JP3341377B2 - Power steering device - Google Patents

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 for a motor vehicle, and more particularly, to driving a hydraulic pump serving as a supply source of hydraulic fluid for power assist by an electric motor, thereby saving energy. The present invention relates to a hydraulic power steering apparatus of an electric motor drive type.

[0002]

2. Description of the Related Art In many cases, a conventional hydraulic power steering apparatus is of a type in which a hydraulic pump serving as a hydraulic pressure source is driven by an engine. However, this type has a problem in that the hydraulic pump is driven even during straight running that hardly requires power assist, and the engine output is constantly lost. In order to solve such a problem, for example, as shown in FIG.
An electric motor 40 provided separately from the engine has been considered. When the steering device 910 is operated to reduce the pressure difference between the supply oil pressure in the supply passage 510 and the operation oil pressure in the power cylinder 940, and when the pressure difference falls below a predetermined value, the amount of change is detected. The electric motor 40 is operated by the control means 80 based on the detection result. Then, the hydraulic pump 30 is driven to supply pressure oil (hydraulic oil) to the power assist unit 90. An accumulator 70 also serving as a pulsation absorber is provided in the middle of the supply path 510, and when the hydraulic pump 30 is driven by sensing the steering state of the steering device 910, the accumulator 70 Is released to accumulate pressure oil. As a result, quick supply of pressure oil to the power assist unit 90 is performed.

[0003]

By the way, the conventional power steering apparatus includes a switching valve 20 for drawing the oil pressure in one of the left and right high pressure side cylinder chambers in the power cylinder 940, and a high pressure from the switching valve 20. The differential pressure detector 10 for detecting a change in the differential pressure between the hydraulic pressure and the hydraulic pressure from the supply passage 510 is provided as a separate component, and has a configuration in which these components are connected via a pipe or the like. Things. Therefore, there is a problem that not only the handling of the pipes between the components becomes complicated, but also the pipe resistance increases, leading to pressure loss and energy loss. In addition, there is a problem such as a response delay due to the increase in the pipeline resistance. We decided to solve these problems with less pipeline resistance,
SUMMARY OF THE INVENTION It is an object (problem) of the present invention to provide a power steering apparatus which is made up of a compact differential pressure detecting means and the like without a response delay or the like.

[0004]

Means for Solving the Problems In order to solve the above problems, the present invention takes the following measures. That is, a hydraulic pump driven by an electric motor, a supply path that guides hydraulic oil (hydraulic oil) from the hydraulic pump to a power cylinder, and a hydraulic pump that operates in accordance with steering of a steering device. A center-closed type servo valve that operates to communicate the chamber with the supply path and communicates the other chamber with the reservoir, a power cylinder that performs a power assisting operation in accordance with the operation of the servo valve, A differential pressure detecting means for detecting a differential pressure between the high pressure side cylinder chamber of the cylinder and the supply path; and, when the differential pressure detected by the differential pressure detecting means is a predetermined value or less, the hydraulic pump is Regarding a power steering device comprising control means for controlling the drive of the electric motor so as to operate, one of the left and right of the power cylinder A switching valve that guides hydraulic oil in the high-pressure cylinder chamber to the next differential pressure detecting means, and between a hydraulic pressure in the high-pressure cylinder chamber introduced through the switching valve and a hydraulic oil supplied from the hydraulic pump. And a differential pressure detecting means provided coaxially with the spool and formed by displacement detecting means for detecting the operating displacement of the spool. The switching valve and the differential pressure detecting means are housed in the same housing, and the valve assembly housed in the same housing is arranged integrally with the housing in which the servo valve is housed. I decided that.

[0005]

According to the present invention, the following effects are exhibited in the present invention. First, when the steering device is not steered, the servo valve that operates in conjunction with the steering device does not operate.
In this case, since the servo valve is a center-closed type, no pressure oil (hydraulic oil) is introduced into the power cylinder from the supply path. In such a state, the pressure on the supply path side is high, and the pressure in the line pressure introducing chamber in the differential pressure detecting means is also high. Therefore, the spool is pushed rightward by the pressure in the line pressure introducing chamber (see FIG. 1) and is held. As a result, the displacement detecting means provided coaxially with the spool does not operate. Therefore, a signal for operating the electric motor is not output from the control means, and the electric motor and the hydraulic pump remain stopped. That is, at the time of non-steering such as straight running, the electric motor and the hydraulic pump are in a stopped state, and energy saving is achieved.

