JPH0741664Y2 - Steering force control device for power steering device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] According to the present invention, an appropriate steering force can be obtained by variably controlling a steering assist force by a power steering device according to various traveling conditions of a vehicle such as a vehicle speed. The present invention relates to an improvement of a steering force control device configured as described above.

[Conventional technology]

In a power steering apparatus that is a source of a steering assist force for reducing a steering wheel operation force (steering force) of an automobile, the magnitude of the steering assist force is different from the steering torque accompanying the steering operation.
It is desirable that the control be variably controlled according to various traveling conditions of the vehicle such as the vehicle speed and the steering angle so that the steering force according to the traveling state of the vehicle can be obtained. That is, it is necessary to enable a light steering operation when the vehicle is stopped or traveling at a low speed, and to secure stability when traveling straight ahead by giving the steering wheel a certain degree of rigidity when traveling at a high speed. As means for performing such steering force control, the input and output shafts of the power steering apparatus are relatively rotated or restrained by a reaction force piston that selectively restrains them according to the magnitude of reaction force hydraulic pressure. A steering force control mechanism that uses a hydraulic reaction force device or a steering valve that controls the amount of pressure oil supplied to the left and right chambers of the power cylinder that is the source of steering assist force by a control valve such as a variable throttle. It is known that such a thing is provided. In particular, the latter one can be expected to have advantages such as a relatively simple structure as compared with the former one and the miniaturization and compactness of the entire apparatus.

As a conventional steering force control device of this type, for example,
As shown in JP-A-57-79070, a short-circuit passage for short-circuiting the left and right chambers of the power cylinder is provided, and a variable throttle with a solenoid valve that selectively connects and disconnects this passage according to the vehicle speed is provided. It was known that it was composed of. However, in this way, the left and right chambers of the power cylinder are selectively short-circuited by solenoid valves according to the vehicle speed, reducing the amount of pressure oil fed to the power cylinder,
In the configuration that controls the steering force by reducing the generation of the steering assist force, the hydraulic pressure obtained by the rotary flow passage switching valve or the like that performs the flow passage switching according to the steering operation in the power steering device,
Since the valve is forcibly short-circuited on the downstream side, the pressure difference between the left and right chambers of the power cylinder changes depending on the flow rate of the short circuit. In particular, the above-mentioned short-circuited flow rate changes depending on the steering speed, and this steering speed, that is, the operation speed of the steering wheel is not constant, resulting in the problem that the steering force control characteristic is not stable. It was something that would end up.

Further, as a steering force control device of this type, for example, in Japanese Patent Laid-Open No. 63-166658, a four-way switching valve for switching a flow path between a pump, a tank and a power cylinder left and right chambers is connected in an annular shape. The first variable throttle that interlocks with the steering operation is provided in each flow path of the hydraulic bridge circuit consisting of four flow paths, and the power cylinder left and right chambers are connected between the connection points on one diagonal line. However, in the rotary type flow path switching valve having a structure in which the other diagonal connection point is connected to a pump and a tank, at least one of the flow paths having the first variable throttle is used for steering operation. There is also known a configuration in which a flow path is connected in parallel by a series circuit of a second variable throttle that responds to the above and an externally controlled variable throttle controlled by an external signal other than the steering operation. With such a configuration, there is no problem such as a change in the differential pressure between the left and right chambers of the power cylinder as in the above-described conventional example.
It was possible to obtain stable characteristics without being affected by the steering speed and the like.

[Problems to be solved by the device]

However, in the above-described conventional device, the second flow path, which has the variable throttle of the hydraulic bridge circuit including the rotary flow path switching valve, is controlled in response to the steering operation together with the first variable throttle. Since the flow paths having the variable throttles are connected in parallel, in the power steering device that constitutes the above-described rotary flow path switching valve, the positions are shifted in the axial direction between the input and output shafts, and extra passage grooves and It is necessary to construct the second variable throttle by arranging the passage holes in parallel, which complicates the valve processing and the like, the overall shape of the device becomes large in the axial direction, etc. The power steering device with a switching valve cannot be used as it is,
It lacked versatility and was a problem in practical use. Further, in the above-described device configuration, in addition to the second variable aperture controlled in response to the steering operation, the external variable aperture controlled in accordance with the external signal is connected in series to configure the external variable aperture. It was necessary to attach a control valve to the side of the device and connect them by communication through a passage hole or the like. Further, in this conventional device, the pressure oil flowing through the control valve is recirculated to the tank side through the second variable throttle provided in parallel with the flow path switching valve. This is a complicated structure that poses a problem in terms of valve workability. Considering these points, it is possible to share parts with conventional products, and some measure that can control the required steering force. It is hoped that

