JPS6080973A - Liquid pressure steering device for vehicle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a hydraulic steering device for a vehicle, and is applicable to wheeled vehicles,
In particular, it is used in the field of hydraulic steering devices used in vehicles that require a relatively large output to steer the running wheels, such as construction and civil engineering articulating vehicles such as shovel loaders.

(b) Prior Art Conventionally, there is a hydraulic steering system for a vehicle that requires a relatively large amount of power to steer the running wheels, such as the one shown in FIG. 1, for example. In this device, when the steering wheel 1 is rotated in the direction of the arrow 2, for example, the double rotary pump 3 which is interlocked with the steering wheel 1 is rotated.
is rotated, and the directional control valve 4 connected to the pump 3 is switched from the neutral position to the position 4A. Therefore, the working fluid from the constant displacement pump 5 driven by an engine (not shown) communicates with the pipe line 6, and the relief valve 7
Since the pressure of the hydraulic fluid regulated by is applied to the suction side of the double-rotary pump 3, the operation of the steering wheel 1 is assisted and lightened, and the operation of the pump 3 is discharged at a flow rate approximately proportional to its rotation speed. The liquid, ie the pilot liquid stream, is conveyed through line 8.9 to the restriction 10 and further through line 11.
and is returned to the reservoir 12 through the switching valve 4. At this time, a pressure drop occurs when the pilot liquid flow passes through the throttle 10, and a pressure difference is generated before and after the throttle 10.
The acting force of the differential pressure and the spring 1
The switching valve 13 is shifted in the direction of position 13A until the elastic force of 3C113d is balanced. Therefore, the hydraulic fluid from the constant displacement pump 14 driven by an engine (not shown) is sent to the cylinder hydraulic pressure line 15 according to the shift amount of the switching valve 13, and is sent to the cylinder hydraulic pressure line 15 between the pair of hydraulic cylinders 16.1.
The hydraulic cylinder 17 is extended and the hydraulic cylinder 16 shrinks. As a result, the pair of hydraulic cylinders 16 and 17 actuate a direction change mechanism (not shown) to change the direction of the running wheels (not shown). Here, when the rotational speed of the steered wheel 1 is low, the flow rate of the pilot liquid sent to the throttle 10 is small and the differential pressure across it is also small, so the shift amount of the switching valve 13 becomes small and the constant displacement pump 14 Of the hydraulic fluid discharged from the cylinder hydraulic pressure line 15
The flow rate of the hydraulic fluid distributed to and sent to is small, and the other
3 to the reservoir 12. When the rotational speed of the steered wheel 1 is high, the differential pressure across the throttle 10 becomes large, and the shift amount of the switching valve 13 also becomes large. Then, when the distribution flow rate of the hydraulic fluid discharged from the constant displacement pump 14 to the cylinder hydraulic pressure line 15 increases, and the shift amount of the switching valve 13 exceeds a set value, almost the entire amount of the hydraulic fluid is distributed to the cylinder hydraulic pressure line 15. The liquid is distributed and sent to channel 15. In other words, the turning speed of the running wheels is adjusted by adjusting the rotational speed of the steered wheels l.

Furthermore, when the operation of the steering wheel 1 is stopped, the directional control valve 4 returns from the position 4A to the neutral position, so that the hydraulic fluid sent from the constant displacement pump 5 does not pass through the directional control valve 4 and the relief valve 7 The water is returned to the reservoir 12 through the . Furthermore, the liquid supply to the throttle lO stops, the switching valve 13 also returns to the neutral position, and the cylinder hydraulic pressure line 15.18 is closed by the switching valve 13, so the pair of hydraulic cylinders 16, 17 remain as they are.
The position of is maintained. Then, the direction change of the running wheels is stopped, and the entire amount of the working fluid sent from the constant displacement pump 14 is returned to the reservoir 12.

When the steering wheel 1 is rotated in the opposite direction to that described above, the directional control valve 4
switches from the neutral position to position 4B. As a result, the hydraulic fluid is conveyed through the line 8.6.11 to the throttle 10 and then returned through the line 9 and the switching valve 4 to the reservoir 12. The switching valve 13 is shifted in the direction of position 13B due to the differential pressure generated by the throttle 10, and the working fluid from the constant displacement pump 14 is distributed and sent to the cylinder hydraulic pressure line 18, and the cylinder hydraulic pressure line 15 is switched. Valve 1
3 to the reservoir 12 so that the hydraulic cylinder 16
．． 17 expands and contracts in the opposite direction to the above.

