JPS61257365A - Steering force control device in power steering device - Google Patents

Abstract

PURPOSE:To obtain a changing characteristic of manual torque which is suitable for any running condition, by providing a flow control valve whose opening degree is controlled in accordance with the speed of a vehicle and a flow control device whose opening degree is set in response to the running condition of the vehicle on, for example, a mountain road, in a reaction force control passage. CONSTITUTION:A first flow control valve 70 whose opening degree is controlled in accordance with the speed of a vehicle produces a pressure in a reaction force control passage 62 in accordance with the vehicle speed. This pressure is introduced into a reaction force mechanism 40 to change the assist force of a power cylinder 66. When the steering angle is made to be large, the pressure of a servo passage 61 rises, and accordingly, a part of working fluid in the passage 61 flows into the reaction force control passage 62 through a second flow control valve 80, and therefore, the pressure introduced into the reaction force mechanism rises to change the inclination of a manual torque assist force characteristic in the decreasing direction. At this time the opening degree of the second flow control valve 80 is controlled in accordance with the vehicle speed, and therefore, the manual torque assist force characteristic is also changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a steering force control device for a power steering device equipped with a reaction force mechanism that changes assist force in accordance with vehicle speed and the like.

[Prior art]

In the steering force control device of this type of power steering device, the working fluid pressure applied to the reaction force mechanism is lowered during low-speed running when an assisting force is required, and conversely, when running at high speeds where almost no assisting force is required, this working fluid pressure is lowered. The pressure is increasing. conventionally,
The working fluid pressure applied to this reaction force mechanism is controlled by a flow control valve or the like that operates based on a vehicle speed signal. As shown in Figure 4, the resulting "manual torque-assist force" characteristic only moves parallel to characteristic C during low speed driving, as shown by the two-dot chain line, during high speed driving; Therefore, when driving at high speeds, there was a problem in that even if the steering wheel was turned, there was little change in manual torque, making it impossible to feel the steering angle.

[Problem that the invention seeks to solve]

In order to solve this problem, a communication path (communication path 63 in the embodiment shown in FIG.
A steering force control device with a fixed throttle has been developed. According to this, when the steering wheel steering angle becomes large and the pressure in the servo valve passage increases, the working fluid flows into the reaction force control passage through the fixed throttle, increasing the pressure applied to the reaction force mechanism, and this is large when driving at high speeds, so the ``manual torque - assist force'' is particularly large when driving at high speeds.
The slope of the characteristics can be reduced. As a result, appropriate changes in manual torque can be obtained even when driving at high speeds, and a sense of steering angle can also be obtained.

However, according to such technology, it is possible to change the "manual torque-assist force" characteristic between high speed and low speed, but if the vehicle speed is the same, the driving condition W3 of the car (for example, driving on a mountain road and driving in a city) ) is different, the characteristics cannot be changed, so there is a problem in that the manual torque required for each driving condition cannot be obtained. The present invention attempts to solve such problems.

[Means for solving problems]

For this purpose, in the steering force control device for a power steering device according to the present invention, as shown in the attached drawings, the power cylinder 66 is actuated based on the relative rotation of the input shaft 23 and the output shaft 21 to generate an assist force. In a steering force control device for a power steering device that includes a servo valve 30 that controls supply and discharge of fluid, and a reaction force mechanism 40 that changes the assist force according to vehicle speed, etc., the working fluid from the supply pump 50 is controlled by the servo valve 30. Valve device 55.5 that divides the flow into the valve passage 61 and the reaction force control passage 62
3, and a reaction force control passage 62 branching from the valve device 55.53 is provided with a first flow rate control valve 70.70A whose opening degree is controlled according to the vehicle speed, and a first flow rate control valve 70. The servo valve passage 61 that supplies the servo valve 30 and the reaction force control passage 62 are communicated by a communication passage 63, and the communication passage 63 has a second opening whose opening degree is set in response to the driving condition such as on a mountain road. The present invention is characterized in that a flow rate control valve 80 is provided to introduce the working fluid pressure generated in the reaction force control passage 62 into the reaction force mechanism 40.

[Effect]

A pressure control passage 62 to which a predetermined flow rate of working fluid is supplied by a first flow control valve 70 whose opening degree is controlled according to vehicle speed.
A pressure is generated depending on the vehicle speed, and this pressure is applied to the reaction force mechanism 40.
is introduced to change the assist force of the power cylinder 66. As the steering angle increases, the pressure in the servo valve passage 61 increases, and a portion of the working fluid in the passage 61 flows into the reaction force control passage 62 through the second flow control valve 80, causing a reaction. The pressure introduced into the force mechanism 40 increases, changing the slope of the "manual torque-assist force" characteristic in a decreasing direction. Since the opening degree of the second flow rate control valve 80 is controlled depending on the running state of the vehicle, the "manual torque-assist force" characteristic also changes depending on the running state of the vehicle.

