JPH0417816B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in power steering devices.

(Prior Art) Generally, a power steering device that assists the steering force is effective when operating a steering wheel that requires a large steering force, such as when driving at low speeds, and is effective when driving at high speeds, for example. However, the assistance of steering force by a power steering device actually impairs driving stability.

Therefore, conventionally, in order to operate the power steering device according to the driving conditions of the vehicle, the drive of the oil pump that supplies pressure oil to the power cylinder of the steering device has been controlled to rotate and stop according to the driving conditions of the vehicle. A technique has been proposed to do this (see Japanese Utility Model Application Publication No. 55-34930).

(Problems to be Solved by the Invention) The above-mentioned proposed technology not only ensures running stability, but also reduces the load on the engine in running conditions that do not require steering assist force, thereby improving fuel efficiency by reducing drive loss. Additionally, it has the advantage of improving the durability of the oil pump drive system. However, when the operation is controlled so that the steering assist force is applied to the steering wheel by starting the oil pump drive, the steering force suddenly decreases, which tends to cause the steering wheel to over-rotate (turn too much). It has the following.

In view of this, the present invention attempts to improve safety by preventing a sudden reduction in steering force when controlling the operation so that steering assist force is applied to the steering wheel by starting the drive of the oil pump. It is something.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention includes a power cylinder having two oil chambers that assist steering force, and a power cylinder that supplies pressurized oil. a controller that controls the rotation and stopping of this oil pump according to the driving conditions of the vehicle; and a controller that is interposed between the oil pump and the power cylinder to control the pressure from the oil pump in response to the rotation of the handle. A switching valve that switches to selectively supply oil to the two oil chambers of the power cylinder, and a first oil passage and a second oil passage that communicate the switching valve and the two oil chambers of the power cylinder, respectively. and a third oil passage that communicates the switching valve and the oil pump. A bypass oil passage that communicates the two oil chambers of the power cylinder, and a single control valve that is interposed in the bypass oil passage and closes and opens the bypass oil passage in response to rotation and stoppage of the oil pump. This control valve is connected to the third oil passage, and the pressure oil on the oil pump side upstream of the switching valve is guided to the control valve, and the pressure oil on the oil pump side upstream of the switching valve is used to control the control valve. and a valve speed delay member that delays at least the speed of the closing operation of the control valve.

(Function) As a result, in the present invention, when the oil pump is rotated from a stopped state and pressure oil is supplied to the power cylinder, the fourth oil passage supplies the control valve with the pressure oil on the oil pump side upstream of the switching valve. is introduced, and the control valve operates to close the bypass oil passage. The speed of the closing operation is slowed down by the valve speed delay member, and in order to gradually close the bypass oil passage, the supply of pressure oil to the power cylinder is also slowed down to prevent a sudden increase in auxiliary force. Become.

In this case, the hydraulic pressure for operating the control valve is led from the oil pump side upstream of the switching valve, so when the oil pump is operating, the hydraulic pressure for operating the control valve is always generated, so the bypass oil path Only one valve body is required as a control valve for opening and closing, simplifying the structure.

(Example) Examples of the present invention will be described below with reference to the drawings. In the overall configuration shown in FIG. 1, the steering wheel 1 is configured in a rack and pinion ring type, and the steering force of the steering wheel 2 is applied to a steering shaft 3, a pinion gear 4, a rack shaft 5 having a rack 5a, tie rods 6, 6, and knuckle arms 7, 7.
The signal is transmitted to the wheels 8, 8 through the steering wheel, and steering is performed.

A power steering device 10 installed on the steering wheel 1 supplies pressurized oil from an oil pump 12 driven by an electric motor 11 to a power cylinder 13 installed on the rack shaft 5 to control the rotation of the steering wheel 2. It is configured to assist in steering power.

A controller 14 controls starting and stopping of the electric motor 11 according to the driving conditions (vehicle speed) of the vehicle.The controller 14 controls the rotation and stopping of the oil pump 12. A vehicle speed sensor 15 and a battery 16 are connected to the controller 14, and when the vehicle speed detected by the vehicle speed sensor 15 is below a predetermined value (approximately 20 km/h), the electric motor 11 is connected to the battery 16 and the oil pump is activated. 1
2 to generate auxiliary force.

