JPH04203371A - Hydraulic pump control method for hydraulically driven vehicles - 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 [Field of Industrial Application] The present invention relates to a hydraulic pump control method for a hydraulically driven vehicle using a variable displacement hydraulic pump such as a wheeled hydraulic excavator or a wheel loader.

[Conventional technology]

As a conventional technique, for example, Japanese Patent Application Laid-Open No. 60-20498
As shown in No. 7, a target rotational speed command (Ns) of the engine is set from the set output state of the engine, and the absorption of the hydraulic pump is adjusted according to the difference between this Ns and the actual rotational speed (Ne) of the engine. There is something that controls torque.

FIG. 8 shows a conventional hydraulic control system for a hydraulically driven vehicle. In FIG. 8, 1 is a variable displacement hydraulic pump driven by an engine 2; A travel (hydraulic) motor is connected to the travel (hydraulic) motor, 5 is a direction control valve installed in the hydraulic circuit 4 to control the rotation direction of the travel motor 3, and 6 is connected to the output shaft 7 of the travel motor 3 for travel. It is a device. 8 is a variable regulator that controls the hydraulic pump 1, and this variable regulator 8 controls the pressure of the hydraulic circuit 4 and the command signal I from the control device 9.
It is controlled by r.

10 is a governor controlled by an accelerator pedal 11; 12;
13 is an accelerator sensor, 13 is an engine rotation sensor, 14 is a forward/reverse switching lever, 15 is a forward/reverse switching valve that switches and controls the direction control valve 5, 16 is a control pump, and 17 is this control pump 16 and the forward/reverse switching valve 15. This is a pressure control valve interposed between the

Then, the accelerator sensor output value (
Va), the actual engine rotation speed (Ne) from the engine rotation sensor 13, and the forward/reverse switching signal from the forward/reverse switching lever 14 are input to the control device 9, and from the control device 9, the variable regulator 8, Forward and backward switching valve 15,
Control signals Ir and IpRsIc are sent to the pressure control valve 17, respectively.
is now output.

As shown in FIG. 9, the control device 9 includes an engine rotational speed command generation section 18 that generates a target rotational speed command (Ns) for the engine 2 from the accelerator sensor output value (Va).
, an arithmetic unit 19 that calculates the deviation (Ns-Ne) between the output signal (Ne) of the engine rotation sensor 13 and the above-mentioned Ns, and an amplifier 20 with a gain that amplifies the deviation (Ns-Ne).

FIG. 11 shows the relationship between the input current Ir to the variable regulator 8 and the absorption torque of the hydraulic pump 1 (when the pump discharge pressure is constant).

Figure 10 shows the torque curve of the engine, and shows the deviation (
Ns-Ne), the pump absorption torque becomes smaller than the engine output torque.

Therefore, the engine rotational speed increases and approaches Ns.

In the direction control valve 5, the output pressure of the pressure control valve 17 is switched through the forward/reverse switching valve 15.

[Problem to be solved by the invention]

When the above conventional technology is applied to a hydraulically driven vehicle,
In particular, the following problems occur when starting and accelerating.

(1) When the accelerator pedal 11 is fully depressed, the engine 2 rotates at the rated point (maximum horsepower point), and the hydraulic pump attempts to absorb the maximum torque. However, since the vehicle does not run immediately, the flow rate to the travel motor (hydraulic motor) 3 is small, and the flow rate from the hydraulic pump 1 is relieved from a safety valve (not shown). In other words, the relieved flow rate becomes energy loss.

(2) Similarly, since the engine 2 rotates at its maximum horsepower point, it produces a lot of noise.

(3) Furthermore, although the engine 2 is rotating at high speed, the vehicle is running slowly (immediately after starting).

This is sensually unpopular because it differs from the acceleration state of a normal automobile (vehicle speed increases as the engine speed increases).

The present invention has been made in consideration of the above-mentioned problems.When the vehicle starts and accelerates, even if the accelerator pedal is fully depressed, if the vehicle speed is slow, the engine's target rotational speed command is reduced.
In other words, the above problem can be solved by controlling the hydraulic pressure of a hydraulically driven vehicle such that the output horsepower of the engine is decreased, the vehicle speed increases, and the command value is increased to increase the output horsepower of the engine. The object of the present invention is to provide a pump control method.

[Means to solve the problem]

In order to achieve the above object, the method of the present invention includes an engine, a variable displacement hydraulic pump driven by the engine, and a travel motor driven by oil discharged from the hydraulic pump. Target rotational speed command generation means for generating a target rotational speed command, and controlling the discharge capacity of the hydraulic pump in order to control the absorption torque of the hydraulic pump according to the difference between the target rotational speed and the actual rotational speed of the engine. In the hydraulically driven vehicle, the target rotation speed command is calculated by the control device based on the operation amount of the speed control means and the rotation speed of the travel motor or the travel speed of the vehicle,
This is input as a command signal Ir to a variable regulator that controls the hydraulic pump.

[For production]

The variable regulator is controlled by the above command signal Ir, and even if the accelerator pedal is fully depressed when the vehicle starts and accelerates,
When the vehicle speed is slow, the discharge pressure of the hydraulic pump is controlled to be low, and as the vehicle speed increases, the discharge pressure is controlled to increase.

〔Example〕

Embodiments of the present invention will be described based on FIGS. 1 to 7. In this embodiment, the same constituent members as those of the conventional example shown in FIG. 8 are designated by the same reference numerals, and the explanation thereof will be omitted.

A travel speed sensor 2I is provided opposite to the output shaft 7 of the travel motor 3, and the detected value thereof is inputted to the control device 9' as a travel speed signal Nm.

The control device 9' performs control as shown in FIG.

That is, the accelerator sensor output (Va) is sent to the first engine target rotational speed command section 22a, and the traveling speed signal Nm
are input to the second engine target rotational speed command unit 22b, and the first and second target rotational speed commands Ns1,
Ne2 is output, both command values Ns1 and Ne2 are compared by a comparator 23, and the smaller value is output as the target rotational speed command Ns. Thereafter, the deviation (Ns-Ne) is determined by the arithmetic unit 19 as in the conventional case, and the result is amplified by the amplifier 20 and output.

A specific example will be explained below.

When the vehicle is stopped with the accelerator off, both Nsl and Ne2 output the minimum value, and as a result, Ns also becomes the minimum value. Since the directional control valve 5 is in the middle position, the hydraulic pump pressure is low and the engine is rotating at low idle.

When the accelerator is fully pressed in this state, the direction control valve 5 is switched, the discharge flow rate of the hydraulic pump 1 flows to the travel motor 3, and the pump pressure increases. At the same time, engine 2 tries to start up.

On the other hand, at this time, the first target rotational speed command Ns1 outputted based on the accelerator output signal Va from the accelerator sensor 12 becomes the maximum value, but since the speed of the vehicle is low, it is outputted based on the traveling speed signal Nm. The second target rotational speed command Ns2 becomes the minimum value. As a result, the output Ns from the comparator 23 also becomes the minimum value.

As a result, Ir becomes K (Ns-Ne), and accordingly, as shown in A in FIG. 4, the absorption torque of the hydraulic pump 1 increases, the output torque of the engine 2 increases, and the output torque of the engine 1 increases. is driven at point a, which coincides with .

Similarly, when the speed of the vehicle increases, the second command value Ns2
increases and Ns also increases.

As a result, the matching point increases as shown in FIG. 4 (s) and (c).

Note that the flow control command (Ic) for controlling the directional switching valve 5 at this time is as shown in FIG. 3 in relation to the accelerator position (Va).

5 and 6 show a second embodiment of the present invention,
The variable regulator 8' is designed to operate only in accordance with the electrical command ``.

In this second embodiment, a pressure sensor 24 is provided to detect the discharge pressure Pp of the hydraulic pump 1, and the output signal of the pressure sensor 24 and the reference absorption torque value (Tt) of the hydraulic pump 1 are used to determine the discharge pressure of the hydraulic pump l. Calculate the capacity. In addition, the control current I to the variable regulator 8' corresponding to that value is
Calculate r2.

Then, the sum (Ir) of the control current Ir1 calculated by the control device 9' and this Ir2 in the same manner as in the first embodiment is output to the variable regulator 8'.

As a result, as shown in FIG. 7, as in the first embodiment,
Even if the accelerator is fully pressed, the rotational speed of the engine 2 does not increase if the vehicle speed is slow, but is controlled so that the rotational speed increases as the vehicle speed increases.

〔Effect of the invention〕

According to the present invention, when the vehicle starts and accelerates, if the vehicle speed is slow even if the accelerator pedal is fully depressed, the target rotational speed command of the engine 2 is decreased, that is, the output horsepower of the engine is decreased. As the vehicle speed increases, the above-mentioned command value is increased to increase the output horsepower of the engine 2, so that there is no relief flow when the vehicle starts, and energy loss can be eliminated. This eliminates engine revving and reduces noise. Furthermore, the traveling speed of the vehicle and the rotational speed of the engine 2 can be changed proportionally, making the driving sensation similar to that of a normal automobile.

[Brief explanation of the drawing]

Figures 1 to 4 show a first embodiment of the present invention, with Figure 1 being a system block diagram, Figure 2 being a control block diagram, and Figure 3 showing the relationship between accelerator position and control commands. The diagram shown in FIG. 4 is a torque diagram of the engine. 5 to 7 show a second embodiment of the present invention, in which FIG. 5 is a system block diagram, FIG. 6 is a control block diagram, and FIG. 7 is an engine torque diagram. Figures 8 to 11 show conventional examples; Figure 8 is a system block diagram, Figure 9 is a control block diagram, Figure 10 is an engine torque diagram, and Figure 11 is a control line for the control section. It is a diagram. 1 is a hydraulic pump, 2 is an engine, 3 is a travel motor, 7 is an output shaft, 8, 8' is a variable regulator, 9.9' is a control device, 10 is a governor, 11 is an accelerator pedal, 12 is an accelerator sensor, 13 is the engine rotation sensor, 22a, 2
2b is an engine target rotational speed command unit, and 24 is a pressure sensor. Applicant Komatsu Manufacturing Co., Ltd. Representative Patent Attorney Masaaki Yonehara

Claims (1)

[Claims] A target rotational speed command generation means that includes an engine, a variable displacement hydraulic pump driven by the engine, and a travel motor driven by oil discharged from the hydraulic pump, and generates a target rotational speed command for the engine. In a hydraulically driven vehicle, the discharge capacity of the hydraulic pump is controlled in order to control the absorption torque of the hydraulic pump according to the difference between the target rotation speed and the actual rotation speed of the engine,
The target rotation speed command is calculated by the control device based on the operation amount of the speed control means and the rotation speed of the travel motor or the travel speed of the vehicle, and is inputted as a command signal Ir to a variable regulator that controls the hydraulic pump. A hydraulic pump control method for a hydraulically driven vehicle, characterized in that: