JP4334975B2 - Power steering device for vehicle - Google Patents

Description

  The present invention relates to a vehicle power steering apparatus that applies an operating force to a steering mechanism in accordance with steering of a steering.

  As this type of power steering device, the one disclosed in Patent Document 1 has been devised.

In this power steering apparatus, a power cylinder is provided in a rack portion of a rack and pinion that constitutes a steering mechanism, and the power cylinder is hydraulically operated by a reversible pump driven by a motor. Specifically, the power cylinder includes a piston integrally provided in the rack, and a cylinder main body that is separated into two working chambers by the piston, and each working chamber has an intake / exhaust on the opposite side of the reversible pump. Each is connected to a port. And the connection path which connects both working chambers and a reversible pump comprises a closed circuit fundamentally, and hydraulic fluid is made to flow in into the other connection path from one connection path by the action | operation of a reversible pump. However, when the power cylinder suddenly operates or the like, the inflow amount of the hydraulic oil is insufficient, and therefore a reservoir tank is connected to each connection path via a check valve in order to compensate for the insufficient hydraulic oil.
JP-A-6-16145

However, in this conventional power steering device, although a reservoir tank is provided to compensate for the shortage of hydraulic oil, the hydraulic oil in the reservoir tank is at atmospheric pressure, so the operating direction of the power cylinder is When it changes suddenly, especially when the viscosity of the hydraulic oil is high during cold weather, the compensation of the hydraulic oil may not catch up and the connection path may become negative pressure. In other words, there is a considerable line resistance between the reservoir and each working chamber, and the check valve must be pushed open to introduce hydraulic oil into the connection path. It will be a cause. Then, if the connection path becomes negative pressure, it is considered that the steering feeling is deteriorated or abnormal noise is generated due to cavitation. Therefore, the present invention reliably eliminates the problem that negative pressure is generated in the hydraulic circuit, and the steering feeling. It is an object of the present invention to provide a power steering apparatus for a vehicle that can improve the noise and the quietness.

The present invention has been devised in view of the above-described conventional technical problems. The invention according to claim 1 is divided into two working chambers by a piston, and hydraulic oil is selected for both the working chambers. A power cylinder that applies an operating force to the steering mechanism by supplying and discharging automatically, a first supply / discharge port connected to the one working chamber, and a second supply / discharge port connected to the other working chamber. And a reversible pump whose driving direction and output are controlled in accordance with steering operation, a first connection path connecting the one working chamber and the first intake / exhaust port, the other working chamber and the second A second connection path that connects the intake and exhaust ports, a reservoir tank that stores hydraulic oil, a first replenishment path that connects the reservoir tank and the first connection path, and the reservoir tank and the second connection path A second replenishment path connecting the first replenishment path and the first replenishment path A first check valve for preventing return of hydraulic oil from the first connection path side to the reservoir tank; and a hydraulic oil provided from the second connection path side to the reservoir tank. And a partition wall provided in the reservoir tank and separating a space in the reservoir tank into a region in which the hydraulic oil is stored and another region. The internal hydraulic pressure is characterized by being maintained at a pressure higher than atmospheric pressure .

  In the case of this invention, since the connection path is maintained at a pressure higher than the atmospheric pressure even when the hydraulic oil is rapidly sucked into the working chamber, no negative pressure is generated in the connection path.

Specifically, it provided a reservoir tank for storing create aggressive media, the reservoir tank, as well as connected to the respective connection path via a check valve to prevent the return of hydraulic oil to the tank side, the reservoir tank The internal hydraulic pressure should be higher than the atmospheric pressure.

  In this case, since the pressure in the reservoir tank is set to be higher than the atmospheric pressure in advance, the connection path temporarily becomes negative pressure even when a short amount of hydraulic oil is replenished from the reservoir to the connection path. Will no longer occur.

According to the present invention, the connection path is always maintained at a pressure higher than the atmospheric pressure, so that it is possible to reliably eliminate a problem that a negative pressure is generated in the hydraulic circuit. Therefore, according to the present invention, it is possible to prevent the deterioration of the steering feeling and the generation of abnormal noise due to the negative pressure.
Moreover, since the hydraulic oil and gas in the reservoir tank are separated by the partition wall, it is possible to prevent the gas in the reservoir tank from being mixed into the hydraulic oil. Therefore, the occurrence of cavitation in the connection path can be suppressed.

  Next, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 2 shows an overall schematic configuration of the power steering apparatus according to the first embodiment. As shown in FIG. 2, the power steering apparatus includes a steering shaft 1 having a steering wheel (not shown) connected to an upper end portion thereof, A rack and pinion 2 provided on the lower end side of the steering shaft 1 to form a steering mechanism, a torque sensor 3 (steering state detecting means) provided on the steering shaft 1 for detecting steering torque, and a rack of the rack and pinion 2 A hydraulic cylinder 6 including a power cylinder 4 provided in a portion for generating a hydraulic assist force corresponding to the steering torque, a reversible pump 5 that sucks and discharges hydraulic pressure to and from the power cylinder 4, and the reversible pump 5 as an output of the torque sensor 3. And a controller 7 that performs control according to the above.

  In the power cylinder 4, a cylinder body 8 is fixedly installed on the vehicle body side, and a piston rod 9 penetrating the cylinder body 8 is integrally coupled to the rack. The piston 10 provided integrally with the piston rod 9 is slidably fitted to the cylinder body 8, and the interior of the cylinder body 8 is divided into a first working chamber 11 and a second working chamber 12.

  As shown in FIG. 1, the hydraulic circuit 6 includes a reversible pump 5 that is driven forward and backward by an electric motor 13, and one intake / exhaust port 5a of the reversible pump 5 (hereinafter referred to as "first intake / exhaust port 5a"). Connecting path 14 connecting the first working chamber 11, the other suction port 5 b of the reversible pump 5 (hereinafter referred to as “second suction port 5 b”) and the second working chamber 12. 15, a reservoir tank 16 for storing hydraulic oil, replenishment paths 17 and 18 connecting the connection paths 14 and 15 and the reservoir tank 16, and the connection paths 14 and 15 bypassing the reversible pump 5. And a fail-safe valve 20 that opens the bypass passage 19 when the electric motor 13 or the like is abnormal. The replenishing passages 17 and 18 are respectively provided with check valves 21 and 22 for preventing a back flow from the connection passages 14 and 15 to the reservoir tank 16 side. The hydraulic circuit 6 basically has both working chambers 11 and 12. Is connected to the connection paths 14 and 15 via the reversible pump 5.

  The reservoir tank 16 has a sealed structure, and the inside thereof is filled with a gas G such as nitrogen gas together with the working oil, and the working oil in the tank 16 is constantly maintained at a set pressure or higher by the gas pressure of the gas G. Yes. The gas pressure in the reservoir tank 16 is such that when the hydraulic oil is introduced into the connection paths 14 and 15 via the replenishment paths 17 and 18, the connection paths 14 and 15 are constantly at a pressure higher than the atmospheric pressure. The high pressure is set in consideration of the pipe resistance, the valve opening pressure of the check valves 21 and 22, and the like.

  A leak passage 23 is provided between the reversible pump 5 and the reservoir tank 16 so that excess oil in the connection paths 14 and 15 is appropriately returned to the reservoir tank 16 side.

  Since the power steering apparatus has the above-described configuration, when the steering wheel is operated during driving of the vehicle, the steering torque is detected by the torque sensor 3, and the electric motor 13 is controlled based on the detection signal at this time. Is done. Thereby, the rotation direction and discharge amount of the reversible pump 5 are controlled according to the steering torque, and the power cylinder 4 generates an assist force according to the steering state of the steering wheel.

  When the power cylinder 4 is operated by the reversible pump 5 in this way, the hydraulic oil is introduced into one working chamber 11 (or 12) through the connection path 14 (or 15) and at the same time the other working chamber 12 ( Alternatively, the hydraulic oil 11) is discharged through another connection path 15 (or 14). The supply and discharge of the hydraulic oil in both the working chambers 11 and 12 is basically performed in a mutually complementary manner via the connection paths 14 and 15, but when the steering operation direction is suddenly switched, the working chamber 11 ( Alternatively, since the hydraulic oil introduced into 12) is insufficient, at this time, the insufficient hydraulic oil is supplied from the reservoir tank 16 through the replenishment path 17 (or 18).

