JP2000001173A - Power steering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce energy loss during idle running of a power steering oil pump. SOLUTION: This power steering system assists operating force of a steering wheel 3 by means of hydraulic pressure that is fed from an oil pump 25. The power steering system employs an electric motor 15 serving as driving means for driving the oil pump 25. This system is also provided with a detecting means 27 for detecting steering torque of the steering wheel 3, and a controlling means 26 for controlling the revolutions of the electric motor 15 in accordance with signals from the detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power steering device.

[0002]

2. Description of the Related Art As a vehicle power steering device,
One that assists the operating force of the steering wheel with the hydraulic pressure supplied from the oil pump is often used. Oil pumps for power steering are generally driven by engines,
2. Description of the Related Art A hybrid electric vehicle is known in which an oil pump is selectively connected to an engine and an electric motor (motor for traveling) (JP-A-7-315059). In some hybrid electric vehicles, the running of the vehicle is prohibited when the engine that drives the oil pump for power steering is stopped (Japanese Patent Laid-Open No. Hei 8-98318).

[0003]

As seen in the example of a hybrid electric vehicle, even when an oil pump is selectively driven by an engine or an electric motor, the oil pump is always operated as in a general case (driven by an engine). However, there is a possibility that the energy loss due to the idle operation of the oil pump is large.

The present invention has been made in view of such a problem, and aims to reduce the energy loss by stopping the operation of the oil pump for power steering when it is unnecessary.

[0005]

According to a first aspect of the present invention, an electric motor is employed as a driving means of an oil pump in a power steering apparatus which assists operating force of a steering wheel with a hydraulic pressure supplied from an oil pump, while a vehicle is provided with a motor. An ignition switch, a shifter that generates an electric signal as a shift operation means of the vehicle, and an oil pump is stopped when the shifter is neutral based on these signals, and when the ignition switch is on and the shifter is other than neutral. Means for controlling the electric motor to operate the oil pump.

According to a second aspect of the present invention, there is provided a power steering apparatus for assisting an operating force of a steering wheel with a hydraulic pressure supplied from an oil pump driven by an engine, wherein an electromagnetic clutch for interrupting transmission of driving force from the engine to the oil pump is provided. On the other hand, a means for detecting engine rotation, a shifter for generating an electric signal as a shift operation means for the vehicle,
Means for stopping the oil pump based on these signals when the shifter is in neutral, and controlling the electromagnetic clutch to operate the oil pump when the engine is rotating and the shifter is in a state other than neutral.

According to a third aspect of the present invention, in a power steering apparatus for assisting an operation force of a steering wheel with a hydraulic pressure supplied from an oil pump, an electric motor is employed as a driving means of the oil pump, and a steering torque of the steering wheel is detected. And means for controlling the number of revolutions of the electric motor according to the detection signal.

[0008]

According to the first aspect of the invention, the electric motor is operated when the ignition switch is on and the shifter is in a state other than neutral, and is stopped when the shifter is in neutral. For this reason, it is possible to reduce the energy loss of the oil pump for power steering due to idling when it is not needed.

In the second invention, the electromagnetic clutch is connected when the engine is rotating and the shifter is other than neutral, and is disconnected by the neutral of the shifter. For this reason,
With respect to the power steering oil pump, it is possible to reduce energy loss due to idling when it is not needed.

[0010] In the third aspect of the present invention, the number of revolutions of the electric motor is controlled in accordance with the steering torque of the steering wheel, so that a necessary and sufficient power assist is always obtained, and the energy loss due to the idling of the oil pump when it is not necessary. Can also be reduced.

[0011]

FIG. 1 shows an application example of a first embodiment to a hybrid electric vehicle. In the integral type power steering device, a power cylinder and a control valve (not shown) are incorporated in the steering gear box 1. Reference numeral 2 denotes an oil pump whose hydraulic pressure is applied to the steering gear box 1
Is supplied to the power cylinder via a control valve that operates in accordance with the operation of the steering wheel 3 (handle), and power assists the steering output by the movement of the piston.

A steering wheel 3 is connected to an input shaft of the steering gear box 1 via a steering shaft 4.
A drag link 6 of a steering linkage is connected to the output shaft via a pitman arm 5. 8
Is a tie rod connecting the knuckle arms 7 on the left and right of the wheel, and the drag link 6 connects the pitman arm 5 to one knuckle arm 7. Reference numeral 10 denotes an oil reservoir.

When the steering wheel 3 is operated, its rotation is input to the steering gear box 1 and output together with the assisting force of the power cylinder as described above. This steering output is transmitted from the pitman arm 5 to each knuckle arm 7, and steers the wheels 9 according to the steering angle of the driver.

Although not shown, in a hybrid electric vehicle (hybrid drive system), a generator driven by an engine, a battery charged by the generator, and a power source driven by the generator and the battery as a power source of the vehicle. A driving motor (electric motor), a drive system for transmitting its output to driving wheels of the vehicle, and an inverter for controlling a current to the driving motor and its controller.

A speed change mechanism is interposed in the drive system, and a shifter 11 is provided in the cab as a speed change operation means. The shifter 11 has a D (drive) mode, an R (reverse) mode, and an N (neutral) mode. When one of these modes is selected by lever operation, a signal from a corresponding mode selection switch (not shown) is issued. Is output.

Reference numeral 12 denotes an ignition switch. When the ignition switch is turned on, the power of the hybrid drive system is turned on. When the accelerator pedal is operated, a current is supplied from the inverter to the traveling motor, and a driving force for traveling the vehicle is generated. When the shifter 11 is in the D mode, the driving force is transmitted to the driving wheels by forward rotation through the transmission mechanism, and when the shifter 11 is in the R mode, it is transmitted to the driving wheels by reverse rotation. When the shifter 11 is in the N mode, the transmission mechanism is in the neutral position, and the transmission of the driving force is cut off.

In FIG. 1, an electric motor 15 is employed as a driving means of the oil pump 2, and a controller 16 for controlling the operation thereof is provided. The controller 16 executes the control as shown in FIG. 2 based on the signal of the shifter 11 and the signal of the ignition switch 12. That is, the electric motor 15 is operated when the ignition switch 12 is on and the shifter 11 is in the D mode or the R mode, and is stopped when the ignition switch 12 is off or the shifter 11 is in the N mode.

FIG. 3 shows the characteristics of the oil pump 2. The flow rate of the pump is adjusted to a constant value by a flow rate control valve at a predetermined rotational speed or more, and an excess amount of oil is released to the low pressure side. The oil pump 2 is provided with a pressure control valve for limiting the maximum pressure in addition to the flow control valve. FIG.
P represents the power required to drive the pump.

With such a configuration, when the ignition switch 12 is turned off or the shifter 11 is in the N mode, the electric motor 15 for driving the oil pump 2 for power steering is stopped. Thus, the energy loss during the idle operation of the oil pump 2 can be reduced.

When the ignition steering 12 is on and the shifter 11 is in the D mode or the R mode, the oil pump 2 is driven by the electric motor 15, so that the power steering function when the vehicle is stationary can be ensured. When the vehicle is stationary, the ignition switch 12
Is turned on, the shifter 11 is put into the D mode or the R mode, and the accelerator pedal is depressed, so that the vehicle starts to move by the driving force of the traveling motor, so that the steering wheel 3 is steered without depressing the accelerator pedal.

FIG. 4 shows an example of application to a hybrid electric vehicle as a second embodiment. An oil pump 2 for power steering is driven by an engine 20 for power generation. An electromagnetic clutch 21 for intermittently transmitting the driving force from the engine 20 to the oil pump 2 is provided. From the viewpoint of safety measures for power steering, the electromagnetic clutch 21 disconnects the transmission path when energized, and connects the transmission path when not energized.

Reference numeral 23 denotes a controller for controlling the electromagnetic clutch 21. In addition to the shifter 11, a means 24 for detecting the number of revolutions of the engine 20 (a gauge for displaying the engine revolution) is provided. Based on these signals, the controller 23 connects the electromagnetic clutch 21 irrespective of the shifter 11 when the engine 20 is stopped as shown in FIG. 5, while the engine 20 is rotating and the shifter 11 is in the N mode. At this time, the electromagnetic clutch 21 is disconnected. When the engine 20 is rotating and the shifter 11 is in the D mode or the R mode, the electromagnetic clutch 21 is connected.

According to this, when the engine 20 is rotating and the shifter 11 is in the N mode, the oil pump 2 is stopped by the disconnection of the electromagnetic clutch 21. The accompanying energy loss can be reduced. The engine 20 is rotating and the shifter 11
Is in the D mode or the R mode, the electromagnetic clutch 21
, The oil pump 2 is driven, so that a power steering function when the vehicle is stationary can be secured.

FIG. 6 shows an example of application to a hybrid electric vehicle as a third embodiment. In an integral type power steering device, reference numeral 25 denotes an oil pump having no flow control valve and no pressure control valve (for example, , A gear pump), and includes an electric motor 15 as a driving means thereof.

A steering wheel 3 is connected to an input shaft of the steering gear box 1 via a steering shaft 4.
A drag link 6 of a steering linkage is connected to the output shaft via a pitman arm 5. When the steering wheel 3 is operated, the rotation is input to the steering gear box 1 and output together with the assisting force of the power cylinder. This steering output is transmitted from the pitman arm 5 to each knuckle arm, and steers the wheels according to the steering angle of the driver.

The controller 26 controls the operation of the electric motor 15, and a torque sensor 27 for detecting a steering torque T inputted to the steering gear box 1 is provided. Controller is ignition switch 12
When the ignition switch 12 is on, while the electric motor 15 is stopped when is off, the rotation speed of the electric motor 15 is controlled according to the steering torque T detected by the torque sensor 27 as shown in FIG.

According to this, the ignition switch 1
When 2 is on, the electric motor 15 is controlled at a rotational speed corresponding to the steering torque T, an oil amount corresponding to the steering torque T is supplied from the oil pump 25 to the steering box 1, and the hydraulic pressure also depends on the steering torque T. Therefore, a necessary and sufficient power assisting force can be obtained even when the vehicle is stationary.

In this case, when the ignition switch 12 is turned on, the electric motor 15 is always operated. However, by controlling the number of rotations in accordance with the steering torque T, no extra oil is generated and the oil pump 25 energy loss can be reduced.

In order to limit the maximum pressure of oil supplied from the oil pump 25 to the steering gear box 1, as shown in FIG. 9, a pressure control valve for releasing excess oil pressure to a low pressure side (oil reservoir 10) in the middle of the piping. Preferably, 28 is provided. As for the control characteristics of the electric motor 15, a dead zone may be set so that the electric motor 15 is maintained in a stopped state when the steering torque T is equal to or smaller than a predetermined value as shown in FIG.

In the first to third embodiments, examples of application to a hybrid electric vehicle have been described.
The present invention is also applicable as a power steering device for a normal vehicle using an engine as a power source. 4 or 6, the same components as those in FIG. 1 are denoted by the same reference numerals.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a first embodiment.

FIG. 2 is a table illustrating control characteristics of the electric motor.

FIG. 3 is a characteristic diagram of the oil pump.

FIG. 4 is a partial configuration diagram illustrating a second embodiment.

FIG. 5 is a table illustrating control characteristics of the electromagnetic clutch.

FIG. 6 is a configuration diagram illustrating a third embodiment.

FIG. 7 is a control characteristic diagram of the electric motor.

FIG. 8 is a control characteristic diagram of the electric motor.

FIG. 9 is a partial configuration diagram in which a pressure control valve is added.

[Explanation of symbols]

 Reference Signs List 1 steering gear box 2, 25 oil pump 3 steering wheel 4 steering shaft 5 pitman arm 6 drag link 7 knuckle arm 8 tie rod 9 wheels 10 oil reservoir 11 shifter 12 ignition switch 15 electric motor 16, 23 controller 21 electromagnetic clutch 24 engine tachometer 27 Torque sensor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D032 CC49 DA15 DA49 DA63 DA91 DA95 DB05 DC34 DE09 EA01 EB11 EC03 GG01 3D033 DB03 DC01

Claims (3)

[Claims] In a power steering apparatus for assisting an operation force of a steering wheel with a hydraulic pressure supplied from an oil pump, an electric motor is employed as a driving means of the oil pump, while an ignition switch of the vehicle and a shift operation means of the vehicle are employed. A shifter that generates an electric signal, and based on these signals, stops the oil pump when the ignition switch is off or the shifter is neutral, and operates the oil pump when the ignition switch is on and the shifter is other than neutral. A power steering apparatus provided with means for controlling an electric motor as described above. 2. A power steering apparatus which assists operating force of a steering wheel with a hydraulic pressure supplied from an oil pump driven by an engine, wherein an electromagnetic clutch for interrupting transmission of driving force from the engine to the oil pump is provided. A means for detecting rotation, a shifter for generating an electric signal as a shift operation means of the vehicle, and an oil pump is stopped when the engine is stopped or the shifter is in neutral based on these signals, and the engine is rotating. And a means for controlling the electromagnetic clutch to operate the oil pump when the shifter is other than neutral,
A power steering device comprising: 3. A power steering apparatus for assisting an operation force of a steering wheel with a hydraulic pressure supplied from an oil pump, wherein an electric motor is employed as a driving means of the oil pump, and a means for detecting a steering torque of the steering wheel, and the detection thereof. Means for controlling the number of revolutions of the electric motor according to a signal.