As a result, the running wheels are turned in the opposite direction to that described above. Adjustment of the turning speed is performed by adjusting the rotational speed of the steered wheels l in the same manner as described above. In addition, the relief valve 19
regulate the maximum pressure of the hydraulic fluid discharged from the constant displacement pump 14, and the relief valves 20.21 regulate the maximum pressures applied to the cylinder fluid lines 15.18, respectively.

In such vehicle hydraulic steering systems, the same engine drives the constant displacement pump, vehicle travel, and cargo handling hydraulic equipment, so even when no steering operation is being performed, the constant displacement pump is driven by the same engine. Positive displacement pumps are constantly operating, discharging hydraulic fluid and returning it to the reservoir. Additionally, during low-speed steering, only a portion of the high-pressure hydraulic fluid from the constant displacement pump is supplied to the hydraulic cylinder, and the remaining hydraulic fluid is returned to the reservoir without contributing to the direction change operation of the running wheels. . In such a situation, all or most of the output of the fixed displacement pump does not contribute to the direction change operation of the running wheels and is wasted, resulting in unnecessary energy consumption. . Moreover, the temperature of the hydraulic fluid at this time increases, causing failure of hydraulic equipment, and deterioration of the hydraulic fluid due to sustained high temperatures.

In addition, as mentioned above, the engine is used to drive both the fixed displacement pump and other drives, so the engine's rotational speed changes depending on the driving of the vehicle, and the engine rotational speed changes depending on changes in the engine rotational speed. The flow rate of the hydraulic fluid supplied from the positive displacement pump to the switching valve also changes. The switching valve distributes the hydraulic fluid to the cylinder hydraulic pressure line and the reservoir at a ratio according to the shift amount, but even if the switching valve shift amount is constant, the flow rate of the hydraulic fluid from the fixed displacement pump changes. For example, the flow rate of the hydraulic fluid distributed to the cylinder hydraulic pressure line changes accordingly. In other words,
Even if the rotational speed of the steering wheel is constant, the turning speed of the running wheels will change according to changes in the engine rotational speed.
A constant change in direction is not performed according to the amount of operation of the steering wheel, giving the driver an unpleasant operation feeling. As a result, the operational feeling of the steering wheel becomes distorted, which also poses a problem in driving safety.

(C) Purpose of the Invention The present invention solves the problems of wasting energy due to unnecessary driving of fixed displacement pumps, failure of hydraulic equipment due to the accompanying temperature rise of the working fluid, and deterioration of the working fluid due to sustained high temperatures. This eliminates the driver's operational discomfort due to the imbalance between the amount of operation of the steering wheel and the amount of direction change of the running wheels, and the accompanying safety problems, and improves the safety of the direction change operation of the running wheels.
An object of the present invention is to provide a hydraulic steering device for a vehicle to realize proper operation of hydraulic equipment.

(d) Structure of the Invention The structure of the present invention will be explained with reference to FIG.
An engine rotation speed detection means 25 having a hydraulic pressure generator 35 interposed in the discharge pipe 34 of the steering wheel 1 is provided.
A pilot liquid flow generation means 28 is provided for generating a pilot liquid flow using a hydraulic fluid adjusted according to the operation amount of the
Hydraulic pressure control means 29 having a variable throttle valve 37 interposed in the flow path of the pilot liquid flow and adjusting the opening degree in response to a pressure signal from the hydraulic pressure generator 35 of the engine rotational speed detection means 25.
and a discharge amount adjusting means 31 for controlling the discharge capacity of the variable displacement pump 30 driven by the engine in response to the hydraulic pressure of the pilot liquid flow controlled by the hydraulic pressure control means 29. This is a hydraulic steering system for vehicles.

(e) Examples Hereinafter, the hydraulic steering system for a vehicle according to the present invention will be explained in detail based on examples thereof.

