JPS62149559A - Stabilizing device for steering during high speed running for heavy load vehicle - Google Patents

Abstract

PURPOSE:To smooth control of steering, to stabilize control during high speed running steering, and to improve reliability, by adding a control valve which limits a steering flow rate to a total hydraulic type power steering device only during high speed running steering. CONSTITUTION:During high speed running steering of a heavy load vehicle, the three solenoids of electromagnetic hydraulic valves 2, 2', and 7 are switched to ON. It is selected by vehicle characteristics or a cost whether the switching is effected by automatic switching by means of a conversion electric signal at a specified car speed or more or manual button control. In which case, a flow rate of oil discharged from a pump 10 is limited by a constant flow rate control branch valve 8, and as a result, high speed steering control of a total hydraulic type power steering device 4 is prevented. For example, when an electromagnetic valve 7 is brought into an OFF-state, relation to a flow rate by which a steering maximum speed Nmax is increased to 120rmp, the electromagnetic valve 7 is brought into an On-state during high speed steering to limit Nmax to 30rmp. As a result, steering control is further smoothed, and stabilized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a steering hydraulic circuit that is stable during high-speed steering in a positively loaded vehicle. This constitutes a hydraulic circuit, but during high-speed steering, it limits the steering ml flowing into the fully hydraulic power steering system, and prevents high-speed steering operations (sudden/'1').
This invention relates to a hydraulic circuit for a fully hydraulic power steering system that improves high-speed steering performance by preventing single-handle operation.

[Conventional technology and its problems]

As is well known, there are integral type, linkage type, semi-integral type, and fully hydraulic type power steering systems that operate hydraulically in order to reduce the torque required to operate a steering wheel in a vehicle. Among these, fully hydraulic power steering devices are widely used in construction vehicles, industrial vehicles, etc., but in general, steering performance during high-speed driving of a vehicle is affected by the influence of the inertia of the vehicle itself, problems with the center of gravity, etc. High-speed steering operations in such conditions are extremely dangerous because they tend to be unstable.Vehicles that use fully hydraulic power steering systems are generally heavy vehicles, and this tendency is particularly high. Therefore, it has been pointed out that some vehicles using fully hydraulic power steering devices have problems such as a feeling of wobbling in high-speed running and a lack of steering stability.

More specifically, in the hydraulic circuit of a vehicle using a fully hydraulic power steering system, the maximum rotational speed of the steering wheel is proportionally determined by the flow rate flowing into the steering system. In other words, the displacement volume of the steering device is qc+1 with the inflow flow +iQn/min! /rev
In the case of , the maximum rotational speed of the steering wheel Nmax, rp11+ that is possible at that time without causing a significant change in the steering force is Nmax (rpm)
=Q (j+/min) Xl 000/Q
(cn/rev,).

In general, the inflow flow rate Q is set with a margin of 10 to 20% plus the maximum steering speed required for steering. Normally, this is a natural setting to ensure the required turning speed when steering, but when steering at high speed, such inflow mff1Q may cause intentional high-speed steering operation. Therefore, safety issues arise.

On the other hand, high-speed running stabilization devices of a flow rate control type and a reaction force control type have been known for example in rack-binion type power steering devices, that is, integral type power steering devices.

For example, there is a known proposal to electronically control the opening degree of an oil pump's metering orifice according to the vehicle speed, and when the vehicle speed is low, the orifice opening degree is large, and in such a case, the steering hydraulic circuit is the power steering itself. This means that a large amount of output can be obtained with a light operating force. As the vehicle speed increases, the opening degree of the orifice becomes smaller, the flow rate to the power steering device becomes smaller, the boosting effect of the hydraulic pressure decreases, and the steering becomes more stable.

However, the high-speed stability device used in such integral type power steering devices is designed to ultimately increase the steering torque by reducing the flow rate flowing into the power steering device during high-speed driving. In particular, it did not prevent the maximum steering speed. In other words, such a stabilizing device applied to an integral type power steering device has the above-mentioned Nm
It does not regulate aχ. Therefore, although merely adjusting the steering flow rate can be sufficiently effective for light and heavy vehicles, it is not preferable as a stabilizing device for high speed running in heavily loaded vehicles.

