JPH042789B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a drive system including an internal combustion engine and a hydraulic pump in a working machine such as a hydraulic excavator that is equipped with a variable displacement hydraulic pump driven by an internal combustion engine. .

[Conventional technology]

Conventionally, in working machines such as hydraulic excavators that drive an internal combustion engine and a hydraulic pump to generate hydraulic power, (a) Individual control system ( Three types of control methods were used: (b) cross-sensing method (c) engine speed sensing method.

For example, in the case of two hydraulic pumps, the individual control method (b) allocates 1/2 of the internal combustion engine's maximum output horsepower to each hydraulic pump, and detects the circuit pressure of each hydraulic pump independently. This method controls the discharge amount of the pump. With this method, even if one hydraulic pump is under no load, the other hydraulic pump cannot utilize its surplus horsepower.
There may be some problems.

The cross-sensing method (b) uses two hydraulic pumps to mutually transmit their respective circuit pressures, so that when the load on one hydraulic pump is light, the other hydraulic pump uses a portion of its excess horsepower. It has been made available. Although this method is superior to the individual control method in terms of horsepower control, the structure of the regulator that controls the pump discharge amount is complicated.

On the other hand, the engine speed sensing method (c) detects a decrease in the rotational speed of the internal combustion engine and limits the discharge amount of the hydraulic pump, and is the most excellent method in terms of horsepower utilization. As a conventional example, for example, SAE-paper 760687 (authored by TPNeal)
Electrohydraulic Control of Hydrostatic
Transmissions). This method is excellent in principle in that it detects a drop in the rotational speed of the internal combustion engine and limits the tilting angle of the hydraulic pump. In the hydraulic pump control device (hereinafter referred to as "anti-stall circuit") described in this SAE-paper 760687, in order to prevent the internal combustion engine from stalling, the output signal of the potentiometer that detects the displacement of the accelerator lever and the internal combustion engine Calculate the deviation ΔN of the output signal of the rotation detector that detects the actual rotation speed of The input torque of the pump is limited.

[Problem to be solved by the invention]

By the way, the control device described in SAE-paper 760687 has the following problems.
That is, in order to use the output of the internal combustion engine most effectively with the hydraulic pump, it is necessary to control the swash plate tilt angle of the hydraulic pump to decrease immediately before the fuel injection amount reaches its maximum value. However, in general, a mechanical all-speed governor is used in addition to the anti-stall circuit to control the fuel injection amount of an internal combustion engine. For this reason, in the conventional device described above, it is difficult to control the swash plate tilt angle to decrease immediately before the fuel injection amount reaches its maximum value. In other words, the mechanical all-speed governor controls the fuel injection amount by the balance between the centrifugal force of the flyweight and the spring.Since the centrifugal force of the flyweight is proportional to the square of the output rotational speed, the rotational speed set by the accelerator lever If the values are different, the amount of adjustment of the fuel injection amount due to the increase/decrease in the rotational speed deviation ΔN will be different. Therefore, even if the value of the rotational speed deviation ΔN that reaches the maximum fuel injection amount at the rotational speed that generates the rated output is the same as the value of the rotational speed deviation ΔN that starts reducing the amount of tilting of the swash plate in the anti-stall circuit. Even if they can be set, changing the set rotation speed using the accelerator lever will cause a "discrepancy" in these values, making it impossible to effectively use the output of the internal combustion engine as input to the hydraulic pump.

In addition, the regulation range of the mechanical all-speed governor is set at a rotation speed of 500~
It is very small at 150 rpm compared to the wide range of 2000 rpm. The mechanical all-speed governor controls from the minimum fuel injection amount to the maximum fuel injection amount, that is, from the minimum output to the maximum output of the internal combustion engine, within this 150 rpm range. by the way,
As mentioned above, in order to make the most effective use of the output of the internal combustion engine with the hydraulic pump, the point at which the swash plate tilting amount of the anti-stall circuit begins to decrease must be accurately set just before the maximum fuel injection amount of the internal combustion engine. Moreover, it is necessary to accurately set the above-mentioned reduction start point at any set rotational speed of the internal combustion engine. However, since the regulation range of the mechanical all-speed governor is extremely small as in Uema, slight manufacturing errors or assembly errors for each product, or errors due to aging can have a large effect, making it extremely difficult to set the above-mentioned reduction starting point. Have difficulty.

