JPH023547A - Control device for self-feed type hydraulic machine - Google Patents

Abstract

PURPOSE:To enable effective utilization of a drive force by a method wherein from the actual number of revolutions of a prime mover, allowable torque is determined and from the load oil pressure of a hydraulic pump for running, demand torque is determined, and from the values, the limit volume of the hydraulic pump is computed to control drive of the hydraulic pump. CONSTITUTION:During stepping on of an accel pedal 12, a number of revolutions control signal NEO and a swash plate angle control signal alphaPO are outputted from a control unit 11 according to the stepping on amount, and are inputted to a governor 13 and a swash plate angle controller 17, respectively. An engine rotation speed is controlled by the governor 13, and the actual number NE of revolutions is inputted to the swash plate angle controller 17 togetherwith a differential pressure PL between oil pipes 3 and 4. In which case, from data NE, a allowable generating torque TEa of an engine 1 is determined, and from data PL and alphaPO, demand torque TP of a hydraulic pump 2 for running is determined. Since in order to prevent the occurrence of an engine stop, it is necessary that TEa is higher than or equal to TP, the limit volume of the hydraulic pump 2 is decided based on NE and PL to control a swash plate driver 10.

Description

[Detailed Description of the Invention] <Industrial Utilization Public Expenses> The present invention relates to an improvement of a control device for a self-propelled hydraulic machine, and specifically aims to improve the utilization efficiency of prime mover output.

<Conventional Technology> Self-propelled hydraulic machines such as wheel loaders and hydraulic shovels are a type of construction and mining machines. These machines are usually equipped with a prime mover such as a diesel engine, and the oil pressure of a hydraulic pump driven by this prime mover operates packets, shovel bells, etc. (hereinafter referred to as work equipment), while the power generated by the same prime mover is used to operate the construction site. We also do some driving.

Conventionally, many self-propelled hydraulic machines have adopted a method of transmitting power by installing an automatic transmission that combines a torque converter and gear transmission between the prime mover and the traveling device (tires, crawlers, etc.). However, with this system, the reduction ratio of the transmission becomes extremely large during extremely low-speed driving, which is a frequent occurrence, resulting in poor transmission efficiency. Another drawback was that it was difficult to delicately control vehicle speed, drive torque, etc. Therefore, in recent years, an increasing number of working devices have adopted a system in which hydraulic pressure generated by a hydraulic pump is used to drive a hydraulic motor connected to a traveling device, similar to working devices.

FIG. 5 is a diagram showing an example of hydraulic control of the traveling system in a wheel loader.

As shown in this figure, a variable displacement hydraulic pump 2 is connected to a diesel engine (hereinafter referred to as engine) 1. As shown in FIG. One end of oil pipes 3, 4 is connected to the suction (discharge) boats 2a, 2b of the hydraulic pump 2, and the other end of these oil vibes 3, 4 is an inflow (discharge) port of a fixed displacement hydraulic motor 5). 5a and 5b. The hydraulic motor 5 is connected to a tire 6, and when the engine 1 rotates, the tire 6 rotates via the hydraulic pump 2 and the hydraulic motor 5. In the figure, reference numerals 7 and 8 are relief valves, which prevent damage to the hydraulic system by releasing hydraulic oil from the high pressure side to the low pressure side when the oil pressure in the oil pipes 3 and 4 exceeds a set value. In addition, 9 in the figure is a differential pressure gauge, and oil vibes 3 and 4
Detects the difference in oil pressure between

Both the hydraulic pump 2 and the hydraulic motor 5 are of the swash plate type piston type, and as mentioned above, the hydraulic pump 2 is of the variable capacity type. This is done by changing the inclination angle α2 of the plate (hereinafter referred to as swash plate angle). The swash plate is driven by a swash plate driver 10 having an actuator such as a swash plate near solenoid, and the swash plate angle a2 varies within a range of -1,0≦a≦1.0. When α2≦1.0, the tires 6 rotate in the forward direction, and when -1,0≦α2≦0, the tires 6 rotate in the backward direction.

Travel control is performed by a control unit 11.

When the accelerator pedal 12 is depressed, the amount Sa of the depression is converted into an electrical signal by a potentiometer, etc., and is input to the control unit 11. The control unit 11 outputs a rotational speed control signal NEo and a swash plate angle control signal α2° to the governor 13 of the engine 1 and the swash plate driver 10, respectively, in accordance with the depression amount Sa. The control unit 11 is equipped with a forward/reverse switching switch (not shown) 9, and by operating this switch, the value of the swash plate angle control signal α2° is switched between positive and negative.

Since the capacity of the hydraulic pump 2 is proportional to the swash plate angle α2, the discharge amount Q of the hydraulic pump 2 per unit time is proportional to the product of the rotation speed N of the engine 1 and the swash plate angle ap, and is QocN6・α2... (1) becomes.