[Means for Solving the Problems]

In order to meet the above-mentioned demand, the steering force control device of the power steering device according to the present invention is configured such that the pressure oil from the pump is selectively fed according to the steering operation from the flow passage switching valve to the power cylinder left and right chambers. In the middle of the hydraulic passage leading to, the respective return passages that directly connect to the tank without passing through the passage switching valve are branched and provided, and the respective return passages are opened and closed according to the traveling conditions of the vehicle. It is equipped with a steering control valve that is equipped with left and right variable throttles and controls the variability synchronously.

[Action]

According to the present invention, the return path to the tank branched from the middle of the hydraulic path between the flow path switching valve, which is a four-way switching valve in the power steering apparatus, and the power cylinder left and right chambers is used as a vehicle under external conditions. By variably controlling the left and right variable throttles by the steering force control valve that opens and closes according to various running conditions,
By controlling the hydraulic pressure to the left and right chambers of the power cylinder, it is possible to perform appropriate steering force control according to various running conditions.

〔Example〕

1 to 3 show an embodiment of a steering force control device for a power steering device according to the present invention. In these figures, first, a schematic configuration of the power steering main body portion in the power steering apparatus indicated by reference numeral 10 and the steering force control apparatus indicated by reference numeral 11 will be briefly described with reference to FIG.
Reference numeral 12 is an input shaft (stub shaft) connected to the steering handle side (not shown), and 13 is a rack 15 which is connected to the left end side of the input shaft 12 via a torsion bar 14 and constitutes a steering link mechanism (not shown). An output shaft (pinion shaft) having a meshing pinion, both shafts 12 and 13 are appropriately rotated in the steering direction. Where these two axes 12,13
As is well known, a fail-safe mechanism for connecting the two shafts by rotating and contacting each other by a predetermined angle or more is provided between them.

In addition, the body 10a that constitutes the power steering main body
In both shafts 12 and 13 described above, a rotor 17 and a sleeve that form a well-known rotary flow path switching valve 16 that serves as a four-way switching valve.
18 are provided integrally with each other, and their relative rotational displacements cause an oil pump P, an oil tank T and a power cylinder PS.
The left and right chambers C1 and C2 are configured to perform flow path switching. Here, such a flow path switching valve 16 is constituted by a hydraulic bridge circuit in which four flow paths 16a to 16d are annularly connected, as shown in FIG. 1 and FIG. Variable throttles 20a, 20b; 21a, 21b are provided which are opened and closed by a relative rotational displacement generated between the output shafts 12 and 13 by the steering operation with respect to the handle 19, and these variable throttles 20a, 21b; 21a, 21b is controlled to be opened and closed by the steering torque and steering angle by steering operation in the left and right directions, so that a predetermined pressure is applied to one of the left and right chambers C1 and C2 of the power cylinder connected via the hydraulic passages 22 and 23. Is supplied with the hydraulic pressure having the above, and the other is connected to the tank T side and opened. The structure and operation of the power steering body 10 and the rotary flow path switching valve 16 are well known in the art, and detailed description thereof will be omitted.

Now, according to the present invention, in the power steering apparatus including the power steering main body portion 10 including the rotary flow path switching valve 16 which is the above-described four-way switching valve, the steering force control device 11 includes: As is apparent from FIGS. 1 to 3, the power cylinder left and right chambers C1 and C from the flow path switching valve 16 that selectively feeds the pressure oil from the pump P in accordance with the steering operation.
2 in the middle of the hydraulic passages 22, 23
Reflux passages 31 and 32, which are directly connected to the tank T without passing through the passage switching valve 16, are provided to be branched, and the respective return passages 31 and 32 are used for running conditions of the vehicle (the vehicle speed sensor 33 in this embodiment). It is characterized in that a steering force control valve 30 is provided, which is provided with left and right variable throttles 35 and 36 which are opened and closed by a controller 34 in response to a vehicle speed signal from the vehicle) and which variably controls them synchronously.

Then, according to such a configuration, the flow path switching valve 16 and the power cylinder left, which are four-way switching valves in the power steering apparatus,
The return passages 31 and 32 to the tank T branched from the middle of the hydraulic passages 22 and 23 between the right chambers C1 and C2 are opened and closed according to various running conditions (vehicle speed in this embodiment) of the vehicle which are external conditions. By controlling the hydraulic pressure to the left and right chambers C1 and C2 of the power cylinder by variably controlling the variable throttles 35 and 36 by the steering force control valve 30, the proper displacement-hydraulic characteristics according to various running conditions can be obtained. The required steering force control can be performed. In particular, according to the present invention, the flow path switching valve 16 in the power steering main body portion 10 of the conventionally known power steering apparatus can be changed in any way (for example, special passage groove processing for its constituent parts). Instead, it is used as it is, and the return passages 31 and 32 from the switching valve 16 to the left and right chambers C1 and C2 of the cylinder to the tank T are branched off. In addition, a unitized steering force control valve 30 controlled by an external signal is additionally provided. And, since it is sufficient to connect the steering force control valve 30 and the flow path switching valve 16 attached in this way by forming a simple passage hole to be the above-mentioned return passages 31, 32, Since it can be used in common with the parts, and in particular, a part that is problematic in terms of workability such as the main body side valve 16 can be shared, the merits in practical use are great.

Here, the steering force control valve 30 constituting the above-described steering force control device 11 will be briefly described. In the present embodiment, the controller 34 is driven by a solenoid 40 that is energized by a signal from a vehicle speed sensor 33. A sleeve 42, which is constituted by a spool valve, is provided by being fitted in a hole 41 formed in a part of the body 10a, and a spool 43 slidably provided in an axial hole of the sleeve 42. The spool 43 is fitted and provided, and includes a movable shaft member 44 that is reciprocally driven by the solenoid 40 to control the position of the spool 43 in the axial direction, and on the axis line of the movable member 44,
A passage hole 45 is formed so as to open to the tip side. In the hole portion 41, passage holes (31, 32) connected to the cylinder left side of the flow path switching valve 16 and the annular grooves (22, 23) reaching the right chambers C1, C2 are opened, Against this, the sleeve 4
On the outer peripheral portion of 2, the annular grooves 42a and 42b are formed, and further, an annular groove 42c which is connected to the passage hole 46 toward the tank T is formed side by side in the axial direction. And each of these annular grooves 4
2a, 42b, 42c face the inside of the sleeve 42 through the passage holes 42d, 42e, 42f, respectively, of which the return passages 31, 32 side passage hole 4
The 2d and 42e are selectively communicated with the annular grooves 43a and 43b on the spool 43 side, and are connected at their chamfer portions to the annular grooves 42g and 42h forming the variable throttles 35 and 36. Further, the annular grooves 43a, 43b of the spool 43 are connected to the passage hole 45 via passage holes 47a, 47b formed in the spool 43 and the movable shaft member 44 to form the return passages 31, 32. There is. Further, the passage hole 45 is connected to the reflux side passage hole 46 to the tank T side through the internal space of the sleeve 42 which is the low pressure side,
The pressure oil that is recirculated after passing through the variable throttles 35 and 36 is recirculated to the tank T side.

Further, according to the steering force control valve 30 having such a configuration, a part of the pressure oil from the hydraulic passages 22 and 23 leading to the cylinder left and right chambers C1 and C2 can be opened and closed at the moving position of the spool 43. It can be recirculated to the tank T side according to the opening area of the throttles 35, 36, which changes the hydraulic pressure to the left and right chambers C1, C2 of the cylinder to change the steering force according to the driving conditions such as vehicle speed. You can control. In this spool valve configuration, the left and right variable throttles 35, 36 are both opened and closed by the movement of the spool 43 by the solenoid 40, but one of them is connected to the tank T side in the steering system. Even if the variable throttle is opened / closed, there is no influence on the recirculation side of the left and right chambers C1, C2 of the cylinder.

In such a configuration, the steering force control valve 30 as a spool valve driven and controlled by the solenoid 40 is
As shown in FIG. 4, the left and right variable diaphragms 35, 36 are controlled so as to increase the opening area by increasing the vehicle speed. Note that FIG. 2 and the like show the positional relationship of each part at the time of high speed running with the maximum opening area. For example, when the vehicle is stopped or running at low speed, the opening areas of these left and right variable diaphragms 35, 36 are The spool 43 is located on the left side in the drawing so as to be the minimum. Then, as the vehicle speed increases, the spool 43 moves to the right side in the figure, and controls the opening areas of the left and right variable apertures 35 and 36 to have the characteristics shown in FIG.

Further, as described above, the steering force control valve 30 partially recirculates the magnitude of the hydraulic pressure supplied to the left and right chambers C1 and C2 of the cylinder in accordance with the vehicle speed, so that the stationary steering valve can be operated as shown in FIG. It is possible to obtain the characteristic of the hydraulic pressure P with respect to the steering angle θ during high speed, medium speed running and high speed running, and as a result, the output to the steered wheels with respect to the input torque during steering as shown in FIG. The characteristics can be obtained. It should be noted that FIG. 6 shows the size at the time of manual steering, and the size relationship can be easily understood by comparing with the output in each state.

Further, FIGS. 7 (a), (b) and (c) to FIGS. 9 (a), (b) and (c) show vehicle speed conditions such as stationary steering, medium speed traveling and high speed traveling. The opening area characteristic for the valve displacement θB of the flow path switching valve 16 in the power steering device when changed ({a in each figure)}, the combination of the flow path switching valve 16 and the steering force control valve 30 according to the present invention. The opening area characteristic for valve displacement θB due to the combination ((b) in each figure) and the hydraulic characteristic for valve displacement θB due to the combination of both valves 16 and 30 ((c) in each figure) are respectively shown.

Here, the characteristics of the opening area S with respect to the valve displacement θB in the flow path switching valve 16 shown in (a) of each figure are all the same characteristic curve. When the steering force control valve 30 that characterizes the present invention is combined with the characteristics on the side of the flow path switching valve 16,
As is clear from (b) in the drawings, the steering force control valve 30 does not change during stationary operation, but as the vehicle speed increases, as shown in FIGS. 8 (b) and 9 (b).
The opening area (indicated by diagonal lines in each figure) is added, and as a result, as shown in (c) in each figure, the hydraulic characteristics for the valve displacement θB of both valves 16 and 30 are obtained. It is possible to obtain the required steering force characteristics. That is, the steering assist force is the largest when stationary,
In addition to enabling a light steering operation, the steering assist force is reduced during high-speed traveling, and the steering handle has a sense of rigidity, which enables stable steering operation.
Particularly, according to the present invention, the steering force control valve 30 can change the relief point (power assist limit point) during stationary steering, medium speed traveling, and high speed traveling, which is appropriate and stable. The steering force control described above can be set in a required state.

Here, according to the steering force control device 11 according to the present invention having the above-described configuration, the hydraulic pressure sent to the power cylinder left and right chambers C1 and C2 is controlled by the flow rate switching valve 16 and the flow rate driven according to the vehicle speed. It is controlled by the steering force control valve 30 that functions as a control valve and is not affected by the steering speed and the like, and stable steering force control can be performed. Also, the two variable throttles 35, 36 that make up the steering force control valve 30 are controlled to open and close in synchronization, but when turning right or left, either one is used for steering force control, and the other is used on the tank return side. The variable diaphragms 35 and 36 function separately, and one of them does not affect the other.