Further, even if an electronic governor using electronic elements is used to control the fuel injection amount, similar problems arise due to variations in accuracy of electronic components such as resistors, capacitors, and operational amplifiers.

An object of the present invention is to solve the above-mentioned problems in the prior art, and to maintain the setting relationship between the fuel injection amount and the input torque of the hydraulic pump as set in advance at any set rotation speed of the internal combustion engine. To provide a control device for a drive system including an internal combustion engine and a hydraulic pump, in which the output of an internal combustion engine can be used most effectively with a hydraulic pump, and the control system has good stability.

[Means to solve the problem]

To achieve the above object, the present invention provides a drive system that includes an internal combustion engine that is controlled by adjusting the fuel injection amount of a fuel injection pump, and at least one variable displacement hydraulic pump that is driven by the internal combustion engine. an operating device that sets a target rotational speed of the internal combustion engine and generates a target rotational speed signal corresponding thereto; and a rotational speed detection device that detects an output rotational speed of the internal combustion engine and generates an output rotational speed signal corresponding thereto. an arithmetic device that calculates a rotation speed deviation signal that is the difference between the target rotation speed signal and the output rotation speed signal; and an arithmetic device that calculates a rotation speed deviation signal that is the difference between the target rotation speed signal and the output rotation speed signal, and an increase in the rotation speed deviation signal when the rotation speed deviation signal exceeds a predetermined set value. In a control device for a drive system including an internal combustion engine and a hydraulic pump, the same rotational speed deviation as that used by the input torque reducing means is provided. A function is stored that increases the target rack displacement amount of the fuel injection pump in accordance with the increase in the signal, and suppresses the increase in the target rack displacement amount when the rotation speed deviation signal reaches another set value near the set value. and a fuel injection amount control device that controls the fuel injection amount by adjusting the rack position of the fuel injection pump according to the target rack displacement amount retrieved from the storage section, and The reducing means includes a pressure detection device that detects the discharge pressure of the hydraulic pump and generates a pressure signal corresponding thereto, and a pressure detection device that detects the discharge pressure of the hydraulic pump and generates a pressure signal corresponding thereto; a second storage section that stores a tilting amount target value such that the tilting amount is set to a predetermined value; and a tilting amount target value retrieved from the second storage section to set the swash plate tilting angle of the hydraulic pump. The present invention is characterized in that it is configured with a swash plate tilt angle control device.

[Effect]

When the target rotation speed Nr is given by the operating device, the rotation speed deviation signal ΔN is calculated from this target rotation speed Nr and the output rotation speed Ne of the internal combustion engine, and this rotation speed deviation signal ΔN
The target rack displacement amount M is calculated from the first storage unit based on
is determined, and the fuel injection amount is controlled so that the rack position becomes the target rack displacement amount M. At the same time, the target swash plate tilting amount is stored in the second storage section based on the same rotational speed deviation signal ΔN as above and the discharge pressure P of the hydraulic pump.
Take out X _H and control the swash plate inclination angle to this value.

As the load on the hydraulic pump increases, the output rotation speed Ne of the internal combustion engine decreases and the rotation speed deviation signal ΔN
The target rack displacement amount M gradually increases, the fuel injection amount is controlled to increase, and the output of the internal combustion engine increases. Further, when the load on the hydraulic pump increases, the rotational speed deviation signal ΔN reaches the other set value ΔN ₁ , and the increase in the fuel injection amount is restricted. On the other hand, on the hydraulic pump side, from the time when the value ΔN _{0, which is close to the set value ΔN 1 ,} is exceeded, the target swash plate tilting _amount The amount of tilting of the swash plate is controlled to achieve a predetermined input torque, and as a result, the torque of the hydraulic pump is reduced, making it easy to match the output characteristics of the internal combustion engine and the input torque of the hydraulic pump. I can do it.