〔Effect of the invention〕

As described above, according to the present invention, "
Since the "manual torque - assist force" characteristic changes, it is possible to obtain the change characteristics of the manual torque through various driving conditions such as mountain road driving and city driving.

〔Example〕

The first embodiment will be explained below with reference to FIGS. 1 to 8. As shown in FIG. 1, a metering orifice 52 and a bypass valve 53 are provided in a discharge passage 51 of a supply pump 50 such as a vane pump driven by an automobile engine. The control spool 53a of the bypass valve 53 operates according to the differential pressure across the metering orifice 52, and when the flow rate of the working fluid discharged from the supply pump 50 increases, the excess flow rate is transferred from the bypass passage 54 to the reservoir 6.
8, the bypass valve 53 thus supplies a constant flow rate Q of working fluid to the diversion control valve 55. Note that if the supply pump 50 is a constant-speed motor-driven pump that discharges a constant flow rate, the bypass valve 53 is not necessary.

The branch control valve 55 supplies the constant flow rate Q of the working fluid to a control spool 5 that operates according to the pressure difference before and after the fixed throttle 56.
5a, constant flow rates Q1 and Q2 are distributed to the servo valve passage 61 and the reaction force control passage 62, respectively. The servo valve passage 61 is connected to a power cylinder 66 via a servo valve 30 which will be described later, and the reaction force control passage 62 is connected to a reaction force mechanism 40 and a first flow control valve 70 which will be described later. A communication passage 63 is provided between the servo valve passage 61 and the reaction force control passage 62, and a second flow rate control valve 80, which will be described later, is provided in this communication passage 63. Double flow control valve 7
0.80 have essentially the same structure, and the opening degree is controlled by the electronic control device 90, respectively.

The electronic control unit 90 is a microprocessor (hereinafter simply CP).
91 (referred to as U), and read-only memory (hereinafter simply RO).
M) 92, writable memory (hereinafter simply referred to as RA)
A vehicle speed sensor 95 is connected to the CPU 91. The CPU 91 receives the vehicle speed signal from the vehicle speed sensor 95, calculates the mountain road index J, which is an index indicating the running state of the vehicle, and adjusts the current applied to the solenoid 76 of the first flow control valve 70 according to the vehicle speed V. and the second flow rate control valve 80 according to the mountain road index J.
The current applied to the solenoid 86 is controlled.

In general, when driving in a city, as shown in Figure 6 (al), the vehicle speed V changes to around the driving speed when it is stopped, but this change does not occur very often.On the other hand, when driving on a mountain road, the number of stops is Although it is small, the vehicle speed V changes frequently around a predetermined running speed.Therefore, the acceleration V changes as shown in Figure 6(b), and the absolute value of the acceleration ■ changes each time the acceleration or deceleration occurs, as shown in Figure 6(C). Mountains occur, and the number of mountains within a certain period of time is greater when driving on a mountain road.Therefore, the integral value of the absolute value of acceleration divided by the absolute value for a certain period of time is larger when driving on a mountain road.In this example, This integral value is used as the mountain road index J, and the driving condition of the vehicle is determined based on this value.

The ROM 92 contains the first. The control pattern of the applied current applied to the solenoid 76, 86 of the second flow control valve 70.80 is stored as a characteristic map. FIG. 5 is a graphical representation of this control pattern. Figure 5A shows the current value i to be applied to the solenoid 86 for the mountain road index J.
The current value iA is set to decrease at a constant rate as the mountain road index J increases. As a result, the "manual torque-assist force" characteristic changes as described below in response to changes in the mountain road index J.

On the other hand, FIG. 5B shows the change characteristics of the current value iB to be applied to the solenoid 76 with respect to the vehicle speed V, and the current value iB is
It increases at an essentially constant rate with respect to the increase in speed, but it is set so that it does not change in the high speed and low speed ranges. As a result, the "manual torque-assist force" characteristic changes in accordance with changes in vehicle speed V as described below. Also, ROM9
2, calculate the mountain road index J from the vehicle speed V, search the current values iB and iA based on the vehicle speed V and the mountain road index J from the characteristic maps B and A in FIG. 2. A control program to be applied to the solenoid 76.86 of the flow control valve 70.80 is stored.

Next, the main body of the power steering device including the servo valve 30 and the reaction force mechanism 40 will be explained. In FIG. 2, an output shaft 21 is supported by two bearings 13 and 14 in a housing body 11 and a valve housing 12 that are fixed to each other.
Rack teeth 22a of a rack shaft 22 that is slidably supported in a direction intersecting the output shaft 21 are engaged with the output shaft 21.

This rack shaft 22 is connected to a piston 66a of a power cylinder 66 (see FIG. 1), and both ends thereof are connected to steering wheels via a steering link mechanism (not shown). Inside the valve housing 12, an input shaft 23, which is a steering shaft, is connected to an output shaft 2.
1, and both shafts 21 and 23 are connected to the input shaft 23.
They are elastically connected by a torsion bar 24 provided in the center hole of.

The servo valve 30 housed in the valve housing 12 is fitted on the outer periphery of a rotary valve member 31 formed integrally with the input shaft 23 so as to be relatively rotatable coaxially, and connected to the output shaft 21 by an engagement pin 25. The main component is a sleeve valve member 32 that is connected in a relatively unrotatable manner, and the outer periphery of the rotary valve member 31 and the inner periphery of the sleeve valve member 32, which fit into each other, are provided with a plurality of lands and grooves extending in the axial direction, respectively. is formed. The input shaft 23 has a center hole and a rotary valve member 31.
A communication passage 36 that communicates with the bottom of the groove and a passage 38 that communicates the concentric hole with the low pressure chamber 37 in the housing 12 are bored, and the sleeve valve member 32 has a distribution hole that communicates from the predetermined groove bottom with the outer periphery. 39a and 39b are bored. From the servo valve passage 61 through the supply port 34 to the sleeve valve member 32
When the servo valve 30 is in the neutral state, the working fluid supplied to the grooves flows evenly to the grooves on both sides of the land portion of the rotary valve member 310, passes through the communication passage 36 and the passage 38, and flows into the low pressure chamber 37.
The liquid then flows to the discharge port 35 and is discharged from the return passage 67 to the reservoir 68. In this state, both distribution holes 39a, 3
Since both the distribution boats 33a and 33b connected to the power cylinder 9b are at the same low pressure, the power cylinder 66 is not operated. If manual torque is applied and the servo valve 30 deviates from its neutral state, a pressure difference will occur between the two distribution ports 338 and 33b. For example, if the pressure at the distribution port 33a becomes large, the servo valve 30 The working fluid from the valve passage 61 is supplied to the power cylinder 66 via the distribution passage 64 from the distribution port 33a.
The working fluid in the other chamber flows into one chamber of the distribution passage 6.
52 distribution port 33b1 distribution hole 39b, communication passage 369 passage 38. It flows from the low pressure chamber 37 to the discharge port 35 and is discharged from the return passage 67 to the reservoir 68 .

Next, to explain the reaction force mechanism 40, in FIG.
At the end of the rotary valve member 31 on the output shaft 21 side, a protrusion 41 is formed that protrudes on both sides in the radial direction, and the output shaft 2 is provided with a protrusion 41 that rotates coaxially with the input shaft 23. A fitting groove 42 is formed to allow loose fitting. Projection 4
Engagement grooves 43 are formed on the outer peripheral surface of 1 and are inclined on both sides in the circumferential direction so that the center is lower. The output shaft 21 has
A radial insertion hole 44 is formed at a position corresponding to the engagement groove 43 in the neutral state of the servo valve 30, and a plunger 45 is fitted into the insertion hole 44 so as to be slidable in the radial direction.

The output shaft 21 has an annular groove 46 on its outer periphery that communicates with the insertion hole 44.
A port 48 is formed in the valve housing 12 and communicates with the annular groove 46 through a passage 47 . The aforementioned reaction force control passage 62 is communicated with the port 48 .
The working fluid pressure in the boat 481 passage 47. Annular groove 46
It is introduced into the rear part of the plunger 45 and operates the reaction force mechanism 40. The reaction force mechanism described above is of a so-called radial type, but may also be of a thrust type that applies a reaction force in the axial direction.

The first flow control valve 70 is an electromagnetic flow control valve as shown in FIG. A union 72 having a throttle hole 72a in the center is coaxially screwed and fixed to the tip of the protrusion 71a of the valve body 71 of the first flow control valve 70, and the first port 70a and the second port ) 70b is formed. The valve body 71 has a yoke 7 on the side opposite to the protrusion 71a.
5 is fixed, and a spool 73 to which a valve shaft 74 is fixed is supported by the inner hole of this yoke 75 so as to be slidable in the axial direction coaxially with the protrusion 71a. Spool 73° and valve shaft 74
is elastically supported via springs 78 and 79 between the valve body 71 and an adjustment screw 77 screwed into the yoke 75. The first flow rate control valve 70 is adjusted in advance using an adjustment screw 77. Normally, the tip of the valve shaft 74 is separated from the throttle hole 72a of the union 72 so that the throttle hole 72a is fully open, and when the solenoid 76 is energized, the current value is adjusted. Spool 7 depending
3 is displaced to the left and the end of the valve shaft 74 opens the throttle hole 72.
The opening degree of a is gradually reduced until it is fully opened. The union 72 is provided with a fixed throttle 72b that allows communication between the ports 70a and 70b even when the throttle hole 72a is fully closed. The first flow control valve 70 is attached by screwing the protrusion 71a of the valve body 71 onto the attachment base 15 such as the valve housing 12.

Since the second flow rate control valve 80 has essentially the same structure as the first flow rate control valve 70, only necessary symbols are shown in parentheses in FIG. 3, and a detailed explanation will be omitted.

As is clear from FIG. 1, the flow rate of the working fluid passing through the first flow control valve 70 is a flow rate Q2 distributed from the branch control valve 55 to the pressure control passage 62, and a flow rate Q2 distributed from the servo valve passage 61 to the communication passage 6.
The sum of the flow rates q supplied through the three second flow control valves 80 is (Q2+q).

However, although the former Q2 is constant, the servo valve passage 61
Since the pressure inside increases as the steering angle increases, the latter q
will also increase accordingly.

When stopped or running at low speed, the current value iB applied to the solenoid 76 is small, so the first flow control valve 70
is fully open, and the pressure applied to the port 48 of the reaction force mechanism 40 is almost zero.

Therefore, the "manual torque-assist force" characteristic in this state remains the same as before, as shown in FIG. As a result, even if the flow rate (Q2+q) of the working fluid passing through the first flow rate control valve 70 changes, the "manual torque-assist force" characteristic remains unchanged at C. In this state, a great assisting force can be obtained.

As the speed V increases, the current value iB applied to the solenoid 76 increases, so the opening degree of the first flow control valve 70 decreases, and a pressure corresponding to the flow rate (Q2+q) of the working fluid passing through it is applied to the reaction force mechanism. 40 port 49.

In this state, when the mountain road index J is small, that is, when driving at a relatively high speed in an urban area, the current value iA applied to the solenoid 86 is large, so the second flow control valve 8
The opening degree of 0 is small, and therefore the flow rate q is relatively small. Therefore, in this case, the "manual torque-assist force" characteristic becomes as shown by Dl in FIG. 4, and the assist force is somewhat reduced compared to the conventional one, so that a change in manual torque suitable for relatively high-speed driving in the city can be obtained. Further, in this state, when the mountain road index J becomes large, that is, when the vehicle travels on a mountain road at a relatively high speed, the current value iA becomes large and the current iq increases.

Therefore, in this case, the "manual torque - assist force" characteristic becomes as shown in D2 in Fig. 4, the assist force further decreases, the manual torque increases, and the road reaction force is accurately transmitted to the driver. This prevents excessive rehandling and provides a stable steering feel.

Next, the control operation of the steering force control device of this embodiment will be explained with reference to the flowcharts shown in FIGS. 7 and 8.

The vehicle speed V, which sometimes changes while the vehicle is running, is detected by the vehicle speed sensor 95, inputted to a counter (not shown), and updated. The CPU 91 executes a processing operation based on a program at the same time that an interrupt signal is input at predetermined short time intervals. First, in step 100 of FIG.
At step 91, the vehicle speed V stored in the counter is read, and then at step 101, the vehicle speed V is differentiated to calculate acceleration÷. This differentiation process is performed by taking the difference from the vehicle speed read immediately before.

A predetermined number of data regarding this acceleration O is stored in the RAM 93 and constantly updated, and based on this data, the CPU 91 calculates a mountain road index J in step 102. As described above, the mountain road index J is the integral value of the absolute value of the acceleration C within a certain past period of time. Next, CPU9
1, in step 103, a current value iA is searched from the characteristic map A based on the mountain road index J, and then in step 1
At step 04, a current of value iA is applied to the solenoid 86 to set the second flow rate control valve 80 to a predetermined opening degree.

When step 104 is completed, the CPU 91 stops executing the program according to the flowchart of FIG. 7 until the next interrupt signal is input.

Simultaneously with the start of the program in the flowchart in FIG. 7 or following the end of the program, the CPU 91 starts executing the program in the flowchart in FIG. The CPU91 is
First, in step 110, the vehicle speed V is read, and in step 111, a current value iA is searched from the characteristic map B based on the vehicle speed V. In the following step 112, the value i is searched.
A current of B is applied to the solenoid 76 to close the first flow control valve 7.
Let 0 be the predetermined opening degree. When step 112 is completed,
The CPU 91 stops executing the program according to the flowchart of FIG.

Thereafter, each time an interrupt signal is output at a predetermined short time interval, the CPU 91 repeatedly executes the programs according to each of the flowcharts described above, and executes the first program according to the running state and speed of the vehicle. The opening degree of the second flow control valve 70°80 is set so that a predetermined steering force can be obtained. Note that the interrupt signal may be output at predetermined short travel distances instead of at predetermined short time intervals.

In the first embodiment described above, a constant flow rate of the working fluid is supplied to the constant flow rate Q1. Q2 was distributed and supplied to the servo valve passage 61 and the reaction force control passage 62, but the configuration of the branch control valve 55 and the connection point of the first flow control valve 70 are not necessarily limited to those of the first embodiment. Instead, it may be as shown in FIG. In this second embodiment, the excess flow rate of the working fluid discharged from the supply pump 50 is bypassed by the bypass valve 53 controlled by the metering orifice 52, and the working fluid at the constant flow rate Q1 is directly supplied to the servo valve 61. has been done. A reaction force control passage 62 branched from the bypass valve 53 is provided with a second bypass valve 58 and a first flow control valve 70A. This first flow control valve 70A functions as a metering orifice, and has a structure as shown in FIG. 3, for example. The control spool 58a of the second bypass valve 58 operates according to the differential pressure before and after the first flow control valve 70A, and the working fluid at a predetermined flow rate Q2 is supplied to the reaction force control passage 6.
2, and the excess flow is returned to the reservoir 68 via the bypass passage 60. As a result, the working fluid at flow rates Ql and Q2 is supplied to the servo valve passage 61 and the reaction force control passage 62, respectively. Here, the first flow control valve 70A
The opening area is controlled by the electronic control device 90 according to the vehicle speed signal, and by controlling the opening area, the distribution flow rate Q2 to the reaction force control passage 62 side is controlled. As in the example, a reaction oil pressure corresponding to the vehicle speed is applied to the reaction force mechanism 40. Therefore, this second
In this embodiment, a fixed throttle is provided at the position of the first flow control well 70 of the first embodiment.

[Brief explanation of the drawing]

1 to 8 show a first embodiment of a steering force control device for a power steering device according to the present invention, FIG. 1 is an overall explanatory diagram, and FIG. 2 is a system equipped with a servo valve and a reaction force mechanism. 3 is a sectional view of the power steering device main body, FIG. 3 is a sectional view of the flow control valve, FIG. 4 is an explanatory diagram of the "manual torque-assist force" characteristic diagram, and FIG. 5A
and B are characteristic diagrams of control current with respect to mountain road index and vehicle speed, respectively. Figures 6 (al to (C) are diagrams showing changes in vehicle speed, acceleration, and absolute value of acceleration, respectively, and Figures 7 and 8 are control current characteristics diagrams. The flowchart showing the program and FIG. 9 are explanatory diagrams showing the main changes in the second embodiment.Description of symbols 21...Output shaft, 23...Input shaft, 30...Servo valve, 40 ... Reaction force mechanism, 50 ... Supply pump, 5
5.53... Valve device, 61... Servo valve passage, 62
...Reaction force control passage, 63... Communication passage, 70... First flow control valve, 80... Second flow control valve. 7th wJ sB! i! Figure 3 Figure 5 Mountain road index Figure 4 Vehicle speed Figure 6 Time t 1[[1r Figure 9

Claims (1)

[Claims] Equipped with a servo valve that controls the supply and discharge of working fluid to a power cylinder that is operated based on the relative rotation of the input shaft and output shaft to generate an assist force, and a reaction force mechanism that changes the assist force according to vehicle speed, etc. In a steering force control device for a power steering system, a valve device is provided that divides working fluid from a supply pump into a servo valve passage and a reaction force control passage, and a reaction force control passage that branches from the valve device is provided with a valve device that divides working fluid from a supply pump into a servo valve passage and a reaction force control passage. a first flow rate control valve whose opening degree is controlled by a flow control valve; the servo valve passage for supplying a predetermined flow rate of working fluid from a supply pump to the servo valve and the reaction force control passage are connected by a communication passage; A second flow control valve whose opening degree is controlled in response to driving conditions such as on a mountain road is provided in the passage, and the working fluid pressure generated in the reaction force control passage is introduced into the reaction force mechanism. A steering force control device for a power steering device.