It should be noted that the present invention is not limited to the structure of the embodiment described above, and the shape, structure, etc. of each part can be freely modified or changed,
Various modifications are conceivable. For example, in the above-described embodiment, the steering force control valve 30 characterizing the present invention is described as a spool valve that is driven and controlled by the direct acting solenoid 40 in response to a signal from the controller 34. The present invention is not limited to this, and a rotary valve using a stepping motor or the like as a drive source may be used, or a valve operated by pilot pressure may be used, and as a control element of such a valve 30,
The control is not limited to the vehicle speed described above, and may be controlled by taking into consideration various driving conditions of the vehicle, such as steering force and steering angle, and the road surface condition. It is recommended that the steering operation can be performed with a sufficient steering force.

[Effect of device]

As described above, according to the steering force control device of the power steering device according to the present invention, the power cylinder left and right chambers are switched from the flow path switching valve that selectively feeds the pressure oil from the pump according to the steering operation. In the middle of the hydraulic passage leading to, the respective return passages that directly connect to the tank without passing through the passage switching valve are branched and provided, and the respective return passages are opened and closed according to the traveling conditions of the vehicle. Since a steering force control valve equipped with left and right variable throttles for synchronously variably controlling these is attached, the flow path switching valve in the power steering device that has been generally used from the past can be used as it is, despite the simple structure. A steering force control valve that can be used and is controlled by external conditions is used as a return path to the tank that branches off from the middle of the hydraulic passage between the flow switching valve that is a four-way switching valve and the power cylinder left and right chambers. By providing each with a variable throttle that opens and closes, the hydraulic pressure to the left and right chambers of the power cylinder is controlled, and appropriate displacement-hydraulic characteristics according to various running conditions are obtained to achieve the required steering force control. In addition, the structure is simple, workability is excellent, and there are various practically excellent effects such as downsizing of the entire device and cost reduction.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a steering force control device for a power steering device according to the present invention, and FIG. 2 is an enlarged cross-sectional view of a main part showing a specific structure of the steering force control device characterizing the present invention. Figure,
FIG. 3 is a schematic cross-sectional view showing a case where the steering force control device in FIG. 2 is attached to a power steering device, and FIG. 4 is a characteristic diagram showing an opening area of a variable throttle with respect to a vehicle speed by a steering force control valve. Fig. 6 and Fig. 6 show hydraulic characteristics with respect to steering angle,
FIG. 7 (a), (b), (c) through FIG. 9 (a), (b), which is a characteristic diagram showing output characteristics with respect to input torque.
(C) is an opening area characteristic with respect to the valve displacement of the flow passage switching valve in the power steering device during stationary steering, medium speed traveling, and high speed traveling, the flow passage switching valve and the steering force control valve according to the present invention. It is a characteristic view which shows the opening area characteristic with respect to the valve displacement by combination, and the hydraulic characteristic with respect to the valve displacement by the combination of these both valves, respectively. 10 ... Power steering main body in power steering device, 11 ... Steering force control device, 12, 13 ... Input / output shaft, 14
...... Torsion bar, 16 …… Rotary flow path switching valve, 16a to 1
6d ... flow path, 17 ... rotor, 18 ... sleeve, 19 ... steering wheel, 20a, 20b; 21a, 21b ... variable throttle, 22, 23 ...
… Hydraulic passage, 30 …… Steering force control valve, 31,32 …… Return path, 33 …… Vehicle speed sensor, 34 …… Controller, 35,36…
... left, right variable throttle, 40 ... solenoid, 42 ... sleeve, 43 ... spool, 44 ... movable shaft member, 45 ... passage hole, 46 ... passage hole to tank, P ... pump, T ......
Tank, PS …… Power cylinder, C1, C2 …… Cylinder left, right chamber.

Claims (1)

[Scope of utility model registration request] 1. A power steering apparatus comprising a flow path switching valve for switching a flow path between a pump, a tank and a power cylinder left and right chambers in accordance with a steering operation. In the middle of the left and right hydraulic passages that connect the left and right chambers of the power cylinder, these hydraulic passages are branched and provided with return passages that are directly connected to the tank without passing through the passage switching valve. Steering of a power steering device, which is provided with left and right variable throttles for opening and closing the return path according to the traveling conditions of the vehicle and additionally provided with a steering force control valve for synchronously variably controlling these variable throttles. Force control device.