Moreover, the setting values ΔN ₁ and ΔN ₀ are set in advance by the first
The same rotational speed deviation signal is used to control the target values for the fuel injection amount and the hydraulic pump swash plate tilting amount, so it can be set accurately. No matter what target rotation speed you set with the operating device,
The relationship between the two can be reproduced with high accuracy.

In addition, in controlling the amount of tilting of the swash plate of the hydraulic pump, the input torque to be controlled is determined as the target amount of tilt of the swash plate _XH from the rotational speed deviation signal ΔN and the discharge pressure P of the hydraulic pump. A control system that is stable against changes can be obtained.

〔Example〕

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a system diagram showing a system of an internal combustion engine and a variable displacement pump according to an embodiment of the control device of the present invention. In FIG. 1, 1 is an internal combustion engine, and 2 and 3 are variable displacement hydraulic pumps (hereinafter simply referred to as hydraulic pumps) driven by the internal combustion engine 1. In FIG. 4 and 5 are swash plate operating mechanisms for controlling the tilting angle of the swash plate (or slant shaft, hereinafter referred to as swash plate) of the hydraulic pumps 2 and 3, respectively, and a specific example of its configuration is shown in FIG. It is shown. 6 is a fuel injection pump for the internal combustion engine 1;
supplies the desired amount of fuel to the internal combustion engine by operating a rack provided thereon. A specific example of the structure of the easy drive means for the fuel injection pump 6 is described in the second section.
It is shown in the figure. Reference numeral 7 indicates an operation amount detector for a throttle lever (not shown) of the internal combustion engine 1, and reference numerals 8 and 9 indicate operation levers (not shown) for externally controlling the maximum value of the swash plate tilting amount of the hydraulic pumps 2 and 3. 1) is a detector for detecting the output rotation speed of the internal combustion engine 1; and 11 is a detector for detecting the displacement of the fuel injection pump 6. Reference numeral 12 denotes a control device for the internal combustion engine 1, and this control device 12 receives a throttle lever operation amount signal (target value of the rotational speed of the internal combustion engine 1) 7a from the detector 7 and a rotational speed of the internal combustion engine 1 from the detector 10. Based on the numerical signal 10a and the rack displacement signal 11a of the fuel injection pump 6 from the detector 11, a rack operation signal 12a is output to the fuel injection pump 6, and a rotation speed deviation signal 12b of the internal combustion engine 1 is output to the hydraulic pumps 2, 3. output to the control device 13 of.

The control device 13 of the hydraulic pumps 2 and 3 receives an external operation signal 8a for the amount of tilting of the swash plate of the hydraulic pump 2, an external operation signal 9a for the amount of tilt of the swash plate of the hydraulic pump 3, and a signal for the amount of tilt of the swash plate of the hydraulic pump 2. 4a, a swash plate tilting amount signal 5a of the hydraulic pump 3, a discharge pressure signal 14a of the hydraulic pump 2 detected by the pressure detector 14, a discharge pressure signal 15a of the hydraulic pump 3 detected by the pressure detector 15, and a discharge pressure signal 15a of the internal combustion engine 1 detected by the pressure detector 15. Based on the rotation speed deviation signal 12b of the internal combustion engine 1 given from the control device 12, the swash plate operation signal 13a of the hydraulic pump 2 and the swash plate operation signal 13b of the hydraulic pump 5 are transmitted to the swash plate operation mechanism 4, Output to 5.

A specific embodiment of the above-mentioned fuel injection pump 6 and rack operating device will be described with reference to FIG. In this figure, the same reference numerals as in FIG. 1 indicate the same parts. The amount of fuel injected into the internal combustion engine 1 is in a functional relationship with the displacement of the rack 16. This rack 16 is driven by a moving train 17. 18 is York, 19
is a permanent magnet, and 20 is a easy return spring. 21
is a current amplifier, and this current amplifier 21 receives the rack operation signal 12a from the control device 12 of the internal combustion engine 1 and drives the movable wire wheel 17 in the form of a direct current signal or a pulse width modulation signal 21a. The rack displacement detector 11 sends its output through an amplifier or a waveform shaping circuit 22 to generate a rack displacement signal 11.
It is returned to the control device 12 of the internal combustion engine 1 as a.

