JPS6212064B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic booster for use in forklifts, truck vehicles, automobiles, etc., and particularly to improvements in the relief valve mechanism incorporated therein.

When using a hydraulic booster for a forklift,
The control system has, for example, an oil passage configuration shown in FIG. In this figure, reference numeral 1 denotes an oil pump, which is driven by an engine 2, sucks hydraulic oil from an oil tank 3 through a pipe 4, and discharges this hydraulic oil to a flow priority valve 5. This valve 5 allows a constant flow of hydraulic oil from the pump 1 to pass through a pipe 6.
While regulating the pressure with the relief valve 7, the hydraulic booster 8
At the same time, the remaining hydraulic oil is commonly supplied to the lift control section 11a and tilt control section 11b of the control valve 11 via the pipe 10. Both control units 11a and 11b are used by the driver to control the movement of the forklift during cargo handling work, and the driver operates the control unit 11a to connect the lift cylinder 12 to the pipe line 10. When the lift cylinder 12 is extended, the fork can be raised, and when the control unit 11b is operated to connect the tilt cylinder 13 to the conduit 10, the tip of the fork is lifted by the extension action of the tilt cylinder 13. It can be tilted like this. When lowering the fork or releasing the tilting, the cylinders 12, 13 are moved to the drain pipes 14, 15 by operating the control units 11a, 11b.
The desired purpose is achieved by causing both cylinders 12 and 13 to contract due to the weight of the fork and the lifting load. In addition, drain pipe 1
A micron filter 16 is inserted into the hydraulic oil to remove foreign matter from the hydraulic oil.

As will be described later, the hydraulic booster 8 uses the hydraulic pressure obtained by throttling the flow of hydraulic oil from the pipe 6 to the operating valve 23 of the power steering 18 via the pipe 17, and doubles the amount of water required to press the brake pedal 19. The master cylinder hydraulic pressure from the master cylinder 20 operates the wheel cylinder 21, thereby braking the forklift. Note that 22 indicates a drain pipe from the hydraulic booster 8, which is joined to the drain pipe 15 together with a drain pipe 24 from the power steering operating valve 23.
In the power steering 18, while the driver holds the steering wheel 25 stationary, the operating valve 23 causes the pipe 17 to communicate with both oil chambers 26 and 27 of the power steering wheel 18, as well as the drain pipe 24. When rotating, the operating valve 23 connects one oil chamber 26 or 27 to the pipe 17 and the other oil chamber 27 or 26 depending on the direction of rotation.
By connecting the drain pipes 24 to the drain pipes 24, power steering becomes possible.

The hydraulic booster 8 uses hydraulic pressure obtained by throttling the flow of hydraulic oil from the pipe line 6 to the pipe line 17, so even when the hydraulic booster is activated, the hydraulic oil flow towards the power steering 18 is secured, and the hydraulic booster In order to prevent damage to the brake system due to too high applied hydraulic pressure, the hydraulic booster 8 is bypassed and the hydraulic oil flow is routed to the conduit 1.
Equipped with a relief valve mechanism that allows the flow to flow to 7.

Conventionally, this relief valve has generally been constructed as shown in FIG.

That is, a relief valve B is provided in the port A, and this relief valve is provided with a main valve E that is slidable in a blind hole D that is bored in the booster body C so as to be orthogonal to the port A. A spring G seated on a plug F that closes the opening of the hole D elastically holds it at the limit position.

In order to prevent the port A from being blocked even after the main valve E is inserted into the blind hole D, a groove H is formed on the inner peripheral surface of the blind hole D so as to overlap with the port A, and the shoulder I
Set.

The end J of the main valve E near the bottom of the blind hole D is made small in diameter to set a shoulder K, and a main valve chamber L is defined.
A pipe line 6 is made to communicate with this main valve chamber L.

The plug F side end face of the main valve E faces the pilot chamber M, and the valve seat N is fitted onto this main valve end face.

The pilot chamber M communicates with the pipeline 6 through an oil passage O and an orifice P provided in the booster body C, and also through an oil passage R provided in the main valve E so as to communicate with the center hole Q of the valve seat N. Connect it to the drain oil path S.

In addition, during processing, the ends of the oil passages O and S that open on the outer surface of the booster body C are sealed by driving seal balls T and U.

The drain oil passage S is formed in the booster body C, and is connected to the drain oil passage 22 for the intended purpose.

Further, a pilot valve V for opening and closing the hole Q of the valve seat N is built into the main valve E, and this pilot valve is restrained in the closed position by a spring W and is made to respond to the pressure in the pilot chamber M.

Regardless of the operating state of the hydraulic booster 8, that is, when the opening area of the throttle in the hydraulic booster is reduced or made zero and hydraulic pressure is generated upstream of this throttle, of course Hydraulic booster 8 whose orifice 48 is not substantially functioning.
Even when the power steering 18 is not in operation, the steering load of the power steering 18 is large and a corresponding hydraulic pressure is generated. When these hydraulic pressures reach a certain value (determined by the set load of the spring W), this hydraulic pressure is applied to the orifice P and the oil passage. Since it acts on the pilot valve V through the pilot chamber M and the valve seat hole Q, this pilot valve is opened. As a result, a portion of the hydraulic oil is extracted from the pipe 6 through the orifice P, the oil passage O, the pilot chamber M, the valve seat hole Q, the oil passage S, and the drain pipe 22 shown in FIG. This flow of hydraulic fluid causes a pressure drop on the downstream side of the orifice P, that is, within the pilot chamber M.
On the other hand, as mentioned above, the pressure in the pipe line 6 is directly led to the main valve chamber L, and the main valve E is moved against the spring G due to the pressure difference between this pressure and the falling pressure in the pilot chamber M. It is moved upward in FIG. In this way, the shoulder K is separated from the shoulder I, and the relief valve B
allows the main valve chamber L to communicate with the groove H. Because of this,
In addition to the path that passes through the hydraulic booster 8 (however, this path is closed in the operating state), the hydraulic oil supplied to port A also passes through the main valve chamber L, groove H, and port A to power steering. 18, the relief valve B limits the hydraulic pressure upstream of the throttle in the hydraulic booster to within a specified value to prevent damage to related parts, and also uses excess hydraulic fluid to power assist the power steering 18. It functions to ensure this under any operating condition of the hydraulic booster 8 (especially when the throttle in the hydraulic booster is fully closed).

In this relief valve mechanism, the hydraulic pressure upstream of the throttle of the hydraulic booster is applied to the pilot valve V from the pipe 6 through the orifice P, and when this pilot valve opens, the operating pressure supplied to the hydraulic booster 8 is In order to operate the relief valve B by drawing oil through the pilot valve V,
When steering without depressing the brake pedal 19, the oil pressure on the upstream side of the throttle in the hydraulic booster increases and even if the relief valve B opens, the main valve chamber L and the groove H are supplied from the pipe line 6 as described above. The amount of hydraulic oil supplied to the power steering via port A is reduced by the amount drawn out via pilot valve V as described above. For this reason, when steering without depressing the brake pedal 19, the amount of oil in the power steering cannot be avoided, and since the steering angle is usually large during such steering, the responsiveness of the power steering is extremely poor. Become.

The present invention has been made to solve the above-mentioned problems, and will be described below based on the embodiments shown in FIGS. 3 and 4.

FIG. 3 shows the detailed structure of the hydraulic booster 8. The booster body 28 is hollow, and the power piston 29 is slidably fitted inside the booster body 28. One end opening is closed with an end cover 30, and the other end is closed. An operating rod 31 is fluid-tightly sealed and slidably fitted into the opening with an O-ring 32. The end cover 30 is attached to the booster body 28 with bolts 33, and the master cylinder 20 shown in FIG.
Further, bolts 35 are installed in the end face of the booster body 28 far from the end cover 30, so that the entire hydraulic booster 8 can be attached to the vehicle body.

A chamber 36 is provided between the power piston 29 and the end cap 30.
This chamber is communicated with a drain port 38 through a communication port 37 to form a drain chamber. A return spring 39 for the power piston 29 is further compressed between the power piston 29 and the end cover 30, which urges the power piston 29 to the right in FIG. 3, thereby boosting the movement of the power piston 29. It is limited by the shoulder portion 28a of the body 28.
An output rod 40 is coaxially attached to the end face of the power piston 29 on the side of the end cover 30 using a retaining ring 41, and this output rod is penetrated into the end cover 30 under liquid-tight sealing by an O-ring 42, so that the output rod 40 protrudes. Attach the end to the master cylinder 20
(See Figure 1) Butt against the piston. A blind hole into which the spool 43 fits is provided on the other end surface of the power piston 29, and two grooves 29a,
29b is formed, and a shoulder portion 29c and a guide 29d are set. Two grooves 4 are formed on the outer peripheral surface of the spool 43.
3a, 43b, and three lands 43c, 4
Set 3d and 43e. Both ends of the land 43c face the chamber 44, a tapered surface 43f is formed between the land 43d and the groove 43a, and the land 43e projects into the boost chamber 45.

The spool 43 is hollow, and one end of the spring 46 extending into the hollow hole 43g is connected to the power piston 29.
Then, the other end is seated on the spool 43, and the spool is biased to the right in FIG. It is restricted by abutting the end of the operating rod 31. The spool 43 also has grooves 43.
A radial hole 43h extending from the hollow hole 43g to the booth chamber 45 is formed from the hollow hole 43g, and a radial hole 43i extending from the hollow hole 43g to the booth chamber 45 is formed. The aperture 4 functions as described later with the shoulder portion 29c and the tapered surface 43f.
The guide 29d and the land 43d constitute the control valve 49, and the guide 29d and the land 43e constitute the control valve 49.
and constitute a return valve 50.

The power piston 29 is further formed with three vertical grooves 29e, 29f, and 29g on its outer peripheral surface as shown in FIG. 4, and the power piston 29 is stopped from rotating by the tip of the bolt 15 screwed into the booster body 28. . The booster body 28 has vertical grooves 29e, 29f,
An inlet port 52, an outlet port 53, and a communication port 54 are provided, which communicate with the inlet port 29g, respectively. The vertical groove 29e communicates with the groove 29a through the through hole 29h, and the vertical groove 29f communicates with the groove 4 through the through hole 29i.
3a, and the vertical groove 29g communicates with the groove 29a through the through hole 29j. The power piston 29 is also provided with a radial hole 29k extending from the groove 29b to the outer peripheral surface, and this radial hole is communicated with the drain chamber 36 by a vertical groove 29l formed in the outer peripheral surface of the power piston 29.

A relief valve 55 is provided in the port 53, and the relief valve includes a main valve 56 that is slidable in a blind hole 28b bored in the booster body 28 so as to be orthogonal to the port 53. 2
Spring 5 seated on plug 57 that closes the opening of 8b
8 to elastically hold it in the limit position. In order to prevent the port 53 from being blocked even after the main valve 56 is inserted into the blind hole 28b, a groove 28c is formed on the inner circumferential surface of the blind hole 28b so as to be orthogonal to the port 53. Set. The end 56a of the main valve 56 near the bottom of the blind hole 28b is made smaller in diameter and the shoulder 56b
At the same time, a main valve chamber 59 is defined, and the port 54 is communicated with the main valve chamber.

Connect the end surface of the main valve 56 on the plug 57 side to the pilot chamber 6.
0, and the valve seat 61 is fitted onto this main valve end face. The pilot chamber 60 communicates with the boost chamber 45 via an oil passage 62 and an orifice 63 provided in the booster body 28, as described later, and a center hole 61a of a valve seat 61 and a main valve 5 connected thereto.
It is made to communicate with the drain oil passage 64 through the oil passage 56c provided in 6. In addition, when processing, booster body 28
The ends of the oil passages 62 and 64 that open to the outer surfaces of the oil passages 62 and 64 are sealed by driving seal balls 65 and 66. Although the drain oil passage 64 is formed in the booster body 28,
This is brought to the drain chamber 36 (see FIG. 3) and used for the intended purpose. Further, a pilot valve 67 for opening and closing the hole 61a of the valve seat 61 is built into the main valve 56, and this pilot valve is restrained in the closed position by a spring 68 and responds to the pressure inside the pilot chamber 60.

Operating rod 3 as shown in Figure 3
A conical blind hole 31a is formed in the outer end surface of the insert rod 69, and one end of the implant rod 69 is abutted against the bottom of the blind hole 31a.
Brake pedal 1 as described above with reference to FIG.
Connect 9. The dust boot 71 is used for dust sealing the operating rod 31 by fitting and locking one end to the booster body 28 and the other end to the implant rod 69, respectively.

The hydraulic booster 8 configured as described above has the oil passages 6, 17, and 22 shown in FIG. They are connected to the drain ports 38 and used, and function as follows.

3 and 4 show the state when the hydraulic booster 8 is inactive. At this time, the hydraulic oil sent into the inlet port 52 from the oil passage 6 shown in FIG. The oil is supplied to the power steering 18 through the groove 28c in 53 and the outlet port 53, and then through the oil passage 17 in FIG. On the other hand, the hydraulic oil supplied to the inlet port 52 flows through the vertical grooves 29e, vertical holes 29h, grooves 29a, through holes 29j, and vertical grooves 29g.
The hydraulic oil is also supplied to the main valve chamber 59 through the communication port 54, but since the main valve chamber 59 is blocked off from the groove 28c by the shoulders 28d and 56b, the hydraulic oil is supplied to the power steering from the outlet port 53. 18 and is confined within the main valve chamber 59. Also, the land 43d is the guide 29d.
The control valve 49 consisting of these is closed, the land 43e is separated from the land 29d, and the return valve 50 consisting of these is open, so that the boost chamber 45 is connected to the radial hole 43i and the hollow hole 43.
g, the radial hole 43h, the grooves 43b, 29b, the radial hole 29k, the vertical groove 29l, the drain chamber 36, the drain port 38, and then through the oil passage 22 shown in FIG. 1 to the drain circuit.

When the brake pedal 19 is depressed, the input rod 69 pushes the spool 43 via the operating rod 31 to the left in FIG. 3 to the position shown in FIG. As a result, the tapered surface 43f approaches the shoulder portion 29c, and the opening area of the aperture 48 formed by these is reduced, thereby restricting the flow of hydraulic oil from the groove 29a to the groove 43a. At the same time, in the left direction of the spool 43, the return valve 50 is closed and the control valve 49 is opened.
As the opening area of the throttle 48 is reduced as described above, the hydraulic pressure generated on the upstream side thereof, that is, in the groove 29a, is transferred to the control valve 49, the groove 43b, and the radial hole 43.
h, it reaches the inside of the boost chamber 45 through the hollow hole 43g and the radial hole 43i. The oil pressure that has reached the boost chamber 45 acts on the right end surface of the power piston 29 in FIGS. 3 and 5, pushing the power piston to a new balance position to the left in these figures. By repeating this action, the power piston 29
is hydraulically operated as the brake pedal 19 is depressed, and by operating the master cylinder 20 via the output rod 40, the vehicle can be braked.

Next, press the brake pedal 19 on the tapered surface 43f.
When the spool 43 touches the shoulder 29c and the throttle 48 is fully opened (at this time, the spool 43 comes into contact with the bottom of the blind hole of the power piston 29 into which it is fitted, and the throttle 48 is fully opened). 48 is fully closed, after which the power steering 18 is closed as described above.
(there is no flow of hydraulic oil toward the groove 29a), and the highest hydraulic pressure (determined by the relief valve 55 as described later) is generated in the groove 29a. This oil pressure is guided to the boost chamber 45 in the same manner as described above, and the power piston 29 is operated strongly hydraulically, thereby making it possible to brake the vehicle suddenly.

In the present invention, as shown in FIG.
One end of the orifice 63 is connected to the oil passage 6 in the same manner as described above.
However, the other end is not opened to the port 52 as described above, but is connected to the oil passage 72 formed in the booster body 28. Although not shown, this oil passage 72 communicates with the boost chamber 45, and as a result, the pilot chamber 60 communicates with the boost chamber 45 via the oil passage 62, the orifice 63, and the oil passage 72.

In the relief valve mechanism of the present invention having such a configuration,
During the operation of the hydraulic booster when the brake pedal 19 is depressed, as is clear from the above, the boost chamber 4
5 is always in communication with the inlet port 52, and both are kept at the same pressure. Therefore, the relief valve 55 and its pilot valve 67 receive the same hydraulic pressure as described above, although the route is different. Therefore, the relief valve 55 functions exactly as described above.
That is, when the hydraulic booster operates, the hydraulic pressure generated on the upstream side of the throttle 48 as described above and transmitted to the boost chamber 45 is transmitted from the boost chamber 45 to the oil passage 72, the orifice 63, the oil passage 62, the pilot chamber 60, The oil pressure acts on the pilot valve 67 through the valve seat hole 61a, and when this oil pressure reaches a certain value (determined by the set load of the spring 68), the pilot valve 67 is opened and some of the hydraulic oil is released from the oil passage 64 through the same path. It is extracted.
This flow of hydraulic oil creates a pressure difference before and after the orifice 63, and the hydraulic pressure on the upstream side of the orifice 63 increases to the port 5.
2 directly reaches the main valve chamber 59 as described above, the main valve 56 is moved by the spring 5 due to the pressure difference.
8, the relief valve 55 functions as described above.

On the other hand, when steering without depressing the brake pedal 19 and with the hydraulic boost inactive, the hydraulic pressure corresponding to the steering load is applied to the port 52, the vertical groove 29e, the through hole 29h, the groove 29a, the throttle 48, and the through hole 29i. , the hydraulic pressure is generated in the passage including the vertical groove 29f, the port 53, and the groove 28c, the oil pressure is transferred from the groove 29a to the through hole 2.
9j, vertical groove 29g, main valve chamber 59 via port 54
supplied within. On the other hand, in this state, as described above, the control valve 49 is closed and the return valve 50 is opened.
Since the boost chamber 45 communicates with the drain circuit,
The pilot chamber 60, which communicates with the boost chamber 45 through an oil passage 72, an orifice 63, and an oil passage 62, also communicates with the drain passage. For this reason, the main valve chamber 5
When the hydraulic pressure corresponding to the steering load up to 9 reaches a value that overcomes the set load of the spring 58, the main valve 56 is moved against this spring and the relief valve 55 is opened. As a result, hydraulic oil is supplied to the power steering via the relief valve 55 in the same manner as described above, but at this time, the pilot valve 67
remains closed, oil passage 6 remains closed as described above.
4, the hydraulic oil is not drawn out through the relief valve 55, and a large amount of hydraulic oil is supplied to the power steering through the relief valve 55, so that the responsiveness of the power steering is good, and this can be prevented from deteriorating as described above.

[Brief explanation of the drawing]

Fig. 1 is a hydraulic control circuit diagram of a forklift showing an example of the use of a hydraulic booster, Fig. 2 is a sectional view of a conventional relief valve, and Fig. 3 is a vertical sectional side view showing an embodiment of the hydraulic booster of the present invention. FIG. 4 is a cross-sectional view of the hydraulic booster shown in FIG. 3, and FIG. 5 is an explanatory diagram of the operation of the hydraulic booster. 1...Oil pump, 2...Engine, 3...
Oil tank, 5...Flow priority valve, 7...Unload valve, 8...Hydraulic booster,
11... Control valve, 12... Lift cylinder, 13... Tilt cylinder, 16... Micron filter, 18... Power steering,
19... Brake pedal, 20... Brake master cylinder, 21... Wheel cylinder, 23
... Power steering operating valve, 25 ... Steering handle, 26, 27 ... Power steering oil chamber, 28 ... Booster body, 29 ... Power piston, 31 ... Operating rod, 36 ... Drain chamber, 38 ... …drain port,
39... Return spring, 40... Output rod, 43... Spool, 45... Boost chamber, 46... Spring, 48... Throttle, 49... Control valve, 50... Return valve, 52... In Let port, 53...Outlet port, 54...Communication port, 55...Relief valve, 56...Main valve, 58...Spring, 59...Main valve chamber, 60...Pilot chamber, 61...Valve seat, 63...orifice, 64...drain oil path, 67...pilot valve, 68...spring, 69...input rod,
72...Oil road.

Claims (1)

[Claims] 1. A throttle valve formed by a spool linked to the brake pedal throttles the flow of hydraulic oil when the brake pedal is depressed, and the hydraulic pressure generated upstream of the flow is transferred to a boost chamber that normally communicates with a drain port. In the hydraulic booster, the power piston is moved to follow the spool in the direction of depression of the brake pedal, and the hydraulic oil that has passed through the throttle valve is supplied to the power steering. a main valve having opposing pressure-receiving surfaces facing the pilot chamber and the main valve chamber, respectively, to which the upstream pressure of the throttle valve is guided, and which responds to the pressure in the pilot chamber and the main valve chamber; a pilot valve configured to allow the main valve to open by releasing excess pressure when the pressure in the chamber exceeds a predetermined value; and a pilot valve configured to allow the main valve to open by releasing the excess pressure; A relief valve mechanism for a hydraulic booster, characterized by comprising a communication port configured to supply power to a steering wheel.