Next, when the steering device is steered,
The servo valve operates in response to the steering of the steering device, and one of the cylinder chambers of the power cylinder communicates with the supply path. At this time, the differential pressure between the oil pressure in the line pressure introduction chamber introduced from the supply passage and the oil pressure in the spring chamber in which the hydraulic oil in the high pressure side cylinder chamber of the power cylinder is introduced via the switching valve is small. Become. Therefore, the spool moves leftward due to the spring reaction force of the spring (see FIG. 1). As a result, the displacement detecting means provided coaxially with the spool operates to output a signal to the control means. The control means operates based on an output signal based on the operation of the differential pressure detecting means, and performs a control action so as to drive the electric motor. As a result, the hydraulic pump starts operating and discharges hydraulic oil (hydraulic oil). By such a series of operations, when the steering device is steered, the supply of the working oil to the power cylinder is promptly performed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. The configuration of the present embodiment includes a hydraulic pump 3 driven by an electric motor 4, as shown in FIGS.
A supply path 51 for supplying discharge oil (hydraulic oil) from the hydraulic pump 3 to the power assist unit 9 including a power cylinder 94 and the like, an accumulator 7 provided also in the supply path 51 and also serving as a pulsation absorbing device, Steering device 91
A servo valve 5 that operates based on the steering of the power valve, a power cylinder 94 that performs a power assisting operation in response to the operation of the servo valve 5, The switching valve 2 introduced into the first spring chamber 14, the hydraulic pressure in the high pressure side cylinder chamber of the power cylinder 94 introduced by the switching valve 2, and the hydraulic pressure in the line pressure introducing chamber 15 introduced from the supply passage 51. And a control means 8 for controlling the operation of the electric motor 4 based on a differential pressure signal from the differential pressure detecting means 1. is there.

In such a basic configuration, the hydraulic pump 3 is of a type appropriately driven by an electric motor 4, and in this embodiment, a hydraulic pump such as a plunger pump or a vane pump is employed. Further, the servo valve 5 that operates based on the steering of the steering device 91 is connected to the steering device 91.
When the vehicle is in a non-steering state (during straight running, etc.), it is of a center-closed type that operates so as to shut off the hydraulic oil from the supply path 51. Note that the servo valve 5 having such a configuration is connected to the housing 59.
Is housed inside. In the non-steering state, both chambers 94A and 94B of the power cylinder 94 are both connected to the reservoir 99. Then, when the steering device 91 is steered, the servo valve 5 is operated, and the supply passage 51 and one of the cylinder chambers of the power cylinder 94 communicate with each other. It is designed to communicate with the side.
Further, a piston 93 is provided in the power cylinder 94 and operates under the influence of oil pressure from the cylinder chamber on the side that is in communication with the supply path 51, and operates by a rack and pinion or the like. Power assist is provided to the gear 92 and the steering device 91.

Also, hydraulic oil is drawn out from one of the left and right high pressure side cylinder chambers of the power cylinder 94,
As shown in FIG. 1, the switching valve 2 that leads to the spring chamber 14 in the next differential pressure detecting means 1 has a ball 21 at the center, and a valve seat 22 is provided with the ball 21 interposed therebetween. On the left and right sides of the ball 21, pressure chambers 23A and 23B are provided to communicate with the cylinder chambers 94A and 94B of the power cylinder 94, respectively. In such a configuration, a port 222 is further formed at the center of the valve seat 22 that is installed so as to sandwich the ball 21.
22 through the port 222 so that the oil pressure in the high pressure side cylinder chamber of the power cylinder 94 is introduced into the spring chamber 14 of the next differential pressure detecting means 1 through the port 222.
5 is provided.

Next, the differential pressure detecting means 1
And a high-pressure cylinder chamber of the power cylinder 94. The data (signal) detected by the differential pressure detecting means 1 is sent to the next control means 8. Is what it is. In such a configuration, as shown in FIG. 1, the differential pressure detecting means 1 basically includes a spool 11, a spring 13 for applying a spring reaction force to the spool 11, and a displacement provided coaxially with the spool 11. It comprises the detecting means 12 and the like. The components 11, 12, and 13 and the switching valve 2 are integrally integrated and housed in a housing 19. Further, the integrated unit is configured so as to be integrated with the housing 59 in which the servo valve 5 is housed as the valve assembly 29.

