JPH1086839A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device in which a condition causing a sticky feeling can be quickly dissolved. SOLUTION: An electronic control unit provided in the subject power steering device drives a motor (S1) when it is determined that steering is carried out (S2: YES). As a result, working fluid is supplied to a power cylinder so as to assist steering. Then, if steering is released, it is determined whether a motor consuming electric current value is lower than the threshold value or not in advance of stopping of the drive of the motor (S3). If the result demonstrates that the motor consuming electric current value is the threshold value or more, it is determined that viscous resistance of the working fluid is high, so that drive of motor is continued for reducing the viscous resistance. Subsequently, when viscous resistance is reduced sufficiently and the motor consuming electric current value is lowered, the motor is stopped (S4). That is, viscous resistance of the working fluid can be lowered sufficiently even if steering is not repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering apparatus, and more particularly, to a so-called hydraulic power steering apparatus in which an oil pump is driven by a motor to generate hydraulic pressure, and steering is assisted by the generated hydraulic pressure. . Note that the term "steering" used in this specification means that the steering wheel is operated while a torque equal to or more than a predetermined value is applied.

[0002]

2. Description of the Related Art Conventionally, there has been known a hydraulic power steering apparatus in which an oil pump is rotated by a motor and hydraulic oil is supplied from the oil pump to a power cylinder to reduce the operating force of a steering wheel.
In this type of power steering device, usually, a motor is driven only when the vehicle is being steered, and steering assist is performed.

[0003]

By the way, when the temperature is low in winter or the like, the hydraulic oil tends to cool down and its viscous resistance often increases. For example, when steering is not performed for a long time immediately after starting the engine at a low temperature or at a low temperature, the temperature of the hydraulic oil is low and its viscous resistance is high.

[0004] In such a case, even if the motor is driven to assist the steering, it takes some time until the required amount of hydraulic oil is supplied to the power cylinder. Therefore, even if the steering is started in such a case, the steering assist is not sufficiently performed, and there is a so-called catching feeling. This feeling of being caught is eliminated by the fact that the temperature of the hydraulic oil rises as a result of the repeated steering assist and the viscous resistance decreases. However, it takes a certain amount of time since steering assist must be repeatedly performed until the viscous resistance of the hydraulic oil is sufficiently reduced. As a result, the driver is uncomfortable for a long time.

[0005] In order to cope with this, it is conceivable to always circulate the hydraulic oil without supplying it to the power cylinder. However, in this case, even when the steering assist is not required, the motor is driven, so that useless electric power is consumed and fuel consumption is deteriorated, which is not preferable. Therefore, an object of the present invention is to
An object of the present invention is to provide a power steering device that can solve the above-described technical problem and can quickly resolve a state in which the vehicle is stuck.

[0006]

According to a first aspect of the present invention, there is provided a power supply for driving an oil pump by a motor to generate a hydraulic pressure, and using the generated hydraulic pressure to assist steering. A steering device, comprising: steering detection means for detecting that steering is being performed; current detection means for detecting a current consumption value of the motor; and consumption of a motor detected by the current detection means. Determining means for determining whether or not the current value is equal to or greater than a predetermined threshold value; and, when steering is detected by the steering detecting means, and when steering is performed by the steering detecting means. Control means for driving the motor, when it is detected that the current consumption value is not greater than the threshold value, and A power steering apparatus which comprises.

In this invention, when the steering detecting means detects that the steering is being performed, the motor is driven. As a result, the oil pump is driven to generate a hydraulic pressure. As a result, steering assist is performed. In the present invention,
Further, even when the steering detecting means detects that steering is not being performed, the motor is driven if the current consumption value of the motor is equal to or larger than the threshold value. That is, when the viscosity resistance of the hydraulic oil is high, it is necessary to drive the oil pump with a larger driving force than when the viscosity resistance of the hydraulic oil is low. Become. Therefore, when the current consumption value of the motor is equal to or greater than the threshold value, it is determined that the viscosity resistance of the hydraulic oil is high, and the motor is driven.

Therefore, even if the steering is released after the steering is performed and the motor is driven, if the viscous resistance of the hydraulic oil is high, the driving of the motor is continued as it is. as a result,
The temperature of the hydraulic oil increases, and the viscous resistance of the hydraulic oil decreases.
Therefore, even if the steering operation is not frequently repeated, a state in which the steering wheel is stuck can be quickly eliminated. Also,
When the steering detecting means detects that steering is not being performed and the determining means determines that the current consumption of the motor is less than the threshold value, If the driving of the motor is stopped, it is possible to limit the driving of the motor when steering is not performed until the viscous resistance of the hydraulic oil is sufficiently reduced.

[0009]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an overall configuration of a power steering device according to an embodiment of the present invention. This power steering device
For example, it is used by being mounted on a vehicle, and is for assisting steering in the steering mechanism 1.

[0010] The steering mechanism 1 is provided with a steering wheel 2. A steering shaft 3 is connected to the steering wheel 2, and a pinion gear 4 is attached to a tip of the steering shaft 3. The pinion gear 4 is a rack gear 5 extending in the vehicle width direction.
Is engaged. A tire 7 is attached to the rack gear 5 via a tie rod 6.