  In the case of the power steering apparatus of this embodiment, the hydraulic oil in the reservoir tank 16 is maintained at a high pressure in advance, and the hydraulic oil is introduced into the connection path 14 (15) at a pressure higher than atmospheric pressure. The connection path 14 (15) and the working chamber 11 (or 12) do not become negative pressure at this time. In particular, when the temperature is cold or cold, the viscosity of the hydraulic oil increases and the flow resistance in the pipe line tends to increase. However, even under such conditions, the hydraulic oil is less than atmospheric pressure in the connection path 14 (15). Since replenishment is performed in a high pressure state, the generation of negative pressure can be reliably prevented.

  Therefore, in this power steering apparatus, since the generation of negative pressure in the connection path 14 (15) can be eliminated, it is possible to prevent the deterioration of steering feeling and the generation of abnormal noise due to the generation of negative pressure. be able to.

  In the case of the power steering device of this embodiment, since the reservoir tank 16 has a hermetically sealed structure, there is no fear that hydraulic oil flows out to the outside even if the reservoir tank 16 is installed at an angle. Therefore, this apparatus has an advantage that the degree of freedom of arrangement of the reservoir tank 16 is high.

  Next, the second embodiment shown in FIG. 3 and the third embodiment shown in FIG. 4 will be described. In these embodiments, the basic configuration is substantially the same as that of the first embodiment, but the structure of the reservoir tank is slightly different. In the following, each embodiment will be described with a focus on this difference, but the same reference numerals will be given to the same parts, and the description of overlapping parts will be omitted.

  The reservoir tank 116 of the second embodiment is formed in a sealed state as in the first embodiment, but the inside of the tank 116 is divided into an oil chamber 31 and a gas chamber 32 by a diaphragm 30 (partition wall). It is divided into. The replenishment passages 17 and 18 are connected to the oil chamber 31, and the gas chamber 32 is filled with the high-pressure gas G similar to that of the first embodiment. The pressure in the gas chamber 32 acts on the hydraulic oil in the oil chamber 31 through the diaphragm 30.

  In the case of the apparatus of this embodiment, since the hydraulic oil and gas G in the reservoir tank 116 are completely separated by the diaphragm 30, it is possible to reliably prevent the gas G in the tank 116 from being mixed into the hydraulic oil. it can. Therefore, the occurrence of cavitation in the connection paths 14 and 15 can be prevented more reliably.

  Further, in the apparatus of this embodiment, the gas is not sucked into the replenishment passages 17 and 18 even if the reservoir tank 116 is installed sideways or upside down. There are advantages. Further, when the diaphragm 30 is used as a partition wall separating the inside of the reservoir tank 116 as in this embodiment, the shape of the reservoir tank 116 itself is not easily limited by the partition wall, and the degree of freedom of the shape of the reservoir tank 116 is increased. .

  On the other hand, in the reservoir tank 216 of the third embodiment, a piston 35 that is a partition wall is slidably accommodated inside, and one space defined by the piston 35 is defined as an oil chamber 31, and the other space is formed in the other space. A spring member 36 (urging means) for urging the piston 35 toward the oil chamber 31 is accommodated. The tank 216 and the piston 35 are sealed by a seal ring 37, and the other space is open to the atmosphere.

  In the reservoir tank 216 of this embodiment, since the internal hydraulic oil is brought into non-contact with the atmosphere by the piston 35, there is no problem that air is mixed into the hydraulic oil, and cavitation occurs in the connection paths 14 and 15. Can be prevented more reliably. Moreover, since the reservoir tank 216 does not enclose the high-pressure gas inside unlike the second embodiment, there is an advantage that the tank 216 can be easily assembled. In the case of this embodiment, there is no concern that hydraulic oil will flow out even if the reservoir tank 216 is installed sideways or upside down, so that there is an advantage that the degree of freedom in the arrangement of the tank 216 is high.

  Next, inventions other than those described in the claims that can be grasped from each of the above embodiments will be described below together with the effects thereof.

  (A) The vehicle power steering apparatus according to claim 2, wherein the reservoir tank is sealed, and the tank is filled with a gas having a pressure higher than the atmospheric pressure together with hydraulic oil.

  In this case, the hydraulic oil pressure can be maintained at a high pressure only by filling the reservoir tank with a high-pressure gas, and leakage of the hydraulic oil from the reservoir tank can be reliably prevented. Furthermore, even if the reservoir tank is installed at an angle, there is no fear that hydraulic oil will flow out, so the degree of freedom of arrangement in the vehicle is increased.

  (B) A vehicular power steering system according to (a) above, wherein a partition wall for separating hydraulic oil and gas is provided inside the reservoir tank, and the pressure of the high-pressure gas is applied to the hydraulic oil through the partition wall. apparatus.

  In this case, since the gas in the tank does not come into direct contact with the hydraulic oil, the occurrence of cavitation due to the gas being mixed into the hydraulic fluid can be eliminated. In addition, even if the reservoir tank is installed sideways or upside down, there is no concern that gas will be sucked in, so there is an advantage that the degree of freedom in arranging the reservoir tank is further increased.

  (C) The valve timing control for an internal combustion engine according to claim 2, wherein a partition wall for separating an oil chamber is provided inside the reservoir tank, and the partition wall is urged by an urging member toward the oil chamber. apparatus.

  In this case, since the hydraulic oil can be maintained at a high pressure without filling the reservoir tank with high-pressure gas, the reservoir tank can be easily assembled. Further, the arrangement side of the urging member does not necessarily need to be sealed, but even in that case, since the hydraulic oil is prevented from flowing out by the partition wall, the reservoir tank can be arranged in any direction. . Therefore, also in this case, the degree of freedom of arrangement increases.

  (D) The valve timing control device for an internal combustion engine according to claim 2, further comprising a leak passage for returning surplus oil in the connection passage to the reservoir tank.

  In this case, it is possible to prevent an abnormal increase in the pressure in the circuit due to excessive flow of hydraulic oil or thermal expansion.

1 is a hydraulic circuit diagram showing a first embodiment of the present invention. The whole block diagram which shows the same embodiment. The hydraulic circuit diagram which shows the 2nd Embodiment of this invention. The hydraulic circuit diagram which shows the 3rd Embodiment of this invention.

Explanation of symbols

2 ... Rack and pinion (steering mechanism)
DESCRIPTION OF SYMBOLS 4 ... Power cylinder 5 ... Reversible pump 5a ... 1st supply / discharge port 5b ... 2nd supply / discharge port 10 ... Piston 11 ... 1st working chamber 12 ... 2nd working chamber 14, 15 ... Connection path 16,116,216 ... Reservoir Tanks 21, 22 ... Check valves

Claims (1)

A power cylinder which is divided into two working chambers by a piston, and applies operating force to the steering mechanism by selectively supplying and discharging hydraulic oil to and from both working chambers;
A reversible pump having a first supply / discharge port connected to the one working chamber and a second supply / discharge port connected to the other working chamber, the drive direction and output of which are controlled in accordance with steering operation; ,
A first connection path connecting the one working chamber and the first intake / exhaust port;
A second connection path connecting the other working chamber and the second intake / exhaust port;
A reservoir tank for storing hydraulic oil;
A first replenishment path connecting the reservoir tank and the first connection path;
A second replenishment path connecting the reservoir tank and the second connection path;
A first check valve provided in the first replenishment path and preventing return of hydraulic oil from the first connection path side to the reservoir tank;
A second check valve provided in the second replenishment path and preventing return of hydraulic oil from the second connection path side to the reservoir tank;
A partition wall provided in the reservoir tank, and partitioning a space in the reservoir tank into a region where hydraulic oil is stored and another region;
With
The vehicular power steering apparatus, wherein the hydraulic pressure in the reservoir tank is maintained at a pressure higher than atmospheric pressure .

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