JPH05270424A - Electro-hydraulic power steering device for vehicle - Google Patents

Abstract

PURPOSE:To compatibly provide a steering force characteristic and a power saving property by providing the first setting means for setting delivery performance of an electro-hydraulic pump in accordance with a steering condition and the second setting means for setting a stop mode at the time of a superlow speed and an operational mode of minimum ability in a speed region thereafter. CONSTITUTION:When a steering wheel 18 is steered, a pressure of oil, generated in an electro-hydraulic pump 22 and supplied/discharged to/from each right/left chamber 31a, 31b in both sides of a piston 30 in a power cylinder device 12, is controlled by a rotary valve 19, thus to assist steering of a front wheel 10. In a device thus obtained, in the case of controlling an electric motor 22b of the oil hydraulic pump 22 by a control unit 37, at the time of deciding steering, assist force in accordance with a car speed and a steering angle is controlled by the first setting means of setting satisfying pump delivery performance. On the other hand, at the time of nonsteering, the assist force is controlled by the second setting means of setting a pump stop mode in a superlow speed region and a pump operational mode of minimum ability of assisting a device riseup in an increasing speed region thereafter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicular electrohydraulic power steering system used to steer the front wheels of an automobile.

[0002]

2. Description of the Related Art An automobile (vehicle) is equipped with a hydraulic power steering device for steering with light operation. In such a power steering device, a structure using an oil pump that uses a running engine as a drive source is generally adopted.

Specifically, a steering mechanism for steering the front wheels (steering wheels) to the left and right according to the operation of the steering wheel,
Engine driven oil pump, rotary valve (supply / discharge valve), power cylinder device (piston mechanism)
A hydraulic circuit configured by connecting the valve to the power passage is used to supply the hydraulic pressure obtained by the rotary valve that is displaced by the rotation of the handle to the power cylinder device to generate the necessary assist force. It is being appreciated. However, the handle force cannot be properly controlled only by the displacement of the rotary valve.

Therefore, in a conventional power steering system using a running engine as a drive source, a reaction force mechanism for varying a steering reaction force and a control valve for controlling the reaction force mechanism are provided in a hydraulic circuit to provide an assist force. Variable,
This is controlled by using a sensor that detects the vehicle speed of the automobile and a sensor that detects the steering wheel angle to obtain appropriate steering characteristics. For example, when the steering wheel is stationary or in the low speed range, the assist force is appropriately increased to lighten the steering wheel force. On the contrary, when steering in the middle and high speed range, the assist force is appropriately reduced to increase the steering wheel force. There is.

However, although such an engine type power steering device can certainly control an appropriate steering force, it has a problem that it is structurally complicated because a reaction force mechanism and a control valve must be added. .. In addition, the load on the running engine is large, which is a factor that impairs the fuel efficiency of the automobile.

Therefore, recently, instead of the engine for running,
Controls the discharge performance of an electric hydraulic pump by using an electric hydraulic pump driven by an electric motor that operates with a battery and an alternator installed in an automobile as a power source, without using a reaction mechanism such as an engine type or a control valve. A power steering device, that is, an electro-hydraulic power steering device, is proposed in which the steering force is appropriately controlled just like the above engine type.

Specifically, a sensor for detecting the vehicle speed and a sensor for detecting the steering wheel angle are used to determine the traveling state, and the operation of the electric hydraulic pump is controlled so as to generate the steering wheel force according to the traveling state. Is being done.

[0008]

By the way, in the electrohydraulic power steering apparatus, the battery and the alternator operate by using the power source as a power source, so that a heavy load is likely to be applied to the battery (because the power consumption increases).

Therefore, the conventional electro-hydraulic power steering apparatus is in a useless area even when it is operated, that is, when the vehicle speed is "10 km / h or less" (extremely low speed area) when not operated (when the steering mechanism is not steered). In (), the operation of the electric hydraulic pump is stopped to reduce the load on the battery. However, this is not enough. Therefore, the vehicle speed is set to “10
It is possible to expand not only when the vehicle is under "km / h or less" but also when the vehicle is in the entire vehicle speed range. By doing so, the power saving property is certainly sufficient. However, on the other hand, there is a problem that the steering force characteristic is deteriorated. That is, the power steering device exhibits good steering performance only when the assist force is generated in the power cylinder device by following the steering wheel operation.

However, if the electric hydraulic pump is operated from the stop as the steering changes from the non-steering to the steering, it takes a long time to start up, so that the assist force is generated in the power cylinder device after the steering wheel is operated, which is a so-called assist delay. Will occur. For this reason, the steering force characteristic is considerably deteriorated and the original function of the power steering device is impaired, and there is a strong demand for improvement.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an electric motor vehicle for a vehicle in which both steering force characteristics and power saving characteristics can be sufficiently achieved. It is to provide a hydraulic power steering device.

[0012]

In order to achieve the above object, a vehicular electrohydraulic power steering apparatus of the present invention is provided with a steering mechanism for steering steered wheels in a steering direction according to an operation of a steering wheel, and an electric motor is a drive source. Is provided with an electric hydraulic pump driven as described above, pressure receptive chambers are provided on both sides of a reciprocating piston, and a piston mechanism for assisting the steering mechanism in the steering direction according to the displacement of the piston is provided. The pump and each pressure receiving chamber of the piston mechanism are connected via a supply / discharge valve that supplies / discharges according to the steering of the steering mechanism, and the assist force according to the steering of the steering mechanism is applied to each pressure. A hydraulic circuit is provided for generating in the receiving chamber, and a determination means for determining whether the steering mechanism is in steering or not is provided. A first setting means is provided in which the discharge performance of the electric hydraulic pump that satisfies the assist force according to the speed and the steering state is set, and the electric hydraulic pressure is provided in an extremely low speed region from the stop of the vehicle to a speed close to the stop. A stop mode for stopping the operation of the pump is set, and a second setting means for setting the operation mode of the minimum capacity of the electric hydraulic pump that assists the apparatus to rise is provided in a speed range in which the speed thereafter increases. According to the determination result of the determining means, the electric hydraulic pump is operated according to the setting of the first setting means during steering, and the electric hydraulic pressure is operated according to the stop mode and the operating mode of the second setting means during non-steering. There is a means for operating the pump.

[0013]

According to the electric hydraulic power steering apparatus for a vehicle of the present invention, the first setting means is set during steering.
The electric hydraulic pump is controlled according to the discharge performance that satisfies the assist force according to the vehicle speed and the steering state. As a result, during steering, an assist force corresponding to the vehicle speed and the steering state is output from the pressure receiving chamber of the piston mechanism, and the steering force is controlled appropriately. On the other hand, at the time of non-steering, according to the stop mode and the operation mode set in the second setting means,
The electric hydraulic pump is controlled. In this way, no electric power is consumed by the electric hydraulic pump in the useless, wasted, non-steering, extremely low speed range from the stop to the speed close to the stop.

In the non-steering speed range thereafter, the electric power consumption of the electric hydraulic pump is the lowest. Moreover, in this non-steering speed range, the electric hydraulic pump operates at the minimum capacity to assist the power steering device in starting up.
Even when the steering is changed from non-steering to steering, a predetermined assisting force is quickly generated, and good steering performance that follows steering operation is brought about. As a result, both the steering force characteristic and the power saving performance are sufficiently satisfied.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in FIGS.

FIG. 1 is a schematic view of an electrohydraulic power steering apparatus for an automobile (vehicle) to which the present invention is applied. In FIG. 1, reference numeral 1a is a rack and pinion type steering gear constituting the steering mechanism 1. ..

The steering gear 1a is constructed by incorporating a rack 3 extending in the vehicle width direction and a pinion gear 4 meshing with the rack 3 in a casing 2. The pinion gear 4 is connected to the input shaft 6 of the steering gear 1a via the torsion bar 5.

One end of the rack 3 is connected to the left front wheel 10 via a steering rod 7, a tie rod 8 and a knuckle 9. Similarly, the other end is connected to the right front wheel 10 via a steering rod 11, a power cylinder device 12 (corresponding to a piston mechanism), a tie rod 13, and a knuckle 14.

Input shaft 6 protruding from the upper part of casing 2
Is connected to a steering wheel 18 via a steering joint 16, for example, a two-part steering shaft 17. This allows the handle 18 to be operated (rotated)
Then, this displacement is transmitted to the knuckles 9 and 14 through the steering shaft 17, the torsion bar 5, the pinion gear 4, the rack 3, and the steering rods 7 and 11, and the left and right front wheels 10 and 10 are steered in the operated direction. ing. Incidentally, 17a is a steering column.
A rotary valve 19 (supply / discharge valve) is provided between the input shaft 6 of the steering gear 1 a and the pinion gear 4.

As is well known, the rotary valve 19 comprises a pinion gear 4 provided with a tubular outer valve 19a, and an input shaft 6 provided with a tubular inner valve 19b which is combined with the outer valve 19a. That is, when the torsion bar 5 is twisted by the handle force from the handle 18, the rotary valve 19 causes relative displacement between the outer valve 19a and the inner valve 19b.

An inflow port portion 20 formed in the rotary valve 19 is connected to a discharge portion of an electric hydraulic pump 22 via a flow passage 21, and an outflow port portion 23 is also provided.
Is connected to the suction section of the electric hydraulic pump 22 via the flow path 24.

That is, in the electric hydraulic pump 22, for example, the electric motor 22b for driving is directly connected to the pump portion 22a,
Further, it has a structure in which a reservoir 22c is connected to the suction portion of the pump portion 22a, the flow passage 21 is connected to the discharge port of the pump portion 22a, and the flow passage 2 is connected to the suction port of the reservoir 22c.
4 are connected.

Further, the electric motor 22b of the electric hydraulic pump 22 is connected to a power supply circuit (not shown) constructed by connecting a battery mounted on the automobile and an alternator in parallel, and the power supply circuit The electric hydraulic pump 22 is operated by using electric power as a power source. The pair of output port portions 26a, 26b formed in the rotary valve 19 are connected to the power cylinder device 12 via the flow paths 27a, 27b.

That is, the power cylinder device 12 includes a piston rod 28 connected to the steering rod 11.
Through a cylinder 29 fixed to a frame of an automobile or the like, and the cylinder 2 is partially attached to the piston rod 11.
Slidable piston 3 that divides the inside of 9 into left and right (vehicle width direction)
It is configured by providing 0.

The chambers 31a and 31 (pressure receiving chambers) on both sides (left and right) of the piston, which are partitioned by the piston 30, have a pair of input port portions 32a and 32b and flow paths 27a and 27b.
Is connected to the output port sections 26a and 26b through.

With the hydraulic circuit 34 thus constructed,
When the handle 18 is in the neutral state, the rotary valve 1
9, the hydraulic pressure generated by the electric hydraulic pump 22 is supplied to both chambers 31a and 31b as neutral pressure. When the steering wheel 18 is steered, the outer valve 1 of the rotary valve 19 corresponding to the steering is
9a and the inner valve 19b, the hydraulic pressure according to the relative displacement supply / discharge operation, that is, the hydraulic pressure corresponding to the steering (steering force and steering direction) is applied to the chamber 31a or the chamber 31b.
Is supplied to the front wheels 10, 10 while assisting the steering force with the hydraulic pressure generated in the chambers 31a, 31b.
To be able to steer.

The electric motor 22 of the electric hydraulic pump 22
A control unit 37 including a microcomputer and its peripheral circuits is connected to b via a drive circuit 36. This control unit 3
Reference numeral 7 denotes a vehicle speed sensor 38 for detecting the vehicle speed of the automobile, and a steering angle sensor 3 for detecting the steering angle of the steering wheel 18 by a pulse.
9 is connected. A circuit configured by connecting these electronic devices causes the power cylinder device 12 to generate a predetermined assist force according to the vehicle speed and the steering state during steering, and when not steering, in the useless extremely low speed range as in the conventional case. The operation of the electric hydraulic pump 22 is stopped, and the electric hydraulic pump 22 is made to stand by at the operation of the minimum capacity in order to assist the start-up during steering in the speed range thereafter.

That is, the map of "motor drive command value Mn according to vehicle speed" as shown in FIG. 3 is displayed in the control unit 37 as "steering" (solid line) and "non-steering".
It is set separately from (broken line).

Here, regarding the relationship between the motor drive command value Mn and the electric hydraulic pump 22, as the motor drive command value Mn increases, the rotation speed of the electric motor 22b increases and as the motor drive command value Mn decreases. Electric motor 2
The number of rotations of 2b decreases, and the pump discharge amount increases as the motor drive command value Mn increases, and the pump discharge amount decreases as the motor drive command value Mn decreases.

The map on the steering side shown by the solid line is the vehicle speed,
The steering force is set to the optimum value according to the steering state. Specifically, in the low speed range, the pump discharge rate is large (assist force: large), in the medium speed range, the pump discharge rate is reduced as the speed increases, and in the high speed range, the pump discharge rate is reduced.
The steering mode is set.

Further, the map on the non-steering side shown by the broken line shows that the vehicle speed is from "stop" to an extremely low speed range close to the stop, that is, "10 km / h".
Below "stop mode A for stopping the operation of the electric motor 22b
Is set. Further, in the speed range of "10 km / h or more", the minimum discharge flow rate of the pump discharge rate that assists the start of the power steering device, specifically, the minimum capacity to set "2 liters / min" is the operation mode. It is set as B.

The control unit 37 has a function of determining whether or not there is a pulse from the steering angle sensor 39 as a function of determining whether or not the handle 18 has been operated. As a result, "steering" and "non-steering" are discriminated (discriminating means).

When the control unit 37 determines "steering", it reads the motor drive command value Mn from the steering side map (solid line) in FIG. 3, and drives the electric motor 22b in accordance with the read motor drive command value Mn. It has a function to do.

Further, when the control unit 37 determines "non-steering", the map on the non-steering side in FIG. 3 (broken line).
It has a function of reading the motor drive command value Mn from and driving the electric motor 22b in accordance with the read motor drive command value Mn. With such a function, control that emphasizes steering feeling is performed during steering, and control that emphasizes power saving is performed during non-steering.

The control unit 37 uses the timer function to prevent the hunting of the electric hydraulic pump 22 from starting and stopping, and the electric hydraulic pump 22 is operated for a predetermined time, for example, 5 seconds even after the steering is completed. It is set to let. The flow chart shown in FIG. 2 shows the control operation in the control unit 37. Next, the control operation in the control unit 37 will be described with reference to the flowchart. The controller unit 37 is activated by an ON signal of a switch of an automobile ignition key.

Then, first, as shown in step S1, the signal from the L terminal of the alternator (not shown) is read. Then, in step S2, it is determined whether or not the output from the L terminal is "Hi".

When the engine of the automobile is normally started by operating the ignition key, the L of the alternator is activated.
Since the "Hi" signal is output from the terminal, the process proceeds to step S3 when the engine is normally started.

In step S3, the initial setting is performed and the steering flag SFLG indicating that the steering wheel 18 is steered is set to "0" and the holding timer Tm is set to "0".

Then, steps S4 and S5
At, the vehicle speed V output from the vehicle speed sensor 38 and the steering wheel angle θH output in pulses from the steering angle sensor 39 are read. When the process proceeds to step S6, it is determined whether or not there is a pulse from the steering angle sensor 39.

At this time, if it is assumed that the vehicle has only started the engine and has not started (running) or operated the steering wheel, there is no pulse output from the steering angle sensor 39. Judges that the steering wheel 18 is not operated (non-steering), and proceeds to step S7. In this step S7, it is determined whether or not steering has been performed before that by determining whether or not the steering flag SFLG is "1". Here, the vehicle is in a state where the initial steering wheel operation has not been performed yet, so it is determined to be "non-steering" (no steering), and the process proceeds to step S8. In this step S8, it is determined whether or not the vehicle speed V is "10 km / h or more" during non-steering.

Based on this determination, the non-steering state is divided into two regions, that is, a region where the electric hydraulic pump 22 is useless even if the electric hydraulic pump 22 is operated, and a region where the electric hydraulic pump 22 needs to be in standby operation for the start of steering. ing.