In this configuration, the spool 11 is provided with a spool head 111,
On one side of the spool head 111, a line pressure introduction chamber 15 for introducing a line pressure (supply path pressure) from the supply path 51 is provided, and on the other side, a line from the switching valve 2 side is connected. Power cylinder 9 through passage 25
4 is provided with a spring chamber 14 into which the hydraulic pressure in the high-pressure side cylinder chamber is introduced. On the other hand, a displacement detecting means 12 formed coaxially with the spool 11 and detecting an operating displacement of the spool 11 includes a core 112 formed on an extension of the spool 11 and a core 112
2 is slidably housed inside the coil 122. An electromotive force (voltage) is generated in the coil 122 in accordance with the sliding movement of the core 112 in the coil 122, and the amount of displacement of the spool 11 is detected based on the value of this voltage. The displacement detecting means 12 is of a switching mechanism type that transmits a predetermined electric signal when the displacement amount of the spool 11, that is, the displacement amount of the core 112 exceeds a predetermined value. There may be.

Next, the control means 8 which operates based on the signal from the differential pressure detecting means 1 comprises a microcomputer or the like, and based on the signal detected by the displacement detecting means 12, detects the differential pressure. When it is determined that the value has become equal to or less than the predetermined value, a control signal is output so as to drive the electric motor 4. The electric motor 4 is operated based on a control signal from the control means 8, whereby the hydraulic pump 3 is driven and hydraulic oil is supplied to the supply path 51. As shown in FIG. 2, an accumulator 7 that also serves as a pulsation absorber is provided in the power steering apparatus having the above-described structure in the supply path 51, so that the power assist unit 9 can be quickly operated. Hydraulic oil is supplied.

The operation of this embodiment having the above-described configuration will be described. First, in FIG. 1, when the steering device 91 is not steered, the servo valve 5 that operates in conjunction with the steering device 91 does not operate. In this case, since the servo valve 5 is a center-closed type, no pressure oil (hydraulic oil) is introduced into the power cylinder 94 from the supply path 51.
In such a state, the pressure on the supply path 51 side is high, but both chambers of the power cylinder 94 are low, so that the differential pressure detected by the differential pressure detecting means 1 exceeds a predetermined value. Has become. Therefore, a signal for operating the electric motor 4 is not output from the control means 8, and the electric motor 4 and the hydraulic pump 3 are stopped. That is,
At the time of non-steering such as straight running, the electric motor 4 and the hydraulic pump 3 are in a stopped state, and energy saving is achieved.

Next, when the steering device 91 is steered, the servo valve 5 is actuated in accordance with the steering of the steering device 91, and one of the cylinder chambers of the power cylinder 94 and the supply passage 51 communicate with each other. Becomes At this time, the hydraulic pressure accumulated from the accumulator 7 is immediately supplied to the supply path 51 and introduced into the power cylinder 94 via the servo valve 5. As a result, the power assist operation is started immediately. At the same time, the pressure difference between the supply path 51 and the high pressure side cylinder chamber of the power cylinder 94 becomes smaller, so that the pressure difference detection means 1
The control action is performed such that the control means 8 is operated by the operation of and the electric motor 4 is driven. As a result, the hydraulic pump 3 starts operating and discharges pressure oil (hydraulic oil).

In such a series of operations, in the present embodiment, the switching valve 2 which draws oil pressure from the high pressure side cylinder chamber of the power cylinder 94 and guides it to the differential pressure detecting means 1
And the differential pressure detecting means 1 comprising a spring chamber 14 for introducing the oil pressure from the switching valve 2 through the communication passage 25 and a line pressure introduction chamber 15 for introducing the line pressure from the supply path 51. Since the communication passages 25 and the like connecting them are also formed short, pressure loss based on pipe resistance is reduced, thereby saving energy. At the same time, the response performance is improved by reducing the pipeline resistance.

[0016]

According to the present invention, a hydraulic pump driven by an electric motor, a supply path for guiding hydraulic oil (hydraulic oil) from the hydraulic pump to a power cylinder, and operation in accordance with steering of a steering device. A center-closed type servo valve that operates so that one chamber of the power cylinder communicates with the supply path and communicates the other chamber with the reservoir, and a power assist system that operates according to the operation of the servo valve. A power cylinder for performing an operation, a differential pressure detecting means for detecting a differential pressure between the high pressure side cylinder chamber of the power cylinder and the supply path, and a differential pressure detected by the differential pressure detecting means being equal to or less than a predetermined value. If
Regarding a power steering device comprising control means for controlling the drive of the electric motor so as to operate the hydraulic pump, the hydraulic oil in one of the left and right high pressure side cylinder chambers of the power cylinder is subjected to the next differential pressure detecting means. , A spool that operates in response to a change in the differential pressure between the hydraulic pressure of the high-pressure cylinder chamber introduced through the switching valve and the hydraulic pressure of the hydraulic oil supplied from the hydraulic pump, and the spool And a differential pressure detecting means formed by a displacement detecting means for detecting an operation displacement of the spool, and the switching valve and the differential pressure detecting means are housed in the same housing. And the valve assembly housed in the same housing is integrated with the housing in which the servo valve is housed. Therefore, when the steering wheel is not steered, such as when traveling straight, and there is no need to use power assist, the hydraulic pump is stopped to save energy, and the electric motor is driven quickly when the steering wheel is steered. As a result, the hydraulic pump can be operated, and thereby energy saving can be achieved. Further, the switching valve and the differential pressure detecting means are integrated together, and the hydraulic passage to the spool driving line pressure introducing chamber and the spring chamber in the switching valve and the differential pressure detecting means is shortened. Therefore, the pipeline resistance is reduced, pressure loss due to the flow of the high-pressure hydraulic oil and the like are reduced, and energy saving can be achieved. In addition, by reducing the pipeline resistance, the response performance is improved, the startup and startup of the hydraulic pump are quickened, and the power assist can be quickly applied.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an overall configuration of a servo valve, a differential pressure detecting means, a switching valve, and the like, which are main components of the present invention.

FIG. 2 is an external view showing the overall configuration of the present invention.

FIG. 3 is a skeleton structure diagram showing an entire configuration of a conventional example.

[Explanation of symbols]

 Reference Signs List 1 differential pressure detecting means 11 spool 111 spool head 112 core 12 displacement detecting means 122 coil 13 spring 14 spring chamber 15 line pressure introducing chamber 19 housing 2 switching valve 21 ball 22 valve seat 222 port 23A pressure chamber 23B pressure chamber 25 communication passage 29 Valve assembly 3 Hydraulic pump 4 Electric motor 5 Servo valve 51 Supply path 59 Housing 7 Accumulator 8 Control means 9 Power assist unit 91 Steering device 92 Steering gear 93 Piston 94 Power cylinder 94A Cylinder chamber 94B Cylinder chamber 99 Reservoir

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hideaki Sugiyama 1-1-1 Asahimachi, Kariya City, Aichi Prefecture Inside Toyota Koki Co., Ltd. (56) References JP-A-60-189873 (JP, A) US Patent No. 4,618,017 ( (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6/02 B62D 6/00 B62D 5/07

Claims (1)

(57) [Claims] 1. A hydraulic pump driven by an electric motor, a supply path for guiding hydraulic oil (hydraulic oil) from the hydraulic pump to a power cylinder, and a hydraulic pump which operates in accordance with steering of a steering device. A center-closed type servo valve that operates so that one chamber of the cylinder communicates with the supply path and communicates the other chamber with the reservoir, and a power cylinder that performs a power assisting operation in accordance with the operation of the servo valve. A differential pressure detecting means for detecting a differential pressure between the high pressure side cylinder chamber of the power cylinder and the supply path; and, when the differential pressure detected by the differential pressure detecting means is equal to or less than a predetermined value, In a power steering device including control means for controlling the driving of the electric motor so as to operate a hydraulic pump, the power steering device may be configured to operate the power pump on either the left or right side. A switching valve that guides hydraulic oil in one of the high-pressure cylinder chambers to a differential pressure detecting means described below, and a hydraulic pressure of the high-pressure cylinder chamber introduced through the switching valve and a hydraulic oil supplied from the hydraulic pump. A spool that operates in response to a change in the differential pressure between the spool and a differential pressure detecting unit that is provided coaxially with the spool and that is formed by a displacement detecting unit that detects an operating displacement of the spool. The switching valve and the differential pressure detecting means are housed in the same housing, and the valve assembly housed in the same housing is arranged integrally with the housing in which the servo valve is housed. A power steering device comprising: