JPH01182165A - Differential pressure detecting device for power steering device - Google Patents

Abstract

PURPOSE:To improve performance of a steering system, by a method wherein a difference in a pressure between the right and left chambers of a power cylinder is converted into an electric signal output through a piston, and the output can be utilized as a control signal to indicate the working state of a power steering device. CONSTITUTION:A cylinder hole 2 is formed in a device body with which a differential pressure detecting device is formed, and a cylindrical member 3 is screwed in the cylinder hole 2. A potentiometer 4 being a displacement electric converting means is mounted to the external end of the cylindrical member 3 through an adapter 5. A differential piston 10 is slidably positioned to the central part in an axial direction of the cylinder hole 2, and small rods 11 and 12 are extended on the both sides of the differential piston. The external end of the rod 12 on the meter 4 side faces on the interior of the cylindrical member 3 and is brought into contact with an input shaft 4a on the meter 4 side. This constitution enables input transmission of movement of the piston 10 to the meter 4.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention detects the indoor pressure difference (differential pressure) between the left and right chambers of the power cylinder in a power steering device mounted on a vehicle. The present invention relates to a differential pressure detection device for a power steering device, which is suitable for use in sending control signals indicating the operating status of the power steering device to various mechanical parts.

[Conventional technology]

Power steering devices are capable of light steering and reduce driver fatigue, and have been known in various configurations, and have recently been widely installed in a variety of vehicles, including small cars. It looks like this. by the way,
This type of power steering device appropriately controls device operation based on various driving conditions of the vehicle, including the steering force and steering angle according to the driver's steering operation, as well as vehicle speed.
It is desirable to have a configuration that can provide steering assist force as needed.

In other words, in a vehicle equipped with a power steering device, when performing a steering operation while the vehicle is stopped, so-called when the vehicle is stationary or when driving at low speed, a large steering force is required to obtain an extremely light steering force. A configuration that can output steering assist force is required. However, on the other hand,
When the vehicle is running at high speeds, if a large steering assist force is generated as when running at low speeds, the operating force on the steering wheel becomes too light, causing problems such as giving the driver a sense of anxiety and impairing driving sensation. On the other hand, it is not preferable to reduce the steering assist force and make the steering wheel heavier to a certain extent, thereby increasing the steering force and ensuring stability when driving straight. It is desirable to have a configuration. In addition, such steering force control is similarly required as the steering angle increases, and furthermore, such steering force control requires consideration of the steering force that changes depending on the conditions on the road surface. Steering resistance from the wheels must also be considered.

In order to meet these demands, for example, steering using hydraulic reaction force can control the stiffness of the steering wheel (steering reaction force) when the vehicle is running at high or low speeds by applying an appropriate steering reaction force to the steering wheel. Many force control devices have been known for a long time.
Kiyama also previously proposed a steering force control device having the configuration shown in Japanese Patent Laid-Open Publication No. 82-175264. In other words, in this steering force control device, the supply source for supplying reaction oil pressure to the oil pressure reaction chamber that performs steering force control is composed of an oil pump driven by an electric motor, which is different from conventional boat fishing. The hydraulic passage from the oil pump to the power cylinder that constitutes the power steering system (hereinafter abbreviated as PS) branches at a branch passage having a pressure control valve, etc., and is connected to a hydraulic reaction chamber. Compared to this, the valve structure is simpler, and it is superior in terms of number of parts and piping connections. especially,
In such a steering force control device, various driving conditions of the vehicle, including vehicle speed and steering angle, are input to the controller, and the pump can be directly driven and controlled via the motor using the control signal obtained thereby. It is possible to quickly and appropriately control the steering force, and it is also advantageous in terms of fine adjustment control and responsiveness, and is highly effective in obtaining an appropriate steering feeling.

In such a steering force control device, the input information to the controller described above includes the vehicle speed, steering angle, and the magnitude of the steering force, as well as the pressure in the hydraulic piping at PSGS, and the pressure in the left and right chambers of the power cylinder. There is also an indoor pressure difference, and the pressure of reaction oil pressure in the hydraulic reaction chamber.In this case, the above-mentioned power cylinder left and right indoor pressure difference is the PS side including movement due to ground resistance on the steering wheel side. This is one of the important things in checking the operating state of the steering wheel and properly controlling the steering force. Conventionally, a proportional pressure sensor, which is a common in-vehicle detection element, has been generally used as a differential pressure detection device to detect the pressure difference between the left and right chambers of a power cylinder. A configuration is adopted in which two such proportional pressure sensors are used, and one each is attached to the left and right chamber sides of the power cylinder. These sensors then detect the pressure in each room,
The pressure difference was calculated by combining the detection signals with a controller.

[Problem to be solved by the invention]

However, the detection device configured as described above requires two proportional pressure sensors in order to detect the difference in indoor pressure between the left and right chambers of the power cylinder. It is also necessary to calculate the detection signal from the controller using the controller, which poses a cost problem.
Furthermore, such a proportional pressure sensor has poor accuracy and cannot be said to be able to appropriately and reliably detect the pressure difference between the left and right chambers of the power cylinder. That is, this type of PS pressure sensor must have a body part that can withstand high pressures of 70 to 100 kg/cal.

Furthermore, the above-mentioned steering force control using the hydraulic reaction force is necessary to prevent the driver from feeling uneasy about steering when driving at high speeds, and at this time the pressure generated on the PS side is 10 Kg/cm2.
In such a low pressure state, an error of about 10 to 20% occurs in the sensor output, which poses a problem in terms of detection accuracy.

In addition, this type of detection signal indicating the PS operating state due to the pressure difference between the left and right chambers of the power cylinder for PS can be used not only as a signal for controlling the hydraulic reaction force as described above, but also as a signal for controlling the hydraulic reaction force, for example, in the hydraulic pressure supply section to the power cylinder. There is a desire for a simple differential pressure detection device that is effective for use as a control signal and also as a control signal for an engine idle-up device, etc., and does not have the above-mentioned problems.

Of course, there are high-precision differential pressure gauges that use diaphragms and the like as measuring instruments, but this type of differential pressure gauge has a complicated structure and is expensive. This is not desirable in practical terms as a device, and it is necessary to take some precautions.

[Means to solve the problem]

In order to meet the above-mentioned demands, the differential pressure detection device for a power steering device according to the present invention detects the pressure difference between the left and right chambers into which pressure is introduced into the power cylinder left and right chambers of the power steering device. a differential piston that slides in a cylinder and has an operating end whose tip extends from one side of the piston through one of the left and right chambers and transmits the pressure difference as an electrical signal output; There are left and right springs installed in the left and right chambers that bias the piston so that it is always at the neutral position within the cylinder. It is formed so that it has the characteristic of being continuously displaced, including movement in the vicinity.

[Effect]

According to the present invention, the pressure difference between the left and right chambers of the power cylinder of the power steering device is detected as a mechanical displacement by the piston, and the working end of the rod tip side that moves together with the piston is converted into an electrical signal output. By converting and sending,
Turning is used in various mechanical parts of an automobile as a control signal indicating the operating status of a power steering device.

〔Example〕

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

1 and 2 show an embodiment of a differential pressure detection device for a power steering device according to the present invention, and in these figures, the symbol l constitutes a differential pressure detection device that characterizes the present invention. A cylinder hole 2 is bored in the device body from the negative side, and a cylindrical member 3 is screwed into the open end of the cylinder hole 2.
An adapter 5 to which a potentiometer 4, which is a displacement/electrical conversion means to be described later, is attached to the outer end of the cylindrical member 3 is screwed onto the outer end of the cylindrical member 3, thereby closing the cylinder hole 2. Note that 6a and 6b are nuts for tightening. Further, the above-mentioned adapter 5 functions as an adjustment member when the input shaft 4a is brought into contact with a rod on the piston side, which will be described later, at an appropriate position and assembled.

Reference numeral 10 denotes a differential piston that is slidably disposed in the center of the cylinder hole 2 in the axial direction, and small diameter rods 11 and 12 extend from both the left and right sides of the differential piston, and the outside of the rod 12 on the meter 4 side. The other end faces the inside of the cylindrical member 3 and is configured to be able to input and transmit the movement of the piston 10 by coming into contact with the input shaft 4a on the meter 4 side. Reference numeral 13.14 denotes a stopper member that is fitted into the left and right sides of the piston 10 in the cylinder hole 2 and restricts the movement of the piston 10 within a predetermined stroke range.
, 12 in a slidable manner, and each rod 11, 1
2, the small diameter cylindrical portion 13a extends toward the piston side along 1
The tip of 4a is applied to the piston 10 by a predetermined stroke amount S.
L and SR face each other, and constitute a stopper portion that restricts the movement of the piston 10. 15.16 are arranged in the left and right chambers 17.18 formed between the respective stopper parts 13.14 on both sides of the piston 10, and are arranged in the left and right chambers 17.18.
The set length is determined by each stopper member 13, 14 by left and right springs that normally bias the stopper members 13 and 14 to be in the neutral position, and the stopper members 13 and 14 are locked at the large diameter portion on the outer end side. Further, in the left and right chambers 17 and 18 defined by the piston lO and in which the springs 15 and 16 are installed, hydraulic passages 17 are bored from either side of the body l.
The configuration is such that pressures CL and CR in the left and right chambers of the power cylinders of the power steering device (not shown) are introduced by a and 18a. In addition, 19a.