When the steering wheel 2 is operated and its rotational force is transmitted to the steering shaft 3, the pinion gear 4 at its tip rotates, and the rack gear 5
Moves in the vehicle width direction. As a result, the movement of the rack gear 5 is transmitted to the tie rod 6, and the direction of the tire 7 changes.
The power steering device is provided with a power cylinder 20 for generating a steering assist force. The power cylinder 20 includes a piston 21 connected to the rack shaft 5,
It includes a pair of cylinder chambers 20a, 20b formed by the piston 21. A hydraulic control valve 23 is connected to the cylinder chambers 20a and 20b via oil supply paths 22a and 22b indicated by broken lines, respectively.

The hydraulic control valve 23 is interposed in the oil circulation path 24 shown by a broken line. The oil circulation path 24
Hydraulic oil stored in the reservoir tank 25 is pumped out by the oil pump 26, and the pumped hydraulic oil is discharged from the oil pump 26, and is then returned to the reservoir tank 25.
This is the route to return to. The drive of the oil pump 26 is controlled by a motor M. When the oil pump 26 is driven by the motor M, the operating oil is supplied to the oil circulation path 24.
And when not driven, the circulation of the hydraulic oil is stopped.

The opening of the hydraulic control valve 23 changes according to the direction and amount of twist of the torsion bar 8 attached to the steering shaft 3, that is, the direction and magnitude of the torque applied to the steering shaft 3. As a result, the supply state of the hydraulic oil to the power cylinder 20 changes. More specifically, when the torsion bar 8 is twisted in one direction, the hydraulic oil is supplied to one cylinder chamber of the power cylinder 20 via one oil supply path. When the torsion bar 8 is twisted in the other direction, the hydraulic oil is supplied to the other cylinder chamber via the other oil supply path. When the torsion bar 8 is hardly twisted, the hydraulic control valve 2
3 is in an equilibrium state, so that the hydraulic oil is not supplied to the power cylinder 20.

When hydraulic oil is supplied to any of the cylinder chambers of the power cylinder 20, the piston 21 moves in any direction along the vehicle width direction. As a result, a steering force is generated, and the movement of the rack shaft 5 is assisted. The driving of the motor M is controlled by the electronic control unit ECU. The electronic control unit ECU includes a CPU, a ROM, and a RAM.
And a microcomputer having the following. Electronic the control unit ECU, each torque signal T and the current signal I _M from the torque sensor 27 and the current detection circuit 28 is adapted to be applied respectively. The electronic control unit ECU, based on the given torque signal T and the current signal I _M, and controls the motor M.

The torque sensor 27 is provided in association with the torsion bar 8 attached to the steering shaft 3, and is proportional to the torque applied to the steering shaft 3,
Further, a torque signal T having a sign corresponding to the direction of the torque is output. As the torque sensor 27, any type such as a type having a mechanical contact formed of a potentiometer and a non-contact type torque sensor can be applied.

The current detection circuit 28 is provided in connection with the motor M, and outputs a current signal I _M which is proportional to the consumption current value of the motor M. As shown in FIG. 2, the current consumption of the motor M increases as the temperature of the hydraulic oil decreases. That is, the hydraulic oil is supplied from the oil pump 26 driven by the motor M to the power cylinder 20 via the hydraulic control valve 23. If the temperature of the hydraulic oil is low and its viscous resistance is high, the hydraulic oil is operated at a required flow rate. In order to supply oil to the power cylinder 20, it is necessary to drive the oil pump 26 with a large driving force. That is, since the load on the motor M increases, the current value consumed by the motor M also increases.

FIG. 3 is a flowchart for explaining the drive control of the motor M by the electronic control unit ECU. When the ignition switch (IG) is turned on and the engine is started, the electronic control unit EC responds accordingly.
U starts the assist control (step S1). That is, driving of the motor M is started. As a result, the oil pump 26 is driven, and the working oil circulates in the oil circulation path 24.

The reason why the assist control is unconditionally started after the start of the engine is to reduce the viscous resistance of the hydraulic oil immediately after the start of the engine particularly at a low temperature. Thereafter, the electronic control unit ECU determines whether or not the absolute value of the torque signal T given from the torque sensor 27 is equal to or greater than a predetermined threshold value T _TH (for example, T _TH = 7 (kgf · cm)) ( Step S2). As a result, when it is determined that the absolute value of the torque signal is equal to or larger than the threshold value _TTH, it is determined that steering is being performed, and the motor M is driven. At this time, the torsion bar 8 is twisted in any direction. As a result, the oil pump 26 is driven to circulate the hydraulic oil through the oil circulation path 24, and the hydraulic oil is supplied to the power cylinder 20 via the hydraulic control valve 23. On the other hand, if it is determined that the absolute value of the torque signal T is less than the threshold value T _TH, it is determined that steering is not being performed, and the current signal I that is proportional to the current consumption value of the motor M is subsequently determined. _M is a predetermined threshold value I _TH (for example, I _TH
= 15 (A)) or more (step S)
3).