The rotation speed N8 of the hydraulic motor 5, that is, the rotation speed N of the tire 6
Since T is proportional to the discharge amount Q of the hydraulic pump 2, if the rotational speed NE of the engine 1 or the swash plate angle a of the hydraulic pump 2 increases or decreases, the traveling speed changes. The rotational speed N and the swash plate angle ap are increased or decreased by the rotational speed control signal N and the swash plate angle control signal 'po, which are output in accordance with the amount of depression of the accelerator pedal 12, respectively. Therefore, with this wheel loader, traveling control from a stopped state to maximum speed can be performed simply by depressing the accelerator pedal 12.

By the way, the allowable generated torque (hereinafter referred to as allowable torque) of the engine 1 is TI! , is the rotation speed N. While there is a limit depending on the amount, the required torque T of the hydraulic pump 2 increases during high loads such as when climbing a hill.

Therefore, the required torque Tp may become larger than the allowable torque T6°, and in that case, engine stall occurs. Since the load is naturally proportional to the pressure of the hydraulic system, the control unit 11 uses the differential pressure P detected by the differential pressure gauge 9 to generate the swash plate angle control signal ' as shown in the formula below.
The actual swash plate angle α2 was determined by correcting po.

α = α − to −P ... (2) ρ
ρ0 Here, k is a constant.

In this way, in this wheel loader, the swash plate angle α2 of the hydraulic pump 2 is determined by the depression amount Sa of the accelerator pedal 12 and the load (=differential pressure PL).

FIG. 6 is a diagram showing another example of hydraulic control of the traveling system in a wheel loader.

The first difference in this example from the above-described one is that the hydraulic motor 5 is of a variable capacity type. The swash plate angle a of the hydraulic motor 5 is driven and controlled by a swash plate driver 14, which is operated by a manual lever 15. The second difference is that no differential pressure gauge is provided in the hydraulic circuit, and the swash plate angle ap of the hydraulic pump 2 can be determined only by the swash plate angle control signal 'po.

Therefore, in this wheel loader, the allowable torque TI of the engine 1! , and when an imbalance occurs in the required torque Tp of the hydraulic pump 2, the driver should appropriately operate the lever 15 to increase or decrease the swash plate angle a of the hydraulic motor 5. For example, the swash plate angle a. When increasing the amount Q, the rotational speed of the hydraulic motor 5 decreases even if the discharge amount Q of the hydraulic pump 2 is constant, the load on the hydraulic pump 2, that is, the engine 1 decreases, and engine stalling is prevented.

<Problems to be Solved by the Invention> However, the self-propelled hydraulic machine described above has the following control problems.

In the former example, the swash plate angle α2 of the pump 2 is expressed by equation (2) (α
P='PG Swash plate angle control signal a as shown in "L"
It is determined by po and differential pressure PL, but in this equation, the constant is α
The setting is made so that engine stall does not occur even when α2° takes the maximum value (α2°=1.0). Therefore, when the depression amount Sa of the accelerator pedal 12 is small and therefore the value of the swash plate angle control signal αpo is small,
Even if the differential pressure PL is a small value, the swash plate angle α2 decreases at a large rate.

However, the cause of engine stall is the allowable torque T.
This is an imbalance between □ and the required torque TP, that is, the differential pressure PL, and there is no direct relationship with the value of the swash plate angle control signal α2°. Therefore, if the depression amount Sa of the accelerator pedal 12 is small and the value of the swash plate angle control signal 'po is less than 1.0, the swash plate angle ap decreases even though the engine stall does not occur, and the engine I couldn't use my first ability effectively. Also, the engine stall is the allowable torque T
This occurs due to an imbalance between E and the required torque Tp,
This allowable torque T varies depending on the rotational speed NE of the engine 1. Therefore, it is desirable to change the swash plate angle ap in accordance with the rotational speed N6, but since conventional methods did not have a means to measure the rotational speed N6, the swash plate angle ap had to be set to a small value. Ta.

On the other hand, in the latter example, the driver operates the swash plate angle α of the hydraulic motor 5 using the lever 15, so if an engine stall is about to occur, it is possible to prevent it by increasing the swash plate angle α1. be. Therefore, the swash plate angle aP of the hydraulic pump 2 and the swash plate angle α of the hydraulic motor 5 can be set relatively freely, and the capacity of the engine 1 can also be used effectively.

However, with this control method, the driver has to operate the accelerator pedal 12 and the lever 15 at the same time during acceleration and deceleration, and the amount of operation of the manipulator 15 also requires skill. This has resulted in driver fatigue and reduced work efficiency.

Means for Solving the Problem> Therefore, in the present invention, as a first means for solving this problem, a variable displacement hydraulic pump driven by a prime mover and a hydraulic pump rotatably driven by the discharge oil of the hydraulic pump are used. A control device provided in a self-propelled hydraulic machine, comprising a traveling hydraulic motor, and in which the rotational speed of the prime mover and the capacity of the hydraulic pump are controlled by an accelerator pedal, the actual rotational speed of the prime mover and the load of the hydraulic pump. A second means is a control device for a self-propelled hydraulic machine characterized by determining the limit capacity of the hydraulic pump from the hydraulic pressure, and a second means is a variable displacement hydraulic pump driven by a prime mover and the hydraulic pump. A tco control device installed in a self-propelled hydraulic machine, which is equipped with a variable displacement traveling hydraulic motor rotationally driven by discharged oil, and in which the rotational speed of a prime mover and the capacity of a hydraulic pump are controlled by an accelerator pedal. , a control device for a self-propelled hydraulic machine, characterized in that the capacity of the traveling hydraulic motor is determined from the actual rotational speed of the prime mover and the load oil pressure of the hydraulic pump.

In the first method, the allowable torque is determined from the actual rotational speed of the prime mover, and the required torque is determined from the load hydraulic pressure of the hydraulic pump, and from these data, the limit capacity of the hydraulic pump that does not cause engine stall is calculated. Then, the drive of the hydraulic pump, which is the drive side element of the hydraulic system, is controlled so that the capacity is below this limit capacity.

In addition, in the second method (the capacity on the hydraulic pump side is determined only by the amount of depression of the accelerator pedal), the capacity is calculated so that the allowable torque and required torque obtained by the same procedure as the first method match. As a result, the drive of the hydraulic motor, which is a driven element of the hydraulic system, is controlled.

Embodiments Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1 shows a hydraulic control diagram showing a first embodiment corresponding to the first means of the present invention, and FIG. 2 shows an algorithm for calculating the swash plate angle in the first embodiment. Further, FIG. 3 shows a hydraulic control diagram showing a second embodiment corresponding to the second means of the present invention, and FIG. 4 shows an algorithm for calculating the oblique e angle in the second embodiment. In the description of the embodiment, the same reference numerals are given to the same devices as those described in the prior art section, and redundant explanation will be omitted.

111 As shown in FIG. 1, the first embodiment has almost the same basic configuration as the conventional example shown in FIG. 16 is provided, as well as the swash plate angle of the hydraulic pump 2. A swash plate angle controller 17 for controlling the swash plate angle controller 2 is provided independently of the control unit 11.

As for the configuration of the electric circuit, in addition to inputting the swash plate angle control signal a2° from the control unit 11 to the swash plate angle controller 17, the differential pressure PL from the differential pressure gauge 9 and the actual rotation speed N from the tachometer 16 are also input to the swash plate angle controller 17. It is designed to be input to the plate angle controller 17.

The operation of this embodiment will be described below with reference to FIG.

When the accelerator pedal 12 is depressed, a rotation speed control signal Ng is generated according to the depression amount Sa.

and swash plate angle control signal 'po are control unit 1-11.
are output to the governor 13 and swash plate angle controller 17, respectively.

The engine 1 rotates under the control of the governor 13, but its actual rotational speed NE is input to the swash plate angle controller 17 as described above, and the swash plate angle controller 17 first calculates the allowable torque T6 of the engine 1. is required. Allowable torque T6. is the rotation speed NI! T=f(
N) ...(3). Here, f+1 is a function or a map.

On the other hand, inside the swash plate angle controller 17, at the same time, the differential pressure PL
From the swash plate angle control signal 'po, the required torque TP of the hydraulic pump 2 can be determined by the following formula.

TP=Dp・a,・PL/2yr1m −・(4)
Here, Dp is the maximum capacity of the hydraulic pump 2, and 7 m is the mechanical efficiency of the hydraulic pump 2.

In order to prevent engine stall from occurring, it is necessary that T6°≧T. Therefore, the limit capacity of the hydraulic pump 2, that is, the allowable swash plate angle α2. is determined by the formula below.

From f(N-=DP-ap,・PL/2π・rim, a,,
-2x ・vm/Dp-PL-f(N,) -(5)
Therefore, from this swash plate angle tolerance 'Ps, the swash plate angle control signal α. If the value of is small, set aP=α2°, and if it is large, set aP−aPo, thereby preventing engine stall.

In this way, in this embodiment, the swash plate angle allowable value 'Pa corresponding to the rotational speed NE of the engine 1 is set as the upper limit of the swash plate angle control signal α2°. In addition, the swash plate angle ap can be set to a relatively large value.

As shown in FIG. 3, the second embodiment has almost the same basic configuration as the conventional example shown in FIG. In addition to a tachometer 15 for measuring , a differential pressure gauge 9 connected to the control unit 11 is provided between the oil pipes 3 and 4. Further, the swash plate driver 14 on the hydraulic motor 5 side is controlled by the control unit 11 instead of a lever.

The operation of this embodiment will be described below with reference to FIG.

By depressing the accelerator pedal 12, a rotation speed control signal N6° and a swash plate angle control signal α2° corresponding to the pedal depression Sa are output from the control unit 11 to the governor 13 and the swash plate driver lO on the hydraulic pump 2 side, respectively. Ru.

The engine 1 rotates under the control of the governor 13, but its actual rotational speed N5 is determined by the control unit 11 as described above.
The allowable torque T6 of the engine 1 is first determined in the control unit 11 from this input.

Allowable torque T1. is T, ,= as determined in the first example
f (N-.

On the other hand, the required torque Tp of the hydraulic pump 2 is simultaneously determined within the control unit.

This is also as obtained in the first example, T=DP・α, ・
PL/2yr ram.

Next, the operating rate β is determined from the allowable torque Te and the required torque.

β; Tp/Tl:, ...(6)
The conditions for engine stall are T ) Tρ
Since εe, if β is 1, the required torque is too small.
If β>1, it will be excessive.

Since the required torque Tp is proportional to the current swash plate angle am0 of the hydraulic motor 5, the operating rate β is set to 1 by multiplying the swash plate angle control signal α by β in the control unit 11.

α□. =β・a,%. (7) In this embodiment, as described above, the allowable torque T1. Since the swash plate of the hydraulic morph is drive-controlled so that the required torque TP becomes 1=1, there is no need to operate the lever 15, and the driver can drive with maximum efficiency simply by pressing the accelerator pedal 12. Now I can do it.

Although the description of the embodiments has been completed above, the present invention is not limited to these embodiments. For example, the present invention may be applied to self-propelled hydraulic machines other than wheel loaders, or may be applied to hydraulic pumps and hydraulic machines. Other types of motors, such as a diagonal shaft type, may also be used.

<Effects of the Invention> The control device for a self-propelled hydraulic machine according to the present invention provides the following effects in terms of performance and handling.

If the limit capacity of the hydraulic pump is determined based on the actual rotational speed of the prime mover and the load oil pressure of the hydraulic pump, the capacity of the hydraulic pump should not be reduced in situations where engine stall does not occur, and the capacity itself should be set relatively large. Therefore, the driving force of the prime mover can be used effectively.

In addition, in cases where the capacity of the hydraulic motor for travel is determined from the actual rotation speed of the prime mover and the load hydraulic pressure of the hydraulic pump, the capacity of the hydraulic motor is adjusted so that the allowable torque of the prime mover and the required torque of the hydraulic pump match. Because the system is controlled, driving can be controlled with maximum efficiency without forcing the driver to operate levers.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic control diagram showing a first embodiment of the present invention, and FIG. 2 is an algorithm for calculating the swash plate angle in the first embodiment. Further, FIG. 3 is a hydraulic control diagram showing a second embodiment of the present invention, and FIG. 4C shows an algorithm for calculating the swash plate angle in the second embodiment. 5 and 6 are both hydraulic control diagrams of a conventional self-propelled hydraulic machine. In the figure, 1 is a prime mover, 1 and 2 are hydraulic pumps, 3.4 are oil pipes, 5 are hydraulic motors, 9 are differential pressure gauges, 10.14 are swash plate drivers, 11 is a control unit 1, 12 is an accelerator pedal, 13 is a governor, 16 is a tachometer, and 17 is a swash plate angle controller.

Claims (2)

[Claims] (1) A motor vehicle that is equipped with a variable displacement hydraulic pump driven by a prime mover and a travel hydraulic motor that is rotationally driven by the oil discharged from the hydraulic pump, and in which the rotational speed of the prime mover and the capacity of the hydraulic pump are controlled by an accelerator pedal. A control device installed in a self-propelled hydraulic machine, characterized in that the limit capacity of the hydraulic pump is determined from the actual rotational speed of the prime mover and the load oil pressure of the hydraulic pump. Device. (2) Equipped with a variable displacement hydraulic pump driven by the prime mover and a variable displacement hydraulic motor for rotation driven by the oil discharged from the hydraulic pump, the rotational speed of the prime mover and the capacity of the hydraulic pump are controlled by the accelerator pedal. A control device installed in a self-propelled hydraulic machine to be controlled, the self-propelled machine being characterized in that the capacity of the traveling hydraulic motor is determined from the actual rotational speed of the prime mover and the load oil pressure of the hydraulic pump. Type hydraulic machine control device.