19b is a connector for introducing the left and right chamber pressures CL and OR. In addition, the left and right chambers 17 and 18 into which these left and right chamber pressures CL and CR are introduced,
It is necessary to provide each of these chambers with a sealed structure that can withstand high pressure such as when the steering is stationary, and for this reason, in this embodiment, the sliding portion of the piston lO that contacts the cylinder hole 2 and the each rod 11 , 12 stopper members 1
3.0 ring 10a; 13b in the part touching 14.

14b and resin ring lO made of resin material such as Teflon
b; 13c and 14c are used to minimize sliding resistance and ensure reliable sealing performance. Furthermore, O-rings 13d and 14 are provided in the large-diameter portion of the stopper member 13.14, which is a simple fitting portion, in contact with the cylinder hole 2.
d is attached. Also, in FIG. 1, 17b, 1
Reference numeral 8b denotes an air bleed plug that communicates with a passageway opening toward the outer end of the left and right chambers 17, 18 and bleeds air from each of these chambers.

In addition, in this embodiment, the rods 13 on both sides of the piston 10,
A low pressure chamber 20.21 which also serves as a pressure oil leakage chamber is formed outside the stopper member 13.
The structure is such that the movement of the piston IO is not restricted. Here, 22 is a hose connector connected to the side of the tank T (not shown), 23 is a passage hole formed in the body l, and the passage hole 23 opens into the cylinder hole 2 to open the low pressure chamber 20. 21 is formed. In addition, 24 is a spacer member having an annular groove and a passage hole that forms one low pressure chamber 20 and connects it to the tank T side. It also plays the role of securing space since it is difficult to finish with high precision to create a sealing surface. In addition, the other low pressure chamber 21
is formed on the inner end side of the cylindrical member 3 and communicates with the tank T side through an annular groove and a passage hole on its outer periphery. Here, 3a is an O-ring that seals the outer periphery of this cylindrical member 3. In addition, when these low pressure chambers 20.21 are provided, the acting pressure on the rod 11.12 is reduced, so even if there is a difference in the pressure acting area of the rods provided on both sides of the piston 10, the unbalanced force can be reduced. There are advantages to getting it. In order to eliminate this unbalanced force, it is preferable to provide a lip seal on the rod portion 11 on one side of the low pressure chamber 20 in the same way as on the other side, so that the area of action is equal on the left and right sides.

Further, in the inner space of this cylindrical member 3, a glue lug seal 25 is used to seal the output transmission part where the tip of the rod 12 faces the input shaft 4a on the meter 4 side from the low pressure chamber 21 and to hold the rod 12 with low friction. is provided inside and is fixed by a retaining ring 26b provided via a step portion inside the cylindrical member 3 and a spacer 26a. The low pressure chamber 21 is configured to use the pressure applied to the tube seal 25 as drain pressure to ensure a reliable sealing state.

Now, according to the present invention, as a differential pressure detection device for a power steering device, a piston structure that can withstand high pressure is adopted as described above, and the left side for biasing the piston 10 to the neutral position is As the right spring 15.16, the third
As shown in the figure, the characteristic is that the composite spring constant K (KS, KS) is formed so that it has a characteristic of continuous displacement including the movement near the neutral position of the piston IO. . That is, such left and right springs 15
．． 16 are simply used in combination so that the set load is zero when the piston 10 is in the neutral position, the load-displacement characteristics will lack continuity, play will occur near the neutral position, and appropriate and reliable differential pressure will not be achieved. In addition, if both springs have a certain set load at the neutral position of the piston IO and both springs do not act simultaneously only in a predetermined area, the characteristics will lack continuity and in this case, That's a problem.

According to the present invention, as is clear from FIG. 3, by combining springs 15 and 16 with the same spring constant and using only the combined spring constant region, a stable piston 10 with continuous load-displacement characteristics can be obtained. This movement eliminates the play that tends to occur near the neutral position, and makes it possible to appropriately and reliably obtain mechanical displacement that changes continuously in response to changes in load. By converting the voltage into a voltage using the potentiometer 4, differential pressure detection can be performed with high precision and excellent reliability.

Since the differential pressure can be detected with high precision in this way, there is no need for electrical components such as the meter 4 to be more reliable than necessary.
It is possible to obtain a highly reliable and inexpensive device by combining simple mechanisms.

Here, according to this embodiment, the movement of the piston IO is set only in the low pressure region, which is a high-speed state where hydraulic reaction force control is most necessary, and the movement of the piston 10 is set mechanically in the high pressure region using the stopper members 13 and 14. The spring 15.
He is right in protecting the 16th. With this configuration, since the springs 15 and 16 are protected, springs with weak spring force can be used, which is advantageous in increasing the degree of freedom in design. However, it is not limited to this, and it will be easily understood that similar effects can be achieved even if the pressure is moved over the entire pressure range used.

According to the differential pressure detection device having such a configuration.

The movement of the piston 10, which is supported for continuous displacement by left and right springs 15 and 16, is controlled by the rod 12.
The detection means (meter 4) can convert it into an electric signal and output it very easily and appropriately, and it is possible to output a detection signal with high accuracy and reliability, and the PS side operation that can be obtained by this. By using the situation as a control signal for a motor that drives an oil pump that generates a hydraulic reaction force, for example, the performance of the steering system can be significantly improved.

However, the application of this type of detection signal is not limited to this, and examples include sending the load state when the PS is activated to a mechanism that controls the supply flow rate in the hydraulic pressure supply system on the PS side, or to an engine idle-up device. This is suitable for use as a control signal, etc. Furthermore, as another example of use,
For example, a control mechanism for a four-wheel drive vehicle or a four-wheel steering vehicle may also be considered. In the case of curved drivers, when using so-called part-time four-wheel drive, braking may occur when making small turns that require a large amount of steering effort, but if the differential pressure between the left and right chambers of the power cylinder of the PS is large, It may be used as a control signal to prevent braking by switching from wheel drive to two-wheel drive. In the latter case, stable rear wheel control can be achieved by using the signal as a signal to confirm the actual steering output of the front wheels and controlling the rear wheels using this signal.

Note that the present invention is not limited to the structure of the embodiment described above, and the shape and structure of each part may be modified or modified as appropriate.
Various modifications may be considered.

For example, in the embodiment described above, the potentiometer 4 is used as a means for converting the movement of the piston 10 into an electric signal via the rod 12, but it will be easily understood that the present invention is not limited to this. In short, any converter that converts mechanical displacement into an electrical signal may be used.

〔Effect of the invention〕

As explained above, according to the differential pressure detection device for a power steering device according to the present invention, the pressure inside the power cylinder is determined according to the pressure difference between the left and right chambers into which the pressure in the left and right chambers of the power cylinder is introduced. A differential piston that slides and has an operating end whose tip extends from one side of the piston through one of the left and right chambers and transmits the pressure difference as an electrical signal output, and this screw is connected to the cylinder. It is equipped with left and right springs placed in both the left and right chambers, which bias it so that it is always in the neutral position.
These left and right springs are formed so that their combined spring constant has the characteristic of continuous displacement, including movement near the piston's neutral position, so the piston remains stable despite its simple and inexpensive configuration. Moreover, by obtaining a movement with a continuous load-displacement characteristic, differential pressure detection can be performed with high reliability, and the operating status of the PS side obtained thereby can be compared with the control signals of various mechanical parts. The performance of the steering system can be greatly improved by using the springs with different spring constants due to processing tolerances. It has a variety of excellent effects, such as being able to use a variety of materials.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view showing one embodiment of the differential pressure detection device according to the present invention, Fig. 2 is a side view thereof, and Fig. 3 is load-displacement characteristics due to left and right springs that bias the piston from both sides. FIG. 1...Device body 4, 2---Cylinder hole, 3...
...Cylindrical member, 4...Adapter, 5...Potentiometer, lO...Piston, 11.12...
・Rod, 13.14...stopper member, 15.1
6...Left, right spring, 17.18...Left,
Right ventricle, 25...Lip seal. Patent applicant: Automotive Equipment Co., Ltd. Agent: Masatsuna Yamakawa (and 2 others) No. 31/13a 14b Procedural amendment (voluntary) 1. Indication of the case 1988 Patent Application No. 6983 2, Name of the invention Differential pressure detection device for power steering device 3, Person making the amendment Relationship to the case Patent applicant name Jidosha Kiki Co., Ltd. 4, Agent address 〒100 Address: Yamakawa International Patent Office, 8th floor, Hidewa Tameike Building, 2-4-2 Nagatacho, Chiyoda-ku, Tokyo

Claims (1)

[Claims] A power cylinder of a power steering device. A piston that is arranged inside the cylinder to define left and right chambers into which pressure is introduced into the left and right chambers, and that slides according to the pressure difference between the two chambers. , left and right springs disposed in both the left and right chambers, which urge the piston to always be in a neutral position within the cylinder, and penetrating one of the left and right chambers from one side of the piston. The left and right springs have a rod whose combined spring constant includes movement near the neutral position of the piston. 1. A differential pressure detection device for a power steering device, characterized in that it is formed so as to have a characteristic of continuously displacing the pressure.