FIG. 2 is an overall system diagram of the hydraulic steering system for a vehicle according to the present invention.
From the engine rotation speed detection means 25, the pyro-throat liquid flow generation means 28 for discharging the unloaded liquid flow to the pipe 26 or 27 depending on the rotation direction and rotation speed of the steering wheel 1, and the engine rotation speed detection means 25. a hydraulic pressure control means 29 for increasing pilot hydraulic pressure in the pilot liquid flow in response to a pressure signal; and a discharge amount adjusting means 31 (not shown) for controlling the discharge amount of the variable displacement pump 30 in accordance with the pilot hydraulic pressure. A pair of hydraulic cylinders 16 for changing direction of the running wheels
．． 17 and a directional switching valve 32 which is interposed in the cylinder hydraulic pressure line 15, 18 and is switched by pilot hydraulic pressure.

The engine rotational speed detection means 25 includes a constant displacement pump 33 driven by an engine (not shown) and the pump 33
It is interposed in the discharge pipe line 34, and has a throttle 35 as a hydraulic pressure generator that generates a differential pressure in accordance with the passing flow rate upstream and downstream thereof. The pilot liquid flow generating means 28 includes a steering wheel 1 attached to the driver's seat, a rerotation pump 3 linked to the steering wheel 1, and a rerotation pump 3 connected to the rerotation pump 3 and the engine. The rotational speed detecting means 25 has a directional switching valve 4 interposed between the throttle 35 and the rotational speed detecting means 25. The hydraulic pressure control means 29 has a shuttle valve 36 and a variable throttle valve 37, and the two primary ports of the shuttle valve 36 are connected to the outlet pipes 26 and 27 of the pilot liquid flow generating means 28, respectively. It is connected. Further, the valve body 37A of the variable throttle valve 37 has an inlet port 38 communicating with the secondary side boat of the shuttle valve 36, an outlet port 39 communicating with the reservoir 12, and a throttle 35 of the engine rotational speed detecting means 25. Two pilot boats 40 and 41 are provided which communicate with the front and rear flow passages, and a spool 42 is slidably inserted, so that the pressure difference before and after the throttle 35 and the elastic force of the spring 43 are The spool 42 is configured to be displaced to a balanced position. This spool 42 is provided with a notched groove 44 that communicates the inlet port 38 and the outlet boat 39, and a flow path that communicates the inlet port 38 and the outlet boat 39 according to the displacement of the spool 42 in the direction of the arrow 45. It is configured to increase the size of the cross-sectional area, that is, the aperture opening. The discharge amount adjusting means 31 is a servo whose shift amount is controlled in accordance with the biloft hydraulic pressure supplied via a pipe 46 branched to the inlet side flow path of the variable throttle valve 37 of the hydraulic pressure control means 29. It has a valve 47, a servo piston 48 that moves according to the shift amount of the servo valve 47, and a variable displacement pump 30 whose discharge capacity changes in conjunction with the movement of the servo piston 48.

The directional switching valve 32 is interposed in a cylinder hydraulic pressure line 15.18 between the variable displacement pump 30 and a pair of hydraulic cylinders 16.17 for changing the direction of running wheels (not shown), and is connected to the pilot liquid flow generating means 28. The discharge side pipe line 51 of the variable displacement pump 30 is controlled by the pilot hydraulic pressure supplied via the pipe lines 49 and 50 branched to the outlet side pipe lines 26 and 27 of the variable displacement pump 30, respectively.
and the cylinder hydraulic line 15 , 18 and the discharge line 52 to the reservoir 12 .

