supplies pressure oil to one of the reaction force chambers 46 and 47 depending on the sliding direction of the control valve spool 40. A pair of reaction force communication ports 52 and 53 are provided.

In particular, the control valve spool 40 has spool grooves 54, 55, 56 formed on the outer peripheral surface thereof in relation to the reaction force communication ports 52, 53 at predetermined axial intervals.

Of course, in the spool grooves 55, 56, reaction force communication ports 52, 53 communicating with the reaction force chambers 46, 47 are opened correspondingly, and as a result, the reaction force communication ports 52, 53 are The position of the spool grooves 55, 56 within the spool bore 39 associated with the movement of the control valve spool 40 causes the power cylinder ports 44, 45 to move into the reaction chamber 46,
47, and its spool groove 54 connects pump port 41 to power cylinder port 43.

Furthermore, the control valve spool 40 is
In response to the steering operation, the valve body 38 is penetrated so as to be slid back and forth in the spool bore 39, and at the tip of the spool shaft 70 extended in the spool bore 39. It connects almost the center of the spool (spool center). Of course, the spool shaft 70 has its rear end connected to the compensating rod.

The flow control valve 14 is a hydraulic pipe that connects the control valve 13 to the oil pump 12 and the oil reservoir 15 in the hydraulic circuit, that is, the supply side hydraulic pipe 60 and the return side hydraulic pipe.
It is located at 61.

The flow control valve 14 includes a pump port 57 connected to the discharge side of the oil pump 12, a control valve port 58 connected to the pump port 41 side of the control valve 13, and A casing provided with a return port 59 connected to the suction side of the oil pump 12, and an oil return control arranged in the casing so as to be reciprocally slidable.
With a structure including a spool, the flow rate of the hydraulic pressure sent to the pump port 57 side is adjusted, a predetermined flow rate is sent to the control valve port 58 side, and the surplus flow rate of the pressure oil is returned to it. -It returns from the port 59 to the oil reservoir 15 via the control valve bypass 65.

Of course, the flow control valve 14 is manufactured in the same structure as the flow cotton roll valve used in the existing power steering, and the detailed description of the structure will be omitted.

The reaction force compensation passage 16 has one end connected to the reaction force port 48 and the other end connected to the reaction force port 49, and their reaction chambers 46, 4 are connected.
7 are connected to each other, according to the movement of the control valve spool 40 in the control valve 13,
The pressure oil can be moved between the reaction force chambers 46 and 47.

The electromagnetic two-way control valve 17 is disposed in the reaction force compensation passage 16, electrically connects a solenoid coil 66 to the controller 19 which will be described in detail later, and opens and closes with an output current from the controller 19. Then, the pressure oil is circulated between the reaction force chambers 46 and 47, and is blocked. That is, in the electromagnetic two-way control valve 17, the reaction force chambers 46 and 47 are communicated with each other, the reaction force chambers 46 and 47 are communicated with each other, and the reaction force chamber 4 is
It operates to stop the flow of pressure oil between 6 and 47. The operation is performed according to the steering load (steering resistance), the vehicle speed and the steering amount to make the steering wheel lighter or heavier. To do.

The pressure sensor 18 has a structure for converting pressure into an electric signal as usual, and between the control valve 13 and the flow control valve 14,
The controller 19 detects the hydraulic pressure corresponding to the steering load (steering resistance) determined by the product of the sliding friction coefficient (μ) and the load on the supply side hydraulic pipe 60 and converts it into an electric signal. And makes the controller 19 control the current flowing through the solenoid coil 66 of the electromagnetic two-way control valve 17.

The pressure sensor 18 is
For example, when a road enters a frozen road, the road resistance suddenly decreases at that moment, the hydraulic pressure in the power steering decreases accordingly, the steering wheel suddenly becomes lighter, and then the wheel cuts sharply. The control valve 13 senses a decrease in the hydraulic pressure and is preferably arranged in the supply hydraulic pipe 60 on the pump port 41 side of the control valve 13.

The controller 19 electrically connects the input side to the pressure sensor 18, the vehicle speed sensor 20, and the steering amount sensor 21, respectively, and electrically connects the solenoid coil 66 of the electromagnetic two-way control valve 17 to the output side. The solenoid two-way control valve 17 is opened and closed by controlling the output current flowing through the solenoid coil 66. Of course, the controller 19
It is composed of an input and output circuit, a memory circuit, an arithmetic circuit, a control circuit and a power supply circuit, and the power supply circuit shares a battery (not shown) of the truck.