The pressure oil supplied by the rotation of the oil pump 12 is passed from the supply oil passage 17 as the third oil passage through the switching valve 19 to the first oil passage 20a or the second oil passage 2.
0b, the first oil chamber 13 of the power cylinder 13
a or the second oil chamber 13b.
Further, the return oil passage 18 carries oil discharged from the first oil chamber 13a or the second oil chamber 13b to which pressure oil is not supplied to the first oil passage 20a or the second oil passage 13b.
0b, the oil pump 12 is connected via the switching valve 19.
It is to be returned to.

Further, the switching valve 19 responds to the rotation of the handle 2 to transfer the pressure oil from the oil pump 12 to the first oil chamber 13a or the second oil chamber 13 of the power cylinder 13.
In addition to selecting and deciding which of b to supply,
The second oil passage chamber 3b or the first oil chamber 1 that does not supply pressure oil
3a and the return oil passage 18 are communicated with each other.

21 is a bypass oil passage that communicates the two oil chambers 13a and 13b of the power cylinder 13;
This short-circuits the first oil passage 20a and the second oil passage 20b. This bypass oil passage 21 is provided with a control valve 22 that closes and opens the bypass oil passage 21 in response to rotation and stoppage of the oil pump 12. The control valve 22 closes the bypass oil passage 21 when the oil pump 12 rotates to cut off communication between the first oil chamber 13a and the second oil chamber 13b of the power cylinder 13, while when the oil pump 12 is stopped , the bypass oil passage 21 is opened and the first oil chamber 13a and the second oil chamber 13b of the power cylinder 13 are operated to communicate with each other.

The control valve 22 opens and closes in response to hydraulic pressure on the oil pump side upstream of the switching valve 19 (that is, the discharge pressure of the oil pump 12) through a branch supply oil passage 17a serving as a fourth oil passage branched from the supply oil passage 17. A branch return oil passage 18a that is activated and merges with the return oil passage 18 is connected thereto.

The piston 13c that partitions the first oil chamber 13a and the second oil chamber 13b of the power cylinder 13 is
It is fixed and integrated with the rack shaft 5. When the oil pump 12 rotates, the control valve 22 closes the bypass oil passage 21 and the first oil chamber 1
3a or the second oil chamber 13b to energize the gear shaft 5 to assist steering force, while when the oil pump 12 is stopped, the control valve 2
2 opens the bypass oil passage 21, and the power cylinder 1
The first oil chamber 13a and the second oil chamber 13b of the power cylinder 13 are communicated with each other to allow the movement of the piston 13c of the power cylinder 13 so as not to create resistance to the movement of the rack shaft 5 accompanying the rotational operation of the handle 2.

In FIG. 1, the oil pump 12 is driven by the electric motor 11 controlled by the controller 14, but as shown in FIG. 2, the oil pump 12 is driven by the output shaft 24 of the engine 23. You can do it like this. that time,
In order to control rotation and stop of the oil pump 12,
An electromagnetic clutch 27 is interposed in a transmission mechanism made up of pulleys 25a, 25b and a belt 26, and this electromagnetic clutch 27 is controlled by the controller 14 as in FIG. Then, the oil pump 12 is rotated and stopped.

In addition, regarding the timing at which the oil pump 12 is rotated, that is, the running conditions for assisting the steering force, in addition to the above-mentioned low vehicle speeds, in addition to this, after the clutch pedal or brake pedal is operated, time (e.g. 40 seconds to 20 minutes)
During this period, the oil pump 12 may be rotated, and the operation of the oil pump 12 may be controlled as appropriate depending on various desired driving conditions.

Next, in the overall configuration shown in FIG. 1, the control valve 22 that opens and closes the bypass oil passage 21 is equipped with a valve speed delay member (not shown in FIG. 1) that slows down the speed of its closing operation. . This valve speed delay member is configured such that the control valve 22 closes the bypass oil passage 21 in response to the rotational operation of the oil pump 12, and the pressure oil of the oil pump 12 is transferred to the first oil chamber 1 of the power cylinder 13.
3a or the first oil chamber 13b,
In order to prevent the steering force of the steering wheel 2 from suddenly decreasing due to the sudden increase in the auxiliary force caused by the sudden supply of pressure oil to the power cylinder 13,
This is to slow down the operating speed of the control valve 22 to the closed state, and specific structural examples thereof will be shown in the following embodiments.

<Example 1> In a control valve 22A shown in FIG. 3, 28 is a spool housed in a cylinder 29, and a branch supply oil passage 17a is connected to a front chamber 29a of the spool 28, while a rear chamber 29b is connected to a branch supply oil passage 17a. A spring 30 is compressed and a branch return oil passage 18a is connected to the spring 30. In addition, a passage 28a is formed in the spool 28, which communicates with the bypass oil passage 21 when the spool 28 returns, and a front chamber 29a from the branch supply oil passage 17a is formed in the spool 28.
When the spool 28 moves due to the action of pressure oil (pressure oil on the oil pump 12 side upstream of the switching valve 19), communication with the bypass oil passage 21 is cut off.

Further, a rod 31 is connected to the spool 28, and the tip of the rod 31 is attached to a piston 34 in a cylinder 33 of the valve speed delay member 32A.
is connected to. This piston 34 is provided with a valve body 34b that opens and closes a communication hole 34a formed in the piston 34, and when the spool 28 of the control valve 22A moves due to the introduction of pressure oil from the oil pump 12, Then, the valve body 34b closes the communication hole 34a and causes the air in the first chamber 33a to flow out into the second chamber 33b through the pore 34c with a narrowed passage area, thereby resisting the movement of the spool 28. It is attached to slow down its movement speed.

Note that when the spool 28 is moved back by the spring 30, the valve body 34b is inserted into the communication hole 34a.
Since the valve speed delay member 32A is opened, the valve speed delay member 32A does not act as a movement resistance for the spool 28, and the spool 28 moves at a fast movement speed to communicate with the bypass oil passage 21.

With the above configuration, when the vehicle speed is lower than the set value and the oil pump 12 is rotated from a stopped state and pressure oil is supplied to the power cylinder 13, the oil pump 12 discharges into the front chamber 29a of the control valve 22A. The pressure acts and the spool 28 moves to close the bypass oil passage 21. However, its movement is slowed down by the valve speed delay member 32A, and in order to slowly close the bypass oil passage 21, the supply of pressure oil to the power cylinder 13 is also slowed down to prevent a sudden increase in auxiliary force. .

In this case, since the hydraulic pressure for operating the control valve 22A is led from the oil pump 12 side upstream from the switching valve 19, the hydraulic pressure for operating the control valve 22A is always generated when the oil pump 12 is operating. Therefore, only one valve body is required as the control valve 22A for opening and closing the bypass oil passage 21, which simplifies the structure.

On the other hand, when the vehicle speed increases beyond the set value and the oil pump 12 stops rotating, the supply of pressure oil to the power cylinder 13 stops, the oil pressure acting on the control valve 22A also decreases, and the spool 28 The return operation is performed by the spring 30. However, at this time, the valve speed delay member 32
A does not work, the spool 28 quickly moves to open the bypass oil passage 21, and the power cylinder 13
This prevents the occurrence of oil lock, etc., and immediately releases the movement resistance of the rack shaft 5.

<Example 2> A control valve 22B of this example is shown in FIG. 4, and the same structures as in the previous example are given the same reference numerals. cylinder 29
The spool 28 housed in the
When pressure oil acts on the front chamber 29a, it moves against the spring 30 of the rear chamber 29b and closes the bypass oil passage 21 communicating with the passage 28a.

The valve speed delay member 32B in this example is provided with a one-way valve 35 interposed in the middle of the branch return oil passage 18a connected to the rear chamber 29b. The one-way valve 35
The oil branches from the rear chamber 29b to the return oil path 18.
It closes when the oil flows out to a, and the oil is throttled by the pores 36 and provides resistance to the movement of the spool 28, slowing down the speed at which the spool 28 closes the bypass oil passage 21. When the spring 30 returns, the one-way valve 35 opens to allow the spool 28 to move quickly. The action of this control valve 22B on the power cylinder 13 is the same as in the previous example.