As a result, the current signal I _M is equal to the threshold I
If it is determined that it is equal to or higher than _TH, it is determined that the viscosity resistance of the hydraulic oil is high, and the motor M is driven. As a result, the oil pump 26 is driven. On the other hand, since the steering is not performed, the torsion bar 8 is hardly twisted. Therefore, the working oil is not supplied to the power cylinder 20 but circulates in the oil circulation path 24.
On the other hand, when the current signal I _M is determined to be less than the threshold I _TH is the viscous resistance of the hydraulic oil is determined to be low, the motor M is stopped to end the assist control (Step S4).

For example, when starting the engine of a vehicle at a low temperature such as winter, the engine is often idling immediately after the engine is started to warm the engine. In this case, the steering wheel 2 is not steered. . That is, the torque signal T is less than the threshold value T _TH . On the other hand, since the viscous resistance of the hydraulic oil is high immediately after the start of the engine at a low temperature, the current consumption of the motor M driven after the start of the engine is high. That is, the current signal _IM is _{equal to} or higher than the threshold value _ITH .

Therefore, the drive of the motor M is continued in a state where the torsion bar 8 is hardly twisted. As a result, the hydraulic oil circulates in the oil circulation path 24 without being supplied to the power cylinder 20. As a result, the temperature of the hydraulic oil increases, and the viscous resistance decreases. Therefore, when driving the vehicle after idling ends,
The power steering device can be kept in a state where steering assist can be quickly performed.

If the viscous resistance of the hydraulic oil is sufficiently reduced, the current consumption of the motor M is also reduced. Therefore, the motor M is stopped on the condition that steering is not performed. Thereby, useless power consumption can be prevented. Thereafter, when the vehicle is driven and, for example, a long period of time has elapsed without steering, the hydraulic oil cools down again and the viscous resistance increases because the motor M continues to be stopped.

When steering is performed in such a state, the torque signal T reaches the threshold value T _TH or more, and the motor M
Is started. Then, when the steering is released,
At low temperatures, the viscous resistance of the working oil is often still high, and the current consumption value of the motor M is also kept high.
That is, the current signal I _M remains at or above the threshold value I _TH , and after a while passes, decreases to below the threshold value I _TH . Therefore, the drive of the motor M is continued in a state where the torsion bar 8 is hardly twisted, and then stopped on the condition that the steering is not performed. That is, the hydraulic oil is circulated through the oil circulation path 24 even after the steering is released, and the viscous resistance is reduced. Therefore, even if the steering is resumed thereafter, the steering can be smoothly performed without causing the feeling of being stuck.

As described above, according to the power steering apparatus of this embodiment, when the viscous resistance of the hydraulic oil is relatively high, the motor M is driven until the viscous resistance becomes low. Even if it is not present, the state where there is a feeling of being stuck can be quickly eliminated. Therefore, a power steering device with good operability can be provided. The description of one embodiment of the present invention is as described above, but the present invention is not limited to the above-described embodiment. For example, in the above embodiment, the steering is detected by the torque sensor 27. However, for example, the steering may be detected by a steering angle sensor, and other various sensors may be applied.

In addition, various design changes can be made within the scope described in the claims.

[0026]

As described above, according to the present invention, when the current consumption value of the motor corresponding to the degree of the viscous resistance of the hydraulic oil is equal to or higher than the threshold value, the motor is controlled even if the steering is not performed. Since the drive is performed, the viscous resistance of the hydraulic oil can be rapidly reduced. For this reason, the state with the feeling of being stuck can be quickly eliminated without repeating the steering. Therefore, a power steering device with good operability can be provided.

According to the second aspect of the present invention, it is possible to limit the driving of the motor when steering is not performed until the viscous resistance of the hydraulic oil is sufficiently reduced, thereby preventing wasteful power consumption. it can.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an overall configuration of a power steering device according to an embodiment of the present invention.

FIG. 2 is a graph showing a correspondence between a current consumption value of a motor and a temperature of hydraulic oil.

FIG. 3 is a flowchart for explaining motor drive control in the electronic control unit.

[Explanation of symbols]

Reference Signs List 1 steering mechanism 2 steering wheel 20 power cylinder 26 oil pump 27 torque sensor 28 current detection circuit ECU electronic control unit I _M current signal M motor T torque signal

Claims (2)

[Claims] 1. A power steering apparatus for driving an oil pump by a motor to generate a hydraulic pressure and assisting the steering with the generated hydraulic pressure, the steering being used to detect that the steering is being performed. Detecting means, current detecting means for detecting the current consumption value of the motor, and determining whether or not the current consumption value of the motor detected by the current detecting means is equal to or greater than a predetermined threshold value. Discriminating means, when steering is detected by the steering detecting means, and when steering is not performed by the steering detecting means, and the current consumption value of the motor is determined by the discriminating means. A power steering device comprising: a control unit that drives the motor when it is determined that the difference is equal to or larger than the threshold value. 2. The control means according to claim 1, wherein said steering detecting means detects that steering is not being performed, and said determining means determines that a current consumption value of said motor is less than said threshold value. 2. The power steering apparatus according to claim 1, wherein driving of the motor is stopped.