[Means for solving problems]

Therefore, the present invention was created in order to solve the disadvantages of the prior art, particularly focusing on preventing the maximum steering speed, and is a fully hydraulic power steering system used in heavy-duty vehicles. In order to reduce the flow rate flowing into the fully hydraulic power steering device or the maximum number of steering circuits only during high-speed steering, a control valve was added to limit the steering flow rate in the steering MIB detour consisting of the The steering hydraulic circuit is provided to I.

Hereinafter, the structure of the present invention will be explained in detail with reference to embodiments shown in the accompanying drawings.
111 will explain. FIG. 1 shows a steering hydraulic circuit consisting of an open center type fully hydraulic steering device used for heavy-duty vehicles.
If the two electrohydraulic switching valves 2.2S7 are set to the solenoid OFF state, the steering hydraulic circuit becomes the same as a commonly used steering hydraulic circuit. In the figure, ■ is the steering cylinder, 3.3° is a check valve with a fixed throttle (restriction check valve), 4 is a fully hydraulic power steering device, 5 is a steering handle, 6 is a check valve, and 8 is a Constant flow control diverter valve (flow regulator),
9 is a main relief valve, and 10 is a pump.

Here, the electromagnetic switching valve 7 and the constant flow control branch valve 8 are configured to show the characteristics of this embodiment, and the electromagnetic switching valve 2.2' and the fixed throttle check valve 3.3
° need only be added if it is particularly necessary in terms of the driving performance of the individual vehicle.

Since this embodiment has the configuration described above, it performs the following operations. In other words, when a heavily loaded vehicle is stationary or when steering at low speed, the three electrohydraulic switching valves 2.2° and 7
When the solenoid is turned off, the water discharged from the pump 10 passes through the check valve 6 and flows entirely to the one-pressure power steering device 4. This fully hydraulic steering device 4 is of an open center type, and when the steering wheel is in a neutral state, the ura is only bypassed by the tank, so the steering wheel 5
When the steering wheel rotates, an amount of oil proportional to the amount of rotation is sent to the steering cylinder 1, and a power steering function is performed by changing the stroke of the cylinder 1.

Next, when steering a heavy-duty vehicle at high speed, the three solenoids of electrohydraulic switching valves 2.2" and 7 are turned ON.The method for this switching is to convert the vehicle speed into an electrical signal, and when the vehicle speed exceeds a certain There is a method of automatically switching on the solenoid of the electromagnetic valves 2.2'' and 7, or a method of manually operating a button, but in either case, the selection should be made taking into account the characteristics of the vehicle and the cost. In such a pleasurable feeling, the flow rate of the oil discharged from the pump IO is restricted by the constant flow control diverter valve 8, and as a result, high-speed steering operation of the fully hydraulic power steering device 4 can be prevented. For example, when the electromagnetic switching valve 7 is OFF, the maximum steering rotational speed Nmax is a flow rate of 120 rpm, whereas when the electromagnetic J switching valve 7 is ON, Nmax is limited to 30 rpm. N max when steering at high speed (when electromagnetic switching valve 7 is ON)
may be arbitrarily determined depending on the characteristics of each vehicle.

Note that the constant flow rate control branch valve 8 may be a normal flow rate adjustment valve.

The electrohydraulic switching valve 2.2° and the check valve with fixed throttle 3.3° were added in consideration of the case where the tracking ability of the steering cylinder 1 due to the inertia of the vehicle becomes a problem when steering at high speed. Similarly to the electromagnetic switching valve 7, it is switched by the N speed.

The addition of the check valve 3.3' with a fixed throttle increases the pressure drop during steering operation, but since the steering force when the vehicle is running generally becomes very small as the vehicle speed increases, it is especially important in terms of steering characteristics. This is not a problem.The check valve with a fixed throttle (3.3°) may be simply a fixed orifice, and the throttle amount can be set by considering the characteristics of each vehicle, as described above6. To reiterate, the biggest feature of this embodiment is the addition of the electromagnetic switching valve 7 and the constant flow control diverter valve 8, which limit the maximum steering speed when a heavily loaded vehicle is running at high speed. The addition of the electromagnetic switching valve 2.2' and the fixed throttle check valve 3.3° is intended to improve the followability of the steering cylinder 1. Therefore, in the second, third, and fourth embodiments described below, 2.2゛, 3.3
゛ is omitted entirely.

Next, FIG. 2 shows a second embodiment of the present invention, in which the electromagnetic proportional type /i! An example using the quantity control valve 11 will be shown. In the second embodiment, the vehicle speed is converted into an electrical signal and the control flow rate is continuously changed in accordance with the vehicle speed. For example,
It is also possible to choose the characteristics shown in FIG. The basic idea is to limit the flow rate flowing into the fully hydraulic power steering system, similar to the first embodiment, but in this second embodiment, the maximum steering speed can be set more easily depending on the vehicle speed. effective.

Furthermore, FIG. 3 shows a third embodiment of the present invention, which is a steering hydraulic circuit for a vehicle using a load-sensing type fully hydraulic power steering device. It is the same as the load sensing steering hydraulic circuit used in

In this hydraulic circuit, 1 is a steering cylinder, 4' is a fully hydraulic power steering device, 5 is a steering handle, 6 is a check valve, 7 is an electrohydraulic switching valve, 9 is a main relief valve, IO is a pump, 12
is a fixed throttle, 13 is a dedicated priority valve (divider valve for load sensing), a is a control orifice, b is a directional control valve for a fully hydraulic power steering system,
C indicates a control spring.

The third embodiment has the above-mentioned configuration and performs the following operations. That is, when a heavy-load vehicle is stationary or when steering at low speed, the electrohydraulic switching valve 7 is turned OFF, and the oil discharged from the pump 10 enters the dedicated priority valve 13 and is transferred from the CF boat of the valve 13 to the engine oil valve 7. It flows through the valve 6 to the fully hydraulic power steering system 4'. When the handle is in the neutral position, almost all of the flow from the pump IO flows from the EF boat of the dedicated priority valve 13, and only a small amount flows to the fully hydraulic power spring device 4° for residual heat. . When the steering handle 5 is rotated, the control orifice a of the fully hydraulic power steering device 4' opens according to the amount of rotation, and the pressure ta passing through the orifice a is controlled by the control spring C of the dedicated priority valve 13. By balancing with the set pressure, only the flow rate necessary for the spring flows to the fully hydraulic power steering device 4°.

The maximum steering speed at this time is determined by the opening area of the control orifice a and the strength of the control spring C in the maximum displacement state of the directional control valve within 4 degrees of the fully hydraulic power steering system. In addition, here,
The pressure loss from the CF port of the dedicated priority valve 13 to the 4° P boat of the fully hydraulic power steering device is assumed to be very small and is ignored.

During high-speed steering of a heavily loaded vehicle, the electromagnetic hydraulic switching valve 7 is turned ON, as in the first embodiment. In this case, the maximum steering speed is determined by the control orifice a and fixed throttle 1 of the fully hydraulic power steering device 4'.
Since the total passing pressure m is 1 and the pressure is balanced by the control spring C, it becomes possible to limit the steering flow rate (that is, i high steering speed).

Other aspects are the same as in the first embodiment.

FIG. 4 shows a fourth embodiment of the present invention, in which an electromagnetic proportional throttle valve 14 is added in place of the electrohydraulic switching valve 7 and fixed throttle 11 of the third embodiment, and as in the second embodiment, Depending on the vehicle speed, a maximum steering speed can be obtained.

〔Effect of the invention〕

Since the vehicle is a heavy-load vehicle, a power steering device is especially necessary.On the other hand, since the vehicle is a heavy-load vehicle, the steering condition is particularly unstable when driving at high speed. Adopts shaped power steering,
In addition to making the steering operation of heavy-load vehicles easier, it also improves the stability of steering operations.
Riffi can be maintained using the /R amount control valve, making it possible to increase the reliability of steering operation.

In addition, since the flow rate control circuit 5B is simply added to the existing steering hydraulic circuit, there is an advantage that the circuit configuration can be changed very easily without changing the pump or the like.

[Brief explanation of drawings]

Fig. 1 is a steering hydraulic circuit diagram of a first embodiment of the present invention, Fig. 2 is a diagram of a second embodiment with main parts changed from the first embodiment, and Fig. 3 is a steering hydraulic circuit diagram of a third embodiment. Hydraulic circuit diagram, Fig. 4 is the fourth embodiment, main part change diagram of the third embodiment, Fig. 5
The figure shows a performance graph diagram. 4.4°...Fully hydraulic power steering device, 7.
...11t magneto-hydraulic switching valve, 8...constant flow control diversion valve. Agent Patent Attorney Yoshihiko Okabe Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] In a steering hydraulic circuit configured with a fully hydraulic power steering device used for heavy-duty vehicles, a control valve is simply added to limit the steering flow rate flowing into the fully hydraulic power steering device only during high-speed steering. Steering hydraulic circuit.