<Example 3> The control valve 22C of this example is shown in FIG.
Similar structures are given the same reference numerals. A branch supply oil passage 17a on which the discharge pressure of the oil pump 12 acts is connected to the front chamber 29a of the cylinder 29, but a branch return oil passage 18a is not connected to the rear chamber 29b. The oil flows into and out of the rear chamber 29b through a communication path 37 provided in the spool 28, and in the middle of this communication path 37, there are
Valve speed delay member 32 equipped with one-way valve 35 and pore 36 similar to valve speed delay member 32B of Example 2
C is provided, and functions similarly to the previous example to slow down the speed of movement of the spool 28 to the closed state.

<Example 4> The control valve 22D of this example is shown in FIG.
Structures similar to those in FIG. 4 are given the same reference numerals.
In this example, the same spool 2 as in Example 2 is used.
8 and a cylinder 29, and to which a branch supply oil passage 17a, a branch return oil passage 18a, and a bypass oil passage 21 are connected, there is a control valve 22D in the middle of a branch return oil passage 18a connected to a rear chamber 29b. An orifice 38 is formed to constitute a valve speed delay member 32D.

In this example, as pressure oil acts on the front chamber 29a and the spool 28 moves to close the bypass oil passage 21, the oil flowing out from the front chamber 29a to the branch return oil passage 18a is transferred to the orifice 38. This restricts the movement of the spool 28 and slows down its closing speed.

In addition, in the first to third embodiments, when the spool 28 is returned by the spring 30, the delay function of the control valves 22A to 22C is not activated, and the spool 28 is moved quickly. However, in the fourth embodiment, even when the spool 28 is returned by the spring 30,
The oil flowing into the rear chamber 29b from the branch return oil passage 18a is throttled by the orifice 38 of the valve speed delay member 32D, and the movement of the spool 28 is delayed. However, in actual use, even if the rotational operation of the oil pump 12 is controlled to stop, the oil pump 12 rotates slightly due to its inertia, so the auxiliary force does not disappear instantaneously but gradually decreases. Even if the return movement of the spool 28 is slightly delayed, there is practically no problem in practice, and the structure is advantageous in that it is simple.

<Example 5> The control valve 22E of this example is shown in FIG.
Structures similar to those in FIG. 5 are given the same reference numerals.
In this example, the same spool 2 as in Example 3 is used.
8 and a cylinder 29, and is connected to the branch supply oil passage 17a and the bypass oil passage 21, and the spool 28 has a front chamber 29a and a rear chamber 29b.
The control valve 22 has a communication passage 37 that communicates with the control valve 22 and
Regarding E, the communication passage 37 itself is formed to have a small diameter and is provided so as to have the function of the orifice 38 of the previous example, thereby forming the valve speed delay member 32E.

In this example, similar to the previous example (Example 4),
Both when pressure oil acts on the front chamber 29a and the spool 28 closes the bypass oil passage 21, and when the spool 28 is returned by the spring 30, the communication passage 37 of the valve speed delay member 32E This acts to restrict the oil flowing in and out of the rear chamber 29b, thereby slowing down the moving speed of the spool 28.

Further, in the fifth embodiment, when pressure oil acts on the front chamber 29a and the spool 28 moves against the spring 30, when a predetermined period of time has elapsed, the pressure in the front chamber 29a and the rear chamber 29b is are balanced, the spool 28 is moved back by the spring 30 to open the bypass oil passage 21 even before the oil pump 12 stops, thereby opening the first oil chamber 13a and the second oil chamber 13b of the power cylinder 13.
As a result, the auxiliary force is reduced as a result, but normally the steering is completed within a predetermined time until the spool 28 returns, and the auxiliary force acts effectively within this time. Therefore, it is not so much of a problem in practice.

<Example 6> The control valve 22F of this example is shown in FIG.
Structures similar to those in FIG. 3 are labeled the same. The control valves 22A to 22E in Examples 1 to 5 are hydraulic valves that operate in response to the discharge pressure of the oil pump 12 to open and close the bypass oil passage 21, but the control valve 22F in this example is , stored in the cylinder 29 and connected to the bypass oil passage 2 in the passage 28a.
The spool 28 that opens and closes the communication of the spool 1 is configured to be switched and operated by a solenoid 39. The solenoid 39 is energized by the controller 1 that controls rotation and stop of the oil pump 12.
4, when the oil pump 12 rotates, the solenoid 39 is energized to move the spool 28 against the spring 30, thereby closing the bypass oil passage 21. At that time, the above spool 28
A valve speed delay member 32F configured similarly to the valve speed delay member 32A of the first embodiment is connected to the valve speed delay member 32F via a rod 31, which delays the moving speed of the spool 28.

Further, when the oil pump 12 is stopped, the energization to the solenoid 39 is cut off, and the spool 28 is moved back by the spring 30 to open the bypass oil passage 21. At this time, the delay function of the valve speed delay member 32F does not work.

In this sixth embodiment, instead of using the valve speed delay member 32F, the controller 14 may control the current supplied to the solenoid 39 to gradually increase, thereby slowing down the moving speed of the spool 28. good.

(Effects of the Invention) As described above, according to the present invention, the control valve that closes and opens the bypass oil passage that communicates the two oil chambers of the power cylinder in response to rotation and stoppage of the oil pump, The hydraulic pressure on the oil pump side upstream of the switching valve is used as the hydraulic pressure for operating the control valve, and at least the speed of the closing operation of this control valve is delayed, so even with a simple structure using one control valve, the vehicle When the oil pump rotates from a stopped state depending on the driving conditions of It is possible to prevent over-speed operation and improve safety. Therefore, it has the advantage that desired effects such as improved running stability, fuel efficiency, and durability, which are obtained by rotating and stopping the oil pump depending on the running conditions, can be fully exhibited.

[Brief explanation of drawings]

The drawings illustrate embodiments of the present invention, with FIG. 1 being an overall configuration diagram of a power steering device, and FIG. 2 being a partial configuration diagram showing a modification of an oil pump drive system.
FIGS. 3 to 8 are cross-sectional configuration diagrams showing embodiments 1 to 6, respectively, of specific structural examples of control valves equipped with valve speed delay members. 1...Steering, 2...Handle, 5...
Rack shaft, 10...Power steering device, 11...Electric motor, 12...Oil pump, 13...Power cylinder, 13a, 13b...
...oil chamber, 14...controller, 17...supply oil passage (third oil passage), 17a...branch supply oil passage (fourth oil passage)
oil passage), 19... switching valve, 20a... first oil passage,
20b...Second oil passage, 21...Bypass oil passage, 2
2, 22A to 22F... Control valve, 28... Spool, 30... Spring, 32A to 32F... Valve speed delay member, 38... Orifice.

Claims (1)

[Scope of Claims] 1. A power cylinder having two oil chambers for assisting the steering force, an oil pump for supplying pressure oil to the power cylinder, and a system that adjusts the oil pump according to the driving conditions of the vehicle. A controller is interposed between the oil pump and the power cylinder to control rotation and stop, and is configured to selectively supply pressurized oil from the oil pump to the two oil chambers of the power cylinder in response to rotation of the handle. a first oil passage and a second oil passage that respectively communicate the switching valve with the two oil chambers of the power cylinder; and a third oil passage that communicates the switching valve with the oil pump. A power steering device comprising: a bypass oil passage that communicates the two oil chambers of the power cylinder; and a bypass oil passage that is interposed in the bypass oil passage and is closed in response to rotation or stoppage of the oil pump.・
A single control valve that opens, and this control valve is connected to the third oil passage, and the pressure oil on the oil pump side upstream of the switching valve is guided to the oil pump side upstream of the switching valve. A power steering device comprising: a fourth oil passage that operates the control valve with pressure oil; and a valve speed delay member that delays at least the speed of the closing operation of the control valve.