At this time, if the vehicle is stopped or runs straight at an extremely low speed, if the vehicle speed V is less than "10 km / h", the process proceeds to step 9, "vehicle speed-motor drive command value Mn" in FIG. The non-steering stop mode A indicated by the broken line in the map of FIG.
Stop b.

If the vehicle travels straight following the above at a vehicle speed V of "10 km / h or more", step S10.
Go to. Then, this time, the "non-steering" operation mode B indicated by the broken line in the same map of FIG. 3 is read, and the electric hydraulic pump 2
The second electric motor 22b is driven at a low speed so as to obtain the lowest discharge flow rate, for example, "2 liter / min". Such pump stop control and pump minimum capacity operation are performed as long as the vehicle is stopped or at an extremely low speed, and as long as the steering is not performed. By this stop control, the operation of the electric hydraulic pump 22 is suppressed. On the other hand, the vehicle speed V is "10 km.
Suppose you steer a car that is running at "/ h or more" by operating the steering wheel. Then, a pulse is output from the steering angle sensor 39, it is determined in step S6 that the steering wheel 18 is operated, and the process proceeds to step S11. In step S11, the operation flag SFLG indicating that steering has been performed is set to "1". That is, steering is detected. Next, in step S12, a holding timer Tm for holding the steering time after the steering is detected.
Is set, and then the process goes to step S13. In step S13, the map setting changes from "non-steering" to "steering", and the discharge flow rate of the electric hydraulic pump 22 is controlled according to the vehicle speed V and the steering state.

That is, in step S13, as shown in FIG.
The vehicle drive command value Mn corresponding to the current vehicle speed V of the vehicle is read from the steering mode indicated by the solid line of "vehicle speed-motor drive command value Mn" shown in FIG.

Then, in step S14, the read motor drive command value Mn is output to the drive circuit 36,
The electric motor 22b of the electric hydraulic pump 22 is driven according to the set performance of the map.

As a result, the electric hydraulic pump 22 shifts from the previous low speed operation (standby operation) of the minimum discharge flow rate to the high speed operation of the discharge flow rate determined by the steering mode, and applies an appropriate assist force to the power cylinder device 12. Specifically, the assist force is generated as follows.

That is, in the electro-hydraulic power steering apparatus, when the handle 18 is rotated, the rotational displacement is the steering shaft 17 and the steering joint 1.
6, the input 6, and the torsion bar 5 are transmitted to the pinion gear 4 to drive the rack 3 in the direction in which the steering wheel 18 is steered.

At this time, the outer valve 19a and the inner valve 19b of the rotary valve 19 are displaced relative to each other according to the torsion bar 5 twisted by the resistance of the road surface.
The oil discharged from the electric hydraulic pump 22 at this time is the outer valve 19a and the inner valve 19b.
According to the difference in rotation between the power cylinder device 12 and the chamber 31a (right side) or the chamber 31b (left side). The assisting force generated in the chamber 31a or the chamber 31b drives the front wheels 10, 10 in the direction steered by the steering wheel 18 to reduce the steering wheel force.

Here, the assist force obtained by switching from "non-steering" to "steering" is not the operation of the electric hydraulic pump 22 that rises from a stop, but the standby operation (minimum flow rate) in consideration of the rising characteristics of the power steering device. Since the operation of the electric hydraulic pump 22 starts from (1), the operation of the steering wheel 18 is not delayed, that is, the assist delay is not generated.

When the steering wheel 18 is returned and the steering operation is finished, it is determined whether or not the steering flag SFLG is "1" in step S7, the timer count of the holding timer Tm in step S15 and the timer count in step S16 are ". Whether 5 seconds have passed ",
As a result of the processing of resetting the steering flag SFLG to "0" in step S17,
As shown in the time chart of (3), the operation is held for a certain holding time (5 seconds) and then stopped (in order to reduce the hunting for starting and stopping the electric hydraulic pump 22).

Such a "non-steering" electric hydraulic pump 22
With the control described above, both the performance of the electric hydraulic pump 22 in terms of power saving and the steering force characteristic of the power steering device can be sufficiently achieved.

In other words, looking at the power saving of the electric hydraulic pump 22, the operation is wasted "1" in "non-steering".
0 km / h or less ”(an extremely low speed region from a stop to a speed close to this stop), the electric hydraulic pump 22 does not consume power. In the subsequent "non-steering" speed range, that is, "10 km / h or more", the electric power consumption of the electric hydraulic pump 22 can be considerably small.

According to the experiment, the electric hydraulic pump 22 needed "current of about 15 A" to obtain the discharge flow rate satisfying the steering mode, but the minimum discharge flow rate "2 liter /
In order to obtain "min", the electric hydraulic pump 22 needs only "current of about 5A". That is, in this area,
It was confirmed that the current consumption was "about 1/3" compared to the conventional one. This can bring about high power saving.

Looking at the steering force characteristic of the power steering device, in the above "non-steering" region of "10 km / h or more", the electric hydraulic pump 22 is set to "2 liters / It is in standby operation at the discharge flow rate of "min".

As a result, the rising speed at the time of changing from "non-steering" to "steering" is fast, and a predetermined assist force can be quickly generated, resulting in good steering performance following the steering wheel operation. .. From these facts, it is understood that both the steering force characteristic and the power saving performance are sufficiently satisfied.

[0056]

As described above, according to the present invention,
The electric hydraulic pump does not consume power in the extremely low speed range where the vehicle is in useless and non-steering, and the electric power consumption of the electric hydraulic pump is minimal in the subsequent non-steering speed range. Moreover, in this non-steering speed range, the electric hydraulic pump operates at the minimum capacity in order to help the power steering device to start up, so even when switching from non-steering to steering, a predetermined assist force is quickly generated. Will be done. Therefore, both the steering force characteristic and the power saving performance can be sufficiently achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an electrohydraulic power steering device of the present invention together with a control system.

FIG. 2 is a flowchart showing steering control of the device.

FIG. 3 is a diagram showing maps of “steering” and “non-steering” motor drive command values of an electric hydraulic pump according to vehicle speed.

FIG. 4 is a time chart showing a control for maintaining the operation of the electric hydraulic pump for a predetermined time even after finishing steering.

[Explanation of symbols]

1 ... Steering mechanism, 10 ... Front wheel (steering wheel), 12 Power cylinder device (piston mechanism), 19 ... Rotary valve (supply / discharge valve), 22 ... Electric hydraulic pump, 22b ...
Electric motor, 22c ... Reservoir, 30 ... Piston, 31a,
31b ... Chamber (pressure receiving chamber), 34 ... Hydraulic circuit, 37 ... Control unit, 38 ... Vehicle speed sensor, 39 ... Steering angle sensor, A ... Stop mode, B ... Operating mode.

Claims (1)

[Claims] 1. A steering mechanism for steering steered wheels in a steering direction according to an operation of a steering wheel, an electric hydraulic pump driven by an electric motor as a drive source, and pressure receiving chambers provided on both sides of a reciprocating piston. ,
A feed mechanism for feeding / discharging a piston mechanism that assists the steering mechanism in the steering direction according to the displacement of the piston, and the electric hydraulic pump and each pressure receiving chamber of the piston mechanism according to the steering of the steering mechanism. A hydraulic circuit that is connected through an exhaust valve and that generates an assisting force in each pressure receiving chamber according to the steering of the steering mechanism, and a determination unit that determines whether the steering mechanism is in the steering state or in the non-steering state. And a first setting means in which the discharge performance of the electric hydraulic pump that satisfies the assisting force according to the vehicle speed and the steering state is set, and the electric motor in the extremely low speed region from the stop of the vehicle to a speed close to the stop. A stop mode is set to stop the operation of the hydraulic pump, and the minimum capacity of the electric hydraulic pump that helps the equipment start up in the speed range where the speed thereafter becomes high. According to the discrimination result of the discriminating means, the electric hydraulic pump is operated according to the setting of the first setting means according to the discrimination result of the discriminating means. And a means for operating the electric hydraulic pump according to the stop mode and the operation mode of the setting means of No. 2.