1 According to the embodiment having the configuration described above, it can be operated as follows.

In FIG. 2, for example, when the driver desires to steer the steering wheel l,
When it rotates in the direction of arrow 2, the re-rotating pump 3 moves in conjunction with the rotation, and according to this movement, the directional control valve 4 connected to the re-rotating pump 3 switches from the neutral position to position 4A, and the fixed displacement pump The hydraulic fluid sent from 33 passes through the pipe 6, and the pressure of the hydraulic fluid regulated by the relief valve 53 is supplied to the suction side of the re-rotation pump 3, so the rotation of the steered wheel 1 is assisted and lightened. As it rotates,
The pilot liquid stream discharged from the rerotating pump 3 at a flow rate dependent on the rotational speed of the steered wheel 1 is sent through line 8.26 to the shuttle valve 36. The shuttle valve 36 communicates the pipe line 26 with the inlet port 38 of the variable throttle valve 37 by the supplied viroft liquid flow, and also switches to close the flow passage with the pipe line 27, so that the pilot liquid flow is controlled by the variable throttle valve. The pilot liquid is discharged to the reservoir 12 through the valve 37, but at this time, the pilot liquid is added to the upstream pilot liquid flow of the variable throttle valve 37 according to the throttle opening of the variable throttle valve 37 and the flow rate of the pilot liquid. The pressure builds up. The pilot hydraulic pressure is supplied to the pilot port 54 of the servo valve 47 of the discharge amount adjusting means 31 through the pipe line 46, and the spool 55 of the servo valve 47 receives the elastic force of the spring 56 and the acting force due to the pilot hydraulic pressure. Move in the direction of arrow 57 to the balanced position. Therefore, the positional relationship between the spool 55 and the sleeve 58 is as shown in FIG. Since the servo piston 48 is supplied to the other cylinder chamber 62 through the valve 55 and the conduit 61, the servo piston 48 moves in the direction of the arrow 63, and the sleeve 58 connected to the servo piston 48 by the connecting member 64 also moves at the same time. Move in the direction of arrow 57. When the amount of movement of the servo piston 48 reaches an amount corresponding to the amount of movement of the spool 55 described above, the positional relationship between the spool 55 and the sleeve 58 becomes as shown in FIG. The liquid is stopped, and the movement of the servo 4 piston 48 is also stopped. Further, the servo piston 48 is connected to the discharge volume adjusting lever 65 of the variable displacement pump 30.
Since it is also connected to the arrow 6 of the servo piston 48
The discharge capacity of the variable displacement pump 30 also increases according to the amount of movement in the three directions. Note that if the pilot hydraulic pressure supplied to the servo valve 47 decreases from the above-mentioned state, the spool 55 will absorb the acting force of the decreased pilot hydraulic pressure and the spring 5.
The positional relationship between the spool 55 and the sleeve 58 is changed to the third position by moving in the direction of the arrow 66 until the elastic force of
In the state shown in Figure (C), the working fluid in the cylinder chamber 62 is returned to the reservoir 12 through the pipe 61 and the servo valve 47, so the servo piston 48 moves in the direction of the arrow 67 and is interlocked with it. When the positional relationship between the sleeve 58 and the spool 55 becomes as shown in FIG. 3(C), the sleeve 58 and the spool 55 stop. therefore,
The discharge volume adjustment lever 65 of the variable displacement pump 30 also operates in the opposite direction to that described above, and the discharge volume of the variable displacement pump 30 also decreases in accordance with the amount of movement of the servo piston 48 in the direction of arrow 67. That is, the discharge capacity of the variable displacement pump 30 is always controlled to follow the amount corresponding to the pilot hydraulic pressure supplied to the servo valve 47. On the other hand, the pilot boat 68 of the directional control valve 32 is also supplied with pilot hydraulic pressure via the pipe 49, and the other pilot boat 69 is supplied with the pilot boat 68 via the pipe 50.2.
7 and the switching valve 4 to the reservoir 12, the directional switching valve 32 is switched to the position 32A by the action of the pilot hydraulic pressure, and the hydraulic fluid discharged from the variable displacement pump 30 is transferred to the cylinder hydraulic pressure line 15. through the respective chambers 16'A, 17 of a pair of hydraulic cylinders 16.17.
B, and the other cylinder chambers 16B, 17
A leads to reservoir 12 via cylinder hydraulic line 18 and line 52, so that hydraulic cylinder 16 contracts and hydraulic cylinder 17 extends. As a result, the pair of hydraulic cylinders 16 and 17 actuate a direction change mechanism (not shown) to change the direction of the running wheels. In the above-mentioned changing operation, the changing speed of the running wheel is approximately proportional to the discharge flow rate of the working fluid from the variable displacement pump 30, but the discharge flow rate is equal to the product of the discharge capacity and rotational speed of the variable displacement pump 30 at that time. When the engine speed is constant, the discharge flow rate is approximately proportional to the discharge capacity of the variable displacement pump 30.

As described above, the discharge capacity of the variable displacement pump 30 is controlled to an amount corresponding to the pilot liquid pressure supplied to the servo valve 47, and the pilot liquid pressure is controlled by the pilot liquid flow from the pilot liquid flow generating means 28. is the variable throttle valve 37
Equal to the pressure drop flow rate due to flow path resistance when passing through,
Since the variable throttle valve 37 has a constant throttle opening when the engine speed is constant, the pilot fluid pressure is an amount corresponding to the pilot fluid flow rate from the pilot fluid flow generating means 28. The pilot liquid flow rate is approximately proportional to the rotational speed of the steered wheel 1 of the pilot liquid flow generating means 28. In other words, when the engine speed is constant, the discharge flow rate of the hydraulic fluid from the variable displacement pump 30 is
The amount corresponds to the rotational speed of the steered wheels 1, and the direction of the running wheels can be changed at a predetermined turning speed corresponding to the rotational speed of the steered wheels 1.

7 6 Next, the direction change speed of the running wheels when the engine rotation speed changes will be described. The constant displacement pump 33 of the engine rotational speed detection means 25 is driven at a speed proportional to the engine rotational speed, and the discharge flow rate from the constant displacement pump 33 is approximately proportional to the engine rotational speed, so the engine rotational speed can be detected. The differential pressure across the throttle 35 of the means 25 corresponds to the engine rotational speed, and the opening degree of the variable throttle valve 37, which supplies the differential pressure across the throttle to the pilot boat 40, 41, depends on the engine rotational speed as described above. Increases as it increases. Therefore, even if the pilot liquid flow rate from the pilot liquid flow generation means 28 is constant, the hydraulic pressure control means 2
The pilot hydraulic pressure controlled at 9 decreases as the engine rotational speed increases, and in the preferred embodiment, the relationship between the pilot hydraulic pressure and the engine rotational speed is as shown in FIG. Therefore, the discharge capacity of the variable displacement pump 30, which is driven by the same engine as the constant displacement pump 33, decreases as the engine rotation speed increases, and in a preferred embodiment, the discharge flow rate from the variable displacement pump 30 decreases. 8 The relationship with the engine rotation speed is as shown in FIG. 5, and within the range of fluctuation of the engine rotation speed under normal operating conditions of the vehicle, the discharge flow rate from the variable displacement pump 30 is approximately equal to the engine rotation speed, regardless of the engine rotation speed. It becomes constant.

In other words, within the variation range of the engine rotation speed in the normal driving state of the vehicle, the running wheels can be operated to change direction at a predetermined turning speed corresponding to the rotation speed of the steered wheels 1, regardless of the engine rotation speed. .

Further, when the rotation of the steering wheel 1 is stopped, the double rotary pump 3 is also stopped, and the directional control valve 4 returns from the position 4A to the neutral position, and the hydraulic fluid from the constant displacement pump 33 is stopped at the directional control valve 4. Further, since the pilot liquid flow is not sent to the hydraulic pressure control means 29 and the pilot hydraulic pressure does not rise, the directional control valve 32 returns from the position 32A to the neutral position, and the cylinder hydraulic pressure conduit 15.18 is connected to the directional control valve 32. and the hydraulic fluid from the variable displacement pump 30 is returned to the reservoir 12 through the conduit 52. Therefore, the expansion and contraction of the hydraulic cylinders 16, 17 is stopped and the direction change of the running wheels is also stopped.

On the other hand, the pilot hydraulic pressure supplied to the servo valve 47 of the discharge amount adjusting means 31 also decreases to almost the pressure of the reservoir 12, so the spool 55 is displaced in the direction of arrow 66 to the stroke end. Therefore, the discharge amount adjusting means 31
operates in the same manner as described above, and the discharge capacity of the variable displacement pump 30 is controlled to a predetermined minimum amount, resulting in an initial state. Further, when the steering wheel 1 is turned in the opposite direction to the arrow 2, the double-rotary pump 3 moves in conjunction with the steering wheel 1, and in accordance with this movement, the directional control valve 4 connected to the double-rotary pump 3 moves.
switches from the neutral position to position 4B. The working fluid sent from the constant displacement pump 33 communicates with the pipe line 8,
Since the pressure of the hydraulic fluid regulated by the relief valve 53 is supplied to the suction side of the double-rotary pump 3, the rotation of the steered wheel 1 is assisted and rotated lightly, and at the same time it rotates both ways at a flow rate corresponding to the rotational speed of the steered wheel 1. The pilot liquid stream discharged from the pump 3 is routed through line 6.27 to the shuttle valve 36. The shuttle valve 36 connects the pipe line 27 and the inlet boat 38 of the variable throttle valve 37 by the supplied flow of the virlot liquid, and also switches to close the flow path with the pipe line 26, so that The flow passes through the variable throttle valve 37 and is discharged to the reservoir 12, but at this time, the pilot liquid is added to the pilot liquid flow on the upstream side of the variable throttle valve 37 in accordance with the throttle opening of the variable throttle valve 37 and the flow rate of the viroft liquid. The pressure builds up. The pilot fluid pressure is supplied to the pilot boat 54 of the servo valve 47 of the discharge amount adjusting means 31 through the pipe line 46, and the discharge amount adjusting means 31 operates in the same manner as described above to control the discharge capacity of the variable displacement pump 30. is controlled to an amount corresponding to the aforementioned pilot hydraulic pressure.

On the other hand, the pilot boat 69 of the directional switching valve 32 is also supplied with pilot hydraulic pressure via the pipe 50, and the other pilot boat 68 communicates with the reservoir 12 via the pipe 49.26 and the switching valve 4. The directional control valve 32 is switched to position 32B by the acting force of the biloft hydraulic pressure, and the hydraulic fluid discharged from the variable displacement pump 30 is communicated with the cylinder hydraulic pipe 10 passage 18, and is connected to each of the pair of hydraulic cylinders 16 and 17. Since the other cylinder chambers 16A, 17B communicate with the reservoir 12 via the cylinder hydraulic conduit 15 and the conduit 52, the hydraulic cylinder 16 is extended and the hydraulic cylinder 17 shrinks. As a result, the pair of hydraulic cylinders 16 and 17 actuate a direction change mechanism (not shown) to change direction of the running wheels in the opposite direction. At this time, the engine rotation speed detection means 25, the hydraulic pressure control means 29, and the discharge amount adjustment means 31 operate in the same manner as described above. Regardless of the rotational speed of the steered wheels 1, the running wheels can be operated to change direction in the opposite direction to that described above at a predetermined direction change speed corresponding to the rotational speed of the steered wheels 1.

By the way, although the throttle 35 was used as a hydraulic pressure generator for the engine speed detection means 25 in the above-described embodiment, it is generally said that the pressure difference before and after the relief valve increases in proportion to the increase in the flow rate passing through the relief valve. There is a characteristic, and if attention is focused on this, it is possible to perform the same function as the above-mentioned throttle 2 valve. Therefore, a relief valve may be used as the hydraulic pressure generator in place of the throttle 35 in FIG. 2. Further, the discharge amount adjusting means 31 of the present invention is not limited to the discharge amount adjusting means shown in FIG.
Cylinder 70 connected to discharge volume adjustment lever 65 of
The pilot hydraulic pressure may be supplied to the cylinder chamber 70A through a pipe line 46 shown in FIG. 2. Also,
The pilot liquid flow generating means 28 is also not limited to the one shown in FIG. 2, but a well-known example, as shown in FIG. Two suction and discharge ports with two check valves 72.7
3 to the reservoir 12 and may also be connected to conduits 26 and 27 shown in FIG. 2, respectively. Also, the second
In the embodiment shown in the figure, the pilot liquid flow generating means 28
The constant displacement pump 33 of the engine speed detection means 25 was used as a hydraulic pressure supply source for driving the servo piston 48 of the discharge amount adjusting means 31; 33 may be replaced with another hydraulic pressure supply source, for example, the fixed displacement pump 33 described above.
Another pump may be additionally installed outside of the pilot liquid flow generating means 28, and the pump may be used as a hydraulic pressure supply source for the pilot liquid flow generating means 28.
It goes without saying that it may be used as a hydraulic pressure supply source for driving the servo piston 48 of the discharge amount adjusting means 31, and the same effect will be produced without changing the overall operation of the present invention.

(f) Effects of the Invention As explained in detail above, in the present invention, the discharge flow rate from the variable displacement pump is controlled to the minimum amount when the direction change operation is not performed, and when the direction change operation is performed. In this case, the discharge flow rate from the variable displacement pump is always controlled to a predetermined amount corresponding to the rotational speed of the steered wheels, and almost all of the discharge flow rate is due to the hydraulic pressure used to change direction of the running wheels. Since it is supplied to the cylinder, the pump discharge liquid can be used effectively. As a result, unnecessary consumption of energy due to unnecessary driving of the constant displacement pump as described in the conventional example can be prevented, and energy loss in the hydraulic steering system can be extremely reduced. moreover,
Since the temperature rise of the hydraulic fluid due to energy loss is small, it is possible to avoid the problem of failure of hydraulic equipment and the problem of deterioration of the hydraulic fluid due to the temperature rise of the hydraulic fluid, and to realize the appropriate use of hydraulic equipment. I can do it. Furthermore, within the range of fluctuations in the engine rotation speed under normal vehicle operating conditions, the steering wheel direction change operation is performed at a predetermined direction change speed commensurate with the rotation speed of the steered wheels, almost independently of fluctuations in the engine rotation speed. This reduces the driver's operational discomfort due to the imbalance between the amount of steering wheel operation and the amount of turning of the running wheels, which is caused by fluctuations in the turning speed of the running wheels due to fluctuations in engine rotational speed, and the resulting safety. By solving the above problem, it is possible to provide the driver with a favorable sense of direction change operation and to ensure safety in direction change operation.

[Brief explanation of the drawing]

Fig. 1 is a conventional control system diagram of a hydraulic steering system, Fig. 2 is an embodiment of the hydraulic steering system for a vehicle according to the present invention, and Figs. 4-3 (a) to (C) are discharge amount adjusting means. Fig. 4 is a graph showing the opening change range of the variable throttle valve in relation to the engine rotation speed and pilot hydraulic pressure, and Fig. 5 is a graph showing the variation range of the opening degree of the variable throttle valve in relation to the engine rotation speed and the variable displacement pump discharge flow rate. FIG. 6 is a graph showing the range of change in the opening degree of the variable throttle valve in relation to
The figure shows another example of the pilot liquid flow generating means. 1-steering wheel, 3.71-double rotary pump, 4 one-way switching valve, 25-engine rotation speed detection means, 28-pilot liquid flow generation means, 29-hydraulic pressure control means, 30-variable displacement pump, 31-discharge rate adjusting means, 33 constant displacement pump, 34-discharge pipe, 35-throttle valve, 37-variable throttle valve Patent applicant Kawasaki Heavy Industries, Ltd. agent Patent attorney Katsutoshi Yoshimura (and one other person) 6 No. 3 Figure (CI) Figure 3 (b) Figure 3 (C) 1 capital - supply '+, sl> G

Claims (4)

[Claims] (1) A constant displacement pump driven by an engine,
engine rotational speed detection means having a hydraulic pressure generator interposed in the discharge pipe of the pump; and pilot liquid flow generation means for generating a pilot liquid flow of hydraulic fluid adjusted according to the amount of operation of the steering wheel. , a hydraulic pressure control means having a variable throttle valve interposed in the flow path of the pilot liquid flow and adjusting the opening degree in response to a pressure signal from a hydraulic pressure generator of the engine rotational speed detection means; and this hydraulic pressure control means. a discharge amount adjusting means for controlling the discharge capacity of the variable displacement pump driven by the engine in response to the hydraulic pressure of the pilot liquid flow controlled by the means; direction equipment. (2) The hydraulic steering system for a vehicle according to claim 1, wherein the hydraulic pressure generator of the engine rotational speed detection means is a throttle that generates a pressure difference between the front and rear depending on the flow rate passing through. . (3) Hydraulic pressure steering of a vehicle according to claim 1, wherein the hydraulic pressure generator of the engine rotational speed detection means is a relief valve that generates a pressure difference between the front and rear depending on the flow rate passing through. Device. (4) The pilot liquid flow generating means includes a dual rotary shaft pump connected to a steering wheel, and a directional switching valve that switches in conjunction with the pump. Hydraulic steering system for the vehicle described.