JPH022700Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention relates to the improvement of a power steering device,
An input shaft connected to a steering handle, an output shaft connected to a steering wheel, a torsion bar connecting the input shaft and the output shaft, a power cylinder connected to the output shaft, and a hydraulic power source. an oil passage switching rotary valve that is interposed in a high-pressure oil passage that communicates with the power cylinder and selectively distributes oil to the power cylinder according to the rotation angle difference between the input shaft and the output shaft; A pressure reducing passage located downstream of the road switching rotary valve and arranged between the input shaft and the torsion bar, and a pressure reducing passage formed between the outer peripheral surface of the input shaft and the valve housing of the power cylinder. A low-pressure oil passage that returns hydraulic pressure to the oil tank, a plurality of reaction force pistons disposed between the input shaft and the output shaft to regulate relative torsional displacement between the two, and each of the reaction forces from the high-pressure oil passage. A branch oil passage branched to the chamber on the reaction force increasing side of the piston, an oil passage opening/closing valve installed in the branching oil passage and opened when the vehicle is running at a certain speed or higher, and the downstream side of the oil passage opening/closing valve. a pressure control valve disposed in the input shaft to maintain the pressure of the hydraulic oil at a substantially constant level, a pore formed in the input shaft to communicate the pressure reduction passage with the low pressure oil passage, and a pilot valve formed in the pressure reduction passage. An oil passage that transmits hydraulic pressure to the pilot hydraulic chamber of the pressure control valve and communicates with the reaction force reduction side chamber of the reaction piston, and an outer side of the low pressure oil passage between the input shaft and the valve housing. It is characterized by having an oil seal disposed therein, and its purpose is not to increase the friction generated around the input shaft. Seal reliability can be improved. Another object of the present invention is to provide an improved power steering device that can smoothly change the effective working pressure of the reaction piston.

Next, the power steering device of the present invention is installed in the first place.
2. To explain with one embodiment shown in the figure, 1a is an engine, 1b is an oil pump driven by the engine 1a, 2 is a rotary valve for switching oil passages,
3 is a power cylinder, 4 is a tank, 5 is a plurality of reaction pistons provided around the oil passage switching rotary valve 2, 6 is a chamber formed behind the piston 5, and 8 is the oil pump 1b and the above. A high pressure oil passage between the oil passage switching valve 2, 9 a low pressure oil passage between the oil passage switching valve 2 and the tank 4, 7 a small hole provided in the middle of the low pressure oil passage 9, and 8'. is from the middle of the high pressure oil passage 8 to the chamber 6 of the reaction piston 5.
10 is an oil passage opening/closing valve interposed in the middle of the branch oil passage 8', and this will be explained in detail with reference to FIG. 3. 21 is a valve housing, 22
is a spool, 23 is a spring that urges the spool 22 to the left, 24 is a solenoid, 25 is a rod on the solenoid 24 side, 25' is a slit provided at the tip of the rod 25, 26 is a plug, 27, 2
8 is an O-ring, 29 is the above-mentioned valve housing 21
Snap spring inserted into the groove of 30, 31, 3
2 is a chamber, and 33 is an oil passage provided in the spool 22. When the vehicle is stopped or running at low speed, the solenoid 24 is energized based on a signal from a vehicle speed sensor (not shown), and the spool 22 is connected to the spool 22 via a rod 25.
moves to the right from the position shown in Fig. 3, and the branch oil passage 8' is blocked, and when driving at medium or high speeds, the energization to the solenoid 24 is stopped based on the signal from the vehicle speed sensor, and the spool 22 is released from the spring. It moves to the left by the reaction force of 23, and the oil passage to the pressure control valve 11 is opened. Also, the first
Reference numeral 11 in Figures 2 and 4 is a pressure control valve installed in the branch oil passage 8' on the downstream side of the oil passage opening/closing valve 10. To explain this in detail with reference to Figures 2 and 4, 21 is a valve housing. , 13 is a spool, 14 is a spring that biases the spool 13 to the left, 15 is a hydraulic oil inlet provided in the valve body 12, 16 is a hydraulic oil outlet provided in the valve housing 21, 1
Reference numeral 7 denotes an oil drain hole provided in the valve housing 21, and the oil drain hole 17 is connected to the low pressure oil path 9 via an oil path 9'. Also 18a, 18b, 18
c and 18d are chambers in the valve housing 21 formed by the spool 13, 19a is a communication hole provided in the spool 13, 19b is a small hole provided in the spool 13, and the chamber 18c connects the low pressure oil path 9'. The chamber 18d is connected to the low pressure oil passage 9 on the tank 4 side downstream of the fine hole 7 through the low pressure oil passage 9, and the chamber 18d is connected to the low pressure oil passage 9 on the oil passage switching valve 2 side upstream of the fine hole 7 through the low pressure oil passage 9''. Next, the oil passage switching rotary valve 2 will be explained in detail with reference to FIG. 1. 35 is the valve housing 2.
Rack support provided at 1, 36 is easy, 37
is a pinion meshed with the rack 36, 39 is an input shaft, 38 is a torsion bar connecting the input shaft 39 and the pinion 37, and 40 is the input shaft 39.
Valve body installed around 41, 42, 4
3 is an annular groove provided on the outer peripheral surface of the valve body 40, 44 is a plurality of oil passages extending radially inward from the annular groove 41, and 45 is a plurality of oil passages provided along the axial direction on the inner peripheral surface of the valve body 40. Each oil passage 45 communicates with the annular groove 42 . Further, there is a similar oil passage (not shown) between each of the oil passages 45, which communicates the annular groove 41 and the annular groove 43. 46 is a plurality of oil passages passing through the input shaft 39 in the radial direction; 47 and 48 are oil passages extending from the annular grooves 42 and 43 through the wall of the valve housing 21 to the cylinder 3; and 49 is the torsion bar. 38 and the input shaft 39, the pressure oil from the oil pump 1b is routed through the high pressure oil passage 8 → annular groove 41 → oil passage 44 → oil passage 45 → oil passage 46 → chamber 49 → low pressure oil. Road 9
→Tank 4→Oil pump 1b When turning the handle (not shown) to the right and rotating the input shaft 39 to the right, the oil passage 4 of the input shaft 39
6 communicates with an axial oil passage (not shown) provided in the axial direction 45, and the pressure oil from the oil pump 1b flows through the high pressure oil passage 8 → annular groove 41 → oil passage 44 → oil passage 45 → annular groove. 42→oil is sent to one side of the cylinder 3 via oil passage 47, and the same cylinder 3 operates to the right, while oil from the other cylinder 3 is sent to oil passage 48→annular groove 43→oil passage 44 (not shown). → Axial oil passage provided between the axial oil passages 45 → Oil passage 46 → Chamber 49 → Turn the handle to the left so that the oil is returned to the tank 4 via the low pressure oil passage 9, and turn the input shaft 39 to the left. When the input shaft 39 rotates, the oil passage 46 of the input shaft 39 communicates with the axial oil passage 45, and the pressure oil from the oil pump 1b flows into the high pressure oil passage 8.
→ Annular groove 41 → Oil passage 44 (not shown) → Axial oil passage provided between axial oil passages 45 → Annular groove 43 → Oil is sent to the other side of the cylinder 3 via oil passage 48 operates to the left, while the oil on one side of the cylinder 3 flows from oil passage 47 → annular groove 42 → axial oil passage 45
→ Oil passage 46 → Chamber 49 → Low pressure oil passage 9 and then returned to tank 4. Also the second
In the figure, 50 and 51 are oil seals, 52 and 53 are bearings, 54 is a cap provided on the axis of the pressure control valve 11, and 55 is a hole provided in a pipe on the side of the cap 54. Note that the hole 55 is an oil relief hole provided to prevent pressure buildup within the pipe, and there is a gap between the pressure control valve 11 and the pipe, and although it is not necessary to provide it, the pressure control valve This is only provided because it will become a problem when the valve 11 rises and the gap is closed. Also 5
6 is a journal bearing that supports the radial load of the pinion 37; 57 is a chamber formed on the lower side of the journal bearing 56;
is the oil passage 58 and the chamber 32 (third
(see figure), an oil passage 33, and a chamber 31, which communicate with a low-pressure oil passage 9'. Note that the chamber 57 may be communicated with the low pressure oil passage 9' without going through the on-off valve 10.

Next, the operation of the power steering device will be explained. The discharge flow rate of the oil pump 1b driven by the engine 1a varies according to the engine speed.
Changes as shown in the figure. That is, it increases rapidly from a stop to when driving at low speed, decreases rapidly when driving at medium speed, and is maintained at a constant value when driving at high speed. Specification No. 4939 (Utility Model No. 58-
109585)). As described above, from when the vehicle is stopped to when the vehicle is running at low speed, when the flow rate of the hydraulic oil discharged from the oil pump 1b increases rapidly, the oil passage opening/closing valve 10 provided in the middle of the branch oil passage 8' is closed. Therefore, all of the hydraulic oil discharged from the oil pump 1b is transferred to the oil passage switching rotary valve 2.
is guided to the power cylinder 3 via the oil passage switching rotary valve 2, so that no reaction force is generated in the reaction piston 5 around the oil passage switching rotary valve 2, and the steering operation using the oil passage switching rotary valve 2 is performed easily. On the other hand, as mentioned above, when the flow rate of the hydraulic oil discharged from the oil pump 1b rapidly decreases and is maintained at a constant value from medium speed to high speed driving, a branch oil passage 8' is provided midway. The oil passage opening/closing valve 10 is opened. Therefore, a part of the hydraulic oil discharged from the oil pump 1b is guided to the pressure control valve 11 via the oil passage opening/closing valve 10. This hydraulic oil has a pressure of 80% depending on the driving condition.
It varies between about Kg/cm ² and 60 Kg/cm ² , and hydraulic oil near the upper limit is flowing from inlet 15 to chamber 18.
a, 18b (more hydraulic fluid than the flow rate passing through the pores 19a) flows into the chambers 18a, 18b.
), the differential pressure between chambers 18a, 18b and chamber 18c is 18a, 18b>18c.
When the pressure reaches the spool 13 due to the same pressure difference
moves to the right against the spring 14, and the entrance 15
The opening area of the spool 13 is reduced to throttle the flow rate (see Fig. 4), and when hydraulic oil near the lower limit enters the chamber 18a from the inlet 15, the spool 13
is moved to the left by the spring 14, and the entrance 15
Increase the flow rate by increasing the opening area. In other words, regardless of the pressure of the hydraulic oil flowing through the branch oil passage 8', the pressure (flow rate) of the hydraulic oil exiting from the outlet 16 is
is held almost constant. On the other hand, the pressure of the hydraulic oil in the low pressure circuit 9 on the side of the rotary valve 2 for oil path switching upstream of the pore 7 is in the range of about 2 to 4 kg/ ^cm2 , but as shown in Fig. 6, when running at medium speed, It rapidly decreases from 2000 to 2000 when driving at high speed, and is maintained at a constant value during high speed driving. Therefore, the pressure within the chamber 18d is lower during high-speed running than during medium-speed running, and the force of the spring 14 to push back the spool becomes relatively large, and the pressure within the chambers 18a and 18b increases by that amount. That is, chamber 18a,1
The pressure in the chamber 18b is Pa, the pressure in the chamber 18c is Pc, the pressure in the chamber 18d is Pd, A is π/4 (D ² - d ² ), D is the large diameter of the spool 13, and d is the small diameter of the spool 13. (diameter of chamber 18d), a
=n/ _4d2 , the pressure Pa in the chamber 18a is expressed as Pa=R/A+Pc-Pda/A, and since (R/A+Pc) is approximately constant, as Pd decreases, Pa increases. As a result, the pressure in the chambers 18a, 18b is reduced to the oil passage opening/closing valve 10.