A specific embodiment of the swash plate operating mechanism 4 of the hydraulic pump 2 described above will be described with reference to FIG. In this figure, the same reference numerals as in FIG. 1 indicate the same parts. The swash plate 2a of the hydraulic pump 2 is driven by hydraulic cylinders 23a and 23b. Hydraulic cylinder 23a, 2
3b is controlled by four two-position two-way solenoid valves 24-27. That is, when the solenoids 24a and 25a of the electromagnetic valves 24 and 25 are energized, pressure oil from the pilot hydraulic pressure source 28 acts on the hydraulic cylinder 23a, and the hydraulic cylinder 23b acts on the tank 2.
9, the amount of inclination of the swash plate 2a of the hydraulic pump 2 increases. Conversely, when the solenoids 26a and 27a of the electromagnetic valves 26 and 27 are energized, the hydraulic pump 2
The amount of tilting of the swash plate decreases. and solenoid valve 25,2
When the solenoids 25a and 27a of No. 7 are energized, all the electromagnetic valves 24 to 27 close their circuits, so that the amount of tilting of the swash plate of the hydraulic pump 2 remains in that state. 3
0 is a detector that detects the amount of tilting of the swash plate 2a of the hydraulic pump 2, and its output signal is fed back to the pump control device 13 as a swash plate tilt amount signal 4a via an amplification amount or waveform shaping circuit 31. Ru. hydraulic pump 3
Since the swash plate operating mechanism 5 is similarly configured, a detailed explanation thereof will be omitted.

Next, the control procedure in the control device 12 of the internal combustion engine 1 will be explained with reference to FIG. FIG. 4 is a control flowchart when a microcomputer is used as the control device 12.

First, in step 40, the state quantities, namely the throttle lever operation amount (target rotation speed Nr), output rotation speed
After reading Ne and easy displacement Z, control device 1
The data is stored at an appropriate memory address in the memory section No.2. Next, in step 41, the rotation speed deviation ΔN of internal combustion engine 1 is
Nr-Ne is calculated and the result is stored, and in step 42, the value of the rotation speed deviation ΔN is outputted to the hydraulic pump control device 13 as a signal 12b. Next, it is determined whether or not it is idling from the value of the target rotation speed Nr, and if it is idling, in step 44,
Rack displacement target function M = fi during idling, which is written in advance in read-only memory (ROM)
(ΔN), determine the target value of easy displacement during idling M, and proceed to step 45.

Here, the rack displacement objective function has a form as shown in FIG. That is, the rack displacement target value M is a monotonically increasing function with respect to the rotational speed deviation ΔN. In Fig. 5, the function f(ΔN) is shown as a broken line function with a predetermined set value ΔN ₁ as the breaking point.
It is not necessarily a broken line like this, but may be a curved line. Note that by using a polygonal line function, the output characteristics of the internal combustion engine can be changed to appropriate characteristics. There is also a method in which three types of easy displacement target value functions are prepared, one for idling, one for medium speed, and one for high speed, and used depending on the target rotational speed Nr. Figure 4 shows this method. In other words, if it is not idling in step 43, step 46
Determine whether it is medium speed or high speed (the maximum value of the medium speed rotation range is indicated by the value Nro), and if it is high speed, in step 47, set the easy displacement target value function M= for high speed. After inquiring f _h (ΔN) and determining the value of the rack displacement target value M at this time, the process moves to step 45. In addition, in the case of medium speed, refer to the easy displacement target value function M=f _p (ΔN) for medium speed in step 48, determine the value of the easy displacement target value M at this time, and then proceed to step 45. Move.

In step 45, the maximum value M _nax of the easy displacement target value M written in advance in the ROM is calculated from the output rotation speed Ne.
=g(Ne), and in the next step 46, the value of this rack displacement target value M and its maximum value M _nax are compared. If M>M _nax , in step 47 the value of M is replaced with M _nax and the process moves to step 48. If M
If M _nax , proceed to step 48 without changing the value of M.

The maximum value M _nax =g(Ne) of the rack displacement target value is in a relationship that decreases with respect to the output rotational speed Ne as shown in FIG. The purpose of this is as follows. That is, in general, the amount of fuel injected per cycle of the fuel injection pump 6 tends to increase as the rotational speed of the internal combustion engine 1 increases when the slack displacement is significant. Therefore, as the rotational speed decreases, the output torque decreases. Therefore, if the maximum value of the easy displacement is adjusted to a large value in order to secure torque in the low rotation range, the amount of fuel injected in the high rotation range will become too large and incomplete combustion will occur, causing the internal combustion engine 1 to black out. Smoke blows out. In order to overcome these problems, the output rotation speed is increased as shown in Figure 6.
The relationship between Ne and the maximum value M _nax of the target value of easy displacement may be set to a downward-sloping characteristic. This is called the Angreich characteristic. Although this characteristic is achieved by a combination of very complex mechanisms in a mechanical governor, it can be achieved very easily by using a microcomputer as the control device.

After determining the target value M of the rack displacement as described above, the rack displacement deviation ΔZ is calculated from the target rack displacement value M and the rack displacement Z in step 48 shown in FIG. The current is output to the current amplifier 21 shown in FIG. 3, and the process returns to the beginning.

Next, the control procedure in the pump control device 13 will be explained with reference to FIG. FIG. 7 is a control flowchart when the pump control device 13 is implemented using a microcomputer.

First, in step 50, the state quantity of the drive system related to the hydraulic pump 2, that is, the external operation signal X _L of the hydraulic pump 2,
The swash plate tilting amount Y, the rotational pressure P, and the rotational speed deviation ΔN of the internal combustion engine 1 are read and stored. Next, in step 51, a swash plate tilting amount command value X _H is determined based on the input torque control function f ₁ (ΔN, P). The procedure for determining this swash plate tilting amount command value _XH will be explained.

The input torque T of the hydraulic pump 2 is proportional to the product of the swash plate tilting amount Y of the hydraulic pump 2 and the discharge pressure P. In this embodiment, the input torque T is controlled in accordance with the increase or decrease in the output rotational speed Ne of the internal combustion engine 1, that is, in accordance with the decrease or increase in the rotational speed deviation ΔN. FIG. 8 shows the relationship between the input torque T of the hydraulic pump and the rotational speed deviation ΔN under such control.
In other words, the input torque T of the hydraulic pump is ΔN≦
At ΔN ₀ (the value ΔN ₀ is a predetermined set value), it is the maximum value T _nax , and when the rotation speed deviation ΔN exceeds the set value ΔN ₀ , it decreases with the increase of the rotation speed deviation ΔN, and at the set value with the rotation speed deviation ΔN If ΔN _nax is exceeded, the input torque T
is determined to be the minimum value T ₀ .

By the way, as mentioned earlier, the input torque T of the hydraulic pump is proportional to the product of the discharge pressure of the hydraulic pump and the amount of tilting. Therefore, in this embodiment, the input torque T is obtained according to the function shown in FIG. 8, which corresponds to a certain rotational speed deviation ΔN. Then, the swash plate tilt amount (target value of the swash plate tilt amount) is determined so that the product of the detected discharge pressure and the swash plate tilt amount becomes the obtained input torque T. If the tilting of the swash plate is controlled by the amount of tilt of the swash plate determined in this manner, it is possible to obtain the corresponding input torque T in FIG. 8 for a certain rotational speed deviation ΔN. The input torque control function shown in Figure 9 represents these relationships.
f ₁ (ΔN, P). The horizontal axis in FIG. 9 is the circuit pressure P, and the vertical axis is the input horsepower control number f ₁ (ΔN,
This is the target value X _H of the swash plate tilt amount based on P). The input torque control function f ₁ (ΔN, P) is a hyperbolic group or an approximate hyperbolic group, and is represented by a curve group that satisfies the input torque characteristics shown in FIG. Using the rotation speed deviation ΔN of the internal combustion engine 1, the corresponding input torque function f ₁ can be determined, and the optimum swash plate tilting amount command value X _H can be determined from the hydraulic circuit pressure P.
That is, the input torque control function f ₁ (ΔN, P) is changed to f ₁₀ , (ΔN ₀ , P),
f ₁₁ (ΔN ₁ , P)...... f1 _i (ΔN _i , P) and a plurality of function tables are stored in advance in the storage section of the control device 13, and the rotation speed deviation closest to the actual rotation speed deviation is determined. The desired swash plate tilting amount command value may be calculated using linear interpolation from a function table corresponding to .

At this time, when the rotation speed deviation ΔN is less than or equal to the set value ΔN ₀ , the input torque function f ₁ is calculated as the function f ₁₀ , and as the rotation speed deviation ΔN becomes larger than the set value ΔN ₀ , the function f ₁₁・f ₁₂ ......f1 _i is calculated.

Furthermore, the following approximate method may be used to obtain the torque control function _f1 . This is the 10th
By moving one hyperbola f ₀ (P) in parallel according to the value of the rotational speed deviation ΔN as shown in the figure, the target value of the swash plate tilt amount corresponding to the hydraulic circuit pressure P and the rotational speed deviation ΔN is determined. This is to find X _H. The method of parallel movement at this time will be described below using FIG.

In Figure 11, the hyperbola f ₀ which is now the standard
As (ΔP), the relationship between the pressure P and the swash plate tilting amount command value X _H that provides the minimum absorption torque T ₀ of the absorption torque T of the hydraulic pump 2 is used. At this time, a pressure signal _P
Instead of P' = P - ΔP, function f ₀ to X _H
Fig. 11 shows f ₀ (P-ΔP)
The shape is obtained by moving f ₀ (P) by ΔP in the horizontal axis direction, as shown by the curve shown as . This curve is quite different from the curve where the absorption torque is approximately constant. Therefore, the target value _XH of the swash plate tilting amount is corrected using another function, ΔX=g ₂ (ΔN), which changes according to the rotational speed deviation ΔN. That is, the calculation X _H = f ₀ (P-ΔP) + ΔX is performed to move the curve f ₀ (P-ΔP) by ΔX in the vertical axis direction. The resulting curve is the first
It is indicated by a broken line in Figure 1. When translating in this way, a fairly good curve of constant absorption torque is obtained depending on the respective rotational speed deviation.

Here, in order to control the absorption torque T of the hydraulic pump 2 to decrease in the form shown in FIG. 8 with respect to the increase in the rotational speed deviation ΔN of the internal combustion engine 1, a correction function ΔP=g ₁ (ΔN) is used. , ΔX=g ₂ (ΔN) are the first
The shape will be as shown in Figures 2 and 13.

FIG. 14 shows the procedure explained above in the form of a flowchart. Note that if a straight line is used instead of a hyperbola as the reference input torque control function f ₀ , the error from the constant input torque curve will increase, but the amount of tilting of the hydraulic pump's swash plate can still be controlled regardless of the circuit pressure P. Since the stability is much better than the conventional method, the use of a straight line as the input torque control function f ₀ does not contradict the spirit of the present invention.

X _H = f ₁ found in step 51 in Figure 7
(ΔN, P) is determined as above, but
In this case, the set value ΔN ₁ of the rotational speed deviation ΔN at the turning point at which the fuel injection amount starts to be restricted shown in FIG.
If the input torque T of the hydraulic pump shown in the figure is set to a value slightly larger than the rotational speed deviation ΔN ₀ at which restriction starts, the output of the internal combustion engine can be used most effectively as the input torque of the hydraulic pump.

Returning again to FIG. 7, the control procedures following step 52 will be explained. After determining the target value X _H of the swash plate tilting amount regarding the input torque from the input torque control function f ₁ (ΔN, P), the value is temporarily stored and the process moves to the next step 52.
Step 52 is performed when the circuit pressure P increases abnormally.
By reducing the swash plate tilting amount Y regardless of the lever operation amount X _L and the target value X _H for limiting the input torque,
This is to prevent pressure oil from being relieved from a relief valve (not shown) in the hydraulic circuit, resulting in energy loss. For this purpose, a function X _c =f ₂ (P) as shown in FIG. 15 is prepared in the storage section. By referring to this function, the target value X _c of the swash plate tilting amount according to the circuit pressure is determined. Next, in step 53, the target values for the amount of swash plate tilting determined in the above steps X _L , X _H , and X _C are compared, and the minimum value is determined as the final target value for the amount of swash plate tilting. Select as X,
The process moves to step 54, which is control of the amount of tilting of the swash plate.

Next, the hydraulic pump control routine executed in step 54 will be explained using FIG. 16. First, in step 61,
The tilting angle deviation Z 2 of the pump 2 from the target value X of the swash plate tilting amount of the hydraulic pump 2 and the tilting angle X ₁₀ of the hydraulic pump ₂
Calculate =X− _X10 . Subsequently, in step 62, it is determined whether the tilt angle deviation _Z2 of the pump 2 is positive or negative. If the result is positive, it is checked in step 63 whether the tilt angle deviation Z ₂ is larger than the dead zone Δ. If Z ₂ > Δ, then
Proceeding to step 64, the command to increase the tilting angle of the hydraulic pump 2 (the solenoid 2 of the solenoid valves 24 and 25 shown in FIG.
4a and 25a) is output and the process returns to the main routine. If Z ₂ Δ in step 63, step
65, the tilting angle holding command of the hydraulic pump 2 (solenoids 25a, 27a of the electromagnetic valves 25, 27 shown in FIG.
(command to excite) is output and the process returns to the main routine. If the value of tilt angle deviation Z ₂ is negative in step 62, step
66, take the absolute value of the tilt angle deviation Z ₂ , and newly calculate
Let Z ₂ = |Z ₂ |. Next, in step 67, the magnitude of the tilt angle deviation Z ₂ and the dead zone Δ is compared. If Z ₂ > Δ, then in step 68 a command to reduce the tilting angle of the hydraulic pump 2 (the solenoid 2 of the solenoid valves 26 and 27 shown in FIG.
6a, 27a) and returns to the main routine. If Z ₂ Δ in step 57, a command to maintain the tilt angle of the hydraulic pump 2 is issued to proceed to step 65, and the process returns to the main routine. The explanation so far has been related to the hydraulic pump 2, but since the control routine for the hydraulic pump 3 is also similar to this, the explanation will be omitted.

Above, we have controlled the hydraulic pump 2 in steps 50 to 54 shown in Figure 7, but the same steps are also performed for the hydraulic pump 3, and once that is completed, we return to the beginning and repeat the same control steps. . Here, if the absorption horsepower distribution of hydraulic pump 2 and hydraulic pump 3 is to be the same, the determination in step 51 is made.
Since X _H can be used as is in step 55, the step of determining X _H can be omitted in step 55.

The above explanation is based on the swash plate tilting amount Y of the hydraulic pumps 2 and 3.
We have described the so-called single-tilt type hydraulic pump in which Y can only take positive values, but Y can take positive and negative values.
A similar concept can be applied to a hydraulic closed circuit drive device using a so-called double tilting type hydraulic pump.

In the above-described embodiment, in order to make the content of the present invention easier to understand, the control device 12 of the internal combustion engine 1 and the control device 13 of the hydraulic pump were explained as separate hardware, but they can be integrated into the same hardware using one microcomputer. It is also possible to configure it as hardware.

〔Effect of the invention〕

As described above, in the present invention, in order to control the fuel injection amount, a function of the target rack displacement amount with respect to the rotational speed deviation signal ΔN is stored in the first storage section,
In addition, in order to control the input torque of the hydraulic pump, the function of the rotational speed deviation signal ΔN and the tilt amount target value for the hydraulic pump discharge pressure, which is the same as above, is stored in the second storage section, so that the fuel injection amount can be controlled. and the target value of the swash plate tilting amount of the hydraulic pump are simultaneously controlled by the same rotational speed deviation signal, and no matter what value is set as the target rotational speed by the operating device, the relationship between the two will be is reproduced with high accuracy.

In addition, the same rotational speed deviation ΔN that controls the internal combustion engine is used to control the hydraulic pump, and the rotational speed deviation ΔN ₁ starts to limit the fuel injection amount, and the input torque to the hydraulic pump starts to be limited. Since the rotational speed deviation ΔN ₀ and It can be effectively used in pumps.

Furthermore, since the target value of the tilting amount of the swash plate is determined from the discharge pressure P of the hydraulic pump together with the rotational speed deviation signal ΔN, stable control can be performed in response to changes in the discharge pressure P.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a drive system for an internal combustion engine and a liquid pump according to an embodiment of the control device of the present invention, and Fig. 2 shows a configuration of a fuel injection pump and a rack drive means of the internal combustion engine shown in Fig. 1. System diagram, FIG. 3 is a system diagram showing the configuration of the swash plate operating mechanism of the hydraulic pump shown in FIG. 1, FIG. 4 is a flowchart explaining the operation of the internal combustion engine control device, and FIG. Characteristic diagram showing the relationship between numerical deviation and easy displacement command value, No. 6
The figure is a characteristic diagram showing the relationship between the rotational speed of the internal combustion engine and the maximum value of the easy displacement command value. Figure 7 is a flowchart explaining the operation of the hydraulic pump control device.
The figure is a characteristic diagram showing an example of the relationship between the rotational speed deviation of the internal combustion engine and the input torque of the hydraulic pump. Figure 9 is the relationship between the circuit pressure, the rotational speed deviation, and the command value of the hydraulic pump swash plate tilting amount. 10 is a graph diagram showing the standard of the hydraulic pump input constant curve used to approximately realize the relationship shown in FIG. 9.
The figure is an explanatory diagram for explaining the method of parallelly moving the line diagram shown in Figure 10, Figure 12 is a characteristic diagram showing the relationship between rotation speed deviation and circuit pressure correction value, and Figure 13 is rotation speed deviation. FIG. 14 is a flowchart illustrating the operation for determining the swash plate tilt amount command value based on the input torque control function, and FIG. 15 is a circuit diagram. FIG. 16 is a characteristic diagram showing a control function used to regulate the maximum value of pressure, and is a flowchart explaining the control operation of the swash plate operating mechanism. 1... Internal combustion engine, 2, 3... Hydraulic pump, 4,
5... Swash plate operation mechanism, 6... Fuel injection pump, 7
...Throttle lever operation amount detector, 8, 9...
10... Output rotation speed detector, 11... Rack position detector, 12... Internal combustion engine control device, 13... Hydraulic pump control device.

Claims (1)

[Claims] 1 A drive system including an internal combustion engine controlled by adjusting the fuel injection amount of a fuel injection pump and at least one variable displacement hydraulic pump driven by the internal combustion engine, sets a target rotational speed of the internal combustion engine. an operating device for setting and generating a target rotation speed signal corresponding thereto; a rotation speed detection device for detecting an output rotation speed of the internal combustion engine and generating an output rotation speed signal corresponding thereto; and the target rotation speed signal and the output. an arithmetic device that calculates a rotation speed deviation signal that is a difference from a rotation speed signal; and when the rotation speed deviation signal exceeds a predetermined set value, the input torque of the hydraulic pump is reduced as the rotation speed deviation signal increases. In a control device for a drive system including an internal combustion engine and a hydraulic pump, the input torque reducing means increases the rotation speed of the fuel injection pump based on the same rotational speed deviation signal used in the input torque reducing means. a first storage section that stores a function that increases a target rack displacement amount of the rotation speed deviation signal and suppresses an increase in the target rack displacement amount when the rotation speed deviation signal reaches another set value near the set value; a fuel injection amount control device that controls the fuel injection amount by adjusting the rack position of the fuel injection pump according to a target rack displacement amount taken from the input torque reducing means;
a pressure detection device that detects the discharge pressure of the hydraulic pump and generates a pressure signal corresponding thereto; and a pressure detection device that detects the discharge pressure of the hydraulic pump and generates a pressure signal corresponding thereto; a second storage unit that stores a tilting amount target value such that
An internal combustion engine and a hydraulic pressure system comprising: a swash plate tilt angle control device that controls a swash plate tilt angle of the hydraulic pump according to a tilt amount target value retrieved from the second storage unit; Control device for drive system including pump.