In particular, this controller 19 has an optimum hydraulic pressure corresponding to a steering load (steering resistance), a vehicle speed, and a steering amount (steering wheel angle) determined by a product of a road friction coefficient (μ) and a load in relation to the truck. A signal from the pressure sensor 18 for sensing the hydraulic pressure of the supply side hydraulic pipe corresponding to the steering load (steering resistance), the vehicle speed, and the steering amount, which has been inputted in advance, and the vehicle speed sensor. The signals from 20 and the steering amount sensor 21 are input and calculated, the calculated value is compared with the optimum value, and the reaction chamber of the control valve 13 is set in a state where the hydraulic reaction force is obtained with the hydraulic pressure of the optimum value. An output current is applied to the solenoid coil 66 of the electromagnetic two-way control valve 17 so that 46, 47 can be maintained, and the electromagnetic two-way control valve 17 is controlled by changes in its steering load (steering resistance), vehicle speed, and steering amount. Opening and closing Created as soon as possible so as to correspond to, or communicating the reaction chamber 46, 47 of the control valve 13 to each other, also by blocking, steering
Keep the wheel in its predecessor, lighter or heavier.

In this way, the controller 19 inputs the pressure of the pressure oil flowing to the pump port 41 of the controller valve 13 from the pressure sensor 18, so that this power
In the steering wheel 10, the steering force adapted to the steering load (steering resistance), the vehicle speed, and the steering amount can be obtained without being affected by the change in the loaded weight.

The vehicle speed sensor 20 detects the traveling speed of the truck and is arranged on the output shaft of a transmission (not shown) mounted on the truck.

The steering amount sensor 21 is a rotation sensor that detects a rotation speed, a rotation direction, and a rotation angle of the steering shaft, and is arranged around the steering shaft at a predetermined position of the steering shaft. ing.

Further, the vehicle speed sensor 20 and the steering amount sensor 21 are
As with its pressure sensor 18, its controller 19
Are electrically connected to the respective input circuits.

The operation of the power steering 10 described above will now be described with reference to the running condition of the truck. Since the internal combustion engine is operating, the oil pump 12 is driven and the oil The flow rate of the pressure oil discharged from the pump 12 is adjusted by the flow control valve 14, and a predetermined flow rate of the pressure oil flows through the supply-side hydraulic pipe 60, so that the pump of the control valve 13
Sent to port 41.

The pressure oil sent to the pump port 41 flows from the tank port 42 through the return hydraulic pipe 61 when the spool 40 is in the neutral position as shown in the figure. -Returned to the reservoir 15.

At the same time, the controller 19 inputs signals from the pressure sensor 18, the vehicle speed sensor 20, and the steering amount sensor 21, and determines the output current flowing through the solenoid coil 66 of the electromagnetic two-way control valve 17, Steering load (steering resistance) determined by the product of road friction coefficient (μ) and load,
The reaction force chambers 46 and 47 of the control valve 13 are ready to obtain a hydraulic reaction force suitable for the vehicle speed and steering amount.

Now, when the truck plunges into a curved road surface where the road surface is frozen, at that moment, the road surface resistance suddenly decreases, and along with that, toward the pump port 41 of the control valve 13, Supply side hydraulic piping 60
Since the pressure drops in the pressure oil flowing inside, the pressure sensor 18 senses the oil pressure reduced corresponding to the steering load (steering resistance) determined by the product of the road friction coefficient (μ) and the load. Then, it is converted into an electric signal and given to the controller 19, and the controller 19 receives the inputted electric signal,
And an output signal for the electromagnetic two-way control valve 17, that is, a calculation based on electric signals from the vehicle speed sensor 20 and the steering amount sensor 21 and a comparison of the calculated value with an optimum value of the hydraulic pressure input in advance. Determine the output current.

The output current flows from the controller 19 to the solenoid coil 66 of the electromagnetic two-way control valve 17, and the electromagnetic two
The directional control valve 17 is closed as soon as possible.

As a result, the reaction chamber 46,4 of the control valve 13
7 are cut off from each other, the flow of pressure oil is stopped between the reaction force chambers 46, 47, and the reaction force chambers 46, 47 of the control valve 13 are in a state where the hydraulic reaction force is obtained with the hydraulic pressure of the optimum value. The steering wheel is maintained in a state just before the track enters the frozen curve point on the road surface, in other words, in a heavy state.

Therefore, even if the truck rushes into a curved portion of the road where the road surface is frozen, the steering wheel is not instantly lightened but is kept heavy,
Then, the steering wheel is prevented from being cut off too much.

In addition, when the truck rushes into a straight place where the road surface is frozen on the road, in this case also, similarly to the case where the truck rushes into a frozen road surface, the power steering 10 Operate.

Further, with respect to the vehicle speed and the steering amount, the power steering 10 operates in the same manner as the above case.

The power steering 10 described above was described as steering the front wheels of the truck, but in a vehicle, if the rear wheels are configured in a steered manner, the power steering 10 will be It can be applied to the steering of rear wheels that are frozen so as to be swingable at both ends.

As is apparent from the specific embodiments of the present invention described above with reference to the drawings, those skilled in the art to which the present invention pertains have ordinary knowledge in that It is readily embodied in another embodiment that derives from the nature and substance of the invention and is objectively admitted to incorporate them. Of course, the subject matter of the present invention is commensurate with the subject of the invention and is essential for the establishment of the invention.

Benefits of the Invention As will be understood from the above, the power steering used in the vehicle of the present invention includes a power cylinder having a pair of cylinder chambers, an oil pump, a control valve having a pair of reaction chambers, and An oil reservoir is included in the hydraulic circuit, and a reaction force compensation passage connects the pair of reaction force chambers of the control valve to each other, and an electromagnetic two-way control valve is disposed in the reaction force compensation passage.
A pressure sensor is located upstream of the control valve in the supply side hydraulic line of the hydraulic circuit, and the controller inputs the optimum value of the hydraulic pressure corresponding to the steering resistance, the vehicle speed, and the steering amount in advance, and , Signals from the pressure sensor, vehicle speed sensor, and steering amount sensor are input and calculated, and the calculated value is compared to the optimum value to determine the output current at which the hydraulic reaction force is obtained at the optimum hydraulic pressure,
Then, since the output current is passed through the solenoid coil of the electromagnetic two-way control valve to close the electromagnetic two-way control valve, in the power steering used in the vehicle of the present invention, the sliding friction coefficient (μ) of the road surface is The steering force that matches the sliding friction coefficient (μ) of the road surface, which is perceived as the steering load (steering resistance) that is determined by the product of the load and the load, is obtained, that is, the road surface friction and load sensitivity characteristics are given. When the vehicle rushes into a place where the surface becomes slippery like frozen, the steering wheel
The steering wheel is maintained in a state just before entering the slippery place, the steering wheel is not instantly lightened, but is kept in a heavy state, the steering wheel is prevented from being cut too much, and it adapts to the vehicle speed. The steering force is controlled, that is, the speed-sensitive characteristic is given, the operation feeling and steering stability are kept constant regardless of the empty and loaded condition, and the driver is freed from physical and mental fatigue due to steering. In particular, the electromagnetic two-way control valve functions as a reaction force adjusting valve for restricting and adjusting the reaction force, and the road surface friction sensitive characteristic and the load sensitive characteristic are given by a simple control means, so that the entire apparatus is simplified, And the rise in production costs is suppressed,
Accordingly, the applicability for large vehicles is improved, and as a result, it is very useful and practical for large trucks and buses.

[Brief description of drawings]

The figure is a schematic diagram showing a specific example of the power steering used in the vehicle of the present invention applied to a truck. 11 …… power cylinder, 12 …… oil pump, 13…
… Control valve, 14… Flow control valve, 15… Oil reservoir, 16… Reaction force compensation passage, 17… Electromagnetic two-way control valve, 18… Pressure sensor, 19…
… Controller, 20 …… Vehicle speed sensor, 21 …… Steering amount sensor, 60 …… Supply side hydraulic piping, 61 …… Return side hydraulic piping, 6
2,63,64 ... Communication passage.

Claims (1)

(57) [Claims] Claim: What is claimed is: 1. A power cylinder comprising a pair of cylinder chambers, an oil pump, a control valve comprising a pair of reaction force chambers, and a hydraulic circuit including an oil reservoir for steering, in which steering force compensation is performed. A passage connects the pair of reaction chambers of the control valve to each other, an electromagnetic two-way control valve is arranged in the reaction force compensation passage, and a pressure sensor supplies the hydraulic circuit immediately upstream of the control valve. It is arranged in the side hydraulic pipe, and the controller inputs the optimum value of the hydraulic pressure corresponding to the steering resistance, the vehicle speed, and the steering amount in advance, and inputs the signals from the pressure sensor, the vehicle speed sensor, and the steering amount sensor. Compute the calculated value and compare the calculated value to the optimum value to determine the output current that the hydraulic reaction force can obtain at the optimum hydraulic pressure. A power steering used in a vehicle characterized by flowing a current through a solenoid coil of the electromagnetic two-way control valve to close the electromagnetic two-way control valve.