It can be controlled according to the vehicle speed. Note that the reaction force of the reaction piston 5 refers to the hydraulic pressure supplied to the reaction force increasing side chamber of the reaction force piston 5 disposed between the output shaft (pinion) 37 and the input shaft 39, and the reaction force decreasing side. This is a force generated due to the difference between the hydraulic pressure supplied to the chamber and the force acting as a resistance that acts on the input shaft 39 together with the acting force of the torsion bar 38, that is, the force necessary to operate the input shaft 39. . Further, although the pore 7 is formed in the input shaft 39, the decompression passage 49 located upstream thereof has a
Low-pressure hydraulic oil discharged from the power cylinder 3 is supplied, and the low-pressure oil passage 9'' and the pilot hydraulic chamber 18d of the pressure control valve 11 are supplied with the pressure reducing passage 4.
Substantially the same hydraulic pressure as 9 is acting. This oil pressure corresponds to the pump discharge amount, resulting in an extremely low pressure (2 to 4 Kg/cm ² ). Also, the above pore 7
Hydraulic pressure at approximately atmospheric pressure acts on the low-pressure oil passage 9 located downstream of. Further, the pressure control valve 11 supplies the hydraulic oil in the high pressure oil passage 8 as a substantially constant control oil pressure to the reaction force increasing side chamber of the reaction force piston 5, and also supplies the oil pressure in the pressure reduction passage 49 to the pilot oil pressure chamber. , a hydraulic pressure corresponding to the pump flow rate is supplied, and as a result, a hydraulic pressure corresponding to the engine rotational speed is supplied to the reaction force increasing side chamber of the reaction force piston 5, and an appropriate reaction force is obtained. In addition, the input side 39 is the valve housing (valve body) 4
0 by a bearing 52, and is kept oil-tight by an oil seal 50. A low-pressure oil passage 9 is disposed directly below this bearing 52, so that the pressure acting on the oil seal 50 is low, and the frictional force generated by the oil seal 50 around the input shaft 39 is reduced. Therefore, the operational feeling and the durability of the oil seal 50 are improved.

As described above, in the power steering device of the present invention, when driving at high speed, a substantially constant flow of hydraulic oil is supplied from the oil pump 1b to the oil passage switching rotary valve 2 via the high pressure oil passage 8, while a portion of the hydraulic oil is supplied to the oil passage switching rotary valve 2. Since the oil is guided to the branch oil passage 8', the input torque-pressure characteristic of the oil passage switching rotary valve 2 becomes as shown by the broken line in FIG. Moreover, the hydraulic oil guided to the branch oil passage 8' is sent to the reaction piston 5 via the oil passage opening/closing valve 10 and the pressure control valve 11, and a reaction force is generated in the same portion, so that the oil passage switching rotary valve 2 input torque of −
The pressure characteristics become as shown by the dashed line in FIG. 8, and the input torque-pressure characteristics of the oil passage switching rotary valve 2 during high-speed running are greatly improved. In addition, an oil passage opening/closing valve 10 and a pressure control valve 11 are provided in a branch oil passage 8' connecting the high pressure oil passage 8 and the chamber 6 of the reaction piston 5.
A small hole 7 is inserted in the low pressure oil passage 9, and a chamber 18c of the pressure control valve 11 is inserted into the low pressure oil passage 9 on the tank 4 side downstream of the hole 7, and a chamber 18d of the pressure control valve 11 is inserted into the low pressure oil passage 9 on the tank 4 side downstream of the small hole 7. The low pressure oil passage 9 on the rotary valve 2 side for oil passage switching upstream of the orifice 7
It is only necessary to connect them to each other, without complicating the structure of the device. It is also configured as above,
The pressure in the chambers 18a, 18b (reaction force of the rotary valve 2 for switching oil passages) can be controlled according to the vehicle speed with the oil passage opening/closing valve 10, and the rotary valve 2 for switching oil passages can be used from medium speed to high speed driving. This has the effect of allowing steering operations to be performed during stable conditions, but in addition, in this case, the chamber directly below the bearing 52 is under low pressure, so the oil seal 5
The pressure acting on the input shaft 39 is also low and does not increase the friction occurring around the input shaft 39. Furthermore, since the pressure acting on the oil seal 50 is low, the reliability of the seal can be improved. Further, as shown in FIG. 5, the discharge flow rate of the oil pump 1b is set to be low when the vehicle is traveling at high speeds and to be large when the vehicle is traveling at low speeds. At this time, the pressure inside the chamber 49 is due to the pores 7.
Further, the pressure inside the chamber 6 changes as shown in FIG. 6 by the pressure control valve 11. Here, the hydraulic pressure acting on the reaction piston 5 is the differential pressure (see the shaded area in Fig. 9), and the effective acting pressure on the reaction piston 5 (ultimately the response of the handle) is the pump flow rate. It has an effect that can be smoothly changed depending on the situation, and is very useful when applied to a power steering device.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal side view showing an embodiment of the power steering device according to the present invention, FIG. 2 is a hydraulic circuit diagram thereof, FIG. 3 is a longitudinal side view showing an embodiment of the oil passage opening/closing valve, and FIG. is a longitudinal side view showing one embodiment of the pressure control valve, FIG. 5 is an explanatory diagram showing the discharge flow rate characteristics of the oil pump, FIG. 6 is an explanatory diagram showing the upstream pressure of the pore,
Fig. 7 is an explanatory diagram showing the pressure in the chamber (inlet/outlet side pressure chamber) of the pressure control valve, Fig. 8 is an explanatory diagram showing the pressure-input torque characteristics, and Fig. 9 is an explanatory diagram showing the pressure change on the back side of the reaction piston. It is an explanatory diagram. 1a...Engine, 1b...Oil pump, 2
...Oil passage switching valve, 3...Power cylinder, 4...
Tank, 5... Reaction piston, 6... Chamber, 7... Pore, 8... High pressure oil passage, 8'... Branch oil passage, 9... Low pressure oil passage, 10... Oil passage opening/closing valve, 1
1...Pressure control valve, 18c...Chamber, 21
... Valve housing, 38 ... Torsion bar, 39 ... Input shaft, 40 ... Valve body.

Claims (1)

[Scope of utility model registration request] an input shaft connected to the steering handle;
An output shaft connected to a steering wheel, a torsion bar that connects the input shaft and the output shaft, a power cylinder connected to the output shaft, and a high-pressure oil passage that communicates the hydraulic power source and the power cylinder are interposed. an oil passage switching rotary valve that selectively distributes oil to the power cylinder according to the rotation angle difference between the input shaft and the output shaft; and a rotary valve located downstream of the oil passage switching rotary valve. a pressure reducing passage disposed between the input shaft and the torsion bar; and a low-pressure oil passage formed between the outer peripheral surface of the input shaft and the valve housing to return the hydraulic pressure of the power cylinder to the oil tank; A plurality of reaction force pistons are disposed between the input shaft and the output shaft to restrict relative torsional displacement between the two, and the high pressure oil passage is branched into a reaction force increasing side chamber of each of the reaction force pistons. A branch oil passage, an oil passage opening/closing valve that is installed in the branching oil passage and is operated to open when the vehicle is running at a certain speed or above, and an oil passage opening/closing valve that is installed downstream of the oil passage opening/closing valve to reduce the pressure of the hydraulic oil. A pressure control valve that maintains a constant pressure, a pore formed in the input shaft that communicates the pressure reduction passage with the low pressure oil passage, and a pilot oil pressure generated in the pressure reduction passage into the pilot oil pressure chamber of the pressure control valve. an oil passage for communicating with the reaction force reduction side chamber of the reaction piston; and an oil seal disposed outside the low pressure oil passage between the input shaft and the valve housing. A power steering device characterized by: